Structure, composition and diversity of restored forest ecosystems on mine-spoils in South-Western Ghana

In response to national policy obligations, many mining companies in Ghana have restored/reclaimed degraded mined out sites through revegetation. The area extent of such restored areas is unknown and there is also paucity of data on success of restoration, species diversity and compositional dynamics of such restored landscapes, particularly using mixed species. This study assessed stand structure, diversity and composition dynamics of sites restored with mixed species and models species abundance distribution on these sites. Three reclaimed and one control site (adjacent natural forest) were inventoried using 27, 30 x 30 m plots on the Hwini-Butre and Benso concession of the Golden Star Wassa Limited. Overall 3057 (per 24 plots) and 150 (per 3 plots) individual trees were recorded in the overstorey of the reclaimed and control sites, respectively. In all, 31 species in 13 families occurred on the reclaimed site while 61 species in 29 families occurred on the control. Species richness, abundance and diversity were significantly lower in the reclaimed sites than the control in the overstorey (p≤0.018), mid-storey (p ≤ 0.032), and understorey (p≤ 0.031). Species composition of the reclaimed and control sites were mostly dissimilar in the overstorey, midstorey, and understorey. However, the midstorey and overstorey of the reclaimed sites showed high similarity in composition (Jaccard’s index = 0.817). Pioneer and shade-tolerant species were most dominant in the understorey of the control while only shade-tolerant species (mostly herbs and grasses) dominated the reclaimed sites. Species abundance distribution of both reclaimed and control sites followed the geometric series model, indicating that both sites are disturbed but at different intensities. It is concluded that reclamation with mixed species does not necessarily lead to rapid restoration of indigenous climax species on mine spoils. Nonetheless, it may lead to accomplishments of short-term goals of stabilizing and protecting landscapes while conditioning the sites for colonisation of the climax species.

Nano-oxides immobilize Cd, Pb, and Zn in mine spoils and contaminated soils facilitating plant growth

Nanoparticles with high reactivity can be applied as amendments to remediate soil metal contaminations by immobilizing toxic elements. Nano-oxides of Fe have been studied but Al and Ti nano-oxides have not been tested for their remediation capacity of toxic metals. The potential of synthesized iron (Fe-O), aluminum (Al-O), and titanium (Ti-O) nano-oxides for stabilizing Cd, Pb, and Zn in mine spoil (Chat) and contaminated soil was compared using adsorption studies and a greenhouse experiment. Chat and soil were amended with nano oxides at two rates (25 and 50 g kg-1) and a pot experiment was conducted with sorghum (Sorghum bicolor L. Moench). Leachates were collected twice per week from plant emergence to harvest at maturity and metals were compared against an unamended control. Chat was contaminated with Cd, Pb, and Zn at 84, 1583, and 6154 mg kg-1, and soil at 15, 1260, and 3082 mg kg-1, respectively. Adsorption conformed to the Langmuir linear isotherm and adsorption maxima of metals were in the order of Al-O > Ti-O ≥ Fe-O. Nano-oxides reduced Cd concentration by 28% (Fe-O) to 87% (Ti-O) and Zn concentration by 14% (Fe-O) to 85% (Al-O) in plant tissues compared with unamended Chat. Nano-oxides significantly reduced Cd, Pb, and Zn in leachates and available Cd and Zn in Chat/ soil relative to the respective unamended controls. Nano-oxides can be used to remediate heavy metal contaminated Chat and soil and facilitate plant growth under proper nutrient supplements. Nano-oxides of Al-O and Ti-O remediated metals more effectively than Fe-O

Assessment and abatement of the eco-risk caused by mine spoils in the dry subtropical climate

The highly rugged mountainous land topography of the Novorossiysk industrial agglomeration (NW Caucasus, Krasnodar Krai, Russia) and arid climate limit the restoration abilities of disturbed mine lands. Abandoned waste-rock dumps of a marl quarry occupy an area of ca. 150,000 m2 next to the cement plant, residential districts, and a commercial seaport. To assess the eco-risk, topsoil horizons of urban and mine-site Technosols and background Rendzinas were sampled and analyzed; measurements of particulate matter fractions PM1, PM2.5, PM4, and PM10 were conducted throughout the agglomeration. Fugitive dust emission from the unreclaimed marl dumps raises the PM2.5 content in the air by a factor of 2.68 on average. The high sorption capacity of the fine eluvium results in the accumulation of urban emissions by the dust and contributes to the subsequent soil pollution; the Cumulative Pollution Index of pedochemical anomalies reaches the high-risk level over the areas of up to 5 km2. Environmental threats caused by the mine dumps can be assessed more reliably by means of land zoning based on accumulated environmental damage indicators and the debris flow and waterspout risk calculation. To abate the technogenic impact caused by the mine spoils, reclamation actions must be taken including soil stabilization on sensitive sites by application of geosynthetic cover, hydroseeding of the mixture of soil improvers and seeds of herbaceous plants on the slopes, and anti-erosion plantation of cades (Juniperus oxycedrus L.) and smoke trees (Cotinus coggygria Scop.) at subhorizontal surfaces.

Prediction of salt release from coal mine spoils at meso-scale

<p>Open-cut coal mining operations remove enormous quantities of overburden material inorder to access coal seam. Upon interaction with atmospheric conditions, this overburden material referred to as spoils from which salts are leached, possesses the risk of affecting surface and groundwater quality around the mine sites. Due to a distinct lack of field data on leachate rates and chemistry for full-scale spoil piles, studies have relied on geochemical testing at laboratory-scale experiments such as free-draining funnels and columns. While laboratory leaching techniques under a controlled environment are a general predictor of how spoil behaves upon weathering, there remain gaps in understanding the leachate rates taking into consideration actual particle size, flow rates, water content, temperature, and oxygen supply. This study proposes and assesses a new mesoscale approach for predicting salinity release from spoils that is designed to obtain data more relevant to the closure options under consideration. 5 coal mine spoils from 3 mines located in Queensland, Australia was sampled, characterised (physical, geochemical, and mineralogical), and were subjected to weathering at mesoscale (1-2 tonnes sample volume) leaching for 11 cycles under natural conditions. Results showed that soil-like spoils with significant pockets of less permeable clayey or silty material have the ability to retain and release solute slowly with time while rock-like spoils followed a steady decay rate. The mesoscale tests produced distinctive characteristic decay curves of salt release from typical soil-like and rock-like spoils and have been useful in the calibration of flow and moisture-dependent salt kinetic parameters. The mesocosm leaching approach developed as a part of this study was close to real-sized spoil conditions such that it mimicked the water/rock ratios, preferential flow paths, and governing solute transport processes.</p>

Preliminary Studies on Revegetating the Mine Spoils of ACC Limited, Madukkarai Cement Works

During the last two decades, the number of cement factories has increased hugely due to expanding requirement of cement materials for construction. A study was taken in ACC cement works, Madukkarai, Coimbatore to assess the floristic composition of shrubs, herbs and tree species that are available in both mine out soils and soils nearby the factory vicinity. A pot experiment was conducted to find the effect of different biofertilizers on the growth of tree seedlings with potting mixture of minespoil, garden soil and vermicompost in the ratio 1:1:1 on volume basis. The results revealed that the application of phosphobacteria @ 10 g/seedlings enhanced the growth of seedlings to about 20 percent over the control. Therefore, it was concluded that utilizing biofertilizer with proper potting mixture can help to revegetate the mined out spoils of cement industry.