Submarine groundwater discharge and associated nutrient influx in surroundings of the estuary region at Gulf of Mannar coast, Indian Ocean.

The influx of fresh groundwater and re-circulated sea water into coastal ecosystem occurs through the submarine groundwater discharge (SGD). Measurement of salinity, radium tracers (224Ra, and 226Ra isotopes) and nutrients in estuarine water, coastal surface water and groundwater during December 2019 estimated the SGD and associated nutrient fluxes near the Karameniyar estuary (Gulf of Mannar) and surroundings of the Manapad region at southern part of Tamil Nadu state in India. The presence of excessive radium tracers revealed that the SGD was contributing to Ra desorption from the sediments and enrichment in the coastal waters. We estimated SGD of approximately 0.03-0.59 m3 m-2 d-1 for the Manapad region and relatively more homogeneous but comparatively less values in the Karameniyar estuary (0.03-0.34 m3 m-2 d-1). Higher average values of dissolved inorganic nitrogen (DIN; 43.62 µmol L-1) and soluble reactive phosphate (SRP; 1.848 µmol L-1) suggested greater influence of SGD on the overall coastal water nutrient budget. This study also indicated simultaneous occurrence of fresh and saline SGD in this region.

Human health risk assessment of heavy metal and pathogenic contamination in surface water of the Punnakayal estuary, South India.

Variation in levels of toxic heavy metals in river system during the COVID-19 pandemic lockdown might potentially assist in development of a public health risk mitigation system associated with the water consumption. The water quality of Punnakayal estuary in the Thamirabarani River system from the south India, a vital source of water for drinking and domestic purposes, industrial usage, and irrigation was assessed here. A comparitive assessment of physico-chemical variables (pH, EC, TDS, DO, BOD, turbidity and NO3), microbiological parameters (total coliform bacteria, fecal coliform bacteria, fecal streptococci and escherichia coli) and toxic metals (As, Cr, Fe, Cu, Zn, Cd, and Pb) suggested a decrease of 20% in the contaminant ratio during the lockdown period in comparison to the pre-lockdown period. The Health risk assessment models (HQ, HI, and TCR) highlighted carcinogenic and non-carcinogenic hazards for both children and adults through the ingestion and dermal adsorption exposures. The HI values for both As and Cr exceeded the acceptable limit (>1) during the lockdown period, but the potential risk for children and adults remained low in compaisio with the pre-lockdown period. Our results suggested that the Thamirabarani River system remained hostile to human health even during the lockdown period, and it requires regular monitoring through a volunteer water quality committee with private and government participations.

Characteristics of microplastics in the beach sediments of Marina tourist beach, Chennai, India.

Marina beach in Chennai metropolitan city attracts numerous tourists from all around the world, and it is an important ecological habitat for many life forms. Rapid urbanisation and industrial developments have led to excessive use of plastics and increased the amount of plastic waste generated in the natural environment. This first baseline study evaluates the microplastic (MP) accumulation in beach surface sediments of Marina and Pattinapakkam beaches through FTIR, AFM and SEM analyses. Sediment samples were collected from 40 stations and different types of MP polymers were identified. On average, 459 (60.8%) and 297 (39.2%) MP particles were found in the samples from Marina and Pattinapakkam beaches, respectively. We found that polyethylene types and additives are the dominant MPs in both areas. This study provided us with new insights into the human activities and natural processes in these marine environments. To solve the problem of plastic accumulation in the marine environment, the government should first play an active role in addressing the problem of plastic waste by introducing laws to control the sources of plastic waste and the use of plastic additives.

Measurement of submarine groundwater discharge (SGD) into Tiruchendur coast at southeast India using 222Rn as a naturally occurring tracer.

Application of natural tracers such as radon isotope mass balance has been useful in estimating the submarine groundwater discharge (SGD). This study used 222Rn and evaluated the magnitude of SGD at Tiruchendur coast of southeast India in the Gulf of Mannar (Indian Ocean). Higher magnitudes of 222Rn in the porewater and seawater in comparison with the groundwater suggest simultaneous SGD with fluxes of 0.1-0.25 m3 m-2 d-1 at offshore and 0.4-0.20 m3 m-2 d-1 at the near shore. These baseline data would contribute to the management and protection of the Gulf of Mannar region in near future.

Hydrogeochemical processes controlling the groundwater salinity in the coastal aquifers of Southern Tamil Nadu, India.

The current study identifies groundwater quality issues and investigates the most important geochemical processes that control seawater intrusion using various ionic ratios, hydrochemical facies evolution, and geochemical modelling. Cl-/Br ratio is an important indicator to identify the origin of groundwater salinity in coastal aquifers. Nineteen percent of the groundwater samples with Cl-/Br- ratio similar to that of Standard Mean Ocean Water (SMOW) are affected by seawater intrusion in the study area. Particularly, nine groundwater samples have high chloride values and are similar to SMOW, and it may derived salinity from seawater sources from the Bay of Bengal due to the over-pumping of production wells in the Uvari zone. Five samples are similar to SMOW, which is due to the presence of salt pan activities. The bivariate plots such as Ca2+ + Mg2+ vs Cl-, EC vs Cl-, and Na+/Cl- ratio indicate that seawater intrusion is the primary source for groundwater salinisation. Evaporation is the dominant process controlling groundwater chemistry, rather than rock-water interaction and precipitation, according to mechanisms controlling groundwater chemistry. Direct ion exchange and converse ion exchange are the critical controlling factors for groundwater salinisation, according to the hydrochemical facies evolution diagram (HFED). The water quality index (WQI) shows that most groundwater belongs to the poor to the marginal category. The saturation indices show that the groundwater samples are saturated with minerals such as dolomite, calcite, aragonite and magnesite. Therefore, these minerals are susceptible to precipitation due to the effective leaching of calcareous minerals from the bedrocks. Compiled hydrogeochemical analysis and multivariate statistical analysis revealed that the Tiruchendur and Uvari zone was affected by the seawater intrusion and led to an increase in the salinity of the groundwater.

Microplastics and trace metals in fish species of the Gulf of Mannar (Indian Ocean) and evaluation of human health.

The importance of microplastic (MPs) contamination in marine environments is reflected by increasing number of studies in fish species. Some even dedicated to the toxicological effects from the ingestion. Microplastics (MPs) and their trace metal composition were examined in the muscle and intestine of five commercially important fish species (i.e., Sufflamen fraenatus, Heniochus acuminatus, Atropus atropos, Pseudotriacanthus and Leiognathus brevirostris) from Thoothukudi at the Gulf of Mannar coast in south India. The abundance and morphology of MPs (size, shape, and texture) in muscle and intestinal were investigated by micro-Fourier Transform Infrared Spectroscopy (µ-FT-IR) and atomic force microscope (AFM). ICP-OES was used to investigate the adsorption/leaching of trace metals in microplastics in order to assess health risk for adults and children. Particles of 100-250 µm and white color dominated, and the mean abundances (items/100 g) of total MPs were more in Pseudotriacanthus (muscle: 51.2; intestine: 50.1) compared to Heniochus acuminatus (muscle: 9.6; intestine: 15), Leiognathus brevirostris (muscle: 12; intestine: 13.2) and Atropus atropus (muscle: 15.2; intestine: 44.1). Polyethylene (35.3%), polypropylene (27.2%), polyamide (nylon) (22.2%) and fiber (15.3%) represented the MPs present in muscles, and polyamide (nylon) (30.2%), polyethylene (28.1%), polypropylene (25.9%), and fiber (15.8%) composed the intestine MPs. We estimated possible consumption of 121-456 items of MPs/week by adults and about 19-68 items of MPs/week by children by considering the sizes of safe meals. Zn, Cu, Mn and Cr in these fish species reflected influence of the sewage waste. However, the non-carcinogenic risk evaluated through EDI, THQ, HI, and CR did not suggest any immediate health problem for the consumers.

Assessment of groundwater from an industrial coastal area of south India for human health risk from consumption and irrigation suitability.

We assessed the groundwater quality in an industrial area (Tiruchendur Taluk) of Tamil Nadu state in coastal south India for human health risk from drinking as well as irrigation suitability by using the drinking water quality index (DWQI), irrigation factors (sodium adsorption ratio, sodium percentage, residual sodium carbonate and permeability index) and health hazard valuation (THQI- by consuming NO3- and F-). About 57% of the samples represented Ca2+-Mg2+-Cl--SO42- facies and the anthropological unhygienic inputs elevated the salinity. Our results indicated that all the samples are unsuitable for drinking (DWQI up to 1063) and almost half of them are also unsuitable for irrigation due to sodium risk. Total hazard quotient index (THQI; HQ nitrate and HQ fluoride) suggested the order of health risk as children > women > men with about 64%, 70% and 79% of the samples posing non-carcinogenic risks for men, women and children, respectively. Different mitigation measures and sustainable development should be enforced to minimize the health issues from contamination caused by industries, fertilizers in agro-fields and natural processes and reduce the sodium dominance in groundwater. The spatial distribution maps of this study could also be helpful in organization of proper treatment plans to provide safe and hygienic groundwater to the community.

Differentially expressed miR-20, miR-21, miR-100, miR-125a and miR-146a as a potential biomarker for prostate cancer.

Prostate cancer is the leading cause of death among men worldwide. Deregulation of microRNAs has been reported in many cancers. Expression of microRNAs miR-20a-5p, miR-21-5p, miR-100-5p, miR-125a-5p and miR-146a-5p in tissue blocks of histologically confirmed prostate cancer patients compared with BPH patients, to identify potential microRNA biomarker for prostate cancer. MicroRNA was isolated and expression was quantified by qRT-PCR using Taqman Advanced microRNA assay kits. The interactions between the microRNA:target mRNA were predicted by using bioinformatics tools such as miRwalk and miRTargetlink. The experimentally validated targets were analysed using gprofiler to identify their molecular function, biological process and related pathways. The expression analysis revealed that miR-21 and miR-100 were significantly down-regulated whereas miR-125a was up-regulated in prostate cancer patients. Comparative analysis of the expression levels with tumor grading reveal that miR-100 was significantly down-regulated (p < 0.05) in high grade tumor, indicating that miR-100 associated with prostate cancer. ROC analysis revealed that combined analysis of down-regulated miRNAs (miR-21 and miR-100) shown AUC of 0.72 (95% CI 0.65-0.79). The combined analysis of all five miRNAs showed AUC of 0.87 (95% CI 0.81-0.92). The targets prediction analysis revealed several validated targets including BCL2, ROCK1, EGFR, PTEN, MTOR, NAIF1 and VEGFA. Our results provide evidence that combined analysis of all the five miRNAs as a panel can significantly improve the prediction level of the presence of prostate cancer and may be used as a potential diagnostic biomarker.

Microbial contamination and its associations with major ions in shallow groundwater along coastal Tamil Nadu.

Microbes in groundwater play a key role in determining the drinking water quality of the water. The study aims to interpret the sources of microbes in groundwater and its relationship to geochemistry. The study was carried out by collecting groundwater samples and analyzed to obtain various cations and anions, where HCO3-, Cl- and NO3- found to be higher than permissible limits in few samples. Microbial analysis, like total coliform (TC), total viable counts (TVC), fecal coliforms (FC), Vibrio cholera (V. cholerae) and total Streptococci (T. streptococci) were analyzed, and the observations reveal that most of the samples were found to be above the permissible limits adopted by EU, BIS, WHO and USEPA standards. Correlation analysis shows good correlation between Mg2+-HCO3-, K+-NO3-, TVC- V. cholerae and T. streptococci-FC. Major ions like Mg+, K+, NO3, Ca2+ and PO4 along with TS and FC were identified to control the geochemical and microbial activities in the region. The magnesium hardness in the groundwater is inferred to influence the TVC and V. cholerae. The mixing of effluents from different sources reflected the association of Cl with TC. Population of microbes T. streptococci and FC was mainly associated with Ca and Cl content in groundwater, depicting the role of electron acceptors and donors. The sources of the microbial population were observed with respect to the land use pattern and the spatial distribution of hydrogeochemical factors in the region. The study inferred that highest microbial activity in the observed in the residential areas, cultivated regions and around the landfill sites due to the leaching of sewage water and fertilizers runoff into groundwater. The concentrations of ions and microbes were found to be above the permissible limits of drinking water quality standards. This may lead to the deterioration in the health of particular coastal region.

Hazardous microplastic characteristics and its role as a vector of heavy metal in groundwater and surface water of coastal south India.

Study of hazardous microplastics in the natural water resources is minimal compared to the sea salt, seafood and even packaged water. We presented results of the first baseline research of microplastics in groundwater and surface water from the coastal south India (Tamil Nadu state) and evaluated the heavy metal adsorption capacities of different polymers. The microplastics (up to 19.9 particles/L) were of relatively larger size in surface water (0.34-4.30 mm) compared to the groundwater (0.12-2.50 mm). Polyamide (nylon), polyester, polypropylene, polyethylene, polyvinyl chloride and cellulose were the common polymers and all of them showed different capacities of heavy metal adsorption. In two different experimental sites, the polypropylene showed higher capacity of adsorption compared to other polymers in the following orders: (i) cadmium > manganese > lead > arsenic and (ii) manganese > zinc > arsenic > lead > copper. The polyamide, however, exhibited better adsorption only for manganese. Similar to other recent findings, our results associate microplastics as a major vector to transport heavy metals in the water system. Formulation of strategies to reduce the environmental risks of particulate plastics as a potent vector for transportation of the toxic trace elements and subsequent, impact on human health through the OSPRC framework (Origins, Sources, Pathways, Receptors and Consequence) in the study area would require future research.

Ureteral Avulsion during Semirigid Ureteroscopy: A Single-Centre Experience.

AIMS: The aim of the study is to present our experience with the management of ureteral avulsions following semirigid ureteroscopy for ureteral stones. This is one of the largest series reported so far. METHODS AND MATERIALS: It is a retrospective and observational study done at Sri Ramachandra Institute of Higher Education and Research over the last 18 years. RESULTS: There were seven cases of ureteral avulsion following semirigid ureteroscopy. All patients were males with a mean age of 35.7 years. All had impacted stones, with proximal ureteric location in 6 patients and distal ureteric location in 1 patient. Five cases had two-point avulsions with loss of entire ureter. Two cases had one-point avulsion: one distal ureteric and the other mid-ureteric. Of the five cases with whole length ureteral avulsion, four were managed by classical ileal replacement of ureter and the the fifth case was managed by ileal replacement of ureter by the Yang-Monti technique. Of the two cases with one-point avulsion, one was managed by uretero-neocystostomy and the other by uretero-ureterostomy. All the patients had successful outcome. CONCLUSIONS: Even though rare, ureteral avulsion can potentially happen especially when dealing with impacted ureteric stones. Being conscious of the possible occurrence of this serious complication during any difficult ureteroscopy and exercising utmost care during the procedure are important preventive measures. However, this catastrophe can be successfully managed by either immediate definitive repair or in a staged manner.

Modeling Commodity Flow in the Context of Invasive Species Spread: Study of Tuta absoluta in Nepal.

Trade and transport of goods is widely accepted as a primary pathway for the introduction and dispersal of invasive species. However, understanding commodity flows remains a challenge owing to its complex nature, unavailability of quality data, and lack of systematic modeling methods. A robust network-based approach is proposed to model seasonal flow of agricultural produce and examine its role in pest spread. It is applied to study the spread of Tuta absoluta, a devastating pest of tomato in Nepal. Further, the long-term establishment potential of the pest and its economic impact on the country are assessed. Our analysis indicates that regional trade plays an important role in the spread of T. absoluta. The economic impact of this invasion could range from USD 17-25 million. The proposed approach is generic and particularly suited for data-poor scenarios.

SARS-CoV-2 pandemic lockdown: Effects on air quality in the industrialized Gujarat state of India.

Two weeks after the world health organization described the novel coronavirus (SARS-CoV-2) outbreak as pandemic, the Indian government implemented lockdown of industrial activities and traffic flows across the entire nation between March 24 and May 31, 2020. In this paper, we estimated the improvements achieved in air quality during the lockdown period (March 24, 2020 and April 20, 2020) compared to the pre-lockdown (January 1, 2020 and March 23, 2020) by analyzing PM2.5, PM10, SO2, CO, NO2 and O3 data from nine different air quality monitoring stations distributed across four different zones of the industrialized Gujarat state of western Indian. The Central Pollution Control Board (CPCB)-Air Quality Index (AQI) illustrated better air qualities during the lockdown with higher improvements in the zones 2 (Ahmedabad and Gandhinagar) and 3 (Jamnagar and Rajkot), and moderate improvements in the zones 1 (Surat, Ankleshwar and Vadodra) and 4 (Bhuj and Palanpur). The concentrations of PM2.5, PM10, and NO2 were reduced by 38-78%, 32-80% and 30-84%, respectively. Functioning of the power plants possibly led to less reduction in CO (3-55%) and the declined emission of NO helped to improve O3 (16-48%) contents. We observed an overall improvement of 58% in AQI for the first four months of 2020 compared to the same interval of previous year. This positive outcome resulted from the lockdown restrictions might help to modify the existing environmental policies of the region.

Imprints of pandemic lockdown on subsurface water quality in the coastal industrial city of Tuticorin, South India: A revival perspective.

Globally, the incidences of environmental improvements owing to seizing the anthropogenic activities during the lockdown have been reported through news articles and photographs, yet a formal scholarly study has been lacking to substantiate the imprints of lockdown. We hereby present the imprints of lockdown on water quality (both chemical and biological) parameters during the nationwide lockdown (COVID-19 epidemic) in India between 25th March to 30th May 2020. The present study describes the changes in chemical and biological water quality parameters based on twenty-two groundwater samples from the coastal industrial city of Tuticorin in Southern India, taken before (10 and 11th February 2020) and during the lockdown (19 and 20th April 2020) periods. The physico-chemical parameters compared are pH, total dissolved solids (TDS) and electrical conductivity (EC), nitrate (NO3), fluoride (F), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), arsenic (As), and selenium (Se), and the bacterial parameters are total coliforms, fecal coliforms, E. coli, and fecal streptococci. Among the metals, the significant reductions in Se (42%), As (51%), Fe (60%) and Pb (50%) were noticed probably owing to no or very less wastewater discharges from metal-based industries, seafood-based industries and thermal power plants during the lockdown. Reduction in NO3 (56%), total coliform (52%) and fecal coliforms (48%) indicated less organic sewage from the fishing industries. Contents of Cr, Cu, Zn and Cd, however, remained similar and fluoride did not show any change, probably as they were sourced from rock-water interactions. Similarly, we did not observe alterations in E. coli and fecal streptococci due to no significant change in domestic sewage production during the lockdown. The multivariate analyses aptly illustrated this and the principal component analyses helped to identify the sources that controlled water qualities of the lockdown compared to the pre-lockdown period. Our observation implies that groundwater is definitely under active interaction with surface waters and thus a quick revival could be observed following the seizing of anthropogenic activities.

Commentary on Ferguson, et al., "Impact of Non-pharmaceutical Interventions (NPIs) to Reduce COVID-19 Mortality and Healthcare Demand".

A recent manuscript (Ferguson et al. in Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand, Imperial College COVID-19 Response Team, London, 2020. https://www.imperial.ac.uk/media/imperial-college/medicine/sph/ide/gida-fellowships/Imperial-College-COVID19-NPI-modelling-16-03-2020.pdf) from Imperial College modelers examining ways to mitigate and control the spread of COVID-19 has attracted much attention. In this paper, we will discuss a coarse taxonomy of models and explore the context and significance of the Imperial College and other models in contributing to the analysis of COVID-19.

Microplastic presence in commercial marine sea salts: A baseline study along Tuticorin Coastal salt pan stations, Gulf of Mannar, South India.

The present baseline research infers that the salts present in the sea may contain microplastics (MPs), as the seawater is contaminated due to a number of anthropogenic activities. Herein, 25 types of sea salt samples were collected from salt pans located in the Tuticorin coastal region. The MPs present in the samples were separated and identified by various methods such as handpicking, visual classification, and micro-Fourier transform infrared spectroscopy (µ-FT-IR) and atomic force microscopy (AFM). The MPs that measured less than 100 µm formed the major part of the salts, accounting to 60% of the MPs among the total pollutants. The MPs that were found in abundance in the sea salts were polypropylene, followed by polyethylene, nylon, and cellulose. This study was conducted in salt pan areas and demarcated the percentage of MPs present in sea salts. Table salt, which is a prime edible commodity, was found to be contaminated with MPs through polluted seawater, which poses a threat to public health.

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

The combined studies on grain size distribution, organic matter contents of sediments, sequential extraction and bulk concentration of heavy metals, statistical analysis, and ecological risk assessments were carried out to investigate the contamination sources and ecological risks of surface sediments at Coleroon River Estuary in Tamil Nadu, India. The sequential extraction of metals showed that a larger portion of the metals was associated with the residual phase and also in other fractions. The low concentrations of heavy metals were found in exchangeable and carbonate bounds (bioavailable phases). It revealed that sediments of Coleroon River Estuary were relatively unpolluted and were influenced mainly by natural sources. The observed order of bulk concentrations of heavy metals in the sediments was as follows: Fe > Mn > Zn > Cu > Pb > Cr > Ni > Co. Factor analyses represented that the enrichment of heavy metals was mostly resulted from lithogenic origins associated with anthropogenic sources. These sources were reconfirmed by cluster analysis. Risk assessment code (RAC) suggested that all metals were not harmful in monsoon season. However, Fe was in medium risk, and Mn and Cu were in low risk in summer. According to pollution load index (PLI) of sediments, all heavy metals were toxic. Cu might be related with adverse biological effects on the basis of sediment quality guidelines (SQG) in both seasons. These integrated approaches were very useful to identify the contamination sources and ecological risks of sediments in estuarine environment. It is expected that this research can give a useful information for the remediation of heavy metals in sediments.

Comprehensive studies of hydrogeochemical processes and quality status of groundwater with tools of cluster, grouping analysis, and fuzzy set method using GIS platform: a case study of Dalcheon in Ulsan City, Korea.

This research aimed at developing comprehensive assessments of physicochemical quality of groundwater for drinking and irrigation purposes at Dalcheon in Ulsan City, Korea. The mean concentration of major ions represented as follows: Ca (94.3 mg/L) > Mg (41.7 mg/L) > Na (19.2 mg/L) > K (3.2 mg/L) for cations and SO4 (351 mg/L) > HCO3 (169 mg/L) > Cl (19 mg/L) for anions. Thematic maps for physicochemical parameters of groundwater were prepared, classified, weighted, and integrated in GIS method with fuzzy logic. The maps exhibited that suitable zone of drinking and irrigation purpose occupied in SE, NE, and NW sectors. The undesirable zone of drinking purpose was observed in SW and central parts and that of irrigation was in the western part of the study area. This was influenced by improperly treated effluents from an abandoned iron ore mine, irrigation, and domestic fields. By grouping analysis, groundwater types were classified into Ca(HCO3)2, (Ca,Mg)Cl2, and CaCl2, and CaHCO3 was the most predominant type. Grouping analysis also showed three types of irrigation water such as C1S1, C1S2, and C1S3. C1S3 type of high salinity to low sodium hazard was the most dominant in the study area. Equilibrium processes elucidated the groundwater samples were in the saturated to undersaturated condition with respect to aragonite, calcite, dolomite, and gypsum due to precipitation and deposition processes. Cluster analysis suggested that high contents of SO4 and HCO3 with low Cl was related with water-rock interactions and along with mining impact. This study showed that the effluents discharged from mining waste was the main sources of groundwater quality deterioration.

An assessment of selected hydrochemical parameter trend of the Nakdong River water in South Korea, using time series analyses and PCA.

Time series analyses (autocorrelation, spectral density, and cross-correlation) and principal component analysis (PCA) were used to understand the characteristics of the selected hydrochemical parameters pH, turbidity, alkalinity, Cl, hardness, total dissolved solids (TDS), and metals Fe and Mn in the Nakdong River, South Korea. Autocorrelation and spectral density for pH, alkalinity, hardness, and Cl were very similar to TDS, whereas Fe, Mn, and turbidity showed different trends from TDS. Cross-correlograms of pH, alkalinity, hardness, and Cl versus TDS were very similar to each other. Those of Fe and turbidity represented the opposite relations with other components. Cross-correlation coefficients had the highest values at zero lag, indicating that pH, alkalinity, hardness, and Cl are controlling factors for TDS. On the other hand, Fe and turbidity showed the highest values at 6-month lag and Mn at a month lag. PCA indicated that TDS had very close relation with hardness, pH, and Cl and very small relation with Mn. Turbidity and Fe had relatively opposite relations with TDS. It was concluded that the geostatistical methods were very useful for evaluating the hydrochemical characteristics of the Nakdong River water in South Korea.

Speciation of selected heavy metals geochemistry in surface sediments from Tirumalairajan river estuary, east coast of India.

Surface sediment samples from the Tirumalairajan river estuary were studied for grain size pattern, organic matter, and heavy metals (Fe, Mn, Zn, and Pb) using the sequential and bulk metal extraction methods to evaluate metal behavior. Ten surface sediment samples were collected during the monsoon and summer seasons of the year 2009. The observed orders of concentrations of heavy metals in the sediments were as follows: Fe > Mn > Zn > Pb. The results obtained from sequential extraction showed that, among the metals studied, a larger portion of the metals were associated with the residual phase, although they are available in other fractions. The low concentration of metals available in bioavailable phases indicated that the sediments of Tirumalairajan river estuary were relatively unpolluted. Correlation analysis was also carried out to understand the associations of metals in different phases with sand, silt, clay, and organic matter. To understand the risk of heavy metals to sediment-dwelling organisms, the data were compared with risk assessment code and sediment quality values using the screening quick reference table. The main source of metals to the estuary is from the irrigation field and its associated activities in the study area.