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991.
Heavy metal concentrations of Wadi El Natrun saline lakes were investigated. Pb, Zn, Mn, Cu, Cd, Ni, Fe and Al were measured in surficial sediments. The heavy metal concentrations largely indicate the influence of weathering of terrigenous sources on land. In comparison with the average in sedimentary rocks, the concentrations of the heavy metals studied are higher than the global average sandstone. This is also reflected in the high enrichment factors. The heavy metal concentration in lakes II and III decrease in the order Pb > Zn > Cu, while in lake I the decreasing order is Cu > Zn > Pb. Sediments with microbial mats were found to concentrate heavy metals above background sediment values. 相似文献
992.
993.
巨鲕的产出时代多见于新元古代和早三叠世,而寒武纪的巨鲕却鲜见报道。近期,笔者在重庆石柱地区下寒武统天河板组中发现厚约35cm的透镜状巨鲕灰岩。在该层巨鲕灰岩中,巨鲕粒径一般为5~7mm,最大可达9mm,约占岩石组分的55%,与大量强烈重结晶的正常鲕粒伴生。钙质生物壳体较常见,颗粒间见亮晶方解石胶结物。研究区巨鲕最外圈纹层上常见蓝细菌化石,形成发育不完全的突起状“夭折的纹层”;巨鲕内的暗色纹层中亦见杂乱交错的、有一定重结晶的蓝细菌等微生物化石。故推测其为微生物成因形成的,且早寒武世频繁的强风暴背景和蓝细菌等微生物的积极参与是该层巨鲕形成的必备条件。 相似文献
994.
太湖北部隐藻生物量时空动态 总被引:11,自引:1,他引:10
利用2005-2009年每月一次的监测资料,对太湖竺山湾、梅梁湾和贡湖湾理化因子和浮游植物,特别是隐藻生物量周年季节变化进行比较研究,探讨环境因子以及蓝藻变化对隐藻生物量的影响.结果显示,竺山湾内隐藻平均生物量(1.89 mg/L)高于梅梁湾(0.87 mg/L)、贡湖湾(0.43 mg/L).2008-2009年隐藻平均生物量(2.12 mg/L)高于2005-2007年平均生物量(0.28 mg/L).通过与环境冈子的时空差异比较分析,竺山湾内高营养盐浓度、高有机质浓度和高悬浮质浓度使得隐藻更具有竞争优势,而贡湖湾内浮游动物的摄食作用可能限制了隐藻生物量.同时,太湖隐藻与蓝藻的竞争演替趋势明显,春夏季高温和蓝藻的过度繁盛可能对隐藻的生长产生抑制作用. 相似文献
995.
Quantitative distribution of planktonic amphipoda in the East China Sea is analyzed and the relation with environmental factors and mackerel and scad fishing grounds is studied. The result shows that the characteristic of biomass is great seasonal and interannual variety during the passing three decades. The distribution of planktonic amphipoda basically reflects the movement, decay and intensification of the different water systems in the survey area. 相似文献
996.
On the basis of the data of oceanographic survey in the East China Sea in four seasons during 1997~2000 (23°30′~33°00′N,118°30′~ 128°E), the variation of total biomass and diet biomass of zooplankton and their spatial-temporal distribution and relationship with the fishing ground of Engraulis japonicus are approached and analyzed. The results show that the average biomass is 65.32 mg/m3 in four seasons, autumn (86.18 mg/m3) being greater than summer (69.18 mg/m3) greater than spring (55.67 mg/m3) greater than winter (50.33 mg/m3). The average value of diet zooplankton hiomass is 40.9 mg/m3.The trends of horizontal distribution both in the total biomass and the diet biomass of zooplankton are similar. The high biomass region (250~500 mg/m3) is very limited, only accounting for 1% of the investigation area. Seasonal variation of the biomass is very remarkable in the west and north parts of East China Sea coastal waters (29°30'N,125°E). The horizontal distribution of diet zooplankton depends on the abundance distribution of crustacean. The distribution of diet zooplankton is related to the fishing ground of Engraulis japonicus and the high-density area of young fish and larval. In spring, the central fishing ground of Engraulis japonicus (>100 kg/h) and the high-density area of young fish and larval (>100 individuals per net) are located at the same place of high-density (100~250 mg/m3)area of diet zooplankton in the middle-southern part of East China Sea or the edge of its waters. 相似文献
997.
998.
999.
土壤中特异性微生物与重金属相互作用机制与应用研究进展 总被引:1,自引:2,他引:1
随着经济的发展,矿产资源的开采和利用程度越来越高,一方面发现有地表露头矿床的几率越来越小,另一方面其造成的重金属污染严重危害环境和人类健康。自然界中的微生物与扩散到环境中的重金属会产生相互作用,具有这种特异性的细菌既可应用于指示隐伏金属矿床,亦可应用于重金属污染生物修复。本文从特异性微生物与重金属相互作用微观机制、微生物找矿、重金属污染土壤的微生物修复三个方面,对其研究现状和进展进行了评述,重点对特异性微生物与重金属离子发生的吸附、累积与转化过程,微生物改变重金属元素分布、赋存状态和毒性作用机理,蜡样芽孢杆菌(Bacillus cereus)与金的作用机制及其在寻找隐伏金矿的应用潜力,特异性微生物通过代谢产物吸附去除土壤中重金属元素及其辅助植物修复重金属污染等方面进行了介绍和阐述。 相似文献
1000.
Establishing a precise chorology is a critical issue when employing cold-water coral as paleoenvironmental archives. Currently, U-Th, 14C and 210Pb dating techniques are the most frequently used methods. The high-magnesium calcite skeleton of bamboo coral has clear growth bands, which is appropriate for 14C and 210Pb dating methods and holds a great potential to be high-resolution archives of mid-to-deep ocean evolution. Aragonitic stony coral is appropriate for both U-Th and 14C dating methods, which is valuable in paleoceanographic research. Because the U-Th method can provide the absolute chronology of coral samples, it can further be used to calculate the 14C age of ocean carbon reservoirs. Therefore, U-Th and 14C dating results of stony coral are currently the most reliable data for exploring the evolution of ocean carbon reservoirs through the Last Glacial Maximum to the present. It has been found that the 14C ventilation ages of intermediate water masses of the equatorial Atlantic and Southern Ocean significantly decreased at the end of the Heinrich Stadial 1. This suggests a massive carbon transfer from deep oceans to the atmosphere, or the Atlantic intermediate depths were ventilated by the southern- and the northern-sourced water masses, respectively, before and after the Heinrich Stadial 1. 相似文献