Table of Contents 



Introduction 5 



Historical review 7 



Observations and experiments 10 



The regions selected 13 



Controlled field experiments 17 



Analyses of soot 18 



Experiments in nursery and greenhouse 18 



Experiments with pea seedlings 20 



Soot fall 21 



General Considerations 22 



Conclusions 24 



Bibliography of references cited in text 26 



