Measurements and Analysis of Concentrations of Gaseous Hydrogen Peroxide and Related Species in the Rural Central Piedmont Region of North Carolina

An~hcnl c~lnc‘cntrull~>n~ of pL~\-phasc 1~>11;11 pcru\ide\ and h>drogcn per<,\lde \rerc measured during mid-Jul> IC) mid-.Aup\t IYY I. and during June ;lnd carI> July. IYY! ;I[ ;I rural SIIC. SONIA, in the rural Ccnlr;il Prcdmon~ rcfiun of North Cnrolrna ;,I 9 part of the Southern Oxrdants Study. Srmultaneous mcasurcments i\\crc also made of trace gases and mrteoroloprcal parameters. The measurements of hydrogen pero\rdc were made in order tcj c\plorc’ the hsha\rour of thus photuchcmrcal oxrdant rn rural southca.,t Ll S.. 2nd I<) study rts correlation 1~1th ozone and meteorology. HzOz showed a pronounced diurrml varrutron wrth peal, conccntratrons during the afternoon (I X~ 1600 EST). The maximum H20Z concentrations ohserved were % 2.2 ppb\ durrng the IYY I intensrve. and % 1.6 ppbv during 1992. The mean daytime HLOr concentratmns observed uerc 0.64~0.56 pphv durrng 1991. and 0.57iO.36 ppbv during 1991. which were found to he signrlicantly hrghcr tat the Y5” (, confidence level) than the nighttrme averages ( 0.15 pphvl. HO, radical concentration of IJ pphv ~‘9s determrned from calculated HzOz production rates. On occasron hrgh levels ofnighttrme H,02 was observed which was found to be associated with the hreahdo\rn in the stahrlrty of the nocturnal boundary layer. A JX h hack trajectory analysis performed on the air masses arrr\rng at Site SONIA mdrcated that srgnrlicant amounts of pollutants could he transported to thus rural SIIC from the surroundrng urban arc;rs and thus could all&t the H,O, levels at this site. An observational based statistIcal analysis ~,as performed. The results ofcorrelstron matrrces show that H202 15 most strongly correlated IO ozone. temperature. solar radration. and rclatr\e humrdrtv. A multiple linear regression H’LL~ carried out hy regcssrnp H,O, on all the measured physicochemical variables. The RL WBS found IU be 0.81 for the IYYI data and 0.71 for IYY2 A sample linear regression between H20L and Ozone ga\e R’ oTO.60 and O.?Y for lY9l and 1992. respectrvrly. \then data from the entire period of measurement was Included. IVTRODL’C‘TIOV secondary pollutants in air are generally thought to be Hydrogen peroxide is considered to be an important due to recombination of peroxy radicals which have been produced by reactions during the photolysis of oxidant for its role in the free radical balance of the atmosphere (Finlayson-Pitts and Pitts. 1986). and for ozone and as oxidation products of hydrocarbons (Logan eI (,I,. 1981; Calvert and Stockwell, 1983; the conversion of atmospheric SO, in cloud water Kleinman. 1986). However. recent studies (Becker et when the pH is 4.5 or lower (Penkett LJI (I/.. 1979: trl.. 1990: Hewitt and Kok. 1991; Simonaitis et al., Martin and Damschen, 1981). In the eastern United 1991) have shown that H,Oz can also be formed from States. the reported pH values for cloud and rainwater the ozonolysis of alkenes in the presence of water are generally below 4.5 (Lazrus et al.. 1983; Daum er vapour, via a reaction not involving HO, radicals. The nl.. 1984: Kelly rr LI/., 1985; Aneja et (I/.. 1992; Li and possibility of other sources of H202 may also exist, i.e. Aneja. 1992: Kim and Aneja. 1997). Thus within this B asevich er (I/. ( 1987) have reported of HzOz observaregion. it is quite probable that the amount of atmotions made during the incomplete combustion of spheric H202 available largely controls the oxidation natural gases. of SO? during the summer months (NAPAP Many measurements of atmospheric concentraSOS&T. 1991). tions of hydrogen and organic peroxides have been Atmospheric hydrogen peroxide and organic peroxmade during the past decade. However, due to interides are believed to be products of photochemical f erence from ozone. SOI and transition metals, data processes in the atmosphere. The formation of these on ambient peroxide concentrations are not entirely reliable. (Heikes et al., 1982; Zika and Saltzmann, *Author to whom correspondence should be addressed. 1982). New monitoring techniques such as fluorescent,