Check out our New Publishers' Select for Free Articles

Atmospheric Environment (v.45, #17)

Editorial board (pp. i).

Estimated contributions and uncertainties of PCA/MLR–CMB results: Source apportionment for synthetic and ambient datasets by Guo-Liang Shi; Fang Zeng; Xiang Li; Yin-Chang Feng; Yu-Qiu Wang; Guang-Xun Liu; Tan Zhu (pp. 2811-2819).

The instability of a receptor model due to nearly collinear sources is often worsened by a large number of unknown sources, which usually results in unacceptable source contributions obtained by a single-stage model. To solve this problem, a combined (principal component analysis/multiple linear regression–chemical mass balance; PCA/MLR–CMB) model comprising two stages has been developed. In this study, synthetic datasets with a serious collinearity problem were generated to evaluate the performance of the combined model, and acceptable results were obtained in the presence of noise. Additional, the uncertainties of the estimated contributions were discussed. It was found that nearly collinear sources usually got higher uncertainties. Ambient data from Chengdu were then studied using both the PCA/MLR–CMB and NCPCRCMB models. For PCA/MLR–CMB model: vehicle exhaust emissions contributed 80.46 μg m⁻³ (28.71%) to the total PM₁₀; coal combustion got 68.52 μg m⁻³ (24.45%); resuspended dust, soil dust, secondary sulfate, secondary nitrate, cement dust and smelters got 53.91 μg m⁻³ (19.24%), 46.31 μg m⁻³ (16.53%), 33.35 μg m⁻³ (11.90%), 17.65 μg m⁻³ (6.30%), 12.47 μg m⁻³ (4.45%) and 1.81 μg m⁻³ (0.65%), respectively. For NCPCRCMB model, the results were: vehicle—86.70 μg m⁻³ (30.94%), cement—49.47 μg m⁻³ (17.65%), resuspended dust—41.22 μg m⁻³ (14.71%), coal—30.43 μg m⁻³ (10.86%), soil—27.45 μg m⁻³ (9.80%), secondary sulfate—16.41 μg m⁻³ (5.86%) and secondary nitrate—3.61 μg m⁻³ (1.29%).► The synthetic datasets were studied by PCA/MLR–CMB. ► The uncertainties of the PCA/MLR–CMB results were discussed. ► The near collinear sources usually got higher uncertainties. ► A Chengdu ambient dataset was studied by PCA/MLR–CMB and NCPCRCMB models.

Keywords: PCA/MLR–CMB model; Source apportionment; Collinearity problem; Uncertainty; Nonnegative Constrained Principal Component Regression Chemical Mass Balance Model

Modeling the atmospheric transport and outflow of polycyclic aromatic hydrocarbons emitted from China by Yanxu Zhang; Huizhong Shen; Shu Tao; Jianmin Ma (pp. 2820-2827).

An Euler atmospheric transport model CanMETOP (Canadian Model for Environmental Transport of Organochlorine Pesticides) was applied to the atmospheric transport and outflow of polycyclic aromatic hydrocarbons (PAHs) in China in 2003 based on a square kilometer resolution emission inventory. The reaction with OH radical, gas/particle partition by considering the adsorption onto total aerosol surface area, and dynamic soil/ocean–air exchange of PAHs were also considered. The results show that the spatial distribution of PAH concentration levels in the atmosphere is greatly controlled by emission and meteorological conditions. Elevated concentration levels are predicted in Shanxi, Guizhou, North China Plain, Sichuan Basin and Chongqing metropolitan areas due to the high emission densities at those locations. High concentrations are also modeled in environments offshore of China and in the western Pacific Ocean. The model also predicts a slightly decreasing vertical profile in the planetary boundary layer (lower than ∼1 km), but concentration decreases ∼2 orders of magnitude in the free atmosphere. The Westerlies as well as the East Asian Monsoon and local topographical forcings are identified as key factors influencing the transport pattern of PAHs in China. In 2003, ∼3800°tons of the sixteen parent PAHs listed on USEPA priority control list were transported out of China with about 80% transported through the eastern boundary. The outflow concentrates near 30°N, signifying a slight discrepancy from the position of emission density peaks. The center of the outflow plume is located at a height of ∼1 km at 120°E, and climbs to 3.5 km and 5 km at 130°E and 140°E, respectively. A seasonal variation of 5–6 fold is also found for the outflow flux with greatly elevated transport flux in spring and winter.► Use a state-of-the-art Euler numerical model to study the transport of PAHs. ► The total outflow flux of PAHs was estimated to be 3800 tons per year. ► The high spatial resolution revealed transport patterns at smaller scales.

Keywords: PAH; Atmospheric transport model; Outflow flux; CanMETOP

Stable carbon and nitrogen isotopic composition of bulk aerosols over India and northern Indian Ocean by Rajesh Agnihotri; T.K. Mandal; S.G. Karapurkar; Manish Naja; Ranu Gadi; Y. Nazeer Ahammmed; Animesh Kumar; T. Saud; M. Saxena (pp. 2828-2835).

Atmospheric carbonaceous aerosols of South Asian origin have received immense concerns in the Anthropocene owing to their plausible role in the observed regional to inter-continental scale climate anomalies. Tracking plausible sources and alterations during their transport (secondary processes) are keys to understanding their net influence on regional climate. Here, we report elemental concentrations of C and N (TC and TN), their isotopes (δ¹³C, δ¹⁵N) and TC/TN ratios of bulk carbonaceous aerosol particles over northern Indian Ocean [Bay of Bengal (BOB) and Arabian Sea (AS)] collected as a part of Integrated Campaign for Aerosol, Gases and Radiation Budget (ICARB) during March–May, 2006. In order to understand typical sources, we also measured same parameters of (i) aerosols emitted from typical biomasses conventionally burnt in north and northeastern India and (ii) aerosols particles present in ambient air over selected Indian cities during pre-monsoon season. Bulk aerosols over AS are characterized by significantly higher TC/TN ratios (∼50 ± 10) compared to aerosol over Indian cities (5.6 ± 2.6) as well as over BOB (6.8 ± 12.5), most likely due to having significant inorganic carbon contributed by mineral dust. δ¹³C of aerosols over AS and BOB do not show significant variation (−25.6‰ ± 0.6, −26.5‰ ± 0.8; n = 24 and 21 respectively), however δ¹⁵N values showed a conspicuous difference between the two braches of northern Indian Ocean (10.6‰ ± 2.7 over BOB and 1.4‰ ± 3.3 over the AS). Depleted δ¹⁵N of aerosols over AS can be interpreted in terms of significant mixing of isotopically depleted nitrogenous compounds (NH₃ and NO_xs) emitted from the underlying (denitrifying) waters.► We provide first set of C and N isotope data of aerosols over northern Indian Ocean. ► Its comparison with aerosols produced over typical urban locations of India. ► We also provide isotopes data of aerosols produced by burning of typical bio-fuels. ► N isotopes of aerosols showed significant variability among sources. ► Aerosols over AS are isotopically distinct from those over BOB and urban locations.

Keywords: Aerosols; Arabian Sea; Bay of Bengal; Biomass; Carbon isotopes; Nitrogen isotopes

Variations in the depositional fluxes of cosmogenic beryllium on short time scales by M. Mann; J. Beer; F. Steinhilber; J.A. Abreu; M. Christl; P.W. Kubik (pp. 2836-2841).

We examined the concentrations and fluxes of⁷Be and¹⁰Be at three different sites, Greenland snow pit Dye3, Jungfraujoch and Dübendorf (both Switzerland, high and low altitude sites). The fluxes of both beryllium isotopes and the fluxes of SO₄, NO₃, NH₄ and Ca were used to perform a principal component analysis (PCA) to find common variances in the deposition signal. At all three sites we find the same first principal component and similar patterns in deposition signals. At Dübendorf 90% of the⁷Be and 80% of the¹⁰Be variance in the depostion signal can be explained by the variance of SO₄, NO₃, NH₄ and Ca, grouped into 2 components. At Jungfraujoch only 40% of the⁷Be and 65% of the¹⁰Be variance in the depostion signal can be explained by the same constituents. Furthermore, the different place of origin of deposited⁷Be and¹⁰Be can be found in the variance signals. A preferred attachment of cosmogenic berylium to SO₄ could not be found.► Different depositional processes are found in the cosmogenic⁷Be and¹⁰Be fluxes. ► A cleaning mechanism can be found at all three sites. ►⁷Be at low altitude Swiss site shows a tropospherical depositional pattern. ►¹⁰Be in Swiss low altitude site shows tropospherical and stratospherical deposition. ► The beryllium deposition pattern at high Swiss altitude is mainly stratospherical.

Keywords: Cosmogenic radionuclides; Aerosols; Beryllium; Principal component analysis

Chemical analysis and ozone formation potential of exhaust from dual-fuel (liquefied petroleum gas/gasoline) light duty vehicles by T.W. Adam; C. Astorga; M. Clairotte; M. Duane; M. Elsasser; A. Krasenbrink; B.R. Larsen; U. Manfredi; G. Martini; L. Montero; M. Sklorz; R. Zimmermann; A. Perujo (pp. 2842-2848).

Measures must be undertaken to lower the transport sector’s contribution to anthropogenic emissions. Vehicles powered by liquefied petroleum gas (LPG) are an option due to their reduced emissions of air pollutants compared to engines with conventional fuels. In the present study, ten different dual-fuel LPG/gasoline light duty vehicles were tested, which all complied with European emission level legislation EURO-4. Tests with LPG and gasoline were performed on a chassis dynamometer by applying the New European Driving Cycle (NEDC) and emission factors and ozone formation potentials of both kinds of fuels were compared. The components investigated comprised regulated compounds, CO₂, volatile hydrocarbons and carbonyls. On-line analysis of aromatic species was carried out by resonance-enhanced multiphoton ionization–time-of-flight mass spectrometry (REMPI–TOFMS).We demonstrate that utilization of LPG can entail some environmental benefits by reducing emissions. However, for dual-fuel LPG/gasoline vehicles running on LPG the benefits are less than expected. The main reason is that dual-fuel vehicles usually start the engine up on gasoline even when LPG is selected as fuel. This cold-start phase is crucial for the quality of the emissions. Moreover, we demonstrate an influence on the chemical composition of emissions of vehicle performance, fuel and the evaporative emission system of the vehicles.► Utilization of LPG as car fuel can entail some environmental benefits. ► Environmental benefits of dual-fuel LPG/gasoline vehicles are less. ► Main disadvantage is the cold-start on gasoline.

Keywords: Liquefied petroleum gas; Exhaust emission; Dual-fuel vehicle; Ozone formation potential

Large eddy simulation of wind field and pollutant dispersion in downtown Macao by Y.S. Liu; G.X. Cui; Z.S. Wang; Z.S. Zhang (pp. 2849-2859).

This paper investigates numerical method for predicting wind field and pollutant dispersion in an urban area with crowded buildings and heavy traffic. Large eddy simulation is employed in numerical computation with Lagrangian dynamic model to close the subgrid scale stress. The fine grids are required in numerical simulation of micro-atmospheric flows in an urban area with crowded and complex building-streets. To realize the numerical simulation on available computer resources a domain decomposition method and a combined model for the building-street layout are proposed that the computed domain of an urban area is decomposed into a central area, where the pollution is the major concern and a surrounding region where the pollutant distribution is not concerned. The combined flow model is proposed for the complex building-street layout that the fine grid mesh and exact flow boundary conditions are prescribed in the central area while the buildings are treated as roughness elements in the surrounding region where the coarse grids are used. The proposed numerical method is applied to simulate the wind field and pollutant dispersion from vehicle exhaust in the Rua Do Campo area of Macau (referred to the site hereafter). The wind speed and temperature fields are computed from 7 am on September 6 2005 to 7 am of the next day and the pollutant concentration field is computed from 7 am to 6 pm on September 6 2005. The results show fairly good agreement with the field observation. The wind field and pollutant concentration distribution are demonstrated in the site by proposed combined model and they are compared with those computed by drag element model in whole computational domain. The results show that the combined model is an appropriate method for predicting wind field and pollutant dispersion in the crowded building area. The paper also reveals the relevance of buoyancy effect in the prediction of urban atmospheric environment.► Proposal of a combined model for complex building-street layout in urban atmosphere. ► Emphasis on the buoyancy effect in pollutant dispersion at pedestrian level. ► Development of LES for numerical simulation of micro-atmospheric flows.

Keywords: Large eddy simulation; Immersed boundary method; Drag element method; Urban atmospheric environment

Quantifying the contributions of individual NO_x sources to the trend in ozone radiative forcing by K. Dahlmann; V. Grewe; M. Ponater; S. Matthes (pp. 2860-2868).

Source attribution of ozone radiative forcing (RF) is a prerequisite for developing adequate emission mitigation strategies with regards to climate impact. Decadal means of ozone fields from transient climate-chemistry simulations (1960–2019) are analysed and the temporal development of ozone RF resulting from individual NO_x sources, e.g. road traffic, industry and air traffic, is investigated. We calculated an ozone production efficiency which is mainly dependent on the altitude of NO_x emission and on the amount of background NO_x with values varying over one order of magnitude. Air traffic and lightning are identified as NO_x sources with a two and five times higher ozone production efficiency, respectively, than ground based sources. Second, radiative efficiency of source attributed ozone (i.e. total induced radiative flux change per column ozone) shows clear dependence on latitudinal structure of the ozone anomaly and, to a lesser extent, to its altitude. Lightning induced ozone shows the highest radiative efficiency because lightning primarily enhances ozone in low latitudes in the mid-troposphere (higher altitudes). Superimposed on these effects, a saturation effect causes a decreasing radiative efficiency with increasing background ozone concentrations. Changes in RF attributed to NO_x induced ozone from 1960 to 2019 are controlled by three factors: changes in emissions, changes in ozone production efficiency and changes in the radiative efficiency. Leading effect is emission increase, but changes in ozone production efficiency increase ozone RF by a factor of three for air traffic, or reduce ozone RF by around 30% for ships. Additionally, changes in the radiative efficiency due to saturation effects change ozone RF by 2–5%.► New methodology to attribute ozone radiative forcing changes to emission sectors. ► Changes in ozone RF are controlled by changes in emissions, chemistry and radiation. ► Impact on climate change are partly damped by chemical saturation. ► Radiative efficiency is largest for low latitude and high altitude perturbations. ► Impact on climate change is damped by radiative saturation.

Keywords: Emission sectors; Road transport; Radiative efficiency; Ozone production efficiency; Air traffic; Climate impact

Importance of activity data for improving the residential wood combustion emission inventory at regional level by Cinzia Pastorello; Stefano Caserini; Silvia Galante; Panagiota Dilara; Fabio Galletti (pp. 2869-2876).

The contribution of residential wood combustion (RWC) to emission inventory at local level was estimated using a bottom–up approach for the Lombardy Region of North Italy. A survey, based on the CATI (Computer Assisted Telephone Interviewing) method, has been undertaken through 18,000 interviews. The interviews had the objective to characterize the RWC use in this region, in term of both total and municipal wood consumption. Details on the type of appliances used in RWC were also gathered.The results of the survey were then statistically analyzed in order to allow an estimate of RWC with high spatial resolution (i.e., at municipal level) in relation to the size and altitude of the territory.The work provides new evidence of the importance of wood combustion as a key source for PM and NMVOC emissions at local level, and thus highlights the importance of technological improvements and new policies aimed at emission reduction in this sector.Considering the great differences in average PM emission factors between low efficiency appliances (fireplaces, old stoves) and high efficiency ones (new stoves, pellet burners), this work emphasizes the importance of obtaining more detailed information on the types of wood appliances used for arriving at a reliable PM emission inventory for RWC.► CATI method allows a detailed assessment of domestic wood use at the local level. ► Old appliances (open fireplace, traditional stove) are still widespread and used. ► Details on the type of appliances used are very important for PM emission assessment. ► Large variability of PM emission factors limits the reliability of local inventory. ► A great potential of PM emission reduction through appliance renewal is identified.

Keywords: Wood smoke; Particulate matter; Residential wood combustion; Air pollution; Stove; Fireplace

Contributions of local and regional sources of NO_x to ozone concentrations in Southeast Texas by Hongliang Zhang; Qi Ying (pp. 2877-2887).

The Community Multi-scale Air Quality (CMAQ) model with a modified SAPRC-99 photochemical mechanism was used to investigate the contributions of local and upwind NO_x sources to O₃ concentrations in Southeast Texas during the 2000 Texas Air Quality Study (TexAQS 2000) from August 25 to September 5, 2000. Contributions from eight different local NO_x source types and eight different source regions to the 8-h average daytime O₃ concentrations from 1100 to 1800 CST (referred to as AD O₃ hereafter) are determined. Both diesel engines and highway gasoline vehicles account for 25 ppb of AD O₃ in the urban Houston area. NO_x from natural gas combustion produces 35 ppb of AD O₃ in the industrial area of Houston. Contributions from industrial sources and coal combustion to AD O₃ have comparatively less broad spatial distribution with maximum values of 14 ppb and 20 ppb, respectively. Although the local sources are the most important sources, upwind sources have non-negligible influences (20–50%) on AD O₃ in the entire domain, with a maximum of 50 ppb in rural and coastal areas and 20 ppb in urban and industrial areas. To probe the origins of upwind sources contributions, NO_x emissions in the entire eastern United States are divided into eight different regions and their contributions to O₃ concentrations in the Houston–Galveston–Brazoria (HGB) and Beaumont–Port Arthur (BPA) areas are determined. Among the various NO_x source regions resolved in this study, other Texas counties near the HGB and BPA areas and southeastern states are the most important non-local sources of O₃. Under favorable transport conditions, emissions from neighbor states and northeastern states could also contribute to non-negligible O₃ concentrations (7–15%) in the HGB and BPA areas. This indicates that in addition to reduce local emissions, regional NO_x emission controls, especially from the neighbor counties and states, are also necessary to improve O₃ air quality in Southeast Texas.► A new technique to determine the contributions of NO_x sources to O₃ is developed. ► Natural gas, diesel and gasoline engines are the largest local NO_x sources to O₃. ► Contributions from upwind sources to O₃ can be as much as 50 ppb in rural areas.

Keywords: Source apportionment; Background ozone; CMAQ; TexAQS 2000

Scaling-up leaf monoterpene emissions from a water limited Quercus ilex woodland by A.V. Lavoir; C. Duffet; F. Mouillot; S. Rambal; J.P. Ratte; J.P. Schnitzler; M. Staudt (pp. 2888-2897).

Mediterranean ecosystems are large emitters of biogenic volatile organic compounds (BVOC), and recent studies illustrate how water stress can decrease these emissions even during hot summer. We present here a spatially explicit modelling experiment of BVOC emissions in a water-limited Mediterranean Region in Southern France dominated by Quercus ilex forests. Emission rates were estimated daily using a leaf-level emission model with appropriate up-scaling procedures. The model was based on Guenther’s empirical equations, where we inserted effects for water limitation and seasonality observed from field measurements. Up-scaling from leaves to canopy was performed using Sellers’ theory. For each grid cell, climate variables were interpolated daily from meteorological stations. Incoming solar radiation was measured at one site and extrapolated for the all region based on slope and aspect. Soil properties were derived from pedological maps as well as a digital elevation model, while soil water content was evaluated daily using a bucket-type model.We estimated monoterpene emissions from Q. ilex woodlands to be 16 kt yr⁻¹ (on average), with most emissions occurring in the summer. When including the water-limitation module, yearly emissions were 50% of the initial estimates, with a significant decrease in the number of days with BVOC high emission peaks. This result highlights the importance of water control on determining air pollution peaks in Mediterranean areas and the need for scaling procedure in this area with its large range of strong emitter species.► Guenther’s algorithm was improved in order to include water-limitation effect on MT emissions. ► Model improves were based on field measurements. ► Considering water limitation in model decreased by two regional MT simulations. ► Yearly MT emission rate depended on drought period (precocious versus late). ► Considering water limitation decreased the number of days with high emission peaks.

Keywords: Biogenic emissions; Volatile organic compounds (BVOC); Monoterpene; Mediterranean ecosystems; Water limitation; Drought

Influence of vertical mixing uncertainties on ozone simulation in CMAQ by Wei Tang; Daniel S. Cohan; Gary A. Morris; Daewon W. Byun; Winston T. Luke (pp. 2898-2909).

This study explores the extent to which uncertainties in the formulation of vertical diffusion schemes and in associated model parameters affect predictions of ozone levels and their responsiveness to emission controls in the Community Multiscale Air Quality (CMAQ) model. CMAQ is applied with two vertical diffusion schemes, eddy viscosity (K-theory) and the asymmetric convective model, version 2 (ACM2), to simulate ozone during the Second Texas Air Quality Study (TexAQS II) in 2006, enabling comparisons with a rich array of both ground-level and aloft ozone measurements. The high-order decoupled direct method (HDDM) was implemented into ACM2, and was extended to quantify the influence of parametric uncertainties in dry deposition velocity and eddy diffusivity in both vertical diffusion schemes in CMAQ. Choices of vertical diffusion scheme and parameter values did not strongly influence model performance in simulating ozone concentrations or predicted ozone-precursor responsiveness over much of the domain. However, in some high ozone locations, results show the 8-h ozone sensitivity to NO _x may vary by approximately 20% due to the choice of vertical mixing scheme and by 5–10% due to the uncertainty in dry deposition velocities.► High-order Decoupled Direct method was implemented into ACM2 scheme. ► Dry deposition velocity and eddy diffusivity parameters were added into HDDM. ► Different vertical diffusion schemes did not strongly influence model performance. ► Ozone sensitivity to NO _x varies by 20% due to choice of vertical mixing scheme. ► Ozone sensitivity to NO _x varies by 5–10% due to dry deposition velocity uncertainty.

Keywords: Dry deposition velocity; Eddy diffusivity; Uncertainty analysis; Sensitivity analysis; Decoupled direct method

Climatology of aerosol optical properties in Southern Africa by Antonio J. Queface; Stuart J. Piketh; Thomas F. Eck; Si-Chee Tsay; Alberto F. Mavume (pp. 2910-2921).

A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August–October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with significant dominance of fine mode particles.► Aerosol optical properties were analyzed for Mongu and Skukuza in southern Africa. ► No long term discernable trends are observable in aerosol concentrations. ► There is a reversal gradient on aerosol loading magnitude between Mongu and Skukuza. ► High aerosol optical thickness values are mainly associated with biomass burning. ► The study suggests a SSA (0.90) for Mongu area and lower values for Skukuza.

Keywords: Aerosol climatology; Aerosol trends; Fine and coarse components

Comparing monoterpenoid emissions and net photosynthesis of beech ( Fagus sylvatica L.) in controlled and natural conditions by M. Šimpraga; H. Verbeeck; M. Demarcke; É. Joó; C. Amelynck; N. Schoon; J. Dewulf; H. Van Langenhove; B. Heinesch; M. Aubinet; J.-F. Müller; K. Steppe (pp. 2922-2928).

Although biogenic volatile organic compounds (BVOCs) only represent a very limited fraction of the plant’s carbon (C) budget, they play an important role in atmospheric chemistry for example as a precursor of tropospheric ozone. We performed a study comparing BVOC emissions of European beech ( Fagus sylvatica L.) in controlled and natural environmental conditions. A young and adult beech tree was exposed to short-term temperature variations in growth room conditions and in an experimental forest, respectively. This study attempts to clarify how short-term temperature variations between days influenced the ratio between monoterpenoid (MT) emissions and net photosynthesis (Pn). Within a temperature range of 17–27 °C and 13–23 °C, the MT/Pn carbon ratio increased 10–30 fold for the growth room and forest, respectively. An exponential increasing trend between MT/Pn C ratio and air temperature was observed in both conditions. Beech trees re-emitted a low fraction of the assimilated C back into the atmosphere as MT: 0.01–0.12% and 0.01–0.30% with a temperature rise from 17 to 27 °C and 13–23 °C in growth room and forest conditions, respectively. However, the data showed that the MT/Pn C ratio of young and adult beech trees responded significantly to changes in temperature.► Comparison of indoor and outdoor measurements of monoterpenoids and photosynthesis. ► Monoterpenoid/photosynthesis showed exponential relationship with air temperature. ► Young and adult beech responded similarly to the changes in air temperature.

Keywords: Biospheric–atmospheric gas exchange; Carbon; Foliar monoterpenoids; Net photosynthesis; European beech; Temperature variation

Measurements of key offensive odorants in a fishery industrial complex in Korea by Seong-Gyu Seo; Zhong-Kun Ma; Jun-Min Jeon; Sang-Chul Jung; Woo-Bum Lee (pp. 2929-2936).

This study was carried out to measure the concentrations of offensive odorants with an emphasis on nitrogenous compounds [NC: ammonia (NH₃) and trimethylamine (TMA)] and reduced sulfur compounds [RSC: hydrogen sulfide (H₂S), methyl mercaptan (CH₃SH), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS)] from various sources in a fishery industrial complex in Yeosu, Korea. Samples were collected from a total of 18 sampling sites including the major fishery facilities (C-1∼C-5) and the border areas (O-1∼O-8) of this fishery industrial complex during spring, summer, and fall. The mean concentrations of odorants at the major fishery facilities were found in the order of NH₃ (638ppb), H₂S (291ppb), CH₃SH (123ppb), TMA (20.6ppb), DMDS (7.71ppb), and DMS (5.25ppb). On the other hand, the mean concentrations of odorants at the border areas were NH₃ (85.3ppb), TMA (1.75ppb), H₂S (0.25ppb), CH₃SH (0.18ppb), DMS (0.07ppb), and DMDS (0.06ppb). The mean concentrations of H₂S, CH₃SH and TMA in the major fishery facilities greatly exceeded the Odorant Emission Guideline (OEG) applied to an industrial area. The concentration gradient of RSC between the major fishery facilities and border areas was more prominent than that of NC. From the correlation analyses, the highest correlation coefficient of 0.976 ( p=3.99E−40, n=60) was found between DMS and DMDS at the major fishery facilities, while NH₃ had a strong correlation with the sum of odorant concentrations (SOC) at the border areas ( r=0.997, p=4.83E−54, n=48). The results of this study thus confirmed that CH₃SH and TMA were the major odorants at the major fishery facilities and the border areas, respectively.► The key offensive odorants in a fishery industrial complex were evaluated. ► The ammonia concentration was higher than those of any other odorant. ► Trimethylamine and methyl mercaptan were the specific and major odorants. ► The relationships among the odorants were examined.

Keywords: Reduced sulfur compounds; Nitrogenous compounds; Fishery; Industrial complex; Odorant

Estimation of ambient BVOC emissions using remote sensing techniques by Janet Nichol; Man Sing Wong (pp. 2937-2943).

The contribution of Biogenic Volatile Organic Compounds (BVOCs) to local air quality modelling is often ignored due to the difficulty of obtaining accurate spatial estimates of emissions. Yet their role in the formation of secondary aerosols and photochemical smog is thought to be significant, especially in hot tropical cities such as Hong Kong, which are situated downwind from dense forests. This paper evaluates Guenther et al.’s [Guenther, A., Hewitt, C.N., Erickson, D., Fall, R., Geron, C., Graedel, T.E., Harley, P., Klinger, L., Lerdau, M., McKay, W.A., Pierce, T., Scholes, B., Steinbrecher, R., Tallamraju, R., Taylor, J., Zimmerman, P., 1995. A global model of natural volatile organic compound emissions. Journal of Geophysical Research 100, 8873–8892] global model of BVOC emissions, for application at a spatially detailed level to Hong Kong’s tropical forested landscape using high resolution remote sensing and ground data. The emission estimates are based on a landscape approach which assigns emission rates directly to ecosystem types not to individual species, since unlike in temperate regions where one or two single species may dominate over large regions, Hong Kong’s vegetation is extremely diverse with up to 300 different species in one hectare. The resulting BVOC emission maps are suitable for direct input to regional and local air quality models giving 10m raster output on an hourly basis over the whole of the Hong Kong territory, an area of 1100km². Due to the spatially detailed mapping of isoprene emissions over the study area, it was possible to validate the model output using field data collected at a precise time and place by replicating those conditions in the model. The field measurement of emissions used for validating the model was based on a canister sampling technique, undertaken under different climatic conditions for Hong Kong’s main ecosystem types in both urban and rural areas. The model-derived BVOC flux distributions appeared to be consistent with the field observations, indicating the robustness of the landscape modelling approach when applied to tropical forests at detailed level, as well as the promising role of remote sensing in BVOC mapping.► High resolution BVOC mapping for tropical landscape. ► Model verification using ambient BVOC concentrations. ► Empirical data from remote sensing sources input to modelling. ► Site-specific allometric biomass data input to BVOC model.

Keywords: Biogenic volatile organic compounds; Foliar density; Leaf area index; Satellite image; Hong Kong

Towards the operational estimation of a radiological plume using data assimilation after a radiological accidental atmospheric release by Victor Winiarek; Julius Vira; Marc Bocquet; Mikhail Sofiev; Olivier Saunier (pp. 2944-2955).

In the event of an accidental atmospheric release of radionuclides from a nuclear power plant, accurate real-time forecasting of the activity concentrations of radionuclides is required by the decision makers for the preparation of adequate countermeasures. The accuracy of the forecast plume is highly dependent on the source term estimation. On several academic test cases, including real data, inverse modelling and data assimilation techniques were proven to help in the assessment of the source term.In this paper, a semi-automatic method is proposed for the sequential reconstruction of the plume, by implementing a sequential data assimilation algorithm based on inverse modelling, with a care to develop realistic methods for operational risk agencies. The performance of the assimilation scheme has been assessed through the intercomparison between French and Finnish frameworks. Two dispersion models have been used: Polair3D and Silam developed in two different research centres. Different release locations, as well as different meteorological situations are tested. The existing and newly planned surveillance networks are used and realistically large multiplicative observational errors are assumed. The inverse modelling scheme accounts for strong error bias encountered with such errors. The efficiency of the data assimilation system is tested via statistical indicators. For France and Finland, the average performance of the data assimilation system is strong. However there are outlying situations where the inversion fails because of a too poor observability. In addition, in the case where the power plant responsible for the accidental release is not known, robust statistical tools are developed and tested to discriminate candidate release sites.► A data assimilation method is developed for the forecast of an accidental pollutant plume. ► Validation of the method at European scale with France and Finland monitoring networks. ► The inverse modelling scheme reduces significantly the bias of large errors. ► Development and validation of simple Bayesian tests to identify the release site.

Keywords: Data assimilation; Atmospheric dispersion; Radionuclides; Emergency response

Emissions of nitrous oxide, nitrogen oxides and ammonia from a maize field in the North China Plain by Yuanyuan Zhang; Junfeng Liu; Yujing Mu; Shuwei Pei; Xiaoxiu Lun; Fahe Chai (pp. 2956-2961).

The exchange fluxes of nitrous oxide (N₂O), nitrogen oxides (NO_x) and ammonia (NH₃) from a maize field with three different treatments were simultaneously measured using static and dynamic chambers in the North China Plain (NCP) from June 28 to October 11, 2009. The three treatments included control plot (CK, without crop, fertilization and irrigation), fertilizer N plot (NP) and wheat straw returning plus fertilizer N plot (SN). N-fertilizer application greatly stimulated the emissions of N₂O, NO_x and NH₃, with durations of about 10 days for N₂O and NO, and about 7 days for NH₃. Fertilizer loss rates were 1.08% (NP plot) and 1.20% (SN plot) as N₂O–N, were 1.93% (NP plot) and 0.76% (SN plot) as NO–N, and were 5.24% (NP plot) and 3.03% (SN plot) as NH₃–N. In comparison with the NP plot, the significant low fertilizer loss rates as NO–N and NH₃–N from the SN plot indicated that the wheat straw returning to the field could reduce NO_x and NH₃ emissions. The molar ratio of NO/N₂O was greater than unity for most data during the pulse emission periods induced by fertilization, and thus, nitrification was the dominant process for N₂O and NO emissions during these periods. Considering the significant amount (>80%) of N₂O and NO_x emissions occurred during the pulse emission periods, the emissions of NO_x and N₂O from the investigated field were mainly ascribed to nitrification process.► N-fertilizer application greatly stimulated the emissions of N₂O, NO_x and NH₃. ► Straw returning to the field significantly reduced NO_x and NH₃ emissions. ► Nitrification made the largest contribution for the total emissions of N₂O and NO.

Keywords: Nitrous oxide; Nitrogen oxides; Ammonia; Fertilizers; Wheat straw

A comparison study between model-predicted and OMI-retrieved tropospheric NO₂ columns over the Korean peninsula by K.M. Han; C.K. Lee; J. Lee; J. Kim; C.H. Song (pp. 2962-2971).

In this study, Community Multi-scale Air Quality (CMAQ) model simulations, using the INTEX-B (Intercontinental Chemical Transport Experiment-Phase B) emission inventory for North Korea and China, CAPSS (Clean Air Policy Support System) emission inventory for South Korea, and REAS (Regional Emission Inventory in Asia) emission inventory for Japan, were carried out over four seasonal episodes from 2006, with a fine grid resolution of 30 km × 30 km, in order to evaluate the accuracy of the NO_x emissions over the Korean peninsula. The tropospheric NO₂ columns from the CMAQ model simulations were then compared with those retrieved from a satellite sensor, Ozone Monitoring Instrument (OMI), over the Korean peninsula as well as briefly over East Asia. The results showed that the CMAQ modeling, using the NO_x emissions from the CAPSS inventory over South Korea, produced tropospheric NO₂ columns that were over-predicted by factors between 1.38 and 1.87 compared to the OMI-retrieved tropospheric NO₂ columns. This appears to be in line with the findings from a previous study, i.e. when the ACE-ASIA emission inventory was used for the episodes from 2001 to 2003, the CMAQ modeling tended to produce NO₂ columns that were ∼1.46 times larger than the GOME-derived NO₂ columns over South Korea. On the other hand, over North Korea, the NO_x emissions of the INTEX-B emission inventory appear to be overestimated by factors between 1.55 and 7.46 (3.18 over the four seasonal episodes), based on the comparison study between the CMAQ-simulated and OMI-retrieved tropospheric NO₂ columns. This may be caused by the large uncertainty in the NO_x emission fluxes from North Korea due to insufficient information on the economic activity and energy consumption related to the political instability in North Korea.Display Omitted► There is a clear contrast between the NO₂ columns over South and North Korea. ► NO_x emission of the 2006-CAPSS inventory was overestimated over South Korea. ► NO_x emission of the INTEX-B inventory was overestimated over North Korea.

Keywords: Tropospheric NO; ₂; columns; CMAQ model; OMI sensor; INTEX-B emission inventory; CAPSS emission inventory

Impacts of residential heating intervention measures on air quality and progress towards targets in Christchurch and Timaru, New Zealand by Angelique J. Scott; Carl Scarrott (pp. 2972-2980).

Elevated wintertime particulate concentrations in the New Zealand cities of Christchurch and Timaru are mostly attributed to the burning of wood and coal for residential heating. A carrot-and-stick approach was adopted for managing air quality in Christchurch, where strict intervention measures were introduced together with a residential heater replacement programme to encourage householders to change to cleaner forms of heating. A similar approach was only recently implemented for Timaru. This paper presents the results of a partial accountability analysis, where the impact of these measures on the target source, PM₁₀ emissions, and PM₁₀ concentrations are quantified. A statistical model was developed to estimate trends in the concentrations, which were tested for significance after accounting for meteorological effects, and to estimate the probability of meeting air quality targets. Results for Christchurch and Timaru are compared to illustrate the impacts of differing levels of intervention on air quality. In Christchurch, approximately 34,000 (76%) open fires and old solid fuel burners were replaced with cleaner heating technology from 2002 to 2009, and total open fires and solid fuel burner numbers decreased by 45%. Over the same time period, estimated PM₁₀ emissions reduced by 71% and PM₁₀ concentrations by 52% (maxima), 36% (winter mean), 26% (winter median) and 41% (meteorology-adjusted winter means). In Timaru, just 3000 (50%) open fires and old solid fuel burners were replaced from 2001 to 2008, with total open fire and solid fuel burner numbers reduced by 24%. PM₁₀ emissions declined by 32%, with low reductions in the PM₁₀ concentrations (maxima decreased by 7%, winter means by 11% and winter medians by 3%). These findings, supported by the results of the meteorology corrected trend analysis for Christchurch, strongly indicate that the combination of stringent intervention measures and financial incentives has led to substantial air quality improvements in the city. The lesser impact of more lenient rules and the late introduction of an incentives programme are obvious on air quality in Timaru. Trends established for the two cities were extrapolated under various scenarios to determine the likelihood of meeting air quality targets. In Christchurch the probability of compliance is low and is essentially impossible for Timaru if recent trends continue.

Keywords: Accountability; Trend analysis; Change-out program; Incentives; Residential heatingAbbreviations; NRRP; Natural Resources Regional Plan; GAMM + AR(1); generalised additive mixed model with auto-regressive errors of lag one day; NES; New Zealand National Environment Standard

A novel approach for the characterisation of transport and optical properties of aerosol particles near sources – Part II: Microphysics–chemistry-transport model development and application by Álvaro M. Valdebenito B; Sandip Pal; Andreas Behrendt; Volker Wulfmeyer; Gerhard Lammel (pp. 2981-2990).

A new high-resolution microphysics–chemistry-transport model (LES-AOP) was developed and applied for the investigation of aerosol transformation and transport in the vicinity of a livestock facility in northern Germany (PLUS1 field campaign). The model is an extension of a Large-Eddy Simulation (LES) model. The PLUS1 field campaign included the first deployment of the new eye-safe scanning aerosol lidar system of the University of Hohenheim. In a combined approach, model and lidar results were used to characterise a faint aerosol source. The farm plume structure was investigated and the absolute value of its particle backscatter coefficient was determined. Aerosol optical properties were predicted on spatial and temporal resolutions below 100 m and 1 min, upon initialisation by measured meteorological and size-resolved particulate matter mass concentration and composition data. Faint aerosol plumes corresponding to a particle backscatter coefficient down to 10⁻⁶ sr⁻¹ m⁻¹ were measured and realistically simulated. Budget-related quantities such as the emission flux and change of the particulate matter mass, were estimated from model results and ground measurements.

Keywords: Large-eddy simulation; Aerosol physical modelling; Agricultural aerosol source; Aerosol optical properties; Lidar signal

Henry’s law constant measurements for formaldehyde and benzaldehyde as a function of temperature and water composition by Lyassine Allou; Lahcen El Maimouni; Stéphane Le Calvé (pp. 2991-2998).

Henry’s law constants H of formaldehyde and benzaldehyde were determined using a dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube. The measurements were conducted over the range 273–293K in (i) deionized water, (ii) 35gL⁻¹ solution of NaCl simulating seawater and (iii) two nitric acid solutions, i.e. 0.63 and 6.3wt%.In pure water, the obtained data were used to derive the following Arrhenius expressions: ln H=(6423±542)/ T−(13.4±2.0) and ln H=(6258±280)/ T−(17.5±1.0) for formaldehyde and benzaldehyde, respectively. The H values, calculated at 293K from Arrhenius expressions cited above were the following (in units of Matm⁻¹): H=5020±1170 (formaldehyde), H=47±5 (benzaldehyde). The temperature dependence of H permits then to derive the solvation enthalpies for both compounds: Δ H_solv=−(53.4±4.5)kJmol⁻¹ and Δ H_solv=−(52.0±2.3)kJmol⁻¹ for formaldehyde and benzaldehyde, respectively.In 35gL⁻¹ salt solution, the H values were 27–66% and 12–21% lower than their respective determinations in deionized water, for formaldehyde and benzaldehyde respectively. The observed salt effect was used to estimate the following Setschenow coefficients at 293K for 0.6M NaCl: formaldehyde (0.21) and benzaldehyde (0.09).In 6.3wt% nitric acid solution, H values of benzaldehyde were approximately 30% higher than those found in pure water although no significant influence was observed for formaldehyde.Finally, our experimental data were then used to estimate the fractions of formaldehyde and benzaldehyde in atmospheric aqueous phase and their derived atmospheric lifetimes.

Keywords: Henry’s law constant; Formaldehyde; Benzaldehyde; Temperature; Salinity; Acidity; Salt effect; Nitric acid

Personal exposure to carcinogenic and toxic air pollutants in Stockholm, Sweden: A comparison over time by Mine Yazar; Tom Bellander; Anne-Sophie Merritt (pp. 2999-3004).

Benzene, 1,3-butadiene, benz(a)pyrene, NO_x and NO₂ were measured by personal sampling, stationary indoor sampling, and at two reference sites (urban background/traffic site) in Stockholm, Sweden during September–December 2009. The aim was to investigate whether the air pollution levels had decreased since a previous study conducted six year earlier, and to compare personal exposure levels (one-week average) and indoor levels with levels at outdoor reference sites. Participants were 20–50 years of age, randomly selected among residents in the Stockholm municipality. The personal exposure levels to benzene and 1,3-butadiene were higher than the levels at the reference sites. Personal exposure to NO_x and NO₂ were higher than urban background levels, but the NO₂ exposure level was lower than traffic site levels. Benz(a)pyrene showed lower concentrations indoors compared to outdoor levels, although a significant correlation was found between indoor and outdoor levels. All of the air pollutant levels had decreased since the previous study, both for personal exposure and reference site levels. The results from the present study indicate that urban background measurements for these compounds are suitable for monitoring decreasing or increasing trends in air pollution levels but since the personal exposure levels did not correlate well with weekly ambient levels, personal sampling seems essential for assessing population exposure.► Personal sampling was carried out to collect air pollutants in Stockholm, Sweden. ► The levels had decreased over a six year period. ► Personal exposure was in most cases higher than background concentrations, but followed a similar time trend. ► Personal sampling seems essential to estimate the general population exposure.

Keywords: Air pollution; Personal exposure; VOC; NO; _x; NO; ₂; PAH

Corrigendum to “Annual and seasonal variability of ambient aerosols over an urban region in Western India” [Atmos. Environ. 44(2010) 1200–1208] by Ramya Sunder Raman; S. Ramachandran (pp. 3005-3005).

Sections

Personal tools

Atmospheric Environment (v.45, #17)

Sections

Personal tools

Local resources

Atmospheric Environment (v.45, #17)