Experimental Determination of the Ammonium Sulfate/Maleic Acid/Water Solid/Liquid Ternary Phase Diagram
The formation of cirrus clouds can be directly affected by aerosols present in the atmosphere. While many systems consisting of inorganic aerosols have been widely studied, work has only recently been undertaken to study systems consisting of organic and mixed inorganic/organic aerosols. Our research group has extensively studied the ice region of the mixed inorganic/organic Ammonium Sulfate/Maleic Acid/Water ternary system using differential scanning calorimetry and IR spectroscopy of thin films. Our data was primarily collected at temperatures below 298 K, maleic acid concentrations below 0.30 total mass fraction, and ammonium sulfate concentrations below 0.40 total mass fraction. Using this data, we have generated a ternary liquid/solid phase diagram which can be used to determine which phases of matter will be present in the system at different compositions and temperatures, and we report a ternary eutectic temperature of 252.14 K. We have directly compared our experimental data to data generated using the Aerosol Inorganics Model (AIM). This thermodynamic model can be used to predict aerosol composition at varying atmospheric conditions. It was found that the AIM predicted final melt temperature deviated most from our experimentally determined final melt temperature at high maleic acid concentrations. Since there is very little existing data for the the ammonium sulfate/maleic acid/water ternary system, our experimental data can be directly used to make corrections and improve the accuracy of this model. This research will prove to be of increasing value as we look to understand the role clouds play on climate systems.
Anomalous Transmission of Infrasound Through Air-Water and Air-Ground Interfaces
Speed of compressional waves in air is smaller than in water and in the ground, while mass density of air is much smaller than mass densities of water and the ground. This results in a very strong acoustic impedance contrast at air-water and air-ground interfaces. Sound transmission through a boundary with a strong impedance contrast is normally very weak. This paper reports theoretical studies of the power output of localized sound sources and acoustic power fluxes through plane gas-liquid and gas-solid interfaces in a layered medium. It is found that the transparency of the interfaces increases dramatically at low frequencies. For low-frequency sound, a phenomenon of anomalous transparency can occur where most of the acoustic power generated by a source in water is radiated into the atmosphere. Contrary to the conventional wisdom based on ray-theoretical predictions and observations at higher frequencies, infrasonic energy from localized waterborne sources can be effectively transmitted into air. The main physical mechanism responsible for the anomalous transparency of air-water interface is found to be an acoustic power transfer by inhomogeneous (evanescent) waves in the plane-wave decomposition of the acoustic field in water. The effects of ocean and atmosphere stratification and of guided sound propagation in water or in air on the anomalous transparency of the air-water interface are considered. In the case of air-ground interface, the increase of the acoustic power flux into atmosphere, when a compact source approaches the interface from below, proves to be even larger than for an underwater source. The physics behind the increase of the power flux into the atmosphere, when the source depth decreases, is shown to be rather different for the air-ground and air-water interfaces. Depending on attenuation of compressional and shear waves in the ground, a leaky interface wave supported by the air-ground interface can be responsible for the bulk of acoustic power flux into the atmosphere. Thus, infrasonic fields on opposite sides of air-water and air-ground interface are much more strongly coupled than was previously believed possible. The phenomenon of anomalous transparency can have significant implications, in particular, for acoustic monitoring, detection, and classification of powerful underwater and underground explosions for the purposes of the Comprehensive Nuclear-Test-Ban Treaty.
Atmospheric Concentrations, Gas/Particle Partitioning And Exposure Risk Of Polycyclic Aromatic Hydrocarbons (PAHs) At Background, Rural Village And Urban Sites In The North China Plain
Particle- and gas-phase PAHs were measured in air collected from a background site (Xiaolongmen), two rural village sites (Gubeikou and Donghe), and an urban site (Beijing) located in the North China Plain for four seasons from September 2007 to August 2008 in order to evaluate their concentrations, relative abundance, and gas/particle partitioning. Sixteen PAHs, included in the U.S.EPA priority pollutant list, were determined in the particle (PM10) and gas phases. The annual average 15 PAH concentration in Donghe was 730.7±608.0 ng/m3, which was 18.2, 3.0, 1.8 times higher than Xiaolongmen, Gubeikou and Beijing, respectively. A good linear relationship between gas/particle partitioning coefficients, Kp and subcooled liquid vapor pressure, pl was obtained. At the rural and urban sites, the regression slopes were much steeper than -1, indicating that adsorption of PAH to particulate matter dominated over absorption possibly because, at these sites, the freshly emitted particulate matter and PAHs had not yet reached equilibrium. However, gas/particle partitioning of PAHs approached equilibrium at the background site because of long- range transport of PAHs. In addition, the gas/particle partitioning was studied according to three different models: The Junge-Pankow adsorption model, the Koa absorption model, and the dual organic matter absorption model combined with the soot carbon adsorption model. The Junge-Pankow model and Koa model both under-predicted our experimental Kp values. However, the dual model fit our experimental Kp values well suggesting that the main partitioning mechanism was PAH adsorption onto soot carbon in this region of China. The different particulate matter characteristics (including organic matter and elemental carbon fraction and available adsorption sites), temperature variation during sampling, the presence of a non- exchangeable PAH fraction and non-equilibrium were considered possible reasons for why our experimental Kp values deviated from the model predictions. Finally, the human exposure risk was assessed using the PAH toxic equivalent concentrations based on benzo(a)pyrene (TEQBaP). The annual average TEQBaP in Donghe was 18.6±20.1 ng/ m3, which was 1.8 times higher than the Chinese national standard of 10 ng/ m3 and 18.6 times higher than the WHO guideline of 1 ng/ m3, and 53.8, 2.3, 2.0 times higher than Xiaolongmen, Gubeikou and Beijing, respectively. In Donghe, coal and biofuel combustion are still the major energy sources and the combustion of these fuels in low-efficiency family stoves, and other combustion facilities, was the major reason for the high PAH levels.
Local and Regional Influences on Atmospheric Nutrient Deposition in Southeast Brazil
The objective of this work was to quantify sources of atmospheric nutrients, which are subsequently deposited to agricultural soils and natural ecosystems of São Paulo State (Brazil). The atmospheric concentrations of soluble ions (NO3-, NH4+, PO43-, SO42-, Cl-, K+, Na+, Mg2+ and Ca2+) in aerosol were evaluated, together with the gases NO2, NH3, HNO3 and SO2. Identification of nutrient sources was achieved using principal component analysis (PCA) followed by multiple linear regression analysis (MLRA). Dry deposition fluxes were estimated using the measured atmospheric concentrations together with dry deposition velocities of gases and aerosols to different surface types. Results showed that the main sources of nutrients to the region´s atmosphere were fossil and biofuel combustion (N and S species), agricultural biomass burning (N, S, K and P), re-suspension of soils and dusts (Ca and Mg), and to a lesser extent long-range transport (S). NO2 concentrations were more influenced by local emissions and subsequent chemical transformations occurring on a scale of up to 200-300 km. HNO3 was much less spatially variable, with consistently higher concentrations during warmer, drier periods, indicating an agreement with gas phase/aerosol phase thermodynamic equilibrium theory. Scavenging of gaseous HNO3 was a source of nitrate, for which deposition fluxes were higher during the dry season, when significant relationships were obtained between nitrate concentrations and biomass burning intensity. Additional sources were indicated for particulate nitrate and sulphate, such as road transport and secondary reactions. During winter, the main source of gaseous ammonia was biomass burning, while emissions from soils and wastes predominated during summer. Modeled deposition fluxes were highest to tropical forest and lowest to water and pasture surfaces. In agricultural areas, the deposition fluxes of aerosol components N, P and K (0.37, 0.029 and 0.59 kg ha-1 yr-1, respectively) were equivalent to < 0.5 % of the amounts in fertilizer applied annually to plantations. Inclusion of gaseous dry deposition of nitrogen-containing compounds increased the total nitrogen flux by around 5 to 10-fold, depending on surface type.
First Gobal Observations of Groundstate CO2 in the MLT by ACE: Observations and Analysis Using CMAM Model Results
The first global set of observations of the ground state CO2 in the mesosphere and lower thermosphere (MLT) obtained by the ACE-FTS instrument on a small Canadian satellite SCISAT-I is presented in this study. The observations use the solar occultation technique and document the fall off in the mixing ratio of CO2 in the MLT region. The beginning of the fall off of the CO2, or "knee" occurs about 78 km and lies higher than in the CRISTA measurements (∼72 km) but lower than in the SABER 1.06 (∼ 82 km) and much lower than in rocket measurements. We also present the measurements of CO obtained concurrently which provide important constraints for analysis. We have compared the ACE measurements with simulations of the CO2 and CO distributions in the vertically extended version of the Canadian Middle Atmosphere model (CMAM). Applying standard chemistry we find that we cannot get agreement between the model and ACE CO2 observations although the CO observations are adequately reproduced. There appears to be about a 10 km offset compared to the observed ACE CO2, with the model knee occurring too high. In analysing the disagreement, we have investigated the variation of several parameters of interest, photolysis rates, formation rate for CO2, and the impact of uncertainty in eddy diffusion, in order to explore parameter space for this problem. Our conclusions are that there must be a loss process for CO2, about 2-4 times faster than photolysis that will sequester the carbon in some form other than CO and we have speculated on the role of meteoritic dust as a possible candidate. In addition, from this study we have highlighted a possible important role for vertical eddy diffusion in 3D models in determining the distribution of candidate species in the mesosphere which requires further study.
Mineral Dust: Modeling and Measurements
Aerosols Collected at a Tropical Marine Environment: Size-Resolved Chemical Composition Using IC, TOC, and Thermal-Optical Analyses
Size-resolved chemical characterization was performed on aerosol samples collected at two different marine sites in the tropics: Dian Point (DP), Antigua and Cape San Juan (CSJ), Puerto Rico. A 13-stage Dekati low- pressure impactor (Dp 0.1 to 10 μm), a 10-stage micro-orifice uniform deposit impactor (Dp 0.054 to 18 μm), and stacked-filter units (Dp < 1.7 μm) were used to collect the samples. Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO2-, NO3-, SO42-, acetate, formate, malonate, and oxalate were determined using ion chromatography (IC). Thermal-optical analysis (TOA) was used to determine the concentrations of aerosol total carbon (TC), organic carbon (OC), and elemental carbon (EC). Five-day back trajectories calculated using NOAA's HYSPLIT (HYbrid Single-Particle Lagrangian Integrated Trajectory) model identified air masses coming from the North Atlantic (maritime air), Northwest Africa (desert dust), and North America (anthropogenic pollution). Size-resolved chemical characterization of aerosol samples using IC and TOA confirmed that aerosols become aged as they are transported to the Caribbean and their composition depends on the air mass origin. Gravimetric analyses showed that average fine mass concentrations for CSJ station were higher than for DP station (CSJ: 1.9 μg m-3; DP: 1.2 μg m-3). The aerosol chemical composition changed with air masses of different origin and with different pollution levels. In both locations the predominant water-soluble ions in the fine aerosol fraction were Cl-, Na+, and SO42-. Sulphate was observed in higher concentrations during the polluted case and particulate organic matter concentrations were higher for the maritime case. During desert dust events an increase in Ca2+ and Mg2+ of 4 and 2 times, respectively, was observed mainly in the coarse mode. Results for the size-resolved chemical composition and complete aerosol chemical apportionment including the residual mass will be presented.
Quantitative Assessment of Upstream Source Influences on TGM Observations at Three CAMNet Sites
Mercury is a persistent and toxic substance in the environment. Exposure to high levels of mercury can cause a range of adverse health effects, including damage to the nervous system, reproduction system and childhood development. Proper recognition and prediction of atmospheric levels of mercury can effectively avoid the adverse affect of Hg, however they cannot be achieved without accurate and quantitative identification of source influences, which is a great challenge due to the complexity of Hg in the air. The objective of this study is to present a new method to simulate Hg concentrations at the location of a monitoring site and quantitatively assess its upstream source influences. Hourly total gaseous mercury (TGM) concentrations at three CAMNet monitoring sites (receptors) in Ontario were predicted for four selected periods using the Stochastic Time-Inverted Lagrangian Transport (STILT) model, which is capable of representing near-field influences that are not resolved by typical grid sizes in transport models. The model was modified to deal with Hg depositions and point source Hg emissions. The model-predicted Hg concentrations were compared with observations, as well as with the results from a CMAQ-Hg simulation in which the same emission and meteorology inputs were used. The comparisons show that STILT-predicted Hg concentrations agree well with observations, and are generally closer to the observations than those predicted by CMAQ-Hg. The better performance of the STILT simulation can be attributed to its ability to account for near-field influences. STILT was also applied to assess quantitatively the relative importance of different upstream source regions for the selected episodes. The assessment was made based on emission fluxes and STILT footprints, i.e., sensitivities of atmospheric concentrations to upstream surface fluxes. The results indicated that the main source regions of observed low Hg concentrations were in Northeastern Ontario, whereas elevated observations were mainly due to contributions from sources in Southern Ontario, Ohio, Virginia and Michigan. These results illustrate the capability of STILT to interpret and identify source regions of pollutants.
New independent software packages based on the MODIS aerosol algorithms
The MODIS aerosol algorithms have nearly an 8 year history of producing validated aerosol products. During this period the algorithms have been adjusted and updated to both improve accuracy of the retrievals and to provide new capabilities. MODIS algorithm codes have always been open source, but users outside of the MODIS team have found them difficult to use because they are so tightly wedded to the operational processing. Recently we have added several new software packages that can be acquired from the MODIS aerosol team, and used independently of the MODIS operational computing environment. Specifically, we now have an easily transported 'stand alone code' that will process MODIS Level 1 radiance data and produce the MOD04/MYD04 Level 2 product without needing the operational MODIS 'tool kits'. Users can take this code and experiment with it, changing the operational algorithm to meet their own particular needs. In addition to this 'stand alone code', we now provide an independent software package that creates a cloud mask based on the spatial variability criteria pioneered by Martins et al., (2002) and the cirrus reflectance tests developed by Gao et al., (2002). This software produces a field of '1's and '0's on a 500 m resolution that indicate which pixels are cloudy and which are not, as defined by the aerosol team's cloud mask. The third piece of software is still in development, but will label each non-cloudy pixel as to its distance from the nearest cloud. This third piece of software will make it easier to estimate the amount of cloud contamination in the aerosol product and to pursue satellite-based studies of aerosol-cloud interaction. These codes, and additional new software that we develop will be available to the international research community, and can be acquired at any time from the MODIS aerosol team. Gao, B.-C., Y.J. Kaufman, D. Tanré and R.-R. Li, 2002: Distinguishing tropospheric aerosols from thin cirrus clouds for improved aerosol retrievals using the ratio of 1.38-µm and 1.24-µm channels. Geophys. Res. Lett., 29, 1890, doi:10.1029/2002GL015475. Martins, J.V., D. Tanré, L.A. Remer, Y.J. Kaufman, S. Mattoo and R. Levy, 2002: MODIS Cloud screening for remote sensing of aerosol over oceans using spatial variability. Geophys. Res. Lett., 29, 10.1029/2001GL013252.
Atmospheric Particulate Metals and Metalloids in Lake Ontario Region 2005- 2007
Particles in rural and urban air were collected at two ground sites along the north-east shorelines of Lake Ontario, Canada. CEPA (Canadian Environmental Protection Act) metals and metalloids As, Cd, Cu, Hg, Ni, Pb, Se, Zn were captured on quartz fibre filters (PM10). Particulate metal concentrations per cubic meter of air was As∼0.1-2.9, Cd∼0.02-2.6, Cu∼2.5-19.5, Fe∼110-4400, Hg∼0.07-0.94, Mn∼30- 140, Ni∼1.0-46.0, Pb∼1.5-10.5, Se∼0.1-0.9 and Zn∼12-53 ng which can generally represent mixed ambient and urban contributions during that time period. Elevated particulate metals and metalloids concentrations were found in the industrial areas of the Lake Ontario region with Fe and Mn reaching 100 times ambient levels. Calculated (2005) dry and wet atmospheric metal deposition (Zhang model 2001) showed a slight gradual decrease from recent years for Pb, Cd, As but remain unchanged for Se. Meteorological conditions were found to have major influences in the characteristics of metal particulates collected and their size fractions. Results of particle size distribution (AGU 2006, 2007) and particulate metal content can provide better estimates of metal loading by dry and wet deposition.
Applying A Lagrangian Dispersion Analysis With Different Parameterizations Of Turbulence Statistics To Infer Carbon Dioxide And Latent Heat Fluxes In A Corn Canopy
Lagrangian dispersion methods have been used as an alternative to infer scalar source/sink distributions and fluxes inside plant canopies. Warland and Thurtell (2000) proposed a method (hereafter WT analysis) to relate source and concentration profiles of scalars within plant canopies using a 'dispersion matrix', which is calculated using turbulence statistics, represented by the Lagrangian time scale (TL) and the standard deviation of the vertical wind speed (ów) . The objective of this study was to assess different turbulence statistics parameterizations on the results net flux provided by WT analysis in a corn field for various atmospheric stability conditions. The WT analysis requires the specification of the turbulence statistics in advance, so parameterizations proposed by Raupach (1989) (TSR), Leuning (2000) (TSL), Denmead (2000) and Styles (2009) (TSDS) were used. The TL and ów profiles were corrected for stability conditions according to methodology proposed by Leuning (2000). The field experiment was carried out in a corn field during the field season in 2007 at the Elora Research Station, Elora, ON. Profiles of water vapour and CO2 concentrations were measured using a multiport sampling system connect to an infrared gas analyzer LI6262 (Li-Cor, Inc., Lincoln, NE, USA) at 6 heights inside and two heights above the canopy. The estimates of CO2 and latent heat fluxes, provided by the sum of source strength profiles from WT analysis, were compared with the measurements taken using an eddy covariance system set up at the same site. In addition a profile of leaf area index was obtained using an area meter LI-3100C (Li-Cor, Inc., Lincoln, NE, USA) to estimate some turbulence statistics. The concentration profiles of CO2 and H2O presented larger gradients close to the ground. During the growing season lower CO2 concentrations were observed at 1/2 of the canopy height during daytime, indicating the existence of a strong CO2 sink at this height. The measurements obtained by the eddy covariance method and WT analysis predictions using the three turbulence statistic parameterizations showed good agreement as shown in scatter plots. However the WT analysis tended to overestimate fluxes especially with small magnitude and when the atmosphere was unstable. These results show that further investigation is required to improve the turbulence statistic parameterizations and the atmospheric stability corrections.
On the temporal scale of the turbulent exchange of carbon dioxide and energy above a tropical rain forest in Amazonia
The LBA (Large Scale Biosphere-Atmosphere in Amazonia) project has been using the eddy covariance technique since 1998 to monitor energy, water and carbon surface fluxes over Amazonia. The results obtained up to date indicate high level of uncertainties, especially regarding the role of the Amazonian ecosystem to the global carbon budget. Besides the problems related to the eddy covariance measuring system (systematic error and nighttime stable conditions), an extremely important factor is associated with the averaging time scale or "time window" used by the scientific community to determine the surface fluxes. This work presents initial efforts to determine the turbulence time scale for long-term carbon and energy surface fluxes over the Amazon rainforest. A total of 198 nights and 218 days, during 2006 were analyzed. The multi-resolution decomposition technique was applied to project the signal into several time scales and determine when the spectral and cospectral gap occurred. This technique permitted evaluating and separating the real contribution from turbulent and mesoscale fluxes to the total surface fluxes, at both diurnal and nocturnal periods. The average turbulence time scale was below 200 s and 1200 s for all scalars at nighttime and daytime, respectively. In all cases, there is seasonal dependence. This result shows that the time scale commonly used to calculate nocturnal surface fluxes (30 minutes) includes a good portion of mesoscale flux in the estimates. The role of these mesoscale fluxes, in terms of seasonal dependence and the uncertainties they add to the estimates, is then analyzed
Measurement and Correlation of Ambient VOCs in Windsor, Ontario, Canada and Detroit, Michigan, USA
An air quality study has been carried out in Windsor, Ontario, Canada and Detroit, Michigan, USA as part of a pilot research study undertaken by the Geospatial Determinants of Health Outcomes Consortium (GeoDHOC), a multidisciplinary, international effort aimed at understanding the health effects of air pollution in urban environments. Exposure to volatile organic compounds has long been associated with adverse health conditions such as atrophy of skeletal muscles, loss of coordination, neurological damage, dizziness, throat, nose, and eye irritation, nervous system depression, liver damage, and respiratory symptoms. Twenty-six species of ambient volatile organic compounds (VOCs) were monitored during a 2-week period in September, 2008 at 100 sites across Windsor and Detroit, using 3M # 3500 Organic Vapour Monitors. Ten species with highest concentrations were selected for further investigation; Toluene (mean concentration =4.14 μm/m3), (m+p)-Xylene (2.30 μm/m3), Hexane (1.87 μm/m3), Benzene (1.37 μm/m3), 1,2,4-Trimethylbenzene (0.87 μm/m3), Dichloromethane (0.77 μm/m3), Ethylbenzene (0.68 μm/m3), o-Xylene (0.63 μm/m3), n-Decane (0.42 μm/m3), and 1,3,5-Trimethylbenzene (0.39 μm/m3). Comparison to a similar investigation in Sarnia, Ontario in October 2005 revealed that the mean concentrations of VOCs were higher in Windsor-Detroit for all species by a significant margin (31-958%), indicating substantial impact of local industrial and vehicular emissions in the Windsor¡VDetroit area. For most VOCs, the concentrations were higher in Detroit than in Windsor. The mean concentration of total VOC was 9.7 μm/m3 in Windsor, which is slightly higher than that in Sarnia in 2005 (7.9 um/m3), whilst total VOC concentration in Detroit was much higher (16.5 μm/m3). There were strong correlations among several of the 10 species, with the highest Pearson correlation coefficients (r=0.78 - 0.99, p<0.05) amongst the BTEX (benzene, toluene, ethylbenzene, and xylenes) group, suggesting common sources of these species. The BTEX correlation for this study was in good agreement with that from the Sarnia results (Spearman rank correlation coefficient r=0.75 - 0.99), suggesting that one species may act as a proxy for the others in geographically similar regions.
Atmospheric Aerosols in the Guánica Dry Forest
Aerosols posses a substantial influence over the development and alteration of climate dynamics on the Caribbean. Among the principal sources of particulate matter that influence this region are the North African desert area, from which dust particles are usually transported by the trade winds, and anthropogenic activities that involve the combustion of fossil fuel. These types of aerosols have the potential to alter forests, among other multiple environments. This study focuses on the effects this type of aerosols can exert on Guánica's Dry Forest (GDF) in Puerto Rico. The GDF is one of the most intact mature dry forests in the Caribbean, is a place that has been chosen as the Atlantic Neotropical core site in the National Ecological Observatory Network (NEON), and is an UNESCO Man and Biosphere Reserve. To chemically characterize the aerosol inputs to the GDF, aerosol samples were collected using Stacked-Filter Units. Samples were analyzed using a thermal-optical analyzer (EC/OC analyzer) to determine the concentrations of organic and elemental carbon. X-ray Fluorescence (XRF) and Inductively coupled plasma (ICP) were also used to determine the elemental concentrations of different ions species. Preliminary ICP results showed the presence of Al, Na, Mg, Fe, and Ca in higher concentrations in the coarse than in the fine fraction, suggesting the influence of mineral dust. This was confirmed by back trajectory analyses using the NOAA HYSPLIT model. The EC/OC analyses showed low organic carbon concentrations during African dust events, which was expected since African dust particles are mainly inorganic. Elemental Carbon concentrations were also very low, showing that the study site had little anthropogenic influence. Results related to the elemental composition as determined using XRF and ICP analyses will also be presented at the meeting.
A Hybrid Regularization for Remote Determination of Atmospheric Aerosol Distribution from Multi-Frequency Optical Measurements
The notion of ill-posed and possibly rank-deficient linear inverse problems of determining the unknown input parameters from sensor measurements forms the underlying mathematical equations in many science and engineering situations. One example is the retrieval of atmospheric-aerosol (microphysical) parameters from the optical measurements. Light scattering by atmospheric aerosols, based on the Mie scattering theory, provides a physical framework for remote determination of the aerosol microstructures from optical data measured at multiple frequencies. In the case of ill-posed and/or rank-deficient inverse problem of light scattering by aerosols, a similarity between the oscillatory behaviors of the singular vectors of the problem matrix and the behaviors of the Fourier bases spanned by harmonic functions, provides the theoretical background on which (semi-) regularization parameters (such as the truncation level in the singular values of the problem matrix in the form of the cut-off point between the high-frequency noisy and the low-frequency undisturbed part of the solution, and the choice of the regularization matrix) can be used. In addition, the number of components that makes up the B-form of a spline, the number of iterations to counteract the semi- convergence, and the selection of a regularization parameter that reflects the noise level, and the order of B- spline, can be combined to stabilize the solution by filtering out unnecessary information. All of the aforementioned parameters together with an iterative regularization scheme are proposed in this study to provide a hybrid framework for remote determination of the aerosol distribution in the atmosphere.
Atmospheric Chemistry of Perfluorobutenes
The atmospheric fate of two perfluorobutenes, CF3CF=CFCF3 and CF3CF2CF=CF2, was investigated using smog chamber techniques. Rate constants for reaction with chlorine atoms and hydroxyl radicals were measured with relative rate techniques. The atmospheric lifetimes of CF3CF=CFCF3 and CF3CF2CF=CF2 are determined by reaction with OH radicals and are approximately 24 and 6 days, respectively. As a result, the contribution of CF3CF=CFCF3 and CF3CF2CF=CF2 to radiative forcing of climate change will be negligible. The chlorine atom- and OH radical-initiated oxidation of CF3CF=CFCF3 in 700 Torr of air gives CF3C(O)F in a molar yield indistinguishable from 200%, while the oxidation of CF3CF2CF=CF2 gives CF3CF2C(O)F and COF2 in molar yields indistinguishable from 100%. The atmospheric fate of CF3C(O)F and CF3CF2C(O)F is hydrolysis to give perfluorocarboxylic acids (PFCAs), CF3C(O)OH and CF3CF2C(O)OH. This is the first observation of this formation mechanism for PFCAs.
Analyzing the Potential Impact of a New Wastewater Treatment Process on the Global Tropospheric Nitrous Oxide Abundance using STELLA Modeling
The primary radiatively important trace gases in the troposphere include water vapor, carbon dioxide, methane, and nitrous oxide. This presentation will focus on the global balance of nitrous oxide in the troposphere, and potential consequences to that balance as the result of a new emerging wastewater treatment approach. While microbial activity in the soils and the ocean account for the major natural sources of N2O, the tropospheric sinks for this trace gas are limited and consequently is long-lived in the troposphere. A new technique being implemented by wastewater treatment plants releases nitrogen to the atmosphere in the forms of N2, NOx and N2O. Could this source of nitrogen in the atmosphere disrupt the global nitrogen balance? If this technology becomes more widespread, could the new source of N2O be significant enough to have an impact on our global climates? To gain a better understanding of how this new nitrogen source will affect the global nitrogen cycle, a systems model was constructed using the modeling software STELLA (http://www.iseesystems.com). The modeled results will explore the strength of this new anthropogenic N2O source and assess its impact on the global nitrogen budget.
Estimation of Carbon Dioxide Emission from Soil Physical and Hydrological Properties
Photochemical Reaction of Oxidized Mercury Species with Selected Thiols and its Environmental Implications
Mercury is a global pollutant with severe potential toxicity. The reduction of oxidized mercury species (HgII) to elemental mercury (Hg0) affects the global distribution of mercury and competes for methylation processes of mercury in aquatic environment. Quantum Calculations have suggested that direct photodecomposition of Hg(SH)2(aq) by sunlight is possible. One study has shown that irradiation of benzene solution of some mercury dimercaptides at part-per-million level by a mercury arc lamp under a nitrogen atmosphere caused the formation of Hg0 to occur. The objectives of this study are to obtain kinetic data and to analyze reaction products for the reaction of oxidized mercury species with selected thiols. The reaction kinetics was studied using Cold Vapor Atomic Fluorescent Spectrometry (CVAFS), and the products of the reaction were analyzed using Electronspray Ionization-Mass Spectrometry (ESI-MS), Matrix-Assisted Laser Desorption Ionization Time- of-Flight Mass spectrometry (MALDI-TOF-MS) and Gas Chromatography-Mass spectrometry (GC-MS). The kinetic data were obtained for 1-propanethiol, and 1-butanethiol, 1-pentanethiol at near environmental conditions. The effects of light, pH, dissolved oxygen and chloride ion on reaction rates were also investigated. We will present our results and discuss its potential environmental implications on mercury cycling.
Measurements of Pollution In The Troposphere (MOPITT): Long-Term Measurements of Carbon Monoxide Across the Globe
The MOPITT instrument was launched on the Terra satellite in December 1999. At the present time it is well on the way (9+ years) to providing a decade-long time series of carbon monoxide in the troposphere. This unique dataset has provided us with great insights into the production, distribution and transport of pollutants around the globe. With a long dataset comes the opportunity to look at multiple instances of events such as El Nino and to assess the longer term variations of carbon monoxide (CO) across the globe. This poster will look at what the MOPITT dataset tells us (and does not tell us) about the long-term issues for CO, whether there is such a thing as a "typical year" and how MOPITT is positioned as it begins a second decade of measurements. The MOPITT instrument was supplied to the Terra spacecraft by the Canadian Space Agency (CSA). The prime contractor for MOPITT was COMDEV of Cambridge, Ontario. Funding for MOPITT science analysis in Canada has been supplied by the Natural Sciences and Engineering Research Council and the CSA. Data processing in the US has been supported by NASA who also funded the spacecraft.
Historical Trends of Trace Metals in Lake Sediments From Adirondack Park, New York
Burning of fossil fuel and many industrial operations emit large quantities of trace metals bearing aerosols along with other pollutants into the atmosphere. The pollutants can be transported thousands of kilometers downwind from their source. They are ultimately removed from the atmosphere by wet and dry deposition. Lake sediments can be used to provide a record of the environmental changes that have occurred in the past. In this study we determined the concentrations of trace metals from two lake sediment cores collected from Clear Pond and West Pine Pond, located in the Adirondack Park region in upstate New York. These lakes were chosen as they are remote and have minimum local sources of pollution. The cores were sliced into thin sections, dried and weighed. The sediment cores were dated using the 210Pb technique. The top sixteen sections of the West Pine Pond and Clear Pond sediment represented deposits from about 1821 to 2005, and around 1880 to 2007, respectively. A microwave digestion procedure was used to separate trace metals from organic matter and silicates. The trace element concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). These samples were analyzed for As, Se, Mo, Cd, Sn, Sb, Co, Ni, Cu, Ag, Ti, V, Cr, Mn, Fe, Zn, K, Na, Ca, Mg, Ba, Sr, Be, Hg, Tl, and Pb. The lithophilic elements Ba, Sr, Al, Ti, K, Na, Ca, Mg and Sr showed little increase over the entire period studied in both lakes. Vanadium and Cr showed little increase in the West Pine Pond core (1.2 and 1.4 times the preindustrial level, resp.), but increased more (1.7 and 2.0, resp.) in the Clear Pond core. The elements As, Se, Mo, Cd, Sn, Sb, Co, Ni, Cu, Mn, Fe, Zn, Hg, Tl, V and Pb showed significant increases due to anthropogenic inputs. Lead showed the greatest increase over the preindustrial baseline concentration, a 12-fold increase in Clear Pond and 24-fold in West Pine Pond. Large increases were also seen in Se and Hg ranging from (2.4 to 10.0) concentration. Se is a good tracer for coal burning and concentrations were found to increase with increase usage of coal during industrialization with concentration peaking around 1970s. Atmospheric Hg is also produced by coal burning, and it showed similar trends in both lakes, reaching a maximum concentration in the 1980s (2.4 and 3.3, resp. in West Pine Pond and Clear Pond). The Hg concentrations subsequently decreased by 10 % and 14 %, respectively. The Pb concentrations began to increase around 1880 and peaked in around 1990 in the West Pine Pond core and 1970 in the Clear Pond core. Pb concentrations were observed to decrease afterwards to 56 % and 51 % of the maximum, respectively, most likely due to improved regulation in paints and gasoline after 1978.
Surface Climate Effects due to Changing Estimates of Century-Scale Solar Variability
Resolving the different roles that natural and anthropogenic forcings have played in the climate system over the past century has been the central effort of many coupled, atmosphere-ocean modelling studies. In particular, the effects of total solar irradiance (TSI) variability on the climate system have been emphasised in these studies, due to the perceived strength of century-scale, solar variability in TSI models. However, estimates of the amplitude of this variability were reduced dramatically in 2005 as a consequence of new developments in solar modelling. Nevertheless, many climate models continue to employ the earlier TSI models. In this study, we present the results of changing TSI models on modelled sea surface temperatures and other aspects of the climate system. In order to address this question, we have run two sets of global warming simulations from 1870 to 2000 using the National Center for Atmospheric Research Community Climate System Model 3.0 (CCSM3). These simulations include both anthropogenic and natural forcings, consistent with those used in the CCSM3 analyses performed in support of the 4th IPCC Assessment Report. The two sets differ only in their TSI datasets: one published by Lean et al (1995) and the second by Wang et al (2005). By intercomparing the variations of surface climate features produced by each of these sets, we will identify some novel differences due to the change in solar forcing alone.