Persistent organic pollutants in remote freshwater ecosystems

Abstract

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 analyzed 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. On the contrary, compounds of present use 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 than in Ladove are in agreement with an impact of agricultural activities in the former. In contrast, the higher PAH concentrations in Ladove, 12 ± 1 ng L−1 (mean ± standard deviation), than in Lake Redon, 0.77–1.6 ng L−1 evidence higher deposition 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 to 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.