Study On The Effect Of Coexisting Contaminants On Sorption Of Three Organic Contaminants In Soils/Sediments

Combind pollution has become one of the important directions of environmental chemistry at present. Sorption of organic pollutants by soils/sediments plays an important role in their transport, fate and bioavailability in natural environment. In response to the serious combind pollution of soils and groundwater, it is interested to understand and evaluate the sorption behaviors of organic pollutants on soils/sediments, and to control the sorption behaviors. In this dissertation, the sorption behaviors and mechanisms of organic pollutants by combind pollution onto soils/sediments were investigated detailedly. The main conclusions of this dissertation are:(1)The effects of different heavy metals (Cd2+ Pb2+), cationic surfactants cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecylbenzenesulfonate (SDBS)) and the chemistry of the solution (pH and ionic strength) on the sorption of bisphenol A (BPA) to sediment were studied. Results showed that the presence of Cd2+ and Pb2+ caused a significant increase on the sorption of BPA to sediment. The effect of surfactants on the adsorption of BPA onto sediment was found to strongly depend on the type of the surfactants. The presence of CTAB promoted BPA sorption and the amount of BPA adsorbed onto sediments increased linearly with concentration of CTAB. In contrast, the presence of anionic surfactant (SDBS) caused a slight reduction on the sorption of BPA. In complex system, the compounding effect of heavy metals and surfactants on BPA sorption was significant. Moreover, with the increase of the surfactant concentration, the increase on BPA sorption caused by surfactants was predominat than that of heavy metals. It was also found that the sorption behavior of BPA was affected by solution pH and ionic strength. The larger amount of BPA was absorbed with higher ionic strength and lower pH.(2)The effects of different heavy metals (Cd2+, Pb2+), surfactants ((CTAB), (CPC)) and the ionic strength (Ca2+, NH4+) on sorption and desorption of BPA were studied using soil column experiment. Results showed that the presence of heavy metals and cationic surfactants caused a significant increase on the BPA sorption. In addition, a clear difference between these sorption curves is the"tailing"in the presence of CTAB and CPC (slow approach to Ce/C0=1), that is characteristics of nonequilibrium sorption during BPA transport. It was also found that the larger amount of BPA was absorbed with higher ionic strength. The cationic surfactants enhanced the desorption ability of BPA form the soil. However, the Cd2+, Pb2+ and Ca2+, NH4+ decrease the sorption of BPA. The results provided a better understanding of BPA behavior in environment and facilitated more accurate assessment of its ecological risk and identification of appropriate management strategies.(3)The sorption behavior of naphthalene in the presence of dissolved organic acid was studied. The presence of dissolved organic acids at lower concentrations had only a little effect on naphthalene sorption. However, when the concentration exceeds a certain concentration, a significant inhibition was observed. Moreover, the inhibition enhanced with the increasing concentrations of dissolved organic acids. In addition, the change of structure of sediment is an important factor that can affect the naphthalene sorption. This suggests the change of solubility of naphthalene and the change of structure of sediment in dissolved organic acids solution both exert effect on naphthalene sorption。(4)Sorption behavior of four chemicals BPA, 2, 4-dicholrophenoxyacetic acid (2, 4-D), 2, 4-dichlorophenol (2, 4-DCP) and p-nitrophenol (PNP) to sediment was investigated by means of batch sorption experiments. Results showed that all the isotherms for each single chemical were in good agreement with Freundlich equation. The influence of BPA, 2, 4-D and 2, 4-DCP as cosolutes on the sorption of PNP as target solute was studied by determining the single isotherm of PNP. Little or no competitive phenomenon was observed in the presence of BPA and 2, 4-D. In contrast, the competitive inhibition occured when 2, 4-DCP were introduced to the solution. In addition, the competitive power enhanced with the increasing of cosolute concentration. The competitive degree depends on the hydrophobicity, concentration and the functional group of cosolute, and can be interpreted by dual-mode model.