Chemical Characterization of Organic Particulate Matter From On-Road Traffic in Sao Paulo, Brazil

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Description

This study reports emission of organic particulate matter by light-duty vehicles (LDVs) and heavy-duty vehicles (HDVs) in the city of São Paulo, Brazil, where vehicles run on three different fuel types: gasoline with 25 % ethanol (called gasohol, E25), hydrated ethanol

This study reports emission of organic particulate matter by light-duty vehicles (LDVs) and heavy-duty vehicles (HDVs) in the city of São Paulo, Brazil, where vehicles run on three different fuel types: gasoline with 25 % ethanol (called gasohol, E25), hydrated ethanol (E100), and diesel (with 5 % biodiesel). The experiments were performed at two tunnels: Jânio Quadros (TJQ), where 99 % of the vehicles are LDVs, and RodoAnel Mário Covas (TRA), where up to 30 % of the fleet are HDVs. Fine particulate matter (PM2.5) samples were collected on quartz filters in May and July 2011 at TJQ and TRA, respectively. The samples were analyzed by thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS) and by thermal–optical transmittance (TOT). Emission factors (EFs) for organic aerosol (OA) and organic carbon (OC) were calculated for the HDV and the LDV fleet. We found that HDVs emitted more PM[subscript 2.5] than LDVs, with OC EFs of 108 and 523 mg kg-1 burned fuel for LDVs and HDVs, respectively. More than 700 ions were identified by TD-PTR-MS and the EF profiles obtained from HDVs and LDVs exhibited distinct features. Unique organic tracers for gasoline, biodiesel, and tire wear have been tentatively identified. nitrogen-containing compounds contributed around 20 % to the EF values for both types of vehicles, possibly associated with incomplete fuel burning or fast secondary production. Additionally, 70 and 65 % of the emitted mass (i.e. the OA) originates from oxygenated compounds from LDVs and HDVs, respectively. This may be a consequence of the high oxygen content of the fuel. On the other hand, additional oxygenation may occur during fuel combustion. The high fractions of nitrogen- and oxygen-containing compounds show that chemical processing close to the engine / tailpipe region is an important factor influencing primary OA emission. The thermal-desorption analysis showed that HDVs emitted compounds with higher volatility, and with mainly oxygenated and longer chain hydrocarbons than LDVs.

Date Created
2016-11-18
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SILVER NANOPARTICLES: SYNTHESIS, SOLUBILITY, AND LEACHING OF COMMERCIAL PRODUCTS

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Description
In recent years, products advertised to contain nanosilver have become increasingly popular; however, while companies often advertise for nanosilver products, little regulation occurs to verify that these products actually contain silver nanoparticles. Furthermore, there currently exists much dispute regarding the

In recent years, products advertised to contain nanosilver have become increasingly popular; however, while companies often advertise for nanosilver products, little regulation occurs to verify that these products actually contain silver nanoparticles. Furthermore, there currently exists much dispute regarding the safety and toxicity of silver nanoparticles. As more and more products incorporate nanosilver, the resolution of this dispute proves progressively important. The present study addressed these issues, with goals to synthesize silver nanoparticles, determine the solubility of the synthesized silver nanoparticles, and to evaluate leaching of nanosilver from commercially produced food storage containers. The silver nanoparticles were synthesized by a procedure devised by Leopold and Lendl, and subsequently evaluated for size and distribution by ICP-MS (Inductively Coupled Plasma Mass Spectrometry), SEC (Size Exclusion Chromatography), and DLS (Dynamic Light Scattering). The results indicated an average particle size of approximately 85 nm and a relatively monodispersed solution with a polydispersity value of 0.1245. The solubility of the nanoparticles was then examined using a dialysis experiment; however, the results of the dialysis experiments were inconclusive due to an aggregation that occurred which prevented the silver from diffusing out of the dialysis tubing. Lastly, commercially produced food storage containers advertised to contain silver nanoparticles were examined. These containers were digested using microwave assisted digestion, and subsequently analyzed using ICP-MS. It was determined that the containers contained between 7 .5 and 27 ug of silver per gram of container, and that the silver was not distributed uniformly throughout the container. While ICP-MS indicated the presence of silver, SEM (Scanning Electron Microscopy) failed to unambiguously identify silver nanoparticles in the container. The food storage containers were also examined for silver leaching under various conditions; it was found that the containers leached most greatly following exposure to an acidic solution and leached the least due to exposure to UV light. However, additional trials of the leaching experiments must be performed to validate the results obtained in these experiments.
Date Created
2012-05
Agent

The Possible Photochemical Origins of Banded Iron Formations

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Description
Banded iron formations (BIFs) are among the earliest possible indicators for oxidation of the Archean biosphere. However, the origin of BIFs remains debated. Proposed formation mechanisms include oxidation of Fe(II) by O2 (Cloud, 1973), photoferrotrophy (Konhauser et al., 2002), and

Banded iron formations (BIFs) are among the earliest possible indicators for oxidation of the Archean biosphere. However, the origin of BIFs remains debated. Proposed formation mechanisms include oxidation of Fe(II) by O2 (Cloud, 1973), photoferrotrophy (Konhauser et al., 2002), and abiotic UV photooxidation (Braterman et al., 1983; Konhauser et al., 2007). Resolving this debate could help determine whether BIFs are really indicators of O2, biological activity, or neither.

To examine the viability of abiotic UV photooxidation of Fe, laboratory experiments were conducted in which Fe-bearing solutions were irradiated with different regions of the ultraviolet (UV) spectrum and Fe oxidation and precipitation were measured. The goal was to revisit previous experiments that obtained conflicting results, and extend these experiments by using a realistic bicarbonate buffered solution and a xenon (Xe) lamp to better match the solar spectrum and light intensity.

In experiments reexamining previous work, Fe photooxidation and precipitation was observed. Using a series of wavelength cut-off filters, the reaction was determined not to be caused by light > 345 nm. Experiments using a bicarbonate buffered solution, simulating natural waters, and using unbuffered solutions, as in prior work showed the same wavelength sensitivity. In an experiment with a Xe lamp and realistic concentrations of Archean [Fe(II)], Fe precipitation was observed in hours, demonstrating the ability for photooxidation to occur significantly in a simulated natural setting.

These results lead to modeled Fe photooxidation rates of 25 mg Fe cm-2 yr-1—near the low end of published BIF deposition rates, which range from 9 mg Fe cm-2 yr-1 to as high as 254 mg Fe cm-2 yr-1 (Konhauser et al., 2002; Trendall and Blockley, 1970). Because the rates are on the edge and the model has unquantified, favorable assumptions, these results suggest that photooxidation could contribute to, but might not be completely responsible for, large rapidly deposited BIFs such those in the Hamersley Basin. Further work is needed to improve the model and test photooxidation with other solution components. Though possibly unable to fully explain BIFs, UV light has significant oxidizing power, so the importance of photooxidation in the Archean as an environmental process and its impact on paleoredox proxies need to be determined.
Date Created
2017
Agent

Physical-Chemical Characterisation of the Particulate Matter Inside Two Road Tunnels in the São Paulo Metropolitan Area

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Description

The notable increase in biofuel usage by the road transportation sector in Brazil during recent years has significantly altered the vehicular fuel composition. Consequently, many uncertainties are currently found in particulate matter vehicular emission profiles. In an effort to better

The notable increase in biofuel usage by the road transportation sector in Brazil during recent years has significantly altered the vehicular fuel composition. Consequently, many uncertainties are currently found in particulate matter vehicular emission profiles. In an effort to better characterise the emitted particulate matter, measurements of aerosol physical and chemical properties were undertaken inside two tunnels located in the São Paulo Metropolitan Area (SPMA). The tunnels show very distinct fleet profiles: in the Jânio Quadros (JQ) tunnel, the vast majority of the circulating fleet are light duty vehicles (LDVs), fuelled on average with the same amount of ethanol as gasoline. In the Rodoanel (RA) tunnel, the particulate emission is dominated by heavy duty vehicles (HDVs) fuelled with diesel (5% biodiesel). In the JQ tunnel, PM2.5 concentration was on average 52 μg m-3, with the largest contribution of organic mass (OM, 42%), followed by elemental carbon (EC, 17%) and crustal elements (13%). Sulphate accounted for 7% of PM2.5 and the sum of other trace elements was 10%. In the RA tunnel, PM2.5 was on average 233 μg m-3, mostly composed of EC (52%) and OM (39%). Sulphate, crustal and the trace elements showed a minor contribution with 5%, 1%, and 1%, respectively. The average OC : EC ratio in the JQ tunnel was 1.59 ± 0.09, indicating an important contribution of EC despite the high ethanol fraction in the fuel composition. In the RA tunnel, the OC : EC ratio was 0.49 ± 0.12, consistent with previous measurements of diesel-fuelled HDVs. Besides bulk carbonaceous aerosol measurement, polycyclic aromatic hydrocarbons (PAHs) were quantified. The sum of the PAHs concentration was 56 ± 5 ng m-3 and 45 ± 9 ng m-3 in the RA and JQ tunnel, respectively. In the JQ tunnel, benzo(a)pyrene (BaP) ranged from 0.9 to 6.7 ng m-3 (0.02–0.1‰ of PM2.5)] whereas in the RA tunnel BaP ranged from 0.9 to 4.9 ng m-3 (0.004–0. 02‰ of PM2.5), indicating an important relative contribution of LDVs emission to atmospheric BaP.

Date Created
2013-12-17
Agent

Organic Composition and Source Apportionment of Fine Aerosol at Monterrey, Mexico, Based on Organic Markers

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Description

Primary emissions from anthropogenic and biogenic sources as well as secondary formation are responsible for the pollution levels of ambient air in major urban areas. These sources release fine particles into the air that negatively impact human health and the

Primary emissions from anthropogenic and biogenic sources as well as secondary formation are responsible for the pollution levels of ambient air in major urban areas. These sources release fine particles into the air that negatively impact human health and the environment. Organic molecular markers, which are compounds that are unique to specific PM2.5 sources, can be utilized to identify the major emission sources in urban areas. In this study, 43 representative PM2.5 samples, for both daytime and nighttime periods, were built from individual samples collected in an urban site of the Monterrey metropolitan area (MMA) during the spring and fall of 2011 and 2012. The samples were analyzed for organic carbon, elemental carbon, and organic molecular markers. Several diagnostic tools were employed for the preliminary identification of emission sources. Organic compounds for eight compound classes were quantified. The n-alkanoic acids were the most abundant, followed by n-alkanes, wood smoke markers, and levoglucosan/alkenoic acids. Polycyclic aromatic hydrocarbons (PAHs) and hopanes were less abundant. The carbon preference index (0.7–2.6) for n-alkanes indicates a major contribution of anthropogenic and mixed sources during the fall and the spring, respectively. Hopanes levels confirmed the contribution from gasoline and diesel engines. In addition, the contribution of gasoline and diesel vehicle exhaust was confirmed and identified by the PAH concentrations in PM2.5. Diagnostic ratios of PAHs showed emissions from burning coal, wood, biomass, and other fossil fuels. The total PAHs and elemental carbon were correlated (r2 =  0.39–0.70) across the monitoring periods, reinforcing that motor vehicles are the major contributors of PAHs. Cholesterol levels remained constant during the spring and fall, showing evidence of the contribution of meat-cooking operations, while the isolated concentrations of levoglucosan suggested occasional biomass burning events. Finally, source attribution results obtained using the CMB (chemical mass balance) model indicate that emissions from motor vehicle exhausts are the most important, accounting for the 64 % of the PM2.5, followed by meat-cooking operations with 31 % The vegetative detritus and biomass burning had the smallest contribution (2.2 % of the PM2.5). To our knowledge, this is only the second study to explore the organic composition and source apportionment of fine organic aerosol based on molecular markers in Mexico and the first for the MMA. Particularly molecular marker were quantified by solvent extraction with dichloromethane, derivatization, and gas chromatography with mass spectrometry (GC/MS).

Date Created
2016-01-26
Agent

Black Carbon Concentrations and Sources in the Marine Boundary Layer of the Tropical Atlantic Ocean Using Four Methodologies

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Description

Combustion-derived aerosols in the marine boundary layer have been poorly studied, especially in remote environments such as the open Atlantic Ocean. The tropical Atlantic has the potential to contain a high concentration of aerosols, such as black carbon, due to

Combustion-derived aerosols in the marine boundary layer have been poorly studied, especially in remote environments such as the open Atlantic Ocean. The tropical Atlantic has the potential to contain a high concentration of aerosols, such as black carbon, due to the African emission plume of biomass and agricultural burning products. Atmospheric particulate matter samples across the tropical Atlantic boundary layer were collected in the summer of 2010 during the southern hemispheric dry season when open fire events were frequent in Africa and South America. The highest black carbon concentrations were detected in the Caribbean Sea and within the African plume, with a regional average of 0.6 μg m-3 for both. The lowest average concentrations were measured off the coast of South America at 0.2 to 0.3 μg m-3. Samples were quantified for black carbon using multiple methods to provide insights into the form and stability of the carbonaceous aerosols (i.e., thermally unstable organic carbon, soot like, and charcoal like). Soot-like aerosols composed up to 45% of the carbonaceous aerosols in the Caribbean Sea to as little as 4% within the African plume. Charcoal-like aerosols composed up to 29% of the carbonaceous aerosols over the oligotrophic Sargasso Sea, suggesting that non-soot-like particles could be present in significant concentrations in remote environments. To better apportion concentrations and forms of black carbon, multiple detection methods should be used, particularly in regions impacted by biomass burning emissions.

Date Created
2014-07-18
Agent

Nanoporous transparent conducting oxides and new solid acid catalysts

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Description
New sol-gel routes were developed to fabricate transparent conducting oxide coatings for energy applications. Sol-gel synthesis was chosen because the metal oxide products have high surface area and porosity. Titanium sol-gel chemistry was the main focus of the

New sol-gel routes were developed to fabricate transparent conducting oxide coatings for energy applications. Sol-gel synthesis was chosen because the metal oxide products have high surface area and porosity. Titanium sol-gel chemistry was the main focus of the studies, and the synthesis of macroporous antimony-doped tin oxide was also explored. The surface chemistry and band characteristics of anatase TiO2 show promise for solar energy purposes as photoelectrodes in DSSCs and as photocatalysts to degrade organic dyes and to split water. Modifying the band structure by increasing the conduction band edge energy is specifically of interest for reducing protons in water. To this end, a new sol-gel method was developed for incorporating Zr-dopant in nanoporous anatase TiO2. The products follow Vegard’s law up to 20 atom%, exhibiting surface area of 79 m2/g and pore volume of 0.20 cm3/g with average pore diameter of 10.3 nm; the conduction band edge energy increased by 0.22 eV and the band gap increased by 0.1 eV.

In pursuit of a greener sol-gel route for TiO2 materials, a solution of TiOSO4 in water was explored. Success in obtaining a gel came by utilizing hydrogen peroxide as a ligand that suppressed precipitation reactions. Through modifying this sol-gel chemistry to obtain a solid acid, the new material hydrogen titanium phosphate sulfate, H1-xTi2(PO4)3-x(SO4)x, (0 < x < 0.5) was synthesized and characterized for the first time. From the reported synthetic route, this compound took the form of macroscopic agglomerates of nanoporous aggregates of nanoparticles around 20 nm and the product calcined at 600 °C exhibited surface area of 78 m2/g, pore volume of 0.22 cm3/g and an average pore width of 11 nm. This solid acid exhibits complete selectivity for the non-oxidative dehydrogenation of methanol to formaldehyde and hydrogen gas, with >50% conversion at 300 °C.

Finally, hierarchically meso-macroporous antimony doped tin oxide was synthesized with regular macropore size around 210 nm, determined by statistical dye trajectory tracking, and also with larger pores up to micrometers in size. The structure consisted of nanoparticles around 4 nm in size, with textural mesopores around 20 nm in diameter.
Date Created
2016
Agent

Polycyclic aromatic hydrocarbon (PAH) redistribution in extreme dust storms and processing in clouds

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Description
Dust storms known as 'haboobs' occur in the City of Tempe, AZ during the North American monsoon season. A haboob classification method based on meteorological and air quality measurements is described. There were from 3 to 20 haboob events per

Dust storms known as 'haboobs' occur in the City of Tempe, AZ during the North American monsoon season. A haboob classification method based on meteorological and air quality measurements is described. There were from 3 to 20 haboob events per year over the period from 2005 to 2014. The calculated annual TSP (total suspended particulate) dry deposition during haboobs is estimated to contribute 74% of the total particulate mass deposited in Tempe, AZ.

Dry deposition is compared with the aqueous chemistry of Tempe Town Lake. Water management and other factors may have a stronger impact on Tempe Town Lake chemistry than haboob dry-deposition. Haboobs alter the Polycyclic Aromatic Hydrocarbon (PAH) concentrations and distributions in Tempe, AZ. PAH isomer ratios suggest PM2.5 (particulate matter with aerodynamic diameters less than or equal to 2.5 μm) sources consistent with approximate thunderstorm outflow paths.

The importance of the atmospheric aqueous phase, fogs and clouds, for the processing and removal of PAHs is not well known. A multiphase model was developed to determine the fate and lifetime of PAHs in fogs and clouds. The model employed literature values that describe the partitioning between three phases (aqueous, liquid organic, and gas), in situ PAH measurements, and experimental and estimated (photo)oxidation rates. At 25 °C, PAHs with two, three and four rings were predicted to be primarily gas phase (fraction in the gas phase xg > 90 %) while five- and six-ring PAHs partitioned significantly into droplets (xg < 60 %) with aqueous phase fractions of 1 to 6 % and liquid organic phase fractions of 31 to 91 %. The predicted atmospheric lifetimes of PAHs in the presence of fog or cloud droplets (< 5 hours) were significantly shorter than literature predictions of PAH wet and dry deposition lifetimes (1 to 14 days and 5 to 15 months respectively) and shorter than or equal to predicted PAH gas phase / particle phase atmospheric lifetimes (1 to 300 hours). The aqueous phase cannot be neglected as a PAH sink due to the large aqueous volume (vs. organic volume) and the relatively fast aqueous reactions.
Date Created
2016
Agent

Investigations into the occurrence, formation and fate of N-nitrosodimethylamine (NDMA) in air and water

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Description
N-Nitrosodimethylamine (NDMA), a probable human carcinogen, has been found in clouds and fogs at concentration up to 500 ng/L and in drinking water as disinfection by-product. NDMA exposure to the general public is not well understood because of knowledge gaps

N-Nitrosodimethylamine (NDMA), a probable human carcinogen, has been found in clouds and fogs at concentration up to 500 ng/L and in drinking water as disinfection by-product. NDMA exposure to the general public is not well understood because of knowledge gaps in terms of occurrence, formation and fate both in air and water. The goal of this dissertation was to contribute to closing these knowledge gaps on potential human NDMA exposure through contributions to atmospheric measurements and fate as well as aqueous formation processes.

Novel, sensitive methods of measuring NDMA in air were developed based on Solid Phase Extraction (SPE) and Solid Phase Microextraction (SPME) coupled to Gas Chromatography-Mass Spectrometry (GC-MS). The two measuring techniques were evaluated in laboratory experiments. SPE-GC-MS was applicable in ambient air sampling and NDMA in ambient air was found in the 0.1-13.0 ng/m3 range.

NDMA photolysis, the main degradation atmospheric pathway, was studied in the atmospheric aqueous phase. Water soluble organic carbon (WSOC) was found to have more impact than inorganic species on NDMA photolysis by competing with NDMA for photons and therefore could substantially increase the NDMA lifetime in the atmosphere. The optical properties of atmospheric WSOC were investigated in aerosol, fog and cloud samples and showed WSOC from atmospheric aerosols has a higher mass absorption efficiency (MAE) than organic matter in fog and cloud water, resulting from a different composition, especially in regards of volatile species, that are not very absorbing but abundant in fogs and clouds.

NDMA formation kinetics during chloramination were studied in aqueous samples including wastewater, surface water and ground water, at two monochloramine concentrations. A simple second order NDMA formation model was developed using measured NDMA and monochloramine concentrations at select reaction times. The model fitted the NDMA formation well (R2 >0.88) in all water matrices. The proposed model was then optimized and applied to fit the data of NDMA formation from natural organic matter (NOM) and model precursors in previously studies. By determining the rate constants, the model was able to describe the effect of water conditions such as DOC and pH on NDMA formation.
Date Created
2016
Agent

Identification of N-Nitrosodimethylamine precursors to improve their control

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Description
N-nitrosodimethylamine (NDMA) is a probable human carcinogen and drinking water disinfection by-product. NDMA forms as the product of reactions between chloramines and precursor compounds in water. This dissertation aims to provide insight into the removal of NDMA precursors, their nature,

N-nitrosodimethylamine (NDMA) is a probable human carcinogen and drinking water disinfection by-product. NDMA forms as the product of reactions between chloramines and precursor compounds in water. This dissertation aims to provide insight into the removal of NDMA precursors, their nature, and a method to aid in their identification. Watershed-derived precursors accounted for more of and greater variability to NDMA formation upon chloramination than polymer-derived precursors in environmental samples. Coagulation polymers are quaternary amines, which have low NDMA yield but high use rates. Watershed-derived precursors were removed up to 90% by sorption to activated carbon, but activated carbon exhibited much less (<10%) sorption of polymer-derived precursors. Combined with literature NDMA molar yields of model anthropogenic compounds, where anthropogenic chemicals in some cases have NDMA yields >90% and biological compounds always have yields <2%, trace, organic, amine containing, anthropogenic chemicals were implicated as the most likely source of NDMA precursors in the watershed. Although activated carbon removes these precursors well, identification of individual compounds may result in more cost effective mitigation strategies. Therefore, I developed a method to isolate NDMA precursors from other organic matter into methanol to facilitate their identification. Optimization of the method resulted in a median recovery of NDMA precursors of 82% from 10 surface waters and one wastewater. The method produces 1,000X concentrated NDMA precursors and, in collaboration with the University of Colorado Center for Environmental Mass Spectrometry, time of flight mass spectrometry (TOF-MS) was performed on multiple treated wastewater and raw drinking water isolates. During TOF-MS, tertiary amines can cleave to form a neutral loss and an R group ion that is dependent on the original structure and I wrote a software program to “trawl” exported TOF-MS spectra for the diagnostic neutral loss resulting from fragmentation of tertiary amines. Methadone was identified as one new NDMA precursor that occurs at concentrations that form physiologically relevant levels of NDMA in surface water and wastewater. The approach used here to identify NDMA precursors is adaptable to other unknown disinfection by-product precursors given that a functional group is known that can 1)control sorption and 2)produce a predictable diagnostic fragment.
Date Created
2015
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