Uptake of 137Cs in vegetable crops grown on a contaminated lakebed.

Mean concentrations and plant:soil concentration ratios of 137Cs were determined for six vegetable crops grown on an exposed, contaminated lakebed of a former reactor cooling reservoir in South Carolina. Each crop species was grown with or without potassium fertilizer. Selected crops were also irrigated with either reservoir water or groundwater. Subsamples of crops were prepared for human consumption before analysis to determine the extent of any loss. Plant:soil concentration ratios (dry basis) ranged from 0.22 to 6.82, values which were substantially higher than those used in generic assessment models. While there was no statistically significant effect of irrigation source or culinary preparation, the effect of potassium-fertilizer was dramatic. In many cases, concentrations of 137Cs in those plants receiving potassium were less than half of the concentrations in plants that did not receive potassium. Significant differences among species and plant parts for 137Cs concentrations were observed. Dose/risk calculations for the ingestion of these vegetables by a hypothetical 30-y resident indicates the possibility of a lifetime fatal cancer risk well-above the U.S. Environmental Protection Agency's regulatory guideline of 10(-4).