Lu Haiming, Yin Chengqing
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
J Environ Sci (China). 2008;20(6):652-7. doi: 10.1016/s1001-0742(08)62108-7.
This field study investigated the nitrogen concentrations in the shallow groundwater from an ephemeral stream and four land uses: cropland, two-year restored (2 yr) and five-years restored (5 yr) 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 2 yr woodland were significantly (p < 0.05) higher than in 5 yr woodland. The lowest nitrogen concentrations were detected in fishponds. Nitrate-N was the main form in cropland and 2 yr woodland, whereas both nitrate-N and dissolved organic nitrogen (DON) were the main species in 5 yr 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 buffer 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.
本实地研究调查了一条季节性溪流以及四种土地利用类型（农田、恢复两年（2年）和五年（5年）的林地、鱼塘）浅层地下水中的氮浓度，以及于桥水库河岸带的氮通量。在四种土地利用类型中，农田地下水中的硝酸盐氮浓度最高。两年林地中的总溶解氮（TDN）和硝酸盐氮浓度显著高于五年林地（p < 0.05）。鱼塘中的氮浓度最低。硝酸盐氮是农田和两年林地中的主要形态，而硝酸盐氮和溶解有机氮（DON）都是五年林地和鱼塘中的主要形态。但是，铵态氮是季节性溪流中的主要形态。在雨季，携带溶解氮的地下水流沿水力梯度从高地排入水库。农田和水库之间的林地可作为缓冲带，截留浅层地下水氮。季节性溪流中地下水中TDN库中铵态氮的主要形态表明，高地村庄和果园的氮通过地下径流流入水库。鱼塘不是通过浅层地下水进行氮转移的重要污染源。
