A chemical model,based on Pitzer activity coefficient model,is developed with a speciation approach to describe the solubility and chemistry of nesquehonite in concentrated chloride solutions.The chemical equilibrium ...A chemical model,based on Pitzer activity coefficient model,is developed with a speciation approach to describe the solubility and chemistry of nesquehonite in concentrated chloride solutions.The chemical equilibrium constants for nesquehonite and aqueous species,i.e.0 3 MgCO,3 MgHCO,and MgOH +,are precisely calculated as a function of temperature according to the Van't Hoff equation by use of standard Gibbs free energy,standard formation enthalpy and heat capacity.The most recent solubility data are regressed to obtain new Pitzer parameters with good agreement.The predictive ability of the new model is improved significantly in comparison with previous models.The behavior of speciation chemistry for nesquehonite in various chloride media is explained through this modeling work on the basis of the 2 3 Mg /CO bearing species distribution,activity coefficient and pH changes.展开更多
An individual-based model, EcoSim, was employed to investigate if specialized resource use could promote sympatric speciation. Prey individuals in the original version of EcoSim were supplied with a single primary foo...An individual-based model, EcoSim, was employed to investigate if specialized resource use could promote sympatric speciation. Prey individuals in the original version of EcoSim were supplied with a single primary food resource. A dual resource version with different food resources (Food 1 and Food 2) was also developed to create favorable conditions for the emergence of specialized food consumption among prey individuals. The single resource version was used as the control to determine the impact of the presence of multiple food resources on the occurrence of sympatric speciation. Each unit of Food 2 contained a higher amount of energy than Food 1, and Food 1 was more accessible than Food 2. Initially, prey individuals mostly fed on Food 1. How-ever, after the emergence of food specialization, the consumption rate of Food 2 signifi-cantly exceeded the consumption rate of Food 1;although prey individuals more frequently encountered Food 1. While sympatric speciation was observed in the dual resource version runs, we could not identify any sympatric species in the single resource version runs. Machine learning techniques were also employed to identify the most influential initial conditions leading to sympatric speciation. According to the obtained results, in most lineages sympatric speciation occurred at the beginning of the food specialization pro-cess. When the lineage had a high special diversity, the lineage needed two different criteria to diverge sympatrically: possessing high genetic diversity and a large population size. In support of previous findings, this study demonstrated that the most accurate determination of initial conditions leading to sympatric speciation can be obtained from lineages that are at the beginning of the divergence process. In conclusion, this study indicated that divergent foraging behavior could potentially lead to the sympatric emergence of new species in the absence of geographic isolation.展开更多
The Xingtai piedmont plain in Hebei Province is a representative area in northern China where endemic fluorosis is serious and shallow high-F ground water is distributed. In this paper, the area is selected as a typic...The Xingtai piedmont plain in Hebei Province is a representative area in northern China where endemic fluorosis is serious and shallow high-F ground water is distributed. In this paper, the area is selected as a typical study area, and on the basis of large amounts of field work and the experiments, through groundwater geochemical modelling and by applying the theory and method of the coupled model of hydrodynamic transport and chemical reactions in a multicomponent system, the author performed numerical modelling of the geochemical behaviour of fluoride in a shallow groundwater system, quantitatively studied the hydrodynamic transport and chemical reaction of fluorine migration, transformation and concentration in a water-heterogeneous unsaturated soil system under the conditions of meteoric water infiltration and quantitatively determined the speciation of fluorine and the saturation state and dissolution/precipitation trend of various solid precipitates in shallow high-F groundwater, thus deepening the understanding of the geochemical behavious of fluorine in shallow groundwater and revealing the essence of some environmental problems at a higher level.展开更多
利用CMAQ-Hg（Community Multi-scale Air Quality-Mercury）模式模拟了我国燃煤排放的大气汞在我国区域的沉降分布状况，其中气象模式为MM5。模式中包括了三种价态汞（气态元素汞（GEM）、气态活性汞（RGM）和颗粒汞（PHg））的气相、...利用CMAQ-Hg（Community Multi-scale Air Quality-Mercury）模式模拟了我国燃煤排放的大气汞在我国区域的沉降分布状况，其中气象模式为MM5。模式中包括了三种价态汞（气态元素汞（GEM）、气态活性汞（RGM）和颗粒汞（PHg））的气相、液相、非均相化学反应过程以及输送、干湿沉降等物理过程。中国燃煤排放的大气汞中RGM所占比例较高，约为58.4%-66.8%，这导致我国汞沉降量较大。模拟结果表明,在我国的西南地区、华东地区以及京津塘地区燃煤汞的沉降较高，在这些区域的沉降通量高达2-6μg m^-2 mon^-1。燃煤大气汞排放形态对汞的沉降有重要影响，减少燃煤汞排放中RGM的比例能够显著降低我国区域汞的沉降通量。展开更多
基金Supported by the National Natural Science Foundation of China (21076212,21076213,21146006)the National Basic Research Program of China (2009CB219904)Key Program in Science and Technology of Qinghai Province (2010-G-A4)
文摘A chemical model,based on Pitzer activity coefficient model,is developed with a speciation approach to describe the solubility and chemistry of nesquehonite in concentrated chloride solutions.The chemical equilibrium constants for nesquehonite and aqueous species,i.e.0 3 MgCO,3 MgHCO,and MgOH +,are precisely calculated as a function of temperature according to the Van't Hoff equation by use of standard Gibbs free energy,standard formation enthalpy and heat capacity.The most recent solubility data are regressed to obtain new Pitzer parameters with good agreement.The predictive ability of the new model is improved significantly in comparison with previous models.The behavior of speciation chemistry for nesquehonite in various chloride media is explained through this modeling work on the basis of the 2 3 Mg /CO bearing species distribution,activity coefficient and pH changes.
文摘An individual-based model, EcoSim, was employed to investigate if specialized resource use could promote sympatric speciation. Prey individuals in the original version of EcoSim were supplied with a single primary food resource. A dual resource version with different food resources (Food 1 and Food 2) was also developed to create favorable conditions for the emergence of specialized food consumption among prey individuals. The single resource version was used as the control to determine the impact of the presence of multiple food resources on the occurrence of sympatric speciation. Each unit of Food 2 contained a higher amount of energy than Food 1, and Food 1 was more accessible than Food 2. Initially, prey individuals mostly fed on Food 1. How-ever, after the emergence of food specialization, the consumption rate of Food 2 signifi-cantly exceeded the consumption rate of Food 1;although prey individuals more frequently encountered Food 1. While sympatric speciation was observed in the dual resource version runs, we could not identify any sympatric species in the single resource version runs. Machine learning techniques were also employed to identify the most influential initial conditions leading to sympatric speciation. According to the obtained results, in most lineages sympatric speciation occurred at the beginning of the food specialization pro-cess. When the lineage had a high special diversity, the lineage needed two different criteria to diverge sympatrically: possessing high genetic diversity and a large population size. In support of previous findings, this study demonstrated that the most accurate determination of initial conditions leading to sympatric speciation can be obtained from lineages that are at the beginning of the divergence process. In conclusion, this study indicated that divergent foraging behavior could potentially lead to the sympatric emergence of new species in the absence of geographic isolation.
基金China National Natural Science Foundation Grant No. 49232040the grant of the State Eightth Five- Year Plan key project "Applications of Geochemistry of Agriculture and Life Science"
文摘The Xingtai piedmont plain in Hebei Province is a representative area in northern China where endemic fluorosis is serious and shallow high-F ground water is distributed. In this paper, the area is selected as a typical study area, and on the basis of large amounts of field work and the experiments, through groundwater geochemical modelling and by applying the theory and method of the coupled model of hydrodynamic transport and chemical reactions in a multicomponent system, the author performed numerical modelling of the geochemical behaviour of fluoride in a shallow groundwater system, quantitatively studied the hydrodynamic transport and chemical reaction of fluorine migration, transformation and concentration in a water-heterogeneous unsaturated soil system under the conditions of meteoric water infiltration and quantitatively determined the speciation of fluorine and the saturation state and dissolution/precipitation trend of various solid precipitates in shallow high-F groundwater, thus deepening the understanding of the geochemical behavious of fluorine in shallow groundwater and revealing the essence of some environmental problems at a higher level.
