Conversely, since the unreacted PEGs did not biodegrade in soils, the effect of forming biodegradable PEG molecules with lower MW from •OH-reaction induced chain scissions was much more pronounced. This finding suggests a much stronger MW dependence of PEG biodegradation in soils than sediments -and that PEG chain scission reactions may lift biodegradation restrictions in soils. In fact, the final mineralization extents closely match the fractions of PEGs with MW < 2000 Da of 21, 35, and 55 wt% for the t1, t2, and t3 samples, respectively, as determined by HPLC-CAD. This finding suggests an upper limit for PEG biodegradation in soils under the given conditions is between 2000 and 2500 Da.