Southern California air quality study: Peroxyacetyl nitrate

Information on the spatial and seasonal variations of ambient peroxyacetyl nitrate (PAN) has been obtained from simulataneous measurements made at five, seven or nine Southern California locations in June-September and November-December, 1987. Summertime (smog season) levels of PAN were consistent with photochemical formation during transport, and increased substantially from coastal to inland locations. Daily maxima (up to 30 ppb) coincided with those of ozone at all locations and shifted from midday at coastal sites to late afternoon inland.Elevated levels of PAN, e.g. up to 19 ppb on 3 December 1987, were observed during the fall at all coastal and central locations, where they consistently exceeded summertime levels.