Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 64

Report describing the accumulation processes of POPs and metals in continental headwaters

This deliverable comprises two manuscripts, one published in Aquatic Sciences (Fernandez et al) and one submitted to Freshwater Biology (Camarero et al.).

Fernandez et al.
Persistent organic pollutants (POPs), including organochlorine compounds (OCs) and polycyclic aromatic hydrocarbons (PAHs) were measured in two European remote mountain lakes situated in the Pyrenees (Lake Redon) and the Tatra Mountains (Ladove). Both dissolved and particulate water phases were analysed at different water column depths. OCs already banned in most European countries showed similar concentrations in the two lakes, e.g. 6.7?8.5 pg L?1 for HCB, 8.0?12 pg L?1 for DDTs, and 60?64 pg L?1 for PCBs (sum of seven individual congeners), being in general lower than those reported in other remote aquatic systems. Conversely, compounds of OCs presently used or currently emitted to the atmosphere exhibited significant concentration differences between sites. Thus, the higher levels of HCHs (1000? 2630 pg L?1) and endosulfans (780?1610 pg L?1) in Lake Redon compared to Ladove reflect the impact of agricultural activities in the former. In contrast, the higher PAH concentrations in Ladove, 12 ± 1 ng L?1 (mean ± standard deviation) compared with Lake Redon, 0.77?1.6 ng L?1 are evidence of higher deposition levels of combustion residues in the Tatras. POP concentration decreases with depth were observed for the compounds present in the dissolved phase such as endosulfan, HCB, and the low molecular weight PCBs and PAH. The vertical differences were higher in Lake Redon, probably due to its deeper basin. These gradients are consistent with the incorporation of these compounds into the lakes by air−water exchange through the gas−dissolved phase. In contrast, PCBs or PAH associated with the suspended particulate material (those of higher molecular weight) showed uniform concentrations throughout the water column, which may reflect high efficiency in the vertical transport of the compounds associated to this phase.

Camarero et al.
Lakes situated above the local tree line (i.e. alpine and arctic lakes) across Europe continent provide good monitoring systems for environmental change. This is because their relative remoteness makes them good indicators of background pollution, whilst their extreme climatic regimes also makes them sensitive to climate variations. Furthermore, they often hold an undisturbed sedimentary record that can be used to reconstruct past environments. In the present study, the distribution of heavy metals in contemporary and ancient sediments have been surveyed for 275 lakes in alpine/arctic lake districts all over Europe including the Pyrenees, Alps, the Rila Mountains, Retezat Mountains, Julian Alps, Tatras, Scottish Highlands, Central Norway and Greenland. Contemporary (surface) and pre−industrial samples were taken from sediment cores extracted at the deepest part of each lake, and these samples were analysed for Ti, Pb, Cd, Zn, Cu, As, Hg, and Se. These analyses showed that the concentration of trace metals and metalloids is considerably high in the contemporary sediments of these relative remote, pristine lakes. With the exception of Greenland, a large percentage of lakes showed enrichment factors for most elements well above 1.5, indicating the effect of atmospheric pollution. The Tatra Mountains and Scotland seem to be the most affected areas. Pb, Hg and As are the elements that present the highest levels of diffuse pollution on the European scale.

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