Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 26

Report comparing the POP composition in soil and sediment cores in the Pyrenees and the Tatra Mountains

This deliverable comprises a paper published in Chemosphere and one published in Environmental Pollution.
1. Persistent organochlorine compounds in soils and sediments of European high mountain lakes. Chemosphere (Grimalt et al, 2004) − The composition of persistent organochlorine compounds (OC) in soils and sediments from two high altitude European mountain lakes, Redon in the Pyrenees and Ladove in the Tatra mountains, has been studied. Sediment cores from two additional lakes in the Tatra mountains, Starolesnianske Pleso and Dlugi Staw, have also been examined. DDTs (1.7?13 ng/ g) were the most abundant OC in soils followed by total polychlorobiphenyls (PCBs; 0.41?1.5 ng/g) and hexachlorobenzene (HCB; 0.15?0.91 ng/g). In sediments, the dominant OC were also DDTs (3.3?28 ng/g1) and PCBs (2.3?15 ng/g). These concentrations are low, involving absence of major pollution sources in these high mountain regions. The downcore OC profiles in soils and sediments were similar but higher concentrations and steeper vertical gradients were observed in the latter. Radiometric determinations showed absence of significant OC transport from catchment to lake. The sediment?soil difference points therefore to a better retention of the OC load in sediments than soils which may be related to the low temperatures that are currently encountered at the bottom of the lake water column and the depletion of sediment bioturbation in these cold environments. Significant qualitative changes in the soil PCB distributions are observed downcore. These involve a dominance of the high molecular weight congeners in the top core sections and those of lower weight (i.e. less chlorinated) in the bottom. Anaerobic dechlorination of higher molecular weight congeners occurring in microsites, e.g. as observed in flooded or poorly drained soils, could be responsible for these changes. This process could be concurrent to bioturbation.

2. Polycyclic aromatic hydrocarbon composition in soils and sediments of high altitude lakes. Environmental Pollution (Grimalt et al, 2004) − Polycyclic aromatic hydrocarbons (PAH) in lake sediments and nearby soils of two European high mountain regions, The Pyrenees and Tatra Mountains, have been studied. Similar mixtures of parent PAH were observed in all cases, indicating predominance of airborne transported combustion products. Nevertheless, the composition of these atmospherically long−range transported PAH was better preserved in the superficial layers of soils than sediments. This difference points to significant PAH degradation process, e.g. during lake water column transport, before accumulation in the latter. Post−depositional transformation was also different in both types of environmental compartments. Thus, lake sediments exhibit higher preservation of the more labile PAH involving lower degree of post−depositional oxidation. However, they also show the formation of major amounts of perylene by diagenetic transformation in the deep sections. This compound is not formed in soils where downcore enrichments of phenanthrene are observed, probably as a consequence of diagenetic aromatization of diterpenoids.

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