Environmental monitoring and assessment of heavy metals in surface sediments at Coleroon River Estuary in Tamil Nadu, India

Inferences on metal pollution in the natural spawning zone of Bangladesh river and pollution management strategies

The purpose of this study was to evaluate the metal concentrations in the Halda River in Bangladesh to determine the quality of the water and sediment in the natural spawning zone. Fe > Zn > Cr > Cd > Cu was the order of the metals in water, whereas Fe > Zn > Cd > Cu was the order in sediments. Almost all of the heavy metals in the water and sediment had been found within the established limits, with the exception of Cr and Fe in the river and Cu in the sediment. In the case of water, Cr vs. Zn was found to have the strongest correlation (r = 0.96). Due to the coagulation and adsorption processes, it was shown that Fe and Zn had a substantial correlation of 0.96, Cu and Cd of 0.91, and Cr of 0.78 with Zn. Hazard quotient values of Cd show the not potable nature of Halda river surface water and might give adverse health effects for all age groups except Cu and Zn. Pollution load index values indicated the uncontaminated nature of the river bottom sediments. Natural and human activities were the key factors influencing the accumulation and movement of heavy metals in the water and sediments. Contamination sources are industrial effluents, garbage runoff, farming operations, and oil spills from fishing vessels which are comparable according to multivariate statistical analysis. Ion exchange, absorption, precipitation, complexation, filtration, bio-absorption, redox reaction, and reverse osmosis were considered to be effective for the degradation of metal concentrations. The feasibility of the suggested metal reduction procedures has to be studied to know which is optimally appropriate for this river region. It is expected that this study could provide a useful suggestion to decrease the metal pollution in the river.

Water resources pollution associated with risks of heavy metals from Vatukoula Goldmine region, Fiji

Although mining is essential for human economic development, is amongst the most polluting anthropogenic sources that influence seriously in water resources. Thus, understanding the presence and concentration of heavy metals in water and sediment in the vicinity of mines is important for the sustainability of the ecosystem. In this work, a multidisciplinary approach was developed to characterize the contamination level, source apportionment, co-existence, and degree of ecological and human health risks of HMs on water resources in the Vatukoula Goldmine region (VGR), Fiji. The outcomes suggested significant contamination by Cd (range: 0.01-0.95 g/L), Pb (range: 0.03-0.53 g/L), and Mn (range: 0.01-3.66 g/L) in water samples surpassed the level set by Fiji and international laws, whereas higher concentration of Cd (range: 2.60-23.16 mg/kg), Pb (range: 28.50-200.90 mg/kg) and Zn (range: 36.50-196.66 mg/kg) were detected in sediment samples. Lead demonstrated a strong significant co-existence network with other metals (e.g., Mn, Ni). Source apportionment recognized four source patterns (Cd, Pb, Ni, and Mn) for water and (Cr, Cd-Pb, Mn, and Zn) for sediment which was further confirmed by principal component analysis. The mine inputs source mainly contributed to Cd (66.07%) for water, while mineral processing mostly contributed to Zn (76.10%) for sediment. High non-carcinogenic (>1) and carcinogenic (>10^-4) health risks, particularly in children, are related to the elevated Cd, Pb and Cr contents from the VGR. Uncertainty analysis demonstrates that the 90th quantile of Cd led to higher carcinogenic risk. Pollution indices disclosed a moderate to extremely contamination status mainly along the Toko dam which poses high ecological risks identified by index calculation. However, sediment quality indicators based on probable effect levels showed that there was a 75% of likelihood that the concentrations of Cd and Pb adjacent to the VGR have a severe toxic impact on aquatic lives.

Unlikely lead-bearing phases in river and estuary sediments near an ancient mine (Huelgoat, Brittany, France)

Anthropocene mineral diversity is the result of the purification of metals naturally combined with other chemical elements in natural environment. Moreover, the advent of human mining and manufacturing mineral-like compounds has experienced a punctuation event in diversity and distribution owing to the pervasive impact of human activities. In this context, the wastes of an abandoned historical mine, Huelgoat mine (Brittany, France), famous during the eighteenth and the nineteenth century contain significant amounts of chemical elements potentially dangerous to the environment. Lead concentration and Pb-bearing phases were quantified in 7 sediments samples located from mine upstream to the Aulne estuary (100 km downstream to the mine). Results show very high concentrations of lead in the stations located upstream and downstream of the Huelgoat mine, using X-ray fluorescence spectroscopy, ranging from 7000 mg/kg downstream of the mine to a natural concentration of about 80 mg/kg upstream. At the same time, Pb-bearing phases were identified depending on the particle sizes, fine (< 50 μm) and coarse (> 50 μm), using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), total organic carbon (TOC), and pH analyses. For the first time, evidence of anthropogenic mineral "iodoplumbate" formation has been described in a natural environment.

Hydrogeochemical investigations to assess groundwater and saline water interaction in coastal aquifers of the southeast coast, Tamil Nadu, India

Groundwater and saline water interaction is the most common processes in the coastal aquifers that alters the quality of aquifer waters. The quaternary alluvium aquifer system is a significant water resource of southeast coastal Tamil Nadu that provides water supplies for industrial, agriculture, and domestic utilities. Hydrogeochemical investigations were attempted to analyze groundwater-saline water interactions for which a total of three hundred and sixty samples representing surface water, pore water, and groundwater samples collected from three significant locations (location A, B, and C) and analyzed for major ion concentrations. Piper plot infers surface and pore water samples representing saline water type (Na-Cl) in all the three locations due to tidal variation and sand dominant surface layer. Groundwater samples represent (Ca-HCO₃) type at location A due to fresh groundwater discharge, mixed or subterranean estuary (Ca, Mg-Cl, HCO₃) at location B due to conversion of freshwater (Ca-HCO₃) at low tide to saline water (Na-Cl) at high tide, and saline (Na-Cl) water at location C due to proximity and influence of tides. The Cl^-/HCO₃^- vs. Cl^- plot represents two water types, such as fresh groundwater (0.5) and strongly affected by seawater intrusion (6.6). The plot (Ca²⁺+Mg²⁺)/(K⁺+Na⁺) vs. log Cl^- represents freshwater in location A, mixing in location B, and saline water in location C. Groundwater samples observed to be fresh in location A (20.0 km away from the coast), recirculated in location B (9.0 km away from the coast), and saline in location C (0.5 km away from the coast).

Assessment of water resources pollution associated with mining activity in a semi-arid region

Mining, although relevant and indispensable for human socioeconomic development, is considered one of the most polluting anthropogenic activities. Water resources are the most vulnerable environmental compartment to the direct impacts of mining, especially in the semi-arid regions. In these regions, mining activity constitutes an important challenge in the management of water resources; since its impacts can be maximized by the adverse meteorological conditions. This study aimed to assess the level of contamination in water resources of three important mining areas in a semi-arid region, where approximately 70,000 people live. The concentrations of eleven heavy metals in sediment, surface and groundwater samples were determined by ICP OES. The results obtained for water samples indicated significant contamination by Cd, Pb, and U, based on the limits established by Brazilian and international regulatory legislation. In the case of sediment samples, higher concentrations of Cr, Cu, Ni, and V were observed. Pollution indices (PLI, CF and I_geo) revealed moderate to extreme contamination mainly along the Jacaré and Contas rivers. The Pearson correlation, Principal Component, and Hierarchical Cluster analyses were performed to identify patterns in the distribution of elements and common sources of pollution. The results suggested that the concentrations of Co, Cr, Cu, Fe, Mn, Ni, and V were mainly related to mining activities and, to a lesser extent, natural sources. In the case of Cd and Pb, contamination may have an important contribution from fertilizers use, whereas Zn has a mixed source of both lithogenic and anthropogenic origin. On the other hand, the high concentrations of U, specifically in groundwater samples, were associated with geogenic causes. Although the potential ecological risk values indicated a low ecological risk; other sediment quality indices (TEL, PEL, ΣTU, and PEL-Q) revealed that there is 25% of the probability that the content of heavy metals in water resources near the mining areas induces adverse toxic effects on aquatic organisms.

Microbial and plant-assisted heavy metal remediation in aquatic ecosystems: a comprehensive review

Heavy metal (HM) pollution in aquatic ecosystems has an adverse effect on both aquatic life forms as well as terrestrial living beings, including humans. Since HMs are recalcitrant, they accumulate in the environment and are subsequently biomagnified through the food chain. Conventional physical and chemical methods used to remove the HMs from aquatic habitats are usually expensive, slow, non-environment friendly, and mostly inefficient. On the contrary, phytoremediation and microbe-assisted remediation technologies have attracted immense attention in recent years and offer a better solution to the problem. These newly emerged remediation technologies are eco-friendly, efficient and cost-effective. Both phytoremediation and microbe-assisted remediation technologies adopt different mechanisms for HM bioremediation in aquatic ecosystems. Recent advancement of molecular tools has contributed significantly to better understand the mechanisms of metal adsorption, translocation, sequestration, and tolerance in plants and microbes. Albeit immense possibilities to use such bioremediation as a successful environmental clean-up technology, it is yet to be successfully implemented in the field conditions. This review article comprehensively discusses HM accumulation in Indian aquatic environments. Furthermore, it describes the effect of HMs accumulation in the aquatic environment and the role of phytoremediation as well as microbe-assisted remediation in mitigation of the HM toxicity. Finally, the review concludes with a note on the challenges, opportunities and future directions for bioremediation in the aquatic ecosystems.

Seasonal variations of trace metals from water and sediment samples in the northern Bay of Bengal

We aimed to determine the temporal variation of trace metals concentrations in surface water and surface sediment samples at Kutubdia Channel, Bangladesh. Trace metals of samples were detected using energy dispersive X-ray fluorescence (Energy-dispersive X-ray spectroscopy) method. The lowest concentration of metals was found in water samples during post-monsoon season and the highest during pre-monsoon season (Cu: 0.030 ± 0.001 μg/L in pre-monsoon and 0.026 ± 0.002 μg/L in post-monsoon, Zn: 0.087 ± 0.003 μg/L in pre-monsoon and 0.073 ± 0.002 μg/L in post-monsoon, Fe: 0.080 ± 0.001 μg/L in pre-monsoon and 0.055 ± 0.001 μg/L in post-monsoon). In contrast, metal concentration in surface sediment samples were higher in post-monsoon than in pre-monsoon season i.e. Cr 11 mg/kg in pre-monsoon and 12 mg/kg in post-monsoon, Mn 571 mg/kg in pre-monsoon and 606 mg/kg in post-monsoon, As (8 mg/kg in pre-monsoon and 10 mg/kg in post-monsoon, Pb (22 mg/kg in pre-monsoon and 24 mg/kg in post-monsoon, and Fe 2317 mg/kg in pre-monsoon and 2435 mg/kg in post-monsoon. We found a spatial gradient of high to medium to low in trace metal concentration from river to river mouth to offshore area. Considering the sources of metals, land erosion by waves and tidal action, an influx of water and sediment from the surrounding rivers, agricultural waste, industrial effluent and sewage are the most likely sources of metal pollution in the study area. We conclude that proper management strategies should be adopted to control the pollution and conserve the ecosystem health.

A comprehensive risk assessment of metals in riverine surface sediments across the rural-urban interface of a rapidly developing watershed

Metal contamination in aquatic environments is a severe global concern to human health and aquatic ecosystems. This study used several risk assessment indices, to evaluate metal (Cu, Zn, Pb, Cd and Cr) environmental risk of riverine surface sediments across the rural-urban interface of the rapidly developing Wen-Rui Tang River watershed in eastern China. Risk assessments were determined for 38 sites based on the potential ecological risk index (RI), consensus-based sediment quality guidelines (SQGs) and risk assessment code (RAC). Land-use cluster analysis showed that sediments were severely contaminated, especially for Cd, whose concentrations were ∼100 times higher than background levels and had a high proportion in the bioaccessible fraction. According to RI, E_r^Cd was identified with extremely high risk potential, resulting in the highest ecological risk of Cluster 4 (industrial). Similarly, risk within Cluster 4 (industrial) was also ranked highest by SQGs assessment due to the high proportion of industrial land use. Zinc was determined with high risk due to its high concentration compared to its effect range medium (ERM) value. Discrepancies in predicting environmental risks from metals among the three indices were mainly attributed to the contrasting definitions of these metrics. Environmental risk uncertainty derived from spatial variation was further estimated by Monte Carlo simulation and ranked as: Zn > Cd > Cr > Pb > Cu. This comprehensive environmental risk assessment provides important information to guide remediation strategies for management of metal contamination at the watershed scale.

Contamination assessment, source apportionment and health risk assessment of heavy metals in paddy soils of Jiulong River Basin, Southeast China

To trace the sources and evaluate the health risks of heavy metals in paddy soils of Jiulong River Basin, seventy-one samples of paddy soils were collected in July 2017. The heavy metals contents were determined using inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectrophotometry (AFS). The geo-accumulation index (I_geo) and potential ecological risk index (RI) methods were applied to evaluate the contamination of heavy metals, principal component analysis (PCA) and absolute principal component scores-multiple linear regression (APCS-MLR) were applied to trace the sources, and dose–response model was applied to assess the health risks to the human body. The results indicated that the paddy soils were moderately to heavily polluted by Cd and slightly polluted by Hg, Pb, As and Zn. Heavy metals in paddy soils presented considerable to high potential ecological risk, mostly contributed by Cd and Hg with contribution rates of 59.4% and 26.2%, respectively. The heavy metals contaminating paddy soils were derived from natural sources, agricultural activities, industrial discharge, coal combustion and unidentified sources, with source contribution rates of 31.37%, 24.87%, 19.65%, 18.05% and 6.06%, respectively. The heavy metals in paddy soils presented carcinogenic risks which humans can tolerate and no non-carcinogenic risks. The total non-carcinogenic risks mainly derived from agricultural activities and coal combustion, with contribution rates of 62.16% and 20.21%, respectively, while the total carcinogenic risks mainly derived from natural sources and industrial discharge, with contribution rates of 51.17% and 18.98%, respectively.

APCS-MLR and dose–response model were combined to identify the sources and human health risks of heavy metals in paddy soils.

Heavy metal monitoring, analysis and prediction in lakes and rivers: state of the art

Several research efforts have been conducted to monitor and analyze the impact of environmental factors on the heavy metal concentrations and physicochemical properties of water bodies (lakes and rivers) in different countries worldwide. This article provides a general overview of the previous works that have been completed in monitoring and analyzing heavy metals. The intention of this review is to introduce the historical studies to distinguish and understand the previous challenges faced by researchers in analyzing heavy metal accumulation. In addition, this review introduces a survey on the importance of time increment sampling (monthly and/or seasonally) to comprehend and determine the rate of change of different parameters on a monthly and seasonal basis. Furthermore, suggestions are made for future research to achieve more understandable figures on heavy metal accumulation by considering climate conditions. Thus, the intent of the current study is the provision of reliable models for predicting future heavy metal accumulation in water bodies in different climates and pollution conditions so that water management can be achieved using intelligent proactive strategies and artificial neural network (ANN) techniques.

Geochemical assessment of heavy metals pollution in surface sediments of Vellar and Coleroon estuaries, southeast coast of India

Surface sediments were collected from Vellar and Coleroon estuaries for determine sediment texture, calcium carbonate, organic matter and heavy metals. Pollution indices such as pollution load index (PLI), contamination factor (CF), enrichment factor (EF) and geo-accumulation index (I_geo) were done for this study to know the level of heavy metals pollution in the estuarine ecosystem. Pearson correlation matrix and factor were used to assess the relationship and source of heavy metals in the estuarine sediments. The results of PLI values reveal that the study area was polluted by all the heavy metals. The calculated values of CF and I_geo followed the decreasing order Cu>Ni>Pb>Co>Cr>Zn>Mn>Fe and illustrate that Cu, Ni and Pb are contaminated due to anthropogenic sources in both estuaries. Correlation and factor analysis suggest that FeMn oxyhydroxides, organic matter and fine particles are responsible for high concentration of heavy metals.

Environmental Status and geochemical assessment Sediments of Lake Skadar, Montenegro

The environmental mobility and geochemical partitioning of ten metals were examined in sediments collected from the six locations around Lake Skadar in Montenegro. A three-step sequential extraction procedure was used to determine the distribution of the metals in various substrates of lacustrine sediments, and the concentrations were measured in the liquid extract by ICP-OES. The largest portion of the total amount of cadmium, strontium and manganese can be found in sediment bound to the hydrated iron and manganese oxides; cobalt, lead, copper and nickel in the oxidizable fraction and the highest portion of chromium, vanadium and zinc are in the residual fraction. The most mobilized and potentially mobile metals are strontium, cadmium and cobalt while the most immobilized metals are chromium, vanadium and zinc. Based on geochemical parameters, an assessment of sediment contamination by the investigated metals was performed and the results showed potential risks ranging from "no risk" to "low risk" to the environment.