Chloroacetic acids in European soils and vegetation

Abstract

Trichloroacetic acid (TCA) and dichloroacetic acid (DCA) are possible minor atmospheric degradation products of perchloroethylene and trichloroethylene, respectively. These acids may be wet- or dry-deposited from the atmosphere to land surfaces and hence possibly affect plant growth. However, the existing database on TCA levels in soil is limited to a few studies carried out in the late 1980's and the early to mid-1990's and it was concluded that there is a need for further measurements of concentrations of TCA and DCA in soils. In this study soil samples from 10 locations in 5 European countries, as well as vegetation samples, and a limited number of rainwater and air samples were collected and analysed for DCA and TCA to determine the concentrations of these compounds. An isotope dilution method using GC-MS was used for the determination of these acids in the samples. The method was briefly validated and the performance characteristics are presented. The results of the analysis of the soil samples show that the DCA and TCA concentrations in soil from different sites in Europe are more or less comparable, with the exception of Germany, especially Freudenstadt, where significantly higher TCA concentrations (up to 12 µg kg⁻¹ dw) were found. The average DCA and TCA concentrations in soil in this study were 0.25 ± 0.12 and 0.64 ± 1.40 µg kg⁻¹ dw, respectively. Generally, the concentration in soils from forest areas are about twice those from open-land areas. The DCA and TCA concentrations in vegetation samples ranged from 2.1 to 73 µg kg⁻¹ dw for DCA and from 4.7 to 17 µg kg⁻¹ dw for TCA. Thus, the concentrations in vegetation samples are 10–20 times higher than the soil concentrations. DCA and TCA concentrations in wet deposition samples and air samples collected in The Netherlands were 0.14 and 0.15 µg l⁻¹ for wet deposition samples and <0.5 and 0.7 ng m⁻³ for air samples respectively. For these samples taken in The Netherlands, the estimated values for soil and air concentrations calculated from the wet deposition concentrations are in agreement with the concentrations measured in this study.