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An analytical method has been developed for the determination of trace levels of trifluoroacetic acid (TFA), an atmospheric breakdown product of several of the hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) replacements for the chlorofluorocarbon (CFC) refrigerants, in water and air. TFA is derivatized to the volatile methyl trifluoroacetate (MTFA) and determined by automated headspace gas chromatography (HSGC) with electron-capture detection or manual HSGC using GC/MS in the selected ion monitoring (SIM) mode. The method is based on the reaction of an aqueous sample containing TFA with dimethyl sulfate (DMS) in concentrated sulfuric acid in a sealed headspace vial under conditions favoring distribution of MTFA to the vapor phase. Water samples are prepared by evaporative concentration, during which TFA is retained as the anion, followed by extraction with diethyl ether of the acidified sample and then back-extraction of TFA (as the anion) in aqueous bicarbonate solution. The extraction step is required for samples with a relatively high background of other salts and organic materials. Air samples are collected in sodium bicarbonate-glycerin-coated glass denuder tubes and prepared by rinsing the denuder contents with water to form an aqueous sample for derivatization and analysis. Recoveries of TFA from spiked water, with and without evaporative concentration, and from spiked air were quantitative, with estimated detection limits of 10 ng/mL (unconcentrated) and 25 pg/mL (concentrated 250 mL:1 mL) for water and 1 ng/m(3) (72 h at 5 L/min) for air. Several environmental air, fogwater, rainwater, and surface water samples were successfully analyzed; many showed the presence of TFA.

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Pulse radiolysis of ferro and ferricyanide aqueous solutions is investigated at various H+ and salt concentrations. It has been found that association and ion pair formation may affect the reactivity toward OH, HO2, and 02" radicals. The following reaction rate constants were determined (in units of M"1 sec"1): ft((QH + Fe(CN)e4")) = (1.25 ± 0.1) X 1010; k((OK + HFe(CN)e3")) = (9.0 ± 0.9) x 10»; fe((OH + H2Fe-(CN)e2")) = (1.7 ± 0.5) X 109; k((H02 + Fe(CN)s4")) = (3.0 ± 1.5) X 104; fe((H02 + HFe(CN)e3")) = (1.4 ± 0.1) X 10»; fe((H02 + H2Fe(CN)62")) = (1.0 ± 0.3) X 104; fe((H02 + KFe(CN)63")) = (3.0 ± 1.5) X 104; fe((02-+ Fe(CN)e3")) = (2.7 ± 0.9) X 102; k((02~+ KFe(CN)e2")) = (6.2 ± 0.6) X 103. The last two values are calculated for zero ionic strength. The formation of ion pairs has only a little effect (~1 0% decrease) on the reactivity of ferrocyanide toward OH radicals.

The radiolysis of aqueous nitrate ion solutions was studied as a function of the concentration in the presence of air, oxygen and hydrogen at different concentrations. In dilute solutions, NO,' is reduced to NO2 by hydrated electrons and H atoms. OH radicals oxidize the NOT formed. In the presence of oxygen at relatively low concentrations of NO;, NO2 reacts with H02. Primary yields of eiq, H, OH and H20z were determined for the range of 10-3-10-' M NO,, GR = Gei,+* increased from 3.21 to 3.46 accompanied by a corresponding decrease of G H ~. The observed yields of GOH = 2.62f0.03 and of G H ~o ~ = 0.73f0.02 were independent of NO,' concentration. For higher NO, concentrations a linear increase of the total yield G R + ~G H ~ was observed. This phenomena may be interpreted as the formation of NOS and OH radicals by subexcitation electrons, which otherwise would form molecular hydrogen or hydrated electrons. Above 1 M, nitrate decomposes by " direct action " to give nitrite. The yield of " molecular " hydrogen decreases with increasing nitrate concentration, whereas the yield of hydrogen peroxide remains constant with a G(H202) = 0.75rfI0.02 over the whole concentration range up to 5 M. Oxygen 18-enriched nitrate ions in H20l6 and H201* used to determine the origin of the hydrogen peroxide at high NO; concentration, show that the part of H20z which originates from the decomposition nitrate ion by direct action is directly proportional to the fraction of energy absorbed by these ions.