Photochemical air pollution: Weekend-weekday differences

On weekends in Los Angeles County the average atmospheric concentrations of the primary reactants, NO and reactive hydrocarbons, leading to photochemical air pollution decrease. The behavior of oxidant concentration (used as a measure of the products of the photochemical reactions) usually does not follow that of the primary pollutants. In fact, we find that for most of the year the average weekend oxidant concentration is higher than the corresponding weekday value, despite the lowered emissions. However, for areas and times of particularly high oxidant concentration, for example at inland stations during the summer months, the oxidant levels do decrease on weekends. Thus care must be taken when designing short-term oxidant control strategies, as indiscriminant application of short-term traffic decreases to random days could be counterproductive. Such strategies, however, might be useful for days and places of particularly high oxidant concentration and further research to delineate the requisite conditions for the success of such strategies is in process.     

天津市大气能见度与空气污染物关系分析及控制措施

利用天津市1990—2004年大气能见度观测资料及天津市2002—2004年空气污染物监测数据,统计分析了天津市大气能见度变化特征及其与空气污染物的关系。结果表明,天津市20世纪90年代大气能见度处于波动下降趋势,2000—2003年大气能见度整体水平有所改善,到2004年空气质量迅速提高。统计数据说明,在非采暖季的春季,天津市大气能见度的下降与PM10浓度有较大相关性;在夏季,与相对湿度有较大相关性;在采暖季(冬季),与SO2和NOX等空气污染物浓度有密切关系。同时,提出改善城市大气能见度的4个措施:(1)制定长期的大气能见度控制策略;(2)合理改善能源结构;(3)加强城市裸露土地的治理;(4)城市交通采用清洁能源。     

Local Arctic air pollution: Sources and impacts

Local emissions of Arctic air pollutants and their impacts on climate, ecosystems and health are poorly understood. Future increases due to Arctic warming or economic drivers may put additional pressures on the fragile Arctic environment already affected by mid-latitude air pollution. Aircraft data were collected, for the first time, downwind of shipping and petroleum extraction facilities in the European Arctic. Data analysis reveals discrepancies compared to commonly used emission inventories, highlighting missing emissions (e.g. drilling rigs) and the intermittent nature of certain emissions (e.g. flaring, shipping). Present-day shipping/petroleum extraction emissions already appear to be impacting pollutant (ozone, aerosols) levels along the Norwegian coast and are estimated to cool and warm the Arctic climate, respectively. Future increases in shipping may lead to short-term (long-term) warming (cooling) due to reduced sulphur (CO₂) emissions, and be detrimental to regional air quality (ozone). Further quantification of local Arctic emission impacts is needed.     

Self-organized criticality of air pollution

In this work, we investigate the frequency-size distribution of three pollution indexes (PM₁₀, NO₂ and SO₂) in Shanghai. They are well approximated by power-law distributions, which suggest that air pollution might be a manifestation of self-organized criticality. We introduce a new numerical sandpile model with decay coefficient to reveal inherent dynamic mechanism of air pollution. Only changing the number value of decay coefficient of pollutants, this model gives a good simulation of three pollutants' statistical characteristic. This work shows that it is the self-organized criticality of the air pollutants that results in the temporal variation of air pollutant indexes and the minor air pollution sources can trigger the occurrence of large pollutant events by SOC behavior.     

空气污染暴露评价研究进展

介绍了暴露及暴露评价的基本概念、人体空气污染暴露评价的指示物及其特征,讨论暴露评价方法的类型,对各种方法的优、缺点进行了比较分析。根据综述和案例分析情况,对空气污染暴露评价研究的发展趋势进行了展望。     

Fast-response measurements of air pollution

Concentrations of sulphur and phosphorus compounds in the atmosphere were measured up to 50 times per second, with flame-photometric apparatus developed for the purpose, at distances of 4–4800 m from the source. Rates of change and autocorrelograms were determined, from which the distance of a point source can be estimated without knowledge of the source strength.     

Contemporary threats and air pollution

It is now well understood that air pollution produces significant adverse health effects in the general public and over the past 60 years, there have been on-going efforts to reduce the emitted pollutants and their resulting health effects. There are now shifting patterns of industrialization with many heavily polluting industries moving from developed countries with increasingly stringent air quality standards to the developing world. However, even in decreasing concentrations of pollutants, health effects remain important possibly as a result of changes in the nature of the pollutants as new chemicals are produced and as other causes of mortality and morbidity are reduced. In addition, there is now the potential for deliberate introduction of toxic air pollutants by local armed conflicts and terrorists. Thus, there are new challenges to understand the role of the atmospheric environment on public health in this time of changing economic and demographic conditions overlaid with the willingness to indirectly attack governments and other established entities through direct attacks on the general public.     

Assessment of air pollution impact

Several essential steps of air quality assessment are described, including identification, prediction, and evaluation of critical variables and potential changes of air quality. A coal-reconversion power plant in New York was selected as an example to illustrate the assessment.     

Arctic air pollution: An overview of current knowledge

From December to April, the Arctic air mass is polluted by man-made mid-latitudinal emissions from fossil fuel combustion, smelting and industrial processes. In the rest of the year, pollution levels are much lower. This is the outcome of less efficient pollutant removal processes and better south (S) to north (N) transport during winter. In winter, the Arctic air mass covers much of Eurasia and N. America. Meteorological flow fields and the distribution of anthropogenic SO₂ emissions in the northern hemisphere favor northern Eurasia as the main source of visibility reducing haze. Observations of SO₄²⁻ concentrations in the atmosphere throughout the Arctic yield, depending on location and year, a January–April mean of 1.5–3.9 μg m⁻³ in the Norwegian Arctic to 1.2–2.2 μg m⁻³ in the N. American Arctic. An estimate of the mean vertical profile of fine particle aerosol mass during March and April shows that, on average, pollution is concentrated in the lower 5 km of the atmosphere. Not only are anthropogenic particles present in the Arctic atmosphere but also gases such as SO₂, perfluorocarbons and pesticides. The acidic nature and seasonal variation of Arctic pollution is reflected in precipitation, the snowpack and glacier snow in the Arctic. A pH of 4.9–5.2 in winter and ~ 5.6 in summer is expected in the absence of calcareous wind blown soil. Glacial records indicate that Arctic air pollution has undergone a marked increase since the mid 1950s paralleling a marked increase in SO₂ and NO_x emissions in Europe. Effects of Arctic pollution include a reduction in visibility and perturbation of the solar radiation budget in April–June. Potential effects are the acidification and toxification of sensitive ecosystems.