Marine Submicron Aerosols from the Gulf of Mexico: Polluted and Acidic with Rapid Production of Sulfate and Organosulfates.

We measured submicron aerosols (PM1) at a beachfront site in Texas in Spring 2021 to characterize the "background" aerosol chemical composition advecting into Texas and the factors controlling this composition. Observations show that marine "background" aerosols from the Gulf of Mexico were highly processed and acidic; sulfate was the most abundant component (on average 57% of total PM1 mass), followed by organic material (26%). These chemical characteristics are similar to those observed at other marine locations globally. However, Gulf "background" aerosols were much more polluted; the average non-refractory (NR-) PM1 mass concentration was 3-70 times higher than that observed in other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico explain 78.3% of the total measured "background" sulfate in the Gulf air. We frequently observed haze pollution in the air mass from the Gulf, with significantly elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid. Analysis suggests that aqueous oxidation of shipping emissions over the Gulf of Mexico by peroxides in the particles might potentially be an important pathway for the rapid production of acidic sulfate and organosulfates during the haze episodes under acidic conditions.

Large historical growth in global terrestrial gross primary production.

Growth in terrestrial gross primary production (GPP)-the amount of carbon dioxide that is 'fixed' into organic material through the photosynthesis of land plants-may provide a negative feedback for climate change. It remains uncertain, however, to what extent biogeochemical processes can suppress global GPP growth. As a consequence, modelling estimates of terrestrial carbon storage, and of feedbacks between the carbon cycle and climate, remain poorly constrained. Here we present a global, measurement-based estimate of GPP growth during the twentieth century that is based on long-term atmospheric carbonyl sulfide (COS) records, derived from ice-core, firn and ambient air samples. We interpret these records using a model that simulates changes in COS concentration according to changes in its sources and sinks-including a large sink that is related to GPP. We find that the observation-based COS record is most consistent with simulations of climate and the carbon cycle that assume large GPP growth during the twentieth century (31% ± 5% growth; mean ± 95% confidence interval). Although this COS analysis does not directly constrain models of future GPP growth, it does provide a global-scale benchmark for historical carbon-cycle simulations.

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H2O2 Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze.

Particulate sulfate is one of the most important components in the atmosphere. The observation of rapid sulfate aerosol production during haze events provoked scientific interest in the multiphase oxidation of SO2 in aqueous aerosol particles. Diverse oxidation pathways can be enhanced or suppressed under different aerosol acidity levels and high ionic strength conditions of atmospheric aerosol. The importance of ionic strength to sulfate multiphase chemistry has been verified under laboratory conditions, though studies in the actual atmosphere are still limited. By utilizing online observations and developing an improved solute strength-dependent chemical thermodynamics and kinetics model (EF-T&K model, EF is the enhancement factor that represents the effect of ionic strength on an aerosol aqueous-phase reaction), we provided quantitative evidence that the H2O2 pathway was enhanced nearly 100 times and dominated sulfate formation for entire years (66%) in Tianjin (a northern city in China). TMI (oxygen catalyzed by transition-metal ions) (14%) and NO2 (14%) pathways got the second-highest contributions. Machine learning supported the result that aerosol sulfate production was more affected by the H2O2 pathway. The collaborative effects of atmospheric oxidants and SO2 on sulfate aerosol production were further investigated using the improved EF-T&K model. Our findings highlight the effectiveness of adopting target oxidant control as a new direction for sustainable mitigation of sulfate, given the already low SO2 concentrations in China.

Persistent sulfate formation from London Fog to Chinese haze.

Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.

Carbonyl sulfide (COS) and carbon disulfide (CS2) exchange fluxes between cotton fields and the atmosphere in the arid area in Xinjiang, China.

Due to the important roles of carbonyl sulfide (COS) and carbon disulfide (CS2) in atmospheric chemistry, this study was designed to determine different proportions of COS and CS2 fluxes contributed from different sources, i.e., vegetation, soil and roots, at monthly and hourly timescales in the arid area in Xinjiang, China. Results indicated that the seasonal net uptake of COS by vegetation was predominant in the growing season. The CS2 fluxes from vegetation and soils had no significant seasonal variations compared with COS. The exchange rates of COS and CS2 have been found to be stimulated by the addition of nutrients in the form of urea fertilizer. Compared with the results of plots that were treated only with nitrogen, the treatments with both nitrogen and sulfur displayed no significant difference in the exchange fluxes. The results of compartment experiments indicated that the aboveground plants had the highest uptake of COS and had a vital role in the uptake of COS during the main growth period. The shares of COS emissions from the soil and roots increased to 6-17% and 55-58%, respectively, in the total COS fluxes when conditions, such as drought and senescence, were unfavorable for the developmental of vegetation. Observations of the preliminary diurnal fluxes indicated that the fluxes that occurred at night, with contributions from soils and plants, accounted for 27% of the total daily uptake of COS uptake. These quantitative results may be reasonably accounted for the use of COS as a promising tracer to obtain independent constraints on terrestrial carbon exchange at regional to global scales for their response to special environmental conditions in semiarid area.

Physical, chemical and biological behaviour of fumigants on cottonseed.

Fumigation is required to protect cottonseed in storage and pre-shipment from insect pests and/or microorganisms. Fumigation of cottonseed with carbon disulphide (CS2), carbonyl sulphide (COS), ethanedinitrile (C2N2), ethyl formate (EF), methyl bromide (MB) and phosphine (PH3) showed that >85% of the fumigants disappeared within 5 h of exposure. COS maintained >20 mg L-1 for 24 h. After 1 day of aeration, 75%-85% of the absorbed COS and MB and 20%-40% of the absorbed CS2, EF and PH3 were released from treated cottonseed. The fumigant residues were reduced by 80% for COS, 50% for EF or MB and 25% for CS2 after 1 day of aeration. After 13 days of aeration, fumigant residues were reduced by 95% for MB, 65% for EF, 55% for CS2 and to natural levels in the COS residue. Carbon disulphide, COS, PH3, EF and C2N2 had no effect on the germination of cottonseed, but germination was reduced to 50% by MB. COS has potential as a fumigant for control of insect pests in cottonseed because it dissipates quickly and does not negatively impact germination. On the other hand, MB appears to strongly absorb and requires an extended period for residues to dissipate, and it negatively impacts germination.

Evaluation of sulfur trioxide detection with online isopropanol absorption method.

Measurement of the SO3 concentration in flue gas is important to estimate the acid dew point and to control corrosion of downstream equipment. SO3 measurement is a difficult question since SO3 is a highly reactive gas, and its concentration is generally two orders of magnitude lower than the SO2 concentration. The SO3 concentration can be measured online by the isopropanol absorption method; however, the reliability of the test results is relatively low. This work aims to find the error sources and to evaluate the extent of influence of each factor on the measurement results. The test results from a SO3 analyzer showed that the measuring errors are mainly caused by the gas-liquid flow ratio, SO2 oxidation, and the side reactions of SO3. The error in the gas sampling rate is generally less than 13%. The isopropanol solution flow rate decreases 3% to 30% due to the volatilization of isopropanol, and accordingly, this will increase the apparent SO3 concentration. The amount of SO2 oxidation is linearly related to the SO2 concentration. The side reactions of SO3 reduce the selectivity of SO42- to nearly 73%. As sampling temperature increases from 180 to 300°C, the selectivity of SO42- decreases from 73% to 50%. The presence of H2O in the sample gas helps to reduce the measurement error by inhibiting the volatilization of the isopropanol and weakening side reactions. A formula was established to modify the displayed value, and the measurement error was reduced from 25%-54% to less than 15%.

Pollutants identification of ambient aerosols by two types of aerosol mass spectrometers over southeast coastal area, China.

Two different aerosol mass spectrometers, Aerodyne Aerosol Mass Spectrometer (AMS) and Single Particle Aerosol Mass Spectrometer (SPAMS) were deployed to identify the aerosol pollutants over Xiamen, representing the coastal urban area. Five obvious processes were classified during the whole observation period. Organics and sulfate were the dominant components in ambient aerosols over Xiamen. Most of the particles were in the size range of 0.2-1.0µm, accounting for over 97% of the total particles measured by both instruments. Organics, as well as sulfate, measured by AMS were in good correlation with measured by SPAMS. However, high concentration of NH4+ was obtained by AMS, while extremely low value of NH4+ was detected by SPAMS. Contrarily, high particle number counts of NO3- and Cl- were given by SPAMS while low concentrations of NO3- and Cl- were measured by AMS. The variations of POA and SOA obtained from SPAMS during event 1 and event 2 were in accordance with the analysis of HOA and OOA given by AMS, suggesting that both of AMS and SPAMS can well identify the organic clusters of aerosol particles. Overestimate or underestimate of the aerosol sources and acidity would be present in some circumstances when the measurement results were used to analyze the aerosol properties, because of the detection loss of some species for both instruments.

A ratiometric fluorogenic probe for the real-time detection of SO32- in aqueous medium: application in a cellulose paper based device and potential to sense SO32- in mitochondria.

A new water soluble and fluorogenic probe (L) that can demonstrate a specific ratiometric detection of a SO2 derivative (SO32-) in 100% aqueous medium and live cells has been designed and synthesized. The detection process can be visualized by the naked eye, as the orange-red fluorescence of L turns into a strong blue fluorescence upon interaction with SO32-. L displayed several beneficial attributes such as detection in complete aqueous medium, extremely fast response time along with high selectivity and sensitivity. The ratiometric sensing was attributed to the selective nucleophilic addition reaction of SO32- with L. The probe was further used to develop a low cost microfluidic sensor device (µPAD). The probe was biocompatible and its potential to sense SO32- in mitochondria was captured in live HeLa cells.

Self-Immolative Thiocarbamates Provide Access to Triggered H2S Donors and Analyte Replacement Fluorescent Probes.

Hydrogen sulfide (H2S) is an important biological signaling molecule, and chemical tools for H2S delivery and detection have emerged as important investigative methods. Key challenges in these fields include developing donors that are triggered to release H2S in response to stimuli and developing probes that do not irreversibly consume H2S. Here we report a new strategy for H2S donation based on self-immolation of benzyl thiocarbamates to release carbonyl sulfide, which is rapidly converted to H2S by carbonic anhydrase. We leverage this chemistry to develop easily modifiable donors that can be triggered to release H2S. We also demonstrate that this approach can be coupled with common H2S-sensing motifs to generate scaffolds which, upon reaction with H2S, generate a fluorescence response and also release caged H2S, thus addressing challenges of analyte homeostasis in reaction-based probes.

Organic Chemical Attribution Signatures for the Sourcing of a Mustard Agent and Its Starting Materials.

Chemical attribution signatures (CAS) are being investigated for the sourcing of chemical warfare (CW) agents and their starting materials that may be implicated in chemical attacks or CW proliferation. The work reported here demonstrates for the first time trace impurities from the synthesis of tris(2-chloroethyl)amine (HN3) that point to the reagent and the specific reagent stocks used in the synthesis of this CW agent. Thirty batches of HN3 were synthesized using different combinations of commercial stocks of triethanolamine (TEA), thionyl chloride, chloroform, and acetone. The HN3 batches and reagent stocks were then analyzed for impurities by gas chromatography/mass spectrometry. All the reagent stocks had impurity profiles that differentiated them from one another. This was demonstrated by building classification models with partial least-squares discriminant analysis (PLSDA) and obtaining average stock classification errors of 2.4, 2.8, 2.8, and 11% by cross-validation for chloroform (7 stocks), thionyl chloride (3 stocks), acetone (7 stocks), and TEA (3 stocks), respectively, and 0% for a validation set of chloroform samples. In addition, some reagent impurities indicative of reagent type were found in the HN3 batches that were originally present in the reagent stocks and presumably not altered during synthesis. More intriguing, impurities in HN3 batches that were apparently produced by side reactions of impurities unique to specific TEA and chloroform stocks, and thus indicative of their use, were observed.

Application of Cavity Enhanced Absorption Spectroscopy to the Detection of Nitric Oxide, Carbonyl Sulphide, and Ethane--Breath Biomarkers of Serious Diseases.

The paper presents one of the laser absorption spectroscopy techniques as an effective tool for sensitive analysis of trace gas species in human breath. Characterization of nitric oxide, carbonyl sulphide and ethane, and the selection of their absorption lines are described. Experiments with some biomarkers showed that detection of pathogenic changes at the molecular level is possible using this technique. Thanks to cavity enhanced spectroscopy application, detection limits at the ppb-level and short measurements time (<3 s) were achieved. Absorption lines of reference samples of the selected volatile biomarkers were probed using a distributed feedback quantum cascade laser and a tunable laser system consisting of an optical parametric oscillator and difference frequency generator. Setup using the first source provided a detection limit of 30 ppb for nitric oxide and 250 ppb for carbonyl sulphide. During experiments employing a second laser, detection limits of 0.9 ppb and 0.3 ppb were obtained for carbonyl sulphide and ethane, respectively. The conducted experiments show that this type of diagnosis would significantly increase chances for effective therapy of some diseases. Additionally, it offers non-invasive and real time measurements, high sensitivity and selectivity as well as minimizing discomfort for patients. For that reason, such sensors can be used in screening for early detection of serious diseases.

Chemical composition of groundwater and relative mortality for cardiovascular diseases in the Slovak Republic.

The study deals with the analysis of relationship between chemical composition of the groundwater/drinking water and the data on relative mortality for cardiovascular diseases (ReI) in the Slovak Republic. Primary data consist of the Slovak national database of groundwater analyses (20,339 chemical analyses, 34 chemical elements/compounds) and data on ReI collected for the 10-year period (1994-2003). The chemical and health data were unified in the same form and expressed as the mean values for each of 2883 municipalities within the Slovak Republic for further analysis. Artificial neural network was used as mathematic method for model data analysis. The most significant chemical elements having influence on ReI were identified together with their limit values (maximal acceptable, minimal necessary and optimal). Based on the results of calculations, made through the neural networks, the following ten chemical elements/parameters in the groundwater were defined as the most significant for ReI: Ca + Mg (mmol l(-1)), Ca, Mg, TDS, Cl, HCO3, SO4, NO3, SiO2 and PO4. The obtained results document the highest relationship between ReI and the groundwater contents of Ca + Mg (mmol l(-1)), Ca and Mg. Following limit values were set for the most significant groundwater chemicals/parameters: Ca + Mg 4.4-7.6 mmol l(-1), Ca > 89.4 mg l(-1) and Mg 42-78.1 mg l(-1). At these concentration ranges, the relative mortality for cardiovascular diseases in the Slovak Republic reaches the lowest levels. These limit values are about twice higher in comparison with the current Slovak valid guideline values for the drinking water.

Characteristics and anthropogenic sources of carbonyl sulfide in Beijing.

Atmospheric mixing ratios of carbonyl sulfide (COS) in Beijing were intensively measured from March 2011 to June 2013. COS mixing ratios exhibited distinct seasonal variation, with a maximum average value of 849±477 pptv in winter and a minimal value of 372±115 pptv in summer. The seasonal variation of COS was mainly ascribed to the combined effects of vegetation uptake and anthropogenic emissions. Two types of significant linear correlations (R2>0.66) were found between COS and CO during the periods from May to June and from October to March, with slopes (ΔCOS/ΔCO) of 0.72 and 0.14 pptv/ppbv, respectively. Based on the emission ratios of COS/CO from various sources, the dominant anthropogenic sources of COS in Beijing were found to be vehicle tire wear in summer and coal burning in winter. The total anthropogenic emission of COS in Beijing was roughly estimated as 0.53±0.02 Gg/year based on the local CO emission inventory and the ΔCOS/ΔCO ratios.

Nitrogen oxides, sulfur trioxide, and mercury emissions during oxy-fuel fluidized bed combustion of Victorian brown coal.

This study investigates, for the first time, the NOx, N2O, SO3, and Hg emissions from combustion of a Victorian brown coal in a 10 kWth fluidized bed unit under oxy-fuel combustion conditions. Compared to air combustion, lower NOx emissions and higher N2O formation were observed in the oxy-fuel atmosphere. These NOx reduction and N2O formations were further enhanced with steam in the combustion environment. The NOx concentration level in the flue gas was within the permissible limit in coal-fired power plants in Victoria. Therefore, an additional NOx removal system will not be required using this coal. In contrast, both SO3 and gaseous mercury concentrations were considerably higher under oxy-fuel combustion compared to that in the air combustion. Around 83% of total gaseous mercury released was Hg(0), with the rest emitted as Hg(2+). Therefore, to control harmful Hg(0), a mercury removal system may need to be considered to avoid corrosion in the boiler and CO2 separation units during the oxy-fuel fluidized-bed combustion using this coal.

Development of a spectrophotometric method for on-site analysis of peroxygens during in-situ chemical oxidation applications.

Activated peroxygens are frequently used as active agents in in-situ chemical oxidation (ISCO) contaminated site remediation applications, and fast and simple quantitative analysis of these species on site is necessary. In this work, the use of a spectrophotometric method based on classic iodometric titration is studied for quantitative analysis of S2O8(2-) and H2O2. Instead of a back-titration step, the absorbance of the yellow iodide colour was measured at 352 nm in the presence of a bicarbonate buffer. A linear calibration curve was obtained from 0 to 0.1 mM for both S2O8(2-) and H2O2. By dilution, the method can be used for all concentrations typically applied in the field. Concerning pH dependence, neutral pH levels caused no significant error whereas pH levels above 8 caused a 9% and 6% deviation from the theoretical peroxygen concentrations. Furthermore, the method showed little dependence on other matrix components, and absorbance was stable (<2% change) for more than a week. Overall, the method proved to be fast and simple, which are important features for a field method.

Sulfur emission from Victorian brown coal under pyrolysis, oxy-fuel combustion and gasification conditions.

Sulfur emission from a Victorian brown coal was quantitatively determined through controlled experiments in a continuously fed drop-tube furnace under three different atmospheres: pyrolysis, oxy-fuel combustion, and carbon dioxide gasification conditions. The species measured were H(2)S, SO(2), COS, CS(2), and more importantly SO(3). The temperature (873-1273 K) and gas environment effects on the sulfur species emission were investigated. The effect of residence time on the emission of those species was also assessed under oxy-fuel condition. The emission of the sulfur species depended on the reaction environment. H(2)S, SO(2), and CS(2) are the major species during pyrolysis, oxy-fuel, and gasification. Up to 10% of coal sulfur was found to be converted to SO(3) under oxy-fuel combustion, whereas SO(3) was undetectable during pyrolysis and gasification. The trend of the experimental results was qualitatively matched by thermodynamic predictions. The residence time had little effect on the release of those species. The release of sulfur oxides, in particular both SO(2) and SO(3), is considerably high during oxy-fuel combustion even though the sulfur content in Morwell coal is only 0.80%. Therefore, for Morwell coal utilization during oxy-fuel combustion, additional sulfur removal, or polishing systems will be required in order to avoid corrosion in the boiler and in the CO(2) separation units of the CO(2) capture systems.

Carbonyl sulfide (COS) as a tracer for canopy photosynthesis, transpiration and stomatal conductance: potential and limitations.

The theoretical basis for the link between the leaf exchange of carbonyl sulfide (COS), carbon dioxide (CO(2)) and water vapour (H(2)O) and the assumptions that need to be made in order to use COS as a tracer for canopy net photosynthesis, transpiration and stomatal conductance, are reviewed. The ratios of COS to CO(2) and H(2)O deposition velocities used to this end are shown to vary with the ratio of the internal to ambient CO(2) and H(2)O mole fractions and the relative limitations by boundary layer, stomatal and internal conductance for COS. It is suggested that these deposition velocity ratios exhibit considerable variability, a finding that challenges current parameterizations, which treat these as vegetation-specific constants. COS is shown to represent a better tracer for CO(2) than H(2)O. Using COS as a tracer for stomatal conductance is hampered by our present poor understanding of the leaf internal conductance to COS. Estimating canopy level CO(2) and H(2)O fluxes requires disentangling leaf COS exchange from other ecosystem sources/sinks of COS. We conclude that future priorities for COS research should be to improve the quantitative understanding of the variability in the ratios of COS to CO(2) and H(2)O deposition velocities and the controlling factors, and to develop operational methods for disentangling ecosystem COS exchange into contributions by leaves and other sources/sinks. To this end, integrated studies, which concurrently quantify the ecosystem-scale CO(2), H(2)O and COS exchange and the corresponding component fluxes, are urgently needed.

Fate of hazardous air pollutants in oxygen-fired coal combustion with different flue gas recycling.

Experiments were performed to characterize transformation and speciation of hazardous air pollutants (HAPs), including SO(2)/SO(3), NO(x), HCl, particulate matter, mercury, and other trace elements in oxygen-firing bituminous coal with recirculation flue gas (RFG) from 1) an electrostatic precipitator outlet or 2) a wet scrubber outlet. The experimental results showed that oxycombustion with RFG generated a flue gas with less volume and containing HAPs at higher levels, while the actual emissions of HAPs per unit of energy produced were much less than that of air-blown combustion. NO(x) reduction was achieved in oxycombustion because of the elimination of nitrogen and the destruction of NO in the RFG. The elevated SO(2)/SO(3) in flue gas improved sulfur self-retention. SO(3) vapor could reach its dew point in the flue gas with high moisture, which limits the amount of SO(3) vapor in flue gas and possibly induces material corrosion. Most nonvolatile trace elements were less enriched in fly ash in oxycombustion than air-firing because of lower oxycombustion temperatures occurring in the present study. Meanwhile, Hg and Se were found to be enriched on submicrometer fly ash at higher levels in oxy-firing than in air-blown combustion.

Carbonyl sulfide and dimethyl sulfide fluxes in an urban lawn and adjacent bare soil in Guangzhou, China.

Carbonyl sulfide (COS) and dimethyl sulfide (DMS) fluxes from an urban Cynodon dactylon lawn and adjacent bare soil were measured during April-July 2005 in Guangzhou, China. Both the lawn and bare soil acted as sinks for COS and sources for DMS. The mean fluxes of COS and DMS in the lawn (-19.27 and 18.16 pmol/(m2 sec), respectively) were significantly higher than those in the bare soil (-9.89 and 9.35 pmol/(m2 sec), respectively). Fluxes of COS and DMS in mowed lawn were also higher than those in bare soils. Both COS and DMS fluxes showed diurnal variation with detectable but much lower values in the nighttime than in the daytime. COS fluxes were related significantly to temperature and the optimal temperature for COS uptake was 29 degrees C. While positive linear correlations were found between DMS fluxes and temperature. COS fluxes increased linearly with ambient COS mixing ratios, and had a compensation point of 336 ppt.