Tracers Of Emissions Research Articles

04/02593 Trace elements and common ions in south eastern Idaho snow: regional air pollutant tracers for source area emissions: Abbott, M. et al. Fuel Processing Technology, 2004, 85, (6–7), 657–671

04/02593 Trace elements and common ions in south eastern Idaho snow: regional air pollutant tracers for source area emissions: Abbott, M. et al. Fuel Processing Technology, 2004, 85, (6–7), 657–671

Application of validation data tests from an on-line volatile organic compound analyser to the detection of air pollution episodes in urban areas

This paper presents the routine and validation tests developed to evaluate 62 volatile organic compound (VOC) measurements (C 2–C 10), in ambient air from an on-line VOC analyser. These tests are based on experience obtained from application on hourly data sets obtained during April–October campaigns (1997–2001) at the Air Quality Monitoring Station sited at the School of Engineering, Bilbao (SEB) (Northern Spain). Every campaign yields 4000–4800 uninterrupted running hours, which amounts to about 1,200,000 valid data over the five intensive measuring campaigns. Quality control through data validation is critical to minimise the amount of faulty data reported, because erroneous individual data values give place to serious errors in data analysis results. These tests also allow the detection of unexpected concentration values of some pollutants. Air pollution episodes detected during data validation and meteorological influence analysis are presented. VOC data analysis together with complementary meteorological data may explain the main observed trends, especially for some of the VOCs. Acetylene and benzene are two clear cases: commonly used in the literature as vehicle emission tracers, the analysis show that, in many cases, they must be attributed to urban or industrial sources.

Fraction and composition of NOy transported in air masses lofted from the North American continental boundary layer

Five field studies have included research aircraft flights over the continental United States and the western North Atlantic Ocean from 1996 through 2000 in spring, summer, and fall seasons. The major source of NOx in this region is fossil fuel combustion, which is localized within the continental boundary layer (CBL). We use CO as a tracer of these anthropogenic emissions to estimate the fraction of the emitted NOx that is exported to the free troposphere (FT), either as NOx itself or as its oxidation products. This export was identified as plumes enhanced in CO above an estimated background by at least 30 ppbv, which account for 20–31% of the air parcels sampled in the FT during the five field studies. These plumes were encountered throughout the FT up to the 8 km ceiling of the aircraft but were primarily located just above the CBL with average altitudes of 3.0–4.1 km above ground level. In the summer over the continent, only 20 ± 5% of the originally emitted nitrogen oxides was transported in those plumes. This fraction is in reasonable accord with model results, but the models include only deep convection and not the shallow CBL venting mechanisms responsible for the observed plumes. During the two field studies in the early fall and in the spring over the western North Atlantic, we find that 9 ± 4% of the NOy was transported, although Li et al. [2004] suggest that this is an underestimate and that 15 ± 11% is more accurate. Both of these numbers indicate that model results in the literature overestimate the amount of NOy transported from the CBL to the FT. In these five field studies, HNO3 generally accounted for one‐half to two‐thirds of the NOy, which is in contrast to the dominance by NOx and organic nitrates suggested by models. Over the North Atlantic, this difference is likely due to further photochemical processing of the NOy species within the FT and over the continent due to the different transport mechanism considered in the models.

Trace elements and common ions in southeastern Idaho snow: regional air pollutant tracers for source area emissions

Snow samples were collected in southeastern Idaho over two winters to assess trace element and common ion concentrations in air pollutant fallout across the region. The objectives were to: (1) develop snow sampling and analysis techniques that produce accurate and ultra-low measurements of a broad suite of fallout elements, (2) identify the spatial and temporal trends of the fallout elements across the region, (3) determine if there are unique combinations of fallout elements that are characteristic to the major source areas in the region (source area profiles), and (4) use pattern recognition and multivariate statistical techniques (principal component analysis and classical least squares regression) to investigate source area apportionment of fallout concentrations measured at downwind locations where plumes from different source areas might mix. In the winter of 2000–2001, 250 snow samples were collected across the region over a 4-month period and analyzed in triplicate using inductively coupled plasma mass spectrometry (ICP MS) and ion chromatography (IC). Thirty nine trace elements and nine common ions were positively identified in most samples. The data were analyzed using pattern recognition tools in the software, Pirouette® (Infometrix). These results showed a large crustal component (Al, Zn, Mn, Ba, and rare earth elements), an overwhelming contribution from phosphate processing facilities located outside Pocatello in the southern portion of the Eastern Snake River Plain, some changes in concentrations over time, and no obvious source area profiles (unique chemical signatures) other than at Pocatello. Concentrations near a major U.S. Department of Energy industrial complex on the Idaho National Engineering and Environmental Laboratory (INEEL) were lower than those observed at major downwind communities. In the winter of 2001–2002, a new sampling design was tested and 135 additional samples collected to estimate pure emission profiles from the major source areas in the region. Classical least squares regression (CLS) was then used to source apportion these profiles at downwind mixing sites where plumes from the different source areas mixed. CLS performed reasonably well, predicting 36–58% of the total fallout concentrations measured at the mixing sites.

A backward modeling study of intercontinental pollution transport using aircraft measurements

In this paper we present simulations with a Lagrangian particle dispersion model to study the intercontinental transport of pollution from North America during an aircraft measurement campaign over Europe. The model was used for both the flight planning and a detailed source analysis after the campaign, which is described here with examples from two episodes. Forward calculations of emission tracers from North America, Europe, and Asia were made in order to understand the transport processes. Both episodes were preceded by stagnant conditions over North America, leading to the accumulation of pollutants in the North American boundary layer. Both anthropogenic sources and, to a lesser extent, forest fire emissions contributed to this pollution, which was then exported by warm conveyor belts to the middle and upper troposphere, where it was transported rapidly to Europe. Concentrations of many trace gases (CO, NOy, CO2, acetone, and several volatile organic compounds; O3 in one case) and of ambient atmospheric ions measured aboard the research aircraft were clearly enhanced in the pollution plumes compared to the conditions outside the plumes. Backward simulations with the particle model were introduced as an indispensable tool for a more detailed analysis of the plume's source region. They make trajectory analyses (which, to date, were mainly used to interpret aircraft measurement data) obsolete. Using an emission inventory, we could decompose the tracer mixing ratios at the receptors (i.e., along the flight tracks) into contributions from every grid cell of the inventory. For both plumes we found that emission sources contributing to the tracer concentrations over Europe were distributed over large areas in North America. In one case, sources in California, Texas, and Florida contributed almost equally, and smaller contributions were also made by other sources located between the Yucatan Peninsula and Canada. In the other case, sources in eastern North America, including moderate contributions from forest fires, were most important. The plume's maximum was mainly caused by anthropogenic emissions from the New York area. To our knowledge, this is the first case reported where a pollution plume from a megacity was reliably detected over another continent.

Measurements of polycyclic aromatic hydrocarbons in airborne particles from the metropolitan area of São Paulo City, Brazil

Polycyclic aromatic hydrocarbons (PAHs) from phenanthrene to benzo[g,h,i]perylene in airborne particles were measured in the winter of 2000 at three different sites within the metropolitan area of São Paulo City (MASP), Brazil. It is one of the largest metropolitan areas in the world and has an unconventional mixture of vehicle types, in which a variety of gasoline blends, including oxygenated ones, are used. In this study, occurrence of PAH, meteorological conditions and inter and intrasite comparisons are presented. Overall, the results revealed low PAH levels due to rainfall episodes during the sampling period. Samples collected in the urban site presented the highest PAH concentrations (av. 3.10 ng m −3 ) when compared to those collected in the urban site with dense vegetation (av. 2.73 ng m −3 ) and in the forest area (av. 1.92 ng m −3 ). PAH measurements in tunnels with different types of vehicles were performed in order to suggest possible tracers of the vehicular emissions in São Paulo. Pyrene followed by chrysene and fluoranthene were emitted mainly from gasohol vehicular motor exhausts, whereas chrysene, pyrene and benzo[a]anthracene were emitted mainly from gasohol and diesel vehicular motor exhausts. Some characteristic ratios from the tunnel measurements were used to identify vehicular sources in the atmosphere of the MASP. Although it is known that losses can occur both by evaporation and sublimation during sampling, measurements of higher molecular weight PAH compounds were taken into consideration due to their high recovery efficiency.

A study of trace metals and polycyclic aromatic hydrocarbons in the roadside environment

A study has been conducted of the concentrations of a range of inorganic elements and polycyclic aromatic hydrocarbons during a winter period at a roadside location in Birmingham, UK. Particle number and NO x concentrations were also determined continuously during the study. The analysis of size distributions of trace metals and the calculation of enrichment factors allows the identification of a number of elements which appear to be related with anthropogenic emissions. Using NO x and particle count as tracers of road traffic emissions, the elements Cu, Zn, Mo, Ba and Pb show significant correlations indicative of a traffic source contribution. When the results for the PM 0.2 size fraction are compared with those for PM 10, correlations with NO x and particle count improve for Ba and to a lesser degree for Pb, indicating association with very fine particles, whereas for Cu and Mo, the correlations are weaker for the smaller size fraction. Correlations between methylphenanthrenes, often used as tracers of diesel exhaust, particle count and NO x are significant, while correlations between methylphenanthrenes and calcium become increasingly strong moving from PM 10 through to PM 0.2, suggesting an exhaust emission of this element. Enrichment factors for lead and its correlation with NO x remain elevated despite the cessation of use of lead in automotive gasoline in the UK, and a large reduction in lead in air concentrations. The data are supportive of the conclusion that the enrichment of most trace elements in roadside aerosol derives from vehicle wear products rather than exhaust emissions, for which organic compounds are likely to prove better source tracers.

Characteristics of biomass burning emission sources, transport, and chemical speciation in enhanced springtime tropospheric ozone profile over Hong Kong

Tropospheric ozone (O3) enhancements have been continuously observed over Hong Kong. We studied the O3 enhancement events and assessed their relation to the springtime O3 maximum in the lower troposphere over Hong Kong using a 6‐year (1993 to 1999) ozonesonde data set. We identified the source regions of biomass burning emission, and established the chemical and transport characteristics of O3‐rich air masses in the enhanced O3 profiles using satellite imagery, air trajectory and trace gas data measured on board the DC‐8 aircraft during the PEM‐West‐B experiment. We identified a total of 39 O3 enhancement events, among which 35 events (90%) occurred from late February to May and 30 events (77%) had O3 enhancement within the 2.0–6.0 km altitude. The excess O3 in the O3‐rich layers adds an additional 12% of O3 into the tropospheric O3 column and results in an overall springtime O3 maximum in the lower troposphere. Forward trajectory analysis suggests that the O3‐rich air masses over Hong Kong can reach central Pacific and the western coast of North America within 10 days. Back air trajectories show that the O3‐rich air masses in the enhanced profiles pass over the Southeast (SE) Asia subcontinent, where active biomass burning occurs in the O3 enhancement period. We identified the Indo‐Burma region containing Burma, Laos and northern Thailand, and the Indian‐Nepal region containing northern India and Nepal as the two most active regions of biomass burning emissions in the SE Asia subcontinent. Ozone and trace gas measurement on board the DC‐8 aircraft revealed that O3‐rich air masses are found over many parts of the tropical SE Asia and subtropical western Pacific regions and they have similar chemical characteristics. The accompanying trace gas measurements suggest that the O3‐rich air masses are rich in biomass burning tracer, CH3Cl, but not the general urban emission tracers. We thus believe that the springtime O3 enhancement over Hong Kong is as a result of transport of photochemical O3 produced from biomass burning emissions from the upwind SE Asian continent. The large‐scale enhancements of O3 in tropical SE Asia and the subtropical western Pacific rim that result from SE Asian biomass burning activities such as presented here thus are of atmospheric importance and deserve further research efforts.

Water movement in a plant sample by neutron beam analysis as well as positron emission tracer imaging system

We present water imaging of a plant sample both by neutron beam and positron emission tracer imaging system (PETIS). The former method provided static water profile in a plant sample as well as that in the vicinity of a root imbedded in soil. Not only X-ray film but also CT method using a cooled CCD camera is presented. Through non-destructive water image in an X-ray film, root development as well as 2-dimensional water movement toward the root was analyzed. Spatial water image was constructed from 180 CT projection images, taken at an interval of one degree while rotating the sample, through a CCD camera. In the case of a soybean root, there was a water gradient toward a root in soil and gave minimum value at about 1 mm far from the surface of a root. The water absorbing part in a root was gradually shifted downward with the root development. We also present real time water movement by PETIS, where water was labeled with a positron emitting nuclide, 15O. The transportation of 15O-water within a plant was relatively slow and water uptake was observed only at the lowest internode, between a root and the first leaf, during 20-minute measurement.

Variation in composition of fine particulate emissions from heavy‐duty diesel vehicles

Samples of fine particle emissions from four heavy‐duty diesel vehicles were analyzed for chemical and molecular composition. Significant variation was found for the composition of particle emissions from vehicles under load, with the fraction of carbonaceous particles emitted as elemental carbon (i.e., soot) varying between 19 and 94%. The emissions from vehicles idling shows little compositional variation with low soot formation and elemental carbon representing between 12 and 21% of total carbon emitted. This variation is important to consider when performing source apportionment calculations as the difference in fraction carbon emitted as elemental carbon is used to separate diesel emissions from gasoline‐powered vehicle emissions and other sources. The molecular composition of the organic particulate matter was quantified for samples collected from each of the four vehicles under load plus a composite sample of all four vehicles while idling. The variation of the molecular composition of organic particulate matter was highest for polycyclic aromatic hydrocarbons and least for petroleum biomarkers, supporting the use of petroleum biomarkers as tracers for diesel vehicle emissions when the compositional information from sources is based on a limited sample set.

Coronary vascular dysfunction in premenopausal women with diabetes mellitus

Background Diabetes mellitus abolishes the sex differential in coronary artery disease morbidity and mortality in premenopausal women. This finding is independent of other diabetes-associated risk factors, suggesting that other mechanisms such as impaired coronary vascular function may contribute to the increased cardiovascular risk in women with diabetes. The objective of this study was to investigate the effect of diabetes on coronary vascular function in premenopausal women. Methods We studied 13 premenopausal women with diabetes (aged 41 ± 10 years) who were free of overt cardiovascular complications, and 21 control women (12 age-matched and 9 postmenopausal [aged 56 ± 8 years]). We used [13N]-ammonia as the flow tracer and positron emission testing to measure myocardial blood flow (MBF) at rest, during maximal hyperemia, and in response to cold pressor testing. Results Baseline MBF was lower in the postmenopausal controls, reflecting the differences in cardiac work and oxygen demand as assessed by the rate-pressure product. However, baseline MBFs were similar in the 3 groups after normalization for differences in the rate-pressure product. During hyperemia, MBF increased and coronary vascular resistance decreased significantly in the 3 groups. However, the increase (from baseline) in MBF in the women with diabetes (164% ± 58%) was less than in the premenopausal controls (258% ± 81%, P =.021), but not significantly different from the postmenopausal control women (204% ± 104%, P =.51). Likewise, the increase in MBF in response to cold pressor testing in the women with diabetes (24% ± 19%) was significantly lower than in the premenopausal controls (60% ± 39%, P =.013), but similar to that in postmenopausal control women (27% ± 15%, P =.97). These differences persisted after adjusting for age and diabetes-associated metabolic abnormalities. Conclusions These results demonstrate reduced coronary vasodilator function and impaired response of resistance vessels to increased sympathetic stimulation in premenopausal women with diabetes, similar to those observed in healthy postmenopausal women in whom the sex differential in coronary artery disease morbidity and mortality is no longer present. (Am Heart J 2002;144:711-8.)

Coronary vascular dysfunction in premenopausal women with diabetes mellitus

Background Diabetes mellitus abolishes the sex differential in coronary artery disease morbidity and mortality in premenopausal women. This finding is independent of other diabetes-associated risk factors, suggesting that other mechanisms such as impaired coronary vascular function may contribute to the increased cardiovascular risk in women with diabetes. The objective of this study was to investigate the effect of diabetes on coronary vascular function in premenopausal women. Methods We studied 13 premenopausal women with diabetes (aged 41 ± 10 years) who were free of overt cardiovascular complications, and 21 control women (12 age-matched and 9 postmenopausal [aged 56 ± 8 years]). We used [13N]-ammonia as the flow tracer and positron emission testing to measure myocardial blood flow (MBF) at rest, during maximal hyperemia, and in response to cold pressor testing. Results Baseline MBF was lower in the postmenopausal controls, reflecting the differences in cardiac work and oxygen demand as assessed by the rate-pressure product. However, baseline MBFs were similar in the 3 groups after normalization for differences in the rate-pressure product. During hyperemia, MBF increased and coronary vascular resistance decreased significantly in the 3 groups. However, the increase (from baseline) in MBF in the women with diabetes (164% ± 58%) was less than in the premenopausal controls (258% ± 81%, P =.021), but not significantly different from the postmenopausal control women (204% ± 104%, P =.51). Likewise, the increase in MBF in response to cold pressor testing in the women with diabetes (24% ± 19%) was significantly lower than in the premenopausal controls (60% ± 39%, P =.013), but similar to that in postmenopausal control women (27% ± 15%, P =.97). These differences persisted after adjusting for age and diabetes-associated metabolic abnormalities. Conclusions These results demonstrate reduced coronary vasodilator function and impaired response of resistance vessels to increased sympathetic stimulation in premenopausal women with diabetes, similar to those observed in healthy postmenopausal women in whom the sex differential in coronary artery disease morbidity and mortality is no longer present. (Am Heart J 2002;144:711-8.)

Mapping the submillimeter spiral wave in NGC 6946

We have analysed SCUBA 850\mum images of the (near) face-on spiral galaxy NGC 6946, and found a tight correlation between dust thermal emission and molecular gas. The map of visual optical depth relates well to the distribution of neutral gas (HI+H2) and implies a global gas-to-dust ratio of 90. There is no significant radial variation of this ratio: this can be understood, since the gas content is dominated by far by the molecular gas. The latter is estimated through the CO emission tracer, which is itself dependent on metallicity, similarly to dust emission. By comparing the radial profile of our visual optical depth map with that of the SCUBA image, we infer an emissivity (dust absorption coefficient) at 850\mum that is 3 times lower than the value measured by COBE in the Milky Way, and 9 times lower than in NGC 891. A decomposition of the spiral structure half way out along the disk of NGC 6946 suggests an interarm optical depth of between 1 and 2. These surprisingly high values represent 40-80% of the visual opacity that we measure for the arm region (abridged).

Turbulent Schmidt number from a tracer experiment

Measurements of pesticide emission from a bare soil were used to calculate the turbulent Schmidt number ( Sc): the ratio of eddy diffusivity for momentum (eddy viscosity) to the diffusivity for tracer mass. The value of Sc has implications for the measurement of trace gas emissions, and there is a broad range of reported values for the atmospheric surface layer. During our experiment Sc averaged 0.6, with large variability between observation periods. The standard deviation in Sc was 0.31, with no obvious correlation to atmospheric conditions. Some of this variability is due to measurement uncertainty, but we believe it also reflects true variability in Sc. We show that flux-gradient formula, which assume higher values of Sc, underestimate the true tracer emission rate Q. We also show that a dispersion model with Sc=0.6, does better at inferring Q than a model with Sc=0.45.

Measurement of emissions from air pollution sources. 5. C1-C32 organic compounds from gasoline-powered motor vehicles.

Gas- and particle-phase organic compounds present in the tailpipe emissions from an in-use fleet of gasoline-powered automobiles and light-duty trucks were quantified using a two-stage dilution source sampling system. The vehicles were driven through the cold-start Federal Test Procedure (FTP) urban driving cycle on a transient dynamometer. Emission rates of 66 volatile hydrocarbons, 96 semi-volatile and particle-phase organic compounds, 27 carbonyls, and fine particle mass and chemical composition were quantified. Six isoprenoids and two tricyclic terpanes, which are quantified using new source sampling techniques for semi-volatile organic compounds, have been identified as potential tracers for gasoline-powered motor vehicle emissions. A composite of the commercially distributed California Phase II Reformulated Gasoline used in these tests was analyzed by several analytical methods to quantify the gasoline composition, including some organic compounds that are found in the atmosphere as semi-volatile and particle-phase organic compounds. These results allow a direct comparison of the semi-volatile and particle-phase organic compound emissions from gasoline-powered motor vehicles to the gasoline burned by these vehicles. The distribution of n-alkanes and isoprenoids emitted from the catalyst-equipped gasoline-powered vehicles is the same as the distribution of these compounds found in the gasoline used, whereas the distribution of these compounds in the emissions from the noncatalyst vehicles is very different from the distribution in the fuel. In contrast, the distribution of the polycyclic aromatic hydrocarbons and their methylated homologues in the gasoline is significantly different from the distribution of the PAH in the tailpipe emissions from both types of vehicles.

Sulfur isotope ratios of coals and oils used in China and Japan

The atmospheric concentrations and isotopic compositions of sulfur and boron were measured for aerosol samples (water soluble fraction) collected from April 2004 to March 2006 at two sites on the Japan Sea coast. SO42− originating from sea salts in the aerosols was negligible (only 1–2% of the total SO42−). The atmospheric concentrations of nonsea-salt SO42− (Snss) and total B (BT) were scattered widely, but the concentration ratio BT/Snss was relatively high during winter and relatively low during summer. Moreover, aerosols during winter were characterized by a high δ34S (δ34Snss) of nonsea-salt SO42− and a low δ11B (δ11BT) of total B, whereas aerosols during summer were characterized by a low δ34Snss and a high δ11BT. A negative correlation (r2 = 0.34, p < 0.001) was observed between δ34Snss and δ11BT in aerosols from the two sites, suggesting that those values are governed primarily by a mixing of two end-members. On the basis of air trajectory analysis, the first end-member is the air mass from “Northern China (>30°N)”, whereas the second end-member is the air mass from “Japan and the Pacific Ocean”. It is likely that SO42− and B in the air mass from northern China are strongly affected by coal burning, which satisfactorily reflects the characteristics of δ34S and δ11B (i.e., high δ34S and low δ11B) of coals formed in this region. Thus, both sulfur and boron isotopes in aerosols are effective as tracers of emissions from coal burning in northern China mainly during winter when the air mass from this region is dominant. On the other hand, the results of source identification suggested that the major sources of SO42− and B in the air mass from Japan and the Pacific Ocean are oil combustion in Japan and ocean sea salts, respectively.

Molecular tracers for biomass burning emissions from species specific fuel sources

The present review focuses on elucidating the chemistry of nitrogen release during coal pyrolysis, in particular, on making clear catalytic roles of inherent Ca and Fe ions in not only the partitioning of volatile-N to tar-N, HCN, NH3 and N2 but also the conversion of char-N to N2.In slow heating rate pyrolysis of low-rank coals at 1000 °C with a fixed bed reactor, the demineralization with acid washing increases tar-N and HCN, but it decreases NH3. On the other hand, the ion-exchange of Ca2+ ions with the demineralized coals shows the nearly reverse effect on the distribution of these nitrogen species, though the physical mixing of Ca(OH)2 is almost ineffective. Since the sum of tar-N, HCN and NH3 is unchanged significantly in any cases, it is likely that Ca cations, which exist originally in the ion-exchanged forms, can control the partitioning of volatile-N to tar-N, HCN, and NH3. The Fe3+ ions precipitated on the demineralized coals catalyze the decomposition of tar-N, HCN and NH3 into N2.The evolution of N2 from coal-N occurs even in the absence of any metal cations added. The extent is generally larger with a lower rank coal, at a slower heating rate and a higher temperature, and at a longer solid residence time when coal is rapidly pyrolyzed. N2 yield at 1350 °C reaches about 70% at maximum. Since a strong reverse correlation exists between N2 and char-N, N2 originates predominantly from char-N (and/or precursors). Demineralization of low-rank coals decreases N2, whereas subsequently added Fe or Ca cations enhance N2 mainly at ≤ 1000 °C or ≥ 1000 °C, respectively. As the sum of naturally present Fe and Ca cations increases, N2 yield at 1350 °C tends to increase up to about 1 mass%. It can be proposed that fine particles of metallic Fe and CaO, which are formed from these inherent ion-exchanged cations, promote efficiently N2 formation from char-N through solid–solid interactions with heterocyclic nitrogen forms in char matrix.

Non‐sea salt sulfate and other aerosol constituents at the South Pole during ISCAT

Bulk aerosol samples collected at the South Pole were analyzed for Na, SO42−, Cl−, NO3−, methanesulfonate (MSA), 210Pb and 210Po. Sea salt concentrations were relatively high compared with previous reports, with Na, averaging 45 ng m−3 Chloride was depleted by ∼65% compared with its ratio to Na in seawater. Non‐sea salt sulfate (NSS) averaged 212 ng m−3, and less than 5% of the sulfate was from sea salt. The mean concentration of MSA (an indicator of marine biogenic sulfur) was 12 ng m−3, and the MSA/NSS mass ratio (0.059) was similar to that in Antarctic ice. Although MSA and NSS were correlated, the data set is not sufficiently robust to draw a quantitative conclusion concerning the fraction of NSS that is biogenic. Data for 210Po and 210Pb showed no evidence for strong volcanic influences on sulfate, and NSS also was not correlated with NO3−, a possible tracer of continental emissions.

Computer aided synthesis of RTD models to simulate the air flow distribution in ventilated rooms

In order to achieve a satisfactory level of hygiene and comfort in ventilated premises and to assess the pollutant transfers, it is necessary to control the air flow distribution. An intermediate approach between predictive numerical simulations and experimental determinations of aerodynamic parameters characterizing air distribution in rooms, is constituted by the systemic approach. This article presents the main principles of this approach, which is based on the residence time distribution (RTD) theory, commonly used in chemical engineering, and gives an illustration of its potential extension to ventilation problems. The aim of the IDTS code developed is to build a model from a combination of elementary systems representing basic ideal flow patterns (perfect mixed flow, plug flow,…). The adjustment of the model lies in the comparison of the response to a stimulus injected into the model with an experimental tracer emission performed in a ventilated room inlet. The general solving strategy adopted, consisting in a two-level dissociated treatment of parametric identification and structural identification of models, is first presented. Then, two problems tackled during the qualification step of the IDTS code are presented to illustrate the applications of this computer-aided design tool for the description and the quantification of air flow patterns and the associated pollutant transfers observed in ventilated indoor spaces, and particularly in nuclear ventilation networks. The comparison between experimental residence time distribution curves recorded in two ventilated laboratory enclosures and the simulated ones shows good agreement. For the last illustrative problem, a comparison with results obtained from a computational fluid dynamics tool has been performed.

GC/ITMS Measurement of Carbonyls and Multifunctional Carbonyls in PM2.5 Particles Emitted from Motor Vehicles

A method was developed and tested to identify and quantitate carbonyls and multifunctional carbonyls in fine particulate matter (PM2.5; <2.5 microm aerodynamic diameter). The method relies on ultrasonic extraction of particulate matter on filters at -8 degrees C; derivatization with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA), and PFBHA along with bis (trimethylsilyl) trifluoroacetamide (BSTFA); and detection of the derivatives by gas chromatography/ion trap mass spectrometry. Ultrasonic extraction of model compounds from enriched particles was affected by solvent polarity (water > methylene chloride > toluene-isopropanol (2 + 1, v/v). Water provided the highest recovery for dihydroxy acetone, pyruvic acid, and hydroxy acetone, compared to methylene chloride, and toluene-isopropanol. Lowering the ultrasonication bath temperature from 0 degrees to -8 degrees C improved the recoveries of the less water soluble and more volatile species-methacrolein, methyl vinyl ketone, 2,3-butanedione, and tolualdehyde. The power of the method was demonstrated by identification and quantitation of carbonyls and multifunctional carbonyls in sample extracts of fine particulate matter (PM2.5) collected in the Caldecott tunnel, CA. The identities of crotonaldehyde, 2,3-butanedione, glyoxal, 9H-fluoren-9-one, glycolaldehyde, glyoxylic acid, levulinic acid, and 3-hydroxybenzaldehyde were confirmed by comparing the relative retention time and mass spectra of the analyte in the sample extract with an authentic standard. Quantitation of crotonaldehyde, glyoxal, 2,3-butanedione, glyoxylic acid, and levulinic acid was accomplished. This is the first report of glyoxylic acid, levulinic acid, and 3-hydroxybenzaldheyde in PM2.5 particles sampled in a roadway tunnel. It is also the first report of a C10 carbonyl with the molecular formula of C10H16O2, a hydroxy carbonyl with the molecular formula of C17H21NO2, and a hydroxy or dihydroxy carbonyl with the molecular formula of C16H14O2 or C9H10O3. The high-molecular weight hydroxy carbonyls, which were found only in the heavy-duty (diesel) bore, may be tracers of diesel emissions in air.