Goa’s rivers polluted with rare earths, metals: study (Herald)

June 21, 2013 TEAM HERALD PANJIM: High concentration of iron, manganese, aluminum and other rare earths has polluted the state’s rivers, a study conducted by the National Institute of Oceanography has revealed. face="Trebuchet MS, sans-serif">The study on the geochemistry of suspended sediments in the Mandovi and Zuari estuaries, found that manganese is ‘significantly polluted’ while other metals are ‘moderately polluted’. “Enrichment factor (EF) of the metals indicates that the Mn concentrations in the entire Mandovi estuary, Zuari channel and Cumbarjua canal and Co and Ni from the Mandovi channel fall in the range of significant pollution. Metals such as Fe, Co, Cr, Cu, Ni and Zn from different domains of both estuaries and Pb from the Zuari canal were in the range of moderate pollution. Pb from other domains, Zn from the Mandovi ore stations and Cumbarjua canal and Cd from all stations of estuaries and canals were in the range of minimal pollution,” the study reveals. “During heavy rains abundant ore is being flushed into the estuaries. Since ore handling i.e., loading in barges, transporting and reloading at the port or mid-stream in giant ships, is done in an open system one would expect abundant ore spilled-over into the estuaries. Industries such as Fe-pellet making factory and ship-building are located on the shores of the Zuari estuary,” the study reveals. The Mandovi and Zuari rivers play an important role in the mining logistics of Goa by providing cheap and efficient means of ore transport. Several big open cast iron and manganese ore mines operate in the basins of the rivers. The effects of ore transport through the rivers hasn’t been thoroughly documented until now and Environment Impact Assessment studies done of mining haven’t taken into consideration the effects of the riverine ecology of the two rivers which are the lifeline of the state. For the purpose of the study researchers set up several stations to gather water samples. Stations close to the ore loading jetties are called ‘ore stations’, stations in the river stream are called ‘channel stations’ and those close to the sea are called as bay stations. Stations in the Cumbarjua canal are called canal stations. “Ore stations of Mandovi, where ore deposits are stored on the shore, exhibit high Fe, Mn, REE (rare earth elements) and middle REE- and heavy REE-enriched REE patterns. Channel stations of both estuaries exhibit middle REE- and light REE-enriched patterns, which gradually changed seaward to middle REE- and heavy REE enriched patterns,” the study found. “Canal stations exhibit highest concentrations of major and trace metals. High metal/Al (aluminum) ratios occur at stations in the upstream of Zuari and at the confluence of canal in the Mandovi estuary. Enrichment factors of metals indicate that Mn is significantly polluted while other metals are moderately polluted,” the study says. http://www.heraldgoa.in/News/Main%20Page%20News/Goa-rsquo-s-rivers-polluted-with-rare-earths-metals-study/75946.html