Sea-to-air flux of contaminants via bubbles bursting. An experimental approach for tributyltin

Although seawater concentration of tributyltin (TBT) should decrease when the direct inputs from ship hulls will cease after the incoming world ban of organotin-based antifouling paints in 2003 or later, the TBT environmental issue will still be present for decades as contaminated sediments in shallow waters will be acting as a long-lasting reservoir for TBT and its degradation products. The lost of TBT to the atmosphere by volatilization has already been proposed as a part of its molecular motion through the aquatic environment but most recent calculated values of water-to-air rate of exchange of TBT (from 20 to 510 nmol m⁻² year⁻¹) do not take into account the potential contribution of aerosols ejection to the atmosphere upon bubbles bursting, an important process for pollutants transport in the marine environment. In this work, an experimental approach to measure the seawater-to-air flux of TBT mediated by bubbles bursting is described, and the influence of phytoplankton cells and dissolved organic matter from exudates and culture weathering on flux rates was assessed. The results demonstrate that TBT can be transferred from water to air via the ejection of droplets from bubbles bursting and that cell density strongly affected the transfer. Under a bubbling regime, the water-to-air flux (pmol TBT cm⁻² min⁻¹ level) is estimated up to 1000-fold the flux measured for the molecular diffusion and volatilization under static quiescent conditions. The surface microlayer acted as a transient boundary between the water column and the atmosphere where the dynamic of TBT accumulation has the same trend as the dynamic of TBT ejection. This physical transfer mechanism might be of high significance in nearshore environments, harbors, and shallow channels where clouds of bubbles generated in the wake of large ships play an important role for the atmosphere/seawater chemical exchanges.     

神府矿区突水溃砂地质灾害研究

针对神府矿区威肋安全生产的最大地质灾害──突水溃砂，本文通过实例，结合勘察成果，对其地质背景形成机理进行了总结分析，认为解决这一地质灾害目前最有效的措施是采前疏排基岩顶部直接充水含水层中地下水，使砂失去地下水载体而无法进入矿井。     

重庆松藻煤矿茅口灰岩岩溶水害与治理

松藻煤矿井下＋335大巷C6岩溶裂隙出水点,由于接受地表汇水洼地水源的补给,最大涌水量达3 500m3/h,对矿井安全构成极大威胁.通过物探、巷探、施工截流巷等勘查方案揭露了C6＇岩溶裂隙通道,经过高压帷幕注浆阻断下渗通道等治理措施,排除了困扰该矿20多年的水害威胁,为煤矿类似水害的治理积累了宝贵经验.     

九里山矿西部水大原因分析及对策

九里山矿水文地质条件复杂,矿井最高排水量为104．20m^3／min,吨煤排水量为116．87m^8,长期达不到生产能力。分析了矿区的地层、构造和水文地质条件,认为L9灰岩含水层是矿区的主要充水水源,充水通道为断层带及底板底鼓引起的裂隙带。另外,钻孔及注浆过程中的水位变化证实了L2潜伏水头的存在。指出矿区突水水量大的主要原因是：在采掘（工作面回采、巷道掘进）、矿压、水压的作用下,煤层底板的完整性被破坏而产生裂隙,当这种裂隙和L2灰含水层的潜伏水头沟通时,就会产生L2灰含水层的突水。据此提出了目前应对突水的措施是在14101工作面布置钻孔注浆,封堵煤层至O2灰含水层之间的所有含水层。     

Turbulent and Macro-turbulent Structures Developed in the Benthic Boundary Layer Downstream of Topographic Features

The characteristics and effects of large-scale flow structures developed in the benthic boundary layer downstream from large topographic features were analysed throughout a tidal cycle. The observed signature of the macro-turbulent features consisted of streamwise modules of low horizontal velocity and high suspended sediment concentration (SSC), alternating with modules of high horizontal velocity and low SSC. These modules extended 10 to 20 m streamwise and exceeded 1 m vertically, and are believed to be related to flow separation effects over large bedforms upstream of the deployment site. The macroscale flow modules intensified the ‘ burst-like ’ turbulent events and favoured sediment transport. ‘ Ejection-like ’ events were magnified during modules of decreasing horizontal velocity and increasing turbidity, whereas ‘ sweep-like ’ events were magnified during modules of increasing horizontal velocity and decreasing SSC. The enhanced turbidity of the macroscale modules may be the result of enhanced upward diffusion of sediment by ejection events, whereas the low-turbidity modules may be induced by increased downward transport of suspended sediment by sweep events. These hypotheses were supported by cross-spectral analysis performed on velocity and suspended sediment concentration time-series recorded at the site. An enhanced (negative) contribution of outward and inward interaction events to the Reynolds stress, compared to those reported in uniform BBLs, resulted in ‘ abnormally ’ low stress values.     

1113机采工作面突水分析与治理

2006年4月19日,山东珑山实业有限公司1113机采工作面发生井下突水事故,突水量300m^3／h。通过水质化验、奥灰孔水位观测等资料分析,得出了突水水源为奥陶系岩溶水,突水的原因是断层、矿山压力及高水压三大因素综合作用波及到了底板奥陶纪石灰岩含水层的结论。在注浆治理中,本着截流封源的思路,在井下先后施工了两个注水钻孔。在注1号钻孔失败后,及时调整了方案,自1111机道7号点,沿方位260°3′44″掘专门堵水平巷130m,重新布置了注2号钻孔,修改了终孔落脚点,结果注2号孔准确命中目标。通过单液水泥注浆技术注入70．3t水泥,浆液的水灰比为：2：1～1．5：1,工作面水量最后稳定在20．16m^3／h,从而顺利完成了注浆堵水任务,为今后井下打钻注浆堵水提供了有益的借鉴。     

An analysis of the characteristics of rough bed turbulent shear stresses in an open channel

Entrainment of sediment particles from channel beds into the channel flow is influenced by the characteristics of the flow turbulence which produces stochastic shear stress fluctuations at the bed. Recent studies of the structure of turbulent flow has recognized the importance of bursting processes as important mechanisms for the transfer of momentum into the laminar boundary layer. Of these processes, the sweep event has been recognized as the most important bursting event for entrainment of sediment particles as it imposes forces in the direction of the flow resulting in movement of particles by rolling, sliding and occasionally saltating. Similarly, the ejection event has been recognized as important for sediment transport since these events maintain the sediment particles in suspension. In this study, the characteristics of bursting processes and, in particular, the sweep event were investigated in a flume with a rough bed. The instantaneous velocity fluctuations of the flow were measured in two-dimensions using a small electromagnetic velocity meter and the turbulent shear stresses were determined from these velocity fluctuations. It was found that the shear stress applied to the sediment particles on the bed resulting from sweep events depends on the magnitude of the turbulent shear stress and its probability distribution. A statistical analysis of the experimental data was undertaken and it was found necessary to apply a Box-Cox transformation to transform the data into a normally distributed sample. This enabled determination of the mean shear stress, angle of action and standard error of estimate for sweep and ejection events. These instantaneous shear stresses were found to be greater than the mean flow shear stress and for the sweep event to be approximately 40 percent greater near the channel bed. Results from this analysis suggest that the critical shear stress determined from Shield's diagram is not sufficient to predict the initiation of motion due to its use of the temporal mean shear stress. It is suggested that initiation of particle motion, but not continuous motion, can occur earlier than suggested by Shield's diagram due to the higher shear stresses imposed on the particles by the stochastic shear stresses resulting from turbulence within the flow.     

缓倾斜地层顶板离层水对综采工作面的危害及防治探讨

以重庆松藻矿区在打通的一综采工作面缓倾斜地层中掘进时发生的两次顶板水灾为例,对其顶板突水原因进行了探讨。通过分析该矿区的矿井地质及水文地质条件,认为矿井充水水源为上覆地层的离层水。该矿井的M7-3煤层开采后,导水裂隙切穿了上覆地层长兴组灰岩,贯通了玉龙山一段灰岩隔水层,进入玉龙岩二段岩溶裂隙含水层。由于含水层的上覆岩层在采掘过程中,因岩性差异发生不均衡沉降,形成了大量的离层空间。离层空间吸收、储存的大量地表降雨在采掘工作面推进到一定位置时,就会发生突水。据估算,S1821工作面上覆岩体离层、裂隙储水空间按三分之一计算为2.064×105m^2,与该工作面抢险救灾期间排出的涌水量基本吻合。根据该矿离层水的赋存特点,提出了保证排水系统畅通,加强采煤设备管理,提高采面设计水平的防治水对策。     

基于突水系数的煤矿底板突水危险性评价系统——以山西太原西山煤田古交矿区为例

通过对煤矿底板突水系数评价系统总体框架的介绍,并以山西太原西山煤田古交矿区为例,阐述了钻孔数据库的建立与查询系统的生成,着重说明了等值线的绘制过程,然后结合大量抽水试验数据,自动生成底板含水层等水压线和底板隔水层等厚线图,最后利用GIS叠加分析功能,根据突水系数的计算公式,生成了突水系数图。根据突水系数图的分析,划分出矿井底板的突水危险地区,对矿井防治水有一定的帮助。     

利用岩性地震反演方法评价煤层突水危险性

针对葛亭煤矿的构造地质和水文地质条件,利用概率神经网络岩性反演方法获得岩性数据体,该数据体包含了煤系地层到奥陶系灰岩顶部的构造、岩性和水文地质信息,构成了评价煤层突水危险性所需的基本数据。将其各种信息进行融合后对3煤层顶板的突水危险性进行定量评价：其中波阻抗反演的岩浆侵入及煤层变焦区域（含水层）与视电阻率反演结果高度一致,同时依据孔隙度反演结果证实该区域具有相应的低孔隙度反应。将该区域3煤层顶板视电阻率与孔隙度值进行乘积归一化处理,计算其突水隶属度,依此划分了该层位的突水程度。