Photochemical Smog Pollution Research Articles

The potential impact of biogenic volatile organic compounds (BVOCs) from terrestrial vegetation on a Mediterranean area using two different emission models

Biogenic Volatile Organic Compounds (BVOCs) emitted from vegetation are precursors of ozone (O3), photochemical oxidants and secondary organic aerosols (SOA) in the lower troposphere. The interaction between urban polluted air plumes originated along the coasts of the Mediterranean basin with biogenic emission occurring inland contributes to the occurrence of exceedances of the air quality standards for O3 and fine suspended particles (PM10, PM2.5). This interaction is favoured by prevailing sea-land breeze circulation during persistent high-pressure conditions. The actual contribution of BVOC to photochemical pollution is still uncertain because the approaches used to assess the emissions from terrestrial vegetation are quite different. There is some evidence in literature that BVOC emissions from Mediterranean vegetation is not accurately estimated by models based on the plant functional types (PFT) approach. To investigate these issues, a Plant Specific Emission Model (PSEM) was developed and applied to the Campania region in Southern Italy, for which a detailed vegetation inventory has been built. BVOC emission maps estimated by PSEM were compared with those generated using a PFT methodology, evidencing significant differences. BVOC emissions from the two models were then used to predict the concentrations of precursors and products of photochemical smog pollution over the Gulf of Naples (Italy) using a chemical-transport model. Simulations were performed during a period characterised by high pressure conditions that favour an enhanced O3 production under a sea-breeze circulation regime. VOCs concentration profiles predicted by the two models were compared with field data collected over Mount Vesuvius using a tethered balloon coupled with a PTR-MS. The results proved the better capability of PSEM to predict the concentrations of many BVOCs, including isoprene and some of its primary oxidation products over the measuring site, and suggested the significant potential of BVOC emission to produce SOA over the gulf of Naples.

Comprehensive diagnosis model of environmental impact caused by expressway vehicle emission.

With the rapid development of the economy, the expressway has been used as a main mode of transportation due to its function to meet traffic demand of people and thus has been given full attention. But, at the same time, it has gradually become the main cause of pollution of traffic environment. To clarify the degree of pollution caused by expressway vehicle and improve the expressway pollution diagnosis system, upon the notion of low-carbon transportation, this paper divides expressway environmental pollution into four types: air pollution, photochemical smog pollution, noise pollution, and vibration pollution, and analyzes each of them, respectively. Then, a comprehensive diagnosis model of environmental pollution caused by running vehicles will be built. This paper monitors the pollution intensity on different spots on the expressway to obtain the single-vehicle factors of various pollutants of the motor vehicles. Combined with the geographic information system, this puts forward the diagnosis methods in terms of the environmental "air pollution," "photochemical smog pollution," "noise pollution" and "vibration pollution" caused by the expressway vehicles, respectively, and further establishes a diagnosis model of vehicle pollution corresponding to the characteristics of the expressway. The result of the case study on the actual monitoring data of six expressways in Jiangsu Province shows that the pollution diagnosis values of six expressways are all between (0.4, 0.6] which symbolizes "slight pollution." The research results can provide technical support for monitoring of environmental pollution caused by expressway more comprehensively and reasonably, and provide data support for formulating effective control strategies.

Collaborative removal of NOx and toluene in flue gas driven by aerobic denitrifying biotrickling filter

Nitrogen oxides (NOx) and volatile organic compounds (VOCs) may cause ozone formation and photochemical smog pollution, which may damage to human health and ecological environment seriously. An aerobic Denitrifying BioTrickling Filter (DBTF) for collaborative removal of nitrogen oxides (NOx) and toluene in flue gas was investigated. NOx and toluene removal efficiency were up to 90% and 95%, respectively. Mycobacterium, Comamonas and Pseudomonas were predominant bacteria; Mycobacterium, Pseudomonas, Comamonas, Microbacterium, Reyranella, Stenotrophomonas and Alicycliphilus were the core toluene oxidizing-denitrifying genera, denitrification genes (narGHI, nirK, nasB, napAB, nosZ and norC) and toluene oxidation genes (tom, E1.14.13.7, xyl, cat, todE, tes, mhp, pch, pob, pca, lig, gal) responsible for bacterial oxidation of toluene and NOx reduction, as shown by16S rDNA and metagenomic sequencing. Bacterial oxidation of toluene was coupled to NOx reduction in which toluene served as the electron donor while NOx served as the electron acceptor and thereby redox between toluene and NOx was formed, toluene was degraded through the classical aerobic aromatic compound degradation pathway. DBTF was capable of both toluene oxidation and NOx reduction by denitrification. These results show that the DBTF is achievable and open new possibilities for applying the DBTF to simultaneous removal of NOx and VOCs.

Direct evidence of local photochemical production driven ozone episode in Beijing: A case study

We present a comprehensive field campaign conducted in Beijing, September 2016, to elucidate the photochemical smog pollution, i.e. Ozone (O3). The observed daily maximum hydroxyl radical (OH) and hydroperoxy radical (HO2) concentrations were up to 1 × 107 cm-3 and 6 × 108 cm-3, respectively, indicating the active photochemistry in autumn Beijing. Photolysis of nitrous acid (HONO) and O3 contributed 1-2 ppbv h-1 to OH primary production during daytime. OH termination were dominated by the reaction with nitric oxide (NO) and nitrogen dioxide (NO2), which were in general larger than primary production rates, indicating other primary radical sources maybe important. The measurement of radicals facilitates the direct determination of local ozone production rate P (Ox) (Ox = O3 + NO2). The integrated P(Ox) reached 75 ppbv in afternoon (for 4 h) when planetary boundary layer was well developed. At the same time period, the observed total oxidant concentrations Ox, increased significantly by 70 ppbv. In addition, the Ox measurement showed compact increase in 12 stations both temporally and spatially in Beijing, indicating that active photochemical production happened homogenously throughout the city. The back-trajectory analysis showed that Beijing was isolated from the other cities during the episode, which further proved that the fast ozone pollution was contributed by local photochemical production rather than regional advection.

Quantifying the impacts of inter-city transport on air quality in the Yangtze River Delta urban agglomeration, China: Implications for regional cooperative controls of PM2.5 and O3.

The Yangtze River Delta (YRD) urban agglomeration is one of the most developed regions in China. During recent decades, this region has experienced severe regional haze and photochemical smog pollution problems. In this study, we used a source-oriented chemical transport model to quantitatively estimate the effects of inter-city transport on fine particulate matter (PM2.5) and ozone (O3) among the 41 cities in the YRD urban agglomeration during the EXPLORE-YRD (EXPeriment on the eLucidation of the atmospheric Oxidation capacity and aerosol foRmation, and their Effects in the Yangtze River Delta) campaign (May 17 to June 17, 2018). The results show that inter-city transport is very significant in the YRD region. On average, the emissions from the local city, the other YRD cities, and the regions outside of the YRD contribute 25.3%, 49.9%, and 24.8% to the PM2.5, respectively, and they contribute 33.7%, 46.8%, and 19.5% of the non-background O3, respectively. On PM2.5 or O3 pollution days, the transport contribution from the non-local YRD cities becomes much more important, while the local emissions and the transport from non-YRD emissions become less important. The results also suggest that the cities within a distance of 184km and 94km contribute 60% of the PM2.5 and O3, respectively. Therefore, we recommend that regional cooperative control programs in the YRD consider emission controls over cities within these ranges. The range for primary PM2.5 (92km) is very different from that for secondary PM2.5 (515km). Cooperative emission controls of SO2 and NOx on a much larger regional scale are required to reduce the secondary PM2.5 in the YRD.

The application of leak detection and repair program in VOCs control in China’s petroleum refineries

ABSTRACT Volatile organic compounds (VOCs) contribute to the formation of ground-level ozone. This causes the phenomena of haze and photochemical smog pollution. Recently, the leak detection and repair (LDAR) program was required to implement in China’s petroleum industry on the background of the huge emissions from equipment leaks. This paper analyzed and compared the application of LDAR program in four petroleum refineries and six typical processing units in these refineries. The results showed that non-flanged connectors, flanges, valves, and open-ended lines were the most common components, which accounted for over 99% in these refineries. And over half were non-flanged connectors. About 0.2% to 0.4% of all components were found to leak and emitted up to 91.8% of VOCs, especially the leaking valves and open-ended lines. And over 88.5% of VOC emissions were from high leaking components. The VOC emissions reduced 42% to 57% by repairing 42% to 81% of leaking components. And 90% of the reduction was achieved by repairing high leaking components. Besides, under the same processing capacity, the gas fractionation unit and continuous catalytic reforming unit have a higher average number of components, leaking components and VOC emissions than the other four units. Finally, this paper proposed some problems and suggestions during the implementation of LDAR program. These findings can enhance and improve the effectiveness of LDAR program, and establish a comprehensive VOCs control system, which provides a scientific basis and technical support for the government and refineries. Implications: Recently, China required industries to implement leak detection and repair (LDAR) program to control volatile organic compound (VOC) emissions, especially the petroleum industry. In this paper, we analyzed and compared the LDAR program implementation in four refineries and six typical processing units in these refineries. The results indicate that the implementation of LDAR program was highly effective in petroleum industry. The comparison helps us to enhance the effectiveness of LDAR program by locating the high VOC emission components and units, which provides technical support for the government and refineries in developing specific regulations and plans.

Simulating the effects of land urbanization on regional meteorology and air quality in Yangtze River Delta, China

Land urbanization caused by human activities is increasingly converting natural land surfaces to artificial ones and modifying land surface parameters. This can lead to changes in weather conditions and further effects on air pollutants. This study examines the influence of land urbanization on meteorology and air quality in the Yangtze River Delta (YRD) by simulating the impacts of land-use/land cover (LULC) changes on meteorology and air quality. Our results show that the temperature at 2m increases by 0.2–0.7 °C, and the planetary boundary layer height exhibits a maximum growth during the daytime of 116.74 m after updating LULC. The average reduction of 10-m wind speed is 0.29 m/s, and the maximum decrease is 0.52 m/s, which occurs in the daytime due to increased surface resistance. Furthermore, PM2.5, NO2, SO2, and ozone are sensitive to these meteorological changes in the WRF-CMAQ model. Additionally, land urbanization results in a decrease in the PM2.5 concentration in most urban areas for the same emission source. However, land urbanization aggravates photochemical smog pollution, which is dominated by O3. The findings of the study can be used as a reference for policymakers and urban planners to help implement effective air pollution prevention and control measures and ensure the rational use of land resources.

Characterisation of semi-volatile hydrocarbon emissions from diesel engines

Exhaust emissions from diesel vehicles have recently been receiving global attention, due to potential human health effects associated with exposure to emitted pollutants. In addition, a link has recently been established between unburnt hydrocarbon (HC) emissions from diesel engines and photochemical smog. Despite being present at very low concentrations in the exhaust, these HCs may act as precursors in the formation of photochemical smog pollution. While short-chain HCs are easier to characterise and have been successfully reduced in many developed cities, longer chain HCs, most likely arising from diesel exhaust emissions, have been poorly quantified and to date, a limited range of HCs from this source has been studied. In this study, transient cycle tests were conducted to collect exhaust emissions from a Euro 3 compliant, 1.6 L test engine fuelled with three diesel fuels (SAM10, PAR10, and EUR10), using portable denuder samplers which were analysed by thermal desorption-comprehensive 2D gas chromatography-time of flight mass spectrometry (TD-GC x GC-TofMS). The SAM10 diesel had the greatest n-alkane emissions with greater emissions observed in the earlier phases (low and medium phase) of the WLTC test cycle. PAR10 diesel had the second highest n-alkane emissions and EUR10 had the lowest n-alkane emissions amongst the three fuels. Substituted alkyl-benzenes were also detected in the gas phase emissions from each fuel. The results showed that long-chain HCs were present at easily detectable concentrations in diesel engine exhaust emissions, which is critical in understanding their contribution to photochemical ozone and informing appropriate mitigation and management strategies.

Tropospheric volatile organic compounds in China

Photochemical smog, characterized by high concentrations of ozone (O3) and fine particles (PM2.5) in the atmosphere, has become one of the top environmental concerns in China. Volatile organic compounds (VOCs), one of the key precursors of O3 and secondary organic aerosol (SOA) (an important component of PM2.5), have a critical influence on atmospheric chemistry and subsequently affect regional and global climate. Thus, VOCs have been extensively studied in many cities and regions in China, especially in the North China Plain, the Yangtze River Delta and the Pearl River Delta regions where photochemical smog pollution has become increasingly worse over recent decades. This paper reviews the main studies conducted in China on the characteristics and sources of VOCs, their relationship with O3 and SOA, and their removal technology. This paper also provides an integrated literature review on the formulation and implementation of effective control strategies of VOCs and photochemical smog, as well as suggestions for future directions of VOCs study in China.

The Representative Day Technique in the Study of Photochemical Smog Pollution in Falconara Industrial Area

The issue of increasing tropospheric Ozone and, more in general, of photochemical smog is of growing in importance. It is, however, a problem of extreme complexity, involving both atmospheric diffusion processes and complex chemical reactions. We present a study carried out to examine the evolution of the Ozone concentration fields and the effects of meteorological conditions on atmospheric pollutant concentrations in an industrial zone, namely Falconara, located on the central Adriatic coast of Italy. The aim of our study was to evaluate the possibility of assessing the diurnal evolution of air pollutants by introducing the Representative Day technique in order to obtain information on chemical reactions and air pollution in poorly monitored areas. The use of the Representative Day allows the compilation of large amounts of data in a compact format that will supply meaningful information on the whole data set.

Review of Photochemical Smog Pollution in Jakarta Metropolitan, Indonesia

An analysis of photochemical smog pollution in Jakarta was attempted using data from the existing air quality monitoring stations. Ground-level ozone potential is high in Jakarta due to the high traffic emissions of ozone precursors and the favorable surface meteorological conditions. Despite the frequent missing data during the 1996-1999 monitoring, which resulted in lower ozone values, ozone episodes were significantly recorded in 1997-1998. The number of hours on which ozone concentrations exceed the 1-hour standard (100 ppb) at an ambient station located in Kelapa Gading (10 km northeast of city center) was 186 hrs in 1997 and 571 hrs in 1998. El Nino phenomenon in 1997-1998 had affected the local meteorology leading to more favorable conditions for photochemical production of ozone. The annual ozone averages in ambient stations located off the city center have exceeded the 1-year standard limit (15 ppb). Although the annual average and 95-percentile values indicated an increasing trend from 1996 to 1998, the trend remains to be seen in the future as more complete data could be expected from the new monitoring system. The number of hours on which ozone exceed the 1-hour standard and the annual average tend to be increasing since 2001 to 2002 in all 3 newly operated stations. The seasonal variations of ozone indicate that ozone level is highest in the dry season (September-November) and is lowest in the wet season (December-March). Correlation between ozone level and meteorological attributes (solar radiation, relative humidity and temperature) was significant at 0.01 confidence level. The diurnal cycle of ozone and its precursors is clearly shown and is typical for polluted urban areas. Improvement of the database of air quality monitoring is very critical for Jakarta. Through better database management, the development and monitoring of cost-effective air pollution control strategy can be made.

Photochemical smog pollution in the Bangkok Metropolitan Region of Thailand in relation to O 3 precursor concentrations and meteorological conditions

Analysis of photochemical pollution was done using the available 5-yr monitoring data (1996–2000) from 11 monitoring stations in Bangkok and 5 stations in other surrounding provinces, i.e. the Bangkok Metropolitan Region (BMR). Status and trend of O 3 as well as the monthly and diurnal variations were analyzed in relation to the local meteorological conditions as well as the regional transport of pollutants associated with the monsoon. The O 3 in Bangkok was found to be typical for the polluted urban areas with a lower concentration in the city center, especially at curbside stations, and higher concentration at the downwind locations. O 3 pollution was highest in 1997 with the maximum hourly average of 370 ppbv and the total hours exceeding the national hourly O 3 standard (100 ppbv) of 314 h, which is most likely related to the strong El Niño and the forest fire in Southeast Asia in this year. Meteorology-unadjusted trend shows a slight increase in O 3 from 1998 to 2000. Local emission and photochemistry are mainly responsible for O 3 episodes in the BMR. Seasonal fluctuations of O 3, however, were found to relate to the regional transport associated with the Asian monsoon. Highest O 3 pollution was found in the period from January to April (winter and local summer) and lowest during mid-rainy season, August. The O 3 increase isopleth diagram was constructed which shows that O 3 production in BMR is effective when the NO x /NMHC ratio is in the range of 0.04–0.15 with optimum ratio of around 0.07. Seasonal variations in NO x /NMHC ratios are consistent with the O 3 variations, i.e., optimum in summer (0.07), followed by winter (0.05), and the lowest in rainy season (0.03).

99/02776 Air quality in Beijing and its transition from coal burning caused problems to traffic exhaust related pollution

Air pollution in Beijing is characterized by coal smoke for a long time because of energy structure highly dependence on coal consumption. SO{sub 2}, TSP, and NO{sub x} ambient concentration are kept in high levels, which exceed the guideline of WHO and National Air Quality Standard NAQS. The trend of SO{sub 2} change is relative stable, its annual average concentration fluctuates around 100 g/m{sup 3} since 1981. TSP show a fast decrease before 1986 and keep a slow decrease afterwards approaching the level of about 300 g/m{sup 3}. NO{sub x} concentration increases continuously all the time. Since 1993, NO{sub x} concentration exceeds SO{sub 2} to be the important pollutant next to TSP in Beijing, especially in summertime and traffic busy areas. As the consequence of NO{sub x} fast increase, the ozone pollution level is elevated greatly since 1980s. Several integrated field measurements were conducted to study the characteristics of photochemical smog and its formation mechanism. Hourly averaged ozone concentration usually exceeded the NAQS (80 ppb) in April to October. The O{sub 3} formation is very sensitive to NO{sub x} concentration because of the high NMHC/NO{sub x} ratio. In recent years, high O{sub 3} concentration is observed in early Spring and more » photochemical smog pollution is getting more and more severe with dramatically increase of vehicles in downtown Beijing. It is predicted that O{sub 3} pollution will be expected to enhance greatly in next 20 years under the development plan of future urban transportation system and increment of vehicles, even in the case that control strategies suggested by municipal government are undertaken. So more strengthen control strategies in Beijing are needed. « less

Simple laboratory-made system for the determination of C2–C7 hydrocarbons relevant to photochemical smog pollution

A simple gas chromatographic system suitable for determining volatile organic compounds from C2 to C7 in air is described. It consists of a capillary cold trap filled with graphitic carbon, a thermodesorbing device, a capillary gas chromatograph equipped with an alumina column and a flame ionization detector. Dry, as well as humid, air samples can be analysed with our system. Up to 2-l samples of air can be enriched on our trapping device by using Nafion membranes for removing water. Direct analysis of air samples is possible by enriching 250 ml on the carbon trap. The recovery, sensitivity and linearity of our system have been checked with standard mixtures and real samples. The performances have been compared with those afforded by a commercially available instrument exploiting a different enrichment procedure. The results obtained show that our analyser can be successfully applied to determinations of C2 to C7 hydrocarbons present in air samples at levels of 0.01 ppb (v/v).

Tropospheric Ozone and Climate Change

Considerable attention has been paid in recent years to photochemical smog pollution close to the earth's surface and to stratospheric ozone depletion. There is reason to suspect that the next round of scientific concern will be devoted to the perturbations in the “free troposphere.” Tropospheric ozone has been building up in many regions of the northern hemisphere. Ozone changes in the upper troposphere will exert a considerable impact on global warming. This could affect moisture levels, cloud amount and distribution, precipitation, and atmospheric dynamics on different scales. This paper analyzes: (1) the physical and chemical processes contributing to changes in tropospheric ozone concentration; (2) the observational evidence of previous ozone change; and (3) results drawn from computer modelling of past and future radiative forcing caused by rising ozone concentrations in the upper troposphere. The solar and longwave radiative model developed by Wang et al. (1991) was used for calculating the change ...