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(051) The control exerted by soil on the global transport and distribution of persistent organic pollutants. Jones, Kevin1, Ockenden, Wendy1, Breivik, Knut2, Sweetman, Andy1, Meijer, Sandra1, 1 2 ABSTRACT- Concern about POPs centres around their potential toxicity, propensity for long-range atmospheric transport (LRAT) and the suggestion that they may condense and accumulate in the colder polar regions. This has resulted in international measures to ban/restrict the use/release of several POPs. Polychlorinated biphenyls (PCBs) are industrial chemicals, which provide a classic illustration of POP behaviour. A latitudinally segmented global PCB inventory was derived which shows that the bulk of their global usage has been in the temperate industrial zone (30-60oN) of the northern hemisphere. We have undertaken a global soil survey of PCBs (and other POPs). This has enabled us to estimate how much of the global burden still remains in the surface soils of this 'source region'. We will show that only a small proportion of the PCB burden has 'made the journey' via LRAT out of this latitudinal band to the tropics, Arctic or southern hemisphere. From soil and air field data and using a novel model, we argue that soils control the retention, occlusion and degradation of PCBs, by limiting the fraction ever likely to be available for air-soil exchange and hence LRAT. These processes, largely ignored or under-estimated in regional/global fate models to date, have 'protected' the polar regions against receiving POPs and help explain the observed declines in PCBs in air and biota globally. Key words: POPs, soil, long range transport, global cycling |
