Fractionation and current time trends of PCB congeners: evolvement of distributions 1950–2010 studied using a global atmosphere-ocean general circulation model

Abstract

PCBs are ubiquitous environmental pollutants expected to decline in abiotic environmental media in response to decreasing primary emissions since the 1970s. A coupled atmosphere-ocean general circulation model with embedded dynamic sub-models for atmospheric aerosols and the marine biogeochemistry and air-surface exchange processes with soils, vegetation and the cryosphere is used to study the transport and fate of four PCB congeners covering a range of 3–7 chlorine atoms. <br><br> The change of the geographic distribution of the PCB mixture reflects the sources and sinks' evolvement over time. Globally, secondary emissions (re-volatilisation from surfaces) are on the long term increasingly gaining importance over primary emissions. Secondary emissions are most important for the congeners with 5–6 chlorine atoms. Correspondingly, the levels of these congeners are predicted to decrease slowest. Changes in congener mixture composition (fractionation) are characterized both geographically and temporally. In high latitudes enrichment of the lighter, less persistent congeners and more delayed decreasing levels in response to decreasing emissions are found. The delivery of the contaminants to high latitudes is predicted to be more efficient than previously suggested. The results suggest furthermore that the effectiveness of emission control measures may significantly vary among substances. The trends of decline of organic contaminant levels in the abiotic environmental media do not only vary with latitude (slow in high latitudes), but do also show longitudinal gradients

Organochlorine pesticides and polychlorinated biphenyls along an east-to-west gradient in subtropical North Atlantic surface water

“…This particulate fraction is expected to be low in surface waters of the studied sea region during winter: <2 % of HCH and low chlorinated PCBs, <4 % of DDT are predicted to be associated, while 5–13 % is expected for the most lipophilic among the targeted substances, PCB180 (log K ow  = 6.9; multicompartment chemistry-transport model with embedded biogeochemical model; Lammel and Stemmler 2012). …”

“…the southern arm of the Antilles current). For PCBs, similarly to DDT, the Azores region, more than the east-to-west (40°–70° W) transect is in fact located in the very region of the Atlantic Ocean which had historically received a major load through atmospheric depositions (Lammel and Stemmler 2012). …”

“…Global PCB distributions 1950–2100 in response to historic emissions have been modelled (Lammel and Stemmler 2012; Octaviani et al 2015), simulating one possible realization of present and future climate. The model-predicted surface seawater concentration of PCBs (i.e.…”

“…They have hardly been primarily emitted since several decades, but their concentrations may be sustained by secondary emissions from oceans and land surfaces (Lammel and Stemmler 2012), only slowly decreasing in the global oceans (Lohmann et al 2007). Their concentrations might even re-rise in the deep sea (Stemmler and Lammel 2013).…”

A Global 3‐D Ocean Model for PCBs: Benchmark Compounds for Understanding the Impacts of Global Change on Neutral Persistent Organic Pollutants

“…2010; Breivik et al, 2002Breivik et al, , 2007. Atmospheric deposition is the main source of PCBs to the global oceans, and rivers are a minor contributor (Jurado et al, 2004;Lammel & Stemmler, 2012;Wania & Daly, 2002). High PCB concentrations in crustaceans from the deep Pacific Ocean illustrate their penetration to even the most remote regions of the ocean (Jamieson et al, 2017).…”