| With the rapid development of national economy, serious contradiction between oil supply and demand would appear in the future, then China needs to use more onshore oil geological reserves to increase crude oil production, this must result in the petroleum exploitation area transfers to low permeability, low yield, and low abundance area, it must bring more cumulative pollution and worsening ecological risk. Thus, find out the oil pollution source and master the typical petroleum pollutant migration transformation rule and their ecological risk could provide scientific evidence for cleaner production and pollution management and control for petroleum exploitation pollution. The pollutants such as polycyclic aromatic hydrocarbon (PAHs) would enter into air, water, and soil compartment in the process of petroleum exploitation. However, the investigation focus more on the organic pollutant derived from petroleum exploitation in the individual environmental media such as water and soil, and lack of the multimedia environmental pollutant and risk assessment in the onshore oilfield. In this study, the multimedia transport, fate, and source apportionment of PAHs in the onshore oilfield were investigated, and then the spatial distribution and pollutant grade of PAHs in the soil compartment were studied to reveal the relationship between the soil luminescent bacteria biological toxicity and the pollutant sources, the dynamic multimedia integrated ecological risks of16PAHs were assessed in the study area, and the quantitative characterization method of uncertainty in the ecological risk was established.The multimedia environmental transport, fate, and source apportionment of PAHs in onshore oilfield were investigated through the established steady-state, dynamic-state, and interval dynamic multimedia fugacity (IDMF) model, including air, water, soil, and sediment compartment. The modeling results showed that, the primarily input pathway of PAHs enter the multimedia environments is crude oil spills on the soil, while the output pathway was the degradation of PAHs in the soil compartment. Soil was identified as the dominate sink of PAHs. The ring size distribution indicated that compounds containing more than four rings were dominant in air, two-and three-ring compounds were prevalent in water, three ring compounds were mainly in soil, and four-ring compounds were predominant in sediment. The dynamic source apportionment was taken on basis of the constructed IDMF model, it was demonstrated that high temperature combustion was the major source of PAHs in the air and soil, while biomass and coal combustion were attributed to water and sediment compartments. Besides, the modeling results showed a tended to be from petroleum sources as evidenced by the accumulation effect of PAHs and continuous oil exploitation.The previous result has showed that, soil compartment was the main sink of PAHs in the multimedia environments. Hence, the methods of principal component analysis (PC A) and artificial neural network (ANN) were applied to identify the sources of PAHs in the soil contaminants, and an ANN model was established to investigate the contribution of the PAHs to soil biotoxicity. The modeling results revealed that the contamination sources included traffic emissions (13.2%), petroleum-related source (37.4%), coal combustion (36.0%), and coke oven source (13.4%). Besides, spatial distribution and pollution grade of PAHs in the soils were analysised based on the actual sampling and analysis of the collected soils from the six oil wells in the study oilfield. Relevant effect factors of the concentrations level were concluded as condition of ground oil, exploitation scale, exploitation time, and surrounding environment (including vegetation condition, primitive soil types, etc.). Soil pollution grade of the six oil wells were also evaluated through the method of a modified Nemerow Index Method. The evaluation result showed that the percentages of heavy pollution, moderate pollution, and slight pollution were8.02%,8.02%, and2.29%, respectively.Finally, the IDMF model assisted dynamic multimedia integrated ecological risk assessment (IDMF-DMIERA) approach framework was developed. The approach framework was on basis of the modeling results of IDMF model, combining with the uncertainty representation approaches of interval parameter, fuzzy theory, and probability analysis. And then the developed IDMF-DMIERA approach was applied to assess the PAHs dynamic ecological risk in the study area, simulated from1975-2020. The assessment results demonstrated that the highest environmental quality risk come from NAP and ANY, achieved by medium risk level of low-medium risk level. Combined the environmental quality risk assessment results and the PAH source apportionment, it was found that the environmental risks in this study mainly result from petroleum spills and coke oven, which are in accordance with the regional characteristic of the petrochemical industry base of China. Meanwhile, the dynamic multimedia human health risk of16PAHs was assessed during1985-2020, it was represented that the human health in the study area mainly from the human exposure to the soil compartment (>90%), including soil ingestion (35%), inhalation of soil particles (35%), and the skin exposure to the soil (25%). And the fuzzy rule base was constructed in order to characterize the PAHs dynamic multimedia integrated ecological risk level, the assessment results demonstrated that the "very high" ecological risk exists in NAP, BaA, CHR, BbF, BkF, BaP, IPY, and DBA, all possible measures should be taken to treat the ecological risk in the oilfield. |
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