Effects of litter feeders on the transfer of 137 Cs to plants.

The effects of the Japanese horned beetle larvae on the transfer of 137 Cs from a contaminated leaf litter to the leaf vegetable, komatsuna (Brassica rapa var. perviridis) was studied. Feces of the larvae which were fed 137 Cs-contaminated leaf litter were added to a potting mix in which komatsuna plants were cultivated. The presence of feces increased the harvest yield of komatsuna, suggesting that feces provided nutrients for the plant growth. In addition, the amount of exchangeable 137 Cs in leaf litter was experimentally confirmed to be enhanced by the presence of feces which were excreted by larvae feeding. However, there was no difference in the soil-to-plant transfer factor of 137 Cs for the presence and absence of feces. Interactions between clay minerals and exchangeable 137 Cs in the soil beneath the litter layer may diminish the root uptake of 137 Cs. From these results, it was concluded that the effect of exchangeable 137 Cs released from feces was limited for the transfer of 137 Cs to plants if plant roots were not present in litter layers.