Assessing the role of trichloroacetyl-containing compounds in the natural formation of chloroform using stable carbon isotopes analysis

► Trichloroacetyl-containing compounds (TCAc) and CHCl3 were detected in forest soils. ► TCAc are much more enriched in 13C compared to natural CHCl3 and NOM. ► Natural CHCl3 has a similar carbon isotope composition as NOM. ► The formation of CHCl3 by hydrolysis of TCAc induced large 13C-isotope fractionation. ► Our model confirms that TCAc are likely precursors of natural CHCl3 in soils.