scholarly journals Hygroscopic behavior of atmospheric aerosols containing nitrate salts and water-soluble organic acids

2018 ◽  
Vol 18 (7) ◽  
pp. 5115-5127 ◽  
Author(s):  
Bo Jing ◽  
Zhen Wang ◽  
Fang Tan ◽  
Yucong Guo ◽  
Shengrui Tong ◽  
...  

Abstract. While nitrate salts have critical impacts on environmental effects of atmospheric aerosols, the effects of coexisting species on hygroscopicity of nitrate salts remain uncertain. The hygroscopic behaviors of nitrate salt aerosols (NH4NO3, NaNO3, Ca(NO3)2) and their internal mixtures with water-soluble organic acids were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA). The nitrate salt ∕ organic acid mixed aerosols exhibit varying phase behavior and hygroscopic growth depending upon the type of components in the particles. Whereas pure nitrate salt particles show continuous water uptake with increasing relative humidity (RH), the deliquescence transition is still observed for ammonium nitrate particles internally mixed with organic acids such as oxalic acid and succinic acid with a high deliquescence point. The hygroscopicity of submicron aerosols containing sodium nitrate and an organic acid is also characterized by continuous growth, indicating that sodium nitrate tends to exist in a liquid-like state under dry conditions. It is observed that in contrast to the pure components, the water uptake is hindered at low and moderate RH for calcium nitrate particles containing malonic acid or phthalic acid, suggesting the potential effects of mass transfer limitation in highly viscous mixed systems. Our findings improve fundamental understanding of the phase behavior and water uptake of nitrate-salt-containing aerosols in the atmospheric environment.

2017 ◽  
Author(s):  
Bo Jing ◽  
Zhen Wang ◽  
Fang Tan ◽  
Yucong Guo ◽  
Shengrui Tong ◽  
...  

Abstract. While nitrates have critical impacts on environmental effects of atmospheric aerosols, the effects of coexisting species on hygroscopicity of nitrates remain uncertain. The hygroscopic behaviors of nitrate aerosols (NH4NO3, NaNO3, Ca(NO3)2) and their internal mixtures with water soluble organic acids at varying mass ratios were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA). The nitrate/organic acid mixed aerosols exhibit varying phase behavior and hygroscopic growth depending upon the type of components in the particles. Whereas pure nitrate particles show continuous water uptake with increasing RH, the deliquescence transition is still observed for ammonium nitrate particles internally mixed with organic acids such as oxalic acid and succinic acid with a high deliquescence point. The hygroscopicity of submicron aerosols containing sodium nitrate and an organic acid is also characterized by continuous growth, indicating that sodium nitrate tends to exist in a liquid-like state under dry conditions. It is observed that in contrast to the pure components the water uptake is hindered at low and moderate RH for calcium nitrate particles containing malonic acid or phthalic acid, suggesting the potential effects of mass transfer limitation in highly viscous mixed systems. Our findings improve fundamental understanding of the phase behavior and water uptake of nitrate-containing aerosols in the atmospheric environment.


Author(s):  
Pengpeng Li ◽  
Shixin Zhou ◽  
Baoqiang Ji ◽  
Xiaopeng Liu ◽  
Jing Li ◽  
...  

2016 ◽  
Vol 16 (7) ◽  
pp. 3875-3883 ◽  
Author(s):  
Paulo S. Carvalho ◽  
Javier Ellena ◽  
Dmitry S. Yufit ◽  
Judith A. K. Howard

2018 ◽  
Author(s):  
Theodora Nah ◽  
Hongyu Guo ◽  
Amy P. Sullivan ◽  
Yunle Chen ◽  
David J. Tanner ◽  
...  

Abstract. The implementation of stringent emission regulations has resulted in the decline of anthropogenic pollutants including sulfur dioxide (SO2), nitrogen oxides (NOx) and carbon monoxide (CO). In contrast, ammonia (NH3) emissions are largely unregulated, with emissions projected to increase in the future. We present real-time aerosol and gas measurements from a field study conducted in an agricultural-intensive region in the southeastern U.S. during the fall of 2016 to investigate how NH3 affects particle acidity and SOA formation via the gas-particle partitioning of semi-volatile organic acids. Particle water and pH were determined using the ISORROPIA-II thermodynamic model and validated by comparing predicted inorganic HNO3-NO3− and NH3-NH4+ gas-particle partitioning ratios with measured values. Our results showed that despite the high NH3 concentrations (study average 8.1 ± 5.2 ppb), PM1 were highly acidic with pH values ranging from 0.9 to 3.8, and a study-averaged pH of 2.2 ± 0.6. PM1 pH varied by approximately 1.4 units diurnally. Formic and acetic acids were the most abundant gas-phase organic acids, and oxalate was the most abundant particle-phase water-soluble organic acid anion. Measured particle-phase water-soluble organic acids were on average 6 % of the total non-refractory PM1 organic aerosol mass. The measured molar fraction of oxalic acid in the particle phase (i.e., particle-phase oxalic acid molar concentration divided by the total oxalic acid molar concentration) ranged between 47 and 90 % for PM1 pH 1.2 to 3.4. The measured oxalic acid gas-particle partitioning ratios were in good agreement with their corresponding thermodynamic predictions, calculated based on oxalic acid’s physicochemical properties, ambient temperature, particle water and pH. In contrast, gas-particle partitioning of formic and acetic acids were not well predicted for reasons currently unknown. For this study, higher NH3 concentrations relative to what has been measured in the region in previous studies had minor effects on PM1 organic acids and their influence on the overall organic aerosol and PM1 mass concentrations.


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