Sulfuric acid-water surface, stratospheric

Stratospheric Significance of the Sulfuric Acid/Water Surface... 

There are many different types of surfaces available for reactions in the atmosphere. In the stratosphere, these include ice crystals, some containing nitric acid, liquid sulfuric acid-water mixtures, and ternary solutions of nitric and sulfuric acids and water. In the troposphere, liquid particles containing sulfate, nitrate, organics, trace metals, and carbon are common. Sea... 

Figure 6.15. The left panel illustrates laboratory data on the efficiency of the reaction between HC1 and CIONO2 for ice, nitric acid/water solid surfaces, and liquid sulfuric acid/water solutions. The right panel depicts the altitude variation of the temperature at which the efficiency of this reaction on liquid sulfuric acid/water solutions becomes greater than 0.3 for water vapor mixing ratios that can be observed in the lower stratosphere.

The reason for the dehydration and denitrification of the Antarctic stratosphere is the formation of the PSCs, whose chemistry perturbs the composition in the Antarctic stratosphere. Polar stratospheric clouds can be composed of small (< 1 pm diameter) particles rich in HNO3 or at lower temperatures (<190 K) larger (10 pm) mainly ice particles. These are often split into two categories, the so-called Type 1PSC, which contains the nitric acid either in the form of liquid ternary solutions with water and sulfuric acid or as solid hydrates of nitric acid, or Type II PSCs made of ice particles. The ice crystals on these clouds provide a surface for reactions such as... 

Liquid and solid particles observed in the atmosphere are generally a mixture of water, sulfuric acid and nitric acid with potentially the presence of traces of other chemical compounds like HC1 (see Table 5.9 in Section 5.7). The determination of the pseudo first-order rate coefficient kx (see Eq. (2.65)) for uptake by such particles in the stratosphere requires an accurate estimate of the surface area density available and of the reaction probability involved. 

Figure 2.6. Reactive uptake coefficient (7) for the heterogeneous conversion of CIONO2 on 55.6 wt% sulfuric acid aerosol particles. The triangles represent the measurements of Hanson and Ravishankara (4994). The solid line represents the parameterization of 7 as a function of the atmospheric partial pressure of HC1. The dashed lines represent the fraction of CIONO2 reacting with water molecules (7H2°), with HC1 in the bulk of the aerosol (T C1), and with HC1 on the surface of the particles (T cl). A HC1 mixing ratio of 2 ppbv at a pressure level of 50 hPa (lower stratosphere) corresponds to a HC1 partial pressure of 10 10atm. From Peter (1997).

The stratospheric aerosol is composed of an aqueous sulfuric acid solution of 60-80% sulfuric acid for temperatures from — 80 to — 45°C, respectively (Shen et al. 1995). The source of the globally distributed, unperturbed background stratospheric aerosol is oxidation of carbonyl sulfide (OCS), which has its sources at the Earth s surface. OCS is chemically inert and water insoluble and has a long tropospheric lifetime. It diffuses into the stratosphere where it dissociates by solar ultraviolet radiation to eventually form sulfuric acid, the primary component of the natural stratospheric aerosol. Other surface-emitted sulfur-containing species, for example, S02, DMS, and CS2, do not persist long enough in the troposphere to be transported to the stratosphere. 

Acidified water surfaces degree of surface sensitivity, 111 experimental description, 107-109 stratospheric significance, 107 sulfuric acid, 109-111 surface composition, 111-113 surface vs. bulk composition, 113-114 Adsorption... 

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