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Atmospheric Environment (v.43, #13)

Editorial board (pp. i).

Evaluation and application of biomagnetic monitoring of traffic-derived particulate pollution by R. Mitchell; B.A. Maher (pp. 2095-2103).
Inhalation of particulate pollutants below 10 μm in size (PM10) is associated with adverse health effects. Here we use magnetic remanence measurements of roadside tree leaves to examine levels of vehicle-derived PM around Lancaster, UK. Leaf saturation remanence (SIRM) values exhibit strong correlation with both the SIRM and particulate mass of co-located, pumped-air samples, indicating that these leaf magnetic values are an effective proxy for ambient PM10 concentrations. Biomagnetic monitoring using tree leaves can thus provide high spatial resolution data sets for assessment of particulate pollution levels at pedestrian-relevant heights. Leaf SIRM values not only increase with proximity to roads with higher traffic volumes, but are also ∼100% higher at 0.3 m than at ∼1.5–2 m height. Magnetic and SEM data indicate that the particle populations are dominated by spherical, iron-rich particles ∼0.1–1 μm in diameter, with fewer larger, more angular, silica-rich particles. Comparison of the roadside leaf-calculated PM10 concentrations with PM10 concentrations predicted by a widely-used atmospheric dispersion model indicates some agreement between them. However, the model under-predicts PM10 concentrations at ‘urban hotspots’ such as major–minor road junctions and traffic lights. Conversely, the model over-predicts PM10 concentrations with distance from the road wherever one tree is screened by another, indicating the filtering/protective effect of roadside trees in leaf.

Keywords: Magnetic biomonitoring; Roadside tree leaves; Vehicle pollution; Atmospheric modelling dispersion Lancaster, UK


Simulation of the daily average PM10 concentrations at Ta-Liao with Box–Jenkins time series models and multivariate analysis by Pao-Wen Grace Liu (pp. 2104-2113).
Southern Taiwan has experienced severe PM10 problems for over a decade. The present paper describes the establishment of a simulation model for the daily average PM10 concentrations at Ta-Liao, southern Taiwan. The study used a regression with time series error models (RTSE models) (multivariate ARIMA time series model), including an explanatory variable resulting from principal component analyses to complete the PM10 simulation. Factor 1 estimated from the factor analyses explained the variance of 44–49%, which indicated the important contribution from the neighbor-city PM10 at Mei-Nung, Lin-Yuang, Zuoying, Chao-Chou, local ozone and NOx. Factor 1 can be interpreted with regional PM10 plus photochemical reactions. To improve the predictability of extremely high PM10, different results from the principal component analysis were introduced to the RTSE models. We constructed four kinds of RTSE models: RTSE model without PC, with PC4S (PM10 at Mei-Nung, Lin-Yuang, Zuoying, and Chao-Chou), with PCTL (meteorological variables and co-pollutants at Ta-Liao), and with PCTL4S (the combination of the above two) and evaluated the statistics model performance. Ozone, dew point temperature, NOx, wind speed, wind directions, and the PC trigger were the significant variables in the RTSE models most of time. When the neighbor-city PM10 was included in the PC trigger, the predictability was apparently improved. The closeness of fit with the inclusion of PC4S and PCTL4S was improved by reducing SEE from 0.117 to 0.092. Using the RTSE models with PC4S or PCTL4S, POD was improved by an increase of 33%, FAR was reduced 30%, and CSI was increased 39%, when simulating the daily average PM10>150μgm−3. Evidently we need to survey source impacts prior to establishing a simulation model. Factor analysis is a useful method to investigate sources that contributed PM10 to a target site prior to establishing a simulation model.

Keywords: RTSE model; Factor analysis; Principal component analysis; Box–Jenkins time series; PM; 10


Air pollution “holiday effect” resulting from the Chinese New Year by Pei-Hua Tan; Chia Chou; Jing-Yi Liang; Charles C.-K. Chou; Chein-Jung Shiu (pp. 2114-2124).
Our study was an attempt to conduct a comprehensive and systematical examination of the holiday effect, defined as the difference in air pollutant concentrations between holiday and non-holiday periods. This holiday effect can be applied to other countries with similar national or cultural holidays. Hourly and daily surface measurements of six major air pollutants from thirteen air quality monitoring stations of the Taiwan Environmental Protection Administration during the Chinese New Year (CNY) and non-Chinese New Year (NCNY) periods were used. We documented evidence of a “holiday effect”, where air pollutant concentrations were significantly different between holidays (CNY) and non-holidays (NCNY), in the Taipei metropolitan area over the past thirteen years (1994–2006).The concentrations of NO x, CO, NMHC, SO2 and PM10 were lower in the CNY than in the NCNY period, while the variation in the concentration of O3 was reversed, which was mainly due to the NO titration effect. Similar differences in these six air pollutants between the CNY and NCNY periods were also found in the diurnal cycle and in the interannual variation. For the diurnal cycle, a common traffic-related double-peak variation was observed in the NCNY period, but not in the CNY period. Impacts of dust storms were also observed, especially on SO2 and PM10 in the CNY period. In the 13-year period of 1994–2006, decreasing trends of NO x and CO in the NCNY period implied a possible reduction of local emissions. Increasing trends of SO2 and PM10 in the CNY period, on the other hand, indicated a possible enhancement of long-range transport. These two mechanisms weakened the holiday effect.

Keywords: Holiday effect; Weekend effect; Long-range transport; Titration effect; Taipei


Estimations of primary and secondary organic carbon formation in PM2.5 aerosols of Santiago City, Chile by Rodrigo Seguel A.; Raúl G.E. Morales S.; Manuel A. Leiva G. (pp. 2125-2131).
High concentration of fine airborne particulates is considered one of the major environmental pollutants in Santiago, the Chilean Capital city, which in 1997 was declared a PM10 saturated zone. To date there is no control of the amounts of fine and coarse aerosols concentrations and the source and chemical characterizations of the PM2.5 particulates in the carbonaceous fractions are not well known even though this fraction could be represented almost the 50% in mass of the PM2.5.In this work, we present for the first time determinations of primary organic aerosol (POA) and secondary organic aerosol composition (SOA) fractions of the total mass of PM2.5 particulates collected in the urban atmosphere of Santiago City. Our purpose is to know the anthropogenic contributions to the formation of SOA. To accomplish this we used the elemental carbon (EC) and organic carbon (OC) determinations developed by automatic monitoring stations installed in the city during the period 2002–2005, with a particular analysis of the summer time occurred in February 2004. Based on the EC tracer method, we have estimated the POA and SOA fraction and our data permit us to estimate the SOA reaching up to 20% of total organic aerosol matter, in good agreement to other measurements observed in large cities of Europe and U.S.A.

Keywords: Organic carbon; Elemental carbon; EC tracer method; PM; 2.5; Urban air pollution


Development and validation of the volatile correction model for PM10 – An empirical method for adjusting TEOM measurements for their loss of volatile particulate matter by David C. Green; Gary W. Fuller; Timothy Baker (pp. 2132-2141).
EU Directives stipulate that PM10 should be measured using the gravimetric reference method as laid out in EN12341 [CEN, 1998. Air Quality – Determination of the PM10 Fraction of Suspended Particulate Matter – Reference Method and Field Test Procedure to Demonstrate Reference Equivalence of Measurement Methods. European Committee for Standardisation], or an equivalent method as demonstrated using EC guidance [EC, 2005. Demonstration of Equivalence of Ambient Air Monitoring Methods. European Commission Working Group on Guidance for the Demonstration of Equivalence]. There is however a conflict between the requirement to measure PM10 using the gravimetric reference method and the need for rapid public reporting, and many member states, including the UK, rely on non-gravimetric techniques to measure PM10. In the UK the majority of PM10 measurements are made using the Tapered Element Oscillating Microbalance (TEOM), which does not meet the equivalence criteria [Harrison, D., 2006. UK Equivalence Programme for Monitoring of Particulate Matter. Defra, London]. The implied need to upgrade or replace TEOMs with an equivalent automated measurement technique has significant cost implications. The model described in this paper was based on analysis of daily mean measurements of PM10 by the Filter Dynamics Measurement System (FDMS) and the TEOM at UK sites. It uses the FDMS measurement of the volatile component of PM10 (referred to here as FDMS purge) to correct for differences in the sensitivity to volatile PM10 between the TEOM and the EU gravimetric reference method. The model equation for the correction of TEOM PM10 measurements is: TEOMVCM = TEOM − 1.87 FDMS purge due to the regional homogeneity of volatile PM, the FDMS purge concentration may be measured at a site distant to the TEOM, allowing the possibility of using a single FDMS instrument to correct PM10 measurements made by several TEOMs in a defined geographical area. The model was assessed against the criteria for the EC Working Group's Guidance for the Demonstration of Equivalence of Ambient Air Monitoring Methods [EC, 2005. Demonstration of Equivalence of Ambient Air Monitoring Methods. European Commission Working Group on Guidance for the Demonstration of Equivalence]. The model satisfies the equivalence criteria using remote FDMS purge measurements for distances up to 200 km (in 22 out of 23 data sets). These data provide strong evidence that the model is a viable tool for correcting measurements from TEOM instruments on the national and local government networks.

Keywords: TEOM; FDMS; Gravimetric reference method; Equivalence; PM; 10


Contribution of isoprene to formaldehyde and ozone formation based on its oxidation products measurement in Beijing, China by Xiaobing Pang; Yujing Mu; Yujie Zhang; Xinqing Lee; Juan Yuan (pp. 2142-2147).
The atmospheric mixing ratios of methacrolein (MACR) and methyl vinyl ketone (MVK), the two specific products from isoprene oxidation in the atmosphere, were measured in Beijing from March to November, 2006. Distinct amounts of MACR and MVK were detected during vegetable growing seasons from April to October with ambient levels of 0.11–0.67ppbv and 0.19–1.36ppbv, respectively. The reacted isoprene and its ozone formation potentials (OFPs) in Beijing were evaluated in the range of 0.49–3.46ppbv and 6.4–44.7ppbv, respectively, from April to October. OFP of the reacted isoprene accounted for 10.6–23.6% of the total OFPs of VOCs (including carbonyls and isoprene) and 6.38–29.9% of the photo-chemically produced ozone. The maximum OFP of the original emitted isoprene prior to its photo-oxidation was calculated as 56.0ppbv in August. The contribution from the reacted isoprene in Beijing to HCHO formation was also estimated to be in the range of 0.35–2.45ppbv from April to October, which accounted for 4.6–11.5% of ambient HCHO.

Keywords: Isoprene; Formaldehyde (HCHO); Methacrolein (MACR); Methyl vinyl ketone (MVK); Ozone formation potential (OFP)


China's grazed temperate grasslands are a net source of atmospheric methane by Zhi-Ping Wang; Yang Song; Jay Gulledge; Qiang Yu; Hong-Sheng Liu; Xing-Guo Han (pp. 2148-2153).
A budget for the methane (CH4) cycle in the Xilin River basin of Inner Mongolia is presented. The annual CH4 budget in this region depends primarily on the sum of atmospheric CH4 uptake by upland soils, emission from small wetlands, and emission from grazing ruminants (sheep, goats, and cattle). Flux rates for these processes were averaged over multiple years with differing summer rainfall. Although uplands constitute the vast majority of land area, they consume much less CH4 per unit area than is emitted by wetlands and ruminants. Atmospheric CH4 uptake by upland soils was −3.3 and −4.8kg CH4ha−1y−1 in grazed and ungrazed areas, respectively. Average CH4 emission was 791.0kg CH4ha−1y−1 from wetlands and 8.6kg CH4ha−1y−1 from ruminants. The basin area-weighted average of all three processes was 6.8kg CH4ha−1y−1, indicating that ruminant production has converted this basin to a net source of atmospheric CH4. The total CH4 emission from the Xilin River basin was 7.29Gg CH4y−1. The current grazing intensity is about eightfold higher than that which would result in a net zero CH4 flux. Since grazing intensity has increased throughout western China, it is likely that ruminant production has converted China's grazed temperate grasslands to a net source of atmospheric CH4 overall.

Keywords: CH; 4; flux; Enteric fermentation; Wetlands; CH; 4; budget; Xilin River basin; Inner Mongolia


Recent trends and projections of primary NO2 emissions in Europe by Susannah Grice; John Stedman; Andrew Kent; Melanie Hobson; John Norris; John Abbott; Sally Cooke (pp. 2154-2167).
An assessment of recent trends in primary NO2 emissions has been carried out for ten case study locations across the European Union. Estimates of the percentage of NO x from road traffic emitted as primary NO2 (f-NO2) have been derived for 1995, 2000 and 2005 by combining the results of a literature survey of primary NO2 emission factors for different vehicle types and technologies with an emission inventory. Estimates of f-NO2 have also been derived from ambient monitoring data at roadside sites in each case study location using a model.The results of the analysis of trends show that f-NO2 has increased in recent years and that the rate of increase has been greatest since 2000. f-NO2 has increased from 8.6% in 2000 to 12.4% in 2004 as an average across the monitoring sites and from an average of 6.3% in 2000 to 10.6% in 2005 as an average of the emission inventory based calculations for the case study countries. f-NO2 is predicted to increase further to an average of 19.6% in 2010 and 32.0% in 2020 as a result of the further penetration of exhaust after treatment technologies for diesel vehicles in the fleets. This increase is expected to be offset by the large reduction in NO x emissions over this period, resulting in an increase in NO2 emissions from road traffic to 2015, followed by a decline to close to 2004 levels by 2020. Estimates of future ambient NO2 concentrations have also been calculated for the roadside monitoring sites included in the study. At 29 out of 45 of these sites the annual mean NO2 limit value is predicted to be exceeded in 2010. At 22 of these sites, the annual mean concentration is expected to remain above the limit value until 2020 and beyond.

Keywords: Limit values; Ambient NO; 2; concentrations; Oxides of nitrogen; Vehicle exhaust emissions; Trends; Projections


Possible particulate nitrite formation and its atmospheric implications inferred from the observations in Seoul, Korea by Chul H. Song; Mi E. Park; En J. Lee; Jae H. Lee; Bo K. Lee; Dong S. Lee; Jhoon Kim; Jin S. Han; Kwang J. Moon; Yutaka Kondo (pp. 2168-2173).
Simultaneous measurements of gaseous species and fine-mode, particulate inorganic components were performed at the University of Seoul, Seoul in Korea. In the simultaneous measurements, a certain level of nitrous acid (HONO) was observed in the gas-phase, indicating possible heterogeneous HONO production on the surface of the ambient aerosols. On the other hand, high particulate nitrite (NO2−) concentrations of 1.41(±2.26)μg/m3 were also measured, which sometimes reached 18.54μg/m3. In contrast, low HONO-to-NO2 ratios of 0.007(±0.006) were observed in Seoul. This indicates that a significant fraction of HONO is dissolved in atmospheric aerosols. Around the Seoul site, sufficient alkalinity may have been provided to the atmospheric aerosols from the excessive presence of NH3 in the gas-phase. Due to the alkaline particulate conditions (defined in this study as a particle pH >∼3.29), the HONO molecules produced at the surface of the atmospheric aerosols appeared to have been converted into particulate nitrite, thereby preventing their further participation in the atmospheric O3/NOy/HOx photochemical cycles. It was estimated that a minimum average of 65% of HONO was captured by alkaline, anthropogenic, urban particles in the Seoul measurements.

Keywords: Particulate nitrite formation; HONO; particle alkalinity; HONO deactivation


Large-eddy simulation for flow and dispersion in urban streets by Zheng-Tong Xie; Ian P. Castro (pp. 2174-2185).
Large-eddy simulations (LES) with our recently developed inflow approach (Xie, Z.-T., Castro, I.P., 2008a. Efficient generation of inflow conditions for large-eddy simulation of street-scale flows. Flow Turbul. Combust., vol. 81(3), pp. 449–470.) have been used for flow and dispersion within a genuine city area – the DAPPLE site, located at the intersection of Marylebone Rd and Gloucester Pl in Central London. Numerical results up to second-order statistics are reported for a computational domain of 1.2km (streamwise)×0.8km (lateral)×0.2km (in full scale), with a resolution down to approximately one meter in space and one second in time. They are in reasonable agreement with the experimental data. Such a comprehensive urban geometry is often, as here, composed of staggered, aligned, square arrays of blocks with non-uniform height and non-uniform base, street canyons and intersections. Both the integrative and local effect of flow and dispersion to these geometrical patterns were investigated. For example, it was found that the peaks of spatially averagedu rms,v rms,w rms and < u′ w′> occurred neither at the mean height nor at the maximum height, but at the height of large and tall buildings. It was also found that the mean and fluctuating concentrations in the near-source field is highly dependent on the source location and the local geometry pattern, whereas in the far field (e.g. >0.1km) they are not. In summary, it is demonstrated that full-scale resolution of around one meter is sufficient to yield accurate prediction of the flow and mean dispersion characteristics and to provide reasonable estimation of concentration fluctuations.

Keywords: Street scale flow; Street scale dispersion; DAPPLE; Wind direction; Multiple-tracers


Wood burning impact on PM10 in three Austrian regions by Alexandre Caseiro; Heidi Bauer; Christoph Schmidl; Casimiro A. Pio; Hans Puxbaum (pp. 2186-2195).
Anhydrosugars (levoglucosan, mannosan and galactosan) were investigated during one year in three Austrian regions at three types of sites (city-heavy traffic-impacted, city-residential and background) in order to assess the magnitude of the contribution of wood smoke to the particulate matter load and its organic fraction. The annually averaged concentrations of levoglucosan ranged from 0.12 to 0.48μgm−3. The levoglucosan concentration exhibited a strong annual cycle with higher concentrations in the cold season. The minor anhydrosugars had a similar annual trend, but their concentrations were lower by a factor of about 5 and about 25 in the cold season for mannosan and galactosan, respectively. Levoglucosan concentrations were higher at the inner-urban as compared to rural sites. The contribution of wood smoke to organic carbon and PM10 levels was calculated using a constant ratio of levoglucosan and OC, respectively PM10 as derived for fire wood typical for Alpine European regions [Schmidl, C., Marr, I.L., Caseiro, A.e, Kotianová, P., Berner, A., Bauer, H., Kasper-Giebl, A., Puxbaum, H., 2008a. Chemical characterisation of fine particle emissions from wood stove combustion of common woods growing in mid-European Alpine regions. Atmospheric Environment 42, 126–141]. The estimated contribution of wood smoke-OC to the OC of PM10 ranged from one third to more than half in the cold season with higher contributions up to 70% in winter (December, January and February) in the smaller cities and the rural background. This indicates, that wood smoke is the predominant source of organic material at rural and small urban sites in central Europe. Consistently, wood smoke was an important contributor to PM10 during the cold season, with contributions of around 10% in the Vienna larger region and around 20% at rural sites in the densely forested regions of Salzburg and Styria during the winter months. In those regions residential sites exhibited highest relative wood smoke contents in PM10 during autumn (September till November), indicating the use of wood stoves for auxiliary heating in the transition of warm to cold season. Using the relationships between the different anhydrosugars the combustion of softwood was found to be dominant for the wood smoke occurrence in ambient air at the investigated sites. Potassium, a commonly used tracer for biomass burning, correlated well to levoglucosan, with a mass ratio of around 0.80 in the cold season.

Keywords: PM; 10; Levoglucosan; Wood burning; Austria


Biogenic emission of dimethylsulfide (DMS) from the North Yellow Sea, China and its contribution to sulfate in aerosol during summer by Gui-Peng Yang; Hong-Hai Zhang; Lu-Ping Su; Li-Min Zhou (pp. 2196-2203).
Seawater, atmospheric dimethylsulfide (DMS) and aerosol compounds, potentially linked with DMS oxidation, such as methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO42−) were determined in the North Yellow Sea, China during July–August, 2006. The concentrations of seawater and atmospheric DMS ranged from 2.01 to 11.79nmoll−1 and from 1.68 to 8.26nmolm−3, with average values of 6.20nmoll−1 and 5.01nmolm−3, respectively. Owing to the appreciable concentration gradient, DMS accumulated in the surface water was transferred into the atmosphere, leading to a net sea-to-air flux of 6.87μmolm−2d−1 during summer. In the surface seawater, high DMS values corresponded well with the concurrent increases in chlorophyll a levels and a significant correlation was observed between integrated DMS and chlorophyll a concentrations. In addition, the concentrations of MSA and nss-SO42− measured in the aerosol samples ranged from 0.012 to 0.079μgm−3 and from 3.82 to 11.72μgm−3, with average values of 0.039 and 7.40μgm−3, respectively. Based on the observed MSA, nss-SO42− and their ratio, the relative biogenic sulfur contribution was estimated to range from 1.2% to 11.5%, implying the major contribution of anthropogenic source to sulfur budget in the study area.

Keywords: Dimethylsulfide; Methanesulfonic acid; Non-sea-salt sulfate; Sea-to-air flux; North Yellow Sea


Modeling the atmospheric transport and deposition of polychlorinated dibenzo- p-dioxins and dibenzofurans in North America by Baoning Zhang; Fan Meng; Chune Shi; Fuquan Yang; Deyong Wen; Jonatan Aronsson; Philip K. Gbor; James J. Sloan (pp. 2204-2212).
The atmospheric fate of polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was simulated for the year 2000 in North America using a SMOKE/CMAQ-based chemical transport model that was modified for this purpose. The 1999 USEPA emission inventories of PCDD/Fs and criteria pollutants were used. The 1995 Canadian emission inventory of criteria pollutants and the 1995 Canadian area source emissions for PCDD/Fs were used with the 2000 Canadian point source emissions. Modifications to CMAQ involved coupling it with dual organic matter (OM) absorption and black carbon (BC) adsorption models to calculate PCDD/F gas–particle partitioning. The model satisfactorily reproduced the particle bound fractions at all rural sites for which there were measured data and across the whole domain, the modeled vs. measured differences in particle bound fractions were less than 20% for nearly all congeners. The model predicted ambient air PCDD/F concentrations were also consistent with measurements. Simulated deposition fluxes were within 58% of direct measurements. PCDD/F atmospheric depositions to each of the Great Lakes were estimated for the year 2000. The results indicate that approximately 76% of the total deposition of PCDD/Fs to the Great Lakes (in W-TEQ, or toxic equivalent units as defined by the World Health Organization) is attributed to PCDD/Fs absorbed into OM in aerosol. For all of the lakes, more than 92% of all deposition is particle phase wet deposition and only 5–8% is particle phase dry deposition. Wet deposition from the gas phase is negligible. Of the 17 toxic PCDD/F congeners, the Cl4–5DD/F compounds contribute approximately 70% to the total atmospheric deposition to the Great Lakes. The seasonal changes in the PCDD/F deposition flux track variations in ambient temperature.

Keywords: Polychlorinated dibenzo-; p; -dioxins; Polychlorinated dibenzofurans; Air-particle partitioning; TEQ; Emission; Deposition


Measurement of surface ozone and its precursors in an urban area in South Brazil by Elba Calesso Teixeira; Eduardo Ramos de Santana; Flavio Wiegand; Jandyra Fachel (pp. 2213-2220).
Weekly and seasonal variations of surface ozone and their precursors – nitrogen oxides, carbon monoxide-associated with meteorological parameters (wind direction, temperature, solar radiation) – are reported. Measurements were performed continuously during 2006 at two sampling stations located in the metropolitan area of Porto Alegre, Brazil. Results have shown that O3 concentrations remained almost constant between weekdays. Levels of NO x precursors decreased especially on Sundays, due to lighter traffic. The seasonal variation has shown a maximum O3 concentration during summer and spring while NO x and NO2 have maxima at the colder months. The daily cycle of highest ozone concentrations reveals a lower nightly level and an inverse relation between O3 and NO x, evidencing the photochemical formation of O3. There are seasonal variation and source heterogeneity.

Keywords: Ozone; Nitrogen oxides; Carbon monoxide; Photochemical oxidants


Some characteristics of a plume from a point source based on analytical solution of the two-dimensional advection–diffusion equation by Tiziano Tirabassi; Alessandro Tiesi; Daniela Buske; Marco T. Vilhena; Davidson M. Moreira (pp. 2221-2227).
The moments of the concentration distribution obtained using a recent analytical solution of the steady-state two-dimensional advection–diffusion equation are presented. The solving methodology is the Generalized Integral Laplace Transform Technique, which allows obtaining a reliable solution of the advection–diffusion equation without any restrictive assumption about the eddy diffusivity coefficients and wind speed profiles. The first four moments and value and position of maximum ground level concentration are calculated. The concentration standard deviation is compared against the semi-empirical ones used in operative Gaussian models.

Keywords: Air pollution modelling; Analytical solution; Advection–diffusion equation; Moments of concentration distribution
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