Collaborative Research: Particulate Organic Carbon in the Air and Snow at Summit, Greenland

这是佐治亚理工学院、新汉普郡大学和威斯康星-麦迪逊分校的首席研究人员共同提出的建议。大气气溶胶之所以令人担忧，是因为它们可以通过改变地球的辐射平衡来影响气候，并对人类健康有害。细颗粒物(直径小于2.5微克的颗粒)含有大量的有机碳(OC)和元素碳(EC)，它们可能占细颗粒物质量的相当大一部分。有机碳组分由来自人为和自然来源的各种化合物组成。人们对碳质气溶胶的历史浓度、来源和排放知之甚少。冰芯中有机碳和特定有机化合物的浓度可以提供有关碳质气溶胶过去对气候的影响以及这些气溶胶的来源的信息。在评估与颗粒物质沉积有关的含碳化合物的冰芯浓度之前，确定空气和雪中的浓度之间的联系是很重要的。此外，在使用特定化合物来推断过去的大气浓度之前，需要确定碳质气溶胶在沉积成雪后被修改的程度。格陵兰岛顶峰雪坑中水不溶颗粒有机碳(IPOC)的初步测量结果显示，50 cm以上的IPOC浓度下降了约50%，这表明早期的后期沉积过程可能是非常重要的。这些结果与最近的建议一致，即地表雪中的有机碳可能在雪光化学中发挥重要作用。首席调查员将于2006年在顶峰进行实地研究，以测量空气、地面雪和雪坑中作为来源示踪剂的颗粒物OC、EC和特定有机化合物的浓度。为了评估地表雪后沉积过程的影响，他们将测量大气和降雪空气中水溶气相有机化合物(WSGOC)的浓度，以期地表雪中IPOC的降解导致WSGOC的形成。他们将碳-13和氚标记的颗粒有机化合物沉积到雪面上，并测量在野外季节持续时间内浓度的变化。此外，他们还将在地表雪被遮挡太阳辐射的情况下进行具体实验，以确定光化学对沉积到地表雪中的颗粒有机化合物降解的相对影响。这项研究将深入了解峰会上影响空气和雪中颗粒碳浓度的过程，并将作为未来建模、实验室和实地研究的基础，这些研究将侧重于雪中颗粒有机化合物的沉积和转化。广泛的影响：这项研究将通过培训几名研究生和本科生来推进教育，包括来自代表性不足的少数群体的学生。这些信息将通过会议报告、出版物和网页以及研究生和本科生课程进行传播。首席调查员将在K-12学校讲解。这项研究工作将导致新的测量技术的开发以及对现有技术的独特修改。该项目将深入了解对大气科学以及古气候界具有重要意义的过程。这项研究可能会为基于雪中沉积的特定有机化合物浓度来研究气溶胶的历史来源和影响的研究打开大门。

This is a collaborative proposal by Principal Investigators at Georgia Institute of Technology, Universities of New Hampshire, and Wisconsin-Madison. Atmospheric aerosols are of concern because they can influence climate by altering the radiation balance of the Earth and are harmful to human health. Fine particulate matter (particles having diameters less than 2.5 micrograms) contains a significant amount of both organic carbon (OC) and elemental carbon (EC), which can account for a considerable fraction of the fine particulate mass. The OC fraction is composed of a wide variety of compounds from both anthropogenic and natural sources. Little is known about the historical concentrations, sources and emissions of carbonaceous aerosols. Ice core concentrations of OC and specific organic compounds could yield information on the past influence of carbonaceous aerosols on climate and the sources of these aerosols. Before ice core concentrations of carbonaceous compounds related to particulate matter deposition can be evaluated, it is important to determine the link between the concentrations in air and snow. In addition, the extent to which carbonaceous aerosol is modified after deposition to snow needs to be determined before specific compounds can be used to infer past atmospheric concentrations. Preliminary results of water insoluble particulate organic carbon (IPOC) in a snow pit from Summit, Greenland show a decrease of ~ 50% in IPOC concentrations in the top 50 cm, hinting that early post depositional processes may be very important. These results are consistent with recent suggestions that organic carbon in surface snow may play an important role in snow photochemistry. The Principal Investigators will conduct a field study at Summit in 2006 to measure the concentrations of particulate OC, EC, and specific organic compounds that serve as source tracers in the air, surface snow, and snow pits. To assess the influence of post depositional processes in surface snow, they will measure the concentrations of water-soluble gas-phase organic compounds (WSGOC) in the atmospheric and firn air with the expectation that the degradation of IPOC in surface snow leads to the formation of WSGOC. They will deposit carbon-13- and deuterium-labeled particulate organic compounds to surface snow and measure the change in concentration over the duration of the field season. In addition, they will conduct specific experiments where surface snow is shaded from solar radiation in order to determine the relative influence of photochemistry on the degradation of particulate organic compounds deposited to surface snow. The research will yield insights into the processes that influence the concentrations of particulate carbon in the air and snow at Summit and will serve as the groundwork for future modeling, laboratory and field studies that will focus on the deposition, and transformation of particulate organic compounds in snow.Broader Impacts: The research will advance education through the training of several graduate and undergraduate students, including students from under-represented minority groups. The information will be disseminated through conference presentations, publications, and a webpage as well as within graduate and undergraduate courses. The Principal Investigators will give presentations at K-12 schools. The research effort will result in the development of new measurement techniques as well as unique modifications to existing techniques. The project will yield insights into processes that are of importance to the atmospheric sciences as well as paleoclimate communities. The research will potentially open the door for studies that address the historical sources and impacts of aerosols based on the concentrations of specific organic compounds deposited in snow.