Suitability of urban waste land use in relation to heavy metal and micronutrient influence on soil and green amaranth production in Southeast Nigeria
An assessment of the impact of long term (>20 years) MSW disposal on soil properties and their suitability for crop productivity was carried out in Anambra and Enugu States of southeast Nigeria. Four dumpsites were selected (two in each state) and, 12 soil auger samples (2 sampling points at 3 depths and 2 repeated measures) each were collected at incremental depth intervals of 0-20, 20-30, and 30-40cm were collected at the dump sites and adjacent non-dumpsites situated 100 meters away from the dumpsites; The auger samples were used for the determination of Fe, B, Pb and Zn content of the soil. Forty Amaranthus spinosus biomass samples were collected from both dump and non-dumpsites in the four locations and also assayed for Fe, B, Pb, and Zn content. Results showed that the mean values of Fe concentration in the dumpsites are between 4.48 – 11.57 mg kg-1 whereas B ranged from 1.19 – 6.73 mg kg-1; Pb ranged from 0.36 – 2.19 mg kg-1 and Zn averaged from 17.2 – 54.0 mg kg-1. The values of these elements were higher than those of the corresponding non-dump sites by between 6-100 %. Pb and Zn with values of 2.0 and 0.06 mg kg-1 respectively in the amaranth plants in the dumpsite soils were higher than the permissive limits for heavy metals in vegetables. Despite the toxicity variance of the elements in the dumpsites and non-dumpsite soils and vegetables, the calculated hazard quotient (ecological risks) values of these elements were less than unity (Q.H.Q < 1), suggesting that harmful effects are not likely to occur in the study areas. Public awareness creation of the dangers of plant cultivation in the unmanaged dumpsite, including health implication of heavy metal pollution and entry into the food chain as well as controlling sources of municipal wastes with appropriate legislations are recommended.