Understanding the fate and bioaccumulation of cyclic volatile methyl siloxanes in an Arctic lake

Abstract

Cyclic volatile methyl siloxanes (cVMS) are used in personal care products and are emitted to aquatic environments through wastewater effluents. Once present in aquatic environments, they can undergo volatilization, hydrolysis or sedimentation. In ice-covered lakes, volatilization of cVMS may be limited and rates of hydrolysis may be slowed down due to low temperatures. This could potentially increase the persistence of cVMS in these systems and hence increase exposure to aquatic organisms. The main objective of this study was to develop a holistic and mechanistic understanding of cVMS behavior by combining multimedia modeling and monitoring for an Arctic lake receiving unintentional wastewater emissions. The dynamic QWASI model and the aquatic module of the ACC-HUMAN model were used to predict the seasonality of cVMS concentrations in Lake Storvannet in Hammerfest, Norway (70 °N, 23 °E). This lake receives sewage emissions from both leaking pipes and sewer overflow events, and is ice covered for approximately 6 months of the year. Lake water, surface sediments, one sediment core, Arctic char (Salvelinus alpinus) and Brown trout (Salmo trutta) from the lake, as well as nearby river water and wastewater were sampled in March and June of 2014. In addition, marine water, surface sediments, and Atlantic cod (Gadus morhua) were sampled from the nearby marine harbor, where the main municipal sewage outlet is currently located. Samples were analyzed for cVMS using established analytical methods. cVMS were detected in sewage, but were below limits of quantification in lake, river, and marine water. However, cVMS were detected in lake and marine surface sediments, and in deeper sediments deposited up to 30 years ago illustrating the persistence of these compounds. cVMS were also measured in liver tissue from both Brown trout, Arctic Char and Atlantic Cod with large variations between individual fish. The cVMS concentrations in freshwater fish are likely to be enhanced through benthic exposure, stressing the importance of the sediment compartment not only for persistence but also for bioaccumulation of cVMS. Temporal variations of cVMS concentrations in Storvannet will be driven by a combination of variable emissions and seasonality in environmental conditions, which will be further investigated through model simulations.