Release of Pb adsorbed on graphene oxide surfaces under conditions of Shewanella putrefaciens metabolism

In this study, Pb(II) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens (S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on lead that was preadsorbed on graphene oxide (GO) surfaces. The results showed that GO was transformed to its reduced form (r-GO) by bacteria, and this process induced the release of Pb(II) adsorbed on the GO surfaces. After 72 hr of exposure in an S. putrefaciens system, 5.76% of the total adsorbed Pb(II) was stably dispersed in solution in the form of a Pb(II)-extracellular polymer substance (EPS) complex, while another portion of Pb(II) released from GO-Pb(II) was observed as lead phosphate hydroxide (Pb₁₀(PO₄)₆(OH)₂) precipitates or adsorbed species on the surface of the cell. Additionally, increasing pH induced the stripping of oxidative debris (OD) and elevated the content of dispersible Pb(II) in aqueous solution under the conditions of S. putrefaciens metabolism. These research results provide valuable information regarding the migration of heavy metals adsorbed on GO under reducing conditions due to microbial metabolism.     

Nano-selenium controlled cadmium accumulation and improved photosynthesis in indica rice cultivated in lead and cadmium combined paddy soils

Selenium nanoparticles (Se NPs) are less toxic and more biocompatible than selenite or selenate. However, studies involving spraying with Se NPs for reducing accumulation of cadmium (Cd) and lead (Pb) in rice grains have been rarely reported as yet. Herein, indica rice seedlings cultivated in Cd+Pb-spiked paddy soils (denoted as positive control) were sprayed with Se NPs sols for four times from tillering to booting stage. Compared to positive control, 50–100 μmol/L Se NPs downregulated Cd transporters-related genes such as OsLCT1, OsHMA2 and OsCCX2 in leaves and OsLCT1, OsPCR1 and OsCCX2 genes in node I at filling stage. Meanwhile, Se-binding protein 1 was distinctly elevated, involving the repression of Cd and Pb transportation to rice grains. Se NPs also differentially improved RuBP carboxylase and chlorophylls especially some key genes and proteins involving photosynthetic system. Besides, 25–50 μmol/L Se NPs diminished reactive oxygen species overproduction from NADPH oxidases whereas boosted glutathione peroxidase, reducing protein carbonylation in rice seedlings. However, the antioxidant isozymes and oxidatively modified proteins were slightly rebounded at 100 μmol/L. Se contents were noticeably elevated and confirmed to exist as selenomethionine in the rice grains following all the treatments by Se NPs. Thus, the optimal dosage of Se NPs for foliar application is 50 μmol/L, which significantly decreased Cd accumulation, improved photosynthesis and Se enrichment whereas caused no distinct reduction of Pb in the grains. Thus, an appropriate dosage of Se NPs can be conducted to decrease Cd accumulation, improve photosynthesis, and organic Se contents in rice grains.     

城市环境污水治理的探析与研究

针对如何搞好城市环境污水的治理探析问题,介绍了中国城市污水治理的现状,同时介绍了城市污水处理的方法,如城市利用活性污泥处理污水方法、利用生物膜处理污水方法、利用氧化处理污水方法,并探讨了如何对城市环境污水进行治理的探究,文中介绍了增强城市污水集中处理的力度、如何加强污水管网的配套建设、如何对城市污水分散处理回用和采用新的污水处理工艺及提高污水再生效率.只有这样才能加快城市的发展,有利于搞好城市环境污水的治理目标.     

水污染源总量控制方法研究

以济南市的水污染源为基础,从排污量、废水组成、产污环节、污染物种类等方面对水污染源进行调查与分析,建立了水污染源各要素的多级递阶结构评价体系,采用层次分析法基础上的模糊评判法筛选出22家代表性企业,并对其连续等比例加密监测,研究浓度-时间、排水量-时间和排污负荷-时间之间的变化关系,得出水污染源排放的浓度主导型、水量主导型、混合型、生活污水型4种排污规律,为水污染源实行浓度控制和总量控制双轨制管理、实施污染物总量监测提供技术支持.      

城市生活垃圾处理技术的现状与发展趋势

针对我国目前城市生活垃圾的现状和特点,简要介绍了处理城市生活垃圾的几种方法和处理技术的发展趋势。     

有机废气处理技术研究进展

有机废气处理问题,是当前工业废气处理的难点、热点问题。本文详细介绍了热破坏法、吸收法、吸附法、生物法、光分解法、脉冲电晕法等有机废气的处理技术,并对以后的研究方向进行了一些展望。     

厨房油烟污染净化技术应用探讨

分析了厨房油烟污染物来源、组成及危害,介绍了运用物理法、化学法、生物法、矿物法及复合法净化油烟污染物的应用情况,提出复合净化是油烟净化的发展方向。     

二噁英类化合物检测标准及技术研究进展

二噁英类化合物是斯德哥尔摩公约中的首批持久性环境污染物之一,对人类社会有巨大的危害性。对二噁英类化合物进行监控和防治一直是各国环境政策研究的重点任务,二噁英类化合物的检测方法也是国内外科学家门研究的热点。通过查阅大量国内外近年关于二噁英类化合物文献及一些国家和国际组织制定的二噁英类化合物检测标准,归纳总结了近年来二噁英类化合物的化学检测法和生物分析方法的前处理技术和检测技术的研究进展,比较了不同方法的特点及适用范围,为建立灵敏度更高、实用性更强的检测方法提供依据。为我国开展二噁英类化合物的研究和制定相关标准提供参考,以进一步完善监控和防治措施。     

成果参照法在自然生态环境价值评估中的应用现状及展望

成果参照法作为自然生态环境价值评估的重要方法之一,越来越受到关注。目前国外对于该方法的研究已经比较成熟,但是国内这方面的研究还比较薄弱,尤其是相应的实证研究较少,有关该方法及其应用现状的总结与研究展望尚未见报道。在回顾国外成果参照法研究进展的基础上,总结、分析了国内的研究现状及其存在问题,最后结合国内外最新的研究动态,提出一些改进意见与研究展望。此项工作对于中国成果参照法研究的深化和拓展具有重要的指导意义。