Trace element concentrations and their potential ecological risk in the reef sediments of coral islands, Vembar group of islands, Gulf of Mannar, India

The present work was undertaken to assess the impact of trace element concentration and the status of potential ecological risk in the reef sediments of the Vembar group of islands, Gulf of Mannar Marine National Park, India. Totally, 114 reef sediments (surface) were collected from the Vembar group of islands (Nallathanni Island - 36 samples; Upputhanni Island - 48 samples; Puluvinichalli Island-30 samples). The reef sediments are enriched with sand-sized calcareous particles. The calcium carbonate percentage (CaCO₃) was primarily controlled by the distribution of coral colonies and available lithogenic grains. The pollution load index (PLI) reveals that the majority of the sediments fall under the unpolluted category. Moreover, the potential ecological risk (PERI) and sediment pollution index (SPI) reveals that the Vembar group of islands fall under the low ecological risk category.

Bioavailable trace metals and their ecological risks in the tourist beaches of the Southeast coast of India

The concentration of Acid Leachable Trace Metals (ALTMs) was assessed in urbanized tourist beaches (96 samples from Marina beach, 34 samples from Edward Elliot's beach, and 28 samples from Silver beach) of southeast coast of India. The concentration of metals accumulated in the beach sediment was less than the Upper Continental Crust (UCC) background reference values. The mean enrichment of ALTMs in the studied urban tourist beaches showed the following descending order: Marina beach - Cr > Pb > Ni > Zn > Cu > Mn > Co; Edward Elliot's beach - Cr > Pb > Ni > Mn > Co > Zn > Cu; Silver beach - Cr > Pb > Ni > Co > Mn > Cu > Zn. The ALTMs such as Fe, Mn, Co, Cu, and Zn were probably derived from natural weathering and mild anthropogenic influences whereas other metals were derived from anthropogenic induced factors.

Characterization and distribution of microplastics and plastic debris along Silver Beach, Southern India

Microplastics are causing serious environmental threats worldwide. To evaluate the current state of microplastics pollution, 28 sediment samples were examined for microplastics and plastic debris contamination along Silver Beach, Southern India. Visual identification followed by FT-IR spectroscopy was used to estimate the overall distribution and characterization of plastic debris. The results reveal that white-colored (44%) and irregularly-shaped (82%) plastics are prevalent in the study area. Moreover, the dominant polymer in the study area is polyvinyl chloride (79%) followed by polyethylene (14%) and nylon (7%). Based on size fractions, mesoplastics are widely distributed in the beach sediments (65%), followed by microplastics (18%) and macroplastics (17%). The regional sources of plastic debris are tourism and fishing activities followed by storm water runoff through the Gadilam river and wave-induced deposition through high tides. Strict policy measures need to be implemented in recreational beaches like Silver beach to reduce plastic pollution.

A baseline study on elemental concentration and potential ecological risk status of the surface sediments of Ashtamudi Lake, south west coast of India

Element concentration (Fe, Mn, Pb, Zn, Cu, Cr, Ni and Co) in the surface sediments of Ashtamudi estuary, Southwest coast of India, has been analyzed to understand the spatial variation and potential ecological risk status. The sediment pollution index and Potential Ecological Risk index suggest that the northeastern part of the estuary exhibits low to moderate polluted sediments with moderate ecological risk. The results of correlation analysis indicate that the natural weathering process and river input play an important role in the distribution of the elements in the surface sediments of the estuary. The extracted factor results indicate that the fine sediment fractions supporting for accumulation of the trace elements, whereas the enriched level of Fe and Mn is chiefly controlled by the riverine process, and other elements are contributed by anthropogenic influences.

Macrodebris and microplastic distribution in the beaches of Rameswaram Coral Island, Gulf of Mannar, Southeast coast of India: A first report

This is the first study on the distribution and characteristics of plastic debris found in the sediments of Rameswaram Island, Gulf of Mannar, India. Studies on the distribution of plastics and microplastic content in highly populated coral islands and their impact on the coral ecosystem are very scarce. For this purpose, marine sediment samples were collected from 20 locations along the coastal areas of the study region. The distribution and characterization study was carried out by visual examination followed by FTIR spectroscopy. The results showed abundance of white-colored and irregular-shaped plastic debris in this study area. Polypropylene was identified as a dominant polymer variety, followed by polyethylene, polystyrene, nylon, and polyvinyl chloride. Tourist activities and fishing practices were found to be the possible sources of the microplastic debris. Additionally, the distribution of the plastics was found to be dominantly controlled by the aeolian process and the nature of the coast.

A baseline study on trace element based sediment pollution and potential ecological risk of reef sediments of Musal, Manoli and Manoli putti Islands, Gulf of Mannar, India

The aim of the present study is to assess the baseline level of the trace element, sediment pollution and potential ecological risk of reef associated sediments of Musal, Manoli and Manoli putti Islands, Gulf of Mannar, India. The grain size distribution of the sediments is chiefly controlled by corals and broken shell debris. The distribution of lithoclastic fractions and element concentration are most probably derived from longshore sediment transport and fluvial process from nearby mainland. The enrichment of organic matter is chiefly controlled by mangrove litters and sea grasses. The concentration of lead in the marine sediments is subjected to sediment matrix, vicinity of the local pollutant sources and distance from the mainland coast. The ecological risk assessment clearly reveals that the sediments belong to the low risk category.

Elemental concentration and potential ecological risk assessment of reef associated surface sediments of Appa Island, Gulf of Mannar Biosphere Reserve, Southeast coast of India

Thirty three surface sediments were collected for the present study to assess the elemental concentration and its associated ecological risk in the reef associated surface sediments, Appa Island, Gulf of Mannar Biosphere Reserve, South east coast of India. The distribution of calcium carbonate in the reef sediments is controlled by coral debris and shell fragments whereas the Organic matter (OM) content are chiefly derived from mangroves and sea grasses. The circulation of trace elements and Fe, Mn are controlled by the fluvial process and re-suspended sediments. The concentration of Pb was primarily controlled by migration of pollutants through long shore sediment transport process. The main source of Pb in the study area is from coal incinerating power plants and coal handling operations from harbors.

A baseline study on the concentration of trace elements in the surface sediments off Southwest coast of Tamil Nadu, India

Forty two surface sediment samples were collected in order to document baseline elemental concentration along the Southwest coast of Tamil Nadu, India. The elements detected were Manganese (Mn), Zinc (Zn), Iron (Fe), Copper (Cu), Nickel (Ni) and Lead (Pb). The concentration of Fe and Mn was primarily controlled by the riverine input. The source of Pb and Zn is attributed to leaded petrol and anti-biofouling paints. The calculated index (EF, Igeo and CF) suggests that the sediments of the study area are significantly enriched with all elements except Pb. The contamination factor showed the order of Mn>Zn>Fe>Cu>Ni>Pb. The sediment pollution index (SPI) revealed that the sediments belonged to low polluted to dangerous category. The correlation matrix and dendrogram showed that the elemental distribution was chiefly controlled by riverine input as well as anthropogenic activity in the coast.

Geospatial risk assessment and trace element concentration in reef associated sediments, northern part of Gulf of Mannar biosphere reserve, Southeast Coast of India

Fifty two surface sediments were collected from the northern part of the Gulf of Mannar biosphere reserve to assess the geospatial risk of sediments. We found that distribution of organic matter and CaCO₃ distributions were locally controlled by the mangrove litters and fragmented coral debris. In addition, Fe and Mn concentrations in the marine sediments were probably supplied through the riverine input and natural processes. The Geo-accumulation of elements fall under the uncontaminated category except Pb. Lead show a wide range of contamination from uncontaminated-moderately contaminated to extremely contaminated category. The sediment toxicity level of the elements revealed that the majority of the sediments fall under moderately to highly polluted sediments (23.07-28.84%). The grades of potential ecological risk suggest that predominant sediments fall under low to moderate risk category (55.7-32.7%). The accumulation level of trace elements clearly suggests that the coral reef ecosystem is under low to moderate risk.

Trace element concentrations in reef associated sediments of Koswari Island, Gulf of Mannar biosphere reserve, southeast coast of India

Extensive field work was conducted in order to assess the sediment pollution level and potential ecological risk on coral reef ecosystem. Thirty three surface sample was collected using grid sampling technique. The calcium carbonate and organic matter were primarily controlled by the distribution of coral rubbles and seagrass meadows. The concentration of trace elements is higher than the crustal average in few locations and the same result was derived from index calculations. However, the significant concentration of lead was observed throughout the study area. The elevated level of lead is probably due to coal incinerating power plants, and confluence of urban runoff from the nearby coastal areas. Based on the sediment pollution index, the majority of the sediments belongs to highly polluted to dangerously polluted category. The ecological risk indicates that the sediments are under low risk to moderate risk category and this result was proved by correlation analysis.

Spatial risk assessment and trace element concentration in reef associated sediments of Van Island, southern part of the Gulf of Mannar, India

Forty eight surface sediment samples were collected from the vicinity of Van Island in order to assess the sediment pollution level and potential ecological risk on coral reef ecosystem. The analytical and correlation results indicate a distribution of elements is chiefly controlled by the CaCO₃ and OM. The enrichment factor and geoaccumulation index show the elevated level of Pb in the surface sediments is due to application of lead petrol and coal incinerating power plants. The sediment pollution index reveals that majority of the sediments falling under highly polluted sediment category (35.4%) followed by moderately polluted (25%) and dangerous sediment category (14.58%). The potential ecological risk suggests that nearly 66.6% of the samples falling under the low risk category, moderate risk category (20.8%) followed by considerable risk category (8.33%) and very high risk category (4.1%). The accumulation level of trace elements clearly suggests that the coral reef ecosystem is under low risk.

Hydrogeochemical study of shallow carbonate aquifers, Rameswaram Island, India

Groundwater quality assessment has been carried out based on physicochemical parameters (pH, EC, TDS, CO(3), HCO(3), Cl, SO(4), PO(4), NO(2), Ca(+2), Mg(+2), Na(+) and K(+)) and metal concentration in the Rameswaram Island from 25 bore wells. The Langelier Saturation Index of the groundwater shows positive values (63% samples) with a tendency to deposit the CaCO(3) in the majority of water samples. Scatter plot (Ca + Mg/HCO(3)) suggests carbonate weathering process, which is the main contributor of Ca(2+), Mg(2+) and HCO(3) ions to the water. Gibbs diagram suggests rock-water interaction dominance and evaporation dominance which are responsible for the change in the quality of water in the study area. NaCl and mixed CaNaHCO(3) facies are two main hydrogeochemical facies of groundwater. Mathematical calculations and graphical plots of geochemical data reveal that the groundwater of Rameswaram Island is influenced by natural weathering of rocks, anthropogenic activities and seawater intrusion due to over exploitation. Weathering and dissolution of carbonate and gypsum minerals also control the concentration of major ions (Ca(+2), Mg(+2), Na(+) and K(+)) in the groundwater. The nutrient concentration of groundwater is controlled to a large extent by the fertilizers used in agricultural lands and aquaforms. Comparison of geochemical data shows that majority of the groundwater samples are suitable for drinking water and irrigation purposes.