首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   20篇
  免费   2篇
  国内免费   4篇
  2023年   1篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2018年   1篇
  2017年   1篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   5篇
  2012年   1篇
  2008年   2篇
  2006年   1篇
  2005年   1篇
  2003年   1篇
  2002年   2篇
  1999年   1篇
  1993年   1篇
排序方式: 共有26条查询结果,搜索用时 15 毫秒
1.
The aim of our study was to compare the sorption properties of a contaminated soil before and after two types of phytoremediation (natural phytoextraction vs. phytostabilization with dolomite limestone (DL) application). Soil from a pot experiment in controlled greenhouse conditions performed for two vegetation periods was used for the study. Lead, as the main contaminant in the studied soil, was easily desorbed by Cu, especially due to the increased affinity of Cu for soil organic matter; hence input of Cu to the studied soil can present another environmental risk in soils contaminated with other metals (such as Pb). In addition, the sorption behavior of chosen metals from single-element solutions differed from multielement solutions. The obtained results proved the different sorption behavior of metals in the single-element solution compared to the multi-element ones. Soil sorption behavior of Cd, Cu, and Zn decreased with the presence of the competitive metals; nevertheless, Pb sorption potential was not influenced by other competitive metals. Natural phytoextraction showed no significant effect on the sorption of Cd, Cu, Pb, and Zn onto the soil On the other hand, phytostabilization associated with DL application improved the soil sorption efficiency of all chosen metals, especially of Cu.  相似文献   
2.
The hydrological system of Lagoa Vermelha, a dolomite-precipitating lagoon in Brazil, was investigated using hydrogen and oxygen stable isotopic composition of the water collected during an annual cycle (1996–1997). These data demonstrated that dolomite formed in May–June during high saline conditions. High salinity apparently provides the ions and saturation state necessary for dolomite precipitation. Ion concentrations in the lagoon water indicated an identical timing of dolomite precipitation and demonstrated that dolomite formed at decreased sulfate concentrations. In Brejo do Espinho, a neighbouring lagoon, the ion concentrations in the water column revealed that dolomite precipitates throughout the year, most likely due to its higher salinity than Lagoa Vermelha during the measured period. In Lagoa Vermelha, high 34S of pore water sulfate and high sulfide concentrations correlated with dolomitic horizons, demonstrating the association of bacterial sulfate reduction with dolomite formation. In Brejo do Espinho high 34S of pore water sulfate and high sulfide concentrations occurred throughout the dolomitic sedimentary column. We conclude that elevated salinity and sulfate reduction are the main factors inducing dolomite precipitation in these lagoons, confirming the microbial dolomite formation theory. These results suggest that there may be other settings where sulfate-reducing bacteria induce dolomite precipitation under saline conditions, such as deep-sea sediments or sabkhas, and imply that microbial dolomite may significantly contribute to the sedimentary carbonate budget, particularly in the earliest Earth's history when anoxic conditions were more prevalent.  相似文献   
3.
New management strategies should be identified to increase the potential of bioenergy crops to minimize climate change. This study quantified the impact of sugarcane (Saccharum spp.) harvest systems, straw and soil management on carbon dioxide (CO2) fluxes prior to crop replanting carried out on February 2010 in southern Brazil. The soil studied was classified as Haplustult (USDA Soil Taxonomy). Three sugarcane harvest systems were considered: burned (BH) and green harvest with straw maintained on (GH SM) or removed from (GH SR) the soil surface. Our hypothesis is that intensive tillage and the management of sugarcane crop straw could lead to higher CO2 emissions from soil. We measured CO2 emissions in no‐till (NT) conditions and after conventional tillage (CT), and with or without dolomite and agricultural gypsum applications. Soil CO2 emissions were measured with a Li Cor chamber (Model Li‐8100). Water content of soil and soil temperature readings were first taken 24 h after tillage, over the next 25 days after tillage with 18 measurement days. The removal of sugarcane straw from the soil surface resulted in the rapid reduction of water content of soil (6% in volume) followed by a 64% increase in soil CO2‐C emissions, supporting our hypothesis. Additional soil CO2‐C emissions caused by removal of crop straw were 253 kg CO2‐C ha?1, which is as high as CO2‐C losses induced by tillage. Dolomite and agricultural gypsum applications did not always increase CO2 emissions, especially when applied on soil surface with crop straw and tilled. The conversion from burned to green harvest systems can improve the soil C sequestration rate in sugarcane crops when combined with reduced tillage and straw maintenance on soil surface. The effect of straw removal and related CO2 emission for electricity generation should be considered in further studies from sugarcane areas.  相似文献   
4.
Andrea Cozzi 《Facies》2002,47(1):151-178
Summary Upper Triassic (Middle-Upper Norian) shallow-water carbonates of the Dolomia Principale and its deep-water counterparts (Forni Dolomite) have been studied in the Carnian Prealps (northeastern Italy). The Dolomia Principale was a storm-dominated carbonate platform; in the Mt. Pramaggiore area, along a well-preserved 3.5 km-long platform-to-basin transition, the inner platform facies of the Dolomia Principale, characterized by m-scale shallowing upward cycles, give way seaward to open marine storm-dominated shallow subtidal lagoon deposits with frequent hardgrounds and evidence of microbial stabilization of the bottom sediment. The margin of the Dolomia Principale platform was colonized by meter-scale stromatolites and serpulid-microbial mounds that thrived due to the local highly stressed environment, characterized by drastic salinity fluctuations and turbid waters, that excluded the Upper Triassic coral-sponge communities. The Forni Dolomite slope-basin complex was characterized by an upper slope facies with debris flows, megabreccias, turbidites and serpulid-microbial mounds. The lower slope and basinal facies show thinning and fining trends. After restoring the original geometry of the slope, the depositional angles of the clinoforms range between 11 and 36 degrees, reflecting closely the coarse-grained character of the Forni Dolomite slope complex, which can be interpreted as a slope apron that, as a model, can be extended to steeply inclined carbonate slopes. The onset of synsedimentary extensional tectonics at the Middle-Late Norian boundary affected the platform-slope depositional system via: 1) localized inner platform collapses and the formation of an intraplatform anoxic depression at Mt. Valmenone, 2) a switch from platform lateral progradation during the Middle Norian to vertical aggradation in the Late Norian, reflected in an increase in platform relief, steeper foreslope angles and coarser-grained slope facies, and 3) controlling the spatial orientation of the margin of the Dolomia Principale.  相似文献   
5.
宋泉颖  徐俊  张宇 《微生物学通报》2014,41(10):2155-2165
【目的】白云石(Dolomite)是一种含有钙镁的碳酸盐矿物[CaMg(CO3)2],广泛存在于陆地和海洋等环境并常与油气埋藏共存。尽管白云石(或岩)的发现已经有三百多年的历史,但是对白云石的成因仍然没有定论,地质学上称之为"白云石之谜"。20世纪90年代Vasconcelos C.提出了"微生物白云石模型",为白云石成因的研究带来了新的思路。但是这一模型并不完善,白云石的形成与所介导的微生物生理状态以及环境参数之间的关系不明确。另外,所有报道的实验都是在地表压强条件下进行,无法表征自然界中白云石所处的高压环境。本研究中引入压力这一环境参数,结合菌株本身生理特性参数,综合考察多重因子对微生物介导形成白云岩的影响。【方法】利用球形赖氨酸芽孢杆菌(Lysinibacillus sphaericus)和嗜冷芽孢八叠球菌(Sporosarcina psychrophila)两株具有尿素水解活性的细菌作为生物材料,在不同的温度(15°C和30°C)压强(常压和20 MPa)氧气浓度(常压好氧条件和常压微氧条件)不同的尿素水解活性下进行生物矿化实验。通过SEM(扫描电子显微镜)和EDS(X射线能谱分析)相结合的方法观察沉淀物形貌和矿物成分构成。通过XRD(X射线衍射分析)定性测定碳酸盐矿物沉淀物的种类。【结果】球形赖氨酸芽孢杆菌和嗜冷芽孢八叠球菌在实验中所设计的所有矿化条件下都能够介导形成碳酸盐矿物沉淀。XRD和SEM检测均证实球形赖氨酸芽孢杆菌在30°C的20 MPa微氧条件下能够介导形成不规则菱面型和椭球型白云石。高压条件更有助于白云石的形成。除了白云石晶体,实验中还观察到有其他矿物(如方解石,碳氢镁石,钙镁碳酸石等)。【结论】实验证实球形赖氨酸芽孢杆菌和嗜冷芽孢八叠球菌具有矿化能力,特别是球形赖氨酸芽孢杆菌具有介导形成白云石的能力。微生物介导形成的碳酸盐矿物组分受到微生物的代谢活性以及温度、压力等生物矿化实验条件控制。这一研究结果帮助完善"微生物白云石模型",为解释白云石的深部成因提供数据支持。  相似文献   
6.
喀斯特土壤主要由白云岩和石灰岩风化而来,植被生长及其分布究竟怎样响应这一特殊地质背景?以人为干扰影响较小的喀斯特自然保护区为研究对象,采用监督分类法对1990年和2011年两期TM影像进行植被分类,并利用景观格局分析方法研究两种岩性上植被变化差异。结果表明,1990年和2011年研究区内两种母岩上均以乔木林和乔灌为主,草灌和草丛分布少,白云岩上乔木林的面积比例大于石灰岩上的比例,而草灌和草丛小于石灰岩上的比例;近20年来白云岩与石灰岩上草丛、草灌、灌丛和乔灌均以正向演替为主,但白云岩上正向演替比例大于石灰岩上的比例;两种岩性上植被斑块连接性均增强、破碎程度均降低,白云岩上植被斑块的破碎化程度和多样性指数较石灰岩上低,内部连接性强。由此可见,喀斯特白云岩较石灰岩有利于草丛、草灌的自然恢复,岩性引起的水土资源配置和养分地球化学循环过程差异制约着喀斯特地区植被的时空格局。  相似文献   
7.
The Miocene Globigerina Limestone of the Maltese islands contains widespread omission surfaces with very different characteristics and origins.The terminal Lower Globigerina Limestone hardground (TLGLHg) formed during a period of falling sea level. Coccolith assemblages suggest shallowness. Sedimentary structures and trace fossil assemblages, indicate increasing frequency of storm events and erosional episodes, towards the surface. Calcite cementation which took place around Thalassinoides burrows and formed irregular nodules was followed by dissolution of aragonite. It is suggested that lithification was linked to microbial reactions involving organic matter.In contrast two later surfaces, the terminal Middle Globigerina Limestone omissionground (TMGLOg), which marks the Lower to Middle Miocene boundary, and the Fomm-ir-Rih local hardground (FiRLHg) both contain early diagenetic dolomite. Lithification took place in two phases. The dolomite is interpreted to have formed beneath the sea floor; it was subsequently exhumed and partially corroded as the precipitation of calcitic and phosphatic cements took place around burrows open to the circulation of sea water.  相似文献   
8.
The applicability of dolomite particlesto control acidificationin a Hyphomicrobium MS3inoculated biofilter removingdimethyl sulphide (Me2S) wasstudied. While direct inoculationof the dolomite particles with theliquid microbial culture was notsuccessful, start-up ofMe2S-degradation in thebiofilter was observed when thedolomite particles were mixed with33% (wt/wt) of Hyphomicrobium MS3-inoculatedcompost or wood bark material.Under optimal conditions, anelimination capacity (EC) of 1680~g Me2S m-3 d-1 wasobtained for the compost/dolomitebiofilter. Contrary to a wood barkor compost biofilter, no reductionin activity due to acidificationwas observed in these biofiltersover a 235 day period because ofthe micro environmentneutralisation of the microbialmetabolite H2SO4 with thecarbonate in the dolomite material.However, performance of thebiofilter decreased when themoisture content of the mixedcompost/dolomite material droppedbelow 15%. Next to this, nutrientlimitation resulted in a gradualdecrease of the EC andsupplementation of a nitrogensource was a prerequisite to obtaina long-term high EC (> 250 gMe2S m-3 d-1) forMe2S. In relation to thisnitrogen supplementation, it wasobserved that stable ECs forMe2S were obtained when thisnutrient was dosed to the biofilterat a Me2S-C/NH4Cl-Nratio of about 10.Abbreviations:DW – dry weight,EC – elimination capacity,Me2S – dimethyl sulphide,OL – organic loading rate,VS - volatile solids  相似文献   
9.
晏妮  张腾  熊康宁  陈倩  郭丁力  刘之威 《生态学报》2021,41(24):9593-9603
藻类是真核生物进化、植物起源与进化、生物地理学研究的良好材料,研究藻类物种多样性对理解生命起源与早期进化,探明地球地质地貌演化有着非常重要的意义。以两世界自然遗产地施秉云台山白云岩喀斯特、赤水丹霞的陆生藻类为研究对象,通过G-F多样性指数、Jaccard相似性系数、Bray-Curtis矩阵比较分析了不同地质地貌的两世界自然遗产地陆生藻类的物种多样性及种组特征,结果如下:(1)两地陆生藻类丰富,均以蓝藻为优势,共有优势科为色球藻科Chroococcaceae、颤藻科Oscillatoriaceae,施秉云台山还具伪枝藻科Scytonemataceae、念珠藻科Nostocaceae优势,优势属为粘球藻属Gloeocapsa、色球藻属Chroococcus,赤水丹霞仅以粘球藻属Gloeocapsa为优势。(2)施秉云台山G-F多样性指数高于赤水丹霞。(3)两地陆生藻类泛热带成分明显,施秉云台山中国特有成分较赤水丹霞丰富;两地科、属、种相似性系数依次为:56.25%、44.05%、37.62%,科的相似性达到中度水平,与同纬度范围其它地区的Bray-Curtis矩阵聚类结果显示不同地质地貌的两地首先聚为一类。从陆生藻类多样性组成上,初步反映两世界自然遗产地的地质历史、地层岩性及地理位置的异同。  相似文献   
10.
水洞沟遗址是中国北方旧石器时代晚期的著名遗址,石制品原料以就地取材的白云岩为主。本文利用水洞沟地区的白云岩生产细石叶和石片,进行了29组复制使用实验。对使用痕迹的观察表明:不同加工对象和使用方式导致细石叶上出现不同的微痕特征,细石叶适于装柄使用,以刮、切、削等利用侧刃缘的运动方式效率为高,尖部用于加工硬度较低的动植物效果较好。对比燧石、黑曜岩等不同石料的微痕实验数据可知,不同石料的产品,其使用痕迹存在一定差异。本文对白云岩细石叶的微痕实验,探讨了其适宜的使用方式和加工对象的范围,为分析水洞沟地区出土的白云岩细石叶功能提供了可资参考、对比的实验数据。  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