山西北部农村区域大气活性氮沉降特征

利用DELTA系统、被动采样器和雨量器在山西省北部生态脆弱区朔州的一个监测点通过一整年的监测试验,研究了该地区农村区域大气氮素干湿沉降的月际变化。结果表明:2011年该地区大气氮素湿沉降为12.43kgN hm~(-2)a~(-1),远低于华北平原大气氮素混合沉降的平均值28.0kg N hm~(-2)a~(-1),降水中铵态氮、硝态氮和有机氮平均分别为1.24 mg N/L、1.27 mg N/L、1.26mg N/L。大气氮素湿沉降的年内分布不均,60%的沉降集中在降水较丰沛的4-10月份。试验区干沉降以氧化态氮(HNO_3NO_2和pNO_3~-)的沉降为主,氧化态氮的干沉降量是还原态氮(NH_3和pNH_4~+)的1.37倍,大气氮素干沉降总量为35.43 kg N hm~(-2)a~(-1)。总体来看,作为典型的干旱区,该地区氮的干沉降是湿沉降的3倍,氮素干湿沉降总量达到47.86kg N hm~(-2)a~(-1)。此外,硝态氮和铵态氮在雨水中呈线性相关,而在PM_(10)颗粒物中乘幂正相关;雨水中总碳和总氮呈线性正相关,而PM_(10)颗粒物中二者呈二次多项式关系。鉴于朔州地区古城镇较高的氮沉降数量,应该对该地区输入农田的氮素环境养分引起足够重视。

The atmospheric deposition characteristics of reactive nitrogen (Nr) species in Shuozhou area

Reactive nitrogen (Nr) emissions and nitrogen deposition have increased rapidly and will continue to increase with the increasing fossil fuel combustion and application of N fertilizer since the industrial revolution. Nitrogen deposition has led to a series of negative effects on ecosystems such as soil acidification, water eutrophication, and loss of biodiversity in grasslands and forests. Therefore, atmospheric Nr pollution and deposition induced by excessive anthropogenic Nr have become an environmental concern worldwide. However, little is known about N deposition in Shanxi Province. The temporal variation of atmospheric N deposition was quantified using DELTA system, passive samplers, and particulate samplers at Gu Cheng, Shanxi Province, in a one year study. Results showed total wet N precipitation was up to 12.43 kg N hm^-2 a^-1 in this area, which was far below the average value (28.0 kg N hm^-2 a^-1) in the North China Plain. During wet precipitation, the concentration of NO₃^--N, NH₄⁺-N, and dissolved organic N averaged 1.24 mg N/L, 1.27 mg N/L, and 1.26mg N/L, respectively. In a year, wet precipitation of N showed a distinguished monthly variation due to different monthly rainfall, and 60% of wet deposition occurred from April to October. The major form of dry deposition was NO₃^--N, the rate of which was 1.12 times that of NH₄⁺-N. As a typical dry land, the rate of dry deposition was 3 times that of wet deposition. The total amount of nitrogen deposition was up to 47.86 kg N hm^-2 a^-1. There was a positive line corelation between NO₃^--N and NH₄⁺-N in rainwater, and that was a power corelation in PM₁₀ particulates. However, dissolved C and N showed a positive line corelation in rainwater and a quadratic polynomial corelation in PM₁₀ particulates. All these relationships can provide a way to determine one of them through another. Such high deposition rates of Nr species in the Shuozhou area indicated a serious pollution from anthropogenic sources and significant atmospheric N input to croplands.