西安大气气溶胶化学组成与吸湿性能特征

发布时间：2018-04-19 10:03

本文选题：雾霾 + 颗粒物　；参考：《中国科学院研究生院(地球环境研究所)》2015年硕士论文

【摘要】：本研究于2013年3月9~12日春季沙尘期间和2013年12月24日~2014年1月27日冬季雾霾期间,在西安市区分别进行TSP离线采集以及PM2.5化学组分、NH3浓度、CCN分档活化率的在线观测,时间分辨率均为1小时,并检测离线样品的无机离子组成、含碳组分及水溶性组分吸湿性。目的在于分析春季沙尘暴和冬季雾霾期间西安大气颗粒物化学演化特征,探讨硫酸盐、硝酸盐、铵盐及钠盐等主要无机盐的来源、形成机制及其对颗粒物吸湿性能的影响。冬季雾霾观测期间,PM2.5是影响能见度的主要因素;其中出现重霾天主要是由于除夕凌晨烟花爆竹的大量燃放以及不利于污染物扩散的气象条件造成的,并且还导致重霾天期间Cl 、K+、Mg2+浓度突然增加。而PM2.5中的NO3 、SO42 、NH4+主要是通过二次转化形成,并呈现出浓度逐渐上升的趋势。Na+主要是人为燃烧秸秆等燃料供暖所产生,仅在0.64~1.63μg·m 3范围内上下波动,无增加趋势。由于NO2 是中间产物不容易积累成高浓度,且气相中的HNO2非常不稳定,所以检测到的NO2 浓度非常低。而观测期间风速很低,无地面扬尘,且Ca2+主要存在于粗颗粒中,因此PM2.5中Ca2+浓度也非常低。NH3浓度在10.7~47.8μg·m 3范围内上下波动,并且由于NH3主要受人为活动影响,而白天人为活动频繁,晚上人为活动减少,所以NH3呈现出明显的昼夜变化特征,即白天上午浓度达到最高,凌晨左右降到最低。使用ZSR规则以及简化模型分别计算冬季雾霾期PM2.5吸湿参数κ的结果显示:重霾天PM2.5吸湿参数(κ=0.36)比轻霾天(κ=0.26)的略高。此外,由于边界层的昼夜变化以及白天的光化学反应,造成吸湿参数κ呈现出比较明显的昼夜变化趋势。冬季SMPS与CCN联用的观测结果,表明颗粒物的粒径相较于化学组分对于其活化成为CCN更重要,以及细颗粒的吸湿性比粗颗粒较强。春季沙尘期间有两次沙尘峰值过境西安,TSP小时浓度最高分别达到7527μg·m 3和3200μg·m 3,同期SO42 分别为180μg·m 3和38μg·m 3。沙尘暴初入西安时NO3 与NH4+浓度较低,其后,二者以1:1的摩尔比同步渐增,至沙尘过后第48小时达最大值(分别为34μg·m 3和8.7μg·m 3)。沙尘期Na+与SO42 、Cl 的相关系数为.95,NH4+与NO3 的相关系数为0.78,由此推测他们的来源相同,是来源于戈壁上干旱湖泊中的岩盐、芒硝、石膏和钙芒硝等矿物;但NH4+和NO3 主要来源于沙尘颗粒表面的非均相反应,并以NH4NO3的形式存在。由于TSP样品水溶性组分中大部分是无机离子,因此样品水溶性组分显示出一定的吸湿性,整个观测期其吸湿增长因子变化范围为1.27~1.44。
[Abstract]:During the spring dust period from March 9 to 12, 2013 and the winter haze from December 24, 2013 to January 27, 2014, the off-line collection of TSP and the on-line observation of the NH _ 3 concentration of the chemical component of PM2.5 and the activation rate of PM2.5 were carried out in Xi'an urban area, respectively.The time resolution was 1 hour, and the moisture absorption of inorganic ions, carbon and water soluble components were detected.The aim of this paper is to analyze the chemical evolution characteristics of atmospheric particulate matter in Xi'an during spring sandstorm and winter haze, and to discuss the source, formation mechanism and effect of sulfate, nitrate, ammonium salt and sodium salt on the moisture absorption of particles.During the winter haze observation, PM2.5 is the main factor affecting visibility. The heavy haze is mainly caused by the massive discharge of fireworks and firecrackers in the early hours of New Year's Eve's morning and the weather conditions that are not conducive to the diffusion of pollutants.It also leads to the sudden increase of Cl ~ (2 +) K ~ (2 +) mg _ (2) concentration during heavy haze days.However, the NH4 in PM2.5 was mainly formed by secondary transformation, and the concentration increased gradually. Na was mainly produced by heating fuel such as burning straw, and only fluctuated in the range of 0.64 ~ 1.63 渭 g / m ~ (3), with no increasing trend.As the intermediate product of NO2 is not easy to accumulate into high concentration, and the HNO2 in gas phase is very unstable, the detected NO2 concentration is very low.However, during the observation period, the wind speed is very low, there is no surface dust, and Ca2 mainly exists in coarse particles. Therefore, the concentration of Ca2 in PM2.5 is very low. NH3 concentration fluctuates in the range of 10.7 ~ 47.8 渭 g / m ~ (3), and NH3 is mainly affected by human activities.But during the day the human activities are frequent and the night human activities decrease so the NH3 shows obvious diurnal variation characteristics namely the highest concentration in the morning and the lowest in the early morning.Using the ZSR rule and the simplified model to calculate the PM2.5 hygroscopicity parameter 魏 in the haze phase in winter, the results showed that the hygroscopic parameters of PM2.5 in heavy haze days (魏 ~ 0.36) were slightly higher than those in light haze days (魏 ~ (26)).In addition, due to the diurnal variation of the boundary layer and the photochemical reaction during the day, the hygroscopic parameter 魏 shows an obvious diurnal variation trend.The observation results of SMPS and CCN in winter show that the particle size is more important than the chemical component in the activation to CCN, and the moisture absorption of fine particles is stronger than that of coarse particles.During spring, the peak concentration of tsp in Xi'an is 7527 渭 g / m ~ (-3) and 3200 渭 g / m ~ (-3), respectively, and SO42 ~ (3) is 180 渭 g / m ~ (-3) and 38 渭 g / m ~ (-3), respectively.The concentrations of NO3 and NH4 were lower at the beginning of dust storm in Xi'an, and then increased at 1:1 molar ratio, and reached their maximum values at 48h after dust dust (34 渭 g / m ~ 3 and 8.7 渭 g / m ~ (3)), respectively.The correlation coefficient between Na and SO42 + Cl ~ (2 +) in sand dust stage is 0.78. The correlation coefficient between Na and NO3 ~ (2 +) is 0.78, which is derived from rock salt, mirabilite, gypsum and glauberite from arid lakes on the Gobi.However, NH4 and NO3 mainly originate from heterogeneous reactions on the surface of dust particles and exist in the form of NH4NO3.Because most of the water-soluble components of TSP samples are inorganic ions, the water-soluble components of TSP samples show a certain moisture absorption, and the range of moisture absorption growth factor is 1.27 ~ 1.44 in the whole observation period.
【学位授予单位】：中国科学院研究生院(地球环境研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X513

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