RAPID: Chemistry and Vertical Transport of Hox Radical Precursors During the Uintah Basin Winter Ozone Study in Utah

在人口稀少的农村地区，受水力压裂天然气钻井活动产生的氮氧化物和挥发性有机化合物排放的影响，冬季的臭氧污染是一个相对较新的现象。臭氧混合比率在冬季超过联邦空气质量标准，但在夏季却没有，这一事实构成了一个科学难题。预计隆冬时节的弱太阳辐照度将导致光化学显著减慢，从而导致臭氧水平降低。人们假设，特定的环境条件，特别是地表积雪的存在，是冬季臭氧形成的一个重要因素。雪增加了地表反照率，因此，冬季的光化通量增加到与热带地区更相似的水平。然而，这种效应似乎只解释了冬季臭氧水平较高的部分原因。还假设雪化学可能是羟基和羟基过氧基(OH+HO2=HOx)自由基前体亚硝酸(HONO)和甲醛(HCHO)的有效来源。这些物种水平的升高可能会进一步加速冬季臭氧的形成。冬季微弱的太阳辐射和雪的高红外发射率也会导致强的和浅的地表逆温的形成，这可以通过在地表附近聚集污染物来进一步加速臭氧的形成。由美国国家海洋和大气局化学科学部、物理科学部、美国国家海洋和大气局太平洋海洋环境实验室和科罗拉多大学(http://www.esrl.noaa.gov/csd/tropchem/2012ubwos/)野外实验联合组织的Uintah盆地冬季臭氧研究计划于2012年1月15日至3月1日期间进行。将要进行的测量为研究受污染的冬季臭氧大气化学提供了一个独特的机会，因为其他研究人员将进行大量补充测量。以下与冬季臭氧形成有关的科学假说将得到检验：-HONO的光解，以及在较小程度上的HCHO，即使不是冬季条件下主要的HOX形成途径，也是重要的。-雪中或被雪覆盖的地面上的化学对HONO和HCHO的混合比率有很大的贡献，因此是HOX和臭氧形成的重要因素。-表面反转和抑制的垂直混合在将污染物集中在浅表面层中起关键作用，从而加速表面臭氧的形成。将通过长程微分光学吸收光谱仪获得臭氧、二氧化氮、HONO和HCHO的垂直剖面。获得的数据以及其他调查人员提供的数据将使用既定的方法进行解释。活动将与犹他州环境质量部和美国环境保护局(第8区)密切协调。因此，结果将直接用于为犹他州盆地发现的臭氧污染制定缓解策略，从而使当地居民受益。这一结果也将使其他有类似问题的地区受益，如怀俄明州的上游格林河流域。目前天然气钻探活动的扩大也使这一提议变得及时，因为犹他州和怀俄明州发现的空气质量问题可能很快也会出现在美国和加拿大的其他地方。该项目还将为研究生提供职业发展机会，建立在之前进行测量和分析痕量气体垂直剖面数据的经验基础上。

Wintertime ozone pollution in sparsely populated rural areas that have come under the influence of nitrogen oxide and volatile organic compound emissions from hydraulic fracturing natural gas drilling activities is a relatively recent phenomenon. The fact that ozone mixing ratios exceed the federal air quality standard in winter but not in summer poses a scientific puzzle. Weak solar irradiance in mid-winter is expected to lead to a considerable slowdown of photochemistry and consequently low ozone levels. It has been hypothesized that specific environmental conditions, in particular the presence of surface snow, are an important factor in the formation of wintertime ozone. Snow increases surface albedo and, thus, enhances the actinic flux in winter to levels more similar to those in the tropics. However, it appears that this effect only explains part of the high wintertime ozone levels. It has also been hypothesized that snow chemistry can be an efficient source of the hydroxyl and hydroperoxyl (OH + HO2 = HOx) radical precursors nitrous acid (HONO) and formaldehyde (HCHO). Elevated levels of these species could further accelerate the formation of ozone in winter. The weak wintertime solar irradiance and high infrared emissivity of snow also lead to the formation of strong and shallow surface inversions, which can further accelerate ozone formation by concentrating pollutants near the surface.The Uintah Basin Winter Ozone Study jointly organized by NOAA/ESRL Chemical Sciences Division, Physical Sciences Division, NOAA Pacific Marine Environmental Laboratory, and the University of Colorado (http://www.esrl.noaa.gov/csd/tropchem/2012ubwos/) field experiment is planned for the time period of January 15 to March 1, 2012. The measurements to be performed offer a unique opportunity to study polluted wintertime atmospheric chemistry of ozone, as a large number of complementary measurements will be performed by other investigators. The following scientific hypotheses related to wintertime ozone formation will be tested:- The photolysis of HONO, and to a lesser extent HCHO, are important, if not the dominant primary HOX formation pathways under wintertime conditions.- Chemistry in the snow or on the snow-covered ground strongly contributes to the mixing ratios of HONO and HCHO, and is thus an important factor for HOX and ozone formation.- Surface inversions and suppressed vertical mixing play a crucial role in concentrating pollutants in a shallow surface layer, thus accelerating surface ozone formation.Vertical profile measurements of ozone, nitrogen dioxide, HONO and HCHO will be obtained by Long-Path Differential Optical Absorption Spectrometery. The acquired data, together with data available from other investigators, will be interpreted using established methods.Activities will be closely coordinated with the Utah Department of Environmental Quality and the U.S. Environmental Protection Agency, Region 8. The results will thus directly be used to develop mitigation strategies for the ozone pollution found in the Uintah Basin and thus benefit the local population. The results will also benefit other locations with similar problems, such as the Upper Green River Basin, Wyoming. The current expansion of natural gas drilling activities also makes this a timely proposal as the air quality problem found in Utah and Wyoming may soon also occur in other places in the U.S. and Canada. The project will also provide a graduate student a career development opportunity, building on previous experience performing measurements and analyzing trace gas vertical profile data.