Ambient volatile organic compound (VOC) concentrations around a petrochemical complex and a petroleum refinery

Air samples were collected between September 2000 and September 2001 in Izmir, Turkey at three sampling sites located around a petrochemical complex and an oil refinery to measure ambient volatile organic compound (VOC) concentrations. VOC concentrations were 4-20-fold higher than those measured at a suburban site in Izmir, Turkey. Ethylene dichloride, a leaded gasoline additive used in petroleum refining and an intermediate product of the vinyl chloride process in the petrochemical complex, was the most abundant volatile organic compound, followed by ethyl alcohol and acetone. Evaluations based on wind direction clearly indicated that ambient VOC concentrations measured were affected by the refinery and petrochemical complex emissions. VOC concentrations showed seasonal variations at all sampling sites. Concentrations were highest in summer, followed by autumn, probably due to increased evaporation of VOCs from fugitive sources as a result of higher temperatures. VOC concentrations generally increased with temperature and wind speed. Temperature and wind speed together explained 1-60% of the variability in VOC concentrations. The variability in ambient VOC concentrations that could not be explained by temperature and wind speed can be attributed to the effect of other factors (i.e. wind direction, other VOC sources).     

Quantile regression of indoor air concentrations of volatile organic compounds (VOC)

There are many factors determining the concentration of volatile organic compounds (VOCs) in indoor air. On the basis of 601 population-based measurements we develop an explicit exposure model that includes factors, such as renovation, furniture, flat size, smoking, and education level of the occupants.As a novel method for the evaluation of concentrations of indoor air pollutants we use quantile regression, which has the advantages of robustness against non-Gaussian distributions (and outliers) and can adjust for unbalanced frequencies of observations. The applied bi- and multivariate quantile regressions provide (1) the VOC burden that is representative for the population of Leipzig, Germany, and (2) an inter-comparison of the effects of the studied factors and their levels.As a result, we find strong evidence for factors of general impact on most VOC components, such as the season, flooring, the type of the room, and the size of the apartment. Other impact factors are very specific to the VOC components. For example, wooden flooring (parquet) and new furniture increase the concentration of terpenes as well as the modifying factors high education and sampling in the child's room. Smokers ventilate their flats in an extent that in general reduces the VOC concentrations, except for benzene (contained in tobacco smoke), which is still higher in smoking than in non-smoking flats. Very often dampness is associated with an increased VOC burden in indoor air.An investigation of mixtures emphasises a high burden of co-occurring terpenes in very small and very large apartments.     

Exposure to volatile organic compounds (VOC) in public buses of Pamplona, Northern Spain

This study examines the exposure level of passengers and drivers to VOC in public buses in a medium-size metropolitan area (Northern Spain). In-vehicle monitoring was performed on different routes, on peak and non-peak hours, during January and February 2007. A total of 112 air samples were collected onto adsorbent tubes and analysed by thermal desorption (TD) and gas chromatography/mass selective detector (GC/MSD) technique. Statistical differences were found among route to route concentrations, with those routes with major prevalence in the commercial area of the city displaying higher values; differences between peak and non-peak hours were also observed. A decrease in VOC concentrations was also registered during the weekend. BTEX ratios were estimated and found to be related to traffic emissions and similar for all the surveyed routes. Correlations confirmed traffic as the main emission source for BTEX and trimethylbenzene, their concentrations being highly associated to changes in meteorological conditions.     

Volatile organic compound (VOC) adsorption on material: influence of gas phase concentration, relative humidity and VOC type

This paper presents the results of a factorial experiment design analysis to investigate volatile organic compounds (VOC) adsorption on a ceiling tile. The impacts of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on adsorption have been investigated. Cyclohexane, toluene, ethyl acetate, isopropyl alcohol and methanol were the five VOCs used in this study. A factor significant level was determined through evaluating its F value and comparing it with the critical value of F distribution at 95% confidence level. It was found that: (i) neither the relative humidity and gas phase concentration nor any interaction effect between them had significant impacts on toluene adsorption on the ceiling tile; (ii) the adsorption isotherm appeared to be linear for the non-polar compounds and non-linear for the semi-polar and polar compounds; (iii) no significant impact of relative humidity on adsorption was observed for most VOC compounds except for methanol; and (iv) the ceiling tile had the highest adsorption capacity toward the polar compounds, followed by the aromatic compounds and aliphatic compounds. In addition, the statistical analysis regarding the experimental results of toluene as a single compound or as a part of a mixture showed that toluene adsorption capacity on the ceiling tile as a single compound was higher than as a part of a mixture. PRACTICAL IMPLICATIONS: Building materials and furnishings may act as source and sink of VOCs in the indoor environment. In this study, a factorial experiment design analysis technique was used to show the impact of three factors, VOC gas phase concentration, relative humidity, and VOC type, as single parameters and as a combination, on the adsorption process (sink effect). The aim was to better understand the interaction between these parameters and to verify the common assumptions made in the model development and measurement of indoor air quality.     

Modeling volatile organic compound (VOC) concentrations due to material emissions in a real residential unit. Part I: Methodology and a preliminary case study

High volatile organic compound (VOC) concentrations following building decoration have been observed frequently. In reality, however, residents do not know the indoor VOC concentration levels until the buildings are tested, which seldom provides a preventive measure. While several indoor air quality (IAQ) simulation programs have been developed to predict indoor contaminant levels, case studies in the literature are scarce regarding the predictability of indoor VOC concentrations as well as how such predictions could be performed in real buildings. In this paper, we intended to conduct a proof-of-concept study whether simulations can help to reveal some of the key features of VOC concentrations during indoor decoration process. We conducted a case study, simulated and measured the VOC concentrations of a residential unit during the room decoration process. Results show that while certain agreement was achieved between the measurement and simulation, application of IAQ models to real buildings is challenging under the best of circumstances—single zone spaces with very few emission materials inside.     

Spatial and temporal trends of volatile organic compounds (VOC) in a rural area of northern Spain

Ambient concentrations of volatile organic compounds (VOCs) were measured at 40 rural sampling points in Navarre (northern Spain). Air samples were collected by means of sorbent passive sampling and analyzed by thermal desorption (TD) and gas chromatography/mass-selective detector (GC/MSD). A total of 140 VOCs were identified during the study, which was carried out between May to October 2004 for a total of a 10 biweekly sampling campaigns. Concentrations of benzene, toluene, ethylbenzene, m/p-xylenes, o-xylene (BTEX) and 1,3,5-trimethylbenzene were determined in order to investigate their temporal and spatial distributions. Geostatistical analysis pointed to traffic as the main emission source of these compounds. Supporting this idea, BTEX and nitrogen oxides concentrations were found to be highly significantly correlated (r = 0.495, P = 0.001), whereas a strong negative correlation between BTEX and ozone was also observed (r = -0.355, P = 0.025). The concentrations for the BTEX group were similar to the values that have been previously reported for other rural areas.     

How to measure and evaluate volatile organic compound emissions from building products. A perspective

The primary emissions of VOCs (e.g. solvents) from building products influence the perceived indoor air quality during the initial decay period. However, secondary emissions will continue thereafter (chemical or physical degradation, e.g. oxidation, hydrolysis, mechanical wear, maintenance), in addition to sorption processes. Emission testing for primary VOC emissions is necessary, but insufficient to characterise the impact of building products in their entire life span on the perceived air quality. Methods to distinguish between the two types of emissions are required. Also, the influence of climate parameters on the emission rates is necessary to know for proper testing. Future product development and selection strategies of new building products should consider the secondary emissions, in addition to the contribution from the use of auxiliary agents for cleaning, maintenance, and other potential impacts either physical or chemical in nature. Some of the requirements for emission testing are discussed in terms of secondary vs. primary emissions in order to develop 'healthier/better' building products for the indoor environment. In addition, some of the assumptions about the possible impact of VOCs on health and comfort in the indoor environment are presented. Odour thresholds for VOCs are one or more orders of magnitude lower than the corresponding airway irritation estimates, and it also appears that chemically non-reactive VOCs are not sufficiently strong irritants to cause airway irritation at concentrations normally encountered indoors. Finally, future requirements for analytical laboratory performances is proposed to accommodate the increasing need to establish which VOCs may be responsible for the perception of odour intensity from building products.     

Risk assessment of exposure to volatile organic compounds in groundwater in Taiwan

The purpose of this study is to assess the risks from exposure to 14 volatile organic compounds (VOCs) in selected groundwater sites in Taiwan. The study employs the multimedia environment pollutant assessment system (MEPAS) model to calculate the specific non-cancer and cancer risks at an exposure level of 1 μg/L of each VOC for a variety of exposure pathways. The results show that the highest specific non-cancer risk is associated with water ingestion of vinyl chloride (VC) and that the highest specific cancer risk is associated with indoor breathing of VC. The three most important exposure pathways for risk assessment for both non-cancer and cancer risks are identified as water ingestion, dermal absorption when showering, and indoor breathing. Excess tetrachloroethylene (PCE), trichloroethylene (TCE), dichloroethylene (DCE), and VC are detected in the groundwater aquifers of one dump site and one factory. However, the study suggests that the pollutants in the contaminated groundwater aquifers do not travel extensively with groundwater flow and that the resulting VOC concentrations are below detectable levels for most of the sampled drinking-water treatment plants. Nevertheless, the non-cancer and cancer risks resulting from use of the contaminated groundwater are found to be hundred times higher than the general risk guidance values. To ensure safe groundwater utilisation, remediation initiatives for soil and groundwater are required. Finally, the study suggests that the current criteria for VOCs in drinking water might not be capable of ensuring public safety when groundwater is used as the primary water supply; more stringent quality criteria for drinking water are proposed for selected VOCs.     

Ambient air levels of volatile organic compounds (VOC) and nitrogen dioxide (NO2) in a medium size city in Northern Spain

Ambient concentrations of volatile organic compounds (VOC) and nitrogen dioxide (NO₂) were measured by means of passive sampling at 40 sampling points in a medium-size city in Northern Spain, from June 2006 to June 2007. VOC and NO₂ samplers were analysed by thermal desorption followed by gas chromatography/mass-selective detector and by visible spectrophotometry, respectively. Mean concentrations of benzene, toluene, ethylbenzene, xylenes, propylbenzene, trimethylbenzenes, and NO₂ were 2.84, 13.26, 2.15, 6.01, 0.59, 1.32 and 23.17 µg m^− 3 respectively, and found to be highly correlated. Their spatial distribution showed high differences in small distances and pointed to traffic as the main emission source of these compounds. The lowest levels of VOC and NO₂ occurred during summer, owing to the increase in solar radiation and to lower traffic densities. Mean concentrations of benzene and NO₂ exceeded the European limits at some of the monitored points.     

Do time‐averaged,whole‐building,effective volatile organic compound (VOC) emissions depend on the air exchange rate? A statistical analysis of trends for 46 VOCs in U.S. offices

We used existing data to develop distributions of time‐averaged air exchange rates (AER), whole‐building ‘effective’ emission rates of volatile organic compounds (VOC), and other variables for use in Monte Carlo analyses of U.S. offices. With these, we explored whether long‐term VOC emission rates were related to the AER over the sector, as has been observed in the short term for some VOCs in single buildings. We fit and compared two statistical models to the data. In the independent emissions model (IEM), emissions were unaffected by other variables, while in the dependent emissions model (DEM), emissions responded to the AER via coupling through a conceptual boundary layer between the air and a lumped emission source. For 20 of 46 VOCs, the DEM was preferable to the IEM and emission rates, though variable, were higher in buildings with higher AERs. Most oxygenated VOCs and some alkanes were well fit by the DEM, while nearly all aromatics and halocarbons were independent. Trends by vapor pressure suggested multiple mechanisms could be involved. The factors of temperature, relative humidity, and building age were almost never associated with effective emission rates. Our findings suggest that effective emissions in real commercial buildings will be difficult to predict from deterministic experiments or models.     

Health risk assessment of personal inhalation exposure to volatile organic compounds in Tianjin, China

Volatile Organic Compounds (VOCs) exposure can induce a range of adverse human health effects. To date, however, personal VOCs exposure and residential indoor and outdoor VOCs levels have not been well characterized in the mainland of China, less is known about health risk of personal exposure to VOCs. In this study, personal exposures for 12 participants as well as residential indoor/outdoor, workplace and in vehicle VOCs concentrations were measured simultaneously in Tianjin, China. All VOCs samples were collected using passive samplers for 5 days and were analyzed using Thermal Desorption GC-MS method. U.S. Environmental Protect Agency's Inhalation Unit Risks were used to calculate the inhalation cancer health risk. To assess uncertainty of health risk estimate, Monte Carlo simulation and sensitivity analysis were implemented. Personal exposures were greater than residential indoor exposures as expected with the exception of carbon tetrachloride. Exposure assessment showed modeled and measured concentrations are statistically linearly correlated for all VOCs (P < 0.01) except chloroform, confirming that estimated personal exposure using time-weighted model can provide reasonable estimate of personal inhalation exposure to VOCs. Indoor smoking and recent renovation were identified as two major factors influencing personal exposure based on the time-activity pattern and factor analysis. According to the cancer risk analysis of personal exposure, benzene, chloroform, carbon tetrachloride and 1,3-butadiene had median upper-bound lifetime cancer risks that exceeded the U.S. EPA benchmark of 1 per one million, and benzene presented the highest median risks at about 22 per one million population. The median cumulative cancer risk of personal exposure to 5 VOCs was approximately 44 per million, followed by indoor exposure (37 per million) and in vehicle exposure (36 per million). Sensitivity analysis suggested that improving the accuracy of exposure measurement in further research would advance the health risk assessment.     

A screening assessment of emissions of volatile organic compounds and particles from heated indoor dust samples

This paper characterizes and compares emissions during heating of different dust samples relevant to the indoor environment. Characterization includes emission of volatile organic compounds when dust samples were heated to 150 and 250 degrees C (gas chromatograph-mass spectrometer), weight loss during heating to 450 degrees C (thermogravimetric analysis), and the number of particles emitted during heating towards 200 degrees C (condensation nucleus counting). Element analyses were performed for non-heated dust (inductively coupled plasma discharge instrument). Emissions of volatile organic compounds from heated dust from different sources were surprisingly similar. However, the temperature at which the emission of volatiles started varied with the dust source. For most of the samples studied, the emissions were considerable already at 150 degrees C, and increased in number of peaks and peak area at 250 degrees C. Particle emissions started around 70 degrees C regardless of the dust source. Particle emissions seemed to be affected by the content of organic material.     

人群散发对高校教室室内TVOC浓度动态影响的实测分析

随机选取南京某高校10间在室人员密集的教室,在其使用期间对室内总挥发性有机化合物(TVOC)和CO₂浓度、温湿度,以及室内人员数量和典型活动状况(如开关门窗)等进行了连续监测和对比分析。研究结果表明:冬、春、夏季测试教室室内TVOC质量浓度分别为(363.1±121.7),(218.4±11.5),(583.3±38.9)μg/m³;室内TVOC浓度变化与CO₂类似,总体呈现先上升后下降的趋势,并与室内人员数量变化呈强正相关性;室内TVOC浓度水平存在季节性差异。室内总源强度的估算结果表明,室内不同样本数量的人群散发强度与室内TVOC浓度变化类似,随着人数变化,呈现出先逐渐增大,然后趋于相对稳定,最后逐渐减小的趋势。     

Chamber testing of adsorption of volatile organic compounds (VOCs) on material surfaces

A simple test chamber method to quantify adsorption and desorption of organic compounds on material surfaces is described. Important environmental parameters such as temperature, relative humidity and air velocity were varied and controlled independently around typical indoor values. Experiments were performed with alpha-pinene and toluene in concentrations of 160-300 micrograms/m3. The measurements show adsorption on and desorption from wool carpet, nylon carpet, polyvinyl chloride (PVC) floor coverings, cotton curtain material and the empty chamber. The ranking of the materials, with respect to their sorption capacity, is as mentioned above. The adsorption of alpha-pinene was higher than the adsorption of toluene for all the materials. Air velocity was not found to influence the sorption of alpha-pinene and toluene on wool carpet, tested with air velocities at 0, 10 and 20 cm/s. The experiments were carried out during both the adsorption and the desorption phase. The uncertainty of the experiments was lowest during the desorption phase. Based on the results obtained, it can be recommended that sorption experiments should be performed as desorption phase experiments. A one-sink model, based on the Langmuir adsorption isotherm, appears adequate to describe the results.     

挥发性有机化合物在复合衬里中的一维扩散解

土工膜和粘土衬里组成的复合衬里已广泛用于填埋场的防渗。有机挥发性化合物在复合衬里中迁移时,其主要的机理是分子扩散作用。本文建立了有机挥发性化合物在复合衬里中的一维扩散模型,并得到了解析解。将该解析解和以往给出的数值解法作了比较,发现两者得到的结果较为接近,从而验证了本文解的可靠性。基于本文计算模型,分析了三种常用复合衬里对挥发性有机化合物的防渗性能。研究发现对于挥发性有机化合物甲苯,土工膜和GCL组成的复合衬里的浸出液总量要比土工膜和较厚粘土衬里组成的复合衬里大好几个量级。     

Durability of 20-year-old external insulation and assessment of various types of retrofitting to meet new energy regulations

The exterior envelope of some social housing scheme buildings constructed at the beginning of the 1970s without thermal insulation has proved to be the cause of great thermal loss and condensation.At the start of the 1980s, in order to resolve these problems, our research group carried out a study which led to the introduction of external thermal insulation (on the basis of previously developed performance specifications) and verification of the thermal performance achieved.With the aim of verifying the efficacy of the intervention after 20 years and in order to assess the thermal-hygrometric performance and the state of conservation of the exterior envelope we carried out a two stage study:

1.

Performance analysis carried out through monitoring and laboratory tests.

2.

Formulation of hypotheses for retrofitting, assessed through simulations and parametric analysis.

The results showed the efficacy and durability from the thermal-hygrometric and mechanical point of view of the external insulation applied in the 1980s. It was also possible to verify energy saving for the different types of retrofit scenarios and to identify the correct positioning of the thermal insulation on the brickwork and on the floors so as to increase the surface temperatures in winter phase.