Observations of peroxyacetyl nitrate (PAN) in air in Southern England

SHORT COMMUNICATIONS OBSERVATIONS

OF PEROXYACETYL NITRATE SOUTHERN ENGLAND

(First recrivrd 28 Junr I974 and irt~firdfom

(PAN) IN AIR IN

30 July 1974)

PhotochemicaIl~ produced ozone has recently been observed both in rural Southern England (Atkins et al., 1972) and in London (Derwent and Stewart, 1973). This has prompted us to look for peroxy acetyl nitrate (PAN), an associated oxidant which is reported to be an eye irritant, using a gas chromatographic method based on the electron capture detector (Darley et nl., 1963). We believe that our measurements are the first reported in Europe. Samples of outside air were taken for analysis in a 5 cm3 glass hypodermic syringe, and these were injected into the chromatograph with the column operating at 25°C and with the carrier gas flow rate set to 60cm3 min- ‘. The chromatographic material was 5 per cent polyethylene glycol supported on chromosorb, as recommended by Stephens (Stephens, 1969); and it was packed into a glass column 43 cm long with an id. of0.4cm. The detector was calibrated against known concentrations of PAN in the range IO-50 parts in IO9 by volume (ppb). These were obtained by diluting higher concentrations of pure PAN which were prepared in the laboratory for quantitative i.r. and nitrite analyses (Stephens, 1969). The chemical nature of the substance was also confirmed from its i.r. spectrum, which was virtually identical to that published by Stephens (Stephens, 1969). A typical chromatogram is shown in Fig. 1, with signals revealing the presence of PAN and PPN (peroxy propionyl nitrate) in the atmosphere at A.E.R.E., Harwell. Figure 2 shows that on a sunny, anticyclonic day there is a good correlation between the concentration of PAN and ozone. (The ozone concentration was measured

I I

I

I

I

I 5

I

I

I

I

I to

/

I

/

/

/

,

15

min Fig.

I. Typical chromatogram Other

showing the presence of PAN and PPN in air at A.E.R.E., Harwell signals come from carbon tetrachloride (a), methyl nitrate (b) and water (e). 139

It has hcen assumed that PAN ib produced sulely h! photolysls of Lchiclc Csh:lu\t Cml\rlo,l’; and 110 tloubt this mechanism does account for the high lcvcls observed in the Los Angeles area. Recently. how.~‘vcr. potcntral P4N ~on~etltr~~tions greater than the Harwell tn~lxilntln~ of 2.3 pph lutve been ohberved in t~~~~oll~~l~~l;ttr o\ct the North Atlantic Ocean (Lowlock and Pcnkett. 1974). and this aggcsts that PAN can hc made I~! procc~sc~ occurring in a natural atmosphere. Further measurements are thus required to determme the source of the I’;\‘\: observed in rural areas. such as Hnrwcll. Also the status of PAN as an atr pollutant needs IO hc re-cvlminccl,

*

Department

of Applied

Ph)sicnl

Sciences. Univcrsita

of Rcadmg.

Whitcknight\

Park.

Rczding.

Kcrl\hzrc

REFERENC’ES Atkins D. H. F.. c‘ox R. .A. and Egglcton A. E. J. (1971) Photochemical ozone and culphurlc acid acro\al formation in the utmosphcrc over Southern England. ~Vu/trvr 235, 372 376. ~‘t!. cliromatoerallli! Darley E. F.. Kettner K. A and Stephens E. R. (1963) Analysis of peroxy acql nitratcc b\ + with electron capture detection. .3nn1. C‘ltt~rn. 35, 589 591, Derwent R. G. and Stewart H. N. M. (1973) Elevated ozone Irr;ris in the 31~.01. fvcntr;:I L.~v~&>II. .~~iiirr~ 241, ij? 34;.

L.S. Dept. of Health.

Education

and Welfare

(1971) Air Quality

Criteria

for Photochemlcal

Oxidants.