The aging process of atmospheric aerosols usually leads to a mixture of inorganic salts and organic compounds of anthropogenic origin.In organic compounds,polyhydroxy organic acids are important components,however,the...The aging process of atmospheric aerosols usually leads to a mixture of inorganic salts and organic compounds of anthropogenic origin.In organic compounds,polyhydroxy organic acids are important components,however,the study on composition and hygroscopic properties of the mixture containing inorganics and polyhydroxy organic acids is scanty.In this study,gluconic acid,the proxy of polyhydroxy organic acids,is mixed with the representative nitrate(Mg(NO_(3))_(2),Ca(NO_(3))_(2))to form aerosols.ATR-FTIR and optical microscopy are employed to study the component changes and hygroscopicity as a function of relative humidity.As relative humidity fluctuates,the FTIR-ATR spectra display that the internal mixed gluconic acid(CH_(2)(CH)_(4)(OH)_(5)COOH)and nitrate can react to release acidic gases,forming relevant gluconate and further affecting the hygroscopicity.The specific presentation is particles cannot be recovered to their original size after the dehydration-hydration process and there will be some disparities in GF for mixed particles.For the gluconic acid-Ca(NO_(3))_(2)/Mg(NO_(3))_(2)mixtures with molar ratios of 1:1,higher degree of reaction resulting in the production of large amounts of gluconate should be responsible to the lower hygroscopicity compared to ZSR model.For 1:2 gluconic acid-nitrate mixed systems(with higher nitrate content),the hygroscopicity of mixtures are higher than the ZSR prediction.A possible reason could be‘salt-promoting effect’on the organic fractions of the surplus inorganic salt in the mixture.These data can improve the chemical composition list evaluation,in turn hygroscopic properties and phase state of atmospheric aerosol,and then the climate effect.展开更多
Water-uptakes of pure sodium carbonate(Na2CO3),pureβ-alanine and internally mixedβ-alanine/Na2CO3 aerosol particles with different mole ratios are first monitored using attenuated total reflectance Fourier transform...Water-uptakes of pure sodium carbonate(Na2CO3),pureβ-alanine and internally mixedβ-alanine/Na2CO3 aerosol particles with different mole ratios are first monitored using attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR)technique.For pure Na2CO3 aerosol particles,combining the absorptions at 877 and 1422 cm-1 with abrupt water loss shows the efflorescence relative humidity(ERH)of 62.9%–51.9%.Upon humidifying,solid Na2CO3 firstly absorbs water to from Na2CO3·H2O crystal at 72.0%RH and then deliquesces at 84.5%RH(DRH).As for pureβ-alanine particles,the crystallization takes place in the range of 42.4%–33.2%RH and becomes droplets at^88.2%RH.Whenβ-alanine is mixed with Na2CO3 at various mole ratios,it shows no efflorescence of Na2CO3 whenβ-alanine to Na2CO3 mole ratio(OIR)is 2:1.For 1:1 and 1:2β-alanine/Na2CO3 aerosols,the ERHs of Na2CO3 are 51.8%–42.3%and 57.1%–42.3%,respectively.Whileβ-alanine crystal appears from 62.7%RH for 2:1 and 59.4%RH for both 1:1 and 1:2 particles and lasts to driest state.On hydration,the DRH is 44.7%–75.2%for Na2CO3 with the OIR of 1:1 and 44.7%–69.0%for 1:2 mixture,and those of β-alanine are 74.8% for 2:1 mixture and 68.9%for two others.After the first dehumidification–humidification,all the water contents decrease despite of constituent fraction.And at^92%RH,the remaining water contents are 92%,89%and 82%at^92%RH,corresponding to OIR of 2:1,1:1 and 1:2 mixed system,respectively.展开更多
基金supported by the National Natural Science Foundation of China(Nos.91644101 and 42127806)。
文摘The aging process of atmospheric aerosols usually leads to a mixture of inorganic salts and organic compounds of anthropogenic origin.In organic compounds,polyhydroxy organic acids are important components,however,the study on composition and hygroscopic properties of the mixture containing inorganics and polyhydroxy organic acids is scanty.In this study,gluconic acid,the proxy of polyhydroxy organic acids,is mixed with the representative nitrate(Mg(NO_(3))_(2),Ca(NO_(3))_(2))to form aerosols.ATR-FTIR and optical microscopy are employed to study the component changes and hygroscopicity as a function of relative humidity.As relative humidity fluctuates,the FTIR-ATR spectra display that the internal mixed gluconic acid(CH_(2)(CH)_(4)(OH)_(5)COOH)and nitrate can react to release acidic gases,forming relevant gluconate and further affecting the hygroscopicity.The specific presentation is particles cannot be recovered to their original size after the dehydration-hydration process and there will be some disparities in GF for mixed particles.For the gluconic acid-Ca(NO_(3))_(2)/Mg(NO_(3))_(2)mixtures with molar ratios of 1:1,higher degree of reaction resulting in the production of large amounts of gluconate should be responsible to the lower hygroscopicity compared to ZSR model.For 1:2 gluconic acid-nitrate mixed systems(with higher nitrate content),the hygroscopicity of mixtures are higher than the ZSR prediction.A possible reason could be‘salt-promoting effect’on the organic fractions of the surplus inorganic salt in the mixture.These data can improve the chemical composition list evaluation,in turn hygroscopic properties and phase state of atmospheric aerosol,and then the climate effect.
基金supported by the National Natural Science Foundation of China(Nos.91644101,91544223 and 21373026)
文摘Water-uptakes of pure sodium carbonate(Na2CO3),pureβ-alanine and internally mixedβ-alanine/Na2CO3 aerosol particles with different mole ratios are first monitored using attenuated total reflectance Fourier transform infrared spectroscopy(ATR-FTIR)technique.For pure Na2CO3 aerosol particles,combining the absorptions at 877 and 1422 cm-1 with abrupt water loss shows the efflorescence relative humidity(ERH)of 62.9%–51.9%.Upon humidifying,solid Na2CO3 firstly absorbs water to from Na2CO3·H2O crystal at 72.0%RH and then deliquesces at 84.5%RH(DRH).As for pureβ-alanine particles,the crystallization takes place in the range of 42.4%–33.2%RH and becomes droplets at^88.2%RH.Whenβ-alanine is mixed with Na2CO3 at various mole ratios,it shows no efflorescence of Na2CO3 whenβ-alanine to Na2CO3 mole ratio(OIR)is 2:1.For 1:1 and 1:2β-alanine/Na2CO3 aerosols,the ERHs of Na2CO3 are 51.8%–42.3%and 57.1%–42.3%,respectively.Whileβ-alanine crystal appears from 62.7%RH for 2:1 and 59.4%RH for both 1:1 and 1:2 particles and lasts to driest state.On hydration,the DRH is 44.7%–75.2%for Na2CO3 with the OIR of 1:1 and 44.7%–69.0%for 1:2 mixture,and those of β-alanine are 74.8% for 2:1 mixture and 68.9%for two others.After the first dehumidification–humidification,all the water contents decrease despite of constituent fraction.And at^92%RH,the remaining water contents are 92%,89%and 82%at^92%RH,corresponding to OIR of 2:1,1:1 and 1:2 mixed system,respectively.
