Formation of chloroform in spruce forest soil - results from laboratory incubation studies

The release of chloroform, 1,1,1-trichloroethane, tetrachloromethane, trich loroethene and tetrachloroethene from an organic rich spruce forest soil wa s studied in laboratory incubation experiments by dynamic headspace analysi s, thermodesorption and gas chromatography. Performance parameters are pres ented for the dynamic headspace system. For spruce forest soil, the results showed a significant increase in chloroform concentration in the headspace under aerobic conditions over a period of seven days, whereas the concentr ation of the other compounds remained fairly constant. A biogenic formation of chloroform is suggested, whereas for the other compounds anthropogenic sources are assumed. The addition of trichloroacetic acid to the soil incre ased the release of chloroform from the soil. It is, therefore, suggested t hat trichloroacetic acid also contributed to the formation of chloroform. U nder the experimental conditions, the spruce forest soil released chlorofor m concentrations corresponding to a rate of 12 mu g m(-2) day(-1). Data on chloroform production rates are presented and compared with literature resu lts, and possible formation mechanisms for chloroform are discussed. (C) 20 00 Elsevier Science Ltd. All rights reserved.