Soil benzene emissions and inhalation health risks affected by various land covers

Accurate quantification of soil volatile organic compounds (VOCs) flux is crucial for assessing inhalation environmental health risks and developing region-specific remediation strategies. However, land cover significantly influences VOCs emissions from soil. This study investigated benzene, a representative VOCs, using a laboratory flux chamber and numerical simulations to evaluate its release patterns under different surface covers, including bare soil (no cover), clay brick, cement, and grass. In the experiment, gaseous benzene was collected using an adsorption tube filled with Tenax-TA adsorbent. The collected samples were subsequently analyzed using thermal desorption coupled with gas chromatography-mass spectrometry. By integrating these findings with environmental health risk assessment methodologies, we developed a tailored approach for assessing inhalation health risks at benzene-contaminated sites with varying land covers. Additionally, we conducted application studies of this method across various scenarios. The results indicate that soil benzene emissions could be reduced by using low-permeability coverings such as clay brick and cement, as well as by planting vegetation. The average fluxes of benzene through covering materials were of the order of 1.22 × 10^-2, 4.37 × 10^-3, 2.47 × 10^-3, and 9.88 × 10^-4 mg m^-2·s^-1 for bare soil, clay brick, grass, and cement, respectively. The application of clay brick and cement coverings on the soil surface results in more pollutants remaining in the soil in liquid and adsorbed states, making them less likely to volatilize. The inhalation carcinogenic risk (CR) values for soil benzene at an abandoned oil refinery site in Northwestern China under bare soil, brick, and cement cover are 1.3 × 10^-6, 1.22 × 10^-6, and 9.73 × 10^-7, respectively. Low-permeability covers such as clay brick and cement reduces the inhalation CR of gaseous benzene from the surface soil, and delays the growth trend of cumulative inhalation CR.