陕西关中地区大气氮湿沉降通量的动态变化

Dynamics of Atmospheric Nitrogen Wet Deposition Fluxes in Guanzhong Area, Shaanxi

为了对陕西关中地区大气氮沉降量进行估算,2009年11月至2010年10月对西安和杨凌两地进行了为期一年的湿沉降观测。结果表明:监测期内,西安、杨凌两地区年降雨量分别为620.5、532.3 mm,西安ρ(NH+4-N)和ρ(NO-3-N)平均值分别为3.058、2.356mg·L-1,杨凌ρ(NH+4-N)和ρ(NO-3-N)平均值分别为3.990、2.709 mg·L-1;季节变化上,西安监测点ρ(TIN)(总无机氮)和杨凌监测点ρ(NH+4-N)呈现春、冬季高于夏、秋季的趋势,而杨凌监测点ρ(NO-3-N)则呈秋、冬季略高于春、夏季的趋势。西安、杨凌TIN沉降通量分别为24.791、28.894 kg·hm-2,且均以NH+4-N为主导,分别占TIN的67.3%和56.3%。氮素沉降量与降雨量之间呈现正相关趋势,随着降雨量的增加,NH+4-N、NO-3-N和TIN的沉降通量均明显增加。湿沉降输入农田的无机氮占施肥投入的比重相当大,在施肥中应予以考虑。

Atmospheric nitrogen(N)deposition has long term impacts on the terrestrial and water ecosystems. In order to estimate the atmo-spheric N deposition fluxes in Guanzhong Area of Shaanxi Province, we monitored N wet deposition in Xi′an and Yangling from November 2009 to Octomber 2010. During the monitoring period, the annual rainfall of Xi′an and Yangling was 620.5 and 532.3 mm, respectively. The mean values ofρ(NH+4-N)andρ(NO-3-N)were respectively 3.058 and 2.356 mg·L-1 in Xi′an, and 3.990 and 2.709 mg·L-1 in Yangling. Theρ(NH+4-N)andρ(NO-3-N)in Xi′an andρ(NH+4-N)in Yangling were higher in spring and winter than in summer and autumn, whereasρ(NO-3-N)in Yangling in autumn and winter was slightly higher than that in spring and summer. The fluxes of total inorganic nitrogen (TIN)deposition in Xi′an and Yangling were up to 24.791 and 28.894 kg·hm-2·a-1, mainly in form of NH+4-N that accounted for 67.3%and 56.3%of the TIN in two sites. The amount of nitrogen wet deposition was positively correlated with rainfall. The present results indicate that wet N deposition contributes to the field inorganic N inputs, which should be taken into consideration when applying fertilizers.