太子河小流域氮素输出特征研究

通过定点监测,对太子河源头小流域降雨量和河流系统中总氮、硝态氮和亚硝态氮的质量浓度及其变化规律进行了研究。结果表明:(1) 2011年5-9月,太子河小流域降雨量占全年降雨总量的81.8%,是非点源氮输出的主要时期; (2)研究时段内,各断面总氮的变化趋势呈波浪式,总氮平均浓度表现为:鸡场> 村庄> 旱田> 林地,与土壤背景值具有一致性; (3) 5月7日至6月10日,长期干旱后的初期降雨使得旱田、村庄和鸡场断面总氮浓度较雨季期间高,6月10日至9月30日,随降雨量和降雨次数的增加,浸提作用与稀释作用交互进行,各断面总氮浓度出现先增加后降低的现象; (4)林地、旱田、村庄和鸡场断面硝态氮和亚硝态氮输出浓度与降雨量呈显著正相关,硝态氮是总氮的主要输出形态,分别占总氮的69.2%,63.4%,61.4%和63.8%。植被覆盖虽能有效地减少土壤侵蚀和总氮的流失,却增加了土壤可溶性氮的流失。

Characteristics of Nitrogen Output in Taizi River Watershed

Rainfall and the concentrations and variations of total nitrogen (TN), nitrate, nitrite and N transformation in the headwater area of Taizi River watershed were studied by filed monitoring. Results showed that:(1) Rainfall from May to September in the watershed accounted for 81.8% of the total annual rainfall, which is the principal period for non-point source nitrogen output. (2) The mean concentration of TN had a waving trend in different monitoring sites. The landuse types, in order of decreasing TN content, were chicken farm, village, dry land and woodland, which was consistent with the soil background value. (3) From May 7th to June 10th, the early rainfall after a long term drought increased the TN content in dry land, village and chicken farm in comparison with rainy season. From June 10th to September 30th, TN content firstly decreased and then increased due to the increases in rainfall amount and frequency. In addition, the interaction of extraction and dilution caused by rainfall also increased the TN content. (4) The concentrations of nitrate and nitrite nitrogen in each site had a significant positive correlation with rainfall amount (p<0.05). Nitrate was the main form of total nitrogen output and accounted for about 69.2%, 63.4%, 61.4% and 63.8% of TN for woodland, dry land, village and chicken farm, respectively. Although vegetation cover had benefits in reducing soil erosion and the loss of TN, it increased the loss of soil soluble nitrogen.