Shallow groundwater nitrogen responses to di erent land use managementsin the riparian zone of Yuqiao Reservoir in North China
LU Haiming , YIN Chengqing
DOI:
Received March 16, 2007,Revised January 25, 2008, Accepted , Available online
Volume 20,2008,Pages 652-657
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This field study investigated the nitrogen concentrations in the shallow groundwater from an ephemeral stream and four land uses:
cropland, two-year restored (2yr) and five-years restored (5yr) woodlands, fishponds, and the nitrogen flux in the riparian zone of
Yuqiao Reservoir. The groundwater nitrate-N concentrations in cropland were the highest among the four land uses. Total dissolved
nitrogen (TDN) and nitrate-N concentrations in the 2yr woodland were significantly (p < 0.05) higher than in 5yr woodland. The lowest
nitrogen concentrations were detected in fishponds. Nitrate-N was the main form in cropland and 2yr woodland, whereas both nitrate-N
and dissolved organic nitrogen (DON) were the main species in 5yr woodland and fishponds. But, ammonium-N was the main form
in the ephemeral stream. During the rainy season, the groundwater flow with dissolved nitrogen drains from upland into the reservoir
along the hydraulic gradient. The woodland between the cropland and reservoir could act as a bu er to retain shallow groundwater
nitrogen. The dominant form of ammonium-N in the groundwater TDN pool in ephemeral stream indicated that nitrogen from the
village and orchard in upland flowed into the reservoir via subsurface flow. The fishpond was not an important pollution source for
nitrogen transfer via shallow groundwater.
