Analysis of Ozone Pollution Characteristics and Influencing Factors in Northeast Economic Cooperation Region, China

The increase in tropospheric ozone (O3) concentration has become one of the factors restricting urban development. This paper selected the important economic cooperation areas in Northeast China as the research object and collected the hourly monitoring data of pollutants and meteorological data in 11 cities from 1 January 2015 to 31 December 2019. The temporal and spatial variation trend of O3 concentration and the effects of meteorological factors and other pollutants, including CO (carbon monoxide), SO2 (sulfur dioxide), NO2 (nitrogen dioxide), and PM2.5 and PM10 (PM particles with aerodynamic diameters less than 2.5 μm and 10 μm) on ozone concentration were analyzed. At the same time, the variation period of O3 concentration was further analyzed by Morlet wavelet analysis. The results showed that the O3 pollution in the study area had a significant spatial correlation. The spatial distribution showed that the O3 concentration was relatively high in the south and low in the northeast. Seasonally, the O3 concentration was the highest in spring, followed by summer, and the lowest in winter. The diurnal variation of O3 concentration presented a “single peak” pattern. O3 concentration had a significant positive correlation with temperature, sunshine duration, and wind speed and a significant anticorrelation with CO, NO2, SO2, and PM2.5 concentration. Under the time scale of a = 9, 23, O3 had significant periodic fluctuation, which was similar to those of wind speed and temperature.

Ambient volatile organic compounds (VOCs) in communities of the Athabasca oil sands region: Sources and screening health risk assessment

An investigation of ambient levels and sources of volatile organic compounds (VOCs) and associated public health risks was carried out at two northern Alberta oil sands communities (Fort McKay and Fort McMurray located < 25 km and >30 km from oil sands development, respectively) for the period January 2010-March 2015. Levels of total detected VOCs were comparatively similar at both communities (Fort McKay: geometric mean = 22.8 μg/m³, interquartile range, IQR = 13.8-41 μg/m³); (Fort McMurray: geometric mean = 23.3 μg/m³, IQR = 12.0-41 μg/m³). In general, methanol (24%-50%), alkanes (26%-32%) and acetaldehyde (23%-30%) were the predominant VOCs followed by acetone (20%-24%) and aromatics (∼9%). Mean and maximum ambient concentrations of selected hazardous VOCs were compared to health risk screening criteria used by United States regulatory agencies. The Positive matrix factorization (PMF) model was used to identify and apportion VOC sources at Fort McKay and Fort McMurray. Five sources were identified at Fort McKay, where four sources (oil sands fugitives, liquid/unburned fuel, ethylbenzene/xylene-rich and petroleum processing) were oil sands related emissions and contributed to 70% of total VOCs. At Fort McMurray six sources were identified, where local sources other than oil sands development were also observed. Contribution of aged air mass/regional transport including biomass burning emissions was ∼30% of total VOCs at both communities. Source-specific carcinogenic and non-carcinogenic risk values were also calculated and were below acceptable and safe levels of risk, except for aged air mass/regional transport (at both communities), and ethylbenzene/xylene-rich (only at Fort McMurray).

Twelve-year trends in ambient concentrations of volatile organic compounds in a community of the Alberta Oil Sands Region, Canada

Environmental exposure to volatile organic compounds (VOCs) in ambient air is one of a number of concerns that the First Nation Community of Fort McKay, Alberta has related to development of Canada's oil sands. An in-depth investigation of trends in ambient air VOC levels in Fort McKay was undertaken to better understand the role and possible significance of emissions from Alberta's oil sands development. A non-parametric trend detection method was used to investigate trends in emissions and ambient VOC concentrations over a 12-year (2001-2012) period. Relationships between ambient VOC concentrations and production indicators of oil sands operations around Fort McKay were also examined. A weak upward trend (significant at 90% confidence level) was found for ambient concentrations of total VOCs based on sixteen detected species with an annual increase of 0.64μg/m(3) (7.2%) per year (7.7μg/m(3) increase per decade). Indicators of production (i.e., annual bitumen production and mined oil sands quantities) were correlated with ambient total VOC concentrations. Only one of 29 VOC species evaluated (1-butene) showed a statistically significant upward trend (p=0.05). Observed geometric (arithmetic) mean and maximum ambient concentrations of selected VOCs of public health concern for most recent three years of the study period (2010-2012) were below chronic and acute health risk screening criteria of the U.S. Agency for Toxic Substances and Disease Registry and U.S. Environmental Protection Agency. Thirty-two VOCs are recommended for tracking in future air quality investigations in the community to better understand whether changes are occurring over time in relation to oil sands development activities and to inform policy makers about whether or not these changes warrant additional attention.

VOC in an urban and industrial harbor on the French North Sea coast during two contrasted meteorological situations

Two measurement campaigns of volatile organic compounds (VOC) were carried out in the industrial city of Dunkerque, using Radiello passive samplers during winter (16-23 January) and summer (6-13 June) 2007. 174 compounds were identified belonging to six chemical families. Classifying sampling sites with similar chemical profiles by hierarchical ascending classification resulted in 4 groups that reflected the influence of the main industrial and urban sources of pollution. Also, the BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) quantification allowed us to map their levels of concentration. Benzene and toluene (BT) showed high concentrations in Northern Dunkerque reflecting the influence of two industrial plants. Differences among spatial distributions of the BT concentrations over contrasted meteorological conditions were also observed. An atypical ratio of T/B in the summer samples led us to investigate the BTEX origins shedding light on the contribution of pollutants transported across various zones of VOC emissions situated in Europe.

Determinants of airborne concentrations of volatile organic compounds in rural areas of Western Canada

We estimated the level and determinants of airborne concentrations of 26 volatile organic compounds (VOC) in rural Western Canada. A multisite, multimonth unbalanced two-factorial design was used to collect air samples at 1206 fixed sites across a geographic area associated with primary oil and gas industry in Alberta, northeastern British Columbia, and central and southern Saskatchewan from April 2001 to December 2002. Principal component factor analysis was used to group VOC into three mixtures. Factor I was a group of compounds dominated by benzene, toluene, ethyl-benzene, xylenes, and hexane. Factor II was mainly a group of vegetation-related monoterpenes and dichlorobenzenes. Factor III was a group of chlorinated VOC. Linear mixed effects models were applied to identify the determinants of airborne concentrations of VOC and evaluate the association between these factors and oil and gas facilities. Our results indicated that the studied VOC were present in small (ng/m3) quantities. Components of Factor I VOC showed a seasonal variation with maxima in winter and minima in summer, whereas components of Factor II displayed an opposite seasonal trend. Components of Factor III did not show a clear seasonal pattern. We observed that oil and gas facilities only contribute to airborne concentrations of components of Factor I. Proximity to batteries (within 2 km) was most influential in determining monthly airborne concentrations of components of Factor I, followed by gas and oil wells. Modification of batteries to reduce evaporation and leakage might be considered as a measure to control airborne concentrations of compounds such as benzene and toluene.

The characteristics of tropospheric ozone seasonality observed from ozone soundings at Pohang, Korea

This paper presents the first analysis of vertical ozone sounding measurements over Pohang, Korea. The main focus is to analyze the seasonal variation of vertical ozone profiles and determine the mechanisms controlling ozone seasonality. The maxima ozone at the surface and in the free troposphere are observed in May and June, respectively. In comparison with the ozone seasonality at Oki (near sea level) and Happo (altitude of 1840 m) in Japan, which are located at the same latitude as of Pohang, we have found that the time of the ozone maximum at the Japanese sites is always a month earlier than at Pohang. Analysis of the wind flow at the surface shows that the wind shifts from westerly to southerly in May over Japan, but in June over Pohang. However, this wind shift above boundary layer occurs a month later. This wind shift results in significantly smaller amounts of ozone because the southerly wind brings clean wet tropical air. It has been suggested that the spring ozone maximum in the lower troposphere is due to polluted air transported from China. However, an enhanced ozone amount over the free troposphere in June appears to have a different origin. A tongue-like structure in the time-height cross-section of ozone concentrations, which starts from the stratosphere and extends to the middle troposphere, suggests that the ozone enhancement occurs due to a gradual migration of ozone from the stratosphere. The high frequency of dry air with elevated ozone concentrations in the upper troposphere in June suggests that the air is transported from the stratosphere. HYSPLIT trajectory analysis supports the hypothesis that enhanced ozone in the free troposphere is not likely due to transport from sources of anthropogenic activity.

An observational case study of ozone and precursors inflow to South East England during an anticyclone

Summertime photochemical air pollution episodes within the United Kingdom have been proposed via modelling studies to be strongly influenced by regional scale inflow of air from the continental European boundary layer. We present a vertically resolved case study using measurements made from the NERC/Met Office BAe 146 research aircraft on 18th August 2005 over the South East of England and the North Sea during a weak anticyclone centred over Northern Europe. The vertical distribution of ozone, CO, NO(x), peroxyacetyl nitrate (PAN) and a wide range of both nonmethane hydrocarbons (NMHC) and oxygenated volatile organic compounds (OVOCs) were determined between 500 ft (approximately 152 m) and 7000 ft (approximately 2134 m) over the East Anglia coastline and 50 km inland. In excess of 80 ppbV ozone was observed within inflowing boundary layer air over the North Sea coast in a broad N-S sloping feature around 60 km wide. The inflowing feature of European origin was also observed further inland within the boundary layer albeit with lower, more variable, ozone mixing ratios. The increased variability in ozone over land was a product of titration by fresh surface emissions of NO via rapid upward transport in thermals, a hypothesis supported by the observed vertical wind speed component. Fast boundary layer mixing over land was further illustrated by a uniform distribution in reactive alkenes. A comparison between aircraft and surface O(3) UK AUN (Automatic Urban Network) measurements showed good agreement with the inland site, Sibton, but marked differences with the coastal monitoring site at Weybourne, potentially due to gradients established by ocean deposition in stably stratified marine air.

Modelling the ambient distribution of organic compounds during the August 2003 ozone episode in the southern UK

A photochemical trajectory model containing speciated emissions of 124 non-methane volatile organic compounds (VOC), and a comprehensive description of the chemistry of VOC degradation, has been used to simulate the chemical evolution of boundary layer air masses arriving at a field campaign site in the southern UK during a widespread and prolonged photochemical pollution event in August 2003. The simulated concentrations and distributions of organic compounds at the arrival location are compared with observations of a series of hydrocarbons and carbonyl compounds, which were measured using GC-FID and multidimensional GC methods. The comparison of the simulated and observed distributions of 34 emitted hydrocarbons provides some support for the magnitude and applied emissions speciation of anthropogenic hydrocarbons, but is indicative of an under representation of the input of biogenic hydrocarbons, particularly at elevated temperatures. Simulations of the detailed distribution of ca. 1250 carbonyl compounds, formed primarily from the degradation of the 124 emitted VOC, focus on 61 aldehydes, ketones, dicarbonyls, hydroxycarbonyls and aromatic aldehydes which collectively account for ca. 90% of the simulated total molar concentration of carbonyls. The simulated distributions indicate that the photolysis of formaldehyde and alpha-dicarbonyls make major contributions to free radical production for the arrival conditions of five case study trajectories. The simulated concentrations of hydroxycarbonyls demonstrate preferential formation of the 1,4-substituted isomers (compared with 1,2- and 1,3-isomers of the same carbon number), which are formed during the initial oxidation sequence of longer chain alkanes.