scholarly journals Ammonium nitrate promotes sulfate formation through uptake kinetic regime

2021 ◽  
Author(s):  
Yongchun Liu ◽  
Zeming Feng ◽  
Feixue Zheng ◽  
Xiaolei Bao ◽  
Pengfei Liu ◽  
...  
Keyword(s):  
Formation Rate ◽  
Ambient Air ◽  
Kinetic Regime ◽  
Particle Phase ◽  
Uptake Kinetic ◽  
Rate Determining Step ◽  
Sulfate Formation ◽  
Kinetics Of ◽  
Haze Days

Abstract. Although the anthropogenic emissions of SO2 have decreased significantly in China, the decrease in SO42− in PM2.5 is much smaller than that of SO2. This implies an enhanced formation rate of SO42− in the ambient air, and the mechanism is still under debate. This work investigated the formation mechanism of particulate sulfate based on statistical analysis of long-term observations in Shijiazhuang and Beijing supported with flow tube experiments. Our main finding was that the SOR was exponentially correlated with ambient RH in Shijiazhuang (SOR = 0.15 + 0.0032exp(RH/16.2)) and Beijing (SOR = −0.045 + 0.12exp(RH/37.8)). In Shijiazhuang, the SOR is linearly correlated with the ratio of aerosol water content (AWC) in PM2.5 (SOR = 0.15 + 0.40AWC/PM2.5). Kinetics studies suggest that uptake of SO2 instead of oxidation of S(IV) in particle-phase is the rate determining step for sulfate formation. NH4NO3 plays an important role in the AWC and the transition of particle phase, which is a crucial factor determining the uptake kinetics of SO2 and the enhanced SOR during haze days. Our results show that NH3 significantly promoted the uptake of SO2, subsequently, the SOR, while NO2 had little influence on SO2 uptake and SOR in the presence of NH3.

scholarly journals Ammonium nitrate promotes sulfate formation through uptake kinetic regime

2021 ◽  
Vol 21 (17) ◽  
pp. 13269-13286
Author(s):  
Yongchun Liu ◽  
Zemin Feng ◽  
Feixue Zheng ◽  
Xiaolei Bao ◽  
Pengfei Liu ◽  
...  
Keyword(s):  
Formation Rate ◽  
Sulfur Oxidation ◽  
Ambient Air ◽  
Particle State ◽  
Kinetic Regime ◽  
Uptake Kinetic ◽  
Rate Determining Step ◽  
Sulfate Formation ◽  
Oxidation Ratio

Abstract. Although the anthropogenic emissions of SO2 have decreased significantly in China, the decrease in SO42- in PM2.5 is much smaller than that of SO2. This implies an enhanced formation rate of SO42- in the ambient air, and the mechanism is still under debate. This work investigated the formation mechanism of particulate sulfate based on statistical analysis of long-term observations in Shijiazhuang and Beijing supported with flow tube experiments. Our main finding was that the sulfur oxidation ratio (SOR) was exponentially correlated with ambient RH in Shijiazhuang (SOR = 0.15+0.0032×exp⁡(RH/16.2)) and Beijing (SOR = -0.045+0.12×exp⁡(RH/37.8)). In Shijiazhuang, the SOR is linearly correlated with the ratio of aerosol water content (AWC) in PM2.5 (SOR = 0.15+0.40×AWC/PM2.5). Our results suggest that uptake of SO2 instead of oxidation of S(IV) in the particle phase is the rate-determining step for sulfate formation. NH4NO3 plays an important role in the AWC and the change of particle state, which is a crucial factor determining the uptake kinetics of SO2 and the enhanced SOR during haze days. Our results show that NH3 significantly promoted the uptake of SO2 and subsequently the SOR, while NO2 had little influence on SO2 uptake and SOR in the presence of NH3.

scholarly journals Heterogeneous Interactions between SO<sub>2</sub> and Organic Peroxides in Submicron Aerosol

2020 ◽  
Author(s):  
Shunyao Wang ◽  
Tengyu Liu ◽  
Jinmyung Jang ◽  
Jonathan P. D. Abbatt ◽  
Arthur W. H. Chan
Keyword(s):  
Aqueous Phase ◽  
Organic Peroxide ◽  
Uptake Kinetics ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Organic Peroxides ◽  
Particle Phase ◽  
Quantitative Evidence ◽  
Sulfate Formation ◽  
Kinetics Of

Abstract. Atmospheric models often underestimate particulate sulfate, a major component in ambient aerosol, suggesting missing sulfate formation mechanisms in the models. Heterogeneous reactions between SO2 and aerosol play an important role in particulate sulfate formation and its physicochemical evolution. Here we study the reactive uptake kinetics of SO2 onto aerosol containing organic peroxides. We present chamber studies of SO2 reactive uptake performed under different relative humidities (RH), particulate peroxide contents, peroxide types, and aerosol acidities. Using different model organic peroxides mixed with ammonium sulfate particles, SO2 uptake coefficient (γSO2) was found to be exponentially dependent on RH. γSO2 increases from 10−3 at RH 25 % to 10−2 at RH 71 % as measured for a multifunctional organic peroxide. Under similar conditions, the kinetics were found to be structurally dependent: multifunctional organic peroxides have a higher γSO2 than those with only one peroxide group, consistent with the reactivity trend observed previously in the aqueous phase. In addition, γSO2 is linearly related to particle-phase peroxide content, which in turn depends on gas-particle partitioning of organic peroxides. Aerosol acidity plays a complex role in determining SO2 uptake rate, influenced by the effective Henry's Law constant of SO2 and the condensed phase kinetics of the peroxide-SO2 reaction in the highly concentrated aerosol phase. These uptake coefficients are consistently higher than those calculated from the reaction kinetics in the bulk aqueous phase, and we show experimental evidence suggesting that other factors, such as particle-phase ionic strength, can play an essential role in determining the uptake kinetics. γSO2 for different types of secondary organic aerosol (SOA) were measured to be on the order of 10−4. Overall, this study provides quantitative evidence of the multiphase reactions between SO2 and organic peroxides, highlighting the important factors that govern the uptake kinetics.

scholarly journals Heterogeneous interactions between SO<sub>2</sub> and organic peroxides in submicron aerosol

2021 ◽  
Vol 21 (9) ◽  
pp. 6647-6661
Author(s):  
Shunyao Wang ◽  
Tengyu Liu ◽  
Jinmyung Jang ◽  
Jonathan P. D. Abbatt ◽  
Arthur W. H. Chan
Keyword(s):  
Aqueous Phase ◽  
Organic Peroxide ◽  
Uptake Kinetics ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Organic Peroxides ◽  
Particle Phase ◽  
Quantitative Evidence ◽  
Sulfate Formation ◽  
Kinetics Of

Abstract. Atmospheric models often underestimate particulate sulfate, a major component in ambient aerosol, suggesting missing sulfate formation mechanisms in the models. Heterogeneous reactions between SO2 and aerosol play an important role in particulate sulfate formation and its physicochemical evolution. Here we study the reactive uptake kinetics of SO2 onto aerosol containing organic peroxides. We present chamber studies of SO2 reactive uptake performed under different relative humidity (RH), particulate peroxide contents, peroxide types, and aerosol acidities. Using different model organic peroxides mixed with ammonium sulfate particles, the SO2 uptake coefficient (γSO2) was found to be exponentially dependent on RH. γSO2 increases from 10−3 at RH 25 % to 10−2 at RH 71 % as measured for an organic peroxide with multiple O–O groups. Under similar conditions, the kinetics in this study were found to be structurally dependent: organic peroxides with multiple peroxide groups have a higher γSO2 than those with only one peroxide group, consistent with the reactivity trend previously observed in the aqueous phase. In addition, γSO2 is linearly related to particle-phase peroxide content, which in turn depends on gas–particle partitioning of organic peroxides. Aerosol acidity plays a complex role in determining SO2 uptake rate, influenced by the effective Henry's Law constant of SO2 and the condensed-phase kinetics of the peroxide–SO2 reaction in the highly concentrated aerosol phase. These uptake coefficients are consistently higher than those calculated from the reaction kinetics in the bulk aqueous phase, and we show experimental evidence suggesting that other factors, such as particle-phase ionic strength, can play an essential role in determining the uptake kinetics. γSO2 values for different types of secondary organic aerosol (SOA) were measured to be on the order of 10−4. Overall, this study provides quantitative evidence of the multiphase reactions between SO2 and organic peroxides, highlighting the important factors that govern the uptake kinetics.

scholarly journals Supplementary material to "Ammonium nitrate promotes sulfate formation through uptake kinetic regime"

2021 ◽  
Author(s):  
Yongchun Liu ◽  
Zeming Feng ◽  
Feixue Zheng ◽  
Xiaolei Bao ◽  
Pengfei Liu ◽  
...  
Keyword(s):  
Ammonium Nitrate ◽  
Kinetic Regime ◽  
Uptake Kinetic ◽  
Sulfate Formation ◽  
Supplementary Material

Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

1977 ◽  
Vol 16 (01) ◽  
pp. 30-35 ◽  
Author(s):  
N. Agha ◽  
R. B. R. Persson
Keyword(s):  
Complex Formation ◽  
Significant Influence ◽  
Room Temperature ◽  
Ph Value ◽  
Maximum Activity ◽  
Reduction Step ◽  
Labelling Yield ◽  
Different Temperatures ◽  
Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

41. Diffusion Badges as a Long-Term, Low-Level Method of Ambient Air Analysis

2005 ◽  
Author(s):  
K. Parker ◽  
S. Rose-Pehrsson ◽  
D. Kidwell
Keyword(s):  
Ambient Air ◽  
Air Analysis ◽  
Low Level ◽  
Level Method

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

scholarly journals Acute and chronic exposure to air pollution in relation with incidence, prevalence, severity and mortality of COVID-19: a rapid systematic review

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Patrick D. M. C. Katoto ◽  
Amanda S. Brand ◽  
Buket Bakan ◽  
Paul Musa Obadia ◽  
Carsi Kuhangana ◽  
...  
Keyword(s):  
Air Pollution ◽  
Chronic Exposure ◽  
Ambient Air ◽  
Short Term ◽  
Incidence And Mortality ◽  
Acute And Chronic Exposure ◽  
Anthropogenic Pollutant ◽  
Incident Cases ◽  
Incidence Prevalence

Abstract Background Air pollution is one of the world’s leading mortality risk factors contributing to seven million deaths annually. COVID-19 pandemic has claimed about one million deaths in less than a year. However, it is unclear whether exposure to acute and chronic air pollution influences the COVID-19 epidemiologic curve. Methods We searched for relevant studies listed in six electronic databases between December 2019 and September 2020. We applied no language or publication status limits. Studies presented as original articles, studies that assessed risk, incidence, prevalence, or lethality of COVID-19 in relation with exposure to either short-term or long-term exposure to ambient air pollution were included. All patients regardless of age, sex and location diagnosed as having COVID-19 of any severity were taken into consideration. We synthesised results using harvest plots based on effect direction. Results Included studies were cross-sectional (n = 10), retrospective cohorts (n = 9), ecological (n = 6 of which two were time-series) and hypothesis (n = 1). Of these studies, 52 and 48% assessed the effect of short-term and long-term pollutant exposure, respectively and one evaluated both. Pollutants mostly studied were PM2.5 (64%), NO2 (50%), PM10 (43%) and O3 (29%) for acute effects and PM2.5 (85%), NO2 (39%) and O3 (23%) then PM10 (15%) for chronic effects. Most assessed COVID-19 outcomes were incidence and mortality rate. Acutely, pollutants independently associated with COVID-19 incidence and mortality were first PM2.5 then PM10, NO2 and O3 (only for incident cases). Chronically, similar relationships were found for PM2.5 and NO2. High overall risk of bias judgments (86 and 39% in short-term and long-term exposure studies, respectively) was predominantly due to a failure to adjust aggregated data for important confounders, and to a lesser extent because of a lack of comparative analysis. Conclusion The body of evidence indicates that both acute and chronic exposure to air pollution can affect COVID-19 epidemiology. The evidence is unclear for acute exposure due to a higher level of bias in existing studies as compared to moderate evidence with chronic exposure. Public health interventions that help minimize anthropogenic pollutant source and socio-economic injustice/disparities may reduce the planetary threat posed by both COVID-19 and air pollution pandemics.

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