Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine Atmospheres
Oxalic acid is the most abundant low-molecular-weight dicarboxylic acid in the atmosphere, and it plays a crucial role in the formation of new particles and cloud condensation nuclei. However, most observational studies have focused on particulate oxalate, leaving a significant knowledge gap on oxal...
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2025-01-01
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| author | Le Yan Yating Gao Dihui Chen Lei Sun Yang Gao Huiwang Gao Xiaohong Yao |
| author_facet | Le Yan Yating Gao Dihui Chen Lei Sun Yang Gao Huiwang Gao Xiaohong Yao |
| author_sort | Le Yan |
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| description | Oxalic acid is the most abundant low-molecular-weight dicarboxylic acid in the atmosphere, and it plays a crucial role in the formation of new particles and cloud condensation nuclei. However, most observational studies have focused on particulate oxalate, leaving a significant knowledge gap on oxalic acid vapor. This study investigated the concentrations and formation of oxalic acid vapor and oxalate in PM<sub>2.5</sub> at a rural tropical coastal island site in south China across different seasons, based on semi-continuous measurements using an Ambient Ion Monitor-Ion Chromatograph (AIM-IC) system. We replaced the default 25 μL sampling loop on the AIM-IC with a 250 μL loop, improving the ability to distinguish the signal of oxalic acid vapor from noise. The data revealed clear seasonal patterns in the dependent daytime and nighttime formation of oxalic acid vapor, benefiting from high signal-to-noise ratios. Specifically, concentrations were 0.059 ± 0.15 μg m<sup>−3</sup> in February and April 2023, exhibiting consistent diurnal variations similar to those of O<sub>3</sub>, likely driven by photochemical reactions. These values decreased to 0.021 ± 0.07 μg m<sup>−3</sup> in November and December 2023, with higher nighttime concentrations likely related to dark chemistry processes, amplified by accumulation due to low mixing layer height. The concentrations of oxalate in PM<sub>2.5</sub> were comparable to those of oxalic acid vapor, but exhibited (3–7)-day variations, superimposed on diurnal fluctuations to varying degrees. Additionally, thermodynamic equilibrium calculations were performed on the coastal data, and independent size distributions of particulate oxalate in the upwind marine atmosphere were analyzed to support the findings. |
| format | Article |
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| institution | Kabale University |
| issn | 2073-4433 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | MDPI AG |
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| series | Atmosphere |
| spelling | doaj-art-75984cc305ba43d1bae9e118d60f812d2025-01-24T13:22:01ZengMDPI AGAtmosphere2073-44332025-01-011619810.3390/atmos16010098Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine AtmospheresLe Yan0Yating Gao1Dihui Chen2Lei Sun3Yang Gao4Huiwang Gao5Xiaohong Yao6Sanya Oceanographic Institution, Ocean University of China, Sanya 572024, ChinaFrontiers Science Center for Deep Ocean Multispheres and Earth System, Ministry of Education, Ocean University of China, Qingdao 266100, ChinaSchool of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, ChinaFrontiers Science Center for Deep Ocean Multispheres and Earth System, Ministry of Education, Ocean University of China, Qingdao 266100, ChinaSanya Oceanographic Institution, Ocean University of China, Sanya 572024, ChinaFrontiers Science Center for Deep Ocean Multispheres and Earth System, Ministry of Education, Ocean University of China, Qingdao 266100, ChinaSanya Oceanographic Institution, Ocean University of China, Sanya 572024, ChinaOxalic acid is the most abundant low-molecular-weight dicarboxylic acid in the atmosphere, and it plays a crucial role in the formation of new particles and cloud condensation nuclei. However, most observational studies have focused on particulate oxalate, leaving a significant knowledge gap on oxalic acid vapor. This study investigated the concentrations and formation of oxalic acid vapor and oxalate in PM<sub>2.5</sub> at a rural tropical coastal island site in south China across different seasons, based on semi-continuous measurements using an Ambient Ion Monitor-Ion Chromatograph (AIM-IC) system. We replaced the default 25 μL sampling loop on the AIM-IC with a 250 μL loop, improving the ability to distinguish the signal of oxalic acid vapor from noise. The data revealed clear seasonal patterns in the dependent daytime and nighttime formation of oxalic acid vapor, benefiting from high signal-to-noise ratios. Specifically, concentrations were 0.059 ± 0.15 μg m<sup>−3</sup> in February and April 2023, exhibiting consistent diurnal variations similar to those of O<sub>3</sub>, likely driven by photochemical reactions. These values decreased to 0.021 ± 0.07 μg m<sup>−3</sup> in November and December 2023, with higher nighttime concentrations likely related to dark chemistry processes, amplified by accumulation due to low mixing layer height. The concentrations of oxalate in PM<sub>2.5</sub> were comparable to those of oxalic acid vapor, but exhibited (3–7)-day variations, superimposed on diurnal fluctuations to varying degrees. Additionally, thermodynamic equilibrium calculations were performed on the coastal data, and independent size distributions of particulate oxalate in the upwind marine atmosphere were analyzed to support the findings.https://www.mdpi.com/2073-4433/16/1/98particulate oxalateoxalic-acid-vaporphotochemical formationdiurnal variationsize distribution of aerosols |
| spellingShingle | Le Yan Yating Gao Dihui Chen Lei Sun Yang Gao Huiwang Gao Xiaohong Yao Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine Atmospheres Atmosphere particulate oxalate oxalic-acid-vapor photochemical formation diurnal variation size distribution of aerosols |
| title | Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine Atmospheres |
| title_full | Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine Atmospheres |
| title_fullStr | Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine Atmospheres |
| title_full_unstemmed | Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine Atmospheres |
| title_short | Seasonally Dependent Daytime and Nighttime Formation of Oxalic Acid Vapor and Particulate Oxalate in Tropical Coastal and Marine Atmospheres |
| title_sort | seasonally dependent daytime and nighttime formation of oxalic acid vapor and particulate oxalate in tropical coastal and marine atmospheres |
| topic | particulate oxalate oxalic-acid-vapor photochemical formation diurnal variation size distribution of aerosols |
| url | https://www.mdpi.com/2073-4433/16/1/98 |
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