Runoff of 1,3-dichloropropene from field plots exposed to simulated and natural rainfall

摘要

Runoff potential of a subsurface soil-injected volatile compound, such as the soil fumigant 1,3-dichloropropene (1,3-D), that diffuses rapidly through the soil profile has not been studied for potential to contaminate surface water bodies through edge-of-field runoff. The objective of this study was to measure the runoff of 1,3-D, a soil fumigant and nematicide, under severe rainfall conditions at a field study site near Blacksburg, Virginia. 1,3-D was injected into the Groseclose clay loam (clayey, mixed mesic Typic Hapludults) at a 30 cm (12 inch) depth on three replicate 0.04 ha test plots. Special considerations for 1,3-D were required to make a uniform application to each plot and maintain worst-case conditions (rainfall timing and plot conditions). The measured application rate was 367-kg/ha (32.4 gallons/acre), which is greater than the typical maximum rate for Telone II~(~R) uses on crops grown in the Southeastern United States. The study was conducted on a hydrologic group C soil with a 5% slope. The 2-hour simulated rainfall water input was 9.4 cm (4.7 cm/h), which is about a 1-in-50-year storm for Blacksburg, Virginia. Concentrations of 1,3-D measured in soil and air prior to the simulated rainfall event suggested that 1,3-D was present at the soil surface and available for runoff. An average of 0.002% of the applied 1,3-D was observed in runoff. Maximum 1,3-D concentration (sum of both isomers) observed in runoff was 17.2 ppb, which is more than one order of magnitude below the lowest aqueous toxicological level of concern (280 ppb).