The team divided the lake into three hydrologically distinct groups based on dominant inflow sources and catchment characteristics. Group 1, influenced by urban development and agricultural runoff, showed significantly higher concentrations of most of the studied rare earth elements together with elevated radionuclide activities. Group 2, representing predominantly forested catchments, exhibited comparatively lower values across the board. Group 3, located near the dam outlet, displayed intermediate characteristics that the authors attribute to sediment mixing processes, where material from different parts of the catchment converges before settling.

Rare earth elements have become strategically critical materials for magnets, batteries, and electronics, so understanding where they accumulate in ordinary environments matters both for resource geology and for ecotoxicology. At the same time, radium-226, thorium-232, and potassium-40 are the principal natural contributors to gamma radiation in soils and sediments, and their concentrations determine whether an area poses any radiological concern. Because rare earth elements often travel geochemically with thorium and uranium decay chains in minerals like monazite, the co-occurrence of elevated REEs and radionuclides is not coincidental but reflects shared mineral hosts.

To quantify contamination, the researchers applied two widely used indices. The geoaccumulation index, or Igeo, compares measured concentrations against background levels and classifies enrichment from unpolluted to heavily polluted. The pollution load index, or PLI, aggregates multiple elements into a single value for each site. Both indices indicated generally low to moderate relative enrichment across the lake, with localized enrichment at several sites, particularly within Group 1. Enrichment factor calculations, however, suggested that the REE distributions are predominantly controlled by natural geological sources rather than by pollution, meaning the elevated values near developed shores likely reflect weathering of local bedrock and soils transported by runoff rather than industrial discharge.

The radiological assessment told a more nuanced story. Radium equivalent activity and the external hazard index, two standard measures used to gauge gamma dose potential from sediment or building materials, remained below recommended reference values at most sampling sites. However, several radiological indices exceeded commonly adopted global reference levels at some locations. The authors identify these spots as areas where continued environmental monitoring is warranted, not as immediate hazards but as signals that parts of the lakebed warrant periodic rechecking as land use evolves.

Multivariate statistical analyses added a key mechanistic insight: strong associations emerged between the rare earth elements and the radionuclides radium-226 and thorium-232, whereas potassium-40 behaved distinctly in space. This pattern is geochemically coherent. Radium-226 sits in the uranium decay chain and thorium-232 heads its own chain, and both tend to reside in the same refractory mineral phases that concentrate rare earths. Potassium-40, by contrast, tracks potassium-bearing minerals such as feldspars and micas, which weather and transport differently, explaining its decoupled spatial behavior.

The study’s spatial variability, the authors conclude, is consistent with the combined influence of the regional geological setting, sediment provenance, catchment-scale sediment transport processes, and recent land use disturbances. In practical terms, the lake is acting as an integrator: every inflow carries the chemical signature of its sub-catchment, and the lakebed preserves a mosaic of those signatures. Urbanized and agricultural areas deliver finer, more weathered, and chemically enriched particles, while forested catchments contribute comparatively pristine material.

For Da Lat, a city whose economy depends heavily on tourism, agriculture, and a clean mountain environment, the findings provide a valuable geochemical baseline for sustainable catchment management. Establishing reference concentrations now allows future monitoring to detect departures from natural variability, whether from expanding agriculture, construction, or changes in hydrology. The work also fits into a broader national effort, as Vietnamese researchers have recently published similar radiological assessments for the Red River, Ha Long Bay, and central coastal lagoons, building a country-wide picture of natural radioactivity in sediments.

Methodologically, the study demonstrates the value of combining nuclear analytical techniques with multivariate statistics and geographic information systems. By classifying sampling sites according to hydrological connectivity rather than arbitrary grid positions, the researchers could link chemical patterns to catchment processes, a design that other lake studies could replicate. The approach turns a routine monitoring exercise into a diagnostic tool for identifying which parts of a watershed contribute the most chemically distinctive sediment.

As demand for rare earth elements grows worldwide, and as awareness of naturally occurring radioactive materials in everyday environments increases, studies like this one fill an important gap. They show that even a seemingly pristine mountain lake carries measurable geochemical gradients shaped by both bedrock and human activity, and that careful baseline mapping is the first step toward protecting both environmental and public health in rapidly developing regions.

Subject of Research: Distribution of rare earth elements and natural radionuclides in lake sediments

Article Title: Assessment and spatial distribution of natural radionuclides and some rare earth elements in the surface sediments of TuyenLam Lake, Central Highlands, Vietnam

Article References: Nguyen, M.-D., Le, X.-T., Tran, Q.-T., Vo, T.-Q.-T., Tran, T.-A., Nguyen, T.-H.-L., Tuong, T.-T.-H., Vo, T.-M.-T., Phan, Q.-T., Chau, T.-N.-Q., Tran, T.-T.-P., Nguyen, D.-K., & Nguyen, H.-N. (2026). Assessment and spatial distribution of natural radionuclides and some rare earth elements in the surface sediments of TuyenLam Lake, Central Highlands, Vietnam. Environmental Monitoring and Assessment, 198(9), Article 998. https://doi.org/10.1007/s10661-026-15854-5

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15854-5

Keywords: rare earth elements, natural radionuclides, lake sediments, radiological risk, Vietnam, TuyenLam Lake, sediment contamination, geochemistry, environmental monitoring, land use, radium-226, thorium-232

The research, led by C. L. Proulx of the University of Ottawa and CanmetMINING of Natural Resources Canada, began with a puzzle from earlier toxicity experiments. When freshwater fingernail clams, Sphaerium striatinum, were exposed to radium-226 in beakers containing a sand substrate and algal food, dissolved radium activity concentrations dropped by roughly 90 percent between water renewals every 48 hours. The clams burrowed in the sand and fed on algae, so the loss could have come from uptake by the animals, adsorption onto mineral grains, binding to organic matter, or some combination of all three. The team designed a tiered set of experiments to disentangle these possibilities, deliberately excluding the clams so that the chemistry of the substrate and the water could be examined on its own.

The experimental design was meticulous. The researchers prepared reconstituted soft water at four calcium levels, 0.9, 7, 35, and 70 milligrams per litre, spanning conditions found in freshwaters both with and without metal-mining effluent, and dosed each with radium-226 at nominal activities of 1, 5, and 50 becquerels per litre. They then ran three tiers of treatments: solution only, solution plus sand, and solution plus sand plus a mixture of algal cells representing organic matter. Across four calcium experiments and three radium levels, with three replicates each, 108 test vessels were monitored over 48 hours, with dissolved radium measured by alpha spectrometry at seven time points. Water quality stayed stable throughout, with temperatures between 21 and 22 degrees Celsius, high dissolved oxygen, and circumneutral pH, ensuring that any changes in radium concentration reflected adsorption rather than shifting chemistry.

The first striking result was what did not happen. In the solution-only treatments, dissolved radium remained completely stable across all calcium and radium combinations for the full 48 hours. Calcium alone, in other words, does not affect radium solubility or speciation. Geochemical modelling with PHREEQC confirmed this picture: roughly 70 percent of dissolved radium existed as the free divalent cation Ra2+, with about 20 percent as RaHCO3+ and 6 percent as RaSO4, and this distribution barely changed across the entire range of tested conditions. Modelling with the Windemere Humic Acid Model likewise predicted negligible interaction, less than 0.001 percent, between radium and dissolved humic or fulvic acids. Whatever removed radium from solution, it was not precipitation or organic complexation in the water column itself.

Adding sand changed everything. In the low-calcium treatments, dissolved radium plummeted, with 46 percent removed within the first hour at 0.9 milligrams per litre calcium and 25 percent within the first hour at 7 milligrams per litre. By 48 hours, removal reached 83 percent under the lowest calcium conditions and up to 86 percent across the full experiment depending on radium and calcium levels. Statistical comparison against the solution-only controls confirmed the effect was highly significant, with the sand increasing radium removal by a median of 38.4 percent across matched conditions. But the effect weakened dramatically as calcium rose: at 35 milligrams per litre, only 61 percent was removed by 48 hours, and at 70 milligrams per litre, just 58 percent. The pattern pointed squarely at competition, with abundant Ca2+ ions muscling Ra2+ off the limited binding sites on mineral surfaces.

To identify which minerals were doing the binding, the team characterized the aquarium sand under a field-emission scanning electron microscope. The sand was overwhelmingly quartz, with a mean grain size of 219 micrometres, but crucially, its grains were pitted and fractured, and those microfractures were filled with an aluminosilicate clay. Energy-dispersive X-ray analysis identified it as kaolinite, a low-cation clay with high aluminum and little potassium or magnesium. There were no significant iron or manganese oxide coatings, which are otherwise important radium sorbents, only trace ilmenite grains. This mineralogical fingerprint guided the decisive follow-up: batch sorption experiments comparing pure quartz against pure kaolinite under the same conditions.

The contrast between the two minerals was stark. Kaolinite stripped more than 90 percent of dissolved radium from solution within just 6 hours, averaging 96 percent removal plus or minus 2 percent, with distribution coefficients between 49 and 62 litres per kilogram. Quartz, by contrast, barely adsorbed any radium at all: removal averaged only 10 percent plus or minus 9 percent at 48 hours, with distribution coefficients between 0 and 0.55 litres per kilogram, roughly a hundredfold weaker than the clay. Geochemical models echoed the experiments. A cation exchange model for kaolinite predicted about 95 percent of radium would partition onto exchange sites, matching the observed 95 to 98 percent removal almost perfectly, while a surface complexation model for quartz overpredicted sorption at around 27 percent but still correctly ranked it far below the clay. The message was unambiguous: a small amount of reactive clay tucked into an otherwise inert quartz sand can dominate the entire partitioning behaviour of radium in the system.

Organic matter, surprisingly, played only a supporting role. Adding algal cells to the sand treatments produced a small but statistically consistent extra removal of about 6 percent, significant across matched conditions but trivial next to the mineral effects. This fits with radium’s chemistry: its large ionic radius, low tendency to hydrolyze, and preference for inorganic exchange sites mean it does not form strong bonds with the carboxyl and phenolic groups that bind transition metals in organic matter. The authors note a broader ecological wrinkle, however. In natural sediments rich in organic matter, microbial activity can create reducing conditions that dissolve iron oxides and radium-bearing barite, indirectly releasing radium back into the water, so organic matter may matter more as a redox driver than as a direct sorbent.

The calcium story carried its own subtlety. Distribution coefficients and sorption rate constants both responded non-linearly to calcium, generally declining as calcium rose, with the clearest inhibition at the lowest radium loading. Yet the total mass of radium sorbed to the solid phase did not change significantly with calcium, suggesting calcium primarily shifted the balance between dissolved and adsorbed radium rather than the overall capacity of the substrate. Even more puzzling, sorption kinetics slowed sharply at 35 milligrams per litre calcium but partially recovered at 70 milligrams per litre, possibly because higher ionic strength compresses the electrical double layer around mineral surfaces and speeds ion transport, even as competition ultimately caps the extent of adsorption. The authors flag this non-linear kinetic response as an open question warranting further study.

The practical implications reach well beyond the laboratory. Sandy sediments laced with reactive clays will sequester dissolved radium, potentially lowering the bioavailable fraction for benthic creatures like fingernail clams that live in and ingest sediment, while quartz-dominated sands with little clay offer little protection and may allow radium to travel freely through the water column. For regulators assessing uranium mining and milling operations, the findings suggest that predictions of radium mobility need to account for sediment mineralogy and water hardness, not just total concentrations. And because adsorption onto clays and oxides is at least partly reversible under changing geochemical conditions, a sediment that binds radium today could release it tomorrow if pH drops or chemistry shifts. In the quiet competition between a radioactive cation, a common dissolved nutrient, and a few specks of clay, the study shows that the smallest players often control the largest outcomes.

Subject of Research: Adsorption and mobility of radium-226 in sandy freshwater sediments as controlled by clay minerals, calcium, and organic matter

Article Title: Mineral-dependent and calcium-inhibited adsorption of radium-226 onto quartz and kaolinite in a natural sand substrate

Article References: Proulx, C. L., Cadieux, C., Knaack, D. R., Fortin, D., & Goulet, R. R. (2026). Mineral-dependent and calcium-inhibited adsorption of radium-226 onto quartz and kaolinite in a natural sand substrate. Frontiers in Environmental Chemistry, 7, Article 1912040. https://doi.org/10.3389/fenvc.2026.1912040

Image Credits: AI Generated

DOI: 10.3389/fenvc.2026.1912040

Keywords: radium-226, kaolinite, quartz, adsorption, cation exchange, calcium, uranium mining, freshwater sediments, radioecology, clay minerals, surface complexation, bioavailability

Naturally occurring radioactive materials, often abbreviated as NORM, are present in virtually all soils and rocks on Earth. The three radionuclides at the center of this investigation are potassium-40, a primordial isotope that makes up a tiny fraction of all natural potassium; radium-226, a member of the uranium-238 decay chain; and thorium-232, the head of its own long decay series. These isotopes are generally harmless at the low concentrations found in most agricultural land, but mining activities can concentrate them. When excavators and hand diggers bring deep material to the surface, process ore, and leave tailings exposed to wind and water, the normal geochemical balance is disturbed, and the radiation environment of a community can change in ways that are impossible to sense without instruments.

To measure those concentrations, the team collected soil samples from the three study regions and analyzed them using a sodium iodide detector doped with thallium, a workhorse instrument of gamma-ray spectroscopy. The NaI(Tl) detector registers the characteristic gamma photons emitted by each radionuclide and its decay products, allowing researchers to convert counts into activity concentrations expressed in becquerels per kilogram of soil. The results placed the average activity concentrations at 18.79 plus or minus 0.91 Bq/kg for radium-226, 7.87 plus or minus 1.23 Bq/kg for thorium-232, and 346.39 plus or minus 10.35 Bq/kg for potassium-40. These figures provide the essential input for any dose assessment, because the intensity of exposure in a contaminated landscape is governed first and foremost by how much radioactive material is actually present.

Measuring concentrations, however, is only the first step. The central question for radiation protection is what those numbers mean for human health over decades of exposure. To answer it, the researchers turned to the RESRAD code, short for residual radioactivity, a simulation package developed originally to support the cleanup of contaminated sites and now a standard tool for translating soil radioactivity into dose and risk estimates. RESRAD models the full web of exposure pathways that connect buried or surface-deposited radionuclides to human beings: direct external gamma irradiation from the soil itself, inhalation of dust particles carrying radioactive atoms, ingestion of soil, and the transfer of radionuclides through water, crops, and animal products into the food chain. By parameterizing the model with site-specific conditions and running it across a one-hundred-year horizon, the team could project how risk accumulates for two distinct populations, artisanal miners who spend long hours in intimate contact with disturbed soil, and resident farmers whose exposure comes through tilling, planting, and living on the same land.

The simulation results are striking for their clarity. Across the entire evaluated time period, from one to one hundred years, the excess lifetime cancer risk ranged from 2.33 times ten to the minus six to 5.40 times ten to the minus six. The minimum value was associated with thorium-232, while the maximum was driven by radium-226. In other words, of the three radionuclides studied, radium-226 emerged as the dominant contributor to long-term cancer risk in the mining soils, followed by thorium-232, with potassium-40 playing a comparatively smaller role despite its higher activity concentration. This inversion is scientifically meaningful: activity concentration alone does not determine risk, because each radionuclide carries its own decay energy, its own decay chain behavior, and its own dose coefficients that describe how effectively a given intake or external exposure translates into absorbed energy in human tissue.

The pathway analysis added another layer of insight. According to the simulation, the dominant exposure routes were direct radiation from the soil, both the direct gamma shine from the ground surface and the airborne component, together with inhalation. This finding matters enormously for practical protection. If inhalation and direct external exposure dominate, then the most effective interventions are those that reduce dust generation and limit time spent on freshly disturbed, unshielded soil. Simple measures such as wetting down working areas, wearing respiratory protection, and restricting the processing of ore in enclosed or poorly ventilated spaces can disproportionately reduce dose when inhalation is a leading pathway. Conversely, if food-chain transfer had dominated, the response would have focused instead on soil remediation and crop selection, a very different and more expensive set of actions.

The excess lifetime cancer risk metric itself deserves explanation, because it is the number that ultimately connects environmental measurement to human fate. The ELCR represents the probability, over and above the baseline cancer rate in any population, that a person will develop fatal cancer as a result of a lifetime of exposure to a given radiation source. Values on the order of ten to the minus six, as found in this study, correspond to roughly one additional cancer case per million exposed individuals, a magnitude that international guidance often treats as a threshold of concern for prolonged public exposure. The fact that the modeled risks in the Niger State mining regions fall within this low range is reassuring at first glance, but the authors emphasize that the findings are intended to inform radiation protection decisions, and the cumulative burden across large populations of miners and farmers, combined with other hazards of artisanal mining, is precisely the kind of information regulators need before risks grow.

The context of artisanal gold mining in Nigeria gives the study its urgency. Artisanal and small-scale mining provides livelihoods across parts of West Africa but operates largely outside formal regulatory frameworks, with minimal environmental monitoring and little occupational health oversight. Previous research in the same region has documented serious chemical hazards, including mercury contamination in soil at artisanal gold mine sites in Niger State, where the metal is used to amalgamate gold. The new radiological assessment adds a third dimension to this picture of cumulative environmental burden, showing that the same soils that carry toxic metals also carry measurable quantities of primordial and decay-chain radionuclides. For communities where mining and agriculture coexist on the same land, the combined evidence paints a portrait of chronic, low-level exposure that is easy to ignore precisely because no single measurement triggers alarm.

Methodologically, the study demonstrates the value of pairing direct spectroscopic measurement with process-based simulation. The NaI(Tl) measurements anchor the model in reality, capturing the actual gamma-emitting inventory of the soil, while RESRAD extends that snapshot across time and across exposure scenarios that would be impossible to observe directly. The one-hundred-year simulation window is particularly important for radionuclides like radium-226 and thorium-232, whose long half-lives mean that contamination does not simply decay away within a human generation. The authors note that the RESRAD-OFFSITE software used for the simulations is publicly available and that the model inputs are described in the article, an openness that allows other researchers to replicate the analysis in other mining regions where NORM data are scarce.

The broader significance of the work lies in its contribution to a growing global dataset on natural radioactivity in mining environments. Comparable assessments have been carried out around gold mines in Ghana, coal mining areas in Brazil, granite quarries in Iran, and iron beneficiation plants in China, each adding pieces to a picture of how extractive industries redistribute the Earth’s natural radioactivity into human contact. The Niger State study stands out for its explicit comparison of two vulnerable populations, miners and farmers, and for its pathway-resolved risk estimates that point directly toward mitigation. As demand for gold and other minerals continues to drive informal mining deeper into rural landscapes, studies of this kind provide the evidence base for radiation protection policies that can be implemented before, rather than after, health effects emerge. For the farming and mining communities of north-central Nigeria, the message of the numbers is measured but clear: the risk today is small, the dominant pathways are known, and the window for inexpensive prevention is open.

Subject of Research: Assessment of radiation dose and excess lifetime cancer risk from naturally occurring radionuclides in soil at artisanal gold mining sites in Nigeria using the RESRAD code

Article Title: Assessment of effective dose and radiation risk due to 226Ra, 40K, and 232Th exposure within the soil of artisanal gold mine using the RESRAD code

Article References: Muhammad, A., & Abbasi, A. (2026). Assessment of effective dose and radiation risk due to 226Ra, 40K, and 232Th exposure within the soil of artisanal gold mine using the RESRAD code. Environmental Monitoring and Assessment, 198(10), Article 1039. https://doi.org/10.1007/s10661-026-15887-w

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15887-w

Keywords: natural radioactivity, radium-226, thorium-232, potassium-40, RESRAD, artisanal gold mining, excess lifetime cancer risk, Nigeria, gamma-ray spectrometry, radiation protection, NORM, exposure pathways

The radionuclides at the center of the investigation, radium-226 and radium-228, are decay products of the uranium-238 and thorium-232 series that occur naturally in the Earth’s crust. They matter for drinking water because of their chemistry and their biology. Radium is relatively soluble compared with its parent elements, so it leaches readily from minerals into groundwater. Its two isotopes have half-lives long enough to persist in aquifers, 1,600 years for radium-226 and 5.75 years for radium-228, and once ingested the body treats radium much like calcium, depositing it in bone. There, the alpha and beta radiation emitted by the isotopes and their short-lived progeny can irradiate bone tissue, a pathway historically linked to elevated risks of bone cancer and other malignancies. The WHO sets guidance levels of 1.0 becquerel per liter for radium-226 and 0.1 becquerel per liter for radium-228, values designed so that lifetime consumption at those levels would deliver an annual committed effective dose of roughly 0.1 millisieverts.

The analytical backbone of the study was high-purity germanium gamma spectrometry performed at the Radiation Protection Institute in Accra. One-liter samples were sealed in Marinelli beakers and stored for three to four weeks, allowing radium-226 to reach secular equilibrium with its short-lived progeny lead-214 and bismuth-214, and radium-228 to equilibrate with actinium-228. The detector, an N-type HPGe with 25 percent relative efficiency and a resolution of 1.8 kiloelectronvolts at 1332 kiloelectronvolts, was calibrated with a mixed radionuclide standard in identical geometry, and each sample was counted for a demanding 36,000 seconds, ten full hours, to push detection limits as low as possible. Radon-226 was quantified through the 609.3 and 351.9 kiloelectronvolt lines of its progeny, while radium-228 was measured through actinium-228 gamma lines at 911.2 and 968.9 kiloelectronvolts. Even so, the minimum detectable activities were 0.12 becquerels per liter for radium-226 and 0.14 becquerels per liter for radium-228.

That second detection limit turns out to be one of the study’s most consequential technical findings. Because the detection limit for radium-228, 0.14 becquerels per liter, sits above the WHO guidance level of 0.1 becquerels per liter, a non-detect cannot demonstrate compliance. Every sachet and tap water sample in the study, across all three regions and both seasons, returned results below the detection limits for both isotopes. For radium-226, whose detection limit is an order of magnitude below its guidance level, that genuinely establishes compliance. For radium-228, the honest reading is more cautious: the true activity could lie anywhere between zero and 0.14 becquerels per liter, a range that spans the guideline. Treating both detection limits as upper bounds yields a screening dose of 0.095 millisieverts per year, which falls just below, but not comfortably below, the WHO individual dose criterion of 0.1 millisieverts per year. The margin is roughly 5 percent, smaller than the analytical uncertainty of the measurement itself.

The untreated sources told a dramatically different story. Borehole water, the primary drinking supply for peri-urban and rural communities without piped infrastructure, contained 5.03 to 5.16 becquerels per liter of radium-226 and 5.06 to 5.34 becquerels per liter of radium-228, exceeding the WHO guidance levels by factors of roughly five and about 51 to 53 respectively. River water was higher still. Samples from the Densu, Kakum, Pra and Anankwar rivers, along with the Weija and Kpong reservoirs, registered 27.02 to 28.39 becquerels per liter of radium-226 and 29.01 to 30.09 becquerels per liter of radium-228, overshooting the guidance levels by factors of roughly 27 to 28 and 290 to 301. These river values are unusually high for surface water anywhere in the world, and the authors themselves flag that they require independent confirmation before being used for regulatory decisions.

Converting activity into dose, the researchers applied standard ingestion dose coefficients, 2.8 times ten to the minus four millisieverts per becquerel for radium-226 and 6.9 times ten to the minus four for radium-228, multiplied by an assumed consumption of two liters per day, or 730 liters per year. Under the deliberately conservative assumption that an adult drinks exclusively from a single source for an entire year, borehole water delivered a screening dose of 3.58 to 3.73 millisieverts per year, roughly 36 times the WHO criterion, while river water delivered 20.14 to 20.96 millisieverts per year, about 200 times that benchmark and twenty times the 1 millisievert per year reference level of the International Basic Safety Standards. Notably, radium-228 contributed about 70 percent of the total dose in both cases despite similar activity concentrations, because its dose coefficient is roughly 2.5 times larger. The authors stress these are screening values, not measured exposures; anyone who switches between sources would receive less, and no age-resolved estimates were made for children, infants or pregnant women.

Season emerged as a meaningful variable. Wet-season activities exceeded dry-season values in every untreated source and region, with average increases of 1.8 to 4.9 percent. Statistical testing by one-way analysis of variance confirmed the seasonal effect was significant for borehole radium-228, river radium-226 and river radium-228, though not for borehole radium-226. The pattern is consistent with enhanced mineral dissolution, groundwater recharge and catchment runoff during the rains, which mobilize radionuclides from aquifer and catchment materials. Equally telling was what the regional comparison did not find: combined radium activities in river water were nearly identical across the three regions, 57.22, 57.26 and 57.24 becquerels per liter, with no statistically significant differences. The dataset therefore provides no basis for attributing regional variation to differences in underlying geology.

What explains the elevated activities in the untreated sources? The coastal belt is underlain by Precambrian crystalline rocks, Birimian metavolcanics, Tarkwaian sediments and coastal sedimentary basins, all of which host uranium- and thorium-bearing accessory minerals such as monazite, zircon and apatite. Weathering, dissolution and alpha-recoil release of radium from these minerals is the most plausible geogenic source, and the catchments of the Kakum, Pra and Anankwar rivers also host extensive artisanal gold mining that disturbs mineralized material and inflates suspended sediment loads. But the authors are careful: the study measured no hydrogeochemical parameters, performed no mineralogical characterization and conducted no source apportionment, so a geogenic origin remains a hypothesis rather than a demonstrated conclusion. A further technical caveat concerns the river samples themselves. They were collected as unfiltered whole-water samples and acidified to below pH 2, a procedure that leaches radium from suspended particles into solution. The reported values therefore represent total radium, dissolved plus particulate-bound, and likely overstate what a consumer actually absorbs.

The authors are equally explicit about what the exceedances do and do not mean. WHO guidance levels are conservative operational screening criteria, not thresholds of harm, and the 1 millisievert reference level is a trigger for planning protective action rather than a dose limit. The findings, they argue, call for confirmatory sampling by independent laboratories, source-specific investigation, and consideration of treatment, not a declaration of health detriment. Proven radium removal technologies exist, including ion exchange, reverse osmosis, activated alumina and lime softening, and the burden of exposure falls disproportionately on communities with the fewest alternatives to boreholes and rivers. The study also carries a regulatory message: Ghana’s national drinking water standards do not mandate routine radiological testing, and any future monitoring program must specify methods sensitive enough to detect activities below the guidance level, since a method whose detection limit exceeds the criterion cannot demonstrate compliance no matter how many samples are analyzed.

As a piece of baseline science, the work fills a genuine gap. Previous Ghanaian studies focused on mining-impacted areas or single municipalities and reported borehole radium-226 at or below 1 becquerel per liter, far lower than the values found here, which sit at or above the upper end of ranges typical of crystalline-basement aquifers worldwide. The recommended follow-up is concrete: paired raw and treated samples to quantify treatment removal, parallel filtered and unfiltered river sampling to separate dissolved from particulate radium, hydrogeochemical and mineralogical work to test the geogenic hypothesis, and an age-resolved dose assessment grounded in an actual consumption survey. Until then, the image that lingers is one of contrast, of city dwellers sipping radiologically quiet sachet water while, a few kilometers away, families draw water from boreholes and rivers that geology has quietly loaded with radium.

Subject of Research: Naturally occurring radium-226 and radium-228 contamination in drinking water sources along Ghana's coastal regions

Article Title: Assessment of 226Ra and 228Ra activity concentrations in drinking water sources along Ghana’s coastal communities

Article References: Agyeman, B. K., Adukpo, O. K., Adotey, D. K., & Serfor-Armah, Y. (2026). Assessment of 226Ra and 228Ra activity concentrations in drinking water sources along Ghana’s coastal communities. Discover Geoscience, 4(1), Article 397. https://doi.org/10.1007/s44288-026-00765-2

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00765-2

Keywords: radium-226, radium-228, drinking water, Ghana, gamma spectrometry, WHO guidance levels, groundwater, natural radioactivity, radiological assessment, borehole water, river water, public health

The research, published in Environmental Monitoring and Assessment, was carried out by a team from Hassan II University, the Moroccan National Centre for Nuclear Energy, Science and Technology (CNESTEN) and the National Institute of Agricultural Research, working within an International Atomic Energy Agency coordinated research project on radionuclide transfer in arid and semiarid environments. Led by Zineb Elaboudi, the scientists sampled soil and nine commonly consumed crops, including coriander, red pepper, potato, onion, pomegranate, cardoon, beet, tomato and eggplant, from farmland in a semiarid Moroccan agricultural area. Their goal was to quantify activity concentrations, calculate soil-to-plant concentration ratios and estimate the potential annual effective dose that people could receive from eating locally grown food.

The analytical work relied on high-resolution alpha- and gamma-spectrometry using high-purity germanium detectors, instruments capable of distinguishing the characteristic energy signatures of individual isotopes even at very low concentrations. The team measured eight radionuclides in both soil and plants: polonium-210, thorium-234, radium-226, thorium-228, radium-228, lead-210, potassium-40 and cesium-137. Together these isotopes span the full spectrum of environmental radioactivity, from members of the uranium and thorium decay chains that have leached slowly through bedrock for millennia, to potassium-40 dispersed uniformly through all living tissue, to cesium-137, a fission product whose global fallout from mid-twentieth-century nuclear weapons testing still lingers in surface soils.

In the soil, activity concentrations painted a picture of typical natural background. Polonium-210 ranged from 16.37 to 39.59 becquerels per kilogram, thorium-234 from 6.21 to 29.15, radium-226 from 4.84 to 26.26, thorium-228 from 9.37 to 46.04, radium-228 from 10.10 to 51.04, and lead-210 from 5.92 to 31.39. Potassium-40, as expected, dominated with values between 107.21 and 434.20 becquerels per kilogram, while cesium-137, the sole anthropogenic contributor, registered only 1.15 to 2.98 becquerels per kilogram, a faint residue of atmospheric fallout rather than any local contamination source.

Inside the plants, the story changed dramatically. Activity concentrations were generally far lower than in the underlying soil, with polonium-210 between 0.12 and 4.76 becquerels per kilogram, radium-226 between 0.36 and 5.89, and thorium-228 between 0.22 and 1.61. Potassium-40, however, ran in the opposite direction, reaching 386.33 to 3265.53 becquerels per kilogram, sometimes exceeding its soil concentration. The reason is biochemical rather than radiological: potassium is an essential plant macronutrient, recruited in large quantities to regulate osmotic pressure and enzyme function, and potassium-40 constitutes a fixed fraction of all natural potassium. Because the isotope cannot be separated chemically from its stable siblings, plants that accumulate potassium necessarily accumulate its radioactivity. Meanwhile thorium-234, radium-228, lead-210 and cesium-137 mostly fell below detection limits in the crops, indicating that roots act as effective barriers against these species.

The concentration ratio, defined as the activity concentration in plant tissue divided by that in dry soil, is the single most important parameter in radiological dose models, and the Moroccan values revealed striking crop-specific differences. Ratios spanned 0.01 to 0.14 for polonium-210, 0.02 to 0.43 for radium-226, and 0.01 to 0.17 for thorium-228, but climbed as high as 20.03 for potassium-40. Two crops stood out as the strongest accumulators: cardoon, a thistle-like vegetable with deep roots and a place of honor in North African cuisine, and eggplant. Elevated transfer in these species suggests that rooting depth, plant family physiology and nutrient demand all shape which isotopes cross the root membrane, a finding consistent with observations from Syria, Saudi Arabia, Abu Dhabi and other dry regions where comparable studies have been conducted.

Perhaps the most scientifically valuable contribution lies in the correlation analysis linking radionuclide uptake to soil chemistry. The researchers found strong interrelationships among the measured isotopes and demonstrated that transfer processes are governed primarily by soil physicochemical properties, particularly organic matter content, cation exchange capacity and the suite of exchangeable cations held on clay and humus surfaces. These parameters control how tightly radionuclides are bound to soil particles and therefore how available they are for root uptake. In contrast, carbonate content and salinity tended to restrict radionuclide mobility, effectively locking the isotopes in place. This has a counterintuitive implication for semiarid agriculture: the very conditions that make soils challenging for crop productivity, including high carbonate levels and salt accumulation under intense evaporation, may also suppress the movement of radioactive elements into the food chain.

The study also estimated the potential annual effective dose from food ingestion, the standard metric used by the International Commission on Radiological Protection to translate environmental measurements into health-relevant terms. By combining crop activity concentrations with consumption rates and isotope-specific dose coefficients, the team could assess whether locally grown vegetables contribute meaningfully to the radiation burden that residents already receive from cosmic rays, radon and terrestrial gamma radiation. The dominance of potassium-40 in plant tissues means it inevitably drives much of the ingested dose, yet because the human body maintains potassium homeostasis, biologically regulated excretion keeps the internal burden from this isotope essentially constant regardless of dietary source, a nuance that distinguishes potassium-40 from radium or polonium, which follow bone and soft-tissue metabolism and are treated with greater regulatory caution.

For the wider scientific community, the Moroccan dataset fills a recognized gap. The IAEA has repeatedly noted that most soil-to-plant transfer parameters in its handbooks derive from temperate European and North American ecosystems, while arid and semiarid environments, home to a large share of the world’s irrigated agriculture, remain underrepresented. Studies from Turkey, Jordan, Nigeria, Vietnam, Australia and now Morocco are steadily building the evidence base needed to adapt radiological environmental impact assessment to dry climates. The finding that organic matter and cation exchange capacity promote transfer while carbonates and salinity suppress it offers modelers concrete, measurable soil descriptors that can be incorporated into transfer predictions without requiring site-specific experiments at every location.

The practical message for consumers is reassuring. Cesium-137 was barely detectable, the natural radionuclides were mostly well below levels of concern, and the estimated doses fall within the range regarded as normal background exposure from food. Yet the research carries lasting value beyond its immediate conclusions. As phosphate fertilizer use, water scarcity and climate change reshape agriculture across the semiarid world, understanding the soil chemistry that governs radionuclide mobility becomes essential for protecting both food safety and the environmental systems that sustain it. This Moroccan study, rooted in rigorous gamma and alpha spectrometry and framed by international collaboration, demonstrates that even the quiet radioactivity of an ordinary vegetable patch can be measured, modeled and managed with precision.

Subject of Research: Soil-to-plant transfer of natural and artificial radionuclides and associated radiological doses in semiarid Moroccan agriculture

Article Title: Radiological impact of radionuclides in Moroccan food crops under semiarid conditions

Article References: Elaboudi, Z., Aouidi, S. E., Saadi, R., Benkdad, A., Mouridi, Z. E., Laissaoui, A., Madinzi, A., & Souabi, S. (2026). Radiological impact of radionuclides in Moroccan food crops under semiarid conditions. Environmental Monitoring and Assessment, 198(11), Article 1160. https://doi.org/10.1007/s10661-026-15992-w

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15992-w

Keywords: radionuclides, soil-to-plant transfer, concentration ratio, potassium-40, radium-226, polonium-210, cesium-137, semiarid agriculture, Morocco, gamma spectrometry, radiological dose, soil chemistry

The Okpara mine, also known as the Iva Valley mine, has stood unmanaged since its closure, with no post-closure environmental monitoring or containment strategy. That neglect matters because the geology of the Anambra Basin is unforgiving. The Enugu Shale that hosts the coal seams is naturally enriched in uranium and thorium decay chains, meaning the spoil heaps left behind are essentially uncontrolled deposits of naturally occurring radioactive material. When rainwater percolates through these dumps, it generates acid mine drainage, an acidic leachate that mobilizes radium, thorium and other radionuclides and carries them downslope into farmland and waterways. Wind adds a second dispersal pathway, lifting contaminated dust from the spoil piles and scattering it across the surrounding agricultural landscape.

To quantify the hazard, the team collected 24 environmental samples from across the affected area and analyzed them using certified gamma spectrometry, with measurements performed at Activation Analysis Laboratories in Ancaster, Canada, and at the Centre for Energy Research and Training at Ahmadu Bello University in Zaria, Nigeria. The technique identifies and quantifies gamma-emitting isotopes, allowing the researchers to determine activity concentrations of potassium-40, radium-226 and thorium-232 in each sample. From these measurements they derived eight separate hazard indices, all compliant with the assessment frameworks of the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection, and they estimated dietary ingestion doses based on local cassava consumption, a staple crop grown throughout the valley.

The numbers are striking. Mean activity concentrations of radium-226 reached 51.23 plus or minus 11.79 becquerels per kilogram, exceeding the global average by a factor of 1.46, while thorium-232 averaged 68.86 plus or minus 16.45 becquerels per kilogram, a factor of 2.30 above the worldwide benchmark. The mean outdoor gamma dose rate of 75.64 nanograys per hour surpassed the world average in 87.5 percent of the samples collected. In practical terms, people living and farming in the valley are receiving measurably higher external gamma exposure than the global baseline, simply from the ground beneath their feet.

But the most alarming finding concerns what residents eat. The mean annual dietary ingestion dose was calculated at 2.43 millisieverts per year, exceeding the ICRP public exposure limit of 1 millisievert per year in every single sample, and radium-226 accounted for 68.8 percent of that total dose. Radium’s dominance on the ingestion pathway stems from its relatively high ingestion dose conversion factor, meaning each becquerel consumed delivers a larger effective dose than the same activity of thorium or potassium-40. Because cassava efficiently transfers radium from contaminated soil into its edible tubers, and because cassava forms such a large share of the local diet, the food chain acts as a powerful concentrating mechanism, funneling subsurface radioactivity directly into the bodies of the community.

The statistical structure of the hazard is also revealing. Thorium-232 emerged as the dominant contributor to the calculated outdoor gamma dose, accounting for roughly 55 percent of the outdoor dose rate with a strong correlation coefficient of R-squared equal to 0.804 and a p-value below 0.0001, while radium-226 dominates the ingestion pathway. This split reflects the different physics of the two exposure routes: thorium’s decay chain emits abundant gamma radiation that irradiates the body externally, whereas radium, chemically analogous to calcium, is readily absorbed through the gut and deposited in bone tissue, where its alpha emissions do the most biological damage. The excess lifetime cancer risk, calculated at a mean of 3.25 times ten to the minus four, exceeded global benchmarks in 66.7 percent of cases, translating into a measurable elevation of lifetime cancer probability for people who live and farm in the most contaminated zones.

Spatial analysis added a crucial layer of precision. Using cubic interpolation of the sample data, the researchers mapped contamination gradients across the valley and found that peak concentrations track the acid mine drainage axis in the central-eastern sector of the site. This pattern confirms the mechanistic picture: the acidic drainage channels act as radioactive highways, carrying radium and thorium from the spoil heaps outward into the fields where food is grown. The mapping also carries practical value for remediation, because it identifies exactly where containment and treatment efforts would deliver the greatest reduction in community dose.

The study also uncovered a regulatory blind spot with immediate construction implications. The representative level index, a screening tool used to judge whether earth materials are safe for building, exceeded the threshold value of 1.0 in 75 percent of samples, classifying those materials as unsuitable for unrestricted construction use. Yet in many Nigerian communities, mine spoil and local soil are routinely used for bricks, road fill and foundations, often without any radiological screening. The finding suggests that the hazard extends beyond farming into the built environment, and that material sourcing decisions in the valley may be compounding exposure without anyone realizing it.

What makes the Iva Valley case particularly significant is its comparative severity. According to the comparative data available at the time of writing, the authors identify the site as the most severe documented case of dietary radionuclide burden at a West African coal mine legacy site. It is also a warning about a broader, largely invisible class of risk. Coal mining worldwide disturbs formations that naturally contain uranium and thorium, and abandoned mines across Africa, Asia and Latin America sit unmonitored beside growing populations. Nigeria alone hosts numerous legacy extraction sites where naturally occurring radioactive materials have never been systematically surveyed, and previous studies have flagged elevated radioactivity around gold, tin and coal operations across the country.

The researchers call for immediate interventions, including treatment of the acid mine drainage, physical containment of the spoil heaps, agricultural restrictions in the most contaminated zones, and systematic monitoring of naturally occurring radioactive materials aligned with international safety standards. None of these measures currently exists at the site. The study’s message is ultimately about time: every year of inaction extends the exposure of 50,000 people through the food they eat, the dust they breathe and the ground they walk on. A mine that closed decades ago is still, in a very literal sense, radiating consequences into the present, and the Iva Valley results make a compelling case that legacy mining sites across the region deserve urgent radiological assessment before the hidden burden grows heavier still.

Subject of Research: Radiological hazard assessment of natural radionuclide contamination from a legacy coal mine in Enugu Iva Valley, Nigeria

Article Title: Elevated radiological hazards in a legacy coal mining area: unveiling hidden cancer risks from natural radionuclides in Enugu Iva Valley, Southeast Nigeria

Article References: Omeje, M., Sabri, S., Owusu-Appiah, J., Gyaase, D., & Orosun, M. M. (2026). Elevated radiological hazards in a legacy coal mining area: unveiling hidden cancer risks from natural radionuclides in Enugu Iva Valley, Southeast Nigeria. Environmental Geochemistry and Health, 48(15), Article 624. https://doi.org/10.1007/s10653-026-03502-3

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03502-3

Keywords: natural radioactivity, radium-226, thorium-232, coal mining legacy, acid mine drainage, cancer risk, Enugu Shale, cassava, gamma spectrometry, Nigeria, ICRP, radiological hazard

The team collected thirty-eight soil samples from across the district, preparing them under controlled laboratory conditions before analysis. The measurement technique of choice was gamma ray spectrometry using a high-purity germanium detector, an instrument prized in radiation science for its exceptional energy resolution. Unlike simpler sodium iodide detectors, high-purity germanium crystals can separate the closely spaced gamma ray lines emitted by different radionuclides, allowing researchers to identify and quantify specific isotopes with confidence. In this study, the detector was calibrated and used to measure the activity concentrations of three radionuclides that dominate the natural radiation environment: potassium-40, thorium-232, and radium-226, the latter serving as a proxy for the uranium decay chain in soil.

The results reveal a clear hierarchy among the three isotopes. Potassium-40, a long-lived isotope that makes up a tiny fraction of all natural potassium, showed the highest activities, ranging from 342 plus or minus 10 to 760 plus or minus 16 becquerels per kilogram, with an average of 568 becquerels per kilogram. Thorium-232 activities ranged from 35 plus or minus 1.0 to 83 plus or minus 3.4 becquerels per kilogram, averaging 55 becquerels per kilogram, while radium-226 ranged from 48 plus or minus 1.9 to 90 plus or minus 3.7 becquerels per kilogram, with a mean of 65 becquerels per kilogram. These values sit within the ranges typically reported for soils worldwide, though the upper end of the potassium-40 distribution is notable, reflecting the mineralogy of the local geological formations from which the soils derive.

What makes the study more than a simple catalog of numbers is its statistical treatment of the data. Because environmental radioactivity measurements are frequently skewed by outliers and by the heterogeneous nature of soil, the authors first applied the Shapiro-Wilk test to assess whether the activity distributions followed a normal distribution. This test, widely regarded as one of the most powerful normality tests for moderate sample sizes, informs which subsequent statistical tools are appropriate. The researchers then employed the Spearman rank correlation test, a non-parametric method that measures monotonic relationships without assuming linearity or normality, to probe whether the three radionuclides vary together across sampling sites. Strong positive correlations between radionuclides can indicate a shared mineralogical origin, for example when uranium, thorium, and potassium-bearing minerals are concentrated together in the same parent rocks and weathering products.

To investigate whether the underlying geology, or lithology, exerts a measurable influence on radionuclide levels, the team turned to the Kruskal-Wallis test, a non-parametric analysis of variance that compares multiple groups without requiring normally distributed data. Gurugram’s geology is diverse, with the Aravali hill range skirting the district and alluvial plains covering much of its area, so differences in radionuclide concentrations between zones with different geological character are scientifically expected. The combination of these tests, descriptive statistics, normality assessment, rank correlation, and group comparison, represents a methodologically rigorous framework that is increasingly standard in environmental radioactivity studies, allowing researchers to distinguish genuine geological signals from random spatial variation.

Beyond characterizing the distribution of radionuclides, the study translated its measurements into quantities that matter for human health. From the measured activity concentrations, the authors calculated the absorbed gamma dose rate in air, which describes the energy deposited by gamma radiation per unit mass of air at ground level, and from that the annual effective dose rate for both indoor and outdoor exposure scenarios. Indoor doses are typically weighted more heavily in radiological assessments because people spend the majority of their time inside buildings, where gamma rays from construction materials derived from soil add to the outdoor background. The comparison of these derived doses with reference values established by international agencies such as the United Nations Scientific Committee on the Effects of Atomic Radiation provides the practical yardstick for judging whether the measured levels pose any concern to the public.

The team also computed two widely used screening indices. The gamma index, which ranged from 0.48 to 0.95 across the sampled soils, is designed to flag materials whose gamma radiation could become significant if used in building construction; values below unity are generally considered acceptable under international guidance. The alpha index, which ranged from 0.24 to 0.45, serves as a screening tool for potential radon inhalation hazards associated with radium-226 content, since radon-222 is a radioactive gas in the uranium decay chain that can accumulate in enclosed spaces. Both indices remained below their conventional thresholds across all thirty-eight samples, indicating that the natural radioactivity of Gurugram’s soils falls within the range considered safe for ordinary exposure and typical construction use.

The Gurugram survey is the latest entry in a growing body of work on natural radioactivity across northern India, much of it involving overlapping research groups. Previous studies by the same lead author and collaborators have examined radon and thoron exhalation from Gurugram soils, radionuclides in the soils of neighboring Palwal district, seasonal and geological influences on gamma radiation in Faridabad, and radon doses from groundwater in the same region. Parallel investigations elsewhere in Haryana and Punjab, including assessments of Rohtak, Jind, Bathinda, and Sirsa, and geospatial surveys of urban soils in Chennai, contribute to a national picture in which terrestrial gamma dose varies principally with local geology rather than with human activity. Such baseline datasets are valuable not only for radiation protection but also as reference points against which any future anthropogenic contamination, whether from industrial activity, construction, or accidents, could be detected and quantified.

For the residents of Gurugram, the practical message of the study is reassuring: the natural radioactivity of the district’s soils, from the potassium-rich alluvium to the thorium-bearing sediments near the Aravalis, produces radiation doses that international agencies would classify as within normal background levels. But the scientific significance runs deeper. As urbanization transforms land use across the National Capital Region, soils that once lay undisturbed are being excavated, processed into building materials, and incorporated into the homes and offices of millions. Understanding the radiological properties of that raw material, and the geological factors that control its variability, is a quiet but essential piece of public health infrastructure. With rigorous measurement, transparent statistics, and comparison against international standards, this study demonstrates how even an invisible, omnipresent hazard can be brought into sharp, quantifiable focus.

Subject of Research: Measurement of natural radionuclides and radiological hazard assessment in soils of Gurugram district, India

Article Title: Monitoring of natural radionuclides in soil of District Gurugram, Haryana (India), by gamma spectrometry and statistical analysis

Article References: Singh, B., Gupta, U., Kant, K., Yadav, S., & Tanwer, N. (2026). Monitoring of natural radionuclides in soil of District Gurugram, Haryana (India), by gamma spectrometry and statistical analysis. Environmental Monitoring and Assessment, 198(10), Article 1106. https://doi.org/10.1007/s10661-026-15925-7

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15925-7

Keywords: natural radioactivity, gamma spectrometry, potassium-40, thorium-232, radium-226, soil, Gurugram, Haryana, radiation dose, gamma index, statistical analysis, environmental monitoring

The study, published in the journal Discover Oceans, involved measuring gamma radiation at thirty locations spread across an area of roughly two kilometres by six hundred metres, arranged on an imaginary grid with two hundred metres between adjacent points. The researchers used a portable sodium iodide detector sealed inside a PVC pipe to record total gamma counts directly on the beach, logging each position with a handheld GPS receiver. Back in the laboratory, sediment collected from the same thirty sites was dried, sieved and analysed with a high-resolution germanium detector to quantify specific radionuclides. The in-situ counts ranged from 1800 to 6498 counts per minute, and the interpolated map showed that radioactivity was noticeably higher toward the south-west of the beach than the north-east.

What makes the pattern scientifically interesting is that different radionuclides behave in opposite ways depending on the size of the sand grains they inhabit. In the finest fraction studied, grains between 53 and 100 micrometres, the mean activity concentrations of radium-226, radium-228 and potassium-40 were 151.2, 369.4 and 209.7 becquerels per kilogram respectively. In the dominant medium fraction, between 101 and 250 micrometres, the same isotopes averaged just 28.7, 60.6 and 272.6 becquerels per kilogram. In other words, radium concentrates in fine grains while potassium-40 favours coarse ones, a split that reflects two entirely different geochemical stories.

The radium story is one of surface chemistry. Radium-226 and radium-228 are daughter products of the uranium-238 and thorium-232 decay chains, and both isotopes are strongly adsorbed onto particle surfaces. Fine grains carry far more surface area per unit mass than coarse grains, so they adsorb more radium from seawater and pore fluids. Potassium-40 behaves differently: it is an integral constituent of silicate minerals derived from igneous rocks, and its compatibility with silica means it travels locked inside the mineral lattice rather than clinging to grain surfaces. Coarse sediments, being richer in such minerals and less easily washed back out by the tide, end up enriched in potassium-40. The tidal sorting mechanism is simple but effective: waves wash lighter fine grains away and leave heavier particles behind on the beach.

To characterise the sediments chemically, the team used energy-dispersive X-ray fluorescence on the medium grain fraction, which makes up more than seventy percent of the sediment by weight at most locations. The dark grey sand proved mineral-rich, with iron, aluminium, calcium, magnesium, titanium, potassium, vanadium, manganese, zirconium, chromium and lanthanum as the major elements. Mean iron concentration reached about 84,900 parts per million, with aluminium near 54,000 and calcium around 50,000 parts per million. This composition points to substantial heavy-mineral content, the kind of material that waves and currents concentrate into placers and that can markedly raise local radioactivity, as seen dramatically in the monazite-rich black sands of Kerala on India’s south-west coast.

Compared with other Indian and international beaches, Jampore sits in a middle ground. Kerala’s high-background radiation area shows thorium-232 activities that can reach thousands of becquerels per kilogram, far beyond anything measured at Daman. Tamil Nadu beach sands typically report radium-226 between 13 and 198 becquerels per kilogram, while the Odisha and Andhra coasts fall in the tens to low hundreds. Globally, beaches in Ghana, Turkey and Thailand report broadly similar values, with radium isotopes in the tens and potassium-40 in the low hundreds of becquerels per kilogram. Jampore’s fine fraction is moderately elevated relative to many of these sites, but remains well below the classical high-background zones, meaning the beach is radiologically ordinary while still being dynamically informative.

The most consequential finding concerns the ratio of the two radium isotopes. Across the fine fraction the radium-226 to radium-228 ratio ranged from 0.29 to 0.55, and in the medium fraction from 0.39 to 0.61. Crucially, zones with lower ratios coincided with higher total gamma counts. Building on earlier work in the Yangtze Estuary, where smaller radium ratios were linked to sediment accretion, the researchers interpret the low-ratio, high-count areas of Jampore beach as zones where sand is accumulating. The strong linear correlation between the two radium isotopes, with a coefficient of determination of 0.9878, suggests they share a common origin and are governed by the same adsorption and desorption processes, which makes their ratio a stable and interpretable indicator.

The in-situ measurements also proved to be a surprisingly faithful proxy for laboratory analysis. Correlation plots showed that the spatial pattern of total gamma counts closely mirrors the distributions of both radium-226 and radium-228, but not potassium-40. The reason lies in nuclear structure: the uranium and thorium series emit multiple high-intensity gamma lines, including strong peaks at 609.3 and 1764.5 kiloelectronvolts for the radium-226 chain and at 583.2 and 2614.5 kiloelectronvolts for the radium-228 chain, whereas potassium-40 emits only a single gamma ray at 1460.82 kiloelectronvolts with a modest ten percent emission probability. The integrated field signal is therefore dominated by the radium chains, which is precisely what makes a rapid field survey with a portable detector a viable stand-in for detailed laboratory spectrometry when the goal is mapping sediment regimes.

The broader motivation is methodological. Since 1954, investigations of coastal sediment dynamics have relied on artificial radiotracers produced in nuclear reactors, materials that are effective but burdened by public concern and strict regulatory clearance requirements from nuclear safety authorities. Natural radionuclides embedded in the sediment offer an alternative that requires nothing to be released. Researchers in Spain, the Canary Islands, South Africa and elsewhere have already proposed radium isotopes and lead-210 as tracers of erosion and accretion, and the Indian team frames its Jampore survey as a first step toward establishing a radiometric database and a methodology for using natural isotopes as tracers along Indian coasts. The data could also serve as benchmarks against which numerical sediment transport models can be validated, increasing confidence in their predictions.

For a beach flanked by the mouths of the Daman Ganga and Kolak rivers, where fluvial supply, wave sorting and monsoon-driven erosion continuously redistribute the sand, the ability to read accretion and erosion directly from the sediment’s own radioactivity is a genuinely practical tool. Harbour dredging, dumping-site selection and coastal protection all depend on knowing where sediment goes, and a technique that replaces costly and regulated artificial tracers with a portable detector and a GPS unit could change how coastal engineers gather that knowledge. The Jampore map is a modest survey of one four-and-a-half-kilometre beach, but it demonstrates a principle with wide reach: every shoreline already carries its own radioactive diary of movement, and learning to read it may be as simple as walking the sand with a detector in hand.

Subject of Research: Spatial distribution of natural radioactivity in beach sediments as a tracer of coastal sediment dynamics

Article Title: Investigation of distribution pattern of natural radioactivity in the sediments of Jampore beach, Daman, India

Article References: Biswal, J., Goswami, S., Yadav, V. B., Sartandel, S. J., Samantray, J. S., Pulhani, V., & Sharma, V. K. (2026). Investigation of distribution pattern of natural radioactivity in the sediments of Jampore beach, Daman, India. Discover Oceans, 3(1), Article 12. https://doi.org/10.1007/s44289-026-00124-6

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00124-6

Keywords: natural radioactivity, Jampore beach, Daman, sediment dynamics, gamma spectrometry, radium-226, radium-228, potassium-40, heavy minerals, coastal erosion, accretion, EDXRF

The research, published in Environmental Geochemistry and Health by a team from Fire University, the Central Laboratory for Radiological Protection and Warsaw University of Technology in Poland, addressed a long-standing blind spot in the assessment of naturally occurring radioactive materials, known as NORM. Most previous studies have treated coal and its combustion residues as independent sample sets, comparing average ash concentrations from power plants with average coal concentrations from mines. That approach obscures the crucial question of whether combustion itself acts as a predictable amplifier of radiological risk. The Polish team instead burned nine hard coals and measured the radioactivity of each ash against its own parent coal, establishing a direct quantitative link between the two.

The nine coals were deliberately chosen for geological diversity. Samples came from the Bowen Basin in Queensland, Australia; the Central Appalachian coalfield in Virginia, United States; the Karaganda and Ekibastuz basins in Kazakhstan; the Moatize Basin in Mozambique; the Cerrejón Formation in Colombia; and two Polish sources, including the Carboniferous Upper Silesian Coal Basin. Together they span depositional ages from the Carboniferous to the Paleogene and represent markedly different tectonic and sedimentary settings. All were collected from shipments transhipped at the Port of Gdansk using a random representative sampling procedure compliant with the ISO 18283:2008 standard, and each was treated as an independent observation of a distinct geological origin.

Measurement relied on gamma-ray spectrometry using a MAZAR analyser coupled to a sodium iodide scintillation probe housed in lead shielding. The activity concentrations of radium-226 and thorium-232 were determined indirectly through their secular equilibrium daughter products, bismuth-214 at 1764 kiloelectronvolts and thallium-208 at 2610 kiloelectronvolts, while potassium-40 was measured directly from its 1460 kiloelectronvolt photopeak. Each crushed and sieved sample was sealed in a 1.7-litre Marinelli vessel and stored for four weeks to allow radioactive equilibrium to be reached before being measured nine times over 18,000-second counting intervals. Combined relative uncertainties typically fell within 10 to 15 percent for radium and thorium and 10 to 12 percent for potassium, with minimum detectable activities of a few becquerels per kilogram.

The combustion stage took place in a Kolton UNIX 20 solid-fuel boiler, a domestic bottom-feed unit operating under natural draught in a fixed-bed grate configuration, with active-zone temperatures typically between 700 and 1050 degrees Celsius. Each coal was burned to completion, the boiler cooled, and the bottom ash carefully collected. The authors acknowledge that domestic grate firing differs from industrial pulverised-coal or fluidised-bed systems in temperature profile, residence time and ash fractionation, but the fundamental mechanism is the same: the organic fraction of coal is oxidised to gas, while mineral-bound radionuclides are retained and concentrated in the solid residue. Notably, fly ash separated in industrial plants often carries even higher radionuclide concentrations than bottom ash, meaning the enrichment factors reported here may be conservative.

In their raw state, all nine coals proved radiologically unremarkable. Activity concentrations of radium-226, thorium-232 and potassium-40 sat below global average values for hard coal and for the Earth’s crust, with the lowest readings in the Colombian sample and the highest radium and thorium values in the Mozambican coal. The Polish Upper Silesian sample contained the most potassium-40. None of the coals exceeded any of the standard radiological screening indices: radium equivalent activity ranged from 19.3 to 57.7 becquerels per kilogram, far below the 370 becquerel per kilogram safety threshold, external hazard indices stayed well under unity, and gamma dose rates of 1.74 to 25.90 nanogray per hour remained below both the global average of 54 nanogray per hour and the Polish average of 47.4. As fuels, these coals posed negligible radiological concern.

Combustion changed the picture dramatically. Enrichment factors relating ash activity to coal activity ranged from approximately 3.8 to 9.9, clustering around a median of about six for every radionuclide and every derived hazard index. A paired Wilcoxon signed-rank test confirmed the increase was statistically robust, with a very large effect size of r = 0.889 and complete directional consistency: in all nine coal-ash pairs, every measured parameter rose. The mechanism is essentially a mass-balance effect. When the organic matter burns away, the ash yield drops to an estimated 10 to 27 percent of the original coal mass, so the same absolute quantity of radionuclides is packed into a much smaller mass. Earlier studies had reported enrichment factors of two to five; the tighter, higher and more uniform amplification observed here likely reflects the paired experimental design, which excludes the confounding effects of fuel blending and heterogeneous ash streams in large power stations.

The radiological consequences of this amplification were visible in every index calculated for the ash. Radium equivalent activity in the ashes ranged from 149 to 418 becquerels per kilogram, external hazard indices from 0.46 to 1.13, gamma dose rates from 68 to 185 nanogray per hour, annual effective doses from 0.018 to 0.226 millisieverts per year, and the radioactivity concentration index from 0.52 to 1.46. The most radioactive ash, derived from the Mozambican coal, exceeded regulatory thresholds across multiple parameters. Critically, the external gamma dose rate surpassed the recommended reference level of 54 nanogray per hour in all nine ash samples, even though most other indices remained within limits. The authors stress that the study assessed the potential for environmental impact based on the elevated activity of the ash itself, not on direct observation of radionuclide migration into soil, water or air.

Why does this matter beyond the laboratory? Coal ash is one of the most heavily reused industrial by-products on Earth, finding its way into concrete, road base layers, land reclamation schemes and even, occasionally, agricultural applications mixed with sewage sludge. Each of these uses creates a potential pathway for concentrated NORM to disperse into soil, groundwater and the built environment. The difference between a two- or three-fold enrichment and a six-fold one is far from trivial when millions of tonnes of residue are involved, and the authors argue that risk assessments based on average literature ash values may systematically underestimate exposure if coal-specific transformation factors are ignored. Under the Euratom Basic Safety Standards, which set activity concentration reference levels for building materials, some combustion residues may fall within regulatory scope when used in construction.

The study’s conclusions come with honest caveats. Nine coal-ash pairs, while sufficient for the non-parametric statistical framework applied, cannot capture the full global variability of coal composition, and a single prepared sample per pair means the reported uncertainties reflect counting statistics rather than within-material heterogeneity. The domestic boiler used cannot reproduce industrial combustion conditions exactly. Yet the central message stands with unusual statistical clarity: combustion acts as a proportional and predictable amplifier of natural radioactivity, so the radiological properties of an ash can be inferred from its parent coal. As Poland and other nations continue importing coals from geologically diverse basins while promoting circular-economy reuse of combustion residues, the authors call for continuous monitoring of both domestic and imported coal, and for transformation processes to be built into environmental risk assessment frameworks. A material that enters the furnace radiologically harmless may not leave it that way.

Subject of Research: Radionuclide enrichment and radiological hazard transformation during coal combustion

Article Title: Radiological characteristics of coal-to-ash transformation: a paired coal-ash assessment of natural radionuclides

Article References: Łukaszek-Chmielewska, A., Rachwał, M., Rakowska, J., Piotrowska, B., Isajenko, K., & Szyłak-Szydłowski, M. (2026). Radiological characteristics of coal-to-ash transformation: a paired coal-ash assessment of natural radionuclides. Environmental Geochemistry and Health, 48(15), Article 612. https://doi.org/10.1007/s10653-026-03509-w

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03509-w

Keywords: coal ash, NORM, radionuclides, gamma-ray spectrometry, radiological hazard, TENORM, bottom ash, coal combustion, environmental radioactivity, radium-226, thorium-232, potassium-40

Every beach on Earth carries a faint trace of the planet’s geological origins. Primordial radionuclides, including uranium-238, radium-226, thorium-232 and potassium-40, have existed since the formation of the Earth and are incorporated into the minerals that make up sand, rock and soil. In most coastal environments, these isotopes occur at modest concentrations that pose little concern. But where heavy minerals accumulate, sands can become strikingly radioactive. The Visakhapatnam coast, with its complex geology and active sediment transport, proved to be exactly such a place, and measuring it required laboratory instrumentation of the highest sensitivity.

The research team collected beach sand samples from locations along the coastline and analysed them using a high-purity germanium gamma spectrometry system, a technique prized for its ability to resolve the characteristic gamma-ray signatures emitted by individual radionuclides. High-purity germanium detectors, cooled to reduce thermal noise, can distinguish the faint energy lines of uranium, radium, thorium and potassium decay chains from the background of ambient radiation, allowing precise quantification of each isotope’s activity concentration in units of becquerels per kilogram. The researchers also measured ambient radiation levels directly on the beaches to connect their laboratory findings to real-world exposure conditions.

The results were remarkable. Activity concentrations of uranium-238 ranged from 8.9 to 868 becquerels per kilogram, with a mean of 167. Radium-226 spanned from 2.8 to 1,282.8, averaging 292. The most dramatic findings concerned thorium-232, which ranged from 6.9 to a staggering 13,691.7 becquerels per kilogram, with a mean of 2,614, while potassium-40 ranged from 77.2 to 1,191.1 with a mean of 449. Each of these mean values exceeds the global averages reported for ordinary soils and sediments, and the thorium figures in particular place the most enriched samples firmly in the territory of monazite-bearing sands, the mineral that has made parts of the Indian coastline famous among radiation scientists for decades.

Thorium’s dominance in these sands is no accident. Monazite, a phosphate mineral rich in thorium and rare earth elements, is a hallmark of India’s eastern and southwestern coastal placer deposits. When waves and longshore currents sort sediments by density and grain size, heavy resistant minerals such as monazite, zircon and ilmenite become concentrated into placer deposits, while lighter quartz is winnowed away. Because thorium and its decay products are locked into monazite’s crystal lattice, these deposits act as natural concentrators of radioactivity. The measured absorbed gamma dose rates on the Visakhapatnam beaches, the study found, are comparable to those in monazite-rich high background radiation areas in India and worldwide, confirming that the same mineralogical processes are at work here.

One of the study’s most valuable contributions is its mapping of spatial variability. Rather than presenting a single average figure, the researchers generated spatial distribution maps that visualize the heterogeneity of radionuclide concentrations along the entire study area. These maps revealed a clear pattern: radioactivity levels rise consistently toward the northern sector of the coastline. This gradient likely reflects the interplay of sediment sources, wave-driven transport directions and the geomorphology of the coast, which ranges from sandy beaches to rocky headlands between Visakhapatnam and Bhimunipatnam. The authors also observed that radioactivity varied across the width of individual beaches, meaning that a visitor standing at the waterline may be on sand with a different radiological character than sand collected near the dunes or backshore.

To translate raw activity concentrations into statements about human risk, the team computed a battery of internationally recognized radiological hazard indices. These included radium equivalent activity, which combines the contributions of the uranium and thorium series and potassium into a single comparable quantity; the absorbed gamma dose rate, which estimates the energy deposited in air per unit time; the annual effective dose equivalent, which converts that dose into a projection of yearly health-relevant exposure; the gamma level index; and the external and internal hazard indices used in building-material and land-use assessments. Together, these indices allow the Visakhapatnam data to be compared directly with safety benchmarks established by bodies such as the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection.

The researchers went beyond measurement and mapping by applying statistical analyses to the relationships among the radionuclides themselves. Correlation analysis indicated a strong relationship between the radium series and the thorium series, a signature that the authors interpret as evidence of a common geological origin for the two decay chains. This makes geochemical sense: both uranium and thorium series isotopes tend to reside in the same heavy mineral phases, so their concentrations rise and fall together as those minerals are concentrated or diluted in the sand. Such correlations transform a set of isolated numbers into a coherent narrative about where the sand comes from and how the coast has sorted it over time.

It is important to keep the findings in perspective. Natural radioactivity in beach sand is not the same as contamination from human activity; these radionuclides are part of the Earth’s crust and have always been present. Millions of people worldwide live safely in high background radiation areas, including the well-studied monazite sands of Chhatrapur in Odisha and regions of Brazil, China and Kerala. What the Visakhapatnam study provides is a rigorous, spatially resolved baseline against which any future changes, whether from coastal engineering, sediment redistribution, or industrial development, can be judged. Baseline data of this quality are the foundation of long-term environmental monitoring and credible radiological risk assessment in coastal ecosystems.

The study also carries a broader message about how science sees ordinary landscapes. A beach that appears uniform to the eye is, to a gamma spectrometer, a patchwork of geological history written in decaying atoms. By combining sensitive nuclear instrumentation, spatial mapping and statistical interpretation, the researchers have shown that radioactivity along a single coastline can vary by three orders of magnitude within short distances. For coastal managers, public health authorities and the millions who visit these shores, the work of Ramesh and his colleagues offers both a caution about localized hotspots and a model of how careful, transparent measurement can turn invisible hazards into mapped, understood and monitorable features of the environment.

Subject of Research: Natural radionuclide distribution and radiological hazard assessment in beach sands of the Visakhapatnam coast, India

Article Title: Spatial distribution of natural radionuclides and radiological hazard assessment in beach sands of the Visakhapatnam coast, Eastern India

Article References: Ramesh, B., Savitri, P. P., Sudhakar, J., Kumar, R. B., Sahoo, S. K., Saradhi, I. V., & Pulhani, V. (2026). Spatial distribution of natural radionuclides and radiological hazard assessment in beach sands of the Visakhapatnam coast, Eastern India. Environmental Monitoring and Assessment, 198(10), Article 1113. https://doi.org/10.1007/s10661-026-15926-6

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15926-6

Keywords: natural radioactivity, gamma spectrometry, beach sand, thorium-232, radium-226, monazite, Visakhapatnam, radiological hazard, spatial distribution, coastal environment, high background radiation, Environmental Monitoring and Assessment