Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil: results of the IAEA–UNESCO SGD project

Results of groundwater and seawater analyses for radioactive (³H, ²²²Rn, ²²³Ra, ²²⁴Ra, ²²⁶Ra, and ²²⁸Ra) and stable (D and ¹⁸O) isotopes are presented together with in situ spatial mapping and time series ²²²Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d⁻¹ to 360 cm d⁻¹; the unit represents cm³/cm²/day), as well as during a few hours (from 0 cm d⁻¹ to 110 cm d⁻¹), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous ²²²Rn measurements is 17 ± 10 cm d⁻¹. Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7 × 10³ m³ d⁻¹ per km of the coast. The isotopic composition (δD and δ¹⁸O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time series measurements of ²²²Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1–2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.     

漓江流域δD和δ18O对蒸发的指示作用

以漓江流域为例查明不同水体之间氢氧稳定同位素组成特征,并探讨氢氧稳定同位素对漓江流域的蒸发过程指示作用.结果表明：流域内不同水体之间,氢氧稳定同位素表现出不同的组成特征,地表水和地下水,在丰水期δD值和δ¹⁸O值要比枯水期更容易富集,地下水的δD值和δ¹⁸O值分布范围较地表水小;随着水温的升高,δ¹⁸O的变化趋势比d-excess明显.从漓江上游到下游高程逐渐下降,河水线的斜率和截距也在逐渐减小,其中漓江下游河水线的斜率和截距要低于当地大气降水线,表明下游受到蒸发作用较强烈;地下河水线、地表河水线在一定程度上偏离当地大气降水线,但偏离程度较小,表明三者之间有很好的水力联系.受温度和湿度的共同影响,漓江干流丰水期河水的蒸发量占最初水体总量的0.7%~9.1%,枯水期河水的蒸发量占最初水体总量的2.6%~9.7%,丰水期的蒸发比例低于枯水期,从上游到下游蒸发比例在逐渐上升.研究区蒸发量估算值为959.40mm,与多年实测值少43.11mm,相对误差4.70%.氢氧稳定同位素对研究区降水、地表水、地下水之间的转换规律具有重要的实际意义,在今后的漓江流域水文研究中有着更加广阔的空间.     

新疆D矿田金矿资源定量评价

本文在建立D矿田找矿信息层次模型基础上,确定矿田统计单元划分和地质变量提取的赋值原则,将该矿田划分出466个统计单元,提取25个地质变量并进行二态赋值,而后应用数量化理论Ⅲ。特征分析法及勃尔法等方法,建立了矿田金矿资源定量评价模型,定位预测了45个勘探靶区。     

Dobbins-Camp水质模型的修正

对多宾斯 坎普 (Dobbins Camp)水质模型进行了修正 ;并分别运用传统多宾斯 坎普模型和修正模型 ,对某河段实测资料进行BOD、D(氧亏 )计算 ,比较两者之间的异同 ,及分析溶解氧对有机物降解的影响     

无缝钢管局部径向模具塑性成形过程的三维有限元数值模拟

采用大变形弹塑性有限元理论,用DYNA3D(研究版)有限元软件,对无缝钢管局部径向模具塑性成形过程中当凸模的凹槽尺寸与凸模的圆弧半径发生变化时进行了数值模拟研究,得出了对成形钢管表面质量控制具有重要参考价值的结论,解决了成形钢管表面的压痕问题。     

一种低功耗高性能数据采集数字处理平台的设计

目的构建一套基于中频信号基带数字信号处理的软件无线电平台。方法通过选择芯片设计硬件电路设计出合适的PCB板。结果主要依据软件无线电平台,提出了一种基于A/D+FPGA+D/A的硬件设计方案,该系统包括了前端的A/D数据采集和后端的D/A模拟数据恢复的详细收发电路原理设计。结论构建了一个从前端数据接收到后端模拟发送的高速基带数字信号处理平台。     

再生水灌溉土壤人工合成麝香累积模型模拟

人工合成麝香(HHCB/AHTN)是近几年来受关注较多的药品与个人护理品(PPCPs)类新型污染物之一,再生水灌溉是HHCB/AHTN输入土壤的主要途径.本研究结合再生水灌溉土壤的实地检测结果,采用HYDRUS-1D模型,模拟了长期灌溉再生水条件下土壤中HHCB和AHTN的迁移转化和累积趋势.结果表明,尽管土壤中这两种麝香的含量极低,但是再生水灌溉土壤中的含量是自来水灌溉土壤的5倍;再生水灌溉下HHCB/AHTN累积趋势从lgKoc较低为3.44时的指数型增加,到lgKoc较高为4.12和4.86时的线性增加;半衰期的变化对再生水灌溉途径输入土壤的HHCB/AHTN的表层累积影响并不明显;再生水灌溉下土壤中HHCB/AHTN的垂直迁移能力较小,灌溉40 a以后最大迁移距离只有53 cm,且受Koc变化的影响较大;通过灌溉水途径进入土壤的HHCB和AHTN通过生物降解与植物吸收途径消解的比例较低,最高只占输入总量的7.69%,但是随着lgKoc的减小和灌溉时间增加,通过生物降解和根系吸收的消解率增加.本研究结果能够为准确评估再生水灌溉途径引起的土壤中人工合成麝香HHCB/AHTN的生态风险提供依据.     

基于强度折减法的港珠澳大桥沉管隧道干坞工程高边坡稳定性分析

在列举和分析比较当前岩土工程领域边坡稳定性分析的各种主要方法的基础上,概述了强度折减法的基本原理、主要特点和优势,并以港珠澳大桥沉管隧道干坞大型临时工程拟建场地的岩质高边坡为实例,应用强度折减法基于FLAC3D软件对该边坡的稳定性进行了计算和分析,确定了边界条件和强度参数,计算了该边坡的安全系数,结果表明自然工况下边坡处于稳定状态,底部开挖以后边坡趋于欠稳定状态,同时指出了边坡的关键变形部位,可为后续的设计和施工提供参考。     

Further evidence of nuclear reactions in the Pd/D lattice: emission of charged particles

Almost two decades ago, Fleischmann and Pons reported excess enthalpy generation in the negatively polarized Pd/D-D₂O system, which they attributed to nuclear reactions. In the months and years that followed, other manifestations of nuclear activities in this system were observed, viz. tritium and helium production and transmutation of elements. In this report, we present additional evidence, namely, the emission of highly energetic charged particles emitted from the Pd/D electrode when this system is placed in either an external electrostatic or magnetostatic field. The density of tracks registered by a CR-39 detector was found to be of a magnitude that provides undisputable evidence of their nuclear origin. The experiments were reproducible. A model based upon electron capture is proposed to explain the reaction products observed in the Pd/D-D₂O system.

基于RFPA2D复合局部挠曲岩体数值模拟

为研究复合局部挠曲岩体强度特征以及破坏规律,采用岩石真实破裂软件RFPA^2D,对水平层面挠曲30°,45°,60°,75°的复合岩体进行单轴压缩试验模拟。模拟结果表明:挠曲角为30°,45°,60°,75°的复合岩体破坏面几乎与挠曲段夹层重合,其挠曲端部均产生了垂直于挠曲段夹层的裂纹;复合单斜岩体与复合挠曲岩体破坏面的形成因素大致相同,夹层强度是2种岩体失稳的主要因素;复合挠曲岩体单轴抗压强度随挠曲角增大同样呈“U”型变化,与单斜岩体变化趋势一致;当水平层状岩体发生挠曲后,其单轴抗压强度减小,当挠曲角为60°时,强度降低25.19%,当挠曲角为75°时,强度降低0.17%。;随着均质系数m的增大,复合挠曲岩体单轴抗压强度以及轴向应变均出现逐渐递增的趋势,且不同m值,其岩体裂隙扩展方式具有明显差别。