Exposure assessment model for odor causing VOCs volatilization from stored pig slurry

A mathematical model taking into account source depletion with time and the actual thickness of manure layer was derived to evaluate indoor inhalation exposure dynamics to three selected odor causing volatile organic compounds (VOC-odors) of p-cresol, toluene, and xylene volatilization from stored pig slurry. The model assumes that pig slurry is undisturbed and the VOC-odors released in a contaminated layer and transported through a clean layer as well as a manure-air interface boundary. The model simulates time-dependent volatilization, the depletion of source contaminant via both volatilization and degradation, and could be used with a contaminated zone of finite thickness. For a given VOC-odor, the predicted total exposure and resulting manure cleanup criteria can be a large variability depending on the model whether a finite or infinite manure layer thickness was considered. Results obtained from model comparisons suggest that the model incorporating depth-varying of manure layer and contaminant source depletion is more suitable to evaluate the VOC-odor exposure dynamics in swine housing bioclimate.