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22661. 题目: Rapid depletion of dissolved organic sulphur (DOS) in freshwaters | |||||
22662. 题目: Spatial distribution of soil phosphorous fractions following 1-year farrowing sows in an outdoor hog-rearing farm in Eastern Canada | |||||
22663. 题目: Biogas slurry as an activator for the remediation of petroleum contaminated soils through composting mediated by humic acid Soil pollution caused by petroleum hydrocarbons is a widespread environmental problem. Composting is one of the cost-effective solutions for petroleum hydrocarbons removal but limited by low efficiency of bioremediation, leading to high phytotoxicity. Given that biogas slurry as nutrients can alter the microbial activity, the aim of this study was to investigate the role of biogas slurry on the remediation of petroleum contaminated soils in composting. Herein, we added biogas slurry into the composting of hydrocarbon contaminated soil to investigate its effect on the biodegradation of petroleum hydrocarbons, humic acid (HA) transformation and the safety of product. The results showed that biogas slurry addition improved the degradation of organic matter and total petroleum hydrocarbons (TPH) (especially C > 16), but also increased 18.0% of germination index and the humification degree of HA. The estrone from biogas slurry was removed during composting and did not affect the phytotoxicity level of compost. Redundancy analysis and structural equation modeling indicated that TPH degradation was significantly related to the humification of HA components and total nitrogen from biogas slurry, which contributed to composting safety. Therefore, biogas slurry could be a possible activator for the remediation of petroleum contaminated soils through composting mediated by HA transformation, which is beneficial to obtain the composts with a lower phytotoxicity and higher maturity for soil application. | |||||
22664. 题目: Soil organic carbon stability under natural and anthropogenic-induced perturbations Soil organic carbon (SOC) plays key roles in determining soil properties, plant nutrients, and land-atmosphere carbon exchange, yet is affected by various natural and anthropogenic perturbations such as wildfire, climate change, land use change and pollution. Herein, we review perturbation types and SOC response mechanisms, as well as new technologies to measure SOC stability, highlighting the resistance and resilience of SOC. Although there is great controversy on the nature and structure of SOC, it has been recognized that the SOC stability not only depends on physiochemical characteristics of SOC, but also on soil microenvironment, soil microbial community composition, and types of perturbations. Based on ecosystem stability theories, the change of SOC stability under perturbation can be keeping stable states, changing to an alternative stable states or system collapse. For future studies, we suggest that understanding responses of soil biogeochemical processes to multiple perturbations, well-designed experiments to quantify threshold and uncertainty of SOC, and integration of novel biological approaches besides physicochemical characterizations into SOC stability are needed. This review helps to better understand the process of SOC stabilization and reduce the uncertainties in assessments of global carbon stocks, not only for mitigating the effects of climate change through negative feedbacks but also for maintaining soil functions such as soil fertility, water quality, and resistance to erosion. | |||||
22665. 题目: Functionalized Biochar with Superacidity and Hydrophobicity as a Highly Efficient Catalyst in the Synthesis of Renewable High-Density Fuels | |||||
22666. 题目: Selective stabilization of soil fatty acids related to their carbon chain length and presence of double bonds in the Peruvian Andes Recent studies show increasing evidence for perseveration of soil organic matter (SOM) controlled by interactions with the soil matrix (i.e. mineral surfaces and aggregates) rather than chemical recalcitrance of the SOM. However, a consensus is still absent for potential controls of SOM chemical composition on SOM stabilization and persistence. Soil fatty acids (FAs), which form an important SOM component, can be used to investigate the effects of chemical properties on SOM stabilization because they are easily degraded by microorganisms but can be stabilized by the soil matrix against decomposition. Here we investigated whether inherent molecular properties of FAs control their stability in soils and their interactions with the soil matrix. Soil samples were collected from alpine grasslands of the Peruvian Andes (Andosols, Umbrisols and Phaeozems), as they are characterized by high carbon stocks and abundant aliphatics. We applied pyrolysis - gas chromatography/mass spectrometry analyses assisted by tetramethylammonium hydroxide (TMAH-pyrolysis-GC/MS) to determine the chemical composition of bulk SOM and FAs before and after a 76-day incubation experiment, comparing a situation with intact versus crushed soil aggregates. The results showed that the TMAH-pyrolysis-GC/MS yielded a large proportion of FAs (>60% relative abundance of identified compounds), with a major contribution of free FAs. FA stability was controlled by the presence of double bonds (unsaturated vs. saturated FAs) and carbon chain length. Unsaturated FAs significantly (P < 0.05) predicted soil organic carbon mineralization rates and were more depleted after the incubation compared to saturated FAs. The depletion of unsaturated FAs is likely explained by their easier degradation compared to saturated FAs. The easier degradation might be explained by the smaller extent of stabilization through association with mineral surfaces and/or chemical properties rather than stabilization through occlusion in aggregates. In terms of carbon chain length, FA stability decreased from short-chain to long-chain FAs. A possible explanation for this is that short-chain FAs received more protection by occlusion in aggregates compared to long-chain FAs or that short-chain FAs were produced during the incubation as a result of microbial transformation of FAs. Such microbial transformation has limited effects on the prediction of FA stability using double bonds and carbon chain length. However, we observed that soil types and horizons did influence the controls of double bonds and carbon chain length on FA stability. Our results corroborate the hypothesis that the inherent properties of soil FAs control their interactions with the soil matrix and indirectly govern their stabilization and persistence in the Peruvian Andean soils under study. | |||||
22667. 题目: Electrochemical-driven carbocatalysis as highly efficient advanced oxidation processes for simultaneous removal of humic acid and Cr(VI) Electrochemical advanced oxidation processes (AOPs) represent an efficient and promising strategy for dealing with the ever-growing water pollution. Meanwhile, carbocatalysis has long and widely been applied in the fields of synthesis and catalysis because of high activity and selectivity. In this work, we combined the advantages of these two methods and for the first time proposed a conceptual new, novel and promising approach of electrochemical-driven carbocatalysis as highly efficient AOPs for water remediation, which was simply performed by adding carbon-based particles into the electrochemical system. This method shows great potentials for the simultaneous removal of both humic acid (HAC) and Cr(VI) in water, in which HAC was effectively mineralized with a TOC removal efficiency as high as 90% and Cr(VI) was completely removed with a total Cr removal beyond 90%. The presence of carbon particulate materials and their physicochemical properties were first indicated to play critical roles in the developed electrochemical AOPs. These added carbonaceous particles such as activated carbon (AC) and a series of modified AC materials, on one side exerted an important carbocatalytic function with typical AOPs features and on another side, they behaved like numerous galvanic cells with quasi-homogeneous catalytic properties, greatly facilitating mass and electron transfers in the electrochemical system and resulting in a synergistic effect for the removal of combined pollutants. The physicochemical properties of these carbon particulate catalysts facilitated the simultaneous occurrence of adsorption and carbocatalysis, where a synergistic effect between adsorption and catalytic oxidation was confirmed in this electrochemical-driven carbocatalysis system. Moreover, the catalytic performances and mechanisms of this system were found to be dependent on the carbon structures (e.g., surface area, functional groups and hybridization structure, etc.). Very importantly, the energy-effective feature and the carbon materials stability showed a promising prospect of this approach with energy consumption much lower than the ever-reported electrochemical AOPs. This work details the first insight into electrochemical-driven carbocatalysis and provides a new, green and promising approach for effective water remediation, as well as gives new evidence for the synergistic effect between adsorption and catalytic oxidation. | |||||
22668. 题目: Depth patterns and connections between gross nitrogen cycling and soil exoenzyme activities in three northern hardwood forests Despite the enormous size of the organic nitrogen (N) pool contained in mineral subsoils, rates of N cycling and soil exoenzyme activities are rarely measured in soils below 10 or 20 cm depth. Furthermore, assumed relationships between N mineralization rates and the activities of various decomposition exoenzymes are poorly characterized. We measured rates of gross and net N mineralization and nitrification as well as the potential activities of hydrolytic and oxidative enzymes at five soil depths (forest floor to 50 cm) in Spodosols at three hardwood forests of varying age (45 and 100 years post-harvest and old growth) at and near the Hubbard Brook Experimental Forest in New Hampshire, USA. As expected, all rates of N cycling and potential enzyme activities per unit soil mass correlated strongly with soil carbon (C) concentration, which decreased exponentially with increasing soil depth. Normalized per unit soil organic matter, N cycling rates and specific enzyme activities generally decreased little with depth within the mineral soil. Gross N mineralization rates correlated with specific activities of those enzymes that hydrolyze cellulose (β-glucosidase, cellobiohydrolase) and N-rich glucosamine polymers (N-acetylglucosaminidase), but not those that degrade protein or more complex C compounds, leading us to suggest that these N cycling measurements largely capture the N released during microbial N recycling, supported perhaps by plant C inputs rather than from decomposition of soil organic matter. Across the three stands, the youngest had a larger ratio of N- to-phosphorus-acquiring enzyme activities, consistent with expectations of greater N demand in younger than older forests. For all three stands, soil below 10 cm–50 cm contributed 30–53% of total gross and net N cycling per unit area. Overall, even though microbial N cycling and enzyme activities per unit soil mass decreased with depth, microbial processes in subsoils contributed substantially to ecosystem-scale gross N fluxes because of the sustained microbial activity per unit soil organic matter at depth and the large size of the organic matter pool in the mineral soil. These results support the inclusion of often-ignored mineral subsoils and microbial N recycling in both ecosystem N budgets and in model simulations of N cycling and limitation, which will otherwise greatly underestimate N fluxes and the importance of microbial N dynamics. | |||||
22669. 题目: Rusty sink of rhizodeposits and associated keystone microbiomes Iron hydroxides serve as an efficient 'rusty sink' promoting the stabilization of rhizodeposits into soil organic carbon (SOC). Our work aimed to understand the physicochemical and microbial mechanisms promoting rhizodeposit (rhizo-C) stabilization as influenced by goethite (α-FeOOH) or nitrogen (N), using 13C natural abundance methodologies and DNA sequencing, in the rhizosphere of maize (Zea mays L.). The addition of N fertilizer to soil increased the mineralization of both rhizo-C and SOC, while amendment with α-FeOOH decreased rhizo-C derived CO2 and lowered the rhizosphere priming effect by 0.57 and 0.74-fold, respectively, compared to the control soil. This decrease resulted from the co-precipitation of rhizo-C at the reactive α-FeOOH surfaces as Fe-organic matter complexes (FeOM), which was 10-times greater than the co-precipitation on short-range ordered minerals. The highest portion of rhizo-C (67% of the total accumulated in soil) was protected within macroaggregates (>2 mm). Carbon overlapped with α-FeOOH mainly in >2 mm aggregates, as shown by HRTEM-EDS imaging, suggesting that α-FeOOH associated rhizo-C stimulated aggregate formation. Random forest analysis confirmed that the stabilization of rhizo-C was controlled mainly by physiochemical binding within FeOM complexes and macroaggregates. Rhizo-C mineralization was regulated by the keystone microbiome: Paucimonas (β-Proteobacteria) being an r-strategist with rapid growth under soil without nutrients limitation (N treated) and Steroidobacter (Actinobacteria) with branched filaments that can access C and nutrients under oligotrophic conditions (goethite enriched soil). Two-way orthogonal partial least squares analysis revealed that the rhizosphere priming effect was facilitated mainly by the same genera, most likely due to co-metabolism. The genera belonging to Acidimicrobiaceae (Actinobacteria), Cryptococcus and Cystofilobasidium (Basidiomycota) were positively correlated with the accumulation of rhizo-C in the >2 mm aggregate size, which might due to their high affinity towards α-FeOOH and contribution to the development of aggregation via filamentary structures that interact with microaggregates. We suggest that rhizodeposit stabilization in soil was balanced by microbial mineralization and abiotic associations with the rusty sink and organisms with branched filaments that contributes to the development of aggregation. | |||||
22670. 题目: Adsorption of humic and fulvic acids onto a range of adsorbents in aqueous systems, and their effect on the adsorption of other species: A review Humic acid (HA) and fulvic acid (FA) are the prime components of natural organic matter (NOM) and can cause several problems in potable water such as odor, taste, and color. They can also produce hazardous disinfectant by-products (DBPs), especially on water chlorination, and can reduce the amount of dissolved oxygen in the aquatic environment. Therefore, removal of NOM from water systems is highly desirable. This review discusses the results found for adsorption of HA and FA on a wide range of adsorbents such as carbonaceous materials, nanosized metal (oxy-hydro) oxides, low-cost agricultural materials, clays, zeolites, biopolymers, composites and miscellaneous adsorbents. Studies investigating the effect of adsorbed humic material on the adsorption of other aqueous species are also presented. The adsorbents used have been assessed in terms of their maximum HA or FA adsorption capacity with special emphasis given to environmental conditions such as contact time, solution pH, initial HA or FA concentration, temperature, and adsorbent dosage. Adsorption mechanisms of HA and FA are discussed taking into account the results of kinetic, isotherm, surface complexation modeling, and thermodynamic studies, together with available spectroscopic evidence. Natural and agricultural waste materials and bio-sorbents were found to exhibit excellent HA and FA adsorption performance. This review aims to provide an overview of research on the removal HA and FA from aqueous systems by various adsorbents. It also shows the strengths and weaknesses of current research and suggests ideas for future research that will improve our ability to remove HA and FA from natural and waste-water systems. | |||||
22671. 题目: Patterns and trends of topsoil carbon in the UK: Complex interactions of land use change, climate and pollution The UK Countryside Survey (CS) is a national long-term survey of soils and vegetation that spans three decades (1978–2007). Past studies using CS data have identified clear contrasting trends in topsoil organic carbon (tSOC) concentrations (0–15 cm) related to differences between habitat types. Here we firstly examine changes in tSOC resulting from land use change, and secondly construct mixed models to describe the impact of indirect drivers where land use has been constant. Where it occurs, land use change is a strong driver of SOC change, with largest changes in tSOC for transitions involving SOC-rich soils in upland and bog systems. Afforestation did not always increase tSOC, and the effect of transitions involving woodland was dependent on the other vegetation type. The overall national spatial pattern of tSOC concentration where land use has been constant is most strongly related to vegetation type and topsoil pH, with contributions from climate variables, deposition and geology. Comparisons of models for tSOC across time periods suggest that declining SO4 deposition has allowed recovery of topsoils from acidification, but that this has not resulted in the increased decomposition rates and loss of tSOC which might be expected. As a result, the relationship between pH and tSOC in UK topsoils has changed significantly between 1978 and 2007. The contributions of other indirect drivers in the models suggest negative relationships to seasonal temperature metrics and positive relationships to seasonal precipitation at the dry end of the scale. The results suggest that the CS approach of long-term collection of co-located vegetation and soil biophysical data provides essential tools both for identifying trends in tSOC at national and habitat levels, and for identifying areas of risk or areas with opportunities for managing topsoil SOC and vegetation change. | |||||
22672. 题目: Variation in black carbon concentration and aerosol optical properties in Beijing: Role of emission control and meteorological transport variability Black carbon (BC), which is a by-product with incomplete combustion of carbonaceous materials, can be used as an indicator of combustion emissions and is an important climate forcer. In this study, a spatial–temporal synthesis of BC aerosols and the affecting factors was conducted in urban Beijing. As observed, BC showed a spatial pattern with high concentration in south and low in north. BC concentration evidently decreased by approximately 61% between 2005 and 2017. From 2015 to 2017, the mass ratio of BC/PM2.5 dropped by 28%, which suggested a more efficient effect of control measures to BC than PM2.5. The BC/CO ratio dropped by 22%, which indicated the decreasing emission from fossil fuel sources. With regard to BC loading, the spectral dependence of absorption aerosol exhibited significant seasonal variations. High absorption Ångström exponent (α) was observed during heating season, which reflected the increasing contribution of brown carbon (BrC) to light absorption. Backward trajectory analysis showed that the levels of BC and PM2.5 were high in Cluster-South and Cluster-West. BrC absorption was high in Cluster-West, Cluster-Northwest and Cluster-Northeast, due to the biomass and coal burning for domestic heating and aging processes on a regional scale. The effects of emission control and transport variability on pollutant variation were estimated on the basis of the cluster analysis. Results indicated that the effect of emission reduction was the major reason for the decrease of BC from 2015 to 2017, which resulted in a 34% reduction of BC concentration. Meanwhile, transport variability caused a 15% reduction. | |||||
22673. 题目: Production of biochar from oil palm frond by steam pyrolysis for removal of residual contaminants in palm oil mill effluent final discharge Advances in biochar production and modification have extended the applications of biochar to wastewater treatment. However, not all feedstocks produced porous biochar at a moderate temperature suitable for wastewater treatment. In this study, biochar was produced from oil palm frond using steam pyrolysis at 500 °C and pulverized to granular and micro-fine particles. Both biochar particles were characterized and applied as adsorbents for treating final discharge of palm oil mill effluent. The effluent was also filtered and treated to examine the effect of suspended solids on adsorption capacity. The biochar had Brunauer-Emmett-Teller surface area of 406.6 m2 g−1. Pulverization eliminated the residual macropores in granular biochar, created new external surface area, and exposed constricted nanopores, which resulted in increasing the surface area to 457.7 m2 g−1. The adsorption capacity decreased from 24.6 to 6.1 mg g−1 for chemical oxygen demand and 49.0 to 10.9 Pt–Co g−1 for color by increasing the dosage of micro-fine biochar from 5 to 30 g L−1. The total suspended solids affected the adsorption capacity of granular biochar by blocking residual macropores that provide access to adsorption sites in micropores and mesopores. At 30 g L−1, the micro-fine biochar exhibited an effective reduction of chemical oxygen demand from 224 to 41.6 mg g−1 and color from 344 to 15 Pt–Co g−1 making the wastewater suitable for reuse in palm oil mills and safe for discharge into the aquatic environment. | |||||
22674. 题目: Spatial variation of fouling behavior in high recovery nanofiltration for industrial reverse osmosis brine treatment towards zero liquid discharge Nanofiltration (NF), as a cost-efficient pre-concentrating process, has been incorporated into Zero Liquid Discharge (ZLD) treatment system to improve economic feasibility. However, NF is required to operate with an extremely high recovery rate to achieve ZLD, which could cause severe and complex membrane fouling. Understanding the variation of fouling behavior with increase in recovery rate is crucial for the development of effective fouling control strategy. Spatial variation of fouling behavior in a 3-stage NF used for industrial RO brine treatment towards ZLD was investigated in present study. Distinctive fouling characteristics were observed in each operation stage. Membrane fouling was dominated by organics at lead stage, which could be completely removed via simple base cleaning. Scaling by deposition of bulk crystallization occurred on fouling layer at middle stage, which required a combination of acid and base cleaning for its removal. At the tail stage, more refractory scaling by surface crystallization accompanied by irreversible silica and ferric fouling led to the formation of fouling layer that was resistant to conventional chemical cleaning. Significant humics in preformed fouling layer could have facilitated the occurrence of surface crystallization. Minor elements present in the feed such as silica, humics and iron could cause significant fouling and alter preformed fouling layer that induced more complex and refractory fouling/scaling as recovery rate increased. | |||||
22675. 题目: The effects of the soil environment on soil organic carbon in tea plantations in Xishuangbanna, southwestern China Increasing soil organic carbon (SOC) reserves in agricultural land is important for mitigating global climate change. The soil environmental factors that affect SOC storage in agricultural cultivation are relatively easy to manage, but the effects of these factors on SOC have not been studied systematically, especially the relative weight of each factor is still unclear. In this study, more than 30 soil environmental factors including SOC, soil physical and chemical properties, mineral types, and microorganisms present in the 0–140 cm soil layer were determined hierarchically within tea plantations. The main and secondary factors affecting SOC storage were then analyzed quantitatively using a structural equation model. The most important factors affecting SOC storage in tea plantations included water content (18.9 %), total nitrogen (N, 18.8 %), oxalate-extractable iron (active iron, poorly crystalline iron, Feox, 16.3 %), sulfur (S, 13.1 %), total phosphorus (P, 8.6 %), calcium (6.1 %), oxidation reduction potential (5.4 %), clay (4.5 %), bromine (4.3 %), and manganese (4.0 %). Variations in soil temperature and pH on this small scale were small and thus these factors had negligible effects on SOC storage in this study. Organic fertilizer application increased C, N, S, and P concentrations, which can contribute to SOC storage. Appropriate irrigation can also improve SOC storage. We identified a set of Fe-N-S-P coupling mechanisms that promoted SOC storage. Soils with high Fe, N, and S concentrations, high water content, and high oxidation reduction potential relate to an increased Feox concentration, which is important for enhancing SOC stability. Therefore, the application of magnetic (iron oxide) fertilizer to increase Feox in soil promotes SOC storage. | |||||
22676. 题目: Accumulation of organic carbon in various soil aggregate sizes under different land use systems in a semi-arid environment Aggregate-protected soil organic matter remains an important platform for organic carbon stabilisation and a sink for atmospheric CO2 emission, which play a crucial role in sustainable functioning of terrestrial ecosystems. This study was conducted to determine water stable soil aggregates, dry stable aggregates, and soil organic carbon (SOC) associated with aggregate sizes in surface (0-5 cm) and subsurface (5-15 cm and 15-30 cm) soil layers under four land use systems (forests, exclosures, grazing lands and cultivated lands) in the semi-arid northern Ethiopia. Dry- and wet-sieving analysis were applied to fractionate the soil into macroaggregates (>0.25 mm) and microaggregates (<0.25 mm). Particle size distribution and SOC content in macroaggregates and microaggregates (from which soil stability indices were developed) were determined using routine laboratory procedures. Result shows that land use systems had impact on soil aggregate distribution: microaggregates were dominant (more than 60 %) under cultivated land while macroaggregates were preponderant in grazing land (72-95 %). Aggregate stability index (ASI) followed the increasing order of grazing land > forest land/exclosure > cultivated land, in the surface layers, while structural stability index (SSI) was in the increasing order of forest > grazing land > exclosure > cultivated land for the top soils. SOC had strong and weak positive correlation with SSI and ASI respectively. This implies that SOC has more limited role in improving aggregation than other unexplained variables (not investigated in this study) like clay mineralogy, wettability characteristics, microbial activity and composition, and biotic factors in the study area. Correlation and regression analyses implied that dry-sieving of soil is as good as wet sieving in determining aggregate size distribution and soil aggregation in the study area. Therefore dry-sieving could be described as a climate-smart and quick sustainable alternative to the more time-consuming and tedious wet sieving method in a semi-arid dryland. Vegetation restoration improved soil organic carbon sequestration associated with aggregate sizes in the exclosures. Land use systems and management practices for reclamation of degraded land, in addition to changes in land use exerts positive and negative impacts on the organic carbon stock in soil aggregate fractions. | |||||
22677. 题目: Effects of biochar, compost and straw input on root exudation of maize (Zea mays L.): From function to morphology Returning crop straw, such as biochar, into the field is increasingly recognized as a valid, environmentally-friendly agricultural strategy to improve soil quality, increase crop yields, and reduce combustion-induced air pollution. Root exudation has potential importance for plant performance, rhizosphere function and plant–soil interactions; however, the effects of crop straw input on maize root exudation remain unclear. After three seasons of a field experiment, a mesh bag experiment was conducted in situ in the fourth season to study the effects of three straw incorporation treatments (chopped maize straw, SD; compost produced by maize straw, SC; biochar produced by maize straw, BC) and control (no straw, CK) on root exudation and their underlying mechanisms in a maize cropping system. Discrimination in the metabolic profiling of the root exudates between the CK and all the straw-incorporated samples was clear, but the separation between the samples from the three different straw strategies was limited. Among the 32 assigned components of maize root exudates, the fluctuations in organic acids (up to 16-fold) were stronger than those in sugars and amino acids when straw was incorporated. The response of the organic acid exudates was linked to the transcript levels of the ZmMATE1 and ZmMATE2 genes, which are associated with root exudation (Spearman correlations, P < 0.05). Straw incorporation influenced the root phenotypic appearance and morphology, which are characterized by longer and thinner root, larger root surface area, and more root tips in BC treatment, whereas shorter and thicker root, and fewer root tips in SD treatment. The changes in the root morphology and metabolomes were responsible for the responses of the maize root exudates to straw incorporation. Regulation of genes (ZmCycD2; 2a, ZmEXPB8, ZmXTH1, and ZmARF1) that associated with root growth and development, and changes in the viability and anatomical structure of root tips were involved in the modifications of root morphology. This information will be useful for modulating rhizosphere processes and soil fertility, and for guiding and recommending residue management practices in crop production with relatively larger yields. | |||||
22678. 题目: Redox-induced mobilization of Ag, Sb, Sn, and Tl in the dissolved, colloidal and solid phase of a biochar-treated and un-treated mining soil The aim of this work was to study the redox-induced mobilization of Ag, Sb, Sn, and Tl in the dissolved, colloidal, and sediment phase of a mining soil treated and untreated with biochar as affected by the redox potential (EH) -dependent changes of soil pH, dissolved organic carbon, Fe, Mn and S. The experiment was conducted stepwise at two EH cycles (+200 mV → -30 mV → +333 mV → 0 mV) using biogeochemical microcosm. Silver was abundant in the colloidal fraction in both cycles, indicating that Ag might be associated with colloids under different redox conditions. Antimony, Sn and Tl were abundant in the colloidal fraction in the first cycle and in the dissolved fraction in the second cycle, which indicates that they are retained by colloids under oxic acidic conditions and released under reducing alkaline conditions. Release of dissolved Sb, Sn, and Tl was governed positively by pH, Fe, S, and dissolved aromatic compounds. Biochar mitigated Ag release, but promoted Sb, Sn, and Tl mobilization, which might be due to the wider range of EH (-12 to +333) and pH (4.9–8.1) in the biochar treated soil than the un-treated soil (EH = -30 to +218; pH = 5.9–8.6). Also, the biochar surface functional groups may act as electron donors for the Sb, Sn, and Tl reduction reactions, and thus biochar may play an important role in reducing Tl3+ to Tl+, Sb5+ to Sb3+, and Sn4+ to Sn2+, which increase their solubility under reducing conditions as compared to oxic conditions. Thallium and Sb exhibit higher potential mobility in the solid phase than Sn and Ag. Biochar increased the potential mobility of Sb, Sn, and Tl under oxic acidic conditions. The results improve our understanding of the redox-driven mobilization of these contaminants in soils. | |||||
22679. 题目: Molecular characteristics of water-soluble dicarboxylic acids, ω-oxocarboxylic acids, pyruvic acid and α-dicarbonyls in the aerosols from the eastern North Pacific Aerosol samples (n = 14), collected over the eastern North Pacific (ENP, 27–52°N and 150–172°W), were studied for dicarboxylic acids (hereafter diacids, C2-C10), ω-oxoacids, pyruvic acid, and α-dicarbonyls as well as water-soluble organic carbon (WSOC) and total nitrogen (WSTN). We found diacids as the most abundant compound class followed by ω-oxoacids and α-dicarbonyls. Molecular distributions of diacids were characterized by the predominance of oxalic (C2) (58%) acid followed by malonic (C3) (15%) and succinic (C4) (13.5%) acids. However, we found a predominance of C4 over C3 in five samples, where 4-oxobutanoic acid (ωC4) was the most abundant ω-oxoacid species (34.6% of its class). Moreover, a strong correlation (r2 = 0.72) was obtained between ωC4 and C4 in those samples, suggesting that high abundances of C4 are associated with sea-to-air emission of unsaturated fatty acids and their further photochemical processing. Good relationships between C2 and C3 (r2 = 0.88) and C3 and C4 (r2 = 0.79) in the marine aerosols further suggest that C2 is produced via photochemical degradation of C3 and C4 over the ENP. WSOC and WSTN showed higher abundances in the longitudinal transect of 165-172oW, where ω-oxoacids were abundantly detected. This study demonstrates that atmospheric levels of water-soluble organic aerosols in the ENP are largely regulated by the primary productivity followed by sea-to-air emissions of unsaturated fatty acids and isoprene and the subsequent photochemical oxidation. | |||||
22680. 题目: Enhancement of soil carbon and nitrogen stocks by abiotic and microbial pathways in three rubber‐based agroforestry systems in Southwest China Agroforestry systems are considered promising alternatives to rubber tree (Hevea brasiliensis) monocultures, but information is limited on the effects of rubber‐based agroforestry systems on soil organic carbon (SOC) and total nitrogen (TN) storage. The current study, which was conducted in Xishuangbanna, China, compared four intercropping treatments, including rubber monoculture and the follow three agroforestry treatments: intercropping with Camellia sinensis, Coffea liberica, or Theobroma cacao. Soil physico‐chemical properties and copy numbers of cbbL and nosZ genes (which indicate the abundance of bacteria that function in C and N cycling) were analyzed. The results showed that Coffea liberica intercropping facilitated SOC and TN contents and enhanced SOC and TN stocks by 36.5% and 33.2% relative to rubber monoculture at 0‐10 cm soil layer, respectively. Structural equation modeling showed that the effects of intercropping on cbbL and nosZ copy numbers were mainly explained by soil pH and bulk density (r2=0.37 and 0.35, respectively), that the abundance of cbbL and SOC content directly affected SOC storage (r2=0.46), and that the abundance of nosZ and TN content directly affected TN storage (r2=0.22). Our results indicate that the use of C. liberica as intercrops should contribute to retard soil degradation and to implement sustainable land management in rubber monocultures. Combining the abiotic and microbial pathways, we suggest that the enhancement of C and N sequestration with C. liberica under rubber monoculture can be probably attributed to the increased input of litter and roots and to the stimulation of the microorganisms that regulate C and N cycles. This article is protected by copyright. All rights reserved. | |||||
