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USGS2012

Mineralogy and environmental geochemistry of historical iron slag, Hopewell Furnace National Historic Site, Pennsylvania, USA

The Hopewell Furnace National Historic Site in southeastern Pennsylvania, which features an Fe smelter that was operational in the 18th and 19th centuries, is dominated by three slag piles. Pile 1 slag, from the Hopewell Furnace, and pile 2 slag, likely from the nearby Cornwall Furnace, were both produced in cold-blast charcoal-fired smelters. In contrast, pile 3 slag was produced in an anthracite furnace. Ore samples from the nearby Jones and Hopewell mines that fed the smelter are mainly magnetite-rich with some sulfides (pyrite, chalcopyrite, sphalerite) and accessory silicates (quartz, garnet, feldspar, and clay minerals). Slag piles 1 and 2 are similar mineralogically containing predominantly skeletal and dendritic aluminian diopside and augite, skeletal forsteritic olivine, glass, rounded blebs of metallic Fe, and exotic quartz. Olivine is a major phase in all samples from pile 2, whereas it occurs in only a few samples from pile 1. Samples of the <2 mm-size fraction of surface composite slag material or crushed slag from at depth in piles 1 and 2 are mineralogically similar to the large surface slag fragments from those piles with the addition of phases such as feldspars, Fe oxides, and clay minerals that are either secondary weathering products or entrained from the underlying bedrock. Pile 3 slag contains mostly skeletal forsteritic olivine and Ti-bearing aluminian diopside, dendritic or fine-grained subhedral melilite, glass, euhedral spinel, metallic Fe, alabandite–oldhamite solid solution, as well as a sparse Ti carbonitride phase. The bulk chemistry of the slag is dominated by Al 2 O 3 (8.5–16.2 wt.%), CaO (8.2–26.2 wt.%), MgO (4.2–24.7 wt.%), and SiO 2 (36.4–59.8 wt.%), constituting between 81% and 97% of the mass of the samples. Piles 1 and 2 are chemically similar; pile 1 slag overall contains the highest Fe 2 O 3 , K 2 O and MnO, and the lowest MgO concentrations. Pile 3 slag is high in Al 2 O 3 , CaO and S, and low in Fe 2 O 3 , K 2 O and SiO 2 compared to the other piles. In general, piles 1 and 2 are chemically similar to each other, whereas pile 3 is distinct – a conclusion that reflects their mineralogy. The similarities and differences among piles in terms of mineralogy and major element chemistry result from the different smelting conditions under which the slag formed and include the fuel source, the composition of the ore and flux, the type of blast (cold versus hot), which affects the furnace temperature, and other beneficiation methods. The three distinct slag piles at Hopewell are enriched in numerous trace elements, such as As (up to 12 mg/kg), Cd (up to 0.4 mg/kg), Co (up to 31.8 mg/kg), Cu (up to 647 mg/kg), Mn (up to 0.69 wt.%), Pb (up to 172 mg/kg) and Zn (up to 393 mg/kg), together with Fe (13.9 wt.%), when compared to the average for the continental crust, with the <2 mm-size fraction commonly containing the highest concentrations. Enrichments in various elements (e.g., Cd, Co, Cu, Pb, Zn) were also found in the ore samples. Despite these enrichments, comparison of bulk chemistry trace-element concentrations to the environmental guidelines suggests most elements are likely not problematic with the exception of As, Co, Fe and Mn. Leachate tests that simulate weathering indicate Fe (up to 973 μg/L) and Mn (up to 133 μg/L) are readily released in potentially harmful concentrations compared to secondary drinking water and some aquatic ecosystem toxicity criteria. Aluminum and Cu, although not high in the solid compared to environmental guidelines, also exceed relevant criteria in leachate extracts with maximum concentrations of 2700 μg/L and 17.7 μg/L, respectively. In contrast, As and Co, which are significant in the solids, are not leached in concentrations that exceed guidelines (i.e., 3 μg/L or less for both elements). The weathering rates of the Fe metal and Fe oxides, which host Cu and some Fe, are likely higher than the silicate glass, which hosts the majority of Al, Mn and some Fe, and the crystalline silicates and spinels affecting which elements and how much are released into the environment and surrounding aquatic ecosystem. The mineral assemblages and their chemical composition, the bulk sample chemistry, and leachability of trace elements are all important components in understanding the potential environmental impacts of the slag piles.

Pennsylvania↗

USGS2015

Biogeochemical aspects of uranium mineralization, mining, milling, and remediation

Natural uranium (U) occurs as a mixture of three radioactive isotopes: 238 U, 235 U, and 234 U. Only 235 U is fissionable and makes up about 0.7% of natural U, while 238 U is overwhelmingly the most abundant at greater than 99% of the total mass of U. Prior to the 1940s, U was predominantly used as a coloring agent, and U-bearing ores were mined mainly for their radium (Ra) and/or vanadium (V) content; the bulk of the U was discarded with the tailings (Finch et al., 1972). Once nuclear fission was discovered, the economic importance of U increased greatly. The mining and milling of U-bearing ores is the first step in the nuclear fuel cycle, and the contact of residual waste with natural water is a potential source of contamination of U and associated elements to the environment. Uranium is mined by three basic methods: surface (open pit), underground, and solution mining (in situ leaching or in situ recovery), depending on the deposit grade, size, location, geology and economic considerations (Abdelouas, 2006). Solid wastes at U mill tailings (UMT) sites can include both standard tailings (i.e., leached ore rock residues) and solids generated on site by waste treatment processes. The latter can include sludge or “mud” from neutralization of acidic mine/mill effluents, containing Fe and a range of coprecipitated constituents, or barium sulfate precipitates that selectively remove Ra (e.g., Carvalho et al., 2007). In this chapter, we review the hydrometallurgical processes by which U is extracted from ore, the biogeochemical processes that can affect the fate and transport of U and associated elements in the environment, and possible remediation strategies for site closure and aquifer restoration. This paper represents the fourth in a series of review papers from the U.S. Geological Survey (USGS) on geochemical aspects of UMT management that span more than three decades. The first paper (Landa, 1980) in this series is a primer on the nature of tailings and radionuclide mobilization from them. The second paper (Landa, 1999) includes coverage of research carried out under the U.S. Department of Energy’s Uranium Mill Tailings Remedial Action Program (UMTRA). The third paper (Landa, 2004) reflects the increased focus of researchers on biotic effects in UMT environs. This paper expands the focus to U mining, milling, and remedial actions, and includes extensive coverage of the increasingly important alkaline in situ recovery and groundwater restoration.

Applied Geochemistry↗

USGS2019

Estimating forest canopy cover dynamics in Valles Caldera National Preserve, New Mexico, using LiDAR and Landsat data

Increasing tree canopy cover has led to increasing wildfire activity in conifer dominated areas of the southwestern United States. Estimating historical changes in the spatial distribution of tree canopy cover can provide further insights into the dynamics of forest and fuel conditions in these landscapes and help prioritize areas for restoration to mitigate wildfire risks and restore biological functioning. In this study, we explored the relationship between LiDAR derived canopy cover data and Landsat reflectance values, and derived a model to estimate percent canopy cover (PCC) on historical Landsat data from 1987 to 2015 for the Valles Caldera National Preserve (VCNP), located in the southwest Jemez Mountains of New Mexico. We developed a regression model between LiDAR generated canopy cover collected in June 2010 and Landsat Thematic Mapper (TM) reflectance values (bands 1–7 except band 6) and vegetation indices collected for the same date. About 5% (17,000) of the total LiDAR points (329,102) were used as training points and a separate, non-overlapping set of 17,000 points as test points to validate the regression model. A simple linear model with the red band (band 3; R 2 = 0.70) was selected as the best model to predict PCC in the rest of the images for 1987–2015. In general, we found a strong consistency between the spatial dynamics of modelled tree canopy cover based on historical Landsat data, wildfire events and forest management practicesthat occurred during the same period. Results showed that about 11% of the study area experienced an increase in PCC for the period of 1987–2015 while 41% of the study area experienced a reduction in PCC during the same time period, mostly in the areas which were affected by stand replacing wildfires in 2011 and 2013. The results indicate an overall increase in medium and high canopy cover classes in specific regions of the study area, which could lead to hazardous wildfires such as those in 2011 and 2013. In the context of ongoing ecological restoration of these montane forests, predicted PCC of contemporary forests could help local managers to identify the areas in the need of immediate restoration efforts by focusing management practices on the areas with closed canopy.

New Mexico↗

USGS2004

Wildfire-resistant biological soil crusts and fire-induced loss of soil stability in Palouse prairies, USA

Frequent low-intensity fires are a natural component of the ecology of the Palouse prairies of northwestern North America. To study the effects of fire upon biological soil crusts (BSCs) occurring in these grasslands, we sampled three burned (in 2000) sites and three unburned sites in the Hell's Canyon area (OR, USA) ???1 year post-fire. We measured vascular plant and BSC cover, soil microbe pigmentation, texture and chemistry, and soil surface physical properties (stability and rugosity). Festuca idahoensis was two times more abundant in unburned plots (P=0.0006), and vascular plant and litter cover were generally higher in unburned plots. At the community scale, there was no difference in the lichen and moss species composition, suggesting much less drastic effects of fire on BSCs than reported in other systems. Soil surface stability (measured using slake value) was significantly lower in burned sites than unburned sites (median value=5 versus 6, P=0.008), a result which is likely due to the greater density of lichens and mosses encountered in the unburned plots. Soil microbe pigmentation was lower in burned plots (P=0.03), suggesting that the biomass of photosynthetic microbes had decreased; however, the presence of intra- and extracellular pigments in burned soils indicates that microorganisms were not eradicated. Pigments most strongly associated with cyanobacteria were more abundant in unburned sites, suggesting that cyanobacteria may have been more strongly impacted by the fire than other BSC components. Composition of nutrients and surface rugosity did not differ significantly between treatments. We hypothesize that Palouse prairie soil crusts are relatively resistant to wildfire because of low fire intensity and their occupation of space away from the vascular plant fuel load.

Applied Soil Ecology↗

USGS2018

Spatial and temporal variation in sources of atmospheric nitrogen deposition in the Rocky Mountains using nitrogen isotopes

Variation in source areas and source types of atmospheric nitrogen (N) deposition to high-elevation ecosystems in the Rocky Mountains were evaluated using spatially and temporally distributed N isotope data from atmospheric deposition networks for 1995-2016. This unique dataset links N in wet deposition and snowpack to mobile and stationary emissions sources, and enhances understanding of the impacts of anthropogenic activities and environmental policies that mitigate effects of accelerated N cycling across the Rocky Mountain region. δ 15 N−NO 3 − at 50 U.S. Geological Survey Rocky Mountain Snowpack (Snowpack) sites ranged from −3.3‰ to +6.5‰, with a mean value of +1.4‰. At 15 National Atmospheric Deposition Program (NADP)/National Trends Network wet deposition (NADP Wetfall) sites, summer δ 15 N−NO 3 − is significantly lower ranging from −7.6‰ to −1.3‰ while winter δ 15 N−NO 3 − ranges from −2.6‰ to +5.5‰, with a mean value of +0.7‰ during the cool season. The strong seasonal difference in NADP Wetfall δ 15 N−NO 3 − is due in part to variation in the proportion of N originating from source regions at different times of the year due to seasonal changes in weather patterns. Snowpack NO 3 − and δ 15 N−NO 3 − are significantly related to NADP Wetfall (fall and winter) suggesting that bulk snowpack samples provide a reliable estimate at high elevations. Spatial trends show higher NO 3 − concentrations and δ 15 N−NO 3 − in the Southern Rocky Mountains located near larger anthropogenic N emission sources compared to the Northern Rocky Mountains. NADP Wetfall δ 15 N−NH 4 + ranged from −10‰ to 0‰, with no observed spatial pattern. However, the lowest δ 15 N−NH 4 + (−9‰), and the highest NH 4 + concentration (35 μeq/L) were observed at a Utah site dominated by local agricultural activities, whereas the higher δ 15 N−NH 4 + observed in Colorado and Wyoming are likely due to mixed sources, including fossil fuel combustion and agricultural sources. These findings show spatial and seasonal variation in N isotope data that reflect differences in sources of anthropogenic N deposition to high-elevation ecosystems and have important implications for environmental policy across the Rocky Mountain region.

Rocky Mountains↗

USGS2021

Trends in precipitation chemistry across the U.S. 1985–2017: Quantifying the benefits from 30 years of Clean Air Act amendment regulation

Acid rain was first recognized in the 1970s in North America and Europe as an atmospheric pollutant that was causing harm to ecosystems. In response, the U.S. Congress enacted Title IV of the Clean Air Act Amendments (CAA) in 1990 to reduce sulfur and nitrogen emissions from fossil fuel burning power plants. This study reports trends in wet-precipitation chemistry in response to emissions reductions implemented as part of the CAA. Trends were calculated for sulfate (SO 4 ), nitrate (NO 3 ) and ammonium (NH 4 ) from 1985 to 2017 at 168 stations operated by the National Atmospheric Deposition Program (NADP); stations were divided into 9 regions across the United States. Trend analyses were conducted for three time periods: Period 1 (1985–1999), Period 2 (2000–2017), and the entire study period (1985–2017). Seasonal and regional Kendall trend analyses reveal significant decreasing trends in mean wet-precipitation SO 4 concentrations in all 9 regions during the entire study period. The largest decreasing trends in monthly mean SO 4 precipitation-weighted concentrations were measured in the Mid-Atlantic (−1.29 μeq/l/yr), Midwest (−1.15 μeq/l/yr), and Northeast regions (−1.10 μeq/l/yr). The trends in monthly mean NO 3 concentrations were not as strong as those for SO 4 , but all of the regions had significant decreasing trends in NO 3 and again the Mid-Atlantic (−0.53 μeq/l/yr), Midwest (−0.44 μeq/l/yr), and Northeast regions (−0.50 μeq/l/yr) had the strongest trends. Trends were steepest during Period 2 for SO 4 and NO 3 , in fact for NO 3 86% of the stations had significant decreasing trends during Period 2 while only 8% of the stations had significant decreasing trends during Period 1. The stations with the highest concentrations of SO 4 and NO 3 at the beginning of the study had the strongest decreasing trends and the relations were stronger during Period 2 than Period 1. For NH 4 , 22% of the stations had statistically significant increasing trends in concentration during Period 1. The largest increasing trends in wet-precipitation NH 4 concentration occurred in the North-Central region during Period 1, Period 2 and throughout the entire study. By comparison, NH 4 trends in the Rocky-North and Rocky-South regions were about half as steep and trends in the South-Central and Midwest regions were about one-third as steep. We compared trends in SO 4 and NO 3 concentrations from NADP stations to emissions of sulfur dioxide and nitrogen oxides, respectively to determine whether there was a relation between emissions and wet-precipitation concentration trends within proximity to NADP stations. There was a statistically significant relation (r 2 = 0.62–0.69, p < 0.01) between the trend in SO 4 concentrations at individual NADP stations and total and mean sulfur dioxide (SO 2 ) emissions from power plants within a range of 750 km and 1000 km from each station. There were also significant relations between NO 3 concentration trends at NADP stations and power plant emissions of nitrogen oxides, but they were not nearly as strong (r 2 = 0.18–0.36, p < 0.01) as those for SO 4 and were strongest for emissions within a range of 1000 km and 1500 km from each NADP station. Decreases in wet-precipitation SO 4 concentrations were more consistent across regions and through time than decreases in NO 3 and SO 4 trends were more closely linked to stationary emissions sources than NO 3 trends. There were statistically significant increases in NH 4 wet-precipitation concentrations, as have been reported in previous studies, but this study found that those increases were strongest during Period 1 and were not consistent across the United States. During the first 3 years of the study period, wet-precipitation acidity was dominated by SO 4 in 8 of the 9 regions; by 2017 NO 3 dominated the acidity of wet-precipitation in 7 of the 9 regions. There has also been a downward shift in the NO 3 :NH 4 ratio of wet-precipitation as the emissions of nitrogen oxides have declined while ammonia emissions have remained essentially constant. This shift has resulted in an increase in wet-precipitation total nitrogen concentrations in 7 of the 9 regions and indicate that efforts to control NH 3 emissions will become increasingly important as emissions of nitrogen oxides continue to decline.

Atmospheric Environment↗

USGS2015

Avoidance of unconventional oil wells and roads exacerbates habitat loss for grassland birds in the North American great plains

Oil development in the Bakken shale region has increased rapidly as a result of new technologies and strong demand for fossil fuel. This region also supports a particularly high density and diversity of grassland bird species, which are declining across North America. We examined grassland bird response to unconventional oil extraction sites (i.e. developed with hydraulic fracturing and horizontal drilling techniques) and associated roads in North Dakota. Our goal was to quantify the amount of habitat that was indirectly degraded by oil development, as evidenced by patterns of avoidance by birds. Grassland birds avoided areas within 150 m of roads (95% CI: 87–214 m), 267 m of single-bore well pads (95% CI: 157–378 m), and 150 m of multi-bore well pads (95% CI: 67–233 m). Individual species demonstrated variable tolerance of well pads. Clay-colored sparrows ( Spizella pallida ) were tolerant of oil-related infrastructure, whereas Sprague's pipit ( Anthus spragueii ) avoided areas within 350 m (95% CI: 215–485 m) of single-bore well pads. Given these density patterns around oil wells, the potential footprint of any individual oil well, and oil development across the region, is greatly multiplied for sensitive species. Efforts to reduce new road construction, concentrate wells along developed corridors, combine numerous wells on multi-bore pads rather than build many single-bore wells, and to place well pads near existing roads will serve to minimize loss of suitable habitat for birds. Quantifying environmental degradation caused by oil development is a critical step in understanding how to better mitigate harm to wildlife populations.

Biological Conservation↗

USGS2017

Declines revisited: Long-term recovery and spatial population dynamics oftailed frog larvae after wildfire

Drought has fueled an increased frequency and severity of large wildfires in many ecosystems. Despite an increase in research on wildfire effects on vertebrates, the vast majority of it has focused on short-term (< 5 years) effects and there is still little information on the time scale of population recovery for species that decline in abundance after fire. In 2003, a large wildfire in Montana (USA) burned the watersheds of four of eight streams that we sampled for larval Rocky Mountain tailed frogs ( Ascaphus montanus ) in 2001. Surveys during 2004–2005 revealed reduced abundance of larvae in burned streams relative to unburned streams, with greater declines associated with increased fire extent. Rocky Mountain tailed frogs have low vagility and have several unusual life-history traits that could slow population recovery, including an extended larval period (4 years), delayed sexual maturity (6–8 years), and low fecundity (< 50 eggs/year). To determine if abundance remained depressed since the 2003 wildfire, we repeated surveys during 2014–2015 and found relative abundance of larvae in burned and unburned streams had nearly converged to pre-fire conditions within two generations. The negative effects of burn extent on larval abundance weakened> 58% within 12 years after the fire. We also found moderate synchrony among populations in unburned streams and negative spatial autocorrelation among populations in burned streams. We suspect negative spatial autocorrelation among spatially-clustered burned streams reflected increased post-fire patchiness in resources and different rates of local recovery. Our results add to a growing body of work that suggests populations in intact ecosystems tend to be resilient to habitat changes caused by wildfire. Our results also provide important insights into recovery times of populations that have been negatively affected by severe wildfire.

Montana↗

USGS2005

Ferric iron-bearing sediments as a mineral trap for CO2 sequestration: Iron reduction using sulfur-bearing waste gas

We present a novel method for geologic sequestration of anthropogenic CO2 in ferrous carbonate, using ferric iron present in widespread redbeds and other sediments. Iron can be reduced by SO2 that is commonly a component of flue gas produced by combustion of fossil fuel, or by adding SO2 or H2S derived from other industrial processes to the injected waste gas stream. Equilibrium and kinetically controlled geochemical simulations at 120 bar and 50 and 100 ??C with SO2 or H2S show that iron can be transformed almost entirely to siderite thereby trapping CO2, and simultaneously, that sulfur can be converted predominantly to dissolved sulfate. If there is an insufficient amount of sulfur-bearing gas relative to CO2 as for typical flue gas, then some of the iron is not reduced, and some of the CO2 is not sequestered. If there is an excess of sulfur-bearing gas, then complete iron reduction is ensured, and some of the iron precipitates as pyrite or other solid iron sulfide, depending on their relative precipitation kinetics. Gas mixtures with insufficient sulfur relative to CO2 can be used in sediments containing Ca, Mg, or other divalent metals capable of precipitating carbonate minerals. For quartz arenite with an initial porosity of 21% and containing 0.25 wt.% Fe2O3, approximately 0.7 g of CO2 is sequestered per kg of rock, and the porosity decrease is less than 0.03%. Sequestration of CO2 using ferric iron has the advantage of disposing of SO2 that may already be present in the combustion gas. ?? 2005 Published by Elsevier B.V.

Chemical Geology↗

USGS2022

Environmentally persistent free radicals and other paramagnetic species in wildland-urban interface fire ashes

Wildland-urban interface (WUI) fires consume fuels, such as vegetation and structural materials, leaving behind ash composed primarily of pyrogenic carbon and metal oxides. However, there is currently limited understanding of the role of WUI fire ash from different sources as a source of paramagnetic species such as environmentally persistent free radicals (EPFRs) and transition metals in the environment. Electron paramagnetic resonance (EPR) was used to detect and quantify paramagnetic species, including organic persistent free radicals and transition metal spins, in fifty-three fire ash and soil samples collected following the North Complex Fire and the Sonoma-Lake-Napa Unit (LNU) Lightning Complex Fire, California, 2020. High concentrations of organic EPFRs ( e.g., 1.4 × 10 14 to 1.9 × 10 17 spins g −1 ) were detected in the studied WUI fire ash along with other paramagnetic species such as iron and manganese oxides, as well as Fe 3+ and Mn 2+ ions. The mean concentrations of EPFRs in various ash types decreased following the order: vegetation ash (1.1 × 10 17 ± 1.1 × 10 17 spins g −1 ) > structural ash (1.6 × 10 16 ± 3.7 × 10 16 spins g −1 ) > vehicle ash (6.4 × 10 15 ± 8.6 × 10 15 spins g −1 ) > soil (3.2 × 10 15 ± 3.7 × 10 15 spins g −1 ). The mean concentrations of EPFRs decreased with increased combustion completeness indicated by ash color; black (1.1 × 10 17 ± 1.1 × 10 17 spins g −1 ) > white (2.5 × 10 16 ± 4.4 × 10 16 spins g −1 ) > gray (1.8 × 10 16 ± 2.4 × 10 16 spins g −1 ). In contrast, the relative amounts of reduced Mn 2+ ions increased with increased combustion completeness. Thus, WUI fire ash is an important global source of EPFRs and reduced metal species ( e.g., Mn 2+ ). Further research is needed to underpin the formation, transformation, and environmental and human health impacts of these paramagnetic species in light of the projected increased frequency, size, and severity of WUI fires.

California↗

USGS2012

Review and update of the applications of organic petrology: Part 1, geological applications

Organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry. Coal petrology was then considered a branch of coal science. Later, with the development of specialized nomenclature, classification of coal components, and the standardization and improvement of analytical (microscopical) methods, this discipline expanded in interests and name, becoming organic petrology. Organic petrology carries a broader context, being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources. At present, organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences. Throughout the 20th century several important monographs have been published on the discipline of organic petrology, including “Stach's textbook of coal petrology” (1st edition 1935, 2nd 1975, 3rd 1982), updated as the more general “Organic petrology” by Taylor et al. (1998). More recently, the text “Applied coal petrology: the role of petrology in coal utilization” was published by Suárez-Ruiz and Crelling (2008). This review is the first in a two-part review series that describes and updates the role of organic petrology in geosciences. A second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow.

International Journal of Coal Geology↗

USGS2015

Enhanced microbial coalbed methane generation: A review of research, commercial activity, and remaining challenges

Coalbed methane (CBM) makes up a significant portion of the world’s natural gas resources. The discovery that approximately 20% of natural gas is microbial in origin has led to interest in microbially enhanced CBM (MECoM), which involves stimulating microorganisms to produce additional CBM from existing production wells. This paper reviews current laboratory and field research on understanding processes and reservoir conditions which are essential for microbial CBM generation, the progress of efforts to stimulate microbial methane generation in coal beds, and key remaining knowledge gaps. Research has been primarily focused on identifying microbial communities present in areas of CBM generation and attempting to determine their function, in-situ reservoir conditions that are most favorable for microbial CBM generation, and geochemical indicators of metabolic pathways of methanogenesis (i.e., acetoclastic or hydrogenotrophic methanogenesis). Meanwhile, researchers at universities, government agencies, and companies have focused on four primary MECoM strategies: 1) microbial stimulation (i.e., addition of nutrients to stimulate native microbes); 2) microbial augmentation (i.e., addition of microbes not native to or abundant in the reservoir of interest); 3) physically increasing microbial access to coal and distribution of amendments; and 4) chemically increasing the bioavailability of coal organics. Most companies interested in MECoM have pursued microbial stimulation: Luca Technologies, Inc., successfully completed a pilot scale field test of their stimulation strategy, while two others, Ciris Energy and Next Fuel, Inc., have undertaken smaller scale field tests. Several key knowledge gaps remain that need to be addressed before MECoM strategies can be implemented commercially. Little is known about the bacterial community responsible for coal biodegradation and how these microorganisms may be stimulated to enhance microbial methanogenesis. In addition, research is needed to understand what fraction of coal is available for biodegradation, and methods need to be developed to determine the extent of in-situ coal biodegradation by MECoM processes for monitoring changes to coal quality. Questions also remain about how well field-scale pilot tests will scale to commercial production, how often amendments will need to be added to maintain new methane generation, and how well MECoM strategies transfer between coal basins with different formation water geochemistries and coal ranks. Addressing these knowledge gaps will be key in determining the feasibility and commercial viability of MECoM technology.

International Journal of Coal Geology↗

USGS2016

Calorific value and compositional ultimate analysis with a case study of a Texas lignite

Measurements to determine coal quality as fuel include proximate analysis, ultimate analysis and calorific value. The latter is an attribute taking non-negative real values, so a simple transformation is sufficient for its spatial modeling applying geostatistics. The analyses, however, involve proportions that follow the properties of compositional data, thus requiring special preprocessing for an adequate modeling already described in a previous publication for the case of proximate analysis data. 1 Here we model the results of calorific value and ultimate analysis. We propose to use two different binary partitions, one per analysis, map the corresponding isometric logratio transformations, and backtransform the results. The methodology is illustrated using the same coal bed in the previous paper modeling proximate analysis data. Results are summarized using probability maps that, in the case of this deposit, show a prominent channel crossing the deposit and separating the best quality coal from that of lower quality.

International Journal of Coal Geology↗

USGS2024

The petrology of dispersed organic matter in sedimentary rocks: Review and update

Organic petrology developed from coal petrology, and, in the 1960s, it began to be applied to the study of dispersed organic matter (DOM) in sedimentary rocks other than coal. Over the last few decades, the petrology of DOM has been used to characterize organic matter in sedimentary basins with an emphasis on fossil fuel resource exploration. Today, due to the global research shift on topics related to climate, organic petrology has expanded into new application areas, such as geothermal exploration, biological carbon storage (biochar), disposal, and management of radioactive waste. From the publication of the International Handbook of Coal Petrology (mid-20th century) to the present day, a large number of standards, books, and articles have been published as a result of the work of organic petrographers and petrologists around the world and efforts of the International Committee for Coal and Organic Petrology (ICCP) and The Society for Organic Petrology (TSOP) to promote the study of organic petrology. The current fundamentals and standards of organic petrology provide the international scientific community with well-informed guidance and recommendations to promote in-depth research. However, this information is currently widely scattered, leading to discrepancies in methodology and terminology. Therefore, this paper aims to present a comprehensive review of the main analytical standard test methods and techniques currently used in the petrology of DOM under reflected white light and UV and blue-light excitation, and to provide an efficient and well-defined reference guide. Furthermore, considering the important role of the ICCP in the development of organic petrology since the 1950s, a brief review of the ongoing activities of ICCP dealing with DOM is also presented.

International Journal of Coal Geology↗

USGS2019

Examination of Bathymodiolus childressi nutritional sources, isotopic niches, and food-web linkages at two seeps in the US Atlantic margin using stable isotope analysis and mixing models

Chemosynthetic environments support distinct benthic communities capable of utilizing reduced chemical compounds for nutrition. Hundreds of methane seeps have been documented along the U.S. Atlantic margin (USAM), and detailed investigations at a few seeps have revealed distinct environments containing mussels, microbial mats, authigenic carbonates, and soft sediments. The dominant mussel, Bathymodiolus childressi , contains methanotrophic endosymbionts but is also capable of filter feeding, and stable isotope analysis (SIA) of mussel-shell periostracum suggests that these mussels are mixotrophic, assimilating multiple food resources. However, it is unknown whether mixotrophy is widespread or varies spatially and temporally. We used SIA (δ 13 C, δ 15 N, and δ 34 S) and an isotope mixing model (MixSIAR) to estimate resource contribution to B. childressi and characterize food webs at two seep sites (Baltimore Seep; 400 m and Norfolk Seep; 1500 m depths) along the USAM, and applied a linear mixed-effects model to explore the role of mussel population density and tissue type in influencing SIA variance. After controlling for location and temporal variation, isotopic variability was a function of proportion of live mussels present and tissue type. Isotopic differences were also spatially discrete, possibly reflecting variations in the underlying carbon source at the two sites. Low mussel δ 13 C values (∼−63‰) are consistent with a dependence on microbial methane. However, MixSIAR results revealed mixotrophy for mussels at both sites, implying a reliance on a mixture of methane and phytoplankton-derived particulate organic material. The mixing model results also reveal population density-driven patterns, suggesting that resource use is a function of live mussel abundance. Mussel isotopes differed by tissue type, with gill having the lowest δ 15 N values relative to muscle and mantle tissues. Based on mass balance equations, up to 79% of the dissolved inorganic carbon (DIC) of the pore fluids within the anaerobic oxidation of the methane zone is derived from methane and available to fuel upper slope deep-sea communities, such as fishes ( Dysommina rugosa and Symphurus nebulosus ), echinoderms ( Odontaster robustus , Echinus wallisi , and Gracilechinus affinis ), and shrimp, ( Alvinocaris markensis ). The presence of these seeps thereby increases the overall trophic and community diversity of the USAM continental slope. Given the presence of hundreds of seeps within the region, primary production at seeps may serve as an important, yet unquantified, energy source to the USAM deep-sea environment.

Delaware, Maryland, North Carolina, Virginia↗

USGS2025

Factors structuring macrofaunal communities of hydrocarbon seeps along the Cascadia margin

Cold seeps, fueled by hydrocarbon-based chemosynthesis, support unique benthic communities that can vary across small spatial scales influenced by local geochemistry. We examined the community structure and function of macrofauna in cold seeps along the Cascadia margin on the edge of gas hydrate stability—a dynamic environment that may fluctuate as seafloor temperatures change. These communities were assessed in relation to their sediment environment to provide baseline data for these previously uninvestigated seeps and decipher the most significant variables structuring them. Specific environmental drivers investigated include sediment organic carbon, total nitrogen, C:N ratios, stable isotopes (δ 13 C and δ 15 N), redox potential, grain size, and porefluid chemistry. Macrofaunal community composition varied across locations separating into twelve distinct clusters. Several co-located cores clustered separately, indicating high heterogeneity in these communities at small spatial scales. Significant drivers of macrofauna communities included clay and sand content, C:N, δ 15 N values, organic carbon content, and depth. Functional trait composition was influenced by similar drivers, including depth, δ 15 N values, C:N, and sand content. Our results indicate similar environmental variables structure macrofaunal community composition and function across small- and large-scale gradients, contributing to our understanding of heterogeneity in local and regional factors that shape seep macrofaunal communities. This is the first investigation of macrofauna at these recently discovered seeps and provides baseline data on the hydrate stability zone for future comparisons, advancing our knowledge of broad-scale trends in seep macrofauna ecology.

California, Oregon, Washington↗

USGS2009

A national look at carbon capture and storage-National carbon sequestration database and geographical information system (NatCarb)

The US Department of Energy's Regional Carbon Sequestration Partnerships (RCSPs) are responsible for generating geospatial data for the maps displayed in the Carbon Sequestration Atlas of the United States and Canada. Key geospatial data (carbon sources, potential storage sites, transportation, land use, etc.) are required for the Atlas, and for efficient implementation of carbon sequestration on a national and regional scale. The National Carbon Sequestration Database and Geographical Information System (NatCarb) is a relational database and geographic information system (GIS) that integrates carbon storage data generated and maintained by the RCSPs and various other sources. The purpose of NatCarb is to provide a national view of the carbon capture and storage potential in the U.S. and Canada. The digital spatial database allows users to estimate the amount of CO 2 emitted by sources (such as power plants, refineries and other fossil-fuel-consuming industries) in relation to geologic formations that can provide safe, secure storage sites over long periods of time. The NatCarb project is working to provide all stakeholders with improved online tools for the display and analysis of CO 2 carbon capture and storage data. NatCarb is organizing and enhancing the critical information about CO 2 sources and developing the technology needed to access, query, model, analyze, display, and distribute natural resource data related to carbon management. Data are generated, maintained and enhanced locally at the RCSP level, or at specialized data warehouses, and assembled, accessed, and analyzed in real-time through a single geoportal. NatCarb is a functional demonstration of distributed data-management systems that cross the boundaries between institutions and geographic areas. It forms the first step toward a functioning National Carbon Cyberinfrastructure (NCCI). NatCarb provides access to first-order information to evaluate the costs, economic potential and societal issues of CO 2 capture and storage, including public perception and regulatory aspects. NatCarb online access has been modified to address the broad needs of a spectrum of users. NatCarb includes not only GIS and database query tools for high-end user, but simplified display for the general public using readily available web tools such as Google Earth???and Google Maps???. Not only is NatCarb connected to all the RCSPs, but data are also pulled from public servers including the U.S. Geological Survey-EROS Data Center and from the Geography Network. Data for major CO 2 sources have been obtained from U.S. Environmental Protection Agency (EPA) databases, and data on major coal basins and coalbed methane wells were obtained from the Energy Information Administration (EIA). ?? 2009 Elsevier Ltd. All rights reserved.

Conference Paper↗

USGS2011

Experimental and simulation studies of iron oxides for geochemical fixation of CO2-SO2 gas mixtures

Iron-bearing minerals are reactive phases of the subsurface environment and could potentially trap CO 2 –SO 2 gas mixtures derived from fossil fuel combustion processes by their conversion to siderite (FeCO 3 ) and dissolved sulfate. Changes in fluid and mineral compositions resulting from reactions, involving the co-injection of SO 2 with CO 2 were observed both theoretically and experimentally. Experiments were conducted with a natural hematite (α-Fe 2 O 3 ) sample. A high pressure-high temperature apparatus was used to simulate conditions in geologic formations deeper than 800 m, where CO 2 is in the supercritical state. Solid samples were allowed to react with a NaCl–NaOH brine and SO 2 -bearing CO 2 -dominated gas mixtures. The predicted equilibrium mineral assemblage at 100 °C and 250 bar became hematite, dawsonite (NaAl(OH) 2 CO 3 ), siderite (FeCO 3 ) and quartz (SiO 2 ). Experimentally, siderite and dawsonite, derived from the presence of kaolinite (Al 2 Si 2 O 5 (OH) 4 ) in the parent material, were present in residual solids at longer reaction time intervals, which agreed well with results from the modelling work.

Energy Procedia↗