Profile characteristics of temporal stability of soil water storage in two land uses

Information on soil water storage (SWS) within soil profiles is essential in order to characterize hydrological and biological processes. One of the challenges is to develop low cost and efficient sampling strategies for area estimation of profile SWS. To test the existence of certain sample locations which consistently represent mean behavior irrespective of soil profile wetness, temporal stability of SWS in ten soil layers from 0 to 400 cm was analyzed in two land uses (grassland and shrub land), on the Chinese Loess Plateau. Temporal stability analyses were conducted using two methods viz. Spearman rank correlation coefficient (r _s) and mean relative differences. The results showed that both spatial variability and time stability of SWS increased with increasing soil depth, and this trend was mainly observed at above 200 cm depth. High r _s (p?<?0.01) indicated a strong temporal stability of spatial patterns for all soil layers. Temporal stability increased with increasing soil depth, based on either r _s or standard deviation of relative difference index. The boundary between the temporal unstable and stable layer of SWS for shrub land and grassland uses was 280 and 160 cm depth, respectively. No single location could represent the mean SWS for all ten soil layers. For temporal stable layers, however, some sampling locations could represent the mean SWS at different layers. With increasing soil depth, more locations were able to estimate the mean SWS of the area, and the accuracy of prediction for the representative locations also increased.     

Heavy-metal accumulation trends in Yixing,China: an area of rapid economic development

Geochemistry of soils encapsulated by urban development and dendrochemistry were evaluated to reconstruct heavy-metal accumulation trends in an area of rapid economic development in China. The urban-covered soil spans a time period of 56 years from 1950 to 2006, and the tree cores cover the period from 1977 to 2006. Results from the six heavy-metal elements (Cd, Cr, Cu, Ni, Pb, and Zn) analyzed in this study indicate that heavy-metal concentrations increase significantly in urban-covered soils dating from 1980, which is corroborated by data from corresponding tree cores. The accumulation rates of Cd, Cr, Cu, Ni, Pb and Zn (1980–2006) were estimated at 0.91, 0.84, 1.42, 1.39, 1.34 and 1.86% per year, respectively. These high rates of accumulation suggest that anthropogenic sources resulting from rapid economic development led to the magnitude and rates of heavy-metal accumulation. Although reconstruction of heavy-metal accumulation trends using the urban-covered soils (substitutes space for time) introduces some uncertainty when compared with long-term experiments, this study demonstrates that urban-covered soils can provide a vehicle by which historical rates of heavy-metal accumulation can be approximated.     

扬子地块东南缘沉积岩的Nd同位素研究

扬子地块东南缘上溪群分布区及其周边沉积岩的Ｎｄ同位素研究结果,支持存在一条苏浙皖古生代裂陷槽（或江南深断裂）的观点。上溪群以北直至长江边所分布的震旦系－古生代的盖层沉积岩,其Ｎｄ模式年龄有两组,表明物源区不同。裂陷槽以北,沉积岩的物源区为Ｎｄ模式年龄约２.０～２.１Ｇａ的扬子物源区;以南的沉积岩表现出明显的幔源物质混染,显示出元古代岩浆活动的影响,而上溪群分布区以南直到江绍断裂附近主要表现上溪物源区的影响,华夏地块古老基底岩石则无显著贡献。     

练江平原第四系的时代

基于钻孔柱状图将练江平原区第四系划分为9个基本层,通过对WYZK-06孔岩心的系统测年,标定了第四系的年代。第四系底部地层时代为中更新世,厚度约40 m,为陆相沉积。中更新统底部地质年龄为(325±32)ka,属中更新世中晚期;顶部为一套厚达10 cm左右的稳定花斑黏土层。上覆地层为上更新统,反映中更新世与晚更新世之间有较长时间的沉积间断。中更新统分布局限于普宁—两英之间,上更新统和全新统占据平原的大部分地区,表明练江平原是在中更新世发生局部断陷,在晚更新世以来开始接受大面积沉积。     

塔克拉玛干地区近四十年来的干湿变化

本文利用塔克玛干,周围山区、及相邻地区的４８个气象站近４０年的降水资料,分析塔克拉玛干地区年与四季干湿变化的阶段与周期,与与周围山区及相邻地区进行相关性分析。     

基于数字城市的关键技术应用研究

阐述了数字城市的产生背景、概念与国内研究现状,提出了数字城市的框架体系和应用研究内容,进一步研究分析了数字城市建设所依赖的关键技术。     

成都粘土动三轴试验研究

振动三轴试验是室内研究土动力特性的有效手段。从分析实际动荷载作用特点入手，结合本实验室设备条件，对成都地区具代表性的两类土的动强度进行了试验研究，获得了其动强度指标及一系列有益的认识。     

西藏冈底斯成矿带南缘喜马拉雅早期成矿作用——来自冲木达铜金矿床的Re-Os同位素年龄证据

采集冈底斯成矿带南部克鲁-冲木达铜金成矿亚带冲木达矽卡岩型铜金矿床的辉钼矿样品进行了Re-Os法精确同位素定年。该矿区辉钼矿的模式年龄介于37.63～41.19Ma之间,6件辉钼矿样品得到187Re-187Os等时线年龄为(40.3±5.6)Ma。该成矿年龄明显早于冈底斯成矿带中带和北带的驱龙、厅宫等斑岩铜矿床和甲马、知不拉、帮浦等矽卡岩型铜铅锌矿床的成矿年龄,而与冈底斯成矿带中广泛发育的碰撞期花岗质岩浆活动的年龄基本一致。据此认为,冲木达铜金矿床形成于喜马拉雅早期,与欧亚-印度大陆碰撞阶段的花岗质岩浆活动密切相关。     

盆东盛夏旱涝成因与环流影响分析

四川盆地东部盛夏旱涝天气气候除受太阳辐射、下垫面和日- - 地关系影响有关外,主要还与西风急流、南亚高压、热带高压、西太平洋副热带高压及东亚季风等大气环流影响有关,它们的强度、位置的变化和异常表现,都会引起天气气候的形成和变化.因此,环流分析,可以为我们掌握和预测天气气候的变化提供背景标料.     

中国气温涨落层次结构的区域性特征

运用近年来发展的湍流层次结构模型分析中国气温序列的涨落,研究其层次相似结构的区域性特征.通过对全国160个站点近50年来的月平均气温距平序列的分析,发现层次相似律基本上都存在,得到的层次相似系数β具有一定的区域分布特征.我们对β的含义进行了讨论,并研究了β的区域分布以及造成这种分布的原因.