1. 题目: An assessment of HgII to preserve carbonate system parameters in organic-rich estuarine waters
2. 题目: Different Bacillus sp. play different roles on humic acid during lignocellulosic biomass composting
The yield of rice straw is increasing year by year, and composting is a common and effective treatment. The genus Bacillus has been widely used in rice straw composting because of its good ability to degrade lignocellulose. In addition, inoculation with Bacillus had an effect on the composting humification degree. However, the route, object, and extent of influence of different Bacillus sp. on the humification degree have not been clarified. In this study, four treatments were carried out for a 75-day experiment, including inoculated with Bacillus siamensis (H1) composting, inoculated with Bacillus halophilus (H2) composting, inoculated with Bacillus parahemolyticus (S1) composting, and composting without inoculation (CK) as a control. The effects of inoculation on precursors and humification indexes were investigated by chemical methods. Also, microbial changes were investigated by high-throughput sequencing. Finally, structural equation models (SEMs) were used to reveal the influence route of Bacillus sp. The humic acid (HA) concentration of CK compost, H1 compost, H2 compost and S1 compost increased by 39.88%, 43.39%, 57.42% and 51.83%, respectively. Network analysis showed differences in core microorganisms and microorganisms related to Bacillus among treatments. The SEMs indicated that H2 and S1 could not only directly affect humification ratio (HR), but also promote humification through their effects on bacterial communities. And H1 could only further affect HR by affecting the microorganisms involved. Collectively, inoculation with Bacillus could increase the HA content. Moreover, the influence routes of H2 and S1 are different from those of H1, with the former having two and the latter only one. Therefore, this study provided a theoretical basis for revealing the influence routes of different Bacillus sp. in the humification process. Meanwhile, it also alleviates the environmental pollution caused by the burning of straw waste, which is of great significance to environmental protection.
3. 题目: Uncovering interactions among ternary electron donors of organic carbon source, thiosulfate and Fe0 in mixotrophic advanced denitrification: Proof of concept from simulated to authentic secondary effluent
To offset the imperfections of higher cost and emission of CO2 greenhouse gas in heterotrophic denitrification (HDN) as well as longer start-up time in autotrophic denitrification (ADN), we synergized the potential ternary electron donors of organic carbon source, thiosulfate and zero-valent iron (Fe0) to achieve efficient mixotrophic denitrification (MDN) of oligotrophic secondary effluent. When the influent chemical oxygen demand to nitrogen (COD/N) ratio ascended gradually in the batch operation with sufficient sulfur to nitrogen (S/N) ratio, the MDN with thiosulfate and Fe0 added achieved the highest TN removal for treating simulated and authentic secondary effluents. The external carbon is imperative for initiating MDN, while thiosulfate is indispensable for promoting TN removal efficiency. Although Fe0 hardly donated electrons for denitrification, the suitable circumneutral environment for denitrification was implemented by OH− released from Fe° corrosion, which neutralized H+ generated during thiosulfate-driven ADN. Meanwhile, Fe° corrosion consumed the dissolved oxygen (DO) and created the low DO environment suitable for anoxic denitrification. This process was further confirmed by the continuous flow operation for treating authentic secondary effluent. The TN removal efficiency achieved its maximum under the combination condition of influent COD/N ratio of 3.1-3.5 and S/N ratio of 2.0-2.1. Whether in batch or continuous flow operation, the coordination of thiosulfate and Fe0 maintained the dominance of Thiobacillus for ADN, with the dominant heterotrophic denitrifiers (e.g., Plasticicumulans, Terrimonas, Rhodanobacter and KD4-96) coexisting in MDN system. The interaction insights of ternary electron donors in MDN established a pathway for realizing high-efficiency nitrogen removal of secondary effluent.
4. 题目: Enhanced degradation of Bisphenol AF by Fe/Zn modified biochar/ferrate(VI): Performance and enhancement mechanism
The use of ferrate (Fe(VI)) as an oxidizing agent is gaining popularity due to its eco-friendly and efficient properties. However, its practical application is constrained by its significant pH-dependence. Consequently, finding cost-effective and environmentally friendly catalysts that can activate Fe(VI) over a wide pH range is crucial for the removal of organic pollutants. In this study, the Fe/Zn-modified biochar (Fe/Zn-BC) was synthesized and it was employed to activate Fe(VI) for the purpose of accelerating the breakdown of bisphenol AF (BPAF). The Fe(VI)+Fe/Zn-BC system can effectively degrade 90.1% of BPAF within three minutes, which is nearly twice as efficient as the single Fe(VI) system and the Fe(VI)+BC system, and significantly higher than the Fe/Zn-BC system alone. During the reaction, the pH increase caused a reduction in the reactivity of Fe(VI), resulting in the observation of a distinct segmentation phenomenon in the results of pseudo-first-order kinetics fitting. Besides, the removal rate of BPAF was influenced by key operating parameters (i.e., Fe/Zn-BC dosage, Fe(VI) concentration, initial pH). Additionally, the study demonstrated that Fe/Zn-BC could still effectively activate Fe(VI) even under higher initial pH conditions. Fe(IV) and Fe(V) were identified as the major active oxidizing species in the system through free radical scavenging and PMSO conversion experiments and a possible activation mechanism was proposed based on results of experiments (including XPS and FTIR). Overall, this study provides a practical and cost-effective approach to improve the oxidation performance of Fe(VI).
5. 题目: Molecular structure of dissolved organic carbon in a sandy soil receiving contrasting quality organic residues
Decomposing plant residues release plant-derived dissolved organic carbon (DOC) which can be transformed by microorganisms resulting in microbial-derived DOC (DOC biological function). The adsorbability of DOC to mineral surfaces, determined by DOC chemistry (DOC chemical function), can affect its vertical distribution down soil profiles (D). This study investigated the temporal characteristics (T) and functions (bioavailability, adsorbability) of DOC across the profile of a sandy soil by using chemically contrasting quality (Q) residues: 1) high-cellulose rice straw (RS), 2) nitrogen-rich groundnut stover (GN), 3) lignin-rich dipterocarp leaf litter (DP), and 4) medium-nitrogen and -lignin tamarind leaf litter (TM). Soil samples were collected at two depths (0–15 cm and 60–80 cm) two and eight weeks after residue application, and water-extractable DOC was determined. For the first time, the chemical structure of the extracted DOC was characterized using pyrolysis coupled with mid-infrared spectroscopy (Py-MIRS). The dominant functional groups found in all DOC samples were aromatic, carboxyl, and polysaccharide compounds. The interactive effects of Q, T, and D (soil depth) influenced DOC-polysaccharides, with the most pronounced effect observed in the RS treatment during the early stage, indicating that DOC-polysaccharides were mainly plant-derived. Evidence of partial adsorption of DOC-aromatics and DOC-carboxyls was found in topsoils. These high molecular weight-DOC functional groups may have displaced adsorbed polysaccharides, resulting in higher subsoil DOC-polysaccharides than topsoil, especially under DP and TM. During the later stage, topsoil DOC-polysaccharides were negatively related to microbial metabolic quotient (qCO2) (R2 = 0.938). This relationship led to our hypothesis that the dominant source of DOC-polysaccharides, particularly in the TM treatment, was of microbial origin. A novel discovery from this study is that the chemical quality of plant residues, which serve as the source of DOC, determines the origin of the polysaccharides in DOC. This origin transitioned from plant-derived to microbial-derived as decomposition progressed. Importantly, the presented findings were the first of its kind based on a field experiment.
6. 题目: Taphonomic experiments on caridean shrimp elucidate the timing and influence of organic matter on diagenetic pyritization and sulfurization
Sulfur is an element particularly valuable for preserving organisms in the fossil record. On one hand, sulfurization (i.e. incorporation of sulfur into organic matter) forms macromolecules more likely to be preserved over geological timescales than their low-weight molecular precursors. On the other hand, pyrite (FeS2) is one of the main minerals replicating organisms and contributes to the exceptional preservation of soft tissues. However, the incomplete understanding of the processes, controls, timing and relation (competition, succession …) of these reactions may conceal critical biases within the fossil record, used to reconstruct past biodiversity and environment. In particular, organic matter (OM) is critical in these fossilization modes, but the roles of its composition and abundance remain to be better assessed, in particular for pyritization. Therefore, laboratory experiments were conducted on crustaceans' carcasses in mesocosms containing natural water and sediment. Tanks were treated with variable conditions to test the relative roles on preservation potential of oxic perturbation, thermal degradation of OM, and internal soft tissues, or lack thereof. Various bio-physico-chemical parameters and sulfur speciation were then monitored. The precipitation of a macroscopic amorphous iron monosulfide was observed after 100 days, both in the sediment and within carcasses; sulfurization of carcasses was detected within tens of days. A periodic aeration of the sediment where the carcasses were decayed impeded neither pyritization nor sulfurization while thermal degradation of OM did. Further, absence of internal soft tissues led solely to sulfurization, which suggests (i) that labile OM may be the factor driving the balance between pyritization and sulfurization and (ii) that internal soft tissues may promote pyritization through an organomineralization process, with sulfur-bearing organic ligands acting as nucleation sites. These results invite further experiments to test additional factors, in order to help refine environmental and taxonomical controls, and further investigation of fossil material, to evaluate the significance of sulfurization in the fossil record by searching sulfurized organisms.
7. 题目: The modified biochar from wheat straw by the combined composites of MnFe2O4 nanoparticles and chitosan Schiff base for enhanced removal of U(VI) ions from aqueous solutions
In the last few decades, U(VI) is a significant environmental threat. The innovative and environmentally friendly adsorbent materials for U(VI) removal were urgent. Preparation of the modified biochar from wheat straw by combined composites of MnFe2O4 nanoparticles and chitosan Schiff base (MnFe2O4@CsSB/BC) was characterized, and adsorption experiments were carried out to investigate the performance and interfacial mechanism of U(VI) removal. The results showed that MnFe2O4@CsSB/BC exhibited high adsorption capacity of U(VI) compared with BC. The adsorption process of U(VI) removal by MnFe2O4@CsSB/BC could be ascribed as pseudo-second-order model and Langmuir model. The maximum adsorption capacity of U(VI) removal by MnFe2O4@CsSB/BC reached 19.57 mg/g at pH4.0, 30 mg/L of U(VI), and 25 °C. The possible mechanism was a chemical adsorption process, and it mainly contained electrostatic attraction and surface complexation. Additionally, it also was an economic and environmental friendly adsorbent.
8. 题目: Impact of biochar on the antibiotic resistome and associated microbial functions in rhizosphere and bulk soil in water-saving and flooding irrigated paddy fields
The addition of biochar in paddies under the condition of water-saving irrigation can simultaneously achieve soil improvement and water conservation, but little is known about the role of these two regulations in mediating the fate of antibiotic resistome in paddy soils. Here, metagenomic analysis was conducted to investigate the effects and intrinsic mechanisms of biochar application and irrigation patterns on propagation of antibiotic resistance genes (ARGs) in paddy soils. The addition of biochar in paddy soil resulted in a reduction of approximately 1.32%–8.01% in the total absolute abundance of ARGs and 0.60%–22.09% in the numbers of ARG subtype. Compared with flooding irrigation, the numbers of detected ARG subtype were reduced by 1.60%–22.90%, but the total absolute abundance of ARGs increased by 0.06%–5.79% in water-saving irrigation paddy soils. Moreover, the combined treatments of flooding irrigation and biochar could significantly reduce the abundance of ARGs in paddy soils. The incremental antibiotic resistance in soil induced by water-saving irrigation was likewise mitigated by the addition of biochar. Correlation analyses indicated that, the differences in soil physicochemical properties under biochar addition or irrigation treatments contributed to the corresponding changes in the abundance of ARGs. Moreover, the variations of microbial community diversity, multidrug efflux abundance and transport system-related genes in paddy soil were also important for mediating the corresponding differences in the abundance of ARGs under the conditions of biochar addition or irrigation treatments. The findings of this study demonstrated the effectiveness of biochar application in mitigating antibiotic resistance in paddy soils. However, it also highlighted a potential concern relating to the elevated antibiotic resistance associated with water-saving irrigation in paddy fields. Consequently, these results contribute to a deeper comprehension of the environmental risks posed by ARGs in paddy soils.
9. 题目: Enhancing humification and microbial interactions during co-composting of pig manure and wine grape pomace: The role of biochar and Fe2O3
Phenol-rich wine grape pomace (WGP) improves the conversion of pig manure (PM) into humic acid (HA) during composting. However, the impact of using combinations of Fe2O3 and biochar known to promote compost maturation remains uncertain. This research explored the individual and combined influence of biochar and Fe2O3 during the co-composting of PM and WGP. The findings revealed that Fe2O3 boosts microbial network symbiosis (3233 links), augments the HA yield to 3.38 by promoting polysaccharide C–O stretching, and improves the germination index to 124.82 %. Limited microbial interactions, increased by biochar, resulted in a lower HA yield (2.50). However, the combination weakened the stretching of aromatics and quinones, which contribute to the formation of HA, resulting in reduced the humification to 2.73. In addition, Bacillus and Actinomadura were identified as pivotal factors affecting HA content. This study highlights Fe2O3 and biochar's roles in phenol-rich compost humification, but combined use reduces efficacy.
10. 题目: Dissolved organic carbon and dissolved oxygen determine the nitrogen removal rate constant in small water bodies of intensive agricultural region
Small water bodies are extensively distributed and play critical roles in nitrogen (N) removal, primarily through sediment denitrification. However, our comprehension understanding of the N removal rate constant in these systems, particularly within the first-order kinetics model, remains limited. To address this gap, a one-year field study was conducted to investigate the N removal rate and N removal rate constant in various small water bodies within a typical intensive agricultural area. We observed a decrease in N removal rates in the downstream direction, from ditches to downstream ponds and streams, potentially due to upstream water bodies receiving higher nutrient inputs. Moreover, our findings revealed that the N removal process in small water bodies generally follows a first-order kinetics reaction model, with the N removal rate constant varying from 0.22 d1 in streams and 0.48 d1 in vegetated ditches. Both water dissolved organic carbon (DOC) and dissolved oxygen (DO) concentrations collectively influenced the N removal rate constants. By leveraging the relationship between the N removal rate constant and these environmental factors, we further estimated that, on average, small water bodies remove 68% of the N loading in the Dongting Lake Basin. We recommend implementing artificial management measures, such as vegetation, to enhance the N removal capacity of water bodies. However, the caution must be exercised in measures like concrete linings in ditches, as they can hinder N removal. These findings not only offer methods for estimating N removal in small water bodies, but also provide an insight into enhancing the N removal capacity of these systems to effectively mitigate non-point N pollution.
11. 题目: Effects of aerosol water content and acidity on the light absorption of atmospheric humic-like substances in winter
Atmospheric humic-like substances (HULIS) could affect regional climate due to their strong light-absorbing capacity. Daily fine particulate matter (PM2.5) samples were collected from December 18, 2016 to January 8, 2017 at an urban site in Chongqing, Southwest China. The mean concentration of HULIS in terms of carbon (HULIS-C) was 6.4 ± 3.4 μg m−3, accounting for 72% of water-soluble organic carbon. The mass absorption efficiency at 365 nm (MAE365) and absorption Ångström index (AAE) of atmospheric HULIS were 2.8 ± 0.30 m2 g−1 C and 4.6 ± 0.37, respectively. Good correlations between the light absorption coefficients of HULIS at 365 nm (Abs365) and the concentrations of K+, elemental carbon, NO3−, and NH4+ were observed, with correlation coefficients higher than 0.83, indicating that biomass burning and secondary formation were potential sources of light-absorbing HULIS, as evidenced by abundant fluorescent components related to less-oxygenated HULIS. Comparing the changes in Abs365 values, concentrations of major water-soluble inorganic ions and carbonaceous compounds in PM2.5, and environmental factors during the clean and pollution periods, we found that extensive biomass burning during the pollution period contributed significantly to the increase of Abs365 values. Moreover, the aerosol pH during the pollution period was close to 4, and NO2 concentration and aerosol water content were about 1.6 and 2.7 times higher than those during the clean period, respectively, which were favorable to form secondary HULIS through aqueous phase reactions in the presence of high NOx, resulting in an evident increase in its light absorption. Knowledge generated from this study is critical for evaluating the regional radiative forcing of brown carbon in southwest China.
12. 题目: Molecular insight of dissolved organic matter and chlorinated disinfection by-products in reclaimed water during chlorination with permanganate preoxidation
Permanganate is a common preoxidant applied in water treatment to remove organic pollutants and to reduce the formation of disinfection by-products. However, the effect of permanganate preoxidation on the transformation of dissolved effluent organic matter (dEfOM) and on the formation of unknown chlorinated disinfection by-products (Cl-DBPs) during chlorination remains unknown at molecular level. In this work, the molecular changes of dEfOM during permanganate preoxidation and subsequent chlorination were characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Permanganate preoxidation was found to decrease the DBE (double bond equivalent) and AImod (modified aromaticity index) of the dEfOM. The identity and fate of over 400 unknown Cl-DBPs during KMnO4-chlorine treatment were investigated. Most Cl-DBPs and the precursors were found to be highly unsaturated aliphatic and phenolic compounds. The Cl-DBPs precursors with lower H/C and lower O/C were preferentially removed by permanganate preoxidation. Additionally, permanganate preoxidation decreased the number of unknown Cl-DBPs by 30% and intensity of unknown Cl-DBPs by 25%. One-chlorine-containing DBPs were the major Cl-DBPs and had more CH2 groups and higher DBEw than Cl-DBPs containing two and three chlorine atoms. 60% of the Cl-DBPs formation was attributed to substitution reactions (i.e., +Cl–H, +2Cl–2H, +3Cl–3H, +ClO–H, +Cl2O3–2H). This work provides detailed molecular level information on the efficacy of permanganate preoxidation on the control of overall Cl-DBPs formation during chlorination.
13. 题目: Effect of grass cover and abandonment on soil surface changes and soil properties in traditional vineyards in Vráble viticultural region in southwestern Slovakia
Land use transition, related to the extensification of management and agricultural abandonment, is a widespread phenomenon across European landscapes. In this study, we examined the effects of protective grassing and abandonment on soil protection and regeneration in traditional vineyards of the Vráble viticultural region, located in the temperate climate zone of central Europe. We analysed changes in the soil surface level, soil profile, and soil properties at various slope positions: shoulder, backslope, and footslope. Variability in the soil surface level was assessed using the poles height method, which was developed to quantify soil erosion and deposition. The results showed that both measures positively affected soil development. In the abandoned vineyard, the soil surface level increased by 0.72 mm yr−1 on the slope shoulder, 0.26 mm yr−1 on the backslope, and 3.58 mm yr−1 on the footslope. In contrast, the cultivated vineyard exhibited minimal changes in the slope shoulder (0.02 mm yr−1), erosion on the backslope (4.52 mm yr−1), and deposition on the footslope (19.30 mm yr−1). The vineyard that was hoed for half of the analysed period and then grassed showed erosion rates of 0.25 mm yr−1 on the shoulder, 1.48 mm yr−1 on the backslope, and deposition of 3.42 mm yr−1 on the footslope. All slope profiles showed evidence of erosion-accumulation processes resulting from past management practices without protective vegetation cover; however, the development of a new humic layer was observed in grassed and abandoned vineyard. Grass cover and abandonment positively influenced soil organic carbon (SOC) content, bulk density, and porosity.
14. 题目: Effect of acid-modified biochar coupled with alternate wetting and drying on P leaching, soil P retention and plant P uptake in paddy fields
H2SO4-modified biochar has been recognized as a means to achieve the advantages of carbon sequestration, and nitrogen loss reduction. However, little information is available on its effect on phosphorus (P) uptake, soil available P, and P leaching under alternate wetting and drying irrigation (IAWD). A split-plot experimental layout was carried out with two irrigation regimes (conventional continuous flooding, ICF, and alternate wetting and drying, IAWD) as main plots and three biochar additions (biochar-free control, B0, non-acidified biochar, B20, and acid-modified biochar, B20A) as subplots. Results indicated that IAWD decreased water percolation by 9.26%–14.74% and P leaching by 50.14%–106.64% and increased surface soil available P by 10.88–29.08%, resulting in 14.21–35.03% apparent phosphorus balance (APB) over the three years as compared with ICF. B20 produced a 6.23% lower grain yield in the 1st year and 5.06% and 11.02% higher yields in the 2nd and 3rd years, while B20A increased or tended to increase it throughout the three years. Both B20 and B20A significantly decreased total water percolation (9.68–28.37%), P leaching (18.26–152.00%), and increased soil available P (9.90–46.24%), dissolved P in surface soil (10.00–62.50%), and P uptake (4.31–49.71%), and thereafter enhanced apparent phosphorus balance (11.06–40.78%). Compared with B20, B20A achieved a better APB due to a 113% lower P leaching and 52.9% lower dissolved P at 60 cm soil profiles. IAWDB20A-M produced the highest APB, surface soil available and dissolved P, and the lowest P leaching, which increased grain yield, APB, surface soil available P, and dissolved P by 9.54%, 129.61%, and 53.19%, and decreased P leaching by 257% over ICFB0, respectively. Therefore, the use of H2SO4-modified biochar could produce higher grain yield with lower P leaching and higher APB for IAWD paddy systems, which is beneficial to enhancing plant P uptake, mitigating P leaching, and ensuring sustainable agricultural production.
15. 题目: The role of extracellular polymeric substances (EPS) in chemical-degradation of persistent organic pollutants in soil: A review
Persistent organic pollutants (POPs) in soil show high environmental risk due to their high toxicity and low biodegradability. Studies have demonstrated the degradation function of microbial extracellular polymeric substances (EPS) on POPs in various matrices. However, the degradation mechanisms and the factors that influence the process in soil have not been clearly illustrated. In this review, the characteristics of EPS were introduced and the possible mechanisms of EPS on degradation of organic pollutants (e.g., external electron transfer, photodegradation, and enzyme catalysis) were comprehensively discussed. In addition, the environmental conditions (e.g., UV, nutrients, and redox potential) that could influence the production and degradation-related active components of EPS were addressed. Moreover, the current approaches on the application of EPS in biotechnology were summarized. Further, the future perspectives of enhancement on degradation of POPs by regulating EPS were discussed. Overall, this review could provide a new thought on remediation of POPs by widely-existing EPS in soil with low-cost and minimized eco-disturbance.
16. 题目: Unveiling the spatial patterns and potential sources of black carbon in lake sediments from diverse developing areas in a representative mining and metallurgy region of Central China
Black carbon (BC) is a crucial component of organic carbon (OC), forming due to incomplete combustion of fossil fuels and biomass. Identifying the distribution characteristics and possible sources of BC is essential for managing carbonaceous pollution in freshwater lakes, especially in a mining and metallurgy region, where the metallurgical activities poses a significant threat to the aquatic ecological environment. This study examined the distribution characteristics and potential sources of BC in surface sediments from three distinct development areas.
Materials and methods
In January 2019, 32 surface sediment samples were collected, including 17 from Wang Lake (WL), five from Lianhua Lake (LL), and 10 from Mati Lake (ML). The BC measurements were conducted using the thermal-optical reflectance (TOR) method with quality control. Additionally, empty silver capsules were thermally treated and acidified as blank controls. Statistical analyses, correlation analyses, BC/OC ratios, and char/soot ratios were employed to examine the spatial distribution and potential sources of BC in the different lakes.
Results and discussion
The measured BC concentrations were 0.722 ± 0.339, 1.99 ± 1.90 and 0.748 ± 0.313 mg g−1 in WL, LL, and ML, respectively. Spatial analysis revealed elevated BC levels in LL, WL, and specific areas within WL. The char/soot ratios exhibited variability, with lower ratios in LL, higher ratios in ML, and variable ratios in WL. Correlation analysis and the relationship between BC/OC ratios and char/soot ratios indicated the influence of local biomass combustion deposition on BC accumulation in lake sediments. Furthermore, by comparing BC/OC ratios and char/soot ratios with local developmental characteristics, contributions from vehicular emissions and coal combustion deposition were observed in LL. The leakage of fossil fuels from boats may also contribute to the accumulation of carbon compounds in WL. Long-term metallurgical-related activities involving various sources of energy burning may account for the BC accumulation in ML, located in an industrial area.
Human activities significantly influenced the distribution and sources of BC in sediments from different types of lakes in areas with diverse developmental characteristics. These findings provide valuable insights for researchers and government authorities to understand the main contributions of BC to sediment and develop targeted policies for preventing and controlling carbonaceous pollution based on the unique developmental characteristics in similar mining areas worldwide.
17. 题目: Reduced arsenic availability in paddy soil through Fe-organic ligand complexation mediated by bamboo biochar
The reuse of arsenic (As)-contaminated paddy fields is a global challenge because long-term flooding would result in As release due to the reductive dissolution of iron minerals. Biochar amendment is a common and effective remediation technique for As-contaminated paddy soil. However, the literature is still lacking in systematic research on the function of biochar in controlling the complexation of released dissolved organic matter (DOM) and iron oxides and its synergistic impact on the availability of As in flooded paddy soil. In the present study, bamboo biochar was prepared at different pyrolysis temperatures (300, 450 and 600 °C), as BB300, BB450 and BB600. Four paddy soil treatments including BB300, BB450, BB600 applications (1% ratio, m/m, respectively) and control (CK, no biochar application) were set and incubated for 60 d in flooding condition. The results showed that As availability represented by adsorbed As species (A-As) was mitigated by BB450 amendment compared with CK. The amendment of BB450 in paddy soil facilitated the complexation of HCl extractable Fe(III)/(II) and DOM and formation of amorphous iron oxides (e.g. complexed Fe species). Moreover, the abundance of Geobacteraceae and Xanthomonadaceae, as common electroactive bacteria, was promoted in the BB450 treated paddy soil in comparison to CK, which assisted to form amorphous iron oxides. The formed amorphous iron oxides then facilitated the formation of ternary complex (As–Fe-DOM) with highly stability, which could be considered as a mechanism for As immobilization after biochar was applied to the flooding paddy soil. Thus, the synergistic effect between amorphous iron oxides and electroactive stains could make main contribution to the passivation of released As in paddy soil under long-term flooding condition. This study provided a new insight for As immobilization via regulating iron-organic ligand complexation amendment with biochar in flooding paddy soil.
18. 题目: Coagulation performance and mechanism of different hydrolyzed aluminum species for the removal of composite pollutants of polyethylene and humic acid
Microplastics (MPs) and natural organic matter (NOM) composite pollutants have become emerging contaminants with potential threats. Coagulation has been widely used to remove MPs and NOM, but the underlying mechanisms for the removal of MPs-NOM composite pollutants by hydrolyzed Al species remain unclear. Therefore, the coagulation performance and mechanism of AlCl3, polyaluminum chloride with basicity of 2.2 (PAC22), and PAC25 in treating polyethylene (PE), humic acid (HA), and PE-HA composite systems were systematically investigated. The results showed that in the single PE system, PAC25 with hexagonal clusters achieved the maximum removal (68.09%) (pH: 5, dosage: 0.5 mM) since adsorption bridging and sweeping effect were the main mechanisms for PE removal. The adsorption of HA on the PE surface enhanced its hydrophilicity and electrostatic repulsion, resulting in decreased PE removal. In the AlCl3-PE-HA system, the oligomeric Al first interacted with the -COOH and C-OH of HA through complexation, followed by the meso- and polymers of Al interacted with PE by electrostatic adsorption. The pre-formed medium polymeric Al species (Alb) and colloidal or solid Al species (Alc) in PAC22 and PAC25 formed complexes with the -OH and -COOH groups of HA, respectively, and then removed PE by adsorption bridging and sweeping effect.
Microplastics (MPs), as an emerging pollutant, can pose a threat to ecosystems and human health. And the environmental hazards of the composite contaminants formed by MPs and humic acid (HA) cannot be ignored as well. Aluminum (Al) salt coagulants are expected to be effective in the removal of MPs and MPs-HA. Elucidating the coagulation mechanism of MPs and MPs-HA by hydrolyzed Al species can provide theoretical guidance for the efficient removal of MPs-HA composite pollutants in actual water bodies.
19. 题目: Intercropping in rainfed Mediterranean olive groves contributes to improving soil quality and soil organic carbon storage
Given the current degradation problems that Mediterranean soils endure, the implementation of alley cropping in olive orchards has been suggested as a sustainable strategy to increase agricultural productivity and improve carbon storage and soil fertility. Therefore, the objective of this study was to evaluate in the short term (3 years) the effect of alley cropping with minimum tillage versus conventional tillage in a traditional rainfed olive grove on soil organic carbon, total nitrogen concentrations, and stocks. Changes in soil quality through a stratification index, and the success of the 4‰ strategy in these soils with this type of management were also evaluated. Three intercropping strategies were tested: Crocus sativus (D-S), Vicia sativa and Avena sativa in rotation (D-O), and Lavandula x intermedia (D-L), all with minimum tillage versus olive with conventional tillage without intercropping, which was used as a control. Intercropping increased soil organic carbon in topsoil (0–10 cm) by 41.1, 28.5, and 30.5% for D-S, D-O, and D-L, respectively, compared to conventional tillage. At a depth of 10–30 cm, the soil organic carbon and the soil organic carbon stock increased slightly, although significant differences were found only in D-L. In the diversified plots, total nitrogen did not vary. However, total nitrogen increased in olive with conventional tillage due to fertilisation. Concerning soil quality, no significant differences were observed when evaluating the soil carbon and nitrogen stratification index in any of the treatments. However, the implementation of intercropping reached the objectives set by the 4‰ initiative in these soils with an increase in soil carbon per hectare and per year of 80, 87.4, and 86.4% for D-S, D-O, and D-L, respectively. Therefore, based on these results, in the short term, intercropping treatment enhances carbon storage in these soils, effectively achieving the objectives of the 4‰ initiative.
20. 题目: Enhancing fluoride removal from wastewater using Al/Y amended sludge biochar
This study explored the potential of utilizing aluminum and yttrium amended (Al/Y amended) sewage sludge biochar (Al/Y-CSBC) for efficient fluoride removal from wastewater. The adsorption kinetics of fluoride on bimetallic modified Al/Y-CSBC followed the pseudo-second-order model, while the adsorption isotherm conformed to the Freundlich equation. Remarkably, the material exhibited excellent fluoride removal performance over a wide pH range, achieving a maximum adsorption capacity of 62.44 mg·g−1. Moreover, Al/Y-CSBC demonstrated exceptional reusability, maintaining 95% removal efficiency even after six regeneration cycles. The fluoride adsorption mechanism involved ion exchange, surface complexation, and electrostatic adsorption interactions. The activation and modification processes significantly increased the specific surface area of Al/Y-CSBC, leading to a high isoelectric point (pHpzc = 9.14). The incorporation of aluminum and yttrium metals exhibited a novel approach, enhancing the adsorption capacity for fluoride ions due to their strong affinity. Furthermore, the dispersing effect of biochar played a crucial role in improving defluoridation efficiency by enhancing accessibility to active sites. These findings substantiate the significant potential of Al/Y-CSBC for enhanced fluoride removal from wastewater.