2007 Annual Report 1a.Objectives (from AD-416) Conduct research on the fate and transport of agricultural pesticides (i.e., fumigants, insecticides and herbicides) and investigate the effect of various soil and cultural processes on pesticide movement from the root zone. Conduct research that provides information applicable to "real-world" conditions both in terms of efficacy and environmental fate. Develop new management approaches that are efficacious and that minimize emissions to the atmosphere, and transport to surface water and ground water. 1b.Approach (from AD-416) An experimental system will be developed to assist in improving our understanding of the effect of soil properties, soil moisture, temperature, soil salinity, and surface environmental conditions on the emission of pesticides from soil. The overall goal of this research is to develop an accurate method to characterize the emissions of pesticides that doesn’t require large-scale, expensive, complex, and time-consuming field experiments. Specifically, (1) an automated laboratory column system consisting of stainless steel cylinders approximately 1.5 m in length and 12 cm in diameter will be constructed. A gas-sampling valve system controlled by a datalogger will be developed to allow automatic sampling of the column headspace. This information will be used to obtain volatilization rates from the column after injection of a soil fumigant at a specified depth from the soil surface. Initial experiments will be conducted using soil from the Buttonwillow, CA field site to provide a baseline for more detailed future studies. (2) A new wind-measurement system will be developed for deployment in remote field locations. The system will consist of a minimum of 5 Windsonic anemometers mounted on a 3 m mast. The center pole of the mast will be constructed of 1 ½ aluminum pipe consisting of two sections and three 1 ¼ aluminum pipe cross bars will be attached with slip-on pipe connectors. A stabilizing system will be developed to ensure the mast remain stationary during high winds. The system will be field tested prior to the next large-scale field experiment. 3.Progress Report The analyses of samples collected during a previous field experiment was completed, collated and entered in to databases. Preparation for a new large-scale field experiment involved designing and constructing new sampling equipment (i.e., new anemometer mast, new gas sampling mast, new temperature profile mast, new flux chamber with automatic sampling capabilities, incorporation of new data loggers, etc.). Our previous research showed that amending the surface soil layer in a field with thiosulfate fertilizers provides an effective and economical approach to reduce the emission of halogenated fumigants. However, with new regulations being enforced on emissions of volatile organic chemicals (VOCs), information is needed whether fumigant transformation by thiosulfate produces secondary VOC. This study investigated the stability of the reaction of thiosulfate and 1,3-D in different environmental media. Transformation of cis-1,3-D in thiosulfate-amended soil form a nonvolatile reaction product via an abiotic mechanism. This initial reaction product undergoes a series of biotic conversions in soil to yield several volatile or semi-volatile organic sulfur compounds. The formation and distribution of four volatile/semi-volatile products in the air and soil were detected in different soils treated with the thiosulfate derivative. This study indicated that odors occurring in soil treated with halogenated fumigants and thiosulfate fertilizers might arise from the generation and release of these and other volatile/semi-volatile organic sulfur products. The environmental fate and effects of such volatile/semi-volatile sulfur compounds should be considered in the application of sulfur-containing fertilizers in fumigated fields. This specific cooperative agreement supports University of California post docs and a staff research associate. These scientists have offices and laboratory space located at the U.S. Salinity Laboratory. Research progress is monitored via frequent informal discussions (several times a week), monthly U.S. Salinity Laboratory meetings, and research project and planning meetings.