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Yong-Jun Tang Ze-Min Xu Zhen-Chen Shao Zhe Ren Kun Wang Kui Yang Jun-Yao Luo Hai-Yan Gao Lin Tian 《地球表面变化过程与地形》2020,45(4):999-1012
Debris-flow runout is a fascinating process to understand due to its implications for downstream alluvial fans. Based on the propagation-deposition behaviors of the Dongyuege (DYG) debris flow, in Yunnan, the effect of biofilms on channel surfaces on debris-flow runout is investigated in laboratory flumes with two different internal surfaces: surfaces are lined with granite slabs (Model I) and gravel (Model II), respectively. Our results show that biofilms can significantly reduce frictional resistance to flows. They increase flow velocities, slow down the deceleration of the snouts, prolong runout distances, and subsequently extend the areas covered with resulting deposits, thus greatly assisting the propagation of experimental debris flows. Slippery biofilms consisting mainly of diatoms and their extracellular mucus (ECM) reduce the contact friction between the flume-beds and the overlying fluids, and greatly promote the propagation of tested flows. Well-developed biofilms are found on the underwater channel surfaces of the DYG Creek. Acting as lubricating layers, they likely played a key role in the DYG debris-flow runout. Most of the debris transported during the DYG event was deposited on overbanks, and the sediment that caused the disaster was transported to the populated fan region through the stream-bed clad in the thick biofilms. Owing to their impacts on the development and width of the temporary debris dam breach, the stream-bed covered with biofilms became a direct contributor to the debris-flow hazard. Because of the ubiquitous presence of biofilms on mountain stream-bed surfaces, the development of perennial streamflows can be viewed as an indicator of gully susceptibility to debris flows threatening creek fans. The underwater areas of pre-event channel cross-sections should be regarded as slip or low-friction boundaries, and the parts above stream-levels can be viewed as no-slip boundaries. © 2019 John Wiley & Sons, Ltd. 相似文献
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多样化的产出环境和30×108年的分布历史表明,鲕粒成因一直是一个谜一样的沉积学难题,争论的关键问题是其究竟是有机(微生物)成因还是无机成因。来自于华北地台寒武系苗岭统徐庄组鲕粒滩相灰岩顶部的方解石巨鲕表现出同心状、放射-同心状和泥晶质的沉积组构,在鲕粒核心和鲕粒皮层中保存着精美的葛万菌(Girvanella)化石所主导的光合作用生物膜的钙化作用残余物,这为研究鲕粒形成与光合作用生物膜之间复杂的成因联系提供了一个较为直接的微生物证据,因为葛万菌可相对较为肯定地类比于近代的钙化织线菌(Plectonema)丝状蓝细菌化石。所以说,在伴随着后生动物辐射的寒武纪蓝细菌繁盛的方解石海中,尽管形成放射状鲕粒皮层的放射纤维状方解石的沉淀作用机理还没有得到完全彻底的了解,但是这些巨鲕确实表现出光合作用生物膜诱发、滋养并促进了鲕粒形成的直接证据,进一步支持了"鲕粒沉积可以作为一种不同的微生物岩体系新类型"的重要科学理念。 相似文献
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采用池塘中设置生物膜净水栅对比实验的方法,在8口土池开展生物膜"细菌-藻类"协同系统改良池塘养殖水质与沉积物的效果、对苗种培育效果的影响及其相关机理等的研究。结果表明,在142d的养殖期间,处理组比对照组节水减排达65.1%,具有极显著差异(P0.01);处理组水质的p H、总氮和亚硝酸盐氮分别极显著低于对照组3.7%、31.3%和38.7%(P0.01),氨氮、总磷、活性磷和硫化物分别显著低于对照组25.6%、41.6%、37.8%和27.9%(P0.05);弧菌数和藻类密度极显著低于对照组63.1%和51.3%,硅藻相对密度极显著高于对照组93.7%;细菌总数显著高于对照组50.8%,蓝藻相对密度显著低于对照组16.6%;处理组的藻类生物均匀度指数显著高于对照组8.9%;生物膜上的细菌总数高达1.30×109 CFU/g,而弧菌数为零;处理组池塘沉积物的氧化还原电位显著高于对照组30.5%,硫化物浓度显著低于对照组47.0%;草鱼苗种起捕规格、成活率、产量和生长速度分别显著高于对照组24.6%、4.3%、29.8%和28.6%,饲料系数极显著低于对照组15.6%,处理组每公顷池塘培育草鱼大规格鱼种可增加净利润约1.92万元。 相似文献
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自然水体生物膜、悬浮颗粒物和沉积物吸附铅、镉的热力学参数比较 总被引：12，自引：5，他引：7
采用实验室模拟的方法研究了松花江自然水体生物膜、悬浮颗粒物和沉积物吸附铅、镉的热力学规律。根据吸附热力学参数(Γmax、k和Kd)综合比较3种固相物质的吸附能力,并讨论吸附能力存在差异的原因。结果表明:Langmuir型及Freundlich等温式可以很好地描述3种固相物质吸附热力学规律,三者吸附铅、镉的能力为生物膜>悬浮颗粒物>沉积物,生物膜、悬浮颗粒物和沉积物对铅的吸附能力均明显高于对镉的吸附能力。 相似文献
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采用改良的微孔板法测定了12株弧菌的形成生物膜的效果,选择形成生物膜效果最好的副溶血弧菌ND-02,进一步研究了环境因子对其生物膜形成的影响。实验结果显示副溶血弧菌ND-02菌株在静置培养24~36 h后形成成熟的生物膜,在起始菌浓度为107~108CFU/mL形成生物膜的量最大;在30 ℃,NaCl浓度为3%~ 5%,pH偏弱碱性时的生物膜OD590值最大;Ca2+ 促进副溶血弧菌生物膜的形成,而Mg2+ 抑制生物膜的形成;副溶血弧菌在分别经大黄鱼表皮黏液、肠黏液和肝脏提取液包被的的基质上形成生物膜的作用明显,鳃黏液和脾脏提取液中次之,肌肉提取液包被后生物膜形成量最低。以上结果表明,副溶血弧菌ND-02菌株能形成稳定而明显的生物膜,而且生物膜的形成受温度、NaCl浓度、pH值等环境因子的影响。 相似文献
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The colonization features of periphytic diatoms were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using glass slides as an artificial substratum. Samples were collected at a time interval of 1, 3, 7, 10, 14, 21 and 28 d from two depths of 1 and 3 m. The dynamics of diatom colonization process had a similar pattern in community structure and fitted the logistic model in growth curve at both depths. The maximum abundance and the time for reaching 50% maximum abundance （10 d） showed no significant differences （P〉0.05） between two depths 1 and 3 m. Although the diatom communities repre- sented similar taxonomic composition, they differed in the temporal pattern of structural parameters and in succession dynamics of dominant species between the two layers. The species richness showed significantly higher values during the colonization period more than 14 d, while the species diversity and evenness rep- resented a higher variability with significantly different values （P〈0.05） at a depth of 1 m than at a deeper layer. The results suggest that the diatom colonization follows the logistic model growth curve and differs in colonization features between different depths in the coastal waters, and that the sampling strategy at i m is more effective to detect the ecological features for bioassessment in marine ecosystems. 相似文献
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In flowing water the incipient motion of sediment can be affected by the presence of microbial biofilm growth. This article documents a series of flume experiments using non‐uniform sediments, in which sediment entrainment was investigated for cases where the sediment was immersed in deionized water, so that no biofilm developed, and for cases where a bio‐sediment was cultivated by placing the sediment in a mixture of natural water and nutrient solution. Differences in entrainment and the velocity at incipient motion were measured over an eight week period, as biofilm grew. It was found that the incipient motion phenomena were quite distinct between the two kinds of sediment. Sediment with biofilm was more stable and, over time, incipient velocity increased to a threshold level, before declining. Biofilm development is clearly an important control on the stability of sediments, especially in eutrophic water bodies. Two incipient velocity formulas were derived for sliding and rolling conditions. Film water theory was utilized to describe the cohesive force between sediment particles and the adhesive force generated by biofilm was introduced into the formula derivation; the time variation characteristics of biofilm strength and the features of the substrate were also taken into consideration. Such analyses can help to predict sediment transport changes due to biofilm presence in nutrient‐rich water bodies. 相似文献
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Wang Hongmei Ma Xiangru Liu Deng Yang Xiaofen Li Jihong 《Frontiers of Earth Science》2007,1(4):399-404
Understanding the dynamics of organic matter in modern marine water columns greatly favors the geobiological evaluation of
hydrocarbon source rocks. Biolipids could make great contribution to petroleum hydrocarbons due to their comparable chemical
components and the slightly refractory characteristics of biolipids during the microbial/thermal degradation. A variety of
environmental factors such as temperature, CO2 and salinity could affect the biochemical contents in microorganisms. As a result, microorganisms living in a changing environmental
condition might have a different contribution to the petroleum formation. Organic carbon flux is shown to bear a positive
correlation with the primary productivity only within a certain range of biomass volumes in a specific biohabitat. Furthermore,
organic matter is degraded much quickly in a water column with oxic conditions. Therefore, the anoxic condition, along with
the enhanced biological productivity, would be one of the significant factors in the formation of high-quality hydrocarbon
source rocks. The formation of biofilms and microbial mats favors the preservation of sedimentary organic matter by decreasing
the degradation rate of organic matter. Identification of biofilms and microbial mats in sedimentary rocks will thus greatly
help to understand the depositional processes of organic matter finally preserved in hydrocarbon source rocks.
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Translated from Earth Science—Journal of China University of Geosciences, 2007, 32(6): 748–754 [译自: 地球科学—中国地质大学学报 相似文献