Total mercury concentration was analyzed in 171 lakes from pre-industrial (>30 cm depth; Hg pre-industrial) and present-day sediments (0.5-1 cm; Hg present-day). Numerous hot or cold spots of sediment mercury enrichment (Hg EF; Hg pre-industrial/Hg present-day) were evident as determined by local tests of autocorrelation, although in most cases, the maximum correlation among sites was not the nearest neighbor, indicating a strong influence of watershed characteristics. Hg EF was correlated with the area of open water (ha) (r = 0.91, p = 0.035), mine tailings (r = 0.94, p = 0.019), and organic deposits in surficial geology of the watershed (r = -0.91, p = 0.034). Through use of local rather than global regression coefficients, R 2 increased from 0.20 (p = 0.005) to 0.60 (p = 0.013). A broad spatial pattern (>500 km) observed only in Hg pre-industrial was best explained by mean annual precipitation (shared variance = 3.5%), while finer spatial patterns only observed in Hg present-day and Hg EF were best explained by pH (average shared variance = 10.8%). © 2009 Elsevier Ltd. All rights reserved.