Distribution Analysis And Environmental Risk Assessment Of Vocs/svocs In Petroleum Oil Contaminated Sites

Petroleum hydrocarbons-contaminated sites are highly of concern for their serious disturbance to environment. In the petroleum hydrocarbons-contaminated sites, VOCs/SVOCs, of which PAHs and BTEX are representative, are intensively contained and highly toxic. So they are serious threats to human's health as well as to the ecosystem, and considered as the typical pollutants of this kind of sites. Currently typical pollutant-based environmental risk assessment is used internationally to supervise petroleum hydrocarbons-contaminated sites. On the other hand, a system to evaluate and supervise petroleum hydrocarbons-contaminated sites has not been established because it is in an initial stage in China.On the basis of primary investigation in the PAHs and BTEX's general distribution of petroleum hydrocarbons-contaminated sites in China, characters of their distributions were analyzed. Result suggested that the proportions of PAHs and BTEX in Chinese petroleum hydrocarbons-contaminated sites were much bigger than other sites'. The carcinogens, which were subclasses of PAHs and BTEX, might become threats to human's health. It was necessary to have an environmental risk assessment. After investigating conventional models for environmental risk assessment and comparing the differences between RBCA model and CLEA model from the principle with taking the calculation of Bap's soil screening standard value as an example, the former was chosen to simulate the process of environmental risk assessment. Simultaneously, risk target level, exposure factor, building parameter, PAHs and BTEX's physicochemical variable as well as their toxic parameter were confirmed. All these works set up an environmental risk assessment method for PAHs and BTEX, which was based on RBCA model. Further more, it was used to analyze two typical petroleum hydrocarbon-contaminated sites.Monitoring results of PAHs and BTEX in the two sites showed that: sixteen PAHs were detected around a sink area contaminated by petrochemical wastewater. Among these matters, low molecular weight compounds, such as Nap and Ane, were in a high level. In this area, the PAHs, which had a low transferability, mainly existed in the topsoil, such as Bap; Nap and Phe, which were the representatives of PAHs with high transferability, distributed in an expanded depth. They were even detected in the groundwater. PAHs'concentration was inverse proportion to its depth in soil. Under the influence of local climate and topography, PAHs on the south of the sink area were more than other parts'. Under a tar workshop of a coke plant, sixteen PAHs and BTEX were detected in soil and groundwater. PAHs'vertical distributions were corresponding with that in the sink area. But the concentrations of 16 PAHs and BTEX monitored from the coke plant were so high that they exceeded screening standard values. BTEX primarily distributed in deep soil and groundwater for its high migration. The concentration of PAHs and BTEX in the manufacturing shop and around the oil tank of the tar workshop were much higher than other parts'. The environmental risk assessment for two typical sites showed that PAHs and BTEX's cancer risks and non-cancer hazard indexes were corresponding with their distribution of concentration. The non-cancer hazard indexes of soil and groundwater around the sink area were all less than one, which meant that they didn't have non-cancer hazardous potentials. Cancer risks of Daa in soil and Bap in groundwater were more than 10^-6, which meant they might induce cancer for human. Under the tar workshop, the non-cancer hazard indexes of Nap, Ane, Fle and Phe in oil were more than one, which meant they had non-cancer hazardous potential. Seven cancerigenic PAHs and BTEX's cancer risks were all more than 10^-6. It suggested that they had notable cancer risk. The non-cancer hazard index of each non-carcinogen in the groundwater was less than one; the cancer risk of benzene in groundwater was more than 10^-6 with the other carcinogens'risks all less than 10^-6. Cancerigenic PAHs and benzene in the area of tar workshop should be considered as the primary compounds to be controlled.