Pollution Load Index of the Mini-Chida Stream, Port Harcourt, Nigeria

Abstract

The Mini-Chida waterbody was a very significant fresh water channel and of great domestic purpose for the natives of the Ikwerre ethnic gropu with the highest population in Port Harcourt, Nigeria being the main hub of the hydrocarbon industry. This plays important role in the lives of the inhabitants which necessitated the need to evaluate the seasonal pollution indices associated with it. This was achieved by determining some heavy metals contents using Atomic Absorption Spectrophotometer (AAS). The sampling was carried using 5-sampling stations for a period of 12 months (in both spatial and temporal dimentions). The longitudinal survey deign was adopted for this study and samplings were done between 7.00 and 10.00 hours on each day. The result showed mean range values in dry and wet seasons respectively for the heavy metals in mg/l as; Cd(0.22±0.15-0.29±0.17, 0.055±0.043-0.098±0.07) and Pb (0.07±0.14-0.31±0.23, 0.39±0.44-0.85±0.72) which showed relatively higher variations. Non-carcinogenic risk assessment showed hazard pollution index (HPI) was higher than the critical limit (threshold value of 100) and higher by the wet season (258.84). The hazard exposure index (HEI) was of moderate risk (1<HEI≤5) in both seasons while degree of contamination (CD) was found to be very high during the wet season for Cd (2600), Cr (700), Pb (5700) and similarly Cd, Cr and Pb were of extremely high CD in both seasons (interpretation of CD>3). The chronic daily intake (CDI_ing and CDI_dermal) as carcinogenic risk via ingestion and dermal were within permissible limits, reference dose, R_fD (0.14mg/kg/day) as well as hazard quotient (HQ), hazard index (HI), having neither risk nor adverse effects. Statistically, no significant variations across the study stations using the one-way ANOVA for all the parameters as well as the Tukey’s HSD Post Hoc test (p<0.01 and p<0.05). Some of the risk assessment models showed low level risk factors but the rising concentration of Cd, Pb and Cr remains a potential threat, hence government regulations on indiscriminate disposal of waste and regular monitoring cannot be over-emphasized.