Measurement of the Deposition and Fate of Sulfur-Dioxide-35 in a Pine Plantation
- D. W. Gay and
- Charles E. Murphy *
An experiment was carried out to determine the uptake rate and fate of SO2 absorbed by the forest canopy. The radioactive tracer, 35S was used. Branches of loblolly pine were exposed to 35SO2 in the field with a portable chamber. The exposed branches were excised and a sample of needles was immediately washed with distilled water. The needles and water collected in the field were analyzed for 35S content. The results indicated that a portion of the 35S could be washed from the needles and another portion was not removed with a water rinse. The portion that could not be removed by rinsing was absorbed at a rate and followed patterns of absorption, which suggested that absorption was controlled by stomatal diffusion, and thus was internal. The 35S that could be removed by rinsing appeared to be surface absorption. The average deposition velocity for the entire leaf surface of the pine plantation was 0.0041 m/s. The distribution of 35S was investigated by serial extractions. The fresh whole needles were rinsed in distilled water. Following rinsing, the dried and crushed leaf material was extracted with acetone, and then extracted with hexane. About 50% of the 35S activity was removed by the water rinse. About one-third, 30 to 38%, of the 35S activity remaining after washing was found in each of the two extracts and about one-third in the residual material left after extraction.
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