1. 题目: Synergistic adsorption and degradation of sulfamethazine by tobacco stalk-derived activated biochar: Preparation, mechanism insight and application
Green preparation of high value-added products from biomass waste for environmental remediation has received significant attention. In this work, activated biochars were developed through two-step thermal process using tobacco stalk as the precursor. Textural properties of biochar can be effectively tuned by adjusting carbonization and activation parameters. An optimized biochar (700TS-1000-5), carbonized at 700 ℃ and then thermally activated at 1000 ℃ for 5 h, showed higher specific surface area (905.61 m2 g−1), rich porous structure, and abundant surface functional groups. 700TS-1000-5 showed excellent performance with a removal capacity of 99.37 mg g−1 for sulfamethazine (SMT) in 720 min, which was 4.3 times that of pristine biochar (700TS). And the SMT removal was high-efficient under normal environmental pH range. Adsorption and degradation simultaneously occurred during the whole process, which mainly relied on defects, functional groups, and ·OH radicals. Moreover, this typical sample showed outstanding recycling ability and effectiveness of column experiment. Compared with KOH-assisted chemical activation, thermal activation had minor environmental impact and lower preparation cost through environmental and economic assessment. These findings not only propose a simple protocol for high-value reuse of agricultural waste but also shed new light on applications of tobacco stalk-derived biochar.
2. 题目: Impact of rhizosphere priming on soil organic carbon dynamics: Insights from the perspective of carbon fractions
In the rhizosphere zone, soil microbes can be stimulated to increase the mineralization of soil organic matter (SOM), which is known as the rhizosphere priming effect (RPE). Soil organic carbon (SOC) can be separated into the coarse fraction (CF-SOC; fast turnover) and the fine fraction (FF-SOC; slow decomposition); however, the turnover of CF-SOC or FF-SOC during the rhizosphere processes remains unclear. Here, C4-plants (maize and sorghum) grew into C3-soil (paddy soil and lou soil), and the dynamic of the carbon fractions (CF-SOC and FF-SOC) and RPEs were monitored using the 13C natural abundance method during three plant growth stages. Positive RPEs were observed in most situations. There was a net SOC loss in both soils at the end of cultivation. The “new” plant-derived C can partially offset the SOC mineralization caused by rhizosphere priming. The formation of “new” FF-SOC was 1.51–60.20 times higher than that of “new” CF-SOC. Growing plants enhanced the sequestration of the “old” CF-SOC in comparison with the control. Moreover, the RPE strengthened the loss of “old” FF-SOC in the lou soil. The shift in microbial variables was found to strongly regulate SOC sequestration, which accounted for 38 % and 70 % of the variations in SOC in paddy and lou soil, respectively. The activated Gram-positive or Gram-negative bacteria were positively associated with soil CF-SOC and negatively correlated with soil “old” FF-SOC, indicating that stimulated rhizosphere bacteria enhanced the formation of “new” or “old” CF-SOC and the loss of “old” FF-SOC by co-metabolism and fast turnover during the priming process. Overall, our study provides insights into C fractions and microbial control of SOC turnover during the rhizosphere processes, which may have significant implications for better understanding the soil C cycle and increasing SOC sequestration.
3. 题目: Nonlinear effects of biochar on greenhouse gas emissions and soil microbial community composition under intensive vegetable production in South China
Biochar amendment in agroecosystems is proposed to mitigate the greenhouse (GHG) emissions and enhance multiple ecosystem services. However, it remains unclear whether and how various biochar amendment rates can influence soil microbial communities linking with GHG mitigation. In a two-year field experiment with five biochar amendment rates (0, 10, 20, 30 and 40 Mg ha−1), we determined cumulative GHG emissions, soil physiochemical properties and soil microbial community composition base one total phospholipid fatty acids (PLFA) under intensive vegetable production from Ultisols in southern China. Results showed that biochar amendment significantly decreased cumulative N2O emissions by 40–66 % during the whole study period (p < 0.01), whereas effects on CH4 emissions were inconsistent across the two study years. In addition, biochar amendment significantly decreased PLFAs and fungi/bacteria ratio by 4–31 % and 12–39 %, respectively. Annual global warming potential (GWP) was effectively reduced by biochar amendment, and random forest analysis showed that soil pH, C/N, humic acid (HA) and fungal PLFAs exhibited the highest mean predictor importance. The nonlinear correlations between the biochar amendment rate and GHG emissions mainly caused by soil pH, and the 20 Mg ha−1 biochar amendment rate was recommended because it produced the lowest GWP with the lowest economic costs. These findings demonstrated that various biochar amendment rates can differently alter GHG emissions and microbial properties under intensive vegetable production, which can provide new insights on optimal biochar amendment rates for GHG mitigation in agricultural production in China.
4. 题目: Advanced synergetic nitrogen removal of municipal wastewater using oxidation products of refractory organic matters in secondary effluent by biogenic manganese oxides as carbon source
Due to the high operational cost and secondary pollution of the conventional advanced nitrogen removal of municipal wastewater, a novel concept and technique of advanced synergetic nitrogen removal of partial-denitrification anammox and denitrification was proposed, which used the oxidation products of refractory organic matters in the secondary effluent of municipal wastewater treatment plant (MWWTP) by biogenic manganese oxides (BMOs) as carbon source. When the influent NH4+-N in the denitrifying filter was about 1.0, 2.0, 3.0, 4.0, 5.0 and 7.0 mg/L, total nitrogen (TN) in the effluent decreased from about 22 mg/L to 11.00, 7.85, 6.85, 5.20, 4.15 and 2.09 mg/L, and the corresponding removal rate was 49.15%, 64.82%, 69.40%, 76.70%, 81.36% and 90.58%, respectively. The proportional contribution of the partial-denitrification anammox pathway to the TN removal was 12.00%, 26.45%, 39.70%, 46.04%, 54.97% and 64.01%, and the actual CODcr consumption of removing 1 mg TN was 0.75, 1.43, 1.26, 1.17, 1.08 and 0.99 mg, respectively, which was much lower than the theoretical CODcr consumption of denitrification. Furthermore, CODcr in the effluent decreased to 8.12 mg/L with a removal rate of 72.40%, and the removed organic matters were mainly non-fluorescent organic matters. Kinds of denitrifying bacteria, anammox bacteria, hydrolytic bacteria and manganese oxidizing bacteria (MnOB) were identified in the denitrifying filter, which demonstrated that the advanced synergetic nitrogen removal was achieved. This novel technology presented the advantages of high efficiency of TN and CODcr removal, low operational cost and no secondary pollution.
5. 题目: Dissolved organic carbon export in a small, disturbed peat catchment: Insights from long-term, high-resolution, sensor-based monitoring
6. 题目: Characteristics of digested sludge-derived biochar for promoting methane production during anaerobic digestion of waste activated sludge
This study investigated a novel method for enhancing methane production during anaerobic digestion of waste activated sludge with digested sludge-derived biochar (DSBC). Using response surface methodology, the following process conditions for DSBC synthesis were optimized: heating rate = 13.23 °C/min, pyrolysis temperature = 516 °C, and heating time = 192 min. DSBC significantly enhanced the methane production by 48 % and improved key coenzyme activity that accelerated the bioconversion of organic matter while promoting the decomposition and transformation of volatile fatty acids. Consequently, the lag period of methane production was shortened to 4.89 days, while the average proportion of methane greatly increased to 73.22%. Thus, DSBC could facilitate efficient methanogenesis in the anaerobic system by promoting electron transfer between syntrophic partners through the charge–discharge cycle of surface oxygen-containing functional groups. The study provides a reference for the resource utilization of anaerobic sludge residues and efficient anaerobic methanogenesis from sludge.
7. 题目: Molecular complexity and diversity of persistent soil organic matter
Managing and increasing organic matter in soil requires greater understanding of the mechanisms driving its persistence through resistance to microbial decomposition. Conflicting evidence exists for whether persistent soil organic matter (SOM) is molecularly complex and diverse. As such, this study used a novel application of graph networks with pyrolysis-gas chromatography-mass spectrometry to quantify the complexity and diversity of persistent SOM, defined as SOM that persists through time (soil radiocarbon age) and soil depth. We analyzed soils from the Cooloola giant podzol chronosequence across a large gradient of soil depths (0–15 m) and SOM radiocarbon ages (modern to 19,000 years BP). We found that the most persistent SOM on this gradient was highly aromatic and had the lowest molecular complexity and diversity. By contrast, fresh surface SOM had higher molecular complexity and diversity, with high contributions of plant-derived lignins and polysaccharides. These findings indicate that persisting SOM declines in molecular complexity and diversity over geological timescales and soil depths, with aromatic SOM compounds persisting longer with mineral association.
8. 题目: Arbuscular mycorrhizal fungi mitigate earthworm-induced N2O emissions from upland soil in a rice-rotated wheat farming system
Earthworms are important for soil processes in arable cropping systems, and affect the development of arbuscular mycorrhizal fungi (AMF) which may combinely play a crucial role in soil nitrogen (N) cycling. However, the information is limited about their interaction on N2O emissions. A two-factorial microcosm field experiment was established to identify the interactive effects of earthworms and AMF on N2O emissions from a rice-rotated wheat field and explore its underlying mechanisms about nitrification and denitrification processes. The results showed that earthworm addition (+E) increased cumulative N2O emissions during the whole growth stage by 236.7 % compared with no earthworms (−E). Cumulative N2O emissions during the jointing and booting stages contributed to 58.7 % of that during the whole growth stage. Higher N2O emissions under +E were attributed to changes in soil organic carbon (SOC) and NH4+ concentration. SOC was positively correlated to gene abundances associated with N2O reduction (e.g., nosZ), and earthworm activity enhanced SOC mineralization and reduced SOC concentration, thus increasing N2O emissions. A negative correlation between NH4+ and N2O emissions, and lower NH4+ under +E indicated that earthworms enhanced nitrification intensity using NH4+ as substrates. Interestingly, AMF normal (+A) significantly decreased cumulative N2O emissions by 37.3 % compared with mycorrhizal suppression (−A) and the interaction with earthworms can further decreased N2O emissions by 37.0 % compared with -E-A (P < 0.05). This can be explained by higher NH4+, lower NO3− concentrations, and lower abundance of nitrification-associated genes (e.g., AOA and AOB) at the booting stage under +A, suggesting that AMF reduced N2O emissions mainly through lowering nitrification intensity. The results highlight that earthworms increase N2O emissions while AMF can mitigate earthworm-induced N2O emissions, and enhance our understanding on the soil N cycle in terms of N2O production in the presence of AMF and earthworms.
9. 题目: Aggregate-associated soil organic carbon fractions in subtropical soil undergoing vegetative restoration
10. 题目: Response of Arctic Black Carbon Contamination and Climate Forcing to Global Supply Chain Relocation
11. 题目: Differential effects of clay mineralogy on thermal maturation of sedimentary n-alkanes
Clay minerals serve as important catalysts for the degradation of a range of biomolecules during diagenesis, yet their effects are seldom considered when interpreting organic molecular and isotopic data in the context of paleoenvironmental reconstruction. We investigated the thermal maturation of immature sedimentary organic matter in the presence of two clay minerals (kaolinite and montmorillonite) using a series of laboratory-based anhydrous pyrolysis experiments. Organic matter was extracted from a modern terrestrial sediment, mixed with each clay mineral, and heated at 100–300 °C for up to 30 days – in this way, initial organic matter was identical in each system. Abundances, molecular distributions, and paired compound-specific stable isotopic compositions (δDn-alkane and δ13Cn-alkane) of n-alkanes were measured as a function of heating time. For both kaolinite and montmorillonite amended experiments, the shifts in molecular distributions are highly controlled by significant secondary production of n-alkanes from molecularly large lipid precursors, as evidenced by significant increases in the total amount of n-alkanes accompanying increased thermal maturation. Significant decreases in carbon preference index (CPI) are observed before minor decreases in average chain length (ACL), leading to behavior in CPI-ACL space that is fundamentally different from identical systems free of clay minerals. Furthermore, distinct distributions of secondary n-alkanes between the clay mineral systems indicate differential mechanisms and sites of precursor degradation. In the presence of clay minerals, δ13Cn-alkane of immature bituminous organics initially decreases with increasing thermal maturation, opposite most data reported from experimental alteration of relatively mature sedimentary matter. This shift is similarly driven by secondary production of n-alkanes, arising from kinetic fractionation associated with preferential cleavage of 12C12C bonds from parent molecules – the kinetics of this process vary per clay mineralogy but are controlled by the same process. Conversely, we see an enrichment in δDn-alkane with increasing maturation, indicating control of the two isotopic systems by separate mechanisms. Moreover, kaolinite and montmorillonite exhibit differential control on δDn-alkane, leading to separate domains in dual isotopic space. Overall, the changes in δ13Cn-alkane and δDn-alkane are relatively small over the timescales studied, even at temperatures as high as 300 °C (less than ~0.6–1‰ for δ13Cn-alkane and ~ 8–15‰ for δDn-alkane). Considering these factors on a geological timescale, variations in clay mineralogy through a buried sedimentary sequence may impart matrix effects on molecular and isotopic signatures that can bias interpretation of paleoenvironmental conditions.
12. 题目: Biochar inhibited hydrogen radical-induced Cd bioavailability in a paddy soil
Herein, hydrogen (H·) radical was observed as a new pathway to produce hydroxyl (OH·) radicals that promoted cadmium sulfide (CdS) dissolution and thus Cd solubility in paddy soils. In soil incubation experiments, the bioavailable Cd concentrations in flooded paddy soils were increased by 8.44 % as the soil was aerated for 3d. For the first time, the H· radical was observed in aerated soil sludge. The association of CdS dissolution with free radicals was thereafter confirmed in an electrolysis experiment. Both H· and OH· radicals in electrolyzed water were confirmed by the electron paramagnetic resonance analysis. In the system with CdS, water electrolysis increased soluble Cd2+ concentration by 60.92 times, which was compromised by 43.2 % when the radical scavenger was introduced. This confirmed the free radicals can lead to oxidative dissolution of CdS. The H· radical was generated in systems with fulvic acid or catechol irradiated by ultraviolet lights, indicating soil organic carbon could be an important precursor for H· and OH· radicals. Biochar application decreased soil DTPA-Cd by 22–56 % invoking mechanisms besides adsorption. First, biochar quenched radicals and reduced CdS dissolution by 23.6 % in electrolyzed water in which -C-OH of biochar was oxidized to CO. Second, biochar boosted Fe/S-reducing bacteria and thus compromised CdS dissolution, as affirmed by a reversal correlation between soil available Fe2+ and DTPA-Cd concentrations. A similar phenomenon occurred in Shewanella oneidensis MR-1-inoculated soils. This study provided new insights into the bioavailability of Cd and offered feasible measures to remediate Cd-contaminated paddy soils with biochars.
13. 题目: Improved Predictions of Dissolved Organic Carbon–Water Partitioning and Unveiling the Chemodiversity of Dissolved Organic Matter
14. 题目: Thermochemical upcycling of food waste into engineered biochar for energy and environmental applications: A critical review
Environmental issues caused by food waste are important concerns for human well-being and ecosystem health. Valorization of food waste into energy and carbon materials has been extensively investigated. Here, we reviewed the most recent advancements in the thermochemical conversion of food waste into engineered biochar. Synthesis routes and practical applications of the food waste-derived biochar was succinctly reviewed. Engineered biochar is a promising alternative for mitigating environmental pollution and alleviating energy crisis. The underlying relationships between engineered biochar properties and specific applications are still unclear, therefore, machine learning-aided engineered biochar design and process optimization was proposed. Moreover, before any industrial scale implementation, detailed assessments of the environmental benefits and economic feasibility must be conducted. In the context of carbon neutrality, thermochemical upcycling of food waste into engineered biochar for energy and environmental applications can significantly contribute to attaining sustainable food waste management, mitigating environmental pollution, and addressing the energy shortage crisis, and thus will eventually facilitate the fulfillment of United Nations Sustainable Development Goals (SDGs). Furthermore, the existing challenges in the practical valorization of food waste into engineered biochar are comprehensively discussed, and outlooks are proposed.
15. 题目: Variation in photochemical properties of dissolved black carbon during bio-transformation and iron mineral fractionation process
The excellent photochemical properties of dissolved black carbon (DBC) have been proven to be a significant contributor to the removal of organic pollutants in environment. However, the photochemical properties of DBC will inevitably be changed during biotic and abiotic processes. Herein, the structures and compositions of DBC during bio-transformation and goethite adsorption processes were comprehensively studied, and their corresponding photochemical properties were also evaluated. Bio-transformed DBC (B-DBC) contained more aromatic, high molecular weight, and phenolic substances compared with pristine DBC (P-DBC). The photodegradation of 17α-ethynylestradiol (EE2) was significantly promoted by B-DBC because of its superior capacity for producing 3DBC*. Moreover, the subsequent goethite fractionation selectively reduced the parts of components with high aromaticity and carboxylic functional groups in B-DBC. The interaction between B-DBC and goethite resulted in the release of Fe2+ into goethite-fractionated DBC (G-DBC), which induced the photodegradation mechanism of EE2 shifting from a single-electron transfer driven by 3DBC⁎ to the oxidation of •OH. This study provides valuable insights into the changes in photochemical behavior of DBC resulting from biotic or abiotic processes, and enhances our understanding of the role of DBC in the fate of organic pollutants.
16. 题目: Global modeling of lake-water indirect photochemistry based on the equivalent monochromatic wavelength approximation: The case of the triplet states of chromophoric dissolved organic matter
Chromophoric dissolved organic matter (CDOM) plays key role as photosensitizer in sunlit surface-water environments, and it is deeply involved in the photodegradation of contaminants. It has recently been shown that sunlight absorption by CDOM can be conveniently approximated based on its monochromatic absorption at 560 nm. Here we show that such an approximation allows for the assessment of CDOM photoreactions on a wide global scale and, particularly, in the latitude belt between 60°S and 60°N. Global lake databases are currently incomplete as far as water chemistry is concerned, but estimates of the content of organic matter are available. With such data it is possible to assess global steady-state concentrations of CDOM triplet states (3CDOM*), which are predicted to reach particularly high values at Nordic latitudes during summer, due to a combination of high sunlight irradiance and elevated content of organic matter. For the first time to our knowledge, we are able to model an indirect photochemistry process in inland waters around the globe. Implications are discussed for the phototransformation of a contaminant that is mainly degraded by reaction with 3CDOM* (clofibric acid, lipid regulator metabolite), and for the formation of known products on a wide geographic scale.
17. 题目: Effect of Arsenic on EPS Synthesis, Biofilm Formation, and Plant Growth-Promoting Abilities of the Endophytes Pseudomonas PD9R and Rahnella laticis PD12R
18. 题目: Natural ageing of biochar improves its benefits to soil Pb immobilization and reduction in soil phytotoxicity
Amendments are good tools for immobilizing metal(loid) and improving phytoremediation success. However, the amendment effect is variable and depends on multiple parameters, including amendment type and ageing. Such an ageing effect is rarely studied. Our study is one of the first focusing on how biochar storage affects its effect on soil properties and metal(loid) immobilization, when biochar was applied alone or in combination with green manure. To answer this, a 33-day pot incubation experiment was set up using contaminated soil, amended with two biochars (differing in ages: old (Bo) and new (Bn)) and/or two green manures (leaves of clover or poplar) and sown with Phaseolus vulgaris (bioindicator plant). Soil pore waters, plant growth and metal(loid) accumulation were evaluated. Biochar reduced soil acidity (Bn: + 0.75 pH unit, Bo: + 0.72 unit) and Pb mobility (Bn: − 42%, Bo: − 50%), while green manures acidified the soil (− 0.30 pH unit) and immobilized Pb only after 10 days (− 44%). All amendments reduced soil phytotoxicity. Moreover, the biochar stored at room temperature for a few years demonstrated better abilities to improve soil properties, particularly for Pb immobilization, than the biochar freshly prepared. Finally, as mixtures maturated, soil parameters changed until about ten days, then tended to stabilize. Therefore, it can be concluded that (1) biochar storage will affect its chemical properties and ameliorate its effects, (2) biochar can ameliorate soil properties and immobilize metal(loid)s, while green manures tended to have adverse effects at first, and (3) soil/amendment mixtures should be left to mature about two weeks before potential plant implementation.
19. 题目: Metal oxide modified biochars for fertile soil management: Effects on soil phosphorus transformation, enzyme activity, microbe community, and plant growth
Metal oxide modified biochars are increasingly being used for intensive agricultural soil remediation, but there has been limited research on their effects on soil phosphorus transformation, soil enzyme activity, microbe community and plant growth. Two highly-performance metal oxides biochars (FeAl-biochar and MgAl-biochar) were investigated for their effects on soil phosphorus availability, fractions, enzyme activity, microbe community and plant growth in two typical intensive fertile agricultural soils. Adding raw biochar to acidic soil increased NH4Cl–P content, while metal oxide biochar reduced NH4Cl–P content by binding to phosphorus. Original biochar slightly reduced Al–P content in lateritic red soil, while metal oxide biochar increased it. LBC and FBC significantly reduced Ca2–P and Ca8–P properties while improving Al–P and Fe–P, respectively. Inorganic phosphorus-solubilizing bacteria increased in abundance with biochar amendment in both soil types, and biochar addition affected soil pH and phosphorus fractions, leading to changes in bacterial growth and community structure. Biochar's microporous structure allowed it to adsorb phosphorus and aluminum ions, making them more available for plants and reducing leaching. In calcareous soils, biochar additions may dominantly increase the Ca (hydro)oxides bounded P or soluble P instead of Fe–P or Al–P through biotic pathways, favoring plant growth. The recommendations for using metal oxides biochar for fertile soil management include using LBC biochar for optimal performance in both P leaching reduction and plant growth promotion, with the mechanisms differing depending on soil type. This research highlights the potential of metal oxide modified biochars for improving soil fertility and reducing phosphorus leaching, with specific recommendations for their use in different soil types.
20. 题目: Formation mechanisms of nano-aluminum oxide-dissolved black carbon and their adsorption for norfloxacin and phenanthrene
Dissolved black carbon (DBC), the soluble fraction of biochar, could interact with inorganic minerals to form organo-mineral complex due to its abundant oxygen-containing functional groups, which will affect the adsorption of organic contaminants. In this study, we want to get the formation mechanisms of DBC-nano-aluminum oxide (n-Al2O3) complexes and their sorption mechanism difference for two specific contaminants, norfloxacin (NOR) and phenanthrene (PHE).
Materials and methods
The DBC-nano-aluminum oxide complexes (DBC-n-Al2O3) were synthesized via adsorption and labeled as OM2-1 to OM2-4, OM3-1 to OM3-4, and OM4-1 to OM4-4, respectively, according to the pyrolysis temperature and the increasing organic carbon content. The adsorption behavior of both n-Al2O3 and DBC-n-Al2O3 towards NOR and PHE was investigated. To examine the adsorption characteristics of organic pollutants by n-Al2O3 and DBC-n-Al2O3, the Freundlich model (FM) and the Polanyi–Mane model (PMM) are widely utilized. The DBC-n-Al2O3 samples prepared with different treatments were comprehensively characterized using elemental analysis, gas chromatography–mass spectrometry, and Fourier transform infrared spectroscopy.
Results and discussion
PHE adsorption by the complexes exceeds that of n-Al2O3 due to hydrophobic and π–π interactions between the PHE and the complexes. Conversely, NOR, which has functional groups (-COOH, -C = O, and -F) that can form hydrogen bonds with n-Al2O3, exhibits higher sorption on n-Al2O3 than the complexes. When organic C content is between 0.44 and 0.49, NOR’s adsorption by the complexes surpasses that of PHE, but this trend reverses when it is between 0.63 and 0.64. After screening for hydrophobic interactions via solubility, all the complexes show higher NOR adsorption than PHE, which could be attributed to hydrogen bonding and electron–donor–acceptor interactions (n–π and π–π) between NOR and the complexes.
We concluded that the hydrophobic and aromatic components of DBC selectively adsorb onto n-Al2O3 through hydrogen bonding as the primary mechanism for complex formation. Hydrophobic interaction and π–π interaction controlled the sorption of hydrophobic contaminants, while hydrogen bonding and electron–donor–acceptor interactions (n–π and π–π) were important for the sorption of hydrophilic contaminants by DBC-n-Al2O3 complexes. This study provides key theoretical data support for the NOR and PHE remediation in the real environment, and it also provides important information for the soil remediation by biochars in practical applications.