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1.
季节性缺氧导致夏季沉积物内源磷强烈释放,加剧水体富营养化,是我国西南地区深水湖泊(水库)面临的重要挑战.有效增加夏季缺氧期深水沉积物-水界面的含氧量,是减少内源磷释放的关键.现有的深水增氧技术由于缺乏对沉积物-水界面增氧的针对性,因此治理效果有限.近年来,纳米气泡已被证实具有的稳定性好、氧传质速率高和环境风险低等优点,为新型深水增氧技术研发提供了巨大潜力.本文以天然矿物材料白云母、绢云母、硅藻土和沸石为基底,负载纳米气泡,研发纳米气泡改性矿物颗粒技术,开展湖泊沉积物-水界面增氧模拟实验研究,运用平面光电极技术评估其界面增氧效果.结果表明,纳米气泡改性矿物颗粒对沉积物-水界面具有比较明显的增氧效果.其中,改性白云母、绢云母和沸石的界面持续增氧时间可达7天以上,增氧后的界面最大溶解氧(DO)浓度达4.40 mg/L,而改性硅藻土不具有增氧能力.其次,矿物粒度对改性颗粒的增氧效果有一定影响:粒度越细,界面的最大增氧浓度越高,且持续增氧时间越长.纳米气泡改性矿物颗粒技术有望成为夏季缺氧期深水沉积物-水界面精准增氧和内源污染控制的有效技术手段.  相似文献   
2.
花粉保存能力差异是影响花粉谱准确性的重要因素之一,采用KMnO4溶液和HNO3溶液作为氧化剂,模拟自然环境氧化条件对油松花粉保存影响情况.结果表明:同一KMnO4溶液浓度条件下,随时间延长油松花粉完好率呈下降趋势;浸泡相同时间,随KMnO4溶液浓度增大油松花粉完好率亦明显下降.经68%HNO3溶液浸泡18 h后,残留的完好花粉外壁变薄,纹饰变模糊,24 h后花粉几乎完全被溶解.一般认为油松花粉保存能力较强,而经2%KMnO4溶液和68%HNO3溶液处理后,发现在短时间内就足以使油松花粉大量破碎或溶解,表明氧化环境对油松花粉保存影响强烈.氧化环境对油松花粉腐蚀作用强于碱性环境.  相似文献   
3.
Porewater nutrient dynamics during emersion and immersion were investigated during different seasons in a eutrophic intertidal sandflat of Tokyo Bay, Japan, to elucidate the role of emersion and immersion in solute transport and microbial processes. The water content in the surface sediment did not change significantly following emersion, suggesting that advective solute transport caused by water table fluctuation was negligible. The rate of change in nitrate concentration in the top 10 mm of sediments ranged from −6.6 to 4.8 μmol N l−1 bulk sed. h−1 during the whole period of emersion. Steep nutrient concentration gradients in the surface sediment generated diffusive flux of nutrients directed downwards into deeper sediments, which greatly contributed to the observed rates of change in porewater nutrient concentration for several cases. Microbial nitrate reduction within the subsurface sediment appeared to be strongly supported by the downward diffusive flux of nitrate from the surface sediment. The stimulation of estimated nitrate production rate in the subsurface layer in proportion to the emersion time indicates that oxygenation due to emersion caused changes in the sediment redox environment and affected the nitrification and/or nitrate reduction rates. The nitrate and soluble reactive phosphorus pools in the top 10 mm of sediment decreased markedly during immersion (up to 68% for nitrate and up to 44% for soluble reactive phosphorus), however, this result could not be solely explained by molecular diffusion.  相似文献   
4.
不同供氧方式对水库底泥氮磷释放的影响   总被引:29,自引:3,他引:29  
采用实验室模拟试验,研究了三种供氧方式——曝气、投加过氧化氢和投加过氧化钙对水库底泥氮磷释放的影响.研究结果表明:(1)溶解氧是控制底泥氮磷释放的重要因素,厌氧条件能加速底泥释放磷和氨氮;(2)曝气、投加过氧化氢和投加过氧化钙均能显著提高底部水体的溶氧水平,并能有效抑制底泥氮磷的释放.三种供氧方式对底泥释磷的控制效率依次为:投加CaO2>曝气>投加H2O2;对氨氮释放的控制效率则为:曝气>投加CaO2>投加H2O2.  相似文献   
5.
汤好书  陈衍景  武广  杨涛 《岩石学报》2009,25(11):3075-3093
2.33~2.06Ga期间发生了全球性大气圈充氧作用及其相关的占δ~(13)C_(carb)正异常,被称为Lomagundi事件.2.2~2.174Ga的辽河群大石桥菱镁矿及其围岩显示了δ~(13)C_(carb)正异常,是运用REY(REE+Y)指纹技术研究Lomagundi事件的良好对象.本文研究表明,6件白云岩围岩样品∑REE为0.988×10-6~2.744×10-6;Y/Ho比值为37.9~49.4(平均42.5±4.7);(La/La~*)_(SN)为1.075±0.317,(Gd/Gd~*)_(SN)为1.390±0.166,均为正异常;HREE富集(Nd_(SN)/Yb(_SN)=0.38~0.78).所有上述特征与现代海水REY配分模式一致,表明这些样品记录了Lomagundi时期海水的REY特征.6件菱镁矿样品∑REE为4.549±2.239,高于围岩白云岩;HREE弱亏损(Nd_(SN)/Yb_(SN)=1.141±0.265),Y/Ho平均值为40.2±3.2;(La/La~*)_(SN)为0.657~1.149(平均0.919±0.203),(Gd/Gd~*)_(SN)=1.036±0.081,正异常程度弱于白云岩,但仍显示以海水来源为主.矿体顶板滑石白云岩∑REE含量最高(10.758);页岩标准化稀土配分模式为平坦型,(Eu/Eu~*)_(SN)正异常高达1.97,Gd和Y正异常最小,Y/Ho比值最低(31.3),(Nd/Yb)_(SN)为0.89,显示受后期热流体交代影响.菱镁矿(Sm/Yb)_(CN)值(2.61±0.45)高于白云岩(1.19±0.27),指示海水由深变浅,大石桥菱镁矿及其围岩白云岩REY主要来自陆源溶解物,洋底热液贡献微弱,制约REY特征的主导因素为大气圈-水圈的性质,如fO_2,pCO-2等.白云岩和菱镁矿(Ce/Ce~*)_(SN)值平均分别为1.11±0.13和1.04±0.08,表明2.2~2.174Ga期间大陆风化作用加剧,海水呈碱性,pH值>8.2.2.33Ga前的化学沉积物(Eu/Eu~*)_(SN)>1.53,2.06Ga后的化学沉积物(Eu/Eu~*)_(SN)<1.53,大石桥组白云岩和菱镁矿(Eu/Eu~*)_(SN)均值分别为1.44±0.11和1.58±0.20.表明2.2~2.174Ga时海相沉积物(Eu/Eu~*)_(SN)≈1.53,2.33~2.06Ga是地球水圈-气圈系统由还原向氧化转变的关键时期.  相似文献   
6.

An overturned angular fold in the Currabubula Formation at Tulcumba Ridge has a north‐south axial trace exposed along the western side of this ridge. The geometry and position of this fold adjacent to the Mooki Thrust is consistent with its formation as a fault‐propagation fold involving a thrust step‐up angle of ~ 30° from a décollement. Overturned strata also occur adjacent to the Mooki Thrust near the Rocky Creek Syncline to the north and to the south on Gunnan Ridge and in the Werrie Syncline. Overturning of strata in these areas may be the result of fault‐propagation folding. It is suggested that folding in the Tamworth Belt involves thin‐skinned deformation that is dominantly fault‐related.  相似文献   
7.
自从地球诞生以来经历了许多重大事件:早期生命的出现、大气氧化事件(Atmospheric oxygenation)、雪球地球及多次生物绝灭与复苏事件。稳定同位素记录在古环境和生命演化研究中具有重要意义,在记录环境变化和生命演化的重大事件中发挥着重大作用:碳同位素的分馏记录了最早生命的开始,硫同位素的非质量相关分馏(Independent mass fractionation of sulphur isotopes)记录了大气中氧含量的重大变化,而在显生宙的几次重大生物灭绝事件中,均有碳同位素的负向漂移。  相似文献   
8.
Hypolimnetic oxygenation by pumping oxygen-rich surface water to the hypolimnion (HLO) is a commonly used tool for the restoration of nutrient-loaded dimictic lakes. However, in recent years its effectiveness has been questioned. In this case study we evaluated monitoring data covering a period of 23-years to show that, although experimental cessation of HLO drastically changed the lake's temperature and dissolved oxygen regimes, it did not significantly affect its trophic status. Thus, we recommend that the limited financial resources available are better directed towards further lowering the lake's external phosphorus load than continuing HLO.  相似文献   
9.
Because oxygen deficient conditions enhance the preservation of depositional organic matter, analysis on paleooxygenation conditions of depositional environments becomes a routine work in evaluations of potential hydrocarbon source rocks. The article focuses on depositional and ecological features relating to oxygen deficient shelfal environments at the Shangsi (上寺) Section, as a part of multidiscipline collaboration to reevaluate the hydrocarbon potential of the Middle and Upper Permian, Guangyuan (广元), Northeast Sichuan (四川) Province. Icbnofabric Zoophycos, sepioilte-bearing limestones (SBL) were interpreted as indicators of dysaerobic environments. Laminated calcareous and/or siliceous mudstones with pelagic ammonites and radiolarians were believed to be the deposits of anaerobic environments. When rhythmic succession was considered, average strategy was adopted for the oxygenation explanation of a given intervaL The anaerobic condition in this Permian section was observed in the upper part of the latest Permian Dalong (大隆) Formation, in which siliceous mudstones with ammonite, radiolarians develop in association with lower U/Mo ratio, lower biomarker ratio of Pr/Ph, and the highest TOC content. The topmost Maokou (茅口) Formation, featured by thin-bedded calcareous and siliceous mudstones with ammonite, thin-shelled bivalves, and laminations would be deposits of the quasianaerobic condition. The middle part of the Members and Ⅲ of the Chihsia Formation is proposed to be dysaerobic condition as indicated by occurrences of SBL and ichnofabric features, with the Member Ⅲ being the severe dysaerobic condition.  相似文献   
10.
This study investigates the interactions of water, oxygen, temperature, suspended sediment and topsoil texture of bedwork watermeadows. These ancient grassland irrigation systems survive on the floodplain around Salisbury, England but recent interest in their conservation and rehabilitation is not matched by detailed understanding of their operation. The dominant ‘bedwork’ form, by which water runs along the top of ridges and down ‘panes’, enables water to move swiftly through the sward and drain to avoid stagnation. This investigation demonstrates that condition of surface flow and rates of infiltration encourage the solution of atmospheric oxygen in the water, offsetting potentially anaerobic conditions in the root zone. Temperature conditions imparted by the flow were measured and found to be conducive to the early growth of grass. Whereas the sediment budget was found to be conservative under a steady‐state hydraulic regime, there is substantial ingress of suspended sediment at the start of an irrigation event and the sward traps coarse to medium‐sized silt particle fractions and influences topsoil texture. It is concluded that a study of watermeadow operation permits insights into the operation of floodplain processes in general. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
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