Atmospheric Environment (v.44, #34)
Editorial board (i).
Stable carbon kinetic isotope effects for the production of methacrolein and methyl vinyl ketone from the gas-phase reactions of isoprene with ozone and hydroxyl radicals by Richard Iannone; Ralf Koppmann; Jochen Rudolph (4135-4141).
The stable-carbon kinetic isotope effects (KIEs) associated with the production of methacrolein (MACR) and methyl vinyl ketone (MVK) from the reactions of isoprene with ozone and OH radicals were studied in a 25 L reaction chamber at (298±2) K and ambient pressure. The time dependence of both the stable-carbon isotope ratios and the concentrations was determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The average yields of 13C-containing MACR and MVK generated from the ozone reaction of 13C-containing isoprene differed by −3.6‰ and −4.5‰, respectively, from the yields for MACR and MVK containing only 12C. For MACR and MVK generated from the OH-radical oxidation of isoprene the corresponding values were −3.8‰ and −2.2‰, respectively. These values indicate a significant depletion in the 13C abundance of MACR and MVK upon their formation relative to isoprene’s pre-reaction 13C/12C ratio, which is supported by theoretical interpretations of the oxidation mechanism of isoprene and its 13C-substituted isotopomers. Numerical model calculations of the isoprene + O3 reaction predicted a similar depletion in 13C for both reaction products upon production. Furthermore, the model predicts mixing ratios and stable carbon delta values for isoprene, MACR, and MVK that were in agreement with the experimental results. The combined knowledge of isotope enrichment values with KIEs will reduce uncertainties in determinations of the photochemical histories of isoprene, MACR, and MVK in the troposphere. The studies presented here were conducted with using isoprene without any artificial isotope enrichment or depletion and it is therefore very likely that these results are directly applicable to the interpretation of studies of isoprene oxidation using stable carbon isotope ratio measurements.
Keywords: Kinetic isotope effects; Isotope fractionation; Isoprene; Tropospheric; Chemistry;
Oxidation of ketone groups in transported biomass burning aerosol from the 2008 Northern California Lightning Series fires by Lelia N. Hawkins; Lynn M. Russell (4142-4154).
Submicron particles were collected from June to September 2008 in La Jolla, California to investigate the composition and sources of atmospheric aerosol in an anthropogenically-influenced coastal site. Factor analysis of aerosol mass spectrometry (AMS) and Fourier transform infrared (FTIR) spectroscopy measurements revealed that the two largest sources of submicron organic mass (OM) at the sampling site were (1) fossil fuel combustion associated with ship and diesel truck emissions near the ports of Los Angeles and Long Beach and (2) aged smoke from large wildfires burning in central and northern California. During non-fire periods, fossil fuel combustion contributed up to 95% of FTIR OM, correlated to sulfur, and consisted mostly of alkane (86%) and carboxylic acid groups (9%). During fire periods, biomass burning contributed up to 74% of FTIR OM, consisted mostly of alkane (48%), ketone (25%), and carboxylic acid groups (17%), and correlated to AMS-derived factors resembling brush fire smoke, wood smoldering and flaming particles, and biogenic secondary organic aerosol. The two AMS-derived biomass burning factors were identified as oxygenated and hydrocarbon biomass burning aerosol on the basis of spectral similarities to smoldering and flaming smoke particles, respectively. In addition, the ratio of oxygenated to hydrocarbon biomass burning OM shows a clear diurnal trend with an afternoon peak, consistent with photochemical oxidation. Back trajectory analysis indicates that 2–4-day old forest fire emissions include substantial ketone groups, which have both lower O/C and lower m/z 44/OM fraction than carboxylic acid groups. Air masses with more than 4-day old emissions have higher carboxylic acid/ketone group ratios, showing that atmospheric processing of these ketone-containing organic aerosol particles results in increased m/z 44 and O/C. These observations may provide functionally-specific evidence for the type of chemical processing that is responsible for biomass burning particle composition in the atmosphere.
Keywords: Organic carbon particles; Ketone; Biomass burning; Organic functional groups;
Does a simulated upland grassland community respond to increasing background, peak or accumulated exposure of ozone? by Felicity Hayes; Gina Mills; Laurence Jones; Mike Ashmore (4155-4164).
Tropospheric ozone concentrations are increasing, which may result in elevated background concentrations at rural high-altitude sites. In this study simulated upland grassland communities containing seven species were exposed to ozone treatments in solardomes for 12 weeks in each of two consecutive summers. Ozone profiles, based on future ozone predictions, were of elevated background concentrations, episodic peaks of ozone and a combination of the two. During the winter between the two exposures the communities were kept outdoors in ambient air. Whereas previous studies have demonstrated that peaks of ozone cause detrimental effects to vegetation, this study shows that for simulated grassland communities an increase in background ozone concentration in the absence of peaks of ozone also corresponded with increased senescence. In many cases senescence was further increased when peaks of ozone were also present. The species used showed no acclimation to ozone and the same relationship between senescence and ozone dose occurred in both years of the study. A decrease in cumulative biomass was demonstrated for Anthoxanthum odoratum, which contributed to a decrease in total community biomass and grass:forb ratio. These results indicate that current and future ozone concentrations could cause detrimental effects on growth and vitality of natural grassland communities and that for some species the consequences of increased background ozone concentration are as severe as that of increased peaks.
Keywords: Grassland; Ozone profiles; Senescence; Biomass; Competition;
Anthropogenic inputs of boron into urban atmosphere: Evidence from boron isotopes of precipitations in Guiyang City, China by Zhi-Qi Zhao; Cong-Qiang Liu (4165-4171).
Boron (B) concentrations and isotopic compositions were measured in the precipitations of Guiyang, China for one year. Most precipitation samples have boron concentrations of from 2.1 to 4.8 ng ml−1, and δ11B values of from +2.0‰ to +30.0‰. Boron concentrations and δ11B values of heavy rain samples are generally higher than those of light rain and snow samples. Anthropogenic inputs provided most of the SO4 2− and NO3 −, which were predominant ions in the precipitation. The major cation Ca2+ in the precipitation was mainly originated from local dust.The total boron in precipitation from Guiyang is explained by the mixing model of three boron sources. Assuming a δ11B value of +45‰ for the seawater component, contributions of marine source, organic matter and biomass combustion, and coal combustion were estimated to be 32%, 49%, and 19%, respectively to the total boron in Guiyang precipitations. The coal combustion and biomass (and/or organic matter) combustion showed different contributions of boron to the rainwaters in different seasons, the former in cold season while the latter in summer season had a more marked influence on the chemical and isotopic composition of the rainwater. The largest contribution of seawater-originated boron was observed for the heavy rain samples, which was up to 68%. This study indicates that the atmospheric environment of Guiyang city was strongly influenced by human activities, and boron isotopic composition is of great sensitivity to anthropogenic sources and can be a powerful technique to trace various sources of atmospheric emissions and even their origins.
Keywords: Boron Isotope; Contaminant sources; Precipitation; Guiyang City;
Ethanol emission from loose corn silage and exposed silage particles by Sasha D. Hafner; Felipe Montes; C. Alan Rotz; Frank Mitloehner (4172-4180).
Silage on dairy farms has been identified as a major source of volatile organic compound (VOC) emissions. However, rates of VOC emission from silage are not accurately known. In this work, we measured ethanol (a dominant silage VOC) emission from loose corn silage and exposed corn silage particles using wind tunnel systems. Flux of ethanol was highest immediately after exposing loose silage samples to moving air (as high as 220 g m−2 h−1) and declined by as much as 76-fold over 12 h as ethanol was depleted from samples. Emission rate and cumulative 12 h emission increased with temperature, silage permeability, exposed surface area, and air velocity over silage samples. These responses suggest that VOC emission from silage on farms is sensitive to climate and management practices. Ethanol emission rates from loose silage were generally higher than previous estimates of total VOC emission rates from silage and mixed feed. For 15 cm deep loose samples, mean cumulative emission was as high as 170 g m−2 (80% of initial ethanol mass) after 12 h of exposure to an air velocity of 5 m s−1. Emission rates measured with an emission isolation flux chamber were lower than rates measured in a wind tunnel and in an open setting. Results show that the US EPA emission isolation flux chamber method is not appropriate for estimating VOC emission rates from silage in the field.
Keywords: Dairy farms; Volatile organic compounds; Emissions; Silage; Ozone precursors;
Quantification of Saharan dust contribution to PM10 concentrations over Italy during 2003–2005 by A. Pederzoli; M. Mircea; S. Finardi; A. di Sarra; G. Zanini (4181-4190).
Italy is frequently affected by Saharan dust intrusions, which result in high PM10 concentrations in the atmosphere and can cause the exceedances of the PM10 daily limits (50 μg m−3) set by the European Union (EU/2008/50). The estimate of African dust contribution to PM10 concentrations is therefore a key issue in air quality assessment and policy formulation. This study presents a first identification of Saharan dust outbreaks as well as an estimate of the African dust contribution to PM10 concentrations during the period 2003–2005 over Italy. The identification of dust events has been carried out by looking at different sources of information such as monitoring network observations, satellite images, ground measurements of aerosol optical properties, dust model simulations and air mass backward trajectory analysis. The contribution of Saharan dust to PM10 monthly concentrations has been estimated at seven Italian locations. The results are both spatially (with station) and temporally (with month and year) variable, as a consequence of the variability of the meteorological conditions. However, excluding the contribution of severe dust events (21st February 2004, 25th–28th September 2003, 23rd–27th March 2005), the monthly contribution of dust varies approximately between 1 μg m−3 and 10 μg m−3 throughout year 2005 and between 1 μg m−3 and 8 μg m−3 throughout year 2003. In 2004 the dust concentration is lower than 2003 and 2005 (<5 μg m−3 at all sites). The reduction in the number of daily exceedances of the limit value (50 μg m−3) after subtraction of the dust contribution is also calculated at each station: it varies with station between 20% and 50% in 2005 and between 5% and 25% in 2003 and 2004.
Keywords: PM10; Air quality; Saharan dust; Mediterranean; Italy;
Secondary organic aerosol formation from ozone-initiated reactions with nicotine and secondhand tobacco smoke by Mohamad Sleiman; Hugo Destaillats; Jared D. Smith; Chen-Lin Liu; Musahid Ahmed; Kevin R. Wilson; Lara A. Gundel (4191-4198).
We used controlled laboratory experiments to evaluate the aerosol-forming potential of ozone reactions with nicotine and secondhand smoke. Special attention was devoted to real-time monitoring of the particle size distribution and chemical composition of SOA as they are believed to be key factors determining the toxicity of SOA. The experimental approach was based on using a vacuum ultraviolet photon ionization time-of-flight aerosol mass spectrometer (VUV-AMS), a scanning mobility particle sizer (SMPS) and off-line thermal desorption coupled to mass spectrometry (TD-GC-MS) for gas-phase byproducts analysis. Results showed that exposure of SHS to ozone induced the formation of ultrafine particles (<100 nm) that contained high molecular weight nitrogenated species (m/z 400–500), which can be due to accretion/acid–base reactions and formation of oligomers. In addition, nicotine was found to contribute significantly (with yields 4–9%) to the formation of secondary organic aerosol through reaction with ozone. The main constituents of the resulting SOA were tentatively identified and a reaction mechanism was proposed to elucidate their formation. These findings identify a new component of thirdhand smoke that is associated with the formation of ultrafine particles (UFP) through oxidative aging of secondhand smoke. The significance of this chemistry for indoor exposure and health effects is highlighted.
Keywords: Indoor environment; Heterogeneous chemistry; Thirdhand smoke; Ultrafine particles; Aerosol mass spectrometry; Indoor exposure;
Assessing photochemical ozone formation in the Pearl River Delta with a photochemical trajectory model by H.R. Cheng; H. Guo; S.M. Saunders; S.H.M. Lam; F. Jiang; X.M. Wang; I.J. Simpson; D.R. Blake; P.K.K. Louie; T.J. Wang (4199-4208).
A photochemical trajectory model (PTM), coupled with the Master Chemical Mechanism (MCM) describing the degradation of 139 volatile organic compounds (VOCs) in the troposphere, was developed and used for the first time to simulate the formation of photochemical pollutants at Wangqingsha (WQS), Guangzhou during photochemical pollution episodes between 12 and 17 November, 2007. The simulated diurnal variations and mixing ratios of ozone were in good agreement with observed data (R 2 = 0.80, P < 0.05), indicating that the photochemical trajectory model – an integration of boundary layer trajectories, precursor emissions and chemical processing – provides a reasonable description of ozone formation in the Pearl River Delta (PRD) region. Calculated photochemical ozone creation potential (POCP) indices for the region indicated that alkanes and oxygenated organic compounds had relatively low reactivity, while alkenes and aromatics presented high reactivity, as seen in other airsheds in Europe. Analysis of the emission inventory found that the sum of 60 of the 139 VOC species accounted for 92% of the total POCP-weighted emission. The 60 VOC species include C2–C6 alkenes, C6–C8 aromatics, biogenic VOCs, and so on. The results indicated that regional scale ozone formation in the PRD region can be mainly attributed to a relatively small number of VOC species, namely isoprene, ethene, m-xylene, and toluene, etc. A further investigation of the relative contribution of the main emission source categories to ozone formation suggested that mobile sources were the largest contributor to regional O3 formation (40%), followed by biogenic sources (29%), VOC product-related sources (23%), industry (6%), biomass burning (1%), and power plants (1%). The findings obtained in this study would advance our knowledge of air quality in the PRD region, and provide useful information to local government on effective control of photochemical smog in the region.
Keywords: Master chemical mechanism; Ozone; Pearl River Delta; Photochemical ozone creation potential;
Experimental and statistical analyses to characterize in-vehicle fine particulate matter behavior inside public transit buses operating on B20-grade biodiesel fuel by Abhilash Vijayan; Ashok Kumar (4209-4218).
This paper presents results from an in-vehicle air quality study of public transit buses in Toledo, Ohio, involving continuous monitoring, and experimental and statistical analyses to understand in-vehicle particulate matter (PM) behavior inside buses operating on B20-grade biodiesel fuel. The study also focused on evaluating the effects of vehicle’s fuel type, operating periods, operation status, passenger counts, traffic conditions, and the seasonal and meteorological variation on particulates with aerodynamic diameter less than 1 micron (PM1.0). The study found that the average PM1.0 mass concentrations in B20-grade biodiesel-fueled bus compartments were approximately 15 μg m−3, while PM2.5 and PM10 concentration averages were approximately 19 μg m−3 and 37 μg m−3, respectively. It was also observed that average hourly concentration trends of PM1.0 and PM2.5 followed a “μ-shaped” pattern during transit hours.Experimental analyses revealed that the in-vehicle PM1.0 mass concentrations were higher inside diesel-fueled buses (10.0–71.0 μg m−3 with a mean of 31.8 μg m−3) as compared to biodiesel buses (3.3–33.5 μg m−3 with a mean of 15.3 μg m−3) when the windows were kept open. Vehicle idling conditions and open door status were found to facilitate smaller particle concentrations inside the cabin, while closed door facilitated larger particle concentrations suggesting that smaller particles were originating outside the vehicle and larger particles were formed within the cabin, potentially from passenger activity. The study also found that PM1.0 mass concentrations at the back of bus compartment (5.7–39.1 μg m−3 with a mean of 28.3 μg m−3) were higher than the concentrations in the front (5.7–25.9 μg m−3 with a mean of 21.9 μg m−3), and the mass concentrations inside the bus compartment were generally 30–70% lower than the just-outside concentrations. Further, bus route, window position, and time of day were found to affect the in-vehicle PM concentrations significantly. Overall, the in-vehicle PM1.0 concentrations inside the buses operating on B20-grade biodiesel ranged from 0.7 μg m−3 to 243 μg m−3, with a median of 11.6 μg m−3.Statistical models developed to study the effects of vehicle operation and ambient conditions on in-vehicle PM concentrations suggested that while open door status was the most important influencing variable for finer particles and higher passenger activity resulted in higher coarse particles concentrations inside the vehicle compartments, ambient PM concentrations contributed to all PM fractions inside the bus irrespective of particle size.
Keywords: In-vehicle air quality; Particulate matter; PM1.0 concentrations; Alternative fuels; Public transit buses;
Simulation of aerosols and gas-phase species over Europe with the Polyphemus system. Part II: Model sensitivity analysis for 2001 by Y. Roustan; K.N. Sartelet; M. Tombette; É. Debry; B. Sportisse (4219-4229).
This paper presents a multi-pollutant sensitivity study of an air quality model over Europe with a focus on aerosols. Following the evaluation presented in the companion paper, the aim here is to study the sensitivity of the model to input data, mathematical parameterizations and numerical approximations. To that end, 30 configurations are derived from a reference configuration of the model by changing one input data set, one parameterization or one numerical approximation at a time. Each of these configurations is compared to the same reference simulation over two time periods of the year 2001, one in summer and one in winter. The sensitivity of the model to the different configurations is evaluated through a statistical comparison between the simulation results and through comparisons to available measurements. The species studied are ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), ammonia (NH3), coarse and fine aerosol particles (PM c and PM2.5), sulfate, nitrate, ammonium, chloride and sodium.For all species, the modeled concentrations are very sensitive to the parameterization used for vertical turbulent diffusion and to the number of vertical levels. For the other configurations considered in this work, the sensitivity of the modeled concentration to configuration choice varies with the species and the period of the year. O3 is impacted by options related to boundary conditions. PM c is sensitive to sea-salt related options, to options influencing deposition and to options related to mass transfer between gas and particulate phases. PM2.5 is sensitive to a larger number of options than PM c : sea-salt, boundary conditions, heterogeneous reactions, aqueous chemistry and gas/particle mass transfer. NO2 is strongly influenced by heterogeneous reactions. Nitrate shows the highest variability of all species studied. As with NO2, nitrate is strongly sensitive to heterogeneous reactions but also to mass transfer, thermodynamic related options, aqueous chemistry and computation of the wet particle diameter. While SO2 is mostly sensitive to aqueous chemistry, sulfate is also sensitive to boundary conditions and, to a lesser extent, to heterogeneous reactions. As with nitrate, ammonium is largely impacted by the different configuration choices, although the sensitivity is slightly lower than for nitrate. NH3 is sensitive to aqueous chemistry, mass transfer and heterogeneous reactions. Chloride and sodium are impacted by sea-salt related options, by options influencing deposition and by options concerning the aqueous-phase module.
Keywords: Air quality model; Sensitivity analysis; Ozone; Precursors; Particulate matter;
How big is big? How often is often? Characterizing Texas petroleum refining upset air emissions by Britney J. McCoy; Paul S. Fischbeck; David Gerard (4230-4239).
This work examines the magnitude and frequency of Texas petroleum refineries upset air emissions over a 44-month period. Upset emissions occur during plant start-ups, shut-downs, maintenance, malfunctions and flaring incidents, and these emissions are typically exempt from regulation. These emissions contain a variety of chemicals, including benzene, nitrogen oxides, sulfur dioxide, and butadiene. Unlike other states, Texas has detailed reporting requirements, regulations in place, and an extensive upset emissions database. A key scientific and public policy question is whether upset emissions have significant impacts on local air quality and public health. However, it is not possible to address this question without first understanding the magnitude and properties of upsets. We merge related databases to examine over 3,900 upset emission events and find that upset emissions are significant in both size and occurrence when compared to routine operation emissions. It is determined that these events are not random, being more likely to occur during the summer, in the morning, and early in the workweek. A regional analysis of Port Arthur suggests that upset emissions from co-located refineries are equivalent to having an additional refinery within the region. Because of uncertainties within the reporting process and an obvious underestimation by some refineries, there is a need for better tracking of upset emissions.
Keywords: Emissions characterization; Upset air emissions; Petroleum refinery; Criteria pollutants;
Seasonal monoterpene and sesquiterpene emissions from Pinus taeda and Pinus virginiana by Chris D. Geron; Robert R. Arnts (4240-4251).
Seasonal volatile organic compound emission data from loblolly pine (Pinus taeda) and Virginia pine (Pinus virginiana) were collected using branch enclosure techniques in Central North Carolina, USA. P. taeda monoterpene emission rates were at least ten times higher than oxygenated monoterpene and sesquiterpene emissions in all seasons. α-pinene and β-pinene were the most abundant emissions, while β-caryophyllene had the highest sesquiterpene emission rate from this species. β-phellandrene was the dominant compound emitted from P. virginiana, followed by the sesquiterpene β-caryophyllene. Sesquiterpene emissions from P. virginiana have not been reported in the literature previously. Summer sesquiterpene emissions from P. virginiana were nearly as high as monoterpene emissions, but were 4–12 times lower than monoterpene emissions in the other seasons. Oxygenated monoterpenes and 2-methyl-3-buten-2-ol were emitted at higher rates from P. taeda than from P. virginiana. Temperature response of the pinenes from P. taeda is similar to previously reported values used in emission models, while that for other compounds falls at the lower end of the previously reported range. Temperature response of all compounds from P. virginiana is in reasonable agreement with previously reported values from other pine species. There is evidence of light dependence of sesquiterpene emission after accounting for temperature response from both species. This effect is somewhat stronger in P. taeda. Bud break, needle expansion, and needle fall (and therefore wind events) seemed to increase monoterpene emission during non-summer seasons. In some instances springtime monoterpene emissions were higher than summertime emissions despite cooler temperatures. Emissions of individual compounds within monoterpene, oxygenated monoterpene, and sesquiterpene classes were highly correlated with each other. Compounds from different classes were much less correlated within each species. This is due to a varying temporal emission patterns for each BVOC class and suggests different production, storage, and emission controls for each. Analysis of enclosure blanks and diurnal patterns indicates that, despite precautions, disturbance due to the enclosure technique may still impact monoterpene emission rate estimates. This did not appear to affect sesquiterpene emissions.
Keywords: Seasonality; Monoterpene; Sesquiterpene; Emissions; Pinus taeda; Pinus virginiana; Loblolly Pine; Virginia Pine; Beta caryophyllene; Alpha pinene; North Carolina;
GARCH modelling in association with FFT–ARIMA to forecast ozone episodes by Ujjwal Kumar; Koen De Ridder (4252-4265).
In operational forecasting of the surface O3 by statistical modelling, it is customary to assume the O3 time series to be generated through a homoskedastic process. In the present work, we’ve taken heteroskedasticity of the O3 time series explicitly into account and have shown how it resulted in O3 forecasts with improved forecast confidence intervals. Moreover, it also enabled us to make more accurate probability forecasts of ozone episodes in the urban areas. The study has been conducted on daily maximum O3 time series for four urban sites of two major European cities, Brussels and London. The sites are: Brussels (Molenbeek) (B1), Brussels (PARL.EUROPE) (B2), London (Brent) (L1) and London (Bloomsbury) (L2). Fast Fourier Transform (FFT) has been used to model the periodicities (annual periodicity is especially distinct) exhibited by the time series. The residuals of “actual data subtracted with their corresponding FFT component” exhibited stationarity and have been modelled using ARIMA (Autoregressive Integrated Moving Average) process. The MAPEs (Mean absolute percentage errors) using FFT–ARIMA for one day ahead 100 out of sample forecasts, were obtained as follows: 20%, 17.8%, 19.7% and 23.6% at the sites B1, B2, L1 and L2. The residuals obtained through FFT–ARIMA have been modelled using GARCH (Generalized Autoregressive Conditional Heteroskedastic) process. The conditional standard deviations obtained using GARCH have been used to estimate the improved forecast confidence intervals and to make probability forecasts of ozone episodes. At the sites B1, B2, L1 and L2, 91.3%, 90%, 70.6% and 53.8% of the times probability forecasts of ozone episodes (for one day ahead 30 out of sample) have correctly been made using GARCH as against 82.6%, 80%, 58.8% and 38.4% without GARCH. The incorporation of GARCH also significantly reduced the no. of false alarms raised by the models.
Keywords: GARCH; FFT; ARIMA; O3-episodes; Air quality modelling; Air pollution;
Broadband UV spectroscopy system used for monitoring of SO2 and NO emissions from thermal power plants by Y.G. Zhang; H.S. Wang; G. Somesfalean; Z.Y. Wang; X.T. Lou; S.H. Wu; Z.G. Zhang; Y.K. Qin (4266-4271).
A gas monitoring system based on broadband absorption spectroscopic techniques in the ultraviolet region is described and tested. The system was employed in real-time continuous concentration measurements of sulfur dioxide (SO2) and nitric oxide (NO) from a 220-ton h−1 circulating fluidized bed (CFB) boiler in Shandong province, China. The emission coefficients (per kg of coal and per kWh of electricity) and the total emission of the two pollutant gases were evaluated. The measurement results showed that the emission concentrations of SO2 and NO from the CFB boiler fluctuated in the range of 750–1300 mg m−3 and 100–220 mg m−3, respectively. Compared with the specified emission standards of air pollutants from thermal power plants in China, the values were generally higher for SO2 and lower for NO. The relatively high emission concentrations of SO2 were found to mainly depend on the sulfur content of the fuel and the poor desulfurization efficiency. This study indicates that the broadband UV spectroscopy system is suitable for industrial emission monitoring and pollution control.
Keywords: Sulfur dioxide; Nitric oxide; Thermal power plant; Pollutant gas; China;
Threat to food security under current levels of ground level ozone: A case study for Indian cultivars of rice by Richa Rai; Madhoolika Agrawal; S.B. Agrawal (4272-4282).
A higher ozone concentration in rural agricultural region poses threat to food production in developing countries. The present study was conducted to evaluate the growth, biomass accumulation and allocation pattern, quantitative and qualitative characteristics of grains for two tropical rice cultivars (Oryza sativa L. cv NDR 97 and Saurabh 950) at ambient O3 concentrations at a rural site in the Indo Gangetic plains of India.Percent inhibition in number of leaves was higher for NDR 97, but in leaf area for Saurabh 950 grown in non filtered chambers (NFCs) compared to filtered chambers (FCs). Higher inhibition in root biomass was recorded in Saurabh 950 and in leaf and standing dead biomass for NDR 97. During vegetative phase, relative growth rate showed more percent inhibition in Saurabh 950, but at reproductive phase in NDR 97. Net assimilation rate showed higher values for Saurabh 950 than NDR 97 in NFCs but percent inhibition in leaf area ratio was higher for former than latter cultivar in NFCs. The ozone resistance was higher in NDR 97 during vegetative phase, but in Saurabh 950 at reproductive phase. Number of grains was higher in NDR 97 than Saurabh 950, but test weight and weight of grains m−2 showed reverse trends. Concentrations of starch, protein, P, N, Ca, Mg and K decreased, while reducing and total soluble sugar increased in grains of both the cultivars in NFCs compared to FCs. The study concluded that under ambient condition of O3 exposure, the two cultivars responded differently. Saurabh 950 favoured biomass translocation priority towards ear in reproductive phase and hence showed higher resistivity due to maintenance of higher test weight. NDR 97, however, showed better growth during vegetative period, but could not allocate efficiently to developing ears, hence higher number of unfilled grains in NFCs led lower test weight.
Keywords: Ambient ozone; Tropical rice cultivars; Biomass; Growth; Test weight; Seed quality;
The ozone source–receptor model – A tool for UK ozone policy by G.D. Hayman; J. Abbott; T.J. Davies; C.L. Thomson; M.E. Jenkin; R. Thetford; P. Fitzgerald (4283-4297).
The Ozone Source–Receptor Model (OSRM) is a Lagrangian trajectory model developed to describe photochemical ozone production in the UK. The OSRM builds on existing boundary layer trajectory models used previously for assisting the development of UK ozone policy, but has a number of notable differences. A novel feature of the OSRM is a surface conversion module to represent the vertical gradient in ozone arising from chemical loss and deposition to the surface. This has significantly improved the performance of the model, especially in urban areas. In this paper, the modelling system is described and its performance against measured ozone concentrations and metrics and other UK ozone models is discussed. The model has been used to calculate future ozone concentrations in the UK and thus to assess a number of possible control measures developed for the UK Air Quality Strategy.
Keywords: Air pollution; Ground-level ozone; Numerical modelling;
Concentration characteristics of bromine and iodine in aerosols in Shanghai, China by Yunchuan Gao; Mingxing Sun; Xiaowei Wu; Yongdi Liu; Yaqi Guo; Ji Wu (4298-4302).
Aerosol samples (TSP and PM10) during each season were collected at a national monitoring point in Shanghai in 2008. Halogens (Br, I) were determined in samples along with sodium (Na) by ICP-MS and ICP-OES after microwave digestion. In this report we focused on the concentration characteristics of halogen elements Br and I and their seasonal distributions. The mean annual concentrations of total Br and I were 24 ng m−3 and 12 ng m−3 for TSP, 21 ng m−3 and 9 ng m−3 for PM10, respectively. Concentrations of Br and I in TSP and PM10 were lowest in summer but an increase occurred in autumn and winter. Water-soluble Br and I accounted for about 32% of the total Br and I in aerosols, and about 68% of Br and I was non soluble which may be non-soluble organic species. These non-soluble organic species are present in aerosols in the possible binding forms as mineral dust, natural organic matter, and adsorption to black carbon or mineral material such as iron oxides. Soluble Br and I in PM10 extracted by a dilute acid solution (HNO3 + H2SO4) increased by 22% and 18%, respectively, compared with water-soluble Br and I. A positive correlation with Na and sea water enrichment factors for Br and I indicated that bromine and iodine in aerosols originated mostly from marine sources in Shanghai.
Keywords: Aerosols; Trace elements; Bromine; Iodine; Shanghai;
Decadal changes in atmospheric CO2 concentration and δ13C over two seas and two oceans: Italy to New Zealand by Antonio Longinelli; Renzo Lenaz; Carlo Ori; Leonardo Langone; Enricomaria Selmo; Federico Giglio (4303-4311).
Continuous measurements of the CO2 concentration were repeatedly carried out from 1996 to 2007 between Italy and New Zealand by means of a Siemens Ultramat 5E analyzer assembled for shipboard use. Along the ship routes discrete air samples were collected from 1998 to 2005 using four-litre Pyrex flasks. The δ13C of the CO2 from the flask air samples was measured according to well-established techniques. The decadal changes of these two variables can now be evaluated from these results. Large variations of the CO2 concentration were normally recorded in the Mediterranean and the Red Sea. Completely different trends of the CO2 concentration were observed in the Red Sea (30° N to about 13° N) between 2007 (a marked southward decrease) and 2005 and 2003 when a marked southward increase is apparent, at least between 23° and 13° N. A further difference among different expeditions is related to the decrease or increase of the CO2 concentration in the Gulf of Aden. The backward trajectories of the air masses help to explain, at least partially, these differences. In the Indian Ocean and Southern Ocean a decrease of a few ppmv of the CO2 concentration takes place from Cape Guardafui (Northern Somaliland) to southern New Zealand, particularly during 2005 and 2007. The yearly rate of increase of the CO2 concentration between 1996 and 2007 for the Indian Ocean is of about 1.9 ppmv yr−1, in excellent agreement with the NOAA/CMDL measurements carried out during the same period at Mahé Isld. (Indian Ocean) and Cape Grim (Tasmania). The δ13C results obtained from the CO2 of flask samples collected in the Mediterranean show the effect of anthropogenic emissions, though this is considerably smaller than expected. This inconsistency may be related to the large terrestrial biospheric sink of CO2 in the Northern Hemisphere. The results obtained from the Red Sea are quite variable through time and space, particularly in its southern section; their interpretation is not easy. The Indian Ocean and the Southern Ocean show rather homogeneous δ13C results even though a variable carbon isotope shift can be calculated from period/cruise to period/cruise. In the case of the Indian Ocean the mean δ13C value from the flask air samples collected in 2005 is −8.29‰ and the calculated rate of the carbon isotope shift between 1998 and 2005 is −0.034‰ yr−1, considerably larger than that calculated at the closest NOAA station (Mahé Isld.) of −0.026‰ yr−1. This discrepancy may be, at least partially, caused by the small number of measurements carried out at sea. However, the atmosphere over the Indian Ocean is less affected by anthropogenic emissions than in other areas.
Keywords: Atmospheric CO2 concentration; δ13C of atmospheric CO2; Mediterranean; Red Sea; Indian Ocean; Southern Ocean;
Stable sulphur and nitrogen isotopes of the moss Haplocladium microphyllum at urban, rural and forested sites by Hua-Yun Xiao; Cong-Guo Tang; Hong-Wei Xiao; Xue-Yan Liu; Cong-Qiang Liu (4312-4317).
Elemental (S and N) and isotopic (δ 34S and δ 15N) contents in the moss Haplocladium microphyllum at urban, rural and forested sites in acid rain area of South China have been analyzed for comparisons to show whether they are different and can be effectively used to identify S and N sources of atmospheric deposition. Average moss S content at rural sites (0.29 ± 0.06%) was found to be in between those at urban (0.35 ± 0.05%) and forested (0.25 ± 0.04%) sites, which are significantly different. Average N contents of urban (2.60 ± 0.56%) and rural mosses (2.84 ± 0.77%) are not significantly different, while both are significantly different to that of forested mosses at most areas, indicating that the atmosphere over rural sites has been polluted by N as seriously as that over urban sites. Nitrogen supply, relative to S supply, was in excess of the requirement for protein synthesis, especially at rural and forested sites. Moss stable isotope signatures have been proven to be effective tools for deciphering atmospheric S and N sources at these sites. Through moss δ 34S signatures, we found that atmospheric S at urban and forested sites was mainly from local coal combustion and domestic biomass burning, respectively, whereas northerly air masses contributed more S to forested sites. The relatively negative moss δ 15N values (−7.5 ± 3.0, −3.4 ± 2.1 and −0.8 ± 2.1‰) demonstrated that the main form in the N deposition was NHx in these sites. More negative δ 15N signatures in urban mosses (−7.5 ± 3.0‰) indicated the contribution of NH3 released from untreated city sewage and wastes, while relatively less negative δ 15N for rural and forested mosses (3.4 ± 2.1 and −0.8 ± 2.1‰) was largely derived from agricultural NH3.
Keywords: Sulphur; Nitrogen; Isotopes; Mosses; Atmospheric deposition; Air pollution;
Nonlinear dynamical analysis of ground level ozone concentrations at different temporal scales by Asha B. Chelani (4318-4324).
The nonlinear dynamical analysis of ground level ozone concentration is carried out by using correlation integral method to examine its scale invariance property. The dynamics of the time series is often studied at one temporal scale. It is assumed that if the time series is determined to be chaotic at one temporal scale, its behavior at another scale can be determined as the scale shifts are allowed due to scale invariance property. The actual dynamics at other scales is however not yet analyzed. The assumption of scale invariance of the time series at different time scales is tested in this study. The analysis is carried out for ground ozone levels observed during 2006 at two sites of different land use characteristics, as traffic and mixed-use in Delhi at four temporal scales as 1 h, 4 h, 8 h and 24 h. The chaotic nature is observed for the ozone concentration with 1 h and 4 h frequency, whereas at 8 h and 24 h time scale, the ozone concentration shows random behavior. As expected, a decrease in the variability is observed in the ozone levels with increase in the scales from 1 h to 24 h. The results indicated the temporal scale shifts are allowed from 1 h to 4 h resolution and vice versa. The ozone time series at 8 h and 24 h scalings however, should be dealt separately. Further analysis for corresponding NO2 concentration at two sites suggested finite d 2 for 1 h, 4 h and 8 h scalings with higher value at traffic site than that at mixed-use site. The analysis also indicated same degrees of freedom for ozone and NO2 concentration at traffic site whereas at mixed-use site the number of variables governing the NO2 pollution are less than the ozone concentration.
Keywords: Ozone time series; Scale invariance; Intermittency; Correlation integral;
Characterisation of particulate exposure during fireworks displays by Alexandre Joly; Audrey Smargiassi; Tom Kosatsky; Michel Fournier; Ewa Dabek-Zlotorzynska; Valbona Celo; David Mathieu; René Servranckx; Réal D'amours; Alain Malo; Jeffrey Brook (4325-4329).
Little is known about the level and content of exposure to fine particles (PM2.5) among persons who attend fireworks displays and those who live nearby. An evaluation of the levels of PM2.5 and their elemental content was carried out during the nine launches of the 2007 Montréal International Fireworks Competition. For each event, a prediction of the location of the firework plume was obtained from the Canadian Meteorological Centre (CMC) of the Meteorological Service of Canada. PM2.5 was measured continuously with a photometer (Sidepak™, TSI) within the predicted plume location (“predicted sites”), and integrated samples were collected using portable personal samplers. An additional sampler was located on a nearby roof (“fixed site”). The elemental composition of the collected PM2.5 samples from the “predicted sites” was determined using both a non-destructive energy dispersive ED-XRF method and an ICP-MS method with a near-total microwave-assisted acid digestion. The elemental composition of the “fixed site” samples was determined by the ICP-MS with the near-total digestion method. The highest PM2.5 levels reached nearly 10 000 μg m−3, roughly 1000 times background levels. Elements such as K, Cl, Al, Mg and Ti were markedly higher in plume-exposed filters. This study shows that 1) persons in the plume and in close proximity to the launch site may be exposed to extremely high levels of PM2.5 for the duration of the display and, 2) that the plume contains specific elements for which little is known of their acute cardio-respiratory toxicity.
Keywords: Fine particulate matter; Fireworks; Human exposure;