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1.
乌江流域水库沉积物中生物硅的测定方法及其环境意义   总被引：1，自引：0，他引：1  
采用碱提取法中的单点法与多点法相结合,测定了乌江流域水库沉积物中生物硅的含量,并对多点提取法进行了改良。采用多个离心管分装定量样品进行连续振荡,每小时提取1个样品进行测定。对多个时间点的提取结果,利用线性回归法分析得出最佳提取时间,优化最佳提取液,然后利用单点提取-硅钼蓝检测法测定沉积物中生物硅的含量。该方法既保证了单点法的快速,也减小了多点法的多次提取操作与提取时的体积误差。本文根据测定结果探讨了乌江流域水库沉积物中生物硅含量变化规律及其环境意义。  相似文献   

2.
利用湿碱式化学提取技术和电感耦合等离子体发射光谱仪,优化样品碱式消解方法,确定仪器最佳工作条件,建立了测定海洋沉积物中不同含量级别生物硅的方法。结果表明,仪器检出限为0.724μmol/L,方法检出限为0.942μmol/L。用于测定硅酸盐-硅溶液成分分析国家一级标准物质(GBW08648和GBW 08649,标准值分别为50.0μmol/L和100.0μmol/L),测定值分别为(49.888±0.275)μmol/L、(99.578±0.651)μmol/L,相对标准偏差为0.443%、0.527%;对于不同生物硅含量级别海洋沉积物样品的平行、独立测量,其相对标准偏差8.9%。方法快速、简便、准确,可满足古海洋学不同时空尺度气候和环境分析的应用。  相似文献   

3.
利用电感耦合等离子体质谱 (ICP- MS)和电感耦合等离子体原子发射光谱 (ICP- AES)方法分析了常规碱液提取海洋沉积物中的生物硅所获取的溶液中的 Si、 Al和 Ti含量.分析结果显示 , 碱液提取法获取的溶液中 Si和 Al明显地由两种来源混合而成,其中, Si有较大比例的陆源碎屑成分的贡献,并不能直接代表沉积物中的生物硅含量,而需要对其中的陆源碎屑贡献进行扣除.通常使用 Al来代表陆源碎屑进行扣除的方法无法给出正确结果,因为碱提取液中 Al存在明显的非碎屑组分.对数个土壤及水系沉积物标准样品物质的试验发现,碱提取可以优先溶解其中的 Si和 Al,而提取液中的 SiO2/TiO2比值相对于土壤和沉积物全样的 SiO2/TiO2比值有一个比较固定的富集系数 (约 14左右 ).对南海沉积物而言,根据这个富集系数和区域的碎屑物质的化学组成算得碱提取液中碎屑组分 SiO2/TiO2比值约为 748,这与根据二端员混合估计的比值相当.这样,根据提取液中的 Ti含量可以较好地扣除出碎屑组分对生物硅的污染,对于更准确测定海洋沉积物中低含量的生物硅具有重要意义.  相似文献   

4.
青海湖沉积物生物硅的环境意义初步研究   总被引：1，自引：0，他引：1  
湖泊沉积物中生物硅含量的变化已经被广泛应用于评价湖泊生产力和古气候变化研究,但大型湖泊不同位置生物硅含量的时空变化及其与环境要素之间的关系仍缺乏详细的现代过程研究.通过对青海湖不同位置表层沉积样品的生物硅含量测定,建立其空间分布模式及最近数百年生物硅含量的时间序列.结果表明,青海湖表层沉积物生物硅含量变化范围是1.75%～2.98%,平均值为2.25%.与世界其他湖泊相比,青海湖生物硅含量处于相对较低水平,可能与其特殊的地理位置和气候条件有关.青海湖生物硅含量的空间分布规律与沉积物质量堆积速率以及陆源组分含量(如SiO2)相反,而与化学/生物沉积组分(如CaCO3)含量的空间分布规律大体一致,说明生物硅的空间分布受到陆源碎屑物质的"稀释效应"影响.时间序列上,生物硅含量与SiO2含量呈相反变化趋势,与指示降雨量变化的C/N比值也是反相变化,说明生物硅含量在时间序列上也受与气候条件密切相关的陆源输入的影响.青海湖湖心低沉积速率区域的生物硅指标具有指示古气候变化的潜力.  相似文献   

5.
人类活动影响下的胶州湾近百年来环境演变的沉积记录   总被引：13，自引：0，他引：13  
本文报道了胶州湾柱状沉积物中各生源要素(C、N、P、BSi)以及重金属(Cd、Cr、Pb、Cu、Ni、Co、Zn等)的地球化学特征,在210Pb精确定年的基础上计算了各项地球化学参数的埋藏通量,并结合元素间的比值(OC/TN、OC/OP、BSi/N、BSi/P;其中OC为有机碳,TN为总氮,OP为有机磷,BSi为生物源硅)和重金属的某些污染指数,给出了胶州湾环境演变的沉积记录以及人类活动影响因子.结果表明:胶州湾近百年的环境演变大致可以分为三个阶段:1980年以前、1980年到2000年左右和2000年至今,经历了环境的未受污染期污染期治理好转期.这些变化除与自然因素有关外,大部分应该归因于人类活动作用的加强.  相似文献   

6.
遥感生物地球化学找金矿方法研究进展   总被引：7，自引：0，他引：7  
总结了金矿的生物地球化学性质、植物的生物地球化学效应特征以及其波谱和遥感影像特征，以及利用遥感图像处理提取生物地球化学效应引起的植被光谱异常信息的专题信息提取方法。研究表明，在金矿区上生长的植物对金及伴生元素有较强的吸收和聚积作用，植物明显受到生物地球化学效应的毒化作用；金及伴生元素的过量吸收，使植物叶片中的叶绿素、类胡萝卜素含量、水含量和叶面温度相应降低；植物叶片细胞结构发生变异，叶冠波谱反射率和波形等光谱特征明显变化；在遥感图像上，金矿区的植被表现出异常特征信息。这些信息可以作为在植被区寻找隐伏矿床的遥感生物地球化学找矿的标志。利用遥感生物地球化学的理论和技术方法，从遥感数据中分析金矿的植被图像特征，提取与金矿化有关的植被异常特征信息，可以优先出金矿化遥感异常区，并列举了几个应用实例。同时，指出了需加强该领域的理论和应用研究，为广大植被覆盖地区寻求一种快速有效的探矿方法。  相似文献   

7.
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。  相似文献   

8.
分析了南海东部53个站位表层沉积物中生物钡、铝以及有机碳和生物硅等生源物质的分布特征。结果表明,南海东部表层沉积物中的有机碳含量在研究区的北部陆架区出现高值,而在吕宋岛以西的深海则最低;生物硅的平面分布则表现为在吕宋岛以西的深海低沉积速率区出现高值,而低值则出现在高沉积速率的北部海域;生物钡的平面分布与生物硅的分布特征相似,高值出现在吕宋岛以西的深海区,且表现出自北而南沉积物中生物钡的含量逐渐增加的趋势。研究区内初级生产力表现为从北向南增加的趋势,而沉积物中生物钡的含量也呈现相似的趋势,表明沉积物中生物钡的含量和上层水体的生产力有一定的相关性。但表层沉积物中生物钡与有机碳呈弱的负相关关系,而与生物硅显著相关,且生物钡和生物硅与水深的相关性均呈现显著的相关性。因此,在采用沉积物中生物钡含量研究南海上层水体初级生产力时应谨慎对待。  相似文献   

9.
土壤中砷的形态分析和生物有效性研究进展   总被引：19，自引：0，他引：19  
土壤砷污染是当今全球十分严重的环境与健康问题之一。土壤砷形态及生物有效性研究是开展污染诊断、评估环境健康风险及开展砷污染土壤修复的重要依据。目前土壤砷形态的研究方法包括化学选择性提取操作定义法、溶剂提取仪器测定或吸附材料选择性分离法和同步辐射X射线近边能谱（XANES）直接测定法，这些方法相互结合在土壤砷的形态转化研究中发挥着重要作用。目前关于生物有效性研究存在多种方法并存的局面，化学提取法相对经济、方便，但存在很大的局限性，往往不能真实反映土壤砷的有效态含量，只能作为环境危害程度识别的参考；植物指示法需选择敏感性植物方能有效地指示土壤砷对环境与健康的潜在危害；土壤动物与微生物指示法代表了未来开展砷污染早期预警的发展方向，具有广阔的应用前景。模拟肠胃液提取法(In Vitro Gastrointestinal Method)比较接近动物或人体对土壤砷污染的真实吸收状态，在环境健康风险评价中发挥着重要作用。目前国外已发展出采用兔、仔猪和猴的动物模型以研究经口摄入的生物有效性砷，但尚不清楚哪种动物模型更能准确反映砷对人体的生物有效性。  相似文献   

10.
依托第3次、第4次、第5次北极科学考察在北极楚科奇海采集的表层沉积物样品,通过碱液连续提取法对生物硅含量进行分析,以探讨楚科奇海的生物硅分布及硅质泵过程。结果显示,楚科奇海表层沉积物中生物硅的含量为1.23%~10.60%。高值区位于楚科奇海陆坡处72°N附近和楚科奇海南部阿纳德尔流和西伯利亚沿岸流的交界处68°N附近,低值区位于楚科奇海东部阿拉斯加沿岸流影响区域,其生物硅含量小于3%。楚科奇海表层沉积物中生物硅的分布与上层水体的初级生产力的分布格局较一致,而影响上层水体浮游植物生产的两个重要因素分别为楚科奇海环流格局(尤其是太平洋入流水的影响)和海冰融化。生物硅和有机碳之间存在很好的正相关关系,表层沉积物中蛋白石/有机碳(Sibio/Corg)的比值为1.6~2.02,与北太平洋中该比例相当,表明上层海洋硅质泵过程对楚科奇海碳埋藏的贡献较大,使得楚科奇海成为全球海洋吸收大气CO2重要的汇之一。  相似文献   

11.
Flow-through experiments have been performed to study the thermodynamics of biogenic silica (opal) dissolution in deep-sea sediments. They were applied for the first time on sediment from the Southern Ocean [Van Cappellen and Qiu 1997a] and [Van Cappellen and Qiu 1997b] We have extended the use of these experiments to other deep-sea settings, thereby covering a wide range of in situ silicic acid asymptotic concentrations (Casympt; 200 to 900 μmol/L) and biogenic opal content (BSi; 0.5 to 80%). Performing these experiments under in situ bottom temperatures allows for the comparison between experimental apparent solubilities and Casympt concentrations. Low values of BSi apparent solubilities have been measured in the deepest sections of the multicores collected in the northeast Atlantic (229 μmol/L) and in the equatorial Pacific (505 μmol/L). They are only 10 to 20% higher than the in situ Casympt concentrations. This demonstrates a clear control of pore water silicic acid concentrations by the in situ apparent solubility of the BSi, i.e., the solubility of BSi within a complex sedimentary matrix that includes important quantities of silicate minerals.In regions where the percentage detrital/percentage biogenic ratio is low, the apparent solubility of the biogenic silica is close to that of in situ biogenic silica. In the opposite case, when the percentage detrital/percentage biogenic ratio is high, reprecipitation reactions induce strong interference on the dissolution properties of the opal, both in situ and in flow-through experiments. In such a sedimentary matrix, it is important to determine the appropriate opal solubility to be used in early diagenetic models, i.e., the solubility of the biogenic silica just before deposition on the seabed. This has been achieved by performing flow-through experiments on sediment trap material from the north Atlantic site. Comparison of apparent biogenic silica solubility measured by flow-through experiments and the silicic acid concentrations measured in the cups of the sediment traps suggested that the solubility of biogenic silica that reaches the sediment-water interface is not unique and varies spatially and temporally. In fact, it is the degree of coupling between surface waters and the sediment-water interface that will control the aging of biogenic silica in the water column and hence the dissolution properties of the biogenic silica deposited at the sediment-water interface. All these results call for a strong improvement of biogenic silica early diagenetic models that should include not only a reprecipitation term that takes into account interaction with silicate minerals but also the existence of several phases of biogenic silica and thus that should operate in a non-steady-state mode to account for seasonal variations in the quality of deposited biogenic silica.  相似文献   

12.
The solution rate of biogenic opal in near-surface sediments in the Central Equatorial Pacific is three to eight orders of magnitude lower than similar acid-cleaned samples. Iron, magnesium and calcium aluminosilicates may be the minerals which are forming on the surface of the opal and reducing its solution rate. The scale height of the system studied suggests that diffusive and not advective processes are primarily responsible for the removal of dissolved silica in sediments. Solution budget calculations for this area suggest that 90–99 per cent of the biogenic opal produced in surface waters dissolves before reaching the sediment-water interface; an additional amount dissolves within the sediment and diffuses into bottom waters leaving 0.05–0.15 per cent of the original amount of opal produced by organisms in the sedimentary record. The relative solution potential of the upper 1000 m of the water column varies by more than an order of magnitude from the Antarctic to Equator and may have a pronounced effect on the accumulation rate of biogenic opal in underlying sediments.  相似文献   

13.
Stirred flow-through experiments were conducted for the first time with planktonic biogenic silica (BSi). We investigated the dissolution kinetics of uncleaned and chemically cleaned BSi collected in ocean surface water, sediment traps, and sediments from the Norwegian Sea, the Southern Ocean, and the Arabian Sea. The solubility at 2°C is rather constant (1000 to 1200 μM). The dissolution rates are, however, highly variable, declining with water depth, and phytoplankton reactivity is two to three orders of magnitude higher than pure siliceous oozes. The reactivity decrease correlates well with an increase in the integrated peak intensity ratios of Si-O-Si/Si-OH measured by Fourier transform infrared (FTIR) spectroscopy. The removal of organic or inorganic coatings enhance the reactivity by at least an order of magnitude. Atomic Al/Si ratios of 0.03 to 0.08 in sedimentary diatom frustules decrease significantly to 0.02 as a result of removal of inorganic coatings and detritals present. Near equilibrium, the dissolution rates exhibit a linear dependence on the degree of undersaturation. At higher degrees of undersaturation—that is, at low concentrations of dissolved silica—the dissolution rates of uncleaned samples define a nonlinear trend.The nonlinear kinetics imply that the dissolution of natural BSi is strongly accelerated in silica-depleted surface waters. The FTIR results suggest that internal condensation reactions reduce the amount of surface reaction sites and are partly responsible for the reactivity decrease with depth. The high content of Al in sedimentary BSi is likely caused by precipitation of dissolved silica with Al dissolved from minerals in sediment. Nonbiogenic silica as coatings or detritals are partly responsible for the solubility and reactivity decrease of BSi in sediments. One order of magnitude different rate constants measured in Norwegian Sea and Southern Ocean sediment trap material support the so-called opal paradox—that is, high BSi accumulation rates in sediments in spite of low BSi production rates in surface waters of the Southern Ocean.  相似文献   

14.
The occurrence and significance of biogenic opal in the regolith   总被引：1，自引：0，他引：1  
Jonathan   《Earth》2003,60(3-4):175-194
Biogenic opal produced by vascular plants, diatoms, and siliceous sponges have been found in soils and terrestrial sediments of all continents except Antarctica since the middle of the 19th century. The opal particles range in size from fine silt to fine sand. Almost all soils contain detectable opal up to levels of 2–3%, and a significant number contain values in excess of 5%. Even higher values have been found from soils and sediments of all continents in a wide range of soil types. The most important factor is poor soil drainage and seasonal to permanent water logging. This encourages the proliferation of silica producing organisms. Such conditions have been found in the soils and aquatic sediments of the monsoonal tropics, tropical rain forests, temperate forests, tropical savanna, tropical islands, semi-arid grasslands and savanna, and temperate woodland and grassland. The presence of a volcanic substrate also appears favourable in some cases, but is not necessary. Biogenic opal preferentially collects in the A horizon of soils and, to a lesser extent, in the B horizon. This preferential distribution facilitates identification of palaeosols in stacked soil sequences. Biogenic opal is also a component of windblown dust, even in arid environments. Biogenic opal is significant to regolith processes in a number of ways. Firstly, as in the case in marine environments, it is likely to be important in silica cycling and storage because of its greater lability compared to quartz. Secondly, dissolution and reprecipitation of opal A as opal CT or micro-quartz may play a role in cementation and silicification of regolith to form silica hardpans and silcrete. Thirdly, the organisms that form biogenic opal can have considerable palaeoenvironmental significance and be valuable in reconstructing regolith evolution. Finally, some forms of biogenic silica, in particular sponge spicules, can present a health hazard. Their high abundance in some soils and sediments needs to be considered when assessing the health implications of airborne dust.  相似文献   

15.
An annual budget for dissolved silica (DSi) and biogenic silica (BSi) was constructed for the Scheldt estuary and for the entire riverine and estuarine Scheldt tidal system (Belgium/The Netherlands) using previously published silica concentrations and fluxes for the period 2003–2005. The annual estuarine DSi mass-balance was established, based on seasonal fluxes estimated using measured DSi concentrations and (fully transient) model simulations of conservative transport. The annual BSi mass-balance was deduced from measured BSi contents in the suspended particulate matter and annual mud fluxes taken from the literature. The Scheldt estuary acted as a net sink not only for the BSi carried by the tidal river as well as that produced by diatoms in the estuary, but also for large amounts of BSi imported from the coastal zone. This results in the retention of dissolved and biogenic silica higher than that of DSi alone, which is in contrast with the classical consideration that rivers act as a source of BSi for the coastal zone. DSi and silica (DSi + BSi) retentions amounted to, respectively, 28 and 64 % in the estuary, and 33 and 66 % in the entire tidal system. This study highlights thus the predominant role of the estuary in the entire Scheldt tidal system when dealing with silica dynamics, as well as the importance of including BSi when investigating estuarine silica retention.  相似文献   

16.
The present study investigated the spatial and vertical distribution of organic carbon (OC), total nitrogen (TN), total phosphorus (TP) and biogenic silica (BSi) in the sedimentary environments of Asia’s largest brackish water lagoon. Surface and core sediments were collected from various locations of the Chilika lagoon and were analysed for grain-size distribution and major elements in order to understand their distribution and sources. Sand is the dominant fraction followed by silt + clay. Primary production within the lagoon, terrestrial input from river discharge and anthropogenic activities in the vicinity of the lagoon control the distribution of OC, TN, TP and BSi in the surface as well as in the core sediments. Low C/N ratios in the surface sediments (3.49–3.41) and cores (4–11.86) suggest that phytoplankton and macroalgae may be major contributors of organic matter (OM) in the lagoon. BSi is mainly associated with the mud fraction. Core C5 from Balugaon region shows the highest concentration of OC ranging from 0.58–2.34%, especially in the upper 30 cm, due to direct discharge of large amounts of untreated sewage into the lagoon. The study highlights that Chilika is a dynamic ecosystem with a large contribution of OM by autochthonous sources with some input from anthropogenic sources as well.  相似文献   

17.
李建  王汝建 《地质学报》2004,78(2):228-233
通过南海北部ODP 1144站蛋白石含量测定及其堆积速率的计算,并结合氧同位素记录等相关资料,获得南海北部1050ka以来高分辨率的表层古生产力变化与冰期旋回和东亚季风的关系。约900ka以来,蛋白石含量及其堆积速率较900ka以前明显增加,反映了“中更新世革命”事件之后,全球气候变冷,并导致表层生产力的提高。由于第四纪冰期旋回中的冬、夏季风的加强,加上1144站特殊的地理位置,使该站在冰期时表层生产力增加,间冰期时表层生产力降低。浮游有孔虫氧同位素记录与蛋白石含量及其堆积速率的时间序列频谱分析结果显示,三者均出现了相对应的偏心率周期、斜率周期和岁差周期,说明该站表层生产力的变化主要受地球轨道周期的驱动。  相似文献   

18.
Past changes in phytoplankton assemblages in Lake Baikal over the last 4.5 Ma, both in population and composition, are inferred from the downcore profiles of the relatively stable chlorophyll derivatives steryl esters of pyropheophorbides a and b (steryl chlorine esters; SCEs) in the 0–200 m section of the BDP-98 drill core, supplemented by the data on biogenic silica (BSi) and total organic carbon (TOC) contents. SCEs-a and -b dominate among sedimentary chlorophyll derivatives in the BDP-98 sediments except for the upper few meters, indicating their high stability during diagenetic alteration of sediments. The depth (age) profiles of SCEs-a are consistent with BSi and TOC profiles and are interpreted as reflecting primary productivity of the lake in the past. Baikal proxies reveal close correlation with marine oxygen isotope records (MIS stratigraphy). These observations confirm that climate change in the northern hemisphere has been a primary factor controlling the total phytoplankton productivity in Lake Baikal during the last several million years.Among SCEs-a, C30 (dinostanol)-SCE-a, a marker of dinoflagellates was identified by GC–MS analysis. SCE-b, a marker of green algae, was identified by its UV–vis spectrum. The ratio of C30-SCE-a to total SCEs-a (TSCEs-a) was higher during 4.5–4.2 and 1.7–1.3 Ma, suggesting that dinoflagellates proliferated preferentially in those periods. The early Pleistocene maximum of this ratio corresponds to the broad minimum of diatom abundance previously suggested to have recorded a prolonged regional cooling. An abrupt increase in the SCE-b/TSCEs-a ratio was observed at 2.5–2.6 Ma, indicating that green algae containing chlorophyll b have proliferated in Lake Baikal during this period. This interval has also been suggested to contain evidence for a significant regional cooling based on minima of diatom abundance and BSi in sediments. The depth profile of C27Δ5 (cholesterol)-SCE-a relative to TSCEs-a showed a trend similar to that of BSi, suggesting that C27Δ5-SCE-a/TSCEs-a ratio is a potential marker of diatoms in Lake Baikal.Certain mismatches between the Lake Baikal profiles of biological indicators and the marine oxygen isotope records, as well as the slight temporal offsets between different Lake Baikal biological marker signals suggest that the regional component of climatic and/or lacustrine environmental changes also have played a role in determining the composition of the Lake Baikal Plio-Pleistocene phytoplankton assemblage.  相似文献   

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