Physicochemical Characteristics and Heavy Metal Levels in Groundwater from Selected Areas of Dar Es Salaam City, Tanzania

Abstract

Groundwater in Temeke and Ilala areas within Dar es Salaam city was analysed for physicochemical characteristics and heavy metal levels to assess its quality as potable water. Random sampling was used to obtain groundwater samples from three sampling sites, namely, residential areas, near petrol stations and dumping sites. Temperature, pH, and electrical conductivity (EC) were measured on-site by a water quality multimeter while heavy metals levels were determined by standard methods using Atomic Absorption Spectroscopy (AAS). Measurement of pH (pH 5.2-7.3) showed that groundwater largely satisfied TBS and WHO standards. Similarly, EC values of groundwater (256.5-5286 μScm-1) largely met TBS specifications while only 33% of groundwater complied with the WHO guidelines. Cd in groundwater from the three sampling sites (0.01-0.50 mgL-1) exceeded TBS and WHO standards. Pb in 89-94% of groundwater collected near petrol stations (0.01-1.10 mgL-1), 80% of groundwater from dumping site (0.01-1.22 mgL-1), and 25%-70% of groundwater from residential areas (0.01-0.65 mgL-1) exceeded the TBS and WHO standards. Cr concentration in 50-66% of groundwater samples collected near petrol stations (0.01-1.1 mgL-1) and 20-42% of groundwater from residential areas (0.01-0.45 mgL-1) exceeded TBS and WHO standards on total Cr. Levels of Cu (0.01-1.70 mgL-1) and Zn (0.01-1.82 mgL-1) were largely within the TBS and WHO standards. Groundwater in the study area is contaminated with non-permissible levels of Cd, Pb and Cr, which makes it unsuitable for human consumption and hence likely to affect public health.