Trace metals and pesticides in water-sediment and associated pollution load indicators of Netravathi-Gurupur estuary, India: Implications on coastal pollution.

Various environmental indicators were used to evaluate the water and sediment quality of the Netravathi-Gurupur estuary, India, for trace metals and pesticide pollution. The descended order of studied metal concentrations (µg/L) in the water was Fe (592.71) > Mn (98.35) > Zn (54.69) > Cu (6.64) > Cd (3.24) > Pb (2.38) > Cr (0.82) and in sediment (mg/kg) was Fe (11,396.53) > Mn (100.61) > Cr (75.41) > Zn (20.04) > Cu (12.77) > Pb (3.46) > Cd (0.02). However, pesticide residues were not detected in this estuarine environment. The various metal indexes categorised the water as uncontaminated, whereas contamination factor, enrichment factor, geo-accumulation index, degree of contamination and pollution load index indicated low to moderate sediment contamination. Multivariate statistics showed that the dominance of natural sources of trace metals with little anthropogenic impact. Improvement in water/sediment quality during the study period might be due to COVID-19 imposed lockdown.

Assessment of water quality of Netravathi-Gurupur estuary, India through chemometric approach for fisheries sustainability.

The present study aimed to assess the water quality dynamics (physicochemical properties, nutrient and chlorophyll-a) in the Netravathi-Gurupur estuary, India across the space and seasons and to simplify the complex water quality dataset through a chemometric approach. The results indicated that pH, EC, temperature, alkalinity, salinity, TDS, hardness, chloride and intense mixing of suspended solids, driven by the semidiurnal tides, are the major factors affecting water quality. Spatial heterogeneity and monsoon have profound impact on nutrient distribution revealing the following values (mg l-1): phosphate-P (0.015-0.105), nitrate-N (0.016-0.094), nitrite-N (0.001-0.012), and silicate (1.83-14.50). The estuary was evaluated for suitability for brackish water fisheries. The results indicated fair water quality during pre- and post-monsoon but marginal quality in monsoon, primarily due to dilution associated with reduced salinity. The outcome of this study can be suitably utilized for the sustainable development of estuaries and their feasibility for brackish water fisheries.

Geochemical distribution and forms of phosphorus in the surface sediment of Netravathi-Gurupur estuary, southwestern coast of India.

Estuaries are the most productive transition ecosystem and phosphorus (P) plays an important role in these ecosystems. Therefore, in the present study, sequential extraction method was used to determine the abundance of five sediment P fractions (calcium (Ca-P), Iron (FeP), aluminum (AlP), exchangeable (Ex-P) and organic (OrgP) bound P) in Netravathi-Gurupur estuary, India. Total phosphorus (TP) content varied from 435-810 mg/kg (non-monsoon) and 258-699 mg/kg (monsoon). Inorganic P was dominant part. Different P fractions followed similar order (Fe-P > Ca-P > Al-P > Org-P > Ex-P) with respect to seasons. FeP was dominant fraction, indicating probable anthropogenic stress. Sediment may act as source of P as bioavailable P constituted 40-69.2 % of TP. Molar ratio of OC to Org-P in sediment indicated terrestrial sources of organic matter. However, the estimated phosphorus pollution index were lower than one except a few cases indicating less ecological risk with respect to sedimentary TP load.

Phosphorus fractions in the sediment of a tropical reservoir, India: Implications for pollution source identification and eutrophication.

Eutrophication level in lakes and reservoirs depends on both internal and external phosphorus (P) load. Characterization of sediment P fractionation and identifying the P pollution sources are important for assessing the bio-availability of P and the dominant P source, for effectively controlling the water pollution. For determining the availability and sources of sediment P and eutrophication status, spatio-temporal variation in different P fractionation of sediment of hyper-eutrophic Krishnagiri reservoir, Tamil Nadu, India, was investigated. Sediment average total P (TP) content ranged from 4.62 to 5.64 g/kg. Main phosphorus form was the inorganic P (IP), and it makes up to 73.4-87.7% of TP. Among the different P fraction, viz. calcium bound (Ca-P), iron bound (Fe-P), aluminium bound (Al-P), exchangeable (Ex-P) and Organic-P (Org-P), Ca-P was the dominating fraction in both IP and TP. Trend of IP fraction was as follows: Ca-P > Fe-P > Al-P > Ex-P in pre-monsoon season, Fe-P > Ca-P > Al-P > Ex-P in monsoon and Ca-P > Al-P > Fe-P > Ex-P in post-monsoon. Overall the trend was as follows Ca-P > Fe-P > Al-P > Org-P > Ex-P. Bio-available-P (BAP) fractions ranged from 35.2 to 64.0% of TP, indicating its comparative higher value. Pearson's correlation matrix revealed that there was strong correlation among the different P fractions. Factor analysis indicates that different fractions of P were the dominating factor than the other sediment parameters. The observed variation in sediment P fractionation indicate the differences in source and characterization of P which is very helpful for implementation of effective management practices in controlling pollution that arises due to phosphorus in this hyper-eutrophic reservoir.