81. 题目: Is soil an organic carbon sink or source upon erosion, transport and deposition?
82. 题目: Spatio-temporal dynamics of soil organic carbon and total nitrogen: evidenced from 2000 to 2020 in a mixed ecosystem
The southwestern part of Bangladesh has a mixed ecosystem, which is directly affected by climate change and undergoing remarkable changes in agricultural activities that are exacerbating the dynamics of soil organic carbon (SOC) and soil total nitrogen (STN). To study the spatial distribution of SOC and STN dynamics in such ecosystem, Dacope Upazila was chosen, and different interpolation methods were applied and compared to find out the best approach to demonstrate the spatial pattern of soil carbon and nitrogen status in 2000 and 2020 and correlated them with the terrain and environmental variables. Soil resource development institute (SRDI) database was used to obtain the SOC and STN of the area in 2000 and 2020. To identify the elevation, aspect, slope, land surface temperature (LST), normalized difference vegetation index (NDVI), and normalized difference water index (NDWI), the digital elevation model (DEM) and satellite images of 2000 and 2020 were downloaded. The results showed that the applied interpolation methods and models did not perform well as the model efficiency (R2) was very low. Furthermore, in 2000, SOC and STN were only positively correlated with EC (p < 0.01) whereas after two decades, SOC and STN showed a positive correlation with elevation (p < 0.01), NDVI (p < 0.01), and negative correlation with NDWI (p < 0.01). In both years, SOC and STN showed a strong positive correlation at p < 0.001 with each other. Due to the poor model performance, it is recommended using extended spatial techniques coupling with environmental variables to increase the accuracy of spatial distribution for a complex ecosystem.
83. 题目: Linking soil microbial community to the chemical composition of dissolved organic matter in a boreal forest during freeze–thaw cycles
Soil dissolved organic matter (DOM) is mainly derived from the microbial degradation of organic matter. Intense freeze–thaw cycles (FTCs) elicited by warming alter the production and consumption of DOM in boreal forest soils, but little is known about the interactions between soil microbial community and DOM chemical composition. In this study, a FTCs incubation experiment was conducted to investigate the association between DOM dynamics and microbial community. DOM fingerprints were characterized using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) technology, and bacterial and fungal community composition was analyzed using high-throughput sequencing and bioinformatics. Both two and six freeze–thaw cycles (2FTCs and 6FTCs) significantly increased soil dissolved organic carbon (DOC) and NH4+-N contents at 0–10 cm and 50–60 cm depths. FTCs significantly decreased the relative abundance of aromatic components in DOM, whereas increasing the relative abundance of polysaccharides and fatty acid methyl esters (FAMEs) in DOM. The degradation of lignin-derived aromatic compounds was accelerated and microbial-derived components accumulated. Also, bacterial community responded more sensitively to FTCs than fungal community. Significant changes in bacterial community network was observed during FTCs with increased linkages, shortened average path lengths, reduced modularity and relative abundance of dominant phyla, and decreased α diversity. However, FTCs only increased the average path length of soil fungal community. The higher connectivity indicated that FTCs enhanced the interactions between microbial community and DOM chemical components. FTCs led to a shift in bacterial keystone taxa from being present in specific DOM molecules to competing for common substrates. Overall, FTCs tended to activate DOM and increase availability, which could promote DOM turnover and increase soil C stabilization. These findings provide new insights into the molecular mechanisms of DOM dynamics in the boreal forest soils under increased FTCs.
84. 题目: Temperature effect on erosion-induced disturbances to soil organic carbon cycling
Erosion exerts control on soil organic carbon (SOC) and both erosion and SOC are affected by climate. To what extent temperature controls the coupling between these erosion–C interactions remains unclear. Using 137Cs and SOC inventories from catchments spanning different climates, we find that increasing decomposition rates with temperature result in the efficient replacement of SOC laterally lost by erosion in eroding areas but lower preservation of deposited SOC in depositional areas. When combined at the landscape level, the erosion-induced C sink strength per unit lateral SOC flux increases with temperature from 0.19 g C (g C)−1 at 0 °C to 0.24 g C (g C)−1 at 25 °C. We estimated that the global C sink of 0.050 Pg C yr−1 induced by water erosion on croplands increases by 7% because of climate change. Our results reveal a negative feedback loop between climate change and erosion-induced disturbance to SOC cycling.
85. 题目: Positive effects of vegetation restoration on the soil properties of post-mining land
Vegetation restoration in post-mining land is one of the most important remediation strategies for rebuilding the soil carbon (C) pool and improving soil quality. We aimed to provide a global perspective on the effects of vegetation restoration on soil properties.
By analyzing a database of 2799 observations extracted from 160 publications, we quantitatively assessed the effects of vegetation restoration on soil C, water holding capacity, electronic conductivity (EC), cation exchange capacity (CEC), and soil structure in post-mining land across the globe.
The results showed that (1) vegetation restoration significantly increased soil organic C (SOC) stock (averagely + 112%), dissolved organic C (DOC) concentration (+ 141%), water content (SWC, + 40%), saturated water content (SSWC, + 40%), hairy tube holding water (HTHW, + 29%), CEC (+ 19%), and the concentrations of sand (+ 17%) and silt (+ 11%), while decreased the EC (-22%) and pH (-7.1%); (2) vegetation type could mediate the effects of vegetation restoration on HTHW, CEC, and sand and silt concentrations, while mineral type of metal mine influenced the effects of vegetation restoration on pH, CEC, bulk density, and sand and silt concentrations; and (3) plant diversity positively affected the effects of vegetation restoration on soil DOC concentration and pH, whilst the effects of soil depth, climate, and restoration year varied for different variables of soil properties.
These results suggested a critical role of vegetation restoration in the remediation of post-mining land.
86. 题目: Insight into the formation mechanism of algal biofilm in soy sauce wastewater
Microalgal-biofilm-based wastewater treatment refers to a microalgae-dominated biofilm community in non-axenic systems, in which co-existing bacteria and microbial extracellular polymeric substances (EPS) are crucial for the formation of algal biofilm. However, algae-bacteria consortium biofilm-forming mechanism has rarely been studied in wastewaters including soy sauce wastewater (SW). In this study, we conducted algal biofilm cultivation in raw SW (RSW) and sterilized SW (SSW), and determined the characteristics of algal biofilm and its EPS in the two SW treatments. The results demonstrated that the co-existing bacteria in the algal biofilm system significantly enhanced attached biomass and nutrient removal from RSW, compared to SSW without bacteria. The enhancement may be attributed to EPS excreted by dominated Acinetobacter and Comamonas (both Proteobacteria) in the co-existing bacteria community. The algae-bacteria consortium from algal biofilm in RSW excreted the contents of relatively high tightly bound EPS (TB-EPS) and its proteins (TB-PN), which were conducive to forming the algal biofilm. The high TB-EPS content was related to soluble microbial by-product-like substances (mainly proteins), and its high TB-PN content was mainly caused by the increases in hydrophobic glycine and serine contents for stable biofilm formation. Based on these results, we enhanced our understanding of the formation mechanism of algal biofilm in SW remediation, which provided the theoretical basis for biofilm formation by algae-bacteria synergism.
87. 题目: Deciphering the microheterogeneous repartition effect of environmental matrix on surface-enhanced Raman spectroscopy (SERS) analysis for pollutants in natural waters
Although surface-enhanced Raman spectroscopy (SERS) offers a promising technology for sensitive detection of environmental pollutants in natural waters, its performance can be greatly affected by the environmental matrix. The lack of identification of the origin of the matrix effect and the underlying mechanism hinders the application of SERS in practical environmental analysis. Herein, with silver nanoparticles (AgNPs) as a solution-based SERS substrate, the matrix effect from environmental waters on SERS analysis and the underlying mechanisms were investigated. It was found that natural organic matter (NOM) could deteriorate SERS performance and cause artefacts in SERS spectra. The components of NOM, including humic substances and protein, mainly contributed to the matrix effect on SERS detection, while polysaccharides or inorganic ions had minor influence. The matrix effect from NOM was found to be prevalent for different analytes and SERS substrates. The mechanism of the matrix effect from NOM in the ternary system of analyte, NOM, and nanoparticles was investigated through three mutual interactions. The microheterogeneous repartition of analytes by NOM, other than the formation of NOM-corona or competitive adsorption between NOM and analytes on nanoparticles, was found to play the dominating role in interfering with SERS detection. This work illuminates the origin and underlying mechanisms of the matrix effect, which will promote the practical application of SERS technology in environmental analysis.
88. 题目: Effect of biochar on the mitigation of organic volatile fatty acid emission during aerobic biostabilization of biosolids and the underlying mechanism
In order to declare the effect and the underlying mechanism of biochar amendment on volatile fatty acid (VFA) emission during aerobic biostabilization of biosolids, different types of biochar (i.e., wheat straw biochar [WHB], sawdust biochar [SDB], and food waste digestate biochar [FRB]; 5% in dry weight) on carbon transformation and VFA emissions during 45-day aerobic biostabilization of biosolids were investigated. The results showed that biochar amendment improved thermophilic phase evolution and product dephytotoxification. During the 45-day period, in comparison to control, biochar addition promoted CH4 reduction by 44.46%–76.90% and enhanced the content of total organic carbon reduction by 20.60%–56.80%. In addition, biochar addition lowered the emissions of acetic, propanoic, isobutyric, butyric, isovaleric, and valeric acids by respectively 23.43%–41.21%, 23.10%–43.92%, 42.62%–56.11%, 26.70%–58.20%, 10.56%–58.27%, and 33.74%–49.45% compared with control values. Moreover, biochar amendment facilitated organic matter humification during biosolid bioconversion as well. Among the applied types of biochar, SDB, with a higher surface area, was more efficient in organic matter degradation and VFA emission mitigation than WHB and FRB. In particular, biochar amendment increased the abundance and diversity of aerobic bacterial communities such as Acinetobacter, Desemzia, Georgenia, Nonomuraea, Psycharobacter, Planococcus, Paenisporosarcina, Physchrobacillus, Staphylococcus, Thermobifida, and Thermopolyspora, while inhibiting the reproduction of anaerobic bacteria including Bacillus, Bacteroides, Corynebacterium, Ruminofilibacter, and Terrisporobacter during biosolid stabilization, thus improving biosolid maturity and stabilization and reducing VFA emissions. These findings offer a novel method with appropriate recommendations for the use and the selection of biochar in increasing the efficiency of biosolid aerobic biostabilization.
89. 题目: Data evaluation strategy for identification of key molecular formulas in dissolved organic matter as proxies for biogeochemical reactivity based on abundance differences from ultrahigh resolution mass spectrometry
The molecular composition of dissolved organic matter (DOM) is of relevance for global carbon cycling and important for drinking water processing also. The detection of variation of DOM composition as function of time and space from a methodological viewpoint is essential to observe DOM processing and was addressed so far. High resolution concerning DOM quality was achieved with Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS).
However almost none of the existing FTICR-MS data sets were evaluated addressing the fate of single mass features / molecular formulas (MFs) abundance during experiments. In contrast to former studies we analyze the function of MF abundance of time and space for such MFs which are present in all samples and which were formerly claimed as recalcitrant in not all but a great number of studies. For the first time the reactivity of MFs was directly compared by their abundance differences using a simple equation, the relative intensity difference (δRI). Search strategies to find out the maximum δRI values are introduced. The corresponding MFs will be regarded as key MFs (KEY-MFs). In order to test this new approach data from a recent photo degradation experiment were combined with monitoring surveys conducted in two drinking water reservoirs. The δRI values varied over one order of magnitude (more than five-fold). MFs like C9H12O6 and C10H14O6 revealed high biogeochemical reactivity as photo products. Some of the KEY-MFs were identical with MFs identified as disinfection byproducts precursors in recent studies. Other KEY-MFs were oxygen-rich and relatively unsaturated (poly-phenol-like) and hence relevant to flocculation procedures.
90. 题目: Interactions between dissolved organic matter and the microbial community are modified by microplastics and heat waves
Dissolved organic matter (DOM) exists widely in natural waters and plays an important role in river carbon cycles and greenhouse gas emissions through microbial interactions. However, information on DOM–microbe associations in response to environmental stress is limited. River environments are the main carriers of microplastic (MP) pollution, and global heat waves (HWs) are threatening river ecology. Here, through MP exposure and HW simulation experiments, we found that DOM molecular weight and aromaticity were closely related to initial microbial communities. Moreover, MP-derived DOM regulated microbial community abundance and diversity, influenced microorganism succession trajectories as deterministic factors, and competed with riverine DOM for microbial utilization. SimulatedHWs enhanced the MP-derived DOM competitive advantage and drove the microbial community to adopt a K-strategy for effective recalcitrant carbon utilization. Relative to single environmental stressor exposure, combined MP pollution and HWs led to a more unstable microbial network. This study addresses how MPs and HWs drive DOM–microbe interactions in rivers, contributes to an in-depth understanding of the fate of river DOM and microbial community succession processes, and narrows the knowledge gap in understanding carbon sinks in aquatic ecosystems influenced by human activities and climate change.
91. 题目: Treatment of sewage sludge hydrothermal carbonization aqueous phase by Fe(II)/CaO2 system: Oxidation behaviors and mechanism of organic compounds
The Fe(II)/CaO2 system with a stable oxidant and a low-cost homogeneous activating agent has been considered as a prospective process for the disposal of wastewater. The system was constructed to treat sewage sludge hydrothermal carbonization aqueous phase (HTC-AP) in this study. As the hydrothermal temperature increased, the organics in the HTC-AP were first decomposed and then cyclized, while the Maillard reaction occurs throughout the stage. The oxidation efficiency of the Fe(II)/CaO2 system was related to the composition of organics in HTC-AP, and the removal of dissolved organic carbon (DOC) by the system was 38.56 % in the HTC-AP obtained by hydrothermal treatment at 220 °C. Redundancy analysis showed that the low molecular weight organics, hydrophobic acids, and hydrophobic neutral components were beneficial to DOC removal, while Maillard products and cyclization products were hard to be oxidized to CO2 and H2O. The CN functional group of the protein facilitated DOC removal, and some organics in HTC-AP were oxidized to acids and phenols. The energy input to remove DOC in Fe(II)/CaO2 system was 27.74 MJ per kg carbon. This study provides a low-energy consumption Fe(II)/CaO2 system for the post-treatment of HTC-APs and explores the applicability of the system.
92. 题目: Mineral protection controls soil organic carbon stability in permafrost wetlands
Mineral protection can slow the effect of warming on the mineralization of organic carbon (OC) in permafrost wetlands, which has an important impact on the dynamics of soil OC. However, the response mechanisms of wetland mineral soil to warming in permafrost areas are unclear. In this study, the soil of the southern edge of the Eurasian permafrost area was selected, and bulk and heavy fraction (HF) soil was subjected to indoor warming incubation experiments using physical fractionation. The results showed that the HF accounted for 51.25 % of the total OC mineralization in the bulk soil, and the δ13C value of the CO2 that was emitted in the HF soil was higher than that of the bulk soil. This indicates the potential availability of mineral soil and that the mineralized OC in the HF was the more stable component. Additionally, the mineralization of the mineral subsoil after warming by 10 °C was only about half of the increase in the organic topsoil, and the temperature sensitivity was significantly negatively correlated with the Fe/Al oxides to OC ratio. The results indicate that under conditions of permafrost degradation, the physical protection of mineral soil at high latitudes is essential for the stability of OC, which may slow the trend of permafrost wetlands becoming carbon sources.
93. 题目: Customized oxygen-rich biochar with ultrahigh microporosity for ideal solid phase microextraction of substituted benzenes
The synergistic effect of high microporosity and abundant heteroatoms is important for improving the performance of biochar in various fields. However, it is still challenging to create enough micropores for biochar, while simultaneously retaining the heteroatoms from biomass. A series of biochar with variable microstructures was successfully prepared by carbonization and following ball milling on lotus pedicel (LP), watermelon rind (WR), and litchi rind (LR). The pore structures and heteroatoms of biochar were characterized in detail. Notably, high microporosity could be realized by the carbonization of LR, and further ball milling resulted in a higher microporous surface area (1323.4 m2·g−1) and richer oxygen. Furthermore, the obtained biochar was fabricated as solid phase microextraction (SPME) coatings with uniform morphologies and similar thicknesses to deeply investigate the relationships between the microstructures and extraction performance. The best performance was demonstrated by the LR800BM, with enrichment factors from 1780 to 155,217. Finally, it was coupled with gas chromatography–mass spectrometry (GC–MS) to develop an analytical method with a wide linear range (1–50,000 ng·L−1), low limits of detection (0.10–1.4 ng·L−1), good repeatability (0.83–7.5 %) and reproducibility (4.2 %–8.9 %). This work provides valuable insights into the structure-performance relationship of biochar, which is important for the design of high-performance biochar-based adsorbents and their applications in the environment.
94. 题目: Chemical speciation determines combined cytotoxicity: Examples of biochar and arsenic/chromium
As both electron donors and acceptors, biochars (BCs) may interact with multivalent metal ions in the environment, causing changes in ionic valence states and resulting in unknown combined toxicity. Therefore, we systematically investigated the interaction between BCs and Cr (Cr(III) & Cr(VI)) or As (As(III) & As(V)) and their combined cytotoxicity in human colorectal mucosal (FHC) cells. Our results suggest that the redox-induced valence state change is a critical factor in the combined cytotoxicity of BCs with Cr/As. Specifically, when Cr(VI) was adsorbed on BCs, 86.4 % of Cr(VI) was reduced to Cr(III). In contrast, As(III) was partially oxidized to As(V) with a ratio of 37.2 %, thus reaching a reaction equilibrium. Meanwhile, only As(V) was released in the cell, which could cause more As(III) to be oxidized. As both Cr(III) and As(V) are less toxic than their corresponding counterparts Cr(VI) and As(III), different redox interactions between BCs and Cr/As and release profiles between BCs and Cr/As together lead to reduced combined cytotoxicity of BP-BC-Cr(VI) and BP-BC-As(III). It suggests that the valence state changes of metal ions due to redox effects is one of the parameters to be focused on when studying the combined toxicity of complexes of BCs with different heavy metal ions.
95. 题目: Characterization of dissolved organic matter in biochar derived from various macroalgae (Phaeophyta, Rhodophyta, and Chlorophyta): Effects of pyrolysis temperature and extraction solution pH
Characterization of biochar-derived dissolved organic matter (DOM) can provide deep insight into potential applications of biochar. Herein, biochar from six macroalgae (Phaeophyta—Sargassum fusiforme, Sargassum thunbergii, and Sargassum vachellianum; Rhodophyta—Grateloupia turuturu and Chondria crassicaulis; and Chlorophyta—Ulva pertusa) were subjected to pyrolysis at different temperatures (200 °C–500 °C). The effects of pyrolysis temperature and extraction solution pH on the characteristics of the macroalgal biochar-derived DOM (MBDOM) were investigated via fluorescence excitation–emission matrix spectroscopy with parallel factor (PARAFAC) analysis. Five humic-like substances and one protein-like substance were identified. The distributions of the six PARAFAC components depended on the macroalgae species, pyrolysis temperature, and extraction solution pH. The proportion of the protein-like substance (0 %–46.77 %) was less than that of the humic-like substances (100 %–53.23 %) in a given MBDOM regardless of the extraction solution pH values. Fluorescence spectral indicators show that DOM from macroalgal biochar is more autochthonous and humified than that from the corresponding biomass. Hierarchical cluster analysis and redundancy analysis results further show that the macroalgae species, pyrolysis temperature, and extraction solution pH jointly affect DOM characteristics with varying contribution levels.
96. 题目: Phosphorus hotspots in pedogenic carbonate coatings determined by zoned microscale arrangement and organo-mineral interactions
Subsoils of calcareous soils are often characterized by pedogenic carbonate precipitates coating soil aggregate and rock surfaces. Numerous studies identified the key mechanisms of pedogenic carbonate formation in calcareous soils. Still, little is known about the ecosystem function of carbonate precipitates for nutrient supply, their microscale structure and the interaction of microscale structure with nutrient distribution such as P. We investigated the mineral composition and P speciation of lithogenic carbonate coated by pedogenic carbonate precipitates. Subsoil horizons of a Rendzic Leptosol (Tuttlingen, C horizon) and a Eutric Cambisol (Benediktenwand, BC horizon) in Central Europe were sampled. We combined wet-chemical methods with X-ray diffraction, synchrotron-based P XANES spectroscopy, and specific surface area analysis (N2-BET). To investigate the spatial arrangement and elemental distribution at the microscale, a complementary approach using light microscopy, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) as well as XANES spectroscopy at the microscale (µXANES) was conducted. In both soils, the pedogenic carbonate coatings showed an intricate porous microstructure and large specific surface area. The δ13C values of the coatings were halfway between those of the primary bedrock and soil organic matter (SOM), proving their formation by re-precipitation of dissolved carbonate through organic and inorganic (H2CO3) acids. Compared to the primary rocks, the coatings were enriched in Al, Fe, Mn, and K and in organic C, N, and P; additionally, they contained silicate minerals (muscovite, illite) and quartz. Whereas the P in the rock interior was mainly present as apatite, the P in the coatings was mainly organic P bound to Ca and Al minerals. NanoSIMS and µXANES analyses at Tuttlingen revealed a zoned microstructure of the pedogenic coating: An inner zone with most P co-localized and bound to Al minerals and an outer zone enriched again in Ca and SOM. The formation of these zones indicates the infiltration and residual accumulation of Al minerals which may contribute to mitigate P losses by leaching. Intensive penetration by fine plant roots and observations of fungal hyphae within the coatings indicate the potential of pedogenically altered carbonates as microbial habitat and ecosystem nutrient source, thus contributing to the scarce ecosystem P nutrition of initial calcareous soils.
97. 题目: Preferential preservation of pre-aged terrestrial organic carbon by reactive iron in estuarine particles and coastal sediments of a large river-dominated estuary
Reactive iron (FeR) plays an important role in the preservation of organic carbon (OC) in coastal sediments, yet changes in the OC bound to FeR (OC-FeR), during transport and deposition, remain poorly understood. The main goal of this work is to investigate the variation of the age and composition of OC-FeR from estuarine suspended particulate matter (SPM) to coastal sediments, to further understand the role of FeR in the preservation of terrestrial OC exported from large rivers into marginal seas. We examined OC and its carbon isotopic composition (Δ14Cbulk, δ13Cbulk), specific surface area (SSA), grain size composition, lignin phenols, FeR, Mössbauer spectroscopy, and isotopic signatures of OC-FeR (Δ14COC-FeR, δ13COC-FeR) in SPM and surface sediments of the Changjiang Estuary. Particulate OC (POC) and FeR concentrations in SPM are significantly higher than in surface sediments, with no significant differences between surface- and bottom-water SPM. This indicates that loss of OC and FeR largely occurs at the sediment-water interface due in part, to rapid Fe cycling. The percentage of OC-FeR (fOC-FeR) in SPM (6.6 ± 1.9%) is similar to that in mobile-mud sediment (8.8 ± 1.8%). There are no significant differences in OC-FeR content (p>0.05) from SPM to mobile-mud sediments, but non-OC-FeR largely decreases, suggesting that terrestrial OC-FeR has greater stability compared to terrestrial non-OC-FeR. Both δ13COC-FeR and Δ14COC-FeR are lower than bulk OC, indicating that FeR is mainly associated with pre-aged soil OC of terrestrial plant origin, especially in estuarine SPM and mobile-mud sediments. Taken together, binding with FeR is a potential long-term protection mechanism for terrestrial OC. Both Δ14Cbulk and Δ14COC-FeR decrease with an increase in the ratio of hematite to (super)paramagnetic Fe3+, indicating that high-crystallinity iron oxide is largely associated with pre-aged terrestrial OC, and there is a potential joint maturation mechanism between FeR and its associated OC. Based on literature comparisons of soils, estuarine SPM, and marine sediments, OC-FeR associations are controlled mainly by sedimentary regimes, FeR compositions, and OC sources. This work supports the notion that FeR plays an important role in the stabilization and transport of river-derived terrestrial OC.
98. 题目: Persulfate activation by sludge-derived biochar for efficient degradation of 2,4-dichlorophenol: performance and mechanism
Porous sludge biochar (PSDBC) and zero-valent iron (ZVI) supported on porous sludge biochar composite (ZVI@PSDBC) were synthesized using municipal sludge through pyrolysis under N2 atmosphere, which manifested upgraded performance in persulfate (PS) activation for 2,4-dichlorophenol (2,4-DCP) degradation. The 2,4-DCP (50 mg/L) could be almost completely removed within 20 min under relatively low PS dosage (0.5 mmol/L) in both PSDBC/PS and ZVI@PSDBC/PS systems, and the mineralization rate could respectively approach 73.7% and 91.6% in 60 min. Combined with a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) characterization and electron spin-resonance (ESR) detection, electrochemical analysis, the radical and non-radical pathways in the catalytic systems were discussed. Graphitized structure and superior conductivity made PSDBC and ZVI@PSDBC not only act as electron donors in PS activation to create radicals (mainly SO4·- and ·OH), but also as “mediators” to facilitate the direct electron transfer from 2,4-DCP to the catalysts-PS complexes. The C=O groups of PSDBC and ZVI@PSDBC aided in the production of 1O2. Meanwhile, zero-valent iron nanoparticles promoted the formation of radicals as the reactive sites of PS, resulting in the most effective 2,4-DCP degradation in the ZVI@PSDBC/PS system. The stability and practicability of sludge biochar materials had been demonstrated in reusability and actual wastewater experiments. The findings provided a promising way for the reuse of municipal sludge and effective PS activation in wastewater treatment.
99. 题目: Homologous series of n-alkanes and fatty acids in the summer atmosphere from the Bering Sea to the western North Pacific
Lipid biomarkers can be used as key tracers for studying organic aerosols. To better understand the effects of anthropogenic and natural sources on Northern Hemisphere organic aerosols over the marine boundary in the context of global warming, we investigated n-alkanes and fatty acids in three years of summer aerosol samples which were collected from the Bering Sea (BS) to the western North Pacific (WNP) atmosphere during the cruise of China Arctic Research Expedition in 2014, 2016 and 2018. Lipid concentrations were the highest in 2018, with the WNP influenced by neighboring Eurasia and the BS influenced by the transport of aerosols from the WNP as well as an increased primary productivity. The sources of n-alkanes and fatty acids were found to be similar, and the qualitative assessment of the characteristic parameters indicated that temporally, n-alkanes were more abundant from higher plant wax in 2016 and 2018 as well as fatty acids in 2018. Furthermore, the quantitative assessment of principal component analysis with multiple linear regression showed that spatially, the WNP and BS were most influenced by terrestrial natural sources (57.8%) and anthropogenic sources (58.8%), respectively, and the contribution of marine emissions to BS was higher. In addition, the evaluation of organic carbon (OC) contribution revealed that lipids from BS contributed more OC and that the contribution of fatty acids to OC was higher than that of n-alkanes. This study provides useful information for further understanding the sources and influencing factors of organic aerosols.
100. 题目: Resistance and recovery of benthic marine macrophyte communities to light reduction: Insights from carbon metabolism and dissolved organic carbon (DOC) fluxes, and implications for resilience
A crucial factor in the long-term survival of benthic macrophyte communities under light-reduction stress is how they balance carbon metabolism during photosynthesis and respiration. In turn, the dissolved organic carbon (DOC) released by these communities, which can be highly light-dependent, stands as a source of carbon, fuelling marine communities and playing an important role in the ocean carbon sequestration. This is the first study to evaluate light-reduction stress and recovery in the seagrass Zostera noltei and the macroalga Caulerpa prolifera. Light reduction led to a significant decrease in the production of both communities from autotrophic to heterotrophic. Results indicated that most of the DOC released by vegetated coastal communities comes from photosynthetic activity, and that the net DOC fluxes can be greatly affected by shading events. Finally, both communities showed resilience underpinned by high recovery but low resistance capacity, with C. prolifera showing the highest resilience to unfavourable light conditions.