Atmospheric Environment (v.41, #3)
Editorial board (i).
Haagen-Smit Prize 2006 (449-451).
Levels of persistent organic pollutants in air in China and over the Yellow Sea by Gerhard Lammel; Young-Sung Ghim; Amélie Grados; Huiwang Gao; Heinrich Hühnerfuss; Rainer Lohmann (452-464).
The occurrence of persistent toxic substances (PTS) in China and possibly their regional transport in the Yellow and East China Seas region was studied. Organochlorines in atmospheric gas-phase and particulate matter were collected by high-volume sampling (filters and polyurethane foams) during 2 weeks in June 2003 (dry season) simultaneously at a Yellow Sea coastal site in an urban area, Qingdao, China, and a rural island site, Gosan, Jeju Island, Korea. Using GC methods, the samples were analysed for 9 persistent organic pollutants (POPs) regulated under the global POP convention, namely aldrin, chlordane (cis- and trans-isomers CC and TC), DDT and metabolites (o,p′-DDT, p,p′-DDD, and p,p′-DDE), dieldrin, endrin, heptachlor, hexachlorobenzene (HCB), mirex and PCB (congeners number 28, 52, 101, 153 and 180), and for hexachlorocyclohexane (α-, β- and γ-isomers), a PTS and now considered for regulation under the convention, too. At the coastal site additionally o,p′-DDE and -DDD, β-endosulfan, isodrin, heptachlorepoxide and δ-HCH, and at the island site additionally p,p′-DDT and 12 additional PCB congeners were analysed. 9 samples were collected at the coastal and 15 (for PCBs 5) at the island site. Long-range advection pathways were determined based on analysed back-trajectory calculations.The mean concentrations of DDT and its metabolites, HCB, HCH, and PCB at the coast were in the 100–1000 pg m−3 range. Higher concentrations prevailed during nighttime. The levels were in general lower at the island site, but not for DDT. Local sources are likely. PCBs were even 2 orders of magnitude lower, suggesting that PCBs are not subject to regional transport but elevated concentrations in air are limited to the source areas. Organochlorine pesticide levels on the other hand were seemingly determined by regional transport over Mainland China rather than by emissions in the coastal area. The currently used pesticides mirex and chlordane were found at elevated levels, i.e. 79 (6.6–255) and 36 (<6–71) pg m−3, respectively, at the coast but not over the island. The POPs pesticides aldrin, dieldrin and endrin, never registered in China, were mostly found at <10 pg m−3 except for endrin at the coastal site (up to 400 pg m−3) and aldrin at the island site (up to 50 pg m−3).
Keywords: Persistent organic pollutants; Organochlorine pesticides; PCB; China; Yellow Sea; Long-range transport;
Bayesian inference for source determination with applications to a complex urban environment by Andrew Keats; Eugene Yee; Fue-Sang Lien (465-479).
The problem of determining the source of an emission from the limited information provided by a finite and noisy set of concentration measurements obtained from real-time sensors is an ill-posed inverse problem. In general, this problem cannot be solved uniquely without additional information. A Bayesian probabilistic inferential framework, which provides a natural means for incorporating both errors (model and observational) and prior (additional) information about the source, is presented. Here, Bayesian inference is applied to find the posterior probability density function of the source parameters (location and strength) given a set of concentration measurements. It is shown how the source–receptor relationship required in the determination of the likelihood function can be efficiently calculated using the adjoint of the transport equation for the scalar concentration. The posterior distribution of the source parameters is sampled using a Markov chain Monte Carlo method. The inverse source determination method is validated against real data sets acquired in a highly disturbed flow field in an urban environment. The data sets used to validate the proposed methodology include a water-channel simulation of the near-field dispersion of contaminant plumes in a large array of building-like obstacles (Mock Urban Setting Trial) and a full-scale field experiment (Joint Urban 2003) in Oklahoma City. These two examples demonstrate the utility of the proposed approach for inverse source determination.
Keywords: Adjoint equations; Bayesian inference; Dispersion modelling; Source determination; Urban flows;
Air quality during the 2008 Beijing Olympic Games by David G. Streets; Joshua S. Fu; Carey J. Jang; Jiming Hao; Kebin He; Xiaoyan Tang; Yuanhang Zhang; Zifa Wang; Zuopan Li; Qiang Zhang; Litao Wang; Binyu Wang; Carolyne Yu (480-492).
China is taking major steps to improve Beijing's air quality for the 2008 Olympic Games. However, concentrations of fine particulate matter and ozone in Beijing often exceed healthful levels in the summertime. Based on the US EPA's Models-3/CMAQ model simulation over the Beijing region, we estimate that about 34% of PM2.5 on average and 35–60% of ozone during high ozone episodes at the Olympic Stadium site can be attributed to sources outside Beijing. Neighboring Hebei and Shandong Provinces and the Tianjin Municipality all exert significant influence on Beijing's air quality. During sustained wind flow from the south, Hebei Province can contribute 50–70% of Beijing's PM2.5 concentrations and 20–30% of ozone. Controlling only local sources in Beijing will not be sufficient to attain the air quality goal set for the Beijing Olympics. There is an urgent need for regional air quality management studies and new emission control strategies to ensure that the air quality goals for 2008 are met.
Keywords: Beijing; Regional air quality; Olympic Games; PM2.5; Ozone;
Optimized variable source-profile approach for source apportionment by Amit Marmur; James A. Mulholland; Armistead G. Russell (493-505).
An expanded chemical mass balance (CMB) approach for PM2.5 source apportionment is presented in which both the local source compositions and corresponding contributions are determined from ambient measurements and initial estimates of source compositions using a global-optimization mechanism. Such an approach can serve as an alternative to using predetermined (measured) source profiles, as traditionally used in CMB applications, which are not always representative of the region and/or time period of interest. Constraints based on ranges of typical source profiles are used to ensure that the compositions identified are representative of sources and are less ambiguous than the factors/sources identified by typical factor analysis (FA) techniques. Gas-phase data (SO2, CO and NO y ) are also used, as these data can assist in identifying sources. Impacts of identified sources are then quantified by minimizing the weighted-error between apportioned and measured levels of the fitting species. This technique was applied to a dataset of PM2.5 measurements at the former Atlanta Supersite (Jefferson Street site), to apportion PM2.5 mass into nine source categories. Good agreement is found when these source impacts are compared with those derived based on measured source profiles as well as those derived using a current FA technique, Positive Matrix Factorization. The proposed method can be used to assess the representativeness of measured source-profiles and to help identify those profiles that may be in significant error, as well as to quantify uncertainties in source-impact estimates, due in part to uncertainties in source compositions.
Keywords: CMB-LGO; Optimization; Source-apportionment; PM2.5; PMF; Health-study;
Estimation of source apportionment and potential source locations of PM2.5 at a west coastal IMPROVE site by InJo Hwang; Philip K. Hopke (506-518).
Particle composition data for PM2.5 samples collected at Kalmiopsis Interagency Monitoring of Protected Visual Environments (IMPROVE) site in southwestern Oregon from March 2000 to May 2004 were analyzed to provide source identification and apportionment. A total of 493 samples were collected and 32 species were analyzed by particle induced X-ray emission, proton elastic scattering analysis, photon-induced X-ray fluorescence, ion chromatography, and thermal optical reflectance methods. Positive matrix factorization (PMF) was used to estimate the source profiles and their mass contributions. The PMF modeling identified nine sources. In the Kalmiopsis site, the average mass was apportioned to wood/field burning (38.4%), secondary sulfate (26.9%), airborne soil including Asian dust (8.6 %), secondary nitrate (7.6%), fresh sea salt (5.8%), OP-rich sulfate (4.9%), aged sea salt (4.5 %), gasoline vehicle (1.9%), and diesel emission (1.4%). The potential source contribution function (PSCF) was then used to help identify likely locations of the regional sources of pollution. The PSCF map for wood/field burning indicates there is a major potential source area in the Siskiyou County and eastern Oregon. The potential source locations for secondary sulfate are found in western Washington, northwestern Oregon, and the near shore Pacific Ocean where there are extensive shipping lanes. It was not possible to extract a profile directly attributable to ship emissions, but indications of their influence are seen in the secondary sulfate and aged sea salt compositions.
Keywords: PM2.5; IMPROVE; Source profile; Mass contribution; PMF modeling; PSCF analysis;
Size-resolved, real-time measurement of water-insoluble aerosols in metropolitan Atlanta during the summer of 2004 by Roby Greenwald; Michael H. Bergin; Rodney Weber; Amy Sullivan (519-531).
During the month of August 2004, the size-resolved number concentration of water-insoluble aerosols (WIA) from 0.25 to 2.0 μm was measured in real-time in the urban center of Atlanta, GA. Simultaneous measurements were performed for the total aerosol size distribution from 0.1 to 2.0 μm, the elemental and organic carbon mass concentration, the aerosol absorption coefficient, and the aerosol scattering coefficient at a dry (RH=30%) humidity. The mean aerosol number concentration in the size range 0.1–2.0 μm was found to be 360±175 cm−3, but this quantity fluctuated significantly on time scales of less than one hour and ranged from 25 to 1400 cm−3 during the sample period. The mean WIA concentration (0.25–2.0 μm) was 13±7 cm−3 and ranged from 1 to 60 cm−3. The average insoluble fraction in the size range 0.25–2.0 μm was found to be 4±2.5% with a range of 0.3–38%. The WIA population was found to follow a consistent diurnal pattern throughout the month with concentration maxima concurring with peaks in vehicular traffic flow. WIA concentration also responded to changes in meteorological conditions such as boundary layer depth and precipitation events. The temporal variability of the absorption coefficient followed an identical pattern to that of WIA and ranged from below the detection limit to 55 Mm−1 with a mean of 8±6 Mm−1. The WIA concentration was highly correlated with both the absorption coefficient and the elemental carbon mass concentration, suggesting that WIA measurements are dominated by fresh emissions of elemental carbon. For both the total aerosol and the WIA size distributions, the maximum number concentration was observed at the smallest sizes; however the WIA size distribution also exhibited a peak at 0.45 μm which was not observed in the total population. Over 60% of the particles greater than 1.0 μm were observed to be insoluble in the water sampling stream used by this instrumentation. Due to the refractive properties of black carbon, it is highly unlikely that these particles could be composed of elemental carbon, suggesting a crustal source for super-micron WIA.
Keywords: Elemental carbon; Black carbon; Soot; Organic carbon; Absorption coefficient; Scattering coefficient;
Hierarchical space-time modelling of PM10 pollution by Daniela Cocchi; Fedele Greco; Carlo Trivisano (532-542).
In this paper, we propose a hierarchical spatio-temporal model for daily mean concentrations of PM10 pollution. The main aims of the proposed model are the identification of the sources of variability characterising the PM10 process and the estimation of pollution levels at unmonitored spatial locations. We adopt a fully Bayesian approach, using Monte Carlo Markov Chain algorithms. We apply the model on PM10 data measured at 11 monitoring sites located in the major towns and cities of Italy's Emilia-Romagna Region. The model is designed for areas with PM10 measurements available; the case of PM10 level estimation from emissions data is not handled. The model has been carefully checked using Bayesian p-values and graphical posterior predictive checks. Results show that the temporal random effect is the most important when explaining PM10 levels.
Keywords: Bayesian hierarchical models; Dynamic linear models; Particulate matter pollution; Spatial models;
Release of gaseous bromine from the photolysis of nitrate and hydrogen peroxide in simulated sea-salt solutions by Ingrid J. George; Cort Anastasio (543-553).
We have carried out a series of laboratory experiments to investigate the oxidation of bromide (Br−) by hydroxyl radical ( • OH) in solutions used to mimic sea-salt particles. Aqueous halide solutions with nitrate or hydrogen peroxide (HOOH) as a photochemical source of • OH were illuminated with 313 nm light and the resulting gaseous bromine (Br*(g)) was collected. While illumination of these solutions nearly always formed gaseous bromine (predominantly Br2 based on modeling results), there was no evidence for the release of gaseous chlorine. The rate of Br*(g) release increased (up to a plateau value) with increasing concentrations of bromide and was enhanced at lower pH values for both nitrate and HOOH solutions. Increased ionic strength in nitrate solutions inhibited Br*(g) release and the extent of inhibition was dependent upon the salt used. In HOOH solutions, however, no ionic strength effects were observed and the presence of Cl− strongly enhanced Br*(g) release.Overall, for conditions typical of aged, deliquesced, sea-salt particles, the efficiencies of gaseous bromine release, expressed as mole of Br*(g) released per mole of • OH photochemically formed, were typically 20–30%. Using these reaction efficiencies, we calculated the Br2(g) release rate from aged, ambient sea-salt particles due to • OH oxidation to be approximately 0.07 pptv h−1 with the main contributions from nitrate photolysis and partitioning of gas-phase • OH into the particle. While our solution conditions are simplified compared to ambient particles, this estimated rate of Br2 release is high enough to suggest that • OH-mediated reactions in sea-salt particles could be a significant source of reactive bromine to the marine boundary layer.
Keywords: Halide oxidation; Bromine; Br2; Sea-salt particles; Hydroxyl radical;
Ambient levels of volatile organic compounds in the atmosphere of Greater Cairo by M.I. Khoder (554-566).
Ambient volatile organic compounds (VOCs) samples were collected at three locations, two in urban areas in Greater Cairo (Ramsis and Haram) and background one in rural area in Menofiya province (Kafr El-Akram), during the period of June, 2004–August, 2004. The highest concentrations of VOCs were found in Ramsis, whereas the lowest concentrations were detected in Kafr El-Akram, and the difference in mean concentrations were statistically significant (p<0.001). Among all of the measured VOCs species, the contribution of individual VOC to the total VOCs concentration were very similar in Ramsis and Haram locations, toluene was the most abundant compound followed by (m, p)-xylene. This similarity implies a similar emission sources of VOCs in both urban locations, vehicle exhausts are the dominant one. Greater Cairo has high levels of volatile aromatic hydrocarbons compared with many polluted cities in the world. The BTEX (benzene: toluene: ethylbenzene: xylenes) concentration ratios were (2.01:4.94:1:4.95), (2.03:4.91:1:4.87) and (2.31:2.98:1:2.59) in Ramsis, Haram and Kafr El-Akram, respectively. The average toluene/benzene (T/B), (m, p)-xylene/benzene ((m, p)-X/B) and o-xylene/benzene (o-X/B) concentration ratios were 2.45, 1.61and 0.85, respectively in Ramsis and 2.42, 1.61 and 0.78, respectively in Haram. The ratios in both urban locations were of the same magnitude and close to those obtained from automotive exhausts, indicating that the ambient BTEX originate mainly from motor vehicle emissions. However, the (T/B), ((m, p)-X/B) and (o-X/B) concentration ratios were 1.29, 0.71 and 0.41 in Kafr El-Akram, respectively. These ratios were lower than those found in Ramsis and Haram locations and in automotive exhaust, suggesting that the BTEX in Kafr El-Akram do not come from a local source and are exclusively results from the diffusion and dispersion of VOCs produced from the traffic density in the surrounding cities. Significant positive correlation coefficients (p<0.001) were found between the concentrations of BTEX compounds at the three sampling locations. The diurnal variation of VOCs concentrations in Ramsis location showed two daily peaks linked to traffic density.
Keywords: VOCs; Urban/rural areas; BTEX ratio; BTEX correlation; Diurnal variation; Air quality in Greater Cairo;
Comparison between sample-species specific uncertainties and estimated uncertainties for the source apportionment of the speciation trends network data by Eugene Kim; Philip K. Hopke (567-575).
In order to use the US Environmental Protection Agency's speciation trends networks (STN) data in source apportionment studies with positive matrix factorization (PMF), uncertainties for each of the measured data points are required. Since STN data were not accompanied by sample-species specific uncertainties (SSU) prior to July 2003, a comprehensive set of fractional uncertainties was estimated by Kim et al. [2005. Estimation of organic carbon blank values and error structures of the speciation trends network data for source apportionments. Journal of Air and Waste Management Association 55, 1190–1199]. The objective of this study is to compare the use of the estimated fractional uncertainties (EFU) for the source apportionment of PM2.5 (particulate matter less than 2.5 μm in aerodynamic diameter) measured at the STN monitoring sites with the results obtained using SSU. Thus, the source apportionment of STN PM2.5 data were performed and their contributions were estimated through the application of PMF for two selected STN sites, Elizabeth, NJ and Baltimore, MD with both SSU and EFU for the elements measured by X-ray fluorescence. The PMF resolved factor profiles and contributions using EFU were similar to those using SSU at both monitoring sites. The comparisons of normalized concentrations indicated that the STN SSU were not well estimated. This study supports the use of EFU for the STN samples to provide useful error structure for the source apportionment studies of the STN data.
Keywords: Uncertainty; Speciation trends network; Source apportionment; PM2.5;
Source apportionment of secondary organic aerosol during a severe photochemical smog episode by Michael J. Kleeman; Qi Ying; Jin Lu; Mitchel J. Mysliwiec; Robert J. Griffin; Jianjun Chen; Simon Clegg (576-591).
The UCD/CIT air quality model was modified to predict source contributions to secondary organic aerosol (SOA) by expanding the Caltech Atmospheric Chemistry Mechanism to separately track source apportionment information through the chemical reaction system as precursor species react to form condensable products. The model was used to predict source contributions to SOA in Los Angeles from catalyst-equipped gasoline vehicles, non-catalyst equipped gasoline vehicles, diesel vehicles, combustion of high sulfur fuel, other anthropogenic sources, biogenic sources, and initial/boundary conditions during the severe photochemical smog episode that occurred on 9 September 1993. Gasoline engines (catalyst+non-catalyst equipped) were found to be the single-largest anthropogenic source of SOA averaged over the entire model domain. The region-wide 24-h average concentration of SOA produced by gasoline engines was predicted to be 0.34 μg m−3 with a maximum 24-h average concentration of 1.81 μg m−3 downwind of central Los Angeles. The region-wide 24-h average concentration of SOA produced by diesel engines was predicted to be 0.02 μg m−3, with a maximum 24-h average concentration of 0.12 μg m−3 downwind of central Los Angeles. Biogenic sources are predicted to produce a region-wide 24-h average SOA value of 0.16 μg m−3, with a maximum 24-h average concentration of 1.37 μg m−3 in the less-heavily populated regions at the northern and southern edges of the air basin (close to the biogenic emissions sources). SOA concentrations associated with anthropogenic sources were weakly diurnal, with slightly lower concentrations during the day as mixing depth increased. SOA concentrations associated with biogenic sources were strongly diurnal, with higher concentrations of aqueous biogenic SOA at night when relative humidity (RH) peaked and little biogenic SOA formation during the day when RH decreased.
Keywords: SOA; Source apportionment; CACM; UCD/CIT air quality model;
Atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Guangzhou, China by Man Ren; Ping’an Peng; Sukun Zhang; Liping Yu; Gan Zhang; Bixian Mai; Guoying Sheng; Jiamo Fu (592-605).
Atmospheric deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was investigated at four locations, namely at Yuancun, Wushan, Haizhu and Changban in Guangzhou City, Guangdong Province. The annual deposition fluxes of tetra- to octa-CDD/Fs (total PCDD/Fs) were found to range from 170 to 3000 (mean 1500) pg m−2 day−1, and the fluxes of total 2, 3, 7, 8-substituted PCDD/F congeners ranged from 2.1 to 41 (mean 20) pg WHO-TEQ m−2 day−1 at Wushan. The average deposition fluxes of total 2, 3, 7, 8-substituted PCDD/F congeners in rainy season were found to be 37, 27 and 28 pg WHO-TEQ m−2 day−1 at Yuancun, Haizhu and Changban, respectively, and the PCDD/F deposition fluxes behaved obviously higher in rainy season than in dry season. Results from regression analysis showed that number of rainy days, the amount of wet precipitation, PCDD/F concentrations in particles and organic carbon content played important roles in the variation of PCDD/F deposition fluxes. Monthly average temperatures change little over the year. Therefore, it only played a minor role in monthly variation of PCDD/F deposition fluxes. Particle deposition fluxes were generally not considered as the factor that could cause the differences in PCDD/F deposition fluxes between rainy and dry season, but were found to be related with PCDD/F deposition fluxes in rainy season or dry season. It was found that the profiles of PCDD/F homologs or congeners in the samples were the same either spatially or temporally, indicating that the PCDD/F emission sources were similar to one another. The similarities in PCDD/F homolog patterns and the differences in deposition fluxes between samples collected from heavy-traffic roadside and nearby residence house roof indicated that vehicle exhaust might be an important source for PCDD/F in Guangzhou. PCDD/F concentrations and profiles of PCDD/F homologs in atmospheric deposition were compared with those in both total suspended particles in air and soils, and conclusions indicated that atmospheric deposition possibly tended to remove lower-chlorinated DD/Fs from air and was one of sources for PCDD/Fs in soils.
Keywords: PCDD/Fs; Atmospheric deposition; Seasonal variation; Vehicle exhaust; Guangzhou;
Long-term changes in the tropospheric column ozone from the ozone soundings over Europe by J. Krzyscin; P. Krizan; J. Jarosławski (606-616).
The tropospheric column of ozone is analyzed from the measurements of the vertical profile of ozone by balloon-born ozonesondes. The data base includes ∼16,000 ozone profiles collected above six European stations—three of them have begun the ozonesoundings since 1970. We present a trend analysis (with data up to 2005) focusing on detection of the long-term tropospheric ozone variability over the European network. The ozone time series have been examined separately for each station and season (DJF, MAM, JJA, SON) using a flexible trend model. A trend component of the model is taken as a smooth curve without a priori defined shape. A large increase in the European tropospheric ozone since the beginning of the 1970s (net change of ∼10% in summers and ∼30% in winters) and a kind of stabilization in the early 1990s have been corroborated by the study. This pattern comes from the most extensive data set of ozonesoundings over Hohenpeissenberg and Payern. The decadal differences in the trend pattern between these and other European stations are disclosed. The results of a stepwise regression model using various characteristics of the ozone and temperature profiles as explanatory variables for the tropospheric column ozone (TCO3) variations show that the ozone changes may be reconstructed using the ozone mixing ratio at 500 hPa, the thermal tropopause (TT) height, and the difference between ozonepause and TT heights. It appears that the last two factors induce 20–30% of the net TCO3 change over Hohenpeissenberg in the 1970–2004 period.
Keywords: Tropospheric ozone; Ozonesonde; Tropopause; Ozonepause; Trend variability;
A statistical approach for estimating uncertainty in dispersion modeling: An example of application in southwestern USA by Darko Koračin; Anna Panorska; Vlad Isakov; Jawad S. Touma; Jenise Swall (617-628).
A method based on a statistical approach of estimating uncertainty in simulating the transport and dispersion of atmospheric pollutants is developed using observations and modeling results from a tracer experiment in the complex terrain of the southwestern USA. The method takes into account the compensating nature of the error components by representing all terms, except dispersion error and variance of stochastic processes. Dispersion error and the variance of the stochastic error are estimated using the maximum likelihood estimation technique applied to the equation for the fractional error. Mesoscale Model 5 (MM5) and a Lagrangian random particle dispersion model with three optional turbulence parameterizations were used as a test bed for method application. Modeled concentrations compared well with the measurements (correlation coefficients on the order of 0.8). The effects of changing two structural components (the turbulence parameterization and the model grid vertical resolution) on the magnitude of the dispersion error also were examined. The expected normalized dispersion error appears to be quite large (up to a factor of three) among model runs with various turbulence schemes. Tests with increased vertical resolution of the atmospheric model (MM5) improved most of the dispersion model statistical performance measures, but to a lesser extent compared to selection of a turbulence parameterization. Method results confirm that structural components of the dispersion model, namely turbulence parameterizations, have the most influence on the expected dispersion error.
Keywords: Uncertainty; MM5 simulations; Complex terrain; Turbulence parameterizations; Lagrangian dispersion model;
Monoterpene and sesquiterpene emissions of three Mediterranean species through calcareous and siliceous soils in natural conditions by E. Ormeño; C. Fernandez; A. Bousquet-Mélou; S. Greff; E. Morin; C. Robles; B. Vila; G. Bonin (629-639).
Little is known about terpene emissions released by plants in response to abiotic factors, except for climate-related factors. Standard emissions (E S) of monoterpenes (E SM) and sesquiterpenes (E SS) of Rosmarinus officinalis, Pinus halepensis and Cistus albidus in siliceous and calcareous sites were examined. Their dependency on some nutrients in these soils was also analyzed. The study was carried out in the south of France at the end of March, when C. albidus exhibited a leaf growth state, while the other two species exhibited a pre-budbreak state. The results revealed that E S of all major monoterpenes released by R. officinalis and E S of α-pinene and α-humulene of P. halepensis were higher in plants growing in calcareous soils. In contrast, for C. albidus, E SM and E S of β-bourbonene and α-humulene were higher in siliceous soils. E SM of all species was mainly correlated with nitrogen (N) and available phosphorous (PA), while dependency on Ca2+ or K+ was variable. None of these nutrients was significantly correlated with E SS, suggesting that sesquiterpene synthesis pathway requires different nutrient supplies. While higher soil nutrient content stimulated E SM of R. officinalis and P. halepensis, it had a negative effect on E SM of C. albidus, probably because C. albidus exhibited a different phenological state. Considering the soil nature, and particularly N and PA as inputs in plant terpene inventories could hence contribute to obtain more accurate terpene estimates.
Keywords: Nitrogen; Phosphorous; Terpenes; Phenological state; Soil nature;
Emissions profile from new and in-use handheld, 2-stroke engines by John Volckens; James Braddock; Richard F. Snow; William Crews (640-649).
The objective of this study was to characterize exhaust emissions from a series of handheld, 2-stroke small engines. A total of 23 new and used engines from model years 1981–2003 were studied; these engines spanned three phases of emission control (pre-control, phase-1, phase-2). Measured emissions included carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NO x ), hydrocarbons (HC), fine particulate matter (PM2.5), and sulfur dioxide (SO2). Emissions reductions in CO (78%) and HC (52%) were significant between pre-control and phase-2 engines. These reductions can be attributed to improvements in engine design, reduced scavenging losses, and implementation of catalytic exhaust control. Total hydrocarbon emissions were strongly correlated with fuel consumption rates, indicating varying degrees of scavenging losses during the intake/exhaust stroke. The use of a reformulated gasoline containing 10% ethanol resulted in a 15% decrease in HC and a 29% decrease in CO emissions, on average. Increasing oil content of 2-stroke engine fuels results in a substantial increase of PM2.5 emissions as well as smaller increases in HC and CO emissions. Results from this study enhance existing emission inventories and appear to validate predicted improvements to ambient air quality through implementation of new phase-2 handheld emission standards.
Keywords: Non-road; Mobile source; Exhaust; PM; NO x ; HC; CO; Spark ignition; Two-cycle; Ethanol; Alternative fuel;
Which ornamental plant species effectively remove benzene from indoor air? by Yan-Ju Liu; Yu-Jing Mu; Yong-Guan Zhu; Hui Ding; Nan Crystal Arens (650-654).
Phytoremediation—using plants to remove toxins—is an attractive and cost effective way to improve indoor air quality. This study screened ornamental plants for their ability to remove volatile organic compounds from air by fumigating 73 plant species with 150 ppb benzene, an important indoor air pollutant that poses a risk to human health. The 10 species found to be most effective at removing benzene from air were fumigated for two more days (8 h per day) to quantify their benzene removal capacity. Crassula portulacea, Hydrangea macrophylla, Cymbidium Golden Elf., Ficus microcarpa var. fuyuensis, Dendranthema morifolium, Citrus medica var. sarcodactylis, Dieffenbachia amoena cv. Tropic Snow; Spathiphyllum Supreme; Nephrolepis exaltata cv. Bostoniensis; Dracaena deremensis cv. Variegata emerged as the species with the greatest capacity to remove benzene from indoor air.
Keywords: VOCs; Indoor air pollution; Portable GC; Crasulla portulacea;
Refining fire emissions for air quality modeling with remotely sensed fire counts: A wildfire case study by Biswadev Roy; George A. Pouliot; Alice Gilliland; Thomas Pierce; Steven Howard; Prakash V. Bhave; William Benjey (655-665).
This paper examines the use of Moderate Resolution Imaging Spectroradiometer (MODIS) observed active fire data (pixel counts) to refine the National Emissions Inventory (NEI) fire emission estimates for major wildfire events. This study was motivated by the extremely limited information available for many years of the United States Environmental Protection Agency (US EPA) NEI about the specific location and timing of major fire events. The MODIS fire data provide twice-daily snapshots of the locations and breadth of fires, which can be helpful for identifying major wildfires that typically persist for a minimum of several days. A major wildfire in Mallory Swamp, FL, is used here as a case study to test a reallocation approach for temporally and spatially distributing the state-level fire emissions based on the MODIS fire data. Community Multiscale Air Quality (CMAQ) model simulations using these reallocated emissions are then compared with another simulation based on the original NEI fire emissions. We compare total carbon (TC) predictions from these CMAQ simulations against observations from the Inter-agency Monitoring of Protected Visual Environments (IMPROVE) surface network. Comparisons at three IMPROVE sites demonstrate substantial improvements in the temporal variability and overall correlation for TC predictions when the MODIS fire data is used to refine the fire emission estimates. These results suggest that if limited information is available about the spatial and temporal extent of a major wildfire fire, remotely sensed fire data can be a useful surrogate for developing the fire emissions estimates for air quality modeling purposes.
Keywords: Biomass burning; Wildfire; Pixel; Emissions reallocation; Spectroradiometer; Satellite; MODIS;
Cost of lower NO x emissions: Increased CO2 emissions from heavy-duty diesel engines by Mohan Krishnamurthy; Daniel K. Carder; Gregory Thompson; Mridul Gautam (666-675).
This paper highlights the effect of emissions regulations on in-use emissions from heavy-duty vehicles powered by different model year engines. More importantly, fuel economy data for pre- and post-consent decree engines are compared.The objective of this study was to determine the changes in brake-specific emissions of NO x as a result of emission regulations, and to highlight the effect these have had on brake-specific CO2 emission; hence, fuel consumption. For this study, in-use, on-road emission measurements were collected. Test vehicles were instrumented with a portable on-board tailpipe emissions measurement system, WVU's Mobile Emissions Measurement System, and were tested on specific routes, which included a mix of highway and city driving patterns, in order to collect engine operating conditions, vehicle speed, and in-use emission rates of CO2 and NO x . Comparison of on-road in-use emissions data suggests NO x reductions as high as 80% and 45% compared to the US Federal Test Procedure and Not-to-Exceed standards for model year 1995–2002. However, the results indicate that the fuel consumption; hence, CO2 emissions increased by approximately 10% over the same period, when the engines were operating in the Not-to-Exceed region.
Keywords: Diesel emissions; CO2 emissions; NO x emissions; Fuel economy;