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排序方式: 共有129条查询结果,搜索用时 363 毫秒
81.
采用微宇宙培养法,分析了不同水动力条件(不循环、水循环和泥循环)对微污染景观水体富营养化模拟过程中藻类演替的影响.结果表明,水循环和泥循环使得水体的TP值前期增加后期减少,前期藻类生长主要受TP影响,而后期浊度成了重要的影响因素;水循环引起的TP值减少及蓝藻聚集状态的破坏,导致了藻类的生长明显减缓,但优势种的演化过程却... 相似文献
82.
水库水源水生物陶粒滤池预处理中试研究 总被引:11,自引:0,他引:11
针对受污染的某水库水源水进行中试规模的生物陶粒滤池试验研究。试验结果表明,生物陶粒滤池预处理能全面净化水源水的水质。在气水比为0.75~1∶1,水力负荷为4~6 m3/(m2·h)条件下,对NH+4-N,NO-2-N和CODMn的去除率分别为89%~97.5%,97.5%~99%,20%~35%;对藻类的去除率为60.1%~84.3%。 相似文献
83.
84.
Comparative acute freshwater hazard assessment and preliminary PNEC development for eight fluorinated acids 总被引:1,自引:0,他引:1
Short-term 48, 72 and 96-h aquatic toxicity tests were conducted to evaluate the acute toxicity of eight fluorinated acids to the cladoceran, Daphnia magna, the green alga, Pseudokirchneriella subcapitata, and the rainbow trout, Oncorhynchus mykiss or the fathead minnow, Pimephales promelas. The eight fluorinated acids studied were tridecafluorohexyl ethanoic acid (6:2 FTCA), heptadecafluorooctyl ethanoic acid (8:2 FTCA), 2H-dodecafluoro-2-octenoic acid (6:2 FTUCA), 2H-hexadecafluoro-2-decenoic acid (8:2 FTUCA), 2H,2H,3H,3H-undecafluoro octanoic acid (5:3 acid), 2H,2H,3H,3H-pentadecafluoro decanoic acid (7:3 acid), n-perfluoropentanoic acid (PFPeA) and n-perfluorodecanoic acid (PFDA). The results of the acute toxicity tests conducted during this study suggest that the polyfluorinated acids, 8:2 FTCA, 8:2 FTUCA, 6:2 FTCA, 6:2 FTUCA, 7:3 acid and 5:3 acid, and the perfluorinated acids PFPeA and PFDA, are generally of low to medium concern based on evaluation of their acute freshwater toxicity (EC/LC50s typically between 1 and >100 mg L−1) using the USEPA TSCA aquatic toxicity evaluation paradigm. For the polyfluorinated acids, aquatic toxicity generally decreased as the number of fluorinated carbons decreased and as the overall carbon chain length decreased from 12 to 8. Acute aquatic toxicity of the 5 and 10 carbon perfluorocarboxylic acids (EC/LC50s between 10.6 and >100 mg L−1) was greater or similar to that of the 6-9 carbon perfluorocarboxylic acids (EC/LC50s > 96.5 mg L−1). This study also provides the first report of the acute aquatic toxicity of the 5:3 acid (EC/LC50s of 22.5 to >103 mg L−1) which demonstrated less aquatic toxicity than the 7:3 acid (EC/LC50s of 0.4-32 mg L−1). The cladoceran, D. magna and the green alga, P. subcapitata had generally similar EC50 values for a given substance while fish were typically equally or less sensitive with the exception that PFPeA was most toxic to fish. Predicted no-effect concentrations (PNECs) were estimated using approaches consistent with REACH guidance and when compared with available environmental concentrations, these PNECs suggest that the fluorinated acids tested pose little risk for aquatic organisms. 相似文献
85.
High rate algal ponds are an economic and sustainable alternative for wastewater treatment, where microalgae and bacteria grow in symbiosis removing organic matter and nutrients. Microalgal biomass produced in these systems can be valorised through anaerobic digestion. However, microalgae anaerobic biodegradability is limited by the complex cell wall structure and therefore a pretreatment step may be required to improve the methane yield. In this study, ultrasound pretreatment at a range of applied specific energy (16–67 MJ/kg TS) was investigated prior to microalgae anaerobic digestion. Experiments showed how organic matter solubilisation (16–100%), hydrolysis rate (25–56%) and methane yield (6–33%) were improved as the pretreatment intensity increased. Mathematical modelling revealed that ultrasonication had a higher effect on the methane yield than on the hydrolysis rate. A preliminary energy assessment indicated that the methane yield increase was not high enough as to compensate the electricity requirement of ultrasonication without biomass dewatering (8% VS). 相似文献
86.
Climate change is likely to impact terrestrial and aquatic ecosystems via numerous physical and biological mechanisms. This study outlines a framework for projecting potential impacts of climate change on lakes using linked environmental models. Impacts of climate drivers on catchment hydrology and thermal balance in Onondaga Lake (New York State) are simulated using mechanistic models HSPF and UFILS4. Outputs from these models are fed into a lake ecosystem model, developed in AQUATOX. Watershed simulations project increases in the magnitude of peak flows and consequent increases in catchment nutrient export as the magnitude of extreme precipitation events increases. This occurs concurrently with a decrease in annual stream discharge as a result of increased evapotranspiration. Simulated lake water temperatures increase by as much as 5 °C during the 2040-2069 time period, accompanied by a prolonging of the duration of summer stratification. Projected changes include shifts in the timing of nutrient cycling between lake sediments and water column. Plankton taxa projected to thrive under climate change include green algae and Bosmina longirostris. Responses for species at higher trophic levels are mixed. Benthic macroinvertebrates may either prosper (zebra mussels) or decline (chironomids), while fish (e.g., gizzard shad) exhibit high seasonal variability without any clear trend. 相似文献
87.
Rong Fang Jilai Gong Weicheng Cao Zengping Chen Danlian Huang Jun Ye Zhe Cai 《环境科学学报(英文版)》2022,34(2):376-387
Nanoparticles(NPs) are widely used for their special physical properties and released into the natural environment. When two types of NPs exist in the same environment, the presence of one type of NP may affect the properties of the other type of NP. This study investigated the toxic effects of multi-walled carbon nanotubes(MWCNTs) and copper oxide nanoparticles(Cu O NPs) on Tetradesmus obliquus. Both NPs had toxic effects on algae, and the toxic effects of MWCNTs were significantly stronger tha... 相似文献
88.
Xiyun Cai Jing Ye Guangyao Sheng Weiping Liu 《Environmental science and pollution research international》2009,16(4):459-465
Background, aim, and scope As emerging contaminants, transformation products of the pollutants via various environmental processes are rather unknown,
and some may predominately contribute to the environmental risks of the parent compounds. Hence, studies on transformation
products complement the assessment of the environmental safety of the parent compounds. In this study, degradation experiments
and toxicity tests using diclofop-methyl (DM), a widely used herbicide, and selected major transformation products were carried
out in algal cultures to assess the time course of DM toxicity and its relevance in the formation of new breakdown products.
Methods The alga Chlorella vulgaris was maintained in the algal growth medium HB IV. The inhibition of algal growth was determined by measuring optical density
at 680 nm (OD680). Initially, DM and two selected breakdown products were added to the algal cultures, and following degradation experiments
analyses were carried out by high performance liquid chromatography. In addition, the possible relationship between DM degradation
and toxicity was assessed, based on physico-chemical properties of the compounds and their toxicity.
Results DM was rapidly absorbed onto the surface of the algal cells where it was hydrolyzed to diclofop (DC). Further degradation
to 4-(2, 4-dichlorophenoxy) phenol (DP) occurred in the cells. However, only a minor amount of DC was degraded to DP under
the same conditions when DC was initially added to the algal culture. When C. vulgaris was exposed to these compounds for 96 h, the determined EC50 showed that DC was about ten times less toxic than DM (EC50 = 0.42 mg/L) and that DP (EC50 = 0.20 mg/L) was the most toxic.
Discussion Due to strong hydrophobicity and rare dissociation, DM has tendency toward absorption as compared to DC. The higher average
degradation rates of DC initially treated by DM revealed the damage of the cell membranes caused by the DM and, thus, enhanced
movement of DC into the cells. Following occurrence of phenolic breakdown products, DP suggested that DC should be intracellularly
degraded to DP, which had a more potent mode of action and a higher acute toxicity. Moreover, the results for EC50 at various intervals were in accordance with degradation processes of the initial compounds, in which rapid formation of
DP was attributed to an increasing toxicity of DM.
Conclusions The toxicity of DM in algal suspensions increased with time due to its degradation to DP, which contributed significantly
to the determined toxicity. These results indicate that the toxicity of the pesticide probably depends significantly on degradation.
It is thus important to consider the time-dependent environmental processes when evaluating the toxicological effects of pesticides
for proper risk assessment.
Recommendations and perspectives Increasing transformation products of these contaminants are identified in the environment, although they seem to be unknown
in terms of the lacking studies on environmental behavior and ecotoxicity concerning them. Certain breakdown products probably
greatly contribute to the apparent toxicity of the parent compounds, which is ascribed to the parent compounds in general
studies ignoring the dependence of their toxicity on various transformation pathways. These studies that identify new intermediates
and assess their toxicity via the environmental processes will be helpful to distinguish the nature of toxicity of the parent
contaminants. 相似文献
89.
Which group is best? Attributes of different biological assemblages used in freshwater biomonitoring programs 总被引:3,自引:0,他引:3
Resh VH 《Environmental monitoring and assessment》2008,138(1-3):131-138
Of the many groups of organisms proposed for use in biomonitoring, assemblages of fish, algae, and benthic macroinvertebrates
are the most commonly selected. Purported advantages and disadvantages of using these groups, along with those of zooplankton,
were assembled from 65 different publications and websites. From these, 13 categories of advantages and nine of disadvantages
were created. The diversity of the assemblage and its importance to the ecosystem were reported as advantages in >20% of citations
for each group; these similarities suggest that some redundancy exists among the different groups in terms of these features.
Likewise, sampling difficulties and lack of analytic metrics were disadvantages listed in >20% of citations for each group.
Few reported advantages (e.g. recreational value of fish) or disadvantages (e.g. short generation time of algae) were unique
for a particular assemblage. The validity of reported advantages and disadvantages were sometimes region specific, other times
incorrect. The choice of which assemblage is most appropriate for a biomonitoring program ultimately depends on the characteristics
of the area to be studied and the program objectives. 相似文献
90.