determined with each set of samples. A check standard (6 µg/L) was analyzed after every tenth sample.Callinan et al | http://dx. Location 1-systems with substantial allochthonous contribution, 2-systems in which some THMFP samples exceeded detector, DOC-dissolved organic carbon, THMFP-trihalomethane formation potentialInset numbers represent percent increase relative to spring minimum.Callinan et al | http://dx.

Most previous studies on the effects of acid rain have been conducted in areas with low acid-neutralizing, or buffering, capacity. In contrast, significantly less study has occurred in calcareous terrane that has high-buffering-capacity and that has traditionally been thought to be ''insensitive'' to the effects of acid rain. To address this fundamental inequity we have conducted a comprehensive study of near-surface (Ͻ1 m), historic age (Ͻ200 yr) sediments in the Finger Lakes of central New York State, a high buffering capacity area that has received significant quantities of acid rain. In particular, we have focused on authigenic calcite contained in historic bottom sediment as well as water-column geochemistry between 1972 and 1999. Results indicate that the open-water precipitation of calcite (''whitings'') returned to 7 of the 11 Finger Lakes during historic time following an ϳ4500 14 C yr hiatus. Only those lakes with calcite in the near-surface sediment have calcareous soils and/or limestone outcrops in their drainage basins and summer surface waters that are supersaturated with respect to calcite. Water-column data indicate that the saturation state of summer surface waters has increased in at least seven Finger Lakes between 1972 and 1999 and that calcium loading to lakes lacking calcite has also increased over the same time interval.

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