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17481. 题目: Insight into the Cd2+ biosorption by viable Bacillus cereus RC-1 immobilized on different biochars: roles of bacterial cell and biochar matrix Biosorption of cadmium in solution by viable bacteria immobilized on biochar was tested under culture conditions, and the relative importance of biosorption by bacterial cell and biochar matrix was investigated. Viable Bacillus cereus RC-1 was immobilized on the biochars derived from rice straw (RSB-beads), chicken manure (CMB-beads), and sewage sludge (SSB-beads), respectively. The biosorption characteristics of immobilized beads was investigated under variable pH, incubation time, and initial Cd2+ concentration. The best results were obtained with RSB-beads that adsorbed Cd2+ of 158.77 mg/g, and the biosorption by these immobilized cells was superior when compared to cells in suspension. High biosorption capacity was the result of simultaneous adsorption resulting from biochar and bacteria, and accumulation resulting from bacteria, in which the bacterial cells contributed more than the abiotic biochar matrix to total removal, but only when initial Cd2+ concentrations were less than180 mg/L. The biochars played a dual role of adsorbent and carrier, and was struggling to provide nutrients to the bacteria. The relative contribution of each mechanism was determined, which demonstrated that ion-exchange was predominant in RSB-beads (contributing 39.5%-45.7% depending on initial Cd2+ concentration) and in CMB-beads (41.4%-46.8%). In contrast, ion-exchange was a minor fraction for SSB-beads (15.6%-20.1%), where complexation was the most important component (56.9%-66.8%). We propose a model regarding the roles of different mechanisms, which may provide insights into the biosorption process by microorganism immobilized onto a biochar matrix for heavy metal removal, as an important step towards improving microbial remediation. | |||||
17482. 题目: The chemical nature of soil phosphorus in response to long-term fertilization practices: Implications for sustainable phosphorus management Developing sustainable phosphorus (P) management strategies is a worldwide challenge in the face of growing food demand, dwindling rock phosphate resources, and deteriorating environmental quality. This requires improved knowledge on the effect of current fertilization practices on long-term P accumulation, bioavailability and mobility, which are functions of the chemical nature of soil P. Using state-of-the-art techniques such as solution 31P-NMR and P K-edge XANES spectroscopy, combined with sequential fractionation, this study investigated the chemical speciation and transformation of P in soils under three fertilization treatments (no fertilization, CK; chemical nitrogen (N), P and potassium (K) fertilization, NPK; and partial substitution of chemical fertilizer with sheep manure, NPKM) from a long-term experiment in China initiated in 1990. Compared to the NPK soil, total P and organic P (Po) concentrations were lower in the NPKM soil in the sampling years of 2000 and 2015, suggesting reduced P accumulation under the NPKM treatment. The NaHCO3-extracted P, considered the most readily plant-available P fraction, significantly increased in the NPKM soil relative to the NPK soil in 2000. The P-XANES results revealed the formation of the magnesium (Mg)-P compound newberyite, which probably contributed to soil P availability with NPKM application. Moreover, P-NMR analysis showed higher deoxyribonucleic acid content and ratio of orthophosphate diesters to monoesters in the NPKM soil relative to the NPK soil, which implied the stronger soil Po lability with NPKM fertilization. This study provides new insights on the significant role of NPKM treatment in optimizing soil P fertilization regimes, which benefits sustainable crop production. | |||||
17483. 题目: Characterization of dissolved organic matter in the rhizosphere of phytostabilizer Athyrium wardii (Hook.) involved in enhanced metal accumulation when exposed to Cd and Pb co-contamination The characterization of DOM and its effect on heavy metal solubility in soils have been widely concerned, while few concerns on the phytostabilization of multi-metal contaminated soils. A pot experiment was performed to characterize dissolved organic matter (DOM) in the rhizosphere of the mining ecotype (ME) and non-mining ecotype (NME) of Athyrium wardii (Hook.) when exposed to Cd and Pb simultaneously, and investigate its effect on Cd and Pb solubility in soils. The ME presented more DOM in the rhizosphere when exposed to Cd and Pb simultaneously than that exposed to single Cd or Pb, and also than the NME. The acid fractions (hydrophilic acid, hydrophobic acid) and hydrophilic fractions (hydrophilic acid, hydrophilic neutral, and hydrophilic base) were the dominant parts of DOM in the ME rhizosphere. The ME presented more acid and hydrophilic fractions in the rhizosphere when exposed to Cd and Pb simultaneously. Meanwhile, there were more O–H, C–O, N–H and C–H, assigned to carboxylic groups, phenolic groups, hydroxyl groups, and/or amino groups, present in DOM from the rhizosphere of ME when exposed to Cd and Pb simultaneously. These results highlighted the acid characteristics of DOM in the rhizosphere of ME when exposed to Cd and Pb simultaneously. DOM in the rhizosphere of ME thereby showed greater complexation degree for Cd (68%) and Pb (77%), thus showing greater ability to enhance Cd and Pb solubility in soils when exposed to Cd and Pb simultaneously. This is thereby considered to be one of the key processes for enhancing Cd and Pb uptake by the ME when exposed to Cd and Pb simultaneously. | |||||
17484. 题目: Phosphorus-rich biochar produced through bean-worm skin waste pyrolysis enhances the adsorption of aqueous lead In China, more than 10,000 tons of bean-worm, which is rich in protein (68.5%) and essential amino acids (52.8%), is consumed annually. Thus, a large amount of bean-worm skin waste is generated, and is often indiscriminately disposed of, potentially causing environment problems. In this study, bean-worm skin (BWS) waste was pyrolyzed at 500 °C to produce biochar (BWS-BC), and the surface properties of BWS and BWS-BC were characterized using various spectroscopic techniques. Pb(II) adsorption properties of BWS and the corresponding biochar as a function of solution pH, contact time, and equilibrium concentration of Pb(II) were examined using adsorption isotherm, kinetics and thermodynamics studies. The maximum Pb(II) adsorption capacities based on the Langmuir isotherm model were calculated as 45 and 62 mg g−1 for BWS and BWS-BC, respectively, which were comparable to the values obtained for biochars derived from other agro-wastes. The adsorption feasibility, favorability and spontaneity of Pb(II), as derived from the thermodynamic parameters, indicated that chemisorption and precipitation (e.g., hydroxypyromorphite) were the main adsorption mechanism in case of BWS and BWS-BC, respectively. Thus, conversion of BWS to biochar for Pb(II) adsorption can be considered as a feasible, promising and high value-added approach for BWS recycling. | |||||
17485. 题目: Size-dependent biochar breaking under compaction: Implications on clogging and pathogen removal in biofilters Breaking of biochar during compaction of amended soil used in roadside biofilters or landfill cover can affect infiltration, clog amended soil, and change its pollutant removal capacity. It is unknown how the initial biochar size affects the biochar breaking, clogging potential, and contaminant removal capacity of biochar-amended soil. We compacted a mixture of coarse sand and biochar with sizes smaller than, similar to or larger than the sand and applied stormwater contaminated with E. coli in columns packed with the compacted sand-biochar mixture. Coating biochar with a dye and analyzing the dye concentration in the broken biochar particles eluted from the columns, we proved that biochar predominantly breaks under compaction by disintegration or splitting, not abrasion, and increases in biochar size decrease the likelihood of biochar breaking. We attribute this result to the effective dissipation of compaction energy through a greater number of contact points between a large biochar particle and the adjacent particles. Most of the broken biochar particles deposited in the pores, resulting in an exponential decrease in hydraulic conductivity of amended sand with an increase in suspended sediment loading. The clogging rate was higher in the columns with smaller biochar. The columns with small biochar also exhibited high E. coli removal capacity, partly because of an increase in straining by the smaller pore size created by the deposition of fine biochar particles created during compaction. These results are useful in selecting appropriate biochar size for its application in soils and roadside biofilters for water treatment. | |||||
17486. 题目: Effects of irrigation quantity and biochar on soil physical properties, growth characteristics, yield and quality of greenhouse tomato Considering the challenges faced by current agricultural industry, such as less cultivable land, lack of soil nutrient value, limited water resources, low yield and fruit quality (Appearance and nutritional values). Biochar application was found effective way to improve soil physical properties, consequently, yield and quality of tomatoes. Biochar at three levels: B0 (0 ton/ha), B1 (25 tons/ha) and B2 (50 tons/ha) with three levels of drip irrigation quantity: full irrigation T1 (1.4 pan evaporation Ep), moderate water deficit T2 (1.2 Ep) and severe water deficit T3 (1.0 Ep) were applied in greenhouse. Thus, nine treatments, i.e. T1B0, T1B1, T1B2, T2B0, T2B1, T2B2, T3B0, T3B1 and T3B2 were set. The effects of applied different levels of irrigation quantity and biochar on soil physical properties, crop growth, yield and fruit quality were observed. Increasing level of applied irrigation quantity and biochar could improve the physical properties of soil effectively: decreased, increased and varied the soil bulk density, porosity and 3-phase composition of soil respectively. It is found that increasing levels of applied irrigation quantity at B2 had good effects on bulk density, porosity and 3-phase proportion of soil, and best composition of 3-phase (solid and pores: liquid + gas were 33.68 % and 66.32 % respectively) at T2B2 was found. The growth rate, considering growth parameters: plant height and stem diameter, was increased by applying adequate level of irrigation quantity and biochar. The yield was found maximum at T1B2, which was increased by 30.92 % as compared to T1B0. For T3 level, biochar application increased tomato yield, as compared to B0 by 83.69 % and 176.60 % at B1 and B2 respectively. It is concluded that application of biochar under full and severe deficit irrigation level increased tomato yield effectively, but tomato growth could inhibit under moderate water deficit irrigation, caused a slight yield reduction. | |||||
17487. 题目: Accelerated antimony and copper removal by manganese oxide embedded in biochar with enlarged pore structure Antimony and copper pollution pose significant threat to water quality security, and their advanced treatment is still a great challenge. In this study, we fabricated a hybrid adsorbent (denoted as MO-L-BC) through dispersing manganese oxide (MO) inside a biochar with enlarged pore structure (namely L-BC). The used carrier L-BC possessed a high proportion of large pores (>2 nm) (87%), and thus lowered the diffusion resistance of target pollutants in pore region of MO-L-BC. Consequently, Sb(III) and Cu(II) adsorption onto MO-L-BC achieved equilibrium within 15 min, and their effective coefficients of intra-particle diffusion (D) were calculated to be 8.6 × 10−8 and 1.5 × 10−7 cm2 s−1, respectively, which were only one-order magnitude lower than that in aqueous phase. XPS analysis indicated that 53.3% of the sorbed Sb(III) was oxidized to Sb(V) by the impregnated MO. Coexisting substances such as HCO3−, SO42−, NO3−, Ca2+, Mg2+ and humic acid up to 20 times higher concentration than target contaminants (Sb(III) or Cu(II)) caused only < 20% drop in sorption capacity of MO-L-BC, and the mutual effect of Sb(III) and Cu(II) was also not noticeable. The fixed-bed column adsorption tests showed that MO-L-BC can achieve the tertiary treatment of either the singly polluted (Sb(III) or Cu(II)) or the co-contaminated wastewater at a high flow rate of 0.27 m h−1, with effective treatment volumes larger than400 BV, and the saturated MO-L-BC can be effectively regenerated. MO-L-BC is a promising engineered biochar to treat Sb(III) and/or Cu(II) contaminated water especially under high-flow conditions. | |||||
17488. 题目: Bayesian calibration of the DayCent ecosystem model to simulate soil organic carbon dynamics and reduce model uncertainty Benefits of carbon sequestration in agricultural soils are well recognized, and process-based models have been developed to better understand sequestration potential. However, most studies ignore the uncertainty arising during model prediction—a critical requirement for scientific understanding, policy implementation and carbon emission trading. Furthermore, the dependencies created in process-based models due to many parameters and a relatively small set of empirical data hinder parameterization. We have implemented a Bayesian approach using the sampling importance resampling (SIR) method to calibrate the DayCent ecosystem model for estimating soil organic carbon (SOC) stocks, and to quantify uncertainty in model predictions. A SOC dataset compiled from 19 long-term field experiments, representing 117 combinations of management treatments, with 491 measurements of SOC, was split into independent datasets for model calibration and evaluation. The most important DayCent model parameters were identified through a global sensitivity analysis (GSA) for parameterization and SIR was used to calibrate the model and produce posterior distributions for the most sensitive parameters. On average, the Bayesian calibration reduced the model uncertainty by a factor of 6.6 relative to the uncertainty associated with the prior. The Bayesian model analysis framework will allow for ongoing updates to the model as new datasets and model structural improvements are made in future research, and overall provide a stronger basis for models to support policy and management decisions associated with GHG mitigation through C sequestration in agricultural soils. | |||||
17489. 题目: Interaction of perfluorooctanoic acid with extracellular polymeric substances - Role of protein Perfluorooctanoic acid (PFOA) is nonbiodegradable, and adsorption is the main pathway for its removal in wastewater treatment plants (WWTPs). This study compared the capability of three types of sludge on adsorbing PFOA and investigated the role of extracellular polymeric substances (EPS) in the adsorption process. Results show that enhanced biological phosphorus removal (EBPR) sludge had the highest adsorption capacity for PFOA. Studies on the interaction between EPS and PFOA reveal that proteins play a crucial role in binding PFOA to EPS/sludge. Specifically, the aromatic and amide groups on the structure of protein can attract the C–F chains and carboxylic head of PFOA via hydrophobic interaction and electrostatic attraction, respectively. EPS of EBPR sludge has the highest amount of protein and binding sites, thus exhibits the highest adsorption capability for PFOA. This study reveals the interaction mechanism between PFOA and sludge EPS and provides new insight into the function of EPS in perfluoroalkyl substances removal in WWTPs. | |||||
17490. 题目: A review on facilitating bio-wastes degradation and energy recovery efficiencies in anaerobic digestion systems with biochar amendment In this review, progress in the potential mechanisms of biochar amendment for AD performance promotion was summarized. As adsorbents, biochar was beneficial for alleviating microbial toxicity, accelerating refractory substances degradation, and upgrading biogas quality. The buffering capacity of biochar balanced pH decreasing caused by volatile fatty acids accumulation. Moreover, biochar regulated microbial metabolism by boosting activities, mediating electron transfer between syntrophic partners and enriching functional microbes. Recent studies also suggested biochar as potential useful additives for membrane fouling alleviation in anaerobic membrane bioreactors (AnMBR). By analyzing the reported performances based on different operation models or substrate types, debatable issues and associated research gaps of understanding the real role of biochar in AD were critically discussed. Accordingly, Future perspectives of developing biochar-amended AD technology for real-world applications were elucidated. Lastly, with biochar-amended AD as a core process, a novel integrated scheme was proposed towards high-efficient energy-resource recovery from various bio-wastes. | |||||
17491. 题目: Biochar combined with gypsum reduces both nitrogen and carbon losses during agricultural waste composting and enhances overall compost quality by regulating microbial activities and functions Composting is an efficient method for treating agricultural wastes. This study investigated the effects of the addition of biochar (B) and gypsum (G) to straw mixed with chicken manure (SC) (i.e. SC, SC + B, SC + G and SC + B + G) on composting performance at different initial C/N ratios (20, 25 and 30). In general, biochar combined with gypsum (BCG) efficiently shortened composting time and reduced N loss, C loss and potential ecological risk. It also enhanced lignocellulose decomposition, nutrient retention and the overall compost quality expressed by a compost quality index (CQI), and increased the biomass of four different test crops. The BCG-induced increase in CQI was closely associated with microbial enzyme activities and C catabolic profiles. These results indicated that the combination of biochar and gypsum is more effective than each single additive during composting, and emphasized that microbial activities and functions play pivotal roles in determining compost quality and thereby agronomic performance. | |||||
17492. 题目: A Highly Efficient Strategy for Enhancing the Adsorptive and Magnetic Capabilities of Biochar Using Fenton Oxidation Fenton modification, involving iron-promoted pyrolysis followed by H2O2 oxidation, was first employed to improve the adsorptive and magnetic capabilities of biochar. Modified biochars were prepared from rubber tree bark and coconut shell through iron-promoted pyrolysis and subsequent H2O2 oxidation, and their adsorption behaviors toward Cr (VI) and MB were evaluated in aqueous solution. The modified biochars pyrolyzed at 300 and 400 ˚C displayed much higher adsorption capabilities than corresponding pristine biochars for Cr (VI) and MB, respectively, ascribing to introduction of COOH, C=O and C-O groups by Fenton oxidation. More importantly, saturation magnetization could be enhanced by transforming nonmagnetic iron oxides into γ-Fe2O3 through H2O2 oxidation. The removal of Cr (VI) and MB could be primarily contributed to the adsorption of biochar matrix by reduction/hydrogen bonding/cation exchange/electrostatic interaction and hydrogen bonding/cation exchange/electrostatic interaction, respectively. This would provide a novel and efficient strategy for making highly adsorptive magnetic biochar. | |||||
17493. 题目: Biochar affects the dissipation of antibiotics and abundance of antibiotic resistance genes in pig manure Manure from medicated livestock contains pharmaceutical antibiotics and antibiotic resistance genes (ARGs). Bioavailable antibiotics trigger further ARGs amplification during manure storage. It was tested whether biochar lowers the bioavailability of the antibiotics sulfamethazine (SMZ), ciprofloxacin (CIP), oxytetracycline (OTC) and florfenicol (FF) in manure and the amplification of sul1 and tet(W) ARGs. To that end, liquid pig manure was treated with 5% (w/w) pinecone biochar (BCP). Antibiotics dissipated during 30-d incubation in the order SMZ < OTC < CIP < FF. Added BCP further immobilized SMZ, OTC and CIP, while the effect was not significant for FF. Both sul1 and tet(W) ARGs copy numbers significantly increased by factors of 5.8 and 2.5, respectively, in OTC and SMZ spiked manure. The abundance of sul1 was significantly decreased in BCP amended manure, while the impact on tet(W) was less. Consequently, biochar is suitable for the management of antibiotics contaminated manure during storage. | |||||
17494. 题目: Combined application of biochar with urease and nitrification inhibitors have synergistic effects on mitigating CH4 emissions in rice field: A three-year study Biochar and inhibitors applications have been proposed for mitigating soil greenhouse gas emissions. However, how biochar, inhibitors and the combination of biochar and inhibitors affect CH4 emissions remains unclear in paddy soils. The objective of this study was to explore the effects of biochar application alone, and in combination with urease (hydroquinone) and nitrification inhibitors (dicyandiamide) on CH4 emissions and yield-scaled CH4 emissions during three rice growing seasons in the Taihu Lake region (Suzhou and Jurong), China. In Suzhou, N fertilization rates of 120–280 kg N ha−1 increased CH4 emissions compared to no N fertilization (Control) (P < 0.05), and the highest emission was observed at 240 kg N ha−1, possibly due to the increase in rice-derived organic carbon (C) substrates for methanogens. Biochar amendment combined with N fertilization reduced CH4 emissions by 13.2–27.1% compared with optimal N (ON, Suzhou) and conventional N application (CN-J, Jurong) (P < 0.05). This was related to the reduction in soil dissolved organic C and the increase in soil redox potential. Addition of urease and nitrification inhibitor (ONI) decreased CH4 emissions by 15.7% compared with ON treatment. Combined application of biochar plus urease, nitrification and double inhibitors further decreased CH4 emissions by 22.2–51.0% compared with ON and CN-J treatment. ON resulted in the highest yield-scaled CH4 emissions, while combined application of biochar alone and in combination with the inhibitors decreased yield-scaled CH4 emissions by 12.7–54.9% compared with ON and CN-J treatment (P < 0.05). The lowest yield-scaled CH4 emissions were observed under combined application of 7.5 t ha−1 biochar with both urease and nitrification inhibitors. These findings suggest that combined application of biochar and inhibitors could mitigate total CH4 and yield-scaled CH4 emissions in paddy fields in this region. | |||||
17495. 题目: Efficient vertical transport of black carbon in the planetary boundary layer Vertical distribution of black carbon (BC) determines the layer where its heating impacts exert. This study presents continuous and simultaneous measurements at surface, and on a mountain site above the wintertime planetary boundary layer influenced by uplifted surface anthropogenic emissions. BC was observed efficiently transported upwards by daytime convective mixing. However, this vertical transport was less for other particulate masses. An about two‐folds higher BC mass fraction was thus present at mountain than surface, hereby a lowered single‐scattering albedo (SSA) by 0.06. This may be caused by the evaporative loss of condensed semi‐volatile materials, prevailing the secondary particulate formation, in a cleaner environment containing less precursors. The elevated BC mass corresponded with the most intensive solar radiation at midday, wielding more heating impacts over the PBL. This phenomenon may apply to other remote regions where a reduced SSA will introduce more positive radiative effects. | |||||
17496. 题目: Black carbon aerosols in the lower free troposphere are heavily coated in summer but largely uncoated in winter at Jungfraujoch in the Swiss Alps Black carbon (BC) particles are responsible for substantial radiative heating of the atmosphere. However, the climate‐relevant properties of BC particles in the free troposphere (FT) are poorly constrained over longer time scales. Here, we report on in‐situ, intensive field campaigns deploying a single‐particle soot photometer during summer and winter seasons at the Jungfraujoch (3580 m a.s.l., Switzerland), a site often located in the lower FT. The refractory BC (rBC) mass size distribution was very stable across the two seasons. BC was generally internally mixed (i.e. heavily coated with other aerosol material) in summer. However, against general expectations, BC was predominantly externally mixed in winter, with a high occurrence of negligibly‐to‐thinly coated BC. This strong seasonality in lower‐FT BC mixing state has not been previously observed, and would substantially influence the lifetime, loading, and climate effects of free‐tropospheric BC. Future measurements should investigate the generality of these results. | |||||
17497. 题目: Surface properties and suspension stability of low-temperature pyrolyzed biochar nanoparticles: Effects of solution chemistry and feedstock sources Intensive application of biochar requires better understanding of their environmental behaviors such as stability, fate, and mobility. The release of bulk biochar into biochar nanoparticles (NPs) may bring risks because of their potential flowing into downstream water bodies with nutrients/containments attached. Low-temperature pyrolyzed biochars, namely fruit tree branch biochar of 350/450/550 °C (FB350, FB450 and FB550), corn straw biochar of 350 °C (CB350) and peanut straw biochar of 350 °C (PB350), were produced, and their NPs were extracted. The yield, elemental composition, mineral composition, surface functional groups and zeta potential of biochar NPs were characterized. Subsequently their suspension stability was evaluated in NaCl and CaCl2 solutions by dynamic light scattering technique. The Hamaker constants and particle interaction energy of the biochar NPs were calculated by adopting Derjaguin–Landau–Verwey–Overbeek theory. For biochar NPs of same feedstock, the stability of FB350/450/550-NPs could be predicted well by their zeta potential values. The types of their surface functional groups were the same while their adsorption intensity differed. The scenarios for biochar NPs of different feedstock sources were different, that is, inconsistent variation was observed between their zeta potential and suspension stability, which were rooted in the variable type and quantity of surface functional groups. In conclusion, feedstock was the most significant factor that influenced the suspension stability of biochar NPs, followed by the pyrolysis temperature and solution chemistry, which were highly dependent on surface potential. The findings provide references for the environmental risk evaluation of biochar NPs and reasonable application of biochar in field. | |||||
17498. 题目: Effects of fulvic acids on the electrochemical reactions and mass transfer properties of organic cation toluidine blue: Results of measurements by the method of rotating ring-disc electrode This study examined effects of aquatic and soil natural organic matter (NOM) exemplified by standard Suwannee River fulvic acid (SRFA) and Pahokee Peat fulvic acid (PPFA), respectively, on the electrochemical (EC) reactivity and mass transfer properties of the cationic organic probe toluidine blue (TB) that forms complexes with NOM. EC measurements that were carried out using the method of rotating ring-disc electrode (RRDE) showed that for disc potentials below −0.4 V vs. the standard Ag/AgCl reference electrode, TB molecules undergo EC reduction accompanied by the formation of EC-active products that undergo oxidation at the ring electrode. EC reactions of TB in the range of potentials −0.2 to −0.4 V were determined to involve free TB+ cations and TB species adsorbed on the electrode surface. The EC reduction of TB species at the disc potentials < −0.4 V was controlled by the mass transfer of the free TB+ cations and TB/NOM complexes to the electrode surface. Formation of TB/NOM complexes caused the mass transfer-controlled TB currents to undergo a consistent decrease. The observed changes were correlated with the extent of TB/NOM complexation and decreases of the diffusion coefficients of TB/NOM complexes that have higher molecular weights (MW) than the free cations. Properties of the intermediates formed upon the reduction of TB+ cations were also affected by NOM. These results demonstrate that RRDE measurements of EC reactions of TB or possibly other EC active probes allow probing the complexation of EC-active organic species with NOM and mass transfer properties of NOM complexes and ultimately NOM itself. | |||||
17499. 题目: Fate and removal of aromatic organic matter upon a combined leachate treatment process Mature leachates contain extremely recalcitrant aromatic organic matter, and require appropriate treatment before discharge. The combined process for treating mature landfill leachate is a common and proper due to its inexpensiveness and high performance. Identification of refractory components and insights into the physicochemical properties transformations of the organics are essential for the development of efficient treatment process. Optical, three-dimensional chromatography and electrochemical techniques were applied to characterize aromatic organic matter in leachate from a pilot landfill leachate treatment plant. Results showed that the combination of biological contact oxidation, iron-carbon micro-electrolysis, Fenton, coagulation and integrated activated sludge system could efficiently remove 95.5% COD and 88.3% DOC in leachate organic matter, together with a simultaneous reduction in its molecular weight (MW), aromaticity, polarity, and humification degree. The low MW proteinaceous, carboxylic acid and amine-containing fractions were preferentially removed in biological contact oxidation process, whereas the hydrophilic humic substances with the MW > 4.0 kDa were the main species against biological treatment. Conversely, the advanced oxidation processes (AOPs) could efficiently destroy high MW, aromatic rings and conjugated moieties fractions, resulting in an increase in the leachate biodegradability. The oxygen-containing moieties generated in the AOPs were bridged by the flocculants to promote precipitate during the coagulation process, and the polymerized metastable organic fractions formed during the process were partly biodegraded in the integrated activated sludge system. This study highlights the potential of combined optical-electrochemical measurements to monitor the intrinsic reactivity of aromatic organic matter and guide the practical leachate treatment. | |||||
17500. 题目: Carbon balance by priming as controlled by single versus repeated addition and soil fertility Labile carbon (C) inputs strongly alter soil organic matter (SOM) turnover by priming, thus affecting soil C dynamics and over long-term the soil fertility. The input patterns of labile C regulating priming effect (PE) intensity, and consequently the soil C balance may differ between the experimentally single addition compared to naturally ongoing continuous inputs via rhizodeposits or litter decomposition. We evaluated the effects of single versus repeated additions of 13C-labeled glucose (with added 13C corresponding to 2% of soil organic C content) to five soils with increasing fertility level on the PE intensity and soil C balance. Repeated glucose addition induced 61–108% higher positive SOM priming than the single addition across the five soils. The PE intensity declined with soil fertility level and mineral nitrogen (N) content, but increased with activities of enzymes for N-acquisition (N-acetyl-glucosaminidase and leucine amino peptidase). Consequently, the decrease in N availability strongly increased PE intensity via enhancing microbial N mining from SOM. Considering the C balance between SOM losses by priming and glucose-C retention, glucose addition induced net C losses in the low and moderate fertility soils (−14.0 to −0.30 mg C g−1 SOC over 14 weeks) but C gains in the high fertility soils (+0.44 to +4.36 mg C g−1 SOC). The increase in soil fertility reduced priming intensity and increased glucose-C retention via high N availability and intensive microbial growth, thus promoting microbial necromass formation and so, soil C sequestration. Compared to single addition, repeated glucose addition caused larger net C losses or lower C gains due to stronger SOM priming. In conclusion, substrate addition pattern and soil fertility are crucial for regulating SOM priming and the C balance. This knowledge should be integrated to evaluate soil C dynamics in response to labile C inputs caused by agricultural managements. | |||||
