EMISSION OF HYDROGEN-SULFIDE BY TWIGS OF CONIFERES - A COMPARISON OF NORWAY SPRUCE (PICEA-ABIES (L) KARST), SCOTCH PINE (PINUS-SYLVESTRIS L) AND BLUE SPRUCE (PICEA-PUNGENS ENGELM)

The emission of reduced volatile sulfur compounds from twigs of Norway spruce (Picea abies (L.) Karst.) was measured in the field by cryosampling and gaschromatographic analysis. Trees were growing in the Erzgebirge (E-Germany) at Oberbarenburg and at the Kahleberg and at a third stand in NW-Bavaria (S-Germany). Emission rates were also measured for Scotch pine (Pinus sylvestris L.) and Blue spruce (Picea pungens Engelm.) at the Kahleberg. Twigs still attached to the trees were enclosed in a flow-through gas exchange cuvette. H2S was detected as the predominant reduced sulfur compound emitted from the twigs. The mean H2S emission rate from twigs of Norway spruce varied between 0.04 pmol kg(-1) dw s(-1) at Wurzburg and 6.21 pmol kg(-1) dw s(-1) at the Kahleberg. Comparing different species at the Kahleberg, the mean H2S emission rate was almost the same from twigs of Norway spruce (6.2 pmol kg(-1) dw s(-1)) and Blue Spruce trees (5.9 pmol kg(-1) dw s(-1)) but it was approximately 18 times higher for Scotch pine (110 pmol kg(-1) dw s(-1)). The percentage of SO2-exclusion via H2S-emission of the tree species investigated at the Kahleberg is calculated on the basis of data on SO2 fluxes. It is very small for Norway spruce and Blue spruce. However, for Scotch pine, H2S emission contributes about 10% to the detoxification of SO2.