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Understanding the mechanisms of bacterial transport in aquifers is important in developing bioremediation strategies. Collision efficiency (alpha) is one important parameter used in modeling bacterial transport. This study was undertaken to measure change in alpha with distance by performing a bacterial transport experiment in Oyster, Virginia. Following injection of a bacterium, Comamonas sp., into a well, water samples were collected at various distances along the flowpath and injected into columns packed with homogenized South Oyster focus area sediment. Zeta potentials of the bacteria in the samples were measured. Values of alpha were determined at various locations in the field in two ways: based on field breakthrough concentrations at the sampling points and based on column breakthrough concentrations. The alpha values estimated from field breakthrough decreased with distance, whereas those estimated from column breakthrough increased with distance. Bacterial cell surface charge became progressively more negative with distance in the field. We hypothesize that the apparent contradiction between field and column alpha values was caused by differences in the flow of the two systems. Flow in the columns was forced to occur through fine-grained zones of iron and aluminum hydroxide coatings that selectively removed the most negatively charged bacteria. In contrast, in the field, the injected cells did not come into contact with the positively charged coatings because the bulk solution bypassed them due to heterogeneous hydraulic properties. These results suggest that laboratory-based models may underestimate bacterial transport distance in the field. A more realistic approach may be necessary to capture the degree of heterogeneity. 相似文献
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In this note, we present a public domain analytical reactive transport modeling tool (ART3D, version 2.0). The tool is developed in FORTRAN and can be used for solving a system of a set of partial differential equations coupled with a first-order reaction network. ART3D uses a novel analytic solution technique proposed by Clement. The new software includes options for performing Monte Carlo simulations and automated parameter estimation. 相似文献
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Jordi A Ferrer MI Vizoso G Orfila A Basterretxea G Casas B Alvarez A Roig D Garau B Martínez M Fernández V Fornés A Ruiz M Fornós JJ Balaguer P Duarte CM Rodríguez I Alvarez E Onken R Orfila P Tintoré J 《Marine pollution bulletin》2006,53(5-7):361-368
The oil spill from Prestige tanker showed the importance of scientifically based protocols to minimize the impacts on the environment. In this work, we describe a new forecasting system to predict oil spill trajectories and their potential impacts on the coastal zone. The system is formed of three main interconnected modules that address different capabilities: (1) an operational circulation sub-system that includes nested models at different scales, data collection with near-real time assimilation, new tools for initialization or assimilation based on genetic algorithms and feature-oriented strategic sampling; (2) an oil spill coastal sub-system that allows simulation of the trajectories and fate of spilled oil together with evaluation of coastal zone vulnerability using environmental sensitivity indexes; (3) a risk management sub-system for decision support based on GIS technology. The system is applied to the Mediterranean Sea where surface currents are highly variable in space and time, and interactions between local, sub-basin and basin scale increase the non-linear interactions effects which need to be adequately resolved at each one of the intervening scales. Besides the Mediterranean Sea is a complex reduced scale ocean representing a real scientific and technological challenge for operational oceanography and particularly for oil spill response and search and rescue operations. 相似文献
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