Abstract  OBJECTIVE: This article reviews panel studies of air pollution on children's respiratory health and proposes future research directions.

METHODS: The PubMed electronic database was used to search published original epidemiological studies in peer-reviewed journals from 2000 to November 2011. Children's age was limited to ≤18 years old. A total of 33 relevant articles were obtained, with 20 articles relating to lung function, 21 articles relating to respiratory symptoms, and 8 articles examining both.

RESULTS: Most studies suggested the adverse effects of air pollution on children's lung function and respiratory symptoms. Particles and NO(2) showed more significant results, whereas effects of SO(2) were not consistent. A few studies indicated that O(3) interacted with temperature and sometimes seemed to be a protective factor for children's respiratory health. Negative associations between air pollutants and pulmonary health were more serious in asthmatic children than in healthy subjects. However, many outcomes depended on the number of lag days. Peak expiratory flow (PEF) was the most usual measurement for children's lung function, followed by forced expiratory volume in 1 second (FEV(1)).

CONCLUSIONS: There are significant adverse effects of air pollution on children's pulmonary health, especially for asthmatics. Future studies need to examine the lag effects of air pollution on children's lung function and respiratory symptoms. Ambient temperature is predicted to change worldwide due to climate change, which will threaten population health. Further research is needed to examine the effects of ambient temperature and the interactive effects between air pollution and ambient temperature on children's lung function and respiratory symptoms.

Abstract  Senescence is a highly regulated process terminating with programmed cell death (PCD). Floral senescence, and in particular petal senescence, forms an interesting model to study this process in that floral lifespan is species specific and linked to biological function. A feature of petal senescence is a rise in reactive oxygen species (ROS) and a change in redox balance. A key question is whether this is merely a consequence of de- regulation of antioxidant systems as cells enter PCD, or whether the rise in ROS may have a regulatory or signalling function. An important division in the physiology of floral senescence is between species in which ethylene is a key regulator, and those in which it appears not to perform an important regulatory role. Another important question we can therefore ask is whether the redox and ROS changes have the same significance in species with different physiologies. Transcriptomic studies in ethylene-sensitive and -insensitive species allow us to further determine whether changes in the activity of ROS-scavenging enzymes are transcriptionally regulated during floral senescence. Finally, it is important to assess how a signalling role for ROS or redox status would fit with known plant growth regulator (PGR) control of floral senescence.

Abstract  Nitrous oxide is a potent greenhouse gas, and it destroys stratospheric ozone(1). Seventeen per cent of agricultural nitrous oxide emissions come from the production of nitrous oxide in streams, rivers and estuaries(2), in turn a result of inorganic nitrogen input through leaching, runoff and sewage. The Intergovernmental Panel on Climate Change and global nitrous oxide budgets assume that riverine nitrous oxide emissions increase linearly with dissolved inorganic nitrogen loads, but data are sparse and conflicting(2,3). Here we report measurements over two years of nitrous oxide emissions in the Grand River, Canada, a seventh-order temperate river that is affected by agricultural runoff and outflow from a waste-water treatment plant. Emissions were disproportionately high in urban areas and during nocturnal summer periods. Moreover, annual emission estimates that are based on dissolved inorganic nitrogen loads overestimated the measured emissions in a wet year and underestimated them in a dry year. We found no correlations of nitrous oxide emissions with nitrate or dissolved inorganic nitrogen, but detected negative correlations with dissolved oxygen, suggesting that nitrate concentrations did not limit emissions. We conclude that future increases in nitrate export to rivers will not necessarily lead to higher nitrous oxide emissions, but more widespread hypoxia most likely will.

Abstract  Sulfate and nitrate records from 5 ice cores spread across Svalbard were compared and revealed strong temporal similarities with previously published global estimates of SO2 and NOx anthropogenic emissions during the 20th century. A significant departure from the early century sulfate and nitrate levels was evident at all drilling sites starting from the mid-1940s. A steady increase was observed in both sulfate and nitrate profiles at most sites until the late 1960s, when the annual concentrations started to increase at a higher rate. This peak activity lasted for about a decade, and was observed to decrease steadily from the early 1980s on, when sulfate levels declined significantly and when nitrate levels finally reached sulfate levels for the first time in 20th century. The timing of these trends in Svalbard with global SO2 and NOx concentration profiles was best appraised when considering composite concentration profiles of all Svalbard ice cores for sulfate and nitrate, respectively. Composite profiles were also found to provide a convenient mean for distinguishing between the most important world source regions. Based on correlation analysis, the major pollutant sources appeared to be Western Europe and North America for both sulfate and nitrate, followed by Central Europe and former U.S.S.R. in generally similar proportions.

Abstract  The paper presents the results from an experimental evaluation of a novel air cleaner based on UVC radiation at 253.7 nm in combination with a titanium dioxide (TiO(2)) catalytic converter. The wavelength of the UV light is selected with the purpose of enhancing the capability of the device to deactivate micro-organisms. Furthermore, the selected UV-wavelength is expected not to cause any substantial generation of ozone.

The air cleaner, denoted PCOC3, consists of three photo catalytic oxidation (PCO) chambers connected in series. The device is equipped with a pre-filter for removal of airborne particles (MERV 11). The air cleaner is intended for in-duct use, i.e. integration in central ventilation systems.

In a subset of the experiments ozone was generated by an electrical spark generator placed upstream of the tested air cleaner and measured downstream by a direct reading instrument based on UV-spectroscopy. In another subset of experiments selected VOCs were injected into the test-rig and the decay was measured after the VOC injection had been stopped.

The measurements showed no signs of any ozone being generated by the PCOC3. Instead the results indicate that ozone is captured by the device at a removal rate corresponding to 67 air changes per hour in the test-rig used, which, in turn corresponds to a single pass efficiency of about 15%.

Also the studied VOCs were found to be removed by the PCOC3, but at substantially lower rates; in the range of a few air changes per hour only.

Abstract  Hydroponic experiments were conducted to investigate whether exogenous addition of nitric oxide (NO) as sodium nitroprusside (SNP) alleviates arsenic (As) toxicity in Luffa acutangula (L.) Roxb. seedlings. Arsenic (5 and 50 μM) declined growth of Luffa seedlings which was accompanied by significant accumulation of As. SNP (100 μM) protected Luffa seedlings against As toxicity as it declined As accumulation significantly. The photosynthetic pigments and chlorophyll fluorescence parameters such as Fv/Fm, Fv/F0, Fm/F0 and qP were decreased while NPQ was raised by As. However, the toxic effects of As on photosynthesis were significantly ameliorated by SNP. The oxidative stress markers such as superoxide radical, hydrogen peroxide and malondialdehyde (lipid peroxidation) contents were enhanced by As, however, these oxidative indices were diminished significantly in the presence of SNP. As treatment stimulated the activities of SOD and CAT while the activities of APX and GST, and AsA content and AsA/DHA ratio were decreased. Upon SNP addition, along with further rise in SOD and CAT activity, APX and GST activity, and levels of AsA and AsA/DHA ratio were restored considerably. Overall results revealed that significant accumulation of As suppressed growth, photosynthesis, APX and GST activities and decreased AsA content, hence led to the oxidative stress. However, the addition of SNP protected seedlings against As stress by regulating As accumulation, oxidative stress and antioxidant defense system.

Abstract  The purpose of this study is to analyze a long term database of the chemical composition of precipitation at three African dry savanna sites in the Sahel. The precipitation samples were collected during the monsoon season at Agoufou (15 degrees 20'N, 01 degrees 29'W, Mali) from 2004 to 2006, Banizoumbou (13 degrees 31'N, 02 degrees 38'E, Niger) from 1994 to 2009 and Katibougou (12 degrees 56'N, 07 degrees 32' W, Mali) from 1997 to 2008. pH and major inorganic and organic ions in precipitation were analyzed by ionic chromatography. A characterization of mean precipitation chemistry with the associated wet deposition fluxes for each species is presented. The first important result is that interannual variability of all volume-weighted mean (VWM) concentrations is low, ranging between +/- 5% and +/- 25%. Acidity in dry savannas is low and indicates the strong alkaline nature of the precipitation. The average annual pH at Agoufou is 6.28, 5.75 at Banizoumbou and 5.54 at Katibougou. This result is correlated with the important terrigenous contribution measured in the chemical content of precipitation, implying acidity neutralization by mineral species such as Ca2+ and NH4+. Mg2+ and K+ are found to play a minor role in neutralization. Enrichment factor calculations for Ca2+, SO42-, K+ and Mg2+ with respect to the sea reference reveal a significant influence of Saharan and Sahelian crustal sources. VWM concentrations of these species dominate the composition of measured precipitation. An estimation of the potential particulate and gas contribution to the total precipitation composition is given for each site: At Agoufou, the mean relative contribution in rainwater is 80% for particles and 20% for gases, while at the Banizoumbou and Katibougou sites, results indicate 70% for particles and 30% for gases. The high particulate phase contribution to precipitation emphasizes the importance of multiphase processes between gases and particles in the atmospheric chemistry typical of African semi-arid savanna ecosystems. The second highest contribution is nitrogenous, with high VWM concentrations of NO3- and NH4+ measured at the three sites. Monthly evolution of NO3- and NH4+ concentrations are studied in relation to gaseous emission sources in the Sahelian region, i.e. biogenic soil emission and ammonia sources from animals. The calculated wet nitrogen deposition flux presents a regular increase throughout the wet season at the three sites. Results suggest total mean nitrogen deposition fluxes of 1.80 kg N ha(-1) yr(-1) at Agoufou, 2.10 kg N ha(-1) yr(-1) at Banizoumbou, and 3.30 kg N ha(-1) yr(-1) at Katibougou. The marine contribution is lower, 23% at Agoufou, 17% at Banizoumbou and 13% at Katibougou. The last contribution concerns organic acidity, which ranges from 5% at Agoufou, 10% at Banizoumbou to 14% at Katibougou. Terrigenous and marine contributions present a negative gradient, whereas nitrogenous and organic contributions a positive gradient along the Sahelian transect defined by Agoufou-Banizoumbou-Katibougou. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  The evolution of organic aerosols (OA) in Mexico City and its outflow is investigated with the nearly explicit gas phase photochemistry model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), wherein precursor hydrocarbons are oxidized to numerous intermediate species for which vapor pressures are computed and used to determine gas/particle partitioning in a chemical box model. Precursor emissions included observed C3-10 alkanes, alkenes, and light aromatics, as well as larger n-alkanes (up to C25) not directly observed but estimated by scaling to particulate emissions according to their volatility. Conditions were selected for comparison with observations made in March 2006 (MILAGRO). The model successfully reproduces the magnitude and diurnal shape for both primary (POA) and secondary (SOA) organic aerosols, with POA peaking in the early morning at 15-20 mu g m(-3), and SOA peaking at 10-15 mu g m(-3) during mid-day. The majority (>= 75 %) of the model SOA stems from reaction products of the large n-alkanes, used here as surrogates for all emitted hydrocarbons of similar volatility, with the remaining SOA originating mostly from the light aromatics. Simulated OA elemental composition reproduces observed H/C and O/C ratios reasonably well, although modeled ratios develop more slowly than observations suggest. SOA chemical composition is initially dominated by delta-hydroxy ketones and nitrates from the large alkanes, with contributions from peroxy acyl nitrates and, at later times when NOx is lower, organic hydroperoxides. The simulated plume-integrated OA mass continues to increase for several days downwind despite dilution-induced particle evaporation, since oxidation chemistry leading to SOA formation remains strong. In this model, the plume SOA burden several days downwind exceeds that leaving the city by a factor of >3. These results suggest significant regional radiative impacts of SOA.

Abstract  BACKGROUND: The ongoing emission of nitric oxide (NO) is a serious persistent environmental problem, because it contributes to atmospheric ozone destruction and global warming. A novel and effective system was developed for the complete treatment of NO from flue gases. The system features NO absorption by FeII(EDTA) and biological denitrification in a rotating drum biofilter (RDB). RESULTS: After 100 mg L1 FeII(EDTA) was added to the nutrient solution, the results show that the NO removal efficiency was improved from 70.56% to 80.15%, the optimal temperature improved from 32.5 degrees C to 40.5 degrees C, and the pH improved from 7.5 to 8.08.3. A maximum NO removal efficiency of 96.5% was achieved when 500 mg L1 FeII(EDTA) was used in the nutrient solution. CONCLUSION: This experiment demonstrates that FeII(EDTA) could not only improve the mass transfer efficiency of NO from gas to liquid, but also serve as an electron donor for the biological reduction of NO to N2. The new integrated treatment system seemed to be a promising alternative for the complete treatment of NO from flue gases. (c) 2012 Society of Chemical Industry

Abstract  The Global Ozone Monitoring Instrument (GOME) was launched in April 1995 on ESA's ERS-2 platform, and the GOME Data Processor (GDP) operational retrieval algorithm has produced total ozone columns since July 1995. We report on the new GDP5 spectral fitting algorithm used to reprocess the 16-year GOME data record. Previous GDP total ozone algorithms were based on the DOAS method. In contrast, GDP5 uses a direct-fitting algorithm without high-pass filtering of radiances; there is no air mass factor conversion to vertical column amount. GDP5 includes direct radiative transfer simulation of earthshine radiances and Jacobians with respect to total ozone, albedo closure and other ancillary fitting parameters - a temperature profile shift, and amplitudes for undersampling and Ring-effect interference signals. Simulations are based on climatological ozone profiles extracted from the TOMS Version 8 database, classified by total column. GDP5 uses the high-resolution Brion-Daumont-Malicet ozone absorption cross-sections, replacing older GOME-measured flight model data. The semi-empirical molecular Ring correction developed for GDP4 has been adapted for direct fitting. Cloud preprocessing for GDP5 is done using updated versions of cloud-correction algorithms OCRA and ROCINN. The reprocessed GOME GDP5 record maintains the remarkable long-term stability of time series already achieved with GDP4. Furthermore, validation results show a clear improvement in the accuracy of the ozone product with reduced solar zenith angle and seasonal dependences, particularly in comparison with correlative observations from the ground-based network of Brewer spectrophotometers.

Abstract  We study the interactions between atmospheric boundary layer (ABL) dynamics and atmospheric chemistry using a mixed-layer model coupled to chemical reaction schemes. Guided by both atmospheric and chemical measurements obtained during the DOMINO (Diel Oxidant Mechanisms in relation to Nitrogen Oxides) campaign (2008), numerical experiments are performed to study the role of ABL dynamics and the accuracy of chemical schemes with different complexity: the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) and a reduced mechanism of this chemical system. Both schemes produce satisfactory results, indicating that the reduced scheme is capable of reproducing the O-3-NOx-VOC-HOx diurnal cycle during conditions characterized by a low NOx regime and small O-3 tendencies (less than 1 ppb per hour). By focusing on the budget equations of chemical species in the mixed-layer model, we show that for species like O-3, NO and NO2, the influence of entrainment and boundary layer growth is of the same order as chemical production/loss. This indicates that an accurate representation of ABL processes is crucial in understanding the diel cycle of chemical species. By comparing the time scales of chemical reactive species with the mixing time scale of turbulence, we propose a classification based on the Damkohler number to further determine the importance of dynamics on chemistry during field campaigns. Our findings advocate an integrated approach, simultaneously solving the ABL dynamics and chemical reactions, in order to obtain a better understanding of chemical pathways and processes and the interpretation of the results obtained during measurement campaigns.

Abstract  Since 1992 semi-continuous in-situ observations of greenhouse gas concentrations have been performed at the tall tower of Cabauw (4.927 degrees E, 51.971 degrees N, -0.7 ma.s.l.). Through 1992 up to now, the measurement system has been gradually extended and improved in precision, starting with CO2 and CH4 concentrations from 200 ma.g.l. in 1992 to vertical gradients at 4 levels of the gases CO2, CH4, SF6, N2O, H-2, CO and gradients at 2 levels for Rn-222. In this paper the measurement systems and measurement results are described for the main greenhouse gases and CO, for the whole period. The automatic measurement system now provides half-hourly concentration gradients with a precision better than or close to the WMO recommendations. The observations at Cabauw show a complex pattern caused by the influence of sources and sinks from a large area around the tower with significant contributions of sources and sinks at distances up to 500-700 km. The concentration footprint area of Cabauw is one the most intensive and complex source areas of greenhouse gases in the world. Despite this, annual mean trends for the most important greenhouse gases, compatible with the values derived using the global network, can be reproduced from the measured concentrations at Cabauw over the entire measurement period, with a measured increase in the period 2000-2009 for CO2 of 1.90 +/- 0.1 ppm yr(-1), for CH4 of 4.4 +/- 0.6 ppb yr(-1), for N2O of 0.86 +/- 0.04 ppb yr(-1), and for SF6 of 0.27 +/- 0.01 ppt yr(-1); for CO no significant trend could be detected. The influences of strong local sources and sinks are reflected in the amplitude of the mean seasonal cycles observed at Cabauw, that are larger than the mean Northern Hemisphere average; Cabauw mean seasonal amplitude for CO2 is 25-30 ppm (higher value for lower sampling levels). The observed CH4 seasonal amplitude is 50-110 ppb. All gases except N2O show highest concentrations in winter and lower concentrations in summer, N2O observations show two additional concentration maxima in early summer and in autumn. Seasonal cycles of the day-time mean concentrations show that surface concentrations or high elevation concentrations alone do not give a representative value for the boundary layer concentrations, especially in winter time, but that the vertical profile data along the mast can be used to construct a useful boundary layer mean value. The variability at Cabauw in the atmospheric concentrations of CO2 on time scales of minutes to hours is several ppm and is much larger than the precision of the measurements (0.1 ppm). The diurnal and synoptical variability of the concentrations at Cabauw carry information on the sources and sinks in the footprint area of the mast, that will be useful in combination with inverse atmospheric transport model to verify emission estimates and improve ecosystem models. For this purpose a network of tall tower stations like Cabauw forms a very useful addition to the existing global observing network for greenhouse gases.

Abstract  Atmospheric concentrations of inorganic gases and aerosols (nitrate, sulfate, and ammonium) are simulated for 2009 over the United States using the chemical transport model GEOS-Chem. Predicted aerosol concentrations are compared with surface-level measurement data from the Interagency Monitoring of Protected Visual Environments (IMPROVE), the Clean Air Status and Trends Network (CASTNET), and the California Air Resources Board (CARB). Sulfate predictions nationwide are in reasonably good agreement with observations, while nitrate and ammonium are over-predicted in the East and Midwest, but under-predicted in California, where observed concentrations are the highest in the country. Over-prediction of nitrate in the East and Midwest is consistent with results of recent studies, which suggest that nighttime nitric acid formation by heterogeneous hydrolysis of N2O5 is over-predicted based on current values of the N2O5 uptake coefficient, gamma, onto aerosols. After reducing the value of gamma by a factor of 10, predicted nitrate levels in the US Midwest and East still remain higher than those measured, and over-prediction of nitrate in this region remains unexplained. Comparison of model predictions with satellite measurements of ammonia from the Tropospheric Emissions Spectrometer (TES) indicates that ammonia emissions in GEOS-Chem are underestimated in California and that the nationwide seasonality applied to ammonia emissions in GEOS-Chem does not represent California very well, particularly underestimating winter emissions. An ammonia sensitivity study indicates that GEOS-Chem simulation of nitrate is ammonia-limited in southern California and much of the state, suggesting that an underestimate of ammonia emissions is likely the main cause for the under-prediction of nitrate aerosol in many areas of California. An approximate doubling of ammonia emissions is needed to reproduce observed nitrate concentrations in southern California and in other ammonia sensitive areas of California. However, even a tenfold increase in ammonia emissions yields predicted nitrate concentrations that are still biased low in the central valley of California. The under-prediction of nitrate aerosol in the central valley of California may arise in part from an under-prediction of both ammonia and nitric acid in this region. Since nitrate aerosols are particularly sensitive to mixed layer depths, owing to the gas-particle equilibrium, the nitrate under-prediction could also arise in part from a potential regional overestimate of GEOS-5 mixed layer depths in the central valley due to unresolved topography in this region.

Abstract  Ozonolysis is a major tropospheric removal mechanism for unsaturated hydrocarbons and proceeds via "Criegee intermediates"--carbonyl oxides--that play a key role in tropospheric oxidation models. However, until recently no gas-phase Criegee intermediate had been observed, and indirect determinations of their reaction kinetics gave derived rate coefficients spanning orders of magnitude. Here, we report direct photoionization mass spectrometric detection of formaldehyde oxide (CH(2)OO) as a product of the reaction of CH(2)I with O(2). This reaction enabled direct laboratory determinations of CH(2)OO kinetics. Upper limits were extracted for reaction rate coefficients with NO and H(2)O. The CH(2)OO reactions with SO(2) and NO(2) proved unexpectedly rapid and imply a substantially greater role of carbonyl oxides in models of tropospheric sulfate and nitrate chemistry than previously assumed.

Abstract  Transpacific transport of dust and pollutants is well documented for spring but less so for other seasons. Here we investigate rapid transpacific transport in autumn utilizing the A-train satellites. In three episodes studied as examples, SO2 plumes over East Asia were detected by the Ozone Monitoring Instrument aboard the Aura satellite and found to reach North America in 5-6 days. They were likely derived from anthropogenic sources, given that identical transport patterns of CO, a tracer for incomplete combustion, were simultaneously observed by the Aqua satellite. Trajectory analysis and meteorological data were employed to explore the meteorological circumstances surrounding these events: like many of their counterparts in spring, all three plumes were lifted to the free troposphere in warm conveyor belts associated with midlatitude wave cyclones, and their migration to the downwind region was regulated by the meteorology over the east Pacific. These cases provide further evidence that a fraction of SO2 could escape wet scavenging and be transported at much greater efficiency than could NOx (NO + NO2). An analysis of the SO2 and CO data from September to November during 2005-2008 found 16 SO2 long-range transport episodes, out of 62 Asian outflow events. While the counts are sensitive to the choice of criteria, they suggest that the long-range transport of Asian sulfur species occurs quite frequently and could exert strong impacts on large downstream areas. This study also highlights the importance of transpacific transport in autumn, which has thus far been rarely studied and deserves more attention from the community.

Abstract  Heterogeneous reactions of nitrogen dioxide (NO2) on soils collected from Dalian (S1) and Changsha (S2) were investigated over the relative humidity (RH) range of 5%-80% and temperature range of 278-328 K using a horizontal coated-wall flow tube. The initial uptake coefficients of NO2 on S2 exhibited a decreasing trend from (10 +/- 1.3) x 10(-8) to (3.1 +/- 0.5) x 10(-8) with the relative humidity increasing from 5% to 80%. In the temperature effect studies, the initial uptake coefficients of S1 and S2 decreased from (10 +/- 1.2) x 10(-8) to (3.8 +/- 0.5) x 10(-8) and from (16 +/- 2.2) x 10(-8) to (3.8 +/- 0.4) x 10(-8) when temperature increased from 278 to 288 K for S1 and from 278 to 308 K for S2, respectively. As the temperature continued to increase, the initial uptake coefficients of S1 and S2 returned to (7.9 +/- 1.1) x 10(-8) and (20 +/- 3.1) x 10(-8) at 313 and 328 K, respectively. This study shows that relative humidity could influence the uptake kinetics of NO2 on soil and temperature would impact the heterogeneous chemistry of NO2.

Abstract  With a growing world population and global warming, we are challenged to increase food production while reducing greenhouse gas (GHG) emissions. We studied the effects of biochar (BC) and hydrochar (HC) produced via pyrolysis or hydrothermal carbonization, respectively, on GHG fluxes in three laboratory incubation studies. In the first experiment, ryegrass was grown in sandy loam mixed with equal amounts of a nitrogen-rich peanut hull BC, compost, BC+compost, double compost, or no addition (control); wetting-drying cycles and N fertilization were applied. Biochar with or without compost significantly reduced NO emissions and did not change the CH uptake, whereas ryegrass yield was significantly increased. In the second experiment, 0% (control) or 8% (w/w) of BC (peanut hull, maize, wood chip, or charcoal) or 8% HC (beet chips or bark) was mixed into a soil and incubated at 65% water-holding capacity (WHC) for 140 d. Treatments included simulated plowing and N fertilization. All BCs reduced NO emissions by ∼60%. Hydrochars reduced NO emissions only initially but significantly increased them after N fertilization to 302% (HC-beet) and 155% (HC-bark) of the control emissions, respectively. Large HC-associated CO emissions suggested that microbial activity was stimulated and that HC was less stable than BC. In the third experiment, nutrient-rich peanut hull BC addition and incubation over 1.5 yr at high WHCs did not promote NO emissions. However, NO emissions were significantly increased with BC after NHNO addition. In conclusion, BC reduced NO emissions and improved the GHG-to-yield ratio under field-relevant conditions. However, the risk of increased NO emissions with HC addition must be carefully evaluated.

Abstract  Wild type (WT) and transgenic tobacco plants expressing isopentenyltransferase (IPT), a gene coding the rate-limiting step in cytokinin (CKs) synthesis, were grown under limited nitrogen (N) conditions. Here, we analyse the possible effect of N deficiency on C-rich compounds such as phenolic compounds, as well as on N-rich compounds such as polyamines (PAs) and proline (Pro), examining the pathways involved in their synthesis and degradation. N deficiency was found to stimulate phenolic metabolism and increase these compounds both in P(SARK):IPT as well as in WT tobacco plants. This suggests that nitrate (NO(3)(-)) tissue concentration may act as a signal triggering phenolic compound accumulation in N deficiency plants. In addition, we found the maintenance of PAs in the WT plants would be correlated with the higher stress response to N deficiency. On the contrary, the reduction of free PAs and Pro found in the P(SARK)::IPT plants subjected to N deficiency would indicate the operation of an N-recycling mechanism that could stimulate a more efficient N utilization in P(SARK)::IPT plants.

Abstract  This paper summarizes current knowledge on the impacts of changes of nitrogen (N-r) use in agriculture on the global warming potential (GWP) by its impact on carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) emissions from agricultural and terrestrial nonagricultural systems and from aquatic and marine ecosystems. Ranges in 'N induced exchange factors', giving responses of CO2-C, N2O-N and CH4-C exchange per kg N input, are presented for all ecosystems. Using these factors, a quantification is made of CO2, NO and CH4 exchange (emissions or uptake) induced by the use of R in agriculture at European scale for the year 2000. This includes: (i) direct impacts in the agricultural systems due to N-r inputs by fertilizer and manure and NH3 deposition and (ii) indirect impacts due to R. leaching and NH3 deposition caused by agriculture on terrestrial, aquatic and marine ecosystems. Results show that the increase in GWP caused by elevated N2O emission due to N-r use in agriculture is completely counteracted by elevated carbon sequestration in nonagricultural systems. N-r effects on biodiversity, eutrophication and human health, however, need to be considered when considering the overall impacts of N-r, use in agriculture.

Abstract  Hematite (alpha-Fe2O3) and barium oxide doped hematite (BaO-Fe2O3) thin films were investigated as ozone (O-3) and nitrogen dioxide (NO2) sensing materials. Fe2O3 and BaO-Fe2O3 films were deposited by radio-frequency sputtering using pure Fe2O3, and 1-2% BaO doped Fe2O3 targets. The 700 degrees C (1 hour) annealed films showed significant responses to O-3 at temperatures ranging from 150 degrees C to 300 degrees C. Although, hematite is an n-type semiconductor, the Fe2O3 and BaO-Fe2O3 films exhibit p-type behavior to O-3 and n-type behavior to NO2 at the studied concentration ranges in this work. The response to oxidizing gases is not strictly an increase in resistance due to a conversion from n-type to p-type depending on gas concentrations. This effect is more visible with increasing Ba concentration. (C) 2011 Published by Elsevier Ltd.

Abstract  Elevated atmospheric CO2 (eCO(2)) and tropospheric O-3 (eO (3)) can alter soil microbial processes, including those underlying N2O emissions, as an indirect result of changes in plant inputs. In this study, effects of eCO(2) and eO(3) on sources of N2O in a soybean (Glycine max (L.) Merr.) agroecosystem in Illinois (SoyFACE) were investigated. We hypothesized that increases in available C and anaerobic microhabitat under eCO(2) would stimulate N2O emissions, with a proportionally larger increase in denitrification derived N2O (N2OD) compared to nitrification plus nitrifier denitrification derived N2O (N2ON+ND). We expected opposite effects under eO(3). Isotopically labeled (NH)-N-15 (4) (14) NO3 and (NH)-N-14 (4) (15) NO3 were used to evaluate mineral N transformations, N2OD, and N2ON+ND in a 12-day incubation experiment. We observed minimal effects of eCO(2) and eO(3) on N2O emissions, movement of (15) N through mineral N pools, soil moisture content and C availability. Possibly, altered C and N inputs by eCO(2) and eO(3) were small relative to the high soil organic C content and N- inputs via biological N-2-fixation, minimizing potential effects of eCO(2) and eO(3) on N- cycling. We conclude that eCO(2) and eO(3) did not affect N2O emissions in the short term. However, it remains to be tested whether N2O emissions in SoyFACE will be unaltered by eCO(2) and eO(3) on a larger temporal scale under field conditions.

Abstract  Biological organic compounds mixed with NaCl and other inorganic compounds in sea-salt aerosol particles react in air with oxidants such as ozone and hydroxyl (OH) radicals. Laboratory studies of model systems can provide insight into these reactions. We report here studies of the kinetics and mechanism of oxidation of unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) on NaCl by gas phase OH in air at room temperature and 1 atm pressure using diffuse reflection infrared Fourier transform spectrometry (DRIFTS) and matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) to identify possible structures of surface-bound reaction products. For comparison, some studies were also carried out on the saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) on NaCl. The calculated concentration of hydroxyl radicals, generated by photolysis of isopropyl nitrite, was (1.6-6.4) × 10(8) radicals cm(-3). Surface-bound aldehydes, ketones, organic nitrates and nitrate ions were identified as products of these reactions and structures of potential products were proposed based on mechanistic considerations combined with the MALDI-TOF-MS and DRIFTS spectra. The loss rate of vinyl hydrogen, [double bond, length as m-dash]C-H, at 3008 cm(-1) was used to obtain a lower limit for the rate constant (k1) for addition of OH to the double bond, k1 > (3 ± 1) × 10(-13) cm(3) molecule(-1) s(-1) (1s), corresponding to a reaction probability of γ(add) > (4 ± 1) × 10(-3) (1s). Assuming that abstraction from -CH2- groups in POPC is the same as for DPPC, the percentage of the reaction that occurs by addition is ∼80%. This is similar to the percent addition predicted using structure-reactivity relationships for gas-phase reactions. Decreasing the amount of POPC relative to NaCl resulted in more nitrate ion formation and less relative loss of POPC, and increasing the OH concentration resulted in a more rapid loss of POPC and faster product formation. These studies suggest that under atmospheric conditions with an OH concentration of 5 × 10(6) radicals cm(-3), the lifetime of POPC with respect to OH is <6 days.

Abstract  Benzo(a)pyrene (BaP) is one of the most dangerous PAH due to its high carcinogenic and mutagenic character. Because of this reason, the Directive 2004/107/CE of the European Union establishes a target value of 1 ng/m(3) of BaP in the atmosphere. In this paper, the main aim is to estimate the BaP concentrations in the atmosphere by using last generation of air quality dispersion models with the inclusion of the transport, scavenging and deposition processes for the BaP. The degradation of the particulated BaP by the ozone has been considered. The aerosol-gas partitioning phenomenon in the atmosphere is modelled taking into a count that the concentrations in the gas and the aerosol phases. If the pre-existing organic aerosol concentrations are zero gas/particle equilibrium is established. The model has been validated at local scale with data from a sampling campaign carried out in the area of Zaragoza (Spain) during 12 weeks.

Abstract  Environmental mycobacteria are common bacteria in man-made water systems and may cause infections and hypersensitivity pneumonitis via exposure to water. We compared a generally used cultivation method and a quantitative polymerase chain reaction (qPCR) method to detect mycobacteria in 3 types of drinking waters: surface water, ozone-treated surface water, and groundwater. There was a correlation between the numbers of mycobacteria obtained by cultivation and qPCR methods, but the ratio of the counts obtained by the 2 methods varied among the types of water. The qPCR counts in the drinking waters produced from surface or groundwater were 5 to 34 times higher than culturable counts. In ozone-treated surface waters, both methods gave similar counts. The ozone-treated drinking waters had the highest concentration of assimilable organic carbon, which may explain the good culturability. In warm tap waters, qPCR gave 43 times higher counts than cultivation, but both qPCR counts and culturable counts were lower than those in the drinking waters collected from the same sites. The TaqMan qPCR method is a rapid and sensitive tool for total quantitation of mycobacteria in different types of clean waters. The raw water source and treatments affect both culturability and total numbers of mycobacteria in drinking waters.

Abstract  In this study, emissions of carbonyl compounds from the use B50 and B100 were measured with a non-road diesel generator. A total of 25 carbonyl compounds were identified in the exhaust, including 10 with laboratory-synthesized standards. Formaldehyde, acetaldehyde, and acrolein were found as the most abundant carbonyl compounds emitted for both diesel and biodiesel. The sulphur content of diesel fuels and the source of biodiesel fuels were not found to have a significant impact on the emission of carbonyl compounds. The overall maximum incremental reactivity (MIR) was the highest at 0 kW and slightly increased from 25 to 75 kW. The MIR of B100 was the highest, followed by diesel and B50, which is consistent with the emission rates of total carbonyl compounds. This suggests that the use of biodiesel blends may be more beneficial to the environment than using pure biodiesel.