Effect of Biosolids and Cd/Pb Interaction on the Growth and Cd Accumulation of Brassica rapa Grown in Cd-Contaminated Soils

Mixed metals in the cropped lands in central Taiwan contaminated about 230 ha. According to the Soil and Groundwater Protection Remediation Act (SGWR Act) of Taiwan, these lands were restored. However, some grains of paddy rice grown in these remediated soils still contained more than 0.5 mg Cd kg^?1, which the Department of Health of Taiwan notified as the maximum allowable Cd content in rice. The suitability of planting edible crops in these soils is now in doubt. Brassica rapa is the crop most often sold in Taiwan's market and is planted in the interval between the first and second stages of planting of paddy rice, especially in central Taiwan where this experiment was conducted. A pot experiment was conducted using soils contaminated artificially with Cd or both Cd and Pb. The soil was then amended with 5% of biosolid and followed by planting of B. rapa. The objectives were to study the effect of biosolid amendment on the soil and the interaction between Cd and Pb on the growth of and Cd accumulation in B. rapa. Experimental result showed that the biomass and the accumulation of Cd by B. rapa were significantly increased in the biosolid-amended soils compared with the control. Lead has a synergistic effect on enhancing the accumulation of Cd by B. rapa grown in artificially Cd-contaminated soils.