The Effects Of Different Soil Organic Matters On The Sorption And Biodegradation Of Phenanthrene

It has been reported that soil organic matter is the predominant sorbent for persistent organic pollutants (POPs). In this study, the sorption characteristics and biodegradations of soil, mineral-bound humic acid (MHA) and mineral-bound humin (MHU) separated from the topsoil of Heilongjiang province to phenanthrene were researched firstly. Experimental results are as follows:1) The fulvic acid, MHA and MHU were separated from the soil by using the solution of 0.1 mol/L NaOH. The scanning electron microscope pictures proved that the MHA united the pieces, but MHU had granular appearance. The results of elemental analysis proved that nearly fifty percents of the soil organic carbon distributed in mineral-bound humin, fulvic acid and mineral-bound humic acid accounted for about 25%separately. The Infrared spectra and i3C Nuclear magnetic resonance spectroscopy spectra of MHA indicated that MHA was richer in the content of carboxyl carbon.2) The sorption kinetics indicated that the sorption of MHA, MHU and soil to phenanthrene were quick at the early period and then became slow gradually. After 48 hours, the three types of materials'adsorptions to phenanthrene were becoming more balance. The adsorption rates:MHU> soil> MHA; the adsorption quantity of equilibrium:MHU> soil> MHA; the time to equilibrium:MHU was the most fast, followed by soil and MHA. The isotherms showed that the distribution coefficients K and nonlinearities followed the orders: MHU>soil>MHA.3) The biodegradation kinetics of phenanthrene adsorbed by MHU, MHA and soil which had aged 60 days suggested that in the early period (6 hours) the biodegradation of phenanthrene adsorbed by MHA was 46.99%, while the soil and MHU were 64.40%and 59.33%separately; the end of the biodegradations (48 hours) biodegradation of phenanthrene adsorbed by MHU was 77.83%, followed by MHA (80.28%) and soil (80.72%). The investigation into biodegradation and sorption character indicated that the MHA with lower distribution coefficients K restrained the biodegradation of phenanthrene significantly, but not to the MHU with higher coefficients K.4) The experiment about the influences of the amount of sorbent on the biodegradation suggested that with the amount of sorbent increasing, the biodegradations of phenanthrene were significantly restrained by MHA; when the amounts of MHA increased by two times, the biodegradations of phenanthrene decreased by 64.9%. While they were not changed by MHU. 5) In the aging experiments we took the biodegradations of phenanthrene adsorbed by MHA as the standards; the ratio of MHU and MHA with 6 hours'degradation was 1.69 when aged 1 day, but decreased to 1.08 when aged 60 days; similarly the ratio of MHU and MHA with 24 hours'degradation at 1 day aging and 60 day were 1.26 and 0.95 separately. So with the aged time increasing the biodegradations of phenanthrene adsorbed by MHU decreased; and at the early period MHA restrained the biodegradation of phenanthrene significantly, but at the later period MHU played an important role in inhibition of biodegradation. The biodegradations of pyrene adsorbed by the MHA, MHU and soil were similar to the phenanthrene.6) When the MHA was dissolved by the NaOH solution, solubility of phenanthrene increased and the surface tension decreased affected by the dissolved MHA.The biodegradation of phenanthrene was raised in the situation of less inoculums concentration with the addition of the dissolved MHA.