Atmospheric Environment (v.100, #C)
Editorial board (i).
Changes in shape and composition of sea-salt particles upon aging in an urban atmosphere by Kouji Adachi; Peter R. Buseck (1-9).
Sea salt is one of the most abundant types of natural aerosol particles and significantly influences local and global climate. It is an important constituent of samples collected between June 10 and 15 in the Los Angeles area during the 2010 CalNex campaign. The sea-salt particles reacted with other species in the atmosphere and became Na-bearing aerosol (NaA) particles. Using transmission electron microscopy, we found that Na occurred in almost half of all analyzed particles (∼3500), although commonly only in minor amounts. Almost all the NaA particles contained S but not Cl, suggesting that Cl was depleted through particle formation to sulfate, nitrate, or both in the urban atmosphere. We observed both rounded and euhedral NaA particles. The rounded ones consisted mainly of aged sea salt (>12 h) that had reacted extensively with sulfate, whereas the euhedral ones occurred in samples from relatively fresh marine air. The shapes and compositions of NaA particles changed within 3 h in the urban atmosphere. Moreover, our calculations indicate that light scattering from NaA particles depends on their shapes (e.g., roughly spherical, flat, or elongated). These compositions and shapes affect hygroscopicities and light scattering, respectively, both of which influence their climate effects.
Keywords: Sea salt; CalNex; Los Angeles; Aging; Light scattering;
Combined effects of nitrogen fertilization and biochar on the net global warming potential, greenhouse gas intensity and net ecosystem economic budget in intensive vegetable agriculture in southeastern China by B. Li; C.H. Fan; H. Zhang; Z.Z. Chen; L.Y. Sun; Z.Q. Xiong (10-19).
Field experiments were conducted to determine the effects of nitrogen (N) fertilization and biochar addition on the net global warming potential (net GWP), greenhouse gas intensity (GHGI) and net ecosystem economic budget (NEEB). These experiments were conducted in an intensive vegetable field with 4 consecutive vegetable crops in 2012 and 2013 in southeastern China. The experiment was conducted with a 32 factorial design in triplicate at N fertilizer rates of 0, 1475, 1967 kg N ha−1 and biochar rates of 0, 20, and 40 t ha−1. Although CH4 emissions were not obviously affected by N fertilization, N2O emissions increased by 27.2–116.2% and the net GWP increased by 30.6–307.2%. Consequently, the GHGI increased significantly, but vegetable yield and the NEEB did not improve. Furthermore, biochar amendments did not significantly influence CH4 emissions, but significantly decreased the N2O emissions by 1.7–25.4%, the net GWP by 89.6–700.5%, and the GHGI by 89.5–644.8%. In addition, vegetable yields significantly increased by 2.1–74.1%, which improved the NEEB. Thus, N fertilization did not increase vegetable yields or the NEEB. However, N fertilization did increase the net GWP and GHGI. In contrast, biochar additions resulted in lower N2O emissions and net GWP and GHGI, but increased vegetable yield and the NEEB in the intensive vegetable production system. Therefore, appropriate biochar amendment should be studied to combat changing climate and to improve the economic profits of vegetable production.Combined effects of nitrogen (N) fertilization and biochar addition on the net global warming potential (net GWP), greenhouse gas intensity (GHGI) and net ecosystem economic budget (NEEB) were assessed based on year round field measurement. Due to the overdose N fertilization typically in vegetable production, N fertilizer cannot increase vegetable yield nor NEEB any further but to the worse, increase net GWP and GHGI in the intensive vegetable agriculture. To the contrary, biochar amendment can increase both vegetable yield and NEEB while still reduce the net GWP and GHGI in the intensive vegetable agriculture.Display Omitted
Keywords: Vegetable agriculture; Biochar; Net global warming potential (net GWP); Greenhouse gas intensity (GHGI); Net ecosystem economic budget (NEEB);
Volatile organic compound flux from manure of cattle fed diets differing in grain processing method and co-product inclusion by Kristin Hales; David B. Parker; N.Andy Cole (20-24).
Odor emissions from livestock production have become increasingly important in the past decade. Odors derived from animal feeding operations are caused by odorous VOC emitted from the mixture of feces and urine, as well as feed and silage which may be experiencing microbial fermentation. Distillers grains are a by-product of corn grain fermentation used to produce fuel ethanol, and this industry has grown rapidly throughout the U.S. in past years. Therefore, the use of wet distillers grains with solubles (WDGS) in feedlot cattle diets has also increased. The objective of this research was to determine specific VOC emissions from feces and urine or a mixture of both, from cattle fed steam flaked or dry-rolled corn (DRC)-based diets containing either 0% or 30% WDGS. Flux of dimethyl trisulfide was greater from feces of cattle fed DRC than steam-flaked corn (SFC) diets. No other differences in flux from feces were detected across dietary treatments for phenol, 4-methylphenol, indole, skatole, dimethyl disulfide, and flux of volatile fatty acids (VFA) such as acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids (P > 0.15). Flux of skatole, acetic acid, and valeric acid from urine was greater for cattle fed SFC than DRC diets (P < 0.05). Moreover, dimethyl disulfide flux was greater for cattle fed DRC vs. SFC diets (P = 0.05). When evaluating WDGS inclusion in the diet, flux of acetic acid and heptanoic acid from urine was greater when cattle were fed diets containing 0% WDGS than 30% WDGS (P < 0.05). When combining urine and feces in the ratio in which they were excreted from the animal, flux of propionic acid was greater when cattle were fed DRC vs. SFC diets (P = 0.05). Based on these results, the majority of the VOC, VFA, and odor flux from cattle feeding operations is from the urine. Therefore, dietary strategies to reduce odor from cattle feeding facilities should primarily focus on reducing excretion of odorous compounds in the urine.
Keywords: Odor; Cattle; Manure; Volatile organic compound;
A budget analysis of the formation of haze in Beijing by Xuexi Tie; Qiang Zhang; Hui He; Junji Cao; Suqing Han; Yang Gao; Xia Li; Xing Chan Jia (25-36).
During recent winters, hazes often occurred in Beijing, causing major environmental problems. To understand the causes of this “Beijing Haze”, a haze episode (from Oct. 21 to Oct. 31, 2013) in Beijing was analyzed. During the episode, the daily mean concentration of fine particulate matter (PM2.5) reached a peak value of 270 μg/m3 on Oct. 28, 2013, and rapidly decreased to 50 μg/m3 the next day (Oct. 29, 2013). This strong variability provided a good opportunity to study the causes of a “Beijing Haze”. Two numerical models were applied for this study. The first model is a chemical/dynamical regional model (WRF-Chem). This model is mainly used to study the effects that weather conditions have on PM2.5 concentrations in the Beijing region. The results show that the presence of high air pressure in northwest Beijing (NW-High) generally produced strong northwest winds with clean upwind air. As a result, the NW-High played an important role in cleaning Beijing's PM. However, the NW-High's cleaning effect did not occur in every situation. When there was low air pressure in southeast Beijing (SE-Low) accompanied by an NW-High, an air convergent zone appeared in Beijing. The pollutants became sandwiched, producing high PM2.5 concentrations in the Beijing region. The second model used in this study is a box model, which is applied to estimate some crucial parameters associated with the budget of PM2.5 in the Beijing region. Under calm winds, the calculations show that continuous local emissions rapidly accumulate pollutants. The PM2.5 concentrations reached 150 μg/m3 and 250 μg/m3 within one (1) day and two (2) days, respectively. Without horizontal dilution, this estimate can be considered as an upper time limit (the fastest time) for the occurrences of haze events in the Beijing region. The wind speed (WSb) is calculated for the balance between the continuous emissions and atmospheric clean processes. The results show that the WSb is strongly dependent on the planetary boundary layer (PBL) height and the wind direction. Under SE-Low weather conditions, the WSb is 2 m/s with a higher PBL height (700 m). However, under lower PBL heights, the WSb rapidly increases, reaching 4.5 m/s and 7.0 m/s with PBL heights of 300 m and 200 m, respectively. In contrast, under NW-High weather conditions, the WSb reduces to 2.5 m/s and 4.0 m/s. These results suggest that when the prevailing wind in Beijing is a northwest wind (with wind speeds of >4 m/s), particulate matter (PM) begins to decrease.
Keywords: PM2.5; Beijing; WRF-Chem; Weather conditions;
Influence of springtime biomass burning in South Asia on regional ozone (O3): A model based case study by Chinmay Jena; Sachin D. Ghude; G.G. Pfister; D.M. Chate; Rajesh Kumar; G. Beig; Divya E. Surendran; S. Fadnavis; D.M. Lal (37-47).
In this study, for the first time, the influence of springtime (MAM) biomass burning in South Asia on regional ozone (O3) distribution has been evaluated using a regional chemical transport model (WRF-Chem) and the Fire Inventory from NCAR (FINNv1). Model results are compared with satellite retrievals of tropospheric column amounts of carbon monoxide (CO) from MOPITT and nitrogen dioxide (NO2) from OMI. With daily varying emissions, the model captures reasonably well the satellite-derived temporal variations in CO and NO2 (index of agreement (R) for CO is 0.83 and for NO2 is 0.76), indicating the effectiveness of the model in estimating the overall fire impact on a regional scale. Simulated tropospheric NO2 concentration shows better agreement with the magnitude of observed NO2 when FINNv1 NO x emissions are reduced by a factor of 2.2 over the model domain. A clear increase in CO and NO2 levels over Burma (35–60%), Central India (15–30%), the Indo-Gangetic (15–25%) region and the Bay of Bengal (15–40%) are simulated with fire emissions. The model results are also used to quantify the net O3 production from fires. Calculated O3 productions are up to 4 ppb h− 1 over inland and up to 0.1 ppb h− 1 over marine regions respectively. Our model-based analysis yields average enhancement ratios ΔO3/ΔCO of 0.12 ppbv/ppbv and a total O3 production of about 3.5 Tg from South Asia during the spring season. The findings demonstrate that the springtime fire emissions in South Asia have a noticeable impact on the O3 in this region.
Keywords: Surface ozone; Fire emissions; FINNv1; WRF-Chem; OMI; MOPITT; South Asia;
Prediction of high concentrations and concentration distribution of a continuous point source release in a semi-idealized urban canopy using CFD-RANS modeling by George C. Efthimiou; Eva Berbekar; Frank Harms; John G. Bartzis; Bernd Leitl (48-56).
One of the key issues in recent research on dispersion in complex urban areas is the ability predicting high concentrations and concentration distribution of a pollutant released continuously from a point source. The present work addresses the question whether the CFD-RANS methodology can provide valid predictions of concentration peaks and distributions. A probabilistic and a deterministic approach are incorporated in the CFD-RANS code ADREA. Innovative algebraic equations for the calculation of the concentration time scales as a function of the hydrodynamic and pollutant travel times are used. The capabilities of the new methodology are validated against wind tunnel experimental data under well described boundary conditions and representative concentration measurements. The comparisons of model and wind tunnel gave fairly good results.
Keywords: High concentrations; Concentration distribution; CFD RANS; Boundary-layer wind tunnel;
Methane and nitrous oxide analyzer comparison and emissions from dairy freestall barns with manure flushing and scraping by Erin L. Cortus; Larry D. Jacobson; Brian P. Hetchler; Albert J. Heber; Bill W. Bogan (57-65).
Continuous methane (CH4) and nitrous oxide (N2O) emission measurements were conducted at two crossflow-ventilated dairy freestall barns located in the state of Wisconsin, USA during a 19-month period from 2008 to 2010. The two cross-flow mechanically ventilated buildings (275 and 375 cow capacities) were evaluated in the National Air Emissions Monitoring Study. In September of 2008, the barns' manure collection systems were changed from flushing open gutter using manure basin effluent to a tractor scrape. A photoacoustic multi-gas analyzer (PAMGA) and a direct methane/non-methane hydrocarbon analyzer (GC-FID) provided side-by-side measurements of methane (CH4) for 13 months. The PAMGA also measured nitrous oxide (N2O), and a side-by-side comparison was performed with a gas-filter correlation analyzer (GFC) for six months. Barn ventilation rates were measured by recording run times of the 127-cm diameter exhaust fans. All 125 belt-driven exhaust fans were identical, and in situ airflow measurements using the Fan Assessment Numeration System (FANS) were conducted once at the beginning and twice during the test. Daily CH4 and N2O emission rates were calculated over approximately 19 and 6 month periods respectively, on per barn, head, animal unit, floor area space and barn capacity bases. The differences between the analyzers' concentration measurements were compared in conjunction with water vapor and other gases. The analyzer type had a significant impact on the average CH4 emission rate (p < 0.001) and the average N2O emission rate (p < 0.05). Based on the CH4 measurements with the GC-FID, average daily mean CH4 emissions were approximately 290 g AU−1 d−1 (390 g cow−1 d−1) with very limited seasonal effects. Little variation was observed in CH4 emission rates before and after the change in manure collection method, suggesting that most of the CH4 emissions were enteric losses directly from the cows. The average daily mean N2O emission rates based on the GFC were very low, with an approximate rate of only 690 mg AU−1 d−1 (970 mg cow−1 d−1). The change in manure collection had no apparent effect on N2O emission.
Keywords: Dairy; Emissions; Methane; Nitrous oxide; Manure handling; Manure collection;
Heterogeneous reactions of ozone with commonly used pesticides adsorbed on silica particles by Joanna Socorro; Sasho Gligorovski; Henri Wortham; Etienne Quivet (66-73).
There is an increasing concern about the pesticides spread in the atmosphere. They can be found in the gas-phase but because of their physico-chemical properties they mostly remain adsorbed on the surface of the atmospheric particles. The kinetic data of the adsorbed pesticides towards atmospheric oxidants such as ozone and hydroxyl radicals are very scarce.Here we present the kinetic data set for the heterogeneous reactions of gas-phase ozone and eight commonly used pesticides adsorbed on silica particles. The obtained rate constants are described by both kinetic patterns, i.e., Langmuir–Rideal (L–R) and Langmuir–Hinshelwood (L–H) mechanisms. Concerning the L–R mechanism the rate constants range between 3.4 · 10−19 cm3 molecules−1 s−1 and 8.8 · 10−19 cm3 molecules−1 s−1. With respect to the L–H mechanism, the values of air–silica partitioning coefficient ( K ( O 3 ) ) vary between 21 · 10−16 cm3 molecules−1 and 358 · 10−16 cm3 molecules−1. The maximum rate constants range between 0.4 · 10−4 and 1.7 · 10−4 s−1. The estimated lifetimes of the selected pesticides according to both L–R and L–H mechanism span from 8 to >33 days, demonstrating that these species are very persistent with respect to ozone reactivity in the atmosphere.The results obtained in this study can contribute to better describe the atmospheric fate of pesticides in the particulate phase.Heterogeneous ozonolysis: slow reaction of 8 commonly used pesticides adsorbed on particles.
Keywords: Aerosols; Ozonolysis; Pesticides; Kinetics;
Detection of nicotine as an indicator of tobacco smoke by direct analysis in real time (DART) tandem mass spectrometry by Ákos Kuki; Lajos Nagy; Tibor Nagy; Miklós Zsuga; Sándor Kéki (74-77).
The residual tobacco smoke contamination (thirdhand smoke, THS) on the clothes of a smoker was examined by direct analysis in real time (DART) mass spectrometry. DART-MS enabled sensitive and selective analysis of nicotine as the indicator of tobacco smoke pollution. Tandem mass spectrometric (MS/MS) experiments were also performed to confirm the identification of nicotine. Transferred thirdhand smoke originated from the fingers of a smoker onto other objects was also detected by DART mass spectrometry. DART-MS/MS was utilized for monitoring the secondhand tobacco smoke (SHS) in the air of the laboratory using nicotine as an indicator. To the best of our knowledge, this is the first report on the application of DART-MS and DART-MS/MS to the detection of thirdhand smoke and to the monitoring of secondhand smoke.
Keywords: Real time tandem mass spectrometry; Tobacco smoke; Nicotine; Secondhand smoke; Thirdhand smoke;
The identification of source regions of black carbon at a receptor site off the eastern coast of China by Qingfeng Guo; Min Hu; Song Guo; Zhijun Wu; Weiwei Hu; Jianfei Peng; Wei Hu; Yusheng Wu; Bin Yuan; Qiang Zhang; Yu Song (78-84).
The black carbon (BC) mass concentration and the particle chemical compositions were continually measured at Changdao Island, which is a regional receptor site off the eastern coast of China. This island is in the transport passage of the continental outflow to the Pacific Ocean when the East Asia monsoon prevails in the winter and spring. The campaign period was for March and April 2011, which corresponded to heating and non-heating periods in northern China. The effect of BC emission source regions on BC measured at Changdao Island between the heating and non-heating periods was determined by integrating the total potential source contribution function (TPSCF) model with the new monthly emission inventory in 2010 and the fire counts retrieved from MODIS during the campaign. BC concentrations were determined to be highest for similar times of day for both the heating and non-heating periods: 4.27 μg m−3 at 8:00 AM and 3.06 μg m−3 at 9:00 AM, respectively. The probable source regions for BC were primarily located in Shandong and Jiangsu provinces (and in other neighboring provinces) for both periods. However, the source regions for the non-heating period extended more to the north and southwest than those of the heating period. TPSCF values were correlated with the emission rates from residential, industry, transportation, and power plants sources in the anthropogenic emission inventory. This correlation provides an indirect and qualitative process to verify the emission inventory. In the heating period, the predominant source was the residential source in the emission inventory, and this source had a significant effect on the BC concentration. The differing peak concentrations between the two periods may be observed because of the increased residential heating during the heating period, which suggested that the measures employed by the government and environmental managers to reduce the emissions of pollutants should be stricter in the identified source regions during the heating period.Display Omitted
Keywords: Black carbon; Changdao island; TPSCF; Source regions; Residential source;
Analysis and interpretation of 18 years of mercury observations since 1996 at Mace Head, Ireland by A. Weigelt; R. Ebinghaus; A.J. Manning; R.G. Derwent; P.G. Simmonds; T.G. Spain; S.G. Jennings; F. Slemr (85-93).
Observations of atmospheric mercury at the Mace Head Atmospheric Research Station on the Atlantic coast of Ireland made from February 1996 to December 2013 are analyzed. Using meteorological analysis and a sophisticated Lagrangian dispersion model, the hourly averaged mercury concentrations were attributed to four different air mass types: baseline, local, European polluted, and sub-tropical maritime. Monthly median Hg concentrations of all types decreased over the analyzed period but the trend for sub-tropical maritime air masses was with −0.016 ± 0.002 ng m−3 yr−1 in absolute terms significantly smaller than the trends for all other classes which varied between −0.021 and −0.023 ng m−3 yr−1. The seasonal variation for sub-tropical maritime air masses is also shallower than for all other classes. This is most likely due to shallower seasonal variation of oxidant concentrations at lower latitudes. The north-south gradient of the trend is qualitatively consistent with the GEOS-Chem model predictions based on decrease of mercury concentrations in surface waters of the North Atlantic but the trends are smaller than predicted. Tests for temporal change of the trends indicate that the decreasing trends of mercury concentrations are leveling off for all air masses with possible exception of the sub-tropical maritime air mass. Quantitative assessment of the trend changes, however, will require a longer time series of the mercury measurements at Mace Head.
Keywords: Atmospheric mercury; Long term measurements; Trend; Seasonality; Trend change; Mace Head;
The effects of emission sources and meteorological factors on sulphur dioxide concentration of Great Isfahan, Iran by Fahimeh Hosseiniebalam; Omid Ghaffarpasand (94-101).
The great Isfahan has experienced an almost fast industrialization during the last years. The different factories and industries near that, cause one of the important environmental problems, air pollution, which has not enough investigated before in this area. The hourly, diurnal and seasonal variations of SO2 concentration as one of the most dangerous air pollutants, are studied to clarify the rule of industry on the air pollution problem. The data had been measured continuously from April 2006 to March 2007 at two stations, Lale & Azadi. The air pollution concentrations in an urban area have a close relationship with meteorological factors. Hence, the variation of SO2 concentration is analysed respect to the meteorological factors such as temperature, relative humidity, wind speed, solar radiation, and pressure. Moreover, the studied air pollutant is also statistically investigated through correlation analysis and step-wise multiple linear regression equation.It was observed that electric power plant near the Isfahan, Montazeri, has significant effects on the SO2 concentration in the east and north of Isfahan. Long-term pattern of Isfahan winds which is westerly during the winter and spring, and easterly during the summer and autumn, was recognized as one of another important factors influenced the SO2 concentration variations. It is also achieved that meteorological factors have considerable contribution, R 2 = 52%, on the SO2 concentration variation and temperature has largest effect among the others.
Keywords: Air pollution; Sulphur dioxide; Isfahan; Meteorological factors; Statistical analysis;
Seasonal trends in the composition and ROS activity of fine particulate matter in Baghdad, Iraq by Samera Hussein Hamad; Martin Merrill Shafer; Ahmed K.H. Kadhim; Sabah M. Al-Omran; James Jay Schauer (102-110).
Baghdad suffers from severe atmospheric particulate matter (PM) pollution and has limited infrastructure to monitor and control PM-pollution. To help better understand the nature of particulate matter in Baghdad, daily PM2.5 samples were collected every 6th day from September, 2012 to September, 2013. The samples were analyzed for chemical composition and cellular oxidative stress activity using a macrophage-based assay. The annual average PM2.5 concentration was 50 ± 19 μg m−3, and was comprised of approximately 28% crustal materials, 26% organic carbon (OC), 17% sulfate, 12% elemental carbon (EC), and 8.0% ammonium ion. No clear seasonal trend was observed for the total PM2.5 mass and PM2.5 OC, but EC exhibited higher concentrations in the warmer months, likely due to the extensive use of electric generators operated by diesel and gasoline for cooling. April showed the lowest levels of both EC and OC compared with other months due to both sand and rainstorm events which led to increased deposition and dispersion of local emissions. Concentrations of nitrate ion were low in all seasons due to the high temperatures and low humidity, but slightly higher levels were observed in the cooler months of winter. The oxidative stress (reactive oxygen species (ROS)) activity (59 ± 35 μg Zymosan equivalents m−3) of the PM was relatively lower than in other studied areas. Association between the water soluble PM constituents and the oxidative activity was investigated using a multi-linear regression model which showed no strong relationships between ROS activity and the water soluble components of PM2.5, but a moderate correlation of water soluble organic carbon from biomass burning (WSOC-BB) was observed (R 2 = 0.52). Biomass burning PM has been shown to be an important contributor to ROS activity in other published studies, but additional work is needed to better understand the sources leading to the ROS activity in Baghdad.
Keywords: Chemical composition; Fine particles; ROS-activity; Baghdad-Iraq;
Evaluation and calibration of Aeroqual series 500 portable gas sensors for accurate measurement of ambient ozone and nitrogen dioxide by C. Lin; J. Gillespie; M.D. Schuder; W. Duberstein; I.J. Beverland; M.R. Heal (111-116).
Low-power, and relatively low-cost, gas sensors have potential to improve understanding of intra-urban air pollution variation by enabling data capture over wider networks than is possible with ‘traditional’ reference analysers. We evaluated an Aeroqual Ltd. Series 500 semiconducting metal oxide O3 and an electrochemical NO2 sensor against UK national network reference analysers for more than 2 months at an urban background site in central Edinburgh. Hourly-average Aeroqual O3 sensor observations were highly correlated (R 2 = 0.91) and of similar magnitude to observations from the UV-absorption reference O3 analyser. The Aeroqual NO2 sensor observations correlated poorly with the reference chemiluminescence NO2 analyser (R 2 = 0.02), but the deviations between Aeroqual and reference analyser values ([NO2]Aeroq − [NO2]ref) were highly significantly correlated with concurrent Aeroqual O3 sensor observations [O3]Aeroq. This permitted effective linear calibration of the [NO2]Aeroq data, evaluated using ‘hold out’ subsets of the data (R 2 ≥ 0.85). These field observations under temperate environmental conditions suggest that the Aeroqual Series 500 NO2 and O3 monitors have good potential to be useful ambient air monitoring instruments in urban environments provided that the O3 and NO2 gas sensors are calibrated against reference analysers and deployed in parallel.
Keywords: Semiconductor gas sensor; Electrochemical gas sensor; NO2; O3; Air pollution exposure;
Spatiotemporal inhomogeneity in NO2 over Fukuoka observed by ground-based MAX-DOAS by Hisahiro Takashima; Yugo Kanaya; Hitoshi Irie (117-123).
Continuous NO2 profile observations have been made using ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) at Fukuoka (33.55°N, 130.36°E), an urban area in Japan. Throughout the year, NO2 variations measured by MAX-DOAS (0–100 m) are in good agreement with in situ surface NO2 measurements on several-day, week-to-week, and seasonal timescales. We investigated the spatiotemporal inhomogeneity in NO2 over Fukuoka by observing at two azimuth angles: the Tenjin (towards the city center) and Itoshima (away from the city center) directions. In terms of diurnal variations, NO2 in both directions show clear morning maxima, on account of local emissions in the morning and the development of a boundary layer. The concentrations in the early morning are nearly the same in both directions, but they are higher in the Tenjin direction during most of the daytime on average. Variability in both directions, as well as spatial inhomogeneity, is large during most of the daytime except for in the morning. The diurnal maximum for 0–1 km between 10 and 13 LT is sometimes observed in the Tenjin direction; in some cases, 1 h after this maximum, a maximum is also observed in the Itoshima direction. The NO2 maxima for the upper level (1–2 km) in both directions are also delayed from the maximum in the Tenjin direction for 0–1 km. Analysis of the surface wind field indicates that the NO2 inhomogeneity is strongly related to vertical/horizontal transport of high concentrations of NO2 from the city center, and to horizontal transport of low concentrations from the ocean via a land–sea breeze. Three-dimensional continuous observations by MAX-DOAS are potentially a powerful tool for increasing our understanding of pollutant transport and mixing in urban areas.
Keywords: Nitrogen dioxide; MAX-DOAS; Boundary layer; Land-sea breeze; Japan;
Ecosystem respiration and its components from a Carex meadow of Poyang Lake during the drawdown period by Qiwu Hu; Qin Wu; Bo Yao; Xingliang Xu (124-132).
Little is known about the components of ecosystem respiration from a subtropical littoral wetland with dramatic annual inundation dynamics. In this study, we investigated ecosystem respiration and its components in a Poyang lake Carex meadow during the drawdown periods from May 2009 to June 2011. Both ecosystem respiration and its components showed clear temporal variation pattern, with temperature being the dominant control. Ecosystem respiration ranged from 98.01 to 1359.25 mg CO2 m−2 h−1. Shoot and root respiration contributed approximately 36% and 26% to the ecosystem respiration, respectively, whereas microbial respiration accounted for 38% of the ecosystem respiration. The ratio of total soil respiration to ecosystem respiration varied from 0.45 to 0.90, depending on growing season stages. Their Q 10 values ranged from 1.72 to 2.51, with the maximum for shoot respiration and the minimum for microbial respiration. In addition, the Q 10 values varied with time and among ecosystem respiratory components and hence could not be treated as a constant. None of the respiration measurements was significantly related to soil moisture, suggesting that soil moisture was not a limiting environmental factor for respiratory activity during the drawdown periods in this meadow. The Carex meadow acted as strong carbon sink during the drawdown periods due to double growing seasons, but the previous summer flood duration could substantially alter carbon sink intensity in the following drawdown period. The total carbon sink of the littoral zone of Poyang Lake during drawdown periods was estimated to be 0.17–0.59 Tg C yr−1.
Keywords: Poyang lake; Carex meadow; Ecosystem respiratory component; Temperature sensitivity; Carbon sink;
Size-resolved effective density of urban aerosols in Shanghai by Zi Yin; Xingnan Ye; Shuqin Jiang; Ye Tao; Yang Shi; Xin Yang; Jianmin Chen (133-140).
Size-resolved effective density of 50–400 nm urban particles was determined by a TDMA–APM system in Shanghai during wintertime. The average effective density ranged from 1.36 to 1.55 g cm−3, increasing with the particle diameter. The size dependent increase of density was consistent with previous hygroscopic measurements. We attributed the increase in density to the condensation of hygroscopic secondary aerosols and large massive organics. The diurnal variation of effective density was pronounced for smaller particles. A similar diurnal pattern was observed between particle density and the contribution of secondary NH4NO3 and (NH4)2SO4 to PM1.0, suggesting that density change in response to particle compositions. The effective density of Aitken mode particles had a considerable increase during the NPF event, in agreement with the contribution of sulfate. Particle mass distribution was derived from particle number distribution in combination with effective density. PM0.6 was highly correlated with PM1.0, revealing that secondary aerosols tend to condense on smaller particles.
Keywords: Effective density; Atmospheric aerosol; DMA–APM system; Yangtze River Delta;
Decadal trend and interannual variation of outflow of aerosols from East Asia: Roles of variations in meteorological parameters and emissions by Yang Yang; Hong Liao; Sijia Lou (141-153).
We apply a global three-dimensional Goddard Earth Observing System (GEOS) chemical transport model (GEOS-Chem) to quantify the decadal trend and interannual variation of aerosol outflow from East Asia. Simulations of aerosols are performed for years 1986–2006, driven by the NASA/GEOS-4 assimilated meteorological fields. The impacts of variations in meteorological parameters and emissions are imposed separately and together by numerical experiments. With variations in both meteorological parameters and anthropogenic emissions, simulated annual outflow of PM2.5 (sum of sulfate, nitrate, ammonium, black carbon, and organic carbon) from East Asia increased by 6.0 Tg (or 53%) over years 1986–2006, in which the outflow fluxes of sulfate, nitrate, and ammonium aerosols had the largest contributions with decadal trends of +1.2, +0.8, and +0.7 Tg decade−1, respectively. Simulated outflow fluxes of aerosols also exhibited large interannual variations; the absolute percent departure from the mean (APDM) values of the annual outflow fluxes of sulfate, nitrate, ammonium, black carbon, organic carbon, and PM2.5 were 5.9%, 7.9%, 5.4%, 5.8%, 4.2%, and 5.2%, respectively, as variations in both meteorological parameters and anthropogenic emissions were considered. Model sensitivity studies show that, for outflow fluxes of aerosols from East Asia, the decadal trends were driven by variations in anthropogenic emissions whereas the interannual variations were dominated by variations in meteorological parameters. The increases in anthropogenic emissions alone explained about 86% of the decadal trend in outflow of PM2.5. Although variations in meteorological parameters can influence the interannual variations in aerosol outflow by changing both aerosol concentrations over East Asia and zonal winds, the latter is identified to be the key factor because of the high positive correlation coefficient between the annual outflow flux of PM2.5 and zonal wind at 700 hPa (the altitude with the maximum outflow fluxes) for years 1986–2006.
Keywords: Aerosols; Outflow from East Asia; Decadal trend; Interannual variation;
Technical note: An improved estimate of uncertainty for source contribution from effective variance Chemical Mass Balance (EV-CMB) analysis by Guo-Liang Shi; Xiao-Yu Zhou; Yin-Chang Feng; Ying-Ze Tian; Gui-Rong Liu; Mei Zheng; Yang Zhou; Yuan-Hang Zhang (154-158).
The CMB (Chemical Mass Balance) 8.2 model released by the USEPA is a commonly used receptor model that can determine estimated source contributions and their uncertainties (called default uncertainty). In this study, we propose an improved CMB uncertainty for the modeled contributions (called EV-LS uncertainty) by adding the difference between the modeled and measured values for ambient species concentrations to the default CMB uncertainty, based on the effective variance least squares (EV-LS) solution. This correction reconciles the uncertainty estimates for EV and OLS regression. To verify the formula for the EV-LS CMB uncertainty, the same ambient datasets were analyzed using the equation we developed for EV-LS CMB uncertainty and a standard statistical package, SPSS 16.0. The same results were obtained by both ways indicate that the equation for EV-LS CMB uncertainty proposed here is acceptable. In addition, four ambient datasets were studies by CMB 8.2 and the source contributions as well as the associated uncertainties were obtained accordingly.
Keywords: CMB; Source apportionment; Improved uncertainty; Particulate matter; Effective variance-least squares (EV-LS);
Non-sulfate sulfur in fine aerosols across the United States: Insight for organosulfate prevalence by Kabindra M. Shakya; Richard E. Peltier (159-166).
We investigated the discrepancies in long-term sulfur measurements from 2000 to 2012 by two separate speciation methods, X-ray fluorescence (XRF) spectroscopy and ion chromatography (IC) across the United States (334 sites). Overall, there was a good correlation between sulfur measurements by XRF spectroscopy and IC (R ≥ 0.90 for most of the sites). However, the inorganic sulfate measured by ion chromatography was not sufficient to account for all the sulfur measured by XRF spectroscopy at many of the sites. Discrepancies were observed with the high ratios of sulfur measured by XRF spectroscopy to that by IC. Such high ratios also exhibited seasonal variation, and differed across land use types; significant differences occurred at locations classified as forest, agriculture, and mobile, but not in locations classified as commercial, desert, industrial, and residential. On average, the excess, or non-sulfate, sulfur (unmeasured organic sulfur or other inorganic species of sulfur) was variable and observed as high as ∼13% of organic carbon and ∼2% of PM2.5. The contribution of such assumed organosulfur was larger in the eastern region than other geographical locations in the United States. Besides the temporal and spatial trends, the additional sulfur was found to be related to other factors such as aerosol acidity and emission sources. The results suggest that these unmeasured sulfur species could have significant contribution to aerosol burden, and the understanding of these could help to control PM2.5 levels and to assess other effects of sulfur aerosols.
Urban air quality simulation in a high-rise building area using a CFD model coupled with mesoscale meteorological and chemistry-transport models by Kyung-Hwan Kwak; Jong-Jin Baik; Young-Hee Ryu; Sang-Hyun Lee (167-177).
An integrated urban air quality modeling system is established by coupling a computational fluid dynamics (CFD) model with mesoscale meteorological and chemistry-transport models. The mesoscale models used are the weather research and forecasting (WRF) model and the community multiscale air quality (CMAQ) model, which provide the initial and time-dependent boundary conditions for the CFD model. For the consistency of chemical processes in the CFD and CMAQ models, the same chemical mechanism used in the CMAQ model is implemented in the CFD model. Urban air quality simulations are performed from 0900 to 1800 LT on 3 June 2010 in a high-rise building area of Seoul, Republic of Korea, where mobile emission sources are concentrated. The NO2 and O3 concentrations in the CFD simulation are evaluated with data measured at a roadside air quality monitoring station, showing better agreements than those in the CMAQ simulation. The NO2 and O3 concentration fields exhibit high spatial variabilities in the high-rise building area. The spatial variabilities near the surfaces are strongly associated with the heterogeneity of mobile emission on roads, whereas the spatial variabilities near the top of high-rise buildings are strongly associated with the heterogeneity of building geometry. The average NO2 and O3 concentrations (46 and 30 ppb, respectively, at z = 30 m) near the surfaces are considerably different from the NO2 and O3 concentrations in the CMAQ simulation (17 and 44 ppb, respectively, at z = 30 m), implying the insufficient urban surface representation in the CMAQ simulation. The heterogeneity of building geometry is found to enhance the vertical pollutant transport, whereas the heterogeneity of mobile emission is found to confine emitted pollutants near the surfaces. When the vertical mixing is efficient, the O3 concentration decreases in substantial vertical ranges with the same amount of NO x emission. The integrated urban air quality modeling system realistically simulates the spatial variabilities associated with the local influences of building geometry and mobile emission. This is a promising modeling approach that accounts for multiscale influences on urban air quality.
Keywords: Urban air quality; Integrated urban air quality modeling system; CFD model; WRF model; CMAQ model; High-rise building area;
A source-independent empirical correction procedure for the fast mobility and engine exhaust particle sizers by Naomi Zimmerman; Cheol-Heon Jeong; Jonathan M. Wang; Manuel Ramos; James S. Wallace; Greg J. Evans (178-184).
The TSI Fast Mobility Particle Sizer (FMPS) and Engine Exhaust Particle Sizer (EEPS) provide size distributions for 6–560 nm particles with a time resolution suitable for characterizing transient particle sources; however, the accuracy of these instruments can be source dependent, due to influences of particle morphology. The aim of this study was to develop a source-independent correction protocol for the FMPS and EEPS. The correction protocol consists of: (1) broadening the >80 nm size range of the distribution to account for under-sizing by the FMPS and EEPS; (2) applying an existing correction protocol in the 8–93 nm size range; and (3) dividing each size bin by the ratio of total concentration measured by the FMPS or EEPS and a water-based Condensation Particle Counter (CPC) as a surrogate scaling factor to account for particle morphology. Efficacy of the correction protocol was assessed for three sources: urban ambient air, diluted gasoline direct injection engine exhaust, and diluted diesel engine exhaust. Linear regression against a reference instrument, the Scanning Mobility Particle Sizer (SMPS), before and after applying the correction protocol demonstrated that the correction ensured agreement within 20%.
Keywords: EEPS; FMPS; SMPS; Morphology; Vehicle emissions; Particle size distributions;
Total sugars in atmospheric aerosols: An alternative tracer for biomass burning by C. Scaramboni; R.C. Urban; M. Lima-Souza; R.F.P. Nogueira; A.A. Cardoso; A.G. Allen; M.L.A.M. Campos (185-192).
Ambient aerosols were collected in an agro-industrial region of São Paulo State (Brazil) between May 2010 and February 2012 (n = 87). The atmosphere of the study region is highly affected by the emissions of gases and particles from sugar and fuel ethanol production, because part of the area planted with sugarcane is still burned before manual harvesting. This work proposes the quantification of total sugars as an alternative chemical tracer of biomass burning, instead of levoglucosan. The quantification of total sugars requires a small area of a filter sample and a simple spectrophotometer, in contrast to the determination of levoglucosan, which is much more complex and time-consuming. Total sugars concentrations in the aerosol ranged from 0.28 to 12.5 μg m−3, and (similarly to levoglucosan) the emissions were significantly higher at night and during the sugarcane harvest period, when most agricultural fires occur. The linear correlation between levoglucosan and total sugars (r = 0.612) was stronger than between levoglucosan and potassium (r = 0.379), which has previously been used as a biomass burning tracer. In the study region, potassium is used in fertilizers, and this, together with substantial soil dust resuspension, makes potassium unsuitable for use as a tracer. On average, ca. 40% of the total sugars was found in particles smaller than 0.49 μm. By including data from previous work, it was possible to identify from 35 to 42% of the total sugars, with biomass burning making the largest contribution. The high solubility in water of these sugars means that determination of their concentrations could also provide important information concerning the hydrophilic properties of atmospheric aerosols.
Keywords: Biomass burning marker; Sugarcane; Ethanol production; Brazil; Aerosol;
The photochemical production of organic nitrates from α-pinene and loss via acid-dependent particle phase hydrolysis by Joel D. Rindelaub; Kevin M. McAvey; Paul B. Shepson (193-201).
The hydroxyl radical oxidation of α-pinene under high NOx conditions was studied in a photochemical reaction chamber to investigate organic nitrate (RONO2) production and fate between the gas and particle phases. We report an organic nitrate yield of 26 ± 7% from the oxidation of this monoterpene in the presence of nitric oxide (NO). However, the apparent organic nitrate yield was found to be highly dependent on both chamber relative humidity (RH) and seed aerosol acidity, likely as a result of particle phase hydrolysis. The particle phase loss of organic nitrates is believed to increase the gas to particle partitioning within the system, leading to decreased RONO2 yields in both the gas and particle phases at elevated RH and an apparent non-equilibrium partitioning mechanism. The hydrolysis of particle phase organic nitrates in this study, starting at low chamber relative humidity, implies that aerosol partitioning of organic nitrates may be an important sink for atmospheric NO x and may have a significant impact on regional air quality.
Keywords: Organic nitrates; Hydrolysis; Alpha-pinene; Secondary organic aerosol;
Ice core profiles of saturated fatty acids (C12:0–C30:0) and oleic acid (C18:1) from southern Alaska since 1734 AD: A link to climate change in the Northern Hemisphere by Ambarish Pokhrel; Kimitaka Kawamura; Osamu Seki; Sumio Matoba; Takayuki Shiraiwa (202-209).
An ice core drilled at Aurora Peak in southeast Alaska was analyzed for homologous series of straight chain fatty acids (C12:0–C30:0) including unsaturated fatty acid (oleic acid) using gas chromatography (GC/FID) and GC/mass spectrometry (GC/MS). Molecular distributions of fatty acids are characterized by even carbon number predominance with a peak at palmitic acid (C16:0, av. 20.3 ± SD. 29.8 ng/g-ice) followed by oleic acid (C18:1, 19.6 ± 38.6 ng/g-ice) and myristic acid (C14:0, 15.3 ± 21.9 ng/g-ice). The historical trends of short-chain fatty acids, together with correlation analysis with inorganic ions and organic tracers suggest that short-chain fatty acids (except for C12:0 and C15:0) were mainly derived from sea surface micro layers through bubble bursting mechanism and transported over the glacier through the atmosphere. This atmospheric transport process is suggested to be linked with Kamchatka ice core δD record from Northeast Asia and Greenland Temperature Anomaly (GTA). In contrast, long-chain fatty acids (C20:0–C30:0) are originated from terrestrial higher plants, soil organic matter and dusts, which are also linked with GTA. Hence, this study suggests that Alaskan fatty acids are strongly influenced by Pacific Decadal Oscillation/North Pacific Gyre Oscillation and/or extra tropical North Pacific surface climate and Arctic oscillation. We also found that decadal scale variability of C18:1/C18:0 ratios in the Aurora Peak ice core correlate with the Kamchatka ice core δD, which reflects climate oscillations in the North Pacific. This study suggests that photochemical aging of organic aerosols could be controlled by climate periodicity.
Keywords: Fatty acids; Alaskan ice core; Marine-derived organic matter; Atmospheric circulation; Atmospheric transport; Climate change;
Effects of straw return on C2–C5 non-methane hydrocarbon (NMHC) emissions from agricultural soils by Ran Wang; Ting Wu; Wanhong Dai; Hui Liu; Juan Zhao; Xinming Wang; Feiyu Huang; Zhe Wang; Chengfei Shi (210-217).
The effect of crop straw return on C2–C5 non-methane hydrocarbon (NMHC) emissions from agricultural soils is investigated using a laboratory-controlled incubation of agricultural soils amended with crop straw for a period of 56 days. The average emission fluxes of total C2–C5 NMHCs from amended agricultural soils are 304 and 173 ng kg−1 h−1 under non-flooded and flooded conditions, respectively. Alkenes are the principal emitted C2–C5 NMHCs from amended agricultural soils, where a predominance of ethene, propene and 1-butene together shared 65% and 59% of the total C2–C5 NMHCs under non-flooded and flooded conditions, respectively. The emissions rates of the above top three alkenes and the total C2–C5 alkenes from amended agricultural soils under non-flooded conditions are one to four times those under flooded conditions, and these average values are 14–89 and 5–34 times those in their corresponding control treatments, respectively. These results imply that straw return contributes substantially to the emissions of light alkenes from agricultural soils, particularly under non-flooded conditions. The high correlation between microorganisms and C2–C5 NMHC fluxes from amended agricultural soils suggest that microbes play an important role in C2–C5 NMHC emissions from straw-amended agricultural soils. A rough estimate indicates that crop straw return could contribute insignificantly to global C2–C5 hydrocarbon budgets.
Keywords: C2–C5 non-methane hydrocarbons (NMHCs); Emission fluxes; Crop straw return; Agricultural soils;
Emissions of NO x , particle mass and particle numbers from aircraft main engines, APU's and handling equipment at Copenhagen Airport by Morten Winther; Uffe Kousgaard; Thomas Ellermann; Andreas Massling; Jacob Klenø Nøjgaard; Matthias Ketzel (218-229).
This paper presents a detailed emission inventory for NO x , particle mass (PM) and particle numbers (PN) for aircraft main engines, APU's and handling equipment at Copenhagen Airport (CPH) based on time specific activity data and representative emission factors for the airport. The inventory has a high spatial resolution of 5 m × 5 m in order to be suited for further air quality dispersion calculations. Results are shown for the entire airport and for a section of the airport apron area (“inner apron”) in focus. The methodology presented in this paper can be used to quantify the emissions from aircraft main engines, APU and handling equipment in other airports. For the entire airport, aircraft main engines is the largest source of fuel consumption (93%), NO x , (87%), PM (61%) and PN (95%). The calculated fuel consumption [NO x , PM, PN] shares for APU's and handling equipment are 5% [4%, 8%, 5%] and 2% [9%, 31%, 0%], respectively. At the inner apron area for handling equipment the share of fuel consumption [NO x , PM, PN] are 24% [63%, 75%, 2%], whereas APU and main engines shares are 43% [25%, 19%, 54%], and 33% [11%, 6%, 43%], respectively. The inner apron NO x and PM emission levels are high for handling equipment due to high emission factors for the diesel fuelled handling equipment and small for aircraft main engines due to small idle-power emission factors. Handling equipment is however a small PN source due to the low number based emission factors. Jet fuel sulphur-PM sensitivity calculations made in this study with the ICAO FOA3.0 method suggest that more than half of the PM emissions from aircraft main engines at CPH originate from the sulphur content of the fuel used at the airport. Aircraft main engine PN emissions are very sensitive to the underlying assumptions. Replacing this study's literature based average emission factors with “high” and “low” emission factors from the literature, the aircraft main engine PN emissions were estimated to change with a factor of 14.
Keywords: NO x ; PM; Particle numbers; Aircraft main engines; APU; Handling equipment;
FT-IR quantification of the carbonyl functional group in aqueous-phase secondary organic aerosol from phenols by Kathryn M. George; Travis C. Ruthenburg; Jeremy Smith; Lu Yu; Qi Zhang; Cort Anastasio; Ann M. Dillner (230-237).
Recent findings suggest that secondary organic aerosols (SOA) formed from aqueous-phase reactions of some organic species, including phenols, contribute significantly to particulate mass in the atmosphere. In this study, we employ a Fourier transform infrared (FT-IR) spectroscopic technique to identify and quantify the functional group makeup of phenolic SOA. Solutions containing an oxidant (hydroxyl radical or 3,4-dimethoxybenzaldehyde) and either one phenol (phenol, guaiacol, or syringol) or a mixture of phenols mimicking softwood or hardwood emissions were illuminated to make SOA, atomized, and collected on a filter. We produced laboratory standards of relevant organic compounds in order to develop calibrations for four functional groups: carbonyls (C＝O), saturated C–H, unsaturated C–H and O–H. We analyzed the SOA samples with transmission FT-IR to identify and determine the amounts of the four functional groups. The carbonyl functional group accounts for 3–12% of the SOA sample mass in single phenolic SOA samples and 9–14% of the SOA sample mass in mixture samples. No carbonyl functional groups are present in the initial reactants. Varying amounts of each of the other functional groups are observed. Comparing carbonyls measured by FT-IR (which could include aldehydes, ketones, esters, and carboxylic acids) with eight small carboxylic acids measured by ion chromatography indicates that the acids only account for an average of 20% of the total carbonyl reported by FT-IR.
Keywords: SOA; Fourier transform infrared spectroscopy; Phenol; Carboxylic acids;