南京市城市不同功能区PM10和PM2.1质量浓度的季节变化特征

使用Anderson-Ⅱ型9级撞击采样器测量了南京市鼓楼商业区、江北工业区、钟山风景区和宁六高速公路交通源春、夏、秋三季的大气气溶胶质量浓度。分析结果表明:南京市PM_2.1和PM₁₀的质量浓度存在明显的季节变化,秋季>春季>夏季;ρ_PM10春季为167.47 μg/m³,夏季为 85.99 μg/m³,秋季为238.99 μg/m³;ρ_PM2.1春季为59.66 μg/m³,夏季为42.80 μg/m³,秋季为100.15 μg/m³。不同季节中ρ_PM10和ρ_PM2.1均存在较好的相关性,夏季相关性最好,相关系数为0.952;秋季次之,相关系数为0.783;春季相对较差,相关系数为0.613。城市不同功能区之间ρ_PM2.1和ρ_PM10的质量浓度值差异很大,交通源>工业区>商业区>风景区。城市不同功能区的质量浓度谱分布基本一致,均为双峰型分布,峰值分别位于0.43~0.65 μm/m³和9.0~10.0 μm/m³。南京市春、夏、秋三个季节大气粒子质量浓度谱为双峰分布,粒子主要集中在0.43~3.3 μm/m³的粒径段。江北工业区ρ_PM10和ρ_PM2.1质量浓度的相关系数为0.814,略高于鼓楼商业区的0.797。     

南京市城市不同功能区PM10和PM2.1质量浓度的季节变化特征

使用Anderson-Ⅱ型9级撞击采样器测量了南京市鼓楼商业区、江北工业区、钟山风景区和宁六高速公路交通源春、夏、秋三季的大气气溶胶质量浓度。分析结果表明:南京市PM_2.1和PM₁₀的质量浓度存在明显的季节变化,秋季>春季>夏季;ρ_PM10春季为167.47 μg/m³,夏季为 85.99 μg/m³,秋季为238.99 μg/m³;ρ_PM2.1春季为59.66 μg/m³,夏季为42.80 μg/m³,秋季为100.15 μg/m³。不同季节中ρ_PM10和ρ_PM2.1均存在较好的相关性,夏季相关性最好,相关系数为0.952;秋季次之,相关系数为0.783;春季相对较差,相关系数为0.613。城市不同功能区之间ρ_PM2.1和ρ_PM10的质量浓度值差异很大,交通源>工业区>商业区>风景区。城市不同功能区的质量浓度谱分布基本一致,均为双峰型分布,峰值分别位于0.43~0.65 μm/m³和9.0~10.0 μm/m³。南京市春、夏、秋三个季节大气粒子质量浓度谱为双峰分布,粒子主要集中在0.43~3.3 μm/m³的粒径段。江北工业区ρ_PM10和ρ_PM2.1质量浓度的相关系数为0.814,略高于鼓楼商业区的0.797。     

江淮之间夏季雨滴谱特征分析

分析了2011—2013年夏季(6—8月)滁州地基雨滴谱观测资料,根据雨强及其随时间的变化将降水分成对流降水和层云降水,分析不同降水类型的雨滴谱特征。结果表明:滁州地区对流降水的质量加权直径D_m和标准化参数lgN_w的平均值分别为1.67 mm和3.91 mm^-1·m^-3,层云降水D_m和lgN_w的平均值分别为1.18 mm和3.57 mm^-1·m^-3,对流降水雨滴平均尺度更大。N_w相比Γ分布参数N₀能更好地反映总数浓度N_t的大小。Γ分布3参数均随雨强的增大而减小,当雨强增长到一定程度时,μ(谱型)和Λ(斜率)趋于常数。研究了μ-Λ关系和Z(反射率因子)-R(雨强)关系。对流降水和层云降水的Z-R关系分别为Z=408R^1.20和Z=301R^1.21。新的Z-R关系和经典Z-R关系(Z=300R^1.40)反演的雨强相比实际观测值均偏小,但新的Z-R关系反演的雨强与实际观测值更接近。     

江淮地区龙卷超级单体风暴及其环境参数分析

利用多普勒雷达探测资料和NCEP再分析资料,对2003—2010年发生在江淮地区的6个龙卷超级单体风暴及其环境参数进行了分析。研究表明：（1）龙卷超级单体风暴H_BASE平均为1.7 km,H_TOP平均为9.1 km;H多在风暴的下部,近于下部的1/4处。H_BASE平均值比江淮地区各种超级单体的平均值低得多,H_TOP则略低。（2）龙卷超级单体I_VIL平均为25.6 kg/m²,Z_MX平均为54.8 dBz。和江淮地区超级单体相比,龙卷I_VIL要小得多,而龙卷Z_MX略低。（3）龙卷超级单体的中气旋M_BASE、M_TOP和M_SHR平均值分别为1.2 km、3.9 km和14.4×10^-3s^-1,和江淮地区超级单体相比,龙卷M_BASE、M_TOP明显低,而M_SHR略高。（4）TVS参数最强时的V_AD在12—45 m/s,V_LLD多大于30 m/s,V_MXD多超过30 m/s,V_MXD的高度不低于0.8 km,T_DPT在2.4—6.4 km,T_BASE在0.7—1.5 km,T_TOP在2.3—6.4 km,T_MXSHR超过22×10^-3s^-1。TVS参数最强时间与龙卷实际时间基本吻合,平均相差4.2 min;平均而言,TVS出现后6 min有龙卷发生。（5）雷达推算的龙卷超级单体的0—6 km风垂直切变比江淮地区超级单体的风垂直切变平均值高15.2%;龙卷发生前I_CAPE平均为1752 J/kg,I_K为38℃,850 hPa到地面风切变平均超过12 m/s,850—500 hPa温差平均为23.7℃。龙卷发生前能量处在中等到强的状态,大气不稳定性较强,风垂直切变大。     

武汉大气能见度与PM2.5浓度及相对湿度关系的非线性分析及能见度预报

武汉作为中部地区高湿度代表城市,大气污染严重,霾天气多发,但有关该地区大气能见度与PM_2.5浓度及相对湿度(RH)的定量关系尚不明确。利用2014年9月—2015年3月武汉地区逐时能见度、相对湿度及颗粒物质量浓度观测数据,研究分析了武汉大气能见度与PM_2.5浓度及相对湿度的关系,并进行能见度非线性预报初探,得到以下结论:武汉霾时数发生比例高,霾的发生和加重是能见度降低的主要原因;能见度降低伴随大量细粒子产生和累积,这是武汉大气能见度恶化的重要诱因。细颗粒物浓度与相对湿度共同影响和制约大气能见度变化,高湿高浓度时能见度显著下降,湿情景下(RH≥40%),能见度恶化主要是由湿度增高诱使细颗粒物粒径吸湿增长导致其散射效率增大造成的。当RH >90%时,能见度随湿度升高成线性递减,相对湿度每升高1%,武汉平均能见度降低0.568 km。而干情景下(RH<40%),能见度迅速降低的关键因素是PM_2.5质量浓度升高。在城市大气细粒子污染背景下,能见度与相对湿度成非线性关系,这主要与PM_2.5对能见度的影响及吸湿性颗粒物的散射效率变化有关。PM_2.5浓度与能见度成幂函数非线性关系,80%≤RH<90%湿度区段下相关性最强。PM_2.5浓度对能见度的影响敏感阈值是随着湿度升高而减小的,干情景下能见度10 km对应的PM_2.5浓度阈值为70 μg/m³,湿情景下该阈值为18—55 μg/m³。当PM_2.5质量浓度低于约40 μg/m³时,继续降低PM_2.5可显著提高武汉大气能见度。预报试验表明,基于神经网络方法建立大气能见度非线性预报模型是可行的,预报能见度相关系数为0.86,均方根误差为1.9 km,能见度≤10 km的TS评分为0.92。网络模型具有较高预报性能,对霾的判别有较高准确性,为衔接区域环境气象数值预报模式,建立大气能见度精细化动力统计模型提供参考依据。     

武汉市冬季灰霾期PM2.5中水溶性无机离子的特征

2018年1月,利用颗粒物采样器采集武汉市大气PM_2.5样品并进行水溶性无机离子（F^-、Cl^-、NO₃^-、SO₄^2-、Na⁺、NH₄⁺、K⁺、Mg²⁺、Ca²⁺）的分析.结果表明,NO₃^-、SO₄^2-、NH₄⁺是PM_2.5中最主要的3种水溶性无机离子,除Mg²⁺与Ca²⁺外,PM_2.5与WSⅡs （水溶性无机离子）之间的相关性显著,且移动源贡献占主导地位.阴阳离子平衡表明武汉市冬季灰霾期PM_2.5呈中性或弱酸性.通过混合单粒子拉格朗日综合轨迹模式模拟并采用分层聚类得出了4种主要的后向气流轨迹及相应的PM_2.5和水溶性离子浓度,结果表明区域传输对此次灰霾期影响较大.     

苏南三市秋冬季PM2.5中水溶性离子和元素特征及源解析

2010年11月16日至12月17日在南京、常州、苏州三城市设置采样点,24 h采集大气PM_2.5样品,并测定其水溶性无机离子和元素的浓度,在此基础上讨论PM_2.5及无机组分的时空分布特征。结果表明,采样期间,PM_2.5污染较严重,且苏州最重,常州次之,南京最轻,南京、苏州、常州日均浓度分别是国家二级标准(75 μg/m³)的1.44、2.32、1.53倍;三市PM_2.5离子组分中,阴离子均以SO₄^2-和NO₃^-为主,阳离子以Ca²⁺和Mg²⁺为主;苏州Na⁺和Cl^-之间的相关性较高,其受到海盐输送影响较大;三城市PM_2.5中Ca是最主要元素,Al次之。运用主成分法分析南京、常州和苏州PM_2.5的来源可知,三城市PM_2.5受多个污染源影响,包括生物质燃烧、地表扬尘、五金工业及汽车尾气排放等。     

福建三明市春季PM2.5中有机碳、元素碳和水溶性离子特征分析

2014年3月13日至4月20日在福建三明市利用PM_2.5中流量采样器采集大气中PM_2.5膜样品,测定了PM_2.5的质量浓度,并用热/光碳分析仪和离子色谱分析了其组分变化特征.结果表明,三明市观测期间PM_2.5的平均质量浓度为73.61±0.73 μg/m³,有机碳(OC)和元素碳(EC)的平均质量浓度分别为7.26±1.00和5.63±0.27 μg/m³,水溶性离子中SO₄^2-、NH₄⁺、NO₃^-和Na⁺的质量浓度分别为18.08±12.19、4.18±3.56、2.77±1.16和2.73±0.23 μg/m³,总和占总水溶性离子的87.76%.结合后向轨迹分析了福建三明市的污染物来源特征.该地区OC/EC的平均比值小于2,SOC(二次有机碳)生成量很少,主要以一次有机污染物为主,OC、EC与K⁺的相关性分析表明OC、EC与K⁺的来源相近,可以判断OC、EC绝大部分来源是生物质燃烧产生的污染物.在水溶性离子分析中,观测期间NO₃^-/SO₄^2-为0.159±0.02,表明三明市主要以固定源为主,机动车辆等移动源贡献较少.     

2014—2019年北京和南京地区PM2.5和臭氧质量浓度相关性研究

自2014年以来,中国细颗粒物（PM_2.5）浓度大幅度下降,但臭氧（O₃）浓度逐年缓慢上升,厘清PM_2.5和O₃（P-O）相关性尤为关键.在本研究中,2014—2019年北京和南京PM_2.5年均质量浓度下降幅度分别为-6.86和-6.15 μg·m^-3·a^-1;而日最大8小时平均O₃质量浓度（MDA8 O₃）年均增长幅度为1.50和1.75 μg·m^-3·a^-1.研究期间,北京地区MDA8 O₃质量浓度小于100 μg·m^-3,P-O呈负相关;而当质量浓度大于100 μg·m^-3时,P-O为正相关.通过Pearson相关系数研究P-O两者相关性.在两个城市每月相关性分析中,在每日时间尺度5—9月为强的正相关;而小时时间尺度11月至次年2月趋于负相关.在北京,P-O每月和季节相关性变化大于南京.在日变化中,夏季在16时为强的正相关,春秋两季在13—17时为弱的正相关,而在春、秋和冬季8时,却为强的负相关.     

多普勒天气雷达1 h降水产品的质量评估

为评估多普勒天气雷达1 h降水量(OHP)产品在降水预报中的质量, 从南通新一代多普勒天气雷达的体扫资料及其覆盖范围内太湖流域34个雨量站的同期逐小时降水资料中选取了19个降水个例。以空报率、漏报率、准确预报临界指数、平均误差、平均绝对误差和均方根误差等, 为评估降水预报质量的指标。根据雨量站实测日降水量(P)和1 h降水量(P₁)大小分级, 对不同情况下的OHP进行质量评估。结果表明:(1)OHP的空报率和漏报率较高, 导致整体的准确预报临界指数偏低。(2)与不同的P和P₁量级相对应, 不同的OHP预报质量有明显差异。除P<10 mm时和P₁<1 mm时稍有高估外, 其他量级都存在低估, 且随着P的增加, 空报率和漏报率都减小。(3)对2007年9月18日的降水个例分析表明:OHP与实测的落区基本一致, 但降水强度上有偏差。不同站点的雨强偏差不同, 距南通雷达站100 km左右的OHP误差较小。     

Impact of intensive fish farming on methane emission in a tropical hydropower reservoir

Fisheries and aquaculture are important sources of food for hundreds of millions of people around the world. World fish production is projected to increase by 15% in the next 10 years, reaching around 200 million tonnes per year. The main driver of this increase will be based on fish farming management in developing countries. In Brazil, fish farming is increasing due to the climate conditions and large supply of water resources, with the production system based on Nile tilapia (Oreochromis niloticus) farming in reservoirs. Inland waters like reservoirs are a natural source of methane (CH₄) to the atmosphere. However, knowledge of the impact from intensive fish production in net cages on CH₄ fluxes is not well known. This paper presents in situ measurements of CH₄ fluxes and dissolved CH₄ (DM) in the Furnas Hydroelectric Reservoir in order to evaluate the impact of fish farming on methane emissions. Measurements were taken in a control area without fish production and three areas with fish farming. The overall mean of diffusive methane flux (DMF) (5.9?±?4.5 mg CH₄ m^?2 day^?1) was significantly lower when compared to the overall mean of bubble methane flux (BMF) (552.9?±?1003.9 mg CH₄ m^?2 day^?1). The DMF and DM were significantly higher in the two areas with fish farming, whereas the BMF was not significantly different. The DMF and DM were correlated to depth and chlorophyll-a. However, the low production of BMF did not allow the comparison with the limnological parameters measured. This case study shows that CH₄ emissions are influenced more by reservoir characteristics than fish production. Further investigation is necessary to assess the impact of fish farming on the greenhouse gas emissions.     

南京一次重霾天气纳米气溶胶观测研究

为加深对南京地区重霾天气过程纳米尺度气溶胶物理特征的了解,对2017年12月21—25日的一次重霾天气过程进行了综合探测,利用宽范围粒径谱仪观测了此次过程中10～1 000 nm颗粒物数浓度,并结合能见度等气象要素,对重霾期间纳米气溶胶谱分布进行了分析。结果表明:此次霾重污染过程出现在低温、高湿、气压上升期间;与非重污染时期相比,重污染期间N_(10-20)与N_(20-100)降低,N_(100-1000)升高;重污染期间气溶胶粒子平均数浓度为17 035个/cm~3,低于非重污染期间粒子数浓度,N_(100-1000)占总数浓度的55.05%;重霾发生期间纳米气溶胶数浓度谱为单峰结构,峰值在100 nm附近,随着污染加重,纳米气溶胶峰值粒径向大粒径偏移,粒子向大粒径段集中;不同温度对不同粒径粒子数浓度的影响不同,20～100 nm粒径段气溶胶与数浓度与温度呈反相关性,100～500 nm粒子数浓度与温度呈正相关性.     

Spatial variability in the chemical composition of the snowcover at high alpine sites

Summary For a comparison of snow chemistry data from different glaciers or snow fields it is important to have informations about the spatial representativeness of the data from each of the individual sites. In order to assess the representativeness of concentration data of major ions (volume weighted means of the winter accumulation) from glacier fields we investigated the variability in the average concentration of major ions from parallel samples within one snow pit and from different pits within one glacier field. The variabilities in the average concentrations of NO ₃ ^- , SO ₄ ^2- and NH ₄ ⁺ for three parallel profiles within one snow pit at Goldbergkees (Austria) were 1.2, 3.3 and 2.0% (coefficient of variation). Cl^– and Na⁺ showed larger variations (6.6 and 56.6%) possibly originating from contaminations. The variability of average concentration data from different snow pits within one glacier field was studied at La Grave (France) and at Goldbergkees (Austria). At La Grave 3 pits and at Goldbergkees 4 pits at distance of several hundred meters were sampled. Variabilities for SO ₄ ^2- and NO ₃ ^- were quite similar for the two sites (17% for both ions at La Grave, 12% and 15% at Goldbergkees). Whereas variabilities for Na⁺, NH ₄ ⁺ , Mg²⁺, Ca²⁺ and Cl^– were quite low at La Grave ( 12% and 27% for Cl^–), higher values were obtained at Goldbergkees for these ions (17–56%). Likely reasons for the higher variability observed at Goldbergkees are a) higher spatial variability of crustal aerosol species (Mg²⁺, Ca²⁺), b) problems with the detection limit of the analytical method (Ca²⁺), c) contaminations (Na⁺, Cl^–).With 4 Figures     

The chemistry of heavy haze over Urumqi,Central Asia

A sampling campaign of aerosols over Urumqi from 2001–2007 and soil samples in the surrounding areas were carried out to investigate the severe air pollution in Urumqi, a typical inland city, located in the center of Asia. Urumqi is one of the heavy polluted cities in the world, as the days of haze spanned over one third of the year and accounted for 60–80% of the heating period for the past 6 years. High concentration of fine aerosols, frequent occurrence, and rapid formation of heavy haze were the three main characteristics. With comparison of the pollution elements, As, Cd, and S, and the ratio of Ca/Al in aerosols and soils in those sites located on the south of Jungger Basin as tracers, it was found that As, Cd, and S highly enriched in the aerosols over urban Urumqi were not only from the re-suspended road dust but also from the soil transported from south of the Jungger Basin. Different from the most cities in China, the high concentration of sulfate in Urumqi was partially from the primary soil dust transported from the surrounding areas. The mixing of the local anthropogenic aerosols with the soil transported from outside the city was the main source of the high sulfate concentration. Ammonium salts were higher than the summed equivalents of SO₄²⁻, NO₃⁻, and Cl⁻ in Urumqi and much higher than that in other Chinese cities. The total water soluble ions and the total ammonium salts were as high as 57.8% and 51.0% in PM_2.5. The high concentration of soluble salts with high hygroscopicity, especially ammonium and sulfate salts, were the main factors contributing to the heavy haze over Urumqi.     

The comparison of two severe Hwangsa (Asian dust) cases of spring and winter in Seoul, Korea

This study investigated meteorological, physical, and chemical characteristics of 2 severe Hwangsa (Asian dust, maximum average of PM₁₀ above 1000 μg m^?3) observed in Seoul, the capital city of Korea, during 30～31^st May, 2008 (DSS2008) and 25～26^th December, 2009 (DSS2009). DSS2008 and DSS2009 had a same source region and route. However, they have different meteorological conditions. DSS2009 had a shorter travel time from the source region to Korea and shorter duration time in Korea than DSS2008 due to a strong winter Siberian anticyclone. One of DSS2008 sample was affected by not only Asian dust but also a long-range transported haze due to consecutive influx after low pressure passed while DSS2009 sample collected only dust aerosol. For both cases, the mass concentration of coarse particles (PM_10-1) increased by 3～14 times compared to that during non Asian dust period, however, that of fine particles (PM₁) increased only in DSS2008. For DSS2008 water-soluble ion balance between anions and cations in fine mode was close to 1:1 while cations were higher than anions in coarse mode. NH₄ ⁺ and Ca²⁺ were found to be the main contributing factors for the neutralization. Cl^? loss was observed about 60% indicating an active interaction of Na⁺ with pollutants. Reconstruction of chemical compositions showed relatively high concentrations of secondary pollutants (NH₄NO₃ and (NH₄)₂SO₄), CaCO₃, and Ca(NO₃)₂ compared to that during non Asian dust period. DSS2009 exhibited the typical characteristics of Asian dust having a high concentration of Ca²⁺ with higher equivalent concentration of cations than anions in all size bins. Cl^? loss was hardly observed. The secondary pollutants were lower than that of non Asian dust cases. The result of reconstruction of ionic components indicated the CaCO₃ derived from soil particle, CaSO₄, and Ca (NO₃)₂ were dominant in DSS2009.     

京津冀一次重度雾霾天气能见度及边界层关键气象要素的模拟研究

本文利用GRAPES_CUACE大气化学模式对京津冀地区2015年12月重度雾霾过程进行了模拟和评估。京津冀地区能见度和PM_2.5模拟值与观测值的对比表明:该模式能较好地模拟京津冀地区能见度和PM_2.5的逐日变化情况,但模式存在对伴随着重污染发生的低能见度模拟偏高的问题。以12月5~10日的重度雾霾过程为重点,针对地面风速、边界层高度、相对湿度、PM_2.5及其对能见度的影响进行了详细分析,研究结果表明:污染过程中大部分地区过程平均风速低于2 m s-1,边界层平均高度低于600 m,相对湿度较高。模式低能见度模拟偏高可能因为:（1）模式模拟重雾霾时段的PM_2.5极大值浓度偏低。（2）模拟相对湿度存在系统性偏低的误差,这一误差对能见度的影响表现为两方面,一是相对湿度会通过影响可溶性气溶胶的吸湿增长过程影响气溶胶质量浓度,导致气溶胶消光系数的计算偏低;二是目前模式中采用的能见度的参数化公式考虑了相对湿度对气溶胶吸湿增长的影响,没有考虑雾滴的直接消光作用。     

Particle-size distribution of inorganic water soluble ions in the venezuelan savannah atmosphere during burning and nonburning periods

The results presented are the first complete analysis of inorganic soluble ions in a tropical savannah region. Atmospheric particles were collected in six rural Venezuelan savannah sites. Concentrations and size distribution of NO₃ ^–, SO₄ ^2-, CI^–, PO₄ ^3-, NH₄ ⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺ were determined in samples collected with Hi Vol samplers equipped with five-stage cascade impactors. Concentrations were higher in the dry season, with a maximum during the burning periods. Using Na⁺ as a reference, the results show a deficit of Cl^– and, with the exception of Mg²⁺, an enrichment of all other ions with respect to marine aerosols. Significant variations were observed in particle-size distribution between different periods. Various pairs of ions present similar size distributions: SO₄ ^2- and NH₄ ⁺; Cl^– and Na⁺; PO₄ ^3- and K⁺; Ca²⁺, Mg²⁺ and NO₃ ^–; indicating that the ions were produced by the same source and/or were involved in similar atmospheric processes. Possible primary sources, the gas-to-particle atmospheric process, environmental implication of long-range transport of nutrients during dry seasons, etc., are discussed.     

Asian Dust effects on Total Suspended Particulate (TSP) compositions at Gosan in Jeju Island, Korea

The compositions of TSP between AD and NAD storm periods were compared to study their long-term variations and chemical characteristics. TSP samples were collected at Gosan site in Jeju Island of Korea from February to May of 1992–2004. The major ionic and elemental species of TSP aerosols were analyzed. During AD periods, the concentrations of crust components (nss-Ca²⁺, Al, Fe, Ca, Mg, Ba, Sr, Ti) increased remarkably, and the concentrations of anthropogenic components (nss-SO₄²⁻, NO₃⁻, S, Zn, Pb, Cr, Ni, Cd), with the exception of NH₄⁺, increased weakly. The concentration ratios of all major components between AD and NAD periods showed ranges from 1.2 to 8.5, except for NH₄⁺. The slope of the linear regression indicated that the contribution of CO₃²⁻ may have comprised up to 17% of the total anions. Our results suggested that the AD storm greatly influenced TSP compositions. Linear regression analyses indicated that NH₄⁺ was not correlated with NO₃⁻, but highly correlated with nss-SO₄²⁻ during both periods. The nss-SO₄²⁻ was also correlated with NH₄⁺, K⁺, nss-Mg²⁺, and nss-Ca²⁺ during both periods. Interestingly, NO₃⁻ was associated with nss-Ca²⁺ and nss-Mg²⁺ during AD periods. Of the metal elements, Fe, Ca, Mg, Ti, Mn, Ba, Sr, V, and Co were highly correlated with Al during both periods, signifying that these metals were mostly originated from soils.     

不同降水强度对PM2.5的清除作用及影响因素

云和降水过程是大气污染物的重要清除途径,但由于降水过程和大气污染颗粒物本身的复杂性,目前降水过程对大气污染物的清除机制及影响因素有待深入研究。该文利用2014年3月—2016年7月在北京地区连续观测的PM_2.5和降水数据,研究了不同降水强度对PM_2.5的清除率,以及雨滴谱、风速和降水持续时间对PM_2.5清除率的影响。研究表明:降水强度越大,对PM_2.5清除效率越高。小雨、中雨和大雨对PM_2.5清除率平均值分别为5.1%,38.5%和50.6%。小雨不但对PM_2.5的清除率最低,而且对PM_2.5的清除效果也存在很大差异,约50%的小雨个例中PM_2.5质量浓度出现减小情况,而另外50%的小雨个例中,PM_2.5质量浓度出现增加情况。在持续时间长或地面风速增大的情况下,小雨也表现出较高的清除率。在中雨和大雨情况下,PM_2.5质量浓度均出现明显减小情况。但降水持续时间和风速对中雨和大雨的清除率影响较小,这是由于中雨和大雨一般在较短时间内即可清除大部分PM_2.5,因此,对降水的持续时间和风速大小不敏感。