Hydrus Simulation of Chloropicrin and 1,3-Dichloropropene Transport and Volatilization in the Lost Hills Fumigation Trials
Abstract
We compared HYDRUS 2D/3D simulated fluxes to flux estimates based on Industrial Source Short Term (ISC) inverse-modeling (i.e. back-calculation) of fumigant air concentrations from a study in Lost Hills, California (Ajwa and Sullivan, 2012). Lost Hills field 1 data were used to calibrate the HYDRUS model. Subsequent HYDRUS simulations of field 2 and field 3 chloropicrin and 1,3-dichloropropene (1,3-D) flux were conducted using the calibrated HYDRUS model without further adjustment. HYDRUS accurately described fumigant soil-gas concentrations, soil-temperature and water content, and both pre- and post-tarpcut fumigant volatilization throughout the field 1 study period. The calibration results show that the model was adequately representing basic process of heat transport, fumigant partitioning, fumigant degradation and volatilization. HYDRUS-simulated cumulative and discrete peak fluxes for fields 2 and 3 were within the likely range of uncertainty of the ISC estimates. However, in all fields HYDRUS tended to predict the occurrence of peak fumigant fluxes one to two days later than in the ISC estimates.