首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
Hashsham SA  Freedman DL 《Water research》2003,37(13):3189-3193
Vitamin B12 is an important component of media used to stimulate the growth of many anaerobic microbes that dechlorinate aliphatic compounds. Its delivery to the subsurface is therefore a concern for enhanced in situ bioremediation and bioaugmentation. In situ circulation of vitamin B12 and a chemical reductant has also been field tested for treatment of chlorinated methanes, ethanes, and ethenes. The objective of this study was to determine the extent of B12 (added as cyanocobalamin) adsorption to aquifer solids. Batch studies indicated a minor amount of adsorption to kaolinite clay (Freundlich Kf = 1.5 (microgram/g) (mL/microgram)1/n and 1/n = 0.39) and sand (Kf = 0.70 (microgram/g) (mL/microgram)1/n and 1/n = 0.84), and no detectable adsorption to alumina. Column studies using a 3H2O tracer and vitamin B12 in distilled water (10 microM) resulted in a B12 retardation factor (R) of approximately 2 for both sand (0.14% organic carbon) and a sandy soil (2.5% organic carbon). Using groundwater containing organic carbon (2.8 mg/L) in place of distilled water did not significantly change R. The relatively low value for R indicates vitamin B12 can be distributed throughout a contaminated aquifer without experiencing significant losses to adsorption.  相似文献   

2.
Analyses of metal and organic contaminants were carried out on 41 sediment cores, dated using 210Pb and 137Cs, from the heavily industrialized region of Sydney Harbour, N.S. to evaluate the history of contamination and to predict the rates of natural containment of the harbour by sediment burial. Geochronologies for metals (eg. Pb, As) and polycyclic aromatic hydrocarbons (PAHs) are correlated with the development of the steel and coke industries in the Sydney region while polychlorinated biphenyl (PCB) geochronologies reflect the disposal of electrical equipment used in the steel mill/coking operations. Pb was derived mainly from atmospheric emissions and its concentration has declined exponentially with time in harbour sediments since the closure of the steel mill/coke ovens in the 1980s with a time constant of about 15 years. This represents the time scale for the circulation of this particle-associated contaminant in transient catchment basins prior to permanent deposition in the sediments. PAH and PCB sediment concentrations have also declined exponentially with time since the 1980s, but with a smaller time constant of 10 years owing to the fact that they enter the harbour directly with steel mill and coke oven effluent rather than through atmospheric pathways. Since the time dependence for the burial of metal and organic inventories can be modeled by first order processes, future contaminant levels can be predicted for surface sediments in Sydney Harbour. Mean sediment concentrations of metal and organic contaminants in the upper 5 cm throughout most of the harbour are predicted to decline to levels below the effects range-medium (above which organisms are very likely to be negatively affected by the presence of a contaminant) by 2030.  相似文献   

3.
Coxheath铜钼矿区前寒武纪火山岩广泛分布,具有玄武岩—安山岩—流纹岩的岩性组合,属钙碱性岩石系列,主量元素A/CNK比值为1.30 ~2.40、K2O/N2O小于1,微量元素亏损Ti、Nb、Ta,富集大阳离子亲石元素(LILE) Rb、K、Cs、Ba和Sr,相对富集轻稀土元素(20×10-6~129×10-6),亏损重稀土元素(2.72×10-6~9.91×10-6),呈现右斜式模型,负铕异常不明显,岩浆早期具有岛弧岩浆活动特征,晚期向陆缘发展,火山岩构造环境应为近陆缘的岛弧环境.  相似文献   

4.
悉尼铜钼矿位于加拿大新斯科舍省阿巴拉契亚成矿带北东部,区内出露有元古宇Coxheath组玄武质、安山质、流纹质火山岩和中酸性侵入岩,在中酸性侵入岩内部查明有数十条铜金钼细脉状、网脉状矿(化)体,矿(化)体及成矿元素的分布、蚀变具有明显的斑岩矿化分布特征.多项地质、物探信息显示地表出露的中酸性岩体不是铜金钼矿(化)体的矿致母岩,仅是赋矿围岩,铜金钼矿(化)体是由深部隐伏岩体形成的,这一认识为该矿勘查工作和找矿的突破提供了新的找矿思路和基础.  相似文献   

5.
加拿大新斯科舍省Coxheath斑岩矿床地表有石英闪长岩、石英二长岩两种侵入岩分布,过去勘查工作和很多学者都认为铜钼矿床是由上述两种侵入岩形成。近年来的勘查工作、研究却发现研究区内还存在另外两种性质不同的、新的中酸性侵入岩分布,一种是暗色闪长岩,另一种是花岗岩的分布,斑岩矿床的形成与最后期次形成的酸性侵入岩关系较大,应与石英闪长岩、石英二长岩无关。  相似文献   

6.
Since the mid-1980s, a 'mysterious' disease has been afflicting the moose (Alces alces L.) population of south-western Sweden. Molybdenosis combined with secondary copper deficiency syndrome has been suggested as the cause of the clinical signs and of necropsy findings, supported by trace element analysis. Copper deficiency has long been associated with disturbed carbohydrate metabolism and also with oxidative stress. When testing the oxidative stress hypothesis, we found increased concentrations of the glycoxidation products pentosidine and carboxymethyl-lysine (CML), both in plasma proteins and in renal tissue, when compared with control values. The concentration of glycated lysine (furosine), a marker of hyperglycaemia, was also increased. These data, together with elevated insulin levels in affected moose, strongly suggest that they are suffering from an environmentally-induced, non-insulin-dependent type 2 diabetes.  相似文献   

7.
This study examines the influence of buffering capacity of the soil on the levels of cadmium in the kidney, liver and muscle of moose and white-tailed deer from nine sampling sites (four buffered and five non-buffered) in Ontario, Canada. Tissues collected from hunter-killed moose and deer during 1984 and 1985 were analysed for cadmium. Tissue from moose in the non-buffered Algonquin Park site (21.9 +/- 1.1 mg/kg wet weight) and the buffered St. Joseph Island site (12.7 +/- 3.2 mg kg-1) had the highest mean levels of kidney cadmium compared with other sites sampled in Ontario. The highest mean levels of kidney cadmium in deer were found in the non-buffered Loring site (15.1 +/- 0.8 mg kg-1) adjacent to Algonquin. From all sites, the level of cadmium was highest in kidney, lower in liver and was often undetectable in muscle. Cadmium level increased with animal age (p less than 0.05). Levels of cadmium in Ontario moose from some regions are comparable to those found in Quebec and Manitoba and are considerably higher than those of Maine and Scandinavia. Levels of cadmium in kidneys and livers of white-tailed deer in parts of Ontario are considerably lower than those in Pennsylvania. As a result of this study, the Ontario Ministry of Natural Resources, in consultation with the Ontario Ministry of Health, has recommended that the public not consume kidneys or livers of Ontario moose and deer.  相似文献   

8.
Arsenic is one of the most widely encountered environmental contaminants because of a number of anthropogenic sources; in Canada the main anthropogenic release of arsenic is from mine tailings ponds. The present study is part of a series of studies to measure chemical and biological effects of exposure for meadow voles (Microtus pennsylvanicus) living on arsenic contaminated sites. Two additional objectives were addressed in the present study: the effect of higher arsenic concentrations compared with previous studies, and the comparison of chemical speciation and biological effects. To obtain the higher environmental concentrations, specimens were collected from a former gold mining site in Montague, NS that contains highly elevated concentrations of arsenic in soils and plants. Meadow voles were collected and their tissues were analyzed for total arsenic to measure uptake, and arsenic speciation to examine the chemical effects of the high arsenic exposure. In addition to the arsenic analysis, a biomonitoring study was undertaken to examine the sub-cellular effects in meadow voles resulting from the elevated arsenic exposure. Meadow voles living on the contaminated site had substantially higher concentrations of total arsenic than animals from the background (reference) location. The extractable arsenic in internal tissues was present mainly as monomethylarsonic acid (up to 14% of total arsenic). A statistically significant relationship was observed between the reduction of glutathione in vole livers and the increase in liver arsenic concentrations, and micronucleated monochromatic red blood cells were also significantly elevated in voles from the arsenic contaminated site. This is one of the few field studies where sub-cellular effects were observed, and the first to show a co-existence of such effects with relatively high proportions of monomethylarsonic acid in voles living near mine tailings.  相似文献   

9.
Total Hg, methyl-Hg (MeHg) and Se levels were measured in the brain of river otters (Lontra canadensis) and wild mink (Mustela vison) carcasses collected from Nova Scotia, Canada. Total Hg concentrations in the otters' brain were highly variable, ranging from 0.3 to 18.0 μg/g dw and were significantly higher in animals caught from inland areas of the province versus coastal animals. Similarly, inland otters contained significantly more MeHg in the brain than did coastal otters. MeHg was highly correlated with total Hg in both inland and coastal otters and represented on average approximately 82% of the total Hg. Selenium concentrations in the otter brain ranged from 1.0 to 7.8 μg/g dw but unlike Hg, there was no significant difference in Se levels between inland and coastal otters. There was a significant positive relationship between Se and total Hg concentrations in the otters with the molar ratio of Se:Hg approximately 1:1 for animals having an Hg concentration > 18 nmol/g dw.The non-random sampling protocol for the mink precluded extensive statistical analysis of the data. However, unlike otters, virtually all (i.e. 98%) of the total Hg in mink brain was present as MeHg in both inland and coastal mink. Also unlike the otter results, Se concentrations showed no relationship with either total or MeHg in both inland and coastal mink.The data suggest that mink and otters may have different mechanisms for managing high levels of Hg in the brain.  相似文献   

10.
Moose (Alces alces L.) affected by a disease with unknown aetiology were compared with healthy moose regarding trace element concentrations in liver and kidneys, as well as certain clinical chemical parameters of blood plasma. The diseased moose showed decreased hepatic concentrations of Cu, Cd and Mg. Renal concentrations of Cd, Co, Mg and Mn were also decreased. Substantially increased concentrations in both liver and kidneys were seen for Al, Ca, Fe, Pb and Zn, while Se and Mo were increased in liver tissue. The hepatic levels of Mo in the affected moose were 36% higher and Cu was approximately 60% lower than in reference animals collected in 1982. The most important clinical chemical changes were decreased concentrations of bilirubin, thyroxine (T4) and the liver-specific enzymes GLDH and g-GT. Also, the activities of the enzymes CuZn-SOD and GSH-Px in erythrocytes were decreased. Increases were recorded for free fatty acids (NEFA), the muscle-specific enzyme CK, but especially for urea and insulin. Changes in the plasma protein pattern were also discernible after electrophoresis on agarose gel membranes, indicating chronic immunostimulation. All the observed changes in trace element concentrations and clinical chemical parameters are compatible with molybdenosis and secondary Cu deficiency in ruminants and most of the parameters are in agreement with those found in experimental copper deficiency and molybdenosis in the goat. It is, therefore, suggested that the moose disease with previously unknown aetiology is mainly caused by molybdenosis.  相似文献   

11.
Blood samples were taken from fourteen sexually mature (ripe) male Atlantic salmon (Salmo salar), eight from the acidic Westfield river (pH 4.7) and six from the less acidic (pH 5.6) Medway river to determine if there is any difference in sex hormone production in the fish in the two rivers.The plasma levels of the two principal male sex hormones, testosterone and 11-ketotestosterone, which normally peak at functional sexual maturity, were significantly lower in salmon from the more acidic Westfield river compared to those in salmon from the Medway river. Since these fish were of the same stock, and were in the same state of sexual maturation, it is suggested that the more acidic Westfield River has affected the production and/or utilization of sex hormones in this species.  相似文献   

12.
张海燕  王琦 《山西建筑》2010,36(30):190-191
结合JGY-12B型氧量分析仪的用途,详细介绍了JGY-12B型氧量分析仪的工作原理,仪表结构及操作方法等内容,指出该仪器具有结构简单、稳定性好、灵敏度高、响应快、使用方便、易于维护等特点,值得推广。  相似文献   

13.
《Fire Safety Journal》1999,33(1):21-34
In order to clarify the mixing that occurs in a gravity current which precedes a backdraft, a two-dimensional simulation, a series of salt water experiments, and backdraft experiments were performed. A compartment in a ratio width/height/length of 1/1/2 is used in the experiments and computations. Two different openings were used in the salt water experiments and numerical computations: a fully open end wall and a h1/3 horizontal slot centred in an end wall, where h1 is the compartment height. For the backdraft experiments only the h1/3 horizontal slot was used. The visual observations from the salt water experiments compare well with the numerical simulation. Both show a small mixed region at the gravity current shear interface for the fully open wall and mixing throughout the entire current for the h1/3 horizontal slot. Quantitative comparisons are made in terms of the normalised density differences, β=(ρ0ρ1)/ρ1, where ρ0 is the higher density and ρ1 is the lower density. The transit time results, i.e., time between opening the compartment and the time the gravity current reaches the wall opposite the opening, for the computations compared favourably with the transit times from the salt water experiments, over the range 0.003<β<0.100. Velocity measurements from the opening of the backdraft compartment, prior to ignition, also are favourable with the numerical simulation.  相似文献   

14.
日本人做事讲究精益求精、不断完善,因此日语中“改善”的发音“kaizen”已逐渐变成一个英文单词。中国人做事则更讲求关系。有一次,我邀请一个德国人到学校讲学,中午吃饭时,大家谈到了一些本单位的事。由于不便让外国人知道,我们说的是汉语。没想到这个不懂中国话的老外居然听懂了一个重要的词汇——“关系”。后来我留心一下,  相似文献   

15.
钱海平  吴璟  林涛 《建筑学报》2007,(11):23-25
以中国威海国际建筑设计大赛金奖作品“杭州亲亲家园B12组团排屋住宅”建筑设计为例,分析特定类型住宅的空间组合模式,探索提升节地型住宅空间品质的设计思路。  相似文献   

16.
目的:比较戊酸雌二醇单药或联合叶酸、维生素 B12治疗围绝经期抑郁症的临床疗效。方法将70例围绝经期抑郁症患者按治疗方法的不同分为2组:治疗组和对照组,每组35例。2组均采用戊酸雌二醇片0.5 mg 口服,1次·d-1,连用28 d。在此基础上,治疗组采用叶酸0.4 mg 口服,3次·d-1;维生素 B1225μg 口服,3次·d-1,连用28 d。观察2组临床疗效及不良反应的情况,并对2组治疗前,治疗2、4周后和随访2、4周抑郁严重程度进行评分[采用汉密尔顿抑郁量表(HAMD)评分]。结果治疗组总有效率明显高于对照组(85.7%比65.7%,P <0.05)。2组治疗2、4周后和随访2、4周 HAMD 得分均较治疗前明显下降(均 P <0.05),治疗组治疗2、4周后和随访2、4周 HAMD 得分均较对照组下降更明显(P <0.05或 P <0.01)。结论戊酸雌二醇联合叶酸和维生素B12治疗围绝经期抑郁症疗效优于单用戊酸雌二醇。  相似文献   

17.
针对各地公安消防监督机构在执行新修订《消防法》及配套的《消防监督检查规定》和《建设工程消防监督管理规定》中容易疏忽的的几个问题提出注意事项和建设性意见。  相似文献   

18.
刘晓 《今日消防》2021,6(12):59-61
随着城市化进程的发展,大型综合体的数量越来越多,尽管这些多功能建筑物为人们的日常生活带来很大便利,但由于其空间结构复杂、火灾荷载高的特点,若遇突发火灾,里面人员密集以及拥挤推搡的情况下,秩序混乱,踩踏事件时有发生.基于此,在突发状况后,消防员如何迅速从复杂的大型综合体里面救援灭火成为一项难度系数高的挑战.可以通过切实做好"六熟悉"工作、制定好灭火救援预案、开展实战演练、创新式组建专业队、灭火救援对策之调足力量、火情侦查;通过积极疏散人员、火场排烟进行灭火救援,运用战术、高科技助力来灭火救援、强化日常装备,抓好战斗行动的主动权、强化理论学习,做好灭火救援知识储备、强化联勤、联训,做好车辆、器材装备和固定消防设施测试工作.综上所述,文章将详细论述关于大型综合体火灾灭火救援相关问题的必要性,以及出现问题后的解决措施.  相似文献   

19.
This paper reports on modern developments related to nanotechnology of cement and concrete. Recent advances in instrumentation and design of advanced nano-composite materials is discussed. New technological directions and historical milestones in nanoengineering and nanomodification of cement-based materials are presented. It is concluded that there is a strong potential of nanotechnology to improve the performance of cement-based materials.  相似文献   

20.
Aquatic animal toxicity is a major criterion used by the U.S. EPA to designate and classify hazardous substances other than oil. This research developed basic toxicity data for twelve industrial chemicals with which little or no previous testing had been done. Static 96h toxicity tests were performed with one freshwater species (fathead minnow, Pimephales promelas) and one saltwater species (grass shrimp, Palaemonetes pugio or white shrimp, Penaeus setiferus) on the following chemicals: ammonium fluoride, arsenic trisulfide, benzoyl chloride, benzyl chloride, cupric acetate, o-dichlorobenzene, p-dichlorobenzene, mercuric acetate, mercuric thiocyanate, resorcinol, sodium hypochlorite and toluene-2,4-diisocyanate (TDI). As defined by 96 h LC50's ≤ 500 mg l−1, all 12 chemicals were hazardous to freshwater minnows, and all but TDI were hazardous to saltwater shrimp. The physicochemical behaviors of the compounds greatly influenced their aquatic toxicities.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号