Abstract
Mine closures necessitate vegetation restoration to cover tailings fields and reduce environmental risks. Sole use of forest soil as growth medium provides only low fertility and slow plant growth especially in the harsh boreal climate conditions. This preliminary study examines the feasibility of recyclable waste materials added to forest till soil for improving vegetation success on reclaimed mine tailings. One compost type, three biochar types (Bc1–3) and two ash types (Ash1-2) were studied for physical and chemical properties as well as their effects on the growth and element accumulation of timothy (Phleum pratense L.), white clover (Trifolium repens L.) and Scots pine (Pinus sylvestris L.) during one growing period in a greenhouse. Oxidized surface tailings soil and Ash2 were the finest media components while compost and Ash1 were the coarsest. Tailings soil also had the highest salt contents and electrical conductivity, while in till soil they were at the lowest levels. Timothy and white clover germinated well in moist pure tailings soil but grew poorest in it. White clover grew poorly also in pure till soil. Best biomass growth was in the mixture of till, compost and Bc2 (from sewage sludge and woodchips). Planted pine seedlings grew relatively well in all media during the first growing season but Ash1 (from wood and peat) tended to promote height growth and pure till soil root biomass. In media containing Ash1, pine tissues accumulated B, Ca, Mg, K, Na and S. Elevated As content in tailings soil accumulated in plant shoot tissues slightly; only in the old needles of pine were As levels elevated. The results suggest that till and tailings media with compost added as a nitrogen source can promote adequate plant growth during initial growing seasons. Suitable types of biochar and ash amendments can further expedite plant establishment.
Highlights
Mine closures after ore-extracting activities need landscape reclamation to reduce the environmental disadvantages associated with tailings fields
To summarise the results of this study, the main study hypothesis was supported. This means that pure tailings or till soil alone as growth media did not promote good plant growth during the first growing season
Our second assumption was that biochar addition to the till soil enhances germination and growth of herbaceous plants in particular, but their responses to various biochars differ
Summary
Mine closures after ore-extracting activities need landscape reclamation to reduce the environmental disadvantages associated with tailings fields. Many of the recyclable waste materials, such as biochar, and composted sewage sludge have been suggested and are increasingly being used for soil improvement, landscaping and carbon sequestration to provide faster vegetation restoration on highly degraded lands (Ali et al, 2017; Mendez et al, 2015; Bolan et al, 2021). These recyclable waste materials have been tested and utilized in landscaping of mine reclamation areas (Fellet et al, 2011; Hagner et al, 2021; Page-Dumroese et al, 2018; Peltz and Harley, 2016; Trippe et al, 2021). There are still few studies that focus on the feasibility of different recyclable waste materials in the cover media and their effects on plant species development in mine reclamation areas under boreal climatic conditions, where cool temperatures and a short growing season restrict vegetative growth
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