Atmospheric Environment (v.41, #27)
Editorial board (i).
Seasonal distribution of polar organic compounds in the urban atmosphere of two large cities from the North and South of Europe by César Oliveira; Casimiro Pio; Célia Alves; Margarita Evtyugina; Patrícia Santos; Virgínia Gonçalves; Teresa Nunes; Armando J.D. Silvestre; Finn Palmgren; Peter Wåhlin; Stuart Harrad (5555-5570).
Polar organic species, including n-alkanols, sterols, anhydrosugars, n-alkanoic acids, n-alkenoic acids and dicarboxylic acids were quantified to typify the composition of fine (PM2.5) and coarse (PM10–2.5) aerosols collected simultaneously at roadside and background sites in Oporto (Portugal) and Copenhagen (Denmark) during separate month-long intensive summer and winter campaigns. As a general trend, both cities exhibit roadside average concentrations higher than their correspondent urban background levels. The polar organics are more abundant in the fine fraction, exhibiting a seasonal pattern with high winter concentrations and low summer loads. Aerosols from both cities showed typical distributions of n-alkanols and n-alkanoic acids in the ranges C12–C28 and C8–C28, respectively. The <C20 homologues, usually attributed to kitchen emissions, vehicular exhausts and microbial origins, dominated the fatty acid fraction. Linear alcohols were mainly represented by higher molecular weight homologues from vegetation waxes. Molecular tracer species for wood smoke (e.g. levoglucosan, mannosan and resinic acids) were found to contribute significantly to the urban aerosol, especially in winter. Ratios between these tracers indicated different biofuel contributions to the atmospheric particles of the two cities. Secondary constituents from both biogenic (e.g. pinonic acid) and anthropogenic precursors (e.g. phthalic and benzoic acids) were detected in both cities and seasons.
Keywords: Urban aerosols; Polar organic compounds; Tracers; Source apportionment;
The formation of organic sulfate esters in the limonene ozonolysis secondary organic aerosol (SOA) under acidic conditions by Yoshiteru Iinuma; Conny Müller; Olaf Böge; Thomas Gnauk; Hartmut Herrmann (5571-5583).
Secondary organic aerosol (SOA) formation from the gas phase ozonolysis of limonene and the influence of particle acidity were investigated in a series of indoor aerosol chamber experiments. The particle acidity was adjusted in three stages using Na2SO4 (neutral), (NH4)2SO4/H2SO4 (acidic) and H2SO4 (strongly acidic) seed particles. Detected low molecular weight carboxylic acids ( M w < 300 ) were found to account only for a smaller fraction of produced SOA mass at all particle acidities. Although SOA components with molecular weights between 300 and 900 were detected regardless of the seed particle acidity, the intensities of these compounds were much higher for acidic seed particle experiments. Compounds with mass to charge ratios ( m / z ) 281, 465 and 481 were only detected in the presence of sulfuric acid. MS n and TOFMS analyses showed a strong fragment of m / z 97 and elemental compositions of C 10 H 17 O 7 S - , C 20 H 33 O 10 S - and C 20 H 33 O 11 S - suggesting organic sulfate structures, possibly formed by a heterogeneous acid catalyzed reaction of limonene oxidation products and sulfuric acid in the particle phase. The high intensities of organic sulfate esters suggest that these compounds contribute at least as much as first and second generation oxidation products to the SOA mass.
Keywords: Limonene; Ozonolysis; Oligomers; Organic sulfate ester; Particle acidity; SOA;
Characteristics of mercury exchange flux between soil and air in the heavily air-polluted area, eastern Guizhou, China by Shaofeng Wang; Xinbin Feng; Guangle Qiu; Xuewu Fu; Zhongqing Wei (5584-5594).
To investigate the characteristics of mercury exchange between soil and air in the heavily air-polluted area, total gaseous mercury (TGM) concentration in air and Hg exchange flux were measured in Wanshan Hg mining area (WMMA) in November, 2002 and July–August, 2004. The results showed that the average TGM concentrations in the ambient air (17.8–1101.8 ng m−3), average Hg emission flux (162–27827 ng m−2 h−1) and average Hg dry deposition flux (0–9434 ng m−2 h−1) in WMMA were 1–4 orders of magnitude higher than those in the background area. It is said that mercury-enriched soil is a significant Hg source of the atmosphere in WMMA. It was also found that widely distributed roasted cinnabar banks are net Hg sources of the atmosphere in WMMA. Relationships between mercury exchange flux and environmental parameters were investigated. The results indicated that the rate of mercury emission from soil could be accelerated by high total soil mercury concentration and solar irradiation. Whereas, highly elevated TGM concentrations in the ambient air can restrain Hg emission from soil and even lead to strongly atmospheric Hg deposition to soil surface. A great amount of gaseous mercury in the heavily polluted atmosphere may cycle between soil and air quickly and locally. Vegetation can inhibit mercury emission from soil and are important sinks of atmospheric mercury in heavily air-polluted area.
Keywords: TGM concentration in air; Mercury exchange flux; Factors controlling mercury exchange flux; Wanshan Hg mining area (WMMA);
Monsoon rain chemistry and source apportionment using receptor modeling in and around National Capital Region (NCR) of Delhi, India by Suresh Tiwari; U.C. Kulshrestha; B. Padmanabhamurty (5595-5604).
Studies on monsoon precipitation chemistry were carried out to understand the nature of rainwater and sources of pollution at eight different locations in and around the National Capital Region (NCR) of Delhi during southwest monsoon in the years 2003–2005. These sites were Bulandshahr (BUL), Garhmuktesar (GAR), Muradnagar (MUR), Sardhana (SAR), Panipat (PAN), Charkhi Dadri (CHA), Hodal (HOD) and Bahror (BAH). The rainwater samples, collected at these locations, were analyzed for major anions, cations and pH. The data were assessed for its quality. In general, the order of concentrations of major ions was observed to be: Ca2+>SO4 2−>HCO3 −>NH4 +>Cl−>NO3 −>Na+>Mg2+>K+>F−. The average pH of rainwater at these stations was observed to be 6.39, ranging from 5.77 to 6.62, indicating alkaline nature. However, a few rain events, 31% at Panipat, 12% at Muradnagar and 29% at Sardhana, were observed to be acidic (pH<5.6). Acidity observed at Panipat and Muradnagar is attributed to industrial influence but at Sardhana to weak organic acids contributed by surrounding vegetation. No definite trends are found for most of the components at all the sites. However, concentrations of Cl− at Bulandshahr; NO3 − at Muradnagar and Hodal; F− at Panipat and Bahror; Na+ at Bulandshahr; K+ at Bahror and Bulandshahr; Ca2+ at Bulandshahr, Muradnagar, Charkhi Dadri and Sardhana; Mg2+ at Panipat, Bahror, Bulandshahr, Hodal and Sardhana have increased from 2003 to 2005. For source identification, principal component analysis (PCA) was made, which showed that in general, at all the sites; suspended soil–dust and sea salts which are natural sources, were identified as the most dominating. Sources like agriculture including cattle, brick kilns and industries were reflected in third or fourth PC indicating moderate influence of anthropogenic activities in this region.
Keywords: Precipitation chemistry; Soil–dust interference; Alkaline pH; Monsoon rain; Receptor modeling;
Area of influence (AOI) sensitivity analysis: Application to Atlanta, Georgia by Sergey L. Napelenok; Florian D. Habermacher; Farhan Akhtar; Yongtao Hu; Armistead G. Russell (5605-5617).
Area of influence (AOI) analysis was applied to determine the geographical extent of the air pollutant precursors contributing to various pollutant levels in the Atlanta metropolitan area. Receptor-oriented sensitivities of ozone and particulate matter (PM) species to emissions of NO x , SO 2 , NH 3 , anthropogenic VOC, and elemental carbon were calculated for various combinations of precursor emissions during 1–10 August, 1999. The episode had high observed concentrations of ozone and PM across several days. AOIs differed significantly by day for each sensitivity as well as spatially between pollutants. Ozone sensitivities peaked at 1.0 ppb per 1.0 mole s - 1 (or per 4.0 ton day - 1 ) per 12 × 12 km 2 model grid of emissions of NO x , but averaged around 0.1 ppb over much of Atlanta. Sulfate was the major component of PM, with an average sensitivity of 0.03 μ g m - 3 per 1.0 mol s - 1 (or per 5.5 ton d - 1 ) per 12 × 12 km 2 model grid of SO 2 emissions and an average of 0.02 μ g m - 3 per 1.0 mol s - 1 per 12 × 12 km 2 of NO x emissions. Ammonia had a significant impact on PM through the formation of ammonium sulfate and ammonium nitrate. Elemental carbon had a geographically small area of influence with high values around the receptor.
Keywords: Area of influence; AOI; Sensitivity analysis; Atmospheric modeling; Air quality; Direct decoupled method;
Air quality impacts of distributed power generation in the South Coast Air Basin of California 2: Model uncertainty and sensitivity analysis by M.A. Rodriguez; J. Brouwer; G.S. Samuelsen; D. Dabdub (5618-5635).
Uncertainty and sensitivity of ozone and PM 2.5 aerosol to variations in selected input parameters are investigated with a Monte Carlo methodology using a three-dimensional air quality model. The selection of input parameters is based on their potential to affect concentration levels of ozone and PM 2.5 predicted by the model and to reflect changes in emissions due to the implementation of distributed generation (DG) in the South Coast Air Basin (SoCAB) of California. Numerical simulations are performed with the CIT air quality model. Response of the CIT predictions to the variation of selected input parameters is investigated to separate the potential air quality impacts of DG from model uncertainty. This study provides a measure of the model errors for selected species concentrations. A spatial sensitivity analysis is used to investigate the effect of placing DG in specific regions of the SoCAB. In general, results show that confidence in the model results is greatest in locations where ozone and PM 2.5 concentrations are the highest. Changes no greater than 80% in the nominal values of selected input variables, cause changes of 18% in ozone mixing ratios and 25% for PM 2.5 aerosol concentrations. Sensitivity analysis reveals that nitrogen oxides ( NO x ) emissions and side boundary conditions of volatile organic compounds (VOC) are the major contributors to uncertainty and sensitivity of ozone predictions. An increase in NO x emissions leads to reductions in ozone mixing ratios at peak times and sites where the maximum values are located. PM 2.5 aerosol is most sensitive to changes in NH 3 and NO x emissions. Increasing these emissions leads to higher aerosol concentrations. Sensitivity analyses show that the impacts of DG implementation are highly dependent on both space and time. In particular, ozone concentrations are reduced during the nighttime nearby locations where DGs are installed. However, during the daytime ozone concentrations increase downwind from the sources. A major finding of this study is that the emissions of DG installed in coastal areas produce a significant impact on the production of ozone and PM 2.5 aerosol in the eastern regions of the SoCAB.
Keywords: Distributed power generation; Uncertainty and sensitivity analysis; Monte Carlo analysis; Spatial sensitivity;
Application of synoptic weather typing to an investigation of nocturnal ozone concentration at a maritime location, New Zealand by B.A. Khan; C.R. de Freitas; D. Shooter (5636-5646).
Relationships between weather types and the air pollutants ozone (O3) and nitrogen oxides ( NO x ) at night are explored through the analysis of two years of data from the east coast of the Auckland urban area. Principal component analysis is used to identify synoptic classes and corresponding weather types, while principal component regression is used to assess relationships between these and O3 and NO x ( NO + NO 2 ) concentrations. Three synoptic classes (labelled cyclonic, anticyclonic and intermediate) consisting of seven discrete weather types were identified. Anticyclonic and cyclonic synoptic conditions were strong determinants of O3 and NO x concentrations. The intermediate class was the most persistent but had less significant effect on O3 and NO x concentrations. In cyclonic conditions, NO x was low due to increased ventilation. NO x concentration under anticyclonic conditions with cold and relatively dry air from Auckland urban areas was large, while that of O3 was generally small, as O3 is efficiently removed as a result of chemical titration with NO in the stable boundary layer. Under these conditions O3 can also be expected to be removed by dry deposition and NO x removed by the heterogeneous hydrolysis of dinitrogen pentoxide (N2O5). In cyclonic conditions and during times when winds from over the ocean prevailed, the concentration of O3 was relatively high, apparently due to a very weak O3 titration reaction and intrusion of regional-scale background O3. Temperature and humidity had no significant effect on nocturnal O3, while both affected NO2 concentrations.
Keywords: Nocturnal ozone; Weather types; Nitrogen oxides; New Zealand; Meteorological variables;
Regulated emissions from biodiesel fuels from on/off-road applications by Thomas D. Durbin; David R. Cocker; Aniket A. Sawant; Kent Johnson; J. Wayne Miller; Bruce B. Holden; Norman L. Helgeson; Jason A. Jack (5647-5658).
This research is one of the largest studies of biodiesel in both on-road and off-road uses. The testing was conducted for the military and encompassed a wide range of application types including two medium-duty trucks, two Humvees, a heavy heavy-duty diesel truck, a bus, two stationary backup generators (BUGs), a forklift, and an airport tow vehicle. The full range of fuels tested included a California ultra-low sulfur diesel (ULSD) fuel, different blend ratios of two different yellow-grease biodiesels and one soy-based biodiesel, JP-8, and yellow-grease biodiesel blends with two different NO x reduction additives. The B20-YGA, B20-YGB, and B20-Soy did not show trends relative to ULSD that were consistent over all applications tested. Higher biodiesel blends were tested on only one vehicle, but showed a tendency for higher total hydrocarbons (THC) and carbon monoxide (CO) emissions and lower particulate matter (PM) emissions. The JP-8 showed increases in THC and CO relative to the ULSD.
Keywords: Emissions; Biodiesel; Diesel; Vehicles;
Exploring relationships between outdoor air particulate-associated polycyclic aromatic hydrocarbon and PM2.5: A case study of benzo(a)pyrene in California metropolitan regions by Agnes B. Lobscheid; Thomas E. McKone; Daniel A. Vallero (5659-5672).
Polycyclic aromatic hydrocarbons (PAHs) and particulate matter (PM) are co-pollutants emitted as by-products of combustion processes. Convincing evidence exists for PAHs as a primary toxic component of fine PM (PM2.5). Because PM2.5 is listed by the US EPA as a “Criteria Pollutant”, it is monitored regularly at sites nationwide. In contrast, very limited data is available on measured ambient air concentrations of PAHs. However, between 1999 and 2001, ambient air concentrations of PM2.5 and benzo(a)pyrene (BaP) are available for California locations. We use multivariate linear regression models (MLRMs) to predict ambient air levels of BaP in four air basins based on reported PM2.5 concentrations and spatial, temporal and meteorological variables as variates. We obtain an R 2 ranging from 0.57 to 0.72 among these basins. Significant variables (p<0.05) include the average daily PM2.5 concentration, wind speed, temperature and relative humidity, and the coastal distance as well as season, and holiday or weekend. Combining the data from all sites and using only these variables to estimate ambient BaP levels, we obtain an R 2 of 0.55. These R 2-values, combined with analysis of the residual error and cross validation using the PRESS-statistic, demonstrate the potential of our method to estimate reported outdoor air PAH exposure levels in metropolitan regions. These MLRMs provide a first step towards relating outdoor ambient PM2.5 and PAH concentrations for epidemiological studies when PAH measurements are unavailable, or limited in spatial coverage, based on publicly available meteorological and PM2.5 data.
Keywords: Toxic air pollutants; Particulate matter; Regression models; Combustion sources;
Chemical characterization of volatile organic compounds near the World Trade Center: Ambient concentrations and source apportionment by David A. Olson; Gary A. Norris; Robert L. Seila; Matthew S. Landis; Alan F. Vette (5673-5683).
Concentrations of 53 volatile organic compounds (VOCs) are reported from four locations near the World Trade Center (WTC) (New York, USA) complex for canister samples collected from September 2001 through January 2002. Across the four sampling sites, mean concentrations ranged from 94.5 to 219 μ g m - 3 for total VOCs. The highest mean concentrations for individual VOCs at any site were for ethane ( 18.7 μ g m - 3 ) , isopentane ( 17.1 μ g m - 3 ) , and m , p -xylenes ( 17.0 μ g m - 3 ) . VOC concentrations were generally highest for samples collected north and west of the WTC complex. Concentrations of total VOCs (and most individual VOCs) decreased from the period when fires were present at the WTC complex (before 19 December 2001) to the period after fires. The EPA Unmix Version 5.0 receptor model was used to assess the impact of WTC fires and recovery efforts on ambient VOC concentrations. Four factors were identified: burning of building debris, a mixed recovery/heating source, motor vehicle exhaust, and a mixed gasoline source.
Keywords: World Trade Center; Receptor modeling; Source apportionment; Building fire;
Fine, ultrafine and nanoparticle trace element compositions near a major freeway with a high heavy-duty diesel fraction by Leonidas Ntziachristos; Zhi Ning; Michael D. Geller; Rebecca J. Sheesley; James J. Schauer; Constantinos Sioutas (5684-5696).
Trace elements and metals in the ultrafine (<0.18 μm) and accumulation (0.18–2.5 μm) particulate matter (PM) modes were measured during the winter season, next to a busy Southern California freeway with significant (∼20%) diesel traffic. Both ambient and concentrated size-segregated impactor samples were taken in order to collect enough mass for chemical analysis. Data at this location were compared to a site located 1 mile downwind of the freeway, which was reflective of urban background. The most abundant trace elements in the accumulation mode detected by inductively coupled plasma mass spectroscopy (ICPMS) were S (138 ng m−3), Na (129 ng m−3), and Fe (89 ng m−3) while S (35 ng m−3) and Fe (35 ng m−3) were the most abundant in the ultrafine mode. The concentrations of several trace elements, including Mg, Al, and Zn, and in particular Ca, Cu, and Pb, did not uniformly increase with size within fine PM, an indication that various roadway sources exist for these elements. Calculation of crustal enrichment factors for the two sites indicates that the freeway traffic contributed to enriched levels of ultrafine Cu, Ba, P and Fe and possibly Ca. The results of this study show that trace elements constitute a small fraction of PM mass in the nanoparticle size range, but these can and should be characterized due to their likely importance to human health.
Keywords: Nanoparticles; Metals; Elements; Diesel; Ultrafine; PM; NanoMOUDI;
Uptake and conversion of carbonyl sulfide in a lawn soil by Junfeng Liu; Yujing Mu; Chunmei Geng; Yunbo Yu; Hong He; Yuanhang Zhang (5697-5706).
Carbonyl sulfide (COS) exchange fluxes between a lawn soil and the atmosphere as well as influencing factors (temperature and water content of soil) were investigated using a static cuvette. The optimal soil temperature and water content for COS consumption were about 298 K and 12.5%, respectively. The converting products of the consumed COS in the lawn soil were researched using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The peaks of gas-phase products of CO 2 and surface HCO 3 - , HS - , SO 3 2 - , HSO 3 - , and SO 4 2 - species were observed. The possible mechanism of COS conversion in the lawn soil was discussed. The conversion rates of consumed COS into water-soluble sulfate in the lawn soil were studied by ion chromatography (IC). The experimental results show that about 50% sulfur from the soil consumed COS was eventually converted into water-soluble sulfate.
Keywords: COS; Sulfate; H 2 S ;
Ultraviolet radiation spatio-temporal characteristics derived from the ground-based measurements taken in China by Bo Hu; Yuesi Wang; Guangren Liu (5707-5718).
Ultraviolet (UV) radiation and broadband solar radiation (R s) measured from January 2005 to June 2006 at 31 stations in Chinese Ecosystem Research Network (CERN) were used to investigate the spatio-temporal characteristics of UV radiation and UV fraction (the ratio of UV radiation to R s) in China. Results indicated that the seasonal variations of UV radiation and R s were consistent with the solar activities, which reached their lower values during winter period, and increased throughout the spring, peaking in June or July, in most sites. The Meiyu weather system and Southwest Monsoon produced different variation characteristics of UV radiation and R s in subtropical and tropical regions. The UV fraction values showed a similar seasonal trend as that of UV radiation, which was mainly determined by the seasonal change of the aerosol optical depth (AOD) and water vapor content in atmosphere. The seasonal variations of UV fraction were much smoother in southern China due to high water vapor content over the whole year.The UV radiation showed an increasing trend from east to west in China. In the western area, a simple increasing trend was observed from north to south, with the largest annual mean daily UV value 0.91 MJ m−2 appearing in the Qinghai-Tibet Plateau area. In east China there was a low center that appeared in the subtropical region due to high aerosol burden, with the lowest value 0.41 MJ m−2 observed in Yanting site. Two high centers were located in the tropics with higher solar altitudes and the north desert region with low atmospheric attenuation. The largest values of UV fraction appeared in the tropical and subtropical regions due to higher relative humidity (RH) in these areas. However, the smallest value did not appear in the north desert region where the RH was the lowest, they were found at the Luancheng site which featured relatively low humidity and abundant fine aerosols. The variations in the UV fraction were not such distinctive as those of the UV radiation in China due to the more complex influences of aerosol and water vapor.
Keywords: Ultraviolet radiation; Ultraviolet fraction; Spatio-temporal characteristics;
A comparison of PAMS and air toxics measurements by Gopal Sistla; Nenad Aleksic (5719-5731).
One of the requirements of the 1990 Clean Air Act Amendments (CAA) is that 1-h ozone nonattainment areas that are classified severe or higher category are required to operate a network of photochemical assessment monitors (PAMS) to provide hourly measurements of volatile organic compounds (VOCs) comprising of Carbon number <12 (C2–C12), along with carbonyl measurements at 3-h intervals during the summer ozone season. Often collocated with PAMS are 24-h-integrated canister and cartridge-based measurements of selected air toxic compounds, thereby providing an opportunity for inter-comparison and validation of both sets of data. In this study, we report such a comparison and estimates of trend for benzene, m-, p- and o-xylene, toluene, ethylbenzene, 1,2,4-trimethylbenzene, formaldehyde and acetaldehyde at Bronx, NY. The analysis shows that hourly PAMS and 24-h-integrated air toxics are in good agreement with each other exhibiting similar trends and that the PAMS with the higher temporal resolution offers information on excursions of the toxic compounds that would be quite useful in assessment of acute health effects. These findings were also found to be applicable to other locations such as South De Kalb, GA; Gary, IN and Lynn, MA.
Keywords: PAMS; Air toxics; Benzene; Carbonyls; Trends; New York City;
Validation of the integrated RAMS-Hg modelling system using wet deposition observations for eastern North America by Antigoni Voudouri; George Kallos (5732-5745).
Using the well-known Regional Atmospheric Modelling System (RAMS) version 4.3 an integrated system able to simulate the atmospheric mercury cycle has been developed. Basic processes of the mercury atmospheric cycle have been incorporated into the atmospheric model. The model deals with elemental Hg (Hg0), divalent gaseous Hg (Hg2) and particulate Hg (HgP). Wet deposition mechanisms used to describe the removal of Hg2 and HgP are merged with the detailed cloud microphysical scheme in order to provide better representation of the wet deposition processes. The advantages of this approach have been examined through results intercomparison with simulated Hg wet deposition using CMAQ-Hg from previous work for two evaluation periods: 4 April–2 May 1995, and 20 June–18 July 1995. An attempt to clarify the main parameters that affect wet deposition mechanism of mercury is also made.
Keywords: Atmospheric mercury; Modelling system; Evaluation; Model coupling intercomparison;
An information theoretic perspective on mesoscale seasonal variations in ground-level ozone by Sean W. Fleming (5746-5755).
Relatively little prior use has been made of information theory in air quality analysis. This paper explores whether basic, but formal, quantitative measures of information content might yield fresh perspectives on seasonal variations in the ground-level ozone concentration field across the lower Fraser Valley (LFV), British Columbia, Canada. I calculate Shannon entropy in daily maximum ozone concentration on a month-by-month, station-by-station basis, using 1 year of hourly measurements from 18 air quality monitoring stations. The values are then qualitatively compared with an eye to identifying spatial and seasonal patterns. The results further demonstrate the potential utility of information theoretic concepts for assessing air quality variability; yield some new insight into tropospheric ozone dynamics across the LFV; and may provide some guidance to the refinement of monitoring network configuration. Of particular note is that, although entropy and mean concentration exhibit some similarities in their respective seasonal patterns, maximum uncertainty and information content appears to occur at times and locations somewhat different from those at which highest concentrations are experienced.
Keywords: Information theory; Communication theory; Entropy; Ozone; Shannon; Lower Fraser Valley; Vancouver;
Characterization of incense smoke by solid phase microextraction—Comprehensive two-dimensional gas chromatography (GC×GC) by Tin C. Tran; Philip J. Marriott (5756-5768).
Comprehensive two-dimensional gas chromatography in tandem with flame ionization detection (GC×GC-FID) was used for the qualitative fingerprint characterisation of four different types of powdered incense headspace (H/S), and incense smoke. Volatile organic compounds (VOCs) in the incense powder and smoke were extracted by using solid phase microextraction (SPME) with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) 65 μm fiber. Low-polarity/polar, and polar/non-polar phase combinations were tested to contrast the GC×GC separation of components in these two column sets.A total of 324 compounds were tentatively identified, with more than 100 compounds in incense powders and more than 200 compounds in the incense smoke, by using GC coupled to quadrupole mass spectrometric detection. Identification required at least 90% match with the NIST library; otherwise they were considered as unidentified. The smoke stream comprised compounds originating from the incense powder, and combustion products such as PAH, N-heterocyclics, and furans. However, GC×GC was able to separate many more volatile compounds (possibly hundreds more) present in the complex smoke samples, many of which cannot be separated by conventional 1D-GC; this is a direct consequence of the high-resolution power of GC×GC. GC×GC fingerprint comparison of powder H/S with smoke allows facile subtraction of the former from the latter to assist identification of compounds generated from burning incense.
Keywords: Incense; Smoke; Headspace; Solid phase microextraction; Comprehensive two-dimensional gas chromatography;
Atmospheric fate of acrylic acid and acrylonitrile: Rate constants with Cl atoms and OH radicals in the gas phase by Mariano A. Teruel; María B. Blanco; Gabriela R. Luque (5769-5777).
Rate coefficients for the reactions of hydroxyl radicals and chlorine atoms with acrylic acid and acrylonitrile have been determined at 298 K and atmospheric pressure. The decay of the organics was followed using a gas chromatograph with a flame ionization detector (GC-FID) and the rate constants were determined using a relative rate method with different reference compounds. Room temperature rate constants are found to be (in cm3 molecule−1 s−1): k 1(OH+CH2 ＝CHC(O)OH)=(1.75±0.47)×10−11, k 2(Cl+CH2 ＝CHC(O)OH)=(3.99±0.84)×10−10, k 3(OH+CH2 ＝CHCN)=(1.11±0.33)×10−11 and k 4(Cl+CH2 ＝CHCN)=(1.11±0.23)×10−10 with uncertainties representing ±2σ. This is the first kinetic study for these reactions under atmospheric pressure. The rate coefficients are compared with previous determinations taking into account the effect of pressure on the rate constants. The effect of substituent atoms or groups on the overall rate constants is analyzed in comparison with other unsaturated compounds in the literature. In addition, atmospheric lifetimes based on the homogeneous sinks of acrylic acid and acrylonitrile are estimated and compared with other tropospheric sinks for these compounds.
Keywords: Acrylic acid; Acrylonitrile; Rate coefficients; Addition reactions; Tropospheric chemistry;
A field comparison of ethylene vinyl acetate and low-density polyethylene thin films for equilibrium phase passive air sampling of polycyclic aromatic hydrocarbons by Karen E. Kennedy; Darryl W. Hawker; Jochen F. Müller; Michael E. Bartkow; Rowan W. Truss (5778-5787).
Ethylene vinyl acetate (EVA) and low-density polyethylene (LDPE) were compared as thin film polymer passive air samplers for polycyclic aromatic hydrocarbons (PAHs). These samplers were co-deployed for periods of up to 27 days at an urban field site in Brisbane. Despite demonstrated air side resistance to mass transfer, sampling rate ratios indicate rapid accumulation kinetics for EVA compared with LDPE. Confirming theoretically predicted values, sampler-air partition coefficients were greater for EVA as compared with LDPE. The relatively high capacity of EVA films may be an advantage in terms of sensitivity, when film thickness and hence amounts accumulated at equilibrium, are low.Predictions of times to effective equilibrium ( t eq ( 95 % ) ) were made for a nominal film thickness of 1 μm. These predictions indicate that both types of films would be effective equilibrium phase samplers for predominantly vapour phase PAHs with log octanol-air partition coefficients ( log K OA ) values of ⩽8.7 (pyrene). Despite comparatively rapid linear stage kinetics for EVA, the predicted times to effective equilibrium for PAHs are less for LDPE. This arises due to the relative magnitude of their respective K SA values. The predicted times to equilibrium (25 °C) for pyrene for example are approximately 94 and 34 days for EVA and LDPE, respectively.
Keywords: Passive air sampling; Polycyclic aromatic hydrocarbons; Low-density polyethylene; Ethylene vinyl acetate;
Study of aluminium distribution and speciation in atmospheric particles of different diameters in Nanjing, China by P. Wang; S.P. Bi; Y.P. Zhou; Q.S. Tao; W.X. Gan; Y. Xu; Z. Hong; W.S. Cai (5788-5796).
Aluminium (Al) is one of the trace inorganic metals present in atmospheric particles. Al speciation study is essential to better evaluate the mobility, availability, and persistence of trace Al and Al species in the atmosphere. This paper reports Al distribution and speciation in atmospheric particles with aerodynamic diameters >10.0, 10.0–2.5 and <2.5 μm in the urban area of Nanjing, China. Urban particles were collected with a high-volume sampling system equipped with a cascade impactor, which effectively separates the particulate matter into three size ranges. Particulate Al was fractionated into five different forms (insoluble, oxide, organic, carbonate, and exchangeable species) by the modified five-step Tessier's sequential extraction procedure. The main points are as follows: (1) The average levels of Al in PM2.5, PM2.5–10 and PM>10 are 2.02±0.35, 3.04±0.43 and 6.32±0.76 μg m−3, respectively, with PM2.5, PM2.5–10 and PM>10 constituting respectively, 17.8±3.1%, 26.7±3.8% and 55.5±6.7% of suspended particulate matter (SPM) mass (11.38 μg m−3). (2) The vertical profile of airborne Al in the above three size fractions has been estimated. A significant increase in airborne Al concentrations was found for PM2.5, PM2.5–10 and PM>10 as the sampling height above the ground increased from 2.5 to 17.5 m; however, there was an obvious decrease in airborne Al concentrations between 17.5 and 40.0 m. The maximum mean of total Al in PM2.5, PM2.5–10 and PM>10 occurred between 12.5 and 20.0 m above the ground. (3) The distribution of Al speciation was studied. It was found that the size distribution of airborne Al species followed the order: insoluble species>oxide species>organic species>carbonate species>exchangeable species.
Keywords: Nanjing air; Particle size effect; Vertical distribution; Al and Al speciation;
Parameter sets for upper and lower bounds on soil-to-indoor-air contaminant attenuation predicted by the Johnson and Ettinger vapor intrusion model by Fred D. Tillman; James W. Weaver (5797-5806).
Migration of volatile chemicals from the subsurface into overlying buildings is known as vapor intrusion (VI). Under certain circumstances, people living in homes above contaminated soil or ground water may be exposed to harmful levels of these vapors. A popular VI screening-level algorithm widely used in the United States, Canada and the UK to assess this potential risk is the “Johnson and Ettinger” (J&E) model. Concern exists over using the J&E model for deciding whether or not further action is necessary at sites, as many parameters are not routinely measured (or are un-measurable). Using EPA-recommended ranges of parameter values for nine soil-type/source depth combinations, input parameter sets were identified that correspond to bounding results of the J&E model. The results established the existence of generic upper and lower bound parameter sets for maximum and minimum exposure for all soil types and depths investigated. Using the generic upper and lower bound parameter sets, an analysis can be performed that, given the limitations of the input ranges and the model, bounds the attenuation factor in a VI investigation.
Keywords: Vapor intrusion; Johnson and Ettinger model; Risk assessment;
Volatile organic compound emissions from Siberian larch by T.M. Ruuskanen; H. Hakola; M.K. Kajos; H. Hellén; V. Tarvainen; J. Rinne (5807-5812).
We determined hourly emissions of isoprene, monoterpenes and sesquiterpenes from Siberian larch, one of the major tree species in Siberian forests. Summer volatile organic compounds (VOCs) emission from Siberian larch consisted mainly of monoterpenes (about 90%). The monoterpene emission spectrum remained constant during the measurement period, almost half was sabinene and other major monoterpenes were Δ 3-carene, β- and α-pinene. During spring and summer, about 10% of the VOCs were sesquiterpenes, mainly α-farnesene. The sesquiterpene emissions declined to 3% in the fall. Isoprene, 2-methyl-3-buten-2-ol (MBO) and 1,8-cineole contributed to less than 3% of the VOC emission during the whole period. The diurnal variation of the emissions could be explained using a temperature-dependent parameterization. Emission potentials normalized to 30 °C were 5.2–21 μg gdw −1 h−1 (using β-value of 0.09 °C−1) for monoterpenes and 0.4–1.8 μg gdw −1 h−1 (using β-value of 0.143 °C−1, mean of determined values) for sesquiterpenes. Normalized monoterpene emission potentials were highest in late summer and elevated again in late fall. Sesquiterpene emission potentials were also highest in late summer, but decreased towards fall.
Keywords: BVOC emission potential; Larix sibirica; Seasonal variation; Monoterpene; Sesquiterpene;
New Directions: The changing role of the terrestrial carbon sink in determining atmospheric CO2 concentrations by David S. Reay; Pete Smith; Graham Hymus; Chris Sabine (5813-5815).