Wood smoke as a source of particle-phase organic compounds in residential areas

The objective of this study was to investigate the organic composition of wood smoke emissions and ambient air samples in order to determine the wood smoke contribution to the ambient air pollution in the residential areas. From November 2005 to March 2006 particle-phase PM₁₀ samples were collected in the residential town Dettenhausen surrounded by forests near Stuttgart in southern Germany. Samples collected on pre-baked glass fibre filters were extracted using toluene with ultrasonic bath and analysed by gas chromatography mass spectrometry (GC-MS). 21 polycyclic aromatic hydrocarbons (PAH) including 16 USEPA priority pollutants, different organic wood smoke tracers, primarily 21 species of syringol and guaiacol derivatives, levoglucosan and its isomers mannosan, galactosan and dehydroabietic acid were detected and quantified in this study. The concentrations of these compounds were compared with the fingerprints of emissions from hardwood and softwood combustion carried out in test facilities at Universitaet Stuttgart and field investigations at a wood stove during real operation in Dettenhausen. It was observed that the combustion derived PAH was detected in higher concentrations than other PAH in the ambient air PM₁₀ samples. Syringol and its derivatives were found in large amounts in hardwood burning but were not detected in softwood burning emissions. On the other hand, guaiacol and its derivatives were found in both softwood and hardwood burning emissions, but the concentrations were higher in the softwood smoke compared to hardwood smoke. So, these compounds can be used as typical tracer compounds for the different types of wood burning emissions. In ambient air samples both syringol and guaiacol derivatives were found which indicates the wood combustion contribution to the PM load in such residential areas. Levoglucosan was detected in high concentrations in all ambient PM₁₀ samples. A source apportionment modelling, Positive Matrix Factorization (PMF) was implemented to quantify the wood smoke contribution to the ambient PM₁₀ bound organic compounds in the residential area.     

Influence of particulate matter on the air quality situation in a mediterranean island

The objective of this study was to describe the ambient levels of particulate matter (PM) and its influence to air quality situation on the dry Mediterranean island of Cyprus. From October 2002 to August 2003 PM₁₀ and PM_2.5 samples were collected at 31 different sampling sites in Cyprus. In addition, continuous measurements of PM₁₀ were carried out from 2003 to 2007 at a traffic and a rural site. It can be recognised that at all traffic and at some residential and urban background sites, the actual EU limit values have been exceeded. Special events e.g. long-range transport of Sahara dust storms were recorded over urban as well as rural areas in the order of 6–8 events per year, with a major frequency in summer and spring periods. The comparison of the PM₁₀ concentrations in Cyprus cities with values of other European cities demonstrates the PM₁₀ problem in Cyprus, especially in the dry summer season, when no rain is cleaning the air and the dry surfaces. This underlines the necessity of PM abatement strategies.     

Neural modelling of the spatial distribution of air pollutants

In this paper, a new method to calculate the average spatial distribution of air pollutants based on diffusive sampling measurements and artificial neural networks evaluation is presented. Most established methods like interpolation algorithms are inflexible or limited in considering important distribution parameters such as emission sources or land use. Of special interest are air quality measurements since they provide a direct view on the actual pollutant level. With diffusive samplers, the average concentration of many gaseous species over a large area can be determined simultaneously. During a project in Cyprus, NO₂ diffusive samplers were exposed at 270 sites in six month-long campaigns throughout one year providing the database for the model described in this paper. A multilayer perceptron was trained with the NO₂ measurement data and distribution parameters like population density and meteorological parameters using a 1 × 1 km grid covering Cyprus. The best fit could be achieved with an emissions inventory including previously simulated concentration plumes and population density data as input nodes for the neural network, resulting in realistic maps of the annual average distribution of NO₂ in Cyprus.     

Detection of sulfur-free odorants in natural gas using ion mobility spectrometry

Beside the primary motivation of the public gas suppliers for odorizing natural gas with a sulfur-free odorant, which relates to the image of the environment-friendly fuel, natural gas, competing with low-sulfur heating fuel and diesel, a question of crucial importance of how to detect such sulfur-free odorants comes up. Concerning the replacement of sulfur-containing by sulfur-free odorization, the availability of a fast and sensitive detection method that can, further, be used on-site plays a key role. The minimum concentration of the new sulfur-free odorant Gasodor S-Free (S-Free) in natural gas should be added at a level of at least 8.8 mg m(-3) to assure a significant warning smell. Therefore, a dynamic range between 0 and approx. 25 mg m(-3) must be realised in the rather complex matrix of natural gas. By means of a handheld ion mobility spectrometer, the odorant content in natural gas is determined within less than 80 s total analysis time directly at the gas pipe. The concentration of S-Free is monitored between 4 and 23 mg m(-3) respecting the quality of the natural gas (high- and low-caloric gas). Results of the validation using a gas chromatograph as a reference standard will be discussed in detail.     

PCDD/PCDF emissions from small firing systems in households

This report presents results of emission measurements of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in the flue gas of seven oil, nine gas, and two wood firing systems under laboratory conditions. The burn rate of the combustion was in the range of the rated useful heat output. Two additional test series varied the amount of combustion air and thus the heat output. The PCDD/PCDF emissions for oil- and gas-fired boilers are in the range of 0.0020-0.0142 ng I-TEQ/m3 (referring to 3% O2 in the dry flue gas). No correlation between the combustion technique and the PCDD/PCDF emissions could be established. In the tests with the wood-fired furnaces PCDD/PCDF concentrations in the flue gas ranging from 0.014 to 0.076 ng I-TEQ/m3 (referring to 13% O2 in the dry flue gas) were found. A significant correlation between the firing rate of the heating insert and the measured PCDD/PCDF concentrations was found. On examination of three typical 2,3,7,8-CDD/CDF congener profiles, a comparable pattern could be observed with natural gas and light fuel oil. The congener distribution for wood combustion is considerably different.     

Identification of PM10 Sources in a Mediterranean Island

Due to the dry Mediterranean climate in Cyprus, particulate matter is resuspended from soils and other surfaces. From November 2002 to August 2003, gravimetric PM₁₀ measurements were carried out at three characteristic sites (traffic, residential and rural). A significant seasonal trend with high winter concentrations was observed at the traffic site. Special events, e.g. long-range transport of Sahara dust storms, were recorded over traffic, residential and rural areas in the order of six to eight events per year, with a major frequency in summer and spring periods. This contributes to the increase of 24-h EU limit value exceedances for PM₁₀ at the three investigated sites. The origin of the PM₁₀ load was determined by enrichment factors based on analyses of the local soil deposition at the investigated sites. Furthermore, positive matrix factorisation modelling was applied to find the sources of PM₁₀. Results indicate that the major emission sources affecting the PM₁₀ load were mineral soil, sea salt, road dust, oil combustion, secondary pollutants and gasoline vehicles. The natural contribution (local mineral soil and sea salt) at the three sites was in the range of 7–9 μg m^?3 in PM₁₀. Besides the Sahara dust storms and natural background concentrations, the vehicular pollution was found as the largest contributor (12–14 μg m^?3) to PM₁₀ load at the traffic site.     

Influence of Inversion Layers on the Distribution of Air Pollutants in Urban Areas

The air quality in urban areas is on the one hand determined by the intensity of emissions. On the other hand atmospheric dispersion and chemical transformation conditions as well as topographic location have great influence on the ambient air concentrations. Within, this study the correlation between pollutant concentrations and the dynamics of atmospheric barrier and mixing layers has been experimentally investigated by tethered balloon soundings.The most important barrier layer is the surface inversion. During clear sky it develops in the late afternoon and is dissolved by warm air from the heated ground in the morning. Emitted pollutants are kept beneath this inversion. But, at the same time, the component ozone is depleted below and stored above the layer within the so called `ozone reservoir layer'. During night elevated mountain sites are decoupled from the ground conditions and stay within this reservoir without a remarkable nocturnal decrease of ozone concentration. The regularly observed ground level ozone increase in the morning hours is firstly caused by down mixing from the reservoir. The conditions and dynamics are illustratively depicted by vertical profiles of the different components and diagrams of temperature and concentration isopleths over the height and the experiment time lasting over five days.     

Temporal variation and impact of wood smoke pollution on a residential area in southern Germany

This paper is a continuation of our previous publication (Bari, M.A., Baumbach, G., Kuch, B., Scheffknecht, G., 2009. Wood smoke as a source of particle-phase organic compounds in residential areas. Atmospheric Environment 43, 4722–4732) and describes a detailed characterisation of different particle-phase wood smoke tracer compounds in order to find out the impact of wood-fired heating on ambient PM₁₀ pollution in a residential area near Stuttgart in southern Germany. The results from previous flue gas measurements help distinguishing different tracer compounds in ambient PM₁₀ samples. In the residential area, significant amounts of hardwood markers (syringaldehyde, acetosyringone, propionylsyringol, sinapylaldehyde) and low concentrations of softwood markers (vanillin, acetovanillone, coniferyldehyde, dehydroabietic acid, retene) were found in the ambient air. The general wood combustion markers Levoglucosan, mannosan and galactosan were detected in high concentrations in all particle-phase PM₁₀ samples. To find out the size distribution of ambient particles, cascade impactor measurements were carried out. It was found that more than 70% of particulate matter was in the particle diameter of less than 1 μm. Using emission ratio of levoglucosan to PM₁₀, it can be demonstrated that during winter months 59% of ambient PM₁₀ pollution could be attributed to residential wood-fired heating.