Collaborative Research: Halogen Activation and Multiphase Chemical Processing in the Continental Boundary Layer

众所周知，卤素的多相化学参与了大气中的一系列化学相互作用，包括O3循环、碳氢化合物和还原硫化合物的氧化、奇数氮和氧（HOx和NOx）循环，以及参与气溶胶成核、生长和异质化学途径。活跃的卤素反应性通常与沿海或海洋地区有关，反映了在那里发现的丰富的海洋卤素源。最近对氯原子前体硝基氯（ClNO2）的夜间反应性的观察似乎预测了这一途径在大陆上的惊人存在，这可能会对我们理解卤素对上述几种非海洋环境中物种的全球影响产生影响。夜间的ClNO2是由N2O5对颗粒氯化物的反应性产生的，这就带来了一个问题，即我们对大陆氯化物来源（包括工业活动、生物质燃烧和风吹矿物粉尘的运输）的了解程度到底有多高。上述怀疑氯活化途径的几个方面仍有待研究。这项调查涉及一些大学研究人员与美国国家海洋和大气管理局（ESRL）的同事一起，对大陆气团中的卤素反应途径进行额外的表征。要研究的主要问题包括：1)大陆空气中卤素光化学过程的定量评价；2)大陆夜间空气中活性卤素化学的产生和再循环的机理研究。这项研究对空气质量、大气中卤素的自然循环以及我们呼吸的空气的氧化能力都有影响。

The multiphasic chemistry of halogens is known to be involved in a range of chemical interactions in the atmosphere ranging from the O3 cycle, oxidation of hydrocarbons and reduced sulphur compounds, the odd nitrogen and oxygen (HOx and NOx) cycles, as well as involvement in aerosol nucleation, growth and heterogeneous chemical paths. Active halogen reactivity is frequently associated with coastal or marine zones, reflecting the abundance of oceanic halide sources found there. Recent nocturnal observations of the reactivity of a chlorine atom precursor, nitryl chloride (ClNO2) has seemed to predict a surprising continental presence of this pathway, which potentially has implications to our understanding of the global impact of halogens on several of the above species in non-marine settings. Nocturnal ClNO2 arises from the reactivity of N2O5 on particulate chloride, which brings into question how well continental chloride sources including industrial activity, biomass burning, and the transport of wind blown mineral dust are really known.Several aspects of the above suspected chlorine activation pathways remain to be investigated. This investigation involves a number of university researchers joining with NOAA (ESRL) colleagues on additional characterization of halogen reactivity pathways in continental air masses. Overarching issues to be investigated include: i) quantitative evaluation of halogen photochemical processes in continental air, ii) mechanistic study of the generation and recycling of active halogen chemistry in nocturnal continental air.This research has implications for air quality, the natural cycle of halogens in the atmsphere and the oxidative capacity of the air we breathe.