The role of the Río de la Plata bottom salinity front in accumulating debris

The Río de la Plata, one of the most important South American estuarine environments, is characterized by a bottom salinity front that generates an ecotone between the river and the estuary. Based on bottom trawls and costal sampling we describe the distribution, types, and amount of debris found in the bottom and shoreline across this front. Plastics and plastic bags were the main debris types in both areas. Concentrations of total debris upriver the front were always significantly higher than downriver the front showing that the front acts as a barrier accumulating debris. Moreover, a large part of debris end ups accumulated in the coastal area upriver the frontal position. This area is particularly sensitive because the coastline encompasses an UNESCO Man and the Biosphere Reserve and a Ramsar site, and due to the ecological significance of the front for many valuable species.     

世界级金银铜铜锌矿床的定量分析

迄今为止，世界范围内已探明的资源总量，计金１９．３万吨，银１７４万吨，铜１５亿２千万吨，铅３亿４千９百万吨，锌７亿１千３百万吨。马上述所探明的每种金属堆积成立方体、则金，边长为２２ｍ的立方体；银，边长为５５ｍ的立方体；铜，边长为５５０ｍ的立方体；铅，边长为３１０ｍ的立方体；锌，边长为４６０ｍ的立方体。     

华北地区京西煤田侏罗纪煤层中伊利石矿物学特征及成因

为了探讨伊利石对煤化作用和沉积环境的指示作用，以华北地区京西煤田侏罗纪煤层夹矸为研究对象，采用X射线衍射方法（XRD）和X射线荧光方法（XRF）分别测定煤层夹矸的矿物组成和化学组成，研究夹矸中伊利石矿物学特征及成因。结果表明，京西煤田侏罗纪煤层夹矸主要由伊利石、绿泥石和石英组成，其中，伊利石质量分数平均为62.92%。将XRD数据和XRF数据进行对比分析，计算得到伊利石平均化学式为（K_0.37（NH₄）_0.03）Al₂（Si_3.60Al_0.40O₁₀）（OH）₂。京西煤田煤层夹矸中伊利石主要由高岭石转化而来，伊利石的NH₄+占层间阳离子的比例具有随沉积古盐度升高而逐渐升高的趋势，n（Si）/n（Al）Ⅳ具有随煤化程度升高而逐渐降低的趋势，这表明京西煤田侏罗纪煤层夹矸中的伊利石矿物学特征对沉积环境和煤化作用具有一定的指示作用。      

贵州省紫云县狗场地热水分析

紫云县地处贵州省南西部,区域上无岩浆活动,地表无温泉地热流体露头和无明显的其他地热显示,增加了地热勘查的难度。燕山期自东往西的构造应力作用下,产生了近南北向、北东向断层和近南北向褶皱的主体构造,以及碳酸盐岩—碎屑岩沉积建造为区内地热资源的产生提供了前提条件;采用基础地质结合物探方法研究优选出了层状热储较好的牛场坡背斜和带状热储F4小桥断裂结合的有利部位,施工了地热钻孔,取得了良好的地热水找矿成果。     

Numerical examination of the factors controlling DNAPL migration through a single fracture

The migration of five dense nonaqueous phase liquids (DNAPLs) through a single fracture in a clay aquitard was numerically simulated with the use of a compositional simulator. The effects of fracture aperture, fracture dip, matrix porosity, and matrix organic carbon content on the migration of chlorobenzene, 1,2-dichloroethylene, trichloroethylene, tetra-chloroethylene, and 1,2-dibromoethane were examined. Boundary conditions were chosen such that DNAPL entry into the system was allowed to vary according to the stresses applied. The aperture is the most important factor of those studied controlling the migration rate of DNAPL through a single fracture embedded in a clay matrix. Loss of mass to the matrix through diffusion does not significantly retard the migration rate of the DNAPL, particularly in larger aperture fractures (e.g., 50 microm). With time, the ratio of diffusive loss to the matrix to DNAPL flux into the fracture approaches an asymptotic value lower than unity. The implication is that matrix diffusion cannot arrest the migration of DNAPL in a single fracture. The complex relationships between density, viscosity, and solubility that, to some extent, govern the migration of DNAPL through these systems prevent accurate predictions without the use of numerical models. The contamination potential of the migrating DNAPL is significantly increased through the transfer of mass to the matrix. The occurrence of opposite concentration gradients within the matrix can cause dissolved phase contamination to exist in the system for more than 1000 years after the DNAPL has been completely removed from the fracture.