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This paper describes results of experiments carried out by participants of the UN/ECE ICP-Crops to investigate the dose response of plants to long-term ozone exposure. The data were analyzed to determine the influences of climatic and geographical factors upon this dose response. Members of the ICP-Crops carried out experiments at 12 sites inEurope, covering a geographical range from Jokioinen, Finland, to Milan, Italy, to generate the database used in this study. The effects of ozone were determined using N-(2-(2-oxo-1-imidazolidinyl)ethyl)-N'phenylurea (ethylene diurea; EDU) as a protectant against ozone damage. Thus, the ratio of biomass in EDU-treated plants to untreated plants indicated the severity of ozone damage. Simple linear regression produced a low r2 of 0.16 for the dose response. Analysis of the residuals identified three groups in the data depending on their mean residual values. Re-plotting the data into separate dose responses for these three groups produced improvements in the r2 values to 0.33, 0.36 and 0.36, for Groups 1 to 3, respectively. Thedata were subsequently used to train artificial neural network (ANN)models to determine the factors that caused the scatter within the dose response. Vapor pressure deficit and temperature were found to beimportant influences on the dose response whereas longitude, year and altitude were weaker influences. Inclusion of these factors in the ANN model increased the r2 of the model to 0.79. [ABSTRACT FROM AUTHOR]

It was known, as far back as the nineteenth century, that rain water from industrial areas was more acid than that from rural areas. The potential risks for life in general were discussed, but no further attention was paid to the issue. At the end of the twentieth century, the ecosystems of Europe, Canada and the United States have been severely damaged by pollutants borne by atmospheric winds to places distant from their origin. The main effects of these atmospheric pollutants are due to sulfur and nitrogen oxide dilution and to photochemical reactions. International organizations have been formed and agreements pronounced and ratified by many countries for a universal study on the pollution process, on the transport of pollutants--mostly sulfur, nitrogen and ozone--and on how to collaborate in order to reduce emissions in the respective countries of origin for the worldwide profit.