The seasonality of chemical persistence in a Swedish lake by benchmarking
Chemicals with high persistence (i.e. long degradation half-lives) could pose high risks to living organisms and humans and be subject to long-range transport. It is challenging to measure persistence directly in the field due to lack of appropriate methods. Chemical benchmarking as an alternative method was evaluated to have potential to assess the persistence in real aquatic environment . It has been further applied in a Swedish lake (Norra Bergundasjön) for measuring the persistence of a group of pharmaceuticals and compared (and validated) with traditional mass balance approach . The degradation of a chemical in a lake could be influenced by several factors including temperature, sunlight, pH and nature of the degrading microorganisms, which may vary in time and space. So in this study benchmarking was used to study the temporal variation of persistence of 7 pharmaceuticals in another Swedish lake (Boren) that receives the discharge from a WWTP and inflowing water from Vättern. The sampling campaigns were conducted in late spring, late autumn and winter of 2013. Acesulfame K (an artificial sweetener) was used as the benchmark chemical. The results show that the strongest seasonal variability was between spring and autumn. The half-lives of 5 chemicals in spring were shorter than in autumn, mainly because of lower temperature and weak irradiation in autumn. The half-lives of chemicals in Boren were also compared with that in Norra Bergundasjön. This could be explained by the difference in the nutrient status and pH in these two Swedish lakes. Benchmarking did open a new door to measure persistence in a broader range than before and more opportunities to study the spatial and temporal variability of persistence in the real environment.
Chemical benchmarking to determine the persistence of pharmaceuticals in a Swedish lake.
Cyclic volatile methylsiloxanes in fish from the Baltic Sea
Laboratory studies suggest that the cyclic volatile methylsiloxanes (cVMS) octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (05) and dodecamethylcyclohexasiloxane (D6) will persist in the aquatic environment and bioaccumulate in fish. Here these cVMS were measured in herring collected in the Swedish waters of the Baltic Sea and the North Sea and in grey seals from the Baltic Proper. D4, D5, and D6 were present in herring muscle at concentrations around 10, 200, and 40 ng g(-1) lipid weight, respectively. The ratio of these concentrations was similar to the relative magnitude of estimated emissions to water, suggesting that the efficiency of overall transfer through the environment and food web was similar (within a factor 2-3) for the three chemicals. The concentrations of D5 and D6 were similar in herring caught in the highly populated Baltic Proper and in the less populated Bothnian Sea and Bothnian Bay. The D4 concentrations were lower at the most remote northern station, suggesting that D4 is less persistent than D5 and D6. Herring from the North Sea had lower levels of all three chemicals. The concentrations of D4, D5 and D6 in grey seal blubber were lower than the lipid normalized concentrations in herring, indicating that they do not biomagnify in grey seals. (C) 2012 Elsevier Ltd. All rights reserved.
Bioaccumulation of decamethylcyclopentasiloxane in perch in Swedish lakes
Decamethylcyclopentasiloxane (D5), a high production volume chemical used in personal care products, enters the environment both via air and sewage treatment plant (STP) recipients. It has been found in fish, and there is concern that it may be a bioaccumulative substance. In this work D5 was analyzed in perch from six Swedish lakes that did not receive STP effluent, and in perch and sediment from six lakes that received STP effluent. In the lakes receiving the STP effluent, the D5 concentrations in sediment varied over three orders of magnitude and were correlated with the number of persons connected to the STP normalized to the surface area of the receiving body. In the lakes not receiving effluent, the D5 levels in perch were all below the LOQ while D5 was above the LOQ in almost all perch from lakes that received effluent. The D5 concentrations in perch and sediment from the lakes receiving STP effluent were correlated. This shows that STP effluent is a much more important source of D5 to aquatic ecosystems than atmospheric deposition, and that the risk of adverse effects of D5 on aquatic life will be greatest in small recipients receiving large amounts of STP effluent. The bioaccumulation of D5 was compared to that of PCB 180 on the basis of multimedia bioaccumulation factors (mmBAFs), which describe the fraction of the contaminant present in the whole aquatic environment (i.e. water and surface sediment) that is transferred to the fish. In four of the six lakes the mmBAF of D5 was >0.3 of the mmBAF of PCB 180. Given that PCB 180 is a known highly bioaccumulative chemical, this indicates that the bioaccumulation of D5 in perch is considerable. (C) 2012 Elsevier Ltd. All rights reserved.
Junge relationships in measurement data for cyclic siloxanes in air
In 1974, Junge postulated a relationship between variability of concentrations of gases in air at remote locations and their atmospheric residence time, and this Junge relationship has subsequently been observed empirically for a range of trace gases. Here, we analyze two previously-published datasets of concentrations of cyclic volatile methyl siloxanes (cVMS) in air and find Junge relationships in both. The first dataset is a time series of concentrations of decamethylcyclopentasiloxane (D-5) measured between January and June, 2009 at a rural site in southern Sweden that shows a Junge relationship in the temporal variability of the measurements. The second dataset consists of measurements of hexamethylcyclotrisiloxane (D-3), octamethylcyclotetrasiloxane (D-4) and D-5 made simultaneously at 12 sites in the Global Atmospheric Passive Sampling (GAPS) network that shows a Junge relationship in the spatial variability of the three cVMS congeners. We use the Junge relationship for the GAPS dataset to estimate atmospheric lifetimes of dodecamethylcyclohexasiloxane (D-6), 8:2-fluorotelomer alcohol and trichlorinated biphenyls that are within a factor of 3 of estimates based on degradation rate constants for reaction with hydroxyl radical determined in laboratory studies. (C) 2012 Elsevier Ltd. All rights reserved.
Concentrations in ambient air and emissions of cyclic volatile methylsiloxanes in Zurich, Switzerland
Tens of thousands of tonnes of cyclic volatile methylsiloxanes (cVMS) are used each year globally, which leads to high and continuous cVMS emissions to air. However, field measurements of cVMS in air and empirical information about emission rates to air are still limited. Here we present measurements of decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) in air for Zurich, Switzerland. The measurements were performed in January and February 2011 over a period of eight days and at two sites (city center and background) with a temporal resolution of 6–12 hours. Concentrations of D5 and D6 are higher in the center of Zurich and range from 100 to 650 ng m−3 and from 10 to 79 ng m−3, respectively. These values are among the highest levels of D5 and D6 reported in the literature. In a second step, we used a multimedia environmental fate model parameterized for the region of Zurich to interpret the levels and time trends in the cVMS concentrations and to back-calculate the emission rate of D5 and D6 from the city of Zurich. The average emission rates obtained for D5 and D6 are 120 kg d–1 and 14 kg d–1, respectively, which corresponds to per-capita emissions of 310 mg capita−1 d−1 for D5 and 36 mg capita−1 d−1 for D6.
Occurrence and Seasonality of Cyclic Volatile Methyl Siloxanes in Arctic Air
Cyclic volatile methyl siloxanes (cVMS) are present in technical applications and personal care products. They are predicted to undergo long-range atmospheric transport, but measurements of cVMS in remote areas remain scarce. An active air sampling method for decamethylcyclopentasiloxane (D5) was further evaluated to include hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), and dodecamethylcyclohexasiloxane (D6). Air samples were collected at the Zeppelin observatory in the remote Arctic (79 degrees N, 12 degrees E) with an average sampling time of 81 +/- 23 h in late summer (August-October) and 25 +/- 10 h in early winter (November-December) 2011. The average concentrations of D5 and D6 in late summer were 0.73 +/- 0.31 and 0.23 +/- 0.17 ng/m(3), respectively, and 2.94 +/- 0.46 and 0.45 +/- 0.18 ng/m(3) in early winter, respectively. Detection of D5 and D6 in the Arctic atmosphere confirms their long-range atmospheric transport. The D5 measurements agreed well with predictions from a Eulerian atmospheric chemistry-transport model, and seasonal variability was explained by the seasonality in the OH radical concentrations. These results extend our understanding of the atmospheric fate of D5 to high latitudes, but question the levels of D3 and D4 that have previously been measured at Zeppelin with passive air samplers.
Consistency in Trophic Magnification Factors of Cyclic Methyl Siloxanes in Pelagic Freshwater Food Webs Leading to Brown Trout
Cyclic volatile methyl siloxanes (cVMS) concentrations were analyzed in the pelagic food web of two Norwegian lakes (Mjosa, Randsfjorden), and in brown trout (Salmo trutta) and Arctic char (Salvelinus alpinus) collected in a reference lake (Femunden), in 2012. Lakes receiving discharge from wastewater treatment plants (Mjosa and Randsfjorden) had cVMS concentrations in trout that were up to 2 orders of magnitude higher than those in Femunden, where most samples were close to the limit of quantification (LOO). Food web biomagnification of cVMS in Mjosa and Randsfjorden was quantified by estimation of trophic magnification factors (TMFs). TMF for legacy persistent organic pollutants (POPs) were analyzed for comparison. Both decamethylcyclopentasiloxane (DS) and dodecamethylcyclohexasiloxane (D6) biomagnified with TMFs of 2.9 (2.1-4.0) and 2.3 (1.8-3.0), respectively. Octamethylcyclotetrasiloxane (D4) was below the LOQ in the majority of samples and had substantially lower biomagnification than for D5 and D6. The cVMS TMFs did not differ between the lakes, whereas the legacy POP TMFs were higher in Mjosa than inRandsfjorden. Whitefish had lower cVMS bioaccumulation compared to legacy POPs, and affected the TMF significance for cVMS, but not for POPs. TMFs of D5 and legacy contaminants in Lake Mjosa were consistent with those previously measured in Mjosa.