Elucidating the Behavior of Cyclic Volatile Methylsiloxanes in a Subarctic Freshwater Food Web: A Modeled and Measured Approach

Ingjerd S Krogseth,Knut Breivik,Guttorm N Christensen,Emma Undeman,Anita Evenset,Mick J Whelan,Nicholas A Warner

doi:10.1021/acs.est.7b03083

Abstract

Cyclic volatile methylsiloxanes (cVMS) are used in personal care products and emitted to aquatic environments through wastewater effluents, and their bioaccumulation potential is debated. Here, a new bentho-pelagic version of the ACC-HUMAN model was evaluated for polychlorinated biphenyls (PCBs) and applied to cVMS in combination with measurements to explore their bioaccumulation behavior in a subarctic lake. Predictions agreed better with measured PCB concentrations in Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) when the benthic link was included than in the pelagic-only model. Measured concentrations of decamethylcyclopentasiloxane (D5) were 60 ± 1.2 (Chironomidae larvae), 107 ± 4.5 (pea clams Pisidium sp.), 131 ± 105 (three-spined sticklebacks: Gasterosteus aculeatus), 41 ± 38 (char), and 9.9 ± 5.9 (trout) ng g-1 wet weight. Concentrations were lower for octamethylcyclotetrasiloxane (D4) and dodecamethylcyclohexasiloxane (D6), and none of the cVMS displayed trophic magnification. Predicted cVMS concentrations were lower than measured in benthos, but agreed well with measurements in fish. cVMS removal through ventilation was an important predicted loss mechanism for the benthic-feeding fish. Predictions were highly sensitive to the partition coefficient between organic carbon and water (KOC) and its temperature dependence, as this controlled bioavailability for benthos (the main source of cVMS for fish).

Highlights

Cyclic volatile methyl siloxanes, such as octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6), are used as ingredients in personal care products and are emitted to aquatic environments through wastewater effluents.[1−3] D4 has been classified as a persistent, bioaccumulative, and toxic (PBT) substance and D5 as a very persistent and very bioaccumulative substance in a European Chemical Agency Member State Committee opinion.[4]
A new bentho-pelagic version of the ACC-HUMAN model was evaluated for polychlorinated biphenyls (PCBs) and applied to Cyclic volatile methylsiloxanes (cVMS) in combination with measurements to explore their bioaccumulation behavior in a subarctic lake
Predictions were highly sensitive to the partition coefficient between organic carbon and water (KOC) and its temperature dependence, as this controlled bioavailability for benthos

Summary

INTRODUCTION

Cyclic volatile methyl siloxanes (cVMS), such as octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6), are used as ingredients in personal care products and are emitted to aquatic environments through wastewater effluents.[1−3] D4 has been classified as a persistent, bioaccumulative, and toxic (PBT) substance and D5 as a very persistent and very bioaccumulative (vPvB) substance in a European Chemical Agency Member State Committee opinion.[4]. Exceptions include applications of the AquaWeb[6] and ACC-HUMAN models.[24,28] ACC-HUMAN predicted trophic dilution of cVMS in zooplankton, herring, and cod from the Inner Oslofjord (which receives high wastewater emissions), in accordance with measurements.[24] given the importance the sediments have as a reservoir of cVMS, there is a need for a benthic link in the model This is important for systems such as Storvannet where fugacities in sediment often exceed those in the water column due to intermittent emission events and rapid advection of the water column.[20] Here, we explore the bioaccumulation behavior of cVMS using the ACCHUMAN model, which was expanded to include a benthic link. Lake Storvannet was chosen as (i) the lake and its food web is relatively well-studied,[29,30] (ii) measurements of PCBs from lake water, sediments, and biota are available for model evaluation purposes,[31] and (iii) a study of cVMS behavior in the physical environment of the lake has already been carried out.[20]

MATERIALS AND METHODS

RESULTS AND DISCUSSION

■ ACKNOWLEDGMENTS

■ REFERENCES