中文关键词
土地利用硝酸盐氢氧同位素氮氧同位素稳定同位素模型 | 英文关键词land usenitratehydrogen and oxygen isotopesnitrogen and oxygen isotopesSIAR model |
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| 中文摘要 |
| 不同的土地利用类型对所在流域内的水质产生不同的影响.本研究选取典型城市河流（京杭运河杭州段）和典型山林农业区河流（余英溪）为研究对象，利用多同位素技术（δD-H2O，δ18O-H2O，δ15N-NO3-和δ18O-NO3-）结合稳定同位素（stable isotope analysis in R，SIAR）模型，对运河和余英溪的硝酸盐来源进行了识别并计算了各污染源的贡献率.结果表明，运河和余英溪均存在不同程度的氮污染，运河以NO3--N和NH4+-N为主，余英溪以NO3--N为主.运河和余英溪水的氢氧同位素（δD-H2O，δ18O-H2O）沿当地大气降水线分布，两者存在明显线性关系（R2=0.78），表明降水是这两条河流的主要补给源.运河和余英溪水体NO3-的氮同位素值（δ15N-NO3-）均小于15‰，说明这两条河流中主要存在硝化作用.部分运河水样NO3-的δ15N-NO3-/δ18O-NO3-值介于1.3~2.1之间且伴随着低浓度的DO和NO2-，可见部分运河水体存在反硝化作用.运河水样δ15N-NO3-值（均值：6.1‰）明显高于余英溪水体δ15N-NO3-值（均值：2.3‰）.各NO3-源对运河的贡献率：生活污水/粪肥（37.0%） > 土壤氮（35.7%） > 化学肥料（19.1%） > 降水（8.2%）；对余英溪的贡献率：化学肥料（46.1%） > 土壤氮（22.8%） > 降水（17.3%） > 生活污水/粪肥（13.8%）.在人类活动强度大的城市区域的河流（运河）中由于生活污水的零星排放和城市降雨径流的汇入导致生活污水/粪肥类氮源的污染明显加剧.化学肥料不可避免地成为山林农业区河流（余英溪）的主要污染源，可见农业面源污染带给所在区域水体的氮污染已非常严重.人类活动强度大的区域，降水对于水体NO3-的贡献降低.反硝化作用产生的同位素分馏对利用SIAR模型计算各NO3-源的贡献率产生不同程度的影响，其中对生活污水/粪肥和化学肥料的影响很大，对土壤氮的影响其次，对降水的影响最低. |
| 英文摘要 |
| Different land uses have different impacts on the water quality of the region. Multiple isotopes (δD-H2O, δ18O-H2O, δ15N-NO3-, and δ18O-NO3-) and the SIAR (stable isotope analysis in R) model were applied to identify the nitrate sources and estimate the proportional contributions of multiple nitrate sources in a river in a typical urban area (the Grand Canal, Hangzhou) and a river in a typical forest and agricultural area (Yuying Riveri). The results indicated that there were different degrees of nitrogen pollution in the Grand Canal and Yuying River; NO3--N and NH4+-N are the predominant forms of nitrogen in the Grand Canal, and the primary form of nitrogen in Yuying River was NO3--N. There was an obvious linear relationship between the hydrogen and oxygen isotopes (R2=0.78). The δD-H2O and δ18O-H2O values for the Grand Canal and Yuying River were distributed along the local meteoric waterline, indicating that precipitation served as the primary water source in these rivers. All of the δ18O-NO3- values of the Grand Canal and Yuying River were lower than 15 ‰. It was revealed that nitrification, rather than denitrification, was the primary N cycling process in the two rivers. The δ15N-NO3-/δ18O-NO3- ratios of some of the samples from the Grand Canal ranged from 1.3 to 2.1, accompanied by low concentrations of DO and NO2-, indicating that denitrification existed in some sections of the Grand Canal. The δ15N-NO3- values of the samples from the Grand Canal (average:6.1‰) were higher than those from the Yuying River (average:2.3‰). The NO3- source contributions differed significantly between the Grand Canal and Yuying River. The contributions of NO3- sources in the Grand Canal were sewage/manure (37.0%) > soil nitrogen (35.7%) > chemical fertilizer (19.1%) > precipitation (8.2%), and those in the Yuying River were chemical fertilizer (46.1%) > soil nitrogen (22.8%) > precipitation (17.3%) > sewage/manure (13.8%). The contribution of the sewage/manure was substantially increased in the Grand Canal in the urban area with stronger human activities primarily due to the sporadic discharge of domestic sewage and urban runoff. Chemical fertilizer is the main NO3- source in the Yuying River near the forest and agricultural area, suggesting that the nitrogen pollution caused by agricultural non-point sources was extremely serious. The contribution of precipitation decreased in the areas of substantial human activities. The isotopic fractionation produced by denitrification was affected by the contributions of the NO3- sources, which were calculated by SIAR model. Sewage/manure and chemical fertilizer produced significant impacts, followed by soil nitrogen and precipitation. |
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