Phytoremediation of petroleum hydrocarbons in tropical coastal soils II. microbial response to plant roots and contaminant

GOAL, SCOPE AND BACKGROUND: The goal of this study was to understand the interaction between plants and microorganisms during petroleum-hydrocarbon bioremediation in Pacific Islands coastal soils. Total bacteria and hydrocarbon-degrading microorganisms population dyanamics were examined in the rhizospheres of tropical trees and shrubs, which were evaluated for their phytoremediation potential in a greenhouse experiment. The respective and combined effects of plant roots and diesel contaminant on the microbial populations were determined in relation to diesel fuel depletion. An increase in the grading populations size of the hydrocarbon-degrading populations of microbes, elicited by rhizodeposition, is generally regarded as conducive to an enhanced degradation of petroleum hydrocarbon pollutants in vegetated soil. METHODS: The soil was a coastal sandy loam (pH 7.8) which was artificially contaminated with 10 g of No. 2 diesel fuel/kg soil or left uncontaminated. The pots were irrigated with fertilizer and 1% NaCl. The enumerations were carried out in the contaminated and uncontaminated rhizospheres of three trees, kiawe (Prosopis pallida), milo (Thespesia populnea), and kou (Cordia subcordata) and three shrubs, beach naupaka (Scaevola sericea), false sandalwood (Myoporum sandwicense), and oleander (Nerium oleander). Unplanted control soils were included in the experiment. Total bacteria and phenanthrene-degrading bacteria were enumerated on plates. Diesel- and pristane-degrading microorganisms were enumerated by the most-probable-number technique in tissue-culture plates. RESULTS AND DISCUSSION: All four types of microorganisms responded to the rhizosphere of the 6 plants in uncontaminated soil and to the diesel contaminant in unplanted soil. In contaminated rhizospheres, no effect of the plant on the hydrocarbon-degrader numbers was visible. Total bacteria responded more to the plant roots than to the contaminant. The phenanthrene-degrading bacteria and pristane-degrading microorganisms were more influenced by the contaminant than by the plants. The diesel-degrading microorganisms were equally stimulated by the plants and the contaminant. The numbers of hydrocarbon degraders were similar in the contaminated rhizospheres of the three effective plants (kiawe, kou, and milo) and in those of the three ineffective shrubs. CONCLUSION: The results suggest the quality of the rhizodeposition is plant-dependent and governs the type of diesel-degrader populations that will be enhanced by a given plant. RECOMMENDATIONS AND OUTLOOK: In the proposed phytoremediation-benefit model plant roots maintain high levels of hydrocaron degraders in uncontaminated soil. When the root enters a contaminated zone of soil, those hydrocarbon degraders that prefer the contaminant would switch to the contaminant as a carbon source, effectively removing the hydrocarbons. If the root exudates and the contaminant are equally attractive to the hydrocarbon degraders, the contaminant degradaton would be less effective.     

水葫芦对萘的降解作用研究

分别在静态和动态两种条件下 ,以水葫芦为对象 ,对水生植物净化塘处理萘污水进行研究。结果表明 ,在静态试验中 ,水葫芦净化塘对浓度为 2 5、6 5和 16 1mg L萘污水的 7d净化率分别为 97 1%、93 7%和 90 4 %。动态试验中 ,相同浓度萘污水 7d后的出水净化效率分别为 99 2 %— 99 9%、97 3%— 98 6 %和 94 6 %— 96 7%。进水浓度分别为1 2mg L和 6 5mg L萘污水在水葫芦净化塘中的最佳停留时间分别为 5d和 7d ,水葫芦净化塘动态过程的净化效率高于静态过程     

Anaerobic digestion of livestock and poultry manures spiked with tetracycline antibiotics

Abstract

We investigated the anaerobic degradation of tetracycline antibiotics (tetracycline [TC], oxytetracycline [OTC] and chlortetracycline [CTC]) in swine, cattle, and poultry manures. The manures were anaerobically digested inside polyvinyl chloride batch reactors for 64?days at room temperature. The degradation rate constants and half-lives of the parent tetracyclines were determined following first-order kinetics. For CTC the fastest degradation rate was observed in swine manure (k?=?0.016?±?0.001 d^?1; half-life = 42.8?days), while the slowest degradation rate was observed in poultry litter (k?=?0.0043?±?0.001 d^?1; half-life = 161?days). The half-lives of OTC ranged between 88.9 (cattle manure) and 99.0?days (poultry litter), while TC persisted the longest of the tetracycline antibiotics studied with half-lives ranging from 92.4?days (cattle manure) to 330?days (swine manure). In general, the tetracyclines were found to degrade faster in cattle manure, which had the lowest concentrations of organic matter and metals as compared to swine and poultry manures. Our results demonstrate that tetracycline antibiotics persist in the animal manure after anaerobic digestion, which can potentially lead to emergence and persistence of antibiotic resistant bacteria in the environment when anaerobic digestion byproducts are land applied for crop production.     

TiO2/GeO2复合膜光催化氧化降解农药废水的研究

提出了一种新的TiO₂/GeO₂复合膜圆形光催化氧化反应器，研究了该反应器对经物化处理后的农药废水进行降解的过程。研究表明，光催化氧化的最佳条件是锌片镀TiO₂/GeO₂复合膜、pH=6.7、过氧化氢（H₂O₂）浓度为400 mg/L。并对其他氧化剂对该过程的影响进行了探讨。有机废水通过该反应器处理后，其COD值降为57mg/L。能使有机污染物全部降解为小分子无机物，废水达到国家一级排放标准。     

电化学催化降解水中有机污染物的研究进展

电化学法催化降解废水中的有机污染物已引起广泛兴趣。在电极的作用下 ,电化学反应和化学催化作用结合 ,可导致有机分子的电催化降解。选用合适的电极材料可以加速电化学反应速率 ,有助于有机物的电化学转化。本文讨论了提高电催化降解速率的方法 ,指出了在该领域的研究中存在的问题和发展方向     

Fe(Ⅲ)微生物还原机理及其研究进展

厌氧异养型微生物还原Fe(Ⅲ)的同时可以氧化降解有机物,在污染环境修复中具有积极的作用.目前对Fe(Ⅲ)微生物还原的物理、生物化学特性的认识还十分有限.总结了近年来自然环境中Fe(Ⅲ)还原菌的单菌种分离情况和混合菌的降解作用,探讨了Fe(Ⅲ)还原以及有机物降解的机理,分析了Fe(Ⅲ)可能对微生物产生的抑制作用,并提出了进一步研究的方向.     

壳聚糖在固定化光合细菌处理染料活性艳红X-3B中的应用研究

采用海藻酸钠对光合细菌进行包埋,并在固定化过程中加入壳聚糖,研究添加了壳聚糖的固定化细胞在不同条件下对活性艳红X-3B的脱色效果及其降解动力学.实验结果表明,在厌氧条件下,X-3B的脱色效果较好;染料浓度在30～300 mg/L之间变化时,厌氧降解动力学方程均符合一级动力学方程;降解速率与染料初始浓度之间关系符合Michaelis-Menten方程,反应动力学参数Km=374.96 mg/L,Vmax=7.53 mg/L·h.振荡有利于脱色并使半衰期缩短;固定化小球可重复使用.     

白腐真菌降解阿维菌素废水的试验研究

利用前期实验筛选出的4株优势白腐真菌，处理阿维菌素废水经厌氧处理后的出水，实验结果表明，白腐真菌对该废水具有较好的处理效果，且其生长特性与处理效果基本正相关。     

n-TiO2光催化机理及其在环境保护中的应用研究进展

本文对半导体二氧化钛的光催化机理、载体形式、反应器等方面的研究进展作了详细概述。并就其在废水处理、杀菌消毒等环境保护方面中的应用作了综述