Metals and metalloids in high-altitude Pyrenean lakes: sources and distribution in pre-industrial and modern sediments.

High-altitude Pyrenean lakes are ecosystems far from local pollution sources, and thus they are particularly sensitive to the atmospheric deposition of metals and metalloids. This study aims to quantify the effect of human activity in 18 lakes located in both side of the France-Spain frontier. Sediment cores were collected in summer 2013, sampled at a 1cm resolution and the concentration of 24 elements was measured by ICP-MS. Statistic and chemometric analysis of the results highlights the influence of the geographical position and lithogenic features of each lake basin on trapping pollutants. More than the 80% of the lakes showed values of enrichment factor (EF) above 2 for at least one of the elements investigated in at least one core interval, which corroborates the existence of historical anthropogenic inputs of elements in the studied area. The results demonstrate the natural origin of As and Ti in Pyrenees, together with the significant anthropogenic inputs of Cd, Pb, Sb and Sn from ancient times. The data set points mining activities as the main historical source of pollution and illustrate the large impact of the industrial revolution. The regional variability could reflect also differential long-range transport, followed by dry or wet deposition.

Simulation climate change impact on runoff and sediment yield in a small watershed in the basque country, northern Spain.

Climate change is likely to have an impact on runoff and fluvial sediments in watersheds. These factors are among those used to characterize water bodies in relation to the European Water Framework Directive (WFD). Hence, it is important to investigate the extent to which climate change may hinder the achievement of the objectives of the WFD. We explored the potential impact of climate change on runoff and sediment yield for the Aixola watershed using the Soil and Water Assessment Tool (SWAT). The model calibration (2007-2010) and validation (2005-2006) results were rated as satisfactory. Subsequently, simulations were run for four climate change model-scenario combinations based on two general circulation models (CGCM2 and ECHAM4) under two emissions scenarios (A2 and B2) from 2011 to 2100. All combinations predicted that runoff and sediment yield would decrease compared with baseline (1961-1990). Three combinations suggested that runoff and sediments would decrease by 0.13 to 0.45 m s and 0.11 to 0.43 t every year from 2011 to 2100. However, the CGCM2-B2 scenario resulted in an "extremely likely" increase in runoff and sediments of 0.94 m s and 0.57 t every year. These variations in annual sediment yield are closely related to changes in precipitation. The high degree of uncertainty in the results must be considered when assessing potential impacts and making decisions about adaptation measures. Nevertheless, this first attempt to estimate future sediment yields in our region could be a useful starting point to explore future hydrological impacts in the area.