Mn In Groundwater Research Articles

Biogeochemical mechanisms of iron (Fe) and manganese (Mn) in groundwater and soil profiles in the Zhongning section of the Weining Plain (northwest China)

High levels of Iron (Fe) and manganese (Mn) in soils may contribute to secondary contamination of groundwater. However, there is limited understanding of the cycling mechanisms of Fe and Mn in groundwater and soil. This study aimed to investigate the biogeochemical processes constituting the Fe and Mn cycle by combining hydrochemistry, sequential extraction and microbiological techniques. The results indicated a similar vertical distribution pattern of Fe and Mn, with lower levels of the effective form (EFC-Fe/Mn) observed at the oxygenated surface, increasing near the groundwater table and decreasing below it. Generally, there was a tendency for accumulation above the water table, with Mn exhibiting a higher release potential compared to Fe. Iron‑manganese oxides (Ox-Fe/Mn) dominated the effective forms, with Fe and Mn in the soil entering groundwater through the reduction dissolution of Ox-Fe/Mn and the oxidative degradation of organic matter or sulfide (OM-Fe/Mn). Correlation analysis revealed that Fe and Mn tend to accumulate in media with fine particles and high organic carbon (TOC) contents. 16S rRNA sequencing analysis disclosed significant variation in the abundance of microorganisms associated with Fe and Mn transformations among unsaturated zone soils, saturated zone media and groundwater, with Fe/Mn content exerting an influence on microbial communities. Furthermore, functional bacterial identification results from the FAPROTAX database show a higher abundance of iron-oxidizing bacteria (9.3 %) in groundwater, while iron and manganese-reducing bacteria are scarce in both groundwater and soil environments. Finally, a conceptual model of Fe and Mn cycling was constructed, elucidating the biogeochemical processes in groundwater and soil environments. This study provides a new perspective for a deeper understanding of the environmental fate of Fe and Mn, which is crucial for mitigating Fe and Mn pollution in groundwater.

ENVIRONMENTAL ASSESSMENT OF POLLUTION IN AN INDUSTRIAL ENVIRONMENT USING HEAVY METAL POLLUTION INDICES AND STABLE ISOTOPES, CASE STUDY OF THE INDUSTRIAL ZONE OF SKIKDA, NORTH-EAST ALGERIA

An environmental assessment study was conducted in the industrial area of Skikda in the Northeast of Algeria which involved physicochemical parameters, heavy metal concentrations, and stable isotopes of surface water, groundwater, and soil. The results revealed high concentrations of Cd, Ni, Fe, Cu, As, Cr, Pb, Co, and Mn in groundwater. The southern part exhibited the lowest heavy metal concentrations, while the industrial zone in the North contained the highest levels. Therefore, the industrial area showed significant pollution in groundwater by Cr, Pb, and As with respectively 0.5, 0.69, and 0.44 mg/l, surpassing the respective WHO(World Health Organization) standards of 0.05, 0.01, and 0.01 mg/l. Spatial analysis showed that the industrial area presents higher concentrations of As, Cr, Cd, Pb, Cu, Zn, Ni, and Fe which demonstrated similar trends in spatial distribution, their concentrations increasing within the industrial zone. However, the western part had no significant pollution sources except for a public landfill and SONATRACH industrial complex, high concentrations of Co and Mn in the south and the west parts were observed. Mean concentration in soils indicated that Cd is ranged between35.32 to 95.12 ppm, for Fe between 145.1 and 702 ppm, As varies between 1.03 and 81.85 ppm, and Zn between 50 and 520.32 ppm and considered as dominant metals. However, Mn, Co and Cr were lower respectively with 1.97, 12.11 and 7.25 ppm. Cd and As were most influenced by the polluting companies, while Cr was mainly influenced by natural factors, such as pH and soil type. Based on the contamination degree index, the soil pollution levels of Cd, Pb, and As were classified as extremely contaminated. The statistical analysis indicated substantial anthropogenic contributions to groundwater contamination concentrated in the industrial area. The groundwater exhibits a range of δ18O and δ2H values, varying from 2.45 to -5.33‰ and 19.82 to -1.67‰ vs. the V-SMOW (Vienna-Standard Mean Ocean Water) standard, respectively. The mean isotopic composition is -2.50‰ for δ18O, -19.32‰ for δ2H, with a mean deuterium excess of 6.45. These values align with the Meteoric Water Line observed in the western Mediterranean region. It indicates a hydrological connection between recharge and groundwater which suggests a significant interaction between groundwater and surface water. Due to their proximity to the river and the shallow aquifer, the downstream area is more vulnerable to surface pollution. Furthermore, the young groundwater in the downstream can be attributed to the rapid recharge and replenishment of the aquifer caused by rainfall and quick infiltration and sustained by the shallow aquifer depth and sandy soil. Consequently, the rainwater and industrial wastes lead to faster pollutant infiltration. Anthropogenic sources, including industrial effluents from smelting, refining, manufacturing, steel and textile industries, electroplating, nickel-cadmium battery production, welding, PVC product and paint pigment manufacturing, were identified as major contributors to heavy metal pollution.

Iron, manganese, and lead contamination in groundwater of Bangladesh: a review

Abstract Groundwater is a vital source of safe drinking water in Bangladesh and most South Asian countries. The study aimed to identify the sources and assess the contamination of Fe, Mn, and Pb in groundwater. The study considered published articles, reports, and data repositories of concerned departments over the past two decades using various search engines, including Web of Science, Scopus, Science Direct, Google Scholar, etc. The study results showed the concentrations of Fe, Mn, and Pb in groundwater exceeded 55.93, 75.44, and 37.50%, respectively, of different standards, including the World Health Organization and United Nations Environmental Protection Agency. The concentrations of Fe, Mn, and Pb ranged from 0.003 to 16.6, 0.00063 to 3.11, and 0.0006 to 5.01 mg/L, respectively, and followed the order Fe > Mn > Pb in the groundwater of Bangladesh. Sources of Fe and Mn in groundwater are mostly geogenic in origin, while Pb contamination in groundwater is anthropogenic and derives from industry dust piles, vehicle exhaust discharge, lead pipes, faucets, fixtures, and batteries. The higher levels of heavy metals in groundwater cause health and environmental hazards. The study recommended that the higher concentrations of Fe, Mn, and Pb in groundwater make it unsuitable for drinking purposes and should be treated before consumption.

Occurrence and influencing factors of high groundwater manganese in the oxbow lakes of the middle reaches of Yangtze River

Oxbow lake, acting as an efficient factory, plays an important role in the attenuation and accumulation of groundwater contamination. However, there are few concerns on the enrichment of manganese in the oxbow lakes. Based on 113 groundwater samples collected from Wuhan Geological Survey Center, China Geological Survey in 2019, the distribution and influencing factors of high groundwater Mn were studied in the oxbow lakes of the middle reaches of Yangtze River. The results showed that the elevated groundwater Mn were mainly distributed in the concave bank with 75 % of Mn concentration exceeded 0.10 mg/L, and up to 3.79 mg/L. Moreover, groundwater Mn concentrations were related to the depth and the well types. According to principal component analysis, Mn and HCO3–, Mg2+, Fe, NH4-N, Ca2+, As, Eh and NO3– dominated in PC1 with significantly correlations which may result from natural attenuation processes. The sedimentary environments including geological properties and reducing conditions in the studied area were responsible for the enrichment. Not only the dissolution of rich Mn-bearing minerals in the studied area driven by redox conditions provided the source of groundwater Mn but also the unique sedimentary architecture characteristics and the slow flow limited the transfer of dissolved Mn in groundwater, resulting in the enrichment of Mn. This study provides us understand the occurrence and influencing factors of high groundwater manganese in the oxbow lakes/wetlands.

Analysis on the Chemical Characteristics and Genesis of Drinking Groundwater in Rural Areas of Suihua City, Northeast China

People living in the rural areas of Suihua City rely mainly on groundwater. Determining the chemical characteristics of groundwater and its impact on human health is very important to support drinking water safety engineering. We conducted a systematic study of water chemistry and human health by using software such as SPSS, SQLEVAL, MapGIS, and other methods such as statistical analysis, correlation analysis, Shukarev analysis, Piper’s trilinear plot analysis, scale factor analysis, and N.L. Nemerow index analysis. It is concluded that the cation in the groundwater is mainly of calcium type, and the anion is of mixed type of chloride, sulfate, and bicarbonate. The four types of water chemistry that account for greater than 10% of the total are 11-A, 4-A, 8-A, and 22-A. The chemical composition of groundwater is mainly controlled by rock weathering; Na+ and K+ come from rock salt and silicate rock; while Ca2+ and Mg2+ mainly come from carbonate rock. Cation Exchange interaction occurs in shallow groundwater. Fe and Mn in groundwater are mainly influenced by geological and lithological factors, while NO3 − and F− are mainly influenced by anthropogenic activity. This study is of great significance for the management of healthy drinking water in rural areas of Suihua City.

Manganese mobilization from sediment to groundwater in alluvial-lacustrine aquifer system along the lower reaches of Han River

Geogenic contaminants in groundwater limit the drinking water safety and sustainable water supply for domestic purposes throughout the world. Elevated concentrations of manganese (Mn) in groundwater have been one of the major concerns since its adverse health effects to humans, whereas the underlying enrichment mechanism within aquifers is poorly understood. This research aims to connect the spatial distributions of groundwater Mn in different units of the aquifer and the variations of sediment geochemistry to provide comprehensive understanding of Mn provenance and its mobilization through sediment pore-networks into groundwater. Along the lower reaches of Han River within the central Yangtze River Basin, significant heterogenous Mn distribution has been observed with over 60 % of groundwater exceeding the World Health Organization drinking water guideline. Groundwater chemistry and sequential extraction results indicated that the oxidation of organic matter and reduction of Mn oxides and Fe (hydr)oxides in sediments could drive groundwater Mn enrichment. Herein, we propose a burial-dissolution type as the major hydrogeochemical process of Mn mobilization in the region. These findings are of great importance in understanding the geogenic sources of Mn and the controlling processes for its spatial heterogeneity in alluvial-lacustrine aquifer system, which might be applicable to similar Mn-affected geological settings.

In vitro evaluation of the cytotoxic and genotoxic effects of Al and Mn in ambient concentrations detected in groundwater intended for human consumption

Environmental exposure to metals can induce cytotoxic and genotoxic effects in cells and affect the health of the exposed population. To investigate the effects of aluminum (Al) and manganese (Mn), we evaluated their cytogenotoxicity using peripheral blood mononuclear cells (PBMCs) exposed to these metals at previously quantified concentrations in groundwater intended for human consumption. The cell viability, membrane integrity, nuclear division index (NDI), oxidative stress, cell death, cell cycle, and DNA damage were analyzed in PBMCs exposed to Al (0.2, 0.6, and 0.8 mg/L) and Mn (0.1, 0.3, 1.0, and 1.5 for 48 h. We found that Al induced late apoptosis; decreased cell viability, NDI, membrane integrity; and increased DNA damage. However, no significant alterations in the early apoptosis, cell cycle, and reactive oxygen species levels were observed. In contrast, exposure to Mn altered all evaluated parameters related to cytogenotoxicity. Our data show that even concentrations allowed by the Brazilian legislation for Al and Mn in groundwater intended for human consumption cause cytotoxic and genotoxic effects in PBMCs. Therefore, in view of the results found, a comprehensive approach through in vivo investigations is needed to give robustness and validity to the results obtained, thus broadening the understanding of the impacts of metals on the health of environmentally exposed people.

Betaproteobacteria are a key component of surface water biofilters that maintain sustained manganese removal in response to fluctuations in influent water temperature

The health risks associated with manganese (Mn) in drinking water, and an improved understanding of Mn accumulation within, and subsequent release from, distribution systems, have increased the need for robust, sustainable treatment options to minimize Mn concentrations in finished water. Biofiltration is an established and effective method to remove Mn in groundwater however, Mn removal in surface water biofilters is an emerging treatment process that has not been extensively studied. Seasonal variations in water temperature can present an operational challenge for surface water biofilters which may see reduced Mn removal under colder conditions. This study examined the microbiomes of surface water biofilters at three utilities (ACWD WTP, WTP B, and WTP D) which all experienced similar seasonal fluctuations in influent water temperature. High Mn removal was observed at the ACWD WTP for much of the year, but Mn removal decreased with a concurrent decrease in the influent water temperature (58% ± 22%). In contrast, both WTP B and WTP D achieved year-round Mn removal (84% ± 5% and 93% ± 8% respectively). Marker gene (16S rRNA) sequencing analysis of the biofilter microbiomes identified a high abundance of Betaproteobacteria in WTP B and WTP D (37% ± 12% and 21% ± 3% respectively), but a low abundance of Betaproteobacteria in the ACWD WTP (2% ± 2%). The microbiomes of new bench-scale biofilters, in operation at the ACWD WTP, were also investigated. The abundance of Betaproteobacteria was significantly greater (p < 0.05) after the biofilters had acclimated than before acclimation, and differential abundance analysis identified 6 genera within the Betaproteobacteria class were enriched in the acclimated microbiome. Additionally, the acclimated biofilters were able to maintain high Mn removal performance (87% ± 10%) when the influent water temperature decreased to 10 °C or less. Further analysis of previously published studies found the abundance of Betaproteobacteria was also significantly greater (p < 0.001) in biofilters with sustained Mn removal than in biofilters which did not treat for Mn as a contaminant, despite differences in design scale, source water, and media type. Microbiome network analysis identified multiple co-occurrence relationships between Betaproteobacteria and Mn oxidizing bacteria in the WTP B and WTP D biofilters, suggesting indirect contributions by Betaproteobacteria to biological Mn oxidation. These co-occurrence relationships were not present in the full-scale ACWD WTP microbiome. Whether the role of Betaproteobacteria in biological Mn oxidation is direct, indirect, or a combination of both, they are consistently present at a high abundance in both groundwater and surface water biofilters with sustained Mn removal, and their absence may contribute to the seasonal fluctuations in Mn removal observed at the ACWD WTP. This new insight to Betaproteobacteria and their role in Mn biofiltration could contribute to water innovation and design that would improve the reliability of Mn removal.

Human Health Risk Assessment of Elevated Fe and Mn Intake in Groundwater in Yangtze Catchment.

Globally, it has been reported that groundwater contains elevated levels of Fe and Mn. However, the risk of prolonged exposure to groundwater with elevated Fe and Mn was often ignored due to their much lower carcinogenic risk. To assess the human health risk of elevated Fe and Mn intake in groundwater, 1863 groundwater samples from the Yangtze catchment, a densely populated and economically prosperous area of China, were collected in this study. The spatial distributions of Fe and Mn in groundwater were investigated by the geographic information system (GIS) and their health risk assessment was done. The results indicated that 38.6% and 50.3% of the groundwater samples were defined as "elevated/high" levels for Fe and Mn, respectively, exceeding 0.3 and 0.1 mg/L (World Health Organization guidelines). Moreover, in the groundwater of Yangtze Catchment, the order of Fe and Mn contents is followed by upper< middle< lower. Based on the calculated hazard index (HI), HIadult and HIchild were in a range of 0-4.91 and 0-11.07, respectively. There was an area of 3,483 and 35,523 km2 with a non-carcinogenic risk from Fe and Mn, correspondingly. The numbers of affected adults and children were about 3,018,066 and 2,775,007, respectively. It means that 0.20% and 2.00% of the study area or 0.64% and 0.59% of the total population will suffer health risks from Fe and Mn intake in groundwater, respectively. Therefore, a significant basis for groundwater safety in the Yangtze catchment and similar areas was provided in this study.

Enrichment of Manganese at Low Background Level Groundwater Systems: A Study of Groundwater from Quaternary Porous Aquifers in Changping Region, Beijing, China

Manganese (Mn) could adversely affect water quality and is a concern for drinking water safety. In contrast to Mn-contaminated groundwater systems, Mn concentrations can increase up to 2 orders of magnitude in low background level groundwater systems (Mn &lt; 100 µg/L). It is interesting to explore related hydrogeological and hydrochemical processes and controlling mechanisms. Our data showed that Mn of groundwater from Quaternary porous aquifers in the Changping region of Beijing in China varied from 0.02 to 522 µg/L, with an average of 45 µg/L. The high Mn concentration (&gt;100 µg/L) in groundwater occurred in the lower plain, while the low Mn concentration was distributed in the upper plain. Association was not obvious between the Mn concentration and the depth of the groundwater. The water–rock interaction (e.g., dissolution of Mn-bearing minerals) and redox reactions dominated the distribution of Mn in groundwater. Particularly, the reduction of Mn4+ was a major cause of increasing Mn2+ concentration in groundwater. This is further evidenced by declining dissolved oxygen (DO) and NO3 in groundwater from the upper plain to the lower plain part. This study contributes to further understandings of hydrochemical processes for the enrichment of Mn in groundwater and offers a reference for the management and oversight of groundwater containing an excessive Mn level.

Disparities in Drinking Water Manganese Concentrations in Domestic Wells and Community Water Systems in the Central Valley, CA, USA.

Over 1.3 million Californians rely on unmonitored domestic wells. Existing probability estimates of groundwater Mn concentrations, population estimates, and sociodemographic data were integrated with spatial data delineating domestic well communities (DWCs) to predict the probability of high Mn concentrations in extracted groundwater within DWCs in California's Central Valley. Additional Mn concentration data of water delivered by community water systems (CWSs) were used to estimate Mn in public water supply. We estimate that 0.4% of the DWC population (2342 users) rely on groundwater with predicted Mn > 300 μg L-1. In CWSs, 2.4% of the population (904 users) served by small CWSs and 0.4% of the population (3072 users) served by medium CWS relied on drinking water with mean point-of-entry Mn concentration >300 μg L-1. Small CWSs were less likely to report Mn concentrations relative to large CWSs, yet a higher percentage of small CWSs exceed regulatory standards relative to larger systems. Modeled calculations do not reveal differences in estimated Mn concentration between groundwater from current regional domestic well depth and 33 m deeper. These analyses demonstrate the need for additional well-monitoring programs that evaluate Mn and increased access to point-of-use treatment for domestic well users disproportionately burdened by associated costs of water treatment.

High Fe and Mn groundwater in the Nanchang, Poyang Lake Basin of China: hydrochemical characteristics and genesis mechanisms.

Based on the water quality test data of 257 groups of phreatic groundwater and 165 groups of confined groundwater in the Nanchang area and the redox conditions, acid-base conditions and the organic matter content in groundwater, we identified hydrochemical characteristics and genesis of groundwater with high Fe and Mn contents in Nanchang. The results showed that Fe and Mn exceeded the standard in both phreatic and confined groundwater. The over-standard rates of Fe and Mn in groundwater were 8.56-11.52% and 33.07-36.36%, respectively. The degree of pollution Fe and Mn in the confined groundwater is higher than that in the phreatic groundwater, and the degree of pollution caused by Mn is higher than that caused by Fe. The high Fe and Mn contents in groundwater were caused by the release of Fe and Mn minerals from the native environment due to changes in the groundwater environment of the study area. A mild redox environment (Eh < 100) and low pH value are favorable for Fe and Mn enrichment in groundwater. The presence of organic matter accelerates microbial activity and promotes the release of Fe and Mn from aquifer sediments. Therefore, the change in the native environment played an important role in the increase in Fe and Mn content in the study area.

Geogenic manganese and iron in groundwater of Southeast Asia and Bangladesh – Machine learning spatial prediction modeling and comparison with arsenic

Naturally occurring, geogenic manganese (Mn) and iron (Fe) are frequently found dissolved in groundwater at concentrations that make the water difficult to use (deposits, unpleasant taste) or, in the case of Mn, a potential health hazard. Over 6000 groundwater measurements of Mn and Fe in Southeast Asia and Bangladesh were assembled and statistically examined with other physicochemical parameters. The machine learning methods random forest and generalized boosted regression modeling were used with spatially continuous environmental parameters (climate, geology, soil, topography) to model and map the probability of groundwater Mn > 400 μg/L and Fe > 0.3 mg/L for Southeast Asia and Bangladesh. The modeling indicated that drier climatic conditions are associated with a tendency of elevated Mn concentrations, whereas high Fe concentrations tend to be found in a more humid climate with elevated levels of soil organic carbon. The spatial distribution of Mn > 400 μg/L and Fe > 0.3 mg/L was compared and contrasted with that of the critical geogenic contaminant arsenic (As), confirming that high Fe concentrations are often associated with high As concentrations, whereas areas of high concentrations of Mn and As are frequently found adjacent to each other. The probability maps draw attention to areas prone to elevated concentrations of geogenic Mn and Fe in groundwater and can help direct efforts to mitigate their negative effects. The greatest Mn hazard is found in densely populated northwest Bangladesh and the Mekong, Red and Ma River Deltas of Cambodia and Vietnam. Widespread elevated Fe concentrations and their associated negative effects on water infrastructure pose challenges to water supply. The Mn and Fe prediction maps demonstrate the value of machine learning for the geospatial prediction modeling and mapping of groundwater contaminants as well as the potential for further constituents to be targeted by this novel approach.

Interactions between anthropogenic pollutants (biodegradable organic nitrogen and ammonia) and the primary hydrogeochemical component Mn in groundwater: Evidence from three polluted sites

Anthropogenic pollutants (organic nitrogen and ammonia) can change the dynamic balances of hydrogeochemical components of groundwater, and this can affect the fates of the pollutants and groundwater quality. The aim of this paper is to assess the long-term impact of pollutants on groundwater component concentrations and species in three sites that has been polluted with illegal discharge wastewater containing organic nitrogen and ammonia, in order to reveal the interactions between nitrogen species and Mn. We analyzed semi-monthly groundwater data from three sites in northwestern China over a long period of time (2015–2020) by using statistical analyses, correlation analyses, and a correlation co-occurrence network method. The results showed that wastewater entering groundwater from surface changed the hydrogeochemical component concentrations and species significantly. The main form of inorganic nitrogen species changed from nitrate to ammonia. The Mn concentration increased from undetectable (<0.01 mg/L) to 1.64 mg/L (the maximum), which surpassed the guideline value suggested by China and WHO. The main mechanism for Mn increase is the reductive dissolution of Mn oxide caused by the oxidation of organic nitrogen. Mn‑nitrogen species interaction complicates the transformation of nitrogen components. Chemoautotrophic denitrification and dissimilatory nitrate reduction to ammonium (DNRA) mediated by Mn are the major mechanisms of nitrate attenuation when dissolved oxygen is greater than 2 mg/L. Mn oxides reductive dissolution and reoxidation of Mn by nitrate reduction cause Mn to circulate in groundwater. The results provide field evidence for interactions between nitrogen species transformation and Mn cycle in groundwater. This has important implications for pollution management and groundwater remediation, particularly monitored natural attenuation.

Elevated Fe and Mn Concentrations in Groundwater in the Songnen Plain, Northeast China, and the Factors and Mechanisms Involved

Groundwater is an essential source of drinking and irrigation water. However, elevated Fe and Mn concentrations in groundwater have been found in recent decades, which can adversely affect human health and decrease crop quality and yields. The roles of hydrogeochemical changes and groundwater pollution (exogenous reductive material inputs) in this have not been studied adequately. We determined the distribution of Fe and Mn concentrations in groundwater in the Songnen Plain, northeast China, which is known for elevated Fe and Mn concentrations, and investigated the factors and mechanisms involved in causing the elevated concentrations. Chemical and statistical analyses indicated that the Fe and Mn concentrations in groundwater significantly correlated with climate parameters (precipitation and temperature), surface features (altitude, distance from a river, soil type, soil texture, and land use type) and hydrogeochemical characteristics (chemical oxygen demand and NH4+, NO3−, and P concentrations). In particular, the Fe and Mn concentrations in groundwater are higher in areas containing paddy fields and water bodies than other land use type areas. Areas with groundwater containing ultra-high Fe and Mn concentrations have almost all of the favorable factors. The main reasons for the elevated Fe and Mn concentrations in groundwater in the study area are the Fe/Mn mineral-rich strata and soil with abundant organic matter acting as sources of Fe and Mn to the groundwater and the reductive environment in the lower terrain and areas containing water bodies favoring Fe and Mn dissolution in the groundwater. Inputs of pollutants from agricultural activities have caused the Fe and Mn concentrations in groundwater to increase. Future studies should be performed to study interactions between pollutants from agricultural activities and Fe and Mn in groundwater and develop environmental management strategies for preventing future increases in Fe and Mn concentrations and promoting sustainable development of agriculture.

Distributions and interactions of dissolved organic matter and heavy metals in shallow groundwater in Guanzhong basin of China

Groundwater as the primary source of fresh water particularly in semi-arid regions is heavily threatened by various pollutants such as dissolved organic matter (DOM) and heavy metals due to anthropogenic activities. In this study, 113 shallow groundwater samples were collected from Guanzhong basin of China to explore spatial distributions and interactions of DOM and heavy metals (Fe, Mn and Cu). Fluorescence excitation-emission spectrophotometry with parallel factor analysis showed that DOM in groundwater mainly contained three humic-like and two protein-like substances with an average dissolved organic carbon (DOC) concentration of 12.85 mg L−1. Average Mn and Cu concentrations in groundwater were 19.92 μg L−1 and 7.05 μg L−1 with an increasing trend from west to east, whereas Fe concentration in central regions was much higher (34.23 μg L−1). Structural equation modeling analysis indicated that DOM in groundwater could be significantly affected by surface water, and heavy metals were influenced by urbanization. Moreover, DOM could strongly influence the bioavailability, migration, and transformation of Mn in groundwater. These findings would be beneficial for the effective utilization and protection of groundwater resources.

Anthropogenic Organic Pollutants in Groundwater Increase Releases of Fe and Mn from Aquifer Sediments: Impacts of Pollution Degree, Mineral Content, and pH

In many aquifers around the world, there exists the issue of abnormal concentrations of Fe and Mn in groundwater. Although it has been recognized that the main source of this issue is the release of Fe and Mn from aquifer sediments into groundwater under natural environmental conditions, there lacks enough reliable scientific evidence to illustrate whether the pollutants imported from anthropogenic activities, such as organics, can increase this natural release. On the basis of time series analysis and comparative analysis, the existence of an increasing effect was verified through laboratorial leaching test, and the impacts of aquatic chemical environment conditions, such as pH, on the effect were also identified. The results showed that the increase of organics in groundwater made the release of Fe and Mn more thorough, which was favorable for the increase of groundwater concentrations of Fe and Mn. The higher the contents of Fe- and Mn-bearing minerals in aquifer sediments, the higher the concentrations of Fe and Mn in groundwater after the release reaches kinetic equilibrium. Lower pH can make the leaching more thorough, but the neutral environment also increases the amount of Mn. It can be deduced that the pollutants such as organics imported by anthropogenic activities can indeed increase the releases of Fe and Mn from aquifer sediments into groundwater, thus worsening the issue of groundwater Fe and Mn pollution. The findings provide a deeper insight into the geochemical effects of Fe and Mn in the natural environment, especially in the groundwater system.

Evaluating the geochemistry of groundwater contamination with iron and manganese and probabilistic human health risk assessment in endemic areas of the world’s largest River Island, India

Iron (Fe) and manganese (Mn) are harmful for human health, if present in a higher concentration, particularly in groundwater. The results of the study revealed that the concentration of Fe and Mn exceeded the WHO guideline for safe drinking water in 88 % and 74 % of groundwater samples, respectively. The non-carcinogenic health risk as assessed through computation of hazard quotient (HQ) due to intake of Fe and Mn contaminated groundwater was found much higher for children and adults. The values of HQ were recorded up to 1.96 for children and 1.52 for adult in case of Fe; and up to 2.13 for children and 1.61 for adult associated with Mn. On the basis of occurrence and spatial distribution of Fe and Mn in groundwater, the study area was delineated under high, elevated and low risk zone for priority attention.

Effects of the natural environment and human activities on iron and manganese content in groundwater: a case study of Changchun city, Northeast China.

Excessive Fe and Mn in groundwater of the Songnen Plain, northeast China, pose a threat to water security. Human activities over recent decades have had significant effects on the water quantity and quality of the Songnen Plain. By adopting the large city of Changchun in the Songnen Plain as a research area, this study analyzed the effects of the natural environment (including characteristics of soil and aquifer, climate, and groundwater level) and human activities (including groundwater salinization, groundwater exploitation, and nitrate effects) on groundwater Fe and Mn using statistical and spatial analysis methods. The results showed that the characteristics of soil and aquifer determine the source of groundwater Fe and Mn. The correlations between Fe and Mn with TDS (total dissolved solids) increased with increasing TDS from southeast to northwest in different microclimate regions. The salinization of groundwater caused by human activities will also lead to the increase of Fe content. The decrease in groundwater Fe and Mn was attributed to an increase in groundwater [Formula: see text], through the use of chemical fertilizers. The variation of Fe concentration in groundwater corresponded well with that of groundwater depth, but the excessive exploitation will lead to the continuous decrease in groundwater level and a corresponding decrease in the concentration of groundwater Fe. This study provides a reference for understanding the influence of human activities and the natural environment on groundwater hydrochemistry in the Songnen Plain.

Evaluation of contamination of manganese in groundwater from overburden dumps of Lower Gondwana coal mines

Inappropriate management of coal mine overburden (OB) dumps creates environmental hazards. In many countries, high concentration of Mn was observed in groundwater near the coal mine OB dump sites. Comparatively new coal mines in Barjora coalfield were chosen in this study to assess the impact of OB dumps in groundwater. Acid Digestion (AD), Toxicity Characteristics Leaching Procedure (TCLP) and Batch Leaching Test (BLT) were performed to estimate Mn concentration in OB dumps and its leaching behaviour. Shale present in OB dump has potential to leach high concentration of Mn. The aquifer in this region is mainly unconfined type and water table is very shallow. In situ soil is characterized by 44.3% sand, 37.5% silt and 18.2% clay with a saturated hydraulic conductivity of 5.58 cm/day. Column study and HYDRUS 1D numerical modelling were used to simulate the migration of Mn in vadose zone. Subsurface soil does not possess appreciable attenuating potential to retard the transport of Mn in vadose zone. HYDRUS 1D model explains that 1.6 m thick soil profile of the study area may release Mn in groundwater after 11th year and it can attain the complete breakthrough at 17th year. A groundwater contaminant transport model based on available hydrogeological data has been developed using VISUAL MODFLOW 2009.1 software. The movement of Mn in aquifer has been determined using MT3DMS code. It indicates ≃ 8 km2 area around the two Open Cast Coal Mines (OCCMs) namely OCCM 1 and OCCM 2 may suffer groundwater contamination of Mn by 2050.