Sulphur cycling in organic-rich marine sediments from a Scottish fjord   总被引：1，自引：0，他引：1  

SIMON H. BOTTRELL  ROBERT J.G. MORTIMER  IAN M. DAVIES†  S. MARTYN HARVEY‡  MICHAEL D. KROM 《Sedimentology》2009,56(4):1159-1173

In this study, the biogeochemical transformations of sulphur in organic‐rich marine sediments in a Scottish fjord are investigated by a combination of pore water and sediment geochemistry with sulphide diffusive gradient thin‐film probes and sulphate isotopic data (δ³⁴S and δ¹⁸O). Particular attention is paid to sulphur cycling in the upper sediment profile where sulphate reduction occurs but free sulphide is below the detection limits of conventional pore water geochemical analysis but quantifiable by sulphide diffusive gradient thin film. In the uppermost part of the sediment core, δ¹⁸O sulphate decreased from near‐sea water values to +7‰, indicating that anoxic sulphide oxidation dominated during this interval. Sulphate δ³⁴S remained unchanged as there was no net sulphate reduction (i.e. reduction was balanced by re‐oxidation). Below 4 cm depth, there was a slight increase in sulphate δ³⁴S from 20‰ to 23‰ associated with minor accumulation of iron sulphide. The δ¹⁸O of the sulphate also increased, to around +10‰ at 10 cm depth, as a result of the isotopic exchange of sulphate–oxygen with pore water and/or sulphur disproportionation reactions mediated during sulphur cycling. These processes continued to increase the δ¹⁸O of the sulphate to 14‰ at 20 cm depth with no further change in the δ³⁴S of the sulphate. Below 20 cm depth, free sulphide is detectable in pore waters and both the δ³⁴S of the sulphate and sulphide increase with depth with an offset controlled by kinetic fractionation during bacterial sulphate reduction. The δ³⁴S of the sedimentary organic fraction shifted towards lower, more bacteriogenic, values with depth in the profile, without any increase in the size of this sulphur pool. Thus, the organic sulphur fraction was open to interaction with bacteriogenic sulphide without the occurrence of net addition. Therefore, caution should be exercised when using sulphur isotopic compositions to infer simple net addition of bacteriogenic sulphide to the organic sulphur fraction.  相似文献   

喀斯特生态系统生物地球化学过程与物质循环研究:重要性、现状与趋势   总被引：9，自引：0，他引：9       下载免费PDF全文

刘丛强  郎赟超  李思亮  朴何春  涂成龙  刘涛泽  张伟  朱书法 《地学前缘》2009,16(6):1

喀斯特地质与生态系统是地球表层系统中的重要组成部分,其变化将对其他地区以及整个地球系统产生影响.生物地球化学循环是全球和区域变化研究的核心内容,而生态系统的演化与系统内水分和养分的生物地球化学循环密切相关。因此,我们有必要将喀斯特生态系统纳入到更大区域或全球生态系统中进行分析研究,在充分研究认识整个喀斯特生态系统物质生物地球化学循环规律的基础上,进一步研究喀斯特生态系统的全球变化响应或影响机制,为喀斯特生态系统优化调控对策和措施提供科学基础。研究生态系统演化过程中物质的生物地球化学循环规律,是研究植物适生性、物种优化配置和适应性生态系统调控机理的关键基础。在介绍前人工作基础的同时,本文全面而概括地总结了我们近年利用元素、同位素(如δ13C、δ15N、δ34S、87Sr/86Sr)示踪和化学计量学理论和方法对喀斯特生态系统中不同界面和流域中物质的生物地球化学循环及其生态环境效应的研究成果。认识到:喀斯特流域生物地球化学循环活跃,相互耦合,并与流域生态环境变化相互制约;人类活动正干预流域物质的自然生物地球化学循环过程,并导致相应的生态和环境效应;全球变化科学深化有赖于区域生态环境变化及物质生物地球化学循环的研究。这些认识是我们将来系统深入开展喀斯特以及其他流域生态系统物质生物地球化学循环研究的重要方向。  相似文献   

Cr(Ⅵ)抗性菌株的筛选及其Cr(Ⅵ)去除特性研究   总被引：3，自引：0，他引：3  

吴淼  汤岳琴  于萍  周元祥  吴晓磊 《岩石矿物学杂志》2009,28(6):520-526

采用微生物分离纯化方法,从制革厂含铬污泥中筛选分离Cr (Ⅵ)抗性菌株,并研究菌株对Cr(Ⅵ)的去除能力.共分离得到对50 mg/L Cr(Ⅵ)去除率大于50%的菌株20株,16S rRNA基因测序结果表明这些细菌主要属于Acinetobacter、 Microbacterium、Leucobacter、Ochrobactrum和Brachymonas属.对其中7株细菌,考察了菌株生长期、pH值和Cr(Ⅵ)浓度对菌株去除Cr(Ⅵ)效果的影响,结果表明,细胞在有较高代谢活性的条件下具较高的Cr(Ⅵ)去除能力;pH值对菌株去除Cr(Ⅵ)的能力具有显著影响,在50 mg/L Cr(Ⅵ)、pH值为7～8的条件下,Microbacterium属16号和21号菌株在36 h时对Cr (Ⅵ)的去除率达80%～95%;高浓度的Cr(Ⅵ)抑制菌株对Cr(Ⅵ)的去除能力,其中21号菌株在110 mg/L的Cr(Ⅵ)浓度下去除效果最佳,Cr(Ⅵ)去除率达80%.  相似文献   

Variations of Microbial Communities and the Contents and Isotopic Compositions of Total Organic Carbon and Total Nitrogen in Soil Samples during Their Preservation   总被引：1，自引：0，他引：1  

TAO Qianye  LI Yumei  WANG Guo’an  QIAO Yuhui  LIU Tung-Sheng 《《地质学报》英文版》2009,83(1):114-120

Semi-sealed preservation of soil samples at different moisture of 4% and 23%, respectively, was simulated to observe the variations of soil microbial communities and determine the contents and isotopic compositions of the total organic carbon and total nitrogen on the 7th and 30th day, respectively. The results show that during preservation, the quantity of microbial communities tended to increase first and then decrease, with a wider variation range at higher moisture (23%). At the moisture content of 23%, the microbial communities became more active on the 7th day, but less after 30 days, and their activity was stable with little fluctuation at the moisture content of 4%. However, there were no significant changes in the contents and isotopic compositions of the total organic carbon and total nitrogen. During preservation, the responses of soil microbes to the environment are more sensitive to changes in the total nitrogen and organic carbon contents. It is thus suggested that the variations of microbial communities have not exerted remarkable impacts on the isotope compositions of the total nitrogen and total organic carbon.  相似文献   

The distribution characteristics of nitrogen and phosphorus in the ecological system of Mt. Beigu wetland     

Yanyou Wu  Pingping Li  Jianchao Hao  Chundu Wu  Weiguo Fu 《中国地球化学学报》2009,28(1):55-60

The Mt. Beigu wetland, which has undergone periodical changes in water level, lies by the Yangtze River, and its dominant plants are Phragmites communis, Phalaris arundinacea and Polygonum lapathifolium. In order to study the distribution characteristics of nitrogen and phosphorus in the ecological system of the Mt. Beigu wetland, the authors measured the contents of total nitrogen and total phosphorus in Phragmites communis, Phalaris arundinacea and Polygonum lapathifolium, and the contents of nitrogen and phosphorus in the wetland soils with different plant species. In addition the authors investigated the influence of various plants on the spatial and seasonal (spring/autumn) distributions of nitrogen and phosphorus in the wetland soil. The contents of nitrogen and phosphoms in Phalaris arundinacea are significantly higher than those of the other two plant species in the same part. Secondary pollution of phosphorus in the wetland results mainly from Phalaris arundinacea. Phragmites com-munis effectively carries away nitrogen and phosphorus in the wetland soil in the wet season. The capacity of Poly-gonum lapathifolium to remove nitrogen is lowest among the 3 species of plants. These findings offer a theoretical foundation for the selection of plant species to restore the ecological environment and for the selection of time and depth for purging silt on the riverside wetland.  相似文献   

Analysis of the influence of free ammonia on the accumulation of nitrite in the nitrite nitrification system     

Chen Wei 《中国地球化学学报》2009,28(4):440-444

Low- and high-concentration nitric wastewater can induce stable nitrite accumulation and realize the nitrification system, with the nitrite accumulation rate between 50% and 90%. In the low-concentration nitrite nitrification system, the average FA concentrations during the period of stable nitrite accumulation remained at 7 to 10 mg/L. In the high-concentration nitrite nitrification system, the nitrogen oxidation activity will not be affected by biomass, the nitrite oxidation activity is related to the system biomass, it is recommended to be measured by FA/MLSS. Keeping the FA sludge load below 0.1 is the precondition of making good nitrite accumulation and nitrogen degradation rate. Nitrite oxidation bacteria cannot be totally eliminated or washed out from the system.  相似文献   

Current and future impacts of ultraviolet radiation on the terrestrial carbon balance     

W. Kolby Smith  Wei Gao  Heidi Steltzer 《Frontiers of Earth Science》2009,3(1):34-41

One of the most documented effects of human activity on our environment is the reduction of stratospheric ozone resulting in an increase of biologically harmful ultraviolet (UV) radiation. In a less predictable manner, UV radiation incident at the surface of the earth is expected to be further modified in the future as a result of altered cloud condition, atmospheric aerosol concentration, and snow cover. Although UV radiation comprises only a small fraction of the total solar radiation that is incident at the earth’s surface, it has the greatest energy per unit wavelength and, thus, the greatest potential to damage the biosphere. Recent investigations have highlighted numerous ways that UV radiation could potentially affect a variety of ecological processes, including nutrient cycling and the terrestrial carbon cycle. The objectives of the following literature review are to summarize and synthesize the available information relevant to the effects of UV radiation and other climate change factors on the terrestrial carbon balance in an effort to highlight current gaps in knowledge and future research directions for UV radiation research.  相似文献   

放牧草地生态系统中氮素的损失和管理   总被引：13，自引：0，他引：13  

李香真  陈佐忠 《气候与环境研究》1997,2(3):241-250

对于大多数放牧草地,Ｎ素都是限制生产力的最重要因素之一,而生态系统中Ｎ素的损失量又很大,Ｎ素以ＮＯ－３、ＮＨ３、Ｎ２Ｏ等形态进入水圈和大气圈,不仅造成了生产上的资源浪费,而且对全球环境和人类健康都产生了深远的影响。本文将对草地生态系统中Ｎ素损失的主要过程（如氮挥发、反硝化和ＮＯ－３淋溶等）及影响因素研究的进展情况进行简要地综述,然后对ＩＭＧＡＲＳＳ项目研究中关于Ｎ素损失研究部分提出一些建议。草地生态系统中Ｎ素损失的主要途径包括：土壤、植物、动物排泄物和肥料的氨挥发;生物和化学反硝化;淋溶;动物体和动物产品对Ｎ素的固持;动植物残体和动物排泄物的燃烧;动物以排泄物形式将Ｎ素从生产区转移到非生产区;通过土壤侵蚀而损失等。放牧加速了草地生态系统中Ｎ素的损失速率。从全球角度分析ＮＨ３的来源后认为,生物残体燃烧是最大的ＮＨ３源,其次是自然土地。对欧洲ＮＨ３来源的研究表明,与人类活动有关的ＮＨ３挥发总量的大部分来源于牲畜排泄物的氨挥发。由于方法的限制,对田间条件下的反硝化测定较少,动物排泄物对Ｎ２Ｏ的贡献及对全球变化影响的研究数据较少。但研究表明,草地尿、粪斑处Ｎ２Ｏ释放速率很高,动物排泄物可能是最重要的Ｎ２Ｏ源。在半干  相似文献   

变换光谱数据对土壤氮素PLSR模型的影响研究     

乔星星  冯美臣  杨武德  孙慧  郭小丽  史超超 《地球信息科学学报》2016,18(8):1123-1132

光谱数据变换对消除背景、噪音影响以及提取光谱特征有重要的作用,是光谱数据分析过程中的必要步骤。为了研究光谱变换处理对土壤氮素PLSR模型的影响精度,并选择最佳光谱变换处理方法,本文对原始光谱数据进行了15种典型光谱变换,通过比较不同变换光谱与土壤氮素的相关性,实现土壤氮素的PLSR精确诊断,并综合评定最佳光谱数据变换方法。结果表明,涉及微分处理后的光谱变换,尤其是先进行开方（T₈、T₁₁）、对数（T₆、T₁₂）等变换后再进行微分处理,可提高其与土壤氮素的相关性。在引入较少因子变量个数的条件下,该方法使因变量解释量达到了98%。综合考虑模型的校正、验证效果及模型复杂度（模型最佳因子变量个数）,可得出光谱平方根的一阶微分变换处理（T₈）为最佳的土壤光谱变换算法。该条件下的土壤氮素的校正模型表现为R²=0.985、RMSE_C=0.000132、F_n=6,验证模型的表现为R²=0.9853、RMSE_V=0.000162,结果表明基于T₈的光谱数据变换可实现本试验条件下土壤氮素的光谱估算。另外,可以考虑将原始光谱的一阶微分（T₉）、对数和对数倒数的一阶微分（T₆、T₇）以及平方根和对数的二阶微分（T₁₁、T₁₂）作为光谱数据变换方法。本文研究结果可为土壤氮素估算和光谱数据预处理提供技术参考。  相似文献   

青藏高原昆仑山垭口不同深度土壤可培养细菌群落特征研究     

张宝贵  刘晓娇  吴青柏  刘光琇  陈拓  张威  章高森  伍修锟  邓友生 《冰川冻土》2016,38(3):776-784

以青藏高原昆仑山垭口不同深度土壤样品为研究对象,研究了可培养细菌数量及多样性。结果表明：可培养细菌数量与多样性在一定程度上均与土壤深度呈负相关关系。可培养细菌数量以表层土壤最多,而细菌多样性最低。基于16S rDNA基因序列分析共发现了6个门,18个属,21种细菌,其中表层土壤Arthrobacter siccitolerans为绝对优势种,比例达95%;冻土区（0~82.15m）之间不同土样Mycetocola miduiensis菌株所占比例较大;而冻土层以下没有明显的优势菌。冗余分析（RDA）显示：可培养细菌数量主要受土壤有机碳影响,土壤含水量则是影响细菌多样性的主要因素。  相似文献