Nutrient and heavy metal composition in select biotic and abiotic components of Varthur wetlands, Bangalore, India

Abstract

Lakes or wetlands in urban landscapes provide services such as groundwater recharge, provide fish, fodder and food to the dependent local population, mitigate floods, habitat for fauna, support recreation, etc. Unplanned rapid urbanization with globalization and industrialization has led to the sustained inflow of untreated wastewater from domestic and industrial sectors to water bodies leading to eutrophication and heavy metal contamination. This necessities treatment of sewage and industrial effluents, which needs to be technically feasible and economically viable. This communication investigates the distribution and accumulation of nutrients (carbon and nitrogen) and six heavy metals (cadmium, chromium, copper, nickel, lead and zinc) in the sediment and macrophyte samples of Varthur lake, Bangalore. Higher carbon and nitrogen values in sediment samples of the northwest and northeast shorelines were observed, whereas lower carbon and nitrogen values were observed in the samples of middle and outlets of the lake. Shoots of Colocasia esculenta and Alternanthera philoxeroides accumulated higher amount of carbon and nitrogen. Sediment samples of north shoreline and inlet portion of the Lake had high concentration of heavy metals in Alternanthera philoxeroides and Eichhornia crassipes accumulated heavy metals in higher extent among macrophyte species. Sediment samples had higher concentrations of copper (Cu) followed by zinc (Zn), chromium (Cr), lead (Pb), nickel (Ni) and cadmium (Cd). Compared to this, accumulation of heavy metals in macrophyte samples is in the order Cu > Zn > Cr > Pb > Ni > Cd. Assessment of bioconcentration factor and translocation factor of metals in macrophytes revealed the prospects of select macrophytes in phytoremediation for mitigating metal pollution through phytoextraction and phytostabilization.