Urban NO2 concentrations in the U.K. in 1987

A mational air quality monitoring network has been established in the U.K. by Warren Spring Laboratory, on behalf of the U.K. Department of the Environment, to determine compliance with the European Community Directive for nitrogen dioxide. Data from the six network sites for 1987 are presented and analysed.No site in the U.K. breached the NO₂ Directive Limit Value during this year, though the closest approaches were at the two London stations. Annual average NO₂ concentrations, which varied from 23 to 39 ppb, were consistent with the top five percentile of long-term measurements from a national survey of over 360 U.K. urban areas carried out in 1986.The temporal variability of NO₂ concentrations was substantially lower over all time scales than that for NO: winter/summer ratios for all sites averaged 2.9 for NO and 1.3 for NO₂. Most sites showed strong diurnal variations for NO which were primarily influenced by traffic emissions during rush hours, although these variations were less marked for NO₂.A markedly non-proportional relationship between annual and daily average NO₂ and NO_x levels was observed, and this has important implications for its efficacy of possible NO_x emission control strategies. An analysis of measured NO₂/NO_x ratios over weekends and weekday periods demonstrates, for instance, that a 20% emission cutback may result, typically, in a corresponding NO₂ reduction of 12% at urban locations in the U.K. NO_x reductions, however, exert a more proportional effect on NO₂ concentrations at kerbside and rural locations.     

Air pollutant concentrations in Varanasi,India

This study reports the diurnal patterns in the concentrations of ozone (O₃), nitrogen dioxide (NO₂), sulphur dioxide (SO₂) and total suspended particulate matter (TSP) in the urban atmosphere of Varanasi city in India during 1989. The city was divided into five zones and three monitoring stations were selected in each zone.Ambient concentrations of NO₂ and SO₂ were maximum during winter but ozone and TSP concentrations were highest during summer. The measured maximum concentrations (2-h average) were 150 and 231 μg m⁻³ (0.078 and 0.086 ppm) for NO₂ and SO₂, respectively, for the winter season. Ozone and TSP concentrations reached a maximum of 160 (0.08 ppm) and 733 μg m⁻³, respectively, in the summer. NO₂ and SO₂ concentrations peaked in the morning and evening. Peak concentrations of O₃ occurred in the afternoon, generally between noon and 4 p.m. Maximum concentrations of O₃, NO₂, SO₂ and TSP were measured in zones I and II, and minimum in zone V.     

Trends analysis of vegetation exposure indices in rural areas of the U.S.

In this work, statistical models based on a linear time term are tested to determine if they can adequately represent the behavior over time of indices that relate vegetation exposure to air pollutants at a large number of monitoring sites in the rural U.S. Three pollutants are addressed: ozone (O₃), sulfur dioxide (SO₂)and nitrogen dioxide (NO₂. The formulations selected to generate the values of the exposure indices were the sum of all hourly average concentrations (SUM0); in addition, for O₃, the sum of all hourly average concentrations weighted with a sigmoidal function, which assigned larger weights to the higher concentrations. The basic hourly average concentration data were selected from routine air monitoring stations of existing networks that met minimum criteria for quality assurance and data completeness. The statistical methodology used was based on a linear regression model which accounted for seasonality and changes in experimental procedures. An additional lag-one autoregressive term was added to the model for those stations which exhibited significant autocorrelation in the data, based on the Durbin-Watson statistic. Long-term analyses included data for 7 to 10 years; short-term analyses included data for 4 to 5 years. Results show that over rural areas of the U.S., these models do not adequately represent the behavior of vegetation exposure indices, both in the long-term and the short-term analyses; the majority of stations did not have statistically significant (5% level) coefficients for the term representing linear dependence on time. Emissions data for SO₂, NO_x and volatile organic compounds (VOC) over the same time period are also presented. Over the contiguous U.S., emissions between 1979 and 1987 have decreased by a maximum of 3%; emission changes for individual states have generally decreased between 1979 and 1987, but between 1983 and 1987 both increases and decreases have occurred.     

Source-receptor relationships for wet SO42− and NO3− production

Precipitation chemistry data for the years 1982–1985 from 110 stations distributed across the continental U.S. and southern Ontario Province are used to describe the geographic distributions of SO₄²⁻ and NO₃⁻ in precipitation. Volume-weighted, wet SO₄²⁻ and NO₃⁻ concentrations, averaged over the 4 years of observation by season and annullly, show coherent patterns with maxima in the northeastern U.S. and southeastern Canada about ten times greater than the minima observed in the Intermountain and Pacific Northwest regions.Tests for empirical source-receptor relationships indicate that, in land areas with relatively low emissions of SO₂ and NO_x, the associations between wet SO₄²⁻ concentrations and SO₂ emissions and between wet NO₃⁻ concentrations and NO_x emissions within 560 km of each precipitation chemistry station are weak or nonexistent (r²⩽0.42). The remaining land areas show moderate to strong associations between SO₂ and SO₄²⁻ and NO_x and NO₃⁻ during the spring and summer, but only weak to nonexistent associations during the winter. The associations between emissions and concentrations, e.g. SO₂ and SO₄²⁻, are equally well represented by either a linear or a power law function. However, at the level of aggregation employed, the data do not substantiate a linear-proportional relationship between concentrations and anthropogenic emissions. Furthermore, emissions of SO₂ and NO_x are highly correlated, as are the emissions of RHC and NO_x.     

Dispersion modelling of nitrogen oxides in the United Kingdom

This paper describes the construction and application of an Eulerian-dispersion model for the calculation of NO₂ and NO_x concentrations in the U.K. Model results are compared with measurements from 44 U.K. sites. The sensitivity of the model results to chemical and dispersion parameterisations is assessed. The model is also used to verify the validity of ‘instantaneous mixing’ assumptions used in trajectory models. Finally, the distribution of ground-level NO_x concentrations from power stations, motor vehicles and other stationary sources is calculated across the U.K., including a preliminary assessment of the possible contribution from natural sources.     

Evaluating the influence of air pollution on solar radiation observations over the coastal region of Alicante (Southeastern Spain)

The present study evaluates ground-based downward surface shortwave radiation (R_s) over the coastal region of Alicante (Southeastern Spain). Hourly measurements collected over the eleven-year period 2010-2020 are used. Two weather stations located over the region capital, Alicante, have been selected as representative of urban and suburban typologies. Two additional weather stations far from the city have been selected representing rural typologies. R_s is significantly reduced over the urban station during the morning hours within the winter season compared to the observations recorded over the suburban and rural stations, with a global mean difference of -81 and -120 W/m² at 10 LT, respectively. However, no significant differences are obtained during the midday sun, with a global mean difference of -20 W/m² between the urban and rural stations. With the aim of explaining these differences, the current paper investigates the relationship between R_s and different air pollutants: NO_x, SO₂, and fine particulate matter (PM_2.5 and PM₁₀) as well as the wind field measured at the urban and suburban stations. The results found in this work point towards a close relationship between R_s and NO_x concentrations annual cycles, which are also influenced by the prevailing wind circulations observed over the study area. A global mean NO_x concentration of 107 µg/m³ is observed over the urban station at 10 LT during the winter season. In contrast, these high concentrations are significantly reduced over the suburban station, with global mean value of 40 µg/m³ at 10 LT, for this period of the year.     

Evaluation of a model for hourly spatial concentration distributions

A time-dependent finite difference model in three levels combined with a puff model to account for subgrid effects close to single sources was used to calculate hour-to-hour concentration distributions. Measurements from several selected stations were used to account from time variation in background concentrations. For each hour, weight was given to observed values in areas that were not influenced by local sources.Results of concentration calculations based on hourly data on emission and dispersion are validated by measured time series of SO₂ and NO_x at five stations. A combination of hourly nephelometer readings and 12-h measurements of small particles at three stations are compared with calculated values.Hourly observed and calculated values from two periods (3 January–15 March 1988 and 18 April–24 June 1988) were used for the evaluation of the model for calculating hourly pollution concentrations in each square kilometre. The results showed that prediction of short-term average concentrations (e.g. hourly data) are usually poorly correlated with observations at the same time and location. Slight displacement errors may cause point-to-point correlation to be poor as a result of errors in input data.The pattern of NO_x concentration variation with time was reproduced well at all stations. A subgrid model taking into account the influence of nearby roads would probably improved the model for NO_x at some stations. For SO₂ and small particles, industrial sources have the dominant influence and the correspondence between observed and calculated values were improved by taking into account spatial uncertainty and an hourly variation in background concentrations.     

Methanesulphonic acid,dimethyl sulphoxide and dimethyl sulphone in aerosols

Aerosol concentrations of methanesulphonic acid (MSA), dimethyl sulphoxide (DMSO), dimethyl sulphone (DMSO₂) and major anions have been measured from landbased stations (principally Plymouth, Devon, U.K.) and various shipboard stations in the North Sea and North Atlantic Ocean. Aerosol samples collected between July 1985 and July 1987 are analyzed both in terms of their back trajectories, and variation with time. These analyses suggest that NO₃ and NSSS are anthropogenic in origin while DMSO₂ appears to have a maritime source. MSA concentrations are highest in air masses with both oceanic and anthropogenic influences. DMSO, MSA, and DMSO₂ all show seasonal cycles, with concentrations similar to previous published results. MSA was found to be concentrated on sub-μm particles. Rainfall MSA concentrations were measured over 2 years at Norwich and were found to exhibit a similar seasonality to the aerosol MSA concentrations.     

Lake Michigan Ozone Study (LMOS): Measurements from an instrumented aircraft

As part of the Lake Michigan Ozone Study, the NOAA instrumented King Air research aircraft made a series of flights over Lake Michigan during the summers of 1990 and 1991 to characterize the atmospheric conditions prevailing during times when O₃ concentrations exceeded the air quality standard. Most of the time, O₃ concentrations were within the normal range (40–70 ppbv) for the location and season, but higher concentrations were measured during the afternoon flights at several isolated locations. During three afternoon flights, high O₃ concentrations (> 120 ppbv) were observed along portions of the flight path; the highest 1-min average exceeded 160 ppbv. In two flights the highest O₃ concentrations were observed in the lower boundary layer over the eastern portion of the flight track; in one case the high concentrations were found over the western side of the lake throughout the boundary layer. The increased O₃ was accompanied by moderately increased SO₂ and NO_x (10–20 ppbv); outside the region of elevated O₃, the SO₂ and NO_x were less than 2–3 ppbv. The elevated zone concentrations were related to emissions from the urban region located near the southern and southwestern shores of Lake Michigan.     

被动采样法观测研究京津冀区域大气中气态污染物

为了对京津冀区域的大气污染物进行观测,揭示污染物浓度和组分的时空分布和变化规律,深入了解区域复合型污染,从2007年12月开始使用造价低、操作简捷的被动采样方法对区域10个站点大气中的SO2、NO2、O3和NH3等主要污染物进行了监测,对被动采样方法的区域适用性进行了比较全面的评估并根据监测结果对污染物的浓度水平和区域分布进行了研究.方法适用性评估表明被动采样方法在污染较严重的京津冀区域能进行长时间采样,采样频率设定为每月1次;平行采样结果显示,SO2、NO2、O3和NH3的变异系数分别为6.4%、7.1%、4.2%和3.9%,方法表现出良好的稳定性;每月1次的被动采样浓度结果与主动采样仪器观测结果月平均值相比具有较好的一致性,SO2、NO2和O3这2种方法监测结果的相关系数达到0.91、0.88和0.93,拟合曲线斜率分别为1.25、0.98和0.93,平均相对标准偏差分别为23.3%、14.9%和8.5%,能基本满足大气采样的要求,NH3的短时监测也表明2种方法具有可比性.评估结果说明被动采样方法是一种可靠的大气污染监测方法,可用于区域污染的监测.2008年夏季京津冀区域10个站点SO2、NO2、O3和NH3的被动采样平均浓度分别(12.3±6.3)×10-9、(13.2±7.0)×10-9、(40.5±9.5)×10-9和(24.0±13.7)×10-9.浓度区域分布显示SO2和NO2在城市站点具有较高浓度,而NH3在农业站点的浓度较高,SO2、NO2和NH3的大气浓度水平明显受局地排放影响,浓度分布较直观的反应了站点的局地源排放;而O3除了背景站兴隆,在北京和天津周边的大小城市,平均浓度都在40×10-9左右,表现出区域协同污染特征.     

Fast increasing of surface ozone concentrations in Pearl River Delta characterized by a regional air quality monitoring network during 2006-2011

Based on the observation by a Regional Air Quality Monitoring Network including 16 monitoring stations, temporal and spatial variations of ozone(O3), NO2and total oxidant(Ox) were analyzed by both linear regression and cluster analysis. A fast increase of regional O3concentrations of 0.86 ppbV/yr was found for the annual averaged values from 2006 to 2011 in Guangdong, China. Such fast O3increase is accompanied by a correspondingly fast NOx reduction as indicated by a fast NO2 reduction rate of 0.61 ppbV/yr. Based on a cluster analysis, the monitoring stations were classified into two major categories – rural stations(non-urban) and suburban/urban stations. The O3concentrations at rural stations were relatively conserved while those at suburban/urban stations showed a fast increase rate of 2.0 ppbV/yr accompanied by a NO2 reduction rate of 1.2 ppbV/yr. Moreover, a rapid increase of the averaged O3 concentrations in springtime(13%/yr referred to 2006 level) was observed, which may result from the increase of solar duration, reduction of precipitation in Guangdong and transport from Eastern Central China. Application of smog production algorithm showed that the photochemical O3production is mainly volatile organic compounds(VOC)-controlled. However, the photochemical O3production is sensitive to both NOx and VOC for O3pollution episode. Accordingly, it is expected that a combined NOx and VOC reduction will be helpful for the reduction of the O3 pollution episodes in Pearl River Delta while stringent VOC emission control is in general required for the regional O3 pollution control.     

太原市五年降尘及降水中主要离子特征

随着我国工业化和城镇化的深入推进,人们对城市大气环境质量关注日益增加。连续五年对山西省太原市5个点位进行监测,考察降水中主要离子时间变异及大气干湿沉降规律。结果表明:太原市五个监测点年均干沉降量排序为太钢工业区坞城(东)桃园(市中)晋祠(景区)上兰(市郊),其中太钢年均沉降量是上兰的三倍。降尘量除了在不同点位差异较大外,相同点上不同季节也有较大波动,表现为各监测点春季和冬季降尘量为全年最高。而夏季由于降雨较多,干沉降最少。总体上,近五年各点干沉降量呈现逐年下降的趋势。湿沉降方面以桃园为市区代表分析,SO_4~(2-)、NO_3~-、Ca~(2+)和NH_4~+是太原市桃园降水中主要的无机离子,其加权平均浓度范围为3.1～19 mg/L,各离子浓度在干燥的冬春季较高,且近五年其浓度及沉降量快速增加。桃园降雨中SO_4~(2-)和NO_3~-仍然是最主要的致酸离子,SO_4~(2-)年均沉降量分别是NO_3~-、Ca~(2+)和NH_4~+的1.7、3.9、5.9倍。Ca~(2+)、NH_4~+和Mg~(2+)的中和因子分别是0.42、0.30、0.14,说明Ca~(2+)、NH_4~+对酸雨缓冲作用大于Mg~(2+)。2013～2017年太原市桃园降雨SO_4~(2-)/NO_3~-和NH_4~+/NO_3~-比值分别为1.7和0.3,表明酸雨类型由硫酸型向混合型发展,主要是近年来NO_3~-浓度增幅大于SO_4~(2-)和NH_4~+。总的来看,近些年太原市政府大力提倡节能减排带来明显效果,但工业厂矿区周边降尘污染依然严重,属于今后城市环境治理的重点。     

The impact of changing regional emissions on precipitation chemistry in the eastern United States

From 1975 to 1987 a 19% change in SO₂ emissions a 16% change in NO_x emissions have occurred over the eastern and mid-western U.S. Six continental precipitation chemistry sites from the MAP3S network, plus the Hubbard Brook Experimental Forest, NH, show a direct relationship between emission levels and precipitation H⁺ and SO₄^2- concentrations, except for Penn State, PA. MAP3S sites at Illinois and Ohio, located closest to the major SO₂ source regions, demonstrates statiscally significant (P <0.05) linear regressions of SO₄^2- concentrations on SO₂ emissions. Whiteface Mt., NY, shows a weaker relationship (P <0.01), and Hubbard Brook shows the strongest relationship (P <0.01) between SO₂ emissions and SO₄^2- concentration in precipitation. No site shows a significant relationship (P <0.10) for NO_x emissions and NO₃⁻ concentrations in precipitation. Illinois, Ohio, Ithaca and Hubbard Brook show significant linear regressions of H⁺ concentrations on emissions of SO₂ + NO_x (P <0.10, 0.05, 0.01, and 0.01, respectively). Overall, for the entire region examined, decreasing SO₂ emissions levels appear to have decreased SO₄^2- concentrations with an efficiency of 74% ± 15% (s.e.). Decreasing SO₂ plus NO_x emissions (18%) have been accompanied by a decreasing H⁺ concentrations (18%) suggesting an efficiency of conversion of 100% ± 15% (s.e.) for the study region as a whole. While significant reductions in acid species have occured at Hubbard Brook, further reductions in excess of 50% of present deposition are necessary to protect acid-sensitive ecosystems.     

基于BP神经网络的大气污染物浓度预测

利用BP神经网络结合变量筛选的方法建立了SO_2、NO_2、O3、CO、PM_(10)、PM_(2.5)等6种污染物的浓度预测模型,并选取2014-01-01至2015-11-28时段,昆明市区5个环境监测点以上6种污染物浓度的监测数据建立了昆明市污染物日均浓度预测模型.采用平均影响值(Mean Impact Value,MIV)的方法筛选出分别对6种污染物日均浓度值有主要影响的变量,作为BP神经网络的输入变量,利用建立的预测模型分别对6种污染物的日均浓度进行预测.结果表明,在关上监测点利用浓度预测模型对SO_2、NO_2、O3、CO、PM_(10)、PM_(2.5)等6种污染物浓度进行预测,污染物浓度预测值和实测值趋势吻合度较高.变量筛选后SO_2、PM_(2.5)预测效果比变量筛选前的预测效果好.O3的均方根误差和PM_(10)的标准化平均偏差,变量筛选前的预测效果比变量筛选后的预测效果好.变量筛选前的NO_2和CO的预测结果比变量筛选后的预测效果好.其他4个环境监测点的污染物浓度预测结果与关上监测点的结果相似.     

重庆市大气二(口恶)英污染水平及季节变化

一年内分季节对重庆市不同功能区大气中二英(PCDD/Fs)污染情况进行了监测研究.结果表明,重庆市大气中PCDD/Fs浓度范围和平均值(以TEQ计)分别为0.017~0.21 pg·m-3和(0.094±0.054)pg·m-3.PCDD/Fs污染水平区域分布和季节变化明显,分别为:商住区>郊区>对照点,冬季>春季>秋季>夏季.其中,冬季时大气中的二英浓度约为夏季时的2.2~4.6倍.主成分分析结果显示,PCDD/Fs同系物分布特征季节变化明显:冬、春季时主要表现为颗粒相中的分布特征,夏、秋季节则主要表现为气相中的.相关性分析表明,PCDD/Fs异构体质量浓度与SO2、NO2、PM10和TSP等常规参数含量大都呈显著正相关,与O3则呈负相关,但未达显著性水平.这表明,重庆大气PCDD/Fs的空间分布和季节变化与SO2、NO2、PM10和TSP等环境空气质量常规指标的分布情况基本一致,重庆大气PCDD/Fs污染与常规污染物的排放源密切相关.     

1997~2011年北京市空气中酸性物质与降水组分变化趋势的相关性分析

依据北京市环境保护监测中心1997～2011年降水监测资料、大气环境质量监测资料,结合北京经济发展和能源结构变化,分析了酸雨前体物的排放与环境空气中酸性物质及降水中组分的相关性,为政府部门评定大气污染治理效果,制定未来防控政策和规划提供科学决策依据.研究表明,环境空气中NO2、NOx、SO2年均浓度显著相关,说明北京地区环境空气中氮与硫的来源基本相同,均来自化石燃料燃烧排放,这也是酸雨形成的根本原因.北京市大气中的污染物主要来自局地排放源,而降水中硫、氮的湿沉降量与环境空气中SO2、NO2、NOx浓度变化趋势的相关性较差,表明降水中各离子浓度受局地源和外来大气输送共同作用的影响.同时发现降水中硝酸根浓度与机动车数量呈现相同变化趋势,反映出机动车尾气排放的NOx与降水中硝酸根浓度增长密切相关.     

谭裕沟隧道CO,SO2和NOx排放因子研究

通过1997年7月谭裕沟隧道内CO,SO₂和NO_x的连续分析,研究了其污染状况和特征,根据分析结果计算了机动车排放CO,SO₂和NO_x的平均排放因子.结果表明,机动车能排放出较高水平的CO和NO_x,在城市中CO和NO_x有相当大的部分来源于机动车排放,而SO₂的排放量则非常小.      

2013年成都财富论坛期间空气质量状况分析研究

利用2013年5月20日-6月20日成都市区7个环境质量监测站点可吸入颗粒物(PM₁₀)、细颗粒物(PM_2.5)、SO₂、NO₂、CO和臭氧的实测资料及地面气象观测资料,对成都举办财富全球论坛期间及前后的空气质量变化特征和成因进行分析.结果表明,由于市政府采取交通管制措施,使机动车尾气排放的NO₂浓度与财富论坛前后相比降幅达27.2%;财富论坛期间臭氧前体物质浓度的降低,使地面臭氧日均浓度在相同太阳日辐射值下与财富论坛前后相比较低;对城区扬尘控制和周边重污染企业限产停产,分别对PM₁₀和SO₂的排放起到了明显的削减作用;后向轨迹分析表明市区SO₂浓度累积与来自东南部低空的气团有关.当相对湿度小于60%时颗粒物容易吸湿增长,而当相对湿度大于60%时降雨概率增大,颗粒物容易被清除.综合分析,成都市区财富论坛期间空气质量改善是政府减排举措的有效实施和较好的气象条件共同作用的结果.     

Interactions of aerosols (ammonium sulfate,ammonium nitrate and ammonium chloride) and of gases (HCl,HNO3) with fogwater

The concentrations of aerosols (NH₄NO₃, (NH₄)₂SO₄ and NH₄Cl) and of gases (HCl_(g), HNO_3(g), NH_3(g) were determined by denuder methods under different conditions (in the absence of fog, before, during and after fog events). At this site situated in an urban region, high concentrations of the gaseous strong acids HCl_(g) and HNO_3(g) are observed. NH₄Cl and NH₄NO₃ aerosols represent a major fraction of the Cl⁻ and NO₃⁻ aerosols (<2.4 μm)collected by denuders. During a fog event, very high concentrations of SO₄²⁻ were found in small aerosols, which are attributed to the aqueous phase oxidation of SO₂ under the influence of high pH due to the presence of NH₃. Differences in SO₄²⁻ concentrations measured in aerosols (<2.4 μm) and in fog droplets were probably due to mass-transport limitations of the SO₂ oxidation. Ammonium sulfate aerosols represent in some cases a significant fraction of the total S present (SO_2(g) + SO₄²⁻. Soluble aerosols and gases contribute to the composition of fogwater and are released again after fog dissipation.     

Heterogeneous reactions of SO2 and NO2 on carbonaceous surfaces

Four different types of carbonaceous material (active carbon, graphitized carbon black, source samples from a power plant and from an urban heating boiler) were exposed to synthetic gas mixtures of SO₂ and SO₂ + NO₂ in sub-ppm ranges at two different relative humidities (60 and 90% r.h.). The interaction of SO₂ and NO₂ with the carbonaceous materials led to sulfate and to three other products: NO, HONO and NO₂⁻. Formation of NO and NO₂⁻ was observed only on active carbon while the other three materials yielded HONO. It was also found that NO₂ enhances the deposition of SO₂ only on the source sample from the power plant at 60% r.h., whereas the material from the urban heating boiler had no effect both at low and high r.h. The results obtained show that no general statements on the effect of NO₂ on the heterogeneous reaction of SO₂ on these carbonaceous materials can be made and also that NO₂ reactions in the presence of SO₂ on carbon-containing surfaces should be considered as a source for the production of HONO in the urban environment.