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In this study, the thaw consolidation properties of fine-grained permafrost soils are investigated in terms of the characteristics of the relationships between the effective stress (σv′), the void ratio (e), and the hydraulic conductivity (kv). A total of 182 individual soil samples are included in the analysis covering a wide range of hydromechanical properties. The data are obtained from geotechnical studies undertaken for the Canadian Arctic Gas Pipeline project in the 1970s in the Mackenzie River Valley, Canada. The investigated characteristics are defined in agreement with the definition formulated by previous thaw consolidation models for fine-grained soils. Based on the general interpretation of the behavior of thawing soils, relationships are developed for the compression index of the thawed soil, the residual stress, the hydraulic conductivity change index of the thawed soil, and the initial hydraulic conductivity of the thawed soil. All properties are influenced by the ice content, which is characterized by the initial thawed void ratio for ice-rich soils and by the thawed void ratio for ice-poor soils. The liquid limit, the clay content, and the median grain size of the fine fraction are used as predictive parameters in combination with the initial ice content. The median grain size of the fine fraction yields the lowest error for the prediction of the characteristics of the σv′−e−kv relationships. [ABSTRACT FROM AUTHOR]

Disturbed sites, such as borrow pits and oil and natural gas well sites, require reclamation to restore and sustain levels of productivity similar to those prior to the disturbance. However, salvaged topsoil at many sites is often insufficient to meet the 80% topsoil replacement depth (TRD80) required for successful reclamation in western Canada. This 5‐year study evaluated soil responses to 50% topsoil replacement depth without organic amendment (TRD50) or amended with either peat (PTRD50) or biochar (BTRD50), relative to the TRD80 treatment (Control), following borrow pit reclamation at a disturbed boreal site near Cold Lake, Alberta, Canada. Amendments were applied once at rates calculated to raise the soil organic carbon (SOC) content in the TRD50 soil to a level equal to that in the TRD80 treatment. Results showed a 143%, 87%, and 116% increase in total Kjeldahl nitrogen concentration in the PTRD50 relative to the TRD80, TRD50, and BTRD50 treatments, respectively, while soil potassium (K) concentration was significantly greater for BTRD50 than PTRD50. Peat and biochar significantly increased SOC concentrations by 83% and 88%, respectively, relative to the mean of TRD80 and TRD50 treatments. Our results show that peat and biochar can improve soil properties of disturbed boreal sites reclaimed with insufficient salvaged topsoil to a level suitable for successful reclamation. This has important implications on the reclamation of a multitude of disturbed sites, in Canada and globally, that have insufficient volumes of salvaged topsoil needed for successful reclamation. [ABSTRACT FROM AUTHOR]

Efficient management of fertilizer phosphorus (P) is crucial for enhanced resilience of agro‐ecosystems. We assessed five rates (0, 5, 10, 15, and 20 kg P ha−1) of starter P fertilizer on silage corn (Zea mays L) yield in high‐P manured soils at eight sites in 2020 and 2021 in the Fraser Valley, Canada, monitoring soil phosphate concentrations using anion exchange membranes (AEM‐P). At the V3 and V6 (3‐ and 6‐leaf) stages, corn dry matter (DM) weight response to starter P was not significant, except at one site where the critical rate was 5 kg P ha−1. At maturity, corn DM yields were in the optimum provincial range (20–25 Mg ha−1), with the exception of two sites, one with low initial soil P concentrations and the other with waterlogged soils. These results indicate that during the growing season, phosphate supply from manure application alone was sufficient for silage corn growth. Root length and diameter were not affected by starter fertilizer, while root surface area, volume, and root DM weight decreased with increasing starter fertilizer at the V3 stage in 2020. In addition, AEM‐P increased with starter P only during the first week after application. We conclude that starter fertilizer P, at any application rate, in high‐P manured soils does not improve silage corn yield; farmers applying manure at plowing in soils with high P concentrations can reduce or eliminate starter fertilizer P without impacting silage corn yields, decreasing reliance on off‐farm P inputs, and reducing potential P loss to the environment. Core Ideas: Response of silage corn to starter fertilizer phosphorus (P) in high‐P manured soils was not consistent across eight sites.Critical starter fertilizer P rate was maximum 5 kg P ha−1 in one responsive site.Mature silage corn yield was not increased by starter fertilizer P across sites.Anion Exchange Membrane‐P mimicked starter P rates only during the first week.Mineral starter P has no benefit in fields with high soil test P receiving manure. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The green manure residual effect on soil health 2 years later in crop rotation is understudied. Little is known about weed biomass impact on soil microbial communities or their interactions. A Colchester County, NS, Canada, organic grain research trial during 2016-2017 comprised 2 or 3-year rotations with or without green manure crop prior to wheat, and then soybeans. Fall soil sampling was conducted both years. The soybean phase of the crop rotation was managed as weedy or non-weedy. Weedy soil showed significantly increased soil respiratory activity and fungal microbial biomass. Green manure treatments did not significantly influence soil health indicators. [ABSTRACT FROM AUTHOR]

BACKGROUND: The disturbance of colonized trees and soil, such as through forestry activities, has been proposed to disperse soil- and tree-inhabiting fungal pathogens. Cryptococcus gattii sensu lato is one such pathogen that was detected on Vancouver Island, British Columbia, Canada, beginning in 1999 and caused human and animal illness. OBJECTIVES: Our aim was to determine if C. gattii s.l. human case incidence on Vancouver Island was correlated with the intensity of landscape-level tree harvesting occurring near human settlement areas. METHODS: We created buffers around human settlement areas with radii increments of 2:5 km, from 2.5 to 20 km, and summed the area of annual tree harvests occurring within each buffer zone. We then performed Spearman rank–order correlation to measure the association between case incidence and annual tree harvest intensity at each radius from 1998 through 2014. RESULTS: The incidence of C. gattii was positively correlated with tree harvesting intensity only at distances of 7:5 km (푟=0.66, 푝=0.004) and 10 km (푟=0.64, 푝=0.005) from human settlement areas. As annual tree harvesting area increased between 1999 and 2003, so did annual C. gattii incidence in humans, before both plateaued around 2002 and decreased after 2007. DISCUSSION: Our findings suggest that tree harvesting plays a role in the spread of C. gattii on Vancouver Island. This may be due to tree cutting or soil disturbance facilitating the aerosolization of spores to increase infection risk. This research also illustrates the contribution that geographic information systems can make to public health research on environmental disturbance and disease outbreaks. [ABSTRACT FROM AUTHOR]

Combined paper mill biosolids (PB) and forest-derived liming by-products improve soil properties, but their residual effects following several years of application have hardly been investigated. A 13-year (2009–2021) field study was initiated at Yamachiche, QC, Canada, to assess the residual effects of PB and liming materials on the properties of a loamy soil. The PB was applied during nine consecutive years (2000–2008) at 0, 30, 60, and 90 Mg wet·ha−1, whereas the 30 Mg PB·ha−1 rate also received one of three liming materials (calcitic lime, lime mud, wood ash) at 3 Mg wet·ha−1. No amendment was applied during residual years. Past liming materials continued to increase soil pH but their effect decreased over time; meanwhile, past PB applications caused a low increase in residual soil NO3-N. Soil total C, which represented 40% of added organic C when PB applications ceased, stabilized to 15% after six years. Soil Mehlich-3-extractable contents declined over the thirteen residual years to be not significant for P, K, and Cu, while they reached half the values of the application years for Zn and Cd. Conversely, Mehlich-3 Ca was little affected by time. Therefore, land PB and liming material applications benefited soil properties several years after their cessation. [ABSTRACT FROM AUTHOR]

Purpose: Risks to native soil-dwelling organisms in terrestrial ecosystems contaminated by petroleum hydrocarbons (PHCs) are difficult to assess due to the range of compounds and their varying toxicity. Weathering of PHCs in soil has been shown to alter their chemical composition and decrease their associated toxicity. Hence, generic regulatory guidelines may inadequately predict risks and exposure scenarios at some sites. Methods: In this study, the toxicity of both coarse- and fine-grained subarctic soils contaminated with weathered PHCs was assessed using two soil invertebrates, Folsomia candida and Proisotoma minuta. In addition to survival and reproduction tests, avoidance behavior was investigated using F. candida, P. minuta, Oppia nitens, and Folsomia bisetosa. Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results and verified the sensitivity of F. candida and P. minuta to contaminants. Results: Despite exceeding the Canada-wide generic guidelines for PHC fraction 3 (F3), weathered contaminated soils at concentrations between 1140 and 5880 mg/kg had no significant negative impacts on the reproduction or mortality rates of F. candida or P. minuta. Furthermore, all four soil invertebrates preferred to inhabit the contaminated soils during the 48 h avoidances tests. Conclusion: Natural weathering processes to PHC-impacted soils at a Canadian Subarctic site have led to a decrease in toxicity on four native soil invertebrates. [ABSTRACT FROM AUTHOR]

The permafrost regions of the boreal forest store a large amount of carbon, which can be affected by ecological disturbance, especially the interference of forest fires. Understanding the dynamic responses of the post‐fire soil fungal community is essential for predicting soil carbon dynamics.We used a post‐fire chronosequence (areas with 3, 25, 46 and >100 years post fire [ypf]) in Canadian boreal forests with continuous permafrost to examine the responses of fungal communities and fungal genes associated with biogeochemical cycling to fire in the surface and near‐surface permafrost layers (0–5, 5–10 and 10–30 cm depth). We hypothesized that as the forest recovers from fire, the fungal communities and functional genes associated with biogeochemical cycling will also recover temporally and spatially, which will in turn affect soil carbon storage.Our results demonstrate that the fire has long‐term effects on fungal communities and functions in the surface and near‐surface soils. The fungal species richness in the 0–5 and 5–10 cm soil layers increased with time since fire, which required at least 46 years to recover to pre‐fire levels. Ascomycota in each of the soil layers in the recently burned area (3 ypf) and ericoid mycorrhizas Oidiodendron maius in the 10–30 cm soil layer in the control area were recognized as indicator taxa.The examination of functional genes revealed that the diversity of potential genes and the expression of genes related to carbon degradation (e.g. chitinase, cellobiase, exoglucanase and endoglucanase) in recently burned area increased in the surface soil, whereas, decreased in the deep soil, suggesting the fire affect the loss of carbon differently in the surface and deep soils in the early stages after fire.In conclusion, the fires significantly altered the fungal communities and functional genes related to carbon storage along the soil vertical gradients and along the post‐fire chronosequence. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Purpose: Although barium (Ba) is a non-regulated element in soil in most European countries, some countries, such as Canada, are adopting quality guidelines for Ba in soil because it can be toxic in high concentrations. The aim of the present study was to assess Ba concentrations and availability in floodplain soils. Methods: Besides the determination of total concentrations, a rapid screening of Ba availability with single extractions recommended by the Standards, Measurements and testing (SMT) program of the European Commission (with CaCl2 (0.01 mol l−1), acetic acid (0.43 mol l−1) and ammonium-EDTA (0.05 mol l−1) solutions) were performed. Additionally, an extraction with a 0.1 mol l−1 CaCl2 solution was executed, to determine 'soluble Ba' in soil as stipulated by the guidelines established in Canada by Alberta Environment. A comparison was also made with Ba concentrations reported in the literature, and with Ba concentrations in floodplain soils included in the FOREGS (Forum of European Geological Surveys) database. Results: Single extractions indicate that in all the soil samples, only a very small proportion of Ba (0.7 to 8.7 mg kg−1, corresponding to 1.5 to 6.6% of the total Ba content) is readily available for uptake by living organisms or for leaching. Elevated total Ba concentrations in soil are not indicative of a higher risk for Ba mobilisation, even when other parameters such as matrix composition and pH are taken into account. Conclusions: The use of single extractions should be considered when environmental quality guidelines are set up for Ba, as they can be useful for a fast screening of potential Ba contamination with an acceptable risk. [ABSTRACT FROM AUTHOR]

Remedial guidelines for petroleum hydrocarbons (PHCs) in soil aid in the mitigation of risks to human health and the environmental. However, some remediation guidelines may overestimate the potential for adverse effects to native plant species, contributing to unnecessary remedial efforts in attempts to meet the guidelines. At sites where PHC-contaminated soils undergo weathering, some PHCs may persist but with decreased bioavailability to organisms. In this study, the toxicity of both coarse and fine-grained subarctic soils, contaminated with weathered PHCs were assessed using five native plant species (Picea mariana, Achillea millefolium, Alnus viridis, Elymus trachycaulus and Salix bebbiana). Soil toxicity tests were conducted in a growth chamber with parameters set to simulate the site's subarctic climate conditions. Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results for the PHC-contaminated soils, and also provide new information on the sensitivities of the four boreal species to boric acid. All plants exhibited reduced growth and germination rates as boric acid concentrations increased. Despite exceeding the Canada-wide standard guidelines for Fraction 3 PHCs, field-collected contaminated soils had no significant negative impacts on the growth (i.e., length, dry weight and emergence) of any of the plant species tested. [ABSTRACT FROM AUTHOR]

Summary: The consequences of soils exposed to hydraulic fracturing (HF) return fluid, often collectively termed flowback and produced water (FPW), are poorly understood, even though soils are a common receptor of FPW spills. Here, we investigate the impacts on soil microbiota exposed to FPW collected from the Montney Formation of western Canada. We measured soil respiration, microbial community structure and functional potentials under FPW exposure across a range of concentrations, exposure time and soil types (luvisol and chernozem). We find that soil type governs microbial community response upon FPW exposure. Within each soil, FPW exposure led to reduced biotic soil respiration, and shifted microbial community structure and functional potentials. We detect substantially higher species richness and more unique functional genes in FPW‐exposed soils than in FPW‐unexposed soils, with metagenome‐assembled genomes (e.g. Marinobacter persicus) from luvisol soil exposed to concentrated FPW being most similar to genomes from HF/FPW sites. Our data demonstrate the complex impacts of microbial communities following FPW exposure and highlight the site‐specific effects in evaluation of spills and agricultural reuse of FPW on the normal soil functions. [ABSTRACT FROM AUTHOR]

Ongoing climate warming in the western Canadian Arctic is leading to thawing of permafrost soils and subsequent mobilization of its organic matter pool. Part of this mobilized terrestrial organic matter enters the aquatic system as dissolved organic matter (DOM) and is laterally transported from land to sea. Mobilized organic matter is an important source of nutrients for ecosystems, as it is available for microbial breakdown, and thus a source of greenhouse gases. We are beginning to understand spatial controls on the release of DOM as well as the quantities and fate of this material in large Arctic rivers. Yet, these processes remain systematically understudied in small, high-Arctic watersheds, despite the fact that these watersheds experience the strongest warming rates in comparison. Here, we sampled soil (active layer and permafrost) and water (porewater and stream water) from a small ice wedge polygon (IWP) catchment along the Yukon coast, Canada, during the summer of 2018. We assessed the organic carbon (OC) quantity (using dissolved (DOC) and particulate OC (POC) concentrations and soil OC content), quality (δ13C DOC, optical properties and source apportionment) and bioavailability (incubations; optical indices such as slope ratio, Sr ; and humification index, HIX) along with stream water properties (temperature, T ; pH; electrical conductivity, EC; and water isotopes). We classify and compare different landscape units and their soil horizons that differ in microtopography and hydrological connectivity, giving rise to differences in drainage capacity. Our results show that porewater DOC concentrations and yield reflect drainage patterns and waterlogged conditions in the watershed. DOC yield (in mgDOCg-1soilOC) generally increases with depth but shows a large variability near the transition zone (around the permafrost table). Active-layer porewater DOC generally is more labile than permafrost DOC, due to various reasons (heterogeneity, presence of a paleo-active-layer and sampling strategies). Despite these differences, the very long transport times of porewater DOC indicate that substantial processing occurs in soils prior to release into streams. Within the stream, DOC strongly dominates over POC, illustrated by DOC/POC ratios around 50, yet storm events decrease that ratio to around 5. Source apportionment of stream DOC suggests a contribution of around 50 % from permafrost/deep-active-layer OC, which contrasts with patterns observed in large Arctic rivers (12 ± 8 %; Wild et al., 2019). Our 10 d monitoring period demonstrated temporal DOC patterns on multiple scales (i.e., diurnal patterns, storm events and longer-term trends), underlining the need for high-resolution long-term monitoring. First estimates of Black Creek annual DOC (8.2 ± 6.4 tDOCyr-1) and POC (0.21 ± 0.20 tyr-1) export allowed us to make a rough upscaling towards the entire Yukon Coastal Plain (34.51 ± 2.7 ktDOCyr-1 and 8.93 ± 8.5 ktPOCyr-1). Rising Arctic temperatures, increases in runoff, soil organic matter (OM) leaching, permafrost thawing and primary production are likely to increase the net lateral OC flux. Consequently, altered lateral fluxes may have strong impacts on Arctic aquatic ecosystems and Arctic carbon cycling. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accuracy of infrared (IR) models to measure soil particle-size distribution (PSD) depends on soil preparation, methodology (sedimentation, laser), settling times and relevant soil features. Compositional soil data may require log ratio (ilr) transformation to avoid numerical biases. Machine learning can relate numerous independent variables that may impact on NIR spectra to assess particle-size distribution. Our objective was to reach high IRS prediction accuracy across a large range of PSD methods and soil properties. A total of 1298 soil samples from eastern Canada were IR-scanned. Spectra were processed by Stochastic Gradient Boosting (SGB) to predict sand, silt, clay and carbon. Slope and intercept of the log-log relationships between settling time and suspension density function (SDF) (R2 = 0.84–0.92) performed similarly to NIR spectra using either ilr-transformed (R2 = 0.81–0.93) or raw percentages (R2 = 0.76–0.94). Settling times of 0.67-min and 2-h were the most accurate for NIR predictions (R2 = 0.49–0.79). The NIR prediction of sand sieving method (R2 = 0.66) was more accurate than sedimentation method(R2 = 0.53). The NIR 2X gain was less accurate (R2 = 0.69–0.92) than 4X (R2 = 0.87–0.95). The MIR (R2 = 0.45–0.80) performed better than NIR (R2 = 0.40–0.71) spectra. Adding soil carbon, reconstituted bulk density, pH, red-green-blue color, oxalate and Mehlich3 extracts returned R2 value of 0.86–0.91 for texture prediction. In addition to slope and intercept of the SDF, 4X gain, method and pre-treatment classes, soil carbon and color appeared to be promising features for routine SGB-processed NIR particle-size analysis. Machine learning methods support cost-effective soil texture NIR analysis. [ABSTRACT FROM AUTHOR]

Multiple metal‐impacted soils are often realistic scenarios for risk assessments, but tools to address these are currently lacking. The objective of this work was to evaluate whether assuming concentration addition (CA) of metal mixture effects was conservative for prospective risk assessment of soils that were elevated mainly in Ni and Cu and somewhat with Co, Pb, or As. Observed whole mixture toxicity for field soils with aged metal mixtures was compared to the expected whole mixture toxicity, assuming additivity of prospective single‐metal thresholds ("toxic units") for the mixture components. Bioavailability‐adjusted single‐metal toxicity thresholds expected for those field soils were the median hazard concentration affecting 5% of species (HC5‐50) from the predicted no‐effect concentration (PNEC) calculator and calculated from the species‐specific dose–response multiple linear relationships (MLRs), all from the European Union Registration, Evaluation, Authorisation and Restriction of Chemicals (EU REACH) dossiers for metals. Generic single‐metal toxicity thresholds were based on Canadian Council of Ministers of the Environment soil quality guidelines (CCME SQGs) for agricultural soils. Observed toxicity thresholds were from the community‐based risk assessments conducted for Port Colborne and Sudbury, Ontario, Canada. Mostly, prospective single‐metal toxicity thresholds were protective relative to the observed toxicity, although that was species or ecological process dependent. The bioavailability‐adjusted single‐metal thresholds were less conservative than the CCME SQG method, even though the former is based on site‐specific EC10 values, and the latter is based on generic EC25 values. When within‐site variability in soil properties was used to calculate the 5th and 95th CI for the HC5 sum of toxic units (∑TUs), CA was conservative for far fewer endpoints. In addition, the prospective ∑TUs were more conservative predictions of the observed whole mixture toxicities for Port Colborne soils than for Sudbury soils. The most appropriate balance of accuracy and conservatism for identifying low‐level risk of the whole mixtures in these soils appeared to be the bioavailability‐adjusted HC5‐50, which was applicable to many endpoints and 2 quite different exposure concentration ratios. Integr Environ Assess Manag 2021;17:753–766. © 2020 SETAC KEY POINTS: Observed whole mixture toxicity for field soils with aged Ni, Cu, Co, Pb, and As mixtures was mostly less than predicted by assuming additivity of prospective single‐metal thresholds (i.e., toxic units) for various receptors, including soil arthropods, plant communities, and microbial processes.The bioavailability‐adjusted single‐metal thresholds (from the European Union predicted no‐effect concentration [PNEC] calculator and its database) were less protective than Canada's Council of Ministers of the Environment soil quality guidelines, even though the former are site‐specific EC10 values and the latter are generic EC25 values.When the 5th and 95th CI for the bioavailability‐adjusted single‐metal thresholds were calculated using Monte Carlo analysis of within‐site variability in the soil properties used for the bioavailability‐adjusted single‐metal thresholds, assuming additivity protected fewer endpoints from the mixture.The most appropriate balance of accuracy and protection for identifying low‐level risk of the whole mixtures in these soils, with a wide variety of endpoints and 2 different soil Ni‐to‐Cu concentration ratios, was the bioavailability‐adjusted HC5‐50, which is derived from many organisms and endpoints. [ABSTRACT FROM AUTHOR]

Stagnating potato tuber yields in Prince Edward Island (PEI) are a major economic concern. Identification of factors influencing within-field yield variation may provide insight into strategies for overcoming yield limitations. A survey approach was used where soil samples were collected from 49 commercial fields from 2014 to 2017 from a total of 289 sampling points, with points identified as having either "high" or "low" yield, determined by yield monitor as being 5.6–11.2 t ha−1 above or below average field yield, respectively. A suite of 33 measures of soil physical and chemical properties and soil pathogens were measured. Principal component analysis identified three principal components (PCs) which accounted for 85.6% of the total variation. The PC1 (reflecting 42.3% of the total variance) was associated primarily with soil texture (i.e., sand, clay) and parameters which were highly correlated with soil texture. Under the rainfed potato production on sandy-loam soils in PEI, finer soil texture is likely related to increased yield through its effect on improved soil water holding capacity. The PC2 (reflecting 29.0% of the total variance) was primarily associated with soil fertility and the PC3 (reflecting 14.4% of the total variance) was associated primarily with soil organic matter quality and soil structure. Although soil pathogens were measured at levels high enough to impact yield, they did not differ significantly between high and low yield locations. The findings of this study highlight the value in using multivariate approaches to overcome the challenges in identifying factors which control within-field yield variability. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study by E. S. Acheson and colleagues on the impact of forest disturbance due to tree harvesting on the incidence of cryptococcus gattii fungal infection. Topics mentioned include the ecological factors that contributed to the spread of cryptococcosis, the increase in aerosolization of cryptococcus gattii spores after tree cutting, and the importance of risk assessment and mitigation in forest practices to protect communities and forest personnel.

The North American Project to Evaluate Soil Health Measurements was initiated with the objective to identify widely applicable soil health measurements for evaluation of agricultural management practices intended to improve soil health. More than 20 indicators were chosen for assessment across 120 long‐term agricultural research sites spanning from north‐central Canada to southern Mexico. The indicators being evaluated include common standard measures of soil, but also newer techniques of visible and near‐infrared reflectance spectroscopy, a smart phone app, and metagenomics. The aim of using consistent sampling and analytical protocols across selected sites was to provide a database of soil health indicator results that can be used to better understand how land use and management has affected the condition of soil ecosystem provisioning for agricultural biomass production and water resources, as well as nutrient and C cycling. The objective of this paper is to provide documentation of the overall design, and methods being employed to identify soil health indicators sensitive across agricultural management practices, pedologies, and geographies. [ABSTRACT FROM AUTHOR]

Ecosystem reconstruction after mining disturbance is a challenge considering the multitude of factors that affect soil formation and revegetation. In the boreal forest of western Canada, peat material is often used as the organic amendment for land reclamation to upland forest. Carbon and water dynamics of peat‐dominated ecosystems differ from natural upland forest soils. The objective of this work was to evaluate the evolution of soils reconstructed after mining disturbance using 13C and 2H analyses of n‐alkane tracers. Ten soils from natural ecosystems were sampled (0–10 cm) and compared with 11 soils from novel ecosystems ranging in age from 0 to 30 yr, as well as a fresh peat sample. Soils supported different vegetation, including pine (Pinus spp.), aspen (Populus spp.), and white spruce [Picea glauca (Moench) Voss]. Despite overlaps for some individual n‐alkanes, we found a dominance of n‐C25 in reconstructed soils, also dominant in the peat material, and a dominance of n‐C27 in natural soils, one of the dominant n‐alkanes in natural forest vegetation. In addition, there was a significant difference in odd n‐alkane δ2H and δ13C values between natural and reconstructed soils (p <.05). Differences in δ2H values, more negative for reconstructed soils than for natural soils, were attributed to changes in soil moisture, from wetter peat‐dominated soils to drier upland forests; among forest types, δ2H values were most negative under pine vegetation. The δ13C composition of odd n‐alkanes, in particular n‐C27, was significantly related to tree age (p <.05). Overall, both 2H and 13C isotopic signatures of odd n‐alkanes exhibited differences between natural and reconstructed soils. However, within the reconstructed soils, neither isotopic signature showed a clear evolution with age since reclamation. [ABSTRACT FROM AUTHOR]

• Experimental investigation on the nutrient metals in potato soils of eastern Canada. • An eXplainable MBA-AdaBoost coupled with SelectKbest to predict copper and zinc. • Optimization of huge physicochemical inputs using the SelectKbest feature selection. • Validating the primary model using MBA-CatBoost, classical AadaBoost, KRR, and MARS. Plant growth is significantly dependent upon the combination and concentration of mineral nutrients in the soil, where the adequate supply of these nutrients is a severe issue in fulfilling the fundamental cellular process requirements. This study collected 22 physicochemical properties of tilled potato soils from eight stations in two Atlantic Canadian provinces (Prince Edward Island and New Brunswick). Along with the experimental investigation, an explainable dual pre-processing inspired-intelligent paradigm comprised of the SelectKbest feature selection (FS), modified bat algorithm (MBA), adaptive boosting (AdaBoost), and Shapley Additive Explanations (SHAP) explainer was designed to monitor the micronutrients, including copper (Cu) and zinc (Zn). The significant data predictors were filtered using the SelectKbest FS to monitor Cu and Zn. The MBA was coupled with AdaBoost for tuning the hyperparameters to ensure accurate predictions. To validate the outcomes of the MBA-AdaBoost, four advanced machine learning approaches, including categorical boosting (CatBoost) coupled with MBA (MBA-CatBoost), classical AadaBoost, ridge kernel regression (KRR), and multivariate adaptive regression splines (MARS), were examined to compare the accuracies. The robustness of the developed framework and the performance of comparative models were examined through several statistical metrics. Results revealed that the MBA-CatBoost performed the best in predicting the Cu (R = 0.9425, U 1 = 0.1020, and U 22 = 0.2036) and Zn in the soil (R = 0.9454, U 1 = 0.0942, and U 2 = 0.1858) when compared with other models. Furthermore, the SHAP explainer interpreted the block-box main model during the training phase by introducing the CEC and Fe as significant predictors to monitor the soil Cu and Zn, respectively. These findings demonstrate a clear and robust relationship between the presented modeling approach and the accurate prediction of soil micronutrient concentrations. Accurate predictions of micronutrients using these advanced techniques can be used to tailor site-specific micromovement management in agriculture fields to reduce production costs, increase farm profitability, and lower environmental contamination. [ABSTRACT FROM AUTHOR]

Kruger 2 is unique among Late Paleoindian sites of eastern Canada because of the presence of a potential hearth (feature #1) characterized by a concentration of blackened fire‐cracked rock and burnt bone embedded in a thick Ae horizon. Comparative mineralogical analysis (X‐ray diffraction) of Ae samples collected inside and outside the feature reveal the absence of calcite and apatite, two minerals commonly found in ashes, and the presence of smectite in the Ae inside feature #1. Smectite genesis is attributed to the weathering of mica and chlorite under geochemical conditions (high base cations, Si and pH; low Al) that are unique in time and space. We hypothesize that these conditions were created by the dissolution, 10,000 years ago, of a layer of hearth ashes resting on an incipient soil. Results confirm the intense weathering of mica and chlorite. We also show that ash dissolution could generate the conditions for smectite formation in the presence of altered mica and chlorite, allowing the development of a chronology explaining this finding. The data largely support our hypothesis and constitute a strong basis for future investigations on the links between hearth ash weathering and smectite genesis in acidic soils. [ABSTRACT FROM AUTHOR]

This paper summarizes the results from a comprehensive laboratory experimental research program conducted at the University of British Columbia, Canada to study the mechanical behavior of natural fine-grained soils. Constant-volume direct simple shear tests were performed on natural silt samples collected from various locations in British Columbia to investigate the monotonic and cyclic shear loading response of these materials. Influencing factors such as effective confining stress, over-consolidation ratio, initial static shear bias, soil plasticity, and soil fabric/micro-structure on the mechanical behavior of silts were systematically investigated using a series of controlled laboratory tests. The key observations arising from these examinations are presented and discussed to serve as input for the development and/or refinement of design practice approaches for seismic geotechnical design. New directions to be considered to advance the current state of understanding and knowledge on the mechanical behavior of natural fine-grained soils are identified. • Seismic response of natural fine-grained soil was experimentally investigated. • Effect of wide range of physical parameters on the soil behavior was investigated. • Behavioral patterns were explored for a number of different natural soils. • Outcomes were interpreted and translated for potential practice usage. • Findings will contribute to advancement of earthquake engineering design practice. [ABSTRACT FROM AUTHOR]

Adequate phosphorus (P) is needed for crop production, but excessive P poses a potential risk to water quality. Results from the cumulative P balance calculations within the indicator of risk of water contamination by phosphorus (IROWC‐P) developed in Canada were assessed to determine the spatial and temporal trends in P accumulation at a regional scale and to consider the implications of these trends. Regional cumulative P balances were calculated from census data as a proxy for soil test P (STP) values, including the contribution of fertilizer or manure P to these balances. Ideally, over time we would see a convergence of soil test values at the low end of the critical response range for crop growth, where agronomic and environmental considerations are balanced, but this does not appear to be the case for many regions in Canada. Nationally, about 61% of agricultural land was predicted to be low in STP, and over half of this land is failing to replace the P that is removed each year. While only about 10% of the agricultural land has accumulated significantly more P than is needed for crop growth, almost all of this land is continuing to accumulate P rather than drawing it down. Manure is the dominant P source for continuing accumulation in regions with high or very high estimated STP; reducing this input will be difficult because of the nature of manure and the investment in buildings and infrastructure tied to specific locations, but it is clear that current Canadian policies need strengthened. Core Ideas: Neither deficiency nor excess of P in soil is desirable.Imbalanced P distribution across Canada shows significant areas of deficiency and excess.Regions with high P soils continue to be enriched while regions with low P soils are depleted.In most high P regions, continued P buildup is dominated by livestock manure.Options to rebalance P inputs in these regions include dispersing livestock operations. [ABSTRACT FROM AUTHOR]

The spatial variability in soil physical and hydraulic properties for a managed podzol was assessed using soil apparent electrical conductivity (ECa). Two EMI sensors, the multi-coil (MC) and multi-frequency (MF), were adopted for measurement of ECa on a silage- corn experimental plot in western Newfoundland, Canada. Results demonstrated a significant relationship between the ECa mean relative differences (MRD) and the soil moisture content MRD (R2 = 0.33 to 0.70) for both MC and MF sensors. The difference in depth sensitivity between MC and MF sensors accounted for the variation (0.015 to 0.09) in ECa standard deviation of the relative differences. A significant linear relationship was found between the ECa MRD and sand (R2 = 0.35 and 0.53) or silt (R2 = 0.43), but not with clay (R2 = 0.06 and 0.16). The spatial variability of the ECa-based predictions (CV = 3.26 to 27.61) of soil properties was lower than the measured values (CV = 5.56 to 41.77). These results inferred that the temporal stability of ECa might be a suitable proxy to understand the spatial variability of soil physical and hydraulic properties in agricultural podzols. [ABSTRACT FROM AUTHOR]

Soil respiration is a crucial source of carbon dioxide (CO 2) in the atmosphere. The underlying processes involved are multifaceted, sequential chemical reactions associated with the conversion of soil organic carbon to CO 2. In this paper, we present a mechanistic, biogeochemical model to simulate soil CO 2 emissions considering the microbial and sequential chemical processes using the well-established hydrological model, Soil and Water Assessment Tool (SWAT) for the first time. The soil CO 2 emissions from multiple sequential soil chemical reactions were compared with the observed data at three sites in Canada. The results show that the modelled CO 2 emission rates are in good agreement with the observed data with performance statistics: PBIAS: 0.13%–23%; NSE: 0.27 to 0.62; RSR: 0.60 to 0.84; R2: 0.29 to 0.83. This approach could be used in future regional to global-scale models for simulating the soil CO 2 emission and hydrological processes. Image 1 • Modelling of soil organic matter (SOM) decomposition. • Soil chemical reactions modelling using microbial kinetics and thermodynamics. • Modelling of soil autotrophic respiration and soil heterotrophic respiration. • Modelling of soil CO 2 emissions using the soil and water assessment tool (SWAT). • Watershed-scale modelling of soil CO 2 emission using SWAT tool. [ABSTRACT FROM AUTHOR]

Earthmaster and the University of Waterloo have successfully developed plant growth promoting rhizobacteria (PGPR) - Enhanced Phytoremediation Systems (PEPSystemsTM) which have been deployed across Canada for the treatment of soil contaminated with petroleum hydrocarbons (PHCs), including CCME fractions F2 and F3. A challenge with phytoremediation is to predict the length of time to remediate a site so that site owners will be inclined to use the technology. In previous field trials of PEPSystems, it was determined that PHC was mostly degraded by microbes in the rhizosphere, following first-order exponential decay kinetics. Using new PEPSystems data collected from multiple commercial remediation sites across Western Canada, the kinetic equations of PHC decay were tested to determine if remediation time was accurately predicted. In general, when compared to the predicted time to remediation endpoint, data from recent commercial field applications showed that 35% and 20% less time was needed to reach remediation endpoints for fractions F2 and F3, respectively. As a result, the predictive kinetic equation for fraction F2 degradation was updated to reflect current remediation outcomes. Insufficient data were available to update the F3 equation. Being able to more accurately predict remediation timelines will enhance the value and utilization of PEPSystems. [ABSTRACT FROM AUTHOR]

Monoaromatic hydrocarbons such as benzene, toluene, ethylbenzene, and o, m, and p-xylenes (BTEX) are high-risk pollutants because of their mutagenic and carcinogenic nature. These pollutants are found with elevated levels in groundwater and soil in Canada at several contaminated sites. The intrinsic microbes present in the subsurface have the potential to degrade pollutants by their metabolic pathways and convert them to non-toxic products. However, the low subsurface temperature (5–10 °C) limits their growth and degradation ability. This study examined the feasibility of subsurface heat augmentation using geothermal heating for BTEX bioremediation. Novel potent BTEX-degrading bacterial strains were isolated from soil at 3.0, 42.6, and 73.2 m depths collected from a geothermal borehole during installation and screened using an enrichment technique. The selected strains were identified with Sanger sequencing and phylogenetic tree analysis, revealing that all the strains except Bacillus subtilis are novel with respective to BTEX degradation. The isolates, Microbacterium esteraromaticum and Bacillus infantis showed the highest degradation with 67.98 and 65.2% for benzene, 72.8 and 71.02% for toluene, 77.52 and 76.44% for ethylbenzene, and 74.58 and 74.04% for xylenes respectively. Further, temperature influence at 15 ± 1 °C, 28 ± 1 °C and 40 ± 1 °C was observed, which showed increased growth by two-fold and on average 35–49% more biodegradation at higher temperatures. Results showed that temperature is a positive stimulant for bioremediation, hence geothermal heating could also be a stimulant for in-situ bioremediation. [Display omitted] • Monoaromatic hydrocarbons such as BTEX are high-risk pollutants. • The isolates, M. esteraromaticum and B. infantis showed the highest degradation. • Bacterial growth and BTEX degradation increased with elevated temperature. • Heat generated from geothermal heating could be useful to enhance bioremediation. [ABSTRACT FROM AUTHOR]

Agriculture produces food, fiber and biofuels for the world's growing population, however, agriculture can be a major contributor of nitrogen (N) losses including emissions of ammonia (NH 3), nitrous oxide (N 2 O) and nitrate (NO 3 −) leaching and runoff. A Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed to estimate the soil N balance in 3487 soil landscape of Canada polygons from 1981 to 2016. The CANBNr model integrates NH 3 emission from fertilizers, manure from housing, storage and field, as well as direct/indirect N 2 O emissions from fertilizers, manures, crop residues and soil organic matter. The NO 3 − leaching is estimated based on the residual soil N (RSN) at harvest and drainage derived with the DeNitrification-DeComposition (DNDC) model. From 1981 to 2016, the N input from fertilizer and N fixation increased at a greater rate than N removal in harvested crops in all provinces of Canada, resulting in an increase in the RSN and N losses. In 2016, the Prairie provinces had lower N losses (11.7 kg N ha−1) from N 2 O, NH 3 and NO 3 − compared with 43.2 kg N ha−1 in central Canada, and 76.5 kg N ha−1 in Atlantic Canada. However, the Prairie provinces had 84.3% of the total Canadian farmland (74.3% of the total Canadian N input), while central Canada had 12.9% of Canadian farmland (21.7% of the total Canadian N input). In the Prairie provinces, the total N 2 O loss from fertilizer N ranged 4.4–8.6 Gg N whereas NH 3 loss ranged from 17.1 to 44.6 Gg N and these values were influenced by both emission intensity and total land area. Total N 2 O losses from manure were highest in Alberta, Ontario and Quebec resulting in 4.8, 4.4, and 3.4 Gg N and NH 3 losses from manure were also highest in these 3 provinces at 61.1, 45.2 and 40.4 Gg N, respectively. Nitrate leaching was impacted by drainage volumes, soil type and N inputs. In the non-growing season, NO 3 − leaching losses (36-yr average) were 63.3 Gg in Ontario and 57.5 Gg N in Quebec compared with 20.8 Gg N for Ontario and 35.5 Gg N for Quebec in the growing season. In contrast, the Prairie provinces showed higher NO 3 − leaching in the growing season (23.1–37.4 Gg N) than in the non-growing season (10.4–13.7 Gg N). In summary, total fertilizer N increased the most over the 36 years in the Prairies which resulted in increased RSN and N leaching losses that will require further intervention. [Display omitted] • Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed. • The N budget were simulated at 3487 soil landscape of Canada polygons from 1981 to 2016. • RSN and N losses increased due to the greater increase in N input from fertilizer and N fixation than N removal by crop. • The Prairie provinces had lower N 2 O, NH 3 and NO 3 − leaching losses per hectare farmland than other provinces. [ABSTRACT FROM AUTHOR]

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In the last decade, Lake Erie, one of the great lakes bordering Canada and the USA has been under serious threat due to increased phosphorus levels originating from agricultural fields. Large scale watersheds contributing to Lake Erie from the USA side are being simulated using hydrological and water quality (H/WQ) models such as the Soil and Water Assessment Tool (SWAT) and the results from the model are being used by policy and decision makers to implement better management decisions to solve emerging phosphorus issues. On the Canadian side, modeling applications are limited to either small watersheds or one major watershed contributing to Lake Erie. To the best of our knowledge, no efforts have been made to model the entire contributing watersheds to Lake Erie from Canada. This study applied the SWAT model for Northern Lake Erie Basin (NLEB; entire contributing basin to Lake Erie). Various provincial, national and global inputs of weather, land use and soil at various resolutions was assessed to evaluate the effects of input data types on the simulation of hydrological processes and streamflows. Twelve scenarios were developed using the input combinations and selected scenarios were evaluated at selected locations along the Grand and Thames Rivers using model performance statistics, and graphical comparisons of time variable plots and flow duration curves (FDCs). In addition, various hydrological components such as surface runoff, water yield, and evapotranspiration were also evaluated. Global level coarse resolution weather and soil did not perform better compared to fine resolution national data. Interestingly, in the case of land use, global and national/provincial land use were close, however, fine resolution provincial data performed slightly better. This study found that interpolated weather data from Environment Canada climate station observations performed slightly better compared to the measured data and therefore could be a good choice to use for large-scale H/WQ modeling studies. [ABSTRACT FROM AUTHOR]

Elemental concentrations and bioaccessibility were determined in background soils collected in Canada as part of the North American Geochemical Landscapes Project. The concentrations of As, Cr, Cu, Co, Ni and Zn were higher in the C-horizon (parent material) compared to 0-5 cm (surface soil), and this observation along with the regional distribution suggested that most of the variability in concentrations of these elements were governed by the bedrock characteristics. Unlike the above-stated elements, Pb and Cd concentrations were higher in the surface layer reflecting the potential effects of anthropogenic deposition. Elemental bioaccessibility was variable decreasing in the order Cd > Pb > Cu > Zn > Ni > Co > As > Cr for the surface soils. With the exception of As, bioaccessibility was generally higher in the C-horizon soils compared to the 0-5 cm soils. The differences in metal bioaccessibility between the 0-5 cm and the C-horizon and among the provinces may reflect geological processes and speciation. The mean, median or 95th percentile bioaccessibility for As, Cr, Cu, Co, Ni and Pb were all below 100 %, suggesting that the use of site-specific bioaccessibility results for these elements will yield more accurate estimation of the risk associated with oral bioavailability for sites where soil ingestion is the major contributor of human health risk. [ABSTRACT FROM AUTHOR]

Drilling at the c. 750 m deep Halliday Lake prospect in the Athabasca Basin has identified features favourable for unconformity-related U mineralization such as sandstone enrichments in pathfinder elements, graphitic metapelite gneiss, sandstone and basement hosted faulting, hydrothermal alteration and sub-economic U mineralization. Soils, jack pine (Pinus banksiana) and black spruce (Picea mariana) tree cores were collected on a 250 m sampling grid to assess their effectiveness as exploration geochemical media for concealed mineralization. The <2 μm soil clay-size fractions comprise mixtures of quartz, chlorite, illite, kaolinite, and plagioclase with the plagioclase reflecting basement boulders transported in the Quaternary cover. Basement rocks in the till impart a geochemical signature enriched in K, Ba, Bi, Co, Cr, Cs, Cu, Li, Mn and Ni, complicating the interpretation of some pathfinder elements in the <2 μm soil clay-size fraction. Tree cores have Mo, Co, Cu and S enrichments in areas of thin overburden also associated with sandstone hosted hydrothermal alteration and pathfinder element enrichment. Radiogenic Pb isotope ratios in the <2 μm soil clay-size fraction are associated with drill holes hosting sub-economic U mineralization whereas barren drill holes are spatially associated with common Pb isotope ratios. Radiogenic tree core Pb isotope ratios are supportive of the <2 μm soil clay-size fraction Pb isotope ratios. [ABSTRACT FROM AUTHOR]

Measuring soil organic carbon (SOC) in riparian forest soils affected by floods is crucial for evaluating their concentration and distribution along hydrological gradients (longitudinal and transversal). Hydromorphological factors (e.g., sedimentation vs. erosion, size of floodplain, flood recurrence) may be the cause of major variations in the concentration of organic matter and SOC in soils and could have a direct impact on C levels in soil profiles. For this study, SOC concentrations were assessed in riparian soils collected along transects perpendicular to the riverbanks which cross through inundated and non-inundated zones. Other soil properties (e.g., acidity, nitrogen, texture, bulk density) that may affect the concentration of SOC were also considered. The main purpose of this study was to assess SOC concentrations in soils subjected to flooding with those outside the flood zones, and also measure various soil properties (in surface soils and at various depths ranging from 0 to 100 cm) for each selected area. Across the various areas, SOC shows marked differences in concentration and spatial distribution, with the lowest values found in mineral soils affected by successive floods (recurrence of 0-20 years). SOC at 0-20 cm in depth was significantly lower in active floodplains (Tukey HSD test), with average values of 2.29 ±1.64% compared to non-inundated soils (3.83 ±2.22%). The proportion of C stocks calculated in soils (inundated vs. non-inundated zones) was significantly different, with average values of 38.22 ±10.40 and 79.75 ±29.47 t·ha-1, respectively. Flood frequency appears to be a key factor in understanding the low SOC concentrations in floodplain soils subjected to high flood recurrence (0-20 years). [ABSTRACT FROM AUTHOR]

Chlorinated organic compounds, such as polychlorinated biphenyls (PCBs), are a threat to both humans and the environment because of their toxicity, persistence, and capacity for long-range atmospheric transport. The concentrations of 28 PCB congeners, including 12 dioxin-like and seven indicator PCBs, were investigated in soils, and indoor and outdoor dusts from Port Harcourt city, Nigeria, in order to evaluate the characteristic distribution patterns in these media, their sources, and possible risk. The PCB concentrations varied from 4.59 to 116 ng g -1 for soils, and from 1.80 to 23.0 ng g -1 and 2.73 to 57.4 ng g -1 for indoor and outdoor dusts respectively. The sequence of PCB concentrations in these matrices was soil > outdoor dust > indoor dust. The composition of PCBs in these matrices indicated the prevalence of lower chlorinated PCBs in indoor and outdoor dusts, while the higher chlorinated congeners were dominant in soils. Di-PCBs were the predominant homologues in indoor dusts, while deca-PCBs were the most prevalent homologues in outdoor dusts and soils. The TEQ values of dioxin-like PCBs in 60 % of the soils, 100 % of the indoor dust, and 30 % of the outdoor dust were above the indicative value of 4 pg TEQ g -1 established by the Canadian authority. The hazard index (HI) values for exposure of adults and children to PCBs in these media were mostly greater than one, while the total cancer risk (TCR) values exceeded the acceptable risk value of 10 -6 , which indicate probable non-carcinogenic and carcinogenic risks resulting from exposure to PCBs in these media. Source analysis for PCBs in these matrices shows that they originated from diverse sources., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Platinum (Pt), palladium (Pd) and rhodium (Rh) are accumulating globally in the environment, due to their use as catalysts to control automotive exhaust emissions. While environmental increases in platinum metal concentrations have been well documented for a number of countries, published data for Canada have been missing to date. The aim of this study is to examine the concentrations of Pt, Pd and Rh, as well as Ce, in soils and dust as a function of traffic volume in Toronto, Ontario. Soils and road and underpass dust were collected from two sites with medium and high volumes of traffic. Samples were acid digested and co-precipitated with Hg (for Pd) and Te (for Pt and Rh), prior to measurement using ICP-Q-MS. Palladium occurred at the highest levels in samples, followed by Pt and Rh. Median concentrations for all soil samples were 63 μg Pd/kg, 8.7 μg Pt/kg, 1.7 μg Rh/kg and 41 mg Ce/kg. The results support existing data regarding PGE accumulation trends in urban and roadside environments, due to their use as catalysts in automotive catalytic converters. This study also confirms a shift toward the heavier use of Pd as the catalyst of choice in recent years, as reflected in the higher concentrations measured for this metal relative to Pt and Rh. The results highlight a need to continue monitoring the accumulation of PGE, most notably Pd, in urban environments. [ABSTRACT FROM AUTHOR]

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are common cover soils and sources of organic matter for reclamation of open-pit mining disturbed land in the Athabasca oil sands region. Coarse woody debris (CWD) can be an additional source of organic matter and can provide nutrient and habitat for plant growth. However, the effect of CWD on nitrogen (N) cycling in reclaimed oil sands soils has not been studied. A laboratory incubation experiment was conducted to assess chemical effects of a CWD extract on gross and net N transformation rates in FMM and PMM using the 15 N pool dilution method. The CWD extract was used to simulate CWD leachates (with rainwater as a control) that are produced in the field. The effect of the simulated CWD leachate on the cover soils was studied in a 2 (FMM vs PMM) × 2 (CWD extract vs rainwater addition) factorial design. There was no difference in gross N mineralization rates between FMM and PMM, although net N mineralization rates were greater in FMM than in PMM ( p < 0.001) due to greater NH 4 + immobilization rates in PMM. Gross and net nitrification rates were greater in FMM than in PMM ( p < 0.001). The ratio of gross nitrification to gross NH 4 + immobilization rates (N/IA) was greater in FMM than in PMM ( p < 0.001), as the greater NH 4 + immobilization rates in PMM decreased gross nitrification rates by decreasing NH 4 + availability. Addition of the CWD extract decreased gross ( p < 0.01) and net ( p < 0.001) N mineralization rates, increased ( p < 0.001) NH 4 + immobilization and decreased ( p < 0.001) gross nitrification rates in both cover soils. The N/IA ratios were decreased by the CWD extract addition, indicating that heterotrophic NH 4 + immobilization was superior to autotrophic nitrification due to the high C/N ratio of the CWD extract. We conclude that FMM will have greater N availability for oil sands reclamation than PMM. Leachates from CWD would decrease N availability by decreasing gross N mineralization and nitrification rates and by increasing N immobilization rates. [ABSTRACT FROM AUTHOR]