The research, published in the journal Advances in Industrial and Engineering Chemistry, was carried out by Priyanka Gupta of Kalinga University, Gaurav Tamrakar of the Department of Mechanical Engineering at Kalinga University, and Shashank Sharma of Sharda University, Greater Noida. Between May and June 2023, the team collected fifteen groundwater samples from bore wells scattered across the Kanker district, with well depths ranging from just 1.7 metres to more than 20 metres. The sampling network was designed to capture the full spatial and geological diversity of the study area, which spans latitudes of roughly 20.24 to 20.6 degrees north and longitudes of 80.48 to 81.48 degrees east, an expanse underlain by marble, schist, limestone, quartzite, granite, dolomite and, in the south, significant iron ore reserves.

The analytical workflow followed internationally recognized protocols. Each sample was immediately preserved with one millilitre of filtered concentrated nitric acid and held at a stable temperature in darkness until processing, in line with United States Environmental Protection Agency procedure 3015 from 1994. Fifty millilitre aliquots were digested with a mixture of 65 percent nitric acid and 35 percent hydrochloric acid, then passed through 0.45 micrometre nylon filters. Quantification of nine metals and metalloids, namely arsenic, cadmium, copper, cobalt-associated iron, nickel, zinc, chromium, lead and manganese, was performed by atomic absorption spectrophotometry, a technique prized for its sensitivity and reproducibility in trace metal analysis. Every sample was run in three consecutive duplicates, and blanks and certified reference materials were processed alongside to verify accuracy and consistency throughout the measurement campaign.

What distinguishes this investigation is not merely the measurement of metal concentrations but the battery of five complementary pollution indices the authors deployed to translate raw numbers into environmental meaning. The team computed the geo-accumulation index, or Igeo, which compares measured concentrations against geological background values on a logarithmic scale; the contamination factor, which ratios each metal against its permissible drinking water limit as set by Indian Bureau of Standards specifications from 2012; the modified degree of contamination, which averages contamination factors across all measured pollutants; the pollution load index, or PLI, a Tomlinson-derived composite calculated as the nth root of the product of individual contamination factors; and finally the metal index, which sums the ratio of each measured concentration to its maximum acceptable concentration. Cross-comparing multiple indices against a common set of standards, the authors argue, provides a far more robust picture of contamination than any single metric alone.

The raw concentrations told the first part of the story. Mean values in the groundwater stood at 5.47 parts per million for iron, 1.41 for lead, 0.94 for chromium, 0.70 for nickel, 0.45 for zinc and 0.32 for manganese, with measured ranges spanning 4.2 to 6.9 milligrams per litre for iron, 0.5 to 3.6 for lead, 0.11 to 2.63 for chromium, 0.25 to 0.68 for zinc, 0.1 to 0.9 for manganese and 0.33 to 1.07 for nickel. Concentrations of arsenic, cadmium and copper fell below acceptable limits, and indeed below the detection threshold required for inclusion in the index calculations, a striking result given that arsenic contamination in the Kanker district had been documented as early as 2006 by Pandey and colleagues, who linked elevated manganese and arsenic to effects on local flora and fauna. During the summer sampling season, the descending order of mean concentration was iron, followed by lead, chromium, nickel, zinc and manganese.

The index calculations then transformed these numbers into a verdict. Every geo-accumulation index value came out strongly negative, with chromium ranging from minus 10.26 to minus 5.68, manganese from minus 13.64 to minus 10.47, iron from minus 14.04 to minus 13.32, lead from minus 5.91 to minus 3.06, zinc from minus 9.15 to minus 7.71 and nickel from minus 8.27 to minus 6.57. On the Igeo scale, where negative values signify geochemical enrichment well below background levels, these figures place the study area firmly in the uncontaminated category for all six metals evaluated. The contamination factors reinforced the picture: mean values declined in the order of lead, chromium, nickel, zinc, manganese and iron, yet every single mean sat below one, the threshold signalling minimal contamination, with individual values as low as 0.00009 for iron and peaking at just 0.18 for lead.

The modified degree of contamination ranged from 0.73 to 1.13 across the six sites where it was computed, indicating extremely low pollution overall, with only sampling site 13 showing a comparatively elevated modified degree and site 12 registering the lowest value of 0.73. The pollution load index averaged 0.91, ranging from 0.72 to 1.14, and only two locations, sites 2 and 7, crossed the critical threshold of one, hinting at modest localized enrichment that the authors attribute tentatively to rising human activity. At every other sampling point, PLI values below one meant that each evaluated metal remained under its baseline reference. Meanwhile, the metal index, ranging from 0.002 to 0.132 across all fifteen sites, placed every single sample squarely within the classification of unaffected water, defined as pure water within the 0.3 to 1.0 band or better. Taken together, the five indices converge on a single conclusion: the groundwater of Kanker district is neither severely nor even slightly degraded.

Why does this geological terrain, so rich in metal-bearing rocks and historically flagged for arsenic, yield such benign water? The authors present a layered explanation rooted in geology, hydrogeology, land use and climate. The district is dominated by stable Precambrian crystalline formations whose low metal solubility restricts the release of heavy metals into the aquifer, and regional weathering contributes only background-level concentrations rather than contamination spikes. The aquifer systems, largely unconfined to semi-confined, enjoy continuous recharge that dilutes dissolved constituents, while groundwater flow dynamics disperse and prevent the localized accumulation of contaminants. Land use amplifies these natural safeguards: forest and agriculture predominate, population density is low, and, crucially, the immediate vicinity hosts no major heavy industry or mining, so anthropogenic point sources are nearly absent. Farming inputs such as fertilizers, pesticides and soil amendments introduce only trace quantities of cadmium, lead and nickel, and domestic wastewater disposal, vehicular emissions and small commercial operations add marginal loading at most. Seasonal monsoon rainfall then flushes the aquifer system periodically, enhancing recharge and dilution and further suppressing any accumulation of dissolved metals.

The broader significance of the study extends beyond one district. Groundwater serves as the primary drinking and household water source across much of rural Central India, and the mineral-rich tribal belt of neighbouring Bastar has previously shown aluminium, arsenic, iron, manganese and nickel levels exceeding permissible limits, with arsenic posing excessive cancer and non-cancer risks according to work by Pervez and colleagues in 2021. Against that backdrop, the Kanker results offer a calibrated baseline and a methodological template. The authors emphasize that the indexical and statistical framework applied here, spanning Igeo, CF, mCdeg, PLI and MI, can be adopted by government agencies for environmental management, assessment and remediation planning, and they stress that periodic groundwater assessment remains essential to safeguard water purity for human consumption. In a region where every data point on water quality carries direct public health weight, this study delivers rare good news, delivered with the quantitative discipline that good news needs to be believed.

Beyond the headline findings, the study illustrates why multi-index approaches have become standard practice in freshwater contamination research worldwide. Each index answers a subtly different question: the contamination factor isolates individual metals, the modified degree of contamination smooths results across the full suite of pollutants, and the pollution load index responds sensitively to whether even one metal exceeds its reference threshold. Because these metrics were computed against a common set of Indian drinking water standards, their agreement carries genuine weight rather than being a statistical artifact.

The geochemical setting deserves particular attention. In Precambrian cratonic terrains, metals are typically locked in silicate and oxide minerals that weather slowly, so background dissolved concentrations remain low unless acidic conditions or sulfide oxidation mobilize them. The absence of such mobilizing processes in Kanker, combined with active monsoon-driven recharge, appears to keep dissolved metal loads suppressed even where ore deposits lie nearby.

The authors also caution that a single dry-season snapshot cannot capture temporal variability. Groundwater chemistry can shift with rainfall cycles, pumping patterns, and changing land use, and shallow bore wells under 2 metres deep are especially vulnerable to surface influences. They therefore frame their results as a baseline against which future monitoring campaigns should be judged, recommending periodic re-sampling and continued use of indexical tools by district authorities to detect any early drift toward contamination before it becomes a public health concern.

Subject of Research: Geo-environmental assessment of heavy metal contamination in groundwater in Kanker district, Central India, using pollution load index and geo-accumulation index

Article Title: Integrated geo-environmental evaluation of groundwater contamination using PLI and Igeo in Kanker, Central India

Article References: Gupta, P., Tamrakar, G., & Sharma, S. (2026). Integrated geo-environmental evaluation of groundwater contamination using PLI and Igeo in Kanker, Central India. Advances in Industrial and Engineering Chemistry, 2(1), Article 9. https://doi.org/10.1007/s44405-026-00049-w

Image Credits: AI Generated

DOI: 10.1007/s44405-026-00049-w

Keywords: groundwater, heavy metals, pollution load index, geo-accumulation index, Kanker district, Chhattisgarh, Central India, water quality, atomic absorption spectrophotometry, contamination factor, metal index, Bastar Craton

Groundwater serves as a critical lifeline for domestic, agricultural, and industrial needs, especially in coastal areas where surface water resources may be limited or polluted. However, the rapid industrialization, urban expansion, and intensive agricultural practices in Weifang have triggered a complex phenomenon of contamination, primarily through the infiltration of toxic heavy metals into distinct groundwater layers. The study meticulously analyzes these multilayer groundwater systems, focusing on the vertical distribution and concentration variations of heavy metals such as lead, cadmium, arsenic, and mercury. The presence of these toxic elements in water used for human consumption and irrigation is a stark warning sign of an escalating environmental health crisis.

The research team employed a robust methodological approach, combining extensive field sampling with advanced geochemical modeling to unravel the pathways through which heavy metals migrate and accumulate in different aquifers. By capturing samples from multiple stratified groundwater layers across diverse locations within the Weifang coastal zone, the study highlights the heterogeneity and complexity of contamination profiles. The interaction of natural geochemical processes with anthropogenic influences creates unpredictable patterns of metal retention and mobilization, underscoring the urgency for comprehensive monitoring and management frameworks tailored specifically to such multilayered hydrogeological settings.

One of the study’s pivotal findings is the identification of zones with elevated heavy metal concentrations that coincide with industrial hotspots and areas of intensive agricultural activity. Industrial discharge, insufficiently treated wastewater, and the overuse of metal-containing fertilizers and pesticides emerge as primary sources contaminating subsurface water reserves. These pollutants infiltrate through soil and sediment strata, leaching into the distinct aquifers that compose the groundwater system. Furthermore, the stratified nature of the aquifers complicates contamination assessments, as each layer differs in permeability, chemical composition, and vulnerability to metal intrusion, demanding a nuanced approach to both detection and remediation.

In addition to mapping contamination levels, the investigation intensively evaluates the health risks posed to local populations by incorporating risk assessment models grounded in the concentration data. The findings elucidate alarming exposure scenarios, where metals such as cadmium and arsenic exceed safe thresholds, potentially contributing to chronic health issues including kidney damage, neurological disorders, and even carcinogenic effects. Vulnerable demographic groups, especially children and the elderly living in proximity to the most affected aquifers, are at heightened risk due to their longer exposure times and physiological sensitivities to toxic metals.

The multilayer groundwater system’s complexity also presents challenges for policymakers and water resource managers, as traditional single-layer assessment techniques prove insufficient for capturing the full scope of contamination. The study advocates for integrated, multilayer monitoring systems that incorporate both geochemical analyses and hydrogeological modeling to effectively trace and predict contaminant fluxes. This holistic perspective is essential for devising adaptive management strategies to safeguard water quality, mitigate pollution sources, and ensure sustainable utilization of aquifers in Weifang and similar coastal zones worldwide.

Fan and colleagues emphasize that the situation in Weifang is emblematic of a broader global trend, where coastal and urbanizing areas grapple with degraded groundwater quality amid escalating anthropogenic pressures. As coastal populations surge and industrial activities intensify, the risk of heavy metal pollution infiltrating vital subsurface water reserves multiplies. The study’s methodology and findings thus offer a crucial template for international research and policy efforts aimed at confronting the silent but severe threat posed by heavy metals in groundwater systems.

Moreover, the research incorporates advanced spatial analysis techniques to visualize contamination hotspots, using Geographic Information Systems (GIS) to overlay industrial density, land use patterns, and groundwater sampling data. This spatial intelligence delivers actionable insights for local authorities, revealing priority zones where interventions such as remediation efforts, pollution control regulations, and community awareness campaigns must be prioritized. The use of GIS not only enhances the precision of risk assessments but also supports transparent communication between scientists, decision-makers, and affected communities.

The study’s implications extend into the realm of agricultural sustainability, a critical consideration in Weifang’s coastal economy. Heavy metals in groundwater used for irrigation pose the risk of bioaccumulation in crops, potentially entering the food chain and exacerbating public health risks. Understanding how multilayer groundwater contamination impacts agricultural practices requires interdisciplinary collaboration, linking geochemistry, agronomy, and health sciences. Strategies such as switching to less vulnerable water sources, developing phytoremediation approaches, or implementing strict controls on pollutant discharge must be urgently evaluated and optimized.

Climate variability adds an additional layer of complexity to the region’s groundwater quality narrative. Seasonal changes, precipitation patterns, and potential sea-level rise in coastal zones influence groundwater recharge rates and salinity levels, potentially altering the mobility and concentration of heavy metals. The researchers advocate for incorporating climate resilience into groundwater management plans, ensuring that interventions maintain efficacy under changing environmental conditions. Anticipating such future challenges is critical to achieving long-term water security and protecting community health in Weifang and beyond.

In response to these findings, the study calls for concerted multi-stakeholder engagement, involving governmental bodies, industrial entities, local communities, and academic institutions. Establishing collaborative platforms for data sharing, joint monitoring efforts, and policy development will be essential to curbing the infiltration of heavy metals into multilayer groundwater systems. Public education campaigns highlighting the risks and promoting sustainable water usage habits are also vital components for empowering local populations to participate actively in safeguarding their resources.

Importantly, the investigation underscores the need for investment in advanced water treatment and purification technologies tailored to the specific challenges of multilayer aquifer contamination. Conventional water treatment methods may fall short in removing trace heavy metals at the concentrations and chemical forms detected in Weifang’s groundwater. Emerging technologies such as membrane filtration, adsorption using novel materials, and electrochemical removal techniques present promising solutions that must be evaluated for scalability and cost-effectiveness in regional contexts.

Lastly, this comprehensive study by Fan, Jia, and Li constitutes a landmark contribution to environmental science, marrying detailed field research with practical risk assessment and forward-looking management recommendations. It serves as a clarion call to address the quiet but potent threat of heavy metal groundwater contamination head-on, employing interdisciplinary science and policy innovation. As the global community intensifies its focus on sustainable water resources amidst accelerating environmental change, insights gleaned from Weifang’s coastal multilayer groundwater system will prove invaluable for crafting resilient and health-protective water governance frameworks.

Subject of Research:

Article Title:

Article References:
Fan, Q., Jia, C. & Li, Y. Health risk of heavy metals in multilayer groundwater of the coastal zone: A case study of Weifang, China. Environ Earth Sci 84, 670 (2025). https://doi.org/10.1007/s12665-025-12504-w

Image Credits: AI Generated

DOI: https://doi.org/10.1007/s12665-025-12504-w