نتایج جستجو برای: noncohesive sediments
تعداد نتایج: 28528 فیلتر نتایج به سال:
Open spaces in epithermal veins of the Bohemia mining district, Oregon, USA, filled with sediments during hydrothermal activity. These sediments consist mainly of chalcedony, rock fragments, and vein quartz fragments. In addition, hematite is deposited during stage three of the vein development. Observed sedimentary features include draping laminae, erosion surfaces, slumping, and graded beddin...
Palygorskite is a widely distributed clay mineral that is commonly found in soils and sediments of arid regions, particularly in the Middle East. This study aimed to determine the distribution of palygorskite in major parent materials of soils developed on central Iranian Tertiary sediments. Based on field observations and geologic maps, 12 geological formations with Tertiary age were sampled a...
Factors affecting the transport and retention of Cd, Cr, Cu, Ni, Pb and Zn in acidic groundwaters as they pass through estuarine sediments were investigated using column experiments. Acidic groundwaters caused the rapid dissolution of iron sulfide (AVS) and other iron and manganese phases from sediments that are important for metal binding and buffering. Metal breakthrough to overlying water oc...
Chromium exists in sediments in two oxidation states: Cr(III), which is relatively insoluble and nontoxic, and Cr(VI), which is much more soluble and toxic. Chromium(VI) is thermodynamically unstable in anoxic sediments, and acid-volatile sulfide (AVS) is formed only in anoxic sediments; therefore sediments with measurable AVS concentrations should not contain toxic Cr(VI). If this hypothesis h...
Microorganisms dominate most Antarctic marine ecosystems, in terms of biomass and taxonomic diversity, and play crucial role in ecosystem functioning due to their high metabolic plasticity. Admiralty Bay is the largest bay on King George Island (South Shetland Islands, Antarctic Peninsula) and a combination of hydro-oceanographic characteristics (bathymetry, sea ice and glacier melting, seasona...
Phosphate release from sediments hampers the remediation of aquatic systems from a eutrophic state. Microbial phosphatases in sediments release phosphorus during organic matter degradation. Despite the important role of phosphatase-expressing bacteria, the identity of these bacteria in sediments is largely unknown. We herein presented a culture-independent method to phylogenetically characteriz...
Fish farm sediments receive a large amount of organic matter from uneaten food and fecal material. This nutrient enrichment, or organic pollution, causes the accumulation of sulphide in the sediment from the action of sulphate-reducing bacteria (SRB). We investigated the effect of organic enrichment around coastal fish farms comparing the SRB community structure in these sediments. Sediment sam...
Water requirements of paddy fields in the Gilan Province are provided for by a large irrigation network including Sepidrud reservoir dam, Tarik diversion dam, Fumanat network, Sangar diversion dam, and Sangar right and left canals. Because of the deposition of sediments in the Sepidrud reservoir, its capacity has been reduced profoundly. To overcome this problem, sediments are flushed in the se...
Phosphate release from sediments hampers the remediation of aquatic systems from a eutrophic state. Microbial phosphatases in sediments release phosphorus during organic matter degradation. Despite the important role of phosphatase-expressing bacteria, the identity of these bacteria in sediments is largely unknown. We herein presented a culture-independent method to phylogenetically characteriz...
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