TY - JOUR
T1 - An interlaboratory comparison of aerosol inorganic ion measurements by ion chromatography: implications for aerosol pH estimate
AU - Xu, Jingsha
AU - Song, Shaojie
AU - Harrison, Roy M.
AU - Song, Congbo
AU - Wei, Lianfang
AU - Zhang, Qiang
AU - Sun, Yele
AU - Lei, Lu
AU - Zhang, Chao
AU - Yao, Xiaohong
AU - Chen, Dihui
AU - Li, Weijun
AU - Wu, Miaomiao
AU - Tian, Hezhong
AU - Luo, Lining
AU - Tong, Shengrui
AU - Li, Weiran
AU - Wang, Junling
AU - Shi, Guoliang
AU - Huangfu, Yanqi
AU - Tian, Yingze
AU - Ge, Baozhu
AU - Su, Shaoli
AU - Peng, Chao
AU - Chen, Yang
AU - Yang, Fumo
AU - Mihajlidi-zelić, Aleksandra
AU - Đorđević, Dragana
AU - Swift, Stefan J.
AU - Andrews, Imogen
AU - Hamilton, Jacqueline F.
AU - Sun, Ye
AU - Kramawijaya, Agung
AU - Han, Jinxiu
AU - Saksakulkrai, Supattarachai
AU - Baldo, Clarissa
AU - Hou, Siqi
AU - Zheng, Feixue
AU - Daellenbach, Kaspar R.
AU - Yan, Chao
AU - Liu, Yongchun
AU - Kulmala, Markku
AU - Fu, Pingqing
AU - Shi, Zongbo
PY - 2020/11/25
Y1 - 2020/11/25
N2 - Water-soluble inorganic ions such as ammonium, nitrate and sulfate are major components of fine aerosols in the atmosphere and are widely used in the estimation of aerosol acidity. However, different experimental practices and instrumentation may lead to uncertainties in ion concentrations. Here, an intercomparison experiment was conducted in 10 different laboratories (labs) to investigate the consistency of inorganic ion concentrations and resultant aerosol acidity estimates using the same set of aerosol filter samples. The results mostly exhibited good agreement for major ions Cl−, SO2−4, NO−3, NH+4 and K+. However, F−, Mg2+ and Ca2+ were observed with more variations across the different labs. The Aerosol Chemical Speciation Monitor (ACSM) data of nonrefractory SO2−4, NO−3 and NH+4 generally correlated very well with the filter-analysis-based data in our study, but the absolute concentrations differ by up to 42 %. Cl− from the two methods are correlated, but the concentration differ by more than a factor of 3. The analyses of certified reference materials (CRMs) generally showed a good detection accuracy (DA) of all ions in all the labs, the majority of which ranged between 90 % and 110 %. The DA was also used to correct the ion concentrations to showcase the importance of using CRMs for calibration check and quality control. Better agreements were found for Cl−, SO2−4, NO−3, NH+4 and K+ across the labs after their concentrations were corrected with DA; the coefficient of variation (CV) of Cl−, SO2−4, NO−3, NH+4 and K+ decreased by 1.7 %, 3.4 %, 3.4 %, 1.2 % and 2.6 %, respectively, after DA correction. We found that the ratio of anion to cation equivalent concentrations (AE / CE) and ion balance (anions–cations) are not good indicators for aerosol acidity estimates, as the results in different labs did not agree well with each other. In situ aerosol pH calculated from the ISORROPIA II thermodynamic equilibrium model with measured ion and ammonia concentrations showed a similar trend and good agreement across the 10 labs. Our results indicate that although there are important uncertainties in aerosol ion concentration measurements, the estimated aerosol pH from the ISORROPIA II model is more consistent.
AB - Water-soluble inorganic ions such as ammonium, nitrate and sulfate are major components of fine aerosols in the atmosphere and are widely used in the estimation of aerosol acidity. However, different experimental practices and instrumentation may lead to uncertainties in ion concentrations. Here, an intercomparison experiment was conducted in 10 different laboratories (labs) to investigate the consistency of inorganic ion concentrations and resultant aerosol acidity estimates using the same set of aerosol filter samples. The results mostly exhibited good agreement for major ions Cl−, SO2−4, NO−3, NH+4 and K+. However, F−, Mg2+ and Ca2+ were observed with more variations across the different labs. The Aerosol Chemical Speciation Monitor (ACSM) data of nonrefractory SO2−4, NO−3 and NH+4 generally correlated very well with the filter-analysis-based data in our study, but the absolute concentrations differ by up to 42 %. Cl− from the two methods are correlated, but the concentration differ by more than a factor of 3. The analyses of certified reference materials (CRMs) generally showed a good detection accuracy (DA) of all ions in all the labs, the majority of which ranged between 90 % and 110 %. The DA was also used to correct the ion concentrations to showcase the importance of using CRMs for calibration check and quality control. Better agreements were found for Cl−, SO2−4, NO−3, NH+4 and K+ across the labs after their concentrations were corrected with DA; the coefficient of variation (CV) of Cl−, SO2−4, NO−3, NH+4 and K+ decreased by 1.7 %, 3.4 %, 3.4 %, 1.2 % and 2.6 %, respectively, after DA correction. We found that the ratio of anion to cation equivalent concentrations (AE / CE) and ion balance (anions–cations) are not good indicators for aerosol acidity estimates, as the results in different labs did not agree well with each other. In situ aerosol pH calculated from the ISORROPIA II thermodynamic equilibrium model with measured ion and ammonia concentrations showed a similar trend and good agreement across the 10 labs. Our results indicate that although there are important uncertainties in aerosol ion concentration measurements, the estimated aerosol pH from the ISORROPIA II model is more consistent.
U2 - 10.5194/amt-13-6325-2020
DO - 10.5194/amt-13-6325-2020
M3 - Article
SN - 1867-1381
VL - 13
SP - 6325
EP - 6341
JO - Atmospheric Measurement Techniques
JF - Atmospheric Measurement Techniques
IS - 11
ER -