Characteristics of atmospheric non-methane hydrocarbons in Foshan City, China

Foshan is the most air-polluted city in Pearl River Delta. Non-methane hydrocarbons (NMHCs) were investigated for the first time in Foshan in winter 2008. Ethene, ethane, ethyne, propane, i-pentane, and toluene were the most abundant hydrocarbons and observed to be higher in Foshan than those in many other cities in China. Different from other cities, ethene and ethane were observed to be the two highest compounds in Foshan. Generally, the most abundant hydrocarbons showed high mixing ratios in the morning (0930-1030 hours), decreased to the lowest level in the afternoon (1430-1530 hours), and increased to higher value in the evening (1930-2030 hours). But i-pentane exhibited a different diurnal pattern with the highest level (13.4 ± 5.8 ppbv) in the afternoon, implying the acceleration of solvent evaporation resulting from higher temperature. Correlation coefficients (R(2)?= 66% for n = 6 at 95% confidence level) of the individual hydrocarbons with ethyne and i-pentane indicated vehicular emissions were the main sources of ethene, propene, i-butene, isoprene, benzene and toluene, while gasoline evaporation was responsible for n-pentane, n-hexane, and n-heptane. The good correlation of most of the hydrocarbons with ethyne, indicating vehicular emissions, were the main sources of NMHCs. B/T ratio was 0.36 ± 0.06, implying vehicular emissions acted as the major contributors as well as additional emissions of toluene emitted from solvent usage. According to investigation, it also suggested that LPG leakage was the main source of propane, while NG leakage was responsible for ethane in Foshan City.     

Relationship between CH₄ and N₂O flux from soil and their ambient mixing ratio in a riparian rice-based agroecosystem of tropical region

Temporal variations of the ambient mixing ratio of greenhouse gas (CH(4) and N(2)O) in a riparian rice-based agro-ecosystem of tropical region were studied during 2005-2006 in coastal Odisha. The endeavour was made with the hypothesis that the ambient mixing ratio of CH(4) and N(2)O depends on the changes in the flux of CH(4) and N(2)O from the rice fields in the riparian rice ecosystems. A higher ambient mixing ratio of CH(4) was recorded during the tillering to grain filling stages of the rice crop, during both dry and wet seasons. The higher ambient mixing ratio of CH(4) during the wet season may attribute to the higher CH(4) emission from the rice field. The average mixing ratio of CH(4) was recorded as 1.84 ± 0.05 ppmv and 1.85 ± 0.06 ppmv during 2005 and 2006, respectively. The ambient CH(4) mixing ratio was recorded negatively correlated with the average ambient temperature. The N(2)O mixing ratio ranged from 261.57 to 399.44 ppbv with an average of 330.57 ppbv during 2005. However, the average mixing ratio of N(2)O was recorded as 318.83 ± 20.00 ppbv during 2006. The N(2)O mixing ratio was recorded to be negatively correlated with rainfall and average ambient temperature. Significant negative correlation (r = -0.209) of N(2)O with sunshine hours may attribute to the photochemical break down of N(2)O. The temporal variation of N(2)O flux from the rice field does not affect the ambient mixing ratio of N(2)O in the same way as in the case of the ambient mixing ratio of CH(4). However, the higher mixing ratio of N(2)O during the fallow period of the post monsoon period may attribute to the N(2)O flux from soil. Results indicate that intensively cultivated coastal ecosystems can be a major source of ambient greenhouse gas.     

南通市夏季VOCs污染特征与来源研究

运用大气挥发性有机物(VOCs)快速在线连续自动监测系统,于2018年7月对南通市区环境空气中VOCs进行观测,分析VOCs的浓度状况、组成特征、对臭氧生成潜势的贡献及主要来源。结果表明:观测期间共检出100种VOCs,总挥发性有机物(TVOCs)的平均体积分数为(38. 18±23. 63)×10^-9,各物种体积分数从大到小顺序依次为烷烃>含氧有机物>芳香烃>卤代烃>烯、炔烃;芳烃和烯烃是最主要的活性物种,间/对二甲苯、甲苯、邻二甲苯等是VOCs的关键活性组分;利用PMF模型解析得到VOCs的主要污染来源是工业排放与溶剂使用、机动车尾气排放、燃料挥发排放和生物源排放。     

基于城市大气挥发性有机物特征分析的数据质量评估方法及案例

城市大气挥发性有机物(VOCs)监测是空气质量监测网的重要组成部分,而数据质量控制和质量保证是VOCs监测的基础。基于8次中国城市大气VOCs外场监测,通过挖掘VOCs浓度、组成和化学活性的内在规律,对VOCs监测数据质量进行评估并总结方法。分析结果显示:城市大气乙烷和苯等长寿命组分具有明显的背景浓度,且区域背景值较为接近,可以用来诊断长寿命VOCs组分浓度异常偏低或偏高现象。而示踪组分的季节(日)变化规律可以用来识别VOCs组分定性问题(如夏季大气异戊二烯和烷基硝酸酯浓度日变化规律应反映植被排放和光化学反应特征)。另外,在气团混合均匀的情况下,VOCs浓度波动与其活性之间存在负相关,这一规律可以用来核查数据准确性或局地源影响。     

Monitoring variation in greenhouse gases concentration in Urban Environment of Delhi

Cities across the globe are considered as major anthropogenic sources of greenhouse gases (GHG), yet very few efforts has been made to monitor ambient concentration of GHG in cities, especially in a developing country like India. Here, variations in the ambient concentrations of carbon dioxide (CO₂) and methane (CH₄) in residential, commercial, and industrial areas of Delhi are determined from fortnightly daytime observations from July, 2008 to March, 2009. Results indicate that the average daytime ambient concentration of CO₂ varied from 495 to 554 ppm in authorized residential areas, 503 to 621 ppm in the slums or jhuggies in the unauthorized residential areas, 489 to 582 ppm in commercial areas, and 512 to 568 ppm in industrial areas with an average of 541?±?27 ppm. CH₄ concentration varied from 652 to 5,356 ppbv in authorized residential areas, 500 to15,220 ppbv in the unauthorized residential areas, 921 to 11,000 ppbv in the commercial areas, and 250 to 2,550 ppbv in the industrial areas with an average of 3,226?±?1,090 ppbv. A low mid-afternoon CO₂ concentration was observed at most of the sites, primarily due to strong biospheric photosynthesis coupled with strong vertical mixing.     

Pollution characteristics of volatile organic compounds in the atmosphere of Haicang District in Xiamen City, Southeast China

The compositions, spatial distributions, seasonal variations and ozone formation potential (OFP) of volatile organic compounds (VOCs) were investigated in the atmosphere of Haicang District, Xiamen City, Southeast China. Twenty-four types of VOCs were measured in this study, and ethanol, methylene chloride, toluene, ethyl acetate and isopropyl alcohol were the abundant species based on concentration rank. The concentrations of total VOCs (TVOCs) in industrial areas were higher than those in residential and administrative areas and background site. For industrial areas, the TVOCs concentrations in summer were higher than those in winter, which might result from higher emissions from industrial activities because of stronger evaporation in summer. In contrast, non-industrial areas showed higher concentrations in winter due to the unfavorable meteorological conditions. The spatial distribution of BTEX (benzene, toluene, ethylbenzene and xylene) followed the order of industrial areas > residential and administrative areas > background site, and the concentrations in summer were lower than those in winter for most sites. The high ratios (8.9-14.0) of T/B in this study indicated that industrial emissions were the main sources in this district. X/B ratios were used to assess the ages of air parcels and provided evidence of the transport of air parcels among these sites. Total OFP (TOFP) showed the trend of increase with the increase of TVOCs, and toluene was found as the major contributor to TOFP.     

Concentrations of formaldehyde and other carbonyls in environments affected by incense burning

Burning incense to pay homage to deities is common in Chinese homes and temples. Air samples were collected and analyzed for carbonyls from a home and a temple in Hong Kong where incense burning occurs on a daily basis. Carbonyls in the air were trapped on a solid sorbent coated with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine, followed by thermal desorption and subsequent GC/MS analysis. The carbonyls identified include formaldehyde, acetaldehyde, acrolein, 2-furfural, benzaldehyde, glyoxal, and methylglyoxal. The levels of the above carbonyls correlate with the intensity of the incense-burning activities. The total mixing ratios of the carbonyls in the temple exceed those in the ambient air outside the temple by 11-23 times. Formaldehyde is the most abundant species, contributing to approximately 55% of the total carbonyl mixing ratios in both the temple and the home environments during incense burning. The mixing ratio of formaldehyde ranges from 108 to 346 ppbv in the temple and averages 103 ppbv in the home during incense burning. These values exceed the World Health Organization (WHO) air quality guideline of 100 microg m(-3) (88 ppbv) for formaldehyde. The highest formaldehyde level in the temple exceeds the WHO guideline by 3 times at peak incense burning hours. The mixing ratio of acrolein in the temple ranges from 20 to 99 ppbv, approaching or exceeding the WHO air quality guideline of 50 microg m(-3) (22 ppbv) for acrolein. Our measurements indicate that incense burning significantly elevates the concentrations of a number of carbonyls, most notably formaldehyde and acrolein, in the surrounding environments. This study provides preliminary insights on indoor air quality problems created by incense burning.     

Seasonal Variation of Toxic Benzene Emissions in Petroleum Refinery

Petroleum refineries are largest chemical industries that are responsible for the emission of several pollutants into the atmosphere. Benzene is among the most important air pollutants that are emitted by petroleum refineries, since they are involved in almost every refinery process. Volatile organic compounds (VOCs) are a major group of air pollutants, which play a critical role in atmospheric chemistry. These contribute to toxic oxidants, which are harmful to ecosystem, human health and atmosphere. The variability of pollutants is an important factor in determining human exposure to these chemicals. The ambient air concentrations of benzene were measured in several sites around the Digboi petroleum refinery, near the city of Gowahati in northeast India, during winter and summer 2004. The seasonal and spatial variations of the ambient air concentrations of this benzene were investigated and analyzed. An estimation of the contribution of the refinery to the measured atmospheric levels of benzene was also performed. The ambient air mixing ratios of benzene in a large area outside the refinery was generally low, in ppbv range, much lower than the ambient air quality standards. This article presents the temporal and spatial variation of air pollution in and around petroleum refinery and showed that no health risk due to benzene is present in the areas adjacent to the refinery.     

Atmospheric BTEX concentrations in the vicinity of the crude oil refinery of the Baltic region

Among chemical industries, petroleum refineries have been identified as large emitters of a wide variety of pollutants. Benzene, toluene, ethylbenzene, and xylene (BTEX) form an important group of aromatic volatile organic compounds (VOCs) because of their role in the troposphere chemistry and the risk posed to human health. A very large crude oil refinery of the Baltic States (200,000 bbl/day) is situated in the northern, rural part of Lithuania, 10 km from the town of Ma?eikiai (Lithuania). The objectives of this study were: (1) to determine of atmospheric levels of BTEX in the region rural and urban parts at the vicinity of the crude oil refinery; and (2) to investigate the effect of meteorological parameters (wind speed, wind direction, temperature, pressure, humidity) on the concentrations measured. The averaged concentration of benzene varied from 2.12 ppbv in the rural areas to 2.75 ppbv in the urban areas where the traffic was determined to be a dominant source of BTEX emissions. Our study showed that concentration of benzene, as strictly regulated air pollutant by EU Directive 2008/50/EC, did not exceed the limit of 5 ppbv in the region in the vicinity of the crude oil refinery during the investigated period. No significant change in air quality in the vicinity of the oil refinery was discovered, however, an impact of the industry on the background air quality was detected. The T/B ratio (0.50-0.81) that was much lower than 2.0, identified other sources of pollution than traffic.     

典型化工园区大气中挥发性有机物污染调查

对常州市某典型化工园区大气中挥发性有机物(VOCs)污染状况进行了调查。结果表明,该化工园区大气中检出挥发性有机物共有58种,组分有芳香烃、饱和烷烃、卤代烃、烯烃、醛酯类化合物及其他类;苯、甲苯、乙苯、二甲苯为主要挥发性有机污染物,质量浓度为1.0~194μg/m~3;均未超出参考标准的限值。背景点位和园区点位大气中主要ρ总(VOCs)在秋冬季最高,敏感点大气VOCs随季节变化也较为明显;园区T1和T2ρ总(VOCs)年均值高于敏感点位,背景点位年均值最低;园区点位除了汽车尾气排放之外,溶剂的挥发和生产工艺中污染物的排放也增加了大气中苯系物的浓度,同时也对敏感点位和对照点位的大气质量产生了一定的影响。     

Personal, indoor, and outdoor exposure to VOCs in the immediate vicinity of a local airport

This study measures the effect of emissions from an airport on the air quality of surrounding neighborhoods. The ambient concentrations of benzene, toluene, ethylbenzene, and o-, m-, and p-xylene (BTEX) were measured using passive samplers at 15 households located close to the airport (indoor, outdoor, and personal), at the end of airport runways and an out-of-neighborhood location. Measurements occurred over a 48-h period during summer 2006 and winter 2006?C2007. The average concentrations were 0.84, 3.21, 0.30, 0.99, and 0.34 ??g/m³ at the airport runways and 0.84, 3.76, 0.39, 1.22, and 0.39 ??g/m³ in the neighborhood for benzene, toluene, ethylbenzene, m-, p-, and o-xylene. The average neighborhood concentrations were not significantly different to those measured at the airport runways and were higher than the out-of-neighborhood location (0.48, 1.09, 0.15, 0.78, and 0.43 ??g/m³, each BTEX). B/T ratios were used as a tracer for emission sources and the average B/T ratio at the airport and outdoors were 0.20 and 0.23 for the summer and 0.40 and 0.42 for the winter, suggesting that both areas are affected by the same emission source. Personal exposure was closely related to levels in the indoor environment where subjects spent most of their time. Indoor/outdoor (I/O) ratios for BTEX ranged from 1.13 to 2.60 and 1.41 to 3.02 for summer and winter. The seasonal differences in I/O ratios reflected residential ventilation patterns, resulting in increased indoor concentrations of volatile organic compounds during winter.     

Trends in motor-vehicle related air pollutants in central London

Results of intermittent monitoring of six aromatic hydrocarbons (benzene, toluene, ethyl-benzene, m-xylene, p-xylene and o-xylene), carbon monoxide and oxides of nitrogen over a thirteen year period at a site in central London (Exhibition Road) are presented. Four monitoring regimes were undertaken; namely, 1979, 1982/83, 1986/87 and 1991/92. The summertime daytime mean ambient concentrations of the measured parameters at this site are presented. The reported concentrations show a reduction from 1979 to 1992 by approximately a factor of two, despite national increases in motor fuel consumption and the volume of traffic. Relevant European Community legislation covering emissions from motor-vehicles are outlined and comparisons are made with emissions from motor vehicles predicted from the UK national inventory. The importance of the frequency of measurements was also noted.     

Temporal and spatial variations of the quality of ambient air in the Kingdom of Bahrain during 2007

The main objective of the present investigation is to study the temporal and spatial variations of the quality of ambient air in the Kingdom of Bahrain. The non-parametric Kruskal-Wallis (KW) test showed significant spatial variations and interactions of spatial-temporal among five mobile monitoring stations for 11 air pollutants. The Mann Whitney (MW) test demonstrated the seasonality of spring over winter for the PM(10), PM(2.5), NO(2), CO and p-xylene, the seasonality of winter over spring for O(3), and no significant seasonal variation for NH(3), benzene, SO(2), toluene and H(2)S. It is concluded that emissions from automobile exhaust, industrial and developmental projects are responsible for the spatial air pollution, and that air temperature is the controlling factor for the seasonal variations.     

VOCs走航观测在城市污染源排查中的应用

为推进城市空气质量精细化管理工作的实施,实现VOCs污染源精准排查,2019年3-4月,利用单光子电离飞行时间质谱对青岛市重点区域进行了VOCs走航观测。在排查到的污染源中,工业区的VOCs浓度较生活区整体偏高,且生活区、工业区夜间的VOCs浓度均较白天高。VOCs各类组分中,生活区白天苯系物、卤代烃、烯烃、烷烃的占比均在20%左右,夜间苯系物占比明显升高;工业区苯系物在白天和夜间的占比均最高,其他组分相对较小。浓度较高的前10位VOCs物种中,生活区白天烯烃物种占主导,夜间烷烃物种的比重明显增加;工业区苯系物、烯烃物种在白天和夜间的比重均较大,烷烃物种较小。生活区VOCs的污染源主要为机动车尾气排放和油品挥发,工业区主要为企业排放。烯烃和苯系物臭氧生成贡献较烷烃高,特别是丁烯、戊烯、己烯、甲苯、二甲苯/乙苯、三甲苯贡献显著,建议作为优控物种重点管控。     

杭州秋季大气VOCs变化特征及化学反应活性研究

2017年9月1日至11月30日采用Syntech Spectras GC955在线气相色谱仪对杭州市不同功能区大气环境中的挥发性有机化合物(VOCs)进行了在线连续监测,分析了不同功能区VOCs及各组分的体积分数、日变化规律及大气化学反应活性。结果显示,下沙周边工业区总VOCs浓度整体高于朝晖周边居民区,其中夜间更为显著。烷烃和芳香烃浓度在夜间时段工业区较居民区高得更为明显,其中芳香烃组分表现尤为突出,2个功能区烯烃体积分数相差不大。杭州市主要VOCs体积分数总体上在国内处于中间水平。不同功能区烷烃和芳香烃均呈现夜间浓度高于白天的日变化特征,居民区各VOCs组分日变化基本呈现双峰结构,工业区烷烃和芳香烃体积分数日变化呈现单峰结构,烯烃体积分数没有明显的日变化特征。不同功能区中芳香烃对臭氧生成潜势贡献最大,烯烃次之,烷烃贡献最小。下沙周边工业区大气化学活性(尤其是芳香烃组分)较朝晖周边居民区强。同种VOCs物质在不同功能区对臭氧生成潜势的贡献大小不同,但关键贡献物质均为低碳烷烃、低碳烯烃及苯系物。     

Emissions of VOCs at Urban Petrol Retail Distribution Centres in India (Delhi and Mumbai)

Air pollution has assumed gigantic proportion killing almost half a million Asians every year. Urban pollution mainly comprises of emissions from buses, trucks, motorcycle other forms of motorized transport and its supporting activities. As Asia's cities continue to expand the number of vehicles have risen resulting in greater pollution. Fugitive emissions from retail distribution center in urban area constitute a major source. Petrol vapours escape during refueling adding pollutants like benzene, toluene, ethylbenzene and xylene to ambient air. This paper discusses a study on fugitive emissions of Volatile Organic Compounds (VOC) at some refueling station in two metropolitan cities of India, i.e., Mumbai and Delhi. Concentration of VOCs in ambient air at petrol retail distribution center is estimated by using TO-17 method. Concentration of benzene in ambient air in Delhi clearly shows the effect of intervention in use of petroleum and diesel fuel and shift to CNG. Chemical Mass Balance (CMB) model is used to estimate source contributions. At Delhi besides diesel combustion engines, refueling emissions are also major sources. At Mumbai evaporative emissions are found to contribute maximum to Total VOC (TVOC) concentration in ambient air.     

Characteristics of atmospheric non-methane hydrocarbons during haze episode in Beijing, China

This study firstly focused on non-methane hydrocarbons (NMHCs) during three successive days with haze episode (16–18 August 2006) in Beijing. Concentrations of alkanes, alkenes, aromatic hydrocarbons, and ethyne all peaked at traffic rush hour, implying vehicular emission; and alkanes also peaked at non-traffic rush hour in the daytime, implying additional source. Especially, alkanes and aromatics clearly showed higher levels in the nighttime than that in the daytime, implying their active photochemical reactions in the daytime. Correlation coefficients (R ²) showed that propane, n-butane, i-butane, ethene, propene, and benzene correlated with ethyne (R ²?=?0.61–0.66), suggesting that their main source is vehicular emission; 2-methylpentane and n-hexane correlated with i-pentane (R ²?=?0.61–0.64), suggesting that gasoline evaporation is their main source; and ethylbezene, m-/p-xylene, and o-xylene correlated with toluene (R ²?=?0.60–0.79), suggesting that their main source is similar to that of toluene (e.g., solvent usage). The R ² of ethyne, i-pentane, and toluene with total NMHCs were 0.58, 0.76, and 0.60, respectively, indicating that ambient hydrocarbons are associated with vehicular emission, gasoline evaporation, and solvent usage. The sources of other hydrocarbons (e.g., ethane) might be natural gas leakage, biogenic emission, or long-range transport of air pollutants. Measured higher mean B/T ratio (0.78?±?0.27) was caused by the more intensive photochemical activity of toluene than benzene, still indicating the dominant emission from vehicles.     

PM2.5 and volatile organic compounds (VOCs) in ambient air: a focus on the effect of meteorology

PM(2.5) and VOCs (benzene, toluene, m-p-o-xylenes) concentrations were measured in an urban and a suburban site in Athens, Greece, during the period between April and November 2004. This period, which is considered to be the warmer period in Greece, is characterized by the development of sea-breeze over the Attica Basin. Additionally strong Northern, North-eastern winds called "The Etesians", predominate during the summer months (July-August), acting positively to the dispersion of pollutants. In this campaign, 24 days with sea-breeze development were observed, 15 days with northern winds, 6 days with southern winds while the rest of the days presented no specific wind profile. Maximum concentrations of PM(2.5), VOCs and nitrogen oxides, were detected during the days with sea-breeze, while minimum concentrations during the days with northern winds. Ozone was the only pollutant that appeared to have higher concentrations in the background site and not in the city centre, where benzene presented strong negative correlation with ozone, indicating the photochemical reaction of hydrocarbons that lead to the ozone formation. The BTX ratios were similar for both sites and wind profiles, indicating common sources for those pollutants. T/B ratio ranged in low levels, between 3-5 for site A and 2-5 for site B, suggesting vehicles emissions as the main sources of volatile compounds. Finally, the strong correlations of PM(2.5) and benzene concentrations, between the two sampling sites, indicate that both the city centre and the background site, are affected by the same sources, under common meteorological conditions (sea-breeze, northern winds).     

On-site Comparison of Canister and Solid-Sorbent Trap Collection of Highly Volatile Hydrocarbons in Ambient Atmospheres

A field experiment for the comparison of the efficiency of canisters and adsorption multibed tubes for sampling atmospheric highly volatile hydrocarbons at ppbv levels is described. The canister was passivated by the Summa process and the adsorption tubes were filled with Carbotrap C, Carbotrap B and Carbosieve S-III. The sampling with the adsorption tubes was performed at ambient temperature and at -10°C. The highest concentrations were generally obtained with canisters but these results are very similar to those obtained with refrigerated multibed adsorption tubes. Both methods appear to be equivalent for most of the highly volatile hydrocarbons encountered in moderately polluted urban areas. In contrast, sampling with ambient temperature tubes provides lower concentrations. This study has also shown that K2CO3 drying efficiently removes humidity from air samples allowing the obtention of reliable concentration data on highly volatile hydrocarbons at ppbv levels. These drying tubes can easily be re-conditioned and tested for blanks and memory effects, which greatly facilitates the control of external contamination and sample cross-contamination.     

中国沿海三省主要饮用水源有机物监测

采用固相萃取、吹扫捕集和气相色谱-质谱联用仪(GC-MS)对江苏、浙江、山东省的21个主要地表饮用水源、126份水样中的25种VOCs、38种SVOCs进行定量检测。结果有19种VOCs、10种SVOCs至少在一个水源地多次被检出,其中挥发性氯代烃、苯系物、氯代苯类、酚类、硝基苯类、酞酸酯类、农药为中国或美国环境保护局提出的"水中优先控制污染物",最高检出量为27.79μg/L。三省主要地表水受到有机物轻度污染,水体中VOCs、SVOCs含量尚未超过《地表水环境质量标准》(GB 3838-2002)和《生活饮用水卫生标准》(GB 5749-2006)限值,工业废水排放及农田雨水径流是地表水有机物的重要来源。