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The present study aims to document the contamination levels and ecological risks of heavy metals in the sediments of Kavaratti lagoon, India. A total of 15 sediment samples were collected for the analysis of Al, Pb, Cd, Cu, Cr, Mn, Ni and Zn. The decreasing trend of heavy metals was observed in the lagoon sediment as Pb Zn Al Mn Ni Cr Cd Cu. The Geo-accumulation index (Igeo) results indicate that Cu, Cr, Mn, Ni and Zn were uncontaminated, while Cd was strong to extremely contaminated and Al and Pb were moderately contaminated. The enrichment factors (EF) of Cd and Pb range from moderate to extremely high (EF 1) indicating that they have anthropogenic origin on Kavaratti Island. The Contamination factor (Cf) indicated that Cd, Pb and Al belong to a high risk of contamination (Cf 6). The pollution load index (PLI) value near one suggested that a moderate level of pollution occurs in the study area. The modified degree of contamination (mCd) shows that Al, Cd and Pb have an ultra- higher degree of contamination (mCd ≤ 32). The potential ecological risk (RI) index confirmed that Pb and Cd have considerable to the serious thread of ecological risk (RI 600). Additionally, multivariate statistical analysis and pollution indexes showed that the Kavaratti lagoon is moderate to considerably polluted by heavy metals. Diesel-based power generation, activities related to shipping, untreated sewage, fishing and tourism activities are the main anthropogenic sources of heavy metal pollution on Kavaratti Island.

This paper summarizes the spatio-temporal variation of phytoplankton and zooplankton assemblages in Kavaratti lagoon and offshore water of Lakshadweep Archipelago, India. The objective of this study was to evaluate phytoplankton and zooplankton assemblage with responses to changing environmental conditions in Kavaratti lagoon and offshore water. Samples were collected and analysed during the pre-monsoon and post-monsoon season during 2016. During this period, in total, 69 species of zooplankton and 54 species of phytoplankton were identified. The population density of various groups of zooplankton found to be of the following order: Crustacea > Foraminifera > Porifera > Chaetognatha > Ciliophora > Appendicularia. Similarly, phytoplankton composed of the order of Bacillariophyceae > Dinophyceae > Chlorophyceae > Cyanophyceae. The highest population densities were recorded in the pre-monsoon period of the study. The lagoon region recorded the maximum plankton distribution than the offshore region. Crustaceans exhibit maximum diversity and richness in all the stations and seasons studied. Macrosetella gracilis (711 nos/m3) was the most dominant zooplankton species observed and which may be attributed to the availability of preferential food and favorable environmental conditions. There is a significant effect of water salinity on the population density of Daphnia magna (652 nos/m3) has been noticed during the pre-monsoon season of the study. Daphnia magna is well adapted to certain fluctuations, such as low oxygen conditions, high pH, wide ranges of salinity, and temperature. Among the phytoplankton, diatoms, such as Bellerochea malleus (20,160 nos/m3), Coscinodiscus gigas (1180 nos/m3), Eucampia zodiacus (880 nos/m3), and Rhizosolenia alata (2380 nos/m3), were dominant during the study. The Shannon–Wiener Diversity Index (0.183–2.587) for phytoplankton represents moderate level of pollution in the Kavaratti Island. The canonical correspondence analysis (CCA) confirms that the positive correlation of environmental parameters, such as water temperature, salinity, ammonia, nitrates, and silicates, on the distribution and assemblages of the plankton community.

In our laboratory, we synthesized a novel surface tailored activated charcoal in removing nitrite species from fertilizer industrial effluents. A customized high temperature carbonate-steam activation technique was adopted to develop the sodium carbonate impregnated activated charcoal (SCIAC). The surface properties of the material were determined using SEM, TG and X-RD techniques. Batch adsorption experiments were performed for optimizing various conditions such as solution pH, contact time, temperature and adsorbent dose for maximizing the nitrite adsorption onto SCIAC. Considerably, a very high nitrite adsorption percentage of 83.8 was obtained for an initial nitrite concentration of 5.0 mg/L at pH 3.0. Among the various equilibrium and kinetic models, Freundlich and pseudo-second-order expressions, respectively, were well enough to explain the adsorption processes. In general, it may conclude that the change in surface characteristics of the adsorbent material after the pyrolysis process is highly favorable for effective removal of nitrite ions from aqueous systems. Adsorption capacity of SCIAC was 27.03 mg/g and studies revealed that the material was feasible in removing nitrite from industrial effluents.

The continuum fluctuations of river water quality and the metal contamination within the sediments of Netravati river basin were analysed using multivariate techniques and environmental indices. Water and sediment samples were collected from ten locations along the flow path of river in the basin and the hydrogeochemical features were investigated. The results were compared with maximum permissible limit values recommended by World Health Organization. A comprehensive Water Quality Index methodology was applied to come up with transparent understanding of overall excellence in water quality status. The dominant water cations and anions were within the order of Na+ > Mg2+ > Ca2+ > K+ and HCO3− > Cl− > SO42− > NO3−. The average abundance of sediment heavy metals was in the order of Pb > Mn > Ni > Zn > Cr > Cu > Co. An approach of exploiting environmental indices: enrichment factor, geoaccumulation index, contamination factor, degree of contamination, modified degree of contamination and Pollution Load Index were accustomed to assess the pollutant level. Geochemical investigation and spatial distribution of heavy metals were represented by geographic information system based maps. The results indicate that lead contamination of surficial sediments might pose a significant threat to aquatic biota and the persistent exposure of pollutants even in low concentration causes changes in metabolic activities and alterations in the community structure of river biota.

This study investigates the natural and anthropogenic processes that influence the chemistry of surface and groundwater within the subbasin of Netravati river using multivariate statistical techniques. From this work, 24 samples of groundwater and surface water of post-monsoon (2019) season have been collected and analyzed for various parameters and indices. Groundwater and surface water suitability for drinking usage was evaluated according to World Health Organization (WHO) guidelines. Based on WQI, the water resources were classified mainly into excellent (86%) and good (14%) categories and suitable for drinking usage. Dominant cation in most of the water samples are Ca2+ and Na+ and dominant anion is HCO3−. To understand the geochemical processes Piper and Gibbs plot has used for the study and the results revealed that water–rock interaction has caused groundwater and surface water to transform. In contrast, 65% of samples showed positive CAI, indicating direct ion exchange reaction. Irrigation water suitability was assessed based on various widely accepted methods such as SAR, MAR, %Na, KR, RSC, and PI. The results show that majority of samples were suitable/excellent for irrigation with some places in the study location that belongs to the good and permissible categories.

The paper describes a sustainable way of approach in limiting the dye pollution in surface water systems. An active formaldehyde modified ragi husk (FMRh), a bio adsorbent, was prepared and effectively adopted for the adsorption of Orange-G from aqueous phase. The adsorption data were evaluated using response surface model and created an ideal statistical validation of the significant interactive variables such as pH to 4.8 and contact time to 99.0 min for achieving 100% removal of Orange-G. The kinetic and equilibrium data suited with pseudo-second-order and Langmuir isotherm model with an adsorption capacity of 14.6 mg/g. The ΔG0 and ΔH0 values were − 36.1 and − 282.1 kJ /mol, respectively and confirms the spontaneous and exothermic behaviour of the dye adsorption. The FTIR and SEM analysis of FMRh (before and after adsorption) confirms the changes attributed to Orange-G uptake. The kinetically driven adsorptive mechanism holds the dye within the FMRh active-centers.

Lakshadweep Archipelago is comprised of several tiny coral atolls and scattered in the Arabian Sea off the south-west of India. Ground water is the only available fresh water resource for the islanders. The groundwater quality is decreased in this island due to population growth and anthropogenic activities like sewage dumping and agricultural activities. For this study, a total of 20 groundwater samples was collected randomly from the open wells that cover the entire area of the island. The physico-chemical parameters of groundwater were analysed in pre- and post-monsoon seasons during the year 2016–2017. The concentration of a majority of the chemical constituents exceeds the standards of WHO during post-monsoon than pre-monsoon season. EC content exhibited the violation of drinking water quality standards. The highest value of EC range 1023–6874 μS/cm recorded in post-monsoon than pre-monsoon. TDS concentration range from 574.6 to 1503.4 mg/l and 665–4468 mg/l in pre and post-monsoon seasons. Geochemical evolution diagram categories the groundwater facies into Na+-K+-Cl--SO42-, Ca2+-Mg2+-HCO3-, and Ca2+-Mg2+-Cl--SO42- in both seasons. Gibbs plot revealed that the evaporation is the dominant factor controlling the mechanism of ground water hydrochemistry. The water quality index suggested that both pre-monsoon and post-monsoon around 93.95% of the samples are unsuitable for drinking purposes. The suitability of groundwater for irrigation was studied by calculating the percent of sodium, sodium adsorption ratio, magnesium hazard and Reveille's index. The Wilcox and USSL plots also indicated that most of the groundwater samples are found to be unsuitable for irrigation. HFE diagram productively delineates that groundwater of the study area has strong influence of sea water in the fresh water aquifers. The highest level of significant correlation was observed between Mg-TH (r = 0.87), EC-TDS (r = 0.86), and Cl–Na (r = 0.77) respectively. As a whole, it is observed that the groundwater is not suitable for drinking, irrigation and industrial purposes due to the exceeding of chemical parameters from their standard limits. Therefore, groundwater management measures may be worked out regionally to improve water quality by artificial recharge, rain water harvesting, periodic disinfection of the wells and saving the fresh water stocks in the island accordingly.

The present paper reports the synthesis, surface characterization, and application of a grafted adsorption bed material namely carboxylate functionalized chitosan copolymer (CFCCP–COOH). The functionalized copolymer prepared by expanding the landscape of chitosan through co-grafting glycidyl methacrylate with methacrylic acid. The –COOH group introduced through grafting imparted a zwitterionic nature to chitosan copolymer which results in increasing the adsorption capacity. The surface of CFCCP-COOH was profiled by XPS, XRD, CHNS Analyzer, Surface Area Analyzer, Zetasizer, and FTIR. A wide spectrum of batch-adsorption studies carried out for optimizing the conditions for effectively removing heavy metals using CFCCP-COOH from water and industrial wastewaters. In a multi-metal system, for an initial concentration of 150 mg/L of each adsorbing ions, CFCCP-COOH maintains an adsorption capacity values of 92.27, 108.42, 127.91 and 123.50 mg/g in removing Zn(II), Cd(II), Pb(II) and Cu(II) at pH of 6.0. Conditions of Pb(II) adsorptive removal was optimized through response surface methodology (RSM) considering pH (4.0–7.0), adsorbent dose (1.0–5.0 g/L) and time (1–60 min) at a temperature of 40 °C and initial concentration (25 mg/L). The equilibrium and kinetic-data showed good regression with Langmuir isotherm and pseudo-second-order kinetic models. The CFCCP-COOH was feasibly applied in the treatment of wastewater streams.

The present study aimed to analyse the influence of physico-chemical properties on zooplankton assemblages and species diversity in a lagoon system. The study was carried out in coral reef lagoon of Kavaratti Island, Lakshadweep Archipelago, India during the monsoon of the year 2017. Zooplankton assemblages, distributed among 56 taxonomic units, were found to be dominated by copepods (63.27%, 34 taxa) followed by cladocerans (11.14%, 7 taxa), ostracods (9.87%, 2 taxa), ciliates (6.23%, 6 taxa), chaetognaths (4.32%, 3 taxa), leptomedusae, (1.25%, 1 taxa), and appendicularians (3.92%, 3 taxa). Copepods assemblages showed maximum density of 14326 ind m−3 from S1, in which leptomedusea was the lowest abundant taxa (284 ind m−3). Shannon–Wiener-index between 3.725–3.860 attested to the fact that the species diversity and richness predominated in lagoon than that in offshore. Canonical Correspondence Analysis revealed the environmental parameters influencing the abundance and occurrence zooplankton community in the study area.

Phytoplankton community structure and dynamics of Kochi estuary (bar mouth) have been studied seasonally. Three seasonal samplings namely pre-monsoon, monsoon and post-monsoon were made, and a wide variation was observed in phytoplankton community with respect to nutrients and other physicochemical parameters. Contrary to other seasons, dinoflagellate cell density increased during pre-monsoon season though species diversity was less pronounced (D0.15). Peridinium oceanicum was the dominant dinoflagellate during pre-monsoon season. Significant fluctuation in three principal nutrients namely total nitrogen, total phosphorous and silicate were observed during pre-monsoon (TP1.8 micromol l(-1), TN40 micromol l(-1) and SiO420 micromol l(-1)) season as compared to monsoon season (TP3.20 micromol l(-1), TN20 micromol l(-1) and SiO427 micromol l(-1)). Salinity values were also found to be high during pre-monsoon (25 psu). Study suggests that variation in salinity and nutrient concentration during transition of seasons could result in succession of species, thereby causing change in phytoplankton community structure. High salinity and nitrogen values along with low values of silicate and phosphorous resulted in proliferation of dinoflagellates during pre-monsoon season.