Comparative Analyses of Levels of Some Trace Metals in Boreholes and Hand-Dug Wells Water Sources Within and Around Lafia Metropolis

Abstract

In this study, the levels of some trace metals (As, Co, Cr, Cd, Pb, Al, Ni and Mn) were determined in boreholes and hand-dug well water sources in Lafia town and its environs using Atomic Absorption Spectrophotometry (AAS). Sampling, preservation of the water samples, pre-concentration and analyses of the trace metals were carried out as prescribed by APHA, AWWA, and WEF Standard Methods for the Examination of Water and Waste Water. In the wet season(WS), the highest mean concentrations(mg/L) of trace metals from boreholes (BH) was Mn(0.7787 +0.2389) in Lafia West while the least was Pb(0.0049 +0.0001) in Lafia South. Similarly for hand -dug wells (HDW) in wet season, the highest was Mn(0.6227 + 0.0260) in Lafia West while the least was As(0.0106 + 0.0001) in Lafia East. In dry season(DS), the highest mean concentration of trace metals from BH was Mn(0.3815 + 0.0907) in Lafia West while the least was Cr(0.0042 + 0.0001) in Lafia South. Similarly for HDW in dry season, the highest was Mn(0.3588 + 0.0762) in Lafia West while the least was Ni(0.0065+0.0001) in Lafia Central. However Cd and Al were not detected within the two seasons. In all, the analyses revealed the presence of 40%As, 40%Co, 37.5%Cr, 25%Pb, 25%Ni and 97.5%Mn from the total ground water samples. Their mean concentrations were compared with standards of a number of regulatory bodies such as World Health Organization (WHO), National Agency for Food Drug and Control (NAFDAC), National Standard for Drinking Water Quality (NSDWQ for Borehole). In comparison, the results showed higher levels of these metals than the maximum tolerable limits, particularly those of As(0.2710+0.0001 - 0.0106+0.0001), Co (0.2406+0.2114-0.0281+0.0001), Cr(0.5049+0.5871-0.0272+0.0001) for all the water samples throughout the seasons. However those of Pb(0.0423+0.0537-0.0049+0.0001),Ni(0.3729+0.0001- 0.0841+0.0001),Mn(0.7787+0.2329-0.1049+0.0322) were within tolerable limits in most cases. The results indicate that these ground water sources were polluted more prominently in wet season; BH (WS)>HDW(WS)>BH(DS)>HDW(DS) in all locations, with specific reference to As, Pb, because of their high toxicities and therefore not safe for drinking.