Evaluation of environmental risk of micropollutants in Lake Maggiore, Lugano and other subalpine deep lakes

DDx, PCBs, PBDEs, Hg and As contamination in sediments (recent layers) and aquatic organisms of different trophic levels (zooplankton, zebra mussel, fish) were analyzed in Lake Maggiore and Lugano, two large deep perialpine lakes, using data deriving from monitoring activities. We analyzed spatial (between sites) and temporal (2001-2015 period) trends of pollution in order to detect potential contamination sources, to compare concentrations with existing Quality Standards (QSs), and to analyze the bioaccumulation/biomagnification process according to a stable isotope approach (SIA). DDx and Hg contamination in Lake Maggiore, derived from past industrial activities in the Pallanza Basin, still exceed QSs both in actual sediments and fish, with potential risks for the ecosystem. Banned from EU in 1985, PCBs accordingly showed low residual values, while PBDE peaks in recent periods in both lakes exceed BQSs, probably due to current industrial activities. The As concentrations reported mainly derives from geochemical origin. The analysis of the biomagnification of toxicants in a pelagic food chain in Lake Maggiore (zooplankton-fish) is also presented here, according both to the Trophic Magnification Factor (TMF) and to the Trophic Level-adjusted BioMagnification Factor (BMFTL): the importance of seasonality and a Hg > DDx ? PBDEs biomagnification capacity were observed. Low PCB concentrations in biota were detected, probably because of an age-dependent biomagnification.