Rare Earth Element Patterns in the Karst Terrains of Guizhou Province, China: Implication for Water/Particle Interaction

The authors determine the concentrations of dissolved (<0.22 μm) rare earth elements (REE) and suspended particulate matter (SPM) of typical karst rivers in Guizhou Province, China during the high-flow period. The concentrations of acid-soluble REE extracted from SPM using diluted hydrochloric acid are also obtained to investigate water/particle interaction in the river water. The dissolved REE contents in the river water are extremely low in the rivers of the study. The dissolved REE distribution patterns normalized by the Post Archean Australia Shale (PAAS) in the karst rivers are not flat, show slight enrichment of heavy REE to light REE, and also have significant negative Ce and Eu anomalies. The acid-soluble REE appears to have similar distribution patterns as characterized by MREE enrichment and slight LREE depletion, with unremarkable Ce and Eu anomalies. The PAAS-normalized REE distribution patterns of SPM are flat with negative Eu anomalies. The contents and distribution patterns of REE in the SPM are closely related to the lithological character of the source rocks. The SPM contains almost all the REE produced in the process of surficial weathering. This demonstrates that particle-hosted REE are the most important form of REE occurrence. REE fractionation, which takes place during weathering and transport, leads to an obvious HREE enrichment in the dissolved loads relative to the SPM. Y/Ho ratio can be used to shed light on REE behaviors during water/particle interaction.     

Chemical composition of rainwater and anthropogenic influences in Chengdu,Southwest China

A comprehensive study on the chemical compositions of rainwater was carried out from Jan. to Dec. in 2008 in Chengdu, a city located on the acid rain control zone of southwest China. All samples were analyzed for pH and major ions (F^–, Cl^?, NO₃^?, SO₄^2?, K⁺, Na⁺, Ca²⁺, Mg²⁺, and NH₄⁺). The pH increased due to the result of neutralization caused by the base ions. It was observed that Ca²⁺ was the most abundant cation with a VWM value of 196.6 μeq/L (17.3–1568.7 μeq/L), accounting for 49.7% (9.4%–79.2%) of the total cations. SO₄^2? was the most abundant anion with VWM value of 212.8 μeq/L (41.8–1227.6 μeq/L). SO₄^2? and NO₃^? were dominant among the anions, accounting for 90.4%–99.1% of the total measured anions.The concentrations of NO₃^? were higher than the most polluted cities abroad, which indicated Chengdu has been a severe polluted city over the world. The high fuel consumption from urbanization and the rapid increase of vehicles resulted in the high emission of SO₂ and NO_x, which were the precursor of the high concentration of acidic ions NO₃^? and SO₄^2?. It was the main reason of the severe acid rain in Chengdu.The high concentrations of alkaline ions (mainly Ca²⁺, NH₄⁺) in Chengdu city atmosphere have played an important role to neutralize the acidity of rainwater and the pH value has increased by 0.7 units since 1989. It is worth noting that the emission of NO_x from the automobile exhaust is increased and is becoming the important precursor of acid rain now.     

广西永福县土地利用变化驱动力分析

以永福县1996--2005年土地利用变更数据和经济统计年鉴为依据,研究其10年间土地利用类型的变化,分析土地利用动态变化和利用程度变化情况,探讨土地变化的驱动因素。认为社会发展和经济增长、人口和城镇化水平以及宏观政策是影响其土地利用变化的3个主要驱动力因素。     

扬子克拉通北缘中元古界神农架群层序的厘定

神农架群被认为是除天津蓟县剖面外,我国出露相对最好的中元古界。由于其大致形成于1400～1000 Ma,故普遍被看好作为中国地层表中1320～1000 Ma时期地层记录缺失的候选层型剖面。尽管近年来神农架群的年代地层学、沉积学、古生物(叠层石形成与分布)及古海洋地球化学等方面研究进展显著,但有关神农架群的划分仍未达成共识。本文在神农架上前寒武系专题研究及神农架1：20万填图划分方案基础上,通过近十余年来对神农架群系统综合研究,重新厘定了神农架群层序。研究认为,神农架群由下至上可划分为下、中、上3个亚群,下亚群由下至上为鹰窝洞组、大岩坪组、马槽园组、乱石沟组、大窝坑组及矿石山组;中亚群包括台子组、野马河组、温水河组和石槽河组;上亚群则为下部送子园组与上部瓦岗溪组。神农架群的上述划分和层序厘定充分结合了神农架群同位素年代学、沉积地质演化、叠层石形态类型及旋回性发育特征、同位素与元素地球化学异常等特征和发育规律。本文是近10年来神农架群研究进展的总结,尽管神农架群目前已具备了建立待建系候选层型的基本条件,但其尚缺少顶界与底界层位年龄,也未见到下伏地层或基底,未来还需进一步开展综合研究。     

Effects of land use on water chemistry in a river draining karst terrain,southwest China

Abstract

The effects of land use on river water chemistry in a typical karst watershed (Wujiang River) of southwest China have been evaluated. Dissolved major ions and Sr isotopic compositions were determined in 11 independent sub-watersheds of the Wujiang River to investigate the spatio-temporal variations in river water chemistry and their relationship to land use. The results show significant spatial variability in pH, major ions, total dissolved solids (TDS), and Sr isotopic compositions throughout the basin. Correlation analysis indicates that nitrogen content is significantly related to forest coverage. Nitrogen and potassium generally have higher values in the rainy season, and the percentage of agricultural land controlled NO₃^- levels, which originate from anthropogenic sources. Forest cover, which varies between 35% and 71%, has no statistically significant impact on river solute concentrations, but the TDS flux is low in sub-watersheds with greater forest cover. Geological sources have a significant influence on pH and Sr isotopic compositions in river water throughout the basin.

Editor D. Koutsoyiannis

Citation Han, G., Li, F., and Tan, Q., 2014. Effects of land use on water chemistry in a river draining karst terrain, southwest China. Hydrological Sciences Journal, 59 (5), 1063–1073.     

An Experimental Study of Mixture Corrosion Effects of Carbonate Rocks in the Transitional Zone of Littoral Karst Areas

The mechanism for development of littoral karst differs from that of inland karst, and the mixture corrosion effects are one of the most important factors that control the development of littoral karst. Through seven groups of static experiments carried out in a closed CO2-H2O system, basic conclusions can be drawn as follows: (1) the basic law of corrosion process in a transitional zone of seawater-freshwater in littoral karst areas is identical with that in the fresh water, i.e., the lithologic characteristics and rock structure are the main factors which control the development of littoral karst; (2) the mixture corrosion rate of the carbonate rock in the above transitional zone is faster than that in fresh water or seawater; (3) the mechanism for development of carbonate rocks differs at various pressures of CO2 in a transitional zone in littoral karst areas.     

Hydrogeochemistry of Wujiang River Water in Guizhou Province,China

The chemical composition of Wujiang River water represents that of river water from the typical carbonate areas.Ite hydrogeochemical characteristics are different from those of global major rivers.The Wujiang River and its tributaries have high total dissolved solid concentrations,with Ca^2 and HCO3^- being dominant,Mg^2 and SO4^2- coming next.Both Na^ K^ and Cl^- Si account for 5%-10% of the total cations and anions,respectively,These general features show the chemical composition of river water is largely controlled by carbonate weathering,with the impact of silicate and evaporate weathering being of less importance.Production activity,minin practice and industrial pollution also have some influence on the chemical composition of rive water.     

电位双二次变化二维地电断面电阻率测深有限元数值模拟

以异常电位为研究对象,给出了一种新的二维地电断面电阻率测深的有限元数值模拟方法.该方法与以往这类方法的主要区别在于,网格单元中的电导率采用双线性插值,电位则用二次函数进行双二次插值,从而使得电位的正演结果以及由电位导出的视电阻率更加符合实际地电场的变化规律;另外,有限元网格单元数也大为减少.对几例模型的试算结果表明,文中提出的计算方法是行之有效的.