Uncertainty and transient contamination of river water by agricultural use of industrial products: Release and run-off of hazardous chemicals from agricultural plastic film

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An organophosphoric acid triester, tricresyl phmphate (TCM was detected in the Kurose river. Hiroshima, Japan. The concentration was low during dry weathcr and increased after rainy days suggesting typical contamination originating from non-point sources. However, precipitation did not always increase the concentration of TCP in the river. Some rainevents increased TCP in river water and bottom sediments, whereas others did not. To clarify the uncertainty and mechanism of the transient contamination, we carried out an intensive survey both in the river and catchment area. Small amounts of TCP were dctaud both in domestic and industrW waste waters. Also, urban run-oft dry and wet procrpitation and other possible non-point sources did not eonWn significant amounts of TCP. Occasionally, we could detect high concentration of TCP in agricultural runoff from greenhouses. Must greenhouses in the region are covered by plastic films for insulation. Although TCP used in many industrial products in the basin, it seemed most likely that the major sources of TCP were plastic films for agricultural purposes. Release of TCP from an agricultural plastic film by rainwater was confirmed. However, the release did not always reach the river or its tributaries. Most of the released TCP seemed to be transported to the soil and was decomposed in the soil. This mean that run-off of TCP from the field was not associated with rainfall. Only a part of the TCP seemed ot be released from the film to be transported to soil and finally to the river with surface run-off of soils.