Distribution of ozone and other air pollutants in forests of the Carpathian Mountains in central Europe

Abstract

Ozone (O 3) concentrations were monitored during the 1997–1999 growing seasons in 32 forest sites of the Carpathian Mountains. At all sites (elevation between 450 and 1320 m) concentrations of O 3, nitrogen dioxide (NO 2), and sulfur dioxide (SO 2) were measured with passive samplers. In addition, in two western Carpathian locations, Vychodna and Gubałówka, ozone was continuously monitored with ultraviolet (UV) absorption monitors. Highest average hourly O 3 concentrations in the Vychodna and Gubałówka sites reached 160 and 200 μg/m 3 (82 and 102 ppb), respectively (except for the AOT40 values, ozone concentrations are presented as μg/m 3; and at 25 °C and 760 mm Hg, 1 μg O 3/m 3=0.51 ppb O 3). These sites showed drastically different patterns of diurnal O 3 distribution, one with clearly defined peaks in the afternoon and lowest values in the morning, the other with flat patterns during the entire 24-h period. On two elevational transects, no effect of elevation on O 3 levels was seen on the first one, while on the other a significant increase of O 3 levels with elevation occurred. Concentrations of O 3 determined with passive samplers were significantly different between individual monitoring years, monitoring periods, and geographic location of the monitoring sites. Results of passive sampler monitoring showed that high O 3 concentrations could be expected in many parts of the Carpathian range, especially in its western part, but also in the eastern and southern ranges. More than four-fold denser network of monitoring sites is required for reliable estimates of O 3 distribution in forests over the entire Carpathian range (140 points). Potential phytotoxic effects of O 3 on forest trees and understory vegetation are expected on almost the entire territory of the Carpathian Mountains. This assumption is based on estimates of the AOT40 indices for forest trees and natural vegetation. Concentrations of NO 2 and SO 2 in the entire Carpathian range were typical for this part of Europe and below the expected levels of phytotoxicity.