Interaction Between PAEs And Algae

Toxicity, bioconcentration and biodegradation of two of the most widely usedphthalate esters (PAEs) -dibutyl phthalate (DBP) and diethylhexyl phthalate (DEHP)in Chlorella vulagaris and Microcystis aeruginosa were investigated in this thesis.The toxicity of PAEs on algae existed. At normal culture condition, the 96 h-IC₅₀of DBP on Chlorella vulgaris was 7.78±0.39 mg/L. Chlorophyll was more sensitive toDBP than absorbency of algal solution and density of algal cells. With the increase oftemperature (13, 20, 25, 30℃), the algae growth rate constants increased. The 96h-IC₅₀ was 7.78 mg/L at 25℃, and had no 96h-EC50 of inhibition in the range of theirwater solubility at other experimental temperatures. The algae growth rate constantsincreased with increasing pH (5.30, 6.07, 7.00, 9.35). The 96 h-IC₅₀ at pH 5.30, 6.07and 7.00 was 12.09, 8.19 and 7.78 mg/L, respectively, while the 96 h-IC₅₀ at pH 9.35were excess the solubility of DBP. At normal culture condition, the 96 h-IC₅₀ of DBPon Microcystis aeruginosa was far more excess the solubility of DBP. Chlorophylland activity of nitrate redutase were much more sensitive to DBP than absorbency ofalgal solution.Algae had an ability to accumulate and degradate PAEs. The decrease of PAEs inalgal solution was described satisfactorily by a first-order kinetic equation. With theincrease of initial DBP concentrations, DBP accumulation in Chlorella vulgaris andBCFs increased. To 1.82 mg/L DBP, the biodegradation rate constant (k) was thehighest. To 0.198 mg/L DBP, accumulation amount in algal cells was small, whichmight cause biodegradation to a small extent. To 4.85 mg/L DBP, it might be highertoxicity of DBP that inhibited algal growth and activity of enzyme. The DBPaccumulation in Chlorella vulgaris, BCFs, and k increased with increasingtemperature. Low temperature inhibited activity of enzyme, resulting in decrease ofthe biodegradation ability of DBP. The bioconcentration of DEHP were higher thanDBP by in both Chlorella vulgaris and Microcystis aeruginosa, because KOW ofDEHP is higher. The biodegradation rate constants were 0.00 and 4.5×10^-3 h^-1 forDBP and DEHP by Chlorella vulgaris, 5.9×10(-3) and 2.0×10(-3) h^-1 by Microcystisaeruginosa, respectively. The difference of biodegradation ability between the twoalgae might be related to the background of PAEs in algae and initial algal density.Also physiological structure, bioactivity of different algae might accuount for it.In lake water, the k of DBP in dark experiment was much higher than that in lightexperiment. But there was no significant difference in both experiments for DEHP.