Acceleration of the Fe(III)EDTA(-) reduction rate in BioDeNO(x) reactors by dosing electron mediating compounds

BioDeNO(x), a novel technique to remove NO(x) from industrial flue gases, is based on absorption of gaseous nitric oxide into an aqueous Fe(II)EDTA(2-) solution, followed by the biological reduction of Fe(II)EDTA(2-) complexed NO to N(2). Besides NO reduction, high rate biological Fe(III)EDTA(-) reduction is a crucial factor for a succesful application of the BioDeNO(x) technology, as it determines the Fe(II)EDTA(2-) concentration in the scrubber liquor and thus the efficiency of NO removal from the gas phase. This paper investigates the mechanism and kinetics of biological Fe(III)EDTA(-) reduction by unadapted anaerobic methanogenic sludge and BioDeNO(x) reactor mixed liquor. The influence of different electron donors, electron mediating compounds and CaSO(3) on the Fe(III)EDTA(-) reduction rate was determined in batch experiments (21mM Fe(III)EDTA(-), 55 degrees C, pH 7.2+/-0.2). The Fe(III)EDTA(-) reduction rate depended on the type of electron donor, the highest rate (13.9mMh(-1)) was observed with glucose, followed by ethanol, acetate and hydrogen. Fe(III)EDTA(-) reduction occurred at a relatively slow (4.1mMh(-1)) rate with methanol as the electron donor. Small amounts (0.5mM) of sulfide, cysteine or elemental sulfur accelerated the Fe(III)EDTA(-) reduction. The amount of iron reduced significantly exceeded the amount that can be formed by the chemical reaction of sulfide with Fe(III)EDTA(-), suggesting that the Fe(III)EDTA(-) reduction was accelerated via an auto-catalytic process with an unidentified electron mediating compound, presumably polysulfides, formed out of the sulfur additives. Using ethanol as electron donor, the specific Fe(III)EDTA(-) reduction rate was linearly related to the amount of sulfide supplied. CaSO(3) (0.5-100mM) inhibited Fe(III)EDTA(-) reduction, probably because SO(3)(2-) scavenged the electron mediating compound.     

Relationship between leaf antioxidants and ozone injury in Nicotiana tabacum ‘Bel-W3’ under environmental conditions in São Paulo,SE – Brazil

Previous studies have reported that the extent of leaf injury in Nicotiana tabacum “Bel-W3” exposed to environmental conditions in the city of São Paulo is influenced by weather conditions. This influence may occur by means of antioxidant responses. Thus, this study aimed to evaluate whether daily antioxidant responses to environmental variations interfere on the progression of leaf injury on plants of this cultivar during their exposure in a state park of São Paulo and to determine a linear combination of variables, among antioxidants and environmental factors, which mostly explain this visible response. Plants were exposed at the mentioned site for 14 days in four different experiments. During each experiment, three plants were daily sampled to determine the accumulated percentage of leaf area affected by necrosis and antioxidant responses (concentrations of total ascorbic acid (AA) and activity of superoxide dismutase (SOD) and peroxidases (POD)). Ozone concentrations and weather conditions were also daily measured. Pearson correlations and multivariate analyses assessed the relationship between biological and environmental variables. Leaf injury appeared between the 3rd and 6th days of exposure and increased over the exposure periods. The daily concentrations of AA tended to decrease with time of exposure in all experiments, but the activity of SOD and POD oscillated during plant exposure. Positive correlations were observed between AA or SOD and O₃ concentrations, as well as negative correlations between AA and air temperature. The increasing percentage of leaf necrosis across the whole period was explained by decreasing levels of AA 2 days before injury estimation and by higher O₃ concentrations 5 days before (R² = 0.36; p < 0.001). The use of N. tabacum Bel-W3 as a bioindicator can be restricted by leaf antioxidant responses to both atmospheric contamination and weather conditions.     

Surface ozone background in the United States: Canadian and Mexican pollution influences

We use a global chemical transport model (GEOS-Chem) with 1° × 1° horizontal resolution to quantify the effects of anthropogenic emissions from Canada, Mexico, and outside North America on daily maximum 8-hour average ozone concentrations in US surface air. Simulations for summer 2001 indicate mean North American and US background concentrations of 26 ± 8 ppb and 30 ± 8 ppb, as obtained by eliminating anthropogenic emissions in North America vs. in the US only. The US background never exceeds 60 ppb in the model. The Canadian and Mexican pollution enhancement averages 3 ± 4 ppb in the US in summer but can be occasionally much higher in downwind regions of the northeast and southwest, peaking at 33 ppb in upstate New York (on a day with 75 ppb total ozone) and 18 ppb in southern California (on a day with 68 ppb total ozone). The model is successful in reproducing the observed variability of ozone in these regions, including the occurrence and magnitude of high-ozone episodes influenced by transboundary pollution. We find that exceedances of the 75 ppb US air quality standard in eastern Michigan, western New York, New Jersey, and southern California are often associated with Canadian and Mexican pollution enhancements in excess of 10 ppb. Sensitivity simulations with 2020 emission projections suggest that Canadian pollution influence in the Northeast US will become comparable in magnitude to that from domestic power plants.     

A validated 2-D diffusion–advection model for prediction of drift from ground boom sprayers

Correct field drift prediction is a key element in environmental risk assessment of spraying applications. A reduced order drift prediction model based on the diffusion–advection equation is presented. It allows fast assessment of the drift potential of specific ground boom applications under specific environmental wind conditions that obey the logarithmic wind profile. The model was calibrated based on simulations with a validated Computational Fluid Dynamics (CFD) model. Validation of both models against 38 carefully conducted field experiments is successfully performed for distances up to 20 m from the field edge, for spraying on flat pasture land. The reduced order model succeeded in correct drift predictions for different nozzle types, wind velocities, boom heights and spray pressures. It used 4 parameters representing the physical aspects of the drift cloud; the height of the cloud at the field edge, the mass flux crossing the field edge, the settling velocity of the droplets and the turbulence. For the parameter set and range considered, it is demonstrated for the first time that the effect of the droplet diameter distribution of the different nozzle types on the amount of deposition spray drift can be evaluated by a single parameter, i.e., the volume fraction of droplets with a diameter smaller than 191 μm. The reduced order model can be solved more than 4 orders of magnitude faster than the comprehensive CFD model.     

Spatiotemporal modelling of ozone distribution in the State of California

This paper is concerned with the spatiotemporal mapping of monthly 8-h average ozone (O₃) concentrations over California during a 15-years period. The basic methodology of our analysis is based on the spatiotemporal random field (S/TRF) theory. We use a S/TRF decomposition model with a dominant seasonal O₃ component that may change significantly from site to site. O₃ seasonal patterns are estimated and separated from stochastic fluctuations. By means of Bayesian Maximum Entropy (BME) analysis, physically meaningful and sufficiently detailed space–time maps of the seasonal O₃ patterns are generated across space and time. During the summer and winter months the seasonal O₃ concentration maps exhibit clear and progressively changing geographical patterns over time, suggesting the existence of relationships in accordance with the typical physiographic and climatologic features of California. BME mapping accuracy can be superior to that of other techniques commonly used by EPA; its framework can rigorously assimilate useful data sources that were previously unaccounted for; the generated maps offer valuable assessments of the spatiotemporal O₃ patterns that can be helpful in the identification of physical mechanisms and their interrelations, the design of human exposure and population health models, and in risk assessment. As they focus on the seasonal patterns, the maps are not contingent on short-time and locally prevalent weather conditions, which are of no interest in a global and non-forecasting framework. Moreover, the maps offer valuable insight about the space–time O₃ concentration patterns and are, thus, helpful for disentangling the influence of explanatory factors or even for identifying some influential ones that could have been otherwise overlooked.     

Characterization and sources assignation of PM2.5 organic aerosol in a rural area of Spain

The results from a year-long study of the organic composition of PM2.5 aerosol collected in a rural area influenced by a highway of Spain are reported. The lack of prior information related to the organic composition of PM2.5 aerosol in Spain, concretely in rural areas, led definition of the goals of this study. As a result, this work has been able to characterize the main organic components of atmospheric aerosols, including several compounds of SOA, and has conducted a multivariate analysis in order to assign sources of particulate matter. A total of 89 samples were taken between April 2004 and April 2005 using a high-volume sampler. Features and abundance of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), alcohols and acids were separately determined using gas chromatography/mass spectrometry and high performance liquid chromatography analysis. The Σn-alkane and ΣPAHs ranged from 3 to 81 ng m^?3 and 0.1 to 6 ng m^?3 respectively, with higher concentrations during colder months. Ambient concentrations of Σalcohols and Σacids ranged from 21 to 184 ng m^?3 and 39 to 733 ng m^?3, respectively. Also, several components of secondary organic aerosol have been quantified, confirming the biogenic contribution to ambient aerosol. In addition, factor analysis was used to reveal origin of organic compounds associated to particulate matter. Eight factors were extracted accounting more than 83% of the variability in the original data. These factors were assigned to a typical high pollution episode by anthropogenic particles, crustal material, plant waxes, fossil fuel combustion, temperature, microbiological emissions, SOA and dispersion of pollutants by wind action. Finally, a cluster analysis was used to compare the organic composition between the four seasons.     

Quantifying road dust resuspension in urban environment by Multilinear Engine: A comparison with PMF2

Atmospheric PM pollution from traffic comprises not only direct emissions but also non-exhaust emissions because resuspension of road dust that can produce high human exposure to heavy metals, metalloids, and mineral matter. A key task for establishing mitigation or preventive measures is estimating the contribution of road dust resuspension to the atmospheric PM mixture. Several source apportionment studies, applying receptor modeling at urban background sites, have shown the difficulty in identifying a road dust source separately from other mineral sources or vehicular exhausts. The Multilinear Engine (ME-2) is a computer program that can solve the Positive Matrix Factorization (PMF) problem. ME-2 uses a programming language permitting the solution to be guided toward some possible targets that can be derived from a priori knowledge of sources (chemical profile, ratios, etc.). This feature makes it especially suitable for source apportionment studies where partial knowledge of the sources is available.In the present study ME-2 was applied to data from an urban background site of Barcelona (Spain) to quantify the contribution of road dust resuspension to PM₁₀ and PM_2.5 concentrations. Given that recently the emission profile of local resuspended road dust was obtained (Amato, F., Pandolfi, M., Viana, M., Querol, X., Alastuey, A., Moreno, T., 2009. Spatial and chemical patterns of PM₁₀ in road dust deposited in urban environment. Atmospheric Environment 43 (9), 1650–1659), such a priori information was introduced in the model as auxiliary terms of the object function to be minimized by the implementation of the so-called “pulling equations”.ME-2 permitted to enhance the basic PMF solution (obtained by PMF2) identifying, beside the seven sources of PMF2, the road dust source which accounted for 6.9 μg m^?3 (17%) in PM₁₀, 2.2 μg m^?3 (8%) of PM_2.5 and 0.3 μg m^?3 (2%) of PM₁. This reveals that resuspension was responsible of the 37%, 15% and 3% of total traffic emissions respectively in PM₁₀, PM_2.5 and PM₁. Therefore the overall traffic contribution resulted in 18 μg m^?3 (46%) in PM₁₀, 14 μg m^?3 (51%) in PM_2.5 and 8 μg m^?3 (48%) in PM₁. In PMF2 this mass explained by road dust resuspension was redistributed among the rest of sources, increasing mostly the mineral, secondary nitrate and aged sea salt contributions.     

Analysis of cloud and precipitation chemistry at Whiteface Mountain,NY

Federal and state programs over the past two decades have resulted in the reduction of emissions of precursors of acid rain. Concomitant with these changes, measured concentrations of acidity in precipitation and in watersheds have shown a downward trend or improvement. However, another pathway for these precursors is through cloud and fog events that often tend to occur at high-elevation regions affecting the fauna and flora as well. In this study we report on long-term measurements of cloud water and precipitation chemistry made from 1994 onwards at a high-elevation location, Whiteface Mountain NY, in the northeastern United States. Trends and inter-relationship between the ions were examined along with ambient SO₂ measurements and Adirondack lakes chemistry data.     

Assessment of source apportionment by Positive Matrix Factorization analysis on fine and coarse urban aerosol size fractions

This study was conducted in order to investigate the differences observed in source profiles in the urban environment, when chemical composition parameters from different aerosol size fractions are subjected to factor analysis. Source apportionment was performed in an urban area where representative types of emission sources are present. PM₁₀ and PM₂ samples were collected within the Athens Metropolitan area and analysed for trace elements, inorganic ions and black carbon. Analysis by two-way and three-way Positive Matrix Factorization was performed, in order to resolve sources from data obtained for the fine and coarse aerosol fractions. A difference was observed: seven factors describe the best solution in PMF3 while six factors in PMF2. Six factors derived from PMF3 analysis correspond to those described by the PMF2 solution for the fine and coarse particles separately. These sources were attributed to road dust, marine aerosol, soil, motor vehicles, biomass burning, and oil combustion. The additional source resolved by PMF3 was attributed to a different type of road dust. Combustion sources (oil combustion and biomass burning) were correctly attributed by PMF3 solely to the fine fraction and the soil source to the coarse fraction. However, a motor vehicle's contribution to the coarse fraction was found only by three-way PMF. When PMF2 was employed in PM₁₀ concentrations the optimum solution included six factors. Four source profiles corresponded to the previously identified as vehicles, road dust, biomass burning and marine aerosol, while two could not be clearly identified. Source apportionment by PMF2 analysis based solely on PM₁₀ aerosol composition data, yielded unclear results, compared to results from PMF2 and PMF3 analyses on fine and coarse aerosol composition data.     

Atmospheric nitrogen deposition in south-east Scotland: Quantification of the organic nitrogen fraction in wet,dry and bulk deposition

Water soluble organic nitrogen (WSON) compounds are ubiquitous in precipitation and in the planetary boundary layer, and therefore are a potential source of bioavailable reactive nitrogen. This paper examines weekly rain data over a period of 22 months from June 2005 to March 2007 collected in 2 types of rain collector (bulk deposition and “dry + wet” deposition) located in a semi-rural area 15 km southwest of Edinburgh, UK (N55°51′44″, W3°12′19″). Bulk deposition collectors are denoted in this paper as “standard rain gauges”, and they are the design used in the UK national network for monitoring precipitation composition. “Dry + wet” deposition collectors are flushing rain gauges and they are equipped with a rain detector (conductivity array), a spray nozzle, a 2-way valve and two independent bottles to collect funnel washings (dry deposition) and true wet deposition. On average, for the 27 weekly samples with 3 valid replicates for the 2 types of collectors, dissolved organic nitrogen (DON) represented 23% of the total dissolved nitrogen (TDN) in bulk deposition. Dry deposition of particles and gas on the funnel surface, rather than rain, contributed over half of all N-containing species (inorganic and organic). Some discrepancies were found between bulk rain gauges and flushing rain gauges, for deposition of both TDN and DON, suggesting biological conversion and loss of inorganic N in the flushing samplers.