21. 题目: Understanding drivers of the spatial variability of soil organic carbon in China's terrestrial ecosystems
22. 题目: Drivers of microbially and plant-derived carbon in topsoil and subsoil
23. 题目: Multiple roles of humic acid in the photolysis of sulfamethoxazole: Kinetics and mechanism
24. 题目: Aged biochar for simultaneous removal of Pb and Cd from aqueous solutions: Method and mechanism
In this study, we prepared maize stover biochar and used artificial simulated aging to prepare three types of aged biochar. The effects of aging on the adsorption capacity of Pb and Cd of biochar were studied. It was found that the pH, ash, and aromaticity of the aged biochar decreased compared to fresh maize straw biochar. On the contrary, the polarity, oxygenated functional groups, specific surface area, and average pore size of the aged biochar increased. The sorption behavior of Pb and Cd on biochar can be well explained by quasi-second-order kinetics and the Langmuir equation. The maximum adsorption of Pb in the single metal system was CBC-N (74.401 mg g−1)>CBC (72.959 mg g−1)>CBC-H (69.421 mg g−1)>CBC-F (66.460 mg g−1), the maximum adsorption of Cd was CBC-N (52.983 mg g−1)> CBC-H (52.728 mg g−1) > CBC-F (50.692 mg g−1) > CBC (45.966 mg g−1). The adsorption of both Pb and Cd by biochar is lower in the binary metal system than in the single metal system, implying a competitive relationship and that biochar is more selective for Pb than Cd. The mechanisms for removing Pb and Cd from solution by aged biochar consist mainly of pore filling, electrostatic adsorption, ion exchange, mineral precipitation, interaction, and surface complexation. This paper demonstrates that aged biochar is an ideal adsorbent but that environmental changes and pollutant types should be considered in practical applications.
25. 题目: Discriminative Behavior of Cyclodextrin Polymers against Dissolved Organic Matter: Role of Cavity Size and Sorbate Properties
26. 题目: Spatial-temporal variation of soil organic matter decomposition potential in China
Soil organic matter decomposition is an essential process of the ecosystem biogeochemical cycle. However, the comprehension of soil organic matter decomposition mechanisms at a large-scale level remains relatively inadequate, especially due to the high variability in organic matter quality, which poses challenges for standardized analysis of decomposition. Therefore, in this study, standardized cotton strips (to represent cellulose) and wooden sticks (to represent lignin) were used to conduct field research on the decomposition potential of soil organic matter, comparing the mass loss of these standardized materials across 23 sites situated in different climate types in China. After 6 months of incubation, the decomposition rate of both substrates displayed an increasing trend from north to south and a decreasing trend from east to west, driven by variations in temperature and precipitation at a large scale. However, the decomposition pattern of wooden sticks along the latitude exhibited a reversal during summer, with a positive correlation between mass loss per unit temperature and latitude, possibly attributable to reduced constraints on decomposer activity at high latitudes in summer. These results suggest that the decomposition ability of decomposers is more powerful at high latitudes compared with the decomposers at low latitudes. Random forest analysis showed that decomposers, soil conditions and climate had significant effects on the decomposition of standardized organic matter at the large-scale. Notably, as decomposition progressed, the relative influence of the decomposers on the cotton strips mass loss significantly increased, while for wooden sticks, the relative influence of climate significantly increased. In summary, this study provides crucial evidence for the spatial characteristics and temporal dynamics of soil organic matter decomposition in large-scale patterns.
27. 题目: The environmental transformation mechanism of the coal- and oil shale-bearing interval in the Eocene Dalianhe Formation, Yilan Basin, Northeast China
Assemblages of multiple organic matter (OM)-related sedimentary energy systems are common in the Eocene nonmarine basins of Northeast China. During the Middle Eocene Climatic Optimum, oil shale developed in large quantities in the Yilan Basin. Numerous scientific papers have concentrated on the sedimentary cycle and industrial quality of the coal- and oil shale-bearing intervals, whereas few studies have studied the genetic environmental transformation mechanism of the coal and oil shale deposits. The Dalianhe Formation cover thick oil shale member and coal unit, which is a natural archive for studying the environmental evolution of lake swamp systems. In the present paper, the thermal maturity of organic matter (OM), oil shale industrial quality, coal rank, source of OM and paleoenvironmental conditions associated with OM accumulation in the Yilan Basin are investigated through bulk geochemical analyses, organic maceral analyses and biomarker composition analyses. The coal in the Yilan Basin is classified as subbituminous coal with high total organic carbon (TOC) values, high oil yields, low ash yields, and type II OM. The quality of the low-maturity oil shale in the Coal-Bearing Member is better than that in the Oil Shale Member. The oil shale in the Yilan Basin has type I-II OM and relatively high oil yields, which corresponds to the considerable content of liptinite with a predominantly alginite composition. Based on the higher Pr/pH values, coal was deposited under oxic- dysoxic conditions, and the OM in the coal mainly originated from terrestrial plants, whereas the oil shale accumulated in a dysoxic environment with lower Pr/pH values, and featured mixed OM sources, including terrestrial plants and low aquatic organisms. Affected by lake level fluctuations and wide peat swamping, the thickest and highest-quality coal and oil shale developed in swamps under a dysoxic–oxic water column in freshwater environments. Subsequently, the lake basin expanded rapidly, and the sedimentary environment changed to a dysoxic–oxic semideep–deep lake, in which extremely thick mudstone and a large amount of inferior oil shale with low oil yields accumulated under the influence of gravity flows. The basin continued to rapidly subside, the water column became anoxic–dysoxic, and the deposition of mudstone, siltstone and fine sandstone predominated.
28. 题目: Biochar with nanoparticle incorporation and pore engineering enables enhanced heavy metals removal
Biochar is a desirable candidate for environment remediation of heavy metals in water due to wide availability and environmental-friendliness. In practical application, however, biochar suffers from inferior adsorption capacity owing to poor surface properties and limited pore structure. Herein, a combined strategy of nanoparticle incorporation and pore engineering was proposed to synthesize KOH activated porous biochar embedded MgO composite (K-MgO-RB) derived from waste ramie. Specifically, KOH as the chemical activator developed regular porous structures, which not only facilitated the increase in surface area and the MgO incorporation, but also effectively suppressed the aggregation of MgO nanoparticles due to the nanoconfinement effect. Thanks to the favorable nanostructures and incorporation of nano-MgO, K-MgO-RB presented superior adsorption capacities for Pb2+ (1276.46 mg/g) and Cd2+ (861.82 mg/g), which was approximately 100 and 19 times higher than those of the pure RB, respectively. The adsorption mechanism study indicated that electrostatic effect, precipitation, ion exchange, and cation-π electrons complexation were the dominant adsorption driving force of Pb2+ and Cd2+. Further, outstanding dynamic adsorption performance of 3480 mL (174 BV) for Pb2+ and 2520 mL (126 BV) for Cd2+ in fixed-bed column experiment, exceptional reusability as well as low economic cost demonstrated the excellent potential of K-MgO-RB for practical application.
29. 题目: Importance of inner-sphere P-O-Fe bonds in natural and synthetic mineral-organic associations
Sorption of organic molecules on mineral surfaces can occur through several binding mechanisms of varying strength. Here, we investigated the importance of inner-sphere P-O-Fe bonds in synthetic and natural mineral-organic associations. Natural organic matter such as water extracted soil organic matter (WESOM) and extracellular polymeric substances (EPS) from liquid bacterial cultures were adsorbed to goethite and examined by FTIR spectroscopy and P K-edge NEXAFS spectroscopy. Natural particles from a Bg soil horizon (Gleysol) were subjected to X-ray fluorescence (XRF) mapping, NanoSIMS imaging, and NEXAFS spectro-microscopy at the P K-edge. Inner-sphere P-O-Fe bonds were identified for both, adsorbed EPS extracts and adsorbed WESOMs. Characteristic infrared peaks for P-O-Fe stretching vibrations are present but cannot unambiguously be interpreted due to possible interferences with mono- and polysaccharides. For the Bg horizon, P was only found on Fe oxides, covering the entire surface at different concentrations, but not on clay minerals. Linear combination fitting of NEXAFS spectra indicates that this adsorbed P is mainly a mixture of orthophosphate and organic P compounds. By combining atomic force microscopy (AFM) images with STXM-generated C and Fe distribution maps, we show that the Fe oxide surfaces were fully coated with organic matter. In contrast, clay minerals revealed a much lower C signal. The C NEXAFS spectra taken on the Fe oxides had a substantial contribution of carboxylic C, aliphatic C, and O-alkyl C, which is a composition clearly different from pure adsorbed EPS or aromatic-rich lignin-derived compounds. Our data show that inner-sphere P-O-Fe bonds are important for the association of Fe oxides with soil organic matter. In the Bg horizon, carboxyl groups and orthophosphate compete with the organic P compounds for adsorption sites.
30. 题目: Effects of Cr(VI) oxyanion, humic acid and solution chemistry on the aggregation and colloidal stability of green synthesized chlorapatite nanoparticles
Aggregation is a crucial process determining the fate, mobility and ecological risks of nanomaterials. Chlorapatite nanoparticles (nClAP) exhibit widely applications in environmental remediation and consequently will inevitably enter aquatic systems. However, the aggregation characteristics of nClAP are still mostly uncovered. This study investigated the aggregation kinetics and colloidal stability of nClAP as a function of pH, humic acid (HA), Cr(VI) oxyanions, monovalent and divalent electrolytes. Results showed that pH values from 5 to 9 had a notable impact on the aqueous behaviors of nClAP. The addition of HA made the zeta potential (ZP) of nClAP more negative and thus enhanced nClAP stability through electrostatic and steric effects. Similarly, the adsorption of Cr(VI) on the surface of nClAP created a physical barrier and negative charge, improving the stability of nClAP by inducing steric force. Lower ZP and hydrodynamic diameter (HDD) reflected that the enhanced stability of nClAP by HA was more significant than Cr(VI). In comparison, the presence of Ca2+ ions were more effective than monovalent Na + ions in promoting the aggregation of nClAP. The classical DLVO theory incorporating the steric repulsion were used to interpret the aggregation and dispersion of nClAP, making it was easier to overcome energy barriers and agglomerate. This study provides new mechanistic insights which could help better understand the effects of Cr(VI) oxyanions and HA on nClAP's colloidal stability.
31. 题目: Soil aggregate-associated organic carbon mineralization and its driving factors in rhizosphere soil
Understanding the determinants of soil carbon mineralization at both the aggregate and rhizosphere levels is crucial for providing precise feedback on climate change. However, the specific patterns and relative contributions of rhizosphere effects on carbon mineralization at the aggregate scale remain unclear. To address this, we conducted an incubation experiment to examine the impact of warming on soil carbon mineralization. We also assessed variations in microbial activities and soil properties across different aggregates in both rhizosphere and non-rhizosphere soils, while exploring how the rhizosphere effects modulated the response of soil respiration to warming. Our findings revealed that rhizosphere soil provides a favorable environment for microbial activities through increased nutrient input and aggregate stability, leading to significant increases in microbial biomass and enzyme activity, thus promoting soil carbon mineralization. Moreover, the spatial heterogeneity of soil aggregates contributes to the differentiation and diversity of microbial community distribution, which further enhances the diversification of carbon mineralization at the aggregate level. Notably, macroaggregates play a significant role in soil carbon flux, making a substantial contribution to carbon turnover in the ecosystem. The partial least squares (PLS) path analysis indicated that the rhizosphere positively increased the contributions of soil properties and microbial variables to the overall amount of soil cumulative mineralization, with soil nutrients playing a crucial role among these factors. These findings highlight the complex regulatory role of substrate quality in soil carbon mineralization dynamics at the aggregate scale, underscoring its far-reaching implications for accurately predicting the feedback to climate change in soil carbon mineralization.
32. 题目: Differential impacts of sewage sludge and biochar on phosphorus-related processes: An imaging study of the rhizosphere
Recycling of phosphorus (P) from waste streams in agriculture is essential to reduce the negative environmental effects of surplus P and the unsustainable mining of geological P resources. Sewage sludge (SS) is an important P source; however, several issues are associated with the handling and application of SS in agriculture. Thus, post-treatments such as pyrolysis of SS into biochar (BC) could address some of these issues. Here we elucidate how patches of SS in soil interact with the living roots of wheat and affect important P-related rhizosphere processes compared to their BC counterparts. Wheat plants were grown in rhizoboxes with sandy loam soil, and 1 cm Ø patches with either SS or BC placed 10 cm below the seed. A negative control (CK) was included. Planar optode pH sensors were used to visualize spatiotemporal pH changes during 40 days of plant growth, diffusive gradients in thin films (DGT) were applied to map labile P, and zymography was used to visualize the spatial distribution of acid (ACP) and alkaline (ALP) phosphatase activity. In addition, bulk soil measurements of available P, pH, and ACP activity were conducted. Finally, the relative abundance of bacterial P-cycling genes (phoD, phoX, phnK) was determined in the patch area rhizosphere. Labile P was only observed in the area of the SS patches, and SS further triggered root proliferation and increased the activity of ACP and ALP in interaction with the roots. In contrast, BC seemed to be inert, had no visible effect on root growth, and even reduced ACP and ALP activity in the patch area. Furthermore, there was a lower relative abundance of phoD and phnK genes in the BC rhizosphere compared to the CK. Hence, optimization of BC properties is needed to increase the short-term efficiency of BC from SS as a P fertilizer.
33. 题目: Eco-Corona Formation on Plastics: Adsorption of Dissolved Organic Matter to Pristine and Photochemically Weathered Polymer Surfaces
34. 题目: Assessment of the straw and biochar application on greenhouse gas emissions and yield in paddy fields under intermittent and controlled irrigation patterns
Water-saving irrigation and straw and biochar application are common agronomic practices in rice production, and their profound impact on greenhouse gas (GHG) emissions from paddy soils cannot be ignored. A three-year field experiment was conducted in typical paddy fields in the subtropical region of eastern China. The methane (CH4) and nitrous oxide (N2O) emissions with straw or biochar application under intermittent irrigation (II) and controlled irrigation (CI) patterns were systematically assessed, and relevant soil physicochemical properties were measured to clarify the internal linking mechanisms. Five treatments were established: conventional flooding as the control group (CG), intermittent irrigation + straw (II + S), intermittent irrigation + biochar (II + B), controlled irrigation + straw (CI + S), and controlled irrigation + biochar (CI + B). The cumulative CH4 emissions with II + S, II + B, CI + S, and CI + B were reduced by 11.2%, 33.2%, 14.1%, and 40.3%, respectively； while the cumulative N2O emissions increased by 20.2%, 5.8%, 13.6%, and 1.2%, respectively (three-year average). Each treatment significantly reduced the global warming potential (GWP) by 10.1–44.8%, and increased rice grain yield by 7.9–13.3%, significantly reducing the greenhouse gas emission intensity (GHGI) by 16.7–46.7%. With II and CI, straw or biochar application increased the soil pH, ground temperature at 5 cm depth, and soil nitrogen levels and regulated the SOM and DOC contents, which may be closely related to greenhouse gas emission regulation and improvements to soil fertility. Notably, the decrease in the soil mcrA/pmoA gene abundance ratio was a dominant factor in CH4 reduction. Overall, each treatment has the potential to reduce GHG emissions and increase crop productivity in paddy fields, and CI + B achieved the best results. These practices facilitate the development of optimal management strategies for rice cultivation.
35. 题目: Soil organic carbon changes in China's croplands: A newly estimation based on DNDC model
Soil Organic Carbon (SOC) in cropland represents a significant facet of the terrestrial ecosystem's carbon reservoirs, playing a pivotal role in global climate change mitigation efforts. Within the specific context of China, cropland SOC not only extends its implications beyond environmental impact but also serves as a critical factor in ensuring the stability and security of the nation's food supply. However, there is an ongoing argument about the changes in SOC and their spatial and temporal distribution patterns within China's croplands. In this study, we constructed a new county-level DNDC database for 2020, building upon 2003 research that quantified SOC stock in China's cropland using the DNDC model. Our aim was to assess the SOC storage and temporal changes of China's cropland in 2020 using same methodology to enhance estimation accuracy. The simulation results of the validated DNDC model revealed that the average SOC storage of China's croplands (0–30 cm) in 2020 was 6.02 Pg C, with the Northeast region contributing 23 % (1.37 Pg C). The SOC density in China varied from 18.55 to 152.57 t C ha−1, averaging at 49.65 t C ha−1. In 2020, China's cropland transitioned from a net loss of SOC in 2003 to a carbon sink, with cropland SOC density and SOC storage increased by 18.2 % and 21.6 % respectively. Notably, despite experiencing a loss of SOC compared to 2003, the Northeast region had the highest average SOC density in China. This study highlights that despite the increase in SOC density and storage in China's croplands over the last 17 years, there remains substantial potential for carbon sequestration given the current spatial distribution of SOC density's significant heterogeneity within China. The findings of this study offer data support for China's strategy to achieve food security and carbon neutrality.
36. 题目: The dual effect of disodium anthraquinone-2,6-disulfonate (AQDS) on the Cr(VI) removal by biochar: The enhanced electron transfer and the inhibited adsorption
Due to large specific surface area, abundant surface functional groups, and stable chemical structure, biochar has been widely used in many environmental fields, including the remediation of Cr pollution. Alternatively, electrochemically active organic matter (e-OM), which is prevalent in both natural environments and industrial wastewater, exerts an inevitable influence on the mechanisms underlying Cr(VI) removal by biochar. The synergistic interplay between biochar and e-OM in the context of Cr(VI) remediation remains to be fully elucidated. In this study, disodium anthraquinone-2,6-disulfonate (AQDS) was used as a model for e-OM, characterized by its quinone group's ability to either donate or accept electrons. We found that AQDS sped up the Cr(VI) removal process, but the enhancement effect decreased with the increase in pyrolysis temperature. With the addition of AQDS, the removal amount of Cr(VI) by BC300 and BC600 increased by 160.0% and 49.5%, respectively. AQDS could release more electrons trapped in the lower temperature biochar samples (BC300 and BC600) for Cr(VI) reduction. However, AQDS inhibited the Cr(VI) removal by BC900 due to the adsorption of AQDS on biochar surface. In the presence of the small molecule carbon source lactate, more AQDS was adsorbed onto the biochar surface. This led to an inhibition of the electron transfer between biochar and Cr(VI), resulting in an inhibitory effect. This study has elucidated the electron transfer mechanism involved in the removal of Cr(VI) by biochar, particularly in conjunction with e-OM. Furthermore, it would augment the efficacy of biochar in applications targeting the removal of heavy metals.
37. 题目: Splash erosion-induced soil aggregate turnover and associated organic carbon dynamics
The splash erosion-induced soil aggregate turnover is important to understand the mechanisms of soil degradation and soil organic carbon (SOC) cycling. However, the relationship between aggregate turnover and rainfall impact has not been explored directly because of methodological difficulties. The soil samples, developed from Quaternary red clay, were adopted from three land use types: natural forest (NF), garden/shrubs (AS), and abandoned meadow (AM). By using rare earth oxides to trace the transformation in soil aggregates of four size-fractions (>2 mm, large macroaggregate; 0.25–2 mm, small macroaggregate; 0.053–0.25 mm, microaggregate; <0.053 mm, silt and clay fraction), we investigated aggregate turnover based on splash experiments at four different rainfall kinetic energies (501.95, 326.00, 252.50 and 153.39 J·m−2·h−1). After splash erosion, the rare earth oxides concentrations and SOC content in different soil aggregate fractions were measured. Our results indicated that the soil aggregates mainly followed the direction of breakdown, with higher cumulative breakdown rates than formation rates. Specifically, with the rainfall kinetic energy increased to 501.95 J·m−2·h−1, the three soil samples (NF, AS, AM) exhibited the highest breakdown rates of 48.35%, 31.95% and 39.29% in large macroaggregates, respectively. Meanwhile, the formation pathway was mainly in the direction of forming small macroaggregates. Compared to soil aggregate from NF, AS and AM aggregates had higher proportion of silt and clay fraction transformed into larger aggregates. Moreover, the changes of SOC varied in aggregates during splash process. With the increase of rainfall kinetic energy, the organic matter content gradually decreased in large aggregates and microaggregates in AM and AS (P < 0.05), in contrast to a trend of first increasing and then decreasing (P < 0.05) in their small aggregates. In the clay particles, with the increase of rainfall kinetic energy, the SOC content gradually decreased in NF (P < 0.05) and fluctuated in AS, with both their organic matter content lower than before the splash test (P < 0.05). The loss of SOC in total soil was linearly related to the net breakdown rate of soil aggregates (P < 0.05, R2 =0.635). Therefore, we proposed a framework to highlight the quantitative relationship between aggregate turnover and SOC degradation under splash, which may enrich the mechanisms of soil erosion and soil degradation in the positions where erosion takes place.
38. 题目: How water table level influences C balance under different fertilization regimes
Carbon sequestration in soil has been extensively sought in the agroecosystems through practices which increase organic carbon inputs and/or decrease soil organic carbon (SOC) degradation processes. Less is known about the extent of shallow water table influences in mineral soils, despite being soil moisture a major driver in modifying the C cycle. To examine its effects, a 4-yr lysimetric experiment was set up to measure the C balance components under free drainage and shallow water table at 60 and 120 cm depth. Two levels of N input (250 and 368 kg N ha−1 y−1) were also studied, using dry manure in 2011 and 2012 and fresh manure in 2013 and 2014. Carbon balance was estimated through the difference between inputs (C from organic inputs and root residues and exudates) and outputs (heterotrophic respiration, methane, and C leaching). A negative C balance was measured under all treatments (−3487 kg C ha-1), being respiration not compensated by the consistent C input of organic fertilizer. Furthermore, high N inputs increased SOC mineralization, decreasing the C balance. The role of soil was also observed by the SOC analyses, which confirmed the losses estimated through C balance. The study substantiated also the interacting effect between shallow water table and type of organic carbon, which was revealed crucial for C balance in mineral soils. To conclude, results suggested that water table level around 120-cm depth could limit SOC depletion.
39. 题目: Effect of microplastics on the adherence of coexisting background organic contaminants to natural organic matter in water
Microplastics (MPs) may interact with background organic substances (including natural organic matter and organic pollutants) after entering the aquatic environment and affect their original binding. Thus, the interaction of MPs with background organic substances (i.e, humic acid (HA), polychlorinated biphenyls (PCBs), and hydroxy PCBs) were elucidated. According to the results, PCB and hydroxy PCB displayed a strong propensity to adhere to HAs in the absence of MPs. However, the PCBs and hydroxy PCBs that were initially bound to HAs shifted from HAs to MPs in the presence of MPs. Further analysis demonstrated that this transfer was dominated by van der Waals interactions, with hydrogen bond interactions as an additional driving force. Upon the interaction, large MPs-HA-PCB/ hydroxy PCB aggregates with MPs as the core and HAs as the outermost layer were formed. Significant changes in the properties of background organic matter, including the distribution of PCB/hydroxy PCB around HA, diffusion coefficient, and hydrogen bond networks in the HA-PCB/ hydroxy PCB domains, occurred during the MP–HA–PCB/hydroxy PCB interaction. These results provide molecular-level evidence that the intrusion of MPs changes the binding preference of background organic pollutants and can lead to a redistribution of background organic pollutants.
40. 题目: Unveiling the enhancement mechanisms of algogenic extracellular organic matters on chlortetracycline photodegradation: Constitutive relationships of compound components and reactive oxygen species generation
Algogenic extracellular organic matters (EOMs) have been found to play a crucial role in the photodegradation of antibiotics. However, the specific molecular structure compositions of EOMs have not been fully characterized, and the intrinsic association between the structure and the production of ROS remains unclear. In this study, EOMs from Chlorella Vulgaris were characterized using FT-ICR-MS. Based on the FT-ICR-MS results, nine representative model compounds (MCs, i.e., benzene, naphthalene, anthracene, phenanthrene, glucose, l-glutamic, triglyceride, tannic and lignin) were applied to investigate the physicochemical properties of EOMs and the ROS changes induced by the photoreaction of chlortetracycline (CTC). With the help of quenching assays, nine MCs were classified into prone-ROS and non-prone-ROS fractions. Prone-ROS compounds generate O2− upon electron transfer to 3O2, which then produces ·OH after disproportionation to generate hydrogen peroxide. The formation of 1O2 is attributed to energy transfer from prone-ROS to 3O2. Density functional theory revealed that prone-ROS exhibited higher reactivity compared to non-prone-ROS, this finding is as well supported by the result of steady-state photolysis measurement. Our study gives a new insight into photochemical fate of CTC in aquatic environments, providing theoretical basis for assessing antibiotics' ecological risk accurately.