基于苔藓氮含量及d15N分析探讨农村大气氮沉降状况

2009~2010年在江西抚州市崇仁县10个乡镇采集了85个细叶小羽藓样品,通过对苔藓氮含量及氮同位素(d15N)的测定,估算了该地区大气氮沉降水平,并探讨了大气氮输入的主要来源.结果表明,研究区苔藓平均氮含量变化范围为2.24%~3.43%,其中农业覆盖率较大郭圩乡和礼陂镇苔藓氮含量均超过3%(平均值分别为3.07%、3.43%).研究区大气氮沉降的变化范围为29.62~54.39kg/(hm2·a),反映了大气氮沉降成为农村生态系统氮输入的重要补充.苔藓平均d15N值为-3.11‰~0.078‰,指示研究区主要受农业氨源的影响.崇仁县城区苔藓d15N为-1.7‰,低于其它农业乡镇(d15N为0‰±1‰),表明该地区还受到城市污水和人畜排泄物所释放的氨影响;孙坊镇苔藓d15N 变化范围为-5.89‰~0.61‰,提示大气氮沉降除受到农业排放的氨作用以外,还存在露天垃圾填埋场挥发氨的贡献.

Nitrogen concentrations and stable isotope in mosses to investigate atmospheric nitrogen deposition in rural areas

Atmospheric N deposition and their N sources in Chongren County were investigated on the basis of the nitrogen concentrations and nitrogen isotope in mosses, which were collected from 10 towns during 2009~2010. Nitrogen concentrations in mosses ranged from 2.24% to 3.43% and showed a significant regional difference. The highest N concentrations (N>3%) were found in Guoxu and Lipi Towns, where agricultural activity is strong. The level of atmospheric N deposition in the county was calculated according to the quantitative relationship between moss N concentration and atmospheric N deposition. The level of atmospheric N deposition ranged between 29.62~54.39 kg/(hm2·a), showed that atmospheric nitrogen deposition was an important N input in rural areas. The d15N values in mosses varied from -3.11‰ to 0.078‰, indicative of the large contribution of NH3 emission sources connected with fertilizer application. The moss d15N values (-1.7‰) in Chongren County suggested that atmospheric N deposition was also influenced by the city excretory wastes and sewage NH3 emission. The moss d15N values in Sunfang Town were in the range of-5.89‰~0.61‰, associated with the extensive NH3 emission from landfill.