INCREASE IN BIOAVAILABILITY OF AGED PHENANTHRENE IN SOILS BY COMPETITIVE DISPLACEMENT WITH PYRENE

摘要

Competitive sorption to natural solids among mixtures of organic compounds has been documented in the literature. This study was conducted to determine co-solute competitive effects on the biological and physical availability of polycyclic aromatic hydrocarbons in soils after long contact periods (aging). Sterile suspensions of Mount Pleasant silt loam (Mt. Pleasant, NY, USA) and Pahokee peat soils were spiked with phenanthrene and allowed to age for 3 or 123 d before inoculation with a phenanthrene-degrading bacterium in the presence or absence of the nonbiodegradable co-solute pyrene. As expected, mineralization decreased with aging in the samples not amended with pyrene. However, addition of pyrene just prior to inoculation at 123 d significantly mitigated this decrease, that is, the extent of mineralization was greater in the 123-d pyrene-amended samples than in the 123-d nonamended samples. Parallel experiments on sterile soils showed that pyrene increased the physical availability of phenanthrene by competitive displacement of phenanthrene from sorption sites. First, the addition of pyrene increased recovery of 123-d-aged phenanthrene by mild solvent extraction. Second, addition of pyrene (at three concentrations) dramatically reducecd the apparent distribution coefficient (K~(app)_d) of several concentrations of 60-, 95-, and 111-d-aged phenanthrene. At the lowest phenanthrene and highest pyrene concentrations, reductions in the K~(app)_d of phenanthrene in the peat soil reached 83. The competitive displacement effect observed in this study adds further support to t