Impacts of palustrine wetlands on surface water quality in the Lamprey River watershed, New Hampshire

Surface water chemistry was measured monthly at ten wetlands in New Hampshire from January, 2005 through October, 2006. An additional wetland was sampled intensively and only during summer-autumn, 2005, and summer, 2006. Nitrate, ammonium, dissolved organic nitrogen, total dissolved nitrogen, nitrous oxide, and dissolved organic carbon concentrations in surface waters immediately up- and downstream of the wetlands were compared and changes in concentration were modeled. Nitrate, total nitrogen, organic nitrogen, and organic carbon concentrations differed significantly between upstream and downstream sampling stations. Ammonium and nitrous oxide did not show strong differences between upstream and downstream during much of the sampling period. However, in late summer of 2006, nitrous oxide concentrations increased by three orders of magnitude. The models indicate that inflowing solute concentrations, season of year, and dissolved oxygen concentrations significantly affect changes in some solutes. Wetlands play a critical role in maintaining surface water quality in this watershed.