南宁市大气颗粒物TSP、PM10、PM2.5污染水平研究

2002年在南宁市的5个典型城市功能区内,共采集了125个大气样品(按季节分别采集),初步调查了大气中颗粒物TSP、PM10、PM2.5的污染状况。结果表明,南宁市TSP、PM10、PM2.5的污染很严重,超标率分别为67．5％、82．5％、92．5％,对人体健康危害更大的PM2．5占到了PM10的63．5％左右。重污染区PM2.5的浓度超过轻污染区近一倍。     

常州市颗粒物湿清除和雨后PM2.5浓度增长研究

通过2015—2018年常州市逐时的PM2.5、PM10数据及降水资料,研究降水对大气颗粒物的湿清除特征、雨后PM2.5的增长速度及PM2.5低浓度持续时间规律.结果表明:(1)对PM2.5和PM10有正清除作用的降水量占比分别为79.9％和82.7％.降水对PM2.5和PM10的湿清除量分别占PM2.5和PM10年均...     

山东省高分辨率大气颗粒物排放清单

为探讨山东省大气颗粒物(PM2.5和PM10)排放的时空分布特征,创建了包含生物质燃烧源、扬尘源、化石燃料燃烧源、工艺过程源、废弃物处理源和道路移动源6大类共281个子源的排放源分类系统,应用排放因子法和COPERT v5模型建立了山东省高分辨率(4 km×4 km)颗粒物排放清单.结果表明:(1)2017年,山东省P...     

珠江三角洲夜间降雨对大气颗粒物清除作用的研究

因独特的发生时段与气象边界条件,夜间降雨(以下简称夜雨)对大气污染物的迁移转化过程影响较大。利用珠江三角洲56个环境监测站于2014年5月至2019年3月记录的逐时大气颗粒物(PM2.5、PM10)浓度数据及同期18个气象监测站记录的逐时降雨观测资料,统计分析夜雨和日间降雨(以下简称日雨)影响下的大气颗粒物浓度变化特征,比较了不同降雨强度、降雨持续时间的夜雨和日雨对大气颗粒物的清除作用,并通过相关分析证明了降雨清除作用的滞后效应。结果表明:降雨通过湿沉降作用可以有效清除大气颗粒物,对PM10的清除效率高于PM2.5,其中夜雨对大气颗粒物的清除效率相对日雨更高;降雨强度越大,降雨持续时间越长,夜雨清除效果的优越性越明显;在降雨后6d内,夜雨和日雨对大气颗粒物仍存在清除作用。     

承德市降水对细颗粒物和可吸入颗粒物的清除作用分析

利用承德市2018—2020年逐小时细颗粒物(PM_2.5)和可吸入颗粒物(PM₁₀)监测数据和气象观测资料,分析PM_2.5和PM₁₀基础浓度时间变化特征及不同风速影响下浓度变化规律,探讨基础浓度和风速订正后降水对污染物的湿清除作用。结果表明：(1)PM_2.5和PM₁₀基础浓度均值均为11月至次年3月较大,4、10月次之,5—9月较小。(2)秋、冬季风对PM_2.5清除效果较明显;风对PM₁₀全年总体有清除作用,但风速大于8 m/s,会导致春季PM₁₀浓度暴增。(3)降水过程对PM_2.5和PM₁₀均有很好的清除作用,清除率大多随着降水等级的增大而增大,降水对PM₁₀的清除率高于PM_2.5。(4)中雨及以上等级降水过程结束后,PM_2.5和PM₁₀空气质量指数均为良好及...     

重庆市春季大气颗粒物浓度的对比监测分析

通过2012年春季在重庆大气超级站进行的PM10和PM2.5手工采样与自动仪器的对比监测,分析了自动监测与手工监测的一致性及造成偏差的原因,并对PM2.5与PM10浓度的比值关系进行了分析。结果表明:MP101M型颗粒物自动监测仪用于监测PM10时系统性误差偏高,仪器初始精密度存在负偏差;用于监测PM2.5时系统性误差在允许范围之内,仪器初始精密度存在较大负偏差;PM10和PM2.5的手工采样和自动仪器监测值之变化趋势具有非常高的一致性;PM2.5与PM10浓度比值范围在56.5%～90.4%,平均比值为(73.8±7.4)%。     

某高密度街区大气颗粒物质量浓度分布特征实测研究

为研究城市高密度街区大气颗粒物浓度分布特征,2019年秋季对上海市某高密度街区道路大气颗粒物浓度、空气温度、相对湿度、地理位置、车辆与道路图像视频信息进行了同步移动在线监测,并结合街区内固定站数据和后向轨迹模拟结果,总结了影响街区大气颗粒物浓度变化的主要因素。结果表明:城市大气颗粒物背景拟合值处于较低水平时,街区内的大气颗粒物浓度变化和影响因素易被识别;机动车污染源对大气颗粒物浓度贡献大,其中大型机动车的影响明显;户外施工和道路清扫会引起大气颗粒物浓度上升,其中PM₁₀上升更明显;交通密度大的十字路口大气颗粒物浓度通常较高;城市高架的盖状结构会阻碍大气颗粒物在垂直方向上的扩散,引起局部大气颗粒物浓度上升;街区内高大浓密的乔木对近地面的大气颗粒物屏蔽效果不理想,甚至有助于颗粒物累积;早晚高峰时段大气颗粒物浓度较非高峰时段高。     

某高密度街区大气颗粒物质量浓度分布特征实测研究

为研究城市高密度街区大气颗粒物浓度分布特征,2019年秋季对上海市某高密度街区道路大气颗粒物浓度、空气温度、相对湿度、地理位置、车辆与道路图像视频信息进行了同步移动在线监测,并结合街区内固定站数据和后向轨迹模拟结果,总结了影响街区大气颗粒物浓度变化的主要因素。结果表明:城市大气颗粒物背景拟合值处于较低水平时,街区内的大气颗粒物浓度变化和影响因素易被识别;机动车污染源对大气颗粒物浓度贡献大,其中大型机动车的影响明显;户外施工和道路清扫会引起大气颗粒物浓度上升,其中PM₁₀上升更明显;交通密度大的十字路口大气颗粒物浓度通常较高;城市高架的盖状结构会阻碍大气颗粒物在垂直方向上的扩散,引起局部大气颗粒物浓度上升;街区内高大浓密的乔木对近地面的大气颗粒物屏蔽效果不理想,甚至有助于颗粒物累积;早晚高峰时段大气颗粒物浓度较非高峰时段高。     

南京市大气气溶胶中颗粒物和正构烷烃特征及来源分析

于2002年夏季（7月）和冬季（12月）采集南京市5个功能区的大气气溶胶（PM2．5和PM10）样品，对两个季节不同功能区颗粒物及其颗粒物中正构烷烃的分布特征和污染来源进行了分析。结果表明，南京市大气颗粒物含量冬季高于夏季，细颗粒高于粗颗粒。正构烷烃的变化规律同颗粒物一致，且主要分布在细颗粒物上。根据各个功能区正构烷烃（C15-C32）的CPI（CPI1、CPI2和CPI3）结果，可知南京市大气气溶胶中正构烷烃由生物源和人为源共同排放产生。％waxCn的结果表明生物源对气溶胶中正构烷烃的贡献率为20％～43％，对南京市大气颗粒物的贡献率为1．66％～4．76％。     

Estimating contribution of precipitation scavenging of atmospheric particulate mercury to mercury wet deposition in Japan

Mercury wet deposition is dependent on both the scavenging of divalent reactive gaseous mercury (RGM) and atmospheric particulate mercury (Hg(p)) by precipitation. Estimating the contribution of precipitation scavenging of RGM and Hg(p) is important for better understanding the causes of the regional and seasonal variations in mercury wet deposition. In this study, the contribution of Hg(p) scavenging was estimated on the basis of the scavenging ratios of other trace elements (i.e., Cd, Cu, Mn, Ni, Pb and V) existing entirely in particulate form. Their wet deposition fluxes and concentrations in air, which were measured concurrently from April 2004 to March 2005 at 10 sites in Japan, were used in this estimation. The monthly wet deposition flux of mercury at each site correlated with the amount of monthly precipitation, whereas the Hg(p) concentrations in air tended to decrease during summer. There was a significant correlation (P<0.001) among the calculated monthly average scavenging ratios of trace elements, and the values in each month at each site were similar. Therefore, it is assumed the monthly scavenging ratio of Hg(p) is equivalent to the mean value of other trace elements. Using this scavenging ratio (W), the wet deposition flux (F) due to Hg(p) scavenging in each month was calculated by F=WKP, where K and P are the Hg(p) concentration and amount of precipitation, respectively. Relatively large fluxes due to Hg(p) scavenging were observed at a highly industrial site and at sites on the Japan Sea coast, which are strongly affected by the local sources and the long-range transport from the Asian continent, respectively. However, on average, at the 10 sites, the contribution of Hg(p) scavenging to the annual mercury deposition flux was 26%, suggesting that mercury wet deposition in Japan is dominated by RGM scavenging. This RGM should originate mainly from the in situ oxidation of Hg⁰ in the atmosphere.     

Scavenging of atmospheric formaldehyde by wet precipitation

Despite the great importance that formaldehyde has in atmospheric photochemistry, few studies have been reported on rain water. In this paper, concentrations of HCHO in rain fractions within rain events are presented. Two sampling sites were chosen: one at Mexico City, a great polluted urban area, and the second at Rancho Viejo, a forested area under the meteorological influence of the city. The results show a general decrease during the early portion of the rain event. This seems to indicate that below-cloud scavenging is the most important mechanism while, from the small variations observed in the latter portion of the rainfall, it is possible to assume within-cloud scavenging as the predominant mechanism. Using the HCHO concentrations in rain water, the mixing ratios were estimated for the two sampling sites. The values were 0.68 ppb and 0.44 ppb at Mexico City and Rancho Viejo, respectively. Measurements at ground level in Mexico City gave a mean HCHO concentration in air of 24 ppb, much higher than the estimated mixing ratio. The high levels of HCHO found in ambient air and in rain water reflect anthropogenic emissions as the potential atmospheric sources.     

Determination of levoglucosan in atmospheric fine particulate matter

A microanalytical method suitable for the quantitative determination of the sugar anhydride levoglucosan in low-volume samples of atmospheric fine particulate matter (PM) has been developed and validated. The method incorporates two sugar anhydrides as quality control standards. The recovery standard sedoheptulosan (2,7-anhydro-beta-D-altro-heptulopyranose) in 20 microL solvent is added onto samples of the atmospheric fine PM and aged for 1 hr before ultrasonic extraction with ethylacetate/ triethylamine. The extract is reduced in volume, an internal standard is added (1,5-anhydro-D-mannitol), and a portion of the extract is derivatized with 10% by volume N-trimethylsilylimidazole. The derivatized extract is analyzed by gas chromatography/mass spectrometry (GC/MS). The recovery of levoglucosan using this procedure was 69 +/- 6% from five filters amended with 2 microg levoglucosan, and the reproducibility of the assay is 9%. The limit of detection is approximately 0.1 microg/mL, which is equivalent to approximately 3.5 ng/m3 for a 10 L/min sampler or approximately 8.7 ng/m3 for a 4 L/min personal sampler (assuming 24-hr integrated samples). We demonstrated that levoglucosan concentrations in collocated samples (expressed as ng/m3) were identical irrespective of whether samples were collected by PM with aerodynamic diameter < or = 2.5 microm or PM with aerodynamic diameter < or = 10 microm impactors. It was also demonstrated that X-ray fluorescence analysis of samples of atmospheric PM, before levoglucosan determinations, did not alter the levels of levoglucosan.     

Importance of wet precipitation as a removal and transport process for atmospheric water soluble carbonyls

Carbonyl compounds exist in the atmosphere as either gases or aerosols. Some of them are water soluble and known as oxidation products of biogenic and/or anthropogenic hydrocarbons. Five carbonyl compounds, glyoxal (GO), 4-oxopentanal (4-OPA), glycolaldehyde (GA), hydroxyacetone (HA) and methylglyoxal (MG) have been identified in a temporal series of 12 rain samples. The concentrations of the compounds in the samples were high at the beginning of the rain event and decreased with time to relatively low and fairly constant levels, indicating that the compounds were washed out from the atmosphere at the start of the rain event. Possibly, these compounds also existed in the cloud condensation nuclei (CCN). Wet deposition rates of the carbonyl compounds were calculated for nine samples collected during a 20 h period. The deposition rates ranged from 0 (4-OPA) to 1.2×10⁻¹ mg C m⁻² h⁻¹ (MG) with the average of 2.9×10⁻² mg C m⁻² h⁻¹. Production rates of isoprene oxidation products (GA, HA and MG) in the area surrounding the sampling site were estimated with a chemical box model. The deposition rates exceeded the production rates in most samples. This indicates that the rainfall causes a large net flux of the water soluble compounds from the atmosphere to the ground. Insoluble carbonyl compounds such as n-nonanal and n-decanal were expected to be present in the atmosphere, but were not detected in the rain during the sampling period, suggesting that an aerosol containing these insoluble compounds does not effectively act as a CCN.     

Field studies of atmospheric particulate concentration changes during precipitation

The effect of rain on changes in the atmospheric particulate concentration was evaluated, and these measurements were compared with theoretical calculations of particle washout coefficients. Cumulative particle number distributions in two size subranges, around 0.01 and 1 μm, were measured at two different times during three separate precipitation events to establish apparent washout coefficients. Raindrop size distributions and precipitation intensity measurements were also obtained to estimate the theoretical washout coefficients.The experimental washout coefficients were between 2 × 10⁻⁵s⁻¹and 1 × 10⁻⁴s⁻¹, depending on the raindrop size distribution and precipitation intensity. These values were one to two orders of magnitude greater than theoretical estimates that considered the known single droplet collection mechanisms of inertial impaction, interception, Brownian diffusion, thermophoresis, diffusiophoresis, and electrostatic charge effects. Based on these results, it appears that these mechanisms cannot adequately explain the observed decreases in particle number density during a precipitation event.     

Sources of atmospheric carbonaceous particulate matter in Pittsburgh,Pennsylvania

The organic carbon (OC)/elemental carbon (EC) tracer method is applied to the Pittsburgh, PA, area to estimate the contribution of secondary organic aerosol (SOA) to the monthly average concentration of organic particulate matter (PM) during 1995. An emissions inventory is constructed for the primary emissions of OC and EC in the area of interest. The ratio of primary emissions of OC to those of EC ranges between 2.4 in the winter months and 1.0 in the summer months. A mass balance model and ambient measurements were used to assess the accuracy of the emissions inventory. It is estimated to be accurate to within 50%. The results from this analysis show a strong monthly dependence of the SOA contribution to the total organic PM concentration, varying from near zero during winter months to as much as 50% of the total OC concentration in the summer.     

Effects of uncontrolled particulate matter release on precipitation under warfare conditions

This study has shown theoretical, observed and experimental evidence of pollutants released, transported and deposited during the Kosovo conflict in 1999 and their effects on precipitation in Serbia. The greatest bombardment of the chemical industry, oil refineries and fuel storage in Serbia which occurred during April, resulted in releases of many hazardous, toxic and cancerogenic substances. The number of April's days with precipitation greater or equal to 0.1 mm in 1999 are compared to those in the period from 1961 to 1990 registered at thirty meteorological stations in Serbia and especially at the Belgrade-Observatory station in the period from 1888 to 1995. The maximums of days with precipitation greater or equal to 0.1 mm were at the wider Belgrade area and at the central and southwestern parts of Serbia during April 1999. This is confirmed by using the Eta trajectory analysis.     

Effects of airborne particulate matter on the acidity of precipitation in Central Missouri

The pH of rainfall in central Missouri was monitored at four sites during the fall of 1983. Several pH values were well above 5.6, the theoretical pH of pure water in equilibrium with ambient levels of CO₂. Most of the higher pHs were measured on rainfall of short duration or rainfall collected during the first few hours of extended rainfall events. Furthermore, the rainfall associated with storm events lasting several days exhibited a trend of decreasing pH with time approaching values as low as 4.0 during the late stages of rainfall. Precipitation pH values above 5.6 apparently reflect neutralization reactions between wet precipitation and various components of airborne dust, especially clays and carbonates. During extended rainfalls, the neutralization effects gradually diminish as suspended dust is washed from the atmosphere yielding more accurate values of the wet precipitation pH. The results of this study suggest that airborne particulate matter generated from the dust bowl region of the U.S. may affect the chemistry of precipitation in areas hundreds of km downwind.