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USGS2007

Neoproterozoic diamictite-cap carbonate succession and δ 13 C chemostratigraphy from eastern Sonora, Mexico

Despite the occurrence of Neoproterozoic strata throughout the southwestern U.S. and Sonora, Mexico, glacial units overlain by enigmatic cap carbonates have not been well-documented south of Death Valley, California. Here, we describe in detail the first glaciogenic diamictite and cap carbonate succession from Mexico, found in the Cerro Las Bolas Group. The diamictite is exposed near Sahuaripa, Sonora, and is overlain by a 5 m thick very finely-laminated dolostone with soft sediment folds. Carbon isotopic chemostratigraphy of the finely-laminated dolostone reveals a negative δ 13 C anomaly (down to − 3.2&permil; PDB) characteristic of cap carbonates worldwide. Carbon isotopic values rise to + 10&permil; across &sim; 400 m of section in overlying carbonates of the Mina el Mezquite and Monteso Formations. The pattern recorded here is mostly characteristic of post-Sturtian (ca. ≤ 700 Ma), but pre-Marinoan (ca. ≥ 635 Ma) time. However, the Cerro Las Bolas Group shares ambiguity common to most Neoproterozoic successions: it lacks useful radiometric age constraints and biostratigraphically useful fossils, and its δ 13 C signature is oscillatory and therefore somewhat equivocal.

Sonora↗

USGS2014

Geologic assessment of undiscovered oil and gas resources in Aptian carbonates, onshore northern Gulf of Mexico Basin, United States

Carbonate lithofacies of the Lower Cretaceous Sligo Formation and James Limestone were regionally evaluated using established U.S. Geological Survey (USGS) assessment methodology for undiscovered conventional hydrocarbon resources. The assessed area is within the Upper Jurassic–Cretaceous–Tertiary Composite total petroleum system, which was defined for the assessment. Hydrocarbons reservoired in carbonate platform Sligo-James oil and gas accumulations are interpreted to originate primarily from the Jurassic Smackover Formation. Emplacement of hydrocarbons occurred via vertical migration along fault systems; long-range lateral migration also may have occurred in some locations. Primary reservoir facies include porous patch reefs developed over paleostructural salt highs, carbonate shoals, and stacked linear reefs at the carbonate shelf margin. Hydrocarbon traps dominantly are combination structural-stratigraphic. Sealing lithologies include micrite, calcareous shale, and argillaceous lime mudstone. A geologic model, supported by discovery history analysis of petroleum geology data, was used to define a single regional assessment unit (AU) for conventional reservoirs in carbonate facies of the Sligo Formation and James Limestone. The AU is formally entitled Sligo-James Carbonate Platform Oil and Gas (50490121). A fully risked mean undiscovered technically recoverable resource in the AU of 50 million barrels of oil (MMBO), 791 billion cubic feet of natural gas (BCFG), and 26 million barrels of natural gas liquids was estimated. Substantial new development through horizontal drilling has occurred since the time of this assessment (2010), resulting in cumulative production of >200 BCFG and >1 MMBO.

Cretaceous Research↗

USGS2025

Abundance of microplastics in a typical urban wetland in China: Association with occurrence and carbon storage

Microplastics (MPs) are gaining attention for their widespread presence and toxicity in ecosystems. However, their role as a carbon source in urban wetland carbon sinks is still unclear. In this study, the microplastic-carbon (MP-C) was firstly quantified based on the abundance and occurrence characteristics, including MP morphology, size and type in the Sanyang Wetland, a typical urban wetland of China. MP abundances ranged from 2.4 ± 0.6–14.9 ± 1.5 items/L in surface water and 6.6 ± 1.2 × 10 3 to 46.3 ± 5.9 × 10 3 items/kg in sediment. The predominant morphological characterization of MPs was fragments smaller than 200 μm in size, consisting of PP, PE, and PET, which suggests that the main source was domestic wastewater discharge nearby. Notably, in the Sanyang wetland, the contribution of MP-C to total organic carbon (TOC) was estimated to be 0.023 0.20 % in water and 0.026 0.28 % in sediment. With the continuous production of plastics globally, these values were predicted to increase to 0.12 0.71 % and 0.83 4.12 % by 2100, respectively. Although the estimations relied on simplified geometric assumptions for MP volume and theoretical carbon content, these approaches provide a reasonable basis for understanding MP-C dynamics in wetlands under current analytical constraints. The integration of MP-C characterization during environmental monitoring and management strategies would enhance our understanding of MP pollution's role in the carbon cycle.

Journal of Hazardous Materials↗

USGS2020

Carbon storage and sediment trapping by Egeria densa Planch., a globally invasive, freshwater macrophyte

Invasive plants have long been recognized for altering ecosystem properties, but their long-term impacts on ecosystem processes remain largely unknown. In this study, we determined the impact of Egeria densa Planch, a globally invasive freshwater macrophyte, on sedimentation processes in a large tidal freshwater region. We measured carbon accumulation (CARs) and inorganic sedimentation rates in submerged aquatic vegetation SAV dominated by E. densa and compared these rates to those of adjacent tidal freshwater marshes. Study sites were chosen along a range of hydrodynamic conditions in the Sacramento-San Joaquin Delta of California, USA, where E. densa has been widespread since 1990. Cores were analyzed for bulk density, % inorganic matter, % organic carbon, 210 Pb, and 137 Cs. Our results show that E. densa patches constitute sinks for both “blue carbon” and inorganic sediment. Compared to marshes, E. densa patches have greater inorganic sedimentation rates ( E. densa : 1103–5989 g m −2 yr −1 , marsh: 393–1001 g m −2 yr −1 , p < 0.01) and vertical accretion rates ( E. densa : 0.4–1.3 cm yr −1 , marsh: 0.3–0.5 cm yr −1 , p < 0.05), but similar CARs ( E. densa : 59–242 g C m −2 yr −1 , marsh: 109–169 g C m −2 yr −1 , p > 0.05). Sediment stored by E. densa likely reduces the resilience of adjacent marshes by depleting the sediment available for marsh-building. Because of its harmful traits, E. densa is not a suitable candidate for mitigating carbon pollution; however, currently invaded habitats may already contain a meaningful component of regional carbon budgets. Our results strongly suggest that E. densa patches are sinks for carbon and inorganic sediment throughout its global range, raising questions about how invasive SAV is altering biogeochemical cycling and sediment dynamics across freshwater ecosystems.

California↗

USGS2024

Biocrusts modulate carbon losses under warming across global drylands: A bayesian meta-analysis

Biocrusts are critical biological components of drylands and play an important role in soil carbon (C) cycling. However, the effect of biocrusts on soil CO 2 exchange across global gradients of temperature and moisture is poorly understood. Moreover, their response to climate change remains highly uncertain. Bayesian hierarchical meta-analyses were performed on 47 published studies to quantify the impact of biocrusts on net soil exchange (NSE) of carbon- the difference between respiration and photosynthesis. Meta-analyses were also used on 23 studies to examine the effects of experimental warming on NSE in biocrusts. Meta-regressions further explored the thermal and wetness sensitivities of biocrust NSE and potential adaptation of biocrust responses to climate change. The development of biocrusts in dryland soils significantly increased NSE by 66.5 [22.2, 112.2] g C m −2 yr −1 , despite seasonal fluctuations, indicating a net loss of carbon to the atmosphere. Experimental warming, on average, increased biocrust NSE by 22.9 [-0.1, 40.8] g C m −2 yr −1 per °C. However, across the spatial climate gradient, aridity limited the effects of warming, while high temperature decreased the thermal sensitivity of biocrust NSE, thus supporting the thermal adaptation of biocrusts. These results emphasize the critical role of biocrusts in modulating soil carbon exchange in response to climate warming across drylands, with particularly high thermal sensitivity in cool and moist regions. This highlights the need to incorporate biocrusts into global carbon budgets and models for a comprehensive understanding of their impact on the carbon cycle.

Soil Biology and Biogeochemistry↗

USGS2017

Extension of the analytical window for characterizing aromatic compounds in oils using a comprehensive suite of high-resolution mass spectrometry techniques and double bond equivalence versus carbon number plot

In this study, comprehensive two-dimensional (2D) gas chromatography–mass spectrometry (GC–MS), atmospheric pressure photoionization (APPI) quadrupole-Orbitrap mass spectrometry (MS), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to study the aromatic fractions of crude oil and oil shale pyrolysates (shale oils). The collected data were compared and combined in the double bond equivalence (DBE) versus carbon number plot to obtain a more complete understanding of the composition of the oil fractions. The numbers of peaks observed by each technique followed the order 2D GC–MS < Orbitrap MS < FT-ICR MS. The class distributions observed by Orbitrap MS and FT-ICR MS were similar to each other but different from that observed by 2D GC–MS. The DBE and carbon number distributions of the 2D GC–MS and Orbitrap MS data were similar for crude oil aromatics. The FT-ICR MS plots of DBE and carbon number showed an extended range of higher values relative to the other methods. For the aromatic fraction of an oil shale pyrolysate generated by the Fischer assay, only a few nitrogen-containing compounds were observed by 2D GC–MS but a large number of these compounds were detected by Orbitrap MS and FT-ICR MS. This comparison clearly shows that the data obtained from these three techniques can be combined to more completely characterize oil composition. The data obtained by Orbitrap MS and FT-ICR MS agreed well with one another, and the combined DBE versus carbon number plot provided more complete coverage of compounds present in the fractions. In addition, the chemical structure information provided by 2D GC–MS could be matched with the chemical formulas in the DBE versus carbon number plots, providing information not available in ultrahigh-resolution MS results. It was therefore concluded that the combination of 2D GC–MS, Orbitrap MS, and FT-ICR MS in the DBE versus carbon number space facilitates structural assignment of heavy oil components.

Energy & Fuels↗

USGS2020

Molecular identification of water-extractable organic carbon from thermally heated soils: C-13 NMR and accurate mass analyses find benzene and pyridine carboxylic acids

To simulate the effects of wildfire on the combustion process in soils and their potential to leach organic compounds into streams and groundwater, mineral soil samples were heated at temperatures of 150–550 °C. Then, the soils were leached with deionized water, filtered, and analyzed for dissolved organic carbon. The water extract was concentrated by both XAD-8 and XAD-4 resins and analyzed by C-13 nuclear magnetic resonance and liquid chromatography time-of-flight mass spectrometry. Approximately 15–20% of the water-extractable organic carbon was identified as benzene dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acid isomers, commonly called BPCAs. Also identified were isomers of pyridine dicarboxylic acids and tricarboxylic acids (PCAs). The conversion of soil organic carbon to BPCAs occurs at 250 °C and reaches a maximum between 350 and 450 °C. At higher temperatures (>450 °C), the BPCA concentrations decrease, suggesting decarboxylation and conversion to carbon dioxide and water. This is the first report of BPCAs and PCAs in water-extractable organic carbon from thermally altered soil and suggest that these compounds are possible candidates for further water-quality studies in watersheds affected by wildfire. Finally, BPCAs and PCAs could contribute to the black carbon and nitrogen in seawater and are worthy of future investigation.

Environmental Science and Technology↗

USGS1997

Mechanism of SO2 removal by carbon

The reaction of SO 2 with carbon (C) in the presence of O 2 and H 2 O involves a series of reactions that leads to the formation of sulfuric acid as the final product. The rate-determining step in the overall process is the oxidation of SO 2 to SO 3 . Three SO 2 oxidation reactions are possible. Adsorbed SO 2 (C−SO 2 ) can react either with gas phase O 2 or with adsorbed oxygen (C−O complex) to form sulfur trioxide (SO 3 ), or gas phase SO 2 can react directly with the C−O complex. In optimizing the SO 2 removal capabilities of carbon, most studies only assume a given mechanism for SO 2 adsorption and conversion to H 2 SO 4 to be operable. The appropriate SO 2 oxidation step and role of the C−O complex in this mechanism remain to be determined. The ultimate goal of this study was to prepare activated char from Illinois coal with optimal properties for low-temperature (80−150°C) removal of sulfur dioxide from coal combustion flue gas. The SO 2 adsorption capacity of activated char was found to be inversely proportional to the amount of oxygen adsorbed on its surface. A temperature-programmed desorption technique was developed to titrate those sites responsible for adsorption of SO 2 and conversion to H 2 SO 4 . On the basis of these results, a mechanism for SO 2 removal by carbon was proposed. The derived rate expression showed SO 2 adsorption to be dependent only on the fundamental rate constant and concentration of carbon atoms designated as free sites. Recent studies indicate a similar relationship exists between the rate of carbon gasification (in CO 2 or H 2 O) and the number of reactive sites as determined by transient kinetics experiments. Utilizing the concept of active or free sites, it was possible to produce a char from Illinois coal having an SO 2 adsorption capacity surpassing that of a commercial catalytic activated carbon.

Energy and Fuels↗

USGS2010

Federal land management, carbon sequestration, and climate change in the Southeastern U.S.: a case study with fort benning

Land use activities can have a major impact on the temporal trendsandspatialpatternsofregionalland-atmosphereexchange of carbon. Federal lands generally have substantially different land management strategies from surrounding areas, and the carbon consequences have rarely been quantified and assessed. Using the Fort Benning Installation as a case study, we used the General Ensemble biogeochemical Modeling System (GEMS) to simulate and compare ecosystem carbon sequestration between the U.S. Army's Fort Benning and surrounding areas from 1992 to 2050. Our results indicate that the military installation sequestered more carbon than surrounding areas from 1992 to 2007 (76.7 vs 18.5 g C m -2 yr -1 ), and is projected to continue sequestering more carbon from 2008 to 2050 (75.7 vs 25.6 g C m -2 yr -1 ), mostly because of the proactive management approaches adopted on military training lands. Our results suggest that federal lands might play a positive and important role in sequestering and conserving atmospheric carbon because some anthropogenic disturbances (e.g., urbanization, forest harvesting, and agriculture) can be minimized or prevented on federal lands

Georgia↗

USGS1999

Assessing the influence of reacting pyrite and carbonate minerals on the geochemistry of drainage in the Coeur d'Alene mining district

The relative abundance of minerals that react to generate or consume acid in mineralized areas is critical in determining the quality of water draining from such areas. This work examines the fundamental reactions that influence the pH and composition of drainage from mine adits and tailings piles. We construct triangle diagrams that predict stoichiometric relationships between concentrations of dissolved SO4 dissolved Ca and Mg, and either alkalinity or acidity by considering reactions involving the oxidation of pyrite, dissolution of carbonate minerals, and precipitation of iron oxide and iron hydroxysulfate minerals. Drainage data from the Coeur d'Alene mining district are used to test our stoichiometric approach. Comparisons between theoretical predictions and drainage data indicate that the range of pH values in the mining district is due to reacting pyrite to carbonate mineral ratios that range from near 0/1 to 1/1. Calcite and ankerite are the dominant carbonate minerals that buffer the acid produced during pyrite oxidation and ferrihydrite or schwertmannite precipitation.The relative abundance of minerals that react to generate or consume acid in mineralized areas is critical in determining the quality of water draining from such areas. This work examines the fundamental reactions that influence the pH and composition of drainage from mine adits and tailings piles. We construct triangle diagrams that predict stoichiometric relationships between concentrations of dissolved SO4, dissolved Ca and Mg, and either alkalinity or acidity by considering reactions involving the oxidation of pyrite, dissolution of carbonate minerals, and precipitation of iron oxide and iron hydroxysulfate minerals. Drainage data from the Coeur d'Alene mining district are used to test our stoichiometric approach. Comparisons between theoretical predictions and drainage data indicate that the range of pH values in the mining district is due to reacting pyrite to carbonate mineral ratios that range from near 0/1 to 1/1. Calcite and ankerite are the dominant carbonate minerals that buffer the acid produced during pyrite oxidation and ferrihydrite or schwertmannite precipitation.

Idaho↗

USGS2009

Quantifying the spatial details of carbon sequestration potential and performance

Upscaling the spatial and temporal changes of carbon stocks and fluxes from sites to regions is challenging owing to the spatial and temporal variances and covariance of driving variables and the uncertainties in both the model and the input data. Although various modeling approaches have been developed to facilitate the upscaling process, few deal with error transfer from model input to output, and error propagation in time and space. The author has developed the General Ensemble Biogeochemical Modelling System (GEMS) for upscaling carbon stocks and fluxes from sites to regions with measures of uncertainty. This chapter describes the GEMS model, its application to regional- and larger-scale areas, and the new results that demonstrate the challenges of upscaling. GEMS relies on site-scale biogeochemical models to simulate carbon dynamics at the site scale. The spatial deployment of the site-scale model in GEMS is based on the spatial and temporal joint frequency distribution of major driving variables (e.g., land cover and land use change, climate, soils, disturbances, and management). At the site scale, GEMS uses stochastic ensemble simulations to incorporate input uncertainty to quantify uncertainty transfer from input to output, and to identify trends in both input data and simulation results. It permits one to simulate the range of possible permutations of input values and identify the trends and variance in both the input data and results. Using data assimilation techniques, GEMS simulations can be constrained by field and satellite observations, including estimates of net primary production (NPP) from the Moderate Resolution Imaging Spectroradiometer (MODIS), grain yield and cropping practices, and forest inventories. The modeling philosophy embedded in GEMS makes it ideal for assimilating information with various uncertainties to support estimating the spatial details of carbon sequestration potential as well as dynamic monitoring of the performance of carbon sequestration activities over large areas. As a case study, GEMS is applied to simulate the spatial and temporal details of carbon sources, sinks, and uncertainty in the Ridge and Valley ecoregion in the eastern United States

Book chapter↗

USGS2010

Carbonate control of H 2 and CH 4 production in serpentinization systems at elevated P-Ts

Serpentinization of forsteritic olivine results in the inorganic synthesis of molecular hydrogen (H 2 ) in ultramafic hydrothermal systems (e.g., mid-ocean ridge and forearc environments). Inorganic carbon in those hydrothermal systems may react with H 2 to produce methane (CH 4 ) and other hydrocarbons or react with dissolved metal ions to form carbonate minerals. Here, we report serpentinization experiments at 200°C and 300 bar demonstrating Fe 2+ being incorporated into carbonates more rapidly than Fe 2+ oxidation (and concomitant H 2 formation) leading to diminished yields of H 2 and H 2 -dependent CH 4 . In addition, carbonate formation is temporally fast in carbonate oversaturated fluids. Our results demonstrate that carbonate chemistry ultimately modulates the abiotic synthesis of both H 2 and CH 4 in hydrothermal ultramafic systems and that ultramafic systems present great potential for CO 2 -mineral sequestration.

Geophysical Research Letters↗

USGS2011

Simulating the impacts of disturbances on forest carbon cycling in North America: Processes, data, models, and challenges

Forest disturbances greatly alter the carbon cycle at various spatial and temporal scales. It is critical to understand disturbance regimes and their impacts to better quantify regional and global carbon dynamics. This review of the status and major challenges in representing the impacts of disturbances in modeling the carbon dynamics across North America revealed some major advances and challenges. First, significant advances have been made in representation, scaling, and characterization of disturbances that should be included in regional modeling efforts. Second, there is a need to develop effective and comprehensive process‐based procedures and algorithms to quantify the immediate and long‐term impacts of disturbances on ecosystem succession, soils, microclimate, and cycles of carbon, water, and nutrients. Third, our capability to simulate the occurrences and severity of disturbances is very limited. Fourth, scaling issues have rarely been addressed in continental scale model applications. It is not fully understood which finer scale processes and properties need to be scaled to coarser spatial and temporal scales. Fifth, there are inadequate databases on disturbances at the continental scale to support the quantification of their effects on the carbon balance in North America. Finally, procedures are needed to quantify the uncertainty of model inputs, model parameters, and model structures, and thus to estimate their impacts on overall model uncertainty. Working together, the scientific community interested in disturbance and its impacts can identify the most uncertain issues surrounding the role of disturbance in the North American carbon budget and develop working hypotheses to reduce the uncertainty

Journal of Geophysical Research: Biogeosciences↗

USGS2019

Cross-scale interactions dictate regional lake carbon flux and productivity response to future climate

Lakes support globally important food webs through algal productivity and contribute significantly to the global carbon cycle. However, predictions of how broad-scale lake carbon flux and productivity may respond to future climate are extremely limited. Here, we used an integrated modeling framework to project changes in lake-specific and regional primary productivity and carbon fluxes under 21st century climate for thousands of lakes. We observed high uncertainty in whether lakes collectively were to increase or decrease lake CO 2 emissions and carbon burial in our modeled region owing to divergence in projected regional water balance among climate models. Variation in projected air temperature influenced projected changes in lake primary productivity (but not CO 2 emissions or carbon burial) as warmer air temperatures decreased productivity through reduced lake water volume. Cross-scale interactions between regional drivers and local characteristics dictated the magnitude and direction of lake-specific carbon flux and productivity responses to future climate.

Geophysical Research Letters↗

USGS2021

Aquatic-terrestrial linkages control metabolism and carbon dynamics in a mid-sized, urban stream influenced by snowmelt

Freshwater streams can exchange nutrients and carbon with the surrounding terrestrial environment through various mechanisms including physical erosion, flooding, leaf drop, and snowmelt. These aquatic-terrestrial interactions are crucial in carbon mobilization, transformation, ecosystem productivity, and have important implications for the role of freshwater ecosystems in the global carbon budget. We utilized high-frequency oxygen, temperature, and carbon dioxide (CO 2 ) data to infer watershed connectivity in Boulder Creek, a mid-sized (1160 km 2 ) watershed located in Colorado, USA. Daily modeled gross primary production (GPP), ecosystem respiration (ER), net ecosystem production (NEP), and reaeration coefficients ( K 600 ) were paired with high-frequency, in-situ dissolved CO 2 data to characterize changes in metabolic regime and carbon flux on a stream influenced by seasonal snowmelt. GPP and ER were correlated ( ρ = −0.72, p ≪ 0.001) during the non-snowmelt period and NEP was frequently negative. Mean F CO2 during the non-snowmelt period was approximately 302 (±171) mmol C m −2 d −1 and was primarily supported by watershed CO 2 inputs. During snowmelt, GPP and ER were not significantly correlated ( ρ = −0.22, p = 0.05), and mean NEP was significantly more negative than during non-snowmelt. Watershed connectivity was higher during snowmelt, as evidenced by significantly higher F CO2 (843 ± 338 mmol C m −2 d −1 ) and greater allochthonous CO 2 inputs than during non-snowmelt periods, emphasizing the effects of seasonal differences in aquatic-terrestrial linkages in this stream. We suggest that our understanding of watershed carbon budgets is subject to temporal dynamics which control the degree of connectivity between terrestrial and aquatic ecosystems.

Colorado↗

USGS2010

Recent acceleration of biomass burning and carbon losses in Alaskan forests and peatlands

Climate change has increased the area affected by forest fires each year in boreal North America. Increases in burned area and fire frequency are expected to stimulate boreal carbon losses. However, the impact of wildfires on carbon emissions is also affected by the severity of burning. How climate change influences the severity of biomass burning has proved difficult to assess. Here, we examined the depth of ground-layer combustion in 178 sites dominated by black spruce in Alaska, using data collected from 31 fire events between 1983 and 2005. We show that the depth of burning increased as the fire season progressed when the annual area burned was small. However, deep burning occurred throughout the fire season when the annual area burned was large. Depth of burning increased late in the fire season in upland forests, but not in peatland and permafrost sites. Simulations of wildfire-induced carbon losses from Alaskan black spruce stands over the past 60 years suggest that ground-layer combustion has accelerated regional carbon losses over the past decade, owing to increases in burn area and late-season burning. As a result, soils in these black spruce stands have become a net source of carbon to the atmosphere, with carbon emissions far exceeding decadal uptake.

Nature Geoscience↗

USGS2017

Abundant carbon in the mantle beneath Hawai`i

Estimates of carbon concentrations in Earth ’ s mantle vary over more than an order of magnitude, hindering our ability to understand mantle structure and mineralogy, partial melting, and the carbon cycle. CO 2 concentrations in mantle-derived magmas supplying hotspot ocean island volcanoes yield our most direct constraints on mantle carbon, but are extensively modified by degassing during ascent. Here we show that undegassed magmatic and mantle carbon concentrations may be estimated in a Bayesian framework using diverse geologic information at an ocean island volcano. Our CO 2 concentration estimates do not rely upon complex degassing models, geochemical tracer elements, assumed magma supply rates, or rare undegassed rock samples. Rather, we couple volcanic CO 2 emission rates with probabilistic magma supply rates, which are obtained indirectly from magma storage and eruption rates. We estimate that the CO 2 content of mantle-derived magma supplying Hawai‘i ’ s active volcanoes is 0.97 −0.19 +0.25 wt%—roughly 40% higher than previously believed—and is supplied from a mantle source region with a carbon concentration of 263 −62 +81 ppm. Our results suggest that mantle plumes and ocean island basalts are carbon-rich. Our data also shed light on helium isotope abundances, CO 2 /Nb ratios, and may imply higher CO 2 emission rates from ocean island volcanoes.

Hawaii↗

USGS2019

Negligible cycling of terrestrial carbon in many lakes of the arid circumpolar landscape

High-latitude environments store nearly half of the planet’s below-ground organic carbon (OC), mostly in perennially frozen permafrost soils. Climatic changes drive increased export of terrestrial OC into many aquatic networks, yet the role that circumpolar lakes play in mineralizing this carbon is unclear. Here we directly evaluate ecosystem-scale OC cycling for lakes of interior Alaska. This arid, low-relief lake landscape is representative of over a quarter of total northern circumpolar lake area, but is greatly under-represented in current studies. Contrary to projections based on work in other regions, the studied lakes had a negligible role in mineralizing terrestrial carbon; they received little OC from ancient permafrost soils, and had small net contribution to the watershed carbon balance. Instead, most lakes recycled large quantities of internally derived carbon fixed from atmospheric CO 2 , underscoring their importance as critical sites for material and energy provision to regional food webs. Our findings deviate from the prevailing paradigm that northern lakes are hotspots of terrestrial OC processing. The shallow and hydrologically disconnected nature of lakes in many arid circumpolar landscapes isolates them from terrestrial carbon processing under current climatic conditions.

Nature Geoscience↗