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711.
Growth and photosynthetic responses of the bloom-forming cyanobacterium Microcystis aeruginosa to elevated levels of cadmium 总被引:2,自引:0,他引:2
Effects of cadmium (Cd) on the growth and photosynthesis of the bloom-forming cyanobacterium Microcystis aeruginosa Kütz 854 were investigated. The growth was markedly inhibited when it was treated with 4 microM Cd. However, the biomass production was almost not influenced after a prolonged exposure at Cd concentrations < or = 2 microM. Chlorophyll content was more sensitive to Cd toxicity than phycobiliproteins at 0.5 microM Cd. However, the decrease of phycobiliproteins was larger than chlorophyll at the highest Cd concentration. A significant increase of F(v)/F(m) value was observed at Cd concentrations < or = 2 microM. On the other hand, when cells were treated with 4 microM Cd, F(v)/F(m) was significantly increased after 12 h of treatment but decreased after 48 h. The true photosynthesis was decreased with the increase of Cd concentration at 2 h. However, we noticed a recovery when the treatment was prolonged. After 48 h of exposure at the highest Cd concentration, photosynthetic oxygen evolution was markedly inhibited but dark respiration increased by 67%. Cellular Cd contents were augmented with the increase of Cd concentration. To our knowledge, we have demonstrated for the first time that the inhibitory site of Cd in M. aeruginosa is not located at the PSII or PSI level, but is probably situated on the ferredoxin/NADP(+)-oxidoreductase enzyme at the terminal of whole electron transport chain. We noticed also an increase of PSI activity, which is probably linked to the enhancement of cyclic electron transport around PSI. We can conclude that the increase of cyclic electron transport and dark respiration activities, and the decrease of phycobiliproteins might be adaptive mechanisms of M. aeruginosa 854 under high Cd conditions. 相似文献
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713.
无排泥运行MBR处理不同浓度氨氮废水及其生物特性 总被引:1,自引:1,他引:0
考察了水力停留时间(HRT)为10 h时无排泥运行下膜-生物反应器(MBR)处理不同浓度氨氮无机废水的运行性能及微生物特性.结果表明,在处理NH4+-N≤500 mg/L的废水时,氨氮转化率可达99%且反应器内微生物增长缓慢,比硝化速率从0.2kg/(kg·d)升至0.52 kg/(kg·d);当NH4+-N≥700 mg/L时,出水亚硝酸氮和氨氮相继出现明显累积,比硝化速率随之下降至0.4kg/(kg·d)以下,反应器内生物量从3 200 mg/L上升至6 700 mg/L.反应器中的氨氧化菌维持在107CFU/mL,亚硝酸盐氧化菌从106CFU/mL下降至103CFU/mL.系统内的溶解性微生物产物(以TOC表示)升至65 mg/L后保持稳定,出水TOC一直维持在3~4mg/L;细胞外分泌物(EPS)在膜的截流作用下随运行时间的延长积累至600 mg/L. 相似文献
714.
絮凝条件对絮体分形结构的影响 总被引:20,自引:3,他引:17
在85kg/m3的含沙高浊水中投加阳离子高分子聚合物,借助图像分析技术与沉降技术分析探讨了不同絮凝条件下泥沙絮凝形态学参数:絮体粒径、絮体有效质量密度、絮体自由沉速、浑液面沉速与上清液余浊等的变化规律.利用表征参数“分维”定量控制不同絮凝条件(如搅拌速率、搅拌时间、高分子浓度等)对含沙高浊水絮体结构分形特性的影响.实验证明,不合适的絮凝条件将导致絮体分形构造疏松脆弱,分维值低.絮凝条件合适时(快速絮凝强度为:r1=300r/min,t1=10s;慢速絮凝强度:r2=120r/min,t2=180s;CP浓度:0.1%),絮体分形结构处于最佳状态.该状态下的絮体具有粒径较大、沉速快、有效质量密度高、粒度分布均匀,分维值最高(D3=2.16)的特点.而且,由静沉实验测得浑液面沉速高,上清液余浊也低.泥沙絮体分形结构达最佳时的混凝性能、沉降性能与结构密实性均较理想. 相似文献
715.
反硝化生物膜对PBS表面形态及化学组分的影响 总被引:2,自引:0,他引:2
PBS是一种新型的可生物降解聚合物(BDPs),可以用做反硝化碳源和生物膜载体,去除饮用水源水中的硝酸盐.利用红外光谱和扫描电子显微镜对反硝化生物膜生长前后PBS颗粒表面形态、化学组成的变化进行了分析.结果表明,PBS仅在微生物作用下降解并为反硝化菌提供碳源.PBS颗粒可以在12 h内使进水中53 mg·L-1的硝态氮降低到10 mg·L-1以下(我国饮用水水质标准为:NO3--N<15 mg·L-1).红外光谱表明,反硝化微生物附着生长后其PBS在2 925 cm-1和2 850 cm-1附近的吸收带以及3 200 cm-1~3 410 cm-1处峰值减弱,说明PBS材料中甲基、羟基官能团比例下降,而其它官能团没有发生明显的变化,PBS的主要单体组分淀粉和乙烯都可以被反硝化微生物用作碳源.扫描电子显微镜观察结果表明,反硝化生物膜附着生长后,PBS颗粒表面会出现空洞,扩大了生物膜生物附着生长的表面积,有利于形成致密的反硝化生物膜,对反硝化菌形成保护作用. 相似文献
716.
二氯异氰脲酸钠和三氯异氰脲酸对棕囊藻细胞去除的研究 总被引:2,自引:2,他引:0
研究了二氯异氰脲酸钠和三氯异氰脲酸对球形棕囊藻的灭杀和控制作用,及其投药时间对除藻效果的影响,并比较2种药剂的除藻效果,初步探讨了除藻机理.结果表明,这2种除藻剂可以缓释次氯酸,提高其稳定性,有较长的药效期.当有效氯浓度达到4.5mg/L时,2种药剂均能有效地控制和灭杀球形棕囊藻,具有高效、低毒的优点.有效氯浓度为5.0mg/L,藻细胞去除率在24h可达到90%以上.在等于和大于5.0mg/L有效氯浓度时,三氯异氰脲酸的除藻效果优于二氯异氰脲酸钠,通过对2种药剂除藻率的t检验进一步证实了这一结论. 相似文献
717.
Phytoremediation of Cadmium-Contaminated Soils by Rorippa globosa Using Two-Phase Planting (5 pp) 总被引:1,自引:0,他引:1
Background Phytoextraction of contaminated soils by heavy metals can provide a great promise of commercial development. Although there
are more than 400 species of hyperaccumulators found in the world, phytoremediation technology is rarely applied in field
practice for remedying contaminated soils, partially due to low biomass and long growth duration for most of discovered hyperaccumulating
plants. In order to enhance the metal-removing efficiency in a year, the two-phase planting countermeasure of phytoextraction
by harvesting anthesis biomass was investigated on the basis of the newly found Cd-hyperaccumulator Rorippa globosa (Turcz.)
Thell. with 107.0 and 150.1 mg/kg of the Cd accumulation in stems and leaves, respectively, when soil Cd added was concentrated
to 25.0 mg/kg.
Methods The field pot-culture experiment was used to observe the distribution property of R. globosa aboveground biomass and to examine
characteristics of accumulating Cd by the plant at different growth stages. The concentration of Cd in plants and soils was
determined using atomic absorption spectrophotometry (AAS).
Results and Discussion The results indicated that the total dry stem and leaf biomass of R. globosa harvested at the flowering phase was up to 92.3%
of that at its full maturity and the concentration of Cd in stems and leaves harvested at the flowering phase was up to 73.8%
and 87.7% of that at the mature phase, respectively. The Cd-removing ratio by shoots of R. globosa harvested at the flowering
phase was up to 71.4% of that at the mature phase. It was also found, by observing the growth duration of R. globosa, that
the frostless period at the experiment site was twice as long as the growth time from the seedling-transplanted phase to the
flowering phase of the hyperaccumulator.
Conclusion R. globosa could be transplanted into contaminated soils twice in one year by harvesting the hyperaccumulator at its flowering
phase based on climatic conditions of the site and traits of the plant growth. In this sense, the extraction efficiency of
Cd in shoots of R. globosa increased 42.8% compared to that of at its single maturity when the plant was transplanted into
contaminated soils after it had been harvested at its flowering phase and the plant accumulated Cd from soil at the same extraction
ratio at its second flowering phase. Thus, the method of anthesis biomass regulation by the two-phase planting is very significant
to increase the Cd-removing efficiency by phytoremediation used in practice over the course of a year.
Recommendation and Outlook As for some hyperaccumulators that the growth duration from the seedling-transplanted phase to the flowering phase are short
and the concentrations of heavy metals accumulated in their shoots at the flowering phase are high, the efficiency of phytoremediation
can greatly be improved using the method of the two-phase planting. 相似文献
718.
Weisheng Zhou 《Sustainability Science》2006,1(1):115-122
It has been clearly recognized that future global climate change will limit the possibilities for sustainable development in China. To minimize these negative effects, as a practical strategy, we suggest that the Chinese government engage in international cooperation as a key contributor in the prevention of global warming. This suggestion results from numerical estimations of China’s greenhouse gas (GHG) emission trends accompanied with economic growth up to 2100. The results show that China’s gross domestic product (GDP), measured in terms of purchasing power parity (PPP), may overtake the sum of the GDPs of the United States and Canada in 2020. It is predicted that GDP per capita may reach US$20,000 and $80,000 in 2050 and 2100, respectively; meanwhile, CO2 emissions in China will increase from 6.6 billion tons (in carbon equivalent units) in 1990 to 54.6 billion tons in 2100. This means that the global peak concentration of GHG cannot be practically reduced without significant contributions from China. For international cooperation in mitigating global climate change, we introduce a new option, “per-capita emission restricted by assigned amount,” as an accounting rule for GHG reduction. This baseline classifies global CO2 reduction actions into three categories: compulsory reduction, self-imposed reduction, and voluntary reduction. We suggest that China contribute to world CO2 reduction according to the following timetable: voluntary reduction until 2012, self-imposed reduction until 2020, and compulsory reduction from 2020. The simulation results also indicate that China can benefit from this strategy in terms of improvements in its domestic economy and environment, for instance, by reducing fossil fuel consumption and the emission of pollutants.
相似文献
Weisheng ZhouEmail: Phone: +81-75-4663418Fax: +81-75-4663418 |
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