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 cryosam pling and gaschromatographic analysis. Trees were growing in the Erzge birge (E-Germany) at Oberbarenburg and at the Kahleberg and at a third stand in NW-Bavaria (S-Germany). Emission rates were also measured fo r Scotch pine (Pinus sylvestris L.) and Blue spruce (Picea pungens Eng elm.) at the Kahleberg. Twigs still attached to the trees were enclose d in a flow-through gas exchange cuvette. H2S was detected as the pred ominant reduced sulfur compound emitted from the twigs. The mean H2S e mission 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 speci es investigated at the Kahleberg is calculated on the basis of data on SO2 fluxes. It is very small for Norway spruce and Blue spruce. Howev er, for Scotch pine, H2S emission contributes about 10% to the detoxif ication of SO2.