Heavy metals poison mangrove ecosystem

AHMEDABAD: Some of the most prominent rivers in south Gujarat — Ambica, Par, Kolak, Purna, Auranga, Damanganga and Varoli — are serving slow poison to the benign mangrove ecosystem near their estuarine areas. Toxic effluent, laden with heavy metals from nearby industrial clusters, have been detected there.
A team of researchers from Gujarat Ecology Society (GES) have extracted toxic metals like lead, nickel, chromium, copper, cadmium zinc and iron from mangrove species Avicennia Marina leaves, twigs and their pneumatophores. The research clearly pointed out the mangrove species selectively absorbed copper and zinc and almost avoided the rest of the heavy metals.

The GES team, consisting of Sumesh Dudani, Jayendra Lakhmapurkar, Deepa Gavali and Tejas Patel, had taken mangrove samples from these five estuarine zones of the rivers.

The team tested sediments of the esturine area for the five rivers and found that the values of chromium, copper, zinc, nickel, lead, cadmium and mercury were found in the range between 15 to 51 microgram per gram (ug/g) of soil, 20 to 46 ug/g, 18 to 42 ug/g, 18 to 26 ug/g, 8 to 13 ug/g, 8 to13 ug/g and 0 to15 ug/g respectively.

Lead content was found to be relatively high in the plant tissues of Avicennia Marina at Damanganga and Kolak. For instance, the team found lead content of 0.068 ug/g from pneumatophores from Damanganga estuarine area, while they found 0.047 ug/g from pneumatophores of mangrove sample from Kolak estuarine area. Similarly, nickel content was found high at sites – Varoli, Kolak and Damanganga followed by other sites. Among all the estuarines, Par river showed low mean content of lead, chromium, cadmium and nickel in the mangrove plant. The mean copper content in mangroves was found to be high in Kolak estuarine followed by Par, Damanganga and Varoli sites.

The GES research points out that cadmium, along with its compounds, is widely used as heat stabilizers for plastics, for corrosion resistance of steel and cast iron, metal plating, phosphate fertilizers, alloy industries and in battery industries. Similarly, lead is an important metal used in pulp and paper, printing, glass, alloy and storage batteries.

“Main industrial belts surrounding Vapi, Valsad, Navsari, Bharuch and Surat are dominated by industrial equipment, electronics manufacturing, glass, chemicals and pharmaceutical industries along with plywood, paper, food products and textile,” claims the research paper.