Lead, zinc, and chromium concentrations in acidic headwater streams in Sweden explained by chemical, climatic, and land-use variations

[摘要] Long-term data series (1996–2009) for eleven acidic headwater streams(< 10 km²) in Sweden were analyzed to determine factorscontrolling concentrations of trace metals. In-stream chemical data as wellclimatic, flow, and deposition chemistry data were used to develop modelspredicting concentrations of chromium (Cr), lead (Pb), and zinc (Zn). Datawere initially analyzed using partial least squares to determine a set ofvariables that could predict metal concentrations across all sites. Organicmatter (as absorbance) and iron related positively to Pb and Cr, while pHrelated negatively to Pb and Zn. Other variables such as conductivity,manganese, and temperature were important as well. Multiple linearregression was then used to determine minimally adequate prediction modelswhich explained an average of 35% (Cr), 52% (Zn), and 72% (Pb) ofmetal variation across all sites. While models explained at least 50% ofvariation in the majority of sites for Pb (10) and Zn (8), only three sitesmet this criterion for Cr. Investigation of variation between site modelsfor each metal revealed geographical (altitude), chemical (sulfate), andland-use (silvaculture) influences on predictive power of the models.Residual analysis revealed seasonal differences in the ability of the modelsto predict metal concentrations as well. Expected future changes in modelvariables were applied and results showed the potential for long-termincreases (Pb) or decreases (Zn) for trace metal concentrations at thesesites.

[学科分类] 地球化学与岩石