Distribution, Elimination and Rearrangement of Cyclic Volatile Methylsiloxanes in Oil-contaminated Soil of Shengli Oilfield, China

In this study, the authors detected D4-D6 and L3-L16 with high total concentrations (5.20×104 – 1.07×106 ng/g dw) in 18 oil sludge samples collected from Shengli Oilfield during 2008 – 2013. In 306 soil samples from this oilfield, mean concentrations (43.4 – 125 ng/g dw) and detection frequencies (65 – 76%) of D4 – D6 were 10.9 – 11.9 and 2.05 -2.24 times higher than those in reference soil samples. Concentrations of total cyclic siloxanes (?Cyclic) had positive correlations (R2=0.79, p<0.05) with total petroleum hydrocarbons concentration (TPH) in soil, indicating that oil production could release cyclic siloxanes to environment. During 2008 - 2013, increasing tendency (mean 13.4% per annum) of ?Cyclic was found in soil with high TPH (>5000 mg/kg), but not found in soil with lower TPH. Elimination experiments showed that petroleum hydrocarbons could reduce degradation and volatilisation 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 – 40000 mg/kg were 1.19-22.2 and 1.03 -7.43 times larger than those in common soil (TPH = 80 mg/kg), respectively. The authors concluded that the petroleum hydrocarbons could affect the rearrangement reaction rates of D5 and D6 in soil.

Authors: Shi Y, Xu S, Xu L, Cai Y. ;Full Source: Environmental Science & Technology. 2015 Aug 31. [Epub ahead of print] ;