1. 题目: Integrative application of biochar and arbuscular mycorrhizal fungi for enhanced chromium resistance in Medicago sativa
Soil chromium (Cr) contamination has become an environmental problem of global concern. However, the joint effects of combined utilization of biochar and arbuscular mycorrhizal (AM) inoculum, which are considered as two promising remediation strategies of soil heavy metal pollutions, on plant Cr resistance are still poorly understood. In this study, a two-factor pot experiment was conducted to investigate how biochar and AM fungus Rhizophagus irregularis regulate Medicago sativa growth, physiological trait, nutrient and Cr uptake, relevant gene expressions, soil properties, and Cr speciation, independently or synergistically. The results showed that biochar notably decreased AM colonization, while biochar and AM fungus could simultaneously increase plant dry biomass. The greatest growth promotion was observed in mycorrhizal shoots at the highest biochar level (50 g/kg soil) by 91 times. Both biochar application and AM fungal inoculation enhanced plant photosynthesis and P nutrition, but the promoting effects of AM fungus on them were significantly greater than that of biochar. In addition, the combined application of biochar and AM fungus dramatically reduced shoot and root Cr concentrations by up to 92 % and 78 %, respectively, compared to the non-amended treatment. Meanwhile, down-regulated expressions were observed for metal chelating-related genes. Furthermore, Cr translocation from roots to shoots was reduced by both two soil amendments. Transcriptional levels of genes involved in reactive oxygen species and proline metabolisms were also regulated by biochar application and AM colonization, leading to alleviation of Cr phytotoxicity. Furthermore, AM fungal inoculation slightly elevated soil pH but decreased plant-available soil P, which was, by contrast, lifted by biochar addition. The combined application reduced soil acid-extractable Cr concentration by 40 %. This study provides new insights into comprehensively understanding of the mechanisms of biochar and AM combination on improving plant Cr tolerance.
2. 题目: Lipid Biosignatures from SO4-Rich Hypersaline Lakes of the Cariboo Plateau
3. 题目: Enhancing efficient reclaim of phosphorus from simulated urine by magnesium-functionalized biochar: Adsorption behaviors, molecular-level mechanistic explanations and its potential application
Magnesium-functionalized Magnolia grandiflora Linn leaf-derived biochar (MBC) capable of efficiently reclaiming phosphorus from urine was synthesized by slow co-pyrolysis. Four adsorption kinetic and seven adsorption isotherm models were fitted to the batch adsorption and desorption experimental data, and it was found that pseudo-first-order kinetic model and multilayer model with saturation best described the phosphate-phosphorus (PO43−-P) adsorption process by MBC. MBC and phosphorus-saturated MBC (P-MBC) were found to offer outstanding phosphorus adsorption and slow release properties, respectively. Based on material characterization, statistical physics, adsorption energy distribution and statistical thermodynamics, a multi-ionic, inclined orientation, entropy-driven spontaneous endothermic process of MBC on PO43−-P was proposed, involving physicochemical interactions (porous filling, electrostatic attraction, ligand exchange and surface precipitation). Further, seed germination and early seedling growth experiments proved that P-MBC can be used as a slow-release fertilizer. Overall, MBC offers prospective applications as an efficient phosphorus adsorbent and then as a slow-release fertilizer.
4. 题目: Environment and agricultural practices regulate enhanced biochar-induced soil carbon pools and crop yield: A meta-analysis
Using biochar in agriculture to enhance soil carbon storage and productivity has been recognized as an effective means of carbon sequestration. However, the effects on crop yield and soil carbon and nitrogen can vary depending on environmental conditions, field management, and biochar conditions. Thus, we conducted a meta-analysis to identify the factors contributing to these inconsistencies. We found that biochar application significantly increased soil organic carbon (SOC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), easily oxidized carbon (EOC), particulate organic carbon (POC), total nitrogen (TN), and the C:N ratio in topsoil (0–20 cm) and crop yields. Biochar was most effective in tropical regions, increasing SOC, Soil TN, and crop yield the most, with relatively moderate pyrolysis temperatures (550–650 °C) more conducive to SOC accumulation and relatively low pyrolysis temperatures (<350 °C) more conducive to increasing soil carbon components and crop yields. Biochar made from manure effectively increased soil carbon components and TN. Soil with low fertility (original SOC < 5 g kg−1; original TN < 0.6 g kg−1), coarse texture, and acidity (pH < 5.5) showed more effective results. However, biochar application rates should not be too high and should be combined with appropriate nitrogen fertilizer. And biochar application had long-term positive effects on soil carbon storage and crop yield. Overall, we recommend using small amounts of biochar with lower pyrolysis temperatures in soils with low fertility, coarse texture, and tropical regions for optimal economic and environmental benefits.
5. 题目: Humic acid plus manure increases the soil carbon pool by inhibiting salinity and alleviating the microbial resource limitation in saline soils
Fertilization strategies have been widely studied as an effective strategy to improve the structure and fertility of saline soils. However, the effect of the combination of different organic ameliorants on the soil carbon (C) pool is still not clear. We conducted a two-year field experiment to investigate the influences of organic ameliorants on soil organic C (SOC) and inorganic C (SIC) stocks, and enzymatic stoichiometry for both top and subsoil (i.e., 0–20 cm and 20–40 cm) in the semi-arid saline region of Western China. Compared to chemical fertilizer (CK) soils, the content and stock of total C and SOC at 0–40 cm soil layer under organic ameliorant (OM), humus acid plus OM (HA + OM), and biofertilizer plus OM (B + OM) were 9–40% higher, whilst the content and stock of SIC at 0–40 cm soil layer under HA + OM were 18% higher after two years. In addition, soil microorganisms were generally limited by phosphorus (P), and HA + OM reduced microbial P and nitrogen (N) limitations after two years application. Structural equation modeling showed that reduced microbial N and P limitation under HA + OM was mainly directly driven by the decrease in electrical conductivity (EC) content. Redundancy analysis and correlation analysis further confirmed that soil EC and microbial resource limitation were the main factors affecting soil C content. Furthermore, HA + OM promoted the positive regulation of SOC on SIC, which facilitated the formation of SIC content. The higher accumulation of SOC and SIC content under HA + OM were both beneficial to the enhancement of the total C stock in saline soil. Overall, our results provided an effective regime to improve the soil saline and microbial environments, and increase the potential for rapid enhancement of the C stock of saline soil in Northwest China.
6. 题目: Compositional changes of dissolved organic molecules along water flow and their influencing factors in the Three Gorges Reservoir
Molecular composition of dissolved organic matter (DOM) and its influencing factors in river reservoirs remains elusive. Here, molecular compositions of DOM, bacterial community structures, and water physiochemistry were investigated in the field and microcosm samples of the Three Gorges Reservoir (TGR). The results showed that DOM molecular compositions were significantly (R2 = 0.245, p < 0.001) correlated with bacterial community structures in the studied field samples, suggesting that bacteria may actively interact with DOM molecules. The molecular compositions of DOM in the studied field samples were significantly (p < 0.05) affected by the distance between the sample sites and the Three Gorges Dam and by bacterial groups of Actinobacteria and Alphaproteobacteria, suggesting that both hydrological and bacterial processes may contribute to the variation in DOM molecular composition in the TGR water. Furthermore, microcosm experiments demonstrated that both microbial and abiotic processes may transform and/or produce DOM in the TGR, thereby affecting DOM molecular composition. Microbial process increased the average aromaticity index and decreased the carbon number of DOM molecules with increasing incubation duration; whereas average oxygen number, double bond equivalent, and oxidation state of carbon of DOM molecules increased during the first 14 days of incubation and began to decrease thereafter. Taken together, this study expands our understanding of the impact of microbial process on the DOM molecular composition in reservoir ecosystems, and has great implications for carbon cycling in major rivers.
7. 题目: Factors regulating interaction among inorganic nitrogen and phosphorus species, plant uptake, and relevant cycling genes in a weakly alkaline soil treated with biochar and inorganic fertilizer
To shed light on how biochar affect the interaction between inorganic nitrogen (ammonium, nitrate and nitrite nitrogen: NH4+-N, NO3¯-N and NO2¯-N) and phosphorus species (calcium, iron and aluminum phosphorus: CaP, FeP and AlP) in soil and plant uptake of these nutrients, walnut shell (WS)- and corn cob (CC)-derived biochars (0.5 %, 1 %, 2 %, and 4 %, w/w) were added into a weakly alkaline soil and then Chinese cabbages were planted. The results showed that the changes in soil inorganic nitrogen were related to biochar feedstock, pyrolysis temperature and application rate. For soil under the active nitrification condition (dominant NO3¯-N), the significant decrease in NH4+-N/NO3¯-N ratio after biochar addition indicates the enhanced nitrification (excluding WS-derived biochars at 2 % and 4 %), which could be explained by the most positive response of ammonia-oxidizing archaeal amoA to biochar addition. The CC-derived biochar stronger enhanced soil nitrification. Addition 4 % of biochars significantly increased soil inorganic phosphorus and CC-derived biochars more effectively increased Ca2P than WS-derived biochars did. Biochars significantly decreased plant uptake of phosphorus, while generally had little influence on plant uptake of nitrogen. Interestingly, NO2¯-N in soil significantly positively correlated with total phosphorus in both soil and plant, while significantly negatively correlated with phoC, indicating that accumulation of NO2¯-N in soil to a certain extent facilitated plant uptake of phosphorus but inhibited phoC-haboring bacteria. The NO3¯-N in soil significantly positively correlated with Ca2P and Ca8P, while NH4+-N/NO3¯-N ratio significantly negatively correlated with Ca10P and FeP, indicating that the enhanced nitrification seemed to facilitate the change of phosphorus to easily available ones. This study will be helpful for figuring out how to use biochar scientifically and rationally to regulate inorganic nitrogen and phosphorus species in soil and plant uptake of these nutrients.
8. 题目: Preparation of two types plant biochars and application in soil quality improvement
Soil degradation is a global problem that endangers sustainable development. Biochar is a solid, stable, carbon-rich, and highly aromatic material prepared using plant feedstock with a rich pore structure, high specific surface area, and high capacity for holding water and nutrients. This study selected two typical plant resource raw materials, Spartina alterniflora (P. australis) and Spartina alterniflora (S. alterniflora), to prepare biochar at different temperatures, and then investigated the effects of different raw materials and preparation temperatures on the biochar's characteristics. After re-activation treatment, soil improvement experiments were conducted under different carbon application rates. The prepared biochar was alkaline, and contained abundant oxygen-containing functional groups and nutrients (including C, N, Ca, Na, and Mg). Biochar addition had significant effects on the soil microbial community and soil enzyme activity. Finally, by calculating the membership function and factor weights, the various physicochemical and biological properties of the soil were quantified in the form of soil quality indices. The results showed that biochar application had a significant promoting effect on soil quality, mainly through providing rich nutrient sources, enhancing the soil cation exchange capacity and therefore the nutrient effectiveness, and increasing the ability of soil to retain nutrients. The application of biochar (different types) has changed the original nutrient composition, microbial community, and enzyme activity of the soil, and under the combined action of these factors, the soil quality index (SQI) has been improved. This study provides a feasible soil fertility improvement strategy.
9. 题目: Occurrence of organic matter in argillaceous sediments and rocks and its geological significance: A review
The positive correlation between total organic carbon and specific surface area in sediments and mudstones implies the association between sedimentary organic matter (OM) and clay minerals. However, the traditional classification of OM, including insoluble kerogen and soluble OM (SOM), ignores the role of minerals, significantly limiting the understanding of the role of mineral-OM interactions in OM preservation and evolution. This paper reviews the mineral and OM characteristics and their relationship in argillaceous sediments and rocks and classifies sedimentary OM into three forms of occurrence, namely free SOM (FSOM), mineral-bound OM (MOM), and particulate OM (POM). FSOM, dominated by non-polar compounds, is physically adsorbed on the external surface of minerals or free in pores of different sizes, so it is susceptible to oxidation. MOM includes polar SOM and insoluble amorphous OM. The former is chemically adsorbed on the external surface, sheet edge and intercalated into interlayer space, and the latter is encapsulated in the clay microfabric. MOM is preserved by mineral adsorption, physical encapsulation, and degradation-recondensation, so it is very stable. POM is predominantly insoluble structured OM in the form of discrete particles and is preserved by selective preservation at the expense of chemical reactivity. The three forms of OM occurrence result from the synergistic operation of multiple preservation mechanisms, in which mineral-OM interactions dominate long-term OM preservation. Depending on environmental conditions, the change of mineral-OM interaction leads to the OM release or cracking, thereby promoting carbon cycling. Compared to traditional OM classifications, the new model of OM occurrence incorporates mineral protection mechanisms and provides a unifying principle linking inorganic and organic processes in OM preservation and evolution. OM preservation and evolution is essentially the process of mutual transformation of OM between different forms of occurrence, so this model is very useful for understanding carbon cycling and hydrocarbon generation and should be valued.
10. 题目: Rapid evaluation of organic and pyritic δ34S values in immature sedimentary rocks using a Rock-Eval 7S® coupled to MC-ICPMS
Sulfur isotopic values (δ34S) in sedimentary organic matter and pyrite provide essential information about the global S cycle. The measurement of δ34S values is commonly used to reconstruct paleo-environmental conditions of sediment deposition. In petroleum geochemistry, δ34S values are used to trace relationships between disparate elements of petroleum systems. However, the determination of organic and pyrite δ34S values requires a tedious and time-consuming (weeks) stepwise procedure. Here we used the latest version of the Rock-Eval® 7S analyzer, which can quantify different S-fractions in sedimentary rocks. We have coupled the Rock-Eval® pyrolysis cycle with a multi-collector inductively coupled plasma mass spectrometer (RE/MC-ICPMS). The analysis requires a small sample size (5 to 90 mg), and minimum sample preparation of acid treatment to avoid the carbonate effect on the pyrolyzed pyrite-S. The RE/MC-ICPMS system allows for measuring the pyrolysable organic-S and pyrite-S and directly determining δ34S values from a decarbonated rock. The new method was applied to a set of immature sedimentary rocks of various paleoenvironmental origins. The rapid analysis by the RE/MC-ICPMS, which takes only 20 min per sample, achieved an average precision of 0.5‰, for peaks above 5 nanomole of S. Accuracy was determined relative to a common wet chemistry method followed by an offline EA-IRMS analysis and reached an agreement of <1‰.
11. 题目: Effective removal and recovery of phosphorus using ZnAl-COOH-modified biochar via hydrogen bonds
The global community is facing the dual problem of water eutrophication and a shortage of phosphate rock resources. In this study, carboxylated ZnAl-hydroxide-modified biochar (LDH/PMA/BC) was synthesised to remove and recover phosphorus (P) from water through highly selective adsorption and desorption of P. The results of adsorption experiments indicated that LDH/PMA/BC has an high removal rate for low concentrations of P, and the maximum capacity for adsorption of P was 109 mg g−1. Furthermore, when a low concentration of P coexisted with a high concentration of competitive ions, LDH/PMA/BC could selectively adsorb P through hydrogen bonding, and its removal rate for P reached 99 %–100 % of its removal rate without competitive ions. In addition, LDH/PMA/BC maintained 85 %–93 % of its initial adsorption capacity in 10 adsorption–desorption cycles, and the P recovery rate reached 95 %. These results indicate the potential of LDH/PMA/BC as an adsorbent for removing and recovering P from wastewater.
12. 题目: Contribution of water erosion to organic carbon and total nitrogen loads in agricultural discharge from boreal mineral soils
While organic carbon (OC) in agricultural mineral soils is widely studied in terms of soil carbon sequestration and gaseous emissions, discharge-induced OC loss from soil is still poorly understood and estimations of boreal soil OC loads within water erosion are lacking. Loss of organic matter from arable soils is a concern for surface water quality, climate change and soil productivity. The main aim of this study was to quantify the role of water erosion in total OC and nitrogen (N) loads exported in agricultural discharge from boreal mineral soils under various cultivation practices. Surface water and subsurface drainage were collected near-continually over 2 years in two clayey and one sandy soil in Finland. Eroded sediment was mechanically separated by centrifugation from all discharge samples to detect sediment OC% and N% by dry-combustion method. Dissolved OC and N concentrations in selected discharge samples were measured with high-temperature catalytic oxidation of unfiltered supernatant. A multiple linear regression model was used to study the significant factors affecting dissolved, sediment and total OC loads. In the clayey soils, the sediment OC (2–24 kg ha−1 y−1) and N (0.2–1.1 kg ha−1 y−1) export accounted for up to 35 % and 20 % of the annual discharge-induced total loads of OC (19–85 kg ha−1) and N (2–8 kg ha−1), respectively. In the sandy soil, erosion was negligible and dissolved loads of 17–35 kg OC ha−1 y−1and 4–7 kg N ha−1 y−1 were detected. Subsurface drainage exported most of the sediment-associated OC and N loads from clayey soils. For the total OC loads, the distribution varied between the discharge routes, while the total N loads were mostly exported in subsurface drainage in both soil types. Sediment OC and N exports were related to soil plowing and discharge intensity, while dissolved OC loss was promoted by high surface soil OC%. Our results also indicated that a single cultivation practice may affect sediment and dissolved loads in opposite ways. These findings can be used to complement carbon budget estimations for mineral agricultural soils, and to assess soil management effects on terrestrial organic matter loading to boreal surface waters.
13. 题目: Assessing spatial variations in soil organic carbon and C:N ratio in Northeast China's black soil region: Insights from Landsat-9 satellite and crop growth information
Monitoring soil properties, especially soil organic carbon (SOC) and Carbon-to-Nitrogen (C:N) ratios, is vital for understanding degradation and developing black soil conservation strategies. Most soil mapping research has leveraged satellite imagery from limited bare-soil periods. The predictive accuracy using time-series images capturing crop growth is underexplored. Moreover, while the new Landsat-9 satellite surpasses Landsat-8, its use in soil mapping is mostly uncharted. In this study, we compared the performance of single-date bare soil imagery (Landsat-8, Landsat-9, and Sentinel-2) and multi-temporal images (Landsat-8 and Landsat-9 combined, and Sentinel-2) using three machine learning techniques (Boosted Regression Tree, BRT; Random Forest, RF; Extreme Gradient Boosting, XGBoost) for mapping SOC and C:N ratio in a typical Northeast China black soil cropland region. The results revealed that single-date Landsat-9 exhibited great potential for soil mapping with the optimal XGBoost model, improving the prediction accuracy (in terms of R2) of SOC and C:N ratio by 15.01% and 30.07%, respectively, compared to Landsat-8, while also delivering performance slightly inferior to single-date Sentinel-2. Moreover, predictors derived from multi-temporal images significantly outperformed those derived from single-date images. The XGBoost models that utilized multi-temporal Sentinel-2 predictors achieved the highest prediction accuracy for both SOC (R2 = 0.676, RMSE = 1.928 g/kg, MAE = 1.580 g/kg, RPD = 1.535) and C:N ratio (R2 = 0.713, RMSE = 0.585, MAE = 0.484, RPD = 1.718). Interestingly, the combination of Landsat-8 and Landsat-9 demonstrated similar prediction accuracy but lower uncertainties in SOC and C:N ratio mapping compared to multi-temporal Sentinel-2 images. In addition, a comparison of the contemporary prediction soil maps with historical soil data revealed a continual decrease in SOC content and C:N ratio, suggesting a concerning trajectory that is detrimental to organic matter accumulation. Overall, this study highlights the efficacy of Landsat-9 and multi-temporal imagery incorporating crop growth information in accurately predicting soil properties and assessing their spatial variability.
14. 题目: Soil carbon sequestration potential of cultivated lands and its controlling factors in China
Understanding soil organic carbon (SOC) stocks and carbon sequestration potential in cultivated lands can have significant benefit for mitigating climate change and emission reduction. However, there is currently a lack of spatially explicit information on this topic in China, and our understanding of the factors that influence both saturated SOC level (SOCS) and soil organic carbon density (SOCD) remains limited. This study predicted SOCS and SOCD of cultivated lands across mainland China based on point SOC measurements, and mapped its spatial distribution using environmental variables as predictors. Based on the differentiation between SOCS and SOCD, the soil organic carbon sequestration potentials (SOCP) of cultivated land were calculated. Boosted regression trees (BRT), random forest (RF), and support vector machine (SVM) were evaluated as prediction models, and the RF model presented the best performance in predicting SOCS and SOCD based on 10-fold cross-validation. A total of 991 topsoil (0–20 cm) SOC measurements and 12 environmental variables explaining topography, climate, organism, soil properties, and human activity were used as predictors in the model. Both SOCS and SOCD suggested higher SOC levels in northeast China and lower levels in central China. The cultivated lands in China had the potential to sequester about 2.13 ± 0.96 kg m−2 (3.25 Pg) SOC in the top 20 cm soil depth. Northeastern China had the largest SOCP followed by Northern China, and Southwestern China had the lowest SOCP. The primary environmental variables that affected the spatial variation of SOCS were mean annual temperature, followed by clay content and normalized difference vegetation index (NDVI). The assessment and mapping of SOCP in China's cultivated lands holds significance importance as it can provide valuable insights to policymakers and researchers about SOCP, and aid in formulating climate change mitigation strategies.
15. 题目: A review of the next-generation biochar production from waste biomass for material applications
The development of carbonaceous materials such as biochar has triggered a hot spot in materials application. Carbon material derived from biomass could be a vital platform for energy storage and conversion. Biochar-based materials deliver a novel approach to deal with the current energy-related challenges. To design and utilize the maximum potential of biochar for environmentally sustainable applications, it is crucial to understand the recent progress and advancement in molecular structures of biochar to discover a new possible field to simplify structural application networks. However, most of the studies demonstrated the application of biochar in the form of soil enhancers and bio-adsorbents, reducing soil emissions of greenhouse gases and as fertilizers. The present review on biochar highlighted the application of biochar-based materials in various energy storage and conversion sectors, comprising different types of conversion technologies, biochar formation mechanisms, modification techniques on biochar surface chemistry and its functionality, catalysts, biochar application in energy storage gadgets such as supercapacitors and nanotubes, bio-based composite materials and inorganic based composites materials. Finally, this review addressed some vital outlooks on the prospect of the functionalization and best utilization of biochar-supported materials in numerous energy storage and conversion fields. After reviewing the literature, it was directed that advanced and in-depth research is essential for structural analysis and separation, considering the macroscopic and microscopic evidence of the formed structural design of biochar for specific applications.
16. 题目: Microalgae-based biochar production and applications: A comprehensive review
Biochar, a solid carbonaceous substance synthesized from the thermochemical degradation of biomass, holds significant potential in addressing global challenges such as soil degradation, environmental pollution, and climate change. Its potential as a carbon sequestration agent, together with its versatile applications in soil amendments, pollutant adsorption, and biofuel production, has garnered attention. On the other hand, microalgae, with their outstanding photosynthetic efficiency, adaptability, and ability to accumulate carbohydrates and lipids, have demonstrated potential as emerging feedstock for biochar production. However, despite the significant potential of microalgal biochar, our current understanding of its various aspects, such as the influence of parameters, chemical modifications, and applications, remains limited. Therefore, this review aims to provide a comprehensive analysis of microalgae-based biochar, covering topics such as production techniques, pollutant removal, catalytic applications, soil amendments, and synthesis of carbon quantum dots to bridge the existing knowledge gap in this field.
17. 题目: Insight into the pathways of biochar/smectite-induced humification during chicken manure composting
As representative organic and inorganic additives, both biochar and smectite exhibit an excellent capacity to improve humification efficiency during composting. Nevertheless, the mechanisms underlying biochar/smectite-induced compost humification have still not been fully explored from the perspective of overall organic substances. In this study, three composting treatments were performed as follows: 10 % biochar-amended composting, 10 % smectite-amended composting and natural composting without any additive. UV–visible parameters and synchronous hetero two-dimensional correlation spectra showed that biochar accelerated dissolved organic matter (DOM) complications, unsaturation and aromatization. For example, biochar promoted the C2 and simple C3 peaks to convert into a sophisticated C3/360 peak. However, the effect of smectite was negligible in complicating the DOM structure. Both biochar and smectite displayed an invigorating role in promoting humic substance (HS) formation. The strengthened relations between bacterial richness and physicochemical indicators and HS fractions might contribute to the positive action of biochar/smectite on HS synthesis. Network analysis showed that both bacterial functional omnipotence and specialization in response to the addition of catalysts may contribute to compost humification. The chemical pathway involved in DOM humification was intensified by enhancing the role of pH in biochar composting and weakening the degradation of unsaturated aromatic compounds of DOM with smectite addition. These findings benefit the practical application of biochar/smectite in promoting composting efficiency.
18. 题目: Influence of biochar produced from negative pressure-induced carbonization on transformation of potentially toxic metal(loid)s concerning plant physiological characteristics in industrially contaminated soil
Soil contamination and its subsequent impact on the food chain is a pressing challenge in the present day. The application of biochar has demonstrated a significant and positive effect on soil health, thereby enhancing plant growth and development. However, the application of biochar (BC) produced from negative pressure-induced carbonization to mitigate metal(loid) contamination is a new strategy that has been studied in current research. Results depicted that the application of biochar derived from the negative pressure carbonization (vacuum-assisted biochar (VBC) has a significant (p ≤ 0.05) positive impact on plant growth and physiological characteristics by influencing immobilization and speciation of metal(loid) in the soil system. Moreover, the interactive effect of VBC on physiological characteristics (photosynthesis, gas exchange, and chlorophyll contents) and antioxidant activities of maize (Zea mays L.) was significantly (p ≤ 0.05) positive by confining the translocation and movement of metal(loid)s to the aerial part of the maize plant. X-ray diffraction (XRD) provided information on the structural and chemical changes induced by the VBC-500 °C explaining metal(loid) adsorption onto mineral surfaces and complexation that can affect their mobility, availability, and toxicity in the contaminated soil. Fourier transform infrared spectroscopy (FTIR) further provided a more detailed understanding of the metal(loid)s and biochar complexation mechanisms influenced by VBC-based functional groups –OH, C-Hn, –COOH, CO, C–O–C, CC, C–O, C–H, OH, and C–C in the binding process. These results suggest that the application of biochar prepared at 500 °C under negative pressure-induced carbonization conditions to the soil is the most efficient way to reduce the uptake and transfer of metal(loid)s by influencing their mobility and availability in the soil-plant system.
19. 题目: Profile and nano-scale distribution of soil organic carbon for upland and paddy soils from an alluvial plain in South China
Understanding the heterogeneous distribution of soil organic carbon (C) (SOC) in different soil environments is essential for predicting SOC preservation. However, SOC distribution differs in profile scales and molecular levels in various farmland soils, making it challenging to elucidate the environmental behaviors of SOC. In the present study, upland and paddy soil samples were both collected at different depths (0–100 cm) from an alluvial plain in the Pearl River Delta of South China. Wet chemistry experiments coupled with 13C-nuclear magnetic resonance (NMR) and spherical aberration correction scanning transmission electron microscopy (Cs-STEM) were used to determine the vertical distribution, chemical composition, and nano-scale sequestration mechanisms of SOC in upland and paddy soils. SOC content for upland soil, which was highest at the depth of 0–20 cm (6.98 ± 0.34 g·kg−1), decreased with increasing soil depth, while that of paddy soil had the highest content at a depth of 80–100 cm (86.66 ± 5.26 g·kg−1). Statistical analysis revealed that mineral-associated organic C (MAOC) in the upland soil and particulate organic C (POC) in the paddy soil were the major C fractions that were related to SOC content. Further analysis of NMR spectra showed that the molecular composition of upland SOC differs vertically, while the molecular composition and proportion of organic C in paddy soil varied with soil depth. Cs-STEM results revealed that the relative percentage of carboxyl C decreased from 0 to 20 cm (42.1%) to 80–100 cm (28.8%) with an increase in aromatic C from 7.7 to 27.2% for the upland soil, while the four C species showed similar abundance for paddy soil at different depths, consistent with the NMR results. Overall, the upland SOC was not as easily mineralized as that of paddy soil due to a lower percentage of easily oxidized carbon, higher percentage of MAOC, and higher decomposition degree. The results of this study would enrich our quantitative understanding of the profile distribution and chemical diversity of SOC from macro to micro scales in the alluvial plain from South China, and provide insights into C preservation in natural soils.
20. 题目: Facilitated Mechanism of Biological Vaterite Stability Mediated by Bacillus velezensis and Its Secretions