Concentrations Of Primary Pollutants Research Articles

Trends in secondary inorganic particles in Hong Kong, 1995–2020

Hong Kong's secondary inorganic aerosol has changed over the last quarter century. It is important to assess changes in particle formation with a particular aim to assess its relationship with shifting emissions and regulatory policy over a period when air quality improved along with better visibility, likely the result of a decrease in ammonium containing aerosols. The concentrations of primary air pollutants, PM10, SO2 and NOx, declined over recent decades, while secondary pollutants SO42− and NH4+ paralleled these decreases, although NO3− shows an indistinct trend, yet the overall the sum of SO42−, NO3− and NH4+ one of decline. The importance of an automotive source led to increases in the NO3−:SO42− ratio. There is insufficient NH3 to neutralise the acid available from SO42− and NO3−, a deficit especially noticeable in June and July, when there is often not enough NH3 to form (NH4)2SO4, (NH4)HSO4 and NH4NO3 leaving free acid. Spatial variability between sites is less for aerosol SO42− and NO3− than for their precursors, and always more variable for nitrogen than sulfur. The extent of the transformation to the oxidized forms is increasing in Hong Kong, likely the result of less local SO2, and a greater proportion of SO42− transported long distances into the region. It is possible that a changing climate could lead to increased autumn ozone concentrations by 2030, so contributing to further oxidation of precursors to aerosol components. The increasing aerosol contribution via regional transport requires continued cooperation in regulatory policies to improve air quality across the Pearl River Delta.

Simulation Analysis of the Impact of COVID-19 Pandemic Control on Air Quality in Henan Province based on Machine Learning Algorithm

To reduce the risks of COVID-19 on society and the health of the general public, necessary prevention and control measures were implemented throughout China in 2020. Consequently, air quality was greatly improved due to lower emissions. However, the improvement of air quality could also be closely related to meteorological conditions. During quarantine (January 27 to February, 2020), reductions were observed in the concentration of all air pollutants in Henan Province (PM2.5, PM10, SO2, CO, and NO2 decreased by 36.89%, 34.18%, 19.43%, 29.85%, and 58.51%, respectively) relative to measurements taken from January 1 to 26, 2020. The only exception was for the concentration of O3, which increased by 69.64%. This study evaluates the importance of meteorological conditions in air pollution, through simulation with a long-and-short-term memory network (LSTM) and a machine learning algorithm. Results show that meteorological conditions play a crucial role in air pollutant formation. Given favorable meteorological factors, the concentrations of pollutants could be reduced by 15%-30%, while the reduction due to anthropogenic emission control ranges from 6%-40%. During the epidemic, meteorological conditions and human emissions accounted for 34.84% and 34.81% of the increase in O3 concentration, respectively. The results show that primary pollutant concentrations are more sensitive to the intensity of anthropogenic emissions. However, secondary pollutants are more dependent on meteorological factors. Furthermore, a nonlinear relationship has been identified between O3 concentration and to emission intensity. Further investigation into the causes of the rise in O3 concentration is necessary to gain a greater understanding and better control of particulate matter and O3 pollution.

Aircraft-based observation of gaseous pollutants in the lower troposphere over the Beijing-Tianjin-Hebei region

To investigate the spatial and vertical distribution of atmospheric pollutants (SO2, NOx, CO and O3), aircraft-based measurements (model: Yun-12, 12 flights, 27 h total flight time) were conducted from near the surface up to 2400 m over the Beijing-Tianjin-Hebei (BTH) region between June 17th and July 22nd 2016. The results showed that high concentrations of primary gaseous pollutants (SO2, NOx, CO) were generally present in Beijing, Tianjin, Langfang and Tangshan areas, while high values of O3 frequently appeared in areas far from the city. The flights at noon and dusk measured higher O3 concentrations at 600 m and lower O3 concentrations at higher altitudes, implying a strong influence by photochemical production. Back trajectory analysis suggested that the high levels of gaseous pollutants, especially at 600 m, were associated with pollution sources transported from the southerly direction during the observation period. The first simultaneous vertical distribution measurements using aircraft and tethered balloon were conducted in Gaocun (a rural site between Beijing and Tianjin) on June 17th. The results indicated that an inversion layer at the top of the planetary boundary layer (PBL) significantly suppressed vertical exchange through the PBL and resulted in a “two-layer” vertical distribution of pollutants above and below the PBL. Additionally, a residual high O3 layer (79.9 ± 2.5 ppb, 500–1000 m) was observed above the PBL, and it contributed to the surface peak O3 level at noon through downward transport along with the opening up of the PBL. These results indicate that coupled effects of horizontal and vertical transport should be investigated in future studies to improve the chemical transport models used to study the vertical distribution and regional transport over the BTH region.

Numerical model for primary and secondary air pollutants emitted from an area and point source in an urban area with chemical reaction and removal mechanisms

A complete numerical mathematical model is presented to study the consequence of chemical reaction and removal mechanisms on the pollutant radiated from the point source on the boundary of the city region. Life span of secondary pollutant is more than the primary pollutant and it is dangerous to human being and its surroundings so in this model, we are considering secondary and primary pollutants. The realistic wind velocity and eddy diffusivity profiles are considered in this model. The intricate problem is simplified numerically with Crank-Nicolson finite difference technique. In stable and neutral atmospheric conditions primary and secondary pollutant concentration is maximum on the boundary of point source and as well as at bottom surface.

The Impact of COVID-19 Partial Lockdown on Primary Pollutant Concentrations in the Atmosphere of Rio de Janeiro and São Paulo Megacities (Brazil).

As COVID-19 spread all over the world, most of the countries adopted some kind of restrictions to avoid the collapse of health systems. In Brazil, São Paulo and Rio the Janeiro, the two most populated cities in the country, were the first to determine social distancing. In this study, the impact of the social distancing measures on the concentrations of the three main primary air pollutants (PM10, NO2 and CO) was analyzed. CO levels showed the most significant reductions (up to 100%) since it is related to light-duty vehicular emissions. NO2 also showed reductions (9.1%–41.8%) while PM10 levels were only reduced in the 1st lockdown week. The decrease of pollutants was not directly proportional to the vehicular flux reduction, because it depends on other factors such as the transport of air masses from industrial and rural areas. The differences observed can be explained considering the fleet characteristics in the two cities and the response of the population to the social distancing recommendations.

Comparison of Mobile and Fixed-Site Black Carbon Measurements for High-Resolution Urban Pollution Mapping.

Urban concentrations of black carbon (BC) and other primary pollutants vary on small spatial scales (<100m). Mobile air pollution measurements can provide information on fine-scale spatial variation, thereby informing exposure assessment and mitigation efforts. However, the temporal sparsity of these measurements presents a challenge for estimating representative long-term concentrations. We evaluate the capabilities of mobile monitoring in the represention of time-stable spatial patterns by comparing against a large set of continuous fixed-site measurements from a sampling campaign in West Oakland, California. Custom-built, low-cost aerosol black carbon detectors (ABCDs) provided 100 days of continuous measurements at 97 near-road and 3 background fixed sites during summer 2017; two concurrently operated mobile laboratories collected over 300 h of in-motion measurements using a photoacoustic extinctiometer. The spatial coverage from mobile monitoring reveals patterns missed by the fixed-site network. Time-integrated measurements from mobile lab visits to fixed-site monitors reveal modest correlation (spatial R2 = 0.51) with medians of full daytime fixed-site measurements. Aggregation of mobile monitoring data in space and time can mitigate high levels of uncertainty associated with measurements at precise locations or points in time. However, concentrations estimated by mobile monitoring show a loss of spatial fidelity at spatial aggregations greater than 100 m.

Near-road vehicle emissions air quality monitoring for exposure modeling

Exposure to vehicular emissions has been linked to numerous adverse health effects. In response to the arising concerns, near-road monitoring is conducted to better characterize the impact of mobile source emissions on air quality and exposure in the near-road environment. An intensive measurement campaign measured traffic-related air pollutants (TRAPs) and related data (e.g., meteorology, traffic, regional air pollutant levels) in Atlanta, along one of the busiest highway corridors in the US. Given the complexity of the near-road environment, the study aimed to compare two near-road monitors, located in close proximity to each other, to assess how observed similarities and differences between measurements at these two sites inform the siting of other near-road monitoring stations. TRAP measurements, including carbon monoxide (CO) and nitrogen dioxide (NO2), are analyzed at two roadside monitors in Atlanta, GA located within 325 m of each other. Both meteorological and traffic conditions were monitored to assess the temporal impact of these factors on traffic-related pollutant concentrations. The meteorological factors drove the diurnal variability of primary pollutant concentration more than traffic count. In spite of their proximity, while the CO and NO2 concentrations were correlated with similar diurnal variations, pollutant concentrations at the two closely sited monitors differed, likely due to the differences in the siting characteristics reducing the dispersion of the primary emissions out of the near-road environment. Overall, the near-road TRAP concentrations at all sites were not as elevated as seen in prior studies, supporting that decreased vehicle emissions have led to significant reductions in TRAP levels, even along major interstates. Further, the differences in the observed levels show that use of single near-road observations will not capture pollutant levels representative of the local near-road environment and that additional approaches (e.g., air quality models) are needed to characterize exposures.

Impact of COVID-19 Event on the Air Quality in Iran

The first novel coronavirus case was confirmed in Iran in mid-February 2020. This followed by the enforcement of lockdown to tackle this contagious disease. This study aims to examine the potential effects of the COVID-19 lockdown on air quality in Iran. From 21st March to 21st April in 2019 and 2020, The Data were gathered from 12 air quality stations to analyse six criteria pollutants, namely O3, NO2, SO2, CO, PM10, and PM2.5. Due to the lack of ground-level measurements, using satellite data equipped us to assess changes in air quality during the study on Iranian megacities, especially in Tehran, i.e., the capital of Iran. In this city, concentrations of primary pollutants (SO2 5–28%, NO2 1–33%, CO 5–41%, PM10 1.4–30%) decreased with spatial variations. Although, still SO2, NO2, and PM10 exceeded the WHO daily limit levels for 31 days, 31 days, and four days, respectively. Conversely, O3 and PM2.5 increased by 0.5–103% and 2–50%. In terms of the national air quality, SO2 and NO2 levels decreased while AOD increased during the lockdown. Unfavourable meteorological conditions hindered pollutant dispersion. Moreover, reductions in the height of planetary boundary layer and rainfall were observed during the lockdown period. Despite the adverse weather conditions, a decrease in primary pollutant levels, confirms the possible improvements on the air quality in Iran.

Effect of Fireworks, Chinese New Year and the COVID-19 Lockdown on Air Pollution and Public Attitudes

Concentrations of primary air pollutants are driven by emissions and weather patterns, which control their production and dispersion. The early months of the year see the celebratory use of fireworks, a week-long public holiday in China, but in 2020 overlapped in Hubei Province with lockdowns, some of > 70 days duration. The urban lockdowns enforced to mitigate the COVID-19 pandemic give a chance to explore the effect of rapid changes in societal activities on air pollution, with a public willing to leave views on social media and show a continuing concern about the return of pollution problems after COVID-19 restrictions are lifted. Fireworks typically give rise to sharp peaks in PM2.5 concentrations, though the magnitude of these peaks in both Wuhan and Beijing has decreased under tighter regulation in recent years, along with general reductions in pollutant emissions. Firework smoke is now most evident in smaller outlying cities and towns. The holiday effect, a reduction in pollutant concentrations when normal work activities are curtailed, is only apparent for NO2 in the holiday week in Wuhan (2015–2020), but not Beijing. Lockdown in Wuhan was characterised by decreases in NO2, along with more subtle changes in particulate matter and other pollutants. Ozone noticeably increases as there is less NO available for titration, but such change may not be widespread geographically. Beijing, where restrictions were less stringent, showed some improvement in air quality, though this is more difficult to detect, even within the 5th Ring Road.

Why did ozone levels remain high in Rio de Janeiro during the Brazilian truck driver strike?

On May 21st, 2018, Brazilian truck drivers began a 10-day strike to protest high diesel prices. This was Brazil's longest trucker strike, and within a few days, gas stations ran out of fuel, drivers waited in line for hours to fuel their cars, transport was severely affected, and airports began cancelling flights. In Rio de Janeiro, the second largest city in Brazil, Air Quality Indexes (AQI) during the strike showed that the high ozone concentrations, determined in three monitoring stations (Irajá, Bangu and Campo Grande), led to “Moderate” and “Unhealthy” AQI in spite of reduced primary pollutant concentrations: nitrogen oxides (NOx = NO + NO2), particulate matter with a diameter < 10 μm, carbon monoxide (CO) and non-methane hydrocarbons (NMHC). In this work, the causes of the high ozone concentrations were analyzed. Criteria pollutant concentrations, as well as meteorological parameters, were compiled for the interval of May 14th to June 6th, 2018. The NMHC/NOx and NO2/NO ratios indicated that the most likely cause of the high ozone levels was the reduced NOx concentrations under VOC-limited conditions (where VOC stands for volatile organic compounds). VOC speciation also showed that the vehicular fleet composition was altered during the strike. Considering that the legislation regarding emissions and air quality standards is being revised in Brazil and other countries, these results show that the control and speciation of VOC emissions is a desirable strategy, while NOx-focused strategies to reduce O3 in VOC-limited areas should be evaluated carefully.

Analytical Study of Fuel Switching from Heavy Fuel Oil to Natural Gas in clay brick factories at Arab Abu Saed, Greater Cairo

Arab Abu Saed area in Giza governorate, south to Cairo contains more than 228 clay brick kilns represent the largest cluster of brickworks in Egypt. Burning of Heavy Fuel Oil (HFO) in such kilns is the main source of air pollution in the surrounding locations. In this study, investigation of switching the fuel used in brick kilns from (HFO) to Natural Gas (NG) is carried out and the pollution loads are assessed in both cases. In addition, two Gaussian dispersion plume models are employed to estimate the concentration of primary pollutants; PM10, SO2, and NO2 at seven locations in the vicinity of Arab Abu Saed to determine the most adversely affected locations. Statistical analysis is applied to evaluate the correlation and conformity of the results of both models. Results show that using of NG leads to a significant reduction of pollution loads of PM10, SO2 and NO2 reaches 96%, 72%, and 24% respectively. In addition, the reduction of naturally occurring radionuclides in air is analyzed. Activity concentrations of Ra-226, Th-232 and K-40 in Bq/l for HFO were measured using HPGe detector for six HFO samples. Exposure due to air submersion of naturally occurring radionuclides in the study area leads to annual equivalent dose ranged between 2.16 mSv/y (received by Uterus) and 14 mSv/y (received by skin), and average effective dose 2.65 mSv/y which represent valuable exposure.

Ambient air quality changes after stubble burning in rice-wheat system in an agricultural state of India.

Ground-based ambient air monitoring was conducted to assess the contribution of crop residue burning of wheat (Triticum aestivum) and rice (Oriza sativa) at different locations in three districts (Kaithal, Kurukshetra, and Karnal) of the agricultural state of Haryana in India for two successive years (2016 and 2017). The Air Quality Index (AQI) and concentration of primary pollutants (SOx, NOx, and PM2.5) were determined in rice and wheat crop season, for burning and non-burning periods. During crop residue burning periods, concentrations of SOx, NOx, and PM2.5 were exceeded the NAAQS values by 78%, 71%, and 53%, respectively. A significant increase in SOx (4.5 times), NOx (3.8 times), and PM2.5 concentration (3.5 times) was observed in stubble burning periods as compared to pre-burning (p < 0.05). A positive and significant correlation among the three pollutant concentrations was observed (p < 0.01). The AQI of KA site in Karnal district fell in severely polluted category during 2016 for rice as well as wheat residue burning period, and of KK site in Kaithal during wheat residue burning in year 2017. Results of present study indicate a remarkable increase in pollutant concentration (SOx, NOx, and PM2.5) during the crop residue burning periods. To the best of our knowledge, the outcomes of present study in this region have not been reported in earlier reports. Hence, there is an urgent need to curb air pollution by adopting sustainable harvesting technologies and management of residues.

Study the environmental effects of private electrical generators for some locations in Kirkuk city

Two traces of environmental pollution from private electrical generators have been dealt with within the study in Kirkuk city by choosing determined regions. First trace was contain computing concentrations of primary air pollutants that emitted from electrical generators which include (CO,CO2, NO,HC), then compared it with Iraqi standards for pollutants that emitted from exhaust gas of electrical generators, higher concentration of CO gas was found in April month from generators of Asra and Mafqodin which was 4.4ppm higher than the Iraqi standards ,generally higher concentration of other pollutants were found also. Second trace was includes measuring noise pollution from these generators, higher value of LAeq was in Raheem Awa region 102.55dBA which was exceeding the limits from EPA standards which determined 80dBA as higher value in residential regions, and also exceeding WHO standards which determined higher limits of noise 50-55dBA , while lower value of LAeq was in Tisin region 91.02dBA because the generators in this region have cover absorbent to noise as compared to other generators in the study.

Characteristics of marine shipping emissions at berth: profiles for particulate matter and volatile organic compounds

Abstract. Emissions from ships at berth play an important role regarding the exposure of high density human populations to atmospheric pollutants in port areas; however, these emissions are not well understood. In this study, volatile organic compounds (VOCs) and particle emissions from 20 container ships at berth were sampled and analyzed during the “fuel switch” period at Jingtang Port in Hebei Province, China. VOCs and particles were analyzed using a gas chromatography-mass spectrometer (GC-MS) and a single particle aerosol mass spectrometer (SPAMS), respectively. VOC analysis showed that alkanes and aromatics, especially benzene, toluene and heavier compounds e.g., n-heptane, n-octane and n-nonane, dominated the total identified species. Secondary organic aerosol (SOA) yields and ozone (O3) forming potential were 0.017 ± 0.007 g SOA g−1 VOCs and 2.63 ± 0.37 g O3 g−1 VOCs, respectively. Both positive and negative ion mass spectra from individual ships were derived and the intensity of specific ions were quantified. Results showed that elemental carbon (35.74 %), elemental carbon–organic carbon mixtures (33.95 %) and Na-rich particles (21.12 %) were major classes, comprising 90.7 % of the particles observed. Particles from ship auxiliary engines were in the 0.2 to 2.5 µm size range, with a peak occurring at around 0.4 µm. The issue of using vanadium (V) as tracer element was examined, and it was found that V was not a proper tracer of ship emissions when using low sulfur content diesel oil. The average percentage of sulfate particles observed in shipping emissions before and after switching to marine diesel oil remained unchanged at 24 %. Under certain wind conditions, when berths were upwind of emission sources, the ratios before and after 1 January were 35 and 27 % respectively. The impact of atmospheric stability was discussed based on PM2.5 and primary pollutant (carbon monoxide) concentration. With a background of frequent haze episodes and complex mechanisms of particulate accumulation and secondary formation, the impact of atmospheric stability is believed to have been weak on the sulfate contribution from shipping emissions. The results from this study provide robust support for port area air quality assessment and source apportionment.

Atmospheric pollution over the eastern Mediterranean during summer – a review

Abstract. The eastern Mediterranean (EM) is one of the regions in the world where elevated concentrations of primary and secondary gaseous air pollutants have been reported frequently, mainly in summer. This review discusses published studies of the atmospheric dispersion and transport conditions characterizing this region during the summer, followed by a description of some essential studies dealing with the corresponding concentrations of air pollutants such as ozone, carbon monoxide, total reactive nitrogen, methane, and sulfate aerosols observed there. The interlaced relationship between the downward motion of the subsiding air aloft induced by global circulation systems affecting the EM and the depth of the Persian Trough, a low-pressure trough that extends from the Asian monsoon at the surface controlling the spatiotemporal distribution of the mixed boundary layer during summer, is discussed. The strength of the wind flow within the mixed layer and its depth affect much the amount of pollutants transported and determine the potential of the atmosphere to disperse contaminants off their origins in the EM. The reduced mixed layer and the accompanying weak westerlies, characterizing the summer in this region, led to reduced ventilation rates, preventing an effective dilution of the contaminants. Several studies pointing at specific local (e.g., ventilation rates) and regional peculiarities (long-range transport) enhancing the build-up of air pollutant concentrations are presented. Tropospheric ozone (O3) concentrations observed in the summer over the EM are among the highest over the Northern Hemisphere. The three essential processes controlling its formation (i.e., long-range transport of polluted air masses, dynamic subsidence at mid-tropospheric levels, and stratosphere-to-troposphere exchange) are reviewed. Airborne campaigns and satellite-borne initiatives have indicated that the concentration values of reactive nitrogen identified as precursors in the formation of O3 over the EM were found to be 2 to 10 times higher than in the hemispheric background troposphere. Several factors favor sulfate particulate abundance over the EM. Models, aircraft measurements, and satellite-derived data have clearly shown that sulfate has a maximum during spring and summer over the EM. The carbon monoxide (CO) seasonal cycle, as obtained from global background monitoring sites in the EM, is mostly controlled by the tropospheric concentration of the hydroxyl radical (OH) and therefore demonstrates high concentrations over winter months and the lowest concentrations during summer when photochemistry is active. Modeling studies have shown that the diurnal variations in CO concentration during the summer result from long-range CO transport from European anthropogenic sources, contributing 60 to 80 % of the boundary-layer CO over the EM. The values retrieved from satellite data enable us to derive the spatial distribution of methane (CH4), identifying August as the month with the highest levels over the EM. The outcomes of a recent extensive examination of the distribution of methane over the tropospheric Mediterranean Basin, as part of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) program, using model simulations and satellite measurements, are coherent with other previous studies. Moreover, this methane study provides some insight into the role of the Asian monsoon anticyclone in controlling the variability of CH4 pollutant within mid-to-upper tropospheric levels above the EM in summer.

Ecophysiological evaluation of tree species for biomonitoring of air quality and identification of air pollution-tolerant species

Identification of tree species that can biologically monitor air pollution and can endure air pollution is very much important for a sustainable green belt development around any polluted place. To ascertain the species, ten tree species were selected on the basis of some previous study from the campus of the University of Burdwan and were studied in the pre-monsoon and post-monsoon seasons. The study has been designed to investigate biochemical and physiological activities of selected tree species as the campus is presently exposed to primary air pollutants and their impacts on plant community were observed through the changes in several physical and biochemical constituents of plant leaves. As the plant species continuously exchange different gaseous pollutants in and out of the foliar system and are very sensitive to gaseous pollutants, they serve as bioindicators. Due to air pollution, foliar surface undergoes different structural and functional changes. In the selected plant species, it was observed that the concentration of primary air pollutants, proline content, pH, relative water holding capacity, photosynthetic rate, and respiration rate were higher in the pre-monsoon than the post-monsoon season, whereas the total chlorophyll, ascorbic acid, sugar, and conductivity were higher in the post-monsoon season. From the entire study, it was observed that the concentration of sulfur oxide (SO x ), nitrogen oxide (NO x ), and suspended particulate matter (SPM) all are reduced in the post-monsoon season than the pre-monsoon season. In the pre-monsoon season, SO x , NO x , and SPM do not have any significant correlation with biochemical as well as physiological parameters. SPM shows a negative relationship with chlorophyll 'a' (r=-0.288), chlorophyll 'b' (r=-0.267), and total chlorophyll (r=-0.238). Similarly, chlorophyll a, chlorophyll b, and the total chlorophyll show negative relations with SO x and NO x (p<0.005) during the post-monsoon season. Proline shows a positive relationship with SO x in the pre-monsoon season whereas in the post-monsoon season proline content shows a positive relationship with both SO x and NO x . The present study facilitates to screen eight sensitive and two moderately tolerant tree species according to their air pollution tolerance index (APTI) values.

Changes in regional meteorology induced by anthropogenic heat and their impacts on air quality in South China

Abstract. Anthropogenic heat (AH) emissions from human activities can change the urban circulation and thereby affect the air pollution in and around cities. Based on statistic data, the spatial distribution of AH flux in South China is estimated. With the aid of the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem), in which the AH parameterization is developed to incorporate the gridded AH emissions with temporal variation, simulations for January and July in 2014 are performed over South China. By analyzing the differences between the simulations with and without adding AH, the impact of AH on regional meteorology and air quality is quantified. The results show that the regional annual mean AH fluxes over South China are only 0.87 W m−2, but the values for the urban areas of the Pearl River Delta (PRD) region can be close to 60 W m−2. These AH emissions can significantly change the urban heat island and urban-breeze circulations in big cities. In the PRD city cluster, 2 m air temperature rises by 1.1° in January and over 0.5° in July, the planetary boundary layer height (PBLH) increases by 120 m in January and 90 m in July, 10 m wind speed is intensified to over 0.35 m s−1 in January and 0.3 m s−1 in July, and accumulative precipitation is enhanced by 20–40 % in July. These changes in meteorological conditions can significantly impact the spatial and vertical distributions of air pollutants. Due to the increases in PBLH, surface wind speed and upward vertical movement, the concentrations of primary air pollutants decrease near the surface and increase in the upper levels. But the vertical changes in O3 concentrations show the different patterns in different seasons. The surface O3 concentrations in big cities increase with maximum values of over 2.5 ppb in January, while O3 is reduced at the lower layers and increases at the upper layers above some megacities in July. This phenomenon can be attributed to the fact that chemical effects can play a significant role in O3 changes over South China in winter, while the vertical movement can be the dominant effect in some big cities in summer. Adding the gridded AH emissions can better describe the heterogeneous impacts of AH on regional meteorology and air quality, suggesting that more studies on AH should be carried out in climate and air quality assessments.

Quantifying stability influences on air pollution in Lanzhou, China, using a radon-based “stability monitor”: Seasonality and extreme events

A recently-developed radon-based technique is modified to quantify the seasonal influences of atmospheric stability on urban emissions in Lanzhou, China, based on 11 months of observations at three sites with contrasting pollution characteristics. Near-surface concentrations of primary (CO, SO2, NOx) and secondary (O3) gas phase pollutants responded to changing atmospheric stability in markedly different ways in winter and summer, primarily because monsoonal fetch changes strongly influenced the distance between measurement sites and their nearest upwind pollutant sources, but also due to mean diurnal changes in mixing depth. Typically, morning peak primary pollution concentrations increased by a factor of 2–5 from the most well-mixed to stable conditions, whereas nocturnal ozone concentrations reduced with increasing stability due to surface loss processes and the progressively reduced coupling between the nocturnal boundary layer and overlying free atmosphere. The majority of pollution exceedance events (cf. China National Air Quality Standard guideline values) occurred in winter, when all measurement stations were downwind of the city's main pollution sources, and were directly attributed to morning periods and stable atmospheric conditions. In the sheltered valley region of Lanzhou, extremes of winter nocturnal stability states represented a change in mean nocturnal wind speed of only 0.25 m s−1 (from 0.6 to 0.85 m s−1). Daily-integrated PM10 concentrations increased by a factor of 2 in winter from the most well-mixed to stable conditions, and were usually above guideline values at the industrial and residential sites for all atmospheric stability conditions. In summer, however, daily mean PM10 exceedances usually only occurred at the industrial site, under stable conditions. Finally, a simple model – based on mean radon concentrations between 1900 and 0400 h – is proposed to predict haze conditions in the city prior to commencement of the peak morning commuting time.

Effects of building–roof cooling on the flow and dispersion of reactive pollutants in an idealized urban street canyon

This study investigated the characteristics of the flow and dispersion of reactive pollutants in three-dimensional idealized street canyons in the presence of building-roof cooling to provide implications in how a green-roof system contributes to mitigating of pedestrian exposure to near-roadway air pollution in street canyons. The pollutant chemistry was simulated using a coupled CFD-chemistry model. In the presence of building-roof cooling, winds and temperature fields inside the building canopy of the street canyon were significantly modified. Building-roof cooling, intensified the street-canyon vortex strength (up to 26.6% in downdraft, 10.4% reverse flow, and 7.7% in updraft). Building-roof cooling also decreased air temperature in the street canyon by supplying cooler air near the building roof. The changes in the in-canopy distributions of primary pollutants (NOX, VOCs and CO) due to building-roof cooling were mainly caused by the modified mean flow rather than the chemical reactions. High concentrations of primary pollutants occurred near the upwind building because the reverse flows were dominant at street level, making this area the downwind region of emission sources. Ozone concentrations were lower than the background concentration near the ground, where NOX concentrations were high. Building-roof cooling decreased primary pollutant concentrations by approximately −2.4% compared to those under non-cooling conditions. By contrast, building-roof cooling increased O3 concentrations by about 1.1% by reducing NO concentrations in the street canyon compared to concentrations under non-cooling conditions.

Traffic-related Air and Noise Pollution, Birth Outcomes and Infant Mortality in London

Introduction Traffic pollution comprises toxic air pollutants and noise. Air pollution has been associated with infant mortality, and there is also evidence for small effects on birth weight. Research on noise and birth outcomes is limited, but an association with low birthweight is suggested. This study investigates traffic-related air and noise pollution exposures in relation to birth outcomes and infant mortality. Methods The study population comprises 882713 live births and 5452 stillbirths in the Greater London area from 2003-2010. Monthly concentrations of primary traffic air pollutants (NO2, NOx, exhaust and non-exhaust PM2.5 and PM10) and regional/urban background air pollutants (Ozone, and total PM2.5 and PM10) have been estimated using a dispersion model at 20m x 20m resolution. Time-weighted average air pollution estimates at address-level have been calculated for pregnancy and post-natal time windows. Annual road traffic noise levels have been modeled at address-level using the TRAffic Noise EXposure (TRANEX) model. We are analysing the relationship between air pollutant/noise exposures and birth weight, small-for-gestational-age (SGA), stillbirth and infant mortality, adjusting for potential confounders (e.g. maternal age, smoking and deprivation). Results Mean time-weighted average pregnancy exposures were 75μg/m3 for NOx, 15μg/m3 for PM2.5 and 24μg/m3 for PM10, and mean noise exposures were 58dB (day-time) and 53dB (night-time). Preliminary results suggest that traffic-related air pollution and noise exposures during pregnancy are independently associated with reduced mean birth weight and elevated risk of SGA. Conclusions The study is in progress and will be the largest to date examining environmental noise exposures and birth outcomes. This study combines highly spatially refined address-level exposure assessment for both noise and air pollutants, and will improve understanding of the relative influences of these co-exposures upon fetal/infant health.