Abstract:
To deal with the odor pollution during the excavation of VOCs-contaminated soils, the establishment of its risk predication model and the evaluation of its potential risk during the remedial excavation of volatile organic compounds (VOCs)-Contaminated soils is of great practical significance. A conceptual model of odor exposure was developed to estimate the emission rate of pollution source strength in this study, with the processes of soil gas diffusion, VOCs’ volatilization, and groundwater solute volatilization comprehensively considered. Combined with Gaussian Diffusion Model, the diffusion process of pollution sources to surrounding area was simulated, and then the odor intensity was used as the characterization means to predict the atmospheric concentration of VOCs in the surrounding area and its olfactory effect on human body. The risk of odor diffusion in a remediation plot was predicted during its excavation, whose excavated area was 2800 m
2, the depth was 3 m, and the odorous substances involved 9 BTEXs mainly being benzene, methylbenzene, ethylbenzene, and chlorobenzene. The prediction result showed that VOCs were released rapidly and diffused to the surrounding residential area at 20 m away when the excavation speed was 150 m
3/h, which mainly contains 4 components of chlorobenzene, benzene, ethylbenzene, and toluene, with amounts being 6.86, 2.35, 1.56, and 0.85 mg/m
3, respectively. The odor characteristics of VOCs were further analyzed using the odor activity value (OAV) and ln[OAV], which identified as the key odorous substance in the mixture. Therefore, ethylbenzene was chosen to represent the odor characteristics of VOCs. Accordingly, the odor intensity of residents in the breathing area was 3.09, referring to that the surrounding residents would obviously sense the odor during the excavation. Moreover, the key parameters impacting the odor risk were identified based on the model sensitivity analysis, which mainly covered the sensitive target distance(
xair), soil pollution concentration (
Cs), excavation speed (
Q), soil air content (
θair), and ambient air velocity (
Uair). To effectively control the negative effects caused by the diffusion of odor in soil, from the perspective of reducing odor nuisance to the public, the study proposed several control strategies, such as the optimization of soil remediation technologies, control of regional soil conditions, and consideration of weather effect.