Effects of humic acid on the biodegradation of di-n-butyl phthalate in mollisol

Soil phthalic contamination has received more and more attention due to the widespread use of plastic mulching films. Humic acid (HA) is a natural antidote. The effects of HA on the biodegradation of dibutyl phthalate (DBP) in mollisol was investigated in this study. Through the calculation by bi-exponential model, the half-life of DBP was effectively shortened after adding HA, from 11.65 days to 3.36 days, and soil bulk density decreased. The enhancement mechanism for DBP removal by HA was analyzed by fluorescence spectrometry, two-dimensional FTIR correlation spectroscopy (2D-FTIR-COS) and PLFA analysis. Two major functional groups (aryl C–O and alkyl ester CO) were found at the binding site between DBP and HA. By mediating the transportation of DBP, HA could provide more time for soil microorganisms to degrade DBP. Meanwhile, HA effectively stabilized the mollisol microbial community composition and promote the growth of aerobic bacteria, which contributes to the degradation of DBP. The results are valuable for relieving DBP pollution caused by agricultural production and promoting sustainable use of mollisol. •HA shorten the half-life of DBP in black soil.•HA and DBP are bound by static quenching and have only one binding site.•HA stabilizes microbial activity and promotes the growth of aerobic microorganisms.