Analytical Studies on Heavy Metal Contamination of Imo River

Abstract

In river systems, surface water has been widely used as environmental indicators and their chemical analysis can provide significant information on the assessment of anthropogenic activities. The paper evaluates the pollution status of the Imo River with reference to heavy metal enrichment. The mean concentration of the ten metals used in this study was slightly higher than the recommended maximum permissible limit by the Nigerian Standard for Drinking Water Quality except zinc. The results of the metal pollution index revealed that the river is slightly to moderately polluted with metals. The application of factor analysis on the data-set identified three factors which imply that these metals enter the river through three possible sources. Factor one comprises of pH, nickel, lead, iron and cadmium and accounts for 34.46% of the total variance. Factor two has a moderate loading of 25.89% of the total variance with arsenic, mercury, chromium and manganese as contributors. Factor three had the least loading from copper and zinc which constitutes a total variance of 16.64%. The pH of the river water has a mean value of 6.10 which signifies an acidic condition and is traceable to acid-rain ravaging the entire region caused by several years of continuous gas flaring. Aquatic organisms rarely survive under low pH and it also precipitates mobility of metals. The climate, local geology and hydrogeology of the area enhance the release and migration of these metals into the river system. The enrichment of these heavy metals in the river may be attributed to the dumping of waste into the river as well as the discharge of untreated industrial effluent into the river. The prohibition of dumping of waste into the river is strongly advocated. The present study demonstrated application of metal pollution index and factor analysis in understanding the quality of river water and appeared to be promising in the field of water quality management.