Investigation of baseline metal pollution in soils from the Adada River Bank, Enugu State, Nigeria

The Adada River is among the essential rivers in Enugu State which rural dwellers depend on water supply and agriculture farmlands situated beside its channels. Current research was undertaken to ascertain the extent of lethal metals (Co, Zn, Cd, Ni, Pb, As and Fe) pollution in soils from the Adada River bank. Fifteen topsoil (0 cm), subsoil (5 cm) and deep-soil (10 cm) samples were gathered from the downstream, midstream and upstream of the river. The results revealed that the average values of the metals in the three different depths declined in the pattern of As>Pb>Zn>Co>Ni>Fe>Cd. Adada River bank soils possess moderate to critical enrichment for Pb, moderate enrichment for As and Cd, as well as no enrichment for Co, Zn and Ni. The results of the contamination factor (CF) revealed that Cd and As are responsible for the high contamination. The Pollution Load Index (PLI) for some of the sample stations demonstrates that, with the exception of the Amagu and Ogbosu locations, the sampling locations were largely unpolluted. To delineate the different origins of the metals, multivariate tools like correlation matrix and cluster analysis were used. The results indicated that the soil samples obtained from the upstream of the river possess lesser metal values, whereas soils in the downstream of the river had higher metal values as a result of intensive rice farming in the downstream part of Adada River. Our observations can also be beneficial as baseline data for regulatory agencies to implement appropriate action in the future on issues relating to heavy metal contamination in the Adada River.