HEALTH RISK ASSESSMENT AND POTENTIAL ECOLOGICAL RISK OF TRACE METALS OF OGUNPA RIVER, OYO STATE, NIGERIA

Abstract

Background: Heavy metals have been continuously deposited and assimilated into water, biota, and sediments as a result of human activity's contamination of aquatic ecosystems.

Objectives: This study aims to assess the trace metals (Fe, Pb, Co, Zn, Cb, Cu, Mn, Ni) contamination and evaluate the status of pollution in Ogunpa River.

Methods: Water samples were taken monthly to analyze the heavy metal concentration, while several pollution indexes, including the human health risk analysis, degree of contamination (Cd), heavy metal evaluation index (HEI), comprehensive pollution index (CPI), water quality index (WQI), heavy metal pollution load index (HPLI), and single factor pollution index were employed to ascertain the contamination status of the River.

Results: The concentrations mean of the nine heavy metals respectively for dry and wet seasons were;  Pb (ND), Cr (ND), Cd (0.12±0.25), Co (0.30±0.65), Zn (29.90±70), Cu (14.45±23.06), Ni (0.21±0.59), Mn (83.42±36.64), Fe (34.40±76.87) and Pb (0.01±0.01), Cr (0.01±0.01), Cd (0.14±0.25), Co (0.01±0.01), Zn (11.15±24.00), Cu (9.33±20.50), Ni (0.14±0.47), Mn (29.31±27.64), Fe (58.71±48.35). Single factor pollution index were in this order; Pb < Cr < Cd < Co < Zn < Cu < Ni < Mn < Fe. HPLI results showed that Cu, Zn, Ni, Mn, and Fe had a significant impact on the pollution level in both seasons, while WQI results during the dry and wet seasons were determined to be 2384.3 and 1144.2 respectively. CPI had a mean of 203.8 ranging from 4.4 to 923.4 and 101.2 ranging from 2.9 to 191.2 during the dry and rainy seasons respectively. HEI values ranged from 13.0 to 4211.7 during dry seasons and from 3.0 to 648.0 during wet seasons. The average wet season (290.6) and dry season (882.0) degrees of contamination were recorded during the sampling period. The metal hazard index (ingestion) varied from 0.00 (Cr) to 14.83 (Cu), while the values of the hazard index (dermal) varied from 0.00 (Cr) to 0.27 (Cu).

Conclusion: The substantial risk of heavy metal pollution in Ogunpa River implicated an indiscriminate discharge of agricultural, domestic and industrial waste along the Stream.