Modeling variation in 1,3-dichloropropene emissions due to soil conditions and applicator practices

Simulation of chloropicrin emissions in response to soil conditions and applicator practices

HYDRUS 2D was used to simulate chloropicrin (CP) emissions across a range of expected application and environmental conditions present within California, where CP is widely used in the pre-plant treatment of soils for high-value specialty crops. Simulations were developed based on field calibration work and physicochemical parameters from literature with additional consideration of application rate-dependent degradation and applicator practices including application depth, application mode, and tarp material. Model output was compared to the distribution of indirect whole-field flux estimates derived from field monitoring studies using measures of maximum 8-h, maximum 24-h, and cumulative emissions due to their relevance to public health. We observed a strong linear relationship (R2 ≥ 0.80, p < 0.001) between HYDRUS-simulated and field-based maximum flux estimates and no evidence of statistical difference depending on the estimation source for maximum 24-h flux. A linear relationship of similar strength (R2 = 0.82, p < 0.001) was observed between simulated and field-based cumulative emission estimates, although mean HYDRUS estimates were lower than field-estimated values for some high-emission application methods. Analysis of simulation output demonstrated large differences in CP emissions in response to application method and a non-linear increase in CP emissions with increasing application rate, with considerable interaction between application variables including application depth, tarp types, and field layout. The findings generally support the use of simulated CP emission estimates as a tool to address gaps in field-based flux estimates, particularly where characterization of short-term peak emissions is needed.

1,3-Dichloropropene and chloropicrin emission reduction using a flexible CuInS2/ZnS:Al-TiO2 photocatalytic film

Soil fumigation using 1,3-dichloropropene (1,3-D) and chloropicrin (CP) is an important strategy for agriculture production; however, excessive emissions can cause air pollution and possible human exposure. In this study, solar light-driven CuInS₂/ZnS:Al-TiO₂ photocatalytic film was prepared through spin-coating on the flexible polyethylene terephthalate (PET) substrate of 0.1 mm. Using the photocatalytic film, degradation of 1,3-D was inhibited in the Pci-clor 60 formulation of 1,3-D and CP. However, the degradation of CP was accelerated in this formulation, and the half-life was shortened from 0.66 to 0.40 h. Emissions of 1,3-D from soil to the air were reduced by 97.30%, 97.17%, 47.10%, and 7.88%, for treatments of D + Film, D + C + Film, D + PET, and D, respectively. The efficiencies for reducing 1,3-D emission were significantly improved by about 1.1 and 11.3 times using the film, compared with using the PET alone and no film, respectively. Furthermore, fumigation effects on nematodes could still achieve higher than 90%. The findings provided a basis for the practical application of quantum dot films to reduce soil fumigants emissions by photocatalytic degradation.