2012 Annual Report
1a.Objectives (from AD-416):
This project is designed to provide data that will facilitate effective use of “totally impermeable” film (TIF) to reduce fumigant emissions from soil. Air and soil concentrations of fumigant will be examined and modeled spatially and temporally to formulate appropriate tarp cutting times after application of fumigants. The specific objectives are:
1) Determine the best tarp cutting time for fields fumigated with 1,3-dichloropropene and chloropicrin under TIF.
2) Determine fumigant concentration change and distribution in soil profiles down to 1 m depth under the TIF.
3) Generate data on the fumigant emissions using dynamic flux chambers.
4) Determine residual fumigant concentration in soil at the time of tarp cutting to facilitate estimation of potential VOC loss thereafter.
5)Generate the data on the permeability of the plastic film (VaporSafeTM) used in this study for the active ingredients 1,3-dichloropropene and chloropicrin.
1b.Approach (from AD-416):
Objective 1-accumulate fumigant emissions data from ambient air around three large fields treated by broadcast shank fumigation in Ventura County. The test system will use methods preferred by California Department of Pesticide Regulation (CDPR) for assessing potential chloropicrin and 1,3-dichloropropene emissions from field applications. Objective 2-Fumigant concentration changes and movement in soil profile will be monitored throughout the study. A total of four soil-gas sampling probes will be installed in each field: two at the shank line and two between shank lines. Objective 3-Soil samples for residual fumigants by the time of tarp-cutting will be collected for evaluation of fumigant fate. Soil water content and temperature will be measured in the soil samples to facilitate required concentration calculations. Objective 4-The mass transfer coefficient (MTC) will be determined for the TIF using the standardized method (Papiernik et al. 2001; Yates et al., 2008). This method uses static sealed cells, where fumigant vapor is spiked to one side of the film and the concentrations on both side of the film are monitored until equilibrium, or, in the case of very-low-permeability films, at least until valid regression curves can be estimated based on adequate sampling at various pre-determined intervals.
Established in support of Objective 4, the goal being to assess and demonstrate emissions reduction technologies and strategies for fumigant alternatives to MB. The goal of this project is to provide data that will facilitate effective use of "totally impermeable" film(TIF)to reduce fumigant emissions from soil.
This study was conducted in Lost Hills, California, (Kern County) in June 2011. Data analyses were completed in February 2012. This study collected field data to help regulatory agencies make decisions on adoption of “Totally Impermeable Film” (TIF) technology in soil fumigation as it relates to peak emissions (buffer zones) and total emissions (Volatile Organic Compound emissions and seasonal/annual ambient air concentrations). Four large fields were established in close proximity to each other near the town of to ensure that meteorological conditions, soil type, and soil temperature were similar at all fields. All four fields were treated the same with regards to application method (broadcast tarp), application rate (label maximum), fumigant product formulation (chloropicrin/1,3-dichloropropene), application date, and type of tarp utilized (TIF, VaporSafeTM), but where one field also received a soil surface application of potassium thiosulfate (KTS) during application. The primary difference between fields was the duration of the tarping period [5, 10, or 16 days of tarp deployment]. This study generated comparative emissions data from the four tarp cutting periods with respect to peak emissions rates and total mass loss (cumulative emissions). The results of this study demonstrated that peak and total emissions of chloropicrin and 1,3-dichloropropene under TIF tarp are significantly low when tarp cutting is extended from five to ten days. There were only nominal differences in total emissions when tarps were cut at 10 days versus 16 days after application.