Pit Lake Research Articles

Replicated whole‐lake experiment reveals the ineffectiveness of stocking five example fish species in small lakes

AbstractFish stocking is common practice in fisheries management, but its effectiveness to support or increase stock size or catches is debated. In Lower Saxony, Germany, a controlled, replicated stocking experiment of five native fish species in eight gravel pit lakes <20 ha was conducted to examine the potential additive effects of fish releases on abundance, indexed by catch per unit effort (CPUE) in electrofishing and gillnet samples. Fish were stocked twice in four study lakes, while the remaining four control lakes were not subjected to any stocking over a 6‐year study period. Recapture rates of individually marked fishes were extremely low in all five species. Consequently, stocking did not increase species‐specific and total fish community abundance. In additional control experiments in separate ponds all stocked fish species, except bream (Abramis brama), showed high survival in at least one study year, indicating general survival of the stocking material. Fish marking with passive integrated transponders did not affect fish survival, except for roach (Rutilus rutilus), and can thus be ruled out as an explanation for the high post‐stocking mortality. We conclude that stocking failed to enhance stocks of five native fish species in small gravel pit lakes.

Evaluation of rock stability challenges affecting the formation of sustainable pit lake towards mine closure following crown pillar extraction in open pit-underground mines

The extraction of high-grade ore from the crown pillar (CP) in open pit-underground mines poses stability challenges and potential environmental risks. While an open pit has the potential to transition into a pit lake, the extraction of CP can induce failure in the surrounding walls, preventing the formation of the lake. There is also a concern that the backfilling material may not effectively confine toxic water within the pit, thereby risking contamination of the underground environment. To address these issues, a case study was conducted using FLAC3D and 3DEC models to evaluate the extent of failure caused by CP extraction. On-site observation, along with modelling, has revealed rock damage, including deformation stretching about 4 m from the pit wall and extending vertically from the pit floor to the ramp. The study identified three primary factors leading to pit wall failure or damage: steep pit slopes reaching approximately 70° near the pit floor, an underestimated CP thickness by about 4 m, and the concurrent extraction of ore from the pit wall alongside CP. Based on these findings, rehabilitation measures are suggested, including excavation of the deformed wall and cantilever, as well as partial pit backfilling. There is a substantial increase in the volume of backfill material as the extent of failure increases, which raise concerns about the decision-making process regarding CP extraction. Therefore, this article aims to raise environmental awareness and evaluate whether the benefits of ore extraction outweigh the considerations for pit wall support and the rehabilitation efforts during mine closure.

Multi-omics insights into biogeochemical responses to organic matter addition in an acidic pit lake: Implications for bioremediation

Acidic pit lakes (APLs) emerge as reservoirs of acid mine drainage in flooded open-pit mines, representing extreme ecosystems and environmental challenges worldwide. The bioremediation of these oligotrophic waters necessitates the addition of organic matter, but the biogeochemical response of APLs to exogenous organic matter remains inadequately comprehended. This study delves into the biogeochemical impacts and remediation effects of digestate-derived organic matter within an APL, employing a multi-omics approach encompassing geochemical analyses, amplicon and metagenome sequencing, and ultra-high resolution mass spectrometry. The results indicated that digestate addition first stimulated fungal proliferation, particularly Ascomycetes and Basidiomycetes, which generated organic acids through lignocellulosic hydrolysis and fermentation. These simple compounds further supported heterotrophic growth, including Acidiphilium, Acidithrix, and Clostridium, thereby facilitating nitrate, iron, and sulfate reduction linked with acidity consumption. Nutrients derived from digestate also promoted the macroscopic development of acidophilic algae. Notably, the increased sulfate reduction-related genes primarily originated from assimilatory metabolism, thus connecting sulfate decrease to organosulfur increase. Assimilatory and dissimilatory sulfate reduction collectively contributed to sulfate removal and metal fixation. These findings yield multi-omics insights into APL biogeochemical responses to organic matter addition, enhancing the understanding of carbon-centered biogeochemical cycling in extreme ecosystems and guiding organic amendment-based bioremediation in oligotrophic polluted environments.

A global atlas of pumped hydro systems that repurpose existing mining sites

Large amounts of energy storage are required to support high levels of solar and wind power. Pumped hydro energy storage comprises the majority of global energy storage for the electricity industry. A previous study identified 616,000 potential “Greenfield” closed-loop (off-river) pumped hydro sites around the world with combined storage of 23,000 Terawatt-hours (TWh). In this study, we identify 904 sites in mining areas (“Brownfield”) with combined potential storage of 30 TWh. A high spatial resolution global atlas of Brownfield closed-loop pumped hydro energy storage systems is available online. It was developed through Geographic Information System (GIS) analysis of a digital terrain model. The GIS algorithm identified mining pits, pit lakes, and tailings ponds within mining sites and located nearby reservoirs that could form a suitable pair. All Brownfield pumped hydro sites were assigned a cost class of A to E to allow comparison between sites on the global atlas. There are far fewer Brownfield than Greenfield options, with 77 countries found to contain eligible locations. Despite the smaller number of eligible locations, Brownfield sites typically have other advantages including existing transmission infrastructure, water pumping infrastructure, road access, social licence and reduced environmental impact for development on disturbed land.

Hydrodynamic relationships between gravel pit lakes and aquifers: brief review and insights from numerical investigations

Supply of aggregate materials for every construction requires mining of sand and gravel, which leads to the formation of a myriad of freshwater lakes, a now common feature of the landscape in the valleys of large rivers. Typically small in size and shallow, they are filled with waters from the adjacent aquifers and directly exposed to the atmosphere. The creation of gravel pit lakes has various and contrasting effects on their immediate environment. This article first provides a review of these impacts from the hydrodynamic point of view, and illustrates them on simple numerical test cases. It also introduces the gravel pit lake module developed for the occasion within the integrated modelling platform CaWaQS, which formulation was tested on the same test cases against the Lak package, its Modflow counterpart. By accurately simulating gravel pit lake interactions with groundwater in different configurations, this modelling exercise also aims to identify the preponderant factors leading water level fluctuations of those artificial lakes, whose temporal monitoring will soon be accessible to satellite observation.

Metal recovery from spent lithium-ion batteries via two-step bioleaching using adapted chemolithotrophs from an acidic mine pit lake.

The demand for lithium-ion batteries (LIBs) has dramatically increased in recent years due to their application in various electronic devices and electric vehicles (EVs). Great amount of LIB waste is generated, most of which ends up in landfills. LIB wastes contain substantial amounts of critical metals (such as Li, Co, Ni, Mn, and Cu) and can therefore serve as valuable secondary sources of these metals. Metal recovery from the black mass (shredded spent LIBs) can be achieved via bioleaching, a microbiology-based technology that is considered to be environmentally friendly, due to its lower costs and energy consumption compared to conventional pyrometallurgy or hydrometallurgy. However, the growth and metabolism of bioleaching microorganisms can be inhibited by dissolved metals. In this study, the indigenous acidophilic chemolithotrophs in a sediment from a highly acidic and metal-contaminated mine pit lake were enriched in a selective medium containing iron, sulfur, or both electron donors. The enriched culture with the highest growth and oxidation rate and the lowest microbial diversity (dominated by Acidithiobacillus and Alicyclobacillus spp. utilizing both electron donors) was then gradually adapted to increasing concentrations of Li+, Co2+, Ni2+, Mn2+, and Cu2+. Finally, up to 100% recovery rates of Li, Co, Ni, Mn, and Al were achieved via two-step bioleaching using the adapted culture, resulting in more effective metal extraction compared to bioleaching with a non-adapted culture and abiotic control.

Phytoplankton ecology in the early years of a boreal oil sands end pit lake

BackgroundBase Mine Lake (BML) is the first full-scale end pit lake for the oil sands mining industry in Canada. BML sequesters oil sands tailings under a freshwater cap and is intended to develop into a functional ecosystem that can be integrated into the local watershed. The first stage of successful reclamation requires the development of a phytoplankton community supporting a typical boreal lake food web. To assess the diversity and dynamics of the phytoplankton community in BML at this reclamation stage and to set a baseline for future monitoring, we examined the phytoplankton community in BML from 2016 through 2021 using molecular methods (targeting the 23S, 18S, and 16S rRNA genes) and microscopic methods. Nearby water bodies were used as controls for a freshwater environment and an active tailings pond.ResultsThe phytoplankton community was made up of diverse bacteria and eukaryotes typical of a boreal lake. Microscopy and molecular data both identified a phytoplankton community comparable at the phylum level to that of natural boreal lakes, dominated by Chlorophyta, Cryptophyta, and Cyanophyta, with some Bacillariophyta, Ochrophyta, and Euglenophyta. Although many of the same genera were prominent in both BML and the control freshwater reservoir, there were differences at the species or ASV level. Total diversity in BML was also consistently lower than the control freshwater site, but consistently higher than the control tailings pond. The phytoplankton community composition in BML changed over the 5-year study period. Some taxa present in 2016–2019 (e.g., Choricystis) were no longer detected in 2021, while some dinophytes and haptophytes became detectable in small quantities starting in 2019–2021. Different quantification methods (qPCR analysis of 23S rRNA genes, and microscopic estimates of populations and total biomass) did not show a consistent directional trend in total phytoplankton over the 5-year study, nor was there any consistent increase in phytoplankton species diversity. The 5-year period was likely an insufficient time frame for detecting community trends, as phytoplankton communities are highly variable at the genus and species level.ConclusionsBML supports a phytoplankton community composition somewhat unique from control sites (active tailings and freshwater lake) and is still changing over time. However, the most abundant genera are typical of natural boreal lakes and have the potential to support a complex aquatic food web, with many of its identified major phytoplankton constituents known to be primary producers in boreal lake environments.

Biodegradation in oil sands process-affected water: A comprehensive laboratory analysis of the in situ biodegradation of dissolved organic acids

Oil sands process-affected water (OSPW) is a by-product of the extraction of bitumen, and volumes of OSPW have accumulated across the Alberta oil sands region due to the governments zero-discharge policy. Some dissolved organics in OSPW, including toxic naphthenic acids (NAs), can be biodegraded in oxic conditions, thereby reducing the toxicity of OSPW. While there has been much focus on degradation of NAs, the biodegradation of other dissolved organic chemicals by endogenous organisms remains understudied. Here, using the HPLC–ultrahigh resolution Orbitrap mass spectrometry, we examined the microbial biodegradation of dissolved organic acids in OSPW. Non-targeted analysis enabled the estimation of biodegradation rates for unique heteroatomic chemical classes detected in negative ion mode. The microcosm experiments were conducted with and without nutrient supplementation, and the changes in the microbial community over time were investigated. Without added nutrients, internal standard–adjusted intensities of all organics, including NAs, were largely unchanged. The addition of nutrients increased the biodegradation rate of O2− and SO2− chemical classes. While anoxic biodegradation can occur in tailings ponds and end pit lakes, microbial community analyses confirmed that the presence of oxygen stimulated biodegradation of the OSPW samples studied. We detected several aerobic hydrocarbon-degrading microbes (e.g., Pseudomonas and Brevundimonas), and microbes capable of degrading sulfur-containing hydrocarbons (e.g., Microbacterium). Microbial community diversity decreased over time with nutrient addition. Overall, the results from this study indicate that toxic dissolved organics beyond NAs can be biodegraded by endogenous organisms in OSPW, but reaffirms that biological treatment strategies require careful consideration of how nutrients and dissolved oxygen may impact efficacy.

Slope stability of reclaimed coal mines through a new water filling index

A common reclamation practice for closed coal surface mines is filling them with water to form pit lakes. The creation and sustainability of these lakes are significantly affected by the stability of the corresponding slopes. The present study provides a general framework for analyzing the water filling's effect on slope stability based on a new water filling index, which can indirectly consider the factors affecting the process and efficiently quantify the filling speed's influence. The assumptions of the proposed approach are thoroughly discussed, and the range of the water filling index is identified. Furthermore, the safety factor is calculated using the finite element method with the shear strength reduction technique during the filling process for various conditions (soil properties, slope geometry, hydraulic conditions, and water filling speed). Results are presented as normalized stability charts for practical use. During the water filling, the stability gradually decreases until the reservoir reaches a critical level of 10%–40% of the total height; it then increases to even more stable conditions than the initial one. Overall, the present analysis allows for the preliminary stability evaluation of a coal mine during the formation of a pit lake and the appropriate quantification of the water filling's effect.

Impact of water-based recreation on aquatic and riparian biodiversity of small lakes

Lakes offer important recreational sites for people; however, water-based recreation may interfere with conservation objectives. In this study, we examined the impact of recreational use of small stagnant water bodies (<22 ha) on several aquatic and riparian biodiversity indicators (species richness, Simpson diversity-index, and number of endangered species) across multiple taxa (waterfowl, songbirds, damselflies, dragonflies, amphibians, fishes, submerged macrophytes, riparian herbs and trees). Samples were generated from 39 gravel pit lakes in Lower Saxony, Germany. Recreational use intensity was quantified using a stratified roving creel survey design involving citizen scientists. Recreational use had little correlation with the different biodiversity indicators that we examined. Most of the variance in biodiversity was explained by non-recreation related environmental and land use variables. Yet, a consistent negative relationship between recreation and biodiversity was found for dog walking, which was negatively associated with the species richness of songbirds, fish, and riparian herbs. Other recreational effects were positive, e.g., increased human use intensity correlated positively with the species richness of fishes and riparian herbs. Moreover, lakes used exclusively by anglers hosted a larger fish species richness at the expense of amphibian richness, likely due to predation impacts by fish. The abundance of dogs was found to be more influential in terms of recreation-related impacts than human density per se, possibly because wildlife perceives dogs as a stronger threat stimulus than human presence. Experimental work is needed to substantiate the correlative evidence presented here.

Ferric Oxyhydroxylsulfate Precipitation Improves Water Quality in an Acid Mining Lake: A Hydrogeochemical Investigation

Hydrogeochemistry of a lignite pit lake in Lusatia, Germany, was investigated. Anoxic groundwater from the dump aquifer rich in FeII (average ~5911 µmol/L) and SO4 (average ~14,479 µmol/L) contents enter the lake as subsurface inflow; oxidation and subsequent precipitation of poorly crystallized Fe-oxyhydroxysulfate (schwertmannite) occurs and causes acidification (pH~2.8). However, the removal of dissolved loads as solid phases significantly improves the groundwater quality of the downgradient as an outflow. The rainwater isotopic values (δD ~−8.88‰ and δ18O ~−65.86‰) closely matched with the groundwater showing very little isotopic modification, which points to a short residence time of groundwater. The displacement of δD and δ18O values (slope = 5.3) from the meteoric water line reflected the evaporative enrichment of the lake water. The isotopic signature also revealed longer residence times of epilimnion than the hypolimnion waters which are dominated by groundwater. The lake is dimictic and showed abrupt changes in physicochemical parameters along the interface (~0.30 m thick) when separating the epilimnion (upper 4 m) from the hypolimnion (bottom 1.5 m). Lake sediments were found to be dominated by clay size fraction occurring as laminations (thickness: 1~0.5 mm) that reflect seasonal sedimentation. Higher schwertmannite formation in the south as compared to the north (recharge side) also serves as a scavenger of potentially toxic elements which is probably a natural solution to man-made problems. Schwertmannite transformation to goethite releases sulfate which is reduced and fixed as secondary sulfide minerals over time. Overall, waters are of a Ca–SO4 to Ca–Mg–SO4 type with distinct inflow (FeII/FeIII &gt; 2.5) and outflow (FeII/FeIII &lt; 0.5) of groundwater.

Features of cultivation of hydrid forms of sturgeon fish in quarriers of the Rostov region

The paper presents the results of growing juvenile sturgeon species and their hybrid forms in a mine pit lake in the Rostov region. In the Rostov region, there are many mine pit lake that can be successfully used to organize economic activities for the cultivation of valuable aquaculture objects, such as sturgeon fish. It has been established that the hydrochemical regime of the lake from May to September is favorable for the cultivation of juvenile sturgeon fish species and their hybrid forms. Studies have shown that the highest growth rate for 30 days of growing in pools was shown by beluga juveniles, its absolute increase was 1200 mg with a survival rate of 75%. Lenk and Bester had an increase of 565 mg and 710 mg, respectively. The most highly sensitive was the transition of juveniles to active nutrition, when the yolk sac in the larvae resolved by 2/3. The fastest transition and the least waste was observed in the larvae of bester and lenka. Upon reaching the age of 30 days, the juveniles were transplanted into cages, where good growth of beluga juveniles and hybrids was noted. On June 15 (40 days), the juveniles switched completely to dry food. At the same time, the average weight of the beluga was 3.5 g. It should be noted that with the complete transfer of beluga juveniles to dry food, the waste was from 3 to 5%. The young of Lenka and bester adapted better to dry food, the waste did not exceed 2%. The largest growth was in juveniles of all sturgeon species in August and early September.

The Long-Term Detection of Suspended Particulate Matter Concentration and Water Colour in Gravel and Sand Pit Lakes through Landsat and Sentinel-2 Imagery

Over the past half century, the demand for sand and gravel has led to extensive quarrying activities, creating many pit lakes (PLs) which now dot floodplains and urbanized regions globally. Despite the potential importance of these environments, systematic data on their location, morphology and water quality remain limited. In this study, we present an extensive assessment of the physical and optical properties in a large sample of PLs located in the Po River basin (Italy) from 1990 to 2021, utilizing a combined approach of remote sensing (Landsat constellation and Sentinel-2) and traditional limnological techniques. Specifically, we focused on the concentration of Suspended Particulate Matter (SPM) and the dominant wavelength (λdom, i.e., water colour). This study aims to contribute to the analysis of PLs at a basin scale as an opportunity for environmental rehabilitation and river floodplain management. ACOLITE v.2022, a neural network particularly suitable for the analysis of turbid waters and small inland water bodies, was used to atmospherically correct satellite images and to obtain SPM concentration maps and the λdom. The results show a very strong correlation between SPM concentrations obtained in situ and those obtained from satellite images, both for data derived from Landsat (R2 = 0.85) and Sentinel-2 images (R2 = 0.82). A strong correlation also emerged from the comparison of spectral signatures obtained in situ via WISP-3 and those derived from ACOLITE, especially in the visible spectrum (443–705 nm, SA = 10.8°). In general, it appeared that PLs with the highest mean SPM concentrations and the highest mean λdom are located along the main Po River, and more generally near rivers. The results also show that active PLs exhibit a poor water quality status, especially those of small sizes (&lt;5 ha) and directly connected to a river. Seasonal comparison shows the same trend for both SPM concentration and λdom: higher values in winter gradually decreasing until spring–summer, then increasing again. Finally, it emerged that the end of quarrying activity led to a reduction in SPM concentration from a minimum of 43% to a maximum of 72%. In this context, the combined use of Landsat and Sentinel-2 imagery allowed for the evaluation of the temporal evolution of the physical and optical properties of the PLs in a vast area such as the Po River basin (74,000 km2). In particular, the Sentinel-2 images consistently proved to be a reliable resource for capturing episodic and recurring quarrying events and portraying the ever-changing dynamics of these ecosystems.

Geochemical behavior of heavy metals and radionuclides in a pit lake affected by acid mine drainage (AMD) in the Muskau Arch (Poland)

Pit lakes in the ‘anthropogenic lake district’ in the Muskau Arch (western Poland; central Europe) are strongly affected by acid mine drainage (AMD). The studied acidic pit lake, ŁK-61 (pH <3), is also exposed to floods due to its location in the flood hazard area, which may significantly influence the geochemical behavior of elements. The elemental compositions of water and lake sediment samples were measured with ICP–OES and ICP–MS. The sediment profile was also examined for 137Cs and 210Po activity concentrations using gamma and alpha spectrometry, respectively. Grain size distribution, mineralogical composition, diatoms, and organic matter content in the collected core were also determined. The key factors responsible for the distribution of selected heavy metals (e.g., Cu, Ni, Pb, Zn) and radioisotopes (137Cs and 210Po) in the bottom sediments of Lake ŁK-61 are their coprecipitation/precipitation with Fe and Al secondary minerals and their sorption onto authigenic and allogenic phases. These processes are likely driven by the lake tributary, which is an important source of dissolved elements. The data also showed that the physiochemical parameters of Lake ŁK-61 water changed during an episodic depositional event, i.e., the flood of the Nysa Łużycka River in the summer of 2010. The flood caused an increase in the water pH, as interpreted from the subfossil diatom studies. The down-core profiles of the studied heavy metal and radionuclide (HMRs) contents were probably affected by this depositional event, which prevented a detailed age determination of the collected lake sediments with 137Cs and 210Pb dating methods. Geochemical modeling indicates that the flood-related shift in the physicochemical parameters of the lake water could have caused the scavenging of dissolved elements by the precipitation of fresh secondary minerals. Moreover, particles contaminated with HMRs have also possibly been delivered by the river, along with the nutrients (e.g., phosphorus and nitrogen).

Climatic controls on the water balance of a pilot-scale oil sands mining pit lake in the Athabasca oil sands region, Canada

ABSTRACT Energy companies in the Athabasca Oil Sands Region in Alberta, Canada are evaluating the viability of incorporating pit lakes into reclamation closure designs to both sequester tailings and re-integrate the mining lease into the broader natural landscape. Lake Miwasin is a pilot-scale oil sands pit lake encompassed by a constructed catchment where the volume of the water cap is not actively managed. This study compared the water balance during the open water season over two consecutive years with contrasting levels of summertime precipitation. The first year had above average rainfall triggering surface water inflow events that diluted the over-winter water volume by ~ 25%. Flushing of the deepest layers of the water column was restricted from May – September as thermal stratification inhibited complete lake mixing. The second year had below average rainfall resulting in minimal surface water inflow and a drop in lake stage of ~ 30 cm. As the constructed catchment lacks both natural water bodies and connectivity to a legacy groundwater system, freshwater additions to the lake during the summer season were governed by rainfall. This research highlights challenges with constructing sustainable reclamation landscapes within a region characterised by variations in interannual and decadal water cycles.

Phytoplankton Ecology in an Oilsands End Pit Lake

Alberta oilsands mining and extraction have produced over 1 trillion litres of tailings wastewater (AER 2021) containing several compounds of concern (Cossey et al. 2021). End-pit lakes are a low-cost, long-term proposed strategy of tailings reclamation that sequester tailings in a mined-out pit under a freshwater cap. Through dilution and biogeochemical processes, the water cap should over time develop into a functional ecosystem integrable with the local watershed (Cossey et al. 2021, Saborimanesh 2021). Established in 2012, Base Mine Lake is currently the only full-scale pilot end pit lake developed by the Alberta oilsands industry and requires further investigation to validate end pit lakes as a tailings reclamation technology (Cossey et al. 2021). The first stage of reclamation requires the development of a phytoplankton community, which serves as the base of the aquatic food web (CEMA 2012). The primary objective of this study was to characterize the phytoplanktxon community over time in BML from 2016 to 2021 to determine how community composition and abundances shift over seasons and years. Characterization used Illumina gene sequencing targeting 16S rRNA, 18S rRNA, and 23S rRNA gene amplicons, giving relative abundance data over time for phytoplankton. Cell count data was used to verify gene sequencing results. The phytoplankton community composition and diversity in Base Mine Lake was compared to those of a freshwater reservoir and a tailings pond. Analysis of gene sequencing data revealed that major genera of phytoplankton included Cryptomonas (Cryptophyceae), Choricystis (Trebouxiophyceae), Euglena (Euglenales), and Synechococcus (Synechococcales), all of which appear to exhibit seasonal blooms during 2016-2021 (Fig. 1). Sequencing analysis also indicated that Base Mine Lake and its freshwater input source Beaver Creek Reservoir shared many of the same genera but different strains/species of those genera. This suggested that the distinct conditions in each aquatic site may have selected for distinct strains. Diversity analyses of gene sequencing data revealed that phytoplankton diversity in Base Mine Lake was intermediate between that of its freshwater input reservoir and a tailings pond. There currently exists no low-cost, large-scale treatment method that fully reclaims tailings water (Cossey et al. 2021, Saborimanesh 2021). End-pit lakes retain tailings until recalcitrant compounds are degraded to near-environmental levels (Saborimanesh 2021, CEMA 2012), but further research is required before end-pit lakes can be approved as a viable reclamation technology (Cossey et al. 2021). Although research is available now on native microbial communities in tailings waters, knowledge on their contributions to an aquatic microbial food web is limited (Saborimanesh 2021). This proposed research is the first of its kind to examine the contribution of phytoplankton to end pit lake food web ecology. This will advance knowledge of end-pit lakes as a reclamation strategy in effort to reduce the environmental footprint of tailings water.

Quantifying Stochastic Processes in Shaping Dissolved Organic Matter Pool with High-Resolution Mass Spectrometry.

Natural dissolved organic matter (DOM) represents a ubiquitous molecular mixture, progressively characterized by spatiotemporal resolution. However, an inadequate comprehension of DOM molecular dynamics, especially the stochastic processes involved, hinders carbon cycling predictions. This study employs ecological principles to introduce a neutral theory to elucidate the fundamental processes involving molecular generation, degradation, and migration. A neutral model is thus formulated to assess the probability distribution of DOM molecules, whose frequencies and abundances follow a β-distribution relationship. The neutral model is subsequently validated with high-resolution mass spectrometry (HRMS) data from various waterbodies, including lakes, rivers, and seas. The model fitting highlights the prevalence of molecular neutral distribution and quantifies the stochasticity within DOM molecular dynamics. Furthermore, the model identifies deviations of HRMS observations from neutral expectations in photochemical and microbial experiments, revealing nonrandom molecular transformations. The ecological null model further validates the neutral modeling results, demonstrating that photodegradation reduces molecular stochastic dynamics at the surface of an acidic pit lake, while random distribution intensifies at the river surface compared with the porewater. Taken together, the DOM molecular neutral model emphasizes the significance of stochastic processes in shaping a natural DOM pool, offering a potential theoretical framework for DOM molecular dynamics in aquatic and other ecosystems.

Electron Acceptor Addition to Stimulate Anaerobic Methanotrophy in Oil Sands End Pit Lakes

A major question for the Alberta oilsands extraction industry is how to return tailings ponds to their original ecosystem functions at the end of their lifespan. This question is one of the most pressing in the oil industry, and while many potential solutions are being trialed, none are without issue. One solution is the creation of end pit lakes (EPLs), formed by filling a mine pit or tailings pond with fluid tailings and covering this with a freshwater cap. Over time, tailings settle to the bottom of the lake and become sequestered. As of 2018, there were 23 plans to pursue EPLs in Albertan oilsands mining operations (COSIA 2021), so research in oilsands reclamation via EPLs is essential. Alberta has only one full-scale EPL formed using tailings, Base Mine Lake (BML). It has been under reclamation since 2011. Although BML water quality is gradually improving over time, one persistent problem is the production of methane bubbles from the entrenched hydrocarbons. Ebullition of these bubbles carries contaminants into the water column. The potential to limit methane production biologically by stimulating methanotroph metabolism, is therefore of interest. Methanotrophs are microbes that consume methane. These methanotrophs can be aerobic, in the water column, or anaerobic below the sediment interface, where oxygen is depleted. Anaerobic oxidizers of methane, or AOM, are of particular interest due to methane only being produced in anaerobic conditions. However, AOM are not well-studied and there are many gaps in our knowledge about them. Base Mine Lake presents an important opportunity to document the presence of AOM in oilsands ecosystems, and identify if AOM can remove methane before it enters the water column. Methane is probably not the limiting factor for AOM in BML- instead, the electron acceptors used in the absence of oxygen are scarce. If microbiological methane removal were to increase after supplementing electron acceptors such as nitrate, sulfate, or iron, then this could be applied to the reclamation of artificial end pit lake systems. Our research aims to illustrate if AOM are present in BML, and if we can stimulate their metabolism via electron acceptor amendment. We performed amplicon and metagenomic sequencing across 5 sediment cores from BML. These cores penetrate over two meters below the water-sediment interface, up to 14 meters below the water’s surface. We designed anaerobic, 13C-isotope-spiked incubations for this sediment to track if any CH4 to CO2 conversion was underway. By tagging methane molecules with 13C, we are able to follow the biogeochemical transformations and demonstrate if any 13CH4 is converted to 13CO2, which would indicate methanotrophic activity. Additionally, microbes who take up 13C produce heavier DNA, possibly allowing us to identify the DNA of the players at work. Additionally, Illumina sequencing was done on all incubations to compare how electron acceptor addition prompted community shifts. In the incubation experiments, 13CO2 is being produced in several core samples incubated without O2. This finding indicates that methanotrophs are, in some capacity, active in anoxic conditions. When comparing different amendments of electron acceptors, there did appear to be a significant amount (p = 0.027) of 13CO2 produced in the sulfate-added 13CH4 treatment (Fig. 1). Other amendments had encouraging results, but were not statistically significant. Ongoing trials will provide more illuminating results via larger sample sizes, which will be completed by the end of the summer. Next we will characterize communities in the post-incubation sediment, using both amplicon sequencing and DNA stable isotope probing. This will suggest not only the identity of the organisms at play, but will also illuminate which electron acceptors were most beneficial to which groups. This analysis is complex and underway. Overall, the study of methanotrophy in artificial ecosystems with high emissions is an area of great interest, due to the high potential for amendment and improvement of the ecosystems using methanotrophs, as well as the ongoing discovery on AOM in artificial ecosystems. Oilsands end pit lakes are of interest, as an issue of cultural and political emphasis.

Pit lakes from gravel and sand quarrying in the Po River basin: An opportunity for riverscape rehabilitation and ecosystem services improvement

Since the 1950s, an intense sand and gravel quarrying from the river floodplains led to the formation of pit lakes (PLs) that have changed the morphology and the drainage system of several Italian river basins. In the last decade, a renewed interest in PLs has grown as tools for rehabilitating rivers and their floodplains, in order to provide a similar ecological service once offered by pristine riverine wetlands, which were lost due to anthropogenic pressures. The primary aim of this study was to quantify the number, distribution, and major morphometric characteristics of these ecosystems in the Po River basin, in order to assess their relevance and suitability for ecological restoration purposes. To achieve this aim, a synergistic approach was used including remote sensing techniques, satellite archives, and regional databases. The results show that more than 12,650 small lentic water bodies are present in the Po River basin, with agricultural ponds the most represented category, followed by PLs. Specifically, 1580 PLs were identified, divided into three subcategories: active (338), ceased (1188) and doubtful (54). These artificial ecosystems, when compared with pristine riverine wetlands, are more numerous, widely distributed, and on average more extensive, although more regularly shaped. The temporal analysis of satellite imagery showed that the number and the total area of PLs have increased from 1990 to 2021. PLs currently account for 63.5 km2 surface area, an average water volume of 378 × 106 m3 and for a removal of 26.6 mg N m−2 d−1 via denitrification. Therefore, PLs can contribute ecosystem services, e.g., water provisioning and regulation of the nitrogen cycle, and can be exploited for rehabilitating the riverscape. In this context, remote sensing is a very reliable tool for quantifying and analysing PLs and others water bodies in a vast area such as the Po River basin.

Case study of water pollution in Podwiśniówka acid mine pit lake (Holy Cross Mts., Poland)

On the Holy Cross Mountains (southern Poland), located within the tectonic zone of the Trans-European Suture Zone (TESZ), numerous former quarries exist, including those of Cambrian quarzitic sandstones and sandstones with pyrite veins. This article presents the results of geochemical studies on the waters of the acidic mine pit lake Podwiśniówka (with an area of 1.5 ha and a maximum depth of 7.0 m) conducted in 2018. The tests were carried out in a vertical water column (every 1 m) in the central part of pit lake. The mean concentration of metals/metalloids, determined using inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS), was found to form the following sequence in decreasing order: As&gt; Cu&gt; Ni&gt; Co&gt; Cr&gt; Zn&gt; U&gt; Pb&gt; Cd&gt; Tl. With increasing depth, there was a general upwards trend in the concentrations of all the determined elements. In all cases, the average value of the single pollution index in the water column greatly exceeds the very strong level in relation to the geochemical background of surface waters globally (As – above 1250 times). The integrated pollution index for the ten trace elements in the water column increases with depth, and its average value exceeding 250 times the highest reference level. At the same time, the cluster analysis carried out showed the existence of two distinct depth zones in the pit lake: upper (0–4 m) and lower (5–7 m), differing in the scale of the water pollution.