Deriving river networks and catchments at the European scale from medium resolution digital elevation data

The extraction of drainage networks and catchment boundaries from digital elevation models (DEMs) has received considerable attention in recent years and is recognized as a viable alternative to traditional surveys and the manual evaluation of topographic maps. However, most studies have covered limited areas due to the lack of detailed information and/or the lack of highly efficient algorithms. In this paper we present an application that delineates river networks and catchment boundaries across the European continent from a medium resolution (250 m) DEM. We exploit novel algorithms based on the concepts of mathematical morphology and implement a landscape stratification for drainage density.A flow direction grid is computed using an efficient algorithm for the removal of spurious pits. River networks are then derived by imposing a variable threshold for the minimum contributing area needed to form and maintain a channel. This is achieved through a landscape stratification that reflects the ability of the terrain to develop different drainage densities. It is shown that the analysis of environmental characteristics coupled with the analysis of local slope versus contributing area enables river network mapping with a spatially varying drainage density. The result has been validated by comparing the derived data to digital river and catchment data from other sources and with varying scales of observation.     

Evaluating simultaneous impacts of three anthropogenic effects on a floodplain-dwelling marsupial Antechinus flavipes

Regulation of river flows has altered floodplain ecosystems around the world. Floods are less frequent, which leads to reduction of favourable environmental conditions for many terrestrial and aquatic organisms adapted to natural flooding regimes. In Australia, the Murray River floodplains have been subjected to decline in inundations, to extensive logging and to removal of fallen timber. The yellow-footed antechinus (Antechinus flavipes) is the only small, native, ground-dwelling/semi-arboreal mammal on most floodplains of south-eastern Australia, yet the effects of floods on its population dynamics largely are unknown. Here, we found positive effects of proximity to flooding, higher woodloads and of abundance of large, hollow-bearing trees on antechinus numbers. Mean trapping rates of antechinuses were lowest in 2003 following a 3-year period with no inundation, higher in 2004 following the first breeding season during a small, controlled flood in 2003, and higher again in 2005, following a small, controlled flood in 2004. In 2004 and 2005, trapping rates declined with distance from floodwaters. This study provides evidence for the benefits of using management flows to inundate floodplains, conserving large trees and ensuring high woodloads in floodplains for sustaining populations of the yellow-footed antechinus.     

塔里木河下游生态输水及河道生态整治工程探讨

通过近几年向塔里木河下游的应急生态输水，水流到达塔里木河尾间台特玛湖，沿岸地下水位上升，沿河部分地段植被长势得以恢复，局部地区生态环境改善。为了从根本上解决塔里木河下游的生态环境问题．探讨了下游河道生态整治工程，包括河道疏浚输水线路选择和设置生态闸的问题。大西海子水库下游河道疏浚工程有3条输水线路可供选择，通过投资、占地、施工、管理、防洪等综合比较，选择在大西海子水库主坝上新建一座放水闸方案。方案在技术上和经济上是可行的。本着尽量少而又要满足河道疏浚后沿岸植被生长需水的原则，分析了沿岸生态闸设置的必要性和保护的生态植被的面积，并探讨了今后生态输水方式的选择与生态闸的开启顺序。     

塔里木河下游环境退化的因子分析

 为了研究土地荒漠化及其影响因子,对塔里木河下游沿河道布设的39个样地,进行环境退化因子分析。通过数学变换,8个观测指标被转换为3个综合指标(水分指标、沙化指标、盐化指标)。根据本地区的实际,对3个综合指标进行环境解释。依据这3个主分量的贡献率,计算塔里木河下游39个样地的因子得分,并据此进行环境退化程度(荒漠化)的分类。从因子得分结果看,塔里木河下游地区呈明显的随距大西海子水库距离的增加荒漠化程度加重的特点,引起这一结果的主要原因,是水、盐条件逐渐恶化带来的植被衰败。从分类的结果看,与该地区的实际基本相符合。这说明因子分析的方法综合了多指标的综合影响,划分的结果更加客观。     

The Remobilization of Metals from Iron Oxides and Sediments by Metal-EDTA Complexes

Synthetic chelating agents such as EDTA form strong complexes with heavy metals and therefore have the potential to remobilize metals from sediments and aquifers. In natural waters EDTA is present almost exclusively in the form of metal-complexes. Therefore, remobilization of metals is always a metal-metal-EDTA exchange reaction. We have investigated, to our knowledge for the first time, the remobilization of metals from the surface of synthetic iron oxides and from a river sediment by different metal-EDTA complexes. The metals are exchanged as follows:MeEDTA_dissolved + Me^ast _adsorbed Me^astEDTA_dissolved + Me_adsorbed The order of the remobilization rate of Zn²⁺ from goethite is CaEDTA > Fe(III)EDTA, reflecting the slow exchange reaction of Fe(III)EDTA. For the remobilization of Pb²⁺ from goethite, the rate was found to be Fe(III)EDTA > CaEDTA > ZnEDTA. Here, Fe(III)EDTA has surprisingly the fastest exchange rate. Only very limited remobilization of Pb²⁺ is possible from hydrous ferric oxide at pH 8 due to the very strong adsorption of Pb²⁺. The order of remobilization of Zn²⁺ from a natural river sediment was found to be CaEDTA > CuEDTA > Fe(III)EDTA. The remobilization rate of Zn²⁺ with Fe(III)EDTA is only 12% of the rate with CaEDTA, illustrating the importance of EDTA speciation for assessing remobilization.     

大凌河流域水土保持信息系统的建立与应用

将 GIS(地理信息系统 )、RS(遥感技术 )、Fox Pro数据库等技术集成 ,应用于“朝阳市国家重点治理区大凌河流域治理工程”建设实践 ,建立了“国家重点治理区大凌河流域水土保持信息系统”。该系统包括 :1属性数据信息管理子系统 ;2图件空间信息管理子系统 ;3流域规划设计与措施配置子系统 ;4效益监测、评价与预测子系统。使用该信息系统对区域的 81条小流域进行了规划设计、治理开发措施的优化调控和效益的分析评价 ,实现了大凌河流域治理工程管理决策的科学化 ,促进了大凌河流域治理工程的高质量完成 ,达到了工程的高效率管理和工程的高收益 ,对我国水土保持生态环境建设和水土资源可持续利用具有重要指导意义     

岷江上游某建设场地山洪泥石流灾害危险性分析

某建设场地位于岷江上游大沟流域,为山洪泥石流多发区。从主、支沟山洪泥石流特征、泥石流暴发规模及支沟泥石流对主沟山洪特征的影响等方面分析了场地可能遭受山洪泥石流灾害的危险性,并以此为基础对场地按危险程度进行了分区。结果表明,该场地主体位于基本无危险区,其建设计划是可行的。     

不同土地利用方式下渭-库绿洲土壤盐渍化特征分析

基于渭干河—库车河三角洲绿洲土壤盐渍化现象发展的趋势,采用经典统计分析方法,对研究区不同土地利用方式下的土壤电导率、总盐量和pH值进行描述性统计分析,通过单因素方差方法对不同土地利用方式下土壤盐分指标进行差异显著性检验,并利用最小显著极差法(LSD)进行多重比较。研究结果表明:在不同土地利用方式和土层深度下,土壤电导率和总盐量的平均水平差异显著(p0.05),其含量由高到低依次为:荒漠灌丛盐碱草地耕地林地,而土壤pH值则无显著差异,土壤盐分呈现出明显的表层富集现象。本研究的结论对于提高此区域农业生产潜力和盐碱地综合治理具有重要的理论和实际意义。     

塔里木河下游生态环境对输水的积极响应

塔里木河下游是我国西部生态与环境问题最为突出的地区.由于人类不合理的资源开发,导致该地区生态问题日益突出.本文结合塔里木河下游5次生态输水,通过3年对输水后生态环境变化的监测,就塔里木河下游生态环境对输水的积极响应进行了分析.结果显示:(1)生态输水后地下水位在时间上和空间上各有其变化规律,在时间上近河道水位响应快,远河道水位响应慢.在空间上距河道不同距离和不同河段上地下水上升的幅度不同.(2)输水后天然植被的响应主要表现在植被种类和植被盖度的增加上;(3)鉴于输水后生态响应的范围仍然较小,因此输水工程还应该继续进行并适当调整输水的方式.     

Dynamics of arsenic-containing compounds sorption on sediments

Background  River and lake sediments constitute complex and difficult analytical samples. On the other hand, sediments play a fundamental role in the distribution of toxic compounds in aquatic systems and in the evaluation of the current state and the course of changes taking place in the environment. Among elements present in the environment in trace concentrations, but having well-elaborated toxic properties, one of most dangerous is arsenic. The element occurs in the environment in several chemical forms, predominant are inorganic forms of As(V) and As(III), and methylated forms such as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). Objectives  Reported herein are experiments, which were undertaken with the aim of examining the dynamics of arsenic sorption in sediments and its dependence on speciation of the element and the pH in the environment. Simultaneously, influence of organic matter content and chemical composition of the sediments on As sorption, were investigated. Methods  Sediment samples (upper 10 cm layer) were collected from three sites located in the vicinity of Cracow: