HYDROCHEMICAL STATE OF INTERMEDIATE CULTURE POND FOR CHINESE PRAWN JUVENILES     

臧维玲  张建达  戴习林  朱正国  徐桂荣  宋林华  李士华 《中国海洋湖沼学报》1996,14(1):41-46

This study deals with the hydrochemical state and management measures for the intermediate culturepond for Chinese prawn (Penaeus orientalis) juveniles. The test result showed that the intermediate cultureof Chinese prawn juvenile can be advanced to around March 20 in the Shanghai area if they are culturedin ponds in simple greenhouses of plastic knitting cloth.The density of juveniles introduced was about35 million per hectare, survival was up to 55%.  相似文献   

Acidity and organic carbon in lake water: variability and estimation of means     

John F. Boyle 《Journal of Paleolimnology》1991,6(2):95-101

The demand for a single value to characterize the pH (and other chemical variables) of a lake, in order to calibrate palaeolimnological reconstructions, requires an answer to the question of whether means should be of untransformed or log data. The temporal frequency distributions of acidity and organic carbon in seven rivers and lakes (surface samples) in Norway are approximately lognormal. Thus log means describe the distributions better than untransformed means. Estimated standard deviations, which are similar for the rivers and lakes, are independent of the mean values. Restricting observations to the autumn does not result in better estimation of mean annual values.  相似文献   

摩尔配比和矿物掺合料对盐湖提锂镁渣制作磷酸钾镁水泥性能影响的研究   总被引：1，自引：1，他引：0       下载免费PDF全文

陈文海  吴成友 《盐湖研究》2022,30(3):83-88

使用盐湖提锂镁渣和矿物掺合料,如粉煤灰、硅灰和矿渣等,与磷酸二氢钾反应,制作磷酸钾镁水泥(Magnesium Potassium Phosphate Cement,MKPC)。研究了MgO/KH₂PO₄摩尔配比(M/K)和矿物掺合料对MKPC凝结时间、抗压强度和水化放热速率的影响,并使用X射线衍射(X-ray diffraction,XRD)和低真空扫描电子显微镜(Scanning Electron Microscopy,SEM)分析MKPC的水化产物。研究表明,M/K对MKPC抗压强度影响显著,最佳M/K为4~6。M/K为5时,MKPC在各龄期的抗压强度值均较高,28d抗压强度高达98MPa。掺加矿物掺合料会降低MKPC的抗压强度,当粉煤灰、硅灰和矿渣的掺量分别为水泥质量的20%,10%和20%时,28d抗压强度可以分别达到45.9MPa、33.3MPa和36.7MPa。凝结时间超过20min,能够满足快速修复的要求。在不考虑Mg₃B₂O₆的影响下,掺加矿物掺合料会延缓MKPC凝结时间和降低放热速率。  相似文献   

原料配比对硫氧镁水泥力学性能、物相和微观形貌的影响          下载免费PDF全文

刘秀泉  董金美  常成功  郑卫新  刘启元  肖学英  文静 《盐湖研究》2022,30(3):89-97

以盐湖提锂副产镁渣为原料,经洗涤煅烧制备活性MgO,并与七水硫酸镁混合制备硫氧镁水泥。研究了原料配比(活性MgO:MgSO₄:H₂O,摩尔比)对硫氧镁水泥试件凝结时间、安定性和抗压强度的影响,并利用XRD和SEM分析试件的物相组成和微观形貌。结果表明:固定H值,随着M值的增大,MOS浆体的凝结时间缩短,28 d的抗压强度先增加后降低,主要水化产物517相先增多后减少,晶体的微观形貌经历了由针丝状晶体—针丝状、短棒状晶体并存—凝胶状、针棒状晶体并存的转变过程;当M=9时,MOS浆体的安定性较差,主要水化产物逐渐变为Mg(OH)₂相;固定M值,随着H值的增大,MOS浆体的凝结时间延长,28 d的抗压强度先增加后降低,主要水化产物的种类没有发生明显的变化,当H≥26时,MOS浆体的安定性较差;得出较佳的M值范围为5~7,H值范围为20~24。  相似文献   

中国大陆强震时空分布特征及2021年玛多7.4级地震后趋势分析     

王芃  邵志刚  石富强  尹晓菲 《地震》2021,41(4):1-14

对中国大陆强震活动的时空分布特征进行分析, 有助于中国大陆强震趋势的判定。 由于地震目录完整性的限制, 目前对中国大陆强震时间间隔的分析多基于1900年以来地震目录。 因为记录时长相对较短, 难以排除当前强震时序特征基于偶然的可能性, 并且可能导致过拟合而影响预测效果。 针对上述问题, 本文根据2021—2030年中国大陆地震重点危险区确定工作中的相关资料, 对合成地震目录进行了分析, 结果表明区域地震活动强弱交替是一种普遍现象, 当假设中国大陆活动断层具有准周期复发特征时, 合成地震目录时序特征与当前目录最为接近。 基于上述认识, 使用适用范围更广的单参数指数分布拟合了中国大陆强震间隔, 并结合相邻强震构造关联随时间的变化对2021年5月22日玛多7.4级地震后中国大陆的强震趋势进行了分析。 结果表明, 继玛多7.4级地震之后, 未来两年中国大陆再次发生7级以上地震的概率较大, 下次强震发生在2022年年底之前的概率为61.81%。 下次强震发生在2021年的概率为30.58%, 最有可能的发震区域是巴颜喀拉地块; 下次强震发生在2022年的概率为44.97%, 重点关注南北地震带中南段。  相似文献   

Formation,mechanism and significance of alluvial-dammed lakes in Golmud River catchment,north-eastern Qinghai-Tibetan Plateau     

Fuyuan An  Tianyuan Chen  Xiangzhong Li  Xiangjun Liu  Yixuan Wang  Zongyan Chen  E Chongyi 《地球表面变化过程与地形》2021,46(12):2421-2436

This study investigated a series of dammed lakes and downstream-adjacent alluvial fans in the upstream to middle reaches of the Golmud River in the eastern Kunlun Mountain, on the north-eastern Qinghai-Tibetan Plateau (QTP). An optically stimulated luminescence (OSL) chronology shows the sediments of five dammed lakes developed from c. 45–40, 30–25, 18–14, and 12–8 ka, corresponding to MIS 3b, late MIS 3a, Last Deglaciation, and early Holocene, respectively. The remote sensing data show these dammed lakes have a total area of 109.4 km², with the lake volume of more than 4.0 km³. Symmetric alluvial fans from north–south tributary valleys produced OSL ages of c. 61–52, 42–31, 26–20, and 16–10 ka, corresponding to glaciation periods: the MIS 3c and MIS 3a, MIS 2, and the Last Deglaciation. This suggests that glacial activity is responsible for the alluvial fan development, where dammed rivers occurred first, but lake formation did not take place synchronously until later periods of strong hydrologic activity, resulting from northward intrusions of the Indian summer monsoon (ISM) or glacier melt. Thus, the blocking pattern is that river valleys were dammed during periods of glacial activity and lakes formed during wet periods. The lake formation and subsequent drainage may have resulted in: (i) impeded headwater incision and strengthening of downstream dissection; (ii) enriched the halite and potash in the distal Qarhan Salt Lake through hydrologic and hydrochemical processes of abundant water input, the salt lake expansion, salt redissolution from playa and final resedimentation during later dry periods. The alluvial-dammed lake pattern in the mountain-basin systems of eastern Kunlun Mountain offers a model for assessing the linkages between monsoon dynamics, geomorphic processes and distal salt lake evolutions in other arid regions.  相似文献   

中文文本中时间信息解析方法   总被引：1，自引：0，他引：1  

张春菊  张雪英  李明  王曙 《地理与地理信息科学》2014,30(6)

探讨了基于触发词汇和规则模型相结合的中文文本中时间信息解析方法。通过分析、归纳中文文本中时间信息描述特点,构建时间词汇词典和时间信息描述模式库,设计时间信息抽取、规范化表达和语义推理算法,实现了中文文本中时间信息的解析。实验结果表明,中文文本中时间信息抽取的准确率、召回率和F1值分别为75.00%、88.24%和40.54%,为泛在时空信息动态关联更新和实时挖掘分析提供数据源,且通过与空间维数据有机地、交互地组织,能够实时展现地理现象和事物的时空演化过程、时空分布特征,从而推动地理信息检索、LBS等地理信息服务向动态化、多维化方向发展。  相似文献   

Redox and pH conditions in the water column and in the sediments of an acidic mining lake     

T. M. Bachmann  K. Friese  D. W. Zachmann   《Journal of Geochemical Exploration》2001,73(2)

Physico-chemical parameters of the acidic mining lake (ML) 111 in the Lusatian region (Germany) were determined in April and August 1997 using a multiparameter probe for the water column and punch-in pH and Eh electrodes for the sediment, respectively. Samples of the sediment profile were taken by a gravity corer. Besides determination of the physico-chemical parameters, grain size and water contents were determined after sediment slicing.Differences in the redox state of the water body, deduced from oxygen saturation between April and August, could not be inferred. However, a shift in pH to lower values was apparent. Data support the conclusion that the enhanced oxygen content was consumed for oxidation of ferrous iron to ferric iron (oxides/hydroxides) coupled with the release of protons.In the sediment, different buffer systems of iron compounds could be detected within separate zones with values below and above pH 3. At higher pH values, the redox conditions are controlled and stabilized by the presence of Fe-oxide-hydroxides and possibly Fe-sulfates.  相似文献   

中国大陆科学钻探主孔0～4500米变质岩石锆石中保存的超高压矿物包体   总被引：14，自引：9，他引：14  

刘福来许志琴  薛怀民孟繁聪 《岩石学报》2005,21(2):277-292

中国大陆科学钻探主孔0-4500米的岩心主要由榴辉岩、斜长角闪岩、副片麻岩、正片麻岩以及少量的超基性岩所组成。岩相学研究结果表明,榴辉岩的围岩普遍经历了强烈角闪岩相退变质作用的改造,峰期超高压变质的矿物组合已完全被后期退变质过程中角闪岩相矿物组合所替代。采用激光拉曼技术,配备电子探针和阴极发光测试,发现主孔224件岩心中有121件(包括榴辉岩、斜长角闪岩、副片麻岩和正片麻岩)样品的锆石中普遍隐藏以柯石英为代表的超高压矿物包体,且不同岩石类型锆石中所保存的超高压矿物包体组合存在明显差异。(含多硅白云母)金红石石英榴辉岩锆石中保存的典型超高压包体矿物组合为柯石英 石榴石、柯石英 石榴石 绿辉石 金红石和柯石英 多硅白云母 磷灰石。黑云绿帘斜长角闪岩锆石中保存的超高压矿物组合为柯石英 石榴石 绿辉石、柯石英 石榴石 多硅白云母和柯石英 绿辉石 金红石,与榴辉岩所保存的超高压矿物组合十分相似,表明该类斜长角闪岩是由超高压榴辉岩在构造折返过程中退变质而成。在副片麻岩类岩石,如石榴绿帘黑云二长片麻岩锆石中,代表性的超高压包体矿物组合为柯石英 多硅白云母和柯石英 石榴石等;而在石榴黑云角闪钠长片麻岩锆石中,则保存柯石英 硬玉 石榴石 磷灰石、柯石英 硬玉 多硅白云母 磷灰石和柯石英 石榴石 磷灰石等超高压矿物包体。在正片麻岩锆石中,标志性的超高压矿物包体为柯石英、柯石英 多硅白云母、柯石英 蓝晶石 磷灰石和柯石英 蓝晶石 榍石等。此外,在南苏鲁东海至临沭一带的地表露头以及一系列卫星孔岩心的锆石中,也普遍发现以柯石英为代表的标志性超高压矿物包体,表明在南苏鲁地区由榴辉岩及其围岩的原岩所组成的巨量陆壳物质(方圆>5000km2,厚度超过4.5km)曾整体发生深俯冲,并经历了超高压变质作用。该项研究对于重塑苏鲁-大别超高压变质带俯冲-折返的动力学模式有着重要的科学意义。  相似文献   

The pattern of sedimentary bacterial communities varies with latitude within a large eutrophic lake     

《Limnologica》2021

We investigated the diversity, composition, and assembly processes of sedimentary bacterial communities across Lake Taihu, China, a large, shallow, and eutrophic water body. Amplicon-based 16S rRNA gene high-throughput sequencing identified the composition and phylogenetic structure of the bacterial communities within the 28 collected samples. Diversity analysis revealed that sedimentary bacterial communities demonstrated significant trends with nutrient loading and habitat along latitude. We used network analysis to disentangle the role of keystone taxa in bacterial communities. Most identified keystone species were from the genus Nitrospira (affiliated with Nitrospirae), subphylum Deltaproteobacteria (affiliated with Proteobacteria), subphylum Gammaproteobacteria (affiliated with Proteobacteria), family Rhodocyclaceae (affiliated with Betaproteobacteria), phylum Bacteroidetes, genus Bacillus (affiliated with Firmicutes), and family Anaerolineaceae (affiliated with Chloroflexi) in order of abundance. These keystone taxa play fundamental roles in carbon and nitrogen cycling within Lake Taihu. Phylogenetic structure analysis indicated that the bacterial communities were more phylogenetically clustered than expected by chance and that deterministic processes dominated the assembly of bacterial communities across Lake Taihu. Niche selection was the crucial factor driving the assembly of bacterial communities. This study enhances the understanding of the distribution of sedimentary bacterial communities and their assembly mechanisms across Lake Taihu.  相似文献