三峡库区大气活性氮组成及干沉降通量
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摘要
为了解三峡库区腹地大气中活性氮的组成及干沉降通量,于2015年每个季节选取代表性月份在万州城区采集了气体和颗粒物样品.利用离子色谱法测定氮素浓度,同时结合大叶阻力模型模拟计算的干沉降速率值,估算了不同形态氮素的干沉降通量.结果表明,HNO_3的干沉降速率值最大,年均值为0.39cm/s,约为其它氮素的3~8倍.NO_2和NH_3是大气活性氮的主要赋存形态,年均浓度值分别为(11.7±3.9)和(11.0±5.3)μg N/m~3,两者之和约占总无机氮浓度的80%.万州城区总无机氮干沉降总量为8.5kg N/(hm~2·a),其中氧化态氮(NO_2、HNO_3、颗粒态NO_3~-)和还原态氮(NH3、颗粒态NH4+)干沉降通量分别为3.5,5.0kg N/(hm~2·a),占干沉降总量的41.4%和58.6%.因此,为有效控制三峡库区腹地的氮素污染,应重点关注NH_3的减排.
To understand the chemical components of reactive nitrogen and estimate their dry deposition flux in the Three Gorges Reservoir Region, gaseous and particulate nitrogen species were collected at urban Wanzhou in each season in 2015. Dry deposition flux was estimated using the inferential method with modelled dry deposition velocities and measured ambient concentrations, which was obtained from the big-leaf resistance model and ion chromatography, respectively. HNO_3 had the highest dry deposition velocity among all the reactive nitrogen species, with an annual mean value of 0.39 cm/s, which was around 3~8 times higher than other nitrogen species. NO_2 and NH_3 were both important nitrogen forms, with an annual mean concentration of(11.7±3.9) and(11.0±5.3) μg N/m~3, respectively, and together contributing around 80% of the total inorganic nitrogen concentrations. Furthermore, the dry deposition fluxes of oxidized nitrogen(NO_2, HNO_3 and particulate NO_3~-) and reduced nitrogen(NH_3 and particulate NH_4~+) were 3.5 and 5.0 kg N/(hm~2·a), accounting for 41.4% and 58.6% of the total inorganic nitrogen dry deposition flux, respectively. Therefore, in order to reduce the nitrogen pollution efficiently in the Three Gorges Reservoir Region, it is key to control NH_3 emission.
To understand the chemical components of reactive nitrogen and estimate their dry deposition flux in the Three Gorges Reservoir Region, gaseous and particulate nitrogen species were collected at urban Wanzhou in each season in 2015. Dry deposition flux was estimated using the inferential method with modelled dry deposition velocities and measured ambient concentrations, which was obtained from the big-leaf resistance model and ion chromatography, respectively. HNO_3 had the highest dry deposition velocity among all the reactive nitrogen species, with an annual mean value of 0.39 cm/s, which was around 3~8 times higher than other nitrogen species. NO_2 and NH_3 were both important nitrogen forms, with an annual mean concentration of(11.7±3.9) and(11.0±5.3) μg N/m~3, respectively, and together contributing around 80% of the total inorganic nitrogen concentrations. Furthermore, the dry deposition fluxes of oxidized nitrogen(NO_2, HNO_3 and particulate NO_3~-) and reduced nitrogen(NH_3 and particulate NH_4~+) were 3.5 and 5.0 kg N/(hm~2·a), accounting for 41.4% and 58.6% of the total inorganic nitrogen dry deposition flux, respectively. Therefore, in order to reduce the nitrogen pollution efficiently in the Three Gorges Reservoir Region, it is key to control NH_3 emission.
引文
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[3]Liu X J,Zhang Y,Han W X,et al.Enhanced nitrogen deposition over China[J].Nature,2013,494(7438):459-462.
[4]Xu W,Luo X S,Pan Y P,et al.Quantifying atmospheric nitrogen deposition through a nationwide monitoring network across China[J].Atmospheric Chemistry and Physics,2015,15(21):12345-12360.
[5]Pan Y P,Wang Y S,Tang G Q,et al.Wet and dry deposition of atmospheric nitrogen at ten sites in Northern China[J].Atmospheric Chemistry and Physics,2012,12(14):6515-6535.
[6]Shen J L,Li Y,Liu X J,et al.Atmospheric dry and wet nitrogen deposition on three contrasting land use types of an agricultural catchment in subtropical central China[J].Atmospheric Environment,2013,67:415-424.
[7]Chen X Y,Mulder J.Atmospheric deposition of nitrogen at five subtropical forested sites in South China[J].Science of the Total Environment,2007,378(3):317-330.
[8]Li X L,Shi H Q,Xu W F,et al.Seasonal and Spatial Variations of Bulk Nitrogen Deposition and the Impacts on the Carbon Cycle in the Arid/Semiarid Grassland of Inner Mongolia,China[J].Plos.One,2015,10(12):e0144689.
[9]王江飞,周柯锦,汪小泉,等.杭嘉湖地区大气氮、磷沉降特征研究[J].中国环境科学,2015,35(9):2754-2763.
[10]Yang R,Hayashi K,Zhu B,et al.Atmospheric NH3 and NO2concentration and nitrogen deposition in an agricultural catchment of Eastern China[J].Science of the Total Environment,2010,408(20):4624-4632.
[11]Luo X S,Liu P,Tang A H,et al.An evaluation of atmospheric Nr pollution and deposition in North China after the Beijing Olympics[J].Atmospheric Environment,2013,74:209-216.
[12]Shen J L,Tang A H,Liu X J,et al.High concentrations and dry deposition of reactive nitrogen species at two sites in the North China Plain[J].Environmental Pollution,2009,157(11):3106-3113.
[13]Zhang L,Brook J R,Vet R.A revised parameterization for gaseous dry deposition in air-quality models[J].Atmospheric Chemistry and Physics,2003,3:2067-2082.
[14]Zhang L M,Gong S L,Padro J,et al.A size-segregated particle dry deposition scheme for an atmospheric aerosol module[J].Atmospheric Environment,2001,35(3):549-560.
[15]Wang H B,Yang F M,Shi G M,et al.Ambient concentration and dry deposition of major inorganic nitrogen species at two urban sites in Sichuan Basin,China[J].Environmental Pollution,2016,219:235-244.
[16]张艳,王体健,胡正义,等.典型大气污染物在不同下垫面上干沉积速率的动态变化及空间分布[J].气候与环境研究,2004,(4):591-604.
[17]许稳,金鑫,罗少辉,等.西宁近郊大气氮干湿沉降研究[J].环境科学,2017,(4):1279-1288.
[18]Flechard C R,Nemitz E,Smith R I,et al.Dry deposition of reactive nitrogen to European ecosystems:a comparison of inferential models across the Nitro Europe network[J].Atmospheric Chemistry and Physics,2011,11(6):2703-2728.
[19]Zhang Q,Streets D G,Carmichael G R,et al.Asian emissions in2006 for the NASA INTEX-B mission[J].Atmospheric Chemistry and Physics,2009,9(14):5131-5153.
[20]Kang Y N,Liu M X,Song Y,et al.High-resolution ammonia emissions inventories in China from 1980 to 2012[J].Atmospheric Chemistry and Physics,2016,16(4):2043-2058.
[21]Sutton M A,Dragosits U,Tang Y S,et al.Ammonia emissions from non-agricultural sources in the UK[J].Atmospheric Environment,2000,34(6):855-869.
[22]Pan Y P,Tian S L,Liu D W,et al.Fossil Fuel CombustionRelated Emissions Dominate Atmospheric Ammonia Sources during Severe Haze Episodes:Evidence from N-15-Stable Isotope in Size-Resolved Aerosol Ammonium[J].Environmental Science&Technology,2016,50(15):8049-8056.
[23]Stelson A W,Seinfeld J H.Relative-Humidity and TemperatureDependence of the Ammonium-Nitrate Dissociation-Constant[J].Atmospheric Environment,1982,16(5):983-992.