Arctic lakes exhibit a full range of chemistries, from very dilute waters with electrical conductivities approaching rainwater to waters concentrated by evaporation to beyond the salinity of seawater. Within this range, however, the majority of lakes are relatively dilute (conductivity <300 mS cm-1); this is due in large part to the underlying permafrost, which isolates surface waters and soils from weathering interactions with deeper mineral soils and rocks. The unfrozen zone beneath lakes (talik) may extend for many meters, but the impact of weathering in this zone on lake chemistry is almost entirely unknown. In the rest of the catchment, weathering reactions are confined to the very shallow unfrozen layers at the surface. In addition, weathering rates are slowed by cold temperatures and essentially stopped by lack of liquid water, and thus rivers that drain arctic tundra and feed lakes tend to be very dilute. Finally, the particular chemical compositions of lakes are dependent on several factors, including proximity to the ocean and the land surface age and geology for inorganic materials, and for organic materials compositions depend on the extent and type of terrestrial vegetation in the surrounding catchment.
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