Accumulation And Biodegradation Of Phthalate Acid Esters By Chlorella Vulgaris In Aqueous Environment

In this thesis, bioaccumulation and biodegradation of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP), listed on Priority Control List of EPA, by Chlorella vulgaris were conducted.The experimental results showed that distribution equilibrium of DBP and DEHP between water and freshwater microalgae was reached rapidly in about 0.5 to 1h. Bioconcentration factors (BCFs) for DBP and DEHP in Chlorella vulgaris related to their physical and chemical property and aquatic matrix. It was found that the bioconcentration factors of DBP and DEHP were increasing with the increase of the alkyl chain length, which leads to a higher hydrophobicity. The BCFs of DBP and DEHP were different in different aquatic matrix. BCF in lake water was lower than that in cultural medium. BCF was also different in different algal growth phase.From control test, the loss of DBP and DEHP was mainly due to algal biodegradation, not photolysis, oxidation and hydrolysis. The decrease of DBP and DEHP in algal solution was well fitted with a first-order kinetic equation. The degradation rate constants related with PAEs initial concentration, property of PAEs, algal density and algal growth rate. Nutrient (N, P) enrichments can stimulate algal growth and enhance biodegradation rate of DBP and DEHP by algae.Further study showed that bioconcentration and biodegradation of DBP and DEHP by algae were related to algae growth status and dissolved organic carbon (DOC) in the medium. During growth there is a considerable amount of exudate secretion by algae, expressed as DOC. The exudate with active surface is capable of sorption of PAEs in aqueous phase. Therefore, the decrease of the apparent BCFs of the PAEs is due to reduction in bioavailability of the contaminants in the aqueous phase, when a fraction of the contaminants in the aqueous phase is bound to algal exudates.