Buffer Capacity of Open Atmospheric Gas–Liquid Systems

Abstract

Buffer capacity analysis of open atmospheric gas-liquid systems containing main acidic and basic atmospheric pollutants was carried out. Usually the buffer capacity is considered as a function of pH as an independent variable. In this work the buffer capacity is analysed including the dependence of pH on the composition of a system. Such an approach allows finding an important, from the viewpoint of atmospheric water acidification, relationship between the gas phase composition and the buffer capacity. It was found that buffer capacity of the open gas-liquid systems may be very high and it may cause the liquid phase pH to remain at low levels. The buffer capacity of the analysed systems is most strongly affected by the simultaneous presence of ammonia and strong acids in the gas phase. The higher concentrations of strong acid gases the lower NH 3 concentration is sufficient to achieve high buffer capacity. In the presence of strong acid gases, calcium ions affect both the buffer capacity and the liquid phase pH only at low NH 3 concentrations. High buffer capacity of open gas-liquid systems may be one of the reasons why the reduction in emissions of acidic gas pollutants has little effect on decrease in atmospheric water acidity.

Role of Carbon Dioxide, Ammonia, and Organic Acids in Buffering Atmospheric Acidity: The Distinct Contribution in Clouds and Aerosols

“…Some studies suggested a large potential of organic acids to buffer the pH of aerosols and fogs and therefore influence the atmospheric processing, 22,27−29 while some others suggested negligible buffering effects. 67,68 Here, we examined the potential contribution of organic acids to system buffering effects with the methods outlined in Section 2. One major concern is whether the organic acids can buffer in the typical pH ranges of atmospheric water, i.e., the influence of |pH−pK a,i *|.…”

“…The importance and mechanisms of organic acids in influencing the in situ acidity of atmospheric water, however, are still under debate. Some studies suggested a large potential of organic acids to buffer the pH of aerosols and fogs and therefore influence the atmospheric processing, ,− while some others suggested negligible buffering effects. , …”

“…Some studies suggested a large potential of organic acids to buffer the pH of aerosols and fogs and therefore influence the atmospheric processing, 22 , 27 − 29 while some others suggested negligible buffering effects. 67 , 68 …”