High resolution profiles of trace metals in pore waters of marine and riverine sediments assessed by DET and DGT     

Yue GAO Martine Leermakers Gabriel Billon Baghdad Ouddane Jean-claude Fisher Willy Baeyens 《中国地球化学学报》2006,25(B08):199-199

In polluted aquatic systems, toxic metals are often accumulated in bottom sediments. They are, however, not necessarily stored definitively because diagenetic processs can modify redox, pH and even the amount of complexing ligands, releasing the trace metals back into the pore waters and the water column. Especially the labile metal fraction in the pore waters is important since this is the bioavailable fraction determining the bio-toxicity of the sediments. The goal of our study was therefore to assess, with novel sampling techniques, this bioavailable metal fraction in the pore waters as well as the flux towards the overlying water column. High-resolution profiles of trace metals in pore waters of marine and riverine sediments were assessed by DET （diffusive equilibrium in thin films） and DGT （diffusive gradients in thin films） gel techniques. The DET technique uses a diffusive gel layer that equilibrates with the aquatic system and with this technique the concentrations of total dissolved trace metals are obtained directly. The DGT technique uses an acrylamide diffusive gel backed by a resin gel （Chelex） which binds trace metals. With the DGT technique only labile species of selected metals can be captured. According to the redox potential measurements, the marine sediments were suboxic （200 mV to -220 mV versus Ag/AgCl electrode）, while the riverine sediments were completely anoxic （-160 mV to -220 mV versus Ag/AgCl electrode）. This redox potential was apparently controlling the trace metals species in the pore waters： for example a strong correlation between Mn and Co was found in the riverine sediments （for DET and DGT sampling）, while in the marine sediments trace metals presented various behaviors.  相似文献   

Hydrogeochemical controls on surface and groundwater chemistry in naturally acidic, porphyry-related mineralized areas, southern Rocky Mountains     

Philip L. Verplanck D. Kirk Nordstrom Geoff S. Plumlee Richard B. Wanty Dana J. Bove Jonathan S. Caine 《中国地球化学学报》2006,25(B08):231-231

In southern Rocky Mountains, catchments characterized by acidic, metalliferous waters that are relatively unaffected by human activity usually occur within areas that have active or historical mining activity. The US Geological Survey has utilized these mineralized but unmined catchments to constrain geochemical processes that control the surface- and ground-water chemistry associated with near surface acid weathering as well as to estimate premining conditions. Study areas include the upper Animas River watershed, Lake City, Mt. Emmons, and Montezuma in Colorado and Questa in New Mexico. Although host-rock lithologies range from Precambrian gneisses to Cretaceous sedimentary units to Tertiary volcanic complexes, mineralization is Tertiary in age and associated with intermediate to felsic composition, porphyritic plutons. Pyrite is ubiquitous. Variability of metal concentrations in water is caused by two main factors： mineralogy and hydrology. Parameters that potentially affect water chemistry include： host-rock lithology, intensity of hydrothermal alteration, sulfide mineralogy and chemistry, gangue mineralogy, length of flow path, precipitation, evaporation, and redox conditions. Springs and headwater streams have pH values as low as 2.5, sulfate up to 3700 mg/L and high dissolved metal concentrations （for example： Al up to 170 mg/L; Fe up to 250 mg/L; Cu up to 3.5 mg/L and Zn up to 14 mg/L）. With the exception of evaporative waters, the lowest pH values and highest Fe and Al concentrations occur in water draining the most intense hydrothermally altered areas consisting of the mineral assemblage quartz-sericite-pyrite. Stream beds tend to be coated with iron floc, and some reaches are underlain by ferricrete. When iron-rich ground water interacts with oxygenated waters in the stream or hyporheic zone, ferrous iron is oxidized to ferric iron, which is less soluble, leading to the precipitation of iron oxyhydroxides.  相似文献   

Naturally acidic and metalliferous waters at unmined volcanogenic massive sulfide deposits in the Bonnifield mining district, Alaska Range, east-central Alaska     

Robert G. Eppinger Paul H. Briggs Cynthia Dusel-Bacon Stuart A. Giles Larry P. Gough Jane M.Hammarstrom Bernard E. Hubbard 《中国地球化学学报》2006,25(B08):232-232

The Bonnifield district hosts 26 tmmined volcanogenic massive sulfide （VMS） occurrences. Environmental geochemical samples of water and stream sediment were collected at several occurrences, concentrating on the two best-exposed and largest deposits, Red Mountain （RM） and Sheep Creek （SC）. Limited samples were also collected at the poorly exposed WTF deposit. The deposits are Late Devonian to Early Mississippian, and are hosted by felsic metavolcanic and carbonaceous schist members of the Totatlanika Schist or Keevy Peak Fm. Spring and stream waters at RM and SC have pH values commonly 〈3.5 （as low as 2.4 at RM and 2.5 at SC）, high conductivity （up to 11000 μS/cm）, and very high （Is to 100s mg/L） dissolved contents of Al, Cd, Co, Cu, Fe, Ni, and Pb. Waters at RM are characterized by extremely high REE contents （summed REE median 3200 μg/L, n=33）. At both RM and SC, pyrite oxidation and dissolution produce low pH waters that interact with and dissolve bedrock minerals, resulting in acidic, metal-laden, naturally degraded streams that are mostly devoid of aquatic life. Ferricrete is common. In contrast, WTF barely produces a surficial environmental footprint, mostly due to topography and relief. RM and SC are well exposed in the areas of relatively high relief, and both exhibit extensive areas of quartz-sericite-pyrite-alteration. While WTF shares many of the same deposit-and alteration characteristics, it is concealed by tundra in a large, nearly flat area. Surface water at WTF is absent and outcrops are sparse. Even though WTF is roughly the same size as Red Mountain （both around 3 million tonnes） and has similar base- and precious-metal grades, the surficial geochemical manifestation of WTF is minimal. However, exposure through mining of the altered, mineralized rock at WTF potentially could initiate the same processes of pyrite oxidation, acid generation, and mineral dissolution that are observed naturally at RM and SC.  相似文献   

Changes to cadmium associations in canal sediments on drying and oxidation     

Samantha R. Cook John M. Chamock Andrew Parker 《中国地球化学学报》2006,25(B08):247-247

The mainly 19th Century canal system in the UK, largely managed by British Waterways, has been increasingly brought back into operation over the last few decades, and is now widely used for both leisure, and, increasingly, transport. Both initial and routine dredging of the canal sediment is carried out and these sediments are generally disposed of to land. Because many of the canals were connected with primary industries, their sediments can locally be significantly contaminated with heavy metals, and the behaviour of these metals under differing redox conditions, when introduced into a new environment （i.e., on land） is of importance for environmental risk-assessment purposes. Canal sediments are often rich in sulfidic mineral phases, and we have attempted to quantify the influence of these sulfidic phases on the release and retention of metals in dredged canal sediments, using a combination of traditional chemical techniques （e.g. sequential extraction） and X-ray absorption spectroscopy （XAS）. Sediment samples have been collected from urban fresh-water canals, one in the British Midlands and one in Northern France. It appears from XAS that Cd is largely associated with oxygen in air-dried sediment, and with sulphur in vacuum-dried sediment.  相似文献   

Origin and three-dimensional fluorescence spectrum of the chromophoric dissolved organic matter in Yangtze estuary, East China     

Fan YANG Qinghui HUANG Jianhua LI Xiaomin ZHU 《中国地球化学学报》2006,25(B08):262-262

Dissolved organic matter （DOM） is an important chemical component in natural water. Chromophoric dissolved organic matter （CDOM）, a fraction of optical properties, plays art important role in the biogeochemical cycle of nutrients in aquatic environment. People realized that DOM cycle is crucial in the global carbon and nitrogen flux, and also is inherently related to nutrients and trace metal elements. Therefore, CDOM was concerned by scientists in global oceanography and limnology fields. Water samples were collected from three sections （North Channel, South Channel and Zhuyuan） of the Yangtze （Changjiang River） estuary in March 2006 Three-dimensional excitation emission matrix （3-DEEM） fluorescence spectra were analyzed for those filtrates through Whatman GF/F filters. Dissolved organic carbon （DOC） was also measured by TOC analyzer. The tidal variety was also taken into account. The 3-D EEM fluorescence scans suggested the fluorescence characteristics of humic acid （Ex=332-344 nm, Em=439-451 nm） and fulvic acid （Ex=250-254 nm, Em=472-478 nm） were obvious, and the fluorescence group of protein-like and tyrosine （Ex=230 nm, Em=283 nm） was also found. They are mainly composed of CDOM in the Yangtze estuary. Further data analysis, especially the fluorescence index （f 450/500）, showed that terrestrial signal was rather strong （1.41-1.65） in the surface water, however, some terrestrial CDOM signals of bottom water showed excursions （1.28-1.39）. On the other hand, anthropogenic sign was impressed in the waters of Zhuyuan, which is one of the main drain outlets of Shanghai Metropolis. DOC concentrations ranged from 2.2 mg/L to 3.4 mg/L in Zhuyuan and South Channel, and from 2.0 mg/L to 2.4 mg/L in North Channel. The tide effect played a role in the composition of the CDOM measured by 3-D fluorescence scan technology.  相似文献   

Effect of particles on the photodegradation of PAHs in natural waters-A case study for the Yellow River     

Xinghui XIA 《中国地球化学学报》2006,25(B08):263-263

Photodegradation of chrysene, benzo （a） pyrene and benzo （g, h, i） perylene in natural water of the Yellow River was studied using simulation sunlight. The effects of particulates on the photodegradation were explored. Several results arose from this study. （1） The photodegradation of PAHs can be fitted with first-order kinetics when no particulate exists in water system, and the first-order constant increases with decreasing of initial concentration of PAHs. The photodegradation rates of the three PAHs are related to their molecule absorption spectrum. （2） The existence of loess exerts two kinds of effects on the photodegradation of PAHs, including the inner filter effects and the photosensitizing effects of humic substance in loess. These two contrary effects lead to the difference of net effects among different contents of loess. When the loess contents are 0.1 and 5.0 g/L, the existence of loess stimulates the photodegradation of chrysene, benzo （a） pyrene. When the loess content is 5.0 g/L, the existence of loess stimulates the photodegradation of benzo （g, h, i） perylene. In addition, the photodegradation of PAHs can be fitted with the second-order kinetics when there is loess in the water system. （3） The soluble humic substances in loess can accelerate the photodegradation of PAHs while the in soluble part cannot. （4） Since the soluble humic substances in the suspended solids of the river have been dissolved in water,  相似文献   

西北地区的自然环境类型   总被引：3，自引：0，他引：3  

何芳  李英  徐友宁  张江华  陈社斌 《西北地质》2005,38(3):93-99

自然环境区划是国土规划的重要基础，是自然环境综合特征的基本反映.以西北地区的气候分区、地貌分区、植被分区（生态分区）为基础，将西北地区的自然环境类型划分为5个自然分区：阿尔泰-准噶尔区，塔克拉玛干-毛乌素沙漠区，青藏高原东北缘区，黄土高原区，秦巴山地与汉水谷地区.这5个区有完全不同的自然环境特征和资源优势特征，因而开发对策和环境对策是不同的，应予以分别对待.正确认识各区的自然环境特征，才能实现西北地区社会经济及环境的可持续发展。  相似文献   

盛源盆地南部铀成矿水文地球化学条件分析     

石平 《铀矿地质》2005,21(1):38-44,51

本文阐述了盛源盆地南部铀成矿的地质、水文地质和水文地球化学条件 ,分析了区内放射性水异常的产出、分布特征和控制因素 ,认为坝口等地段水的循环深度大 ,深部氧化 还原过渡带发育 ,大面积、交互叠加的放射性水异常是寻找大型隐伏铀矿床的重要标志。  相似文献   

吐哈盆地十红滩铀矿床水文地球化学特征   总被引：6，自引：0，他引：6  

乔海明  张天太  张复新  尚高峰  宋哲 《铀矿地质》2005,21(6):345-352

本文根据水化学资料的研究,探讨了十红滩铀矿床含矿含水层高矿化度地下水的成因,分析了高矿化度水对铀溶解迁移的影响及碳酸盐的形成机理.  相似文献   

中国农业干旱脆弱性分区研究   总被引：23，自引：0，他引：23       下载免费PDF全文

倪深海  顾颖  王会容 《水科学进展》2005,16(5):705-709

根据各地水资源的特点、农业受旱成灾的情况及水利设施抗旱能力,确定农业干旱脆弱性分区的原则和指标,构造层次分析模型。应用MapInfo6.0软件绘制了中国农业干旱脆弱性分区图,结果表明:在全国340个农业干旱脆弱性分区中,极严重脆弱区47个,严重脆弱区104个,一般脆弱区175个,轻度脆弱区14个。  相似文献