Carbonaceous materials in size-segregated atmospheric aerosols from urban and coastal-rural areas at the Western European Coast

A high-volume cascade impactor, equipped with a PM10 inlet, was used to collect size-segregated aerosol samples during the summer of 2004 at two Portuguese locations: a coastal-rural area (Moitinhos) and an urban area (Oporto). Concentrations of airborne particulate matter (PM), total carbon (TC), organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were determined for the following particle size ranges: < 0.49, 0.49–0.95, 0.95–3.0, and 3.0–10 µm. The total PM mass concentrations at the urban and coastal-rural sites ranged from 22.8 to 79.6 μg m^− 3 and 19.9 to 28.2 μg m^− 3, respectively, and more than 56% of the total aerosol mass was found in the fractions below 3.0 μm. At both locations the highest concentrations of OC and EC were found in the submicrometer size range. The regional variability for the OC and EC concentrations, with the highest concentrations being found in the urban area, was related to the contribution of local primary sources (mostly traffic emissions). It was also verified an enrichment of the small size particles in WSOC, representing on average 37.3(± 12.4)% and 59.7(± 18.0)% of OC in the very fine aerosol at the coastal-rural and urban areas, respectively. The amount of secondary OC calculated by the minimum OC/EC ratio method indicates that secondary organic aerosol formation was important throughout the study at both sites. The obtained results suggest that long-range transport and favourable summer conditions for photochemical oxidation are key factors determining secondary OC formation in the coastal-rural and urban areas. The ultraviolet absorption properties of the chromophoric constituents of the WSOC fractions were also different among the different particle size ranges and also between the two sampling locations, thus suggesting the strong impact of the diverse emission sources into the composition of the size-segregated organic aerosol.     

Determination of inorganic ions and trace elements in total suspended particles at three urban zones in the Mexico City Metropolitan Area and one rural site

Inorganic ions and trace metals in total suspended particles were measured during the period 2006–2007 at four sites; three urban sites in the Mexico City Metropolitan Area (MCMA) and one nearby rural site in the state of Morelos. SO₄²⁻, NO₃⁻, Cl⁻ and NH₄⁺ ions were analyzed by ion chromatography; Na⁺, K⁺, Ca²⁺ and Mg²⁺ by flame atomic absorption spectroscopy, and Al, Cd, Cr, Mn, Pb and V by an atomic absorption spectrometer with a graphite furnace attachment. The results indicated that SO₄²⁻ was the most abundant ion. All trace elements except Mn and V showed statistically significant differences between sampling sites. Pearson's correlation applied to all data showed a high correlation among SO₄²⁻, NO₃⁻ and NH₄⁺, indicating a common anthropogenic origin. In addition, the correlation observed between Ca²⁺ and Al indicated a crustal origin, as supported by the enrichment factors. Over the total sampling period, significant differences in particles and trace metals were found between sites and meteorological seasons. To gain a better insight into the origin of trace metals and major inorganic ions, a Principal Component Analysis was applied to the results for six trace metal and eight inorganic ions.     

应用MODIS资料对城乡地表热通量的估算

为了揭示城市热岛形成机制,基于MODIS资料,结合自动气象站实测的气象资料,利用地表能量参数化方法估算了地表热通量,分析了城乡地表热通量的空间分布及变化特征.结果表明城乡地气热交换差异明显,与相关文献对比证明该方法是可行、有效的.     

Organic composition of atmospheric urban aerosol: Variations and sources of aliphatic and polycyclic aromatic hydrocarbons

The non-polar organic composition of airborne particulate matter was analysed over a two year period in an urban area under oceanic climate conditions (Errenteria, Basque Country, Spain). In addition, the distribution of polycyclic aromatic hydrocarbons (PAH) among different aerosol particle sizes was determined. Clues as to the origin of various particle types were gained by using scanning electron microscopy to view the morphology of the particulates in each size fraction. Samples were collected on glass fibre filters and analysed by means of soxhlet extraction and gas chromatography (either with a flame ionization detector or coupled to a mass spectrometry). In general, total PAH levels were moderate (0.96–50 ng m^− 3) as compared to other studies conducted in Europe, and showed clear seasonal variation with maxima in winter and minima in summer. Vehicular traffic was identified as a major source of PAHs in the study area. Regarding particle size, a bimodal distribution was observed. The large sized particles exhibited an apparent seasonal variation with higher concentrations in winter than in summer. The dependences between particle size, PAH distribution and meteorological variables were studied with multivariate statistics. Three main sources of organic compounds were identified: combustion, vegetation, and atmospheric oxidation.     

地基GPS遥感西藏改则站大气可降水量变化特征及其与夏季降水的关系

利用中日JICA项目2010-2011年期间的地基GPS探测逐时大气可降水量（PWV）资料,分析了西藏西部改则站PWV的季节变化和日变化特征及其与夏季降水的关系。结果表明：（1）该站PWV存在明显的季节变化特征,其高（低）值出现在6-9（12-3）月,呈现出明显的单峰型变化特征,同时表现出春季持续上升和秋季快速下降的特点。（2）谐波分析表明,改则站各季PWV日变化均以日循环为主,只是夏季也表现出一定的半日循环特征。（3）改则站PWV存在明显的日变化特征,低值一般出现在当地时间的凌晨至次日上午,各季谷值普遍出现在当地时间10：00前后;高值通常出现在当地的午后至午夜,但各季最大值出现时间不固定;（4）改则站降水通常都发生在PWV高值期,降水发生前后PWV有明显的逐渐积累与迅速下降的变化特征,PWV达到峰值的时间提前于降水。PWV对累积降水频次的影响要比累积降水量更显著。     

1960-2009年武汉城区与郊区气候季节变化

利用1960-2009年武汉城区与郊区气象站逐日平均气温资料,采用相同气候季节划分方法,系统分析武汉城区与郊区气候季节起始时间、季节长度的变化趋势及其差异。结果表明：1980-2009年,武汉城区入春、入夏时间比郊区分别提前10 d和5 d,入秋、入冬时间城区比郊区推迟;武汉夏季长度城区比郊区长12 d,冬季、春季长度城区比郊区短6 d和5 d。1960-2009年武汉四季平均起始时间城区与郊区差别较小,但四季最早、最晚出现时间年际差别较大;武汉入春、入夏时间城区与郊区均提前,入秋、入冬时间均推后,但城区四季变化较显著,郊区仅入秋变化显著;武汉城区夏季长度呈极显著延长,冬季长度呈较显著缩短,城区春季、秋季及郊区四季长度变化均不显著。2000-2009年武汉城区与郊区季节起始时间和季节长度的变化较大,这是因为近10 a武汉作为中部地区崛起的支点,城区发展迅速。     

Characteristics of reactive nitrogen compounds and other relevant trace gases in the atmosphere at urban and rural areas of Korea during May–June, 2004

This study examines the general characteristics of reactive nitrogen oxides (NO_y) at urban and rural sites in terms of measurement- and modeling-based analyses. In this field study, NO_x at urban and rural sites were 92 and 89% of NO_y on average, respectively. HONO levels (e.g., 1.8 ppbv) at the urban site were significantly higher than those at the rural site by a factor of 4.5. HONO concentrations at the urban site during the night were clearly higher than those during the day, which were likely to result from heterogeneous reactions on the surfaces of airborne aerosols and/or grounds. In contrast, there were no significant differences of PAN concentrations in either the temporal or spatial distributions. The significantly low ratios of NO_z/NO_y at both sampling sites indicated a more limited chemical aging process in air mass. O₃ levels were weakly related to NO_x oxidation at both sites, especially at the rural site.     

Variations of levels and composition of PM10 and PM2.5 at an insular site in the Western Mediterranean

The insular suburban site of Castillo de Bellver was selected for the study of the variability of PM levels and composition in the Western Mediterranean Basin (WMB).Mean annual (in 2004) PM₁₀ and PM_2.5 levels at this site were 29 and 20 µg/m³, respectively. These levels may be regarded as relatively low when compared with other suburban insular locations in the Eastern Mediterranean Basin (EMB), but they are higher than those recorded at most of the European suburban sites, especially in Northern and Western Europe. Seasonal variability of PM levels at this site is governed by meteorology rather than local emissions, whereas the daily cycles are clearly defined by the anthropogenic emissions, mainly coming from the urban area of Palma de Mallorca and the harbour area of the same city.Concerning the aerosol composition at this site, the main PM constituent is the mineral matter (29% in PM₁₀ and 16 % in PM_2.5), more than 50% (in PM₁₀) being attributable to African dust. The amount of secondary inorganic aerosols is also very high (27% in PM₁₀ and 34% in PM_2.5), with the predominance of fine ammonium sulphate, and in a less proportion fine ammonium nitrate (in winter) and coarse Ca and Na nitrate (with higher importance in summer). The carbonaceous particles, dominantly fine, account for 17% of PM₁₀ and 25% of PM_2.5. The elemental carbon/organic carbon (EC/OC) ratio reached a mean value of 0.17, similar to those observed at regional background sites in the WMB coast of Spain. The sea spray aerosols (mainly coarse) represented around 10% of PM₁₀, and only 4% in PM_2.5. Finally, the unaccounted fraction increased from 15% to 20% in PM_2.5, being mostly attributed to water.The concentrations of trace elements in PM₁₀ and PM_2.5 were usually in the range to those observed in regional background sites in the Iberian Peninsula, with the exception of the typical tracers of road traffic such as Cu, Sb, Zn, Sn and Ba, which presented concentrations in the range of urban sites of Iberia. Other elements such as Cr, Zr, Hf and Co have been identified as the main tracers of the harbour contributions.     

面向地震设防风险的未来中国城乡人口情景及暴露特征

中国城镇和乡村住房建筑地震设防水平差距较大,暴露在低设防农村与高密集城镇下的人口因此面临较高的地震风险,面向地震设防风险分析未来城乡人口及暴露特征具有重要意义。本文基于地震烈度区划图和人口-发展-环境（PDE）模型,模拟分析了5种共享社会经济路径（SSPs）情景下的未来城乡人口地震灾害时空暴露。结果表明：(1)除SSP3下城镇人口数量持续增加外,其他SSP情景下各地区城镇人口数量均先增后降,农村人口数量受城镇化影响呈持续下降趋势;(2)城镇与农村地震灾害高、较高人口暴露等级空间分布相似,集中在华北、西南与东部沿海地区;(3)相较于有设防的城镇地区,无设防农村地震人口暴露等级偏高,高暴露、较高暴露等级的数量偏多,未来城镇人口暴露等级有所上升,而农村人口暴露等级逐渐降低。     

Observational study of surface ozone at an urban site in East China

In this study, we present the observational data of near surface ozone and some meteorological parameters during 2004, at an urban site (36°42′ N, 117°08′ E, 34.5 m a.s.l.) of Jinan, China. Hourly ozone concentrations exceeding the standard value of China, 100 ppbv, were observed for 65 h (in 23 days) from April to October, and values exceeding US NAAQS (National Ambient Air Quality Standard) for 1 h ozone, 120 ppbv, were observed for 15 h (in 7 days) from late May to early July. Ozone formation presented the phenomenon of “weekend effect”, especially in summer. Monthly variation of ozone coincided with temperature except for July and August. The low ozone levels in July and August may be due to the short sunshine duration and much rainfall during this period. Among these meteorological parameters, daily averaged ozone shows a significant correlation with temperature (r = 0.66) in the year and with relative humidity (r = − 0.75) in summer. Throughout the year, high ozone concentrations were mainly associated with the wind from 180 to 247.5°, while high ozone concentration seemed to have no obvious correlation with a given wind direction in summer. An anomalous nocturnal high ozone episode during 23–25 May 2004 was investigated. Growth fractions of ozone during the nighttime episode were 62.2% and 71.1% for 23 and 24 May, respectively. Synoptic analysis shows that favorable synoptic condition had presumably elevated the background ozone level in this region. Backward trajectory analysis shows that the increase of ozone concentration and the relatively constant high ozone concentrations during the night of May 23 might originate from the transport of ozone rich air mass above boundary layer. Transport of ozone from Yangtze Delta and East Central China might be a significant process for the high ozone level during night May 24 at Jinan.     

夏季长三角城市群热岛效应及其对大气边界层结构影响的数值模拟

利用WRF/Noah/UCM模拟系统对长三角地区城市群进行了2003—2007年共5个夏季的高分辨率数值模拟,研究了夏季长三角城市群热岛效应及其对大气边界层影响。开展了2组平行的积分试验,控制试验为MODIS遥感资料给出的地表特征分布,敏感性试验将长三角地区的城市表面改为农田类型,其他与控制试验完全相同。两组试验的对比分析表明城市群热岛存在明显的日变化特征,热岛效应白天向上发展较高,夜间地表热岛强度明显增强。城市热岛导致午后城市上空产生强烈的局地上升气流,从而使得低层大气以补偿流的形式向城市辐合,然而在夜间上升运动很微弱。伴随这种热力状况的日变化,大气边界层高度也存在明显的日变化,白天增高,夜间降低。同时,白天城市边界层内风速明显减小,夜间地面风速减小加剧,但夜间边界层顶风速却有所增强。另外,城市化还会导致“城市干岛”现象,且其白天强度大于夜间。     

神农架及周边地区夏季气象要素时空特征初步分析

采用2010—2011 年6—8 月神农架及周边地区高山自动气象站观测的逐时资料,初步分析了神农架及周边地区夏季降水、气温、风场等气象要素的时空分布特征。结果发现：降水时数基本呈现随着海拔的增高而增多的趋势。东北坡和东南坡降水时数日变化整体均呈单峰型变化趋势,峰值出现在午后至傍晚,西南坡降水时数的日变化分布均匀。西南坡最高气温出现时间偏晚。多数站点2010—2011 年夏季盛行风向具有一致性。局地风场受地形影响很大,日变化明显,可能由山谷风效应引起。海拔较高的站点水汽昼夜变化较大,海拔较低的站点水汽昼夜变化较小。东北坡松柏站夜间盛行西北风,水汽大幅度减少,白天盛行东南风,水汽增加,可能是午后降水时数明显增多的原因之一。     

Distribution and source apportionment of Polycyclic aromatic hydrocarbons from atmospheric particulate matter PM<Subscript>2.5</Subscript> in Beijing

A total of 11 PM2.5 samples were collected from October 2003 to October 2004 at 8 sampling sites in Beijing city. The PM2.5 concentrations are all above the PM2.5 pollution standard （65 μg m^-3） established by Environmental Protection Agency, USA （USEPA） in 1997 except for the Ming Tombs site. PM2.5 concentrations in winter are much higher than in summer. The 16 Polycyclic aromatic hydrocarbons （PAHs） listed as priority pollutants by USEPA in PM2.5 were completely identified and quantified by high performance liquid chromatography （HPLC） with variable wavelength detector （VWD） and fluorescence detector （FLD） employed. The PM2.5 concentrations indicate that the pollution situation is still serious in Beijing. The sum of 16 PAHs concentrations ranged from 22.17 to 5366 ng m^-3. The concentrations of the heavier molecular weight PAHs have a different pollution trend from the lower PAHs. Seasonal variations were mainly attributed to the difference in coal combustion emission and meteorological conditions. The source apportionment analysis suggests that PAHs from PM2.5 in Beijing city mainly come from coal combustion and vehicle exhaust emission. New measures about restricting coal combustion and vehicle exhaust must be established as soon as possible to improve the air pollution situation in Beijing city.     

Elemental composition of PM2.5 and PM10 at Mount Gongga in China during 2006

In order to investigate the chemical characteristics of atmospheric aerosols in a regional background site, PM_2.5 and PM₁₀ were collected at Mount Gongga Station once a week in 2006. The concentrations of fifteen elements including Na, Mg, Al, K, Ca, V, Fe, Ni, Cu, Zn, As, Ag, Ba, Tl, and Pb were detected by Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The results showed that Na, Mg, Al, K, Ca, Fe were the major components of elements detected in PM_2.5 and PM₁₀, occupied 89.5% and 91.3% of all the elements. Crustal enrichment factor (EF) calculation indicated that several anthropogenic heavy metals (Ni, Cu, Zn, As, Ag, Tl, Pb) were transported long distances atmospherically. The concentrations of all elements (except Na) measured in PM_2.5 and PM₁₀ in spring and winter were higher than those in summer and autumn. The backward air mass trajectory analysis suggests that northeast India may be the source region of those pollutants.     

城市分类对中国城市化影响评估的不确定性分析

采用美国国防气象卫星计划的夜间灯光数据DMSP/OLS、MODIS土地覆盖数据、人口数据进行城、乡气象站点的划分,探讨了三种不同划分方法对城市化不确定性的影响,并根据三种方法认定的城、乡站点,使用均一化订正的地面观测气温数据,分析了1961—2004年我国不同区域和12个城市群的城市热岛效应(Urban Heat Island effect,UHI effect)对气温变化的影响。结果表明:东南、西南和东北地区城市化影响研究的不确定性主要体现在UHI effect的数值大小上,而西北地区的不确定性则多体现在变化趋势的方向上;用三种方法同时认定的城、乡站点对比表明,中国东南地区城市化对区域气温增暖的贡献较强,西北地区较弱,东北和西南地区则无明显一致的影响;城市化对季节平均温度的影响存在南北差异,春、秋季在南方的影响显著,冬、春季在北方的影响显著。     

北非地区海-陆热力差异与夏季江淮流域旱涝的关系

基于NCEP/NCAR月均再分析资料和中国743站降水资料,根据夏季江淮流域51 a(1954-2004年)区域旱涝指数的年代际变化特征,确定北非地区作为研究的关键区.分析发现,关键区的地表温度异常在冬季具有较好的持续性,冬季北大西洋涛动是导致这种异常持续性的重要原因之一.通过对前冬北非地区地表温度和夏季江淮流域降水的SVD分析发现:当北非大陆地区偏冷,其西北侧的海区偏暖时,江淮流域夏季的降水将整体偏多;反之,江淮流域夏季的降水整体偏少.进一步研究发现,北非地区海陆地表温度异常的对比,要比其中单一海洋或陆地区域的异常对夏季江淮流域的旱涝有更好的指示能力.文中定义了一个海陆热力差异指数来表征这种地表温度异常的对比程度,该指数和夏季江淮流域旱涝指数呈较好的正相关关系,并且对夏季江淮流域极端旱涝年份也有较好的指示,认为该指数可以作为一个指示江淮流域整体旱涝事件的预报因子.     

2015—2050年中国分省城乡人口变化及其影响因素研究

社会经济发展道路的选择影响城乡发展模式,带来城市和农村人口新的分布格局.本文基于IPCC共享社会经济路径（SSPs）框架,采用第六次中国人口普查数据,综合考虑中国人口政策和迁移规律,对人口-发展-环境分析模型（PDE）中的生育率、死亡率和迁移率参数进行本地化处理,开展5种SSPs路径下的中国及分省（区、市）城乡人口预估研究,并分析其变化的主要影响因素.结果表明：1）5种SSPs路径下中国城市人口均有所增加,2015-2050年增长3.4（2.2~3.7）亿人;农村人口持续降低,减少约3.0（1.1~4.0）亿人;到2050年中国城市化率将达到79%（67%~86%）.2）未来中国大部分省份城市人口都将较2015年有所增加,西部省份的增长速度高于东部省份;所有省份农村人口都将明显减少,东部地区农村人口减少幅度高于西部地区.相比2015年,2050年西藏、新疆等地城市人口最多可增加两倍以上;大部分省（区、市）农村人口可减少60%以上.3）未来大部分路径下自然变动对城市和农村人口均由正的影响逐渐变为负影响;机械变动对城市人口影响为正,对农村人口影响为负,影响程度逐渐减小.人口自然变动在东西部省份的差异是导致东西部城乡人口不同变化的主要因素.     

Characteristics of organic and elemental carbon in PM2.5 samples in Shanghai, China

Shanghai is the largest industrial and commercial city in China, and its air quality has been deteriorating for several decades. However, there are scarce researches on the level and seasonal variation of fine particle (PM_2.5) as well as the carbonaceous fractions when compared with other cities in China and around the world. In the present paper, abundance and seasonal characteristics of PM_2.5, organic carbon (OC) and elemental carbon (EC) were studied at urban and suburban sites in Shanghai during four season-representative months in 2005–2006 year. PM_2.5 samples were collected with high-vol samplers and analyzed for OC and EC using thermal-optical transmittance (TOT) protocol. Results showed that the annual average PM_2.5 concentrations were 90.3–95.5 μg/m³ at both sites, while OC and EC were 14.7–17.4 μg/m³ and 2.8–3.0 μg/m³, respectively, with the OC/EC ratios of 5.0–5.6. The carbonaceous levels ranked by the order of Beijing > Guangzhou > Shanghai > Hong Kong. The carbonaceous aerosol accounted for  30% of the PM_2.5 mass. On seasonal average, the highest OC and EC levels occurred during fall, and they were higher than the values in summer by a factor of 2. Strong correlations (r = 0.79–0.93) between OC and EC were found in the four seasons. Average level of secondary organic carbon (SOC) was 5.7–7.2 μg/m³, accounting for  30% of the total OC. Strong seasonal variation was observed for SOC with the highest value during fall, which was about two times the annual average.     

Elemental and organic carbon in atmospheric aerosols at downtown and suburban sites in Prague

Organic and elemental carbon (OC and EC) content in PM₁₀ was studied at two sites in Prague, which were located in a suburb and in the downtown. Similar overall average levels were found for both species and also for the PM₁₀ mass at the two sites (i.e., 5.5 and 4.8 μg/m³ for OC, 0.74 and 0.80 μg/m³ for EC, and 33 μg/m³ and 37 μg/m³ for the PM₁₀ mass at the suburb and downtown site, respectively), but substantial differences were observed between the two sites in some seasons and/or meteorological situations. Approximately three times higher values were found for OC in winter compared to summer, with a higher winter/summer ratio for the suburban site. The differences for EC were smaller, but still, compared to summer, more than two times higher EC levels were observed during autumn at the suburban site and 1.5 higher EC levels in winter and autumn at the downtown site. The lowest OC to EC ratios at the suburban site were 3.4, while they were around 1.3 for the downtown site. It was found that the origin of the air masses had a major impact on the observed PM₁₀ mass and OC levels, with largest concentrations noted for air masses recirculating over central Europe and arriving from southeastern Europe in winter. Trajectories coming from the west and northwest originating above the Atlantic Ocean and the Artic brought the cleanest air masses to the sites. For EC the largest difference between the two sites was observed for northwesterly winds during the non-heating season when the suburban site was upwind of Prague.     

北半球近地层典型区CO_2体积分数时空分布及成因

利用GEOS-Chem全球三维大气化学传输模式,分析了北半球近地层CO2体积分数的时空变化特征及其成因。2006—2010年的5 a的模拟结果表明:北半球中纬度近地层CO2体积分数存在着两个高值中心,即亚洲东部和北美东北部。在季节尺度上,亚洲东部CO2体积分数最大值出现在春季,而北美东北区域CO2体积分数最大值出现在冬季;而两个地区的CO2体积分数最低值都出现在夏季。在年际尺度上,两个区域CO2体积分数的年际变率增幅明显高于北半球其它区域,且CO2体积分数高值出现时间的年际差异较大。另外,模拟分析发现北半球森林、农田、草原典型区域,所对应的CO2体积分数具有不同的季节变化特点,它们的CO2季节内变幅依次减小。进一步分析发现3种不同典型区域的CO2体积分数与叶面积指数(LAI)季节变化,具有很好的负相关性。可见陆地生态系统作为碳汇,对近地层CO2体积分数的季节变化具有重要的作用。而温度和降水是影响LAI的最重要的两个气象因子,它们与CO2体积分数季节变化存在内在联系,模拟结果表明北半球大部分陆地近地层CO2体积分数与温度、降水呈现显著的负相关。