Chemical pollution in inland shallow lakes in the Mediterranean region (NW Spain): PAHs, insecticides and herbicides in water and sediments

Abstract

The possible effect of land uses and human-related geographic patterns (presence of roads and urban settlements) on chemical pollution was evaluated in the waters and sediments of fifty-three Mediterranean shallow lakes. The presence of fifty-nine pollutants (belonging to PAHs, insecticides and herbicides groups) was analysed in these lakes by GC–MS. The studied lakes had similar pollutant concentrations to other lakes worldwide. The distribution of the compounds between water and sediment compartments was strongly influenced by log Kow values (an average of 3.61 for compounds found in water and of 4.69 for compounds found in sediments). A multivariate analysis suggested that the concentration of PAHs in water could be related to agricultural activities and not related to local road traffic. When assessing nutrient levels in the lakes, it was observed that eutrophicated lakes [>300μgL−1 total phosphorus (TP)] appeared in areas affected by urban or industrial use (at least 2% urban use in a 1-km radius around the lake), whilst lakes with lower TP concentrations were placed in forest areas (60% of forest use in a 1-km radius); in addition, the aqueous concentrations of Σ(PAH) were lower in lakes with higher TP concentrations (>150μgL−1 TP), which could be related to the adsorption capacity of PAHs onto suspended matter which is present in mesotrophic and eutrophic lakes, thus being removed from the aqueous phase.