本文選題：大氣氣溶膠　切入點(diǎn)：有效密度　出處：《中國(guó)氣象科學(xué)研究院》2016年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：密度是大氣氣溶膠重要的物理性質(zhì)之一。研究大氣氣溶膠密度可以為了解氣溶膠化學(xué)組分、評(píng)估氣溶膠形成過(guò)程提供參考依據(jù),對(duì)于探究氣溶膠粒子在大氣中的行為以及在人體內(nèi)的沉積效率有重要意義。本文利用差分遷移率粒徑分析儀(DMA)-氣溶膠粒子質(zhì)量分析儀(APM)-凝結(jié)粒子計(jì)數(shù)器(CPC)系統(tǒng)于2015年8~9月和12月先后在上甸子區(qū)域大氣本底站對(duì)50~350nm分粒徑亞微米氣溶膠的有效密度進(jìn)行觀測(cè),基于這些觀測(cè)資料,分析了上甸子夏、冬季大氣氣溶膠有效密度的分布特征和變化規(guī)律,并探究了新粒子形成過(guò)程中和污染時(shí)段氣溶膠密度的變化。夏季有效密度的變化范圍是0.96~1.65 g/cm~3,冬季有效密度的變化范圍是0.98~1.55g/cm~3,50~350 nm粒子的有效密度均隨著粒徑的增大而增大,反映出顆粒物化學(xué)組分的差異對(duì)密度的影響。結(jié)合同步觀測(cè)的亞微米氣溶膠的化學(xué)成分資料,可以看出,有效密度隨粒徑增大而增大主要與顆粒物中硫酸銨、硝酸銨等二次無(wú)機(jī)組分的含量升高有關(guān)。冬季氣溶膠粒子的分粒徑密度有顯著的日變化。整體上50~300 nm的粒子有效密度在上午呈現(xiàn)增加的趨勢(shì),在中午12:00~14:00達(dá)到峰值,之后再逐漸下降,主要和居民燃煤取暖有關(guān)。不同粒徑的氣溶膠平均有效密度有輕微的季節(jié)變化。冬季時(shí)各粒徑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機(jī)氣溶膠,即顆粒物中有機(jī)氣溶膠的含量冬季時(shí)大于夏季,從而導(dǎo)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,而其他粒徑段無(wú)顯著變化,可能是由于硫酸蒸氣參與顆粒物成核和增長(zhǎng)過(guò)程而導(dǎo)致的。冬季清潔時(shí)段的50~200nm的有效密度略高于污染時(shí)段,而300 nm的粒子有效密度在清潔時(shí)期略低于污染時(shí)段,主要與顆粒物內(nèi)部化學(xué)組分有關(guān)。100 nm和200 nm的有效密度隨著PM1質(zhì)量濃度的增加有逐漸較小的趨勢(shì),這與污染時(shí)段下有效密度偏低結(jié)果一致。結(jié)合同期氣溶膠質(zhì)譜儀(AMS)資料分析,得到冬季時(shí)顆粒物內(nèi)部有機(jī)物約占37%,由100~300 nm粒子有效密度與Org/PM1擬合結(jié)果得出:隨著有機(jī)物所占比例升高,粒子對(duì)應(yīng)的有效密度逐漸減小;當(dāng)有機(jī)物所占比例達(dá)到60%時(shí),100~200 nm粒子的有效密度接近于1.2 g/cm~3,由此推斷低的有效密度和粒子內(nèi)部的有機(jī)物含量高有關(guān)。
[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.
【學(xué)位授予單位】：中國(guó)氣象科學(xué)研究院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：X513

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