PARENT SESSION

1H b - Pesticides
Hall 9
1:45 PM - 3:30 PM, Wednesday, 30 April 2003
Chair: Pluecken, U.¹, ¹
Co-chair: Koerdel, W.², ²

(WE9/15) Transport of modern pesticides into beech forests.

Bernhardt, Andreas¹, Palm, Wolf-Ulrich¹, Ruck, Wolfgang ¹, ¹ University of Lüneburg, Lüneburg, Lower Saxony, Germany

ABSTRACT- Despite of more than two decades of intensive forest decline research, there is still a lack of knowledge concerning the reasons. The input of inorganic substances like nitrate or ozone as well as unpolar organic substances like PAHs or DDT into forest ecosystems has extensively investigated. However, the input of polar substances like modern pesticides into forest ecosystems, their fate and their possible responsibility for forest decline is still unknown. Concentrations and fluxes of 20 polar pesticides in stemflow, crown-throughfall and rainfall in three beech forests in the north-western low-lands of Germany were determined during a period of two years. Stemflow samples were collected by tin foil gutters laid spirally around the stem, crown-throughfall and rainfall samples were collected by rainfall collectors made of stainless steel. Samples were enriched by solid phase extraction and analysed by HPLC-MS. Isoproturon, Metolachlor, Prosulfocarb and Terbuthylazine were detectable in and partially some weeks after the period of application in all analysed water samples. In rainfall-samples concentrations up to 300 ng/L were found during very short periods matching their application time. In stemflow and crown-throughfall samples the same substances were still detectable up to four weeks later compared to rainfall samples but the detected concentrations were partly much higher. For instance, concentrations for Isoproturon increased to 60 g/L in autumn 2002 in stemflow samples. Comparing the deposition of pesticides on free grassland nearby the investigated forests and below the trees (by the crown-throughfall), deposition per square meter on the forest-ground was found to be up to 50 times higher than in rainfall. Maximum deposition for example for Isoproturon of 3 g per square meter and day was found. Forests are well known to act as a very effective filter for unpolar pesticides like DDT, dieldrin or aldrin from the atmosphere. Results of this investigation prove, that beeches are even effective scavengers for modern polar pesticides. The impact of regional and nearby transport of polar and unpolar pesticides will be discussed.

Key words: beech-forests, pesticides, rain