The effects of soil contamination with copper, lead and arsenic on the growth and composition of plants

Summary

The effects of soil pH and a prior waterlogging treatment on the uptake of copper, lead and arsenic by radish and silver beet were investigated in a glasshouse experiment. Eight soils were compared, two of which were former orchard soils, two existing orchard soils, two dosed with copper, lead and arsenic, and two affected either by mining or by orebody mineralisation.

Both the lead and copper concentrations of the plants decreased with increasing soil pH, the effect being more marked in the more highly contaminated soils. Relatively more copper than lead was translocated to the tops of the radish plants. Arsenic concentrations were less sensitive to changes in soil pH. Lower yields, lower copper concentrations in silver beet and toxicity symptoms in some acid soil treatments were more likely due to aluminium and/or manganese than to excess copper, lead or arsenic. The prior waterlogging treatment had few effects that were interpretable in terms of soil analysis or plant composition.

The soils used behaved similarly no matter what the source of contamination, with two exceptions. Soils dosed with copper, lead and arsenic did not always behave in the same manner as did soils contaminated with orchard sprays in the field and some toxic elements may be occluded or locked away in a mineral form that is not available to plants. The findings emphasize problems of interpretation of results obtained with freshly amended soils compared to soils contaminated in the field.

Under some conditions in contaminated soils, DTPA extractions for copper and lead may be inappropriate as the amounts extracted increased with increasing soil pH while plant uptake decreased.