Effect Of Dissolved Organic Matter On The Stress Of Tetracycline To Photosynthesis Of Chlorella Vulgaris

Tetracycline is a common antibiotic pollutant in aquatic environment.Dissolved organic matter(DOM)is a ubiquitous chemical in water environment,which has a strong complexing effect on pollutants,and therefore has a profound impact on the ecotoxicity of pollutants.The effect of DOM to tetracycline stress to aquatic plants is not clear.In this experiment,Chlorella vulgaris was used as the material to explore the toxic mechanism of tetracycline to Chlorella photosynthetic system.The effect of tetracycline on PSI and PSII of Chlorella vulgaris was studied by chlorophyll fluorescence technique.The toxic sites of tetracycline on Chlorella photosynthetic system was revealed by a simultaneous measurement on Photosystem Ⅰ/PhotosystemⅡ(PSⅠ/PSⅡ)electron yield and electron transfer rate,and measurement on the electron transport at PSⅡ donor/receptor side and the activity of reaction center.With 3DEEM,FTRI,and ITC techniques,the combination between tetracycline with different polarity and different molecular weight of DOM was studied as well as the impact of different groups DOM on tetracycline toxicity.The main results are as follows:(1)25 mg L-1 of tetracycline can decrease the electron yield of photosystem Ⅱ,and decrease the electron transfer rate of Photosystem Ⅱ,but has little effect on the electron yield and electron transfer rate of Photosystem Ⅰ.25 mg L-1 of tetracycline inhibits both the donor and the acceptor sides of photosystem Ⅱ.Tetracycline inhibits the transfer of electrons from QA-to QB/QB-,enabling more QA-to undergo S2(QAQB)-charge recombination oxidation.(2)Tetracycline can be complexed with DOM with different polarity,and the ability of hydrophobic DOM to bind with tetracycline is stronger than that of hydrophilic DOM.Both hydrophilic DOM and hydrophobic DOM complexed with tetracycline can reduce the toxicity of tetracycline.(3)Tetracycline has strong complexation with DOM of various molecular weights.The molecular weight of 100-1000u,1000-3500u and above 10000u of DOM have strong complexation with tetracycline,while 3500-10000u has weak complexing ability.The binding ability of protein and tetracycline in DOM is stronger than that in humus.Protein has an important Influence on the behavior of tetracycline in the environment.Can alleviate the tetracycline on Chlorella photosynthesis toxicity of the presence of DOM,the molecular weight of 100-1000u DOM compared to the other groups to relieve the weaker ability.