Evaluation of heavy metal pollution status of Anambra River basin using different indices

Eighty-one (81) water samples were collected to investigate the concentrations of heavy metal and pollution status using synthetic pollution index (SPI), Comprehensive pollution index (CPI), Heavy metal evaluation index (HMEI) and Heavy metal pollution index (HPI). Eight (8) heavy metals, iron (Fe), manganese (Mn) zinc (Zn), copper (Cu), chromium (Cr) cadmium (Cd), nickel (Ni) and lead (Pb) were analysed following standard procedure and protocols. The results of analysis showed that Fe fluctuated between 1.32 and 4.10 mg/l, Mn between 0.51 and 2.04 mg/l, Zn between 0.81 and 3.20 mg/l, Cu between 0.43 and 1.92 mg/l, Cr fluctuated between 0.26 and 1.02 mg/l, Cd between 0.15 and 1.13 mg/l, Ni between 0.12 and 0.70 mg/l, and Pb fluctuated between 0.22 and 1.24 mg/l. Through results, it was also found that the mean concentrations of Fe, Mn, Cr, Cd, Ni and Pb exceeded their permissible values for drinking water (SON, 2015) whereas Mn, Cr, Cd, Ni and Zn levels exceeded their permissible values for health aquatic environment (FMEnv., 2011). The order of heavy metal concentration in the river basin were: Fe > Zn >Mn > Cu >Cr > Pb > Cd > Ni. The results of computed pollution indices revealed that most of pollution indices values were exceeded their highest classification values; SPI values were greater than 3, CPI > 2.0, HMEI >20 and HPI >1000, thus indicating that water from the river basin is unfit for drinking. In conclusion, water from Anambra River Basin pose a threat of heavy metals-related diseases to users/communities, thus, needs urgent attention for treatments by appropriated authorities.