2 Volumes Final Proceedings - Washington 1984.pdf - IARC Research

ON THE PHYSICOCREMICAL PROPERTIES OF THESURFACE OF DISPERSED ICE (SNOW)N. F. Fedoseev, V. I. Fedoseeva, E. A. NechaevPermafrost Institute, Siberian BranchAcademy of Sciences, Yakutsk, USSRThe interaction between a dispersed ice (snow) surface and toluene and hexanol solutionsin a large number of organic compounds was studied. It was found that the ice surfaceadsorbed only substances with an ionization potential 9,6 of eV. Formation of aliquid-like layer on the ice surface occurred in 48, 15 and 2.5 hours at temperaturesof -10, -5, and -2°C respectively. The solubility of carbon acids in the liquid-likelayer was shown to be lower in than the water.All large-scale processes occurring in nature tion (Figure 1) using a transformed Langmuir equaandassociated with the existence of water in a tion it becomes possible to determine the specificsolid dispersed state are in some way or othercon- surface of samples of non-metamorphized (S SP -nected with small-scale processes occurring on the 110 m2 /kg) and metamorphized (Ssp = 25 m2 /kg) snow.surface of dispersed ice, whether it is substance In addition to the aforementloned substances,migration over chin films in permafrost or sublima- those highly soluble in water and having a hightion phenomena during the metamorphosis of snow, etc. water-toluene distribution factor (inferior alco-Therefore, the study of physico-chemical properties hols and acids) are markedly absorbed by snow,of a dispersed ice surface is of interest to a exposed at the temperature of -10,-5, -2°C. Thelarge group of specialists. Until now, strongevidence has been acquired (Kvlividze et al. 1974,1978) for the existence on the dispersed ice surfaceof a so-called liquid-like film, representingan intermediate structure between ice and water.The properties of this film have been the subjectof a considerable number of papers (KvZividzeet al. 1974, 1978). There are, however, practicallyno data on the interaction of the ice surface withsubstances introduced into the system. We havenature of the interaction, however, is quite different;the sorption ability is independent of theionization potential and the amount of sorptionincreases linearly with increasing solution strength*The above-mentioned facts can be explained byassuming that the sorption of substances highlysoluble in water is due to the transition of theirmolecules from the layer of the organic solvent tothe liquid-like film.We studied the absorption by snow of formic (I),studied the interaction of dispersed ice (snow)with toluene and hexane solutions of many organiccompounds. Samples of fresh snow were taken on theleeward side far outside the limits of a town. Thesnow cover held for a Considerable and time all theexperiments were conducted at a temperature of -hacunder conditions when a liquid-like film is presenton the surface of dispersed ice.It turned out that of the numerous (more than50) organic compounds sampled, representing differentclasses of molecules, only 1,2-naphthahynoneand 0-brombenzoic acid are absorbed by the icesurface. It should be noticed that the ionizationpotential of these compounds is 9.6 eV,In this respect, adsorption regularities on icedo not differ from those on oxides. As has beenshown in Nechaev et aL. (1978, 1979). out of aqueoussolutions on the oxide surface, organic substancesare adsorbed which have a strictly defined ionizationpotential, referred to as the oxide resonancepotential (Ires.). When the ionization potentialof a substance deviates from the Ires value by morethan 0.1-0.2 eV, adsorption is not detectable.On the basis of the data obtained it seemspossible to conclude that for ice Ires = 9.6 eV.This inference is also supported by the fact thaton the ice surface anions having an ionizationpotential in between 9 and 10 eV are specificallyadsorbed.By processing data on 0-brombenzoic acid adsorp-222chloracetic (11) and acetic (111) acids fromsolutions in toluene (1,II) and hexane (111). Theconcentration variation of substance after introducinga weighed snow sample was determined by theneutralization method. At high concentrations meltingof the snow sample occurred to produce a bulkphase of aqueous solution.0 f “ O000 0I0 I 2 3 IO+.C,~FIGURE 1 Isotherms of 0-brombenzoic acid adsorptionfrom a solution in hexane on snow samples,taken from a water reservoir surface (1) and anarea at some distance from (2). it