Assessment of heavy metal concentration levels in water from underground shallow boreholes in Olasiti, Muriet and Kisongo wards in Arusha using atomic absorption spectroscopy

This work aimed to assess the levels of heavy metal concentration in water from underground boreholes in Olasiti, Muriet and Kisongo wards Arusha. Forty (40) samples were collected from the study area, acidified, refrigerated, digested and then filtered. Nine heavy metals, which are: Fe, Cr, Cd, Pb, Cu, Zn, Mn, As and Ag were analyzed using Atomic Absorption Spectrometers at the Chemistry Department of University of Dar es Salaam and at Environmental Laboratory of Ardhi University. All elements except Pb were detected in all samples. Silver concentration was observed to be seven times higher than the recommended permissible value. The other identified heavy metal concentrations when compared with the (WHO) World Health Organisation and (TBS) Tanzania Bureau of Standards permissible levels were found to be; 100%, 29.5%, 3.6% and 3.4% for Cd, Fe, Mn and Cu which require remedial measures to be taken. The identified heavy metal concentrations decreased with increase of distances from the landfill. Boreholes with depth below 30 meters were more risky compared to those with greater depth. Water in boreholes less than 30 meters had maximum concentration level of 4.2126 mg/l, 4.3252 mg/l, 0.7742 mg/l, 1.4799 mg/l, 0.3310 mg/l for Fe, Cu, Zn, Mn, Cr, respectively while boreholes of above 30 metres depth had concentrations of 0.0759 mg/l, 0.0851 mg/l, 0.3558 mg/l, 0.1430 mg/l, 0.0313 for Fe, Cu, Zn, Mn and Cr respectively. Ag and As were found in boreholes less than 30 m deep only with 0.791 mg/l and 0.01 mg/l respectively. The results from this study show that high concentrations of Cd, Fe, Mn, Cu and Ag might be associated with leachates from a landfill, burning of municipal wastes, parent’s rock and improper disposal of wastes.