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991.
2015世界互联网大会期间嘉兴市大气细颗粒物污染特征及来源研究——以单颗粒气溶胶质谱技术为例 总被引:2,自引:0,他引:2
基于单颗粒气溶胶质谱技术,于2015年12月12—23日互联网大会期间开展了嘉兴市细颗粒物污染特征和来源研究.结果显示,观测期间共捕捉到5次不同的污染过程,分别为:管控期的区域输送(P1)-清洁天(P2)-本地排放(P3)过程,以及管控后的污染反弹(P4)-重污染程(P5)过程.污染期间(P1、P5),硝酸盐含量及比例均有显著增加,并且增加的主要是老化的硝酸盐颗粒,表明硝酸盐的二次转化对长三角地区高浓度细颗粒物形成具有重要影响.受管控措施和南下的强冷空气影响,会议期间,除有机碳和生物质燃烧组分外,PM_(2.5)质量浓度及其它各组分浓度均有不同程度的下降.管控措施解除后(P5),受区域输送和本地污染物积累共同作用,颗粒物浓度开始反弹并持续升高,硝酸盐和EC组分均有明显增加,并且呈现出早、晚高峰值.源解析结果显示,P5期间颗粒物浓度反弹与机动车尾气排放密切相关.研究表明,实施管控措施对降低机动车尾气排放和PM_(2.5)质量浓度、改善环境空气质量等效果显著. 相似文献
992.
利用自制气溶胶反应器研究了NO_x和/或NH_3气氛下SO_2在高岭土表面的非均相转化过程,应用扫描电镜(SEM)对高岭土颗粒物形貌进行了表征.结果表明:高岭土颗粒表面的SO_2非均相转化致使其成分和形貌产生了较大变化.相同实验条件下,SO_2转化的协同作用程度由高到低依次为NH_3、NO_x/NH_3和NO_x气氛,相对湿度40%、有光照条件下,SO_2转化量增幅最高可分别达125%、75%和50%.所有气氛下,协同作用在无光照时在高相对湿度(40%~70%)区间更为突出,有光照时其显著性则体现在低相对湿度(20%~40%)区间.SO_2、NO_x、NH_3三者共存时,在高岭土颗粒表面发生的非均相反应过程既有协同作用又存在竞争反应. 相似文献
993.
Huaiyu Fu Mei Zheng Caiqing Yan Xiaoying Li Huiwang Gao Xiaohong Yao Zhigang Guo 《环境科学学报(英文版)》2015,29(3)
Marine aerosols over the East China Seas are heavily polluted by continental sources. During the Chinese Comprehensive Ocean Experiment in November 2012, size and mass spectra of individual atmospheric particles in the size range from 0.2 to 2.0 μm were measured on board by a single particle aerosol mass spectrometer(SPAMS). The average hourly particle number(PN)was around 4560 ± 3240 in the South Yellow Sea(SYS), 2900 ± 3970 in the North Yellow Sea(NYS), and 1700 ± 2220 in the Bohai Sea(BS). PN in NYS and BS varied greatly over 3 orders of magnitude, while that in SYS varied slightly. The size distributions were fitted with two log-normal modes. Accumulation mode dominated in NYS and BS, especially during episodic periods. Coarse mode particles played an important role in SYS. Particles were classified using an adaptive resonance theory based neural network algorithm(ART-2a). Six particle types were identified with secondary-containing, aged sea-salt, soot-like, biomass burning, fresh sea-salt,and lead-containing particles accounting for 32%, 21%, 18%, 16%, 4%, and 3% of total PN,respectively. Aerosols in BS were relatively enriched in particles from anthropogenic sources compared to SYS, probably due to emissions from more developed upwind regions and indicating stronger influence of continental outflow on marine environment. Variation of source types depended mainly on origins of transported air masses. This study examined rapid changes in PN, size distribution and source types of fine particles in marine atmospheres. It also demonstrated the effectiveness of high-time-resolution source apportionment by ART-2a. 相似文献
994.
995.
1954—2013年湖北省黄石市气溶胶光学厚度与降水关系研究 总被引:1,自引:1,他引:0
通过对地面观测资料进行均一性处理和反演,建立了湖北省黄石市近60年气溶胶光学厚度(AOD)的时间序列,采用气候趋势分析、相关分析等方法,研究了AOD与降水之间的关系.结果表明:近60年黄石市气溶胶光学厚度(AOD)总体上呈显著增加趋势,最大值出现在1991年.随着AOD值的显著增加,年平均降水发生日数显著减少,其中,小雨日数下降更明显,而中雨、大雨日数有增加趋势,暴雨日数的变化趋势不明显.小雨雨量随着AOD值的显著增加而减少,而中雨及以上等级降水量的变化趋势不明显.总之,近60年黄石市气溶胶光学厚度(AOD)的增加,对降水日数和降水量都有一定的影响,其相关性有待进一步研究. 相似文献
996.
2013年冬季海口市一次气溶胶粒子污染事件特征及成因解析 总被引:3,自引:2,他引:1
海口市在2013年12月份发生了一次气溶胶粒子污染事件.本文利用相关资料对此进行诊断,发现海口市PM2.5在12月9日超过了国家环境空气质量二级标准限值,在11日达到该污染时段的最高值(日平均为87.96μg·m-3),同时与能见度有一定的负向关系.分析表明,前期(7—9日上午),污染物主要以本地排放为主,而后期(9日中午到11日)与珠江三角洲地区的输送作用有密切关系,后向轨迹分析也表明后期海口市大气污染物可能来自珠三角地区.分析发现,气象背景场为这次气溶胶污染事件提供了有利的气象条件,500 h Pa高度场冷空气活动偏北,925 h Pa高度场的暖中心控制,形势稳定,逆温层的存在使得大气近地层更加稳定,低层风速偏小不利于近地面附近的污染物向外输送,水平风垂直切变偏弱有利于污染物在近地层堆积,其变化趋势与PM2.5浓度有一定的相关性. 相似文献
997.
A Hierarchical Model for Estimating Long‐Term Trend of Atrazine Concentration in the Surface Water of the Contiguous U.S. 下载免费PDF全文
Atrazine is a herbicide frequently detected in both surface and groundwater in the United States (U.S.), but its spatiotemporal distribution and concentration trends have only been analyzed recently at regional or local scales. We employed a Bayesian hierarchical modeling approach to assess spatial and seasonal variation in atrazine concentration trends between 1990 and 2010 for the contiguous U.S. A Markov chain Monte Carlo simulation algorithm was used to address the problem of left‐censored data (i.e., atrazine concentration values below method reporting levels). We observed opposing temporal trends in the northern (flat or decreasing) and southern (increasing) regions of the U.S. This spatial variation in temporal trends can be partially explained by the relative amount of cropland in the region. Flat or decreasing trends in the north are more likely in regions with high cropland coverage while positive trends in the south are more likely in regions with low cropland coverage. 相似文献
998.
Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, but the lack of kinetics data significantly limited the evaluation of this process in the atmosphere. Here we report the first measurement of the uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide. Isoprene cannot readily partition into the solution because of its high volatility and low solubility, which hinders its further liquid-phase oxidation. Both methacrylic acid and methyl methacrylate can enter the solutions and be oxidized by hydrogen peroxide, and steady-state uptake was observed with the acidity of solution above 30 wt.% and 70 wt.%, respectively. The steady-state uptake coefficient of methacrylic acid is much larger than that of methyl methacrylate for a solution with same acidity. These observations can be explained by the different reactivity of these two compounds caused by the different electron-withdrawing conjugation between carboxyl and ester groups. The atmospheric lifetimes were estimated based on the calculated steady-state uptake coefficients. These results demonstrate that the multiphase acid-catalyzed oxidation of methacrylic acid plays a role in secondary organic aerosol formation, but for isoprene and methyl methacrylate, this process is not important in the troposphere. 相似文献
999.
Mingqiang Huang Weijun Zhang Xuejun Gu Changjin Hu Weixiong Zhao Zhenya Wang Li Fang 《环境科学学报(英文版)》2012,24(5):860-864
Secondary organic aerosol (SOA) formed from Cl-initiated oxidation of toluene was investigated in a home-made smog chamber. The size distribution and chemical composition of SOA particles were measured using aerodynamic particle sizer spectrometer and the aerosol laser time-of-flight mass spectrometer (ALTOFMS), respectively. According to a large number of single aerosol diameter and mass spectra, the size distribution and chemical composition of SOA were obtained statistically. Experimental results showed that SOA particles created by Cl-initiated oxidation of toluene is predominantly in the form of fine particles, which have diameters less than 2.5 m (i.e., PM2.5), and glyoxal, benzaldehyde, benzyl alcohol, benzoquinone, benzoic acid, benzyl hydroperoxide and benzyl methyl nitrate are the major products components in the SOA. The possible reaction mechanisms leading to these products are also proposed. 相似文献
1000.
Most previous O3 simulations were based only on gaseous phase photochemistry. However, some aerosol-related processes, namely, heterogeneous reactions occurring on the aerosol surface and photolysis rate alternated by aerosol radiative influence, may affect O3 photochemistry under high aerosol loads. A three-dimensional air quality model, Models-3/Community Multi-scale Air Quality-Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution, was employed to simulate the effects of the above-mentioned processes on O3 formation under typical high O3 episodes in Beijing during summer. Five heterogeneous reactions, i.e., NO2, NO3, N2O5, HO2, and O3, were individually investigated to elucidate their effects on O3 formation. The results showed that the heterogeneous reactions significantly affected O3 formation in the urban plume. NO2 heterogeneous reaction increased O3 to 90 ppb, while HO2 heterogeneous reaction decreased O3 to 33 ppb. In addition, O3 heterogeneous loss decreased O3 to 31 ppb. The effects of NO2, NO3, and N2O5 heterogeneous reactions showed opposite O3 concentration changes between the urban and extra-urban areas because of the response of the reactions to the two types of O3 formation regimes. When the aerosol radiative influence was included, the photolysis rate decreased and O3 decreased significantly to 73 ppb O3. The two aerosol-related processes should be considered in the study of O3 formation because high aerosol concentration is a ubiquitous phenomenon that affects the urban- and regional air quality in China. 相似文献