Diuron is frequently detected in surface- and groundwater under the vineyards, where organic amendments are often used, in Burgundy of France. Undisturbed column experiments were conducted to study the influence of th...Diuron is frequently detected in surface- and groundwater under the vineyards, where organic amendments are often used, in Burgundy of France. Undisturbed column experiments were conducted to study the influence of three composted organic amendments on diuron leaching through columns of two vineyard soils from Vosne-Roman′ee(VR, calcareous Cambisol) and Beaujolais(Bj, sandy Leptosol), France. Bromide(used as non-reactive tracer) and diuron breakthrough curves(BTCs) were analyzed using convectivedispersive equation(CDE), two-region(mobile-immobile, MIM) and two-site models. No influence of the composts was observed on the bromide recovery rates. The CDE model described well the bromide BTCs for all columns of the Bj soil and seven of the VR soil, suggesting a homogeneous water flow. However, for five VR soil columns, the MIM model fitted better, suggesting a partition of the water flow(15%–50% of matrix flow). The texture, the coarse material content and the tillage of the VR soil could explain this heterogeneity. However, for all columns, diuron leaching was greater through the Bj soil(46%–68%) than the VR soil(28%–39%). The compost addition resulted in a contrasting effect on diuron leaching: no difference or a decrease was observed for the VR soil, probably due to an increase of adsorption sites, whereas no difference or an increase was observed for the Bj soil possibly because of interactions and/or competition of diuron with the compost water-extractable organic matter which could facilitate its transport. All the diuron BTCs were best described using the two-site model, suggesting a large proportion of time-dependent sorption sites(30%–50%). The soil type and the nature of the amendments had contrasting influences on diuron transport. Composts with a high water-soluble fraction must be avoided in sandy soils to reduce the risk of groundwater contamination.展开更多
In this paper, a nonlinear mathematical model is proposed and analyzed to study the role of dissolved oxygen （DO）-dependent bacteria on biodegradation of one or two organic pollutant（s） in a water body. In the cas...In this paper, a nonlinear mathematical model is proposed and analyzed to study the role of dissolved oxygen （DO）-dependent bacteria on biodegradation of one or two organic pollutant（s） in a water body. In the case of two organic pollutant（s）, it is assumed that the one is fast degrading and the other is slow degrading and both are discharged into the water body from outside with constant rates. The density of bacteria is assumed to follow logistic model and its growth increases due to biodegradation of one or two organic pollutant（s） as well as with the increase in the concentration of DO. The model is analyzed using the stability theory of differential equations and by simulation. The model analysis shows that the concentration（s） of one or both organic pollutant（s） decrease（s） as the density of bacteria increases. It is noted that for very large density of bacteria, the organic pollutant（s） may be removed ahnost completely from the water body. It is found that simulation analysis confirms the analytical results. The results obtained in this paper are in line with the experimental observations published in literature.展开更多
文摘Diuron is frequently detected in surface- and groundwater under the vineyards, where organic amendments are often used, in Burgundy of France. Undisturbed column experiments were conducted to study the influence of three composted organic amendments on diuron leaching through columns of two vineyard soils from Vosne-Roman′ee(VR, calcareous Cambisol) and Beaujolais(Bj, sandy Leptosol), France. Bromide(used as non-reactive tracer) and diuron breakthrough curves(BTCs) were analyzed using convectivedispersive equation(CDE), two-region(mobile-immobile, MIM) and two-site models. No influence of the composts was observed on the bromide recovery rates. The CDE model described well the bromide BTCs for all columns of the Bj soil and seven of the VR soil, suggesting a homogeneous water flow. However, for five VR soil columns, the MIM model fitted better, suggesting a partition of the water flow(15%–50% of matrix flow). The texture, the coarse material content and the tillage of the VR soil could explain this heterogeneity. However, for all columns, diuron leaching was greater through the Bj soil(46%–68%) than the VR soil(28%–39%). The compost addition resulted in a contrasting effect on diuron leaching: no difference or a decrease was observed for the VR soil, probably due to an increase of adsorption sites, whereas no difference or an increase was observed for the Bj soil possibly because of interactions and/or competition of diuron with the compost water-extractable organic matter which could facilitate its transport. All the diuron BTCs were best described using the two-site model, suggesting a large proportion of time-dependent sorption sites(30%–50%). The soil type and the nature of the amendments had contrasting influences on diuron transport. Composts with a high water-soluble fraction must be avoided in sandy soils to reduce the risk of groundwater contamination.
文摘In this paper, a nonlinear mathematical model is proposed and analyzed to study the role of dissolved oxygen （DO）-dependent bacteria on biodegradation of one or two organic pollutant（s） in a water body. In the case of two organic pollutant（s）, it is assumed that the one is fast degrading and the other is slow degrading and both are discharged into the water body from outside with constant rates. The density of bacteria is assumed to follow logistic model and its growth increases due to biodegradation of one or two organic pollutant（s） as well as with the increase in the concentration of DO. The model is analyzed using the stability theory of differential equations and by simulation. The model analysis shows that the concentration（s） of one or both organic pollutant（s） decrease（s） as the density of bacteria increases. It is noted that for very large density of bacteria, the organic pollutant（s） may be removed ahnost completely from the water body. It is found that simulation analysis confirms the analytical results. The results obtained in this paper are in line with the experimental observations published in literature.
