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581.
582.
Ying Zhu Lu Chen Hong Xiao Fei Shen Shihuai Deng Shirong Zhang Jinsong He Chun Song Xie Wang Jianhua Zhang Li Gong Chun Hu 《环境科学学报(英文版)》2020,32(2):273-282
The effects of disinfection efficiency on microbial communities and the corrosion of cast iron pipes in drinking water distribution systems (DWDSs) were studied. Two annular reactors (ARs) that simulated actual running conditions with UV/Cl2 disinfection and chlorination alone were used. High chlorine consumption and corrosion rate were found in the AR with UV/Cl2. According to functional genes and pyrosequencing tests, a high percentage of iron recycling bacteria was detected within the biofilm of the AR with Cl2 at early running stage, whereas siderophore-producing bacteria were dominant in the biofilm of the AR with UV/Cl2. At the early running stage, the sequential use of UV light and an initial high chlorine dosage suppressed the biomass and iron-recycling bacteria in both bulk water and biofilms, thereby forming less protective scales against further corrosion, which enhanced chlorine consumption. Non-metric multidimensional scaling analysis showed that the bacterial communities in the ARs shaped from within rather than being imported by influents. These results indicate that the initial high disinfection efficiency within the distribution system had not contributed to the accumulation of iron-recycling bacteria at the early running stages. This study offer certain implications for controlling corrosion and water quality in DWDSs. 相似文献
583.
In this work, the gold nanoparticles (Au-NPs) were in-situ generated on the surface of MnO2 nanosheets to form MnO2/Au-NPs nanocomposite in a simple and cost-effective way. Multiple experiments were carried out to optimize the oxidation of basic dye (Methylene Blue (MB)),including the molar ratio of MnO2 to chloroauric acid (HAuCl4), the pH of the solution and the effect of initialmaterial. Under the optimal condition, the highest degradation efficiency for MB achieved to 98.9% within 60 min, which was obviously better than commercial MnO2 powders (4.3%) andMnO2 nanosheets (74.2%). The enhanced oxidative degradationmight attribute to the in-situ generation of ultra-small and highly-dispersed Au-NPs which enlarged the synergistic effect and/or interfacial effect betweenMnO2 nanosheets and Au-NPs and facilitated the uptake of electrons by MnO2 from MB during the oxidation, thus validating the application of MnO2/Au-NPs nanocomposite for direct removal of organic dyes from wastewater in a simple and convenient fashion. 相似文献
584.
从泄漏扩散控制系统结构原理、预警方法、关断触发、泄漏量计算、泄漏后的处置、泄漏点定位等介绍了CPP管道泄漏控制新技术,并通过虚拟空间均匀扩散模型,计算了失误情况下扩散范围,推荐了管道环空封隔长度、触发压力阈值和搬迁距离。通过建设实验管道证实了CPP管道泄漏安全连锁控制比普通管道具有显著的优越性。 相似文献
585.
藻类在水体污染监测中的运用 总被引:15,自引:0,他引:15
利用藻类进行水体污染监测在水生生物监测中占有重要的地位。各种不同的水体污染对藻类的种类,数量,结构等产生相应的影响,在一定程度上表明了水质的某种变化。 相似文献
586.
587.
牛粪发酵过程中抗生素耐药基因及相关菌群组成变化规律 总被引:2,自引:0,他引:2
随着规模化奶牛养殖迅速发展,牛粪带来的环境污染问题日益严重。实验探究牛粪及其堆肥过程中养分变化、抗生素耐药基因消减情况以及细菌群落演替规律,探讨细菌菌群与养分、抗生素耐药基因之间的相关性。采集牛粪及其堆肥过程样品,测定样品中养分、检测抗生素耐药基因相对丰度,采用16S r RNA高通量测序技术研究牛粪堆肥过程细菌群落变化。结果表明,从新鲜牛粪(组FM)到发酵牛粪(组C),样品中有机质含量下降,全氮和全磷含量有不同程度增加,全钾(TK)显著升高(P<0.05)。堆肥发酵后,抗生素耐药基因erm B、tet M、bla CTX-M和aac(6')-Ib-cr的相对丰度呈现不同程度的下降,而基因sul1相对丰度增加。高通量测序结果表明,在门水平,各组均以Firmicutes、Proteobacteria和Bacteroidetes这3个菌门为主,在属水平,各组具有不同的优势物种,其中发现Bacteroides、Paeniclostridium和Pseudomonas等7个潜在病原菌属的相对丰度在堆肥后有效降低。通过相关性分析发现,潜在病原菌属与基因tet M和sul1呈显著正相关(P<0.05),此外,大部分优势菌属与养分TK有显著相关性(P<0.05)。研究结果表明,牛粪经堆肥发酵后,病原菌相对丰度有效降低,抗生素耐药基因相对丰度的下降与细菌菌群结构变化存在相关关系。 相似文献
588.
长春市南湖大气降尘长期演变规律 总被引:1,自引:0,他引:1
本文统计分析了1984-1993年长春市南湖大气降尘数据,探讨了冬季与夏季的代表月份以及10年间的代表年份大气降尘长期演变规律。10年间冬季降法量呈波浪式递减趋势;从统计来看,冬季1月份降尘最是夏季7朋份降尘量的2.3倍左右;同年度内冬季、春季大风时段的除尘量一般高于夏、秋季;冬季煤烟型大气污染已逐年在所改善,一些自然因素对大气除尘的影响逐渐突出。 相似文献
589.
590.
Pine needles collected from 22 sites of six areas in Beijing city, China, were analyzed by instrumental neutron activation analysis (INAA) combined with organic extraction for extractable organohalogens (EOX) and extractable persistent organohalogens (EPOX). The concentrations of EOX (EOX = ECl + EOBr + EOI) were in the order of EOCl > EOBr > EOI. About 1.6-34% of EOCl remained as extractable persistent organochlorine (EPOCl) after treatment with concentrated sulfuric acid, which suggested that major fractions of EOCl in pine needles were an acid-liable or acid-soluble fraction. The fact that pine needle contained higher EOCl contents in chemical industrial and traffic hub areas indicated that chemical industries and exhaust emission from vehicle were the main sources of organochlorines in the Beijing's air. The relative proportions of the known organochlorines (such as HCHs, DDTs, chlordanes, HCB and PCBs) to total EOCl and EPOCl were 0.32-0.76% and 2.5-11.4%, respectively, which implied that a major portion of the EOCl and EPOCl measured in pine needles was unknown. The organochlorinated pesticides (OCPs) and PCBs concentrations in six areas were as follows: sigma HCH (sigma HCH = alpha- + beta- + gamma- + delta-HCH), 11.7-20.8 ng/g; sigma DDT (p,p'-DDT + p,p'-DDE + p,p'-DDD), 12.5-113.3 ng/g; hexachlorobenzene (HCB), 1.1-5.3 ng/g; sigma chlordane (cis-chlordane + trans-chlordane + heptachlor), 1.7-9.5 ng/g, sigma PCB, 41.8-270.5 ng/g, on dry weight basis. The samples from chemical industrial area and residential area nearby chemical industries contained the highest concentrations of sigma DDT, HCB, sigma chlordane and sigma PCB, while the contamination levels of most OCPs and PCBs in iron-steel industrial area were the lowest. The ratios of alpha/gamma-HCH (ranged from 0.9-1.5) and p,p'-DDT/DDTs (ranged from 72.1% to 91.0%) revealed the presence of the recent use of lindane and DDTs or impure dicofol in Beijing. 相似文献