Ozone-monitoring in Mendoza, Argentina: Initial results

A series of continuous ambient tropospheric ozone measurements were taken i n Mendoza, Argentina, for a period of one year starting in November 1995. T he data obtained were analyzed in terms of diurnal and annual variation. In dications were found of the strong impact of the mountain-valley circulatio n system, which ventilates and considerably cleans the air in Mendoza. The data are discussed in comparison with air pollution in the German city of L eipzig. In Mendoza, the high concentration of precursors and the strong solar radia tion contribute to high levels of ozone. In fact, monitoring reveals consid erably lower concentrations than in Leipzig, owing to the diluting effect o f local meteorology. The low-level jet is mainly active during the summer. It lowers the peak mid-day ozone concentration and produces a temporary con centration increase at night. The Environmental Protection Agency standard of a maximum one-hour mean concentration of 0.250 mg ozone/m(3) (125 ppb) i s never reached, and the World Health Organization standard of 0.113 mg ozo ne/m(3) (56.5 ppb) is only rarely exceeded during winter.