Global Elemental Cycles Research Articles

Marine clay maturation induces systematic silicon isotope decrease in authigenic clays and pore fluids

Marine silicate alteration exerts a major influence on marine carbon and cation cycles, but has proven difficult to quantify. In this context, silicon isotopes of marine pore fluids became an important tracer. However, poorly constrained silicon isotope signatures of precipitates produced during silicate alteration (i.e. authigenic clays) remain a major source of uncertainty. Here we present in situ silicon isotope analyses of marine authigenic clays (intergrown iron-smectites and iron-glauconites) occurring within recent sediments from the Oregon margin, eastern North Pacific. We identify a trend to lower silicon isotopes (from −2.24‰ to −3.17‰), accompanied by decreasing aluminum/silicon ratios and increasing potassium oxide contents, which we interpret as an isotopic shift caused by progressive clay maturation via dissolution-reprecipitation reactions. Our modelling suggests that this clay maturation pathway, together with mixing of other fluid sources, may induce pore fluid silicon isotope shifts of up to −1.7‰, if sufficient newly precipitated clays are re-dissolved. This could potentially produce silicon isotopes values significantly lower than seawater and implies that conventional isotope-based approaches underestimate the prevalence of marine silicate alteration. Our findings highlight that clay maturation must be considered when interpreting silicon isotope signatures in terms of marine silicate alteration and upscaling to global element cycles.

Spatial and environmental drivers of temperate estuarine archaeal communities

Archaea play a crucial role in the global biogeochemical cycling of elements and nutrients, helping to maintain the functional stability of estuarine systems. This study characterised the abundance and diversity of archaeal communities and identified the environmental conditions shaping these microbial communities within six temperate estuaries along approximately 500 km of the New South Wales coastline, Australia. Estuarine sediments were found to exhibit significantly higher species richness than planktonic communities, with representative sequences from the Crenarchaeota phylum characterising each environment. Ordinate analyses revealed catchment characteristics as the strongest drivers of community variability. Our results also provide evidence supporting distance-decay patterns of archaeal biogeography across intermediate scales within and between temperate estuaries, contributing to a growing body of evidence revealing the extent spatial scales play in shaping microbial communities. This study expands our understanding of microbial diversity in temperate estuaries, with a specific focus on archaeal community structure and their role in maintaining ecosystem stability.

Decomposing a San Francisco estuary microbiome using long-read metagenomics reveals species- and strain-level dominance from picoeukaryotes to viruses.

Ocean and estuarine microbiomes play critical roles in global element cycling and ecosystem function. Despite the importance of these microbial communities, many species still have not been cultured in the lab. Environmental sequencing is the primary way the function and population dynamics of these communities can be studied. Long-read sequencing provides an avenue to overcome limitations of short-read technologies to obtain complete microbial genomes but comes with its own technical challenges, such as needed sequencing depth and obtaining high-quality DNA. We present here new sampling and bioinformatics methods to attempt decomposing an estuarine microbiome into its constituent genomes. Our results suggest there are only a few strains that comprise most of the species abundances from viruses to picoeukaryotes, and to fully decompose a metagenome of this diversity requires 1 Tbp of long-read sequencing. We anticipate that as long-read sequencing technologies continue to improve, less sequencing will be needed.

Demystifying anaerobic respiration: a problem-solving exercise.

Anaerobic respiration reactions are of fundamental importance to global biogeochemical cycling of elements. Yet, the idea that cellular respiration can occur not only in the absence of oxygen but also involve the oxidation of inorganic substrates (e.g., AsO33-, Fe2+, H2, H2S, Mn2+, NH3, and S0) is often foreign to many undergraduate students. This article describes a problem-solving exercise where students are introduced to the thermodynamic fundamentals of respiration with a particular focus on the role of redox (reduction-oxidation) potentials (E0´). In the exercise, the students investigate how the difference in redox potential (ΔE0´) between different pairs of reductants and oxidants affects the range of permissible microbial metabolic reactions in natural environments when oxygen is absent.

A protocol for the synthesis of [35S]-labeled 3-dimethylsulfoniopropionate and dimethylsulfide from L-methionine for use in biogeochemical studies

Radiotracers are highly sensitive tools for quantifying the rates of important biogeochemical processes and the fates of specific atoms and/or compounds within major global elemental cycles, especially those that are requisite for life. Important radiolabeled organosulfur compounds, like dimethylsulfide (DMS) and its precursor 3-dimethylsulfoniopropionate (DMSP), are not commercially available, but their well-documented use has been key in furthering our understanding of the marine sulfur cycle. [35S]-DMSP obtained by chemical synthesis has been used extensively in radiotracer studies involving DMS and DMSP, but its synthesis has been restricted to 2 research groups. Presented here is a protocol for the chemical synthesis of [35S]-DMSP from [35S]-L-methionine, though the method could be used for other radiolabels (e.g. [14C], [3H]). The synthesis consists of 2 reaction steps, (1) the sequential oxidative deamination and decarboxylation of [35S]-L-methionine to [35S]-3-methylmercaptopropionate and (2) the methylation of [35S]-methylmercaptopropionate to yield the product [35S]-DMSP. The product is purified by liquid chromatography and two cation-resin exchanges. Average final [35S]-DMSP yield was 5.34% (n = 16; range: 1.26% to 14.84%, excluding failures), although updated instrumentation could likely improve final yields. The objective of this work is to standardize the synthesis of [35S]-DMSP to widen its availability and use among the community and hence facilitate increased understanding of the reduced sulfur and carbon cycles.

Acceleration of phosphorus weathering under warm climates.

The release of phosphorous (P) via chemical weathering is a vital process that regulates the global cycling of numerous key elements and shapes the size of the Earth's biosphere. It has long been postulated that global climate should theoretically play a prominent role in governing P weathering rates. Yet, there is currently a lack of direct evidence for this relationship based on empirical data at the global scale. Here, using a compilation of temperature and P content data of global surface soils (0 to 30 cm), we demonstrate that P release does enhance at high mean annual surface temperatures. We propose that this amplification of nutrient supply with warming is a critical component of Earth's natural thermostat, and that this relationship likely caused expanded oceanic anoxia during past climate warming events. The potential acceleration of phosphorus loss from soils due to anthropogenic climate warming may pose threats to agricultural production, terrestrial and marine ecosystems, and alter marine redox landscapes.

Physical insights into uranyl diffusion and sorption in bentonite: Theoretical and molecular dynamics study

Mechanistic understanding of diffusion and sorption of radionuclides and metals in clay-based engineered barriers is essential to develop models and define parameters for transport calculations for the safety analysis of disposal systems. Here we studied diffusion of uranyl (UO22+) species in the clay interparticle pore or macropores of bentonite clay by means of molecular dynamics simulation (MDS) for pore sizes ranging from 8.37 to 33.5 nm. The conceptual model of the clay pore system considered diffusion as a combination of pore diffusion (Dp) and surface diffusion DS (i.e. diffusion of adsorbed cations within the electrical double layer of the clay surfaces), from which the apparent diffusion Da was calculated as the weighted sum of Dp and DS, using a weighing factor f calculated as the ratio of adsorbed to total UO22+ in the system. Diffusivities at equilibrium for the largest pore size of 33.5 nm were: Da=7.37×10−10 m2 s−1, Dp=1.14×10−9 m2 s−1, and Ds=1.97×10−13 m2 s−1. The Ds was several orders of magnitude smaller than Dp. This was evident from the much smaller gradient of the mean-square displacement vs time lag curve for the adsorbed species than that of the species in the pore space. We found a remarkable consistency between our theoretical derivation and independent MDS evidence. For the slit-shaped interparticle pore, the retardation factor Rf was found to be the reciprocal of the unabsorbed fraction (Rf=1/1−f) and the capacity factor α was a ratio of the porosity to the unadsorbed fraction (α=ε1−f) or the ratio of the diffusant density in the bulk sample to the corresponding density in the pore solution. MD simulations of diffusion and sorption processes can be applied to other transport related problems at continuum scale, pore scale and molecular scale, such as for improved modelling of global elemental cycles, CO2 geosequestration, or the performance of desalination membranes.

Hydrogeological controls on microbial activity and habitability in the Precambrian continental crust.

Earth's deep continental subsurface is a prime setting to study the limits of life's relationship with environmental conditions and habitability. In Precambrian crystalline rocks worldwide, deep ancient groundwaters in fracture networks are typically oligotrophic, highly saline, and locally inhabited by low-biomass communities in which chemolithotrophic microorganisms may dominate. Periodic opening of new fractures can lead to penetration of surface water and/or migration of fracture fluids, both of which may trigger changes in subsurface microbial composition and activity. These hydrogeological processes and their impacts on subsurface communities may play a significant role in global cycles of key elements in the crust. However, to date, considerable uncertainty remains on how subsurface microbial communities may respond to these changes in hydrogeochemical conditions. To address this uncertainty, the biogeochemistry of Thompson mine (Manitoba, Canada) was investigated. Compositional and isotopic analyses of fracture waters collected here at ~1 km below land surface revealed different extents of mixing between subsurface brine and (paleo)meteoric waters. To investigate the effects this mixing may have had on microbial communities, the Most Probable Number technique was applied to test community response for a total of 13 different metabolisms. The results showed that all fracture waters were dominated by viable heterotrophic microorganisms which can utilize organic materials associated with aerobic/facultative anaerobic processes, sulfate reduction, or fermentation. Where mixing between subsurface brines and (paleo)meteoric waters occurs, the communities demonstrate higher cell densities and increased viable functional potentials, compared to the most saline sample. This study therefore highlights the connection between hydrogeologic heterogeneity and the heterogeneity of subsurface ecosystems in the crystalline rocks, and suggests that hydrogeology can have a considerable impact on the scope and scale of subsurface microbial communities on Earth and potentially beyond.

Spatial distribution characteristics and interaction effects of DOM and microbial communities in kelp cultivation areas

The influence of macroalgae cultivation on aquaculture carbon sinks is significant, with microbial carbon (C) pumps contributing to a stable inert dissolved carbon pool in this context. Concurrently, dissolved organic matter (DOM) exchange at the marine sediment-water interface profoundly affects global ecosystem element cycling. However, the interactions between DOM and bacterial communities at the sediment-water interface in kelp cultivation areas, especially regarding microbial function prediction, have not been fully explored. This study analyzed the DOM characteristics, environmental factors, and bacterial community structure in the Tahewan kelp——Saccharina japonica cultivated area and compared them with those in non-cultivated areas. The results indicated significantly higher dissolved organic carbon (DOC) concentrations in the kelp culture area, particularly in surface seawater and overlying water. The dominant bacterial phyla in both regions included Pseudomonadota, Actinomycetota, and Bacteroidota in both regions, while Desulfobacterota was more prevalent in the sediment environment of the cultivated region. Parallel factor analysis (EEM-PARAFAC) was used to identify DOM components, among which component C2 (a microbial humic-like substance DOM) was highly resistant to microbial degradation. We infer that C2 has similar properties to recalcitrant dissolved organic matter (RDOM). Analysis of the predicted functional genes based on 16S rRNA gene data showed that methanol oxidation, methylotrophy, and methanotrophy were significant in the bottom seawater of the cultivation area. The carbon (C), nitrogen (N), and sulfur (S) cycle functional genes in the sediment environment of the kelp cultivation area were more active than those in other areas, especially in which sulfate reduction and denitrification were the two main processes. Furthermore, a DOM priming effect was identified in the cultivated sediment environment, where kelp-released labile dissolved organic matter (LDOM) stimulates rapid degradation of the original RDOM, potentially enhancing C sequestration.

Physiological and metabolic insights into the first cultured anaerobic representative of deep-sea Planctomycetes bacteria.

Planctomycetes bacteria are ubiquitously distributed across various biospheres and play key roles in global element cycles. However, few deep-sea Planctomycetes members have been cultivated, limiting our understanding of Planctomycetes in the deep biosphere. Here, we have successfully cultured a novel strain of Planctomycetes (strain ZRK32) from a deep-sea cold seep sediment. Our genomic, physiological, and phylogenetic analyses indicate that strain ZRK32 is a novel species, which we propose be named: Poriferisphaera heterotrophicis. We show that strain ZRK32 replicates using a budding mode of division. Based on the combined results from growth assays and transcriptomic analyses, we found that rich nutrients, or supplementation with NO3- or NH4+ promoted the growth of strain ZRK32 by facilitating energy production through the tricarboxylic acid cycle and the Embden-Meyerhof-Parnas glycolysis pathway. Moreover, supplementation with NO3- or NH4+ induced strain ZRK32 to release a bacteriophage in a chronic manner, without host cell lysis. This bacteriophage then enabled strain ZRK32, and another marine bacterium that we studied, to metabolize nitrogen through the function of auxiliary metabolic genes. Overall, these findings expand our understanding of deep-sea Planctomycetes bacteria, while highlighting their ability to metabolize nitrogen when reprogrammed by chronic viruses.

Physiological and metabolic insights into the first cultured anaerobic representative of deep-sea Planctomycetes bacteria

Planctomycetes bacteria are ubiquitously distributed across various biospheres and play key roles in global element cycles. However, few deep-sea Planctomycetes members have been cultivated, limiting our understanding of Planctomycetes in the deep biosphere. Here, we have successfully cultured a novel strain of Planctomycetes (strain ZRK32) from a deep-sea cold seep sediment. Our genomic, physiological, and phylogenetic analyses indicate that strain ZRK32 is a novel species, which we propose be named: Poriferisphaera heterotrophicis. We show that strain ZRK32 replicates using a budding mode of division. Based on the combined results from growth assays and transcriptomic analyses, we found that rich nutrients, or supplementation with NO3- or NH4+ promoted the growth of strain ZRK32 by facilitating energy production through the tricarboxylic acid cycle and the Embden-Meyerhof-Parnas glycolysis pathway. Moreover, supplementation with NO3- or NH4+ induced strain ZRK32 to release a bacteriophage in a chronic manner, without host cell lysis. This bacteriophage then enabled strain ZRK32, and another marine bacterium that we studied, to metabolize nitrogen through the function of auxiliary metabolic genes. Overall, these findings expand our understanding of deep-sea Planctomycetes bacteria, while highlighting their ability to metabolize nitrogen when reprogrammed by chronic viruses.

Exploring the pore fluid origin and methane-derived authigenic carbonate properties in response to changes in the methane flux at the southern Ulleung Basin, South Korea

We investigated the geochemistry of gas, pore fluid, and methane-derived authigenic carbonate (MDAC) from four sites in the southern Ulleung Basin, South Korea. In contrast to Sites 16GH-P1 and 16GH-P5, Sites 16GH-P3, and 16GH-P4 are characterized by acoustic chimney structures associated with gas flux. The composition of gas and isotopic signatures of methane (CH4) (C1/C2+ > 300, δ13CCH4 < -60‰, δDCH4 ≤ -190‰) indicate microbial source CH4 at all sites. The upward migration of CH4 can affect the chemical and isotopic properties of pore fluid and gas-related byproducts (e.g., gas hydrate (GH) and MDAC) within the shallow sediments including the current sulfate-methane transition (SMT) (< 5 meters below seafloor). Although no GH was found, elevated Cl- concentrations (maximum = 609 mM) with low δD and δ18O values in Site 16GH-P4 pore fluids delineate the influence of massive GH formation in deeper sediment. In contrast, relatively constant Cl-, δD, and δ18O values in fluids from Sites 16GH-P1, 16GH-P3, and 16GH-P5 indicate a predominant origin from seawater. Pore fluids also exhibit higher concentrations of H4SiO4, B, Mg2+, and K+, along with increasing alkalinity compared to seawater. These observations suggest that marine silicate weathering alters fluid chemistry within the sediment, affecting element and carbon cycles. High alkalinity (up to 60 mM) and Mg2+/Ca2+ ratios (> 6) alongside decreasing Ca2+ and Sr2+ concentrations imply carbonate precipitation. MDACs with diverse morphologies, mainly composed of aragonite and magnesian calcite, and characterized by low carbon isotopic values (δ13CMDAC < -31.3‰), were found at Sites 16GH-P3 and 16GH-P4. Interestingly, δ13CMDAC values at Site 16GH-P3 are clearly differentiated above and below the current SMT. High δ13CMDAC values above the SMT (> -34.3‰) suggest the combined influence of seawater and CH4 migrating upward on MDAC precipitation, whereas low δ13CMDAC values below it (< -41.6‰) indicate a predominant impact of CH4 on MDAC formation. Additionally, the vertical variation of δ18OMDAC values at Site 16GH-P4, compared to the theoretical values, reflects an association with GH dissociation and formation. Our findings improve the understanding of fluid, gas, and MDAC geochemistry in continental margin cold seeps, providing insights into global carbon and element cycles.

Trace Element Geochemistry in North Pacific Red Clay Sediment Porewaters and Implications for Water‐Column Studies

AbstractGeochemical analyses of trace elements in the ocean water column have suggested that pelagic clay‐rich sediments are a major source of various elements to bottom‐waters. However, corresponding high‐quality measurements of trace element concentrations in porewaters of pelagic clay‐rich sediments are scarce, making it difficult to evaluate the contributions from benthic processes to global oceanic cycles of trace elements. To bridge this gap, we analyzed porewater and bulk sediment concentrations of vanadium, chromium, cobalt, nickel, copper, arsenic, molybdenum, barium and uranium, as well as concentrations of the major oxidants nitrate, manganese, iron, and sulfate in the top 30 cm of cores collected along a transect from Hawaii to Alaska. The data show large increases in porewater concentrations of vanadium, manganese, cobalt, nickel, copper, and arsenic within the top cm of the sediment, consistent with the release of these elements from remineralized organic matter. The sediments are a sink for sulfate, uranium, and molybdenum, even though conditions within the sampled top 30 cm remain aerobic. Porewater chromium concentrations generally increase with depth due to release from sediment particles. Extrapolated to the global aerial extent of pelagic clay sediment, the benthic fluxes in mol yr−1 are Ba 3.9 ± 3.6 × 109, Mn 3.4 ± 3.5 × 108, Co 2.6 ± 1.3 × 107, Ni 9.6 ± 8.6 × 108, Cu 4.6 ± 2.4 × 109, Cr 1.7 ± 1.1 × 108, As 6.1 ± 7.0 × 108, V 6.0 ± 2.5 × 109. With the exception of vanadium, calculated fluxes across the sediment–water interface are consistent with the variability in bottom‐water concentrations and ocean residence time of the studied elements.

Soil physical structure drives N-glycan mediated trophic interactions in soil amoebae: Mechanisms and environmental implications

Soil protozoa are an essential part of the terrestrial ecosystem, playing a vital role in the global element cycling and energy flow. However, one research gap is what are the key factors driving their diversity and environmental fates. In this study, we hypothesized that soil texture could affect soil protozoa's predation and their interactions with environmental pollutants, and we tested it by using a soil amoeba Dictyostelium discoideum as a model system. We found that soil texture affected amoeba's growth and development. In addition, environmental factors cannot explain the variation of amoeba's fitness in different soil textures. Soil sandy particles and water content rather than particle size contribute to amoeba's fitness. Furthermore, different soil textures induced distinct transcriptional responses to amoebae, especially N-glycan-related and multiple signaling pathways and the expression of key genes (e.g., Ras superfamily, cxgE, trap1). The expression of N-glycan-related pathways, which is positively correlated with amoeba predation, was inhibited in sand soil, decreasing amoeba's fitness. Finally, the results showed that soil texture also affects amoeba's interaction with environmental pollutants. In conclusion, this study shows that soil physical structures affect amoeba's interactions with bacteria and environmental pollutants. SynopsisSoil texture affects soil protozoa's growth and development and their interactions with environmental pollutants.

Sequence similarity network and protein structure prediction offer insights into the evolution of microbial pathways for ferrous iron oxidation.

Dissimilatory ferrous iron [Fe(II)] oxidation is a well-established microbial energy generation strategy. This study aims to comprehensively investigate the distribution and evolution of recognized Fe(II) oxidation pathways through comparative analysis. Interestingly, we have discovered a wide range of taxonomic groups that harbor homologs to known Fe(II) oxidation proteins. The presence of these homologs among phylogenetically distant lineages and their frequent association with mobile genetic elements strongly suggest horizontal gene transfer events involving Fe(II) oxidation proteins, such as the rus operon of Acidithiobacillus and Cyc572 from Leptospirillum lineages belonging to classes Gammaproteobacteria and Betaproteobacteria often present at the hub positions of the protein sequence similarity networks from which homologs of other taxa are derived. In addition, RoseTTAFold predictions have provided valuable insights into the structural characteristics of previously unknown Fe(II) oxidation components. Despite having limited sequence identity, a significant number of acknowledged proteins involved in different Fe(II) oxidation pathways exhibit close structural similarities, including Cyc2 and Cyc572. Collectively, this study significantly enhances our understanding of the distribution and evolution of microbial ferrous iron oxidation pathways. IMPORTANCE Microbial Fe(II) oxidation is a crucial process that harnesses and converts the energy available in Fe, contributing significantly to global element cycling. However, there are still many aspects of this process that remain unexplored. In this study, we utilized a combination of comparative genomics, sequence similarity network analysis, and artificial intelligence-driven structure modeling methods to address the lack of structural information on Fe(II) oxidation proteins and offer a comprehensive perspective on the evolution of Fe(II) oxidation pathways. Our findings suggest that several microbial Fe(II) oxidation pathways currently known may have originated within classes Gammaproteobacteria and Betaproteobacteria.

The Behavior of Rare Earth Elements during Green Clay Authigenesis on the Congo Continental Shelf

Clay mineral authigenesis at continental margins plays an important role in global marine element cycles. However, despite being increasingly used as tracers for both modern and past oceanographic conditions, the behavior of the rare earth elements (REEs) and their isotopes during marine clay authigenesis still remains poorly known. In this study, we report on a detailed geochemical investigation of glauconite from the West African continental shelf, near the mouth of the Congo River. Elemental, neodymium, and hafnium isotope analyses were conducted on both acid leachate and separated clay-size fractions of glauconite pellets, in order to investigate the behavior of REE during the formation of authigenic clays. Our data indicate that kaolinite dissolution and subsequent Fe-bearing clay authigenesis act as a net source of REEs to seawater. We show that enhanced glauconitization, as inferred from increasing Fe and K contents, is accompanied by significant decoupling of the REE toward markedly LREE-enriched shale-normalized patterns in neoformed clay separates. Using both Nd and Hf isotopes and SEM observations, we rule out any seawater influence and argue that this shift primarily reflects the progressively overwhelming presence of insoluble nanocrystals of detrital LREE-rich phosphates, which are known to occur in close association with kaolinite in tropical soils. Due to their marked insolubility in surface environments, such nanocrystals can be preserved during kaolinite dissolution and subsequently incorporated into the aggregates of authigenic green clays forming the peloids. Most strikingly, we show that the combined influence of net REE loss (due to kaolinite dissolution) and decoupling (due to subsequent entrapment of inherited LREE-bearing accessory phases into neoformed clay minerals) is accompanied by preferential release of a dissolved REE fraction characterized by seawater-like distribution patterns. These findings reinforce the emerging view that clay mineral dissolution and authigenesis at continental margins possibly play a major role in marine REE cycling.

Soil heavy metals in tropical coastal interface of eastern Hainan Island in China: Distribution, sources and ecological risks

Coastal interface is the most active in the global element cycling, linking the terrestrial and ocean ecosystem. However, little attention is paid to the ecological risk of multiple heavy metals (HMs) residues in tropical coastal soil and its relationships with human activities. Here, 199 coastal topsoils were collected from the eastern Hainan Island of China in 2021. Furthermore, the pollution characteristics, spatial distribution, and ecological risk of eight HMs were evaluated. The results showed that the mean contents of eight HMs were in the order of Cr (47.96 mg·kg−1) > Zn (40.93 mg·kg−1) > Pb (21.28 mg·kg−1) > Cu (14.89 mg·kg−1) > Ni (8.67 mg·kg−1) > As (5.64 mg·kg−1) > Cd (0.06 mg·kg−1) > Hg (0.05 mg·kg−1). These HMs contents were larger than the soil background values of Hainan Province, indicating the accumulation risk. Based on the Nemerow integrated pollution index, the sample sites with moderate and severe pollution accounted for 28.5% and 28.0%, respectively. In contrast, the sum of sites with no and slight pollution was only 10%. The ecological risk assessment revealed that 25% and 5% of sites displayed moderate or extreme ecological risks with the mean RI value larger than 90, and As and Cd were the most dangerous HMs. Spatially, the pollution hotspots of Zn, Pb, Cd and Hg were distributed in the middle urban of the study area and the dense road network in the west, while that of Cr, Ni, and Cu were distributed in the woodland in the northeast and southwest. The pollution hotspots of As were distributed in northeast cropland. The PMF model further indicated that the largest contributor to Zn, Pb, and Cd were the combined sources of traffic and agricultural activities, accounting for 55.66%, 56.30%, and 55.36%, respectively. Soil parent materials contributed to the Cr, Ni, and Cu, accounting for 77.1%, 58.4%, and 38.2%, respectively. Coal combustion was the main source of Hg, accounting for 81.3%, while agricultural activities accounted for 80.8% of the As in the soils. Overall, anthropogenic activities (63.60%) were the main source for HMs residues in the studied coastal soils, but the contribution of soil parent materials (36.40%) could not be neglected.

Antigorite Dehydration under Compression and Shear Loadings in a Rotational Diamond Anvil Cell

Mineral dehydration in the subduction zone enormously affects Earth’s geodynamics and the global geochemical cycles of elements. This work uses Raman spectroscopy and X-ray diffraction to investigate the dehydration process of antigorite under compression and shear loading conditions in a rotational diamond anvil cell (RDAC) at room temperature. In order to compare the shear effects, T301 stainless steel and Kapton plastic are applied as the gasket materials. In the experiment using a high-strength T301 stainless steel gasket, two new broad OH-stretching peaks of H2O and H3O2− appear at 3303 and 3558 cm−1, respectively, at 1.7 GPa. The original sharp OH-stretching peaks of antigorite at 3668 and 3699 cm−1 remain, while the central pressure is increased to 8.0 GPa, and the largest pressure gradient is about 2.5 GPa in the sample chamber. In another experiment with a low-strength gasket of Kapton plastic, two new OH-stretching broad peaks of H2O and H3O2− also start to appear at 3303 and 3558 cm−1, respectively, at a lower pressure of 0.3 GPa, but the original sharp OH-stretching peaks of antigorite at 3668 and 3699 cm−1 almost completely vanish as the central pressure reaches 3.0 GPa, with the largest pressure gradient at around 4.8 GPa. The comparison between the two experiments shows that antigorite is easier to dehydrate in the chamber of a Kapton plastic gasket with a larger gradient of shear stress. However, its axial compression stress is lower. The high-pressure Raman spectra of MgO2(OH)4 octahedron and SiO4 tetrahedron in the low wavenumber zones (100–1200 cm−1) combined with the micro-beam X-ray diffraction spectrum of the recovered product strongly support the structural breakdown of antigorite. This investigation reveals that the water-bearing silicate minerals have strong shear dehydration in the cold subduction zone of the plate, which has important applications in predicting the physical and chemical properties of subduction zones and deducing the rate of plate subduction.

Searching for Principles of Microbial Ecology Across Levels of Biological Organization.

Microbial communities play pivotal roles in ecosystems across different scales, from global elemental cycles to household food fermentations. These complex assemblies comprise hundreds or thousands of microbial species whose abundances vary over time and space. Unraveling the principles that guide their dynamics at different levels of biological organization, from individual species, their interactions, to complex microbial communities, is a major challenge. To what extent are these different levels of organization governed by separate principles, and how can we connect these levels to develop predictive models for the dynamics and function of microbial communities? Here, we will discuss recent advances that point towards principles of microbial communities, rooted in various disciplines from physics, biochemistry, and dynamical systems. By considering the marine carbon cycle as a concrete example, we demonstrate how the integration of levels of biological organization can offer deeper insights into the impact of increasing temperatures, such as those associated with climate change, on ecosystem-scale processes. We argue that by focusing on principles that transcend specific microbiomes, we can pave the way for a comprehensive understanding of microbial community dynamics and the development of predictive models for diverse ecosystems.

Quantification of 68 elements in river water monitoring samples in single-run measurements

Triple-quadrupole inductively coupled plasma mass spectrometry (ICP-QQQ-MS) is a unique analytical technique which is, next to speciation analyses, applied for the determination of total element concentrations in several matrices. Due to its wide linear range, short analysis times, and the collision-reaction gas technology, it is capable of addressing a high number of analytes in a single run with sufficient low limits of quantification for river water monitoring. Over the last decades, the focus of the environmental monitoring changed from “traditional” and regulated analytes to elements of possibly rising concern from new applications such as the so-called technology-critical elements (TCE). By widening the analytical window of this method for applications in networks of future river water monitoring, a better understanding of natural transport processes and global biogeochemical element cycles will be established and the total number of methods can be reduced. During method development and validation, certified reference materials, calibration check solutions, and spiked river water samples from 12 major German rivers covering different catchment areas were measured and evaluated with the three cell gases He, H2 and O2. The method delivers a best as possible undisturbed simultaneous determination for 68 out of 71 target analytes with recoveries in an accepted range of 80–120% for river water samples (dissolved fraction; <0.45 μm). After comprehensive evaluation, we offer a novel best-practice multi-element method for river water monitoring with the goal of fostering the exchange and discussion between practitioners in long-term river monitoring. It enables the readers to create their own methods based on the scientific needs to monitor elemental “fingerprints” of rivers and their catchments.