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.     

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.     

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.     

Ozone concentrations at a remote mountain site and at two regional locations in southwestern Alberta

Ozone concentrations at a remote site in the Rocky Mountains of southwestern Alberta averaged 43.4 ppb over a 2 year period and the Canadian air quality objective of an 80 ppb hourly average was exceeded 1.5% of the time. The diurnal variation in O₃ concentrations was small, 2.9 ppb, indicative of a remote location, above the nocturnal inversion and not greatly influenced by local emissions. During the period when O₃ concentrations were highest, winds were generally from the southwest, suggestive of the long range transport of anthropogenic pollutants from distant sources rather than the generation of O₃ from local emissions. In contrast, hourly O₃ concentrations at two regional air quality monitoring sites showed an average diurnal variation of 14 ppb. Only two hourly averages exceeded 80 ppb during the 2 years, and the mean O₃ concentration was 26 ppb. When these regional sites were within the urban plume from Calgary, the O₃ concentrations were depressed to a mean of 18 ppb. Ozone concentrations in downtown Calgary averaged 13 ppb. Under Alberta climatological and meteorological conditions, hourly O₃ objectives are most likely to be exceeded in remote areas, rather than in cities or in areas under the direct influence of urban emissions.     

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.     

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.     

快速城市化区河流温室气体排放的时空特征及驱动因素

河流是大气温室气体重要的排放源,近十多年来全球城市化导致河流生态系统各要素发生改变,对河流水体温室气体排放产生影响.为研究快速城市化区不同土地利用方式下河流温室气体排放的时空特征及其影响因素,采用薄边界层模型法,于2014年9月(秋季)和12月(冬季)及2015年3月(春季)和6月(夏季)的晴天对重庆市区内梁滩河干、支流水体pCO_2、CH_4、N_2O溶存浓度进行监测.结果表明,梁滩河干、支流水体pCO_2范围为(23. 38±34. 89)～(1395. 33±55. 45) Pa、CH_4溶存浓度范围(65. 09±28. 09)～(6 021. 36±94. 36) nmol·L~(-1)、N_2O溶存浓度范围为(29. 47±5. 16)～(510. 28±18. 34)nmol·L~(-1); CO_2、CH_4和N_2O排放通量分别为-6. 1～786. 9、0. 31～27. 62和0. 06～1. 08 mmol·(m~2·d)~(-1);流域水体温室气体浓度空间格局与快速城市化带来的污染负荷空间梯度吻合,干流温室气体浓度与通量从上游向下游均呈先增加后降低,在城市化速度最快的中游出现峰值,其中城市河段CO_2和CH_4浓度约为非城市河段的2倍,同时支流水体自上游农业区向下游城市区呈显著增加;由于受到降雨、温度、外源输入的综合影响,河流CO_2排放通量呈秋季冬季夏季春季的季节模式,CH_4排放通量春季最高夏季最低,N_2O排放通量季节差异不显著.流域水体碳、氮含量均较高,水体CO_2的产生和排放不受生源要素限制,但受水温、pH、DO、叶绿素a等生物代谢因子影响; CH_4的产生和排放受水体碳、氮、磷含量和外源污水输入的共同驱动; N_2O的产生和排放主要受高N_2O浓度的城市污水排放影响.本研究认为流域快速城市化加快了河流水体温室气体排放,形成排放热源,因此城市河流温室气体排放对全球河流排放通量的贡献可能被忽视,在未来研究中应受到更多关注.     

Emission of linalool from Valencia orange blossoms and its observation in ambient air

Emission measurements made over a 5-month period of a Valencia orange tree showed the significant emission of the terpenoid linalool (C₁₀H₁₈O) from Valencia orange blossoms. The average annual emission rate of this Olinda Valencia orange, derived from emission measurements which include the blossoming season, is a factor of ∼10 higher than the average annual emission rate derived from measurements taken outside of the blossom season. Ambient monoterpene and linalool concentrations were measured in Riverside, California, in the spring and supported the chamber plant emissions data, with linalool concentrations as high as 17 μg m⁻³ being observed in an orange grove. These results show that current biogenic emission inventories which are formulated from limited survey data, generally not including seasonal variations in the vegetative emissions, can be subject to large uncertainties.     

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.     

Effects of plant diversity on greenhouse gas emissions in microcosms simulating vertical constructed wetlands with high ammonium loading

Wastewater with relatively high nitrogen concentrations is a major source of nitrous oxide (N₂O) and methane (CH₄) emissions and exerts multiple stresses on the environment. Studies have shown that plant diversity plays an important role in ecosystem functioning. However, the effects of plant species diversity on CH₄ and N₂O emissions under high ammonium (NH₄⁺-N) loading rates remain unclear. In this study, a microcosm experiment simulating vertical constructed wetlands supplied with high NH₄⁺-N water levels was established. The treatments included four species richness levels (1, 2, 3, 4) and 15 species compositions. There was no significant relationship between species richness and N₂O emissions. However, N₂O emissions were significantly reduced by specific plant species composition. Notably, the communities with the presence of Rumex japonicus L. reduced N₂O emissions by 62% compared to communities without this species. This reduction in N₂O emissions may have been a result of decreased N concentrations and increased plant biomass. CH₄ emissions did not respond to plant species richness or species identity. Overall, plant species identity surpassed species richness in lowering N₂O emissions from constructed wetlands with high NH₄⁺-N water. The results also suggest that communities with R. japonicus could achieve higher N removal and lower greenhouse gas emissions than other wetland species.     

The influence of long term trends in pollutant emissions on deposition of sulphur and nitrogen and exceedance of critical loads in the United Kingdom

In the United Kingdom, as with other European countries, land-based emissions of NO_x and SO₂ have fallen significantly over the last few decades. SO₂ emissions fell from a peak of 3185 Gg S in 1970 to 344 Gg S in 2005 and are forecast by business-as-usual emissions scenarios to fall to 172 Gg by 2020. NO_x emissions were at a maximum of 951 Gg N in 1970 and fell to 378 by 2005 with a further decrease to 243 Gg N forecast by 2020. These large changes in emissions have not been matched by emissions changes for NH₃ which decreased from 315 Gg N in 1990 to 259 in 2005 and are forecast to fall to 222 by 2020. The Fine Resolution Atmospheric Multi-pollutant Exchange model (FRAME) has been applied to model the spatial distribution of sulphur and nitrogen deposition over the United Kingdom during a 15-year time period (1990–2005) and compared with measured deposition of sulphate, nitrate and ammonium from the national monitoring network. Wet deposition of nitrogen and sulphur was found to decrease more slowly than the emissions reductions rate. This is attributed to a number of factors including increases in emissions from international shipping and changing rates of atmospheric oxidation. The modelled time series was extended to a 50-year period from 1970 to 2020. The modelled deposition of SO_x, NO_y and NH_x to the UK was found to fall by 87%, 52% and 25% during this period. The percentage area of sensitive habitats in the United Kingdom for which critical loads are exceeded is estimated to fall from 85% in 1970 to 37% in 2020 for acidic deposition and from 73% to 49% for nutrient nitrogen deposition. The significant reduction in land emissions of SO₂ and NO_x focuses further attention in controlling emissions from international shipping. Future policies to control emissions of ammonia from agriculture will be required to effect further significant reductions in nitrogen deposition.     

Can further mitigation of ammonia emissions reduce exceedances of particulate matter air quality standards?

Several studies point out the importance of agricultural emissions to particulate matter (PM) concentrations, and particularly of NH₃ emissions to PM_2.5. Our study used three different chemical transport models (CHIMERE, EMEP and LOTOS-EUROS) to quantify the reductions of PM_2.5 and PM₁₀ concentrations due to reductions of NH₃ emissions beyond the Gothenburg Protocol (GP), as well as due to the GP alone compared to 2009. Simulations of PM_2.5 and PM₁₀ concentrations using 2009 meteorology were undertaken for five emission scenarios: 2009 emissions (as the reference simulation), GP emissions in 2020, and further 10%, 20% and 30% NH₃ emission reductions in EU27 beyond the GP. The modelling results for the scenarios with further 10%, 20% and 30% NH₃ agriculture emission reductions in EU27 beyond the GP show that the reduction achieved in PM concentrations is not linear with the emission reductions. In fact, the results from the study show that the impact of ammonia emissions reduction is significantly more efficient when the emission reduction rises. Moreover, based on the evaluation on 2009, the modelling study shows that the expected impact of ammonia emissions on the formation of particulate ammonium was underestimated by all models. This would imply that the role of ammonia on PM concentration and exceedances of PM_2.5 and PM₁₀ limit values is likely to be even larger than quantified in this study. This study shows that the implementation of the emission reductions imposed by the revised GP for 2020 will not suffice to achieve compliance with PM limit values everywhere in Europe; hence further European and local measures may be considered. NH₃ emissions from agriculture can be further reduced with the implementation of proven and feasible measures (substitution of fertilizers, improved storage of manure, way fertilizer injections, etc., …), in order to reduce PM concentrations and their impacts on human health across Europe.     

A photochemical box model for urban air quality study

The photochemical box model (PBM) developed in the present study is based on the principle of mass conservation. It has a horizontal domain of the size of a typical city and a vertical dimension defined by the mixed-layer height. The concentration of any pollutant is determined by horizontal advection, vertical entrainment, source emissions and chemical reactions. A one-dimensional high resolution boundary layer model by Blackadar (Preprints, Third Symp. on Atmospheric Turbulence, Diffusion, and Air Quality, Raleigh, Am. Met. Soc., pp. 443–447, 1976; Advances in Environmental Sciences and Engineering, Vol. 1, No. 1 (edited by Pfafflin J. and Ziegler E.), pp. 50–85. Gordon and Breach, New York, 1979) has been incorporated in the PBM and further developed to consider the effect of urban heat islands in the simulation of mixed layer height. The predicted mixed-layer heights compare very well with observations. The gas phase chemical kinetic mechanism used in the Regional Acid Deposition Model II (RADM2) and that of an earlier version of PBM have been used to calculate the contributions of chemical reactions to the changes of pollutant concentrations. Detailed analysis and comparisons of the two chemical mechanisms have been made. The simulated pollutant concentrations using both chemical mechanisms are in very good agreement with available observations for CO, NO, NO₂ and O₃. A radiative transfer model developed by Madronich (J. geophys. Res.92, 9740–9752, 1987) has been incorporated in the PBM for the calculation of actinic flux and photolytic rate constants. Height-averaged and radiation-corrected photolytic rate constants are used for the photochemical reactions. Budget analyses conducted for CO, NO, NO₂ and O₃ have enhanced our understanding of the relative contributions of horizontal advection, vertical entrainment, source emissions and chemical reactions to the overall rate of change of their concentrations. Model predictions are not sensitive to the large number of peroxy radical-peroxy radical reactions in the RADM2 chemical mechanism under urban conditions.     

Transverse approach between real world concentrations of SO2, NO2, BTEX, aldehyde emissions and corrosion in the Grand Mare tunnel

With regard to automotive traffic, a tunnel-type semi enclosed atmosphere is characterized by a higher concentration of gaseous pollutants than on urban traffic roads and highlights the gaseous effluent species having an impact on material degradation. Therefore, a transverse approach between air quality and its consequences upon the longevity of materials is necessary, implying better knowledge of tunnel atmosphere and a better understanding of material degradation inside a tunnel for operating administration. Gaseous pollutant measurements carried out in a road tunnel in Rouen (Normandy) give the real world traffic concentrations of experimental exposure conditions. The sampling campaigns, achieved in summer and winter include SO₂, NO₂, BTEX and aldehyde analyses. Effluent profiles in the upward and downward tubes have been established. The current work shows that SO₂, NO₂, formaldehyde, acetaldehyde, propanal and butanal must be considered in the degradation process of materials in a stuffy environment. As regards NO₂, its concentration depends on the modification of the automotive fleet. The total aldehyde concentrations indicate no particular trend between the two bores. Formaldehyde, acetaldehyde, propanal, butanal and acrolein species are the most abundant species emitted by vehicles and represent 90% to 95% of the total aldehyde emissions.     

Predicted and observed concentrations of SO2, SPM and NOχ over Delhi

Three air pollutants, SO₂, SPM and NO_χ, which are identified as major pollutants in urban cities, have been considered for a comparative study between predicted and observed concentrations of these pollutants at different receptor points over Delhi. A receptor-oriented Gaussian plume model (IITLT) and Climatological Dispersion Model (CDM) have been used to estimate the long term concentration of non-reactive pollutants due to emissions from area and point sources. Modified stability parameters are used for low wind speed and calm intervals. Monthly mean concentrations of these pollutants for the period of November, December and January 1987–1988 have been computed and the results obtained from the two models are found to be close to the observed values for this period. An error analysis of 54 pairs of observed and predicted concentrations show that performances of both the models are highly satisfactory, giving an RMSE of 1.61 for IITLT Model and 1.50 for CDM.     

Analyzing the efficacy of subtropical urban forests in offsetting carbon emissions from cities

Urban forest management and policies have been promoted as a tool to mitigate carbon dioxide (CO₂) emissions. This study used existing CO₂ reduction measures from subtropical Miami-Dade and Gainesville, USA and modeled carbon storage and sequestration by trees to analyze policies that use urban forests to offset carbon emissions. Field data were analyzed, modeled, and spatially analyzed to compare CO₂ sequestered by managing urban forests to equivalent amounts of CO₂ emitted in both urban areas. Urban forests in Gainesville have greater tree density, store more carbon and present lower per-tree sequestration rates than Miami-Dade as a result of environmental conditions and urbanization patterns. Areas characterized by natural pine-oak forests, mangroves, and stands of highly invasive trees were most apt at sequestering CO₂. Results indicate that urban tree sequestration offsets CO₂ emissions and, relative to total city-wide emissions, is moderately effective at 3.4 percent and 1.8 percent in Gainesville and Miami-Dade, respectively. Moreover, converting available non-treed areas into urban forests would not increase overall CO₂ emission reductions substantially. Current CO₂ sequestration by trees was comparable to implemented CO₂ reduction policies. However, long-term objectives, multiple ecosystem services, costs, community needs, and preservation of existing forests should be considered when managing trees for climate change mitigation and other ecosystem services.     

Anthropogenic land use substantially increases riverine CO2 emissions

Carbon dioxide (CO₂) emissions from inland waters to the atmosphere are a pivotal component of the global carbon budget. Anthropogenic land use can influence riverine CO₂ emissions, but empirical data exploring cause-effect relationships remain limited. Here, we investigated CO₂ partial pressures (pCO₂) and degassing in a monsoonal river (Yue River) within the Han River draining to the Yangtze in China. Almost 90% of river samples were supersaturated in CO₂ with a mean ± standard deviation of 1474 ± 1614 µatm, leading to emissions of 557 - 971 mmol/m²/day from river water to the atmosphere. Annual CO₂ emissions were 1.6 - 2.8 times greater than the longitudinal exports of riverine dissolved inorganic and organic carbon. pCO₂ was positively correlated to anthropogenic land use (urban and farmland), and negatively correlated to forest cover. pCO₂ also had significant and positive relationships with total dissolved nitrogen and total dissolved phosphorus. Stepwise multiple regression models were developed to predict pCO₂. Farmland and urban land released nutrients and organic matter to the river system, driving riverine pCO₂ enrichment due to enhanced respiration in these heterotrophic rivers. Overall, we show the crucial role of land use driving riverine pCO₂, which should be considered in future large-scale estimates of CO₂ emissions from streams. Land use change can thus modify the carbon balance of urban-river systems by enhancing river emissions, and reforestation helps carbon neutral in rivers.     

Proportionality between SO2 emissions and wet SO42− concentrations: The effect of area of averaging

An earlier analysis of empirical associations between SO₂ emissions and wet SO₄²⁻ concentrations in central North America (Hilst and Chapman, 1990, Atmospheric Environment 24A, 1889–1901) showed that local wet SO₄²⁻ concentrations were not proportional to SO₂ emissions averaged over areas up to ∼10⁶ km². Because it is axiomatic that at a global level of averaging a proportionality between total S emissions and S deposition should exist, we have extended these analyses in an attempt to determine whether there is proportionality between S emissions and wet SO₄²⁻ deposition. We have found that for the eastern half of central North America (an area of about 4.3 × 10⁶ km²), the annual average wet SO₄²⁻ concentration exhibits a linear-proportional dependence on anthropogenic SO₂ emissions. However, the internal structure of this association for subareas of the eastern half of central North America suggests the “global” proportionality is achieved by a combination of imported SO₂ from major source areas and an oxidant-limited conversion of SO₂ to SO₄²⁻ within the major source areas. If this inference is even approximately correct, a rollback SO₂ control strategy for the eastern United States and southeast Canada should result in an immediate proportional decrease in wet SO₄²⁻ concentrations in minor SO₂ source areas, but no appreciable reduction of wet SO₄²⁻ concentrations in major SO₂ source areas until the oxidant limitation has been overcome.     

北京市控制大气污染四期紧急措施环境有效性分析

对北京市控制大气污染的四期紧急措施进行量化,分别计算出各项控制措施实施后的排放削减量,建立排放清单.采用空气质量模型,模拟了紧急措施实施的各阶段市区内一次大气污染物SO₂、NO_x和PM10浓度的时空分布情况,分析和评价了四期紧急措施的环境有效性.结果表明,四期紧急措施对SO₂和NO_x的控制效果较好,PM10的环境浓度下降不明显.     

基于能源-环境情景模拟的北京市大气污染对居民健康风险评价研究

保护居民健康是北京市能源系统优化管理和大气污染治理的重要目标.本研究基于北京市的社会经济发展目标并结合相关节能减排和环保要求,针对全市2010-2020年间的能源消费分别设计了高、中、低3种约束情景,通过LEAP模型预测了全市至2020年的能源消费量与S02、NOx、PM10和PM2.5等4种主要大气污染物的排放强度,并采用泊松回归模型对3种情景下主城区居民受环境空气中这4种大气污染物的暴露危害所导致的健康风险进行了评估.结果显示:相对低约束情景,高约束情景至2020年可避免与S02、NOx、PM10和PM2.5污染相关的死亡危害分别为2663、6359、4720和4104人·a-1,而且在高约束情景下煤炭消费比重每下降1％,可相应地避免约1400人·a-1的污染急性死亡.由此建议北京市实施更加严格的节能和减排措施,严控煤炭消费总量,进一步优化能源结构,最大程度地降低能源消费导致的大气污染所产生的居民健康风险.