ADIRONDACK LAKE GEOCHEMISTRY REVISITED: WHAT CHANGES CAN WE OBSERVE AFTER 25 YEARS?

In the mid 1980's, in response to acidification of Adirondack lakes, the Adirondack Lake Survey Corporation (ALSC) began a field program measuring geochemical parameters in over 1469 lakes and ponds in the region. To assess possible changes we re-examined 41 ALSC lakes and ponds in 4 specific regions of the Adirondack Park. These regions included; St. Lawrence County (SLC), the Western Adirondacks (WA), the High Peaks region (HP), and the Eastern Adirondacks (EA). The four regions (~10 lakes) were chosen because of their location and geological differences. Limited recovery of pH was found in less than half of the lakes. The more acidic lakes are located in the Western Adirondacks and St. Lawrence County, while those with more neutral pH values are located in the High Peaks Region and the Eastern Adirondacks. The most acidic lake was Pine Pond, in St Lawrence County (pH - 5.1) and the most basic lake was Wolf Pond, in the High Peaks (pH - 7.8). The acid neutralizing capacity (ANC) of each lake was measured and ranged between 10 μeq/L and 140 μeq/L. The ANC was not well correlated with pH (R² = .39) but was better correlated with Ca concentration (R² = .64). Fourteen elements were found above detection limits in >90% of the samples including Ca, Na, S, and Si (>1000 ppb), K and Mg (100-1000 ppb), Al, Sr, and Zn (10-100 ppb), and Ba, Cu, Rb, Li, and Y (<10 ppb). Total dissolved solids averaged 23 ppm and ranged between 265.1 ppm (Lower Cascade Lake - HP) and 1.4 ppm (Pine Pond – SLC). Elevated levels of Cl, Na, Mg and Ca were found in a few lakes along roadways. While most of the lakes and ponds sampled had a chlorine concentration of less than 1 ppm, Lower Cascade Lake had a concentration of 139 ppm. The correlation between Cl and Na in high TDS lakes was strong (R2 = .99) and likely stems from the use of road salt. Calcium and Magnesium concentrations in all lakes are highly correlated (R2 value of .89). Mean Mercury concentrations varied little throughout the region (SLC = 3.80+/-0.85; WA = 3.53+/-1.08; HP = 3.03+/-0.66; EA = 4.03+/-2.11 ppt). The highest (Newport Pond – 9.05 ppt) and lowest concentration (Upper Casade Lake – 1.78 ppt) were found in the EA and HP regions, respectively. There is little correlation between pH and mercury concentrations (R² =.23). The results suggest little or no pH recovery across the Adirondack Park but ubiquitous Mercury in lake waters.