Trichloroacetic acid in conifer needles and arboreal lichens in forest environments

In the past, trichloroacetic acid (TCA) was a commonly used herbicide, which caused alterations in the properties of surface wax, inhibited growth and caused leaf necrosis. TCA is also a degradation product of short chain chlorocarbons which are used as solvents and degreasers in industry. TCA may also originate from the bleaching of kraft pulp with agents containing chlorine. In this study TCA concentrations in conifer needles were determined in several rural forest areas in subarctic regions in Finland. TCA was analyzed as its methyl ester by View the MathML source. The TCA levels in the third-year needles varied in the range 1–180 μg kg−1 (median 23 μg kg−1, n = 130); 90% of the values being between 5 and 70 μg kg−1. No regional concentration trends could be observed. TCA was also present in arboreal lichens of conifers, which is further proof of its atmospheric origin. Comparison of the TCA levels in Usneaceae lichens with lichen biomass gave a significant negative correlation (P = 0.02), whereas TCA concentrations in needles and visible symptoms of tree vitality did not show causal relationships.