Abstract
Cyclic volatile methyl siloxanes (cVMS) are emitted to aquatic environments with wastewater effluents. Here, we evaluate the environmental behavior of three cVMS compounds (octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6)) in a high latitude lake (Storvannet, 70°N 23°E), experiencing intermittent wastewater emissions and high latitude environmental conditions (low temperatures and seasonal ice cover). Measured cVMS concentrations in lake water were below detection limits in both March and June 2014. However, mean concentrations in sediments were 207 ± 30, 3775 ± 973 and 848 ± 211 ng g-1 organic carbon for D4, D5 and D6, respectively. To rationalize measurements, a fugacity-based model for lakes (QWASI) was parametrized for Storvannet. The key removal process for cVMS from the lake was predicted to be advection due to the low hydraulic retention time of the lake, followed by volatilization. Predicted cVMS behavior was highly sensitive to the partition coefficient between organic carbon and water (KOC) and its temperature dependence. Predictions indicated lower overall persistence with decreasing temperature due to enhanced partitioning from sediments to water. Inverse modeling to predict steady-state emissions from cVMS concentrations in sediment provided unrealistically high emissions, when evaluated against measured concentrations in sewage. However, high concentrations of cVMS in sediment and low concentrations in water could be explained via a hypothetical dynamic emission scenario consistent with combined sewer overflows. The study illustrates the importance of considering compound-specific behavior of emerging contaminants that may differ from legacy organic contaminants.
Highlights
We evaluate the environmental behavior of three Cyclic volatile methyl siloxanes (cVMS) compounds (octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6)) in a high latitude lake (Storvannet, 70°N 23°E), experiencing intermittent wastewater emissions and high latitude environmental conditions
Cyclic volatile methyl siloxanes are used in polymer production, personal care products (PCPs) and various technical applications.[1−3] The majority of environmental emissions arise from use of PCPs
We investigate the occurrence and behavior of cVMS in a high latitude lake (Storvannet, 70°N 23°E). This lake was chosen because (i) cVMS contamination was expected as it receives emissions of raw sewage through leaks and combined sewer overflows (CSOs), (ii) the lake is relatively well-studied from investigations on native Arctic Char (Salvelinus alpinus) populations[22] and persistent organic pollutants (POPs) from local sources[23] and (iii) it is located in a high latitude environment with low temperatures and seasonal ice cover providing an opportunity to study the behavior of cVMS under these conditions
Summary
Cyclic volatile methyl siloxanes (cVMS) are used in polymer production, personal care products (PCPs) and various technical applications.[1−3] The majority of environmental emissions arise from use of PCPs. We investigate the occurrence and behavior of cVMS in a high latitude lake (Storvannet, 70°N 23°E) This lake was chosen because (i) cVMS contamination was expected as it receives emissions of raw sewage through leaks and combined sewer overflows (CSOs), (ii) the lake is relatively well-studied from investigations on native Arctic Char (Salvelinus alpinus) populations[22] and persistent organic pollutants (POPs) from local sources[23] and (iii) it is located in a high latitude environment with low temperatures and seasonal ice cover providing an opportunity to study the behavior of cVMS under these conditions. Fugacity-based multimedia modeling[24−26] is used as a mechanistic framework in combination with measurements to understand the behavior of cVMS in this lake and to explore the influence of physicochemical properties, environmental characteristics, and steady-state vs dynamic assumptions
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