A probabilistic analysis was performed on soil arsenic concentration data from 4 brownfield sites at Beijing （Chaoyang and Haidian Districts）, involved in environmental assessment studies. The available data sets we...A probabilistic analysis was performed on soil arsenic concentration data from 4 brownfield sites at Beijing （Chaoyang and Haidian Districts）, involved in environmental assessment studies. The available data sets were processed to provide a statistical characterization of the background populations and differentiate ＂anomalous data＂ from the natural range of variation of arsenic concentrations in soil. The site-specific background distributions and the existing wide-scale background values defined for the Beijing area were compared, discussing related implications for the definition of metal contamination soil screening levels （SSLs） in site assess- ment studies. The statistical analysis of As data sets discriminated site-specific background populations, encompassing 88% to 94% of the sample data, from oufliers values, associated with either subsoil natural enrichments or possible anthropogenic releases. Upper Baseline Concentration （UBC） limits （＋ 2σ level）, including most of the site-specific metal background variability, were derived based on the statistical characterization of the background populations. Sites in the Chaoyang South District area had UBC values in the range 10.4-12.6mg·kg^-1. These ranges provide meaningful SSL values to be adopted for As in local site assessment studies. Using the wide-scale background value for the Beijing area would have erroneously classified most of the areas in the subject sites as potentially contaminated.展开更多
A 2-D vertical dynamic near-field numerical model is developed for the simulation of a vertical jet discharging into tidal flows. This model is a k-εturbulent model. The semi-implicit method for pressure-linked equat...A 2-D vertical dynamic near-field numerical model is developed for the simulation of a vertical jet discharging into tidal flows. This model is a k-εturbulent model. The semi-implicit method for pressure-linked equations is used to solve all the governing equations, which are discretized by control volume method. The model has been tested by water channel experiments. On this basis, the designed hydrological condition for one plan of wastewater of the Dachang district discharging into the Changjiang River has been obtained by this model.展开更多
文摘A probabilistic analysis was performed on soil arsenic concentration data from 4 brownfield sites at Beijing （Chaoyang and Haidian Districts）, involved in environmental assessment studies. The available data sets were processed to provide a statistical characterization of the background populations and differentiate ＂anomalous data＂ from the natural range of variation of arsenic concentrations in soil. The site-specific background distributions and the existing wide-scale background values defined for the Beijing area were compared, discussing related implications for the definition of metal contamination soil screening levels （SSLs） in site assess- ment studies. The statistical analysis of As data sets discriminated site-specific background populations, encompassing 88% to 94% of the sample data, from oufliers values, associated with either subsoil natural enrichments or possible anthropogenic releases. Upper Baseline Concentration （UBC） limits （＋ 2σ level）, including most of the site-specific metal background variability, were derived based on the statistical characterization of the background populations. Sites in the Chaoyang South District area had UBC values in the range 10.4-12.6mg·kg^-1. These ranges provide meaningful SSL values to be adopted for As in local site assessment studies. Using the wide-scale background value for the Beijing area would have erroneously classified most of the areas in the subject sites as potentially contaminated.
文摘A 2-D vertical dynamic near-field numerical model is developed for the simulation of a vertical jet discharging into tidal flows. This model is a k-εturbulent model. The semi-implicit method for pressure-linked equations is used to solve all the governing equations, which are discretized by control volume method. The model has been tested by water channel experiments. On this basis, the designed hydrological condition for one plan of wastewater of the Dachang district discharging into the Changjiang River has been obtained by this model.
