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，冬季臭氧污染是一个相对较新的现象，受到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。臭氧混合比率在冬季超过联邦空气质量标准，而在夏季却没有，这一事实构成了一个科学难题。冬季中期太阳辐照度弱，预计会导致光化学反应显著减缓，从而导致臭氧水平降低。据推测，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，从而使冬季的光化通量提高到与热带地区相似的水平。然而，这种效应似乎只能部分解释冬季臭氧含量高的原因。也有人假设，雪化学可以是羟基和氢过氧（OH + HO2 = HOx）自由基前体亚硝酸盐（HONO）和甲醛（HCHO）的有效来源。这些物质含量的增加会进一步加速冬季臭氧的形成。冬季较弱的太阳辐照度和雪的高红外发射率也导致强而浅的地表逆温的形成，这可以通过将污染物集中在地表附近进一步加速臭氧的形成。由NOAA/ESRL化学科学部、物理科学部、NOAA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/）联合组织的犹他盆地冬季臭氧研究计划于2012年1月15日至3月1日进行野外实验。由于其他研究人员将进行大量的补充测量，因此将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。以下与冬季臭氧形成有关的科学假设将被测试：-在冬季条件下，HONO的光解，以及在较小程度上的HCHO，即使不是主要的主要HOX形成途径，也是重要的。-积雪或积雪覆盖地面上的化学物质对HONO和HCHO的混合比例有很大影响，因此是HOX和臭氧形成的重要因素。-地表逆温和抑制垂直混合在将污染物集中在浅层的过程中起着至关重要的作用，从而加速地表臭氧的形成。臭氧、二氧化氮、HONO和HCHO的垂直剖面测量将通过长程差分光学吸收光谱获得。所获得的数据，连同其他研究者提供的数据，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八区密切协调。因此，研究结果将直接用于制定减轻在法塔赫盆地发现的臭氧污染的战略，从而使当地居民受益。研究结果也将使其他有类似问题的地区受益，如怀俄明州的上格林河盆地。目前天然气钻探活动的扩大也使这一建议变得及时，因为在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.