Characterization of iron hydroxides
The soil system is the largest terrestrial pool of organic carbon (OC) (Schlesinger and Bernhardt, 2013). Estimates of the soil organic carbon (SOC) stocks range from 1415 Gt C in the top meter (Scharlemann et al., 2014), to 2344 Gt C in the top three meters (Jobbágy and Jackson, 2000). Jobbágy and Jackson (2000) estimated that 150 Gt C is stored in boreal forests, while the study by Scharlemann et al. (2014) increases that estimate to 425,8 Gt C in boreal climate regions (top 1 m), and further to 804,5 Gt C if cool temperate climate regions are included.
Studies on subsoil carbon stocks have shown that OC bound to minerals in deep soil is depleted in Δ14C compared to topsoil carbon. This indicates the existence of a stable pool of OC, with slow turnover (Torn et al., 1997, Mathieu et al., 2015). The accumulated SOC in boreal and arctic regions is vulnerable to climate change (Karhu et al., 2010, Nowinski et al., 2010) , with a potential of increased CO2 and methane respiration, which can be a strong positive carbon cycle feedback (Dorrepaal et al., 2009, Nowinski et al., 2010).
The ability of soils to store OC is related to the geochemistry of the soil matrix. Singh et al. (2018) presents three main stabilization mechanisms, physical-, chemical-, and biological protection. Clay minerals together with iron- and aluminum- (oxy)hydroxides (goethite, hematite and Al(OH)3) are the main minerals reacting with OC in soils.
This master thesis takes aim at better understanding the chemical and structural properties of iron hydroxides. It will be part of an ongoing Phd-project studying how OC reacts with these iron hydroxides.
The study will incorporate geochemical modelling and laboratory work using relevant methods to determine the characteristics of synthetic and naturally occurring iron hydroxides, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical analyses using mass spectrometry.
The thesis will give the student good experience with methods commonly used in environmental geology and geochemistry
- Basic knowledge of chemistry
- Basic programming skills
- Students who want to work with this thesis is required to take GEO5900 – Chemical processes in soil and groundwater