To assess the effects of TCA on forest health, TCA uptake by Sitka spruce saplings (<i>Picea sitchensis</i>) via atmospheric and soil routes, and its effects on growth, enzyme activity and water retention of needles and visible damage were investigated. Mean TCA concentrations in soils from an upland forest site and a lowland agricultural site were 48 (±85, n=84) ng g<sup>-1</sup> and 26 (± 18, n = 5) ng g<sup>-1</sup> (fresh weight). TCA concentrations varied greatly between soil types and decreased significantly with soil depth. In spruce soils TCA concentration was negatively related to water content, and positively related to soil organic matter content. A strong positive relationship (R<sup>2</sup> = 0.9, P<0.001) observed between soil TCA concentration and soil microbial biomass carbon, in a variety of soil types, may be evidence for formation of TCA in soils by micro-organisms. In a 6-month field experiment, lysimeters (2.5 l) at forest and agricultural sites were dosed fortnightly with solutions containing 20 or 50 mg TCA, and soil leachates collected over 2 week periods. In all lysimeters less than 30% of TCA applied to soil was recovered in soil leachate. The “lost” TCA was not detected in the soil, indicating that the applied TCA was degraded, or bound to organic matter within the soil. In experiments where soil was spiked with radioactive [1,2-<sup>14</sup>C] TCA (»380 ng g<sup>-1</sup> (fwt)), <sup>14</sup>CO<sub>2</sub> was produced, confirming that TCA in soil is rapidly degraded by micro-organisms, with a half-life of approximately 12 - 46 days depending on soil type. In a controlled greenhouse experiment 6-year old Sitka spruce saplings were exposed twice a week over two growing seasons, to 0, 10 or 100 mg l<sup>-1</sup> solutions of TCA via either the foliage or soil. TCA was taken up into tree needles via both routes (with foliage route being more significant than previously thought). There was no effect of different treatments on sapling growth, but increased activity of detoxification enzymes in saplings exposed to TCA via the foliage suggested that this route of uptake causes greater stress.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649523 |
| Date | January 2004 |
| Creators | Dickey, Catherine Anne |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13649 |
Page generated in 0.0021 seconds