Environment, health and risk assessment: A case study of the use of an abandoned municipal waste dump site for agricultural purposes

The study was carried out on abandoned municipal waste dump site which has been converted to agricultural land. Three profile pits each of 100 cm depth were dug along a toposequence on the land. The profile pit P1 was dug on the crest while P2 and P3 were on the middle and down slope (valleybottom), respectively. Soil samples were collected at 10 cm interval from each profile and cassava (Mannihot esculenta Cranz) and cocoyam (Colocesia esculenta) were selected at random and harvested from the whole farm. Heavy metal content (Pb, Ni, Cd, Cu and Zn) of soils and the crops (roots and leaves) were determined. The level of Pb was found to be highest in both soils and food crops with the total mean concentration of 133.74±10.60 mg/kg in soil. The Pb level was 83.02±27.84 and 105.37±45.37 mg/kg in the roots and leaves of cocoyam, respectively, and 76.6±19.94 and 111.51±17.78 mg/kg in the roots and leaves of cassava, respectively. Cadmium had the least mean concentration in both soil andfood crops with 2.08±0.12 mg/kg in soil and 4.10 in the roots and leaves of both cassava and cocoyam. When the individual profile pits were examined, no regular variation of heavy metal was observed but there was tendency of accumulation of heavy metal in soils of down slope P3 because it had thehighest mean concentration of all the heavy metal except for Zn. Correlation analysis was used to examine the dependency of the heavy metals upon themselves, Cu and Zn had positive correlation withPb, Cd with Zn, and Zn with Cu

Levels of toxic elements in soils of abandoned waste dump site

The soils of an abandoned waste dumps sites which has been presently used for crop cultivation was investigated. Three points on the location of the waste dump site were selected and three pits of 100 cmdepth were dug at selected points. Soils samples were collected at an interval of 10 cm from the three pits. The physico-chemical properties and toxic heavy metal (As, Cd, Cr, Ni and Pb) levels were determined. The results of the study showed that the mean percentage of sand, silt and clay were 75.01±2.31, 12.87±0.93 and 10.45±1.47, respectively, while the mean pH was 6.89±0.01. The mean percentage organic matter content were high and was 3.47±0.41. The mean exchangeable Ca, Mg, K and Na in meq/100 g of soil were 4.20±0.42, 3.41±0.32, 0.31±0.004 and 0.47±0.006, respectively. The mean exchangeable acidity (EA) and exchangeable AI were 0.23±0.002 and 0.69±0.004, respectively. Of all the five toxic elements studied, the highest mean concentration (mg/kg) of 133.74±10.60 was recorded for Pb followed by Cr (22.27±3.03), Ni (8.14±0.33) and As (5.97±0.32) in the soils while the least mean concentration of 1.64±0.11 was recorded for Cd. The toxic elements were examined for dependency upon some soil factors through the use of correlation analysis, sand, organic matter and effective cation exchange capacity (ECEC) correlated significantly and positively with Cr and Pb indicating that these factors largely control the concentration of these elements in the soils

Risk and health implications of polluted soils for crop production

Studies of polluted soils have shown heavy metals contamination of the soils as well the uptake of these toxic elements by plants. Consequently, there are reasons for concern over elevated concentration levels of heavy metal/toxic elements in polluted soils. This can ultimately result in high human and animal exposure to these toxic elements through food-chain transfer, ingestion of wind blown dust or direct ingestion of soils. The toxic effects caused by excess concentrations of heavy metals in living organisms include competition for sites with essential metabolites, replacement of essential ions, reactions with –SH groups, damage to cell membranes and reactions with the phosphate groups

Models for evaluating the effects of variations in pH of rain water on the leaching of fertilizer components in soils

No Abstract. Global Journal of Pure and Applied Sciences Vol. 12 (4) 2006: 531-53