Ground level ozone and oxidant (Ox, sum of 03 and NO) concentrations in the Netherlands have been calculated for the growing season (May to September) by means of a Lagrangian longrange transport model. In a number of sensitivity runs the influence of European anthropogenic NOx and VOC emissions on the oxidant concentrations in the Netherlands have been investigated. In general, the influence of European emissions on the 98-percentile vaues is 2-3 times as large as on the averaged concentrations. This indicates that long-term averaged concentrations more strongly depend on the concentrations in the free troposphere whereas the episodic concentrations are determined by photochemical than NO emission reduction. For longterm averagd concentrations, however, NOx and VOC emission reduction of 50 % or more are nearly equally effective. In a second set of sensitivity runs the influence of increases in UV-radiation and surface temperature have been examined. For a 10 % increase in ozone column density and 10 % increase in surface temperature (on the averaged an increase of 1.6 Grad C) a slight increase (+ 2.7 %) in =3 and Ox 98percentile values was calculated. However, large increases are calculated for the number of hours with O3 concentrations exceeding 75 ppb (for summer 1989 this number increases from 56 hours in the reference case to 72 hours in the scenario run) and 100 ppb (increases from 1 hour of exceedence in the reference case to 6 hours in the scenario run). This may lead to an enhanced human exposure during episodes.
