THE EFFECT OF THE EXCLUSION OF DRY AND WET DEPOSITION ON VISIBLE SYMPTOMS AND ACCUMULATION OF SULFUR AND FLUORIDE BY PICEA-ABIES NEEDLES NEAR POINT-SOURCES

The effect of air pollutants on conifers was studied throughout the ye ar near industrial point-sources using two types of half-open chambers for excluding wet or dry deposition around selected trees. Results in dicate that pollutant uptake from dry deposition and wash-off effect b y rain have overriding influence in the internal accumulation of pollu tants by needles. The exclusion of wet deposition substantially enhanc ed pollutant accumulation in the needles and suggests that wet deposit ion itself has a minor direct effect on accumulation near point-source s. Near the fertilizer plant the trees growing in filtered air exhibit ed fewer visible symptoms and had lower accumulations of fluoride. Thi s suggests that decreasing the gaseous air pollutants would improve th e condition of conifers at this site. Results suggest also that beside s high needle pollutant content, winter conditions are needed to facil itate visible injury development.