Development of the Risk Assessment and Management Strategies for TPH-Contaminated Sites Using TPH Fraction Methods

Petroleum hydrocarbon–contaminated soil and groundwater is a worldwide environmental problem, which results in environmental hazard and human health risk problems. Because petroleum is a complex composition mixture rather than a single compound, health risk assessment for a petroleum hydrocarbon–contaminated site is a complicated process. In this study, a modified total petroleum hydrocarbons (TPH) fraction method was applied to determine the health risk level for each TPH fraction. The concentrations and toxicity data of total of 13 TPH fraction categories were evaluated and used for risk calculation. Results show that up to $\mathrm{1,772}\mathrm{mg}/\mathrm{kg}$ of TPH concentration was observed in soils collected from the studied site. Results indicate that benzene was the most concerning chemical that appeared in TPH. The calculated cancer risk for benzene was $4.48\times {10}^{-7}$, which was lower than the minimum total cancer risk level ($1\times {10}^{-6}$). The calculated hazard quotient for the noncarcinogenic compounds was slightly higher than the minimum target risk level of 1, and this was due to the $C_{12-16}$ group, which had higher concentration in groundwater. Results indicate that the major exposure pathway was through groundwater ingestion rather than vapor inhalation. The TPH fractions that needed to be analyzed would be aliphatic $C_{8-10}$, $C_{10-12}$, and $C_{12-16}$ due to their higher toxicity effect. In the exposure pathway of groundwater ingestion, the TPH fractions that needed to be analyzed included aromatic $C_{5-7}$, $C_{10-12}$, and $C_{12-16}$ due to their higher exposure potential. Light petroleum compounds (e.g., aliphatic $C_{6-10}$ and aromatic $C_{5-10}$) also need to be considered during the risk assessment process because of their higher volatility behavior. Analysis of heavy TPH ranges are unnecessary due to their low volatility and high adsorption effects. The suggested method allows a more flexible application depending on exposure routes as explained, which makes human health risk assessment more feasible and practicable. The TPH fractionation analysis could be regarded as one feasible for future health and risk assessment for the TPH-contaminated site. This study provides a streamlined process to develop a more practical and economical RBCA strategies for TPH-contaminated sites.