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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. [Display omitted] • Quantification of groundwater discharge (SGD) at southeast coast of India using 222Rn mass balance. • SGD fluxes of 0.1–0.25 m3 m−2 d−1 at offshore and 0.4–0.20 m3 m−2 d−1 at nearshore. • Simultaneous SGD through comparison of magnitudes of 222Rn in porewater and seawater with the groundwater. • Necessity of public awareness for better coastal management and environmental protection at Gulf of Mannar (Indian Ocean). [ABSTRACT FROM AUTHOR]

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. Image 1 • The present attempt was carried out to Preliminary study on Microplastics pollution in commercial marine sea salt along Tuticorin Coast, Gulf of Mannar, SE coast of India. • Various types of microplastics was identified, including nylon (NY) cellulose (CL), polyethylene (PE), polypropylene (PP) and some microplastics or nonplastic particles, were also unidentified. • A microplastic was measuring less than 100 μm represented the major part of the particles, computing for 60% of the total microplastics. • The possible anthropogenic sources of the microplastics in the salt pans are from city people dumped plastic waste via buckle channel. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • The radium isotopes-based SGD flux estimations in the Manapad region and Karamaniyar estuary (Gulf of Mannar) were 0.03–0.59 m3 m−2 d−1 and 0.03–0.34 m3 m−2 d−1, respectively. • The radon mass balance model estimated SGD flux for the Manapad region and Karamaniyar estuaries remained 0.02–0.43 m3 m−2 d−1 and 0.04–0.38 m3 m−2 d−1, respectively. • SGD influx was the primary source of dissolved inorganic nitrogen (DIN) into the marine system and the contribution of nutrient by the Karamaniyar River was lower compared to the SGD. • In the near future, a more detailed investigation of seasonal fluctuations in SGD and SGD-derived nutrient fluxes should be conducted. [ABSTRACT FROM AUTHOR]

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 NO 3 − and F −). About 57% of the samples represented Ca2+-Mg2+-Cl−-SO 4 2− 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. [Display omitted] • Three-dimensional approach (drinking water quality, irrigation and human health) of groundwater evaluation from south India. • DWQI based unsuitability of all samples for drinking. • Almost half of the samples are inappropriate for irrigation due to sodium risk. • HQ fluoride and HQ nitrate-based estimation of the low-risk range violation for men, women and children. [ABSTRACT FROM AUTHOR]

The potential for health risks to humans consuming seafood is investigated in this paper through a sampling study of 6 fish species at 7 sites of the Tuticorin coastal region, India, in terms of 8 trace metals measuring their excess concentrations at gills, livers and muscles. An understanding of the complexity of the problem is systematised using Sources-Pathways-Receptors-Consequences framework, in which quantitative results are produced as follows: (i) multivariate statistical techniques provide a focus on sources-pathways by both factor and cluster analyses; (ii) ecological health risk assessment for both children and adults provide a focus on consequences in terms of Hazard Index (HI) and Carcinogenic Risk (CR). An analysis of the data shows that concentrations of metallic elements are found to be mostly in the following order: Zn > Cd > Mn > Cu > Cr > Pb > Fe > Co; likewise the fish species from higher to lower mean concentrations were found to be in the following order: 1.Megalops cyprinoides; 2.Leiognathus brevirostris; 3.Atropus atropos 4.Pseudotriacanthus; 5.Terapon jarbua; 6.Terapon puta. The mean concentration of fish in gills, muscles and livers are indicative of serious pollution with observed impacts on especially children. Pollution sources are detected by factor analysis (e.g. Factor 1: Pb, Mn and Cr); as well as by cluster analysis (e.g. Cluster 1: Cu). The relationship between the metals provide positive loading, which indicates that metals are derived from the same sources. Their variegated sources can now be associated with chemical industries, agricultural discharges and municipal sewage. The results confirm that various fish organs are effective bio-indicators for the identification of coastal areas unprotected to metallic poisons; and as such they are pathways to risks to children and adults by accumulation of trace metallic concentrations and measured in terms of a number of indicators. • The study measured 8 trace metals at gill, liver and muscle with 4 being excessive. • Sources for health risks were identified to be related to industrial and other plants. • Fishes at the study area act as receptors of trace metal in risk exposure processes. • Indexed risk consequences to children/adults of the region are evidenced in the region. [ABSTRACT FROM AUTHOR]