Major factors dominating the fate of dibutyl phthalate in agricultural soils

Dibutyl phthalate (DBP) is a ubiquitous soil contaminant. We have investigated the sorption, degradation and residue of DBP in 20 types of agricultural soils and aimed to identify the major soil properties that dominate the fate of DBP. Sorption isotherms of DBP in all soils were fitted well with the Freundlich model. The sorption coefficient (K-f) varied between 3.99 and 36.1 mg(1-1/n)L(1/n)/kg. Path analysis indicated that 59.9% of variation in K-f could be explained by the combination of pH, organic carbon (OC) and clay content. Degradation of DBP in the 20 soils was well described by the first-order kinetic model, with half-lives (t(1/2)) ranging from 0.430 to 4.99 d. The residual DBP concentration after 60 d of incubation (R-60) ranged from 0.756 to 2.15 mg/kg and the residual rates ranged from 3.97% to 9.63%. The K-f value was significantly positively correlated with t(1/2) and R-60. Moreover, soil pH, microbial biomass carbon (C-mic) and OC were identified as dominating factors that explained 84.4% of variation in t(1/2). The R-60 data indicated 72.2% of its variability attributable to the combination of OC and C-mic. The orders of the relative importance of dominating factors on the K-f, t(1/2) and R-60 were OC > pH > clay, C-mic, > pH > OC and OC > C-mic, respectively. This work contributes to better understand the fate of DBP in soils and make scientific decisions about accelerating its dissipation in different soils.