| As an important part of natural organic matter, humus has a major impact on global carbon cycle and natural behavior of organic and inorganic compounds including migration, transformation and fate. Humus, which is able to bind heavy metals and change heavy metal ions’shape, solubility and bioavailability, is one of the main factors in the effectiveness of heavy metals bioavailability. Furthermore, humus plays a vital part in the biogeochemical behavior, migration and transformation of heavy metals. As different components of humus, humic acid (HA) and humin (HM) have different mechanism of action with heavy metal ions. The interaction relations between different humus components and heavy metal ions are closely related to humus’structure. Therefore, it is necessary to get a fully understanding of humus’structure and composition.It has lots of lakes and wide area of the region in Inner Mongolia Plateau, which occupies an important position in the overall study of lakes and wetlands. Wuliangsuhai Lake has a higher humification degree in lakes of Inner Mongolia Plateau, acting as a typical research area for studying interaction relations between humus and heavy metals.This work is based on separation, extraction and purification of different humus components in natural lake sediments, and focused on the adsorption property of different humus components to heavy metals in different ecological functional zones. The primary goal of this works is adsorption mechanism of humus to heavy metals in different ecological functional areas. In combination with spectroscopy and morphology characterization, these works are helpful in explaining humus environmental effects, accounting for humus’role in the carbon cycle, and understanding the geochemical behavior of humus in lake ecological environment. The main results are as following:1. In the sediments from the Phragmites australis Area, Potamogeton pectinatus Area and Myriophyllum spicatum L Area, the absorp-tive capacity of the HA to the Cu2+, Pb2+, Zn2+ and Cd2+ is Pb2+> Cu2+> Cd2+> Zn2+ at different pH conditions; the absorptive capacity of the HM to the heavy metal ions differ with ecological functional area, the majority of the Pb2+ can be adsorbed, the absorptive capacity of Cu2+ and Zn2+ is roughly equal. The absorptive capacity of the HA from the different ecological functional area to the heavy metal ions have the significant changes under different temperature conditions, the low temperature condition is advantageous to the adsorption reaction. The influence of ionic strength to the adsorption is less than the temperature conditions. The adsorption of HM to the heavy metal ions is mainly affected by temperature and weakly affected by ionic strength.2. According to the results of the thermodynamic parameter calculation, the adsorption the HA and HM to the heavy metal ions is a exothermic process, and the adsorption process can occur spontaneously without gaining energy from the outside. HA in Phragmites australis Area adsorbed heavy metal has a spontaneity sequence with Pb2+> Cd2+ ≈ Cu2+> Zn2+. HM in Phragmit-es australis Area adsorbed heavy metal has a spontaneity sequence with Cu2+> Pb2+> Cd2+> Zn2+. HA in Potamogeton pectinatus Area adsorbed heavy metal has a spontaneity sequence with Cd2+> Cu2+ ≈ Pb2+> Zn2+. HM in this area adsorbed heavy metal has a spontaneity sequence with Zn2+> Pb2+> Cu2+ ≈ Cd2+. HA and HM in Myriophyllum spicatum L Area adsorbed heavy metal has a same spontaneity sequence with Pb2+> Cu2+> Zn2+> Cd2+.3. Results of element analysis and Ultraviolet-visible spectra analysis show that different plant type area of HA is given priority to aromatic structure. HM reputation is given priority to fat structure. Results of Fourier transform infrared spectral analysis indicate that the functional structure of the HA and HM all give priority with hydroxyl, but carboxyl content is relatively low. Comprehensive spectral analysis, three plant type areas can be estimated in the sediment of aromatic structure of HA accounted for about 60%, fat structure proportion about 40%, hydroxyl content proportion about 70%, carboxyl content proportion about 30%. Aromatic structure of HM accounted for about 40%, fat structure accounted for about 60%, the proportion of hydroxyl and carboxyl content of HM is the same with HA. Adsorption experiments and characterization results reveal that the free hydroxyl of Phragmites australis Area in HA and HM, and Potamog-eton pectinatus Area in HA adsorption Pb2+, Zn2+ and Cd2+ plays an important role. Free hydroxyl of Myriophyllum spicatum L Area in HA and HM adsorption Pb2+, Zn2+ and Cd2+ acts absolutely dominant role. Associating the hydroxyl of Phragmites australis Area in HM and Potamoge-ton pectinatus Area in HA adsorption Cu2+ plays a main role. Free hydroxyl, associating the hydroxyl and carboxyl of Phragmites australis Area in HA and Myriophyllum spicatum L Area in HM adsorpted Cu2+ plays a main role, also for Potamogeton pectinatus Area in HM adsorb Cu2+, Pb2+, Zn2+and Cd2+. Combining with the adsorption to heavy metals components of humus in the different ecological functional areas in sediments from Wuliangsuhai Lake and characterization results, we can get that different influencing factors can change the activity of hydroxy and carboxyl in the humus and affect the complexation of the humus and heavy metal ions, which lead to the different adsorption mechanism.4. Complexation between humic acid and heavy metal ions, humic acid under different conditions and the amount of heavy metal ions complexation products difference, humic acid of sediments in different ecological functional areas exists complexation-precipitation reaction with heavy metal ions, caused by the rise of the initial concentration and the pH value.5. Explore the adsorption mechanism of humus in sediments and heavy metal ions in different ecological functional areas, Wuliangsuhai Lake, discovering the oxygen groups contain hydroxyl and carboxyl, which can make the humic acid and humin has coordination with heavy metal ions. In fact, HA and HM forms heavy metal chelate in salicylic acid salts and phthalates parts. In the molecular structure of the humic acid, the number of catechol and salicylic acid and its approximate structural unit is more; in the molecular structure of humin, the number of catechol, malonic acid and and its approximate structural unit is in the majority. |
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