天然丝光沸石表面重构改性及其在水中去除重金属的应用

天然丝光沸石作为一种绿色廉价多孔材料广泛应用于环境治理中去除重金属,目前报道的天然沸石对重金属的去除率多在60%～90%,提升其去除效率已成为研究热点。本文采用正硅酸乙酯对天然丝光沸石进行表面重构改性,通过TEM、XRD、BET等手段表征其形貌和结构。结果表明:正硅酸乙酯水解生成的SiO_2可与天然丝光沸石复合形成新颖的"SiO_2/丝光沸石",原沸石表面包覆了新生纳米SiO_2孔结构,同时没有损坏原始沸石的多孔结构,使改性沸石材料兼具了天然丝光沸石和纳米SiO_2孔结构优点,增强了对重金属离子的吸附能力。该改性材料对水中Pb~(2+)、Cd~(2+)、Zn~(2+)和Mn~(2+)的最高吸附率为99. 3%、97. 1%、98. 3%和97. 0%,且极少解吸,性能稳定。考虑经济成本并保证合适吸附率的情况下选择吸附效率最佳的投加量,得到改性材料对初始浓度10 mg/L的Pb~(2+)、Cd~(2+)、Zn~(2+)、Mn~(2+)溶液的最佳投加量分别为0. 5 g/L、2 g/L、2 g/L、5 g/L,可为中试和规模应用提供参考。较之焙烧、酸、碱、盐和有机改性,本改性方式对多种重金属均有高的吸附率,并显现出操作简便、成本低和环境友好等优势,具有较好应用前景。     

桂北硅质岩结构面抗剪强度研究

在广西壮族自治区桂林市天门村进行了硅质岩结构面强度的原位试验,结合现场调查,基于Barton模型,估算了硅质岩结构面抗剪强度。结果表明,硅质岩结构面的剪应力-位移曲线呈现出塑性变形的特征,剪切过程具有爬坡、空化、剪胀的特点。剪切曲线分为剪胀、剪断凸台和完全接触三个过程。结构面受剪力初期,剪应力上升较快,剪切位移随剪应力的增大而几乎呈线性增大,处于弹性状态;随着剪应力的不断增大,在剪切面处发生爬坡作用和啃断作用这两种力学效果;当将结构面上的凸台被啃断后,剪应力上升的梯度变小,直至峰值强度,处于完全接触状态。原位试验得到的抗剪强度参数与Barton模型计算的结果具有较好的一致性,但Barton模型参数的确定带有很强的主观性而造成的误差较大,导致其计算结果偏小,因此在没有经验值和相关工程参考的地区进行现场大剪试验是十分必要的,既保证了工程的可靠性,又避免过于保守,本次实验的结果为类似工程的取值提供了参考。     

近33ka以来辽河口沉积环境演变与生物硅记录

沉积物岩心记录着沉积环境的演变过程,其中生物硅(BSi)记录能反映硅质生物的生产力时间和空间变化,2012年5月在下辽河平原西南缘得到了ZK2钻孔柱状样,通过对其沉积物原位密度、生物硅、碳埋藏、粒度、AMS~(14)C和OSL测年、有孔虫鉴定、孢粉鉴定,将ZK2孔的沉积环境主要划分为上三角洲平原相沉积、海洋主导的沉积、湖相沉积、河道沉积4个沉积单元,其相应的生物硅(BSiO_2)浓度分布依次为(2.85±0.23)%、(1.55±0.10)%、(1.96±0.10)%、(0.92±0.05)%,并且生物硅的波动与颗粒有机碳浓度的波动同步。特别是在17~25 cal ka BP冰期形成的湖沼沉积出现较大的颗粒无机碳(PIC)浓度的波动,推测与当时干冷气候条件下CaCO_3过饱和从湖水中沉淀析出有关。钻孔沉积物生物硅浓度记录对格陵兰冰芯~(18)O同位素值的响应存在大约300 a的滞后现象。     

High‐resolution diatom δ18O records,from the last 150 years,reflecting changes in amount of winter precipitation in two sub‐Arctic high‐altitude lakes in the Swedish Scandes

Waters from high‐altitude alpine lakes are mainly recharged by meteoric water. Because of seasonal variations in precipitation and temperature and relatively short hydraulic residence times, most high‐altitude lakes have lake water isotopic compositions (δ¹⁸O_lake) that fluctuate due to seasonality in water balance processes. Input from snowmelt, in particular, has a significant role in determining lake water δ¹⁸O. Here we compare two high‐resolution δ¹⁸O_diatom records from lake sediments in the Swedish Scandes with instrumental data from the last century obtained from nearby meteorological stations. The time period AD 1900–1990 is characterised by an increase in winter precipitation and high winter/summer precipitation ratios and this is recorded in δ¹⁸O_diatom as decreasing trends. Lowest δ¹⁸O_diatom values and highest amount of winter precipitation are found around AD 1990 when the winter North Atlantic Oscillation index was above +2. We conclude that for the last 150 a the main factor affecting the δ¹⁸O_diatom signal in these sub‐Arctic high‐altitude lakes with short residence times has been changes in amount of winter precipitation and that δ¹⁸O_diatom derived from high‐altitude lakes in the Swedish Scandes can be used as a winter precipitation proxy. Copyright © 2010 John Wiley & Sons, Ltd.     

石灰岩中游离二氧化硅化学物相分析方法的标准化研究

介绍了石灰岩中游离二氧化硅的化学物相分析方法,选择磷酸溶矿,再以氟硼酸解聚已溶出的硅酸,使游离二氧化硅与其他矿物分离,再用重量法进行测定,并按ＧＢ３７９－８６测试方法的精密度,通过实验室间试验确定标准测试方法的重复性和再现性,通过取样、制样、样品均匀性检查、精密度试验等步骤,对该方法进行了标准化研究。     

Holocene climate changes in southern Greenland: evidence from lake sediments

A Holocene lake sediment record is presented from Lake N14 situated on Angissoq Island 15 km off the main coast of southern Greenland. The palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica, clastic material, organic material and sulphur as well as sedimentation rate, moss content and magnetic susceptibility. A total of 43 radiocarbon dates has ensured a reliable chronology. It is argued that varying sediment composition mainly reflects changing precipitation. By analogy with the present meteorological conditions in southern Greenland, Holocene climate development is inferred. Between 11 550 and 9300 cal. yr BP temperature and precipitation increase markedly, but this period is climatically unstable. From 9300 yr BP conditions become more stable and a Holocene climatic optimum, characterised by warm and humid conditions, is observed from 8000 to 5000 cal. yr BP. From 4700 cal. yr BP the first signs of a climatic deterioration are observed, and from 3700 cal. yr BP the climate has become more dry and cold. Superimposed on the climatic long‐term trend is climate variability on a centennial time‐scale that increases in amplitude after 3700 cal. yr BP. A climatic scenario related to the strength and position of the Greenland high‐pressure cell and the Iceland low‐pressure cell is proposed to explain the Holocene centennial climate variability. A comparison of the Lake N14 record with a terrestrial as well as a marine record from the eastern North Atlantic Ocean suggests that the centennial climate variability was uniform over large areas at certain times. Copyright © 2004 John Wiley & Sons, Ltd.     

Seasonal variations of particulate silicon in the Changjiang (Yangtze River) Estuary and its adjacent area

Temporal and spatial distribution of biogenic (BSi) and lithogenic (LSi) silica were studied in the Changjiang (Yangtze River) Estuary and its adjacent area. The annual average BSi and LSi concentrations were (1.71 ± 1.79) μmol/L and (0.56 ± 1.41) mmol/L, respectively. Both BSi and LSi were high in the inshore areas, where they received terrigenous discharge from the Changjiang, and decreased towards the offshore region. BSi and LSi were most abundant at the near bottom layer due to the high sedimentation rates and resuspension of sediment. Diatom blooms occurred in summer with high Chl a concentration in the surface layer, which induced that BSi in the surface layer during summer was obviously higher than that in the surface layer of other seasons. LSi concentration was maximal in autumn and spring and minimum in summer, associated with the seasonal variation of SPM values. Drifting investigation and mesocosm experiments were conducted during dinoflagellate bloom, aiming to understand the effect of nutrients on BSi by changing the phytoplankton composition. The results show that the low dissolved inorganic phosphorus concentration and high molar ratio of N/P (dissolved inorganic nitrogen vs. dissolved inorganic phosphorus), were the important factors for decreasing diatom biomass in the study area, and it would subsequently decrease the BSi concentration in aquatic ecosystem.     

Bioavailability of different chemical forms of dissolved silica can affect marine diatom growth

In this study, we demonstrate that dissolved silica obtained from mineral (crystalline quartz), biogenic amorphous (diatomaceous earth) and artificial amorphous sources (Aerosil) influence the growth rate of two marine diatoms, Chaetoceros sp. and Skeletonema marinoi. Diatoms were reared in four different experimental conditions in artificial seawater containing either dissolved silica previously obtained through dissolution of the mineral crystalline quartz or two amorphous substrates, biogenic diatomaceous earth or artificial Aerosil silica. Sodium metasilicate was used as control. When the silica in the different media reached concentrations higher than 107 μm , particles were eliminated by filtration and the diatom cells were inoculated. Maximum cell density, growth and silica assimilation rates of both species in the presence of dissolved silica derived from crystalline quartz and metasilicate were higher than those obtained with the other silica sources. These results are discussed against the background of previous geochemical studies that have shown that silica–water interactions are strictly dependent on the silica polymorphs involved and on the ionic composition of the solution. Our results demonstrate that the soluble silicon compounds generated in seawater by crystalline sources are highly bioavailable compared with those generated by biogenic and amorphous materials. These findings are potentially of considerable ecological importance and may contribute to clarifying anomalous spatial and temporal distributions of siliceous organisms with respect to the presence of lithogenic or biogenic silica sources in marine environments.     

渤海颗粒有机碳与生物硅的分布及来源

海洋碳、硅循环及其相关联的生物地球化学过程是全球环境变化的热点问题,也是海洋科学关心的重要领域。利用2012年5月和11月份对渤海海域的调查结果,对该海域颗粒有机碳和生物硅的分布特征及来源进行了讨论。主要结论为:渤海有机碳以溶解有机碳为主,具有春季高和秋季低的特征;由陆地来源和海洋自生的有机碳组成,且以海洋来源的有机碳为主。渤海生物硅分布具有明显的梯度特征,河流输入同样对其含量的影响较为突出。渤海沉积物中生物硅含量较高,明显高于中国东部陆架海。渤海表层沉积物中生物硅主要是海源的,依次由浮游藻类、植硅体和海绵骨针所构成,其中浮游藻类占62.9%,陆源植硅体占31.1%。渤海沉积物发现了来自于草本植物的植硅体,这说明了陆地产生的植硅体对海洋生物硅的贡献。