Air quality assessment of benzo(a)pyrene from asphalt plant operation

A study has been carried out to assess the contribution of Polycyclic Aromatic Hydrocarbons (PAHs) from asphalt plant operation, utilising Benzo(a)pyrene (BaP) as a marker for PAHs, to the background air concentration around asphalt plants in the UK. The purpose behind this assessment was to determine whether the use of published BaP emission factors based on the US Environmental Protection Agency (EPA) methodology is appropriate in the context of the UK, especially as the EPA methodology does not give BaP emission factors for all activities. The study also aimed to improve the overall understanding of BaP emissions from asphalt plants in the UK, and determine whether site location and operation is likely to influence the contribution of PAHs to ambient air quality. In order to establish whether the use of US EPA emissions factors is appropriate, the study has compared the BaP emissions measured and calculated emissions rates from two UK sites with those estimated using US EPA emission factors. A dispersion modelling exercise was carried out to show the BaP contribution to ambient air around each site. This study showed that, as the US EPA methodology does not provide factors for all emission sources on asphalt plants, their use may give rise to over- or under-estimations, particularly where sources of BaP are temperature dependent. However, the contribution of both the estimated and measured BaP concentrations to environmental concentration were low, averaging about 0.05 ng m(-3) at the boundary of the sites, which is well below the UK BaP assessment threshold of 0.25 ng m(-3). Therefore, BaP concentrations, and hence PAH concentrations, from similar asphalt plant operations are unlikely to contribute negatively to ambient air quality.     

基于地基监测的人为源温室气体排放通量反演研究进展

不同尺度下温室气体的空间分布及变化趋势是研究气候变化的基础,也是评估相关减排政策实施效果的重要依据。当前碳排放核算主要基于排放清单,不确定性较大。基于监测数据的碳排放核算能够有效评估和修正排放清单结果,是对当前方法的有效补充。国内温室气体的监测主要针对污染源和环境浓度,对于人为源温室气体排放通量的监测研究较少。该文分析了近年来国内外基于地基监测的人为源温室气体排放通量研究,主要的研究方法可分为2类:柱浓度空间分布结合三维风场数据反演排放通量;结合实测体积分数、大气扩散模型和统计优化模型修正先验排放通量结果,以获取更准确的后验排放通量。通过分析和对比2种方法的优势和局限,讨论不同通量反演方法的适用场景。建议我国未来应构建适用于不同空间尺度的温室气体通量监测反演体系,综合利用多种监测手段,以校核验证排放清单,并为制定温室气体减排策略和评估应对气候变化工作成效提供技术支撑。     

Determining the ventilation and aerosol deposition rates from routine indoor-air measurements

Measurement of air exchange rate provides critical information in energy and indoor-air quality studies. Continuous measurement of ventilation rates is a rather costly exercise and requires specific instrumentation. In this work, an alternative methodology is proposed and tested, where the air exchange rate is calculated by utilizing indoor and outdoor routine measurements of a common pollutant such as SO₂, whereas the uncertainties induced in the calculations are analytically determined. The application of this methodology is demonstrated, for three residential microenvironments in Athens, Greece, and the results are also compared against ventilation rates calculated from differential pressure measurements. The calculated time resolved ventilation rates were applied to the mass balance equation to estimate the particle loss rate which was found to agree with literature values at an average of 0.50 h^?1. The proposed method was further evaluated by applying a mass balance numerical model for the calculation of the indoor aerosol number concentrations, using the previously calculated ventilation rate, the outdoor measured number concentrations and the particle loss rates as input values. The model results for the indoors’ concentrations were found to be compared well with the experimentally measured values.     

Organic Liquids Storage Tanks Volatile Organic Compounds (VOCS) Emissions Dispersion and Risk Assessment in Developing Countries: The Case of Dar-Es-Salaam City, Tanzania

The emission estimation of nine volatile organic compounds (VOCs) from eight organic liquids storage tanks companies in Dar-es-Salaam City Tanzania has been done by using US EPA standard regulatory storage tanks emission model (TANKS 4.9b). Total VOCs atmospheric emission has been established to be 853.20 metric tones/yr. It has been established further that petrol storage tanks contribute about 87% of total VOCs emitted, while tanks for other refined products and crude oil were emitting 10% and 3% of VOCs respectively. Of the eight sources (companies), the highest emission value from a single source was 233,222.94 kg/yr and the lowest single source emission value was 6881.87 kg/yr. The total VOCs emissions estimated for each of the eight sources were found to be higher than the standard level of 40,000 kg/yr per source for minor source according to US EPA except for two sources, which were emitting VOCs below the standard level. The annual emissions per single source for each of the VOCs were found to be below the US EPA emissions standard which is 2,000~kg/yr in all companies except the emission of hexane from company F1 which was slightly higher than the standard. The type of tanks used seems to significantly influence the emission rate. Vertical fixed roof tanks (VFRT) emit a lot more than externally floating roof tanks (EFRT) and internally floating roof tanks (IFRT). The use of IFRT and EFRT should be encouraged especially for storage of petrol which had highest atmospheric emission contribution. Model predicted atmospheric emissions are less than annual losses measured by companies in all the eight sources. It is possible that there are other routes for losses beside atmospheric emissions. It is therefore important that waste reduction efforts in these companies are directed not only to reducing atmospheric emissions, but also prevention of the spillage and leakage of stored liquid and curbing of the frequently reported illegal siphoning of stored products. Emission rates for benzene, toluene, and xylene were used as input to CALPUFF air dispersion model for the calculation of spatial downwind concentrations from area sources. By using global positioning system (GPS) and geographical information system (GIS) the spatial benzene concentration contributed by organic liquid storage tanks has been mapped for Dar-es-Salaam City. Highest concentrations for all the three toxic pollutants were observed at Kigamboni area, possibly because the area is located at the wind prevailing direction from the locations of the storage tanks. The model predicted concentrations downwind from the sources were below tolerable concentrations by WHO and US-OSHA. The highest 24 hrs averaging time benzene concentration was used for risk assessment in order to determine maximum carcinogenic risk amongst the population exposed at downwind. Established risk for adult and children at 2.9×10^-3 and 1.9×10^-3 respectively, are higher than the acceptable US-EPA risk of 1×10^-6. It is very likely that the actual VOCs concentrations in some urban areas in Tanzania including Dar-es-Salaam City are much higher than the levels reported in this study when other sources such as petrol stations and motor vehicles on the roads are considered. Tanzania Government therefore need to put in place: an air quality policy and legislation, establish air quality guidelines and acquire facilities which will enable the implementation of air quality monitoring and management programmes.     

Temporal evolution of the main processes that control indoor pollution in an office microenvironment: a case study

The aim of this study is to examine the relative contribution of the outdoor concentration, the ventilation rate, the geometric characteristics of the indoor environment (i.e., extent of indoor surfaces and indoor volume), the deposition, and chemical reactions to the indoor air quality of the office microenvironment. For this case study, the NO, NO₂, and O₃ concentrations indoors and outdoors and TVOCs and CO₂ concentrations indoors were measured in an office microenvironment in Athens, Greece, that was ventilated both naturally and mechanically. The calculated ventilation and loss rates and the measured outdoor concentrations of NO, NO₂, and O₃ were set as input to Multi-chamber Indoor Air Quality Model in order to study the temporal variation of the indoor NO, NO₂, and O₃ concentrations. Results showed that when the ventilation rate and outdoor concentration are high, the relative contribution of the transport process contributes significantly, while the chemical process depends on the contemporary interplay between the indoor O₃, NO, and NO₂ concentrations and lighting levels. The significance of each process was further examined by performing sensitivity tests, and it was found that the most important parameters were the deposition velocities, the UV infiltration rates (which determines the indoor chemical reaction rates), the ventilation rates, and the filtration (when a mechanical ventilation system is used). The effect of the hydrocarbon chemistry was not significant.     

Influence of processing parameters on VOC emission from particleboards

Volatile organic compound (VOC) emissions from furnishings have created a major indoor air pollution problem in China. The aim of this study was to investigate the VOC emission of larch particleboard under different processing conditions. VOCs collection chamber, parts per billion VOC monitor, and gas chromatography–mass spectrometer were used to analyze the VOC components and quantities. The results were shown as follows: (1) concentration and emission rate of VOCs were significantly affected by hot-pressing temperature and time. With the increase of hot-pressing temperature and time, both the earlier emission concentration and the amount of total volatile organic compounds increased. (2) The composition of VOCs was also influenced by temperature and time, especially the variety of terpene, benzene, and derivative. The existence and quantities of esters were still the main components of VOCs emissions.     

Vehicular particulate matter emissions in road tunnels in Sao Paulo, Brazil

In the metropolitan area of S?o Paulo, Brazil, ozone and particulate matter (PM) are the air pollutants that pose the greatest threat to air quality, since the PM and the ozone precursors (nitrogen oxides and volatile organic compounds) are the main source of air pollution from vehicular emissions. Vehicular emissions can be measured inside road tunnels, and those measurements can provide information about emission factors of in-use vehicles. Emission factors are used to estimate vehicular emissions and are described as the amount of species emitted per vehicle distance driven or per volume of fuel consumed. This study presents emission factor data for fine particles, coarse particles, inhalable particulate matter and black carbon, as well as size distribution data for inhalable particulate matter, as measured in March and May of 2004, respectively, in the Janio Quadros and Maria Maluf road tunnels, both located in S?o Paulo. The Janio Quadros tunnel carries mainly light-duty vehicles, whereas the Maria Maluf tunnel carries light-duty and heavy-duty vehicles. In the Janio Quadros tunnel, the estimated light-duty vehicle emission factors for the trace elements copper and bromine were 261 and 220 microg km(-1), respectively, and 16, 197, 127 and 92 mg km(-1), respectively, for black carbon, inhalable particulate matter, coarse particles and fine particles. The mean contribution of heavy-duty vehicles to the emissions of black carbon, inhalable particulate matter, coarse particles and fine particles was, respectively 29, 4, 6 and 6 times higher than that of light-duty vehicles. The inhalable particulate matter emission factor for heavy-duty vehicles was 1.2 times higher than that found during dynamometer testing. In general, the particle emissions in S?o Paulo tunnels are higher than those found in other cities of the world.     

室内氨气污染的净化试验研究

近几年 ,由于建筑施工使用含氨的添加剂和使用室内装饰材料 ,造成现代建筑物室内氨气 (NH3)污染问题 ,严重影响了人们的工作和生活。本研究采用改性的吸附材料 ,在管道系统和封闭空间两种不同工况条件下 ,对以改性吸附剂做吸附材料的氨气净化装置进行净化性能的评价 ,为室内氨气污染的净化治理提供了新的思路。     

Design and validation of a passive deposition sampler

A new, passive particle deposition air sampler, called the Einstein-Lioy Deposition Sampler (ELDS), has been developed to fill a gap in passive sampling for near-field particle emissions. The sampler can be configured in several ways: with a protective hood for outdoor sampling, without a protective hood, and as a dust plate. In addition, there is an XRF-ready option that allows for direct sampling onto a filter-mounted XRF cartridge which can be used in conjunction with all configurations. A wind tunnel was designed and constructed to test the performance of different sampler configurations using a test dust with a known particle size distribution. The sampler configurations were also tested versus each other to evaluate whether or not the protective hood would affect the collected particle size distribution. A field study was conducted to test the sampler under actual environmental conditions and to evaluate its ability to collect samples for chemical analysis. Individual experiments for each configuration demonstrated precision of the sampler. The field experiment demonstrated the ability of the sampler to both collect mass and allow for the measurement of an environmental contaminant i.e. Cr(6+). The ELDS was demonstrated to be statistically not different for Hooded and Non-Hooded models, compared to each other and the test dust; thus, it can be used indoors and outdoors in a variety of configurations to suit the user's needs.     

Multisource emission retrieval within a biogas plant based on inverse dispersion calculations—a real-life example

Open digestate storage tanks were identified as one of the main methane (CH₄) emitters of a biogas plant. The main purpose of this paper is to determine these emission rates using an inverse dispersion technique in conjunction with open-path tunable diode laser spectroscopy (OP-TDLS) concentration measurements for multisource reconstruction. Since the condition number, a measure of “ill-conditioned” matrices, strongly influences the accuracy of source reconstruction, it is used as a diagnostic of error sensitivity. The investigations demonstrate that the condition number for a given source-sensor configuration in the highly disturbed flow field within the plant significantly depends on the meteorological conditions (e.g., wind speed, stratification, wind direction, etc.). The CH₄ emissions are retrieved by removing unrepresentative periods with high condition numbers, which indicate uncertainty in recovering the individual sources. In a final step, the CH₄ emissions are compared with the maximum biological methane potential (BMP) in the digestate analyzed under laboratory conditions. The retrieved methane emission rates represent an average of 50 % of the maximum BMP of the stored digestate in the winter months, while they comprised an average of 85 % during the measurement campaigns in the summer months. The results indicate that the open tanks have the potential to represent a substantial emission source even during colder periods.     

The use of semipermeable membrane devices as passive samplers to determine persistent organic compounds in indoor air

In the study reported here semipermeable membrane devices (SPMDs) were used to sample 28 PAHs and 19 PCBs in the gas phase in 15 single-family houses located in an area where domestic wood burning is widespread. Eight of the households used wood burning appliances whereas the others used other systems for residential heating. Most of the studied compounds were found in the houses: the PAHs at levels that were similar to or slightly higher than published SPMD-sampled levels for background or urban sites in Sweden, and the PCBs at levels that were somewhat lower than those recently found in both indoor and outdoor urban locations. A principal component analysis revealed that wood-burning heating systems may contribute to PAHs in indoor air. The sources may be emissions indoors or penetration from outdoors. The convenience of SPMD technology facilitates its use for semi-quantitative screening and monitoring of various persistent organic compounds indoors in dwellings and working environments.     

The Impact of Road Traffic in Madrid Community by Using a Nested Gaussian-Mesoscale Air Quality Model (GAMA)

In this contribution we show the integration of a mesoscale air quality model OPANA with the ISCST3 Gaussian model (EPA) in order to analyze the impact of different emission sources and particularly the traffic emission into the different gridboxes which define the OPANA Eulerian structure. The application is done over the Madrid (Spain) regional area with 80 × 100 km and gridboxes of about 5 km. Thousands of Gaussian runs over interested gridboxes are executed in order to simulate the traffic emissions from each gridbox. Each mobile unit is represented by a Gaussian point emitter. Input meteorological variables for the ISCST3 are taken from the OPANA mesoscale air quality model. Results shows that it is possible to model the impact of traffic emissions over each gridbox. A short comparison with air quality monitoring in each gridbox is also shown.     

Combining a road pollution dispersion model with GIS to determine carbon monoxide concentration in Tennessee

The purpose of this paper is to develop an air pollution model that is independent from pollution monitoring sites and highly accurate through space and time. Total carbon monoxide concentration is computed with the use of traffic flow data, vehicle speed and dimensions, emission rates, wind speed, and temperature. The data are interpolated using a geographic information system universal kriging technique, and the end results produce state level air pollution maps with high local accuracy. The model is validated against Environment Protection Agency (EPA) pollution data. Overall, the model has 71 % agreement with EPA, overestimating values of carbon monoxide for less than 1 ppm. The model has three advantages over already assessed air pollution models. First, it is completely independent of any air pollution monitoring stations; thus, possible temporary or permanent unreliability or lack of the data is avoided. Second, being based on a 5,710 traffic count network, the problem of remote places coverage is avoided. Third, it is based on a straightforward equation, where minimal preprocessing of traffic and climatic data is required.     

Estimation of Emissions of γ-Hexachlorcyclohexane from the Great Lakes–St. Lawrence Ecosystem Using a Coupled Efficient Kalman Filter–Atmospheric Transport–Soil Model

An efficient linear Kalman filter has been combined with a coupled atmospheric transport and soil–air exchange model to determine organochlorine pesticides emissions on the regional scale. In this study, results of -HCH emissions from the Great Lakes–St. Lawrence ecosystem, estimated from the coupled model, are presented and discussed. A source receptor technique is used to identify a priori the locations of emission sources of -HCH, the emissions are then updated through a Kalman filtering procedure which minimizes the weighted difference between the predicted mixing ratios from the coupled model and the measured concentrations over the Great Lakes–St. Lawrence river region. Two experiments using the inverse algorithm are carried out. In the first experiment, the coupled atmospheric transport and soil–air exchange model is implemented to predict -HCH air and soil concentrations. Emissions are then updated every 12 days using the updated soil concentrations and emission factors. However, the updated emissions are not input into the coupled atmospheric transport and soil–air exchange model. On the other hand, in the second experiment the updated emissions are fed back to the coupled model, so that the model is reinitialized in each 12 days. The results from the inverse technique for the year 1995 have been compared with grided -HCH emission inventory in Canada, generated by emission factors. It is shown that the estimated emissions of -HCH are consistent with the measured emissions. It is found that the St. Lawrence valley has larger emissions of -HCH than the Great Lakes region, indicating an opposite distribution to the emission usage inventory, but in agreement with the measured -HCH concentration.     

Assessment of pumped mercury vapour adsorption tubes as passive samplers using a micro-exposure chamber

Mercury vapour adsorption tubes manufactured for pumped sampling and analysis have been evaluated for their performance as passive samplers. This has been done by exposing these tubes in a novel micro-exposure chamber. The uptake rates of these tubes have been found to be low (approximately 0.215 ml min(-1)) as compared to bespoke passive samplers for mercury vapour (typically in excess of 50 ml min(-1)). The measured uptake rates were shown to vary significantly between tubes and this was attributed to the variability in the air-sorbent interface and the proportion of the cross sectional area removed by the crimp in the quartz tubes used to secure the sorbent material. As a result of this variability the uptake rate of each tube must be determined using the micro-exposure chamber prior to deployment. Results have shown that the uptake rate determined in the micro-exposure chamber is invariant of concentration, and therefore these uptakes rates may be determined at a high mercury vapour concentration for many tubes at once in less than one hour. The uptake rate of the adsorption tubes under these conditions may be determined with a precision of 5%. Measurements made on a limited field trial in indoor and outdoor ambient air have shown that these tubes give results in acceptable agreement with more traditional pumped sampling methods, although longer sampling periods are required in order to reduce the uncertainty of the measurement, which is currently approximately 30%.     

Introduction of a method for presenting health-based impacts of the emission from products,based on emission measurements of materials used in manufacturing of the products

A method for presenting the health impact of emissions from furniture is introduced, which could be used in the context of environmental product declarations. The health impact is described by the negative indoor air quality potential, the carcinogenic potential, the mutagenic and reprotoxic potential, the allergenic potential, and the toxicological potential.An experimental study of emissions from four pieces of furniture is performed by testing both the materials used for production of the furniture and the complete piece of furniture, in order to compare the results gained by adding emissions of material with results gained from testing the finished piece of furniture.Calculating the emission from a product based on the emission from materials used in the manufacture of the product is a new idea. The relation between calculated results and measured results from the same products differ between the four pieces of furniture tested. Large differences between measured and calculated values are seen for leather products. More knowledge is needed to understand why these differences arise.Testing materials allows us to compare different suppliers of the same material. Four different foams and three different timber materials are tested, and the results vary between materials of the same type. If the manufacturer possesses this type of knowledge of the materials from the subcontractors it could be used as a selection criterion according to production of low emission products.     

炼油企业挥发性有机物无组织排放通量监测现状与发展

炼油企业是重要的挥发性有机物(VOCs)人为排放源,排放的VOCs主要来自无组织源,监控及排放核算困难。笔者总结了国内外炼油企业VOCs排放通量监控及核算技术体系,综述了各类VOCs无组织排放通量监测技术的原理及适用范围,着重评述了工业场地VOCs无组织排放通量监测最佳实用技术--红外掩日通量监测(SOF)和差分吸收激光雷达(DIAL)及其在炼油企业的应用进展。总体上,SOF仪器及监测费用适中,但易受阳光等天气条件限制;DIAL几乎可全天候监测,但仪器及监测费用较高。SOF和DIAL监测的欧美炼油企业VOCs排放系数一般为0. 02%~0. 10%,约为排放清单值的3~10倍。国内炼油厂VOCs排放核算采用的排放系数约为美国排放清单值(0. 01%~0. 02%)的10倍,尚待实测校验和修订。VOCs无组织排放通量监测技术也可用于检查或评估炼油企业泄漏检测与修复(LDAR)等VOCs无组织排放控制效果。     

Volatile hydrocarbon emissions from vehicles and vertical ventilations in the Hsuehshan traffic tunnel, Taiwan

The concentrations of 56 volatile organic hydrocarbons (VOCs) were measured simultaneously in the southbound bore, the northbound bore and the exhaust air shafts of the Hsuehshan tunnel near Yilan, Taiwan during 2007 and 2008. A total of 60 integrated air samples were collected using stainless steel canisters and analyzed using GC/FID and GC/MS. The highest temperature and lowest relative humidity were observed at the exit of the tunnel owing to the accumulation in the tunnel of waste heat that was exhausted from vehicles. The five most abundant species in all samples were ethylene, acetylene, isopentane, propylene, and toluene. The exit/entrance ratios of total non-methane hydrocarbon (NMHC) concentration were 7.8 and 4.8 for the southbound and northbound bores, respectively. Furthermore, the most abundant species of emission rate (ER) is toluene (21.93-42.89 mg s(-1)), followed by isopentane, ethylene, propylene and 1-butene, with ER ranging from 2.50 to 9.31 mg s(-1) for the three shafts. The ozone formation potential (OFP)/total NMHC ratios in three exhaust air shafts show that the reactivities of these emissions are similar to those of vehicle emissions.     

Analysis of the Daily Variations of Wintertime Air Pollution Concentrations in the City of Graz, Austria

Measured air pollution concentrations in a city reflect the influence of different kinds of sources as well as varying meteorological conditions. In the city of Graz in southern Austria, frequent stagnant meteorological conditions can cause elevated levels of air pollution although emission levels are not exceptionally high. With the aid of a detailed emission inventory and an array of sodars and tethersondes as well as lidar systems supplementing the routine meteorological and air chemistry network during a field experiment in January 1998, the daily variations of air pollution concentrations of selected components within the complex topography of the city of Graz are explained. Main results show the almost linear dependence of the morning maximum concentrations on the predicted emission rates. Throughout the day the rising of the well mixed layer reduces concentrations considerably. Concerning NO_X the fast reaction from NO to NO₂ is important due to the down-mixing of O₃ from the residual layer. The maximum in the afternoon is influenced by emission rates and pollution transport due to the mountain wind.     

Methane emissions from ricefields as affected by organic amendment, water regime, crop establishment, and rice cultivar

Methane fluxes from Beijing ricefields as affected by organic amendment, water regime, crop establishment method, and rice cultivar were measured with a closed chamber method in 1990, 1991, 1995, and 1996. Total fluxes from plots receiving high organic amendment always exceeded those from the low-input plots. Compared with continuous flooding, intermittent irrigation (there were a few days of no standing water between two irrigations) and constant moisture (the field had no standing water, but remained saturated) reduced methane emission rate by 25.4 and 58.4%, respectively. Methane flux from a dry-seeded rice field was 75.2% lower than from a transplanted ricefield although both dry-seeded rice plots and transplanted ricefields were initially flooded at the same time. Rice cultivars differed in methane emission rates by 9.0–55.7%. Emission rates were positively correlated with aboveground dry matter production and root weight, but not grain yield. Intermittent irrigation and rice cultivar seem to be the most promising methods for mitigating methane emission from ricefields; they do not affect rice yield and are easily implemented at the farm level.