Project

The effect of pH on the determination of permanganate-oxidisable carbon (POXC)

Soil organic matter (SOM) is crucial for a healthy soil; yet, changes in SOM content due to e.g. different land management are generally slow. Active or easily degradable soil carbon is more responsive to such changes and also an important indicator of soil functions. An example of such a fraction is permanganate-oxidisable carbon (POXC), which determination has become increasingly popular.

Background

POXC is highly sensitive to land management changes, and its measurement is cheap and fast. In the method, soil samples are subjected to a permanganate solution, which oxidises part of the soil organic carbon (SOC). However, there are several methodological uncertainties with this method, including the effect of pH and the exact species to which the permanganate is reduced. This has important implications for the final concentration of POXC that is calculated from the change in permanganate concentration, and the use of POXC as indicator of soil health.

In this project, we aim to investigate which manganese species is formed during the default POXC procedure. Using a mass balance approach, the student will measure various manganese species as well as total manganese before and after being subjected to soil samples. The student will also investigate the effect of both soil pH and pH of the permanganate solution on the manganese mass balance and on the measured POXC value.

Research theme

Soil Carbon

Used skills

  • Literature review;
  • Proposal and thesis writing;
  • Chemical laboratory work (POXC measurements, Aqua Regia extractions; 0.01 CaCl2 extractions);
  • Data analysis.

Requirements

  • Required courses for the MSc Thesis Soil Chemistry and Chemical Soil Quality (SOC81336);
  • For this topic, some laboratory experience is required.

Supervisor