Occurrence And Risk Assessment Of Heavy Metals And Organochlorine Pesticides In Surface Soils,central Kenya

The present study investigated pollution in surface soils of five dominant land use types in central Kenya.The mean concentration of heavy metals(Zn,Hg,Cd,Cu,Cr,As and Ni)in(mg/kg)and two organochlorine pesticides,(DDTs and HCHs)were determined.Heavy metal contamination and potential ecological risk using the Nemerow pollution index and Hakanson ecological risk indice respectively were used in examining pollution level.With the help of multivariate analysis sources of heavy metal pollution were identified which were mainly from anthropogenic activities.Notably,heavy metal concentration in our study was compared to other regions within the country,results showed regional variation.Total levels of DDTs,HCHs pesticide and their constituent isomers in the surface soil were determined by a gas chromatography that's coupled with micro-electronic capture detector(GC-?ECD).As expected,organochlorine pesticide were higher in agricultural land use,DDTs levels were comparatively higher than HCHs levels.Results on DDTs ratio(p,p?-DDT/p,p?-DDD + p,p?-DDE)were < 1 in all land use types which showed that their residues originated from historical sources.However lower ?/ ? HCH ratio in forest and peri-urban land uses indicated current input of lindane.Correlation analysis showed significant relationship between TOC and HCHs.When compared to study done in other rural and suburban agricultural soil(Nairobi surroundings),present study of OCPs(DDTs and HCHs)concentration was relatively high.The quality of soil in Central Kenya was classified as considerably polluted by OCPs but low polluted by heavy metals.