Determination of Retardation Effect of SOM on Aqueous Leaching of Polycyclic Aromatic Hydrocarbons Using Confocal Laser Scanning Microscope

Abstract

Influence of soil organic matter (SOM) on the adsorption, desorption and transport of polycyclic aromatic hydrocarbons (PAHs) has already been given full investigation in soils. In this paper, confocal laser scanning microscope (CLSM) was used to elucidate aqueous leaching of PAHs in different types of soil with soil columns, which enhanced understanding on transport of PAHs appreciably. Four typical soils in China including fluvo-aquic soil (FAS), aquic brown soil (ABS), red soil (RS) and black soil (BS) were selected in the experiment. Target pollutants of phenanthrene and pyrene were extracted from the leachate by solid phase extraction (SPE) and then determined by high performance liquid chromatography (HPLC). The experimental results showed that the retardation ability of pollutants to the four selected types of soil increased in the order: FAS H" ABS < RS < BS. To better expatiate the dissimilar ability of the PAHs transported in the four typical soils, the retardation factor (R), distribution constant (Kd) and partition coefficient (Koc) were evaluated based on the observed breakthrough curves (BTCs). Furthermore, CLSM was used to visualize the effects of SOM on the transport ability of PAHs in different types of soil. All the results provided vivid understanding with mathematical and especially optical measures that SOM was considered the single most important factor limiting the availability and mobility of PAHs in soil over the duration of the experiment.