REE and <Emphasis Type="Italic">ε</Emphasis><Subscript>Nd</Subscript> of clay fractions in sediments from the eastern Pacific Ocean: Evidence for clay sources     

Jihua?LiuEmail author  Xuefa?Shi  Lirong?Chen  Yongyang?Huang  Yinxi?Wang  Yingchun?Cui  Wenrui?Bu 《中国科学D辑(英文版)》2005,48(5):701-712

Clay fractions in the non-calcareous surface sediments from the eastern Pacific were analyzed for clay minerals, REE and ¹⁴³Nd/¹⁴⁴Nd. Montmorillonite/illite ratio (M/I ratio), total REE contents (ΣREE), LREE/HREE ratio and cerium anomaly (δCe) may effectively indicate the genesis of clay minerals. Clay fractions with M/I ratio <1, δCe >0.85, ΣREE <400 μg/g, LREE/HREE ratio ≈4, and REE patterns similar to those of pelagic sediments are terrigenous and autogenetic mixed clay fractions and contain more autogenetic montmorillonite. Clay fractions with M/I ratio >1, δCe=0.86 to 1.5, ΣREE=200 to 350 μg/g, LREE/HREE ratio ≈6 and REE distribution patterns similar to that of China loess are identified as terrigenous clay fraction. The ¹⁴³Nd/¹⁴⁴Nd ratios or _ɛNd values of clay fractions inherit the features of terrigenous sources of clay minerals. Clay fractions are divided into 4 types according to _ɛNd values. Terrigenous clay minerals of type I with the _ɛNd values of ™8 to ™6 originate mainly from North American fluvial deposits. Those of type II with the ε Nd values of ™9 to ™7 are mainly from the East Asia and North American fluvial deposits. Those of type III with ε Nd values of ™6 to ™3 could come from the central and eastern Pacific volcanic islands. Those of type IV with ε Nd values of ™13 to ™12 may be from East Asia eolian. The terrigenous and autogenetic mixed clay fractions show patchy distributions, indicating that there are volcanic or hot-spot activities in the eastern Pacific plate, while the terrigenous clay fractions cover a large part of the study area, proving that the terrigenous clay minerals are dominant in the eastern Pacific.  相似文献   

AGE STRUCTURES OF MODULES OF CLONAL PEATLAND SEDGE Carex middendorffii     

BU Zhao-jun YANG Yun-fei Hakan RYDIN LANG Hui-qing 《中国地理科学(英文版)》2005,15(3):269-274

Age structure of a plant population carries important information on population dynamics. The traditional age classification of individuals by development phases could not explain the generation relationship neither between individuals nor between modules, and it could not accurately predict the future of population or the tendency of peatland evolution. In a peatland of the Xiao Hinggan Mountains, China, at the middle of the growth season, the age structures of 3 modules, ramets, active buds and rhizomes of a Carex middendorffii clonal population were investigated, with the method of classifying age classes of ramets and active buds by counting generation quantity of tiller nodes, and classifying age classes of rhizomes by their real survival time. The quantity of vegetative ramets was dominant. Tiller nodes of ramets can propagate vegetatively for a maximum of 3 generations. The population of ramets consisted of 3 age classes of ramets at the middle of the growth season, and showed a stable age structure. In the two sampling events, there was no significant difference between quantities and age structure of the population. The maximum age of an excavated rhizome was 12 years old. Rhizomes were classified in 8 age classes, and age classes 4-6 contributed most to the total biomass. There was no significant difference in total length and total biomass per unit area, or in biomass per unit length in rhizomes between the two samplings. Four age classes of active buds were recognized, and their number increased from July to August. The Carex middendorffii clonal population achieved regeneration by budding from the tiller nodes of ramets. The age structures of the 3 modules suggested that the Carex middendorffii clonal population could persist in the early development phase of the oligotrophic peatland in the Xiao Hinggan Mountains, but it could not be dominant. It also faces the risk to disappear from the community as the peatland develops further.  相似文献   

莱芜市酸雨特征分析     

王西磊  王琪珍  卜庆雷 《山东气象》2006,26(1):70-71

利用莱芜市2003-2004年酸雨观测资料和气象资料,统计分析了莱芜市降水PH值的季节和年分布,研究酸雨的变化特征,通过酸雨与有关要素的对比分析,揭示了相关因子对形成酸雨的影响程度,并对莱芜市酸雨成因进行了初步探讨。  相似文献   

边界层特征量在河南省沙尘天气短期预报中的应用     

贺哲  布亚林  梁钰  乔春贵 《河南气象》2007,(3)

介绍了利用边界层特征量——摩擦速度和梯度Richardson数制作河南省沙尘天气短期预报的方法。结果表明,该动力学方法更能够从本质上反映沙尘天气产生的机制,定性预报准确率为62.5%。  相似文献   

气象影视素材数字化存储系统的设计及应用     

陶平  杨蒙  布亚林 《气象与环境科学》2007,30(2):86-89

介绍了利用非线性编辑系统和磁盘阵列等相关设备，对河南省气象影视中心保存的视音频素材进行数字化处理的方法，以及利用SQL数据库技术和ASP．NET编程语言，实现气象影视素材的数字化采集、信息标引编目、存储及管理、检索及共享等功能，建立河南省气象影视素材存储系统的关键技术。  相似文献   

长江正源区可持续发展对策探讨     

卜建军  段其发  牛志军  王建雄 《华南地质与矿产》2005,(4):45-49,60

长江源区自然环境恶劣，生态脆弱，资源较缺乏，居民生活贫困，区域经济的发展和生态环境的保护面临着严峻的挑战。综合分析源区的现状和有利条件，认为旅游资源具有得天独厚的优势，如果加强基础设施建设，逐渐使牧民从散居到聚居，以旅游业为龙头，带动第三产业的发展，促进居民生活方式的多元化，提高居民生活质量和思想素质，树立环保意识，逐渐摆脱对草地的过分依赖，自觉保护生物多样性，优化和重建生态环境，从而实现人和自然的协调发展，步入可持续发展的轨道。  相似文献   

海底取样器的理论探讨及参数计算--海底取样技术介绍之五   总被引：2，自引：0，他引：2  

鄢泰宁  补家武  陈汉中 《地质科技情报》2001,20(2):103-106

阐述了海底取样时岩芯形成的理论过程，推导了有关理论计算公式，得出了形成“桩效应”的条件，并论述了取样器静压力及振动锤多项参数的理论计算公式。  相似文献   

航空与地面物探数据图像处理在鄯善地区的应用研究     

卜国兴 《地质与勘探》1997,33(4):35-40

以新疆鄯善地区为研究区，对该区的航磁、航空甚低频、重力和遥感数据进行了多种方案的综合图像处理，并做了野外调绘和地质解释，总结出线性构造、环形构造以及与矿体的关系。为指导该区一步找矿提出依据。  相似文献   

人类干扰对土壤侵蚀及土壤质量的影响——以苏南宜兴低山丘陵区为例   总被引：11，自引：6，他引：11  

张燕  彭补拙  高翔  唐翔宇  杨浩 《地理科学》2002,22(3):336-341

以苏南低山丘陵区茶园土壤侵蚀与土壤质量改变为研究对象，并取自然状态的杂木林为参照，用^137Cs法估算土壤侵蚀速率；以土壤粗化度、土壤有机质含量及土壤含水量描述土壤质量；在绝对数值的基础上，用变化量探讨研究对象的变化方向与幅度。对比耕作土与非耕作土的土壤侵蚀与土壤质量改变及将它们结合起来研究表明，人类活动有可能加剧土壤侵蚀，加快土壤质地粗化；合理的农业措施虽可减缓土壤质量下降，但防治侵蚀方可治本。  相似文献   

Simulation of regional temperature change effect of land cover change in agroforestry ecotone of Nenjiang River Basin in China     

Liu  Tingxiang  Zhang  Shuwen  Yu  Lingxue  Bu  Kun  Yang  Jiuchun  Chang  Liping 《Theoretical and Applied Climatology》2017,130(3-4):971-978

Currently, US forests constitute a large carbon sink, comprising about 9 % of the global terrestrial carbon sink. Wildfire is the most significant disturbance influencing carbon dynamics in US forests. Our objective is to estimate impacts of climate change, CO₂ concentration, and nitrogen deposition on the future net biome productivity (NBP) of US forests until the end of twenty-first century under a range of disturbance conditions. We designate three forest disturbance scenarios under one future climate scenario to evaluate factor impacts for the future period (2011–2100): (1) no wildfires occur but forests continue to age (S_aging), (2) no wildfires occur and forest ages are fixed in 2010 (S_{fixed_nodis}), and (3) wildfires occur according to a historical pattern, consequently changing forest age (S_{dis_age_change}). Results indicate that US forests remain a large carbon sink in the late twenty-first century under the S_{fixed_nodis} scenario; however, they become a carbon source under the S_aging and S_{dis_age_change} scenarios. During the period of 2011 to 2100, climate is projected to have a small direct effect on NBP, while atmospheric CO₂ concentration and nitrogen deposition have large positive effects on NBP regardless of the future climate and disturbance scenarios. Meanwhile, responses to past disturbances under the S_{fixed_nodis} scenario increase NBP regardless of the future climate scenarios. Although disturbance effects on NBP under the S_aging and S_{dis_age_change} scenarios decrease with time, both scenarios experience an increase in NBP prior to the 2050s and then a decrease in NBP until the end of the twenty-first century. This study indicates that there is potential to increase or at least maintain the carbon sink of conterminous US forests at the current level if future wildfires are reduced and age structures are maintained at a productive mix. The effects of CO₂ on the future carbon sink may overwhelm effects of other factors at the end of the twenty-first century. Although our model in conjunction with multiple disturbance scenarios may not reflect the true conditions of future forests, it provides a range of potential conditions as well as a useful guide to both current and future forest carbon management.  相似文献