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Collaborative Research: Heterogeneous Chlorine Activation from Saline Playas

合作研究：盐湖中的异质氯活化

基本信息

批准号：
1663740
负责人：
Cassandra Gaston
金额：
$ 46.26万
依托单位：
University of Miami
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-05-01 至 2021-04-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1663740&HistoricalAwards=false
关键词：
Collaborative Research Heterogeneous Chlorine Activation

项目摘要

Droughts mobilize natural dust from salt playas that can react with nitrogen oxides, criteria pollutants that are emitted by combustion sources. This reaction releases chlorine atoms that are potent atmospheric oxidants but are neglected in models used to assess regional air quality because of lack of measurements. The proposal will measure the fundamental rate constants of real-world playa dust particles with nitrogen oxides to enable robust assessments of regional air quality impacts in salt playas regions such as Texas.Reactive chlorine (Cl) atoms when activated can serve as potent atmospheric oxidants that would effect lifetimes of greenhouse gases like methane and also tropospheric ozone abundance. The proposal hypothesizes that wind blown chloride-containing dust from dried saline lake beds (playas) can be converted to nitryl-chloride (ClNO2) by heterogeneous reactions with gaseous dinitrogen pentoxide (N2O5). The ClNO2 photolysis produces Cl atoms that could alter the ozone production photochemistry and the methane lifetime significantly. The research will measure the kinetics of ClNO2 production from reactions of salt with N2O5 in a trace gas-aerosol flow reactor. Chemical ionization mass spectrometry will be used to monitor ClNO2 in the reactor and the playa dusts will be analyzed using single-particle mass spectrometry, ion chromatography and X ray diffraction. The in depth analysis of the chemical and atmospheric conditions under which chlorine can be released from the saline playas will provide a mechanistic framework that could be implemented in chemistry-climate and air-quality models to make more robust predictions and assessments.

干旱调动了盐田中的天然粉尘，这些粉尘可以与氮氧化物发生反应，氮氧化物是由燃烧源排放的标准污染物。这种反应释放出氯原子，氯原子是强效的大气氧化剂，但由于缺乏测量，在用于评估区域空气质量的模型中被忽略了。该提案将测量含氮氧化物的真实盐湖尘埃颗粒的基本速率常数，以便对德克萨斯州等盐湖地区的区域空气质量影响进行可靠的评估。活性氯（Cl）原子在被激活时可以作为有效的大气氧化剂，影响温室气体如甲烷和对流层臭氧丰度的寿命。该提案假设，从干燥的盐湖床（playas）吹来的含氯粉尘可以通过与气态五氧化二氮（N2O5）的非均相反应转化为硝基氯（ClNO2）。ClNO2光解产生的Cl原子可以显著改变臭氧生成、光化学和甲烷寿命。该研究将在微量气体-气溶胶流动反应器中测量盐与N2O5反应产生ClNO2的动力学。化学电离质谱法将用于监测反应器中的ClNO2，而playa粉尘将使用单粒子质谱法、离子色谱法和X射线衍射法进行分析。对氯气从盐碱地释放的化学和大气条件的深入分析将提供一个机制框架，可以在化学-气候和空气质量模型中实施，以做出更可靠的预测和评估。