Simultaneous Monitoring of Phosphine and of Phosphorus Species in Taihu Lake Sediments and Phosphine Emission from Lake Sediments

Phosphine (PH₃) was monitored in the Taihu Lake in China by a GC/NPD method, coupled with cryo-trapping enrichment technology. Results showed that PH₃ was universally detected in sediments, lake water and atmosphere of the Taihu Lake area. Total phosphorus (TP_s) and fractions of different phosphorus species in lake sediments were separately measured as dissolved phosphate (DP), phosphorus bound to aluminum (Al-P), iron (Fe-P) and calcium (Ca-P), occluded phosphorus (OP), and organic phosphorus (Org-P) by sequential chemical extraction. High PH₃ levels were correlated with high TP_s values in sediments and with eutrophication at different sites. In addition, a positive linear correlation equation was obtained between the concentrations of PH₃ in lake sediments and of the phosphorus fractions. The resulting multiple linear regression equation is PH₃ = −165 + 63.3 DP + 0.736 Al-P + 2.33 Ca-P + 2.29 Org-P. The flux of PH₃ across the sediment–water interface was estimated from sediment core incubation in May and October 2002. The annual average sediment–water flux of PH₃ was estimated at ca. 0.0138±0.005 pg dm⁻² h⁻¹, the average yearly emission value of PH₃ from Taihu Lake sediments to water was calculated to be 28.3±10.2 g year⁻¹, which causes a water PH₃ concentration of up to 0.178±0.064 pmol dm⁻³. The real importance of PH₃ could be higher, because PH₃ could be consumed in the oxic sediment–water boundary layer and in the water column. Spatial and temporal distributions of total phosphorus (TP_w) and chlorophyll a (Chl-a) in the water column of Taihu Lake were measured over the study period. Higher water PH₃ has also been found where the TP_w content was high. Similarly, high Chl-a was consistent with higher water PH₃. Positive relationships between PH₃ and TP_w (average R² = 0.47±0.26) and Chl-a (average R² = 0.23±0.31) were observed in Taihu Lake water.     

光照对水环境变化和沉积物吸收磷酸盐的影响

在富氧和缺氧环境下室内模拟研究光照对清洁湖区沉积物吸收磷酸盐和对上覆水质变化的影响.结果表明,光照使缺氧环境上覆水体中的pH值显著提高,并增加其溶解氧的含量.上覆水体中磷酸盐浓度的变化在实验初期主要受水-沉积物界面溶解氧含量的影响,表现为富氧组磷酸盐的浓度下降迅速,但随实验时间的推移,光照逐渐起主要作用,表现为实验结束时有光条件下的磷酸盐浓度明显低于无光条件,磷酸盐的减少量和减少速度明显高于无光条件.无论是富氧、缺氧,还是有光、无光,当上覆水体中磷酸盐的浓度很高时,沉积物都能够吸收磷酸盐,但吸收量各不相同.光照对沉积物吸收上覆水中溶解性无机磷酸盐(DIP)的影响受缺氧和富氧环境的限制.     

人工湿地的氮去除机理

湖泊等水环境的富营养化给人类带来诸多损害,如环境、生态和经济等方面的损害。富营养化的原因和控制途径引起了包括中国在内的很多国家的关注。我国针对水环境的富营养化问题开展了大量的工作。氮是引发水环境富营养化的主要营养物之一。外源氮负荷（分点源和非点源两部分）是水环境污染负荷的重要组成部分。传统污水处理技术应用于收集系统欠缺的非点源污染的治理时成本过高。人工湿地是有效削减水环境中外源氮负荷的重要技术手段,在处理非点源污染源带来的氮负荷时更是如此。人工湿地具有氮去除效果好、耐冲击负荷能力强、投资低和生态环境友好等优点。因此人工湿地非常适合于水环境富营养化的防治。阐明人工湿地中氮的去除机理对水环境的富营养化等具有重要的意义。防渗人工湿地的氮去除机理主要包括挥发、氨化、硝化／反硝化、植物摄取和基质吸附。未防渗的人工湿地中,周围水体与人工湿地的氮交换影响着人工湿地中氮的去除。一般情况下,人工湿地中硝化／反硝化是最主要的氮去除机理。pH值小于7．5时,氨挥发可忽略。pH值在9．3以上时,氨挥发很显著。处理生活污水的人工湿地中氮的去除主要是依靠微生物的硝化／反硝化作用。在进水负荷低、气候适宜、植物物种适宜和收割频率与时机适宜的条件下,植物收割可能成为主要的去氮途径。人工合理导向的湿地的氮去除效果通常优于天然湿地。合理的设计（填料的搭配、植物物种的配置以及布水和集水的优化）对人工湿地系统中氮去除的改善有重要影响。合理的运行,如有效的水位控制,正确的植物培育、合理的植物收割等,能有效地改善湿地中的氮去除。     

Current status and future tendency of lake eutrophication in China

Current trophic status and trend of Chinese freshwater lakes were investigated in this study. The results showed that all lakes studied were commonly undergoing the eutrophica-tion process, water quality decreased and lake's ecosystem is being declined. Most of the urban lakes are facing serious eutrophication. Many medium-sized lakes are in metrophic or eutrophic status, some local water are even approaching the hypertrophic level. The famous five freshwater lakes in China have entered into eutrophication in the condition of higher nutrient load. Lake Taihu, Hongze and Caohu are already in eutrophic state. Eutrophic lakes are mainly distributed in the middle and lower reaches of Yangtze River and Yungui plateau. Lake eutrophication developed rapidly. Among the 34 lakes studied in 1970's, most of lakes were in the mesotrophic status, mesotrophic water area accounted for 91.8%. With the nine year of 1978-1987 the area percentage of oligotrophic lakes decreased from 3.2% to 0.53%, and that of eutrophic lakes increased from 5.0% to 55.01%. Recent data showed 57.5% lakes were in eutrophic and hyper trophic status of the 40 surveyed lakes. Eutrophic trend of Lake Taihu, Chaohu and Xuanwu in the region of the middle and lower reaches of Yangtze River was predicated using the ecological stress model. The results showed that in 2008 Lake Taihu, Chaohu and Xuanwu might be of eutrophication, eutrophication and hypertrophication, respectively if no control measurement is taken. Provided the pollution water treatment rate is 60% in 2030, approximately 30 billion ton pollution water would still be discharged directly in the lakes. Therefore, in 2030 the urban lakes in China might be eutrophication or hypertrophication, and most of the medium-sized lakes at the urban-rural fringe might be in eutrophication or hypertrophication. The famous five biggest freshwater lakes in China might be eutrophication if control countermeasures are taken as now. Lake eutrophication has become a serious environmental problem in China. Based on the domestic and foreign experiences of the eutrophic control technologies, both nutrient pollution control and lake ecological restoration should be carried out and this may be the guidance for the eutrophic control of lakes in China.     

Current status and future tendency of lake eutrophication in China

Current trophic status and trend of Chinese freshwater lakes were investigated in this study. The results showed that all lakes studied were commonly undergoing the eutrophication process, water quality decreased and lake’s ecosystem is being declined. Most of the urban lakes are facing serious eutrophication. Many medium-sized lakes are in metrophic or eutrophic status, some local water are even approaching the hypertrophic level. The famous five freshwater lakes in China have entered into eutrophication in the condition of higher nutrient load. Lake Taihu, Hongze and Caohu are already in eutrophic state. Eutrophic lakes are mainly distributed in the middle and lower reaches of Yangtze River and Yungui plateau. Lake eutrophication developed rapidly. Among the 34 lakes studied in 1970’s, most of lakes were in the mesotrophic status, mesotrophic water area accounted for 91.8%. With the nine year of 1978–1987 the area percentage of oligotrophic lakes decreased from 3.2% to 0.53%, and that of eutrophic lakes increased from 5.0% to 55.01%. Recent data showed 57.5% lakes were in eutrophic and hypertrophic status of the 40 surveyed lakes.

Eutrophic trend of Lake Taihu, Chaohu and Xuanwu in the region of the middle and lower reaches of Yangtze River was predicated using the ecological stress model. The results showed that in 2008 Lake Taihu, Chaohu and Xuanwu might be of eutrophication, eutrophication and hypertrophication, respectively if no control measurement is taken. Provided the pollution water treatment rate is 60% in 2030, approximately 30 billion ton pollution water would still be discharged directly in the lakes. Therefore, in 2030 the urban lakes in China might be eutrophication or hypertrophication, and most of the medium-sized lakes at the urban-rural fringe might be in eutrophication or hypertrophication. The famous five biggest freshwater lakes in China might be eutrophication if control countermeasures are taken as now.

Lake eutrophication has become a serious environmental problem in China. Based on the domestic and foreign experiences of the eutrophic control technologies, both nutrient pollution control and lake ecological restoration should be carried out and this may be the guidance for the eutrophic control of lakes in China.

     

Cells derived from human umbilical cord blood support the long-term growth of undifferentiated human embryonic stem cells

Various types of human cells have been tested as feeder cells for the undifferentiated growth of human embryonic stem cells (hESCs) in vitro. We report here the successful culture of two hESC lines (H1 and H9) on human umbilical cord blood (UCB)-derived fibroblast-like cells. These cells permit the long-term continuous growth of undifferentiated and pluripotent hESCs. The cultured hESCs had normal karyotypes, expressed OCT-4, SSEA-4, TRA-1-60, and TRA-1-81, formed cystic embryonic body in vitro and teratomas in vivo after injected into immunodeficient mice. The wide availability of clinical-grade human UCB makes it a promising source of support cells for the growth of hESC for use in cell therapies.     

Buoyancy regulation of Microcystis flos-aquae during phosphorus-limited and nitrogen-limited growth

The dominance of gas-vacuolate cyanobacteria is often attributedto their buoyancy and to their ability to regulate buoyancyin response to environmental conditions. Changes in absolutegas vesicles volume, carbohydrate content, protein content andcolony buoyancy of Microcystis flos-aquae were investigatedduring nitrogen-limited, phosphorus-limited and nutrient-repletegrowth. When nutrient-replete, M. flos-aquae cells consistentlyhad excess gas vesicles, which provided sufficient buoyancythat the influence of daily carbohydrate changes on cells uponfloatation was negligible. However, during nitrogen-limitedgrowth, gas vesicle volume per cell decreased significantlywith nitrogen exhaustion. The maximum decrease of gas vesiclevolume was up to 84–88%. At the same time, cellular carbohydratecontent had an accumulation trend. The decrease of gas vesiclebuoyancy together with the daily increase in carbohydrate aresuggested to explain the daily changes in the cell floatation.During phosphorus-limited growth, gas vesicle volume per celldecreased slightly (maximum to 22–32%), and they stillprovided sufficient buoyancy that most cells kept floating eventhough there were significant daily carbohydrate changes. Sincenitrogen limitation caused more significant buoyancy loss thanphosphorus limitation did, surface water blooms may disappearor appear frequently in nitrogen limited water bodies whilethey may persist a longer time in phosphorus limited water bodies.The quantitative analysis in buoyancy change by gas vesicles,carbohydrate and protein suggested that long-term buoyancy regulationwas mainly determined by changes of gas vesicle volume whereasshort-term buoyancy regulation was mainly determined by carbohydrateaccumulation and consumption. Both long-term and short-termbuoyancy regulation were influenced by cell nutrient status.Furthermore, gas vesicle volume per cell and protein contentchanged in the same way in both nitrogen-limited and phosphorus-limitedgrowth, which implied that the decrease of gas vesicles wereassociated with controls of total protein synthesis.     

人工湿地处理农业径流的研究进展

人工湿地（CW）是独特的土壤-植物-微生物-动物系统。按水流方式分为表面流湿地（FWS）和潜流湿地（SFW）。FWS投资低,但占地大,低温地区冬季运行需要独特的考虑。SFW的保温保水效果好,卫生条件较好,但投资高,易堵塞。SFW分为水平潜流湿地（HF）和垂直潜流湿地（VF）。HF床供氧较差,适于去除SS和BOD,但NH3-N的去除较差。VF床供氧好,占地小,适于硝化和去除BOD,但对SS的去除不如HF床,而且构建费高,易堵塞。FWS按系统中的主体植物的不同分为大型自由漂浮植物湿地、大型沉水植物湿地和大型挺水植物湿地。农业径流（AR）由农田排水、灌溉余水、村落污水、畜禽养殖污水和部分雨水径流组成。其污水源具有面广、量大、分散、间歇的峰值和高无机沉淀物负荷的特点。中国大多数农村经济基础薄弱,管理水平不高。农村中的低洼地、低产田和公共用地均可作为生态环境保护用地。农村的污水收集系统欠完善。传统污水处理技术处理AR时难度大、维护管理复杂、投资和运行费高。而CW的耐冲击负荷能力强、投资低、运行费低、维护管理简便,但占地较大。因此CW适合于有地可用的农村的AR的处理。小结了1982年起CW技术在AR处理中的研究和应用。已有研究结合AR的水质、水量规律及农村的特点,进行了CW的设计与工艺改进。对氮、磷、有机物、农药和杀虫剂等污染物的去除效果有较多的研究。关于CW的运行、维护和管理的研究有沉积物积累、水量平衡、去除效果的衡量、植物收割和费用分析。CW的运行效果的衡量应当基于进出水负荷量而非基于进出水浓度。总之CW在AR污染控制中具有良好的应用前景。CW经合理设计和管理后有望实现“零费用运行”或者“盈利性运行”。     

洞庭湖流域区域生态风险评价

对于生态系统 ,灾害性事件的产生多为外界胁迫因素与系统内部生态结构不稳定性因素共同作用的结果 ,因此对流域生态风险进行评价时应充分考虑系统内部的生态结构与外界的胁迫性因素。目前国内外对于外界胁迫性因素的研究多集中在自然灾害 (如洪涝灾害 )以及外界污染物主要集中在重金属类的排入 ,而事实上 ,其他类型的污染物 ,如氮、磷等也将对生态系统产生一定的危害 ,由于这些污染物浓度在个别地区超标程度较高并可能对受体产生巨大的影响 ,因此将该类污染物作为一类重要因素纳入生态风险评价体系中是非常必要的 ,而由此得出的评价结果也更为系统和全面。以洞庭湖地区的东、南、西三部分作为研究区域 ,根据其特殊的背景 ,将工业污染、农业污染及血防污染作为其污染类风险源 ,引入由氮毒性污染指数、磷毒性污染指数、重金属类毒性污染指数共同构成的毒性污染指数与自然灾害指数和系统本身的生态指数 ,包括生物指数、多样性指数、物种重要性指数以及脆弱性指数完成了对洞庭湖流域的区域生态风险评价。