Soil is a large terrestrial carbon pool so that the evaluation and prediction of soil respiration is important for understanding and managing carbon cycling between the pedosphere and the atmosphere. For better unders...Soil is a large terrestrial carbon pool so that the evaluation and prediction of soil respiration is important for understanding and managing carbon cycling between the pedosphere and the atmosphere. For better understanding about characteristics and mechanisms of soil respiration, this study monitored seasonal behaviors of soil gaseous CO<sub>2</sub> concentration profile with relevant soil physical conditions in a meadow field, and numerically analyzed the monitored data sets to inversely determine time-series of depth distributions of CO<sub>2</sub> production rate in the field by assuming optimum ranges of depth and moisture condition for aerobic respiration of soil fauna and flora. The results of the inverse analyses showed that the depth range of intense CO<sub>2</sub> production resided in top soil layers during summer and moved down into subsoil layers in winter, implying that the depth range of main CO<sub>2</sub> sources can change dynamically with seasons. The surface CO<sub>2</sub> emission rates derived from the inverse analyses fell in the range typically found in the same kind of land use. The evaluated mean residence time of gaseous CO<sub>2</sub> in the study field was around half a day. These findings suggested that the modelling assumptions about soil respiration in this study are effective to probe spatial and temporal behavior of respiratory activity in a soil layer, and it is still important to integrate facts about in-situ CO<sub>2</sub> concentration profiles with soil physical parameters for quantitatively predicting possible behaviors of soil respiration in response to hypothetical changes in atmospheric and soil climates.展开更多
The complexation of Cd with cysteine has been investigated at pH ~9, and in constant ionic medium 0.59 M NaNO3 and borate buffer. Reduction signals of the hydrated Cd2+ and Cd-cysteinate complex were resolved on the p...The complexation of Cd with cysteine has been investigated at pH ~9, and in constant ionic medium 0.59 M NaNO3 and borate buffer. Reduction signals of the hydrated Cd2+ and Cd-cysteinate complex were resolved on the potential scale during amperometric titration of 2 × 10-6 M Cd2+ with cysteine and cysteine with Cd2+, in a differential pulse (DP) mode on HMDE. The 1:1 molar ratio of Cd2+ to cysteine, and cysteine to Cd2+, was defined for Cd-cysteinate complex formed under the defined conditions. The appearance of the prepeak on the Cd-cysteinate reduction signal is showed, as the result of cysteine adsorption in reduced form. From the mass balance equations, the stoichiometric stability constants of Cd-cysteinate complex were calculated. Under various experimental conditions, comparable log K values were obtained. The grand average log K = 7.83 M-1 refers to 0.59 M ionic strength and 23℃.展开更多
文摘Soil is a large terrestrial carbon pool so that the evaluation and prediction of soil respiration is important for understanding and managing carbon cycling between the pedosphere and the atmosphere. For better understanding about characteristics and mechanisms of soil respiration, this study monitored seasonal behaviors of soil gaseous CO<sub>2</sub> concentration profile with relevant soil physical conditions in a meadow field, and numerically analyzed the monitored data sets to inversely determine time-series of depth distributions of CO<sub>2</sub> production rate in the field by assuming optimum ranges of depth and moisture condition for aerobic respiration of soil fauna and flora. The results of the inverse analyses showed that the depth range of intense CO<sub>2</sub> production resided in top soil layers during summer and moved down into subsoil layers in winter, implying that the depth range of main CO<sub>2</sub> sources can change dynamically with seasons. The surface CO<sub>2</sub> emission rates derived from the inverse analyses fell in the range typically found in the same kind of land use. The evaluated mean residence time of gaseous CO<sub>2</sub> in the study field was around half a day. These findings suggested that the modelling assumptions about soil respiration in this study are effective to probe spatial and temporal behavior of respiratory activity in a soil layer, and it is still important to integrate facts about in-situ CO<sub>2</sub> concentration profiles with soil physical parameters for quantitatively predicting possible behaviors of soil respiration in response to hypothetical changes in atmospheric and soil climates.
文摘The complexation of Cd with cysteine has been investigated at pH ~9, and in constant ionic medium 0.59 M NaNO3 and borate buffer. Reduction signals of the hydrated Cd2+ and Cd-cysteinate complex were resolved on the potential scale during amperometric titration of 2 × 10-6 M Cd2+ with cysteine and cysteine with Cd2+, in a differential pulse (DP) mode on HMDE. The 1:1 molar ratio of Cd2+ to cysteine, and cysteine to Cd2+, was defined for Cd-cysteinate complex formed under the defined conditions. The appearance of the prepeak on the Cd-cysteinate reduction signal is showed, as the result of cysteine adsorption in reduced form. From the mass balance equations, the stoichiometric stability constants of Cd-cysteinate complex were calculated. Under various experimental conditions, comparable log K values were obtained. The grand average log K = 7.83 M-1 refers to 0.59 M ionic strength and 23℃.
