Using atmospheric chemistry and storm track information to explain the variation of nitrate stable isotopes in precipitation at a site in central Pennsylvania, USA
Using atmospheric chemistry and storm track information to explain the variation of nitrate stable isotopes in precipitation at a site in central Pennsylvania, USA
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DOI：
10.1016/j.atmosenv.2009.06.027
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发表时间：
2009-09
影响因子：
5
通讯作者：
A. Buda;D. R. Dewalle
中科院分区：
文献类型：
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作者：
A. Buda;D. R. Dewalle
在2005年的六次风暴事件中，在宾夕法尼亚州中部的降水中监测了NO3−（δ 15 N-NO3 −和δ 18 O-NO3 −）的稳定同位素，以确定大气氧化剂的信息（例如，O3，NO2和NOx）和风暴路径（使用NOAA HYSPLIT模型）能够解释观测到的季节性和风暴内同位素变化。结果表明，降水中的δ 15 N-NO3-和δ 18 O-NO3-在不同的暴雨过程中变化显著。降水中的δ 15 N-NO3 −和δ 18 O-NO3 −在季节性上遵循夏季减少和冬季增加的模式。NO3−前体浓度和大气氧化剂有助于解释所有6次风暴事件中δ 15 N-NO3 −的季节性和风暴内变化，这一点与NO2：NOx比值和臭氧（O3）呈负相关。相比之下，δ 18 O-NO3-与O3在三个休眠季节风暴呈正相关，这表明O3氧化途径是重要的，产生高δ 18 O-NO3-在冬季降水中观察到。风暴路径信息对于描述δ 15 N-NO3 −的差异特别有用。来自E/NE的冷扇区风暴产生了汽车排放的δ 15 N-NO3 −值，而来自SW/S/SE的暖扇区风暴产生了燃煤排放的δ 15 N-NO3 −值。闪电也可能是两次暖区雷暴期间大气NO3-的重要来源。这项研究表明，（1）有关氧化剂水平的信息可以用于预测降水中NO3−稳定同位素的季节性和风暴内变化，（2）风暴轨迹（暖区与冷区）的知识对于确定湿沉降中NO3−的来源可能很重要。
Stable isotopes of NO3−(δ15N–NO3−and δ18O–NO3−) were monitored in precipitation at a central Pennsylvania site during six storm events in 2005 to determine whether information on atmospheric oxidants (e.g., O3, NO2, and NOx), and storm tracks (using the NOAA HYSPLIT model) were capable of explaining observed seasonal and within-storm isotopic variation. Results showed that δ15N–NO3−and δ18O–NO3−in precipitation varied significantly during individual storm events. Seasonally, δ15N–NO3−and δ18O–NO3−in precipitation followed a pattern of depletion during the summer months and enrichment during the winter months. NO3−precursor concentrations and atmospheric oxidants were useful for explaining the seasonal and within-storm variation of δ15N–NO3−for all six storm events as evidenced by negative relationships with NO2:NOxratios and ozone (O3). In comparison, δ18O–NO3−was positively related to O3in three dormant season storms, which suggested that the O3oxidation pathway was important for producing the high δ18O–NO3−observed in wintertime precipitation. Storm track information was especially useful for describing differences in δ15N–NO3−. Cool-sector storms originating from the E/NE produced slightly negative δ15N–NO3−values characteristic of automobile emissions, whereas warm-sector storms with tracks from the SW/S/SE produced slightly positive δ15N–NO3−values characteristic of coal-fired emissions. Lightning also may have been an important source of atmospheric NO3−during two warm-sector thunderstorms. This study showed that (1) information about oxidant levels can be useful to predict the seasonal and within-storm variation of NO3−stable isotopes in precipitation, and (2) knowledge of storm tracks (warm-sector versus cool-sector) may be important for determining sources of NO3−in wet deposition.