[Objective] This study aimed to investigate the nitrogen release kinetics and nitrification-denitrification on surface sediments under aerating disturbance condition, with the purpose to solve the sediment nitrogen re...[Objective] This study aimed to investigate the nitrogen release kinetics and nitrification-denitrification on surface sediments under aerating disturbance condition, with the purpose to solve the sediment nitrogen release and secondary pollution problems. [Method] The effect of in situ sediments aeration on the release of nitrogen pollutants was investigated, and the nitrogen release kinetics parameters were analyzed. The process of nitrification and denitrification under sediments aeration condition was investigated in laboratory. [Result] The nitrogen released from sediments was enhanced by aeration disturbance. The concentration of NH4＋-N and TN reached the maximum value in 30 min, and release rates were proportional to the disturbance strength. In this study, with the distance of aerator to the sediments surface of 0, 1, 2 and 3 cm, the suspended sediments concentrations were 3.52, 3.41, 3.26 and 3.01 g/L, respectively. Maximum release concentration of NH4＋-N and TN were 14.3, 13.8, 13.2, 12.2 mg/L and 33.21, 30.98, 29.83, 27.30 mg/L, respec- tively. In addition, both NH4＋-N and TN release kinetics could be described by Double Constant Equation as InC=A＋Blnt. Nitrification reaction occurred and was promoted by continued aerating to sediments.The concentration of NH4＋-N dropped down from 12.4 mg/L to 0.2 mg/L in 8 d, with the concentration of NO3--N increased to the maximum value of 10.8 mg/L. In addition, concentration of NO3--N and TN decreased from 10.8 mg/L and 37.4 mg/L to 0.36 mg/L and 23.2 mg/L after the stop of aeration for 12 d, indicating the occurrence of denitdfication reaction. Therefore, sediment aeration could accelerate nitrogen release and nitrification reaction, and with intermittent aeration, nitrogen could be removed from sediments in-situ by nitrification and denitrification. [Conclusion] The results provided technical reference for the in situ sediment remediation for the black-odor rivers in cities.展开更多
The kinetics of catalytic hydrogenation of ortho-nitrochlorobenzene to 2,2′-dichloroazoxybenzene on platinum/carbon catalyst is investigated in a slurry reactor with the temperature range of 313-343 K, and orthochlor...The kinetics of catalytic hydrogenation of ortho-nitrochlorobenzene to 2,2′-dichloroazoxybenzene on platinum/carbon catalyst is investigated in a slurry reactor with the temperature range of 313-343 K, and orthochloroaniline is formed as a byproduct. Models based on Rideal-Eley and Langmuir-Hinshelwood mechanism have been proposed based on the rate data and the kinetic regime. The former model can be used to fit the experimental data better. Reaction controlling steps are physical adsorption of hydrogen and adsorbed ortho-nitrochlorobenzene reacted on the surface of catalyst.展开更多
A laboratory-based aerobic incubation was conducted to investigate nitrogen （N） isotopic fractionation related to nitrification in five agricultural soils after application of ammonium sulfate （（NH4）2804）. The s...A laboratory-based aerobic incubation was conducted to investigate nitrogen （N） isotopic fractionation related to nitrification in five agricultural soils after application of ammonium sulfate （（NH4）2804）. The soil samples were collected from a subtropical barren land soil derived from granite （RGB）, three subtropical upland soils derived from granite （RQU）, Quaternary red earth （RGU）, Quaternary Xiashu loess （YQU） and a temperate upland soil generated from alluvial deposit （FAU）. The five soils varied in nitrification potential, being in the order of FAU 〉 YQU 〉 RGU 〉 RQU 〉 RGB. Significant N isotopic fractionation accompanied nitrification of NH4＋. 615N values of NH4＋ increased with enhanced nitrification over time in the four upland soils with NH4＋ addition, while those of NO3 decreased consistently to the minimum and thereafter increased. 515N values of NH4＋ showed a significantly negative linear relationship with NH4＋-N concentration, but a positive linear relationship with NO3-N concentration. The apparent isotopic fractionation factor calculated based on the loss of NH4＋ was 1.036 for RQU, 1.022 for RGU, 1.016 for YQU, and 1.020 for FAU, respectively. Zero- and first-order reaction kinetics seemed to have their limitations in describing the nitrification process affected by NH4＋ input in the studied soils. In contrast, N kinetic isotope fractionation was closely related to the nitrifying activity, and might serve as an alternative tool for estimating the nitrification capacity of agricultural soils.展开更多
基金Supported by the National Science Foundation for Young Scientists of China(51108196)the FDYT in Higher Education of Guangdong,China(LYM10034)+1 种基金the Natural Science Foundation of Guangdong Province,China(S2011040001251)the Key Laboratory Fund of Ecological Agriculture of Ministry of Agriculture of China(2010-LH12)~~
文摘[Objective] This study aimed to investigate the nitrogen release kinetics and nitrification-denitrification on surface sediments under aerating disturbance condition, with the purpose to solve the sediment nitrogen release and secondary pollution problems. [Method] The effect of in situ sediments aeration on the release of nitrogen pollutants was investigated, and the nitrogen release kinetics parameters were analyzed. The process of nitrification and denitrification under sediments aeration condition was investigated in laboratory. [Result] The nitrogen released from sediments was enhanced by aeration disturbance. The concentration of NH4＋-N and TN reached the maximum value in 30 min, and release rates were proportional to the disturbance strength. In this study, with the distance of aerator to the sediments surface of 0, 1, 2 and 3 cm, the suspended sediments concentrations were 3.52, 3.41, 3.26 and 3.01 g/L, respectively. Maximum release concentration of NH4＋-N and TN were 14.3, 13.8, 13.2, 12.2 mg/L and 33.21, 30.98, 29.83, 27.30 mg/L, respec- tively. In addition, both NH4＋-N and TN release kinetics could be described by Double Constant Equation as InC=A＋Blnt. Nitrification reaction occurred and was promoted by continued aerating to sediments.The concentration of NH4＋-N dropped down from 12.4 mg/L to 0.2 mg/L in 8 d, with the concentration of NO3--N increased to the maximum value of 10.8 mg/L. In addition, concentration of NO3--N and TN decreased from 10.8 mg/L and 37.4 mg/L to 0.36 mg/L and 23.2 mg/L after the stop of aeration for 12 d, indicating the occurrence of denitdfication reaction. Therefore, sediment aeration could accelerate nitrogen release and nitrification reaction, and with intermittent aeration, nitrogen could be removed from sediments in-situ by nitrification and denitrification. [Conclusion] The results provided technical reference for the in situ sediment remediation for the black-odor rivers in cities.
文摘The kinetics of catalytic hydrogenation of ortho-nitrochlorobenzene to 2,2′-dichloroazoxybenzene on platinum/carbon catalyst is investigated in a slurry reactor with the temperature range of 313-343 K, and orthochloroaniline is formed as a byproduct. Models based on Rideal-Eley and Langmuir-Hinshelwood mechanism have been proposed based on the rate data and the kinetic regime. The former model can be used to fit the experimental data better. Reaction controlling steps are physical adsorption of hydrogen and adsorbed ortho-nitrochlorobenzene reacted on the surface of catalyst.
基金Supported by the Natural Science Foundation of Jiangsu Province,China(No.BK2010612)the Foundation of State Key Laboratory of Soil and Sustainable Agriculture(No.Y052010034)the Knowledge Innovation Program of the Institute of Soil Science,Chinese Academy of Sciences(No.ISSASIP0723)
文摘A laboratory-based aerobic incubation was conducted to investigate nitrogen （N） isotopic fractionation related to nitrification in five agricultural soils after application of ammonium sulfate （（NH4）2804）. The soil samples were collected from a subtropical barren land soil derived from granite （RGB）, three subtropical upland soils derived from granite （RQU）, Quaternary red earth （RGU）, Quaternary Xiashu loess （YQU） and a temperate upland soil generated from alluvial deposit （FAU）. The five soils varied in nitrification potential, being in the order of FAU 〉 YQU 〉 RGU 〉 RQU 〉 RGB. Significant N isotopic fractionation accompanied nitrification of NH4＋. 615N values of NH4＋ increased with enhanced nitrification over time in the four upland soils with NH4＋ addition, while those of NO3 decreased consistently to the minimum and thereafter increased. 515N values of NH4＋ showed a significantly negative linear relationship with NH4＋-N concentration, but a positive linear relationship with NO3-N concentration. The apparent isotopic fractionation factor calculated based on the loss of NH4＋ was 1.036 for RQU, 1.022 for RGU, 1.016 for YQU, and 1.020 for FAU, respectively. Zero- and first-order reaction kinetics seemed to have their limitations in describing the nitrification process affected by NH4＋ input in the studied soils. In contrast, N kinetic isotope fractionation was closely related to the nitrifying activity, and might serve as an alternative tool for estimating the nitrification capacity of agricultural soils.
