Evaluation of groundwater quality in coastal areas: implications for sustainable agriculture

Seawater intrusion is a problem in the coastal areas of Korea. Most productive agricultural fields are in the western and southern coastal areas of the country where irrigation predominantly relies on groundwater. Seawater intrusion has affected agricultural productivity. To evaluate progressive encroachment of saline water, the Korean government established a seawater intrusion monitoring well network, especially in the western and southern part of the peninsula. Automatic water levels and EC monitoring and periodic chemical analysis of groundwater help track salinization. Salinization of fresh groundwater is highly associated with groundwater withdrawal. A large proportion of the groundwaters are classified as Na–Cl and Ca–Cl types. The Na–Cl types represent effects of seawater intrusion. The highest EC level was over 1.6 km inland and high Cl values were observed up to 1.2 km inland. Lower ratios of Na/Cl and SO₄/Cl than seawater values indicate the seawater encroachment. A linear relation between Na and Cl represents simple mixing of the fresh groundwater with the seawater. The saline Na–Cl typed groundwaters showed Br/Cl ratios similar to or less than seawater values. The Ca–HCO₃ type groundwaters had the highest Br/Cl ratios. Substantial proportions of the groundwaters showed potential for salinity and should be better managed for sustainable agriculture.     

安徽庐枞盆地中巴家滩岩体的岩石地球化学特征及成因

巴家滩岩体位于长江中下游庐枞中生代火山岩盆地的中心地带,出露面积约4km2.岩性主要为辉石二长岩和含英辉石二长岩,发育黄铁矿化和黄铜矿化.野外及室内证据表明该岩体可分为两期,第一期表现为闪长质岩石包体;第二期主要为旱阶段的辉石二长岩和晚阶段的含石英辉石二长岩.巴家滩岩体随着由早到晚的演化,其SiO2含量、总碱含量(Na2O K2O)和岩石的氧化度不断增高.稀土配分整体呈右倾趋势,轻稀土富集,重稀土分馏不明显.岩石学、稀土和微量元素地球化学特征表明巴家滩岩体成岩物质来源于富含金云母的富集地幔Ⅱ.巴家滩岩体属于橄榄玄粗岩系,形成于伸展构造环境.巴家滩岩体具有高Al2O2、Sr、St/Y、La/Yb,低Y、Yb、Sr正异常,Eu弱负异常,与沙溪岩体的特征相似,早期包体的Cu含量高达0.8402,推断在其深部可能有可能有类似沙溪岩体的矿化岩浆存在.     

中蒙强、弱沙尘暴年春季平均环流及沙尘活动变化分析

利用NCEP/NCAR再分析资料,对比分析了中蒙东、中及西区强、弱沙尘暴年春季(3—5月)平均环流的特征和差异,讨论了过去50年3分区沙尘暴活动的变化。主要结论是:(1)根据诱发沙尘暴的诱生系统、沙尘源地、冷空气入侵路径及主要影响,中蒙沙尘暴活动区可以划分为中蒙东区、中区及西区3个区系,并分区整体讨论与预测中蒙3分区的沙尘活动。(2)中蒙东区沙尘暴强年春季盛行日本海或中国东北低压活动,常随偏东的北路及东北路冷空气入侵,带来蒙古国东部的沙尘,造成蒙古东部及中国华北的沙尘天气;而弱年春季日本海及东北低压活动则少。(3)中蒙中区沙尘暴强年春季盛行蒙古低压,多西北路及偏西的北路冷空气入侵,常造成中蒙南边界西段附近的沙尘暴天气;而沙尘暴弱年春季则相反。(4)中蒙西区沙尘暴强年春季盛行南疆热低压,多西路冷空气入侵,诱发沙尘暴,常影响南疆及柴达木盆地等;弱年春季则相反。(5)近50年中蒙地区的沙尘暴活动呈波动变化,荒漠化环境、特别是大气环流的变化是导致上述3个分区沙尘活动波动变化的主要原因。主要从大气环流角度考虑,在目前全球增暖持续的背景下,近1—2年应注意中、东区(特别是东区)沙尘活动加强的可能性。     

"04·8"山东远距离台风暴雨成因的数值模拟

利用非静力平衡模式MM5,对由台风"艾利"和西风带冷空气相互作用造成的2004年8月26—28日山东大到暴雨天气过程进行了数值模拟,并对暴雨形成机理进行了分析。结果表明,"艾利"台风外围的急流带在华东沿海到山东南部地区产生深厚的湿层和强水汽辐合,从而导致不稳定能量的积聚;干冷空气从高层入侵使降水区对流不稳定增强,并使不饱和湿空气达到饱和,对降水具有增幅作用;低层正涡度和辐合作用的加强,导致中尺度低涡的形成和暴雨中心的产生。     

Thermochronology and exhumation rates of granitic intrusions at Mesa Central,Mexico

ABSTRACT

The Mesa Central of Mexico (MC) is an elevated plateau located 2000 m above sea level in central Mexico, where intrusions outcrop that register the history of exhumation-erosion occurring during the Late Cretaceous-Paleogene. The tectonic history of the region records formation of the Late Cretaceous-Paleogene ‘Mexican orogen’; this was followed by extension of the entire region and several plutons were then exhumed. The age and magnitude of the crustal uplift and erosion occurring during exhumation has not been addressed to date. Therefore, this study reports the crystallization and cooling ages of two plutons, the Tesorera Granodiorite and the Comanja Granite, and estimates their emplacement depths. Based on these data, the exhumation age of the Tesorera Granodiorite is estimated to be between ~73 Ma and ~63 Ma at an exhumation rate of ~528 m/m. y. and that of the Comanja Granite is 52 Ma and 48 Ma at an exhumation rate of ~2500 m/m. y. Exhumation-erosion event of the Tesorera Granodiorite was located on the trace of the San Luis-Tepehuanes Fault System and that of the Comanja Granite on the a trace of the El Bajío Fault System. Furthermore, the high exhumation rate in the Comanja Granite suggests that gravitational collapse played an important role during exhumation.     

云南金厂金矿床蚀变超基性岩体与金的成矿作用

金矿化与蚀变超基性岩体的空间关系、矿化特征、蚀变超基性岩体、成矿流体、微量元素、硫同位素组成、表明金主要来源于金厂蛇纹石化、滑石化、碳酸盐化超基性岩体。在岩体蚀变过程中,在碱性相对还原的介质条件下,金主要以硫络合物的形式进入成矿溶液,在Ｔ、Ｐ、ＰＨ、Ｅｈ等物理化学参数发生变化的条件下沉淀。     

河北沿海海侵灾害初探

文中以包含海进、海岸侵蚀和海水入侵的广义“海侵”概念,论述河北沿海地区海侵现状及其危害,探讨海侵产生的自然原因和人为活动的影响,在此基础上,评估海侵发展趋势。     

海水入侵水化学指标及侵染程度评价研究

选择Ｃｌ＾,Ｍ、Ｂｒ＾－,ｒＨＣＯ３／ｒＣｌ及ＳＡＲ５项水化学要素作为综合判断海水入侵的指标：染程度划分为４级;确定了各项指标入程度的等级范围。入侵程度的衡理采用模糊数学综合判模型。     

长江河口盐水入侵对大通枯季径流量变化的响应时间

应用河口海岸三维数值模式, 计算区域包括大通至长江河口及其邻近海域, 设计高分辨率网格, 数值模拟和分析不同潮型下长江河口盐水入侵对大通径流量变化的响应时间。计算结果表明, 不同潮型期间大通径流量的增加, 河口盐度响应的时间在4.0～6.2 d之间, 但小潮期的响应时间明显长于其他潮型期的响应时间。本文给出了长江河口盐水入侵对大通枯季径流量变化的响应时间, 可为河口水文、泥沙和环境等研究中取何时径流量提供了依据。     

小秦岭地区金矿成矿机理分析

小秦岭成矿带是我国重要的贵金属成矿带之一,金矿受地层、构造和岩浆岩控制,具有＂三位一体＂的成矿模式。太古宙太华群地层为成矿提供了物质基础,区域变质作用使金发生初次富集;早期自北而南的挤压形成规模巨大的推覆构造为含金石英脉的生成提供了有利空间;燕山期构造—岩浆活动对金的活化、迁移、富集起主导作用