Freely Dissolved Concentrations and Sediment-Water Activity Ratios of PCDD/Fs and PCBs in the Open Baltic Sea

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• 作者：Gerard Cornelissen ; Karin Wiberg ; Dag Broman ; Hans Peter H. Arp ; Ylva Persson ; Kristina Sundqvist ; Per Jonsson
• 刊名：Environmental Science & Technology
• 出版年：2008
• 出版时间：December 1, 2008
• 年：2008
• 卷：42
• 期：23
• 页码：8733-8739
• 全文大小：198K
• 年卷期：v.42,no.23(December 1, 2008)
• ISSN：1520-5851

文摘

Aqueous concentrations of polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) as well as polychlorinated biphenyls (PCBs) in the open sea have heretofore been measured by filtering and extracting large amounts of water. Measurement of freely dissolved concentrations with this technique is difficult because of corrections for sorption to dissolved organic matter. In this study we use a novel, more economic technique using equilibrium passive samplers consisting of 17-μm thin polyoxymethylene (POM-17), capable of measuring freely dissolved aqueous concentrations (C_W) in pristine (i.e., background) locations. POM-17 was employed in an extensive field campaign at five stations in the open Baltic sea to obtain C_W at two depths (1 m above the seafloor and 25 m below the surface). Median C_W in the overlying water was 2.3 pg toxic equivalents (TEQ)/m³ PCDD/Fs and 15 pg/L sum 7-PCB, with generally less than a factor two variation among sites and depths. Also freely dissolved concentrations of native compounds in the surface sediment porewater (C_PW) were determined in laboratory batch experiments. The data were used to derive sediment−water activity ratios, which indicate the diffusive flux direction. It was found that the PCDD/Fs and PCBs were in close equilibrium between the sediment porewater and the overlying water. Comparison of C_PW with total sediment concentrations indicated that more than 90% of the compounds were sorbed to sedimentary black carbon.