毕节市七星关区若干点位大气无机氮湿沉降特点及通量估算

Characteristics and flux estimation of atmospheric wet deposition of inorganic ni trogen in several locations of Qixingguan District of Bijie

在毕节市七星关区城市功能差异明显的地域布置大气湿沉降采集器,检测了三类无机氮指标(氨氮、亚硝态氮和硝态氮),研究表明:①氨氮湿沉降通量最大值主要集中在夏季,全年湿沉降最大点位是热电站,月均达到了15. 73 mg/m^2。由城市核心区向城郊方向,沉降通量明显递减的趋势表明氨氮污染源主要来自于城市。②拥军路硝态氮沉降量超过热电站,月均达到5. 29 mg/m^2,而与其空间毗邻的非公路路域的人民公园样点沉降量则显著偏小,这表明公路路域是硝态氮的主要沉降区域,这与石油中微量氮素的燃烧并以氧化态的(亚)硝态氮排放有关。西南地域氨硝比多大于1,是高原环境积温低和当地城市交通与工业经济欠发达等因素共同导致的。③大气中亚硝态氮与硝态氮有相似的污染来源。所有样点亚硝态氮冬季湿沉降通量比秋季大。④以DIN占TDN为50%比率估算,七星关区全年总氮湿沉降通量为2. 61 kg/hm^2。

Atmospheric wet deposition collectors were set outside seasonally in different environments in Qixingguan District of Bijie,and three types of inorganic nitrogen indicators( ammonia nitrogen,nitrite nitrogen and nitrate nitrogen) was tested. The research results showed that: ① The maximum wet deposition flux of ammonia nitrogen appeared mainly in summer. The maximum deposition location throughout the year was the thermal power station,the deposition of which reached 15. 73 mg/m^2 per month. The decreasing tendency of deposition flux from the core area to the outskirts of the city indicated that the pollution source of ammonia nitrogen was mainly from the city. ② The deposition of nitrate nitrogen around Yongjun Road exceeded that of the thermal power station,and the monthly deposition was 5. 29 mg/m^2 on average. However,the data from Renmin Park,which was adjacent to Yongjun Road,was significantly lower. This indicated that the main area of nitrate deposition was around the roads,which was caused by the combustion of trace amount of nitrogen in the oil,and the emission in the oxidized forms of nitrite or nitrate nitrogen. In the southwest region of China,the ratio of ammonia nitrogen to nitrate nitrogen was more than 1,which was affected mainly by the low environmental temperature on the plateaus and the underdevelopment of local urban transportation and industrial economy. ③ Compared with nitrate nitrogen,nitrite nitrogen was affected by a similar pollution source. The wet deposition flux of nitrite nitrogen in winter was larger than that in autumn at all sampling locations. ④ Assuming that the ratio of DIN to TDN was 50%,the total nitrogen wet deposition in Qixingguan District reached 2. 61 kg/hm^2.