4 Transport of Solutes
The structure of peat and peatlands that creates the inherent complexity in water flow significantly impacts the transport of nutrients, carbon, and contaminants. The complexity of transport is not only related to physical factors but also to biogeochemical conditions. Similar to transport in mineral soils, mass transport in peat and peatlands is controlled by the physical structure of the matrix, hydraulic gradients, the character of the pore network, as well as the properties of the solute.
The movement of solutes through the pore network along with flowing water is called the advective flux. If the solute does not react with the other solutes or the soil, it is considered a conservative solute. Biogeochemical conditions in peat are broadly governed by the reactivity of organic matter and presence of redox sensitive chemical species (i.e., NO3-, SO24–). As such, the hydrophysical structure of the peat aquifer both controls and is subsequently controlled by the mass transport processes (McCarter et al., 2020).
Rapid horizontal and vertical spatial changes in both physical and biogeochemical conditions in peatlands result in complicated solute transport and transformation processes at various spatial scales. Effectively, transport processes at two spatial scales govern the overall solute transport in peatlands:
- processes with the pores of the peat; and,
- processes at the scale of peatlands affected by the spatial distribution of pore properties and influenced by micro-topographic features.
These are discussed in subsections of this chapter.