High Pollution Episodes Research Articles

Who Among the Elderly Is Most Vulnerable to Exposure to and Health Risks of Fine Particulate Matter From Wildfire Smoke?

Wildfires burn more than 7 million acres in the United States annually, according to the US Forest Service. Little is known about which subpopulations are more vulnerable to health risks from wildfire smoke, including those associated with fine particulate matter. We estimated exposure to fine particles specifically from wildfires, as well as the associations between the presence of wildfire-specific fine particles and the amount of hospital admissions for respiratory causes among subpopulations older than 65 years of age in the western United States (2004-2009). Compared with other populations, higher fractions of persons who were black, lived in urban counties, and lived in California were exposed to more than 1 smoke wave (high-pollution episodes from wildfire smoke). The risks of respiratory admissions on smoke-wave days compared with non-smoke-wave days increased 10.4% (95% confidence interval: 1.9, 19.6) for women and 21.7% (95% confidence interval: 0.4, 47.3) for blacks. Our findings suggest that increased risks of respiratory admissions from wildfire smoke was significantly higher for women than for men (10.4% vs. 3.7%), blacks than whites (21.7% vs. 6.9%), and, although associations were not statistically different, people in lower-education counties than higher-educated counties (12.7% vs. 6.1%). Our study raised important environmental justice issues that can inform public health programs and wildfire management. As climate change increases the frequency and intensity of wildfires, evidence on vulnerable subpopulations can inform disaster preparedness and the understanding of climate change consequences.

Ambient Particles (PM10, PM2.5 and PM1.0) and PM2.5 Chemical Components in Western Yangtze River Delta (YRD): An Overview of Data from 1-year Online Continuous Monitoring at Nanjing

Understanding particle chemical composition is important in source apportionment and health impact assessment. Since 2012, a Complex Air Pollution Research Station located on the top roof of a 22-floor building (~80 m) in Jiangsu Provincial Academy of Environmental Science was established as a platform to characterize components and temporal variations of hazy and air transport in the region, so as to provide scientific supports on Joint Prevention and Control of Regional Air Pollution control in the Yangtze River Delta. Here, based on 1-year online measurement, we present a preliminary result on occurrence of ambient particles and chemical components, and reconstructed light extinction coefficients based on measured species. In 2015, the annual average concentration of PM2.5 was 68 ± 40 µg/m3, comprising up to nearly 75% of the total PM10. The submicron PM1.0 had an annual average concentration of 48 ± 28 µg/m3 and contributed about 70% of the total PM2.5 mass. Secondary inorganic composition including sulfate, nitrate and ammonium (SNA) was the major fraction of PM2.5, accounting for ~70% on an annual average. The estimated light extinction of ambient particle averaged at 422 ± 256 Mm−1, of which 412 ± 257 Mm−1 was induced by fine PM2.5. SNA contributed largely to the light extinction induced by fine PM2.5 (about 72%), followed by organic matter (18%). During the high-pollution episodes, the mass fraction of SNA increased notably, calling for necessary controls on key gaseous precursors.

Spatial and Temporal Characteristics and Main Contributing Regions of High PM2.5 Pollution in Hong Kong

ABSTRACTFine particulate matter (PM2.5) pollution episodes occur frequently in most Chinese metropolises. Because Hong Kong is affected by the East Asian monsoon, its high PM2.5 pollution is potentially contributed to by a combination of local and regional emissions. This study identified the spatial and temporal characteristics and contributing regions of PM2.5 pollution episodes in Hong Kong. We analyzed the hourly monitoring data collected at various monitoring stations in Hong Kong for the year 2014 in addition to spatial distributions of PM2.5 in China in the days preceding high pollution episodes, and we identified the spatial and temporal characteristics of high PM2.5 pollution in Hong Kong. The relative contributions of local and regional sources to high PM2.5 episodes were then quantified. Finally, backward trajectories of air masses arriving in Hong Kong during high PM2.5 episodes were generated to determine the main contributing regions. The results indicated that PM2.5 levels were higher in the northwestern and southeastern parts of Hong Kong and the Yuen Long station observed the most serious pollution, with a highest daily average PM2.5 concentration of 118 µg m–3; other areas noted relatively lower concentrations, with maximum daily average concentrations less than 100 µg m–3. Regional sources accounted for almost 70% of the PM2.5 pollution and were mostly from the northern and northeastern areas of Hong Kong. Six main contributing regions were identified: the northern region of Guangdong province, Henan–Shandong, the Yangtze River Delta, Jiangxi, Fujian, and Anhui-Hubei. Among these, Guangdong province contributed the highest proportion of the pollution. Because PM2.5 is a major air pollutant in Hong Kong, the findings of this study will be useful for forecasting PM2.5 pollution episodes. Moreover, the developed methodology can be extended to other pollutants if their characteristics and main contributing regions can be identified.

Variability of winter and summer surface ozone in Mexico City on the intraseasonal timescale

Abstract. Surface ozone concentrations in Mexico City frequently exceed the Mexican standard and have proven difficult to forecast due to changes in meteorological conditions at its tropical location. The Madden–Julian Oscillation (MJO) is largely responsible for intraseasonal variability in the tropics. Circulation patterns in the lower and upper troposphere and precipitation are associated with the oscillation as it progresses eastward around the planet. It is typically described by phases (labeled 1 through 8), which correspond to the broad longitudinal location of the active component of the oscillation with enhanced precipitation. In this study we evaluate the intraseasonal variability of winter and summer surface ozone concentrations in Mexico City, which was investigated over the period 1986–2014 to determine if there is a modulation by the MJO that would aid in the forecast of high-pollution episodes. Over 1 000 000 hourly observations of surface ozone from five stations around the metropolitan area were standardized and then binned by active phase of the MJO, with phase determined using the real-time multivariate MJO index. Highest winter ozone concentrations were found in Mexico City on days when the MJO was active and in phase 2 (over the Indian Ocean), and highest summer ozone concentrations were found on days when the MJO was active and in phase 6 (over the western Pacific Ocean). Lowest winter ozone concentrations were found during active MJO phase 8 (over the eastern Pacific Ocean), and lowest summer ozone concentrations were found during active MJO phase 1 (over the Atlantic Ocean). Anomalies of reanalysis-based cloud cover and UV-B radiation supported the observed variability in surface ozone in both summer and winter: MJO phases with highest ozone concentration had largest positive UV-B radiation anomalies and lowest cloud-cover fraction, while phases with lowest ozone concentration had largest negative UV-B radiation anomalies and highest cloud-cover fraction. Furthermore, geopotential height anomalies at 250 hPa favoring reduced cloudiness, and thus elevated surface ozone, were found in both seasons during MJO phases with above-normal ozone concentrations. Similar height anomalies at 250 hPa favoring enhanced cloudiness, and thus reduced surface ozone, were found in both seasons during MJO phases with below-normal ozone concentrations. These anomalies confirm a physical pathway for MJO modulation of surface ozone via modulation of the upper troposphere.

Particulate Air Pollution from Wildfires in the Western US under Climate Change.

Wildfire can impose a direct impact on human health under climate change. While the potential impacts of climate change on wildfires and resulting air pollution have been studied, it is not known who will be most affected by the growing threat of wildfires. Identifying communities that will be most affected will inform development of fire management strategies and disaster preparedness programs. We estimate levels of fine particulate matter (PM2.5) directly attributable to wildfires in 561 western US counties during fire seasons for the present-day (2004-2009) and future (2046-2051), using a fire prediction model and GEOS-Chem, a 3-D global chemical transport model. Future estimates are obtained under a scenario of moderately increasing greenhouse gases by mid-century. We create a new term "Smoke Wave," defined as ≥2 consecutive days with high wildfire-specific PM2.5, to describe episodes of high air pollution from wildfires. We develop an interactive map to demonstrate the counties likely to suffer from future high wildfire pollution events. For 2004-2009, on days exceeding regulatory PM2.5 standards, wildfires contributed an average of 71.3% of total PM2.5. Under future climate change, we estimate that more than 82 million individuals will experience a 57% and 31% increase in the frequency and intensity, respectively, of Smoke Waves. Northern California, Western Oregon and the Great Plains are likely to suffer the highest exposure to widlfire smoke in the future. Results point to the potential health impacts of increasing wildfire activity on large numbers of people in a warming climate and the need to establish or modify US wildfire management and evacuation programs in high-risk regions. The study also adds to the growing literature arguing that extreme events in a changing climate could have significant consequences for human health.

Intense secondary aerosol formation due to strong atmospheric photochemical reactions in summer: observations at a rural site in eastern Yangtze River Delta of China

High pollution episodes of PM2.5 and O3 were frequently observed at a rural site (N31.0935º, E120.978°) in eastern Yangtze River Delta (YRD) in summer. To study the impacts of photochemical reactions on secondary aerosol formation in this region, we performed real-time measurements of the mass concentration and composition of PM2.5, particle size distribution (13.6~736.5 nm), concentrations of gas pollutants including O3, SO2, NO2, CO, non-methane hydrocarbons (NMHC)), and nitrate radical in 2013. During the sampling period, the average concentration of PM2.5 was 76.1 (± 16.5) μg/m3, in which secondary aerosol species including sulfate, nitrate, ammonium, and secondary organic aerosol (SOA) accounted for ~ 62%. Gas-phase oxidation of SO2 was mainly responsible for a fast increase of sulfate (at 1.70 μg/m3/h) in the morning. Photochemical production of nitric acid was intense during daytime, but particulate nitrate concentration was low in the afternoon due to high temperature. At night, nitrate was mainly formed through the hydrolysis of NO3 and/or N2O5. The correlations among NMHC, Ox (= O3 + NO2), and SOA suggested that a combination of high emission of hydrocarbons and active photochemical reactions led to the rapid formation of SOA. In addition, several new particle formation and fast growth events were observed despite high ambient aerosol loading. Since the onset of new particle events was accompanied by a rapid increase of H2SO4 and SOA, enhanced formation of sulfate and SOA driven by photochemical oxidation likely promoted the formation and growth of new particles. Together, our results demonstrated that strong atmospheric photochemical reactions enhanced secondary aerosols formation and led to the synchronous occurrence of high concentrations of PM2.5 and O3 in a regional scale. These findings are important for better understanding the air pollution in summer in YRD.

Modeling high aerosol loads in China in January 2013

In January 2013 exceptionally high levels of particulate matter (PM) concentrations were reported for the area around Beijing (40 N, 116 E) with maximum concentrations exceeding 500μg/m3. Observations of the aerosol optical depth (AOD) within the Aeronet sun-photometer network showed an AOD of more than 2 on several days. In order to analyze this high pollution episode PM concentrations in China were simulated with the Community Multiscale Air Quality (CMAQ) model for the period from 10 December 2012 to 31 January 2013. Emissions were taken from the EDGAR data base. The most recent emission rates from 2008 were further increased considering the growth of China's gross domestic product. The results were compared to ground based total PM and speciated PM measurements as well as to Aeronet sun-photometer observations. The model was generally able to reproduce the high PM levels measured in situ close to ground, however the largest peak on 12 January was not captured, because of an exceptionally strong temperature inversion close to ground that was not reproduced in the meteorological fields. The meteorological model significantly underestimated the relative humidity in the lowest layer, leading to some underestimations of the aerosol optical depth. An analysis of the most important source sectors showed that residential heating was the main emission source sector on those days with the highest aerosol concentrations.

Aerosol composition and sources during high and low pollution periods in Ningbo, China

Due to the rapid industrialization of the Yangtze River Delta (YRD) region in China, heavy air pollution episodes have occurred frequently over the past five years which are of great concern due to their environmental and health impacts. To investigate the chemical characteristics of the highly polluted aerosols in this region, a sampling campaign had been conducted in Ningbo from 3 December 2012 to 27 June 2013, during which a month long high pollution episode had been captured. Daily average PM2.5 concentrations during high and low pollution periods were 111μgm−3 and 53μgm−3, respectively. The most polluted day was 8 January 2013 with a PM2.5 concentration up to 175μgm−3. To understand the origin of the highly polluted aerosols, meteorological conditions, air mass backward trajectories, distribution of fire spots in surrounding areas and various categories of aerosol pollutants were analyzed, including trace metals, inorganic species, PAHs and anhydrosugars. Total metal concentrations were 3.8 and 1.6μgm−3 for the high and low pollution episodes, respectively, accounting for 3.4% and 3.1% of the total PM2.5 mass. Total concentrations of ionic species accounted for more than 50.0% of the PM2.5 by mass, with dominant ions (nitrate, sulfate, ammonium) accounting for over 42.0% of the PM2.5 mass concentrations in both periods. During the high pollution episode, enhanced Cd–Pb and biomarker (levoglucosan, mannosan) levels indicated the contributions from coal combustion, traffic and biomass burning to fine aerosol PM2.5. The average diagnostic ratio of Fla/(Fla+Pyr) was 0.54 in high pollution episode, which was intermediate between that for wood (>0.50) and coal combustion (0.58). BaP/Bpe was 0.49 and 0.30 for the highly and lightly polluted aerosols respectively, associated with the significant non-traffic emissions (<0.60). In addition, stagnant weather conditions during the high pollution period and long-range transport of air masses from heavy industries and biomass burning from northern China to Ningbo could be considered as the main factors for the formation of the aerosols during high pollution period.

Long-term Changes in Extreme Air Pollution Meteorology and the Implications for Air Quality.

Extreme air pollution meteorological events, such as heat waves, temperature inversions and atmospheric stagnation episodes, can significantly affect air quality. Based on observational data, we have analyzed the long-term evolution of extreme air pollution meteorology on the global scale and their potential impacts on air quality, especially the high pollution episodes. We have identified significant increasing trends for the occurrences of extreme air pollution meteorological events in the past six decades, especially over the continental regions. Statistical analysis combining air quality data and meteorological data further indicates strong sensitivities of air quality (including both average air pollutant concentrations and high pollution episodes) to extreme meteorological events. For example, we find that in the United States the probability of severe ozone pollution when there are heat waves could be up to seven times of the average probability during summertime, while temperature inversions in wintertime could enhance the probability of severe particulate matter pollution by more than a factor of two. We have also identified significant seasonal and spatial variations in the sensitivity of air quality to extreme air pollution meteorology.

Comprehensive modelling study on observed new particle formation at the SORPES station in Nanjing, China

Abstract. New particle formation (NPF) has been investigated intensively during the last 2 decades because of its influence on aerosol population and the possible contribution to cloud condensation nuclei. However, intensive measurements and modelling activities on this topic in urban metropolitan areas in China with frequent high-pollution episodes are still very limited. This study provides results from a comprehensive modelling study on the occurrence of NPF events in the western part of the Yangtze River Delta (YRD) region, China. The comprehensive modelling system, which combines the WRF-Chem (the Weather Research and Forecasting model coupled with Chemistry) regional chemical transport model and the MALTE-BOX sectional box model (the model to predict new aerosol formation in the lower troposphere), was shown to be capable of simulating atmospheric nucleation and subsequent growth. Here we present a detailed discussion of three typical NPF days, during which the measured air masses were notably influenced by either anthropogenic activities, biogenic emissions, or mixed ocean and continental sources. Overall, simulated NPF events were generally in good agreement with the corresponding measurements, enabling us to get further insights into NPF processes in the YRD region. Based on the simulations, we conclude that biogenic organic compounds, particularly monoterpenes, play an essential role in the initial condensational growth of newly formed clusters through their low-volatility oxidation products. Although some uncertainties remain in this modelling system, this method provides a possibility to better understand particle formation and growth processes.

Can Ultra-violet Mie Lidar Be an Effective Instrument During High Pollution Episode?

Vertical profiles of particulates were measured by a 355 nm Mie scattering lidar during a dust-storm event. A high energy pulse laser was employed as the light source to detect the extinction coefficient in the altitude up to 6 km in the day and 9 km at night. The extinction profiles showed layers of high aerosol concentrations in good agreement with ground-based pollution measurements, which indicated that such ultra-violet lidar is a very useful remote sensing instrument for monitoring extinction profiles during extreme high aerosol loading and low visibility atmospheric conditions when low energy lidar systems cannot obtain effective results.

Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta, China

Abstract. Absorbing aerosols can significantly modulate short-wave solar radiation in the atmosphere, affecting regional and global climate. The aerosol absorption coefficient (AAC) is an indicator that assesses the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption Ångström exponent (AAE) in the urban area of Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the seven-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which result in consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m−1 in the urban area of Nanjing, which is much lower than that in Pearl River Delta and the same as in rural areas (Lin'an) in Yangtze River Delta. The AAC in the urban area of Nanjing shows strong seasonality (diurnal variations); it is high in cold seasons (at rush hour) and low in summer (in the afternoon). It also shows synoptic and quasi-2-week cycles in response to weather systems. Its frequency distribution follows a typical log-normal pattern. The 532 nm AAC ranging from 15 to 65 M m−1 dominates, accounting for more than 72 % of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollution. Air masses flowing from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable than from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly occur in summer, likely due to high relative humidity (RH) in the season. AAC increases with increasing AAE at a fixed aerosol loading. The RH–AAC relationship is more complex. Overall, AAC peaks at RH values of around 40 % (1.3 &lt; AAE &lt; 1.6), 65 % (AAE &lt; 1.3 and AAE &gt; 1.6), and 80 % (1.3 &lt; AAE &lt; 1.6).

Source apportionment of fine particles and its chemical components over the Yangtze River Delta, China during a heavy haze pollution episode

Abstract An extremely high PM 2.5 pollution episode occurred over the eastern China in January 2013. In this paper, the particulate matter source apportionment technology (PSAT) method coupled within the Comprehensive air quality model with extensions (CAMx) is applied to study the source contributions to PM 2.5 and its major components at six receptors (Urban Shanghai, Chongming, Dianshan Lake, Urban Suzhou, Hangzhou and Zhoushan) in the Yangtze River Delta (YRD) region. Contributions from 4 source areas (including Shanghai, South Jiangsu, North Zhejiang and Super-region) and 9 emission sectors (including power plants, industrial boilers and kilns, industrial processing, mobile source, residential, volatile emissions, dust, agriculture and biogenic emissions) to PM 2.5 and its major components (sulfate, nitrate, ammonia, organic carbon and elemental carbon) at the six receptors in the YRD region are quantified. Results show that accumulation of local pollution was the largest contributor during this air pollution episode in urban Shanghai (55%) and Suzhou (46%), followed by long-range transport (37% contribution to Shanghai and 44% to Suzhou). Super-regional emissions play an important role in PM 2.5 formation at Hangzhou (48%) and Zhoushan site (68%). Among the emission sectors contributing to the high pollution episode, the major source categories include industrial processing (with contributions ranging between 12.7 and 38.7% at different receptors), combustion source (21.7–37.3%), mobile source (7.5–17.7%) and fugitive dust (8.4–27.3%). Agricultural contribution is also very significant at Zhoushan site (24.5%). In terms of the PM 2.5 major components, it is found that industrial boilers and kilns are the major source contributor to sulfate and nitrate. Volatile emission source and agriculture are the major contributors to ammonia; transport is the largest contributor to elemental carbon. Industrial processing, volatile emissions and mobile source are the most significant contributors to organic carbon. Results show that the Yangtze River Delta region should focus on the joint pollution control of industrial processing, combustion emissions, mobile source emissions, and fugitive dust. Regional transport of air pollution among the cities are prominent, and the implementation of regional joint prevention and control of air pollution will help to alleviate fine particulate matter concentrations under heavy pollution case significantly.

Investigation of Ground-Level Ozone and High-Pollution Episodes in a Megacity of Eastern China.

Differential Optical Absorption Spectroscopy (DOAS) was used for the long-term observation of ground-level ozone (O3) from March 2010 to March 2013 over Shanghai, China. The 1-hour average concentration of O3 was 27.2 ± 17.0 ppbv. O3 level increased during spring, reached the peak in late spring and early summer, and then decreased in autumn and finally dropped to the bottom in winter. The highest monthly average O3 concentration in June (41.1 ppbv) was nearly three times as high as the lowest level recorded in December (15.2 ppbv). In terms of pollution episodes, 56 hourly samples (on 14 separate days) in 2010 exceeded the 1-hour ozone limit of 200 μg/m3 specified by the Grade II of the Chinese Ambient Air Quality Standards (CAAQS, revised GB 3095-2012). Utilizing the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, the primary contribution to high ozone days (HODs) was identified as the regional transportation of volatile organic compounds (VOC) and high concentrations of O3 from the chemical industrial zone in the Jinshan district of Shanghai. HODs showed higher concentrations of HONO and NO2 than non-episode conditions, implying that HONO at high concentration during HODs was capable of increasing the O3 concentration. The photolysis rate of HONO was estimated, suggesting that the larger number of OH radicals resulting from high concentrations of HONO have a considerable impact on ozone concentrations.

The environmental effects of changing speed limits: A quantile regression approach

Two speed management policies were implemented in the metropolitan area of Barcelona aimed at reducing air pollution concentration levels. In 2008, the maximum speed limit was reduced to 80km/h and, in 2009, a variable speed system was introduced on some metropolitan motorways. This paper evaluates whether such policies have been successful in promoting cleaner air, not only in terms of average pollutant levels but also during high and low pollution episodes. To do so, we use a quantile regression approach for fixed effect panel data, which allows us analyzing different scenarios (beyond the average levels). We find that the variable speed system improves air quality with regard to the two pollutants considered here, being most effective when nitrogen oxide levels are not too low and when particulate matter concentrations are below extremely high levels. However, reducing the maximum speed limit from 120/100km/h to 80km/h has no effect – or even a slightly increasing effect – on the two pollutants, depending on the pollution scenario.

Water Soluble Ionic Components in Particulate Matter (PM10) during High Pollution Episode Days at Mohal and Kothi in the North-Western Himalaya, India

Particulate pollutants and their water soluble ionic components were collected and analyzed on the occasion of high pollution episode days in the period 2009 to 2011. Among the water soluble ionic constituents at Mohal (valley base), SO_4 ^(2-) (34%) was the largest contributor; followed by Cl^- (20%), NO_3 ^- (17%), Ca^(2+) (9%), Na+ (7%), NH_4 ^+ (5%), F^- (2%), Zn^(2+) (2%) and Mg^(2+) (1%). While at Kothi (hill slope), Cl– (27%) was the largest contributor; followed by SO_4 ^(2-) (25%), NO_3 ^- (14%), Na^+ (11%), Ca^(2+) (9%), NH_4 ^+ (7%), K^+ (3%), F^- (3%) and Zn^(2+) (1%). The average ratios of NO_3 ^- + Cl^-/SO_4 ^(2-) were 1.08 and 1.64 for Mohal and Kothi, respectively; indicating that a small fraction of HNO_3 and HCl influenced the acidic nature of ions. The mass ratios of NH_4 +/NO_3 ^- and NH_4 +/SO_4 ^(2-) were 0.29, 0.5 and 0.15, 0.28; at Mohal and Kothi, respectively. The ratios were below unity showing the predominance of NH_4NO_3 and (NH_4)_2SO_4 in the atmosphere. The descending order of neutralizing factors were observed as Ca^(2+) ＞ NH_4 ^+ ＞ K^+ ＞ Mg^(2+) assuming that the origin is of a crustal source. The non-sea salt fraction for Mohal was found in the descending order of Cl^-, Ca^(2+) and SO_4 ^(2-), which are more than 50% of the total ions except Mg^(2+) and K^+. While for Kothi, the percentage of Cl^- and SO_4 ^(2-) stood to be more than 50% indicating that these ions are of non-marine origin. The first factor from principal component analysis for Mohal explains 75.59% of the total variance i.e., highly loaded with NH_4 ^+ (0.986), K^+ (0.685), F^- (0.935), Cl^- (0.919) and Zn^(2+) (0.969) indicating influence of anthropogenic activities on PM10 concentration. While at Kothi, the first factor explains 45.41% of the total variance, highly loaded with K^+ (0.981), SO_4 ^(2-) (0.965), NO^(3-) (0.953) and Zn^(2+) (0.948) also indicating influence of anthropogenic activities in the region.

Measurement and Analysis of Fine Particulate Matter (PM2.5) in Urban Areas of Pakistan

In order to assess the extent of air quality within the major urban environments in Pakistan, PM_(2.5) pollutant has been analyzed during the period 2007-2011 in Islamabad; and 2007 to 2008 in Lahore, Peshawar and Quetta (high elevation, 1680 m MSL). Seasonal and diurnal variations of PM_(2.5) mass concentration formation and accumulation within these areas have been analyzed. Air quality monitoring data and meteorological data (both QA/QCed) were obtained from Federal and Provincial Pakistan Environmental Protection Agencies. In Islamabad, the annual average PM_(2.5) mass concentrations were 81.1 ± 48.4 μg/m^3, 93.0 ± 49.9 μg/m^3, 47.8 ± 33.2 μg/m^3, 79.0 ± 49.2 μg/m^3, and 66.1 ± 52.1 μg/m^3 during 2007 to 2011 respectively. Comparison of the four cities during summer 2007 to spring 2008 shows that all the four cities had PM_(2.5) concentration exceeding the Pakistan National Environmental Quality Standards (annual average concentration of 25 μg/m^3; and 24 hourly average concentration of 40 μg/m^3) for ambient air. During the same time period, the highest seasonal PM_(2.5) mass concentrations for Islamabad were observed as 98.5 μg/m^3 during spring 2008; 150.4 ± 87.9 μg/m^3; 104.1 ± 51.1 μg/m^3 and 72.7 ± 55.2 μg/m^3 for Lahore, Peshawar, and Quetta during fall 2007, respectively. Wind speed and temperature have a negative correlation with the mass concentration of PM_(2.5). Diurnal profile for all the cities suggests an association of PM_(2.5) with vehicular traffic. Back trajectory analysis conducted using the NOAA HYSPLIT model indicates that air trajectories, during high pollution episodes, influencing the urban regions commonly originate from either western India, especially in summer as part of the prevailing monsoon circulation; or are located in eastern Afghanistan. The source areas in Western India i.e., states of Gujarat, Rajasthan and Punjab have high concentration of industrial activities and crop residue burning, and are likely sources of enhanced PM_(2.5) concentrations, in addition to the local sources.

Peat-fire-related air pollution in Central Kalimantan, Indonesia

The past decade marked record high air pollution episodes in Indonesia. In this study, we specifically focus on vegetation fires in Palangkaraya located near a Mega Rice Project area in Indonesia. We analyzed various gaseous air pollution data such as particulate matter (PM10), SO2, CO, O3, and NO2 study region. We also conducted elemental analysis at two different sites. Results from 2001 to 2010 suggested the longest hazardous air pollution episode during 2002 lasting about 80 days from mid-August to late-October. Maximum peak concentrations of PM10, SO2, CO, and O3 were also observed during 2002 and their values reached 1905, 85.8, 38.3, and 1003 × 10−6 gm−3 respectively. Elemental analysis showed significant increase in concentrations during 2011 and 2010. Satellite retrieved fires and weather data could explain most of the temporal variations. Our results highlight peat fires as a major contributor of photochemical smog and air pollution in the region.

A Modeling Study of Boundary Layer Wind Flow over Tehran Region during a High Pollution Episode

The influence of a mega-city on the atmospheric boundary layer wind field was examined in the complex-terrain, semi-arid Tehran region using the Pennsylvania State University/National Center for Atmospheric Research fifth-generation Mesoscale Model (MM5) during a high pollution period. In addition, model sensitivity studies were conducted to evaluate the performance of the urban canopy and urban soil model SM2-U (3D) parameterization on the wind field. The topographic flows and urban effects were found to play important roles in modulating the wind field, and the urbanized areas exerted important local effects on the boundary layer meteorology. An emission inventory of heat generation was developed and updated for 2005 in this work. By using a detailed methodology, we calculated spatial and temporal distributions of the anthropogenic heat flux (Qf) for Tehran during 2005. Wintertime Qf is found larger than summertime Qf, which reflects the importance of heating emissions from buildings and traffic during cold and warm periods respectively. Different urban parameterizations were used as a tool to investigate the modifications induced by the presence of an urban area in the area of interest. It is found that, for local meteorological simulations, the drag-force approach (DA) coupled with an urban soil model (SM2-U) is preferable to the roughness approach (RA) coupled with a slab soil model. The comparisons indicated that the most important features of the wind field, in urban areas are well reproduced by the DA-SM2-U configuration with the anthropogenic heat flux being taken into account. This modeling option showed that the suburban part of the city is dominated by topographic flows whereas the center and south of Tehran are more affected by urban heat island (UHI) forcing especially during the night in studied episodes.

An integrated process rate analysis of a regional fine particulate matter episode over Yangtze River Delta in 2010

A high PM2.5 pollution episode was detected in Shanghai in November 2010. The integrated process rate method, an advanced diagnostic tool, was applied to account for the contribution of different atmospheric processes during the high pollution episode in the Yangtze River Delta region (YRD). The PM2.5 process analysis indicates that the emission of fine particles is the dominant source of high surface PM2.5 concentrations in the major cities of the YRD like Shanghai, Nanjing, and Hangzhou, following horizontal transportation and aerosols. The PM2.5 concentration could be reduced due to vertical advection and diffusion from lower levels to the upper air. The aerosols process such as homogeneous nucleation and condensation producing PM2.5 occurs throughout the PBL layer in urban areas, causing vertical transport from upper levels down to the surface layer. The aerosols process is much more significant in a downwind rural and coastal site like Zhoushan than in the urban areas. The PM2.5 change initiated by both horizontal transport and vertical transport is much stronger at 40–2000 m height than in the surface layer, while the PM2.5 change caused by horizontal diffusion is very small. Dry deposition can significantly reduce concentration of the particulates in the surface level of the atmosphere, and wet deposition can remove the particles in the planetary boundary layer (PBL). The cloud processes can either increase PM2.5 due to the aqueous-phase oxidation of SO2 and NO2 or remove PM2.5 due to cloud scavenging. Solar radiation and humidity are more important to secondary pollution, and they are the significant external factors affecting the chemical reactions among sulfur dioxide, nitrogen oxides, ammonia, volatile compounds and fine particles.