Pollution Status of Soils and Vegetation around Busy Motor Parks in Selected Areas of Delta State, Nigeria

Abstract

Soil and vegetation samples were collected from busy motor parks in selected parts of Delta State and analysed with the aim of ascertaining the potential and environmental impact of the motor park activities on the surroundings. The physicochemical characteristics of the soil samples were investigated using various standard methods while the heavy metal concentrations were determined using Atomic Absorption Spectrophotometric technique. The pH values ranged from 5.59 to 8.52 with a mean value of 7.21 showing that the soils were slightly acidic to slightly alkaline. The electrical conductivity values ranged from 66.54 to 252.9 µs/cm with mean value of 163.48 µs/cm, indicating presence of high level of soluble inorganic salts in the soil samples. The cation exchange capacity values (cmolkg -1 ) ranging from 0.040 to 0.147 with mean value of 0.097 implied that the exchange sites on the soil minerals will be less available for metals retention. The mean percentages of Total Organic Carbon and Total Nitrogen which were 0.488 and 0.107 respectively could be attributed to presence of some biodegradable and compostable materials. The mean concentrations of the heavy metals in the soil samples (mgkg -1 ) were 57.78 for Fe, 1.112 for Pb, 0.482 for Cu, 1.334 for Zn and 0.13 for Cr with the abundance trend of Fe > Zn > Pb > Cu >Cr. The mean metal levels in the vegetation samples ranged from (mgkg -1 ) 0.152 to 12.426 with the abundance trend of Fe > Pb > Zn > Cu > Cr. Soil plant transfer coefficient values for all the metals in all the sites indicate medium accumulation while contamination/pollution index values showed generally very slight contamination. The metal levels in both the soil and vegetation samples in all the sites were relatively higher than the levels recorded in the control sites. The overall results showed evidence of some heavy metals enrichment on the soils and vegetation. This effect could be cumulative over time.