Organic amendments that consume oxygen can function as reactive barriers, limiting sulfide mineral oxidation in acid-generating tailings; however, they may also promote metal mobilization in surface-oxidized horizons. One decade after applying a 1-m thick organic cover, we observed notable yet stratified biogeochemical and microbial transformations down the reclaimed Anthroposol profile. The surface organic cover layer showed increased nutrient availability alongside declines in organic matter and C:N ratio, reflecting ongoing mineralization and decomposition, and became slightly acidic (pH decreasing from 7.1 to 6.7). Beneath this layer, the interface zone exhibited microbial and geochemical convergence toward more soil-like conditions, where bioavailable P, Zn, Fe, and Cu increased by up to two orders of magnitude. Deeper tailings were slightly acidified, enriched in sulfur- and iron-oxidizing microbial taxa, potentially indicating continued sulfide weathering. Despite the improvements in the interface layer, switchgrass roots largely remained confined to the organic cover, hinting at possible chemical or physical barriers limiting deeper rooting. These findings highlight the short-to-medium-term success of organic covers in enhancing nutrient cycling and fostering microbial succession near the surface. However, persistent weathering underscores the need for complementary strategies, such as deeper amendments or reactive barriers. Given projected climate warming could accelerate organic matter decomposition and sulfide oxidation, increasing the risk of acid generation over time, these findings underscore the importance of sustained organic inputs and adaptive management to ensure long-term reclamation success.

A recently developed Integral Suspension Pressure (ISP) sedimentation-based particle size analysis technique was tested as an alternative to the hydrometer method. The ISP method determines the particle size distribution using an electronic device, namely the PARIO meter. The PARIO meter provides an alternative to collecting manual readings with the hydrometer, by automatically recording differences in suspension pressure during a settling period of up to 24 h at a depth of 18 cm below the surface of the test suspension. The particle size distribution of the samples is then determined by inverse modeling the recorded pressure data. The objective of this study was to validate the accuracy of the ISP method compared to the hydrometer method using a number of soil mixtures manufactured from materials with known particle size composition. Nine soil mixtures with known reference values were analysed by the hydrometer and ISP methods. Statistical comparison of the results revealed that both measurement methods overestimated clay content and underestimated silt content, the hydrometer method providing more accurate results compared to the ISP method. Thirty-eight mixtures of soil were tested using the ISP method to further validate the accuracy. The results indicated that the accuracy of the ISP method depends on the mass of clay-sized particles and the species composition of the clay minerals in suspension. The ISP method obtained more accurate results for soil mixtures containing expandable clay minerals than to those containing non-expandable clays.

The manual addition of lime to soil, in addition to tree planting and fertilization have been the dominant strategy described in restoration protocols for ecosystems damaged by acid rain and metal contamination. Investigations on aerial-limed soils in inaccessible lands are limited. The objective of this study was to assess the effects of aerial liming on soil pH, organic matter, microbial biomass, and enzymatic activities, and aboveground plant population quality in metal-contaminated lands in northern Ontario, Canada. Soil samples were collected from three sites around the City of Greater Sudbury with each pair being composed of a reclaimed (areal-limed) site and an adjacent undisturbed (unlimed) area. Soil physico-chemistry, microbial biomass (assessed by Phospholipid fatty acid analysis) and enzymatic activities were analyzed. Soil pH was higher in limed sites compared to unlimed at recently restored sites (Baby Lake and Wahnapitae) but not at the oldest reclaimed site (HWY 80 N). Organic matter was higher in limed areas compared to the unlimed reference site only at most recently reclaimed site at Baby Lake. Aboveground plant population health was visibly improved in limed sites compared to unlimed areas. Metal concentrations of iron (Fe) and arsenic (As), total microbial biomasses, gram-negative bacterial, fungal, and eukaryotic biomasses were all significantly increased in the limed soils compared to the unlimed samples. The same trend was observed for the activities of three of the enzymes tested, β-N-acetylglucosaminidase (BG), aryl sulfatase (AS), and glycine aminopeptidase (GAP). Interestingly, strong positive correlations between the levels of soil organic matter, microbial biomasses, and NAGase and ALP activities were observed. Although expensive, aerial liming is effective in restoring inaccessible sites impacted by smelting operations where other methods cannot easily be used.

Peatlands are found on all continents, covering 3% of the global land area. However, the spatial extent and causes of metal enrichment in peatlands is understudied and no attempt has been made to evaluate global patterns of metal enrichment in bog and fen peatlands, despite that certain metals and rare earth elements (REE) arise from anthropogenic sources. We analyzed 368 peat cores sampled in 16 countries across five continents and measured metal and other element concentrations at three depths down to 70 cm as well as estimated cumulative atmospheric S deposition (1850–2009) for each site. Sites were assigned to one of three distinct broadly recognized peatland categories (bog, poor fen, and intermediate-to-moderately rich fen) that varied primarily along a pH gradient. Metal concentrations differed among peatland types, with intermediate-to-moderately rich fens demonstrating the highest concentrations of most metals. Median enrichment factors (EFs; a metric comparing natural and anthropogenic metal deposition) for individual metals were similar among bogs and fens (all groups), with metals likely to be influenced by anthropogenic sources (As, Cd, Co, Cu, Hg, Pb, and Sb) demonstrating median enrichment factors (EFs) > 1.5. Additionally, mean EFs were substantially higher than median values, and the positive correlation (< 0.40) with estimated cumulative atmospheric S deposition, confirmed some level of anthropogenic influence of all pollutant metals except for Hg that was unrelated to S deposition. Contrary to expectations, high EFs were not restricted to pollutant metals, with Mn, K and Rb all exhibiting elevated median EFs that were in the same range as pollutant metals likely due to peatland biogeochemical processes leading to enrichment of these nutrients in surface soil horizons. The global patterns of metal enrichment in bogs and fens identified in this study underscore the importance of these peatlands as environmental archives of metal deposition, but also illustrates that biogeochemical processes can enrich metals in surface peat and EFs alone do not necessarily indicate atmospheric contamination.

As the global human population and associated anthropogenic activities rapidly increase, so does the areal extent of dis-turbed soils. Regulatory frameworks must incorporate reclamation criteria and management options for these disturbed soils, requiring consistent descriptions and interpretations. Many human-altered soils cannot be classified using the current Cana-dian System of Soil Classification (CSSC), thus an Anthroposolic order is proposed. Anthroposols are soils that are highly modified or constructed by human activity, with one or more natural horizons removed and replaced, added to, or signif-icantly modified. Disturbed horizons are anthropic in origin and contain materials significantly modified physically and/or chemically by human activities. Three great groups are defined by the presence of anthropogenic artefacts and organic carbon content. Eight subgroups are based on the amount of organic material, thickness of horizons, material composition, hydro-logic regime, and presence of permafrost. Traditional phases and modifiers are used as in the CSSC. The proposed classification has been revised from the original publication in 2012 after field testing and discussion among soil scientists across Canada. This revised classification is proposed for inclusion in the revised CSSC, to account for the very large and expanding aerial extent of disturbed soils in Canada, and to remain current with other global soil taxonomy systems.

Investigations of restored metal contaminated tailings in Canada with regard to their long-term ability to sustain plant and associated microbiological populations are limited. The specific objectives of the present study were to assess (1) The current levels of total and bioavailable metals and (2) Microbial biomass in Cobalt Coleman mine tailings reclaimed in 1990. The level of microbial biomass was determined using Phospholipid Fatty Acid analysis (PLFA). Metal analysis revealed that the concentration of total Arsenic (As) was >100 and 20 ´ higher in the Nipissing tailing compared to the non-tailing site and the Cart Lake tailing. The same trend was observed to a lesser degree for total Cobalt (Co) and Copper (Cu) concentrations. Overall, the total metal levels remain high >30 years after phytoremediation, but the bioavailable metal amount was low. This suggests that soil metal impacts on biota are minimal. The reclaimed tailing exhibited significantly lower levels (p≤0.05) of organic matter compared to non-tailing reference areas. More importantly, the analyses revealed significantly high (p≤0.05) total microbial biomass in non-tailing soil samples (with higher organic matter content) compared to tailing soils. A strong positive correlation (r = 0.87) was observed between organic matter and total microbial biomass. In contrast to other studies, the pH of the two tailing sites was neutral (7.1 and 7.5) and negatively correlated (r = -95) with bacterial and fungal abundance. Bacteria dominated the microbial communities in all the sites including the non-tailing area, indicating that the targeted region is still under severe environmental stress. Overall, the metal levels in the targeted tailings remain high and the phytoremediation did not improve significantly the soil quality (organic matter, microbial biomass) over the last three decades.

Given the ability of engineered metal nanoparticles to be transformed in natural waters in unpredictable manners, various sampling methods must be developed. Here, we took a novel approach to collection silver nano particles (AgNPs) that involved the use of the intact periostracum, the outer proteinaceous organic layer, of freshwater unionid mussels Pyganodon sp. Eight adult mussels were collected in August 2019 from a small boreal lake (L222) at the International Institute for Sustainable Development Experimental Lakes Area (northwestern Ontario), which had been dosed with 15 kg of poly(vinylpyrrolidone)-coated silver nanoparticles (PVP-AgNPs) in 2014-2015. Additionally, three adult mussels were collected from a control lake (L375). Numerous silica (SiO2) diatom frustules were adhered to periostracum of all mussels. Intact periostracum promotes the formation of layer composed of diatoms and sand grains. The Ag content in soft tissues and shells of the mussels from L375 was as low as & LE; 0.1 mu g/g. In mussels from L222, Ag concentrations in the periostracum of five shells were in detectable amounts (1-4 mu g/g); in three shells concentrations were as high as 86, 122, and 494 mu g/g. The underlying mineral shell is depleted in Ag (< 0.1 mu g/g). The Ag content in soft tissue organs (whole body) ranged from 44 to 191 mu g/g. AgNPs occur on the surface of both periostracum and diatoms. Single AgNPs (d = 20-60 nm) were partly sulfidized to Ag2S. The observed AgNPs often form aggregates with an average and a maximal size of circa 100 nm and 1.5 mu m, respectively. Scraping small fragments of intact periostracum of unionid shell is non-lethal to mussels, and is easy to do under field conditions. This simple sampling protocol could be used to detect metal-based nanoparticles (engineered or accidental) with the use of unionid and dreissenid bivalves.

Large areas of metal–contaminated tailings have been revegetated in Northern Ontario (Canada). The specific objective of the present study is to determine if variations in vegetation, and soil physico-chemistry in sulfide tailings is associated with microbial biomass, abundance and diversity. Microbial biomass was determined using Phospholipid fatty acid analysis (PLFA). Amplicon based analysis of the soil bacterial and fungal microbiota was assessed by high throughput sequencing of 16S rRNA gene for bacteria and internal transcribed spacer (ITS) region for fungi. Significant differences in soil pH, organic matter content, and total metals (Cu, Fe, Ni, and Zn) were observed among sites. There were significant variations in microbial biomass among the tailing sites with areas covered with white birch showing the highest level of bacterial and fungal biomass compared to areas vegetated by pines species or pine-white birch mixture. Proteobacteria was the most dominant bacterial phylum while Basidiomycota was the predominant fungal phylum. The most abundant bacterial genus was Mucilaginibacter, followed by Acidobacterium, Acidisphaera, Burkholderia, and Steroidobacter. Site-specific bacterial and fungal genera were identified. However, there were no significant differences for # of OTUs, Chao 1, Simpson index, Shannon index, and species richness among the bacterial populations from different soil tailing areas despite differences in plant populations and soil physico-chemistry. The relative abundance of fungi was associated with the variation in ecology of specific areas. Chao 1, # of OTUs, Simpson index, Shannon index, and species richess were significantly lower at Vale 3 compared to Vale 1 and Vale 5.

Sudbury, Ontario, Canada experienced severe environmental degradation from intensive logging, mining, and smelting activities. Acidification and erosion of soils, as well as heavy metal deposition led to widespread vegetation mortality and the creation of 20 000 ha of barren and 80 000 ha of semi-barren land within the Sudbury region. Restoration processes, consisting of limestone application, fertilization, seeding, and tree planting, was initiated in 1978 and continues to present day. Although initial assessments made immediately following restoration predicted a stable, self-sustaining vegetation community would develop, no formal monitoring protocol was initiated. In this study, we describe the state of four restored sites (3 barren, 1 semi-barren), and their naturally recovering (untreated) analogues, within the Sudbury technogenic barrens 25 to 30 years post-restoration. At each site, two belt transects were established in the restored and untreated areas within which soil pH, tree height and diameter, and ground cover of vegetation identified to species were assessed. Soil pits were excavated to examine pedological development. Soils were Dystric Brunisols in all sites. In restored areas, soil pH and humus layer thickness were generally greater than in areas left to recover naturally. Elevated pH through the soil profile at treated sites indicate limestone application effectively reduced acidity and was sustained up to 30 years post-application. In untreated areas, moss and lichen were abundant, and although vascular plant cover was greater in restored areas, vegetation communities are still significantly different from the reference site. Adequate cover of native understory species was not obtained in any of the treated areas. Results indicate that aerial application of limestone, fertilizer, and seed is less effective than ground application, especially in areas with a high proportion of exposed bedrock. Active restoration has been beneficial to the recovery of the Sudbury technogenic barrens. Continued monitoring will be essential to facilitate the development of a self-sustaining vegetation community.

Peatlands account for 15 to 30% of the world’s soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10–20 cm layer, were 440 ± 85.1 g kg -1 and 13.9 ± 7.4 g kg -1 , with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446–532 g kg -1 ) and lowest in intermediate and extremely rich fens (375–414 g kg -1 ). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.

Mining activities lead to serious land deterioration and large scale mine waste generation. Reclamation has been carried out on several technogenic materials to encourage the development of soils. To date no detailed studies have been conducted to assess if soil developed in reclaimed tailings can be suitable for microbial community sustainability and associated plant population. This study investigated if 1) soil metal contamination affects microbial biomass and composition in sulphide tailings and 2) phytoremediation of tailing increases microbial abundance, diversity, and function. Microbial biomass was assessed using Phospholipid fatty acid analysis (PLFA). Soil bacterial and fungal microbiota was determined by high throughput sequencing of 16S rRNA gene for bacteria and internal transcribed spacer region for fungi using the Illumina platform. Total copper, nickel, iron, and titium were higher in unreclaimed sites compared to vegetated areas but the total microbial biomass was significantly higher in reclaimed sites compared to reference areas. More importantly, the levels of microbial biomass were not impacted by metals since the bioavailable Cu, Ni, and Ti were low in all the sites. Site-specific bacterial and fungal genera were identified. Proteobacteria was the most dominant bacterial phylum while Ascomicota was the predominant fungal phylum. Interestinlgy, Acidiferrobacter, an acidophilic, thermotolerant and facultatively anaerobic was the most predominant genus in unreclaimed site that is characterized by extreme acidity (pH = 2.8). Analysis of microbial diversity revealed higher Chao 1, # of OTUs, Shannon index, and species richness in bacterial and fungal populations from reclaimed sites compared to controls. The levels of β-glucosidase (BG), cellobiohydrolase (CBH), β-N-acetylglucosaminidase (NAGase), aryl sulfatase (AS), acid phosphatase (AP), alkaline phosphatase (AlP), glycine aminopeptidase (GAP), and leucine aminopeptidase (LAP) activities were significantly higher in vegetated sites compared to reference areas. Strong positive correlation coefficients were observed between soil organic matter and total microbial biomass (r = 0.99). These two factors were positively correlated with enzymatic activities and bacterial population diversity. Overall, newly developed soils can sustain diverse microbial communities and associated vegetations.

As evidenced from literature, exposure to non-lethal concentrations of dissolved copper (Cu2+) and copper nanoparticles (CuO NPs) promotes blue mussels susceptibility to various bacterial infections. We study whether pre-exposure (3.5 h) with CuSO4 (100 ?g Cu L-1) and CuO NPs (1000 ?g Cu L-1) will result in infection of M. edulis L. with pathogenic microalga Coccomyxa sp. under field conditions. In May ? September 2019, cages were installed in the site Metis-sur-Mer, St. Lawrence Estuary (QC, Canada) where the native mussel population is known to be infected with the pathogen. Untreated and pre-exposed mussels were grown for up to 130 days. Only the mussels pre-exposed to copper were infected by Coccomyxa. This finding allows proposing that occurrences of Coccomyxa-infected mussels worldwide might have an association with water pollution with xenobiotics. Pre-exposure of caged mussels to copper, as a protocol monitoring for other infectious agents, can be recommended to test.

A detailed analysis of the current state of knowledge of the problems and prospects for phymoremediation of metal(loid) polluted soils illustrate that phytoextraction and phytostabilization have been the foci as widespread and alternative methods of soil phytoremediation. This chapter focuses on the enhancement of phytostabilization by the use of organic soil amendments. The number of publications on organic amendments in phytostabilization of heavy metal(loid) (HM) contaminated soils increases each year and covers all studied groups of additives – composts, sewage sludge/biosolids, humic substances and, especially, fast growing biochar. From the range of forestry by-products such as sawdust, bark chips, and woodchips, pine bark has been demonstrated to be an effective sorbent of both HMs and hydrocarbons. Development of soil remediation approaches for lands contaminated with HMs in recent decades has led to the implementation of a variety of potential technologies.

Application of stable soil amendments is often the key to successful phytostabilization and rehabilitation of mine tailings, and microbial guilds are primary drivers of many geochemical processes promoted by these amendments. Field studies were set up at a tailings management area near Sudbury, Ontario to examine performance of blends of lime stabilized municipal biosolids and compost at nine different rates over thick (1 m) municipal compost covers plantedwith agricultural crops. Based on biogeochemical variability of the substrates four and ten years after application of the initial compost cover, the experimental plots could be classified into three categories: "Low" rate (0-100 t ha(-1) biosolids), "Medium" rate (200-800 t ha(-1)), and "High" rate (1600-3200 t ha(-1)) treatments. The addition of biosolids materials to the thick compost cover at rates higher than 100 t ha(-1) significantly reduced C: N ratio of the substrates, available phosphorus, and some of the nutrient cations, while notably increasing inorganic carbon and the potential solubility of Ni and Cu. This suggests that increasing biosolids application rates may not equivalently ameliorate soil quality and geochemical stability. Correspondingly, microbial communities were altered by biosolids additions, further intensifying the negative impacts of biosolids on long-termefficiency of the initial compost cover. Abundance of cellulose, hemicellulose, and lignocellulose decomposers (as key drivers of mineralization and humification) was significantly reduced by "Medium" and "High" rate treatments. Most DNA sequences with high affinity to denitrifiers were detected in "High" rate treatments where geochemical conditions were optimal for higher microbial denitrification activities. These findings have implications for improving the long-termefficiency of reclamation and environmental management programs inmine tailings of northern temperate climates. Crown Copyright (C) 2020 Published by Elsevier B.V. All rights reserved.

The long-term emission impacts of the nickel processing industry in the Kola Peninsula, the largest source of sulfur dioxide and heavy metals emissions in Northern Europe, have created vast technogenic barrens near the mineral industry complexes. The pace of rehabilitation using the improved remediation technologies to enhance sustainable environmental management and regional economic development is of crucial social and economic importance. In a 120-day incubation experiment, we evaluated the prospects for the restoration of two soils at different degradation stages via carbon pool regulation comparing to mineral ameliorants – NPK fertilizer, and liming agent. Organic additives used included a humic preparation based on an alkaline brown coal extract, wood-derived biochar, and peat-derived gel, supplied by mycorrhizae fungi. The results demonstrate that the selected organic amendments are suitable for restoration of acidic metal contaminated soils. Specifically, the treatments provided a measurable increase in soil carbon content, a marked decrease in acidity, a decrease in extractable metal contents, together with an enhanced nutrient uptake and vegetative growth. A stabilization effect increased from biochar to peat-gel, liming agent and humic preparation, with an accompanying increase in soil pH. Although biochar showed a reduced ability to metal stabilization, the associated treatments were the most productive. The most effective amendments in multi-metallic contaminated soils need to be able to stabilize bioavailability of metals, adjust pH to the optimum for plant growth, and regulate nutrient consumption.

Following the Fukushima Daiichi nuclear power plant accident in 2011, some marine radionuclide monitoring studies report a lack of evidence for contamination of Japanese coastal waters by U and Pu, or state that marine contamination by them was negligible. Nevertheless, Fukushima-derived U and Pu were reported as associated with Cs-rich microparticles (CsMPs) found in local soil, vegetation, and river/lake sediments. Over time, CsMPs can be transported to the sea via riverine runoff where actinides, as expected, will leach. We recommend establishing a long-term monitoring of U and Pu in the nearshore area of the Fukushima Prefecture using marine bivalve mollusks; shells, byssal threads and soft tissues should all be analyzed. Here, based on results from Th biosorption experiments, we propose that U and Pu could be present at concentrations several times higher in shells with a completely destroyed external shell layer (periostracum) than in shells with intact periostracum.