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Title Interaction of and in : Implications for analysis of H 2 O 2 in air

Permalink https://escholarship.org/uc/item/7j7454z7

Journal Geophysical Research Letters, 9(3)

ISSN 00948276

Authors Zika, R. G Saltzman, E. S

Publication Date 1982-03-01

DOI 10.1029/GL009i003p00231

License https://creativecommons.org/licenses/by/4.0/ 4.0

Peer reviewed

eScholarship.org Powered by the Digital Library University of California GEOPHYSICLARESEARCH LETTERS, VOL. 9, NO. 3, PAGES231-234 , MARCH1982

INTERACTION OF OZONE AND IN WATER: IMPLICATIONSFORANALYSIS oFH20 2 IN AIR R.G. Zika and E.S. Saltzman

Division of Marine and , University of Miami, Miami, Florida 331#9

Abstract. We have attempted to measure gaseous Analytical Methods H202 in air usingan aqueoustrapping method. With continuousbubbling, H 20 2 levels in the traps reacheda a. Hydrogen Peroxide. Hydrogen peroxide in aqueous plateau, indicating that a state of dynamic equilibrium solution was measured using a modified fluorescence involving H202 destrbction was established. We decay technique [Perschke and Broda, 1976; Zika and attribute this behavior to the interaction of ozone and its Zelmer, 1982]. The method involved the addition of a decompositionproducts (OH, O[) withH 20 2 inacld:•ous known amot•at of scopoletin (6-methyl-7-hydroxyl-i,2- solution. This hypothesis was investigated by replacing benzopyrone)to a pH 7.0 phosphatebuffered. sample. the air stream with a mixture of N2, 02 and 0 3. The The sample was prepared bY diluting an aliquot of the results Of this experiment show that H O was both reaction solution to 20 mls with low contaminant producedand destroyedin the traps. Theseresults have distilledwater. Thesize of the reactionsolution aliqu0t led us to question the validity of techniques which wassuch that the concentr.•tion of H202 in the20 ml employaqueous traps to measureH 20 2 in air. samplewas less than 2x 10- M. Additionøf (HRP) mixture catalyzed oxidation of Introduction the scopoletin by H202 resulting in a decrease in fluorescence of the sample. Fluorescence measurements Theoccurrence of H202 in theatmosphere has. been were madeon a TurnerDesigns Model 10 fluorometer explained exclusively through photochemical With excitationand emissionwaveler•gths centered at reaction mechanismS. Model calculations suggest that 36.• and #90 nm, respectively. the lower troposphericconcentration of H20 2 produi:ed Calibration curves were prepared by .analyzing a via these processes Should be of the order 1-#.ppbv series of solutions Of known peroxide [Levy, 1973]. Measurementsof gas phase 1'1202 preparedby dilutionof a I x 10-2 M H202 stock concentrationsgive valuesO f 2-180 ppbv [Bufalini et al., solution. By varying the amount of scopoletin added, 1972• Kok et al., 1978 ]. The higher values in this range peroxideconcentrations of 2 x 10-9 M to .• x 10-7 could have been recorded for polluted atmospheric be accuratelydetermined with a precisionof + 2%. environments and the lower levels are probably more Low contaminant distilled water was t•ed for all typical of ambient concentrations•andwould therefore be reagents preparations, dilutions.and in. the traps. It was in agreement with the model predicted values. . prepared by slow from a neutral The data basefor environmentalH 20 2 measurements -Milli-Qwater solution. The water Was is limited and little information exists for true ambient distilled througha 55 cm packedcolumn .and collected in background values. The Complete lack of such a reservoir which was isolated from the by measurements for the southeastern United States and our means of an activated filter. Water prepared in current interest in determining the atmospheric input of thisway was found to below in organic,transition H202 tO the oceansled usto make H202 measurements (i.e., Cu• Fe andMn), and residual oxidant COntaminants. in ground level air in South Flori•da and the Bahamas. b. OzOne.Ozone in the gasstream was determined The air measurements appeared to be in good agreement bY plac!nga 296neutral KI solutionin the first fritted with those determined elsewhere by other analytical gas washing trap. After sampling a known volume of the methods [Kok et al., 1978 ] which, like this study, equilibrated gas stream the absorbance of the trapping employ aqueous trapping of gas phase H20 2. Further solution was measured at 362 rim. At neutral pH the evaluation of our experimental procedure indicated that reaction, the validity of the air measurements was in question because of the anomalous behavior of H202 in the 03+3I +H20+I 3 +O2+2OH aqueoustraps. It is possiblethat the observedanomalies are the resultof aqueousreac•:ions of mixturesof H2 O2 yieldsone of I• f.oreach m0ie of ozoneconsumed and ozone. Although the chemistry of aqueousozone is [Schechter,1973 ]. The absorbancesof standard!3_- not usually recognized in the atmospheric literature, solutionswere Usedto calibratethe method, The 13 there are numerous studies on its reactivity in water in solution was standardized by with standard the chemical literature [ Hoigne and Bader, 197.5;Peleg, thiosulfate solution. 1976; Weinstein and Bielstd, 1979]. Although much of While I• does react with H202, the kinetics are this information is inconsistent, it is proposedthat ozone much slower than those of reaction with Ozone. Based on decaysto produceH 202 [Hoigne and Bader, 1976] via this criteria there was no evidence for the occurrence of the following pathway: H 202 in the KI trap solutions.

Experimental Procedures 203+OH-+OH+O 2 +202 (1) a. H202 in Air. The apparatus used to measure (2) H202 in air consists of two .500 ml fritted gas washing 202 +2H++H202+O 2 traps, each containing .500ml Of water, a vacuum pump, and a flowmeter (Figure 1). Teflon tubing was used to Copyright 1982 by the American Geophysical Union. connect the various components, and to draw air into the

Paper number 1L1876. 231 0094-8276/82/001L-1876501.00 232 Zika andSaltzman: Interaction of Ozoneand H202 in Water

Ozonizer . increase was again observed as was the plateau. Figure 2 showsa casewhere the secondtrap plateauoccurred at a lower ot• H20 2 than the first. In some

Washing cases there was virtually no difference between the measured plateau H20 2 Concentrations in the two traps. In view of H202's low and infinite in water, the first trap should have removed all of the H20 2 from the air stream. This is contrary to what was found by Pilz and Johann [1974] who reported O3 that H 202 is very difficult to quantitatively extract outflow fromair withwater traps. Thispossibility was tested by outside(• replacing the air in the scrubbing experiments with a air I'" ....' .....J mixture of oxidantfree 99.999%N2 and H 202 (g). This Meter experiment conclusively demonstrated that the first trap was > 99% efficient in extracting H 202 and that the Flow concentrationincreased linearly with gas volumeover a Fritted Gas Vacuum rangeof < 10-8Mto > 10-aM. It is likelythat Pilz and • WashingTraps Pump johann observedthe same phenomenonthat we did in our air sampling methods. Fig.1. Schematicdiagram of the apparatusused to The only plausible explanation we have for these collect peroxide from air, and for ozone experiments. results is that some partially soluble and reactive component(s)in air is generatingH20 2 in the second trap. Since the dual trap experiments gave similar laUratoryapparatus from the outside.The traps were results on the open ocean as in the laboratory, the filled with distilledwater and air was drawnthrough component(s)is not restricted to near shore or city air. them at a controlled flow rate. At various intervals the The H202 precursor must be present in substantial flow was briefly interrupted, and samples were concentrations to generate the peroxide levels observed Withdrawnfrom the traps for H2 02 analysis. The in the two traps. The only possible candidate known to VOlumeof sampleremoved was replacedwith distilled us is ozone. During the experiment, shown in Figure 2, water; this caused only a small dilution effect of the the O3 concentration in the air at the experimental site large volumein the traps. Prior to analysis,samples on Key varied between 35 and 45 ppb as were degassealwith high purity helium to remove any monitored by Dade Environmental Resources ozonethat mayhave been present. Management. The efficiency of this system for the extraction of In dual trapping experiments with outside air, we H202from air was tested by passing a controlled stream observedan inductionperiod for the formationof H2 02 of over 30% H 202 and then through the traps. The first trap wasfound to be in excessof 99% efficient 10.0 ...... in removingH202 fromthe gasstream and for the range of H202 concentrationstested, 10-Uto 10-3 molar,no }---analyticalerror H 20 2 carry over could be detected in the secondtrap. b. AqueousOzone Reactions. The effect of aqueous ozone chemistry on the H202 levels in the collection o o traps was investigated by replacing the air used in the 8.0 Previous experiment with a gas stream of N2, 02 and O3. The collectors were again filled with water and the H20 2 concentrations were measured at various intervals during the experiment. Ozone was introduced into the

N2 stream by flowing 02 through a Supelco micro 6.0 o ozOnizer. The gas stream was bubbledthrough two in- o line wash traps, the first containing .1 molar HCIO• and the second, water to remove any H202 that may have been produced in the ozonizer. These wash traps were equilibrated with the ozone mixture prior to the start of the experiment. The N2 flow was 250 ml/min and the O2 flow was 25 ml/min. After 30 minutes the 02 flow was reduced to 5 ml/min. This effectively reduced the ozone level to 1/6 of its original value in the flow o system. o 2.0 Results and Discussion o o o Experiments were conducted by scrubbing measured o volumes of outside air in aqueous gas washing bottles o ß (Figure1). The trap solutionswere analyzedfor H20 2 with the HRP-phenol method at intervals during the 0•----"' i i i i i i i i Course of scrubbing procedure. The validity of this 0 40 80 120 160 200 approach for the determination of H 202 in the gas phase TIME (minutes) was questionedwhen it was discoveredthat the H20 2 increased steadily with increasing air volume scrubbed, Fig. 2. Hydrogen peroxide concentrations in aqueous but only to a point where it reached a plateau. When a bubbletraps with 2 l/rain flow of outsideair. O = first secondtrap was placed in series with the first the H20 2 trap, ß = second trap. Zika andSaltzman: Interaction of Ozoneand H202 in Water 233

H aO2 to be a simple linear function of ozone 3.0 - concentration. In the experiments discussed here, elaborate measures were taken to clean the glassware and to purify the water used in the experiments. It is, however, virtually impossibleto eliminate all traces of I transition and organic materials from the water. I This coupledwith the fact that ozoneis ubiquitousand I variable in concentration in the atmosphere raises I ß I serious questions about methods which attempt to I measureatmospheric H 2 0 2 levels by aqueoustrapping. I o Furthermore, these experimentsindicate that interaction I between H20 2 and 0 3 may be important to the I chemistry of these substancesin cloud and rain water I [ Zika et al., 1981 ]. I I o Conclusions I ß o I I 1. Experiments show that ozone and/or its i decompositionproducts can both produceand destroy I Ha O 2 in aqueoussolution. I OZONE I CONCENTRATION 2. Therefore, techniques which employ aqueous traps to REDUCED measure H202 in air are subject to large interferences from 03- H202 reactions. i i--analyticalerror • % I Acknowledgements.This researchwas supportedby I I I I I NSF Grants OCE78-25628 and ATM 79-09239. We wish 10 20 30 40 50 60 to acknowledge Victor Rossinsky for translations of TIME (minutes) foreign language manuscripts and DaleAspy for providing atmospheric ozone data. Fig. 3. The effect of ozone decompositionon hydrogen peroxide concentrations in aqueousbubbling traps using a N2-O2-O3 gas stream. The ozone flow rate was References constant for the first 30 minutes. At 30 minutes the ozone flow rate was reduced to 1/6 of its original value. Bufalini, 3.3., B.W. Gay, Jr., and K.L. Brubaker, O = first trap, ß = second trap. Hydrogen peroxide formation from photooxidationand its presencein urban , Environ. Sci. Technol., 6, 816-821, 1972. in the second trap. This delay probable reflects the Hoigne,3., and H. Bader, Ozonationof water: role of saturation of the first trap with ozone and some initial hydroxyl radicals as oxidizing intermediates, Science, consumption of ozone by reaction with impurities in the 190, 782-780, 1975. secondtrap. A long induction period was not observedin Hoigne,3., and H. Bader, The role of hydroxyl laboratory experiments using much higher concentrations reactions in ozonation processesin aqueous solutions, of ozonein the gasstream (Figure 3). Water Res., 10, 377-386, 1976. To test the possibility that aqueous ozone reactions Kilpatrick, M.L., C.C. Herrick, and M. Kilpatrick, The were producingH20 2 in the traps, a NZ+ Oz+ O3 decomposition of ozone in , 3. Am. mixture (100:10:06 by volume) was passed through the Chem. Soc., 7_•8,178#-1789, 1956. dual trap system. The concentration of H202 was Kok, G.L., K.R. Darnall, A.M. Winer, 3. N. Pitts, Jr., and measuredin both traps with time. The results(Figure 3) B.W. Gay, Ambient air measurements of hydrogen clearly show the accumulation of H202 in both traps peroxide in the California South Coast air basin, and the approach to a steady state concentration Environ.Sci. Technol., 1_•2,1077-1080, 1978. near3 x 10-6Min the first trapafter about30 minutes. Levy II, H., Photochemistryof minor constituentsin the At this time the concentration of ozone in the gas was troposphere,Planet. SpaceSci., 2__1,575-591,1973. reduced to 1/6 its original value, or •.$ ppm, as measured Peleg, M., The chemistryof ozone in the treatment of with the neutral KI method. The H2 02 concentration in water, Water Res., 10, 361-365, 1976. the traps respondedby declining to a new, lower steady Perschke, H., and E. Broda, Determination of very small state. amounts of hydrogenperoxide, Nature., 190, 257-258, To explain these observations it is necessary to 1961. invoke a mechanism involving both formation and decay Pilz, w., and I. Johann, Die Bestimmung Kleinster reactions of H202. The observed concentration of Mengert yon Wasserstoff peroxyde in Luft, Intern. 3. H20 2 is ultimately controlledby thoseproperties of the Environ. Anal. Chem., 3, 257-270, 1970. system which affect the ozone decompositionrate. Schechter,H., Spectrophotometric method for The mechanism proposed in equations I and 2 for determination of ozone in aqueous solutions, Water H202 formation involve both strong oxidizing and Res., 7, 729-739, 1973. reducingfree radicals (i.e., OH and O2-) which are Tau---•,IT., and W.C. Bray, Chain reactions in aqueous reactive with ozoneand H202. Solutionproperties such solutions containing ozone, hydrogen peroxide and as pH and the presence of free radical initiators or , O. Am. Chem. Soc., 6_•2,3357-3373, 19#0. scavengersmay have a dramatic affect on the rate of Weinstein, 3., and B.3. Bielski, Kinetics. of the decay of ozone and on the rate of formation and interaction of HO2 and O2 radicals with hydrogen preservationof H2 02 in aqueoussolutions [Taube and peroxide. The Haber-Weiss reaction, 3. Am. Chem. Bray, 19#0;Kilpatrick et al., 1956]. As a result of these Soc., 101.,58-62, 1979. factors we would not expect the rate of formation of Zika, R.G., E. Saltzman, W.L. Chameides, and 234 Zika andSaltzman: Interaction of Ozoneand H202 in Water

D.D. Davis, H202 levels in rainwater collected in peroxide in natural , Anal. Chem., submitted, South Florida and the Bahama Islands, 3. GeoDhys. 1982. Res., submitted, 1981. Zika, R.G., and P. Zelmer, An evaluation of the HRP- (Received September 28, 1981; Scopoletinmethod for the measurementof hydrogen accepted December 7, 1981.)