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Surface water samples collected from Thrissur Kole wetland (UNSECO-protected Ramsar Site) were analysed for hydrogeochemical characteristics. The objectives of this work were to: (i) study the spatial and seasonal variability in water quality and (ii) analyse the hydrogeochemical characteristics of different water types and suitability status for irrigation. Remarkable season-wise and station-wise variation in salinity was attributed to the mixing of freshwater and seawater. Relatively lower values of pH during post-monsoon were due to the freshwater discharge and mineralisation of organic matter. Besides natural sources, agriculture activities, and droppings from birds also serve as sources of nutrients in the wetland. The average relative abundance of major cations and anions was Cl- > Na+ > Mg2+ > K+ > SO42- > HCO3- > Ca2+. In addition, the contribution of dissolved ions from tidal ingression was established by the dominance of magnesium and sulphate. Based on Piper plot, three major hydro-chemical facies (Ca–Mg-HCO3 type, Ca–Mg-Cl-SO4 type, and Na-K-Cl-SO4 type) were identified. Irrigational suitability of water throughout the wetland was excellent during monsoon as per irrigational water quality indices. Piper plot indicated that the surface water chemistry was controlled by silicate weathering with contribution from seawater ingression and anthropogenic sources. [ABSTRACT FROM AUTHOR]

Silicon dioxide nanoparticles (SiO2-NPs), is widely used in the fields of medicine, engineering and industries. In the present study, sublethal concentration (12 mg.L-1) of SiO2-NPs was exposed to the freshwater fish, Oreochromis mossambicus (Peters 1852) for short-term (24, 72 and 96 h) and long-term (15, 30 and 60 days) durations, maintaining a control group. Gill tissues showed significant (P < 0.05) reduction in the activities of antioxidant enzymes, superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase with a concomitant increase in the production of hydrogen peroxide and lipid peroxidation. Liver tissue also showed induction of oxidative stress which was evident by the significant decrease in the activities of antioxidant enzymes and generation of hydrogen peroxide and lipid peroxidation. In brain tissue, the alteration of antioxidant defence system was more prominent only after 96 h. The activities of tissue marker enzymes were also decreased in gill, liver and brain tissues indicating tissue-specific nanotoxicity. The reversible of treatment for 60 days showed no withdrawal effect of nanoparticles in all tissues. The present results conclude that exposure to silicon dioxide nanoparticles induced oxidative stress and the effects are found irreversible in the gill, liver and brain tissues of the fish, O. mossambicus. [ABSTRACT FROM AUTHOR]

The investigation focused on identification and quantification of microplastics in surface waters of Chalakudy River, Kerala. Microplastics were detected in the surface waters of the study area with a recovery rate of 108.33 mg particles L−1. The abundance of microplastics ranged from 15.13 ± 4.13 – 170 ± 17.75 particles L−1 (mean: 55.81 ± 34 particles L−1). A maximum number of microplastics were obtained from site C3 and the least from site C8. The weight distribution of microplastic on sites exhibited strong positive correlation with the abundance (r = 0.83). Microplastics of size <20 µm were in higher abundance in the study area. Microscopic examination revealed fragments (47.06%) as predominant plastics and the dominant colour was brown/mud (26.99%). Abundance of coloured plastics indicated the probability of damage to aquatic life. Raman spectrum analysis revealed that Low-Density Poly Ethylene (40%) as the predominant polymer that could be observed at all the sampling sites. Lower-sized microplastics would cause accidental ingestion by organisms. The estimated release of a higher average number of microplastic particles (55.81 ± 4.25) into the marine environment is of serious concern. The observed overall abundance and recovery rate of microplastics in the study area indicated the status of contamination due to a multitude of sources. [ABSTRACT FROM AUTHOR]