Stability of iron minerals in Icelandic peat areas and transport of heavy metals and nutrients across oxidation and salinity gradients – a modelling approach

Abstract

District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand -outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. AbstractThe storage of carbon, metals and nutrients in peat lands at high latitude is sensitive to climate-and land usage changes. This work shows that the thermodynamically most stable iron phases in Icelandic peat areas, like hematite or magnetite do not form, but rather the metastable ferrihydrite, which forms in abundance. Model calculations suggest that this ferrihydrite is able to adsorb high concentrations of natural derived heavy metals (Pb, As, Cr, Cu) and nutrients (P). If this ferrihydrite comes in contact with the oceans, these elements will be released through ferrihydrite-seawater interaction. This process may have significant effects to the chemistry of the near shore environments if ferrihydrite transport to the oceans increase due to future increased flooding and sea level rise.

High-resolution induced polarization imaging of biogeochemical carbon turnover hotspots in a peatland

“…This indicates the ability of IP imaging to resolve the geometry of the peat unit. However, for the survey design used in this study, σ images are not sensitive to materials deeper than ∼ 1.25 m. Images of the electrical conductivity reveal much more considerable variability and a lack of clear contrasts between the peat and the granite materials, likely due to the weathering of the shallow granite unit (Lischeid et al, 2002;Partington et al, 2013).…”

Iron speciation changes and mobilization of colloids during redox cycling in Fe-rich, Icelandic peat soils

“…Upon re-oxidation, the resurgence of ferrihydrite fractions in the soils suggests the rapid oxidation of solid-associated or aqueous Fe(II); a process which is likely to widely occur in-situ: As the majority of wetlands in Iceland are minerotrophic (Arnalds et al, 2016), the continual influx of Fe-rich anoxic porewater combined with the oxidation of Fe(II) in surface soil horizons caused by water table fluctuations or wetland drainage may account for the high accumulation of Fe in the soil horizons. Indeed, recent modeling of the thermodynamic stability of Fe phases in Icelandic peat soils suggests that ferrihydrite is expected to be dominant (Linke and Gislason, 2018). However, neoformation of ferrihydrite occurred only in soil horizons which initially contained ferrihydrite.…”

Comparison of metals content in peatlands with different anthropopressure in Welski Landscape Park (Poland)

“…Heavy metal contamination is characterized by a very long half-life in the surface soil levels. 22 Ombrotrophic bogs bring useful information about human activity on heavy metal contamination in the past. On Oostriku (Estonia) the content of metals (Fe, Zn, Mn, Cu, As) was researched.…”