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A total of 21 surface sediment samples collected from Arasalar River are subjected to sediment texture (sand-silt-clay ratio), trace elements, organic matter, and CaCO 3 studies to understand the accumulation dynamics of sediments. To assess the impact of metal pollution in estuarine sediments, the essential parameters should be done by checking the sediment characteristics, spatial distribution of heavy metal sources, sediment dynamics, and geochemical analysis. To evaluate the contamination level of metal pollution, a basic standard reference is required to decipher the values ranging from natural to anthropogenic contribution. From this research analysis, it is observed that the study area predominantly comprises silty sand and sand silty nature. The calcium carbonate content in the sediment is found to be proportional to the presence of shell fragments, whereas the organic matter (OM) is derived from riverine and coastal input which acts as a primary source. The obtained results confessed the average contents (mg/g) for the following selected eight elements in the order of Fe (35249-49068) > Mn (286-519) > Ni (107-279) > Cu (78.30-155.70) > Cr (50-99) > Zn (38.70-91.90) > Pb (39.90-62.40), and Co (12.6-29.1) by using an atomic absorption spectrophotometer (AAS) are utilized for this analysis. Multivariate analysis of heavy metals affirms geogenic sources (weathering of parent rocks) for Fe, Mn, Cr, Co, and Zn, whereas Cu, Ni, and Pb originated from anthropogenic activities (urban and industrial activities). The pollution load index, sediment pollution index, I geo index, and PERI are categorized as under polluted, low to moderate polluted, and low potential environmental risk variety. Constant inspection and guidance are needed to prevent effluences from various agriculture and industrial activities in the nearby regions. The findings from this research may support and help the government to follow the suitable remediation on the better management of river and coastal areas., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Roadside soil contamination is mostly caused by human-caused pollutant deposition. PTEs are among the many substances that are harmful for both humans and the environment. PTE concentrations in roadside soil in Chennai, southern India, have been determined in this study. To evaluate the seriousness of the threats, more environmental and geochemical indices have been applied. 83 soil samples have been obtained from the study regions and focusing on important roads. Elemental analysis has been analyzed with ED-XRF and sieve-filtered samples focused on PTEs such as arsenic, barium, cobalt, chromium, copper, iron, potassium, nickel, lead, thorium, titanium, zinc, and uranium. Significant metallic variations have been found in soil samples around roads by the investigation. The elements this study examined section ascending in the following sequence: Fe > Ti > Zn > Cr > Pb > Cu > Ni > Th > As > U > K. In the research area, the CD classification denotes high contamination, whereas the CF indices show mild to significant pollution. PLI indicates moderate to high pollution, whereas EF suggests excessive enrichment. Igeo demonstrates a range from uncontaminated to highly contaminated. PERI showed high levels in the northern study region, whereas GUFI shows several hot spots indicating moderate to severe pollution. The Hazard Index (HI) values for all metals were less than one, demonstrating the absence of non-carcinogenic risks for both adults and children. Multivariate data show natural and anthropogenic PTEs in roadside soil. In addition, a soil quality monitoring system is needed to mitigate continual contamination risks., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Cyclones and heavy rainfalls are the main reasons for incessant environmental aggravation in the coastal regions and the distribution of pollutants from the contaminated terrestrial areas to the offshore regions. Twenty-five surface sediment samples were collected off Kameswaram, SE coast of India, and assessed for their geochemical and sedimentological characteristics post Cyclone Gaja. Sediment texture and various geochemical analyses were carried out to assess the metal distribution in the study area. Environmental impacts caused by heavy metal contamination in the marine sediments were assessed using different sediment pollution indices and it was found that metals such as Cu, Zn, Ni, and Co were moderately contaminated. Fe and Cr were uncontaminated to moderately contaminated, and Mn fall under the uncontaminated category. Multivariate statistical analyses revealed that the enrichment of organic-rich mud helps in entrapping the heavy metals, thus polluting the environment. Moreover, these metals were mainly derived from anthropogenic activities., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Groundwater is the major freshwater resource in urban and rural areas of India that provides potable water. The quality evaluation of existing groundwater resources is vital and it's quantity for the optimal utilization and maintenance. The bounding coordinates of the selected study area of Tuticorin industrial area is between 8°38'24" and 8°51'0" latitude and between 77°54'36" and 78°12'36" longitude. Groundwater samples were collected as grid form at 40 locations during the pre- and postmonsoon seasons in the year 2017. Fe, Zn, Co, Pb, Mn, Ni, Cr, and Cu metal concentrations were determined using AAS (Atomic Absorption Spectrophotometer)-Perkin Elmer makes the model AAnalyst 200. Most of the groundwater samples were exceeded by the WHO 2008; USEPA 2009; and BIS 2012 guideline for drinking water standards. Further to assess the groundwater pollution status based on the heavy metal indices such as heavy metal pollution index (HPI), heavy metal evaluation index (HEI), degree of contamination (DOC), hazard quotient (HQ), hazard index (HI). Statistical analyses to found the appropriateness of groundwater for consumption and factors of contamination. The evaluation results indicate that groundwater is highly deteriorated and unsuitable for drinking in premonsoon period. While evaporation of water which increases the heavy metal concentration in premonsoon and dilution factor was affected in postmonsoon season. The increased concentration of heavy metals in groundwater might have been caused by evaporation, anthropogenic activities, and dissolution of rock formations which poses risk to human health. If this kind of growing contamination in the groundwater is unattended, it may lead to various health issues to the people from this region. Therefore, a consistent and sustainable water management should be carried out in this region in order to improve the groundwater quality.

Heavy metal content in water, sediment, and tissues of six commonly used edible fishes from Adyar estuary, southeast coast of India, was assessed for metal bioaccumulation. The enrichment of metals in estuarine sediment is due to the discharge of contaminated water from the Chennai Metropolis. The enrichment factor indicated that metals such as Cr (EF=30.9) and Cu (EF=31.9) are highly enriched and fall under the very severe category. Bioaccumulation factor (BAF) revealed that the concentration of heavy metals viz. Ni, Cr, Pb, Cu, Co, Zn, Fe, and Mn in different tissues of fishes was several times higher than their concentrations in water. Moreover, high concentration of heavy metals, especially Cu and Cr was noticed in the muscle and liver tissues of the fishes which are higher than the WHO standards. Among the studied fishes, Arius parkii and Gerres oyena showed higher levels of bioaccumulation in terms of toxic metals., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Twenty-five offshore sediment samples were collected after the Gaja cyclone to evaluate the sediment quality in terms of its metal concentration. The samples were examined for organic matter, textural characteristics, calcium carbonate, and trace metals (Fe, Mn, Ni, Co, Cu, and Cr). The geo-accumulation index, enrichment factor, contamination factor, and pollution load index revealed that the study area was highly contaminated with Cu, Zn, and Co. Reasonable to extensive contamination was observed for Fe, Cr, and Ni, whereas Mn was under the uncontaminated category. Statistical analyses revealed that the contamination of Cu, Zn, and Ni are mainly originated from human activities such as boat navigation, fuel combustion, and tourism. Cyclones such as Gaja cause ecological disturbances of the terrestrial and transitional environments and also increase the level of offshore contamination by flooding the contaminated coastal landforms and transporting the contaminants to the sea., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this study, twenty seven surface sediments were collected off Pushpavanam, Nagapattinam coast, southeast coast of India for understanding the sedimentological and geochemical behaviour after the Cyclone Gaja. The sediment samples were analysed for texture, organic matter (OM), carbonates, and trace metals such as Cr, Cu, Zn, Ni, Co including Fe and Mn. The Geoaccumulation index, contamination factor, enrichment factor and pollution load index revealed that Cu, Zn, Ni and Co is highly contaminated in the study area. Fe and Cr are moderately to considerably contaminated, while Mn shows uncontaminated. The principal component analysis also confirms the concentration of Cu, Zn, Ni and Co were mainly derived from the anthropogenic sources and related activities. Since Cyclones like Gaja often causes frequent ecological disturbance to the coastal environments and it distributes pollutants such as trace elements from localized area of contamination to offshore., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The current status of the water quality in terms of nutrients and trace elements were assessed in the Uppanar river estuary, Southern India. Twenty-five sampling stations were monitored in the study area, which is dominated by anthropogenic activities such as agriculture, settlements and fishing harbour in the downstream. Whereas, the upstream and midstream is dominated by barren lands and industrial hub respectively. Nutrients and trace elements such as nitrate, phosphate, iron and lead exceed the permissible limit of WHO drinking water guidelines. The water quality index derived from WHO permissible limits reveal that most of the samples fall under fair to good category. The marginal to fair water quality is noticed in the midstream to downstream region, where anthropogenic activities are high. The multivariate statistical analysis divulges that the overall water quality is controlled by two major sources such as natural weathering of soil/bedrock and agricultural and industrial activities., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Twenty four surface sediments were gathered from the Uppanar river estuary, southern India to evaluate the trace element contamination risk in the sediments. The circulation of organic matter and calcium carbonate were controlled by algal blooms and shell fragments. Moreover, the concentrations of iron and manganese in the estuarine sediments were possibly contributed by riverine sources and geogenic processes. The geoaccumulation index, enrichment factor and contamination factor reveals that the sediments were contaminated by copper and chromium. The pollution load index recommends that the estuarine sediments have the risk of pollution. The sediment pollution index highlights that the majority of the sediments are low polluted sediments. The potential ecological risk index discloses that the Uppanar river estuary is under moderate risk. The statistical analysis reveals that the organic matter content is managed by fine fractions and the majority of the trace elements are associated with each other having similar origin., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Seawater intrusion promotes the salinity of groundwater, and it poses a great environmental impact on a global scale. The present study was carried out to determine the hydrogeochemical processes and influence of seawater intrusion in the coastal aquifers using geophysical, geochemical, and stable isotope techniques. The true resistivity value ranges from 0.5 to 8008.5 Ω-m which has been measured using vertical electrical sounding (VES) based on the Schlumberger method. About 33 groundwater samples were collected during post-monsoon (POM) (January 2012) and pre-monsoon (PRM) (June 2012) seasons from open and bore wells and were analyzed for major ions and stable isotopes. EC, Na + , and Cl - were high in groundwater of wells near salt pan, the Buckingham Canal, and backwater regions. Around 45% of the groundwater of this study area is of Na + -Cl - type due to salinisation. Reverse ion exchange and silicate weathering are the dominant processes controlling the geochemistry of groundwater. Saturation indexes (SI) of halite (SI halite ) and gypsum (SI gypsum ) versus sulfate show an increasing trend line from > 0 to < 0, which implies higher dissolution of minerals and hints increasing salinization during both seasons. The value of Na + /Cl - ranges between 0.7 and 2.4 (POM) and from 0.6 to 2.8 (PRM). The molar ratio suggested that around 25% of the groundwater samples are with values similar to those of seawater. Further, the groundwater is also affected by saline backwater, salt pan activities, and Buckingham Canal. Some locations are also are affected by anthropogenic, agricultural activities and geochemical processes. Heavy stable isotopes were found to be dominant in the coastal region due to seawater intrusion. Stable isotopes of δ 18 O range from - 5.6 to - 2.9‰ during both periods. About 201 km 2 of this area is affected by salinization. It is necessary to reduce pumping and plan for physical barriers to create freshwater ridges for controling the seawater intrusion.

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., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The present study was conducted to assess the trace element concentration in marine surface sediments after major flood event of Chennai metropolis, India. Thirty surface samples were collected from off Chennai coast. Trace elements, organic matter, CaCO 3 , sand-silt-clay and C/N ratios were studied to understand the accumulation dynamics on sediments. The elemental concentration, calcium carbonate and OM distribution suggest that they are derived from urban runoff and transported through Adyar and Cooum Rivers. The enrichment factor reveals that the sediments are enriched by Pb, Cu, Zn, Cr, Co, Ni followed by Fe. The observed Igeo value shows that the samples are contaminated by Pb, Cu and Zn. The elemental concentration of the surface sediments is low when compared to other coastal region except Pb. The elevated level of Pb in the surface sediments is probably due to migration of contaminated urban soil from industrial and transportation sectors into marine environment., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Accumulation of trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were investigated in water, sediment (n=20) along with six fish of diverse feeding guilds (Sillago sihama, Liza parsia, Etroplus suratensis, Oreochromis mossambicus, Arius parkii and Gerres oyena) from the Ennore creek, northern part of Chennai metropolitan megacity, southeast coast of India. Dissolved trace metals (DTMs) in surface water samples and total trace metals (TTMs) in surface sediments (top 0-10cm) indicate that concentration pattern of metals was higher in the discharge point of the river/channels entering the main creek. The maximum mean values of DTMs exhibited the following decreasing order (expressed in µg/L): Fe (1698)>Mn (24)>Zn (14.50)>Pb (13.89)>Ni (6.73)>Cu (3.53)>Co (3.04)>Cr (2.01) whereas the trend is somewhat different in sediments (µgg(-1)): Fe (4300)>Mn (640)>Cr (383)>Zn (155)>Cu (102)>Ni (35)>Pb (32)>Cd (0.51) are mainly due to the industrial complexes right on the banks of the river/channels. Species-specific heterogeneous patterns of tissue metal loads were apparent and the overall metal enrichment exhibited the following decreasing order (expressed in µgg(-1)): Cu (7.33)>Fe (6.53)>Zn (4.91)>Cr (1.67)>Pb (1.33)>Ni (0.44)>Mn (0.43)>Co (0.36)>Cd (0.11). This indicates that metals are absorbed onto the different organs, which is also endorsed by the calculated values of bioaccumulation factor (BAFs) (avg. muscle 117, gill 126, liver 123, intestine 118) in fishes. The high calculated biota sediment accumulation factor (BSAF) (0.437) for the species Arius parkii is considered to be a potential bioindicator in this region. The enrichment of trace metals is also supported by the association of metals in water, sediments and different body organs (muscle, gill, liver, intestine) of fish samples. Comparative studies with other coastal regions indicate considerable enrichment of DTMs & TTMs in sediments as well as in various organs of fish samples. Holistic spatial, temporal monitoring and comprehensive regional strategies are required to prevent health risks and ensure nutritional safety conditions., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The present study was done to assess the sources and the major processes controlling the trace metal distribution in sediments of Buckingham Canal. Based on the observed geochemical variations, the sediments are grouped as South Buckingham Canal and North Buckingham Canal sediments (SBC and NBC, respectively). SBC sediments show enrichment in Fe, Ti, Mn, Cr, V, Mo, and As concentrations, while NBC sediments show enrichment in Sn, Cu, Pb, Zn, Ni, and Hg. The calculated Chemical Index of Alteration and Chemical Index of Weathering values for all the sediments are relatively higher than the North American Shale Composite and Upper Continental Crust but similar to Post-Archaean Average Shale, and suggest a source area with moderate weathering. Overall, SBC sediments are highly enriched in Mo, Zn, Cu, and Hg (geoaccumulation index (I(geo)) class 4-6), whereas NBC sediments are enriched in Sn, Cu, Zn, and Hg (I(geo) class 4-6). Cu, Ni, and Cr show higher than Effects-Range Median values and hence the biological adverse effect of these metals is 20%; Zn, which accounts for 50%, in the NBC sediments, has a more biological adverse effect than other metals found in these sediments. The calculated I(geo), Enrichment Factor, and Contamination Factor values indicate that Mo, Hg, Sn, Cu, and Zn are highly enriched in the Buckingham Canal sediments, suggesting the rapid urban and industrial development of Chennai Metropolitan City have negatively influenced on the surrounding aquatic ecosystem.

The salient features of the river water chemistry and the seasonal variations on the individual chemical parameter were evaluated and characterized. The order of abundance of the ions in the water is determined for both seasons. The contribution of chemical weathering to the water chemistry has been determined using the (Ca(2+) + Mg(2+))/(Na(+) + K(+)) ratio, ternary, and Gibb's diagrams. The results show that the chemical composition of river water during premonsoon is controlled mainly by evaporation-crystallization, while in the postmonsoon, the rock-water interaction dominates. The unique characteristic of the river water is the linear relationship among the principal ions. Hydrochemical characteristics of ions in the water were studied using 1:1 equiline diagrams. The nature of the water samples was determined using the piper diagram. The influence of trace metals on the chemical composition and the quality of the river water in the study area has been assessed using Wilcox and US Salinity Laboratory diagrams.

Multivariate statistical techniques were applied to identify and assess the quality of river water. Thirty samples were collected from the River Cooum, and basic chemical parameters--such as pH, effect concentration, total dissolved solids, major cations, anions, nutrients, and trace metals--were evaluated. To evaluate chemical variation and seasonal effect on the variables, analysis of variance and box-and-whisker plots were performed. Cluster analysis was applied, and pre-monsoon and post-monsoon major and minor clusters were classified. The relations among the stations were highlighted by cluster analysis, which were represented by dendograms to categorize different levels of contamination. Cluster analysis clearly grouped stations into polluted and unpolluted regions. The analysis classified the upper part of the river course into one unpolluted cluster; the middle and lower parts of the river clustered together, reflecting the presence of pollution. Factor analysis revealed that water quality is strongly affected by anthropogenic activities, rock-water interaction, and saline water intrusion. Seasonal variations in water chemistry were clearly highlighted by both cluster and factor analysis. Factor-score diagrams were used successfully to delineate the stations under study by the contributing factors, and seasonal effects on the sample stations were identified and evaluated. These statistical approaches and results yielded useful information about water quality and can lead to better water resource management.

The River Adyar flows through the fault of south Chennai for about 50 Km and enters into the Bay of Bengal. This river is almost stagnant and do not carry enough water except during rainy season. Rapid industrialization and urbanization along the river course during 80s and 90s of last century has increased the pollution of the river water. The main objective of this study is to identify and assess the nature of pollution. In order to achieve this objective, necessary geochemical parameters were determined and the quality of water is evaluated using various tools, such as Wilcox diagram, USIS, Piper, sodium absorption ratio (SAR), 3D scattered diagrams, and seasonal variation diagrams. The monsoonal variations in the data matrix of the river water (River Adyar) was monitored at 33 stations for the premonsoon and postmonsoon periods during September 2005 and February 2006.

We present the results from a detailed study based on five metals (Cr, Cd, Zn, Pb and Fe) measured in four organs (gills, liver, intestine and muscle) of two fish species (Carangoidel malabaricus and Belone stronglurus) from Pulicat Lake in southeast coast of India. The results show marked differences between the two species and organs as well as significant variations within the five analyzed metals. Although the metal concentrations measured in fish muscle are low, high levels of Pb and Fe were observed in the liver and gills of the two fish species. The concentrations of heavy metals in edible parts (muscle) of fish were within the permissible levels and are safe for the human consumption.

Pulicat Lake sediments are often severely polluted with mercury compounds and other toxic heavy metals. Several mercury-resistant bacteria were isolated and identified from the sediments and all the isolates exhibited broad spectrum resistance (both organic and inorganic mercuric compounds). Mercury volatilization showed that four of the isolated Bacillus cereus strains were able to reduce water soluble ionic form of mercury into volatile form via the well known enzymatic reduction. The effect of increasing concentration of mercuric chloride and phenyl mercuric acetate in the growth of this mercury reducing strain was also determined. To study the native physico-chemical parameters, which influence the bioavailability of mercury to bacteria in Pulicat Lake ecosystem, a total of 60 water and 30 sediment samples were collected and analyzed for pH, temperature, dissolved oxygen, salinity, nitrate, nitrite, silicate, phosphate, organic matter and organic carbon. Increased levels of phosphate, nitrite, nitrate, silicate, organic matter and organic carbon during the post monsoon reduce the bioavailability of mercury by forming complexes which may increase the concentration of mercury in the sediments during post monsoon.

Pulicat Lake sediments are often severely polluted with the toxic heavy metal mercury. Several mercury-resistant strains of Bacillus species were isolated from the sediments and all the isolates exhibited broad spectrum resistance (resistance to both organic and inorganic mercuric compounds). Plasmid curing assay showed that all the isolated Bacillus strains carry chromosomally borne mercury resistance. Polymerase chain reaction and southern hybridization analyses using merA and merB3 gene primers/probes showed that five of the isolated Bacillus strains carry sequences similar to known merA and merB3 genes. Results of multiple sequence alignment revealed 99% similarity with merA and merB3 of TnMERI1 (class II transposons). Other mercury resistant Bacillus species lacking homology to these genes were not able to volatilize mercuric chloride, indicating the presence of other modes of resistance to mercuric compounds.