| This study examined the hydrology and nitrate removal capacity of spring-fed surface flowpaths with high initial [NO3-] (10-30 mg/l) in three southern Ontario riparian zones. Surface flow volume declined during the summer and ceased in some areas when the WT declined below 10-20 cm. [NO3-] remained consistently high along rapid (>1 cm/s) and long (>50 m) rivulet flowpaths found in upslope cedar/peat dominated areas, and ranged significantly in slow (<0.1-0.5 cm/s) diffuse and ponded flow paths found in flatter downslope herbaceous areas. High residence times, low [DO], and warm temperatures during summer months reduced [NO3 -] by 50-95% along diffuse flowpaths due to denitrification and some plant uptake but required long riparian widths (>50 m). [NO3 -] also decreased significantly in some ponded areas during spring due to dilution from precipitation/snowmelt and seepage of previously denitrified groundwater. Overall, surface water nitrate exports to streams were largely controlled by seasonal volumetric flux. |
