Physicochemical and Heavy Metals Concentration in Qua Iboe River and Health Risk Assessments on Tissues of Clarias Gariepinus (Burchell, 1822) and Callinectes Amnicola (Rochebrune, 1883)

Abstract

Physicochemical and heavy metals concentration in Qua Iboe River and health risk assessments on tissues of Clarias gariepinus and Callinectes amnicola was investigated for the period, Feburary to September, 2018. The river was partitioned into three stations: Onna, Atabong and Estuary. Physicochemical characteristics of the water were assessed using standard procedures. Heavy metal in water, sediment, and fish (C. gariepinus) and crab (C. amnicola) tissues were analyzed after digestion using atomic absorption spectrometer. Human health risks of heavy metals were estimated using estimated daily intake (EDI) and target hazard quotient (THQ). Among the 13 physicochemical parameters evaluated, only temperature, pH and DO were similar between the three stations, Onna, Atabong and Estuary. All three parameters also showed little variations during the sampling periods, coefficient of variation (CV) = 1.89%, 4.84% and 8.86% respectively. TSS and TDS were significantly higher at Estuary compared to the other two sites (p < 0.05). Conductivity of the water was significantly in the order of magnitude at the stations, Atabong> Onna> Estuary (F = 1799.84, p < 0.05). On a seasonal temporal scale, temperature, pH, DO, BOD, nitrate, sulphate and phosphate showed clear seasonal influence. Nitrate, sulphate and phosphate were significantly higher in the wet season (p < 0.05). Principal component analysis (PCA) reduced the dimension of relationships of physicochemical parameters into three principal components. The first, second and third components accounted for 38%, 31% and 23% respectively of total variance. Cumulatively, all three components explained 92% of the total variations in physicochemical properties of the Qua Iboe River. On the first principal component, conductivity, TSS (Total suspended solids), TDS (Total dissolved soids), alkalinity and phosphate loaded strongly (|r| > 0.75). Turbidity loaded moderately (0.75 > r > 0.50) while nitrate and DO loaded weakly (r < 0.50). There was a strong positive linear relationship between conductivity, alkalinity and turbidity on the first component. Also, a strong positive relationship occurred between TSS, TDS and phosphate. Comparatively, on a monthly scale and overall, Cd was significantly higher in crab tissues; the difference overall was very significant (p < 0.05). Pb on the other hand was higher in fish tissue in each of the months; overall the difference was significant (p = 0.003). Crab tissue Cu concentration was very high compared to fish; the difference was significant (p < 0.05). Fe and Cr were both significantly higher in fish tissue on a monthly scale and overall (p < 0.05).There was a very strong linear relationship between each of the heavy metal in fish and its concentration in water. The relationship was positive and significant for Cd, Pb, Cu and Fe (p < 0.05). However, when Cr concentration in water increased, its concentration in fish tissue decreased (r = - 0.552, p < 0.05). In crab, tissue level of Cu, Fe and Cr were strongly related to water levels of each of these metals. Cd had the highest BCF in both organisms; Its BCF was 106.16 ± 9.21 and 135.44 ± 15.28 in fish and crab tissue respectively. Fe had the least BCF, 9.99 ± 0.66 and 7.59 ± 0.37 respectively in fish and crab tissues. The EDI of all the metals except Fe was less than one in fish and crab tissues. THQ for all the metals in both fish and crab tissues was below one. Conclusively, the Qua Iboe River is considered not contaminated; and the fish and crabs from the river are considered safe for consumption as the THQ of heavy metals were below