Landscape factors that affect acid-base chemistry of Adirondack Long-Term Monitoring (ALTM) lakes

The Adirondack region has been affected by acid deposition for multiple decades. The objective of this study was to investigate the relations of volume-weighted concentrations and long-term changes of surface water chemistry of the Adirondack region with landscape characteristics of watersheds to improve the understanding of the factors that drive chemical recovery of surface water from declines in acid deposition.;I observed that changes in NO3- concentrations in precipitation after 2004 had a very similar pattern as SO4 2- at all three National Atmospheric Deposition Program (NADP) sites in the Adirondacks (NY20, NY29, and NY98), and that more than 80 percent of the variation in annual volume-weighted H+ concentrations in atmospheric deposition can be explained by the variation in the sum of SO 42- and NO3- concentrations. I also interpolated from 8 NADP sites using the Kriging method to achieve continuous maps of precipitation concentrations of major ions in the Adirondacks, and validated the results against the measurements from an additional NADP site (NY29) at Moss Lake.;Results of this study indicated that spatial variation in volume-weighted lake SO42- concentrations and lake SO4 2- decreasing rates were influenced by wet atmospheric deposition of SO42- but were also affected a combination of landscape factors including elevation, lake hydraulic residence time, wetland and canopy coverage, and thickness of glacial till deposits. Higher volume weighted concentrations of SO42- were found in drainage lakes than seepage lakes and lakes of higher elevation, shorter hydraulic residence time, lesser wetland coverage, and thicker deposits of glacial till.;Volume weighted NO3- concentrations and NO 3- decreasing rates in ALTM lakes, in contrast to SO 42-, showed no relationship with atmospheric deposition. Regression analyses indicated that higher volume weighted NO3 - concentrations were found in drainage lakes at higher elevation, with steeper land slope, or lower chlorophyll a concentrations.;The spatial variation in volume weighted Ca2+ concentrations and rates of Ca2+ decreases in ALTM lakes were attributed to the processes of weathering and leaching from soil exchange complex. I used lake Na+ and dissolved SiO2 as indicators of weathering input. Regression analyses demonstrated that ALTM lake watersheds with greater input from weathering and higher concentrations of soil exchangeable Ca 2+ had higher volume weighted Ca2+ concentrations. I also observed more rapid decreases of Ca2+ in lake watersheds of more rapid changes in weathering and leaching processes.;Results of this study suggested that spatial variation in volume weighted acid neutralizing capacity (ANC) of ALTM seepage lakes were primarily driven by wet deposition of SO42- + NO3 - and in-lake processes. Volume weighted ANC of ALTM drainage lakes were influenced by atmospheric deposition of SO42- + NO3-, but were also affected by a combination of landscape factors including wetland coverage, land slope, cation weathering, and cation exchange.;Higher volume-weighted DOC was found in lakes with lower concentrations of SO42- and NO3-, higher O horizon C:N ratio, B horizon base saturation, and greater color. More rapid increases in DOC concentrations were observed in lakes with more rapid decreases in SO42- and NO3-, more rapid changes in color of lake water, and higher O horizon exchangeable Al and Fe. (Abstract shortened by UMI.).