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341.
Xiang Tan Xiaoling Xia Qiaoling Zhao Quanfa Zhang 《Environmental science and pollution research international》2014,21(1):434-444
Benthic diatoms are the main component in many aquatic ecosystems such as streams, creeks and rivers, and they function as important primary producers and chemical modulators for other organisms in the ecosystems. In this study, the composition of benthic diatoms was investigated and further explored the primary physicals and chemicals affecting their temporal variations in the upper Han River, China. There were seasonal variations in physical and chemical variables in waters over the sampling period of 2007–2010. Water temperature (t), chemical oxygen demand, total nitrogen, dissolved organic carbon (DOC), silica and fluoride were much higher in the high flow season (i.e., July or August) than these in the base flow season. Three species Achnanthidium minutissimum (composed of 10.7 % of the total diatom abundance), Achnanthidium pyrenaicum (11.9 %), and Achnanthidium subatomus (12.7 %) accounting for more than 5 % of the total diatom abundance were persistently dominant in all seasons, while the other two prostrate and motile species including Eolimna minima and Nitzschia dissipata also dominant in the base flow season. The species richness always peaked in autumn with significant difference with summer (p?<?0.01), and density of benthic diatom varied and peaked in April. Analyses indicated that the temporal variation in benthic diatom communities was strongly related to t, nitrogen, organic pollutants (indicated by COD and DOC), and hydrological regime. The research will expand the understanding of water chemistry monitoring, and improve watershed- scale management and conservation efforts in the upper Han River, China. 相似文献
342.
以处理生活污水的平板膜-生物反应器为依托,通过将进水调配成30、200和500 mg/L 3种不同的钙离子浓度,考察钙离子对短期膜污染的影响。结果表明,随着钙离子浓度的增加,TMP增长趋势变小,膜污染得到缓解;钙离子浓度为200 mg/L时,膜的渗透性最好,而过高的钙离子浓度并不利于降低膜污染。钙离子的投加强化了生物絮凝作用,可以降低SMP和LB-EPS的含量,主要通过降低外部阻力减缓膜污染;投加钙离子也可以增加絮体的大小,较大的絮体形成的泥饼有更好的过滤性,然而过高的钙离子浓度会使无机颗粒的量增加,造成平均粒径下降,将会加重内部污染,进而加剧膜污染。 相似文献
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344.
Fan W Cui M Liu H Wang C Shi Z Tan C Yang X 《Environmental pollution (Barking, Essex : 1987)》2011,159(3):729-734
The acute toxicity of engineered nanoparticles (NPs) in aquatic environments at high concentrations has been well-established. This study demonstrates that, at a concentration generally considered to be safe in the environment, nano-TiO2 remarkably enhanced the toxicity of copper to Daphnia magna by increasing the copper bioaccumulation. Specifically, at 2 mg L−1 nano-TiO2, the (LC50) of Cu2+ concentration observed to kill half the population, decreased from 111 μg L−1 to 42 μg L−1. Correspondingly, the level of metallothionein decreased from 135 μg g−1 wet weight to 99 μg g−1 wet weight at a Cu2+ level of 100 μg L−1. The copper was found to be adsorbed onto the nano-TiO2, and ingested and accumulated in the animals, thereby causing toxic injury. The nano-TiO2 may compete for free copper ions with sulfhydryl groups, causing the inhibition of the detoxification by metallothioneins. 相似文献
345.
346.
Quantifying Terrestrial Ecosystem Carbon Dynamics in the Jinsha Watershed, Upper Yangtze, China from 1975 to 2000 总被引:1,自引:0,他引:1
Shuqing Zhao Shuguang Liu Runsheng Yin Zhengpeng Li Yulin Deng Kun Tan Xiangzheng Deng David Rothstein Jiaguo Qi 《Environmental management》2010,45(3):466-475
Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial
biosphere and the atmosphere is critical to our understanding of regional patterns of carbon budgets. Here we use the General
Ensemble biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China’s
upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces,
such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that
the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975–2000, with an average rate of 0.36 Mg/ha/yr,
primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation
accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to a lower net gain of carbon in the watershed,
and after that soils became a small sink. Ecosystem carbon sink/source patterns showed a high degree of spatial heterogeneity.
Carbon sinks were associated with forest areas without disturbances, whereas carbon sources were primarily caused by stand-replacing
disturbances. It is critical to adequately represent the detailed fast-changing dynamics of land use activities in regional
biogeochemical models to determine the spatial and temporal evolution of regional carbon sink/source patterns. 相似文献
347.
Jiun-Yee Chee Yifen Tan Mohd-Razip Samian Kumar Sudesh 《Journal of Polymers and the Environment》2010,18(4):584-592
A consortium of microorganisms from oil polluted wastewater sample was cultivated to promote polyhydroxyalkanoate (PHA) accumulation
before subjecting the mixed cultures to sucrose density gradient ultracentrifugation. This resulted in the fractionation of
the bacterial cells according to their physical features such as size, morphology and/or densities. An isolate was identified
as Burkholderia sp. USM (JCM15050), which was capable of converting palm oil products [crude palm kernel oil (CPKO), palm olein (PO), palm
kernel acid oil (PKAO), palm stearin (PS), crude palm oil (CPO), palm acid oil (PAO) and palm fatty acid distillate (PFAD)],
fatty acids and various glycerol by-products into poly(3-hydroxybutyrate) [P(3HB)]. Up to 70 and 60 wt% of P(3HB) could be
obtained when 0.5%(v/v) CPKO and glycerol was fed, respectively. Among the various fatty acids tested, lauric acid followed
by oleic acid and myristic acid gave the best cell growth and PHA accumulation. Compared to Cupriavidus necator H16, the present isolate showed better ability to grow on and produce PHA from various glycerol by-products generated by
the palm oil industry. This study demonstrated for the first time an isolate that has the potential to utilize palm oil and
glycerol derivatives for the biosynthesis of PHA. 相似文献
348.
Hao Chen Xiaosong Chang Ji-an Chen Yebin Guo Yao Tan 《Environmental pollution (Barking, Essex : 1987)》2010,158(7):2459-2464
The spreading of extended-spectrum β-lactamases (ESBL)-producing thermotolerant coliforms (TC) in the water environment is a threat to human health but little is known about ESBL-producing TCs in the Yangtze River. We received 319 ESBL-producing stains obtained from the Chongqing basin and we investigated antibiotic susceptibility, bla gene types and the presence of integrons and gene cassettes. 16.8% of TC isolates were ESBL-producing bacteria and blaTEM+CTx-M was the predominant ESBL type. 65.2% of isolates contained class 1 integrons, but only 3 carried intI 2. Gene cassettes were amplified and sequenced. aadA, drfA, cmlA, sat1, aar3 and two ORF cassettes were found. In conclusion, Yangtze River is heavily polluted by ESBL-producing TC bacteria and the combined bla gene type could enhance antibiotic resistance. Class 1 integrons were widespread in ESBL-producing isolates and play an important role in multi-drug resistance. Characterization of gene cassettes could reveal the dissemination of antibiotic resistance genes. 相似文献
349.
350.
十七大提出建设生态文明的奋斗目标,具有极其重大的意义.生态保护在建设生态文明中具有保护生存条件、保障生态安全、保护自然资源及生产力、保障可持续发展、促进生态文明观念在全社会牢固树立等重要作用.因此,生态保护是建设生态文明的物质基础、实现生态现代化的前提、建设生态道德的重要载体. 相似文献