Distribution, Elimination, and Rearrangement of Cyclic Volatile Methylsiloxanes in Oil-Contaminated Soil of the Shengli Oilfield, China
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文摘
Cyclic methylsiloxane standards (D4, D5, and D6) and linear methylsiloxanes (L3 through L16) were detected with high total concentrations (from 5.20 脳 104 to 1.07 脳 106 ng/g dw) in 18 oil sludge samples collected from the Shengli oilfield during 2008鈥?013. In 306 soil samples from this oilfield, the mean concentrations (43.4鈥?25 ng/g dw) and the detection frequencies (65鈥?6%) of D4鈥揇6 were 10.9鈥?1.9 and 2.05鈥?.24 times higher than those in reference soil samples, respectively. The concentrations of total cyclic siloxanes (危Cyclic) had positive correlations (R2 = 0.79, p < 0.05) with the total petroleum hydrocarbons concentration (TPH) in soil, indicating that oil production could release cyclic siloxanes to the environment. During 2008鈥?013, an increasing tendency (mean of 13.4% per annum) of 危Cyclic was found in soil with high TPH (>5000 mg/kg) but was not found in soil with lower TPH. Elimination experiments showed that petroleum hydrocarbons could reduce the degradation and volatilization rates of D4, D5, and D6 in impacted oilfield soil. The half-lives of D4, D5, and D6 in the opened and capped soil systems with TPH = 400鈥?0鈥?00 mg/kg were 1.19鈥?2.2 and 1.03鈥?.43 times larger than those in common soil (TPH = 80 mg/kg), respectively. Furthermore, the petroleum hydrocarbons could affect the rearrangement-reaction rates of D5 and D6 in soil.