地下水化学组分在强震活动下的突变

为了探索地震预测预报途径,根据地下水化学监测资料,研究了地震活动中经常出现的地下水化学异常组分及其突变特征.结果表明,在强烈地震活动前后,经常发生地下水水化学异常突变.反应最敏感的地下水水化学组分为放射性元素Rn,其不仅在7级以上地震中普遍出现异常,而且在5～6级或更小的地震中也会出现异常;Rn异常范围不同,其最大半径可达500～600 km,异常集中分布在距震中200 km以内.其次,还有一些组分发生异常,如微量元素(B、F、Li和Sr)、常量成分(SiO2和Cl-)、气体组分(CO2、N2、CH4、H2和He)及气体总量等,它们仅在7级以上地震中较为常见.加强地下水动态监测,研究地下水水化学异常突变与地震的关系,对于构造活动性评价和地震预测预报具有重要意义.     

矿用六边形折痕构件吸能防冲特性数值分析

为有效防治煤矿冲击地压,或在一定程度上减小冲击地压事故造成的损失,提出了一种矿用六边形折痕吸能防冲构件,构件防冲体现在构件被压溃过程中吸收冲击能、压溃空间给煤岩提供了一定的能量释放空间和构件恒力变形阶段为液压阀打开提供了时间.采用ABAQUS有限元软件模拟了不同壁厚、不同凹角宽度、轴向“堆积”不同模块个数的构件的吸能特性,并与常规六边形薄壁进行了对比分析.结果表明,折痕引入能有效降低常规六边形构件的峰值载荷、载荷波动系数,提高能量吸收和增加冲程效率,验证了折痕构件的有效性.六边形折痕构件具有较高的冲程效率,模块凹角宽度及壁厚对冲程效率、吸能评价指标影响较小.载荷波动系数随壁厚增加而降低,构件的峰值载荷、平均压溃载荷及吸收能量随壁厚增加而增加.模块凹角宽度对构件的防冲性能影响较大,应选择合适的模块凹角宽度.随“堆积”模块数增加,峰值载荷降低,反力波动增大.防冲构件与现有液压支柱结合使用能提高支柱的防冲性能.     

基于GIS和RUSLE的三峡库区小流域土壤侵蚀量估算研究

本研究以三峡库区菱角塘小流域为研究对象,在GIS技术的支持下,通过遥感技术和野外调查进行信息采集,对修正的通用土壤流失方程(RUSLE)各因子进行量化分析,从而对三峡库区菱角塘小流域土壤侵蚀量进行定量评价,并对土壤侵蚀强度进行分级;在此基础上分析不同坡度和土地利用类型的土壤侵蚀空间分布特征。结果表明,菱角塘小流域年土壤侵蚀量为208.32t/a,土壤侵蚀模数为1 987.75t/(km2·a),属于轻度侵蚀。28.62%的区域为中度、强度或极强度侵蚀,但是其侵蚀量却占总侵蚀量的82.36%,是预防和加强水土流失治理的重点区域。土壤侵蚀主要发生在坡度为15°~35°的区域,其中15°~25°的坡度土壤侵蚀属于中度侵蚀;坡耕地侵蚀最为严重,15°~25°的坡耕地侵蚀量占总侵蚀量的57.15%,表明坡耕地是该小流域水土流失的主要策源地。同时用137 Cs核素示踪技术测定的坡耕地和林地土壤侵蚀模数证实了RUSLE模型具有较高的准确性和可靠性,该模型在库区地块尺度具有一定的推广价值。     

大沽河水质自动监控点位布设初探

通过对大沽河流域常年水文状况,现有国、省控人工监测点位设置情况,污染源分布、污水处理厂、取水口、饮用水源地保护区分布及水利工程建设情况的调查,确定在大沽河上游、江家庄、韩家汇到麻湾桥段、小沽河汇入口、云溪河桃源河汇入大沽河口下游,落药河和南胶莱河等7个断面充分利用跨河桥梁等构筑物构建水质自动监控站点。主要监测指标除常规指标以外,在重点监控断面和工业企业分布较多的污染较重河段,可增加总磷、总氮等特征指标和重金属监测项目。     

Agricultural BMP Effectiveness and Dominant Hydrological Flow Paths: Concepts and a Review

We present a conceptual framework that relates agricultural best management practice (BMP) effectiveness with dominant hydrological flow paths to improve nonpoint source (NPS) pollution management. We use the framework to analyze plot, field and watershed scale published studies on BMP effectiveness to develop transferable recommendations for BMP selection and placement at the watershed scale. The framework is based on the location of the restrictive layer in the soil profile and distinguishes three hydrologic land types. Hydrologic land type A has the restrictive layer at the surface and BMPs that increase infiltration are effective. In land type B1, the surface soil has an infiltration rate greater than the prevailing precipitation intensity, but there is a shallow restrictive layer causing lateral flow and saturation excess overland flow. Few structural practices are effective for these land types, but pollutant source management plans can significantly reduce pollutant loading. Hydrologic land type B2 has deep, well‐draining soils without restrictive layers that transport pollutants to groundwater via percolation. Practices that increased pollutant residence time in the mixing layer or increased plant water uptake were found as the most effective BMPs in B2 land types. Matching BMPs to the appropriate land type allows for better targeting of hydrologically sensitive areas within a watershed, and potentially more significant reductions of NPS pollutant loading.     

Cost‐Effective Placement of Best Management Practices in a Watershed: Lessons Learned from Conservation Effects Assessment Project

This article reviews the key, cross‐cutting findings concerning watershed‐scale cost‐effective placement of best management practices (BMPs) emerging from the National Institute of Food and Agriculture Conservation Effects Assessment Project (CEAP) competitive grants watershed studies. The synthesis focuses on two fundamental aspects of the cost‐effectiveness problem: (1) how to assess the location‐ and farmer‐specific costs of BMP implementation, and (2) how to decide on which BMPs need to be implemented and where within a given watershed. Major lessons learned are that (1) data availability remains a significant limiting factor in capturing within‐watershed BMP cost variability; (2) strong watershed community connections help overcome the cost estimation challenges; (3) detailing cost components facilitates the transferability of estimates to alternative locations and/or economic conditions; and (4) implicit costs vary significantly across space and farmers. Furthermore, CEAP studies showed that (5) evolutionary algorithms provide workable ways to identify cost‐effective BMP placements; (6) tradeoffs between total conservation costs and watershed‐scale cost‐effective water quality improvements are commonly large; (7) quality baseline information is essential to solving cost‐effectiveness problem; and (8) systemic and modeling uncertainties alter cost‐effective BMP placements considerably.     

上海市大气散射消光特征及其与颗粒物化学组成关系研究

为研究上海市大气颗粒物散射系数分布特征以及颗粒物化学组分贡献率,2009年用浊度仪对散射系数进行观测,同时采集PM2.5,分析其主要化学成分浓度.观测发现,秋、冬季散射系数较高,夏季最小.散射系数日变化有早、晚两个峰,午间出现低谷.散射系数与温度、风速有显著负相关性.多元回归得到OC、NO-3、NH+4是影响消光系数的主要化学成分.依据IMPROVE估算公式,将OC分为吸湿性和非吸湿性部分,并加入海盐影响,使估算bext值更接近监测值.OC、EC和硫酸铵盐为估算消光系数主要贡献成分.     

Hydrologic Effects of Surface Coal Mining in Appalachia (U.S.)

Surface coal mining operations alter landscapes of the Appalachian Mountains, United States, by replacing bedrock with mine spoil, altering topography, removing native vegetation, and constructing mine soils with hydrologic properties that differ from those of native soils. Research has demonstrated hydrologic effects of mining and reclamation on Appalachian landscapes include increased peakflows at newly mined and reclaimed watersheds in response to strong storm events, increased subsurface void space, and increased base flows. We review these investigations with a focus on identifying changes to hydrologic flow paths caused by surface mining for coal in the Appalachian Mountains. We introduce two conceptual control points that govern hydrologic flow paths on mined lands, including the soil surface that partitions infiltration vs. surface runoff and a potential subsurface zone that partitions subsurface storm flow vs. deeper percolation. Investigations to improve knowledge of hydrologic pathways on reclaimed Appalachian mine sites are needed to identify effects of mining on hydrologic processes, aid development of reclamation methods to reduce hydrologic impacts, and direct environmental mitigation and public policy.     

Evaluating the Eco‐Geomorphological Condition of Restored Streams Using Visual Assessment and Macroinvertebrate Metrics

The Stream Performance Assessment (SPA), a new rapid assessment method, was applied to 93 restored, 21 impaired, 29 reference, and 13 reference streams with some incision throughout North Carolina. Principal component analysis (PCA) indicated restored streams align more closely with reference streams rather than impaired streams. Further, PCA‐based factor analysis revealed restored streams were similar to reference streams in terms of morphologic condition, but exhibited a greater range of scores relative to aquatic habitat and bedform. Macroinvertebrate sampling and GIS watershed analyses were conducted on 84 restored streams. SPA and watershed data were compared to Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa to determine which factors indicate stream health. SPA and watershed factors were used in least squares, ridge, and principal component regression (PCR) to develop a prediction model for EPT taxa. All three methods produced reasonable predictions for EPT taxa. Cross‐validation indicated ridge regression resulted in the lowest prediction error. The ridge model was then used to predict EPT taxa numbers for 21 impaired and 25 reference streams in addition to the 84 restored streams. Statistical comparisons of the predicted scores indicated urban streams (>10% impervious watershed cover) have lower expected numbers of EPT taxa. Rural restored streams have macroinvertebrate metric scores similar to those predicted for rural reference streams.     

Controls on Temperature in Salmonid‐Bearing Headwater Streams in Two Common Hydrogeologic Settings,Kenai Peninsula,Alaska

Headwater streams are the most numerous in terms of both number and length in the conterminous United States and play important roles as spawning and rearing grounds for numerous species of anadromous fish. Stream temperature is a controlling variable for many physical, chemical, and biological processes and plays a critical role in the overall health and integrity of a stream. We investigated the controls on stream temperature in salmon‐bearing headwater streams in two common hydrogeologic settings on the Kenai Peninsula, Alaska: (1) drainage‐ways, which are low‐gradient streams that flow through broad valleys; and (2) discharge‐slopes, which are high gradient streams that flow through narrow valleys. We hypothesize local geomorphology strongly influences surface‐water and groundwater interactions, which control streamflow at the network scale and stream temperatures at the reach scale. The results of this study showed significant differences in stream temperatures between the two hydrogeologic settings. Observed stream temperatures were higher in drainage‐way sites than in discharge‐slope sites, and showed strong correlations as a continuous function with the calculated topographic metric flow‐weighted slope. Additionally, modeling results indicated the potential for groundwater discharge to moderate stream temperature is not equal between the two hydrogeologic settings, with groundwater having a greater moderating effect on stream temperature at the drainage‐way sites.