12741. 题目: Humic substances as electron acceptors for anaerobic oxidation of methane driven by ANME-2d
期刊: Water Research
作者: Ya-Nan Bai, Xiu-Ning Wang, Jun Wu, Yong-Ze Lu, Liang Fu, Fang Zhang, Tai-Chu Lau, Raymond J. Zeng
摘要: Humic substances (humics) are ubiquitous in terrestrial and aquatic environments where they can serve as electron acceptors for anaerobic oxidation of organic compounds. Methane is a powerful greenhouse gas, as well as the least reactive organic molecule. Anaerobic oxidation of methane (AOM) coupled to microbial reduction of various electron acceptors plays a crucial role in mitigating methane emissions. Here, we reported that humics could serve as terminal electron acceptors for AOM using enriched nitrate-reducing AOM microorganisms. AOM coupled to the reduction of humics was demonstrated based on the production of 13C-labelled carbon dioxide, and AOM activity was evaluated with different methane partial pressures and electron acceptor concentrations. After three-cycle reduction, both AOM activity and copy numbers of the archaea 16S rRNA and mcrA genes were the highest when anthraquinone-2,6-disulfonic acid and anthraquinone-2-sulfonic acid were electron acceptors. The high-throughput sequencing results suggested that ANME-2d were the dominant methane oxidation archaea after humics reduction, although the partner bacteria NC 10 trended downward, other reported humics reduction bacteria (Geobactor and Anammox) appeared. The potential electron transfer models from ANME-2d to humics were proposed. These results enable a better understanding of available electron acceptors for AOM in natural environments and broaden our insight into the significant role of ANME-2d.
12742. 题目: Sensitivity of atmospheric CO2 to regional variability in particulate organic matter remineralization depths
作者: Jamie D. Wilson, Stephen Barker, Neil R. Edwards, Philip B. Holden, Andy Ridgwell
摘要: The concentration of CO2 in the atmosphere is sensitive to changes in the depth at which sinking particulate organic matter is remineralized: often described as a change in the exponent b of the Martin curve. Sediment trap observations from deep and intermediate depths suggest there is a spatially heterogeneous pattern of b, particularly varying with latitude, but disagree over the exact spatial patterns. Here we use a biogeochemical model of the phosphorus cycle coupled with a steady-state representation of ocean circulation to explore the sensitivity of preformed phosphate and atmospheric CO2 to spatial variability in remineralization depths. A Latin hypercube sampling method is used to simultaneously vary the Martin curve independently within 15 different regions, as a basis for a regression-based analysis used to derive a quantitative measure of sensitivity. Approximately 30 % of the sensitivity of atmospheric CO2 to changes in remineralization depths is driven by changes in the subantarctic region (36 to 60∘ S) similar in magnitude to the Pacific basin despite the much smaller area and lower export production. Overall, the absolute magnitude of sensitivity is controlled by export production, but the relative spatial patterns in sensitivity are predominantly constrained by ocean circulation pathways. The high sensitivity in the subantarctic regions is driven by a combination of high export production and the high connectivity of these regions to regions important for the export of preformed nutrients such as the Southern Ocean and North Atlantic. Overall, regionally varying remineralization depths contribute to variability in CO2 of between around 5 and 15 ppm, relative to a global mean change in remineralization depth. Future changes in the environmental and ecological drivers of remineralization, such as temperature and ocean acidification, are expected to be most significant in the high latitudes where CO2 sensitivity to remineralization is also highest. The importance of ocean circulation pathways to the high sensitivity in subantarctic regions also has significance for past climates given the importance of circulation changes in the Southern Ocean.
12743. 题目: Food waste based biochars for ammonia nitrogen removal from aqueous solutions
期刊: Bioresource Technology
作者: Shan Xue, Xinbo Zhang, Huu Hao Ngo, Wenshan Guo, Haitao Wen, Chaocan Li, Yongzhao Zhang, Chanjuan Ma
摘要: Biochar derived from waste has been increasingly considered as a potential green adsorbent due to its significant ability and affordable production costs. This study prepared and evaluated 7 types of food waste-based biochars (FWBBs) (including meat and bone, starchy staples, leafy stemmed vegetables, nut husks, fruit pericarp, bean dreg and tea leaves). The impacts of raw materials, pyrolysis temperatures (300, 400, 500, 600 and 700 °C), and residence time (2 h and 4 h) on the removal of ammonia nitrogen at different ammonia nitrogen concentrations (5, 10, 20, 50, 100, 150 mg/L) were investigated. The batch equilibrium and kinetic experiments confirmed that a FWBB dosage of 3 g/L at 25℃ could remove up to 92.67% ammonia nitrogen. The Langmuir isotherm model had the best fit to equilibrium experimental data with a maximum adsorption capacity of 7.174 mg/g at 25◦C. The pseudo-second order kinetic model well describes the ammonia nitrogen adsorption.
12744. 题目: Kinetics of Ni reaction with organic matter-ferrihydrite composites: Experiments and modeling
期刊: Chemical Engineering Journal
作者: Pei Wang, Yang Lu, Shiwen Hu, Lei Tian, Yuzhen Liang, Zhenqing Shi
摘要: The interactions between organic matter (OM) and minerals are among the most important environmental processes, which significantly affect the fate of carbon and contaminants in the environment. How the interactions between OM and ferrihydrite (Fh), one of the most reactive iron oxides, affect the kinetic reactions of heavy metals with both OM and iron oxides, however, are still largely unknown. In this study, two typical OM, humic acids (HA) and fulvic acids (FA), were used to synthesize OM-Fh co-precipitation composites. We investigated the interactions between OM and ferrihydrite and their impact on kinetic reactions of nickel (Ni) with OM-Fh composites using spherical aberration corrected scanning transmission electron microscopy (Cs-STEM), batch and kinetic experiments, and X-ray adsorption spectroscopy (XAS). Cs-STEM results, at both nano and sub-nano scales, showed three typical distributions of OM on ferrihydrite, adsorbed on ferrihydrite surfaces, accumulated as OM nanoparticles, and being blocked in tiny pores in composites. Batch experiments and modeling quantified the effects of OM and ferrihydrite interactions, which was supported by XAS results. The kinetics model developed in this study integrated both WHAM 7 and CD-MUSIC models and successfully predicted the kinetics of Ni adsorption and desorption on OM-Fh composites under the impact of OM-Fh interactions. The model can quantitatively assess the dynamic changes of Ni speciation on different OM and Fh binding sites during the kinetic processes. Our results contribute to developing a comprehensive model for predicting the dynamic metal behavior in the environment when multiple adsorbents are present.
12745. 题目: Fate of dissolved organic nitrogen during the Anammox process using ultra-high resolution mass spectrometry
期刊: Environment International
作者: Li Zhang, Yongzhen Peng, Zheng Ge, Kechen Xu
摘要: Anaerobic ammonium oxidation (Anammox) is a cost-effective process for treating highly nitrogenous wastewater. However, the fate of organic nitrogen during Anammox treatment is still unclear, which limits its practical application. In this work, the changes in the quality of dissolved organic nitrogen (DON) in coal liquefaction wastewater (CLW) during Anammox were studied in relation to its chemical composition, which was determined by Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The molecular-level characterization of extracellular polymeric substances (EPS) in the Anammox sludge is also reported for the first time in this paper. The relative contribution of N-containing compounds to the total dissolved organic matter (DOM) determined by summating the normalized intensities exceeded 30%, highlighting the complexity of the nitrogenous compounds in the influent. Additionally, Anammox appeared to be better suited to removing DON compounds with fewer carbonyl or carboxyl groups, more aromatic structures, and higher oxidative properties. Lignin-like substances were verified as the predominant component of N-containing compounds in Anammox EPS, followed by protein and substances with condensed aromatic structures. DON compounds with higher degrees of saturation, lower molecular weight, and higher lignin-like properties were more prone to absorption by Anammox EPS. A series of microbe-mediated pathways were demonstrated to be responsible for DON biodegradation, which revealed the organic and inorganic nitrogen removal mechanisms in the Anammox reactor. The obtained results provide great support to the ongoing efforts to optimize the Anammox process.
12746. 题目: Impact of hydraulic retention time and organic matter concentration on side-stream aerobic granular membrane bioreactor
期刊: Science of The Total Environment
作者: Arezoo Tavana, Roya Pishgar, Joo Hwa Tay
摘要: This study investigated the effect of hydraulic retention time (HRT) and chemical oxygen demand (COD) concentration on membrane fouling in aerobic granular membrane bioreactor (AGMBR) in a systematic approach. Changes in HRT (7, 10, and 15 h) and COD (500, 1000 and 1500 mg/L) were applied in five operational phases, to determine the most significant parameters to control membrane fouling for enhanced AGMBR performance. Membrane permeability loss was dramatically intensified with increase in HRT from 7.5 to 15 h and COD from 500 to 1000 mg/L. The highest polysaccharide content of loosely bound EPS (0.41 mg PS/mg VSS) and soluble microbial products (SMPs) (27 mg PS/L) occurred alongside poor AGMBR performance. Variations in membrane fouling were accompanied with considerable changes in Flavobacterium, Thauera and Paracoccus populations. Analysis of variance (ANOVA) demonstrated that HRT and interaction between HRT and COD were the most significant parameters in controlling membrane fouling.
12747. 题目: Simulated Arctic Ocean response to doubling of riverine carbon and nutrient delivery
期刊: Global Biogeochemical Cycles
作者: J. Terhaar, J.C. Orr, C. Ethé, P. Regnier, L. Bopp
摘要: The Arctic Ocean, more than any other ocean, is influenced by riverine input of carbon and nutrients. That riverine delivery is likely to change with climate change as runoff increases, permafrost thaws, and tree lines advance. But it is unknown to what extent these changes in riverine delivery will affect Arctic Ocean primary production, air‐to‐sea CO2 fluxes, and acidification. To test their sensitivity to changing riverine delivery, we made sensitivity tests using an ocean circulation model coupled to an ocean biogeochemical model. In separate idealized simulations, riverine inputs of dissolved inorganic carbon (CT), dissolved organic carbon (DOC), and nutrients were increased by 1% per year until doubling. Doubling riverine nutrient delivery increased primary production by 11% on average across the Arctic basin and by up to 34‐35% locally. Doubling riverine DOC delivery resulted in 90% of that added carbon being lost to the atmosphere, partly because it was imposed that once delivered to the ocean, the riverine DOC is instantaneously remineralized to CT. That additional outgassing, when considered alone, reduced the net ingassing of natural CO2 into the Arctic Ocean by 25%, while converting the Siberian shelf seas and the Beaufort Sea from net sinks to net sources of carbon to the atmosphere. The remaining 10% of DOC remained in the Arctic Ocean, but having been converted to CT, it enhanced acidification. Conversely, doubling riverine CT increased the Arctic Ocean's average surface pH by 0.02 because riverine total alkalinity delivery increased at the same rate as riverine CT delivery.
12748. 题目: Radiotracer evidence that the rhizosphere is a hot-spot for chlorination of soil organic matter
期刊: Plant and Soil
作者: Malin Montelius, Teresia Svensson, Beatriz Lourino-Cabana, Yves Thiry, David Bastviken
摘要: Aims: The ubiquitous and extensive natural chlorination of organic matter in soils, leading to levels of chlorinated soil organic matter that often exceed the levels of chloride, remains mysterious in terms of its causes and regulation. While the composition of plant species and the availability of labile organic matter was recently shown to be important, the physical localization of chlorination in soils remains unclear but is a key for understanding regulation and patterns observed. Here we assess the relative importance of organic matter chlorination in (a) bulk soil, (b) the plant roots plus the rhizosphere zone surrounding the roots, and (c) above-ground plant biomass, in an experimental plant-soil system. Methods: A radiotracer, 36Cl, was added to study translocation and transformations of Cl− and Clorg in agricultural soil with and without wheat (Triticum vulgare) over 50 days. Results: The specific chlorination rates (the fraction of the added 36Cl− converted to 36Clorg per day) in soil with plants was much higher (0.02 d−1) than without plants (0.0007 d−1) at peak growth (day 25). The plant root and rhizosphere showed much higher formation of 36Clorg than the bulk soil, suggesting that the rhizosphere is a hotspot for chlorination in the soil. In addition, the treatment with plants displayed a rapid and high plant uptake of Cl−. Conclusions: Our results indicate that the rhizosphere harbour the most extensive in-situ chlorination process in soil and that root-soil interaction may be key for terrestrial chlorine cycling.
12749. 题目: Phosphorus speciation and bioavailability in diverse biochars
期刊: Plant and Soil
作者: Terry J. Rose, Cassandra Schefe, Zhe (Han) Weng, Michael T. Rose, Lukas van Zwieten, Lei Liu, Andrew L. Rose
摘要: Background and aims: Erosion of phosphorus (P)-rich soil into waterways is a major contributor to eutrophication. To minimize the build-up of P in agricultural soils, greater knowledge of the bioavailability and fate of P from soil amendments is required. Methods: We used X-ray Absorption Near Edge Structure (XANES) spectroscopy to resolve the major P species in nine diverse biochars. We then examined the relationship between biochar P extracted using a range of typical soil (water, Bray2 and Colwell) and plant (2% citric acid, and 2% formic acid) assays. We compared these with ryegrass P uptake via bioassay. Results: Linear combination fitting indicated Al-phosphate (variscite) was the dominant P species in biochars derived from cattle feedlot manure, sugarcane trash and sugarcane bagasse, reflecting the likely Al content of the feedstock. Non-apatite Ca-phosphates (monocalcium phosphate or CaHPO4) were the major P species in poultry litter, green waste, papermill sludge, wheat chaff, sugarcane mill mud and rice husk biochars. Biochar P was poorly water soluble but largely soluble in weak acids (formic and citric acids). Despite this, biochar P extracted by citric and formic acid was a poor predictor of P bioavailability to ryegrass, with the percentage of total P extracted by water or by the Bray2 reagent providing the best prediction of ryegrass P uptake. Conclusions: The P in biochar was identified by XANES spectroscopy as predominantly Ca and/or Al-P. Water and Bray2 extraction provided the best predictors of plant available P from biochars in a plant bioassay.
12750. 题目: Impact of iron oxides and soil organic matter on the surface physicochemical properties and aggregation of Terra Rossa and Calcocambisol subsoil horizons from Istria (Croatia)
作者: Goran Durn, Srečo D. Škapin, Neda Vdović, Thilo Rennert, Franz Ottner, Stanko Ružičić, Nuša Cukrov, Ivan Sondi
摘要: We investigated the influence of Fe oxides and soil organic matter (SOM) on the surface physicochemical properties of mineral particles involved in the formation of nanostructured and micron-sized mineral aggregates of two Terra Rossa and one Calcocambisol soils developed on limestone. We determined the mineral composition and particle-size distribution (PSD) by X-ray diffraction (XRD) and laser diffraction (LD), respectively. The morphologies of the mineral particles were investigated using field-emission scanning electron microscopy (FE-SEM), while soil organic matter (SOM) was characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). The electrophoretic mobility (EPM), specific surface area (SSA) and cation exchange capacity (CEC) of the samples were also examined. We analysed surface physicochemical properties on soil prior and after selective removal of SOM and Fe oxides. The soils were characterized by their relatively simple bulk and clay mineral compositions, distinctly different contents of SOM and diverse Fe oxides. The EPM data showed that the removal of the SOM did not significantly affect the negative charge of particles, but the removal of Fe oxides shifted the EPM to more negative values, indicating an increase in permanently negatively charged clay surfaces. The removal of SOM did not affect the SSA of the Terra Rossa soils, but doubled the SSA in the Calcocambisol. The SSA of the Terra Rossas were exceptionally high, up to 130–145 m2 g−1, probably because of nano-sized authigenic (pedogenic) kaolinite. The presence of larger clay mineral particles in the Calcocambisol samples resulted in lower SSA (32–76 m2 g−1). The LD analyses showed that the removal of the SOM did not influence the PSD of the Terra Rossa soils, while the removal of the Fe oxides, mainly nanosized hematite, governed the disintegration of the micron-sized soil aggregates and induced a significant increase of the submicron-sized mineral fraction. In contrast, the removal of the SOM significantly influenced the PSD of the Calcocambisol, causing the disintegration of the native, micron-sized aggregates and an increase in the clay fraction. This study demonstrated the important role of the SOM in the aggregation processes for the Calcocambisol and the Fe oxides, especially hematite, in the Terra Rossa subsoil horizons. It was also shown that the surface properties of the Terra Rossa, particularly EPM and SSA, were determined by the presence of a nano-sized mineral fraction that mostly contains authigenic kaolinite.
12751. 题目: Metal-free activation of persulfates by corn stalk biochar for the degradation of antibiotic norfloxacin: Activation factors and degradation mechanism
作者: Bo Wang, Yan-ni Li, Li Wang
摘要: This study investigated the degradation of norfloxacin by persulfate activated with corn stalk biochar. The results demonstrate that corn stalk biochar is a green and low-cost carbon material with excellent catalytic activity for the metal-free activation of persulfate to degrade norfloxacin. The removal rate of norfloxacin increased with the increase in the dosage of persulfate, but the increased ratio gradually decreased. With alcohols and phenols as free radical trapping agents, it was determined that norfloxacin degradation by SO- 4· and HO· in the biochar/persulfate system occurred mainly on the surface or boundary layer of biochar. pH has an important effect on norfloxacin degradation in the biochar/persulfate system. Norfloxacin degradation performances under different initial pH conditions are decreased according to the following order: (initial pH 6.5) > (initial pH 3.4) > (initial pH 10.6). The effects of pH on norfloxacin degradation in the biochar/persulfate system was mainly realized through affecting norfloxacin adsorption on corn stalk biochar surface.
12752. 题目: A novel sewage sludge biochar and ferrate synergetic conditioning for enhancing sludge dewaterability
作者: Jiahuan Wu, Tao Lu, Jingwang Bi, Haoran Yuan, Yong Chen
摘要: A great prospect of sewage sludge self-recycling as a conditioner supports the research. A synergetic conditioning effect and mechanism were reflected after the synergistic conditioning experiment, and the corresponding separated experiment of biochar, K2FeO4 or acid treatment on WAS. All of the biochar, K2FeO4 and acid treatment could reduce the water content of sludge cake. Biochar had good effect on WAS settleability, although the influence of the biochar dosage was weak. Similar to K2FeO4, acid treatment also could reinforce the disintegration degree effectively, but it deteriorated the filter property of WAS. In the situation of synergistic condition, owing to the strong oxidation of K2FeO4, most of the sludge flocs was disintegrated, thus the settleability and filter property of WAS were still bad, even the biochar worked as a skeleton builder. It is encouraging to find that, even without acid treatment, there is a great decline of water content of sludge cake in the situation of synergistic condition.
12753. 题目: An empirical method for source apportionment of black carbon aerosol: Results from Aethalometer observations at five different locations in India
期刊: Environmental Pollution
作者: V. Ravi Kiran, M. Venkat Ratnam, B.V. Krishna Murthy, Yogesh Kant, P. Prasad, M. Roja Raman, S.V.B. Rao, T.V. Lakshmi Kumar, Animesh Maitra
摘要: Black carbon (BC) aerosol emitted in incomplete combustion processes is known for causing warming in the climate system also poses serious health issues. Identification of the sources of BC is essential for the development of mitigation strategies to regulate their effects in changing climate. Among different observational and analytical techniques currently available, source apportionment methods based on optical measurements are relatively simple. For example, ‘Aethalometer model’ was developed based on Aethalometer observations. However, there are a few limitations with this model arising from assumption of wavelength and angstrom exponent pairs. We have developed an empirical method which also relies on Aethalometer observations named as ‘Two alpha method’ which assumes angstrom exponent from fossil fuel as 1 and estimates bio-mass fraction and angstrom exponent for bio-mass burning. This method has been applied to Aethalometer observations from five different locations (rural, semi-urban and urban) over Indian sub-continent to quantify sources of BC. Fossil fuel is found to be the major source of BC (∼70%) irrespective of the location. Collocated measurements of Carbon Monoxide (CO) over rural site correlated well with derived bio-mass fraction. Results from this study demonstrated the capabilities of empirical method and shall provide spatio-temporal variability in sources of BC if applied to more locations.
12754. 题目: Molecular isotopic insights into hydrodynamic controls on fluvial suspended particulate organic matter transport
期刊: Geochimica et Cosmochimica Acta
作者: Meng Yu, Timothy I. Eglinton, Negar Haghipour, Daniel B. Montluçon, Lukas Wacker, Zicheng Wang, Gui'e Jin, Meixun Zhao
摘要: Hydrodynamic sorting has been shown to strongly influence the composition and age of organic carbon (OC) during sediment transport and burial in the marine environment, yet sorting effects on terrestrial OC (OCterr) in fluvial systems remain poorly understood. We conducted size fractionation of suspended particle samples from the lower Yellow River, China, and examined variations in mass distribution and carbon isotopic (δ13C and Δ14C) composition of bulk OC and specific biomarkers among grain size fractions in order to investigate the influence of hydrodynamic sorting and selective transport on organic matter export. In general, the 16-32 μm and 32-63 μm fractions contributed the most of sediment mass while the majority of the OC resided in the 16-32 μm fraction. Over 80% of OC and n-fatty acids (FAs) were concentrated in <32 μm fractions. Significant differences in OC%, surface area (SA), Δ14COC, n-FAs contents, and compound-specific 13C and 14C compositions were found among size fractions. Of particular note was a progressive decrease of Δ14C values (i.e., increase in 14C age) of long-chain (C26+28+30) FAs with decreasing grain size. Taken together, the bulk and molecular characteristics imply two distinct types of selective OCterr transport in the Yellow River. Coarser particles (>32 μm), characterized by relatively low SA, OC%, and Δ14COC values, but higher Δ14C values of C26+28+30 FAs, are inferred to reflect a combination of bedrock-derived detrital sediment and fresh vascular-plant material (e.g., plant fragments). In contrast, finer particles (<32 μm), exhibiting higher SA, OC%, and lower Δ14C26+28+30FAs values, reflect preferential transport of pre-aged, mineral soil-derived OC that is susceptible to repeated mobilization, as well as widespread dispersal in marginal seas. The latter, once buried in marine sediments, could account for the high burial efficiency of OCterr in the adjacent Bohai Sea and Yellow Sea. Thus, hydrodynamic sorting processes induce heterogeneity of composition and selective transport of OC. Bulk and molecular 14C measurements of size-fractionated particles facilitate both elucidation of these processes and assessment of their impact on OC cycling in (and export from) rivers.
12755. 题目: Cd Isotopes trace periodic (bio)geochemical metal cycling at the verge of the Cambrian animal evolution
期刊: Geochimica et Cosmochimica Acta
作者: Simon V. Hohl, Shao-Yong Jiang, Hai-Zhen Wei, Dao-Hui Pi, Qian Liu, Sebastian Viehmann, Stephen J.G. Galer
摘要: Cadmium (Cd) isotopes are an emerging proxy for biological controlled metal and nutrient cycling in the modern oceans, but its potential as a geochemical proxy in ancient environments is still uncertain yet. Sequential leaching experiments of organic matter (OM)-rich shales from the early Cambrian Niutitang Formation (Fm.) were performed in order to understand the cycling of bioessential metals short after the Cambrian animal evolution.Carbonate, OM, sulphide and silicate leachates of OM-rich shales show an overall Cd isotope variation of 6 ε112Cd/110Cd (ε112Cd) units, indicating preferential incorporation of light Cd isotopes in the order sulphide > OM > carbonate > silicate. Carbonate leachates not only show negative correlations of ε112Cd with bulk-rock total organic carbon (TOC) and δ13Corg but also show co-variations with redox-sensitive elements and bioessential metal concentrations, indicating a combined redox and primary productivity evolution of the early Cambrian Nanhua Basin on the Yangtze. Together with increased Cd/Zn ratios and decreasing total organic carbon (TOC) and redox-sensitive elements (RSE) concentrations in the upper Niutitang, this argues for an increase in essential metal availability for primary producers. Coinciding with the transition from a highly unstable ecosystem shortly after the Precambrian/Cambrian boundary to a more habitable environment increased nutrient uptake, oxygen availability and enhanced dissolved organic carbon (DOC) recycling match with the diversification of early metazoan fossil findings at the studied local. Our findings demonstrate that Cd isotopes in combination with trace metals can be used to infer changes in biogeochemical metal cycling in paleoenvironments and further allow establishing Cd isotope systematics as a reliable paleoproductivity proxy in the search for Earth’s earliest phototrophic life.
12756. 题目: Balancing nutrient stoichiometry facilitates the fate of wheat residue‑carbon in physically defined soil organic matter fractions
作者: Yunying Fang, Bhupinder Pal Singh, Annette Cowie, Weiqi Wang, Meragal Henaka Arachchi, Hailong Wang, Ehsan Tavakkoli
摘要: Preserving and enhancing soil organic carbon (SOC) stocks is one of the major objectives for sustainable agriculture. The exogenous nutrient supply along with returning crop residues, i.e., integrated residue-nutrient management, may increase carbon (C) cycling and residue-derived microbial biomass, and therefore to affect SOC stocks. However, there is a lack of knowledge about how the integrated residue-nutrient management, that balances the resource nutrient stoichiometry, facilitates the fate (or partitioning) of residue-C in physically defined SOC fractions. Hence, through a laboratory study, we quantified the fate of wheat residue (δ13C-enriched, 494‰) into sequentially separated physical SOC fractions, under the interaction of different residue rates (6.7 and 20.0 g kg−1 soil) and nutrient inputs (nil, low and high supplies of nitrogen, phosphorus, and sulfur) in two contrasting soils (Luvisol and Vertisol). The results showed that after 245 days, 42.7–54.2% of the newly-added residue-13C remained in organic matter (OM) fractions in the soils, with 22.1–40.8% in the light fraction [LF; defined as free particulate organic matter (f-POM)] and 13.9–19.5% in the heavy fraction [HF; defined as aggregate- & mineral-protected OM, which included silt-clay OM and occluded POM (o-POM)]. Following the sequential separation of HF, 8.3–15.3% of residue-13C was distributed to silt-clay OM and 4.2–6.1% to o-POM after 245 days. The high-residue rate (cf. low-residue) increased the amount of residue-C in SOC fractions. Narrowing the C-nutrient stoichiometric ratio in the residue treated soils via the exogenous nutrient input affected the proportional distribution of residue-C in SOC fractions at the high-residue rate only. With the high-residue rate in both soils, nutrient input (cf. no-nutrient) at both rates increased “new” residue-derived stable C formation in the HF by 17% or silt-clay associated OM by 27%, while decreased the distribution of residue-13C in the f-POM (LF) by 26% or o-POM by 18%. In the current study, soil type also affected the incorporation of residue-C in the organo-mineral fractions, i.e., 20% higher residue-C was incorporated in the silt-clay OM in the Vertisol than Luvisol. This study improved our knowledge on the distribution of residue-C in SOC fractions in response to integrated residue-nutrient management, which could be used to refine conceptual and mechanistic models for predicting changes in SOC storage.
12757. 题目: Removal of steroid hormone micropollutants by UF-PBSAC composite in presence of organic matter
期刊: Journal of Membrane Science
作者: Julia Wolters, Matteo Tagliavini, Andrea I. Schäfer
摘要: The present study investigated ultrafiltration (UF) membranes in a combination with a polymer-based spherical activated carbon (PBSAC) thin layer on the permeate side (UF-PBSAC) to remove the steroid hormone micropollutant (MP) estradiol (E2) from water. The impact of dissolved organic matter on the process was assessed using two types of water: one synthetic water containing humic acid (HA) and one natural water from Tanzania (Maji ya Chai River in Swamp).In both cases, only a minor impact of organic matter on the adsorption of MP was observed proving that the permeate side PBSAC layer is an effective polishing step in MP removal. The significance of UF molecular weight cut off (MWCO) was further investigated. The removal of the MP by UF-PBSAC was generally not affected by the MWCO even though a higher organic matter rejection could be achieved for lower MWCO membranes. For UF MWCOs lower than 10 kDa the UF-PBSAC is effectively removing both the MP and a major fraction of organic matter. Static adsorption investigations highlighted a significant difference in the adsorption kinetics between organic matter and MP. This can explain the preferential adsorption of the MP on PBSAC even in presence of organic matter, and hence an absence of competition.
12758. 题目: Insights into the roles of the morphological carbon structure and ash in the sorption of aromatic compounds to wood-derived biochars
期刊: Science of The Total Environment
作者: Caiting Wang, Weifeng Chen, Liuming Yang, Ran Wei, Jinzhi Ni, Yusheng Yang
摘要: Currently, it is still lack of systematic and in-depth knowledge regarding the co-effect of carbon-based fractions and ash in the sorption behavior of biochars. Therefore, pristine wood-derived biochars (PBCs) produced at different temperatures and their corresponding de-ashed versions (DBCs) were used to determine the roles of carbon's morphological structure and ash in sorption of aromatic compounds (toluene, m-toluidine, and m-nitrotoluene) to biochars. The results showed that biochars produced at 300–400 °C (mainly uncarbonized organic matter, UCOM) and 900 °C (turbostratic carbon, TC) may have stronger partition effect and pore filling effect with π-π interaction, respectively, and thus have greater sorption coefficients (Lg Kd) than biochars produced at 600 °C (pyrogenic amorphous carbon, PAC), which are probably dominated by surface hydrophobic effect. Meanwhile, TC had a greater Lg Kd than UCOM at low adsorbate concentrations (Ce), but exhibited an opposite trend at high Ce. The Lg Kd values of DBCs are always greater than those of PBCs, indicating ash has an inhibitory effect on sorption of aromatic compounds to biochars. Furthermore, the role of ash in sorption behavior of PBCs would vary with solution pH. At a neutral pH, PBCs have the maximum sorption quantity for aromatic compounds due to the formed cation-π bond between cations of ash and aromatic compounds. However, the acidic pH enhanced the dissolution of cations in ash and the basic pH enhanced the hydroxylation of cations in ash. Therefore, both acidic and basic pH weakened the cation-π bond between ash and aromatic compounds and decreased the sorption of aromatic compounds on PBCs. The results suggest that de-ashed biochars with more UCOM or TC are effective sorbents for sequestration of aromatic compounds, and provide a well-designed method for improving the sorption efficiency of biochars.
12759. 题目: Biochar can mitigate methane emissions by improving methanotrophs for prolonged period in fertilized paddy soils
期刊: Environmental Pollution
作者: Zhen Wu, Yanfeng Song, Haojie Shen, Xueyang Jiang, Bo Li, Zhengqin Xiong
摘要: Biochar application to fertilized paddy soils has been recommended as an effective countermeasure to mitigate methane (CH4) emissions, but its mechanism and effective duration has not yet been adequately elucidated. A laboratory incubation experiment was performed to gain insight into the combined effects of fresh and six-year aged biochar on potential methane oxidation (PMO) in paddy soils with ammonium or nitrate-amendment. Results showed that both ammonium and nitrate were essential for CH4 oxidation though high ammonium (4 mM) inhibited PMO as compared to low ammonium (1 mM and 2 mM), and that nitrate was better in promoting PMO than ammonium. Moreover, ammonium-amendment promoted type I pmoA, and nitrate-amendment enhanced type II pmoA abundance. Both fresh and aged biochar increased PMO as well as nitrification by enhancing the total, type I and type II methanotrophs as compared to the control. Increased soil PMO with mineral N input in both six-year aged biochar and fresh biochar amendment, indicating that biochar mitigated CH4 by promoting PMO for prolonged period in fertilized paddy soils.
12760. 题目: Adsorption of 17β-estradiol onto humic-mineral complexes and effects of temperature, pH, and bisphenol A on the adsorption process
期刊: Environmental Pollution
作者: Xin Tong, Yanxia Li, Fengsong Zhang, Xingcai Chen, Yan Zhao, Boyang Hu, Xuelian Zhang
摘要: The long-term use of animal manure in agriculture has resulted in estrogen pollution, which poses risks to facility vegetable soils. Owing to the complex soil composition, estrogen may exhibit a variety of behaviors at the water/soil interface. This study demonstrated the role of humic acid (HA) on the 17β-estradiol (E2) adsorption by clay minerals (montmorillonite, kaolinite, and hematite). The interfacial behaviors were investigated using adsorption kinetics and isotherms data. Then, the effects of temperature, pH, and bisphenol A (BPA) on the interactions between humic-mineral complexes and E2 were explored. The adsorption of E2 is an exothermic and spontaneous process, and the addition of HA to minerals significantly promoted their E2 adsorption capacities. Higher pH levels (>10) and the presence of BPA decreased the adsorption capacities of minerals and mineral complexes for E2. Moreover, intercalation, hydrophobic partitioning, π-π interactions and hydrogen bonding could dominate the E2 adsorption onto complexes. These results provided insight into the interfacial behaviors of E2 on the surfaces of humic-mineral complexes and promoted the understanding of the migration and transport of estrogens in soils.