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

这是乔治亚理工学院、新罕布什尔大学和威斯康辛-麦迪逊大学的主要研究人员合作提出的一项建议。大气气溶胶令人担忧，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），它们可以占细颗粒物质量的相当一部分。OC馏分由各种各样的人为和自然来源的化合物组成。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OC和特定有机化合物的浓度可以提供关于碳质气溶胶过去对气候的影响以及这些气溶胶来源的信息。在评估与颗粒物沉积有关的冰芯碳化合物浓度之前，确定空气中碳化合物浓度与雪之间的联系是很重要的。此外，在使用特定化合物推断过去大气浓度之前，需要确定含碳气溶胶在沉积成雪后被改变的程度。格陵兰峰顶雪坑水不溶性颗粒有机碳（IPOC）的初步结果显示，顶部50 cm的IPOC浓度下降了约50%，提示早期沉积后过程可能非常重要。这些结果与最近提出的表层雪中有机碳可能在雪光化学中起重要作用的观点一致。主要研究人员将于2006年在Summit进行实地研究，以测量空气、地表雪和雪坑中作为源示踪剂的颗粒物OC、EC和特定有机化合物的浓度。为了评估地表雪沉积后过程的影响，他们将测量大气和大气中水溶性气相有机化合物（WSGOC）的浓度，并期望地表雪中IPOC的降解导致WSGOC的形成。他们将把碳-13和氘标记的颗粒有机化合物沉积到雪表面，并测量在野外季节期间浓度的变化。此外，他们将进行特定的实验，使地表雪不受太阳辐射的影响，以确定光化学对沉积在地表雪上的颗粒有机化合物降解的相对影响。这项研究将深入了解影响首脑会议空气和雪中颗粒碳浓度的过程，并将为未来的建模、实验室和实地研究奠定基础，这些研究将侧重于雪中颗粒有机化合物的沉积和转化。更广泛的影响：这项研究将通过培训一些研究生和本科生，包括来自代表性不足的少数群体的学生，来促进教育。这些信息将通过会议发言、出版物和网页以及在研究生和本科生课程中传播。首席研究员将在K-12学校做报告。这项研究工作将导致新的测量技术的发展以及对现有技术的独特修改。该项目将产生对大气科学和古气候群落具有重要意义的过程的见解。这项研究可能会为根据沉积在雪中的特定有机化合物的浓度来解决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.