The influence of compost on the growth of bean plants irrigated with As-contaminated waters and its
influence on the mobility of As in the soils and the uptake of As (as NaAsIIIO2) by plant components was
studied at various compost application rates (3$104 and 6$104 kg ha1) and at three As concentrations (1,
2 and 3 mg kg1). The biomass and As and P concentrations of the roots, shoots and beans were
determined at harvest time, as well as the chlorophyll content of the leaves and nonspecific and specifically
bound As in the soil.
The bean plants exposed to As showed typical phytotoxicity symptoms; no plants however died over
the study. The biomass of the bean plants increased with the increasing amounts of compost added to
the soil, attributed to the phytonutritive capacity of compost. Biomass decreased with increasing As
concentrations, however, the reduction in the biomass was significantly lower with the addition of
compost, indicating that the As phytotoxicity was alleviated by the compost. For the same As concentration,
the As content of the roots, shoots and beans decreased with increasing compost added
compared to the Control. This is due to partial immobilization of the As by the organic functional groups
on the compost, either directly or through cation bridging. Most of the As adsorbed by the bean plants
accumulated in the roots, while a scant allocation of As occurred in the beans. Hence, the addition of
compost to soils could be used as an effective means to limit As accumulation in crops from Ascontaminated
waters.