Concentration of Nitrates and Phosphates in Soil and Sediment from Decommissioned Kibarani Dumpsite and Adjacent Water Body, Mombasa-Kenya

Abstract

Nutrients in desired amounts are essential for plants, animals and humans. However, their elevated concentration in
soils and sediment is of concern. This study focused on establishing the nitrate and phosphate loading in soil and sediment
resulting from crude dumping of municipal solid waste at the decommissioned Kibarani dumpsite adjacent to Makupa Creek in
Mombasa. Soil samples suspected to have been impacted by the crude waste dumping activities were collected at the site, with
soils collected at a distance of 50 metres from the dumpsite constituting the reference material. This similarly done for the
sediment collected at the mouth of Makupa creek, with Gazi creek, in Kwale County sediment samples forming the reference
material. The nutrients in soil and sediments were extracted using potassium chloride and sent to an automatic analyzer. In the
soil, average nitrate concentration was 8.94mg/kg (±1.97) - 52.65mg/kg (±5.59), while phosphate was 7.02mg/kg (±2.40) -
54.74mg/kg (±45.32). Nitrates concentration in soil from the reference point was 12.58mg/kg (±4.40) - 15.32mg/kg (±4.91) and
phosphates were 33.73mg/kg (±9.08) - 75.22mg/kg (±24.47), respectively. In sediment, concentration of nitrate was 0.12mg/L
(±0.03) - 1.60mg/L (±0.26), while phosphate was 0.27mg/L (±0.07) - 1.42mg/L (±1.06) as compared to reference point, which
yielded average nitrate figure of 0.01mg/L (±0.01) - 0.26mg/L (±0.23) and phosphates concentration of 0.41mg/L (±0.15) -
0.77mg/L (±0.31), respectively. Municipal solid waste dumped at Kibarani had sufficient contamination of nitrates in the soil to
cause alarm. Continued input of nutrients in the sink, would fertilize the water body with growth of algae leading to further
depletion of dissolved oxygen. Dispose municipal solid waste away from water sources and preferably line dumpsites.