北京上甸子地区分粒径亚微米气溶胶密度测量研究

发布时间：2018-03-13 23:36

本文选题：大气气溶胶　切入点：有效密度　出处：《中国气象科学研究院》2016年硕士论文　论文类型：学位论文

【摘要】：密度是大气气溶胶重要的物理性质之一。研究大气气溶胶密度可以为了解气溶胶化学组分、评估气溶胶形成过程提供参考依据,对于探究气溶胶粒子在大气中的行为以及在人体内的沉积效率有重要意义。本文利用差分迁移率粒径分析仪(DMA)-气溶胶粒子质量分析仪(APM)-凝结粒子计数器(CPC)系统于2015年8~9月和12月先后在上甸子区域大气本底站对50~350nm分粒径亚微米气溶胶的有效密度进行观测,基于这些观测资料,分析了上甸子夏、冬季大气气溶胶有效密度的分布特征和变化规律,并探究了新粒子形成过程中和污染时段气溶胶密度的变化。夏季有效密度的变化范围是0.96~1.65 g/cm~3,冬季有效密度的变化范围是0.98~1.55g/cm~3,50~350 nm粒子的有效密度均随着粒径的增大而增大,反映出颗粒物化学组分的差异对密度的影响。结合同步观测的亚微米气溶胶的化学成分资料,可以看出,有效密度随粒径增大而增大主要与颗粒物中硫酸铵、硝酸铵等二次无机组分的含量升高有关。冬季气溶胶粒子的分粒径密度有显著的日变化。整体上50~300 nm的粒子有效密度在上午呈现增加的趋势,在中午12:00~14:00达到峰值,之后再逐渐下降,主要和居民燃煤取暖有关。不同粒径的气溶胶平均有效密度有轻微的季节变化。冬季时各粒径的平均有效密度略低于夏季,可能是由于冬季燃煤取暖排放出大量低密度的有机气溶胶,即颗粒物中有机气溶胶的含量冬季时大于夏季,从而导致有效密度略低。50~100 nm粒子的平均有效密度在新粒子形成事件中略高,而其他粒径段无显著变化,可能是由于硫酸蒸气参与颗粒物成核和增长过程而导致的。冬季清洁时段的50~200nm的有效密度略高于污染时段,而300 nm的粒子有效密度在清洁时期略低于污染时段,主要与颗粒物内部化学组分有关。100 nm和200 nm的有效密度随着PM1质量浓度的增加有逐渐较小的趋势,这与污染时段下有效密度偏低结果一致。结合同期气溶胶质谱仪(AMS)资料分析,得到冬季时颗粒物内部有机物约占37%,由100~300 nm粒子有效密度与Org/PM1拟合结果得出:随着有机物所占比例升高,粒子对应的有效密度逐渐减小;当有机物所占比例达到60%时,100~200 nm粒子的有效密度接近于1.2 g/cm~3,由此推断低的有效密度和粒子内部的有机物含量高有关。
[Abstract]:Density is one of the important physical properties of atmospheric aerosols. It is of great significance to study the behavior of aerosol particles in the atmosphere and the deposition efficiency in human body. In this paper, the differential mobility particle size analyzer (DMA-aerosol particle mass analyzer) is used to study the behavior of aerosol particles in the CPC system. The effective density of 50 ~ 350nm sub-micron aerosol was observed at the Shangdian regional atmospheric background station from 2015 to September and December, respectively. Based on these observational data, the distribution and variation of atmospheric aerosol effective density in summer and winter are analyzed. The change of aerosol density during the formation of new particles and during the pollution period was investigated. The variation range of effective density in summer is 0.96 ~ 1.65 g / cm ~ (-3), and that in winter is 0.98 ~ 1.55 g / cm ~ (3) ~ (50) ~ (50) nm. The effective density of aerosol density increases with the increase of particle size. Combined with the data of the chemical composition of submicron aerosol observed simultaneously, it can be seen that the effective density increases with the increase of particle size, and it is mainly associated with ammonium sulfate in particulate matter. The particle size density of aerosol particles in winter has a significant diurnal variation. Overall, the effective density of 50 ~ 300 nm particles increases in the morning and reaches its peak at 12: 00 to 14: 00 at noon. The average effective density of aerosol with different diameters varies slightly in season. The mean effective density of each particle size in winter is slightly lower than that in summer. This may be due to a large amount of low-density organic aerosols emitted from coal-fired heating in winter, that is, the content of organic aerosols in particulate matter is larger in winter than in summer. As a result, the average effective density of the 100 nm particle with slightly lower effective density is slightly higher in the new particle formation event, while the other particle size segments have no significant change. It is possible that sulfuric acid vapor is involved in the nucleation and growth of particulate matter. The effective density of 50 ~ 200 nm in winter cleaning period is slightly higher than that in pollution period, while the effective density of 300 nm particle is slightly lower in clean period than in pollution period. The effective densities of 0.100nm and 200nm are mainly related to the internal chemical components of particulate matter. With the increase of mass concentration of PM1, the effective densities tend to decrease gradually, which is consistent with the results of low effective densities in the polluted period. The results of fitting the effective density of 100 ~ 300nm particles and Org/PM1 show that the effective density of particles decreases with the increase of the proportion of organic matter. When the proportion of organic matter reaches 60, the effective density of 100nm particle is close to 1.2 g / cm ~ (-1). It is concluded that the low effective density is related to the high content of organic matter inside the particle.
【学位授予单位】：中国气象科学研究院
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X513

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