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Hollister, CA, United States

Spurlock F.,U.S. Environmental Protection Agency | Johnson B.,U.S. Environmental Protection Agency | Tuli A.,U.S. Environmental Protection Agency | Gao S.,U.S. Department of Agriculture | And 6 more authors.
Vadose Zone Journal | Year: 2013

We evaluated the HYDRUS 2D/3D model for simulating chloropicrin and 1,3-dichloropropene fate and transport in broadcast applications. The calibrated model provided relatively accurate estimates of fumigant soil gas concentrations, and volatilization in two data sets using input data were measured, estimated, or obtained by independent calibration. We evaluated the ability of the HYDRUS 2D/3D model to simulate chloropicrin (CP) and 1,3-dichloropropene (13D) fate, transport, and volatilization. Three fields with similar soil conditions were broadcast fumigated under a totally impermeable film (TIF). One field was used to calibrate HYDRUS by adjusting fumigant degradation rates, soil sorption coefficients, and TIF tarp resistance factors. In comparisons of simulated and measured soil gas concentrations, soil temperature, soil water contents, and inverse-modeled estimates of fumigant volatilization flux, the model accurately simulated the basic individual processes of fumigant partitioning and degradation, heat transport, and soil water dynamics in the calibration field. Subsequent flux simulations of the remaining two fields were performed using only measured, independently estimated or calibrated inputs with no further adjustments. The magnitudes of simulated cumulative fluxes and both pre- and post-tarpcut discrete flux densities were within the estimated range of uncertainty (factor of ~2) of conventional inverse-modeled field-based flux estimates. However, the timing of maximum discrete flux densities was delayed by 1 to 2 d relative to inverse-modeled estimates. While HYDRUS provided reasonably accurate flux estimates, it was also evident that parameterization, particularly for TIF tarp permeability properties, generally requires field-based calibration because of a lack of representative field effective permeability data. © Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved. Source

Ashworth D.J.,University of California at Riverside | Ashworth D.J.,U.S. Department of Agriculture | Yates S.R.,U.S. Department of Agriculture | Van Wesenbeeck I.J.,Dow AgroSciences | Stanghellini M.,TriCal Inc.
Journal of Agricultural and Food Chemistry | Year: 2015

Co-formulations of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) are commonly used for preplant fumigation in the production of high-value crops. Various ratios of 1,3-D to CP are available in these co-formulations. Collation of previous field data suggested that when the two fumigants were co-applied, the emissions of CP were significantly lower than when CP was applied singly. However, none of these previous studies had a control treatment with CP applied alone, alongside a treatment where CP was co-applied with 1,3-D under the same climatic and edaphic conditions. This work aimed to address this issue by measuring emission fluxes from soil columns maintained under controlled conditions in which 1,3-D and CP were applied alone and as four commercial co-formulations with various 1,3-D:CP ratios. A strong positive relationship between CP emissions and CP percentage in the formulation was observed. Furthermore, strong positive relationships between CP degradation half-life and CP percentage in the formulation and between CP degradation half-life and total column emissions suggested that the lower emissions were due to faster CP degradation when the CP percentage (and hence initial application mass) in the formulation was low. The presence of 1,3-D did not significantly affect the degradation rate of CP, and, therefore, it is hypothesized that co-application was, in itself, not a significant factor in emission losses from the columns. The findings have implications for the accurate modeling of CP because the effect of initial mass applied on CP degradation rate is not usually considered. © 2014 American Chemical Society. Source

Gao S.,U.S. Department of Agriculture | Ajwa H.,University of California at Davis | Qin R.,U.S. Department of Agriculture | Qin R.,University of California at Davis | And 2 more authors.
Environmental Science and Technology | Year: 2013

Tarping fumigated fields with low permeability films such as commercial Totally Impermeable Film (TIF) can significantly reduce emissions, but it can also increase fumigant residence time in the soil such that extended tarp-covering durations may be required to address potential exposure risks during tarp-cutting and removal. In an effort to develop safe practices for using TIF, a large field study was conducted in the San Joaquin Valley of California. Comprehensive data on emissions (measured with dynamic flux chambers), fate, and transport of 1,3-dichloropropene and chloropicrin were collected in a 3.3 ha field fumigated with Pic-Clor 60 via broadcast shank application. Low emission flux (below 15 μg m-2 s-1) was observed from the tarped field throughout the tarp-covering period of 16 days with total emission loss of <8% of total applied for both chemicals. Although substantially higher flux was measured at tarp edges (up to 440 μg m-2 s-1), the flux was reduced to below 0.5 μg m -2 s-1 beyond 2 m of tarp edge where total mass loss was estimated to be ≤1% of total applied to the field. Emission flux increased following tarp-cutting, but was much lower compared to 5 or 6 d tarp-covering periods determined in other fields. This study demonstrated the ability of TIF to significantly reduce fumigant emissions with supporting data on fumigant movement in soil. Proper management on use of the tarp, such as extending tarp-covering period, can reduce negative impact on the environment and help maintain the beneficial use of soil fumigants for agricultural productions. © 2012 American Chemical Society. Source

TriCal Inc. | Date: 2016-02-08

Chemicals used in agriculture and horticulture; chemical substances for preserving foodstuffs; fertilizers, fumigants, fungicides and herbicides, agricultural machinery and equipment, irrigation systems, components and supplies, agriculture and horticulture services, including plant grafting; nursery services; soil testing, analysis and consulting; and irrigation system design, installation services.

Trical Inc. | Date: 2016-06-09

Propylene Oxide.

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