HEAVY METAL STATUS OF MUNICIPAL SOLID WASTE AND SOIL AT KOSHE OPEN DUMPING SITE OF ASSELA TOWN ,OROMIA REGION, ETHIOPIA

Abstract

Dumping of heavy metals wastes has environmental impacts on soil and water at the nearby waste dump sites. The purposes of this study was to identify the sources and also status of selected heavy metals in municipal solid waste and soil at koshe open dumping site of Assela Town. For seven consecutive days metal wastes were manually separated from all wastes dumped at the site to identify the sources of heavy metals.Sources of the metals were categorized under three groups; household (1.29) commercial (5.69) & institution (3.32 kg/day). For assessing heavy metal concentration in decompose municipal solid waste and soil at the dumping site, three decomposed waste and soil samples were collected. Heavy metals such as: Fe, Mn, Cu, Zn, Ni, Co, Cr, Pb and Cd in waste and soil samples were analyzed using AAS. Results showed the concentration of these heavy metals in the DMSW were in the order of Fe>Mn>Zn>Cu>Ni>Cr>Co> Pb>Cd. The pH, EC, OC values of DMSW where 8.3, 1.59 dS/m, and 3.33% respectively. The textural class of the soil under the waste and the nearby site was sandy clay loam. pH, EC,OC and CEC were 6.45, 0.09 dS/m,1.27 % and 48.6 cmolkg-1 respectively for the depth of 0- 20 cm. In soil the trend of heavy metal concentration was Fe>Mn>Cu>Zn>Cr>Ni>Co>Pb>Cd .The concentrations of the analyzed heavy metals in soil under the waste were greater than that of the control. Different sources of heavy metals are carried by waste which is then transferred to dumping site. Iron concentration was the highest across the depth followed by Mn, Cu,Zn and Cr at the dumpsite. the concentration of Fe, Mn,Zn, Cu and Ni decrease with depth while Pb and Cd, concentration increase with the depth while Cobalt and chromium concentration the remains the same across the depth at the study area. The concentrations of heavy metals were above acceptable level of different standards. Other processing and treatment of waste such as energy recovery from waste technologies need to be considered in all Ethiopian towns and cities