Sulfate exports from multiple catchments in a glaciated forested watershed in western New York, USA

Abstract

Sulfate ($SO^{{2 - }}_{4}$) concentrations and fluxes were studied for multiple storm events in the Point Peter Brook watershed, a glaciated, forested watershed located in Western New York, USA. Investigations were performed across one large (696 ha) and three small (1.6–3.4 ha) catchments with varying extent of riparian and wetland areas. Concentrations of $SO^{{2 - }}_{4}$ in groundwater sources (mean values: 238–910 μmol_c L⁻¹) were considerably greater than concentrations recorded for rainfall (60 μmol_c L⁻¹) and throughfall (72–129 μmol_c L⁻¹). Seasonality in $SO^{{2 - }}_{4}$ concentrations was most pronounced for valley-bottom riparian waters with maximum concentrations in late winter–spring (February–March) and a minimum in late summer (August). Concentrations of $SO^{{2 - }}_{4}$ in wetland water were considerably less than riparian water indicating the likelihood of $SO^{{2 - }}_{4}$ reduction in anoxic wetland conditions. Storm events displayed a dilution pattern in $SO^{{2 - }}_{4}$ concentrations with a minimum coinciding with the maximum in throughfall contributions. End member mixing analysis (EMMA) was able to predict the storm event concentrations of $SO^{{2 - }}_{4}$ for four of the six comparisons. Concentrations of $SO^{{2 - }}_{4}$ at the outlet of the large (696 ha) catchment were much greater than values recorded for the smaller catchments. Exports of $SO^{{2 - }}_{4}$ in streamflow exceeded the inputs from atmospheric deposition suggesting that watersheds like Point Peter Brook may not show any immediate response to decreases in atmospheric $SO^{{2 - }}_{4}$ deposition.