Abstract

Lakes or wetlands in urban landscape 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 bio-concentration factor (BCF) and translocation factor (TF) of metals in macrophytes revealed the prospects of select macrophytes in phyto-remediation for mitigating metal pollution through phyto-extraction and phyto-stabilization.

Research Highlights

• Assessed nutrients (carbon and nitrogen) and heavy metal (cadmium, chromium, copper, nickel, lead and zinc) accumulation in sediment and macrophytes of Varthur Lake.
• Rapid urbanization in Bangalore led to the sustained inflow of untreated domestic sewage and industrial wastewater into lakes.
• Sediment samples at northwest and northeast side of the lake shoreline recorded high values, while samples at outlet had lesser quantity of nutrients.
• Macrophytes Colocasia esculenta and Alternanthera philoxeroides accumulated relatively higher nutrients than other species.
• Alternanthera philoxeroides and Eichhornia crassipes are the dominant macrophytes found in the lake and accumulated higher content of metals in their tissues

Keywords Heavy metal, sediment, macrophytes, phytoremediation, Bangalore, Varthur Lake