200 years of mining activities at La Paz/San Luis Potosí/Mexico - Consequences for environment and geochemical exploration

The Ag---Pb---Zn---Cu---Au mining district of Santa María de La Paz has been extensively exploited for approximately 200 years. Consequences of these activities are several deposits of tailings with high As and heavy metal concentrations, which are completely unstable. The climate is semiarid and as the dumps have no protective cover, material from the dumps is dispersed by strong winds. It is also washed out during seasonally heavy rainfalls. By these processes approximately 100 km² of surrounding have been contaminated by dump material. The As and heavy metal content of the soils was determined as well as their level in crops (Zea Maize) from agricultural lands in the vicinity of the dumps. In the direction of prevailing winds concentrations up to 1000 ppm Zn, 400 ppm Pb, 16 ppm Cd, 550 ppm Cu and 300 As have been detected in top soils. Using fuzzy cluster analysis the different contamination sources could be identified. Grains of corn from contaminated sites showed no critical concentrations, but leaves which are also used tor fodder, have As-concentrations up to 20 ppm.     

Mobility of heavy metals as a function of pH of samples from an overbank sediment profile contaminated by mining activities

Parts of the flood plains north of the Harz Mountains are contaminated with heavy metals, such as Pb, Cu, Zn and Cd derived from mining, which has been carried out in the Harz Mts. since the Middle Ages. It is important to know the mobility of the heavy metals in these overbank sediments in order to estimate the danger to the environment arising from this source. This paper deals with the effect of pH on heavy-metal mobility, using a constant-pH method. The investigations were carried out on an overbank sediment profile near Salzgitter Bad, north of the Harz Mts. The mobility of the heavy metals in the overbank sediment profile is described as a function of pH and depth. Besides the mobile heavy-metal fraction at a certain pH, the buffering capacity of the sediment at this pH must be taken into consideration. The different layers of the overbank sediment profile show distinct differences in buffering capacity and a natural pH harrier could be identified in the upper part of the profile. Therefore, to avoid increasing heavy-metal mobility the natural layering of the overbank sediment profile should not be disturbed. Two different kinds of desorption experiments at constant pH are also discussed, as well as the conversion of the heavy-metal species in the ore minerals into the species in the sediment.     

气相色谱和薄层色谱法在形态分析中的应用

评述了气相色谱和薄层色谱法用于氯、溴、碘、硫、硒、碲、铬、氮、磷、砷、钒、碳、锡、铅、铁和汞１６种元素的不同形态分析的进展。这些形态包括不同价态、有机态、无机态、阳离子和阴离子态等。由于气相色谱和薄层色谱法都具有分离和检测两种功能结合的特点，因此它们是用于元素形态分析的有效和方便的方法。引用１９８０～１９９４年文献９２篇     

Comparison of Cu and Zn cycling in eutrophic lakes with oxic and anoxic hypolimnion

Data on the cycling of Cu and Zn in two eutrophic lakes are presented: Lake Greifen that becomes seasonally anoxic in its hypolimnion and Lake Sempach that is aerated during winter and oxygenated during summer. They suggest that hypolimnetic oxygenation 1) enhances the release of copper from the sediment but 2) also accelerates the entrapment and deposition of Cu and Zn by freshly formed Mn- and Fe-oxides.     

云宵县5月暴雨客观预报模型

采用文献[1]提出的技术模型，研制了云宵县5月暴雨预报方法，建立了4个因子结构简单而天气学意义明了的客观预报模型。经2000～2003年试用，这种基于场量因子的预报模型，未漏报，严格评定的准确率为67％，明显优于主观预报。     

2003年7月上旬张家界特大暴雨山洪分析

对造成 2 0 0 3年 7月 8～ 1 0日张家界特大暴雨山洪的主要影响系统、物理量诊断场资料、多普勒雷达回波资料及自动气象站要素进行了分析 ,并重点分析了张家界特定的地形条件对降水的增幅作用及暴雨的夜发特征 ,为湘西北的暴雨山洪预报提供了一些有益的启示。     

一次强暴雨形成的动力机制

分析了1998年7月武汉强暴雨的天气演变特征，并从理论上探讨了强暴雨形成的动力机制。结果表明：低空急流先于暴雨生成，暴雨最强时低空急流也最强；高空急流入口区右侧及低空急流左侧非热成风梯度的存在，使得中尺度不稳定波的波振幅出现空间不稳定现象，高空急流右侧不稳定波的波振幅和低空急流左侧不稳定波的波振幅向暴雨区增加，暴雨区恰为这两支波叠加后振幅最大的区域，高低空急流耦合下的非热成风、中尺度对流-对称不稳定可能是这类强暴雨产生的动力原因之一。     

98.7湖北特大暴雨的天气分析与降水模拟

1998年7月20～23日，湖北省南部发生了一次持续性特大暴雨过程，采用双向嵌套的非静力中尺度数值模式(MM5)对这次强暴雨过程进行初步模拟试验。结果表明，粗、细网格均能较好地模拟出雨带的走向和变动以及武汉地区的暴雨中心，尤其是嵌套域(细网格)模拟的降水强度比粗网格有明显改进，和实际观测结果更接近；另外，对引发这次特大暴雨的对流层低层的中尺度系统也能够很好地模拟出来。     

2002年6月13日重庆区域大暴雨分析

通过对重庆西部“6 1 3”区域大暴雨的分析 ,发现此次天气过程是一次典型的高原涡与西南涡耦合 ,结合地面弱冷空气条件下产生的 ,同时对ECMWF和T2 1 3数值预报产品进行了简要的分析 ,发现ECMWF和T2 1 3的形势预报能力都比较好 ,但T2 1 3的部分物理量要素和降水量预报能力还有待提高。     

1997年7月19日影响北京地区的暴雨个例分析

针对在实际业务预报中经常遇到的北京地区降水的两种特殊性(明显天气系统移来时，北京地区降水明显比周围偏多或偏少)，选取一个实例利用中尺度非静力模式(MM5)对降水比周围偏多情况进行了高分辨率数值模拟和敏感性试验。结果表明，该模式比较成功地模拟了此次天气过程及其相关的中尺度系统的发生发展，凝结潜热对天气过程的发生发展有重要作用，而地形在天气过程中也起着主要作用，低层潜在不稳定能量的储备和输送是暴雨发生不可缺少的条件。