Humic acid (HA) derived from rice straw decomposed for 1 (HA-1), 3 (HA-3), 6 (HA-6) and 12 (HA-12) months was characterized by potentiometric titration and solid-state cross-polarization magic-angle spinning 13C nuclear magnetic resonance spectroscopy (CPMAS 13C NMR). The sorption of Cu on examined HA was investigated using a combination of batch sorption, isothermal titration calorimetry (ITC) and sequential desorption. Results showed that the functional group content and the humification degree of HA tended to increase with increasing decomposition time especially in the latter stage of examined decomposition period. Cu sorption on HA was a rapid process that occurred within the first 1 h and the sorption capacity increased from 245.4 mmol kg−1 on HA-1 to 294.6 mmol kg−1 on HA-12. The sorption of Cu was endothermic, spontaneous and the randomness was increased during Cu sorption. Sorbed Cu on examined HA can be hardly released by NH4Ac but nearly fully released by EDTA. Forming inner-sphere complexes was the main mechanism of Cu sorption on examined HA. This study could provide valuable information for a better understanding on the environmental impacts of the decomposition of organic waste.
Mercury (Hg) distribution and migration in different landfill stabilization processes were evaluated in this study. Wide ranges of Hg concentrations were observed because of the heterogeneity and variability of landfill refuse. In addition, temporally variable conditions, including pH, organic matter, and vegetation cover, which influence Hg migration in landfills, may also affect the temporal distribution of Hg in landfill refuse. The main fraction of Hg, elemental Hg, decreased with time, while the stable fractions of Hg increased. The fulvic acid (FA) extracted from the landfill leachate had much lower overall Hg-complexation stability constants, which suggests that organic S groups might have been rapidly saturated by small amounts of Hg while leaving oxygen functional groups, such as carboxylic functional or phenolic groups, acting as the primary binding sites for Hg. 相似文献