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"Sedimentation and deposition."
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Contributions to Modern and Ancient Tidal Sedimentology
Tidal deposits have been a specific research topic for about 40 years, and whilst this has resulted in a proliferation of papers in scientific journals, there have only been a few book-length syntheses. Over the years, tidal sedimentology has been reinforced by fluid mechanics and numerical modelling but has remained rooted in facies and stratigraphic studies. Recent developments in tidal sedimentology lean toward a more quantitative assessment of the imprint of tides in the facies record of intertidal and shallow subtidal areas. They highlight the increasing relevance of tidal deposits studies, from high resolution subsurface reservoir geology to climate change and sea-level rise. This volume gathers 17 contributions to the Tidalites 2012 congress held in Caen, France. It reflects current advances in the sedimentology and stratigraphy of tidal deposits, in both ancient and modern environments. It shows the current diversity of this field of research, through a wide spectrum of methods including remote sensing, in-situ hydrodynamical measurements, and ichnology, in addition to classic field studies and petrography.
eBook
A 3D Monte Carlo Simulation for Aerosol Deposition onto Horizontal Surfaces by Combined Mechanisms of Brownian Diffusion and Gravity Sedimentation
A three-dimensional Monte Carlo model was developed to simulate the deposition of aerosol particles onto horizontal solid surfaces. The random walk method was employed to solve the particle transport equation, which allowed obtaining the trajectory of particle motion by a combined mechanism of Brownian diffusion and gravity sedimentation. The particle transport mechanism was described in terms of a Peclet number (Pe). The local structures of the dust layer, the relationship between the structure of the dust layer and particle transport mechanisms, and the number of the particles attached to the solid surface were investigated. The results showed that for a small Pe, when Brownian diffusion was a controlling mechanism for aerosol transport, the dust layer might exhibit a more open and looser structure, while for a large Pe, the dust layer was dense and tight. The differences of deposition morphologies under different transport mechanisms were caused by the different random intensities of particle motion. There was an upper limit of the maximum number of particles attached to the surface, and it strongly depended on particle transport mechanisms and size distributions. Additionally, the deposit morphologies obtained with the 3D Monte Carlo model were in good agreement with the experimental results found in the literature.
Journal Article
Optimization of sequencing batch reactor for wastewater treatment using chemically enhanced primary treatment as a pre-treatment
The sequencing batch reactor (SBR) is a wastewater treatment option feasible for low flows. The objective of this research was to optimize SBR by varying its operational parameters, viz. (i) settling time and (ii) reaction time. The study was conducted in two phases. In Phase 1, raw wastewater was fed into the SBR after conventional settling, while in Phase 2 raw wastewater was fed into the SBR after coagulation-flocculation-sedimentation. A bench-scale model was set up and domestic wastewater was used for this study. Performance of the treatment system was evaluated through 5-day biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS). The results demonstrated that reaction time was reduced to 4 h in Phase 2 compared to 10 h in Phase 1. The BOD, COD and TSS removal efficiencies observed in Phase 1 were 80%, 80% and 73%, respectively, and for Phase 2 the removal efficiencies were 74%, 75% and 80% respectively. National Environmental Quality Standards (NEQS) were met in both cases and the treatment cost per cubic metre of wastewater for Phase 2 was 2.5 times lower compared to Phase 1.
Journal Article
Soil and human security in the 21st century
Global soil resources under stressThe future of humanity is intertwined with the future of Earth's soil resources. Soil provides for agriculture, improves water quality, and buffers greenhouse gases in the atmosphere. Yet human activities, including agricultural soil erosion, are rapidly degrading soil faster than it is naturally replenished. At this rate, human security over the next century will be severely threatened by unsustainable soil management practices. Amundson et al. review recent advances in understanding global soil resources, including how carbon stored in soil responds to anthropogenic warming. Translating this knowledge into practice is the biggest challenge remaining.Science, this issue 10.1126/science.1261071 Human security has and will continue to rely on Earth's diverse soil resources. Yet we have now exploited the planet's most productive soils. Soil erosion greatly exceeds rates of production in many agricultural regions. Nitrogen produced by fossil fuel and geological reservoirs of other fertilizers are headed toward possible scarcity, increased cost, and/or geopolitical conflict. Climate change is accelerating the microbial release of greenhouse gases from soil organic matter and will likely play a large role in our near-term climate future. In this Review, we highlight challenges facing Earth's soil resources in the coming century. The direct and indirect response of soils to past and future human activities will play a major role in human prosperity and survival.
Journal Article
Significant depositional changes offshore the Nile Delta in late third millennium BCE: relevance for Egyptology
No environmental factor has been as critically important for Egypt's ancient society through time as sufficiently high annual flood levels of the Nile River, the country's major source of fresh water. However, interpretation of core analysis shows reduced depositional accumulation rates and altered compositional attributes of the sediment facies deposited seaward of the Nile Delta during a relatively brief period in the late third millennium BCE. These changes record the effects of displaced climatic belts, decreased rainfall, lower Nile flows, and modified oceanographic conditions offshore in the Levantine Basin, primarily from 2300 to 2000 BCE, taking place at the same time as important geological changes identified by study of cores collected in the Nile Delta. It turns out that integrated multi-disciplinary Earth science and archaeological approaches at dated sites serve to further determine when and how such significant changing environmental events had negative effects in both offshore and landward areas. This study indicates these major climatically induced effects prevailed concurrently offshore and in Nile Delta sites and at about the time Egypt abandoned the Old Kingdom's former political system and also experienced fragmentation of its centralized state. In response, the country's population would have experienced diminished agricultural production leading to altered societal, political, and economic pressures during the late Old Kingdom to First Intermediate Period at ca. 2200 to 2050 BCE.
Journal Article