Saturation states of carbonate minerals in a freshwater-seawater mixing zone of small tropical island’s aquifer     

Ahmad Zaharin Aris  Sarva Mangala Praveena  Mohd Harun Abdullah 《中国地球化学学报》2010,29(3):278-286

Groundwater is a crucial resource on the Manukan Island as it is the only source of freshwater available on the island. The aquifer has deteriorated to a high degree, during the last decade. Nine domestic wells were sam-pled from March 2006 to January 2007 to probe the hydrochemical components that influence the water quality. Geochemical data on dissolved major constituents in groundwater samples from the Manukan Island revealed the main processes responsible for their geochemical evolution. The results using statistical analyses, graphical method and numerical model output (PHREEQC) showed that the groundwater was chemically highly enriched in Na and Cl, indicative of seawater intrusion into the aquifer as also supported from the Na-Cl signature on the Piper diagram. From the PHREEQC simulation model, calcite, dolomite and aragonite solubility showed positive values of the saturation indices (SI), indicating supersaturation which led to mineral precipitation condition of water by these min-erals.  相似文献   

涠洲岛珊瑚礁近千年的发育过程及其对气候变化的响应*     

张婷  胡敏航  张文静  陈天然  刘猛 《热带海洋学报》2020,39(4):70-79

高纬度珊瑚栖息地能否成为气候变暖背景下热带珊瑚物种的“避难所”仍不明确, 南海北部的相关研究更是稀少。本文以取自涠洲岛的2根珊瑚礁沉积岩心为研究对象, 通过U-Th定年、沉积组分分析以及珊瑚种属鉴定等方法, 探讨近千年以来珊瑚礁的发育过程及其对气候变化的响应。研究结果发现, Core1(石螺口)岩心沉积的3个快速堆积阶段分别与罗马暖期、中世纪暖期和现代暖期大致对应; 而2个缓慢堆积阶段则分别与黑暗时代冷期和小冰期大致对应, 证实了温暖的气候对珊瑚礁发育有促进作用, 而寒冷的气候则不利于珊瑚礁的发育; 此外, 现代强烈的人为干扰可能也导致了涠洲岛珊瑚礁的迅速退化。Core2(南湾)中陆源沉积含量高, 珊瑚年龄主要集中在800AD—950AD和现代这两个时间段内, 其原因可能与环境变化、风暴作用及湾内现代珊瑚分布特征有关。通过对比这两个站位的珊瑚礁沉积特征, 本文进一步提出“完全避难所”和“非完全避难所”的概念, 揭示涠洲岛珊瑚可能同时具有低纬度热带珊瑚礁和高纬度珊瑚群落这两种发育特征和趋势。  相似文献   

A 477‐year dendrohydrological assessment of drought severity for Tsable River,Vancouver Island,British Columbia,Canada          下载免费PDF全文

Bethany Coulthard  Dan J. Smith 《水文研究》2016,30(11):1676-1690

Summer streamflow droughts are becoming more severe in many watersheds on Vancouver Island, British Columbia, as a result of climate warming. Small coastal basins that are the primary water source for most communities and essential to Pacific salmon populations have been particularly affected. Because the most extreme naturally occurring droughts are rarely captured within short instrumental records water managers likely underestimate, and are unprepared for, worst‐case scenario low flows. To provide a long‐term perspective on recent droughts on Vancouver Island, we developed a 477‐year long dendrohydrological reconstruction of summer streamflow for Tsable River based on a network of annual tree‐ring width data. A novel aspect of our study is the use of conifer trees that are energy limited by spring snowmelt timing. Explaining 63% of the instrumental streamflow variability, to our knowledge the reconstruction is the longest of its kind in British Columbia. We demonstrate that targeting the summer streamflow component derived from snowmelt is powerful for determining drought‐season discharge in hybrid runoff regimes, and we suggest that this approach may be applied to small watersheds in temperate environments that are not usually conducive to dendrohydrology. Our findings suggest that since 1520, 21 droughts occurred that were more extreme than recent ‘severe’ events like those in 2003 and 2009. Recent droughts are therefore not anomalous relative to the ~400‐year pre‐instrumental record and should be anticipated within water management strategies. In coming decades, worst‐case scenario natural droughts compounded by land use change and climate change could result in droughts more severe than any since 1520. The influence of the Pacific Decadal Oscillation on instrumental and modelled Tsable River summer streamflow is likely linked to the enhanced role of snowmelt in determining summer discharge during cool phases. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

海南五指山地区花岗片麻岩锆石LA-ICP-MS U-Pb年代学特征及其地质意义   总被引：4，自引：0，他引：4  

陈新跃  王岳军  范蔚茗  张菲菲  彭头平  张玉芝 《地球化学》2011,(5):454-463

海南五指山地区出露大面积花岗片麻岩,且广泛发育NW向定向变形构造,表明经历了明显的动力变形变质作用;4个花岗片麻岩样品的LA-ICP-MS锆石U-Pb年代学测试数据表明它们形成于263～269 Ma,代表了中二叠世的一次重要地质构造热事件.结合前人研究成果认为,海南五指山地区263～269Ma花岗片麻岩可能形成于华南与...  相似文献   

香港国家地质公园粮船湾组火山岩岩石学研究   总被引：2，自引：0，他引：2       下载免费PDF全文

邢光福吴振扬陶奎元伍世良  陈荣 姜杨 李龙明  余明刚 《中国地质》2011,38(4):1079-1093

在香港国家地质公园西贡火山岩园区,核心地质景观是白垩纪粮船湾组(Kkh)火山岩优美的六方形石柱(柱状节理),它们的岩石类型长期存在熔岩和火山碎屑岩之争。笔者等经野外调查和薄片岩石学研究,确认粮船湾组火山岩实属一种特殊的熔岩——流纹质碎斑熔岩,以普遍的柱状节理、斑晶具有碎斑结构和珠边结构、基质发育霏细结构和流动构造为特征;它们不仅代表了香港地区中生代最晚期火山喷发的产物,而且构成了西贡破火山机构的中央侵出相岩穹。推断粮船湾组火山岩石柱是地球上已知面积最大的流纹质碎斑熔岩石柱群(～150 km2),目前所见的火山岩石柱仅是长期剥蚀后的残余部分。  相似文献   

A 2200-year Record of Seabird Population on Ganquan Island, South China Sea     

XU Liqiang  LIU Xiaodong  SUN Liguang  YAN Hong  LIU Yi  LUO Yuhan  HUANG Jing 《《地质学报》英文版》2011,85(4):957-967

Geochemical characteristics of a 107 cm long sediment profile, collected from Ganquan Island, South China Sea, were analyzed. Based on concentrations of bio-elements (Cu, Zn, Cd, Ba, As, Se, P), 210Pb and AMS14C dating, we reconstructed seabird population of Ganquan Island over the past 2200 years. Seabirds inhabited this island more than 2200 years ago, and their population displayed remarkable fluctuations with two peaks around 2100–1850 yr BP and 900–300 yr BP, respectively. The seabird population change profile on Ganquan Island is similar to that on Dongdao Island over the past 1800 years. We examined the relationship between the seabird population and climate, and found it quite complicated. The seabird population did not reach the maximum during the Medical Warm Period (MWP) with relatively high average temperature; however, it remained near the peak value for about 600 years during the climatic transition period and the Little Ice Age (LIA), indicating that a relatively cool climate is favorable for seabirds on Ganquan Island.  相似文献   

印度尼西亚塔里亚布岛锡铁多金属矿床的地质地球化学特征与成因   总被引：1，自引：0，他引：1  

丁俊  张术根  徐忠发  秦新龙 《地球学报》2011,32(3):313-321

印尼塔里亚布岛新近发现大型锡铁多金属矿床,初步探明铁储量超过l亿吨,全铁品位可达50%.塔里亚布岛锡铁多金属矿床以矽卡岩型与矿浆型为主,兼具热液型,构成一个完整的成矿系统.印支期二长花岗岩源自地壳部分熔融产生的岩浆,是矿床的主要成矿物质来源与控矿因素;岩浆经过高度的演化分异过程,生成富铁矿浆贯入充填成矿,主要赋存于花岗...  相似文献   

Particle dynamics of Be,Pb and the implications of sedimentation of heavy metals in the Wenjiao/Wenchang and Wanquan River estuaries,Hainan, China     

Dekun Huang  Jinzhou DuJing Zhang 《Estuarine, Coastal and Shelf Science》2011

Radionuclides (i.e., ⁷Be and ²¹⁰Pb) can be used to trace particle and sediment dynamics and to quantify coastal oceanic processes with time scales ranging from a few days to a hundred years. Here, we study the settling dynamics of suspended particles and the implication by sedimentary heavy metals in the Wenjiao/Wenchang River and Wanquan River estuaries through the measurement of the particulate ⁷Be and ²¹⁰Pb nuclides. Activity in the particulate phase had a range of 2.1–54.5 and 4.6–67.9 Bq kg⁻¹ for ⁷Be and excess ²¹⁰Pb (²¹⁰Pb_xs), respectively, in the Wenjiao/Wenchang River estuary. In the Wanquan River estuary, activity is in the range of 1.2–43.5 Bq kg⁻¹ for ⁷Be and 6.2–194.5 Bq kg⁻¹ for ²¹⁰Pb_xs. At the same time, activity in the dissolved phase had a range of 0.46–1.26 and 0.30–1.17 Bq m⁻³ for ⁷Be and ²¹⁰Pb, respectively, in the Wenjiao/Wenchang River estuary; ranges of 0.10–2.31 and 0.09–1.87 Bq m⁻³ for ⁷Be and ²¹⁰Pb, respectively, were observed in the Wanquan River estuary. The distribution coefficients (K_d) for the two nuclides decreased within increased in suspended particle matters (SPM) concentration and/or salinity in Wanquan River estuary. The residence times of particulate ⁷Be and ²¹⁰Pb_xs had ranges of 0.4–1.6 and 1.65–5.15 days, respectively, in the Wenjiao/Wenchang River estuary; and ranges of 0.02–3.2 and 0.61–4.44 days, respectively in the Wanquan River estuary. All residence times for the two nuclides increased in the seaward direction. In the Wenjiao/Wenchang River estuary, we found that 11.8–21.0% of Cu, 3.0–9.0% of Zn and 43.2–69.9% for Cd is removed from the water column and deposited into the estuary, and 24.2–34.8% for Cu, 7.2–23.8% for Zn, and 70.0–82.5% for Cd in the Wanquan River estuary, respectively.  相似文献   

南海北部白云凹陷-东沙岛西南海区的浅地层探测与深水沉积特点   总被引：1，自引：0，他引：1  

阎贫  王彦林  郑红波 《热带海洋学报》2011,30(2)

采用新引进的海洋深水浅层剖面仪,从珠江口外陆架进入白云凹陷-东沙岛西南海区中陆坡区,进行了浅地层探测,获得了高分辨率反射记录.分析发现,白云凹陷上陆坡段沉积连续性较好,海底反射强度侧向变化平缓,显示了比较均一的沉积底质和微弱的海底水动力条件;在白云凹陷-东沙岛西南海区中陆坡区,海底滑坡严重,局部存在强烈的、平行陆坡的海底洋流冲蚀,海底地形崎岖不平,反射强度侧向变化大,表明海底底质不均匀,海底水动力强.浅地层记录还显示中陆坡海底山丘有海底气体泄露现象,结合常规反射地震识别的海底泥底辟特征,确定海底山丘为泥火山.气体泄露和海底反射振幅的变化代表了海底浅层聚有丰富的气体以及嗜甲烷生物链活动的钙化,因而推断该区不仅是油气的聚集区,也是水合物的聚集带.  相似文献   

西沙群岛永兴岛礁坡石珊瑚覆盖率的空间变化   总被引：5，自引：0，他引：5  

施祺  严宏强  张会领  赵美霞 《热带海洋学报》2011,30(2)

连续影像样方调查方法较常用的截线样条法具有空间分辨率高的特点.采用该方法于2008年7月在西沙群岛永兴岛礁坡开展了5条垂直岸线断面和2条平行岸线断面的石珊瑚覆盖率调查.调查发现,永兴岛珊瑚覆盖率存在显著的空间差异,北、西北和东部断面珊瑚分布相对较多,覆盖率较高;西和西南部断面珊瑚分布稀少,覆盖率低.其中北、西北和东部断面沿礁坡方向珊瑚分布明显减少,礁坡中上部30-50m以上、水深5-6m以浅的区域,珊瑚覆盖率高;而礁坡中下部50m以下、水深约6m以深区域,珊瑚分布少,覆盖率低.此外,北和西北部断面还发现由棘冠海星Acanthaster planci和黑皮海绵Terpios hoshinota分别造成的珊瑚白化和珊瑚黑死现象,一定程度上降低了珊瑚覆盖率.永兴岛珊瑚覆盖率的下降以及空间变化格局的形成主要与30年以来日益增加的人类活动和珊瑚礁区过度开发有关.  相似文献