How Forest Trees Actively Promote Acid Deposition. The Role of Terpenes in the Dry Deposition of Ozone and Ozone Sulphuridioxide Mixtures

TERPENES AND ISOPRENE ARE EMITTED FROM CONIFERS AND DECIDUOUS TREES IN RATHER IMPORTANT QUANTITIES. THE TOTAL WORLDWIDE EMISSION OF TERPENES PLUS THE ISO- PRENE ARE ABOUT 9.108 METRIC TONS PER YEAR (1). BECAUSE OF THEIR CHEMICAL NATURE, MOSTLY UNSATURATED HYDROCARBONS, TERPENES REACT QUITE RAPIDLY WITH AM- BIENT OZONE AND LEAD, VIA OZONIDES, TO HIGHLY OXIDIZING SPECIES AND CONSECUTI- VE PRODUCTS, PARTLY AS AEROSOLS (2). WHILE OZONE AS SUCH IS NOT ABLE TO OXI- DIZE SULPHUR DIOXIDE UNDER AMBIENT CONDITIONS AS ANY CONSIDERABLE RATE, (K = 1,5 .10-8 PPM MIN-1) A MIXTURE OF IT WITH TERPENES CONVERTS SULPHUR DIOXI- DE, AS WE AND OTHERS SUGGESTED EARLIER (3), VERY QUICKLY AND EFFICIENTLY TO SULPHURIC ACID, EVEN IN THE PPB RANGE. IT HAS LIKEWISE BEEN SHOWN BY US THAT THE FORMED AEROSOLS MIGHT BE IMMEDIATELY ADSORBED TO THE PLANT SURFACE (OR E- VEN INSIDE THE PLANT). SO, THE OVERALL RESULT IS A NET DEPOSITION OF OZONE OR OZONE/SULPHUR DIOXIDE MIXTURES. IN THIS CONTEXT WE HAVE BEEN STUDYING THE REACTION OF SO2/O3 BOTH WITH A SE- LECTED TERPENE (BETA-PINENE) AND WITH THE INTEGRAL EMISSION OF A SPRUCE BRANCH (PICEA ABIES)

GEISS Friedrich;  STANGL Heinz;  KOTZIAS Dimitrios; 

1995-03-15

JRC5474

https://publications.jrc.ec.europa.eu/repository/handle/JRC5474,