In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NO_x(@NO + NO_2) and VOCs(volatile organic compounds) with light. Due to the highly nonli...In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NO_x(@NO + NO_2) and VOCs(volatile organic compounds) with light. Due to the highly nonlinear relationships between ozone and its precursors, proper ozone mitigation relies on the knowledge of chemical mechanisms. In this study, an observation-based method is used to simulate ozone formation and elucidate its controlling factors for a rural site on the North China Plain. The instantaneous ozone production rate is calculated utilizing a box model using the dataset obtained from the Wangdu campaign. First, the model was operated in a time-dependent mode to calculate the ozone production rate at each time stamp. The calculated ozone formation rate showed a diurnal average maximum value of 17 ppbv/h(1-h diurnal averaged). The contribution of individual peroxy radicals to ozone production was analyzed. In addition, the functional dependence of calculated P(O_3) reveals that ozone production was in a NO_x-limited regime during the campaign. Furthermore, the missing peroxy radical source will further extend NO_x-limited conditions to earlier in the day, making NO_xlimitation dominate more of a day than the current chemical model predicts. Finally, a multiple scenarios mode,also known as EKMA(empirical kinetic modeling approach), was used to simulate the response of P(O_3) to the imaginary change in precursor concentrations. We found that ozone production was in the NO_x-limited region. However, the use of NO_2 measured by the molybdenum converter and/or the absence of a peroxy radical source in the current chemical model could over-emphasize the VOC-limited effect on ozone production.展开更多
The capability of carbon nanotubes （CNTs） to adsorb lead （Pb） in aqueous solution was investigated. Batch mode adsorption experiment was conducted to determine the effects of pH, agitation speed, CNTs dosage and c...The capability of carbon nanotubes （CNTs） to adsorb lead （Pb） in aqueous solution was investigated. Batch mode adsorption experiment was conducted to determine the effects of pH, agitation speed, CNTs dosage and contact time. The removal of Pb（II） reached maximum value 85% or 83% at pH 5 or 40 mg/L of CNTs, respectively. Higher correlation coefficients from Langmuir isotherm model indicates the strong adsorptions of Pb（II） on the surface of CNTs （adsorption capacity Xm = 102.04 mg/g）. The results indicates that the highest percentage removal of Pb （96.03%） can be achieved at pH 5, 40 mg/L of CNTs, contact time 80 min, and agitation speed 50 r/min.展开更多
基金supported from the research projects of the Environmental Public Welfare Industry in China (201509001,201409005)the National Science and Technology Support Program of China (2014BAC21B01)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB05010500)the Special Fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (18K03ESPCP)the EU-project AMIS (Fate and Impact of Atmospheric Pollutants,PIRSES-GA-2011295132)
文摘In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NO_x(@NO + NO_2) and VOCs(volatile organic compounds) with light. Due to the highly nonlinear relationships between ozone and its precursors, proper ozone mitigation relies on the knowledge of chemical mechanisms. In this study, an observation-based method is used to simulate ozone formation and elucidate its controlling factors for a rural site on the North China Plain. The instantaneous ozone production rate is calculated utilizing a box model using the dataset obtained from the Wangdu campaign. First, the model was operated in a time-dependent mode to calculate the ozone production rate at each time stamp. The calculated ozone formation rate showed a diurnal average maximum value of 17 ppbv/h(1-h diurnal averaged). The contribution of individual peroxy radicals to ozone production was analyzed. In addition, the functional dependence of calculated P(O_3) reveals that ozone production was in a NO_x-limited regime during the campaign. Furthermore, the missing peroxy radical source will further extend NO_x-limited conditions to earlier in the day, making NO_xlimitation dominate more of a day than the current chemical model predicts. Finally, a multiple scenarios mode,also known as EKMA(empirical kinetic modeling approach), was used to simulate the response of P(O_3) to the imaginary change in precursor concentrations. We found that ozone production was in the NO_x-limited region. However, the use of NO_2 measured by the molybdenum converter and/or the absence of a peroxy radical source in the current chemical model could over-emphasize the VOC-limited effect on ozone production.
基金the Kulliyyah of Engineering(KOE) and Department of Biotechnology Engineering,IIUM for supporting and providing the laboratory facilities
文摘The capability of carbon nanotubes （CNTs） to adsorb lead （Pb） in aqueous solution was investigated. Batch mode adsorption experiment was conducted to determine the effects of pH, agitation speed, CNTs dosage and contact time. The removal of Pb（II） reached maximum value 85% or 83% at pH 5 or 40 mg/L of CNTs, respectively. Higher correlation coefficients from Langmuir isotherm model indicates the strong adsorptions of Pb（II） on the surface of CNTs （adsorption capacity Xm = 102.04 mg/g）. The results indicates that the highest percentage removal of Pb （96.03%） can be achieved at pH 5, 40 mg/L of CNTs, contact time 80 min, and agitation speed 50 r/min.
基金The authors are indebted to associate Prof.Shen Jiagui,Prof.Liu Jinzhong and associate Prof.Xu An for their help in pyrolysis experiments and Prof.Tang Yongchun for his constructive comments on kinetic modeling.The work was financially supported by the Natural Science Fund for Distinguished Young Scholars(Grant No.40625011)the National Key Technologies R&D Program(Grant No.2004BA616A02-01-01-04)the National Natural Science Foundation of China(Grant No.40572085).
