Source apportionment of heavy metals and their ecological risk in a tropical river basin system

Evaluation of hydro-chemical facies and surface water quality dynamics using multivariate statistical approaches in Southern Nigeria

The geochemical and chemical constituents of river water quality could be influenced by human activities and organic processes like water interacting with the lithogenic structure that the river flows through. Evaluating evidence based primary root of the predominant pollutant ions, their interactions as well as the factors controlling their dominance is crucial in studies regarding water environment and hydrology especially as most studies focus on theoretical methods. In order to understand the water cycle, safeguard surface water resources, and preserve the human environment, this study evaluated surface water hydro-chemical facies, quality dynamics, and portability in southern Nigeria using multivariate statistical approaches by analyzing selected hydro-chemical characteristics as indicators of pollution along the river during wet and dry seasons. Twenty water samples were taken, analyzed, and subjected to mathematical statistics: Gibbs plot, trilinear piper analysis, stiff pattern analysis, ionic scatter analysis, correlation, and principal component analysis. Result of surface water recorded mean pH ranges from 4.8 for wet season and 5.3 for dry season, above the WHO, and during dry season TDS, Mg2+, Pb, and Cd were above the WHO limits, respectively. Abundance of cation and anion in surface water was in a decreasing trend of: HCO3 > Ca2+ > Mg2+ > Cl- > Na+ > SO42- > K + > NO3-. Trilinear plot, stiff pattern, and Gibbs ratio indicated hydrochemical facie of water dominated by calcium bicarbonate (Ca-HCO3) water type. From plots and ionic ratio, the major hydrochemical process of water chemistry during wet and dry seasons was rock-water interaction arising majorly from weathering processes. Ionic ratios of Ca2+ and Mg2+1, Ca2+ and HCO2- [1:2], Ca2+ + Mg2+ and HCO3- + SO42- [1:1], revealed dissolution of dolomite as their common origin, with total cations in wet and dry seasons ranging between 43 and 57% and total anions: 37.3-62.7, with dry season dominance. The overall WQI of the river seemed good quality due to rapid flow and self-purification of the river but may be harmful in the future. It was recommended that constant surveillance and monitoring of human activities along waterways be enforced in order to ensure that undesirable pollution levels don't occur in the river.

Study of the cyto- and genotoxic activity of water from the Kapshagai reservoir (Kazakhstan) on laboratory mice

Chemical compounds in the environment, which exhibit toxic and genotoxic activity, increase the mutational pressure on biota. This study aimed to investigate the genotoxic, mutagenic, and toxic effects of water from the Ile River and the Kapshagai Reservoir, both sites of active economic activities. Cytogenetic analysis of bone marrow from mice exposed to water samples from the Ile River and the Kapshagai Reservoir revealed a statistically significant increase in aberrant (p<0.05) and polyploid cells (p<0.01), as well as a decrease in the mitotic index (p<0.001), compared to the negative control. The water samples caused statistically significant increases in single- and double-strand DNA breaks in cells across various organs in the experimental mice compared to unexposed animals (p<0.001). These observations suggest the existence of chemical compounds within the water samples from the Kapshagai Reservoir and the Ile River, which exhibit genotoxic, mutagenic, and toxic properties.

Exploring the alteration of environmental radioactivity in terms of compositional elements of heavy minerals in an anthropogenically affected urban river: Radiological and ecological risks assessment

This study explored the alteration of naturally occurring radioactive materials (NORMs: 226Ra (≈238U), 232Th, 40K) in an anthropogenically disrupted urban river-basin (Turag, Bangladesh) in terms of constitutional substances (Sc, Ti, V, Fe, La, Ce, Sm, Eu, Tb, Dy, Ho, Yb, Lu, Hf, Ta, W, Th, U) of heavy-minerals. Average activity concentrations of 226Ra (≈238U), 232Th, and 40K were 41.5 ± 12.9, 72.1 ± 27.1, and 639 ± 100 Bqkg-1, respectively which were relatively higher compared to crustal origin. ∑REEs, Ta, W, Th, and U were ~2 times higher compared to crustal values with Ce and Eu-anomalies. APCS-MLR and PMF receptor models were used to determine the various anthropogenic and/or geogenic sources of NORMs and elements. Layer-wise variations of NORMs and elements were observed to trace the response of sedimentary processes towards the incoming pollution load. Presence of REEs indicates moderate degree of ecological risk to aquatic biota. However, carcinogenic risk (3.84 × 10-4 Sv-1) were significantly higher than threshold limit.

Assessment of soil heavy metal pollution and associated ecological risk of agriculture dominated mid-channel bars in a subtropical river basin

The elevated concentrations of heavy metals in soil considerably threaten ecological and human health. To this end, the present study assesses metals pollution and its threat to ecology from the mid-channel bar's (char) agricultural soil in the Damodar River basin, India. For this, the contamination factor (CF), enrichment factor (EF), geoaccumulation index (I_geo), pollution index, and ecological risk index (RI) were measured on 60 soil samples at 30 stations (2 from each station, i.e., surface and sub-surface) in different parts of the mid-channel bar. The CF and EF indicate that both levels of char soil have low contamination and hence portray a higher potential for future enrichment by heavy metals. Moreover, I_geo portrays that soil samples are uncontaminated to moderately contaminated. Further, pollution indices indicate that all the samples (both levels) are unpolluted with a mean of 0.062 for surface soils and 0.048 for sub-surface soils. Both levels of the char have a low potentiality for ecological risk with an average RI of 0.20 for the surface soils and 0.19 for the sub-surface soils. Moreover, Technique for order preference by similarity to ideal solution (TOPSIS) indicates that the sub-surface soils have lower pollution than the surface soils. The geostatistical modeling reveals that the simple kriging technique was estimated as the most appropriate interpolation model. The present investigation exhibits that reduced heavy metal pollution is due to the sandy nature of soils and frequent flooding. However, the limited pollution is revealed due to the intensive agricultural practices on riverine chars. Therefore, this would be helpful to regional planners, agricultural engineers, and stakeholders in a basin area.

Assessing water quality in the Dong Nai River (Vietnam): implications for sustainable management and pollution control

Dong Nai River provides essential water resources for millions of people across 11 provinces and cities in Vietnam. However, the different pollution sources such as household, farming, and industrial operations have caused the river water quality to deteriorate over the past decade. To gain a comprehensive understanding of the river's surface water quality, this study employed the water quality index (WQI) across 12 different sampling sites. In total,144 water samples with 11 parameters were analyzed in accordance with the Vietnamese standard 08:2015/MONRE. Results revealed a range of surface water quality, from poor to good according to the VN-WQI (Vietnamese standard), and a medium even bad level in some months according to the NS-WQI (American standard). The study also identified temperature, coliform, and dissolved oxygen (DO) as strong contributors to WQI values (VN_WQI standard). Principal component analysis/factor analysis was used to determine pollution sources, with the results highlighting agricultural and domestic activities as the main contributors to river pollution. In conclusion, this study underscores the importance of effective planning and management of infrastructure zoning and local activities to improve the river's surface water quality and surrounding areas, as well as safeguard the well-being of the millions who depend on it.

Heavy Metals in Groundwater of Southern Italy: Occurrence and Potential Adverse Effects on the Environment and Human Health

This study reports the data on the contamination caused by heavy metals in the groundwater of the Campania Plain (CP) in Southern Italy. A total of 1093 groundwater samples were obtained from the following aquifers: coastal plains (GAR, VCP, VES, SAR, and SEL), volcanic districts (PHLE and VES), and carbonate massifs (MAS and LAT). In this study, the investigation depth ranged from 5 m (GAR) to 200 m (PHLE). The sequence of heavy metal content in groundwater samples was B > Fe > Al > Mn > Zn > Ba > Ni > As > Cu > V > Se > Pb > Cd. The heavy metal pollution index (HPI) and heavy metal evaluation (HEI) demonstrated that the study areas in which groundwater samples were sampled are not risk zones. Moreover, health risk assessment shows that hazard index (HI) values for heavy metals were found to be significantly low in groundwater samples. In non-carcinogenic risk evaluation for the adult group, the risk was low, whereas for children and infants, the risk was >1 for arsenic alone. Carcinogenic risk assessment (CR) was found lower for adults, children, and infants. The Jenks optimization method was used to evaluate the distribution of heavy metals in the groundwater of CP, and the principal component analysis technique (PCA) was employed to determine the source of heavy metals, and it was found that mixed sources (natural and anthropogenic) may be responsible for heavy metals presence.

Hydrochemical appraisal of surface water from a subtropical urban river in southwestern Bangladesh using indices, GIS, and multivariate statistical analysis

The Gorai River is a significant river  in Bangladesh's southwestern region, where residents make great use of the water despite a lack of adequate and reliable information concerning water quality and pollution levels. Thus, the goal of this research was to examine the spatio-temporal variations in water quality and determine whether it was suitable for drinking, agriculture, industrial, or livestock purposes, as well as the influencing factors and potential sources of water pollution. Surface water samples were collected in wet and dry seasons from ten sampling sites, and twenty water quality parameters were evaluated. The results showed that some studied water quality parameters, e.g., temperature, electrical conductivity, alkalinity, and nitrate, exceeded the maximum allowable limit. Water quality index values exhibited that the water quality of all sampling sites was found to be poor to very poor during the wet season, while only St-4 and St-5 were found to be poor and the rest of the investigated sites were good category during the dry season. Based on sodium adsorption ratio, soluble sodium percentage, residual sodium carbonate, residual sodium bicarbonate, and permeability index values, it was depicted that river water was suitable for irrigation purposes, but when compared to Kelly's ratio (KR) and magnesium hazard ratio values, river water was found to be unfit for irrigation. Moreover, potential salinity (PS) and sodium-to-calcium activity ratio (SCAR) values allow the water as moderately suitable for use in irrigation purposes. Langelier saturation index (LSI) and aggressive index (AI) values revealed that the river water was under saturated to supersaturated and moderate to non-aggressive in nature. However, Ryznar stability index (RSI), Puckorius scaling index (PSI), and Larson-Skold index (LS) values describe whether the water was high or severely corrosive, signifying its inappropriateness for industrial consumption. Principal component analysis (PCA) analysis depicted that the fluctuations in water quality are mostly related to point and non-point contaminations, such as urban and industrial effluent discharged and agricultural runoff of fertilizers. Cluster analysis (CA) revealed relative geographical and seasonal changes in water quality, showing the impact of hydrological changes and contamination.

Spatial Distribution, Source Analysis and Health Risk Study of Heavy Metals in the Liujiang River Basin in Different Seasons

Three high-frequency sampling and monitoring experiments were performed at the Lutang and Luowei transects of the Liujiang River entrance and at the southeast exit of the Liuzhou during 2019 for the purpose of assessing physico-chemical variables and human health hazards of water heavy metals in different rainfall processes. There were significant seasonal variations in concentrations of 11 heavy metals and most variables showed higher levels during the dry season. The distribution of heavy metals in the Liuzhou area varied significantly by region. Pollution source analysis indicated distinct seasons of wetness and dryness. The dry season is dominated by anthropogenic activities, while the wet season is dominated by natural processes. The results of hazard quotient (HQ) and carcinogenic risk (CR) analysis showed that the health risk of non-carcinogenic heavy metals in the wet season is slightly higher than that in the dry season. Seasonal changes in carcinogenic risk are the opposite; this is due to the combined influence of natural and human activities on the concentration of heavy metals in the river. Among them, Al was the most important pollutant causing non-carcinogenic, with As being a significant contributor to carcinogenic health risk. Spatially, the downstream Luowei transect has a high health risk in both the dry and rainy seasons, probably due to the fact that the Luowei transect is located within a major industrial area in the study area. There are some input points for industrial effluent discharge in the area. Therefore, high-frequency monitoring is essential to analyze and reduce the heavy metal concentrations in the Liujiang River during dry and wet seasons in order to protect the health of the residents in the area.

Receptor model-oriented sources and risks evaluation of metals in sediments of an industrial affected riverine system in Bangladesh

Toxic metals in river sediments may represent significant ecological concerns, although there has been limited research on the source-oriented ecological hazards of metals in sediments. Surface sediments from an industrial affected Rupsa River were utilized in this study to conduct a complete investigation of toxic metals with source-specific ecological risk assessment. The findings indicated that the average concentration of Ni, Cr, Cd, Zn, As, Cu, Mn and Pb were 50.60 ± 10.97, 53.41 ± 7.76, 3.25 ± 1.73, 147.76 ± 36.78, 6.41 ± 1.85, 59.78 ± 17.77, 832.43 ± 71.56 and 25.64 ± 7.98 mg/kg, respectively and Cd, Ni, Cu, Pb and Zn concentration were higher than average shale value. Based on sediment quality guidelines, the mean effective range median (ERM) quotient (1.29) and Mean probable effect level (PEL) quotient (2.18) showed medium-high contamination in sediment. Ecological indexes like toxic risk index (20.73), Nemerow integrated risk index (427.59) and potential ecological risk index (610.66) posed very high sediment pollution. The absolute principle component score-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) model indicated that Zn (64.21%), Cd (51.58%), Cu (67.32%) and Ni (58.49%) in APCS-MLR model whereas Zn (49.5%), Cd (52.7%), Cu (57.4%) and Ni (44.6%) in PMF model were derived from traffic emission, agricultural activities, industrial source and mixed sources. PMF model-based Nemerow integrated risk index (NIRI) reported that industrial emission posed considerable and high risks for 87.27% and 12.72% of sediment samples. This work will provide a model-based guidelines for identifying and assessing metal sources which would be suitable for mitigating future pollution hazards in Riverine sediments in Bangladesh.

Genotoxic effect of heavy metals on Astyanax lacustris in an urban stream

Uncontrolled urbanization growth contributes to the pollution of aquatic environments. Heavy metals released by domestic and industrial effluents can negatively affect aquatic organisms. This study aimed to evaluate the effect of environmental pollutants, such as metals, on fish DNA damage, in stretches of an urban stream. Specimens of the Neotropical fish, Astyanax lacustris, were exposed in situ for 96 h along the Antas stream, a Brazilian aquatic system deteriorated by anthropogenic factors. Water and sediment samples were collected simultaneously for physicochemical and heavy metal analyses. The comet assay was performed as a biomarker of genotoxicity. Fish located downstream had a higher frequency of DNA damage than in the reference site. We found concentrations of Cr and Ni above acceptable levels in sediment samples. Generally, Ba, Mn, Mg, Zn, Cr, and Ni were the elements most associated with genotoxic damage. Water and sediment of the Antas stream showed genotoxic potential in A. lacustris according to the urbanization gradient, demonstrating the importance to prevent the release of environmental pollutants, especially heavy metals in urban areas.

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.

Characterization of heavy metal pollution in an anthropogenically and geologically influenced semi-arid region of east India and assessment of ecological and human health risks

The present study evaluated the heavy metal contamination in groundwater and associated ecological and human health risks of a geologically and anthropogenically diverse semi-arid region of Birbhum district, India. For a reliable evaluation, concentrations of nine heavy metals in 680 groundwater samples (N = 680) which were collected during premonsoon and postmonsoon seasons of consecutive two years from 170 wells were measured. The human health risk assessment using the USEPA model which is based on single value for each parameter may inherit certain inaccuracy and uncertainties in the evaluation. Unlike earlier studies, a higher degree of accuracy in carcinogenic and noncarcinogenic health risk assessments was achieved through Monte Carlo simulations, sensitivity analysis and uncertainty analysis. The study revealed the occurrence of the target heavy metals in groundwater with mean dominance order of Fe > Zn > Sr > Mn > Cr > Pb > Ni > Cu > Cd where mean concentrations of the carcinogens, Pb and Fe exceeded their maximum permissible limits. The water quality status evaluated using the modified heavy metal pollution index, Nemerow index and Heavy metal evaluation index methods resulted in medium to high heavy metal contamination in groundwater within a large portion of the study area which indicated its unsuitability for drinking purpose. The study suspects a moderate to very high risk for the groundwater dependent ecosystems in major part of the study area. The study further revealed cancer risks, ranging from high to very high within the residents due to accumulative exposure of the carcinogenic heavy metals in groundwater through ingestion and dermal contact. Minor populations of the study area were found to be more vulnerable to the carcinogenic and noncarcinogenic diseases than teenagers and adults, mainly through oral exposure. The study recommends the residents to consume treated groundwater since the primary route of heavy metal exposure was identified to be the ingestion route.

Assessment of trends and emission sources of heavy metals from the soil sediments near the Bohai Bay

Anthropogenic emission sources (mainly vehicular and industrial emission) are one of the major emission sources of the heavy metals in aquatic ecosystems which have significant potential to perturb the marine geochemistry and ecosystem as well as human life also. In the present study, we tried to investigate the accumulation of heavy metals (Zn, Cr, Ni, Cu, Pb, Co, As, Cd, and Hg) at two sediment cores near the Bohai Bay in Southern Tianjin and reconstruct their historical trends over the last hundred years to understand the impacts of anthropogenic activities. The concentration of Zn and Cr is found maximum than the other studied heavy metals. Results suggest that in the mid-twentieth century, the maximum concentrations of Zn, Cr, Ni, Cu, and Pb are mainly because of the opening of Dagang Oilfield which emits a huge amount of heavy metals into the environment. Source apportionment analysis has been carried out using positive matrix factorization (PMF) model which suggests three major emission sectors of heavy metals, i.e., coal combustion, manufacturing, and smelting dust, having different contribution 32%, 40%, and 28% respectively to the total heavy metal burden. Industrial emissions are found to be the major sources of Cr, Ni, and Co while Pb is mainly originated from the coal combustion. The risk assessment analysis shows the value of mean effects range median (ERM) quotients ~ 0.17 for the two sediment cores which suggest nearly 21% toxicity of the studied metals indicating towards the policymakers for the mitigation of air pollution surrounding Tianjin.