Source apportionment of organic carbon in Centreville, AL using organosulfates in organic tracer-based positive matrix factorization

Organic tracer-based positive matrix factorization (PMF) was used to apportion fine particulate (PM_(2.5)) organic carbon (OC) to its sources in Centreville, AL, USA, a rural forested site influenced by anthropogenic emissions, during the Southern Oxidant and Aerosol Study (SOAS) in the summer of 2013. Model inputs included organosulfates, a group of organic compounds that are tracers of anthropogenically-influenced biogenic secondary organic aerosols (SOA), as well as, OC, elemental carbon, water-soluble organic carbon, and other organic tracers for primary and secondary sources measured during day and night. The organic tracer-based PMF resolved eight factors that were identified as biomass burning (11%, average contribution to PM_(2.5) OC), vehicle emissions (8%), isoprene SOC formed under low-NO_x conditions (13%), isoprene SOC formed under high-NO_x conditions (11%), SOC formed by photochemical reactions (9%), oxidatively aged biogenic SOC (6%), sulfuric acid-influenced SOC (21%, that also includes isoprene and monoterpene SOC), and monoterpene SOC formed under high-NO_x conditions (21%). These results indicate that OC in Centreville during summer is mainly secondary in origin (81%). Fossil fuel combustion is the major source of NO_x, ozone, and sulfuric acid that play a key role in SOA formation in the southeastern US. Fossil fuel was found to influence 61–76% of OC through vehicle emissions and SOA formation. Together with prescribed burns, which were the major type of biomass burning during this study, the OC influenced by anthropogenic activities reached 87%. The organic tracer-based PMF results were further compared with two complementary source apportionment techniques: PMF factors resolved for submicron organic aerosols measured using aerosol mass spectrometry (AMS) by Xu et al. (2015a) in Centreville during SOAS; biomass burning organic aerosols (BBOA, 11% of OC), isoprene-derived organic aerosols (isoprene-OA, 20% of OC), more-oxidized oxygenated organic aerosols (MO-OOA, 34% of OC), and less-oxidized oxygenated organic aerosols (LO-OOA, 35% of OC); and PM_(2.5) OC apportioned by chemical-mass balance model (CMB), considering the same chemical species as this study, save for organosulfates; biomass burning (5%), diesel engines (2%), gasoline smokers (3%), vegetative detritus (1%), isoprene SOC (23%) and monoterpene SOC (34%), and other (likely biogenic secondary) sources (33%). Overall, this study indicates the primary and secondary sources resolved by the organic tracer-based PMF are in good agreement with CMB and AMS-PMF results, while the organic tracer-based PMF provides additional insight to the SOC formation pathways through the inclusion of organosulfates and other organic tracers measured during day and night

Organosulfates in Atlanta, Georgia: anthropogenic influences on biogenic secondary organic aerosol formation

Organosulfates are secondary organic aerosol (SOA) products that form from reactions of volatile organic compounds (VOC), such as isoprene, in the presence of sulfate that is primarily emitted by fossil fuel combustion. This study examines the anthropogenic influence on biogenic organosulfate formation at an urban site in Atlanta, Georgia (GA) in the southeastern United States (US). Organosulfates were analyzed in fine particulate matter (PM2.5) collected during August 2015 in Atlanta using hydrophilic interaction liquid chromatography (HILIC), tandem mass spectrometry (MS/MS), and high-resolution time-of-flight (ToF) mass spectrometry. By their MS/MS response, 32 major organosulfate species were identified, selected species were quantified, and other species were semi-quantified using surrogate standards. Organosulfates accounted for 16.5&thinsp;% of PM2.5 organic carbon (OC). Isoprene-derived organosulfates were the most abundant, dominated by methyltetrol sulfate which accounted for 12.6&thinsp;% of PM2.5 OC. Together, the isoprene-derived organosulfates accounted for the majority of the isoprene-derived SOA that had been previously observed in Atlanta, but had not been identified at the molecular level. Other major species included seven monoterpene-derived organosulfates, five diesel and/or biodiesel-derived organosulfates, and three new organosulfates that are also expected to derive from isoprene. Organosulfate species and concentrations in Atlanta were compared to those in a rural forested site in Centreville, Alabama (AL) during summer 2013, which were also dominated by isoprene-derived organosulfates. In Atlanta, isoprene-derived organosulfate concentrations were 2–6 times higher and accounted for twice as much OC. The greatest enhancement in concentration was observed for 2-methylglyceric acid sulfate whose formation is enhanced in the presence of nitrogen oxides (NO and NO2; NOx) and is a tracer for isoprene high-NOx SOA. The isoprene-derived organosulfates indicated a stronger influence of NOx in Atlanta compared to Centreville. Overall, these results suggest that SOA in the southeastern US can be reduced by controlling NOx and SO2 emissions from fossil fuel combustion. This study gives insights into the major organosulfate species that should be targets for future measurements in urban environments and standard development.</p

Response of the Aerodyne Aerosol Mass Spectrometer to Inorganic Sulfates and Organosulfur Compounds: Applications in Field and Laboratory Measurements

Organosulfur compounds are important components of secondary organic aerosols (SOA). While the Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS) has been extensively used in aerosol studies, the response of the AMS to organosulfur compounds is not well-understood. Here, we investigated the fragmentation patterns of organosulfurs and inorganic sulfates in the AMS, developed a method to deconvolve total sulfate into components of inorganic and organic origins, and applied this method in both laboratory and field measurements. Apportionment results from laboratory isoprene photooxidation experiment showed that with inorganic sulfate seed, sulfate functionality of organic origins can contribute ∼7% of SOA mass at peak growth. Results from measurements in the Southeastern U.S. showed that 4% of measured sulfate is from organosulfur compounds. Methanesulfonic acid was estimated for measurements in the coastal and remote marine boundary layer. We explored the application of this method to unit mass-resolution data, where it performed less well due to interferences. Our apportionment results demonstrate that organosulfur compounds could be a non-negligible source of sulfate fragments in AMS laboratory and field data sets. A reevaluation of previous AMS measurements over the full range of atmospheric conditions using this method could provide a global estimate/constraint on the contribution of organosulfur compounds

Source apportionment of organic carbon in Centreville, AL using organosulfates in organic tracer-based positive matrix factorization

Organic tracer-based positive matrix factorization (PMF) was used to apportion fine particulate (PM_(2.5)) organic carbon (OC) to its sources in Centreville, AL, USA, a rural forested site influenced by anthropogenic emissions, during the Southern Oxidant and Aerosol Study (SOAS) in the summer of 2013. Model inputs included organosulfates, a group of organic compounds that are tracers of anthropogenically-influenced biogenic secondary organic aerosols (SOA), as well as, OC, elemental carbon, water-soluble organic carbon, and other organic tracers for primary and secondary sources measured during day and night. The organic tracer-based PMF resolved eight factors that were identified as biomass burning (11%, average contribution to PM_(2.5) OC), vehicle emissions (8%), isoprene SOC formed under low-NO_x conditions (13%), isoprene SOC formed under high-NO_x conditions (11%), SOC formed by photochemical reactions (9%), oxidatively aged biogenic SOC (6%), sulfuric acid-influenced SOC (21%, that also includes isoprene and monoterpene SOC), and monoterpene SOC formed under high-NO_x conditions (21%). These results indicate that OC in Centreville during summer is mainly secondary in origin (81%). Fossil fuel combustion is the major source of NO_x, ozone, and sulfuric acid that play a key role in SOA formation in the southeastern US. Fossil fuel was found to influence 61–76% of OC through vehicle emissions and SOA formation. Together with prescribed burns, which were the major type of biomass burning during this study, the OC influenced by anthropogenic activities reached 87%. The organic tracer-based PMF results were further compared with two complementary source apportionment techniques: PMF factors resolved for submicron organic aerosols measured using aerosol mass spectrometry (AMS) by Xu et al. (2015a) in Centreville during SOAS; biomass burning organic aerosols (BBOA, 11% of OC), isoprene-derived organic aerosols (isoprene-OA, 20% of OC), more-oxidized oxygenated organic aerosols (MO-OOA, 34% of OC), and less-oxidized oxygenated organic aerosols (LO-OOA, 35% of OC); and PM_(2.5) OC apportioned by chemical-mass balance model (CMB), considering the same chemical species as this study, save for organosulfates; biomass burning (5%), diesel engines (2%), gasoline smokers (3%), vegetative detritus (1%), isoprene SOC (23%) and monoterpene SOC (34%), and other (likely biogenic secondary) sources (33%). Overall, this study indicates the primary and secondary sources resolved by the organic tracer-based PMF are in good agreement with CMB and AMS-PMF results, while the organic tracer-based PMF provides additional insight to the SOC formation pathways through the inclusion of organosulfates and other organic tracers measured during day and night

Response of the Aerodyne Aerosol Mass Spectrometer to Inorganic Sulfates and Organosulfur Compounds: Applications in Field and Laboratory Measurements

Organosulfur compounds are important components of secondary organic aerosols (SOA). While the Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS) has been extensively used in aerosol studies, the response of the AMS to organosulfur compounds is not well-understood. Here, we investigated the fragmentation patterns of organosulfurs and inorganic sulfates in the AMS, developed a method to deconvolve total sulfate into components of inorganic and organic origins, and applied this method in both laboratory and field measurements. Apportionment results from laboratory isoprene photooxidation experiment showed that with inorganic sulfate seed, sulfate functionality of organic origins can contribute ∼7% of SOA mass at peak growth. Results from measurements in the Southeastern U.S. showed that 4% of measured sulfate is from organosulfur compounds. Methanesulfonic acid was estimated for measurements in the coastal and remote marine boundary layer. We explored the application of this method to unit mass-resolution data, where it performed less well due to interferences. Our apportionment results demonstrate that organosulfur compounds could be a non-negligible source of sulfate fragments in AMS laboratory and field data sets. A reevaluation of previous AMS measurements over the full range of atmospheric conditions using this method could provide a global estimate/constraint on the contribution of organosulfur compounds

Source apportionment of fine particulate matter in Houston, Texas: insights to secondary organic aerosols

Online and offline measurements of ambient particulate matter (PM) near the urban and industrial Houston Ship Channel in Houston, Texas, USA, during May 2015 were utilized to characterize its chemical composition and to evaluate the relative contributions of primary, secondary, biogenic, and anthropogenic sources. Aerosol mass spectrometry (AMS) on nonrefractory PM1 (PM  ≤  1&thinsp;µm) indicated major contributions from sulfate (averaging 50&thinsp;% by mass), organic aerosol (OA, 40&thinsp;%), and ammonium (14&thinsp;%). Positive matrix factorization (PMF) of AMS data categorized OA on average as 22&thinsp;% hydrocarbon-like organic aerosol (HOA), 29&thinsp;% cooking-influenced less-oxidized oxygenated organic aerosol (CI-LO-OOA), and 48&thinsp;% more-oxidized oxygenated organic aerosol (MO-OOA), with the latter two sources indicative of secondary organic aerosol (SOA). Chemical analysis of PM2.5 (PM  ≤  2.5&thinsp;µm) filter samples agreed that organic matter (35&thinsp;%) and sulfate (21&thinsp;%) were the most abundant components. Organic speciation of PM2.5 organic carbon (OC) focused on molecular markers of primary sources and SOA tracers derived from biogenic and anthropogenic volatile organic compounds (VOCs). The sources of PM2.5 OC were estimated using molecular marker-based positive matric factorization (MM-PMF) and chemical mass balance (CMB) models. MM-PMF resolved nine factors that were identified as diesel engines (11.5&thinsp;%), gasoline engines (24.3&thinsp;%), nontailpipe vehicle emissions (11.1&thinsp;%), ship emissions (2.2&thinsp;%), cooking (1.0&thinsp;%), biomass burning (BB, 10.6&thinsp;%), isoprene SOA (11.0&thinsp;%), high-NOx anthropogenic SOA (6.6&thinsp;%), and low-NOx anthropogenic SOA (21.7&thinsp;%). Using available source profiles, CMB apportioned 41&thinsp;% of OC to primary fossil sources (gasoline engines, diesel engines, and ship emissions), 5&thinsp;% to BB, 15&thinsp;% to SOA (including 7.4&thinsp;% biogenic and 7.6&thinsp;% anthropogenic), and 39&thinsp;% to other sources that were not included in the model and are expected to be secondary.This study presents the first application of in situ AMS-PMF, MM-PMF, and CMB for OC source apportionment and the integration of these methods to evaluate the relative roles of biogenic, anthropogenic, and BB-SOA. The three source apportionment models agreed that  ∼ &thinsp;50&thinsp;% of OC is associated with primary emissions from fossil fuel use, particularly motor vehicles. Differences among the models reflect their ability to resolve sources based upon the input chemical measurements, with molecular marker-based methods providing greater source specificity and resolution for minor sources. By combining results from MM-PMF and CMB, BB was estimated to contribute 11&thinsp;% of OC, with 5&thinsp;% primary emissions and 6&thinsp;% BB-SOA. SOA was dominantly anthropogenic (28&thinsp;%) rather than biogenic (11&thinsp;%) or BB-derived. The three-model approach demonstrates significant contributions of anthropogenic SOA to fine PM. More broadly, the findings and methodologies presented herein can be used to advance local and regional understanding of anthropogenic contributions to SOA.</p

Shared decision-making, teacher morale, and pupil performance in public schools

The school-based management/shared decision-making strategy is important for schools in general. It enables teachers to be more responsive to the needs of the students by giving them the authority to use the resources, space and time, and personnel to enhance student learning. It is even more important in schools serving urban disadvantaged communities where the needs of the children are more acute.^ Teachers in urban schools are defeated by the large bureaucracy, the feeling of powerlessness, in the face of urban decay and crimes. The school-based managed/shared decision-making strategy gives teachers a sense of empowerment, control, autonomy, and efficacy. When the teachers have greater control over the parameters of their jobs, they would be more responsive to the needs of the children. If urban schools and teachers serving children coming from disadvantaged families are to be accountable for results, they should share in making decisions about how the school will operate. Hence pupil performance, attendance, and teacher morale will improve.^ This study examined the degree to which school-based management/shared decision-making programs became a strategy for guiding school improvement. There were many general studies conducted nationally to investigate the effectiveness of schools of the school-based management/ shared decision-making strategy in educating our student population. This general focus was narrowed down to investigate whether the school-based management/shared decision-making strategy was as effective, when implemented, in school districts where the majority of the minority children come from poor families on welfare.^ Teacher involvement in shared decision making was measured by making use of the TIPS 2 and teacher morale was measured by the Purdue Teacher Opinionaire. Student performance was measured by Reading, Math scores, and Attendance.(UNFORMATTED TABLE OR EQUATION FOLLOWS)\vbox{\halign{#\hfil&&\quad#\hfil\cr&Design:\cr\cr &Teacher &Teacher &School and\cr &Involvement&&\cr &Shared & &Pupil\cr &Decision Making\quad$\longrightarrow$ &Morale\quad$\longrightarrow$ &Performance\cr}}(TABLE/EQUATION ENDS)The academic performance of students who attended schools where teachers participated in shared decision making positively improved. The morale of teachers who work in these schools improved, and a positive relationship between the degree of participation in shared decision making and morale of teachers was found.

Shared Decision Making, Teacher Morale, and Pupil Performance in Public Schools

Abstract not availabl

Formation of Secondary Brown Carbon in Biomass Burning Aerosol Proxies through NO3 Radical Reactions.

Atmospheric brown carbon (BrC) is an important contributor to the radiative forcing of climate by organic aerosols. Because of the molecular diversity of BrC compounds and their dynamic transformations, it is challenging to predictively understand BrC optical properties. OH radical and O-3 reactions, together with photolysis, lead to diminished light absorption and lower warming effects of biomass burning BrC. The effects of night-time aging on the optical properties of BrC aerosols are less known. To address this knowledge gap, night-time NO3 radical chemistry with tar aerosols from wood pyrolysis was investigated in a flow reactor. This study shows that the optical properties of BrC change because of transformations driven by reactions with the NO3 radical that form new absorbing species and lead to significant absorption enhancement over the ultraviolet-visible (UV-vis) range. The overnight aging increases the mass absorption coefficients of the BrC by a factor of 1.3-3.2 between 380 nm and 650 nm. Nitrated organic compounds, particularly nitroaromatics, were identified as the main products that contribute to the enhanced light absorption in the secondary BrC. Night-time aging of BrC aerosols represents an important source of secondary BrC and can have a pronounced effect on atmospheric chemistry and air pollution