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Application of organic wastes to subsoil materials can provide sustained soil  quality in engineered soil covers for mine tailings rehabilitation: A 7  years study

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posted on 2023-05-29, 09:41 authored by Mariagrazia .ProtoMariagrazia .Proto, RONAN COURTNEYRONAN COURTNEY

Improper disposal or poor management practices at mine Tailings Storage Facilities (TSF) can give rise to fugitive emissions with risk to both the surrounding environment. Establishing sustainable vegetation covers (rehabilitation) on TSFs is a critical objective and effective management strategy to mitigate pollution risk. Although direct revegetation is a potential strategy, tailings can exhibit properties such as extreme pH, salinity, elevated metal content, deficiency of nutrients and organic matter that inhibit vegetation establishment and necessitate the provision of a cover soil medium (≥ 30 cm). This requires a high amount of topsoil sourcing, which is often in limited supply at mine sites because of degradation, contamination, or previous removal. Moreover, materials often used as a soil cover for tailings may not favour plant establishment and development due to the poor soil structure and the low level of organic matter and nutrient content.

Thus, improvement of substrate physiochemical characteristics by using organic and/or inorganic amendments is needed to promote plant establishment and drive soil processes. While several studies have assessed the feasibility of different plant growth media (soils) they are often based on short-term evaluation in greenhouse and lack the longer term implications of field based studies.

Soil cover materials were evaluated using 1 m3 plots at a Pb/Zn TSF. Treatments included tailings, subsoil and subsoil amended with Compost like Output (CLO) and Spent Mushroom Compost (SMC). Following 7 years' revegetation, soil samples were taken at two depths (0–10 cm and 10–20 cm) and pH, salinity (EC), structure, nutrient and metal content were determined. Vegetation nutrient content was determined after 1 yrs. growth (2015) and again at 7 yrs. (2021).

Bare tailings and subsoil displayed poor physico-chemical properties, whereas SMC or CLO amendment, improved physical characteristics and nutrient content both in soil and in vegetation, showing that the benefits of organic amendment to subsoil materials for rehabilitation are effective in the long-term. Moreover, results showed a higher content of C, N and P in all treatments at the depth 0–10 cm than at 10–20 cm, highlighting the role played by the rhizosphere. While lower vegetation nutrient content was recorded in the in the 2021, in some cases below deficiency criteria, results highlight the need for rehabilitation criteria specific rather than applying standard agronomy guidelines.


Ecological engineering solutions for the long-term and sustainable management of mine processing wastes

Science Foundation Ireland

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Ecological Engineering. 2023, 192, 106971



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