Measurements of the mass concentration and chemical speciation of aerosols are important to investigate their chemical and physical processing from near emission sources to the most remote regions of the atmosphere. A common method to analyze aerosols is to collect them onto filters and analyze the filters offline; however, biases in some chemical components are possible due to changes in the accumulated particles during the handling of the samples. Any biases would impact the measured chemical composition, which in turn affects our understanding of numerous physicochemical processes and aerosol radiative properties. We show, using filters collected onboard the NASA DC-8 and NSF C-130 during six different aircraft campaigns, a consistent, substantial difference in ammonium mass concentration and ammonium-to-anion ratios when comparing the aerosols collected on filters versus an Aerodyne aerosol mass spectrometer (AMS). Another online measurement is consistent with the AMS in showing that the aerosol has lower ammonium-to-anion ratios than obtained by the filters. Using a gas uptake model with literature values for accommodation coefficients, we show that for ambient ammonia mixing ratios greater than 10 ppbv, the timescale for ammonia reacting with acidic aerosol on filter substrates is less than 30 s (typical filter handling time in the aircraft) for typical aerosol volume distributions. Measurements of gas-phase ammonia inside the cabin of the DC-8 show ammonia mixing ratios of 45±20 ppbv, consistent with mixing ratios observed in other indoor environments. This analysis enables guidelines for filter handling to reduce ammonia uptake. Finally, a more meaningful limit of detection for University of New Hampshire Soluble Acidic Gases and Aerosol (SAGA) filters collected during airborne campaigns is ∼0.2 µg sm⁻³ of ammonium, which is substantially higher than the limit of detection of ion chromatography. A similar analysis should be conducted for filters that collect inorganic aerosol and do not have ammonia scrubbers and/or are handled in the presence of human ammonia emissions.

中文翻译：

---

气相氨被酸性硫酸盐过滤器样品吸收会影响气溶胶酸度定量

气溶胶的质量浓度和化学形态的测量对于研究从近排放源到大气最偏远地区的化学和物理过程非常重要。分析气溶胶的常用方法是将其收集到过滤器上，然后离线分析过滤器。但是，由于样品处理过程中积累的颗粒的变化，某些化学成分可能会产生偏差。任何偏差都会影响所测量的化学成分，进而影响我们对众多理化过程和气溶胶辐射特性的理解。我们展示了在六次不同的飞机战役中使用NASA DC-8和NSF C-130上收集的过滤器，将过滤器上收集的气溶胶与Aerodyne气溶胶质谱仪（AMS）进行比较时，铵质量浓度和铵对阴离子比率存在显着差异。另一在线测量结果与AMS一致，表明气雾剂的铵-阴离子比值比过滤器低。使用具有容纳系数文献值的气体吸收模型，我们表明，当环境氨混合比大于10 ppbv时，氨与过滤器基板上的酸性气溶胶反应的时间尺度小于30 s（飞机中典型的过滤器处理时间）用于典型的气溶胶体积分布。对DC-8机舱内部气相氨的测量表明，氨的混合比为 另一在线测量结果与AMS一致，表明气雾剂的铵-阴离子比值比过滤器低。使用具有容纳系数文献值的气体吸收模型，我们表明，当环境氨混合比大于10 ppbv时，氨与过滤器基板上的酸性气溶胶反应的时间尺度小于30 s（飞机中典型的过滤器处理时间）用于典型的气溶胶体积分布。对DC-8机舱内部气相氨的测量表明，氨的混合比为 另一在线测量结果与AMS一致，表明气雾剂的铵-阴离子比值比过滤器低。使用具有容纳系数文献值的气体吸收模型，我们表明，当环境氨混合比大于10 ppbv时，氨与过滤器基板上的酸性气溶胶反应的时间尺度小于30 s（飞机中典型的过滤器处理时间）用于典型的气溶胶体积分布。对DC-8机舱内部气相氨的测量表明，氨的混合比为 对于典型的气溶胶体积分布，氨气与过滤器基材上的酸性气溶胶反应的时间小于30秒（飞机中典型的过滤器处理时间）。对DC-8机舱内部气相氨的测量表明，氨的混合比为 对于典型的气溶胶体积分布，氨气与过滤器基材上的酸性气溶胶反应的时间小于30秒（飞机中典型的过滤器处理时间）。对DC-8机舱内部气相氨的测量表明，氨的混合比为45±20  ppbv，与在其他室内环境中观察到的混合比一致。该分析为减少氨吸收的过滤器处理提供了指导。最后，在空运战役期间收集到的新罕布什尔大学可溶性酸性气体和气溶胶（SAGA）过滤器的更有意义的检测极限是约0.2  µg sm ^-3的铵，这大大高于离子色谱的检测极限。对于收集无机气溶胶且不具有氨洗涤器和/或在存在人类氨气排放的情况下进行处理的过滤器，应进行类似的分析。