Competitive Effects And Influential Factors Of Sorption Of Organic Pollutants Onto Sediments

Sorption/desorption of organic pollutants with soil/sediment plays an important role in their transport, fate and bioavailability in natural environment. Sorption and desorption of organic compounds are also influenced by such factors as its physico-chemical properties, constituents and construction of sorbents, environmental conditions and coexistent organic compounds. Presently, knowledge of sorption and desorption is limited, which results in significant errors in environmental prediction of organic compounds. Also, ignoring sorption/desorption of organic pollutants with suspended solids and sediments often make prediction results of water quality model deviate significantly from observations. Therefore, it is needed for researchers to study deeply sorption/desorption of organic compounds and incorporation of them into water quality mode. Based on review on sorption/desorption of organic pollutants with soil/sediment, mechanisms and influential factors of sorptrbn/desorption were investigated deeply.The results of the present research are as follows, (i) The correlation between physico-chemical properties of organic compounds and their competitive power was studied, and it was indicated that organic compounds preferable to form H-bonding with organic matter of sorbents have stronger competitive power; (ii) Sorption behaviors of ionizable organic compounds in different species and their competitive power were examined, and the results showed that phenols and carbonxylic acids with benzyl circle have much stronger competitive power in molecular species than in ionized species, because negative charges of anionic forms can depressed their adsorption on the surface of the sediment; in contrast, organic bases such as aniline and p-chloroaniline show weaker competitive power in molecular species than in ionized species, and this is because both species of the organic bases could adsorb strongly onto the sediment; there is a correlation between competitive power of organic pollutants in multi-solute systems and their sorption isotherm nonlinearity in single-solute systems, and organic compounds whose sorption isotherms is linear in single-solute systems hardly have competitive power in multi-solute systems; (iii) Competitive sorption effects in more than two-solutes systems was studied, and it was exhibited that mixture of two cosolutes each of which could suppress sorption of nominal solute onto the sediment had synergistically competitive sorption effect on the nominal solute; (iv) A method about incorporating sorption/desorption of organic pollutants into river water quality model was developed, and discussion about degree of sorption/desorption effect on model prediction for different organic compounds was made, which will provide theoretical basis and practical processes for setting up more accurate water quality model.