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22941. 题目: Reducing uncertainties of future global soil carbon responses to climate and land use change with emergent constraints Soil organic carbon changes (ΔSOC) are regulated by climate and land use change. Here, we analyze regional and global ΔSOC from 1861 to 2099 based on five Terrestrial Biosphere Models (TBMs) simulations of the Inter‐Sectorial Impact Model Inter‐comparison Project Phase 2b. The TBMs were driven by harmonized gridded land use change and bias‐adjusted climate forcing data from different General Circulation Models (GCMs) for climate scenarios RCP2.6 and RCP6.0. Between 2005 and the end of this century, we estimated an increase of SOC for two scenarios with large uncertainty, which is dominated by differences between TBMs. We present a new emergent constraint approach to constrain future modeled ΔSOC over natural vegetation from RCP6.0 simulations using recent observed trends of net primary productivity as a proxy of litter inputs to soil pools. Our results showed that the uncertainties in constrained ΔSOC can be reduced in comparison with the original model ensemble, but constrained values of ΔSOC depend on the choice of a GCM and climate regions. For the reduction of the SOC density in areas where cropland expanded (Δsoccropland expansion) over natural vegetation as a result of land use change, the constrained Δsoccropland expansion still features large uncertainties due to uncertain observed data. Our proposed emergent constraint approach appears to be valuable to reduce uncertainty on SOC projections, but it is limited here by the small number of models (five) and by the uncertainty in the observational data. Applications to larger ensembles from Earth System Models should be tested for the future. | |||||
22942. 题目: Mutual Interactions between Reduced Fe-Bearing Clay Minerals and Humic Acids under Dark, Oxygenated Conditions: Hydroxyl Radical Generation and Humic Acid Transformation | |||||
22943. 题目: Influence of biochar and soil properties on soil and plant tissue concentrations of Cd and Pb: A meta-analysis The application of biochar to soils contaminated with potentially toxic elements (PTEs) has received particular attention due to its ability to reduce PTE uptake by the plants. Therefore, we conducted a meta-analysis to identify Cd and Pb concentrations in plant shoots and roots in response to biochar application and soil properties. We collected data from 65 peer-reviewed journal articles published from 2009 to 2020 in which 66% of manuscripts were published from 2015 to 2020. The data were processed using OpenMEE software. The results pinpointed that addition of biochar to soil caused a significant decrease in shoot and root Cd and Pb concentrations as compared to untreated soils with biochar (control), and the reduction rate was affected by plant types and both biochar and soil properties. The biochar size less than 2 mm, biochar pH higher than 10, pyrolysis temperature of 401–600 °C, and the application rate higher than 2% appeared to be effective in reducing shoot and root Cd and Pb concentration. Soil properties such as pH, SOC, and texture influenced the efficiency of biochar for reducing plant Cd and Pb uptake. Biochar application increased SOC (54.3%), CEC (48.0%), pH (0.08), and EC (59.4%), and reduced soil extractable Cd (42.1%) and Pb (47.1%) concentration in comparison to control. A detailed study on the rhizosphere chemistry and uptake mechanism will help to underpin the biochar application rates and their efficiency reducing PTE mobility and plant uptake. | |||||
22944. 题目: Variation in δ15N from shell-associated organic matter in bivalves: Implications for studies of modern and fossil ecosystems Nitrogen stable isotopes (δ15N) of organic matter can aid in the reconstruction of food webs and, when applied to fossil systems, may help resolve uncertainty about trophic position and provide tests for hypotheses developed using traditional paleoecological techniques. However, in order to use those values to reconstruct trophic relationships in ecosystems and assess changes in their dynamics, an understanding of the variability of isotopic signatures within individuals and across populations is critical. The purpose of this study is to develop a methodology by which to characterize the variability in nitrogen isotope values within bivalve shells and to propose an approach for effective paleoecological and paleoceanographic studies using such data. Here we present high-resolution sclerochronological and whole-shell δ15N values of shell-associated organic matter derived from modern Spisula solidissima bivalves from three different localities. High-resolution δ15N values vary by about 4‰ over the sampled life history, which reflects the interplay of factors such as diet, physiological change over ontogeny, and background nitrogen isotopic signatures of dissolved nutrient nitrogen. A significant correlation of temporally aligned δ15N with δ18O at different lags suggests that the δ15N possibly has a seasonal control. Furthermore, an enrichment in δ15N following peak primary productivity in the region suggests that seasonal turnover of nutrients is the primary driver of δ15N variability. Unfortunately, the fossil record does not always yield well-preserved whole shells, and working with limited shell fragments is unlikely to capture the full range of variation exhibited within a shell. To this end, we also analyzed a field-collected sub-fossil set of Spisula for whole-shell δ15N. The sample set demonstrates 5‰ of variation in δ15N among individual shells, similar to the range observed within serially-sampled shells. This likely reflects a variation that we might expect to see in a population over time. Studies involving shell-associated nitrogen isotopes in a paleo setting should analyze numerous specimens in a stratigraphic unit to capture the whole range of δ15N values within a population. Moreover, for understanding trophic relationships it is important to analyze and compare the δ15N values of multiple coeval taxa each taxa. | |||||
22945. 题目: Changes in terrestrial ecosystem across the Cretaceous-Paleogene boundary in western Canada inferred from plant wax lipid distributions and isotopic measurements Changes in terrestrial environments across the Cretaceous-Paleogene boundary, including plant ecology and carbon and water-cycling, remain poorly defined. Fluvial sediments spanning the Cretaceous-Paleogene (K-Pg) boundary of southern Saskatchewan, Canada contain well preserved plant wax n-alkanes that provide a means of reconstructing changes to plant ecology and carbon and water cycling during this mass extinction event. We measured n-alkane carbon (δ13C) and hydrogen (δ2H) isotope ratios in two sedimentary sections and applied established fractionation factors to estimate the isotopic compositions of precipitation and bulk sedimentary organic matter sources. We also analyzed the distribution of n-alkanes as an indicator of the relative abundance of aquatic and terrestrial plants. We find a consistent shift towards a greater relative abundance of longer-chain n-alkanes across the boundary, implying a persistent increase in the relative abundance of terrestrial plants in the sedimentary basin. This is consistent with an increase in birch and elm palynomorphs immediately above the boundary. We hypothesize the extinction of all large herbivores at the boundary may have facilitated this transition to a terrestrial angiosperm dominated flora immediately after the boundary. We also find that the region was characterized by isotopically light precipitation, with δ2H values between −95‰ to −160‰ but do not observe evidence for major millennial-scale changes in regional precipitation isotopic composition spanning the boundary. n-Alkanes derived from both aquatic and terrestrial plants at one site display an upward trend in δ13C values of approximately 2‰ across the K-Pg boundary. This suggests millennial-scale local or global carbon-cycle variability altering either plant carbon isotope fractionation or the carbon isotope composition of dissolved inorganic carbon and atmospheric CO2. Overall our results suggest that carbon and water cycle changes associated with the K-Pg impact in terrestrial environments in western Canada were short-lived, but ecological shifts in plant communities were longer-lasting. | |||||
22946. 题目: Imprint of Kairei and Pelagia deep-sea hydrothermal systems (Indian Ocean) on marine dissolved organic matter Only few studies exist that investigate the dynamics of deep-sea dissolved organic matter (DOM) derived from hydrothermal vents. In this study, we provide first insight into the molecular composition of DOM associated with Indian Ocean hydrothermal systems covering the full range from hot focussed endmember fluids over diffuse fluids to open ocean hydrothermal plumes and deep seawater. We combined geochemical analyses with molecular characterization of DOM using ultra-high resolution mass spectrometry (FT-ICR-MS). We studied two vent systems with fluids venting >330 °C and up to 97% of hydrothermal endmember: the Kairei vents (Central Indian Ridge) with brine phase separation, and the newly discovered Pelagia vents (South-East Indian Ridge). The hot fluids in both systems were highly enriched in dissolved Fe, Si, K, Li, Mn and Zn compared to seawater. The molecular composition of DOM from hot fluids differed substantially from that of diffuse fluids and plumes, in which the composition was highly dominated by the seawater DOM signature. Low O/C ratio average in hot fluids (< 0.38) indicated potential input of more reduced (O-poor) DOM compounds from the vents into the surrounding seawater, independently of the vent location and of whether the fluid has undergone phase separation. To test the importance of pure thermal degradation, we compared our samples to fluids subjected to abiotic thermal degradation under laboratory conditions and we observed that our natural samples largely differed (> 94% Bray Curtis dissimilarity) from the experimental ones, suggesting additional degradation processes of organic compounds at the Indian Ocean hydrothermal systems. | |||||
22947. 题目: Application of laccase immobilized rice straw biochar for anthracene degradation The present study explores the immobilization of ligninolytic enzyme-laccase on the surface of rice straw biochar and evaluates its application for anthracene biodegradation. The rice straw biochar was acid-treated to generate carboxyl functionality on its surface, followed by detailed morphological and chemical characterization. The surface area of functionalized biochar displayed a two-fold increase compared to the untreated biochar. Laccase was immobilized on functionalized biochar, and an immobilization yield of 66 % was obtained. The immobilized enzyme demonstrated operational stability up to six cycles while retaining 40 % of the initial activity. Laccase immobilization was further investigated by performing adsorption and kinetic studies, which revealed the highest immobilization concentration of 500 U g-1 at 25 °C. The adsorption followed the Langmuir isotherm model at equilibrium, and the kinetic study confirmed pseudo-second-order kinetics. The equilibrium rate constant (K2) at 25 °C and 4 °C were 3.6 × 10-3 g U-1 min-1 and 4 × 10-3 g U-1 min-1 respectively for 100 U g-1 of enzyme loading. This immobilized system was applied for anthracene degradation in the aqueous batch mode, which resulted in complete degradation of 50 mg L-1 anthracene within 24 h of interaction exposure. | |||||
22948. 题目: Spatiotemporal variations in chromophoric dissolved organic matter (CDOM) in a mixed land-use river: Implications for surface water restoration A challenge for current surface water restoration and management in China is acquiring the source information for complex pollution scenarios in order to develop effective control strategies. As an important part of dissolved organic matter, chromophoric dissolved organic matter (CDOM) contains unique chemical signals related to various pollution sources. Spectral methods such as fluorescence excitation-emission matrices coupled with parallel factor analysis enable rapid and low-cost CDOM characterization for source tracking. In this study, a typical small-sized river flowing through mixed land-use regions in southeastern China, the Lujiang River, was investigated to determine the responses of CDOM to spatiotemporal factors. The effects of land-use patterns were reflected by the fluorescent components of terrestrial and sewage substances. A high and stable proportion of terrestrial-like components (C1 + C2) in each sampling period (i.e., March: 47.6 ± 5.7% and October: 44.3 ± 2.7%) indicated a high input of non-point source (NPS) pollution from both agriculture and urban areas. In addition, the difference in solar radiation intensity induced by climate and air quality changes was also reflected by variability in the photodegradation product component (C3) of terrestrial precursors between October (24.8 ± 2.6%) and March (4.5 ± 2.0%), suggesting that terrestrial components could be a sensitive indicator for NPS pollutant monitoring. Increased sewage impact in downstream regions was reflected by a spike in the tryptophan-like component (C4); temporal variations in C4 (paired t-Test, p < 0.005) also indicated that sewage substances were more prone to removal by microbial activity in warmer seasons. The dynamics of C4 could serve as a good indicator of sewage disposal performance. The results of this study demonstrate that CDOM data have important practical applications for existing water restoration campaigns in southeastern China, as well as substantial potential for routine water quality monitoring. | |||||
22949. 题目: Heavy metal stabilization and improved biochar generation via pyrolysis of hydrothermally treated sewage sludge with antibiotic mycelial residue Hydrothermally treated sewage sludge was pyrolyzed at temperatures of 300, 500, and 700 °C with antibiotic mycelial residue addition ratios of 0, 10, 25, and 50 wt%. The results showed that co-pyrolysis could obviously improve biochar properties. Specifically, adding antibiotic mycelial residue increased the aromaticity and raised the higher heating value of the biochar, which indicates its better potential as fuel. The enrichment in functional groups improved the surface properties of biochar, indicating its better applicability. Additionally, the heavy metal concentrations in biochar were diluted by adding antibiotic mycelial residue, which led to lower toxic inputs to the environment. Moreover, heavy metals were transformed to more stable fractions after co-pyrolysis. A higher pyrolysis temperature and greater antibiotic mycelial residue amounts led to better immobilization of heavy metals, thus preventing their leaching to the environment. This work proposes a promising technique for the synergetic treatment of sewage sludge and antibiotic mycelial residue for improved biochar formation. | |||||
22950. 题目: Enhanced phosphate scavenging with effective recovery by magnetic porous biochar supported La(OH)3: Kinetics, isotherms, mechanisms and applications for water and real wastewater Herein, La(OH)3 decorated magnetic porous biochar (MPBC) was synthesized via KHCO3 activation and hydrothermal processes. The La-to-MPBC mass ratio of 3:1 described as La3-MPBC possessed a monolayer phosphate adsorption capacity of 116.08 mg/g across a pH range of 3.0–6.0 with fast attainment of adsorption equilibrium in 150 min. Moreover, the phosphate adsorption was substantially stable during the interference of various co-existing ions with over 92% of phosphate removal and 77% of desorption efficiency maintained after four recycles. And La3-MPBC was easily separated by magnet force with negligible La and Fe leakages within the pH range of 3.0–10.0. Furthermore, La3-MPBC was supported to achieve phosphate binding through the synergistic actions of electrostatic attraction, ligand exchange, inner-sphere complexation and weak precipitation. Significantly, La3-MPBC exhibited a high performance for decontaminating low-concentration phosphate to meet regulatory requirements. All these results suggested La3-MPBC to be an ideal candidate for phosphate removal in real applications. | |||||
22951. 题目: Biochar and activated carbon enhance ethanol conversion and selectivity to caproic acid by Clostridium kluyveri Syngas from biomass or steel mills can be fermented into a dilute stream of ethanol and acetic acid, which requires energy intensive distillation for product recovery. This can be circumvented by selective secondary fermentation of the syngas fermentation effluent to caproic acid as easier recoverable platform chemical with Clostridium kluyveri. Here, we explore the impact of biochar and activated carbon on this process. Changes during the fermentation with biochar or activated carbon were monitored, different doses were tested and the recyclability of biochar and activated carbon was assessed. Biochar decreased the lag phase and increased the caproic acid production rate (up to 0.50 ). Upon recycling for subsequent fermentation, biochar retained this property largely. Activated carbon addition, especially at high dose, could potentially increase the conversion and selectivity towards caproic acid to 14.15 (control: 11.01 ) and 92% (control: 84%), respectively. | |||||
22952. 题目: The dynamics and stoichiometry of dissolved organic carbon release by kelp | |||||
22953. 题目: Characterization of graphene/pine wood biochar hybrids: Potential to remove aqueous Cu2+ Biochar-based hybrid composites containing added nano-sized phases are emerging adsorbents. Biochar, when functionalized with nanomaterials, can enhance pollutant removal when both the nanophase and the biochar surface act as adsorbents. Three different pine wood wastes (particle size < 0.5 mm, 10 g) were preblended with 1 wt% of three different graphenes in aqueous suspensions, designated as G1, G2, and G3. G1 (SBET, 8.1 m2/g) was prepared by sonicating graphite made from commercial synthetic graphite powder (particle size 7–11 μm). G2 (312.0 m2/g) and G3 (712.0 m2/g) were purchased commercial graphene nanoplatelets (100 mg in 100 mL deionized water). These three pine wood-graphene mixtures were pyrolyzed at 600 °C for 1 h to generate three graphene-biochar adsorbents, GPBC-1, GPBC-2, and GPBC-3 containing 4.4, 4.9, and 5.0 wt% of G1, G2, and G3 respectively. Aqueous Cu2+ adsorption capacities were 10.6 mg/g (GPBC-1), 4.7 mg/g (GPBC-2), and 5.5 mg/g (GPBC-3) versus 7.2 mg/g for raw pine wood biochar (PBC) (0.05 g adsorbent dose, Cu2+ 75 mg/L, 25 mL, pH 6, 24 h, 25 ± 0.5 °C). Increased graphene surface areas did not result in adsorption increases. GPBC-1, containing the lowest nanophase surface area with the highest Cu2+ capacity, was chosen to evaluate its Cu2+ adsorption characteristics further. Results from XPS showed that the surface concentration of oxygenated functional groups on the GPBC-1 is greater than that on the PBC, possibly contributing to its greater Cu2+ removal versus PBC. GPBC-1 and PBC uptake of Cu2+ followed the pseudo-second-order kinetic model. Langmuir maximum adsorption capacities and BET surface areas were 18.4 mg/g, 484.0 m2/g (GPBC-1) and 9.2 mg/g, 378.0 m2/g (PBC). This corresponds to 3.8 × 10−2 versus 2.4 × 10−2 mg/m2 of Cu2+ removed on GPBC-1 (58% more Cu2+ per m2) versus PBC. Cu2+ adsorption on both these adsorbents was spontaneous and endothermic. | |||||
22954. 题目: Prediction of soil organic carbon and the C:N ratio on a national scale using machine learning and satellite data: A comparison between Sentinel-2, Sentinel-3 and Landsat-8 images Soil organic carbon (SOC) and soil carbon-to-nitrogen ratio (C:N) are the main indicators of soil quality and health and play an important role in maintaining soil quality. Together with Landsat, the improved spatial and temporal resolution Sentinel sensors provide the potential to investigate soil information on various scales. We analyzed and compared the potential of satellite sensors (Landsat-8, Sentinel-2 and Sentinel-3) with various spatial and temporal resolutions to predict SOC content and C:N ratio in Switzerland. Modeling was carried out at four spatial resolutions (800 m, 400 m, 100 m and 20 m) using three machine learning techniques: support vector machine (SVM), boosted regression tree (BRT) and random forest (RF). Soil prediction models were generated in these three machine learners in which 150 soil samples and different combinations of environmental data (topography, climate and satellite imagery) were used as inputs. The prediction results were evaluated by cross-validation. Our results revealed that the model type, modeling resolution and sensor selection greatly influenced outputs. By comparing satellite-based SOC models, the models built by Landsat-8 and Sentinel-2 performed the best and the worst, respectively. C:N ratio prediction models based on Landsat-8 and Sentinel-2 showed better results than Sentinel-3. However, the prediction models built by Sentinel-3 had competitive or better accuracy at coarse resolutions. The BRT models constructed by all available predictors at a resolution of 100 m obtained the best prediction accuracy of SOC content and C:N ratio; their relative improvements (in terms of R2) compared to models without remote sensing data input were 29.1% and 58.4%, respectively. The results of variable importance revealed that remote sensing variables were the best predictors for our soil prediction models. The predicted maps indicated that the higher SOC content was mainly distributed in the Alps, while the C:N ratio shared a similar distribution pattern with land use and had higher values in forest areas. This study provides useful indicators for a more effective modeling of soil properties on various scales based on satellite imagery. | |||||
22955. 题目: Methylmercury formation in boreal wetlands in relation to chemical speciation of mercury(II) and concentration of low molecular mass thiols Methylmercury (MeHg) is a neurotoxin formed from inorganic divalent mercury (HgII) via microbial methylation, and boreal wetlands have been identified as major sources of MeHg. There is however a lack of studies investigating the relationship between the chemical speciation of HgII and MeHg formation in such environments, in particular regarding to role of thiol compounds. We determined HgII methylation potentials, kmeth, in boreal wetland soils using two HgII isotope tracers: 198Hg(OH)2(aq) and HgII bonded to thiol groups in natural organic matter, 200HgII–NOM(ads), representing HgII sources with high and low availability for methylation. The 198Hg(OH)2(aq) tracer was consistently methylated to a 5-fold higher extent than 200HgII–NOM(ads), independent of environmental conditions. This suggests that the concentration of HgII in porewater was a decisive factor for HgII methylation. A comprehensive thermodynamic speciation model (including HgII complexes with inorganic sulfide (H2S), polysulfides (H2Sn), thiols associated with natural organic matter (NOM–RSH) and specific low molecular mass thiols (LMM–RSH) provided new insights on the speciation of HgII in boreal wetland porewaters, but did not demonstrate any clear relationship between kmeth and the calculated chemical speciation. In contrast, significant positive relationships were observed between kmeth and the sum of LMM thiol compounds of biological origin. We suggest two possible mechanisms underlying these correlations: 1) LMM thiols kinetically control the size and composition of the HgII pool available for microbial uptake, and/or 2) LMM thiols are produced by microbes such that the correlation reflects a relation between microbial activity and MeHg formation. | |||||
22956. 题目: Membrane fouling control by UV/persulfate in tertiary wastewater treatment with ultrafiltration: A comparison with UV/hydroperoxide and role of free radicals The membrane fouling caused by effluent organic matter (EfOM) is a bottleneck for application of ultrafiltration (UF) in tertiary wastewater treatment. In this study, two ultraviolet-based oxidation pretreatments, i.e., ultraviolet/persulfate (UV/PS) and ultraviolet/hydrogen peroxide (UV/H2O2), were used to alleviate EfOM fouling at a low UV dose of 2.36×103 mJ cm-2, in consideration of the widely use of UV radiation for disinfection in wastewater treatment plants. Effects of the pretreatments on characteristics of EfOM were investigated in terms of fluorescence spectrum, molecular weight distribution, and hydrophobicity. Moreover, filtration tests were performed to assess impacts of the oxidation pretreatments on flux decline, fouling reversibility, and fouling mechanisms. The results showed that the UV/PS pretreatment substantially reduced flux decline and improved fouling reversibility during filtration of the secondary effluent, attributed to efficient degradation (∼67%, in terms of UV254) and partial mineralization (∼39%, in terms of DOC) of EfOM. In particular, the irreversible resistance was decreased by nearly one order of magnitude at the PS dose of 1.0 mM. UV/H2O2 was not effective in EfOM fouling control under the conditions investigated. The UV/PS pretreatment resulted in a shift of mechanisms for EfOM fouling from successive pore blocking and cake filtration to single standard blocking, attributing to preferential degradation of macromolecular components in EfOM and a weakened role of cake interception. The radical quenching experiment showed that the sulfate radicals played a dominant role in EfOM fouling control by UV/PS, and that transformation of sulfate radicals into hydroxyl radicals negatively affected EfOM fouling control. | |||||
22957. 题目: Spatial and temporal variability of trace metals (Fe, Cu, Mn, Zn, Co, Ni, Cd, Pb), iron and copper speciation, and electroactive Fe-binding humic substances in surface waters of the eastern Gulf of Mexico The concentrations of bioactive trace metals (Fe, Cu, Mn, Zn, Co, Ni, Cd, and Pb), Fe-and Cu-binding organic ligands, and electroactive Fe-binding humic substances were measured in surface waters across the West Florida Shelf in the eastern Gulf of Mexico in June 2015 and in February-March 2018. Seasonal differences in dust deposition were associated with increased concentrations of Fe, Mn and Pb in offshore surface waters in June 2015 compared to Feb-Mar 2018. Total concentrations of Fe-binding ligands offshore were similar between seasons, and this ambient ligand pool acted to stabilize a portion of Fe delivered via dust deposition within the dissolved fraction. Apparent photoreduction of Cu-binding organic ligands in offshore summer surface waters led to bioavailable Cu2+ concentrations that could potentially inhibit the growth of some cyanobacteria species. The concentrations of Fe-binding humic-like ligands were better correlated with Cu-binding ligands than Fe-binding ligands, suggesting that terrestrially derived photoactive ligands may have a significant influence on the cycling of Cu-binding ligands across the West Florida Shelf. Intrusion of the Loop Current into the study region was observed in June 2015 and appeared to entrain bands of low salinity water from the northern Gulf of Mexico. This process brought elevated trace metals and Fe-binding humic-like ligands to the outer West Florida Shelf, which may then be delivered to the North Atlantic via the Loop Current-Florida Current-Gulf Stream system. | |||||
22958. 题目: The influence of native soil organic matter and minerals on ferrous iron oxidation Fe(II) oxidation by O2 is an important process generating Fe (oxyhydr)oxides, which play sorptive, structural and electron-transfer roles in soils. Here we explored how native minerals and organic matter (OM) affect the rate of Fe(II) oxidation and resulting de novo Fe(III) minerals in soil slurries. A topsoil was collected from Luquillo tropical forest, and a topsoil and subsoil were collected from Calhoun cultivated site. We oxidized 57Fe(II) in these soils either untreated or with OM and/or Fe (oxyhydr)oxides removed. We measured Fe oxidation kinetics by tracking the loss of Fe(II) and characterized the de novo Fe(III) solids using 57Fe Mossbauer spectroscopy. We find that OM retarded Fe(II) oxidation, while pre-existing Fe (oxyhydr)oxides played a significant role in catalyzing Fe(II) oxidation. The non-extractable (residual) soil minerals (i.e.phyllosilicates and quartz) after removing Fe (oxyhydr)oxides, had a minor effect on oxidation rates. In the topsoils, OM resulted in a lower-crystallinity Fe(III) minerals, including nanogoethite and highly-disordered Fe phases, relative to OM-removal treatment. Goethite with varying crystallinity was promoted by the pre-existing Fe (oxyhydr)oxides in all soils, in contrast to homogenous oxidation where lepidocrocite was formed. Compared to the topsoils, Fe(II) oxidation resulted in large-particle goethite with the highest crystallinity in the Calhoun subsoil that was more enriched in native crystalline Fe-(oxyhydr)oxides and more depleted in OM. Crystalline hematite, was also formed in the Calhoun subsoil, most likely due to a templating effect of pre-existing hematite. These findings suggest that the nature of de novo formed Fe minerals in soils and sediments may depend strongly on resident existing soil OM and Fe phases. This study extends from previous synthetic systems to complex soils and thus constitutes a significant step forward in understanding Fe transformation in natural environments. | |||||
22959. 题目: Organic Sulfones In The Brine Of Lake Vida (East Antarctica) Located in a closed basin in the McMurdo Dry Valleys, East Antarctica, Lake Vida brine is a cold (-13°C), hypersaline, interstitial, anoxic, and aphotic ecosystem trapped within 27+ m of ice. This brine is not in contact with the atmosphere, and currently hosts a slow-growing, cold-limited bacteria-dominated ecosystem that have persisted for at least ∼2800 years. Analysis of the dichloromethane extractable fraction of dissolved organic matter of Lake Vida brine revealed the presence of seven novel organic sulfones, tentatively identified on the basis of mass spectral fragmentation, as well as eight sulfones that have been structurally described in previous chemistry studies. A total of fifteen organic sulfones, and others that have yet to be identified, were observed in Lake Vida brine, most of which have never been previously detected in any other natural ecosystems. Results suggest that these compounds may be derived from a lake system in which a dissolved organic carbon pool may have been oxidized in lake waters in contact with the atmosphere. Alternative hypotheses on the origin of these sulfones, involving potential abiotic alterations of dissolved organic sulfur as a consequence of long-term brine-rock reactions that generated reactive oxygen species, are also considered. Understanding the origin and formation mechanisms of these organic sulfones may reveal an important pathway that influence the dissolved organic sulfur constituent, not only of Antarctic aquatic systems, but also potentially the global marine environment, as well as extraterrestrial hypersaline, subzero habitats. | |||||
22960. 题目: Coexistence of polyethylene microplastics and biochar increases ammonium sorption in an aqueous solution Biochar is used to remove ammonium (NH4+) from wastewater, where microplastics are emerging pollutants. However, whether microplastics can adsorb NH4+ or how they will affect the sorption of NH4+ by biochars have not been studied. Here, batch sorption kinetics and isotherm experiments were conducted to elucidate the sorption of NH4+ on a manure biochar (MBC), a straw biochar (SBC), a wood sawdust biochar (WBC), a polyethylene microplastic (PE), and their combination. The results showed that PE had a smaller sorption capacity (Qmax = 3.29 mg g−1) but a faster adsorption rate (ks = 0.08 g (mg min)−1) for NH4+ than biochars (Qmax = 5.67 ~ 20.54 mg g−1; ks = 0.02 ~ 0.04 g (mg min)−1). When PE and biochars coexisted in an aqueous solution, the NH4+ sorption capacity was increased by 17.0% in PE+SBC, 7.1% in PE+MBC, and 8.6% in PE+WBC, which likely due to the deprotonation of functional groups and the decreases in small molecular-size dissolved organic carbon. We conclude that microplastics can adsorb NH4+; moreover, they can enhance the NH4+ sorption capacity of biochars. Therefore, when biochar is used for NH4+ removal from wastewater, the interaction of biochar and microplastics needs to be considered. | |||||
