Enhanced deposition of trace elements driven by climate change in a mountain catchment

Sufficient evidence has been gathered from observational records to indicate that climate change has an amplified effect on physical, chemical and biological processes in sensitive regions such as mountain landscapes (IPCC 2007). However, its potential impact on trace elements dynamics in such exposed environments has received little attention. Here, we examined whether change in sedimentary record of a number of trace elements (As, Cu, Mn, and Pb) from Bubal reservoir, a 1085m altitude waterbody from central Pyrenees, can be attributed to recent alterations in the local climate. For this purpose a sediment core was collected from the lake bed in August 2005, covering the depositionary period 1972-2004. The core was subsampled at 1.5cm intervals, corresponding to the annual sedimentation rate in the catchment (Lavilla et al. 2006). The <0.25mm fraction of each subsample was oven dried and digested for trace element contents following USEPA (1999). Arsenic, Cu, Mn and Pb were determined by ICPMS according to standard protocols. Titanium was characterised by ICP-OES. Organic matter was estimated as % loss on ignition at 550ºC. Climate data was provided by the Spanish Institute of Meteorology, Madrid. Sediment trace elements showed strong association with major elements Ti and Mn, and organic matter contents (stepwise multiple linear regression with forward selection procedure, adjusted R2= 0.41, P<0.001). This relationship, together with the generally low values of organic matter (mean %LOI= 3.4%) indicates the source of trace elements largely being the weathered material from the catchment. The metal concentrations also decreased with depth (ANOVA F ≥7.89, P