Chemical Processes Affecting the Subsoil During Reclamation of Highly Acidic Minespoil

Open Access
Author:
von Willert, Frank Joachim
Graduate Program:
Soil Science
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 13, 2002
Committee Members:
  • Herschel Adams Elliott, Committee Member
  • Richard Henry Fox, Committee Member
  • Jon Chorover, Committee Member
  • Richard Charles Stehouwer, Committee Chair
  • Katherine Haines Freeman, Committee Member
Keywords:
  • sorption isotherm
  • error propagation
  • dissolved organic matter
  • capillary electrophoresis
  • colloids
  • acidic minespoil
Abstract:
The objective of this work was to evaluate the effect of different surface amendments on subsoil chemistry in highly acidic minespoil material and to explore new analytical tools for measuring Al-DOM binding under acidic conditions. I first examined the influence of compost age on Ca sorption capacities of compost derived DOM. Secondly, small scale laboratory experiments without plants and larger greenhouse column experiments with plant growth examined effects of different surface treatment combinations on subsoil material. Finally, I evaluated the use of capillary electrophoresis to measure Al-DOM interactions at acidic pH. Ca titrations of DOM extracted from compost at different stages of the composting process indicated that compost age did not significantly affect Ca sorption capacity. Error propagation calculations for adsorption isotherm measurements showed that accuracy is inversely proportional to sorbent concentration and that the relative error in calculated bound metal concentration becomes very large with increasing ratio of free to total metal cation concentration. In both column experiments Ca solubility was high and compost did not affect subsoil chemistry. None of the surface treatments resulted in relevant increase in subsoil pH or decrease in subsoil Al, despite clear evidence for significant Ca transport into the subsoil. Leachate data and solubility calculations pointed to a jurbanite-like solid phase buffering Al activity in the subsoil. Due to this buffering effect and the high acidity of the spoil material, none of the surface treatments would be expected to alleviate subsoil phytotoxicity and improvements would necessitate direct subsoil treatment with acid neutralizing materials. Finally, I was able to demonstrate that capillary electrophoresis (CE) can be used to measure free Fe3+ and Al3+ under acidic conditions without affecting solution equilibria and metal speciation. I showed that CE can also be used for competitive complexation experiments with soluble ligands and several different metal cations. Furthermore, I was able to separate and detect what appeared to be individual DOM macromolecules and colloids in solution. Both CE experiments underline the versatility of capillary electrophoresis for environmental soil chemistry research and show that this technology should find wider use in this area.