On the basis of investigations in situ, it was found that mass exchange on the water-sediment interface occurred chiefly on the superficial sediment within 5-10 cm.The spatial physicochemical character of sediment was...On the basis of investigations in situ, it was found that mass exchange on the water-sediment interface occurred chiefly on the superficial sediment within 5-10 cm.The spatial physicochemical character of sediment was distributed uniformly. The observation of lake currents and waves indicated that the dynamic sources, which act on the interface of water and sediment, came mainly from waves under strong wind forcing, while the critical shear stresses due to the waves and currents were of the same magnitude under weak wind forcing. The critical shear stress that leads to extensive sediment resuspension was about 0.03-0.04N/m2, equivalent to a wind speed in situ up to 4 m/s. If a dynamic intensity exceeded the critical shear stress, such as a wind velocity up to 6.5 m/s, massive sediment re-suspension would be observed in the lake. Furthermore, field investigations revealed that the nutrient concentration of pore water within the sediment was far greater than that of overlaying water, which provides objective conditions for the nutrient release from sediment. According to nutrient analyses in the pore water from the superficial 5-10 cm sediments, a severe dynamic process in the Taihu Lake would bring out a peak nutrient release, i.e. a 0.12 mg/L increase of TN, and 0.005mg/L increase of TP in the lake. In the end, a general scheme of nutrient release from sediment in large shallow lakes was put forward: when the wind-driven forcing imposes on the lake, it will make the sediment resuspension. At the same time, the nutrition from the pore water will follow the sediment resuspension release to overlaying water. Because of oxidation of solid particulates when it resuspends from sediment, the disturbance of hydrodynamics will enhance thesuspension particulates absorbing nutrition. After the withdrawal of wind forcing, the suspended mass would deposit and bring part of the released nutrients back into sediment.The degraded organic particulate would be separated to the pore water within the sediment under the condition of 展开更多
Three treatments were tested to investigate the release concentrations of volatile organic compounds （VOCs） during the bio-drying of municipal solid waste （MSW） by the aerobic and combined hydrolytic-aerobic proce...Three treatments were tested to investigate the release concentrations of volatile organic compounds （VOCs） during the bio-drying of municipal solid waste （MSW） by the aerobic and combined hydrolytic-aerobic processes.Results showed that VOCs were largely released in the first 4 days of bio-drying and the dominant components were：dimethyl disulfide,dimethyl sulfide,benzene,2-butanone,limonene and methylene chloride.Thus,the combined hydrolytic-aerobic process was suggested for MSW bio-drying due to fewer aeration quantities in this phase when compared with the aerobic process,and the treatment strategies should base on the key properties of these prominent components.Malodorous sulfur compounds and terpenes were mainly released in the early phase of bio-drying,whereas,two peaks of release concentrations appeared for aromatics and ketones during bio-drying.Notably,for the combined hydrolytic-aerobic processes there were also high concentrations of released aromatics in the shift from hydrolytic to aerobic stages.High concentrations of released chlorinateds were observed in the later phase.For the VOCs produced during MSW bio-drying,i.e.,malodorous sulfur compounds,terpenes and chlorinateds,their release concentrations were mainly determined by production rates;for the VOCs presented initially in MSW,such as aromatics,their transfer and transport in MSW mainly determined the release concentrations.展开更多
利用室内模拟的方法探讨了排水管道沉淀物在水土比、p H值、温度以及扰动这4个环境因子影响下的氮素转化规律.4个影响因子下的实验结果表明,沉淀物中氮素主要以氨氮的形式向上覆水中释放,各组上覆水中氨氮呈先升高后降低的两阶段变化趋...利用室内模拟的方法探讨了排水管道沉淀物在水土比、p H值、温度以及扰动这4个环境因子影响下的氮素转化规律.4个影响因子下的实验结果表明,沉淀物中氮素主要以氨氮的形式向上覆水中释放,各组上覆水中氨氮呈先升高后降低的两阶段变化趋势,在第4~6 d达到释放峰值,随后质量浓度逐渐下降,而总硝态氮的变化趋势与氨氮相反.4个影响因子中p H对氨氮释放的影响最大,其次为搅动、水土比,温度的影响最小,其中不同初始p H条件下氨氮的最大释放量从大到小排序为p H 6.3>p H 8.0>p H 9.6,释放量最大值分别为54.0、30.9、26.7 mg·L-1.实验中水土比越大,氨氮的释放量越大,在相同的速率下对上覆水搅动时间越长,氨氮的释放量越大.温度的升高促进了上覆水中的氨氮向硝态氮的转化,加快了上覆水中总氮质量浓度的下降.展开更多
Dielectric monitoring of the adsorption or release process of salicylic acid (SA) by chitosan membrane shows that the dielectric spectra of the chitosan membrane/ SA solution systems change regularly in the adsorption...Dielectric monitoring of the adsorption or release process of salicylic acid (SA) by chitosan membrane shows that the dielectric spectra of the chitosan membrane/ SA solution systems change regularly in the adsorption or release process. By analyzing the regularity, a new mechanism for the relaxations is proposed. The concentration polarization layer (CPL) caused by SA adsorption or release is confirmed to be essential for the dielectric relaxations. The changes of the spectra with time are explained by account of the relationship between CPL properties and dielectric strength. Based on this relaxation mechanism, a theoretical method can be established to calculate dynamical parameters of inner structure of the adsorption or release systems from their dielectric spectra. Therefore, dielectric spec- troscopy is demonstrated to be a promising method for estimating interfacial distribution of ionic sub- stances and their binding to membrane in a non-invasive way.展开更多
Water sensitivity phenomenon occurs during saline aquifer freshening process in seawater intrusion area, and clay particles released in the phenomenon can damage the infiltration capacity of the aquifer. In order to f...Water sensitivity phenomenon occurs during saline aquifer freshening process in seawater intrusion area, and clay particles released in the phenomenon can damage the infiltration capacity of the aquifer. In order to find out the factors and mechanisms for clay particle release, laboratory column infiltration experiments simulating saline aquifer freshening process were designed to measure the critical conditions(critical flow velocity, critical salt concentration and critical ionic strength) and force analysis for clay particle according to DLVO electric double layer theory was employed to illustrate the mechanisms for particle release. The research results showed that critical flow velocity for clay particle release is influenced by salt concentration of injecting solution. When salt concentration of injecting solution is very high, clay particles are not released, indicating that there does not exist a critical flow velocity in this situation. As salt concentration of injecting solution decreases, particles start to be released. The critical salt concentration for clay particle release is 0.052 mol L-1 in our work, which was determined by a constant-flux experiment for stepwise displacement of high concentration Na Cl solution. The critical ionic strength for clay particle release decreases as Ca2+ molar content percentage of the mixed solution of Na Cl and Ca Cl2 increases following the first-order exponential decay equation y = 0.0391e-0.266 x + 0.0015.展开更多
文摘On the basis of investigations in situ, it was found that mass exchange on the water-sediment interface occurred chiefly on the superficial sediment within 5-10 cm.The spatial physicochemical character of sediment was distributed uniformly. The observation of lake currents and waves indicated that the dynamic sources, which act on the interface of water and sediment, came mainly from waves under strong wind forcing, while the critical shear stresses due to the waves and currents were of the same magnitude under weak wind forcing. The critical shear stress that leads to extensive sediment resuspension was about 0.03-0.04N/m2, equivalent to a wind speed in situ up to 4 m/s. If a dynamic intensity exceeded the critical shear stress, such as a wind velocity up to 6.5 m/s, massive sediment re-suspension would be observed in the lake. Furthermore, field investigations revealed that the nutrient concentration of pore water within the sediment was far greater than that of overlaying water, which provides objective conditions for the nutrient release from sediment. According to nutrient analyses in the pore water from the superficial 5-10 cm sediments, a severe dynamic process in the Taihu Lake would bring out a peak nutrient release, i.e. a 0.12 mg/L increase of TN, and 0.005mg/L increase of TP in the lake. In the end, a general scheme of nutrient release from sediment in large shallow lakes was put forward: when the wind-driven forcing imposes on the lake, it will make the sediment resuspension. At the same time, the nutrition from the pore water will follow the sediment resuspension release to overlaying water. Because of oxidation of solid particulates when it resuspends from sediment, the disturbance of hydrodynamics will enhance thesuspension particulates absorbing nutrition. After the withdrawal of wind forcing, the suspended mass would deposit and bring part of the released nutrients back into sediment.The degraded organic particulate would be separated to the pore water within the sediment under the condition of
基金financially supported by the National Key Technology R&D Program of China (No.2006BAC06B04,2008BAJ08B13)
文摘Three treatments were tested to investigate the release concentrations of volatile organic compounds （VOCs） during the bio-drying of municipal solid waste （MSW） by the aerobic and combined hydrolytic-aerobic processes.Results showed that VOCs were largely released in the first 4 days of bio-drying and the dominant components were：dimethyl disulfide,dimethyl sulfide,benzene,2-butanone,limonene and methylene chloride.Thus,the combined hydrolytic-aerobic process was suggested for MSW bio-drying due to fewer aeration quantities in this phase when compared with the aerobic process,and the treatment strategies should base on the key properties of these prominent components.Malodorous sulfur compounds and terpenes were mainly released in the early phase of bio-drying,whereas,two peaks of release concentrations appeared for aromatics and ketones during bio-drying.Notably,for the combined hydrolytic-aerobic processes there were also high concentrations of released aromatics in the shift from hydrolytic to aerobic stages.High concentrations of released chlorinateds were observed in the later phase.For the VOCs produced during MSW bio-drying,i.e.,malodorous sulfur compounds,terpenes and chlorinateds,their release concentrations were mainly determined by production rates;for the VOCs presented initially in MSW,such as aromatics,their transfer and transport in MSW mainly determined the release concentrations.
文摘利用室内模拟的方法探讨了排水管道沉淀物在水土比、p H值、温度以及扰动这4个环境因子影响下的氮素转化规律.4个影响因子下的实验结果表明,沉淀物中氮素主要以氨氮的形式向上覆水中释放,各组上覆水中氨氮呈先升高后降低的两阶段变化趋势,在第4~6 d达到释放峰值,随后质量浓度逐渐下降,而总硝态氮的变化趋势与氨氮相反.4个影响因子中p H对氨氮释放的影响最大,其次为搅动、水土比,温度的影响最小,其中不同初始p H条件下氨氮的最大释放量从大到小排序为p H 6.3>p H 8.0>p H 9.6,释放量最大值分别为54.0、30.9、26.7 mg·L-1.实验中水土比越大,氨氮的释放量越大,在相同的速率下对上覆水搅动时间越长,氨氮的释放量越大.温度的升高促进了上覆水中的氨氮向硝态氮的转化,加快了上覆水中总氮质量浓度的下降.
基金the National Natural Science Foundation of China (Grant No. 20673014) Open Topic Research Foundation of Jiangsu Laboratory of Advanced Functional Materials (No. 06KFJJ009)
文摘Dielectric monitoring of the adsorption or release process of salicylic acid (SA) by chitosan membrane shows that the dielectric spectra of the chitosan membrane/ SA solution systems change regularly in the adsorption or release process. By analyzing the regularity, a new mechanism for the relaxations is proposed. The concentration polarization layer (CPL) caused by SA adsorption or release is confirmed to be essential for the dielectric relaxations. The changes of the spectra with time are explained by account of the relationship between CPL properties and dielectric strength. Based on this relaxation mechanism, a theoretical method can be established to calculate dynamical parameters of inner structure of the adsorption or release systems from their dielectric spectra. Therefore, dielectric spec- troscopy is demonstrated to be a promising method for estimating interfacial distribution of ionic sub- stances and their binding to membrane in a non-invasive way.
基金supported by the National Natural Science Foundation of China (Grant No. 41172209)National Public Welfare Scientific Research Project (Grant No. 201301090)
文摘Water sensitivity phenomenon occurs during saline aquifer freshening process in seawater intrusion area, and clay particles released in the phenomenon can damage the infiltration capacity of the aquifer. In order to find out the factors and mechanisms for clay particle release, laboratory column infiltration experiments simulating saline aquifer freshening process were designed to measure the critical conditions(critical flow velocity, critical salt concentration and critical ionic strength) and force analysis for clay particle according to DLVO electric double layer theory was employed to illustrate the mechanisms for particle release. The research results showed that critical flow velocity for clay particle release is influenced by salt concentration of injecting solution. When salt concentration of injecting solution is very high, clay particles are not released, indicating that there does not exist a critical flow velocity in this situation. As salt concentration of injecting solution decreases, particles start to be released. The critical salt concentration for clay particle release is 0.052 mol L-1 in our work, which was determined by a constant-flux experiment for stepwise displacement of high concentration Na Cl solution. The critical ionic strength for clay particle release decreases as Ca2+ molar content percentage of the mixed solution of Na Cl and Ca Cl2 increases following the first-order exponential decay equation y = 0.0391e-0.266 x + 0.0015.
