EFFECTIVENESS OF RIPARIAN BUFFERS IN REDUCING NITRATE-NITROGEN CONCENTRATIONS IN GROUND WATER

摘要

A two-part study was begun in 1997 to evaluate the effectiveness of riparian buffers in reducing ground water nitrate concentrations in Coastal Plain aquifers of North Carolina. The first part of the study statistically compared 14 sites with and 14 sites without riparian buffers to determine possible differences in nitrate concentrations in discharging ground water. Nitrate concentrations were significantly lower (p < 0.10) in young ground water discharging from shallow aquifers at sites with buffers. Decreases in nitrate-nitrogen concentrations were estimated to be about 35% by dilution and 65% by denitrification at sites with riparian buffers. No differences (p > 0.10) in nitrate-nitrogen concentrations were detected between old ground water discharging from buffer and non-buffer areas. The second part of the study compared nitrate in ground water along flow paths from recharge to discharge areas at four selected field sites in different hydrogeologic settings to evaluate the importance of various processes affecting nitrate in ground water. A 50-60% decrease in nitrate concentration due to denitrification occurred in the streambed at one intensively studied site. Dilution by ground water from underlying confined aquifers or from recharge through the buffer was also a factor at two of the sites in reducing nitrate concentrations discharging ground water.