Occurrence and profiles of methylsiloxanes and their hydrolysis product in aqueous matrices from the Daqing oilfield in China.

In the present study, the occurrence and distribution of methylsiloxanes (D4-D6, L5-L16) in the surface water and sediment collected from the Daqing oilfield were explored. For wastewater samples from an oilfield combination station, the concentrations of total cyclic methylsiloxanes (∑CMS, D4-D6) and total linear methylsiloxanes (∑LMS, L5-L16) ranged from 137-1911ng/L to 49.4-190ng/L, respectively. Cyclic methylsiloxanes were the predominant methylsiloxanes in the analyzed wastewater samples from the oilfield combination station. In addition, methylsiloxanes were detected in the surface water from three sampling areas, and the total concentrations varied from <LOQ-785ng/L (mean=219±277ng/L, median=120ng/L) for the new oilfield area, 15.1-1808ng/L (mean=270±409ng/L, median=105ng/L) for the old oilfield area and 18.0-252ng/L (mean=103±90.4ng/L, median=52.3ng/L) for the reference area. In the sediment, the ∑CMS and ∑LMS values in the samples collected from the old oilfield area were almost four to nine times higher than those in the samples from the new oilfield area. In addition, elevated concentrations of dimethylsilanediol were detected in the three sampling areas, especially in the old oilfield area (mean=85.6±98.3ng/L), which confirmed that hydrolysis occurred.