In November 1981 a first symposium with the topics of "Acid Deposition of Atmospheric Pollutants" was organised in OberursellTaunus to introduce the problems and first results of research-activities on wet and dry deposition of pollutants and on acid precipitation. In the meantime the hazard to forest and vegetation became more dramatic and research-projects to investigate the input of pollutants to forest-ecosystems have been initiated by several interdisciplinary groups. The rapidly increasing interest in the problems of forest­ decay and the many open questions with respect to the diagnosis of the forest-damage were the background for the organisation of a second symposium which was held in November 1985 at the same location in Oberursel/Taunus. It was mainly concerned with new techniques of sampling and analyzing pollutants in forest areas. Besides deposition, one important pathway of pollutants in orographic terrain is the interception of fog-droplets by vegetation. Special emphasis was laid on the chemical composition of fog. The symposium successfully assembled scientists from the field of atmospheric research with those studying the effect of pollutants on trees and vegetation in order to reduce the many open questions in connection with forest desease. The proceedings presented in this volume are a substantial contribution to the understanding of deposition and interception of pollutants in forest-areas. Thanks to the authors the volume contains a lot of new research ·results and presents therefore a true picture of our present knowledge.

Deposition in Forest-Ecosystems.- Deposition of gaseous pollutants in a douglas fir forest.- Gasdep - Gaseous deposition measurements of SO2, NOx and O3 to a spruce stand: Conception, instrumentation and first results of an experimental project.- Comparison of SO2-concentrations and immission-rates with bulk precipitation data.- Wet and dry deposition of atmospheric trace elements in forest areas.- Precipitation input of inorganic chemicals in the open field and in forest stands - Results of investigations in the State of Hesse.- Trends of heavy metal pollution by wet deposition in the Federal Republic of Germany during 1980 - 1984.- Bulk deposition into the catchment "Grosse Ohe": Results of neighbouring sites in the open and under spruce at different altitudes.- Input of atmospheric pollutants in a remote highland area.- Winter deposition rates of atmospheric trace constituents in forests: Assessment of total input.- Interception of Fogwater.- Design of a fog water collector for chemical analysis.- The temporal distribution of trace element concentrations in fog water during individual fog events.- Observation on fog water composition in Hamburg.- Case-Studies.- Temporal variations of trace substances during individual rain events.- Preliminary results and experiences with a new in-situ measurement system of rainfall acidity in forest areas of Rheinland-Pfalz / Federal Republic of Germany.- Occurrence of gaseous pollutants in forest stands.- Possible influences of chlorine containing species on forests.- Effects on Ecosystems.- Watersolubility of heavy metals in deposition samples - Interpretation and prediction of bioavailability.- Dry deposition, retention and wash-off processes of heavy metals in beech crowns: analysis of sequentially sampled stemflow.-Cadmium and lead in the food web of a forest ecosystem.- Studies on biocenoses, individual organisms and deposition rates in the Egge mountains, an area heavily affected by forest decline.- Deposition/canopy-interactions in two forest ecosystems of Northwest Germany.- Processes in the canopy of trees: internal and external turnover of elements.- List of Participants.