The review, led by S. Veerasingam and colleagues at Qatar University’s Environmental Science Center, followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, searching Google Scholar alongside Web of Science, PubMed, and Scopus for peer-reviewed studies and national monitoring reports. The team compiled data across an unusually diverse set of environmental matrices: terrestrial soils, marine sediments, seawater, groundwater, building materials ranging from cement to steel slag, and marine organisms as varied as pearl oysters, shrimp, sponges, mangroves, and even the dugong, the region’s iconic sea cow. Measurements were dominated by high-purity germanium gamma spectrometry, often supplemented by sodium iodide detectors for screening and, in some studies, inductively coupled plasma mass spectrometry for ultra-trace analysis of plutonium isotopes and strontium 90.

Qatar’s radiological character is written in its geology. The peninsula sits on carbonate-rich Eocene formations, principally the Rus and Dammam formations, whose limestones and evaporites host the primordial radionuclides uranium 238, thorium 232, and potassium 40, along with decay products such as radium 226. Carbonate rocks tend to immobilize uranium and radium through co-precipitation with calcium carbonate, while clay-rich and phosphatic strata preferentially hold thorium and potassium isotopes. The hyper-arid climate amplifies these geochemical controls: with minimal rainfall, leaching is negligible, so radionuclides accumulate in surface soils and sabkha salt flats rather than migrating downward. High evaporation rates raise salinity and ionic strength, further fixing radium and uranium onto carbonate and sulfate minerals.

The numbers tell a consistent story. Mean uranium 238 activities in Qatari soils ranged from 2.46 to 213.9 becquerels per kilogram depending on location, radium 226 typically averaged around 17.2 becquerels per kilogram, thorium 232 spanned 0.42 to 20 becquerels per kilogram, and potassium 40 ranged from 10 to 327 becquerels per kilogram. Compared with the global averages reported by the United Nations Scientific Committee on the Effects of Atomic Radiation, 33 becquerels per kilogram for uranium 238, 45 for thorium 232, and 420 for potassium 40, Qatar’s natural background sits comfortably low. Marine sediments echoed this pattern, with cesium 137, the fingerprint of mid-twentieth-century atmospheric nuclear weapons testing, detected at a maximum of only 0.66 becquerels per kilogram, and many samples falling below detection limits altogether.

Artificial radionuclides across the country are essentially relics of global fallout rather than evidence of local contamination. Cesium 137 in surface soils ranged from below detection to 7.99 becquerels per kilogram, strontium 90 averaged just 3.364 becquerels per kilogram, and plutonium isotopes appeared only at trace levels. In seawater within Qatar’s Exclusive Economic Zone, cesium 137 concentrations of roughly 1.5 to 1.65 becquerels per cubic meter align closely with measurements from Kuwaiti waters and the Indian Ocean, confirming their origin in historic weapons testing dispersed through the stratosphere before the Partial Nuclear Test Ban Treaty of 1963. Notably, a meta-analysis of depleted uranium in the Middle East found no contamination in Qatar, in contrast to several neighboring countries affected by the Gulf wars.

Groundwater tells a more nuanced story. A nationwide survey of 48 wells measured radon 222, a short-lived gaseous decay product of uranium 238, at concentrations ranging from 2.7 to 60.7 becquerels per liter, with a mean of 20.65. Nearly half of the analyzed drinking water samples exceeded the United States Environmental Protection Agency’s maximum contamination level of 11.1 becquerels per liter. Yet the estimated total annual effective dose from radon inhalation and ingestion, 0.056 millisieverts per year, remained below the World Health Organization’s recommended limit of 0.1 millisieverts per year. Intriguingly, inhalation contributed more than ingestion, a reminder that radon’s volatility makes indoor air, not drinking water, the dominant exposure route in confined spaces.

The review’s most consequential findings concern technologically enhanced naturally occurring radioactive material, or TENORM, generated by Qatar’s hydrocarbon industry. Oil and gas operations, particularly at the onshore Dukhan field, produce scales, drilling muds, and sludges in which radium isotopes concentrate during extraction and processing. Soil near Dukhan showed radium 226 values up to 342 becquerels per kilogram, nearly ten times the global average, and sludge collected from oil-field separation tanks reached a radium equivalent activity of 14,678 becquerels per kilogram, against a recommended safety threshold of 370. Calculated absorbed dose rates in this sludge hit 6,778 nanograys per hour, the annual effective dose equivalent reached 8.313 millisieverts per year, roughly seven times the public dose limit, and the external hazard index climbed to 39.67. The authors stress these figures represent localized occupational and waste-management scenarios, not public exposure, but they underscore why handling, storage, transport, and disposal of TENORM residues require stringent controls.

Industrial by-products recycled into construction raise parallel concerns. Steel slag used in road construction exhibited radium 226 concentrations of 273.2 becquerels per kilogram and thorium 232 of 135.2, pushing its radium equivalent activity to between 467 and 522 becquerels per kilogram, above the safety threshold, with hazard indices exceeding unity. By contrast, conventional materials such as cement, sand, gypsum, clinker, and gabbro aggregates all fell well within international limits, with hazard indices between 0.03 and 0.31 and excess lifetime cancer risk estimates for natural soils averaging 0.12 per thousand, below the global average of 0.29 per thousand. The message is clear: Qatar’s buildings are radiologically safe, but screening of recycled industrial residues before reuse is essential to prevent long-term indoor exposure.

Dust storms add a dynamic dimension to the picture. Winds sweeping from local sabkhas and deserts, and from as far as northern Saudi Arabia and Iraq, transport fine mineral particles enriched in adsorbed radionuclides, with airborne dust showing uranium 238, thorium 232, and potassium 40 concentrations two to three times higher than local soils. Prevailing northwesterly Shamal winds can also carry trace cesium 137 from distant sources, and the semi-enclosed circulation of the Arabian Gulf allows limited marine redistribution near the boundaries of Qatar’s Exclusive Economic Zone. Although these transboundary inputs remain radiologically insignificant, the authors argue they justify regional cooperation, particularly given operational and planned nuclear power plants in neighboring countries and the potential for atmospheric or marine transport following any incident.

Looking forward, the review lays out an ambitious research and policy agenda aligned with Qatar National Vision 2030. Priorities include a long-term nationwide monitoring program spanning terrestrial, freshwater, coastal, and marine ecosystems; isotopic fingerprinting to distinguish natural, technologically enhanced, and anthropogenic radionuclides; site-specific transfer coefficients for arid environments, since most existing parameters derive from temperate ecosystems; and formal ecological risk assessments using frameworks such as the International Atomic Energy Agency’s ERICA approach. The authors also champion emerging digital tools, artificial intelligence, machine learning, geographic information systems, remote sensing, and Internet of Things sensor networks, for near-real-time surveillance and automated risk mapping, alongside integration with the IAEA’s International Radiation Monitoring Information System. For now, the baseline is established: Qatar’s natural environment radiates little more than gentle desert sunshine in particle form, while its industrial wastes, if left unmanaged, could tell a very different story.

Subject of Research: Environmental radioactivity and radiological risk assessment of natural and artificial radionuclides across environmental matrices in Qatar

Article Title: Risk assessment of radionuclides in different environmental matrices in the State of Qatar, Arabian Gulf

Article References: Risk assessment of radionuclides in different environmental matrices in the State of Qatar, Arabian Gulf. (n.d.). https://doi.org/10.1007/s10653-026-03469-1

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03469-1

Keywords: radionuclides, Qatar, environmental radioactivity, TENORM, radiological risk assessment, gamma spectrometry, oil-field sludge, cesium-137, radon, Arabian Gulf, building materials, dust storms

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