Saline-alkali land in the Yellow River Delta: amelioration zonation based on GIS

Globally, an estimated land area of 9.55×108 ha is affected by salinity and sodicity[1]. In the Yellow River Delta, saline-alkali land covers more than 70% of the total area. Soil salinization is the key factor that influences sustainable agricultural development. Geographic information system (GIS) is a powerful tool for spatial data analysis, which can be used to analyze data from different sources for saline-alkali land monitoring. Based on GIS, zonation of saline-alkali land can provi…     

Heavy metals in freshly deposited sediments of the river Subernarekha, India: an example of lithogenic and anthropogenic effects

Heavy metal distribution patterns in river sediments aid in understanding the exogenic cycling of elements as well as in assessing the effect of anthropogenic influences. In India, the Subernarekha river flows over the Precambrian terrain of the Singhbhum craton in eastern India. The rocks are of an iron ore series and the primary rock types are schist and quartzite. One main tributary, the Kharkhai, flows through granite rocks and subsequently flows through the schist and quartzite layers. The Subernarekha flows through the East Singhbhum district, which is one of India’s industrialised areas known for ore mining, steel production, power generation, cement production and other related activities. Freshly deposited river sediments were collected upstream and downstream the industrial zone. Samples were collected from four locations and analysed in <63-μm sediment fraction for heavy metals including Zn, Pb, Cd and Cu by anodic stripping voltammetry. Enrichment of these elements over and above the local natural concentration level has been calculated and reported. Sediments of the present study are classified by Muller’s geo-accumulation index (I _geo) and vary from element to element and with climatic seasons. During pre-monsoon period the maximum I _geo value for Zn is moderately to highly polluted and for Cu and Pb is moderately polluted, respectively, based on the Muller’s standard. Anthropogenic, lithogenic or cumulative effects of both components are the main reasons for such variations in I _geo values. The basic igneous rock layer through which the river flows or a seasonal rivulet that joins with the main river may be the primary source for lithogenic components.     

波浪和潮波作用下黄河口快速沉积海床土非均匀固结试验研究

黄河高含沙量水体在弱潮陆相河口入海,80 %的泥沙在河口附近快速堆积。过去研究发现,黄河三角洲潮滩表层沉积物呈现非均匀固结状态。为了揭示该现象产生的机制,在黄河刁口流路三角洲叶瓣潮坪上,现场取土配置黄河口快速沉积形成的流体状堆积物,研究快速沉积的粉质海床土在波浪和潮波作用下的孔压响应及非均匀固结过程。利用静力触探、十字板剪切试验、孔隙水压力监测等原位测试手段,实时测定快速沉积的海床土强度和孔压变化过程。研究发现,快速沉积的粉质土在自重作用下的固结速度很快,正常固结完成后,强度随时间的发展依然不断增加,沿深度方向出现类似原状土体的固结非均匀现象和似超固结状态;在波浪和潮波作用下快速沉积粉质土孔压沿深度出现非均匀变化,在波浪作用下出现了超静孔压的积累。分析发现,该固结状态和强度沿深度方向非均匀变化是由于土体在潮波及潮波和波浪的联合作用下形成的;潮滩表层土体在波浪荷载长期作用下形成硬壳层。     

江西德兴铜矿大坞河土壤重金属累积特征与成因

江西德兴铜矿是中国超大型斑岩铜矿,随着矿业活动的增加,德兴铜矿区重金属污染问题日益严重。查明德兴铜矿土壤重金属累积作用及原因,可为政府机构、矿山开展环境整冶提供科学依据。在大坞河上游、中游、下游选定3个剖面,采集50件土壤样品,得出其基于地球化学基线的累积特征。整体来讲,Cu、Mo累积作用最为显著,Cr、As累积作用明显,同时发现一级、二级阶地上累积显著,并从矿石组合、地化背景、河流阶地、元素形态、矿山生产等角度开展累积作用的原因分析。     

汉江流域降水多时间尺度特性及其与环流因子的相关性分析

首先利用Morlet小波对汉江流域降水进行多时间尺度分析,然后分析主要周期下汉江流域降水与74个环流因子的相关性.结果表明:近50年,汉江流域降水有4,7和18年的主要周期,其中以18年的主要周期最为突出,降水呈现偏少的趋势,同时降水量与西太平洋副高面积指数、冷空气、东太平洋副高北界、北半球极涡中心位置等14个环流因子具有非常强的正相关,而与东亚槽位置、太平洋区极涡强度指数、亚洲区极涡强度指数有非常强的负相关.研究成果将为今后提高汉江流域降水预报水平和有效开展汉江流域及长江中下游防汛抗旱工作提供科学依据.     

咸阳渭河高漫滩沉积洪水变化研究

根据咸阳高漫滩XY剖面中116个样品的粒度分析,结合历史文献记载的年代资料得出,渭河约120年来形成的高漫滩洪水沉积分层明显,对洪水的变化反映清楚,分辨率高,能够作为很好地指示洪水变化的指标。XY剖面最上层为2003年大洪水沉积,最上层之下的其它15层为古代洪水发生时期形成的沉积层,整个剖面记录了16次规模较大的洪水。XY剖面随深度变化具有明显的粗细变化节律,其中第1、3、5、7、9、11、13、15层粒度组成较第2、4、6、8、10、12、14、16层细。在充分考虑了因洪水沉积逐步叠加引起的地形增高对粒度成分的影响之后,可以确定这16个阶段洪水深度和规模由大到小的变化顺序为:第12阶段>第15阶段>第6阶段>第9阶段>第16阶段>第1阶段>第5阶段>第14阶段>第7阶段>第11阶段>第3阶段>第13阶段>第8阶段>第10阶段>第4阶段>第2阶段。其中第12、15、6、9、16、1阶段的洪水规模较第5、14、7、11、3、13、8、10、4、2阶段洪水规模更大。根据2003年河漫滩上的洪水沉积层粒度成分和洪水深度为2.2 m左右确定,所研究的剖面中第6、9、12、15、16、1层形成时的河漫滩上的洪水深度大于2.2 m,第5、14、7、11、3、13、8、10、4、2层形成时的洪水深度小于2.2 m。通过与现代大洪水发生时期年降水量的对比可知,这些大洪水发生的主要是渭河流域一些地区当年降水量显著增加造成的。在这16个洪水阶段之间没有洪水发生的阶段是降水量正常或偏少的阶段。     

山西大同桑干河流域富锶土壤地球化学特征及资源潜力评价

对山西大同桑干河流域富锶土壤的研究表明, 其表层土壤锶元素含量为108.7×10-6~413.9×10-6, 平均值为261.7×10-6, 是中国土壤A层的1.57倍. 深层土壤锶元素含量为106.2×10-6~467.0×10-6, 平均值279.2×10-6, 是中国土壤C层的1.65倍. 区内表、深层土壤富锶是围岩在地下水的作用下, 锶在水中溶解, 随之迁移并在盆地富集的结果. 区内前寒武纪变质岩中锶的含量最高达1 259×10-6, 是锶的主要物质来源. 表、深层土壤中锶与Ba、B、Cr、La、Nb、Na、As、Sb、Si等关系密切. 盐碱土是主要的储锶土壤类型. 耕地中锶含量高于其他土地利用类型. 通过富锶土壤资源潜力评价, 圈出富锶土壤面积1 104 km2, 占调查区面积的69.87%, 其中适宜开发区面积442 km2. 区内具有较好的富锶优质土地资源开发潜力.     

大渡河长河坝水电站区域泥石流特征及危险性评价

2009年7月23日,四川省甘孜州康定县舍联乡长河坝水电站施工区响水沟发生特大泥石流灾害,造成重大人员伤亡和财产损失。响水沟是大渡河上游段右岸一级支沟,近百年来泥石流活动不明显。由于之前近一个月的连续降雨,沟谷内的不稳定堆积物已基本处于饱水状态,当日的强降雨直接诱发了此次泥石流灾害。本文根据现场调查资料,就该沟泥石流的形成条件、灾害成因及特征进行分析,并应用灰色系统理论关联分析方法和沟谷泥石流危险度计算分析综合评价其危险性。结果表明,在极端气象条件下,响水沟仍有可能发生中等至大规模暴雨型粘性泥石流。     

Annual estimates of water and solute export from 42 tributaries to the Yukon River

Annual export of 11 major and trace solutes for the Yukon River is found to be accurately determined based on summing 42 tributary contributions. These findings provide the first published estimates of tributary specific distribution of solutes within the Yukon River basin. First, we show that annual discharge of the Yukon River can be computed by summing calculated annual discharges from 42 tributaries. Annual discharge for the tributaries is calculated from the basin area and average annual precipitation over that area using a previously published regional regression equation. Based on tributary inputs, we estimate an average annual discharge for the Yukon River of 210 km³ year^–1. This value is within 1% of the average measured annual discharge at the U.S. Geological Survey gaging station near the river terminus at Pilot Station, AK, for water years 2001 through 2005. Next, annual loads for 11 solutes are determined by combining annual discharge with point measurements of solute concentrations in tributary river water. Based on the sum of solutes in tributary water, we find that the Yukon River discharges approximately 33 million metric tons of dissolved solids each year at Pilot Station. Discharged solutes are dominated by cations calcium and magnesium (5.65 × 10⁹ and 1.42 × 10⁹ g year^–1) and anions bicarbonate and sulphate (17.3 × 10⁹ and 5.40 × 10⁹ g year^–1). These loads compare well with loads calculated independently at the three continuous gaging stations along the Yukon River. These findings show how annual solute yields vary throughout a major subarctic river basin and that accurate estimates of total river export can be determined from calculated tributary contributions. Copyright © 2011. This article is a U.S. Government work and is in the public domain in the USA.