Adaptation and land use planning strategies for black shale areas in a changing climate

In the bedrock and soils of Southern Lapland, Kainuu and the Oulu region, black shales and other rock and soil types containing sulfur and heavy metals occur naturally. Rock types containing sulfur and heavy metals are characterized by the production of sulfuric acid when they come into contact with oxygen or surface waters, for example in road cuttings, drainage related to forestry, or other earthworks and rock construction activities. The sulfuric acid formed and the resulting decrease in the pH of surface waters promote the dissolution and transport of heavy metals, causing harmful exposure to humans and ecosystems. As a result of climate change, the risks arising from land use in black shale areas will further increase, as warming, increased precipitation, and the growing frequency of extreme weather events accelerate acidification and the transport of harmful substances.

The objective of Luke’s work package is to study the effects of the restoration of drained peatland forests on the loading of nutrients, heavy metals, and suspended solids into water bodies, as well as the role of constructed wetlands in retaining these loads. The study area is the Sanginjoki Nature Reserve, whose bedrock contains black shales. Metsähallitus is restoring drained peatlands within the protected area by removing trees and blocking drainage ditches. The aim of the restoration is to raise the water table so that the hydrology of the peatlands returns to its pre-drainage state. It is known that peatland restoration initially increases the export of nutrients, dissolved carbon, and suspended solids, but there is no research data on the effects of restoration on acidification and the leaching of heavy metals. As a result of rewetting, the oxygen content of the peat decreases, which may reduce acidification caused by the oxidation of sulfur compounds in black shale and limit the solubility of heavy metals. There is no monitoring data under Finnish conditions on the effectiveness of constructed wetlands in reducing waterborne loads.