基于复合采样系统的路边环境含碳气溶胶及采样偏差变化规律研究

The carbonaceous aerosols emitted by vehicles could have severe impact on the road side environment and human health. However, it is hard to quantify the organic carbon (OC) accurately due to the evaporation and condensation of semi-volatile organic aerosol (SVOC). This study propose to use an Integrated Organic Gas and Particle Sampler (IOGAPS), combining denuder, and sorbent impregnated filters, to quantify the positive and negative artifact of OC by comparing with results from conventional sampling. The gas phase SVOC which causes positive artifact will be measured by extracting the denuder. The OC, EC and characterized particle phase organic compounds collected by quartz filters will also be measured. The SVOC evaporated from particle phase causing negative artifact will be quantified. The current study plans to carry out a 30-day campaign at a selected target road with one sampling site set at upwind side and two sites at downwind side. The impact of vehicle emissions from the road on the spatial distribution of carbonaceous aerosols and the positive and negative artifact of OC will then be analyzed and studied. By categorizing the information of traffic flow and meteorological condition, the key factor influencing the concentration level and variation character of carbonaceous aerosol and the artifacts of OC will be identified. By analyzing the variation of the gas phase SVOC compounds, particle phase organic compounds and the carbon fractions, the study will try to explore the spatial variation trend of OC volatility. This study could provide the scientific findings for evaluating the carbonaceous aerosol pollution and potential health risk in roadside environment. It is also expected to give technical support for policy making of vehicle emissions control.

机动车排放的含碳气溶胶对道路环境中污染物浓度、人体健康造成重大影响，但是在采样中OC因SVOC的吸附与解吸影响而难以准确定量。本研究采用复合采样系统，综合利用溶蚀器、采样膜与吸附膜，对比常规采样方法，定量OC采样正负偏差，并获得修正后的OC浓度。研究计划通过萃取溶蚀器定量造成正偏差的气态SVOC物种，分析石英膜采集的颗粒物样品获得其中碳质组分与特征有机物种，并定量造成负偏差的颗粒态挥发SVOC。研究计划分别设立道路上风向一个背景点与下风向两个采样点，定量道路环境含碳气溶胶及OC正负偏差的空间变化规律；综合分析车流信息与气象参数，识别影响含碳气溶胶与OC正负偏差的浓度水平及其分布特征的关键因素；结合各观测点气态SVOC物种、颗粒态有机物种与碳质组分，进一步探索OC挥发性的空间变化规律。本研究对正确评价道路环境污染特征及其潜在的健康风险提供科学依据，并能够为机动车污染控制策略提供关键技术支持。

机动车排放的颗粒物中主要为含碳气溶胶，包括有机碳（OC）与元素碳（EC），其中OC 对人体健康影响显著。由于机动车同时排放大量半挥发性有机物（SVOC），造成采样中OC因SVOC的吸附与解吸影响而难以准确定量。本研究采用复合采样系统，综合利用溶蚀器、采样膜与吸附膜，对比传统采样方法，定量OC采样正负偏差，并获得修正后的OC浓度。研究设立上下风向采样点，定量道路环境含碳气溶胶及OC正负偏差的空间变化规律。基于传统滤膜法与利用溶蚀器采样获得的OC进行比较，获得临近高速公路的下风向点正偏差占传统滤膜法获得OC的29-42%，随着与道路距离增加，正偏差占比增大为50-53%。下风向站点负偏差在临近高速公路与远离高速公路站点为溶蚀器采样获得的OC质量的99%与51%，反映负偏差不能被忽略。研究通过正负偏差的有效定量，准确定量OC浓度。基于OC、EC、SVOC等物种分布差异，指出SVOC挥发性变化以及SOA的快速生成现象，并基于两个站点间的POC变化，证明在污染物传输过程中形成了不可忽略的SOA生成。本研究通过定量正负偏差，更准确评估了路边环境中OC的污染特征，及其主要影响因素与变化规律，为路边环境的机动车污染定量与人体健康影响提供数据基础与技术支撑。