An index approach to heavy metal pollution assessment of Eme River, Umuahia, Nigeria

Abstract

Rivers are subjected to various kinds of natural eventsand anthropogenic activities among which, indiscriminate and illegal sand mining is a major one. The heavy metal content of a Nigerian river was studied between December 2017 and November 2018 in 6 stations. The objective of the study was to assess the water quality using heavy metal pollution indices for drinking water purpose. It is cumbersome to interpret the results of water quality assessment when it involves large number of parameters hence the index approach. The indices used were Heavy Metal Pollution Index (HPI) and Contamination Index (Cd). Eight metals were evaluated using standard methods and compared with Nigerian Drinking Water Quality Standard. Some metals like iron, cadmium and lead exceeded limits; manganese, chromium and nickel exceeded limits in the dry season in some stations while copper and zinc were all within limits. The dry season values were significantly (P<0.05) higher than the wet season values. HPI showed all the stations exceeded the threshold (100) especially stations 1, 4 –6 while Cdshowed that stations 3 and 2 had low and medium contamination potential risks respectively and stations 1, 4 –6 had high contamination potential risks. The indices effectively captured the effect of the anthropogenic activities (sand mining, swimming, washing, etc) in the river and showed that the water quality was not suitable for human consumption.