The Effects of Dissolved Organic Carbon on Copper, Zinc, and Cadmium Sorption onto Two Soils
| Autor: | Chia-Hsing Lee, 李家興 |
|---|---|
| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 Application of composted swine manure and municipal wastewater sludge is an important procedure for resource recycling as well as one of environment-friendly disposal of wastes. Moreover, instead of incineration by composting of green-wastes presumably reduce carbon dioxide emission, the principal component of greenhouse gases. Application of organic-matter-enriched composts can promote soil physical, chemical, and biological properties. However, science swine fecal content high level of Cu and Zn and municipal wastewater sludge content high level of various heavy metals generally, applying of swine manure compost (SMC) and municipal wastewater sludge compost (MWSC) may lead to heavy metal accumulation in soils, leaching into ground water, uptake by plants, and further, hazards to food chain. Thus, the heavy metal movement in soils is important issue while applying this kind of composts. The retention and release of heavy metals in compost-soil-water suspensions are mainly affected by pH, dissolved organic carbon (DOC) acidity, particulate surface properties, and reaction strength between specific heavy metal and function group. The acidity of particulate surface and DOM implicate acid site density and acidity strength. In this study, one commercial SMC, one prepared MWSC (composting of straw and secondary sludge from Nei-Hu municipal wastewater treatment plant; NH2SC), two soils (Sk sandy loam and Pu silty clay loam), and two source clays (kaolinite and montmorillonite) are investigated to determine the acidity and Cd, Cu, and Zn retention of each material with multi-bounding-site model, and the effects of compost-derived DOC on Cd, Cu, and Zn release from artificial contaminated soils. The results of release experiments show that Cu release from soils was slower than Zn and Cd. Addition of 0.01 M compost-derived DOC accelerated metal release and pH decrease because of the organic matter buffering. The lack consistency of pH effect on accumulated release within different DOC treatments shows that DOC reacted with Cu directly and kept more Cu in solution than water did while DOC increased more Zn retention by particulates. Additionally, heavy metal release from Sk sandy loam was faster than that from Pu silty clam loam. With alkalimetric titration results within field pH range, multi-acid site model fitting revealed that kaolinite, montmorillonite and DOC extracted from SMC and NH2SC content 3 acid sites (model describable). With acidity parameters from multi-acid-site model, multi-bounding site model fitting, incorporating effects of pH, revealed that two or more function group contributed heavy metal retention in the suspensions. Therefore, the model provided better description than the original Langmuir isotherm model did. Metal retentions by particulates were governed by pH. The Coprecipitation of metals and DOC were unapparent. Furthermore, the comparison of estimated stability constants (log KS) of metal-clay complex are described in order as fallow: Cu > Zn > Cd. The results of Cu sorption in Cu-DOC-Clay suspensions supported that DOC can eather compete surface sites with Cu or compete Cu with Clay, and hance, Cu sorption onto clays can be decreased (i.e. release more Cu) by DOC. The application of DOC to enhace soil washing process for metal contaiminated soils couled be considered. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|