Alteration of dominant cyanobacteria in different bloom periods caused by abiotic factors and species interactions

Freshwater cyanobacterial blooms have drawn public attention because they threaten the safety of water resources and human health worldwide. Heavy cyanobacterial blooms outbreak in Lake Taihu in summer annually and vanish in other months. To find out the factors impacting the cyanobacterial blooms, the present study measured the physicochemical parameters of water and investigated the composition of microbial community using the 16S rRNA gene and internal transcribed spacer amplicon sequencing in the months with or without bloom. The most interesting finding is that two major cyanobacteria, Planktothrix and Microcystis, dramatically alternated during a cyanobacterial bloom in 2016, which is less mentioned in previous studies. When the temperature of the water began increasing in July, Planktothrix appeared first and showed as a superior competitor for M. aeruginosa in NO₃^?-rich conditions. Microcystis became the dominant genus when the water temperature increased further in August. Laboratory experiments confirmed the influence of temperature and the total dissolved nitrogen (TDN) form on the growth of Planktothrix and Microcystis in a co-culture system. Besides, species interactions between cyanobacteria and non-cyanobacterial microorganisms, especially the prokaryotes, also played a key role in the alteration of Planktothrix and Microcystis. The present study exhibited the alteration of two dominant cyanobacteria in the different bloom periods caused by the temperature, TDN forms as well as the species interactions. These results helped the better understanding of cyanobacterial blooms and the factors which contribute to them.     

Importance of nutrient availability for soluble microbial products formation during a famine period of activated sludge: Evidence from multiple analyses

Much remains unknown about compositional variations in soluble microbial products (SMP) with the shift of the substrate condition from a feast to a famine phase in biological treatment systems. This study demonstrated that the formation of SMP could be suppressed by up to 75% during the famine phase with the addition of essential nutrients. In contrast, presence of electron acceptor did not play any significant role during the stress condition, showing the similar amounts of SMP (r?=?0.98, p?<?0.05) formation between the bioreactors supplied with air and N₂. The SMP formed in the famine phase was more bio-refractory in the famine versus the feast phase with a linear correlation shown between the production and their aromatic structures in the composition (R²?>?0.95). The fluorescence excitation–emission matrix coupled with parallel factor analysis (EEM-PARAFAC) revealed the presence of four different fluorescent components, including two protein-like (C1 and C4), fulvic-like (C2), and humic-like (C3) components, in the SMP and bEPS formed at different conditions. Both C1 and C4 showed increasing trends (R²?>?0.95) with the length of starvation in the bioreactors without essential nutrients. Nutrient availability was found to be a key factor to quench the production of large-sized biopolymers. This study provides a wealth of information on operation conditions of activated sludge treatment systems to minimize large sized SMP molecules (particularly proteins), which typically exert many environmental concerns to effluent organic matter quality.     

Using fluorescence surrogates to track algogenic dissolved organic matter (AOM) during growth and coagulation/flocculation processes of green algae

Tracking the variation of the algogenic organic matter (AOM) released during the proliferation of green algae and subsequent treatment processes is crucial for constructing and optimizing control strategies. In this study, the potential of the spectroscopic tool was fully explored as a surrogate of AOM upon the cultivation of green algae and subsequent coagulation/flocculation (C/F) treatment processes using ZrCl₄ and Al₂(SO₄)₃. Fluorescence excitation emission matrix coupled with parallel factor analysis (EEM-PARAFAC) identified the presence of three independent fluorescent components in AOM, including protein-like (C1), fulvic-like (C2) and humic-like components (C3). Size exclusion chromatography (SEC) revealed that C1 in AOM was composed of large-sized proteins and aromatic amino acids. The individual components exhibited their unique characteristics with respect to the dynamic changes. C1 showed the highest correlation with AOM concentrations (R²?=?0.843) upon the C/F processes. C1 could also be suggested as an optical predictor for the formation of trihalomethanes upon the C/F processes. This study sheds a light for the potential application of the protein-like component (C1) as a practical surrogate to track the evolution of AOM in water treatment or wastewater reclamation systems involving Chlorella vulgaris green algae.     

Effect of photo-biodegradation and biodegradation on the biogeochemical cycling of dissolved organic matter across diverse surface water bodies

The objective of this research was to quantify the temporal variation of dissolved organic matter(DOM) in five distinct waterbodies in watersheds with diverse types of land use and land cover in the presence and absence of sunlight. The water bodies were an agricultural pond, a lake in a forested watershed, a man-made reservoir, an estuary, and a bay. Two sets of samples were prepared by dispensing unfiltered samples into filtered samples in 1:10 ratio(V/V). The first set was exposed to sunlight(10 hr per day for 30 days) for examining the combined effect of photo-biodegradation, while the second set was stored in dark for examining biodegradation alone. Spectroscopic measurements in tandem with multivariate statistics were used to interpret DOM lability and composition. The results suggest that the agricultural pond behaved differently compared to other study locations during degradation experiments due to the presence of higher amount of microbial humic-like and protein-like components derived from microbial/anthropogenic sources. For all samples, a larger decrease in dissolved organic carbon(DOC) concentration(10.12% ±9.81% for photo-biodegradation and 6.65% ± 2.83% for biodegradation) and rapid transformation of DOM components(i.e., terrestrial humic-like components into microbial humic and protein-like components) were observed during photo-biodegradation experiments.Results suggest that sunlight facilitated DOM biodegradation, resulting in simpler recalcitrant molecules regardless of original composition. Overall, it was found that combined effects of light and bacteria are more efficient than bacterial effects alone in remineralizing and altering DOM, which highlights the crucial importance of sunlight in transforming aquatic DOM.     

A 60-year sedimentary record of natural and anthropogenic impacts on Lake Chenghai, China

Recent sediments from Lake Chenghai, China, were investigated at high temporal resolution to trace both natural and anthropogenic effects on the lake using total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), organic phosphorus (P_o), inorganic phosphorus (P_i) and organic carbon and nitrogen stable isotopes (δ¹³C_org and δ¹⁵N) in a ¹³⁷Cs-dated sediment core. The results indicated that the sedimentary record covers the last 60 years, during which the lake had undergone apparent changes in nutrient sources and productivity in response to nutrient loading. Prior to the late 1980s, the nutrient contents in sediments mainly originated from algae and lake productivity was relatively stable. Since the late 1980s, increasing TOC, TN and TP concentrations together with the change of δ¹³C_org and δ¹⁵N suggested anthropogenic perturbations in nutrient loading and lake productivity. Endogenic nutrients derived from algae and anthropogenic inputs were two important sources of sedimentary nutrients. The anthropogenic nutrients mainly originated from the discharge of industrial wastewater and artificial cultivation of Spirulina after the middle 1980s, and domestic wastewater discharged from Yongsheng County since 1993.     

Algal removal from cyanobacteria-rich waters by preoxidation-assisted coagulation–flotation: Effect of algogenic organic matter release on algal removal and trihalomethane formation

The cyanobacteria-bloom in raw waters frequently causes an unpredictable chemical dosing of preoxidation and coagulation for an effective removal of algal cells in water treatment plants. This study investigated the effects of preoxidation with NaOCl and ClO_2 on the coagulation-flotation effectiveness in the removal of two commonly blooming cyanobacteria species, Microcystis aeruginosa(MA) and Cylindrospermopsis raciborskii(CR), and their corresponding trihalomethane(THM) formation potential. The results showed that dual dosing with NaOCl plus ClO_2 was more effective in enhancing the deformation of cyanobacterial cells compared to single dosing with Na OCl, especially for CR-rich water.Both preoxidation approaches for CR-rich water effectively reduced the CR cell count with less remained dissolved organic carbon(DOC), which benefited subsequent coagulation–flotation. However, preoxidation led to an adverse release of algogenic organic matter(AOM) in the case of MA-rich water. The release of AOM resulted in a poor removal in MA cells and a large amount of THM formation after oxidation-assisted coagulation-flotation process. The reduction in THM formation potential of CR-rich waters is responsible for effective algae and DOC removal by alum coagulation. It is concluded that the species-specific characteristic of cyanobacteria and their AOM released during chlorination significantly influences the performance of coagulation–flotation for AOM removal and corresponding THM formation.     

Phosphorus mobility in dam reservoir affected by redox oscillations: An experimental study

The internal sedimentary phosphorus(P) load of aquatic systems is able to support eutrophication, especially in dam–reservoir systems where sedimentary P stock is high and where temporary anaerobic conditions occur. The aim of this study therefore is to examine the response of sedimentary P exposed to redox oscillations. Surface sediments collected in the Champsanglard dam–reservoir(on the Creuse River, France) were subjected to two aerobic phases(10 and 12 days) alternated with two anaerobic periods(21 and 27 days)through batch incubations. The studied sediment contained 77 ± 3 μmol/g DW of P, mainly associated with the ascorbate fraction(amorphous Fe/Mn oxyhydroxides). The used sediment was rich in organic matter(OM)(21% ± 1%) with primarily allochthone signature.Our results showed that redox oscillations enhance dissolved inorganic phosphorus release at sediment/water interface. During the first anaerobic stage, the P release was mainly controlled by the dissolution/precipitation of iron minerals. The more pronounced increase of P release during the second anaerobic stage(44%) was due to various mechanisms related to the change in quality of dissolved organic matter(DOM), namely a higher SUVA254 and humification indices. The release of more refractory DOM(rDOM) served to lower the microbial metabolism activity, possibly favored iron oxyhydroxide aggregation and thus limiting iron reduction. In addition, rDOM is able to compete for mineral P sorption sites,leading to a greater P release. In reservoir with predominant allochthone OM input, the release of more aromatic DOM therefore plays an important role in P mobility.     

Occurrence, polarity and bioavailability of dissolved organic matter in the Huangpu River, China

Dissolved organic matter （DOM） plays an important role in biogeochemical cycles in aquatic ecosystem. To investigate the characteristics of DOM in Huangpu River {the last tributary of the Yangtze River）, surface water samples were collected along the river from December 2011 to June, 2013. The concentrations of dissolved organic carbon （DOC）, the absorbance and fluorescence spectrum of DOM in water samples were measured. Fluorescent DOM in the Huangpu River was decomposed into four components by the parallel factor analysis （PARAFAC）, including one humic-like substance and three protein-like substances. It showed that high spatial variability of DOC concentration was observed in the upstream water compared to the downstream water, and so did the absorbance coefficients of chromophoric dissolved organic matter and the total fluorescence intensities of different PARAFAC components of DOM. Furthermore, there was a large difference between the polarity and bioavailability of DOM in the Huangpu River. Polar compounds dominated tyrosine-like component of fluorescent DOM in all seasons. Tryptophan-like and humic-like substances had more polar fraction in summer and autumn than those in winter, while aromatic protein-like materials had the highest polar fraction in winter. Almost all of fluorescent DOM components were refractory in spring, while less than 20% of fluorescent DOM in average were biodegradable within 4 weeks in other seasons. We concluded that the spatial variation in the abundance of DOM in the Huangpu River is mainly affected by the water discharges from the Hangjiahu Plain and the seasonal difference in polarity and bioavailability of DOM is largely determined by its origins.     

Off-flavor compounds from decaying cyanobacterial blooms of Lake Taihu

The effect of cyanobacterial bloom decay on water quality and the complete degradation of cyanobacterial blooms in a short period were examined by an enclosure experiment in Gonghu Bay of Lake Taihu,China.Water quality parameters as well as taste and odor compounds during the breakdown of cyanobacterial blooms were measured.Results showed that the decay of cyanobacterial blooms caused anoxic water conditions,decreased pH,and increased nutrient loading to the lake water.The highest concentrations of dimethyl sulfide (DMS),dimethyl trisulfide (DMTS),and β-cyclocitral were observed in the anoxic water,at 62331.8,12413.3,and 1374.9 ng/L,respectively.2-Methylisoborneol was dominant during the live growth phase of cyanobacterial blooms,whereas DMS and DMTS were dominant during the decomposition phase.Dissolved oxygen,pH,and chlorophyll a were negatively correlated with DMS,DMTS,and β-cyclocitral,whereas total phosphorus,total nitrogen,and ammonium (NH4+-N) were positively correlated with DMS,DMTS,β-cyclocitral,and β-ionone.The experimental results suggested that preventing the anaerobic decomposition of cyanobacterial blooms is an important strategy against the recurrence of a malodor crisis in Lake Taihu.     

Electrochemical inactivation of cyanobacteria and microcystin degradation using a boron-doped diamond anode——A potential tool for cyanobacterial bloom control

Cyanobacterial blooms are global phenomena that can occur in calm and nutrient-rich(eutrophic) fresh and marine waters. Human exposure to cyanobacteria and their biologically active products is possible during water sports and various water activities, or by ingestion of contaminated water. Although the vast majority of harmful cyanobacterial products are confined to the interior of the cells, these are eventually released into the surrounding water following natural or artificially induced cell death. Electrochemical oxidation has been used here to damage cyanobacteria to halt their proliferation, and for microcystin degradation under in-vitro conditions. Partially spent Jaworski growth medium with no addition of supporting electrolytes was used. Electrochemical treatment resulted in the cyanobacterial loss of cell-buoyancy regulation, cell proliferation arrest, and eventual cell death. Microcystin degradation was studied separately in two basic modes of treatment: batch-wise flow, and constant flow, for electrolytic-cell exposure. Batch-wise exposure simulates treatment under environmental conditions, while constant flow is more appropriate for the study of boron-doped diamond electrode efficacy under laboratory conditions. The effectiveness of microcystin degradation was established using high-performance liquid chromatography–photodiode array detector analysis, while the biological activities of the products were estimated using a colorimetric protein phosphatase-1 inhibition assay. The results indicate potential for the application of electro-oxidation methods for the control of bloom events by taking advantage of specific intrinsic ecological characteristics of bloom-forming cyanobacteria. The applicability of the use of boron-doped diamond electrodes in remediation of water exposed to cyanobacteria bloom events is discussed.     

森林与径流关系——一致性和复杂性

@论文综述国外近一个世纪以来在配对集水区研究方面所取得的结论,从水的自然属性出发,从森林变化对径流(年径流量、洪峰与枯水径流)的影响,径流响应的干扰临界值及水文恢复各方面探讨森林变化与径流关系的一致性与复杂性。森林变化与径流关系的一致性主要表现在由较长时间尺度表达的年径流量上。绝大多数的配对集水区的试验研究表明,采伐森林就会增加年径流量,而在荒地上造林就会减少年径流量。而由较短时间尺度表达的洪峰径流与枯水流量则呈现较大的复杂性和难预估性。综述表明,对径流特别是洪峰与枯水径流的定义及分析方法的不同也是造成森林与径流关系复杂性的重要原因。森林与径流关系的复杂性要求人们在研究及应用其关系时就必须有系统观,必须考虑植被、径流与其它过程(土壤变化、气候变化等)的相互作用。论文还认为尽管配对集水区试验作为一种研究方法为研究者提供了许多可靠的结论,但由于许多研究者只把集水区看作是“黑箱”Q从而对认识森林与径流关系的复杂性有一定的局限性。未来的研究应把配对集水区的试验与其它对过程的研究技术(同位素、GIS等技术)结合起来。     

机动车尾气与雾霾天气

从雾和霾形成的原因以及与机动车尾气的关系等方面的论述,阐述了机动车尾气对人体健康的危害,提出了对机动车尾气的预防、治理办法。     

阴阳观念与古代文学

阴阳观念与古代文学的关系密切。在文学创作方面,阴阳对举、"物生有两"、"惟两能化"的宇宙发生观,导致了古代文人重视骈丽的创作倾向,是古代骈文发生发展及古代文学语言形式普遍骈化的深层文化原因;在文学的变化方面,"物生有两"、"惟两能化"的自然变化观,导致了古人以天道自然变化以解释文学发展变化的现象,形成了以刘勰为代表的"质文代变,变不失常"文学发展观;在文艺的审美方面,阴阳交感、、刚柔相济、得中为吉的万物根本论,导致了古人普遍以"中和"为美的现象,使"中和"美论成为古代几千来的审美主潮。     

科技与可持续发展

科学技术对生产力发展的巨大作用。不仅表现在它对生产力3个要素的渗透性影响。而且表现在它促进生产力结构的优化和系统功能的发挥，但经济发展会带来资源破坏和环境污染等负面影响。应在发挥科技作为第一生产力作用的同时，遏制其带来的负面影响，以促进可持续发展。     

中国瑞典环境影响评价和战略环境影响评价比较分析

环境影响评价作为各国预防和控制环境污染的一项制度和技术，都与政府的环境管理机制有着直接的关系。中瑞两国的环评制度都体现了“环评为先，项目决策在后”原则。所不同的是，在瑞典，政策颁布前必须进行战略评价；环评审查按A、B、C类项目分别由不同机构负责；公众参与的方式也更为多样。     

真菌和细菌对染料的吸附脱色及再生能力的研究

进行了真菌和细菌共培养对染料的吸附脱色和吸附脱色能力再生的研究。结果表明，青霉菌G－1首先对偶氮染料S－119、蒽醌染料艳紫KN－B（C．I．Reactive violet 22）水溶液中染料进行快速吸附去除，菌丝对同种染料的吸附速度随菌丝培养液中葡萄糖浓度的增加而加快，吸附染料的G－1菌丝在与细菌的共培养中完成对染料的脱色降解，脱色速度受培养液中葡萄和氮源浓度影响较大，从吸附速率和完全脱色时间综合评价，以葡萄糖浓度为5g/L、酒石酸铵为20mmol/L的培养基中培养的菌丝对染料的吸附脱色效果最好，吸附在菌丝上的艳紫KN－B脱色后菌丝吸附脱色能力得到再生，菌丝对100mg/L的艳紫KN－B染料水溶液可重复处理4次。青霉菌G－1对酸性染料废水处理3h，色度去除率为75．9％，吸附染料的菌丝在与细菌共培养中完成对染料的脱色，对试验所用染料废水，菌丝的处理能力获得1次再生。     

砷的污染、检测与防治

在环境化学污染物中,砷是最常见、最严重的污染物之一.随着现代工农业生产的发展,砷对环境的污染日趋严重.为了更好地评价砷污染对环境和人体的影响,介绍了砷污染的来源、对人体的危害、标准的检测方法和目前砷污染治理的现状.     

油气集输联合站火灾爆炸危险分析与事故后果模拟

以某联合站为例,根据油气集输联合站站场功能,将联合站划分为油气处理、储运及污水处理3个单元,对各单元发生火灾爆炸事故的可能条件进行分析,并利用DNV公司的SAFETI软件对事故后果进行模拟计算,根据事故影响范围数据,提出相应的安全措施。