Origin and stormwater runoff of TCP (tricresyl phosphate) isomers

Abstract

TCP concentration in the Kurose River, Higashi-Hiroshima, increases after rainy days, suggesting that typical contamination originates from non-point sources. Our study was focused on a greenhouse as an important source of TCP isomers. The amounts of TCP released from agricultural plastic films were studied. Field surveys during rainy days were also carried out to clarify the processes which release TCP isomers from the greenhouse with rainfall, and its accumulation and degradation processes in soil. The runoff processes of TCP from greenhouse to ditch and river was also investigated. Concentration of TCP isomers in rainfall drop from a greenhouse were significantly higher than those in rainwater and river water, indicating that agricultural plastic films were the probable source of TCP. The ratio of o-TCP concentration in rainfall drop from greenhouse decreased with time, whereas that of m-TCP increased. These results suggest that more o-TCP was released from plastic film than m-TCP. TCP released from plastic film by rainfall was preferentially adsorbed on the silt-clay fraction of the soil. The m-TCP isomer concentration in soil around the greenhouse increased if cumulative precipitation for 3 consecutive days before sampling was less than 20 mm, but decreased if it was more than 20 mm. TCP concentration in the soil was highest in the surface (0–1 cm) and decreased below the surface. The significant decrease with depth is probably affected by adsorption and biodegradation. TCP concentrations in surface soil and water decreased along the flow of surface water from greenhouse to ditch. It is probable that TCP released from the greenhouse was transported to the ditch with adsorption on top soil.