Inorganic Carbon Concentrations Research Articles

Impact of submarine volcanic versus hydrothermal activity onto the strontium and lithium isotopic signatures of the water column (TONGA)

During the TONGA cruise (2019), seawater samples were collected to assess the effect of volcanic eruption versus submarine hydrothermal system on the water column. For this purpose, two locations were investigated, the first one located directly under the influence of the New Late’iki island (eruption in October 2019), and the second one showing ongoing submarine hydrothermal activity. At both locations, the total strontium (TSr) and lithium (TLi) concentrations vary between 94.4 and 152.3 µmol/L and 13.2 and 203.5 µmol/L, respectively. When combined, TSr and TLi concentrations of all samples in the water column are higher than those of the oligotrophic water. Both volcanic eruption and submarine hydrothermal activity (e.g. volcanic ashes, particles, gas condensate) can deliver substantial amount of TSr and TLi to the water column. The distribution of TSr versus TLi evidences linear trends either with a negative or positive slope. The negative correlation is observed in the water column at both sites, directly under the influence of the eruption and in the vicinity of the volcano with hydrothermal activity. The positive TSr versus TLi correlation is observed at site under submarine hydrothermal influence and is in line with black smokers related hydrothermal plumes. The 87Sr/86Sr ratios vary between 0.709147 and 0.709210 and δ7Li values vary between +10.1 and +37.6 ‰. While 92% of the measured 87Sr/86Sr ratios are in line with the mean value of oligotrophic waters, once combined with the δ7Li values, only 20% of them remains within this field. The wide range of δ7Li values decreases from sea-surface down to ~140 mbsl, before increasing at greater depth, while defining different linear trend according to the dissolved inorganic carbon concentrations. The variability of δ7Li values reflect hydrothermal contribution, mineral–seawater interaction and potentially biology–environment interaction. In the particular geological setting of the study, where both hydrothermal and volcanic activities were at play, disentangling both contributions on water column implies a combined use of elemental and isotopic signatures of Sr and Li tracers.

Weathering of Buried Standard Pieces of Serpentine under Varied Soil Treatments and Relevant Analysis of Microbial Community Structure

Carbon sink processes related to the weathering of silicate minerals are often accompanied by physical, chemical, and biological effects. In particular, plant-microbe synergistic effects are important for soil mineral weathering, but relevant correlation analyses and quantitative studies remain sparse. In this research, a standard serpentine test specimens (STSs) with specific specifications were used to study serpentine weathering under different environmental conditions (abiotic or biotic) and correlated it with the microbial community structure under the growth of Setaria viridis. The results showed that the environment with growing S. viridis had the strongest weathering capacity for STSs, which was 35 times higher than that of the abiotic environment group, and a significant increase in soil inorganic and organic carbon contents compared with the abiotic environment and the environment without plant growth. The bacteria with strong weathering ability were enriched in the soil of around STSs, such as Pseudomonas spp. and Sphingomonas spp. In addition, the fungal community of Ascomycetes is also heavily enriched, accelerating STSs weathering. The addition of bacterial agent (Bacillus subtilis) further promoted the STSs weathering under the growth conditions of S. viridis. The soil surrounding the buried STSs was also enriched with heavy metal tolerant Massilia spp. and disease suppressing Lysobacter spp., while the abundance of fungi functionally associated with pathotypes was reduced, thereby benefiting plant growth. This study provides basic information for the serpentine bio-weathering coupled with carbon sequestration by using plant-microbe synergistic effects.

Aluminium bioavailability and toxicity disrupted chloroplast structure and inhibited inorganic carbon utilization and nutrient uptake in Vallisneria natans at acidic and alkaline pH

Vallisneria natans, as submerged aquatic plants, face significant threats from aluminium (Al) toxicity. While the effects of Al at low pH on terrestrial plants have been extensively studied, there is a lack of research on the impacts of both low and high pH on chloroplast ultrastructure and nutrient uptake in submerged plants. This research is important as it aims to fill this gap by exposing the leaves of Vallisneria natans to 100 μM Al at varying pH levels (4.5, 5.5, 7.5, and 9.5) for 48 hours. The results showed that inorganic carbon (CT), CO2, and HCO3 content increased at extreme pH levels (4.5 and 9.5), suggesting decreased inorganic carbon utilization under Al stress. Additionally, photosystem II efficiency and electron transport rate were significantly reduced at extreme pH levels, highlighting the sensitivity of V. natans to Al. Chlorophyll a and total chlorophyll content were significantly lower at pH 4.5 compared to pH 7.5. Chloroplast structural disruptions were evident at extreme pH levels coupled with Al exposure, whereas minimal injury was observed at pH 5.5 and 7.5. The study also noted vacuole enlargement, altered plasma membrane permeability, and hematoxylin staining, indicating Al accumulation in leaves. ICP analysis revealed increased Al content at extreme pH levels, underscoring heightened Al bioavailability and toxicity. Significant reductions in macro and micronutrient content (P, Mg, K, Fe, Zn, B, Mn) were observed, likely due to Al-induced root and cell damage and altered nutrient uptake. These findings emphasize the complex interplay between Al exposure, pH fluctuations, and their cascading effects on the physiology and elemental composition of Vallisneria natans, highlighting the need for further research and environmental management strategies.

Novel three-stage microalgal cultivation system for lipid production utilizing nutrients derived from refinery waste

The pollution and transformation of refineries are receiving increasing attention. The carbonic anhydrase in Tetradesmus obliquus was found exhibiting a hysteresis phenomenon in response to periodic changes in the composition of external carbon sources, with a surge in inorganic carbon concentration stressing the carbonic anhydrase activity to increase by 6–9 times. On this basis, a novel three-stage culture system of T. obliquus was proposed, which mainly uses refinery waste as the nutrients. By controlling the nutrient content in the environment, especially the composition of carbon sources, microalgae could sequentially complete rapid biomass accumulation, efficient inorganic carbon assimilation, and oil production. Compared to a single-environment culture system, the biomass yield increased by 1.34 times, the oil content increased by more than 6%, and the oil productivity increased by 2.08 times. Above findings may lay a partial theoretical foundation for the future evolution of traditional refineries towards “fossil–algal-biomass” hybrid refineries.

In-field carbon dioxide removal via weathering of crushed basalt applied to acidic tropical agricultural soil

Enhanced weathering (EW) of silicate rocks such as basalt provides a potential carbon dioxide removal (CDR) technology for combatting climate change. Modelling and mesocosm studies suggest significant CDR via EW but there are few field studies. This study aimed to directly measure in-field CDR via EW of basalt applied to sugarcane on acidic (pH 5.8, 0–0.25 m) Ultisol in tropical northeastern Australia, where weathering potential is high. Coarsely crushed basalt produced as a byproduct of gravel manufacture (<5 mm) was applied annually from 2018 to 2022 at 0 or 50 t ha−1 a−1, incorporated into the soil in 2018 but not in subsequent years. Measurements in 2022 show increased soil pH and extractable Mg and Si at 0–0.25 m depth, indicating significant weathering of the basalt, but showed no increase in crop yield. Soil inorganic carbon content and bicarbonate (HCO3−) flux to deep drainage (1.25 m depth) were measured to quantify CDR in the 2022–2023 wet season (i.e. one year). Soil inorganic carbon was below detection limits. Mean HCO3− flux was 3.15 kmol ha−1 a−1 (±0.40) in the basalt-treated plots and 2.56 kmol ha−1 a−1 (±0.18) in the untreated plots but the difference (0.59 kmol ha−1 a−1 or 0.026 t CO2 ha−1 a−1) was not significant (p = 0.082). Most weathering of the basalt was attributed to acids stronger than carbonic acid. These were, in decreasing order of contribution, surface-bound protons (inherent soil acidity), nitric acid (from nitrification), organic acids, and acids associated with cation uptake by plants. These results indicate in-field CDR via EW of basalt is low where soil and regolith pH is well below the pKa1 of 6.4 for H2CO3. However, increased soil pH, and the consumption of strong acids by weathering will eventually lead to reduced CO2 emission from soil or evasion from rivers, with continued basalt addition.

Different preferences for inorganic carbon influence CO2 flux under Cyanobacteria or Chlorophyta dominance days

Algae play critical roles in the carbon dioxide (CO2) exchange between the water bodies and the atmosphere. However, the effects of prokaryotic and eukaryotic algae on carbon utilization, CO2 flux, and the underlying mechanisms remain poorly understood. Therefore, this study investigated the differences in carbon preferences and CO2 fluxes under different algal dominance days. Our research revealed that dissolved inorganic carbon (DIC) concentration fluctuations had a limited effect on the relative abundance of algae. However, shifts in dominant algal phyla induced changes in DIC, with Cyanobacteria preferring HCO3− and Chlorophyta preferring CO2. Analysis of the water chemistry balance indicated that the growth of Chlorophyta had a 15.59 times greater effect on CO2 sinks compared with that of Cyanobacteria. During the Cyanobacteria dominance days, the lower DIC concentration did not result in a reduction in CO2 emissions. However, increases in the dissolved organic carbon concentration provided a favorable environment for Cyanobacteria, which promoted CO2 emissions. The CCM model indicated that the growth of Chlorophyta resulted in CO2 uptake rates at least 3.57 times higher and CO2 leakage rates up to 0.97 times lower compared to Cyanobacteria, accelerating CO2 transport into the cell. Overall, CO2 sink was stronger on Chlorophyta dominance days than on Cyanobacteria dominance days. This study emphasized the influence of algal phyla on CO2 fluxes, revealing the significant CO2 sink associated with Chlorophyta. Further research should investigate how to manipulate environmental factors to favor Chlorophyta growth and effectively reduce CO2 emissions.

Wastewater treatment optimization utilizing polyvinyl alcohol cryogel immobilized microalgae for nutrient removal

This study investigated the use of polyvinyl alcohol (PVA) cryogels to immobilize microalgae for wastewater treatment. Chlorella sorokiniana was successfully entrapped in PVA cryogels via repeated freeze/thaw cycles. The nutrient removal efficiency of these cryogels was tested in a continuously stirred photobioreactor under varying conditions, both with and without the addition of an organic carbon source (sodium acetate). The presence of organic carbon significantly enhanced nutrient removal. Specifically, PVA cryogels with immobilized C. sorokiniana achieved 100% nitrogen removal and 97.2% phosphorus removal under mixotrophic conditions. Furthermore, the maximum nutrient removal capacities of the PVA cryogels were found to be 0.033 mg-N/cube·day for nitrogen and 0.0047 mg-P/cube·day for phosphorus. As the inorganic carbon (bicarbonate) concentration increased from 5 to 100 mg/L, the N/P ratio rose from 6 to 8, with a higher N/P ratio of 10 observed when nitrate nitrogen was used as the nitrogen source, compared to ammonia nitrogen, at 100 mg/L bicarbonate. This study offers an effective method for using microalgae immobilized in PVA cryogels for wastewater treatment. The findings highlight the potential for PVA cryogels to significantly improve nutrient removal efficiency, particularly in the presence of organic carbon sources, thereby enhancing bioreactor performance. High nitrogen and phosphorus removal efficiencies can help reduce eutrophication in water bodies, protect aquatic ecosystems, and enable nutrient recovery and reuse, supporting a circular economy in wastewater treatment practices.

Response to the CO2 concentrating mechanisms and transcriptional time series analysis of Ulva prolifera under inorganic carbon limitation

Ulva prolifera is a dominant species in green tides and has been affecting marine ecosystem for many years. Due to the low availability of CO2 in the environment, U. prolifera utilizes the CO2 concentrating mechanisms (CCMs) to increase intracellular inorganic carbon concentration. However, the transcriptional response mechanism and temporal changes of U. prolifera CCMs based on transcriptomics have not been thoroughly described. Therefore, we induced U. prolifera CCMs in a low CO2 environment to explore the dynamic regulation of CCMs expression under inadequate inorganic carbon supply. The results showed that inorganic carbon limitation increased the inorganic carbon affinity of U. prolifera, upregulating CCMs. The first 24 h of inorganic carbon environmental changes were the most active period for U. prolifera's expression regulation. U. prolifera gradually achieved a new steady state by regulating metabolic processes such as nucleic acids, energy, and ethylene-activated signaling pathways. In the carbon fixation system of U. prolifera, there are characteristics of both biophysical and biochemical CCMs. After 24 h of inorganic carbon limitation, the biophysical CCMs becomes more effective under conditions of inorganic carbon depletion. This study aids in exploring the CCMs of U. prolifera and their evolution in response to environmental changes.

Dual carbon isotopes (δ13C and Δ14C) were used to reveal the main sources and input fluxes of dissolved inorganic carbon in a karst reservoir in winter

In karst areas, the dissolved inorganic carbon (DIC) concentrations in aquatic systems are typically higher than that in non-karst areas due to intensive carbonate rock weathering. Understanding the sources and input fluxes of DIC in karst reservoirs is crucial for regional carbon cycle studies. This study utilized dual carbon isotopes (δ13CDIC and Δ14CDIC) to estimate the contribution rates and input fluxes of DIC from various sources in Aha Reservoir (AHR), located in southwestern China. Our results indicated that the DIC concentrations (22.33–32.79 mg L−1) and δ13CDIC values (−10.02‰ to −8.55‰) were nearly homogeneous both vertically and laterally in the reservoir (p > 0.05). The Δ14CDIC values (−246.31‰ to −137.86‰) were homogeneous along the vertical profile (p > 0.05), but showed significant horizontal variation (p < 0.05), with values decreasing from −149.57 ± 10.27‰ to −232.85 ± 2.37‰ at the mouths of the inflowing rivers. We found that the inflowing rivers were the primary DIC sources to AHR, contributing 70% of the total input, while groundwater and atmospheric CO2 contributions were relatively minor, at 18% and 12%, respectively. The Jinzhong River (JZR), influenced by industrial and domestic wastewater discharge, contributed the largest DIC input flux at 2.01 t/(km2·mon). In contrast, the Youyu River (YYR), influenced by acidic mine drainage, and the Baiyan River (BYR), influenced by agricultural activities, contributed relatively smaller DIC input fluxes of 1.29 t/(km2·mon) and 1.03 t/(km2·mon), respectively. This study highlights the significant impact of anthropogenic activities on DIC input in AHR, with industrial and domestic wastewater discharges having a greater influence than agricultural activities and acidic mine wastewater inputs. These findings underscore the critical need to manage and mitigate the impacts of human activities on karst reservoir ecosystems.

CASCADE: Dataset of extant coccolithophore size, carbon content and global distribution

Coccolithophores are marine calcifying phytoplankton important to the carbon cycle and a model organism for studying diversity. Here, we present CASCADE (Coccolithophore Abundance, Size, Carbon And Distribution Estimates), a new global dataset for 139 extant coccolithophore taxonomic units. CASCADE includes a trait database (size and cellular organic and inorganic carbon contents) and taxonomic-unit-specific global spatiotemporal distributions (Latitude/Longitude/Depth/Month/Year) of coccolithophore abundance and organic and inorganic carbon stocks. CASCADE covers all ocean basins over the upper 275 meters, spans the years 1964-2019 and includes 33,119 gridded taxonomic-unit-specific abundance observations. Within CASCADE, we characterise the underlying uncertainties due to measurement errors by propagating error estimates between the different studies. This error propagation pipeline is statistically robust and could be applied to other plankton groups. CASCADE can contribute to (observational or modelling) studies that focus on coccolithophore distribution and diversity and the impacts of anthropogenic pressures on historical populations. Additionally, our new taxonomic-unit-specific cellular carbon content estimates provide essential conversions to quantify the role of coccolithophores on ecosystem functioning and global biogeochemistry.

Potential Carbon Content and Inorganic Carbon Sequestration in the Karst Area of Silokek Geopark, Sijunjung Regency

Climate change caused by increasing greenhouse gas emissions, especially CO2, and deforestation, is an urgent global issue. The REDD+ program initiated by the UN aims to reduce carbon emissions and increase carbon storage in forests. One of the forests that can reserve carbon is the karst area with the ability to reserve carbon dioxide (CO2). This study aims to determine the potential carbon content and carbon dioxide (CO2) sequestration. This study was conducted using the chip sampling method and the XRF (X-ray Fluorescence) method analysis. Based on the research results, it is known that the Silokek Geopark karst area has three different limestone rock characteristics, and sample 3 is the type of rock with the highest CaO percentage. The potential inorganic carbon content is 4,908.07 tons/ha and carbon absorption is 18,012.60 tons/ha, categorized as high. The inorganic carbon content in the Silokek Geopark area is lower than the Biduk-biduk Karst area which is influenced by the area volume area and type of rock composition.

Stoichiometric theory in aquatic carbon sequestration under elevated carbon dioxide

Global climate change projections indicate that the atmospheric concentration of carbon dioxide will increase twofold by the end of this century. However, how the elevated carbon dioxide affects aquatic carbon sequestration and species composition within aquatic microbial communities remains inconclusive. To address this knowledge gap, we formulate a bacteria-algae interaction model to characterize the effects of elevated carbon dioxide on aquatic ecosystems and rigorously derive the thresholds determining the persistence and extinction of algae or bacteria. We explore the impacts of abiotic factors, such as light intensity, nutrient concentration, inorganic carbon concentration and water depth, on algae and bacteria dynamics. The main findings indicate that the elevated atmospheric carbon dioxide will increase algae biomass and thus facilitate carbon sequestration. On the other hand, the elevated atmospheric carbon dioxide will reduce bacterial biomass, and excessive carbon dioxide concentrations can even destroy bacterial communities. Numerical simulations indicate that eutrophication and intensified light intensity can reduce aquatic carbon sequestration, while elevated atmospheric carbon dioxide levels can mitigate eutrophication. Furthermore, higher algae respiration and death rates are detrimental to carbon sequestration, whereas the increased bacterial respiration rates promote carbon sequestration.

Understanding the environmental drivers of summer dissolved carbon in lakes on the Qinghai-Tibetan Plateau

How environmental factors affecting dissolved carbon remains unclear in lakes on the Qinghai-Tibetan Plateau (QTP), which limits the understanding of the lake carbon cycle. In this study, 60 lakes on the QTP in summer were investigated to clarify the variation in dissolved carbon, estimate dissolved carbon storage, and reveal how environmental factors affect the variation in dissolved carbon. The average dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) contents of 60 lakes on the QTP in summer were 12.78 mg/L and 103.66 mg/L, respectively. Salinity and total nitrogen were the important drivers of variations in DIC and DOC, respectively. Lake salinity and temperature were reduced only when precipitation was >50 mm, thus affecting the variations in lake dissolved carbon. Importantly, the elevation and area of the lake also significantly affected the variation in lake dissolved carbon. The total storage amounts of DOC and DIC in the 60 lakes on the QTP in summer were 58.94 Tg and 6.22 Tg, respectively. Lake area was the most direct factor influencing dissolved carbon storage in lakes on the QTP. Moreover, the TN and pH of the lake water also affected the DOC and DIC storage in the lakes, respectively. Interestingly, the lake pH at 9.1 was an important turning point that caused variations in lake DIC storage. Surprisingly, we found that rivers were able to transport 30 % of the DIC into QTP lakes and were the main source of DIC in the lakes in summer. The findings of this study clarify the sources of dissolved carbon and its drivers and improve our understanding of the carbon cycling processes in the lake system on the QTP.

Biogeochemistry of the rare sulfidic glaciovolcanic cave system on Mount Meager, British Columbia, Canada

The Mount Meager Volcanic Complex (Q̓welq̓welústen) is an active glacier-capped volcanic massif in the Garibaldi Volcanic Belt (British Columbia) and the only known glaciovolcanic cave system in North America steadily releasing sulfur-rich gases. In September 2022, leveraging specialized cave explorer expertise, the fumarole-carved ice cave at the Job Glacier on Mt. Meager was surveyed. Direct measurements of fumarolic gas concentrations were taken at the source, with H2S &amp;gt;200 ppm, SO2 &amp;gt;100 ppm, CO2 ∼5,200 ppm, and CO ∼230 ppm. Snowpack and fumarole-associated sediments were characterized for microbial diversity, functional potential, and biogeochemistry including measurements of nutrients, major ions, dissolved organic and inorganic carbon concentrations as well as the stable isotope compositions of carbon, sulfur, hydrogen and oxygen. Green algae (Chlorophyta) dominated the snowpack, consistent with other Pacific Northwest glaciers. Representatives of Firmicutes were the most abundant bacterial sequences detected in our samples, contrasting with other glacier and snowpack samples which harbor abundant Sphingobacteria, Betaproteobacteria, and Alphaproteobacteria. Sediments and water collected inside the cave were mostly high in SO42- (5.3–185.2 mg/L) and acidic (pH = 3.6–6.0), while most other major anions and cations were below detection of the method used. Snow at the cave entrance had more SO42- (0.08 mg/L) and lower pH (5.9) than snow collected at a distance (SO42- undetectable, pH 7.6), suggesting influence by fumarole exhalations. Negative δ13C values of organic matter (−29.0‰ to −26.1‰, respectively) in sediments suggest in-situ microbial carbon transformations, findings that are supported by the presence of genes encoding complete heterotrophic and autotrophic carbon transformation pathways. The δ34S value of H2S was ∼0‰, suggesting a deep magmatic origin; however, both sulfur-oxidizing and sulfate-reducing microbial phyla were present in the sediment samples as were genes encoding both dissimilatory sulfur-oxidizing and sulfate-reducing pathways. Metagenomic data suggest diverse chemosynthetic lifestyles in the cave microbial community. This study provides insight on the microbiomes associated with a sulfidic glaciovolcanic system and identifies unique analog features for icy celestial bodies like Saturn’s moon Enceladus, where cryovolcanic activity may carry biomarkers from the subsurface and deposit them on surface ice.

Simultaneous onboard analysis of seawater dissolved inorganic carbon (DIC) concentration and stable isotope ratio (δ13C‐DIC)

AbstractDissolved inorganic carbon (DIC) and its stable carbon isotope (δ13C‐DIC) are valuable parameters for studying the aquatic carbon cycle and quantifying ocean anthropogenic carbon accumulation rates. However, the potential of this coupled pair is underexploited as only 15% or less of cruise samples have been analyzed for δ13C‐DIC because the traditional isotope analysis is labor‐intensive and restricted to onshore laboratories. Here, we improved the analytical precision and reported the protocol of an automated, efficient, and high‐precision method for ship‐based DIC and δ13C‐DIC analysis based on cavity ring‐down spectroscopy (CRDS). We also introduced a set of stable in‐house standards to ensure accurate and consistent DIC and δ13C‐DIC measurements, especially on prolonged cruises. With this method, we analyzed over 1600 discrete seawater samples over a 40‐d cruise along the North American eastern ocean margin in summer 2022, representing the first effort to collect a large dataset of δ13C‐DIC onboard of any oceanographic expedition. We evaluated the method's uncertainty, which was 1.2 μmol kg−1 for the DIC concentration and 0.03‰ for the δ13C‐DIC value (1σ). An interlaboratory comparison of onboard DIC concentration analysis revealed an average offset of 2.0 ± 3.8 μmol kg−1 between CRDS and the coulometry‐based results. The cross‐validation of δ13C‐DIC in the deep‐ocean data exhibited a mean difference of only −0.03‰ ± 0.07‰, emphasizing the consistency with historical data. Potential applications in aquatic biogeochemistry are discussed.

Unveiling the influence of seawater intrusion and vegetation type on coastal arbuscular mycorrhizal fungal communities in China

AbstractContinuously rising sea levels pose severe threats to the diversity and stability of coastal ecosystems. However, the responses of endospheric and rhizospheric arbuscular mycorrhizal (AM) fungal communities to accelerated seawater intrusion and changing vegetation types unfortunately remains unknown. Such insights will assist in revealing the structure of AM fungi across different tidal zones, enabling the development of effective measures to conserve biodiversity. Here, we investigated changes in endospheric and rhizospheric AM fungal communities associated with four types of coastal vegetation in Dafeng City, Jiangsu Province, China, in response to sea level variations by analyzing their characteristics and connections to selected environmental factors. It was found that the AM fungal communities of coastal vegetation differed significantly in their compositions, diversity, and stability (the resilience or resistance of a community). Despite the responses of endospheric and rhizospheric AM fungi to soil environmental factors, the soil electrical conductivity, cation exchange content, and inorganic carbon were identified as core elements that influenced the characteristics of AM fungal communities between different coastal vegetation species. Lastly, the major endospheric and rhizospheric species of AM fungi were important predictors that explained much of the variation in the soil environment. Consequently, the dynamics of AM fungal communities were correlated with the plant–soil system under different conditions. Apart from the coastal vegetation species, the characteristics of AM fungal communities can also be driven by high salinity and the inorganic carbon content induced by the intrusion of seawater.

Enhanced Soil Fertility and Carbon Sequestration in Urban Green Spaces through the Application of Fe-Modified Biochar Combined with Plant Growth-Promoting Bacteria.

The soil of urban green spaces is severely degraded due to human activities during urbanization, and it is crucial to investigate effective measures that can restore the ecological functions of the soil. This study investigated the effects of plant growth promoting bacteria (Bacillus clausii) and Fe-modified biochar on soil fertility increases and mechanisms of carbon sequestration. Additionally, the effects on C-cycling-related enzyme activity and the bacterial community were also explored. Six treatments included no biochar or Bacillus clausii suspension added (CK), only Bacillus clausii suspension (BC), only biochar (B), only Fe-modified biochar (FeB), biochar combined with Bacillus clausii (BBC), and Fe-modified biochar combined with Bacillus clausii (FeBBC). Compared with other treatments, the FeBBC treatment significantly decreased soil pH, alleviated soil alkalization, and increased the alkali-hydro nitrogen content in the soil. Compared to the individual application of FeB and BC, the FeBBC treatment significantly improved aggregates' stability and positively improved soil fertility and ecological function. Additionally, compared to the individual application of FeB and BC, the soil organic carbon (SOC), particulate organic carbon (POC), and soil inorganic carbon (SIC) contents for the FeBBC-treated soil increased by 28.46~113.52%, 66.99~434.72%, and 7.34~10.04%, respectively. In the FeBBC treatment, FeB can improve soil physicochemical properties and provide bacterial attachment sites, increase the abundance and diversity of bacterial communities, and promote the uniform distribution of carbon-related bacteria in the soil. Compared to a single ecological restoration method, FeBBC treatment can improve soil fertility and carbon sequestration, providing important reference values for urban green space soil ecological restoration.

Climatological distribution of ocean acidification variables along the North American ocean margins

Abstract. Climatologies, which depict mean fields of oceanographic variables on a regular geographic grid, and atlases, which provide graphical depictions of specific areas, play pivotal roles in comprehending the societal vulnerabilities linked to ocean acidification (OA). This significance is particularly pronounced in coastal regions where most economic activities, such as commercial and recreational fisheries and aquaculture industries, occur. In this paper, we unveil a comprehensive data product featuring coastal ocean acidification climatologies and atlases, encompassing the fugacity of carbon dioxide, pH on the total scale, total hydrogen ion content, free hydrogen ion content, carbonate ion content, aragonite saturation state, calcite saturation state, Revelle factor, total dissolved inorganic carbon content, and total alkalinity content. These variables are provided on 1° × 1° spatial grids at 14 standardized depth levels, ranging from the surface to a depth of 500 m, along the North American ocean margins, defined as the region between the coastline and a distance of 200 nautical miles (∼370 km) offshore. The climatologies and atlases were developed using the World Ocean Atlas (WOA) gridding methods of the NOAA National Centers for Environmental Information (NCEI) based on the recently released Coastal Ocean Data Analysis Product in North America (CODAP-NA), along with the 2021 update to the Global Ocean Data Analysis Project version 2 (GLODAPv2.2021) data product. The relevant variables were adjusted to the index year of 2010. The data product is available in NetCDF (https://doi.org/10.25921/g8pb-zy76, Jiang et al., 2022b) on the NOAA Ocean Carbon and Acidification Data System: https://www.ncei.noaa.gov/data/oceans/ncei/ocads/metadata/0270962.html (last access: 15 July 2024). It is recommended to use the objectively analyzed mean fields (with “_an” suffix) for each variable. The atlases can be accessed at https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/synthesis/nacoastal.html (last access: 15 July 2024).

Mid-infrared spectroscopy determines the provenance of coastal marine soils and their organic and inorganic carbon content

Vegetated coastal ecosystems (VCE), encompassing tidal marshes, mangroves, and seagrasses, serve as significant ‘blue’ carbon (C) sinks. Improving our understanding of VCE soils and their spatial and temporal dynamics is essential for conservation efforts. Conventional methods to characterise the dynamics and provenance of VCE soils and measure their total organic carbon (TOC) and inorganic carbon (TIC) contents are cumbersome and expensive.We recorded the mid-infrared (MIR) spectra and measured the TOC and TIC content of 323 subsamples across consistent depths from 106 soil core samples. Using the spectra of each VCE, we determined their mineral and organic composition by depth. We then used a regression tree algorithm, cubist, to model TOC and TIC contents. We rigorously validated the models to test their performance with a 10-fold cross-validation, bootstrapping, and a separate random test dataset.Our analysis revealed distinct mineralogical and organic MIR signatures in VCE soils that correlated with their position within the seascape. The spectra showed decreased clay minerals and increased quartz and carbonate with distance from freshwater inputs. The mineralogy of tidal marsh and mangrove soils differed with depth, showing larger absorptions due to carbonate and quartz and weakening clay minerals and organics absorptions. The mineralogy of the seagrass soils remained the same with depth. The cubist models to estimate TOC and TIC content were accurate (Lin's concordance correlation, ρc≥ 0.92 and 0.93 respectively) and interpretable, confirming our understanding of C in these systems. These findings shed light on the provenance of the soils and help quantify the flux and accumulation of TOC and TIC, which is crucial for informing VCE conservation. Moreover, our results indicate that MIR spectroscopy could help scale the measurements cost-effectively, for example, in carbon crediting schemes and to improve inventories. The approach will help advance blue C science and contribute to the conservation and protection of VCE.

Carbon evolution and mixing effects on groundwater age calculations in fractured basalt, southwestern Idaho, U.S.A.

Using hydrochemical and isotopic compositions of springs and wells, we trace carbon from critical zone carbon dioxide (CO2) into groundwater of the semi-arid Reynolds Creek Experimental Watershed - Critical Zone Observatory, southwestern Idaho, USA. Dissolved inorganic carbon (DIC) concentrations, pH and stable isotope tracers of carbon for DIC (δ13CDIC), are used to show that most groundwater evolves under open system conditions, moving carbon into the groundwater and acting as a carbon sink. However, one sample (−10.94‰ δ13CDIC, 6,350 14C years before present (yrs. BP)) may have evolved under closed system conditions with a higher partial pressure of critical zone CO2 than present-day soils. By characterizing the carbon cycle, we show that (1) carbon evolution is primarily under open-system conditions, (2) shallow groundwater samples are generally less mixed and more recent (10 to 70 3H yrs. BP) than deeper groundwater samples (1,469 to 6,350 14C yrs. BP), and (3) the older portion of the groundwater may be even older than the calculated 14C ages, as indicated by the mixing of age tracers in intermediate wells. Our global conception of the deep critical zone should include carbon cycling of critical zone CO2 in old groundwater. Characterizing the deep critical zone in a semi-arid weathered silicate watershed improves our global understanding of carbon, nutrient and water cycling.