Geochemical Transformation of Trichloroacetic Acid to Chloroform in Fresh Waters – The Results Based Upon Laboratory Experiments

Abstract

In order to explore the geochemical transformation of trichloroacetic acid to chloroform in fresh waters, an experimental study by using laboratory microcosms was performed. The study confirmed the abiotic transformation of TCA to chloroform with various rate constants, ranging from approx. 3.29×10 −4 day −1 to 4.41×10 −4 day −1 , in different fresh waters at 25±1 • C. Also, an induction period (5-6 days) was observed before apparent degradation of TCA. Of the four geochemical factors including pH, oxygen, humic substances and ferric ion, the influence of lake HA, extracted from East Lake, on the transformation has been proven to be more substantial. Several model substances of HA, such as acetic acid, citric acid and β-Resorcylic acid etc., were also found to promote chloroform formation. Whilst, the results of pH effect experiments showed that higher yields of chloroform released from TCA solution occurred in the intensified alkaline media (pH = 10), an unusual condition in environment, indicating the limited effect of pH on the transformation under prevailing conditions in natural waters. According to our study, a mathematic model was built and successfully used to simulate TCA transformation to chloroform in fresh waters. Mathematic simulation demonstrates that the rates of decay for chloroform formation, after induction time, are mainly owing to rapid TCA degradation. In addition, biotic experiments indicated that fresh water algae affect TCA transformation to chloroform in varying degrees. The blue alga Anabaena cylindrica remarkably promoted chloroform formation, in weak acid media (pH = 6.5). While, the green alga Chlorella vulgari seems to indistinctively affect chloroform formation, whether in alkaline or weak acidic media. Enzyme or other byproducts of alga, such as citric acid, might play roles in the TCA transformation.

Formation mechanisms of trichloromethyl-containing compounds in the terrestrial environment: A critical review

“…Such spontaneous decarboxylation has however been shown to be very slow at relevant temperatures in pure water (Fairclough, 1938), lake water (Xiang et al, 2005) and spruce needles (Matucha et al, 2006), while at elevated temperature (>60°C), the decarboxylation is fast. Haselmann et al did find some indications that trichloromethane could be formed by degradation of trichloroacetic acid in forest soil (Haselmann et al, 2000b), but other authors (Forczek et al, 2001;Matucha et al, 2003) were not able to repeat this observation, and in general trichloroacetic acid formed in soil seems to be quickly mineralized to CO 2 and Cl -by microbial activity (Forczek et al, 2001;Matucha et al, 2003;Albers et al, 2010a).…”

Utilizing two detectors in the measurement of trichloroacetic acid in human urine by reaction headspace gas chromatography

“…It was based on HS‐GC detection of the carbon dioxide (CO 2 ) released from the reaction between the fatty acid and sodium bicarbonate in edible oils. According to the literature (Matucha et al, ; Xiang, Xiang, Zhang, Wu, & Tang, ), the TCA can be decomposed into chloroform and CO 2 under high‐temperature conditions, i.e. …”