TITLE:
Trace Element Evaluation of Groundwater in Douala, Cameroon
AUTHORS:
Ngwese Sharon Ntube, Aduck Jovens Nyangang, Ma-Effeti Ngale Agbor, Akoachere Richard Ayuk II
KEYWORDS:
Trace-Elements-Evaluation, Health-Risks-Assessment, Pollution-Indices, Douala-Cameroon
JOURNAL NAME:
Open Access Library Journal,
Vol.9 No.1,
January
14,
2022
ABSTRACT: Douala, situated between latitude 4.00 - 4.15 and longitude 9.65 - 9.95, is the economic capital of Cameroon in the Littoral Region and it hosts more than 80% of the industries in the Country. Increased urbanization and agricultural activities have a potential for trace metal contamination as such, the trace metal evaluation of groundwater in Douala begs our attention. This study investigated the trace metal content of groundwater sources; determined estimates of the health hazard and pollution risk indices; assessed the health hazard and level of risk to trace metal pollution in Douala. Measurement of 153 hand-dug wells for physicochemical parameters and chemical analysis of 10 representative groundwater samples was carried out to determine their trace metal content using Inductively Coupled Plasma Mass Spectroscopy ICP-MS. R-mode statistical analysis; Hierarchical Cluster Analysis (HCA) and Pearson’s correlation analysis (PCA) of the trace metals to the physico-chemical parameters were done. Four pollution hazards were estimated; the average daily dose ADD, carcinogenic risks CR, non-carcinogenic risk hazard quotient HQ and hazard index HI. Six pollution risks indices were determined: the Degree of contamination DC, Enrichment factor EF, Ecological risk factor Er, Ecological risk index RI, Pollution load index PLI, and geo-accumulation index Igeo. The trace elements detected in groundwater in Douala and their relative abundance in decreasing order are: Si > Al > Sb > Sr > Ba > Mn > Li > Zn > As > Bi > Cr > Fe > Se > Ag > Mo > Ni > Pb > Sn > Ti > TI > V. HCA distinguishes trace metals into two clusters: Cluster1; Li, Zn, Sr, Sb, Al, TI, V, Ti, Sn, Pb, Mo, Ni, Ag, Cd, Co, Cu, U, Y, Ba, Mn, Cr, Se, Bi, As, Fe and Cluster2 Si. The values of groundwater pollution hazard indices ranged; ADD (0 - 60 mg/kg/day), CR (0 - 13), HQ (1.0E05 - 1.1E05) and HI (1.05E04 - 1.2E04). The values of the pollution risk indices are DC (-1.93 - 1.91), EF (0.0 - 1.2), Er (-5 - 0), RI (-17.58 - -17.64), PLI (-0.13 - 0.13) and Igeo (0 - 1.16). The Health risk assessment qualified groundwater in Douala as unsafe and intolerable for human consumption but without carcinogenic effects. Pollution indices placed groundwater in Douala in the low degree background contamination with minimal enrichment, low potential ecological risk and geogenically unpolluted to moderately polluted. Very strong correlations were observed among some of the trace element pairs, suggesting common sources, mutual dependence and identical behaviour from provenance and during transport. The severity of trace element toxicity is governed by several factors, such as dose, nutrition, age, and life style. Therefore, these low trends might not guarantee human health due to an increasing level of environmental pollution that might be imposed by increasing human activity on Douala City and environs which might contaminate the groundwater; this demand for monitoring of groundwater sources for drinking purposes.