This study is concerned with the effects of di （2-ethylhexyl） phthalate （DEHP） on two kinds of duckweeds （Spirodela polyrhiza and Lemna minor）.The results indicate that DEHP has aquatic toxicity to Spirodela polyrhiza at 0.4 mg/L and to Lemna minor at over 0.1 mg/L by changing their physiologic-biochemical characteristics.The contents of duckweed chlorophyll and soluble protein decrease with increasing DEHP concentration after 7 d of exposure.DEHP shows the stimulating role in catalase （CAT） and superoxide dismutase （SOD） systems at relative low levels.At 0.01 mg/L and 0.005 mg/L,SOD activities of Spirodela polyrhiza and Lemna minor reach their peak values respectively,while CAT activity reaches its maximum value at 0.05 mg/L and 0.01 mg/L.When DEHP levels are too high,the protection enzyme system would be destroyed and plant growth is inhibited.The analysis of malondialdehyde （MDA） and Fourier transform infrared spectroscopy manifest that DEHP could affect the tested duckweeds by destroying its cell membranes,and Spirodela polyrhiza is more resistant to DEHP exposure than Lemna minor.
Oil spills may considerably damage sensitive coastal wetlands. The phytoremediation potential and restoration of a dominant coastal marsh plant, Cyperus rotundus, for diesel pollutant and its phytoremediation effectiveness were investigated in this open-air pot experiment. Cyperus rotundus was transplanted into soil contaminated with diesel at concentrations of 1 000, 5 000, 10 000, 15 000, 20 000 mg/kg. In order to better elucidate the biochemical and physiological responses to diesel pollutants, activity of the antioxidant enzymes peroxidase （POD）, catalase （CAT） and ascorbic acid oxidase （AAO） were determined in the plant tissue after 50 d treatment at the levels mentioned above. The results showed that CAT and AAO of stem and leaf exhibited peak enzyme activities on 15 000 mg/kg soil and 10 000 mg/kg soil respectively, and declined at higher concentrations. Additionally, the increment of biomass and the content of soluble protein, as well as chlorophyll content were affected by diesel. The highest restoration effectiveness appeared at the level of 5 000 mg/kg. Collectively, Cyperus rotundus is a potential plant which can be used for restoring the diesel-contaminated soil.
E-beam degradation of bisphenol A(BPA) was carried out,under reductive condition of ethanol-water solution and oxidative condition of acetonitrile-water solution.The degradation efficiency is higher in oxidative condition than that in reductive condition,and increases with the dose but decreased with increasing initial concentration.The BPA radiolysis follows the pseudo-first-order kinetics.Adding H_2O_2,or neutral condition,does not benefit BPA degradation in oxidative conditions.Pulsed radiolysis was used to investigate mechanism of the BPA radiolysis.The rate constant for BPA reaction with OH(1.85×10^(10) L·mor^(-1)·s^(-1)) is about an order of magnitude higher than that with e_(aq)^-(1.80×l0~9 L·mor^(-1)·s^(-1)).The degradation products were analyzed by ion chromatograph.Smaller molecules such as formic acid and acetic acid were detected,indicating that ^-OH attacks the BPA molecule.The work is of significance for the practical E-beam treatment of waste water containing BPA.
XU Gang REN Hua WU Ming-Hong LIU Ning YUAN Qing TANG Liang WANG Liang
Oil contaminated soil was collected from Huangpu River-Yangtze River estuary wetland, with the aim of isolating oil-degrading microorganisms and evaluating their ability to degrade diesel. Three bacterial strains were discovered and identified by sequencing their 16S rDNA genes, two were Pseudomonas and one was Alcaligcnes. The proper growth conditions of each bacterium were measured and presented for diesel biodegradation. Biodegradation assays revealed that the degradation rates of three bacterial strains were 42.5%, 14.6% and 15.9% in 7 d respectively. They all play an important role on the nalkanes within the range of C16-C25 components of diesel. The results indicated that the oil-degraders can adapt to degrade diesel. The bacterial strains can be used in wetland diesel pollution control.
The purpose of this study was to evaluate the potential of electron beam to decompose chloramphenicol （CAP） in aqueous solutions. At the absorbed dose of 15 kGy, the decomposition rate of CAP was 95.24%. The degradation of CAP under electron beam irradiation followed pseudo-first-order kinetics. Redox reactions of CAP aqueous solutions with hydroxyl radicals （.OH）, hydrated electrons （eaq） and hydrated atoms （·H） were studied. The increase of the additives would result in the decrease of the degradation efficiency. The concentration of Cl- and NO3- in aqueous solution increased after electron beam irradiation. On the basis of the experimental results, a photocatalytic mechanism was discussed. The rate constant for reactions of .OH and CAP was 9.36×10^7 L/（mol.s） and for reaction of eaq and CAP was 7.33×10^7 L/（mol.s）..OH was supposed to play the key role in the radiation system of aqueous solution. Other free radicals like eaq and .H could also initiate the degradation.
