Effect of Chlorinated Aliphatic Acids on Gas and Volatile Fatty Acid Production in Anaerobic Soil

By means of gas chromatography, inhibitory effects of chlorinated acetic and propionic acids on gas and acid production by amended anaerobic soil were measured in Landlow clay receiving 0, 10, and 100 ppm monochloroacetic (MCA), dichloroacetic (DCA), trichloroacetic (TCA), and 2,2‐dichloropropionic (DCP, dalapon) acids. The data show that the chlorinated acids inhibited methane production with resultant accumulation of acetate and to a lesser extent propionate. The length of methane inhibition was correlated with chlorinated acid disappearance, varying from a few days for MCA to more than 30 days for TCA and DCP at 100 ppm. In the presence of CaCO 3 , DCP (100 ppm) was inhibitory for less than 12 days. The data of these experiments indicate that use of the herbicides dalapon and TCA at concentrations approximating normal field rates probably should have no lasting adverse effects on anaerobic systems buffered near neutral pH.