A SIMPLIFIED STREAM MODEL OF ACID MINE DRAINAGE EFFECTS1

ABSTRACT: Three methods of modeling acid mine drainage effects are discussed. A net alkalinity routing model is the simplest of these, but can be potentially misleading. It typically overestimates the effect of acid sources on pH by neglecting carbon dioxide transfer to the atmosphere. Inclusion of a simple carbon dioxide transfer function can substantially reduce errors in stream quality prediction. A plug flow reaeration equation, coupled with mass balancing at mixing points in a stream network provides modeling results comparable to those of more complex computerized solutions of chemical equilibrium equations. None of the models accounts for carbonate dissolution or oxidation and hydrolysis of ferrous iron.     

Impacts of Rotational Grazing and Riparian Buffers on Physicochemical and Biological Characteristicsof Southeastern Minnesota, USA, Streams

We assessed the relationship between riparian management and stream quality along five southeastern Minnesota streams in 1995 and 1996. Specifically, we examined the effect of rotationally and continuously grazed pastures and different types of riparian buffer strips on water chemistry, physical habitat, benthic macroinvertebrates, and fish as indicators of stream quality. We collected data at 17 sites under different combinations of grazing and riparian management, using a longitudinal design on three streams and a paired watershed design on two others. Continuous and rotational grazing were compared along one longitudinal study stream and at the paired watershed. Riparian buffer management, fenced trees (wood buffer), fenced grass, and unfenced rotationally grazed areas were the focus along the two remaining longitudinal streams. Principal components analysis (PCA) of water chemistry, physical habitat, and biotic data indicated a local management effect. The ordinations separated continuous grazing from sites with rotational grazing and sites with wood buffers from those with grass buffers or rotationally grazed areas. Fecal coliform and turbidity were consistently higher at continuously grazed than rotationally grazed sites. Percent fines in the streambed were significantly higher at sites with wood buffers than grass and rotationally grazed areas, and canopy cover was similar at sites with wood and grass buffers. Benthic macroinvertebrate metrics were significant but were not consistent across grazing and riparian buffer management types. Fish density and abundance were related to riparian buffer type, rather than grazing practices. Our study has potentially important implications for stream restoration programs in the midwestern United States. Our comparisons suggest further consideration and study of a combination of grass and wood riparian buffer strips as midwestern stream management options, rather than universally installing wood buffers in every instance. RID=" ID=" The Unit is jointly sponsored by the US Geological Survey, Biological Resources Division; the Minnesota Department of Natural Resources; the University of Minnesota; and the Wildlife Management Institute.     

贺兰山露天煤矿生态修复前后植物群落差异及地境结构研究

为探究贺兰山露天煤矿生态修复后植被恢复情况,依据生态地质学的相关理论和方法,通过野外植物群落特征和植物根群结构调查,以及植被地下生境土壤肥分养分取样与测试,对背景区与恢复区植物群落结构和物种多样性差异进行了对比分析,确定了不同植物群落的地下生境范围,并进一步探究了影响植被恢复的土壤因子.结果 表明:①贺兰山自然保护区主...     

鲁豫黄河沿线县域经济发展和居住环境差异研究

县级行政区人口占全国人口比重大约70％,改善县城人居环境对于加快中国城镇化进程,提高城市化水平具有重要作用。通过选择具有代表性的人居环境指标,采用主成分和聚类分析方法对鲁豫黄河沿线的12个县域进行了综合评价,分析了各县人居环境现状差异。通过量化比较和综合分析,发现研究区域发展不均衡性明显。主成分分析表明,前三个主成分分别代表人口、经济和财政情况,是影响居住环境的关键因素。通过聚类分析把县城发展程度分为三类。结合实地考察的成果,分析区域差异存在的原因,提出一些改善现状的建议。     

TDE-324CI数据采集器强震实时数据流格式及解码过程浅析

介绍了TDE-324CI数据采集器的软件接口,包括TCP／IP网络数据流通讯协议、命令控制字和网络数据流接口,对实时数据流格式进行了具体的分析和描述,最后通过实例分析了实时数据流解码的实现并列举了程序代码。     

海平面上升和土地利用驱动下红树林生境脆弱性研究

为了探索海平面上升(SLR)和土地利用导致的红树林生境潜在变化,本文以我国红树林分布最集中的雷州半岛为研究区域,基于SLAMM模型和景观生态模型建立了红树林生境脆弱性指数,设置4个SLR-土地利用组合情景(SLR4.5-土地开发利用、SLR4.5-土地自然转换、SLR8.5-土地开发利用、SLR8.5-土地自然转换),预测2050年雷州半岛红树林的生境变化和脆弱程度,并提出应对环境变化的管理策略.结果表明,(1)SLR和土地利用双重压力的叠加将造成红树林生境的显著退化,预测生境面积将减少16.59%～25.61%,减少地点集中在铁山港、安铺港、湛江港、雷州湾和流沙湾沿岸.(2)在土地自然转换情景下,尽管仍应对着海平面上升的压力,红树林潜在生境面积可增加44.66%～67.74%,增加的区域集中在岸线往内陆方向和沿水系向内陆延伸的两岸,但新增生境面临着破碎化程度高的问题.(3)在所有情景下均呈现红树林迁出现有保护区的趋势,保护区内红树林面积由5949.8hm²下降至4732.1～5192.9hm².(4)高脆弱区主要分布在雷州湾、湛江港近岸和流...     

Stage‐Discharge Relationships for U‐, A‐, and W‐Weirs in Un‐submerged Flow Conditions1

Thornton, Christopher I., Anthony M. Meneghetti, Kent Collins, Steven R. Abt, and S. Michael Scurlock, 2011. Stage‐Discharge Relationships for U‐, A‐, and W‐Weirs in Un‐submerged Flow Conditions. Journal of the American Water Resources Association (JAWRA) 47(1):169‐178. DOI: 10.1111/j.1752‐1688.2010.00501.x Abstract: Instream rock weirs are routinely placed into stream systems to provide grade control, reduce streambank erosion, provide energy dissipation, and allow fish passage. However, design and performance criteria for site specific applications are often anecdotal or qualitative in nature, and based upon the experience of the design team. A study was conducted to develop generic state‐discharge relationships for U‐, A‐, and W‐weirs. A laboratory testing program was performed in which scaled, near‐prototype U‐, A‐, and W‐rock weir structures were constructed in 11 configurations. Each configuration encompassed a unique weir shape, bed material, and/or bed slope. Thirty‐one tests were conducted in which each structure was subjected to a sequence of predetermined discharges that minimally included the equivalent of 1/3 bankfull, 2/3 bankfull, and bankfull conditions. All tests were performed in subcritical, un‐submerged flow conditions. Stage‐discharge relationships were developed using multivariant, power regression techniques for each of the U‐, A‐, and W‐rock weirs as a function of the effective weir length, flow depth, mean weir height, rock size, and discharge coefficient. Unique coefficient expressions were developed for each weir shape, and a single discharge coefficient was proposed applicable to the weirs for determining the channel stage‐discharge rating.     

基于水资源调度的平原河网区城市河道氮迁移转化研究

研究平原河网区城市河道在水资源调度过程中的水文特征和理化特征,探讨基于水资源调度的城市河道氮素形态与组成;在实验模拟条件下,研究基于水资源调度的城市河道沉积物NH+4-N释放过程.结果表明,研究河段在水资源调度作用下水深日变化过程明显;以农历月为单位,水资源调度可以分为轻度置换阶段和深度置换阶段;沿调水路径河道上覆水DO有下降趋势,高锰酸盐指数则呈现升高趋势;沿调水路径上覆水NO-3-N浓度逐渐减少,NH+4-N浓度显著升高;DO与高锰酸盐指数是影响上覆水NO-3-N、NH+4-N浓度的主要因素;沉积物内源NH+4-N释放是上覆水NH+4-N的一个重要来源;水资源调度显著影响(P<0.05)上覆水NH+4-N浓度,对沉积物内源NH+4-N的释放影响不显著(P>0.05).     

Attenuation of arsenic in a karst subterranean stream and correlation with geochemical factors: A case study at Lihu, South China

Arsenic （As） pollutants generated by human activities in karst areas flow into subterranean streams and contaminate groundwater easily because of the unique hydrogeological characteristics of karst areas. To elucidate the reaction mechanisms of arsenic in karst subterranean streams, physical-chemical analysis was conducted by an inductively coupled plasma mass spectrometer and an X-ray fluorescence spectrometer. The results show that inorganic species account for most of the total arsenic, whereas organic arsenic is not detected or occurs in infinitesimal amounts. As（III） accounts for 51.0% ± 9.9% of the total inorganic arsenic. Arsenic attenuation occurs and the attenuation rates of total As, As（III） and As（V） in the Lihu subterranean stream are 51%, 36% and 59%, respectively. To fully explain the main geochemical factors influencing arsenic attenuation, SPSS 13.0 and CANOCO 4.5 bundled with CanoDraw for Windows were used for simple statistical analysis and redundancy analysis （RDA）. Eight main factors, i.e., sediment iron （SFe）, sediment aluminum （SAI）, sediment calcium （SCa）, sediment organic matter （SOM）, sediment manganese （SMn）, water calcium （WCa^2＋）, water magnesium （WMg^2＋）, and water bicarbonate ion （WILCOX） were extracted from thirteen indicators. Their impacts on arsenic content rank as： SFe〉SCa〉WCa^2＋〉SAl〉wHCO3^-〉SMn〉SOM〉WMg^2＋. Of these factors, SFe, SAl, SCa, SOM, SMn, WMg^2＋ and WCa＆2＋ promote arsenic attenuation, whereas WHCO3^- inhibits it. Further investigation revealed that the redox potential （Eh） and pH are adverse to arsenic removal. The dramatic distinction between karst and non-karst terrain is that calcium and bicarbonate are the primary factors influencing arsenic migration in karst areas due to the high calcium concentration and alkalinity of karst water.     

长江三角洲北翼兴化-通州地区第四纪地层划分及古环境分析

选取长江三角洲北翼兴化-通州地区(分属东台和南通第四纪地层小区)的5个实测钻孔,以岩石地层、年代地层和磁性地层为基础,应用层序地层学理论与方法,对研究区第四纪地层进行初步划分,共划分出下更新统(Qp1)、中更新统(Qp2)、上更新统(Qp3)和全新统(Qh)4个地层单元。讨论了区内第四纪以来岩相古地理演化特征及古河道变迁的过程。研究区内北部东台地层小区第四纪以来以陆相河湖沉积为主;南部南通地层小区第四纪早期以陆相河湖沉积为主,中晚期为海陆交互沉积。第四纪以来古河道在海安以南区域摆动,至晚更新世晚期南移接近现长江位置。