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Project properties |
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| Title | Effect of pH on organic matter concentrations and humic substance fractions |
| Group | Soil Chemistry and Chemical Soil Quality |
| Project type | thesis |
| Credits | 36-39 |
| Supervisor(s) | Nick Quist; Frank van Raffe |
| Examiner(s) | Rob Comans |
| Contact info | Nick.quist@wur.nl |
| Begin date | 2023/02/01 |
| End date | |
| Description | Nutrient and contaminant availability in soil systems is for a large part determined by their adsorption to reactive surfaces, i.e. clay, metal (hydr)oxides, and organic matter (OM). The “reactive†OM fraction is commonly operationally determined by separating the organic OM into different fractions based on their tendency to precipitate at low pH and their hydrophobicity. Ultimately this leads to the fractions humic acid (HA), fulvic acid (FA), hydrophobic neutrals (HON), and hydrophilic acid (Hy); the HA and FA are considered particularly reactive. These fractions have shown to fulfill an adequate predictability in geochemical modelling. Nevertheless, the extreme conditions to which the OM is subjected to during the fractionation have led to heavy debate. Among others, it is uncertain whether these fractions are representative of natural conditions.
During sampling of pore water samples in landfills in the Netherlands, samples with extreme high pH values were found. These samples showed counterintuitive trends in OM concentrations, with decreasing concentrations for these high pH samples while higher OM concentrations are expected. As pH is a major environmental parameter controlling element availability, its effect on OM and its fractions should be properly understood. Currently, knowledge on the effect of pH particularly on the different OM fractions is scarce. This thesis subject will explore this effect through data analysis on a currently existing data set of landfill pore water samples in conjunction with pH stat experiments. In these pH stat experiments, waste/soil/compost will be extracted at varying pH and are analysed for the OM fractions as well as other OM characteristics. |
| Used skills | - Laboratory work (pH stat experiments, OM fractionation)
- Data analysis |
| Requirements | See: https://ssc.wur.nl/Handbook/Course/SOC-81336 |