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所有论文

401. 题目: Underlying Mechanisms for Low-Molecular-Weight Dissolved Organic Matter to Promote Translocation and Transformation of Chlorinated Polyfluoroalkyl Ether Sulfonate in Wheat
文章编号: N22102315
期刊: Environmental Science & Technology
作者: Jia Guo, Jian Zhou, Siqian Liu, Lina Shen, Xiaoxue Liang, Tiecheng Wang, Lingyan Zhu
更新时间: 2022-10-23
摘要: Dissolved organic matter (DOM) such as fulvic acid (FA) and humic acid (HA) in soil considerably affects the fate of per- and polyfluoroalkyl substances (PFASs). However, the effect of DOM on their behavior in plants remains unclear. Herein, hydroponic experiments indicate that FA and HA reduce the accumulation of an emerging PFAS of high concern, 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA), in wheat roots by reducing its bioavailability in the solution. Nevertheless, FA with low molecular weight (MW) promotes its absorption and translocation from the roots to the shoots by stimulating the activity and the related genes of the plasma membrane H+-ATPase, whereas high-MW HA shows the opposite effect. Moreover, in vivo and in vitro experiments indicate that 6:2 Cl-PFESA undergoes reductive dechlorination, which is regulated mainly using nitrate reductase and glutathione transferase. HA and FA, particularly the latter, promote the dechlorination of 6:2 Cl-PFESA in wheat by enhancing electron transfer efficiency and superoxide production. Transcriptomic analysis indicates that FA also stimulates catalytic activity, cation binding, and oxidoreductase activity, facilitating 6:2 Cl-PFESA transformation in wheat.

402. 题目: Marine plastics alter the organic matter composition of the air-sea boundary layer, with influences on CO2 exchange: A large-scale analysis method to explore future ocean scenarios
文章编号: N22102314
期刊: Science of the Total Environment
作者: Luisa Galgani, Eleni Tzempelikou, Ioanna Kalantzi, Anastasia Tsiola, Manolis Tsapakis, Paraskevi Pitta, Chiara Esposito, Anastasia Tsotskou, Iordanis Magiopoulos, Roberto Benavides, Tobias Steinhoff, Steven A Loiselle
更新时间: 2022-10-23
摘要:

Microplastics are substrates for microbial activity and can influence biomass production. This has potentially important implications in the sea-surface microlayer, the marine boundary layer that controls gas exchange with the atmosphere and where biologically produced organic compounds can accumulate. In the present study, we used six large scale mesocosms to simulate future ocean scenarios of high plastic concentration. Each mesocosm was filled with 3 m3 of seawater from the oligotrophic Sea of Crete, in the Eastern Mediterranean Sea. A known amount of standard polystyrene microbeads of 30 μm diameter was added to three replicate mesocosms, while maintaining the remaining three as plastic-free controls. Over the course of a 12-day experiment, we explored microbial organic matter dynamics in the sea-surface microlayer in the presence and absence of microplastic contamination of the underlying water. Our study shows that microplastics increased both biomass production and enrichment of carbohydrate-like and proteinaceous marine gel compounds in the sea-surface microlayer. Importantly, this resulted in a 3 % reduction in the concentration of dissolved CO2 in the underlying water. This reduction was associated to both direct and indirect impacts of microplastic pollution on the uptake of CO2 within the marine carbon cycle, by modifying the biogenic composition of the sea's boundary layer with the atmosphere.

403. 题目: NaOH-modified biochar supported Fe/Mn bimetallic composites as efficient peroxymonosulfate activator for enhance tetracycline removal
文章编号: N22102313
期刊: Chemical Engineering Journal
作者: Fawen Liang, Zhang Liu, Xueding Jiang, Jiesen Li, Kaibang Xiao, Weicheng Xu, Xin Chen, Jinzhi Liang, Zhifeng Lin, Meng Li, Xiaolian Wu, Hailong Wang
更新时间: 2022-10-23
摘要:

In this study, NaOH-modified biochar supported Fe/Mn bimetallic composite (Fe-Mn/AW-BC) was prepared to remove tetracycline (TC) through activating peroxymonosulfate (PMS). Results showed that about 97.9% of TC was degraded and the rate constant of Fe-Mn/AW-BC+PMS system was 37 folds higher than BC+PMS system. Experimental results confirmed that both radical and non-radical pathway were contribute to the catalytic system. Density functional theory (DFT) results also suggested that Fe-Mn/AW-BC sample was favorable for adsorbing PMS based on the length O-O bond from PMS and the Eads of catalysts. The superior activation ability was ascribed to the accelerating formation of reaction active species and other oxidation species by bimetallic structures of Fe-Mn and oxygenated functional groups of BC. Additionally, the redox cycles of Fe3+/Fe2+ and Mn3+/Mn2+ under Fe-Mn-BC synergism promoted the generation of the radicals, whereas the carbon shell effectively inhibited metals leaching of Fe-Mn/AW-BC, and 77.8% of TC can be still removed within 60 min after five consecutive cycles. Notably, Fe-Mn/AW-BC system has special characteristic of wide pH usable range and broad-spectrum adaptability towards various organic pollutants and various water environments. Based on intermediate identification and Fukui function calculation, the degradation pathways of TC were also proposed. This study highlights the applications of biochar for the environmental catalysis.

404. 题目: Climate evolution in the Adriatic Sea across the last deglaciation: A multiproxy approach combining biomarkers and calcareous plankton
文章编号: N22102312
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Bazzicalupo Pietro, Sicre Marie-Alexandrine, Checa Helena, Maiorano Patrizia, Margaritelli Giulia, Klein Vincent, Pena Leopoldo David, Cacho Isabel, Frigola Jaime, Bonomo Sergio, Cascella Antonio, Lirer Fabrizio
更新时间: 2022-10-23
摘要:

A multiproxy study combining calcareous plankton assemblages (coccolithophore and planktonic foraminifera), terrestrial (n-alkanes) and marine (alkenones) biomarkers was carried out in a sediment core (ND14Q-AR2) from the South Adriatic Sea. The focus of the study is to investigate millennial-to-centennial scale climate variability in the Eastern Mediterranean during the last deglaciation, between 20 and 11 ka BP. The high-resolution reconstruction allows for the characterization of the impact of the Heinrich Stadial 1 (HS1, here identified between 17.1 and 14.9 ka BP) at a centennial/multi-decadal time scale resolution. Based on terrestrial proxies, the HS1 interval has a two-fold partition: HS1a (17.1–15.9 ka BP), characterized by decreasing temperatures and relative high humidity, and HS1b (15.9–14.9 ka BP), characterized by the coldest temperatures and drier conditions on land. Terrestrial proxies suggest changes in moisture availability on land and ice melting delivery from the Alps during HS1. This period is followed by the Bølling-Allerød record (B-A, 14.9–12.3 ka BP) indicating ameliorated climate conditions and distinct local hydrological signals, related to global melt events similar to the Melt Water Pulse-1A. Finally, the comparison of our results with other Northern Hemisphere climatic records shows a good correspondence between the temperature variations in the South Adriatic Sea and the Greenland ice core oxygen isotope record, highlighting the climatic response of the South Adriatic to global climate variations. Comparison with other Mediterranean paleoclimatic records suggests a two-steps reorganization of the ocean/atmospheric circulation during the HS1 in the mid- and low-latitudes during the HS1 interval, but also a connection with the tropical Northern Hemisphere climate.

405. 题目: Humic Acid Nature and Compound Structure together Determine the Capacity of Soil to Sorb Avermectin B1a and Its Derivatives
文章编号: N22102311
期刊: Chemical Engineering Journal
作者: Tong-fang Jing, Da-xia Zhang, Yan Jin, Guo-dong Si, Bei-xing Li, Wei Mu, Feng Liu
更新时间: 2022-10-23
摘要:

Sorption is the key process that regulates the dispersion of pesticides in the environment once they are introduced into the soil. However, the relationship between the molecular structures of these compounds and the sorption mechanism needs to be further clarified. Our objectives were to uncover sorption drivers in distinct soil samples for the parent avermectin B1a (-OH:3) and pharmacophore-altered derivatives [derivative-1 (-OH:2) and derivative-2 (-OH:1) series]. Avermectin B1a sorption to soil was extensive and essentially irreversible, with avermectin B1a exhibiting significantly greater sorption than the derivatives. The sorption difference between avermectin B1a and derivatives in soil suggested that -OH pharmacophore was the main sorption site for avermectin B1a in soil. Further sorption tests on avermectin B1a and derivatives were carried out on humic acid fractions (HA1 and HA2) that we extracted from the soil. Avermectin B1a sorbed most extensively to humic acid fractions, followed by derivative-1 and derivative-2, thereby indicating the -OH pharmacophore remains the main site for the sorption of avermectin B1a and derivatives by the humic acid fractions. The HA1 fraction showed significantly greater sorption of the compound than the HA2 fraction. Elemental analysis and 13C NMR analysis demonstrated that the HA1 fraction contains more polar functional groups than the HA2 fraction. This suggests that the sorption of avermectin B1a and derivatives by the soil is due to the interaction between the -OH pharmacophore and the polar functional groups in the humic acid, implying that hydrogen bonding may be the main sorption mechanism. This study highlighted the potential sorption mechanisms of pharmacophores in pesticide compounds with humic acid fractions.

406. 题目: Origin of synergistic effect between Fe/Mn minerals and biochar for peroxymonosulfate activation
文章编号: N22102310
期刊: Chemical Engineering Journal
作者: Chunyu Du, Shengjiong Yang, Dahu Ding, Tianming Cai, Rongzhi Chen
更新时间: 2022-10-23
摘要:

Biochar possesses attractive structural (highly porous) and chemical (abundant functional groups) properties, exhibiting promising future in diverse applications such as soil amendment and environmental remediation. However, the interaction between biochar and soil active minerals, especially the synergistic effect on peroxymonosulfate (PMS) activation is largely unknown. In this study, we focused on the origin of the observed synergistic effect between biochar and two typical soil active minerals, i.e., goethite (α-FeOOH) and birnessite (δ-MnO2) on the activation of PMS by preparing four mineral-biochar composites, i.e., GBC350, BBC350, GBC700, and BBC700. Interestingly, BBC350, BBC700, and GBC700 exhibited distinct synergistic effects for BPA removal, whilst no obvious synergistic effect was observed for GBC350. The theoretical calculations based on density functional theory (DFT) further confirmed the improved PMS adsorption affinity, ascribing to the delocalization of O electrons (in PMS) to the π bond in C-layer. Furthermore, non-radical regime was elucidated to dominate the BPA oxidation. Mineral species could establish an electron channel between oxidant and catalyst, thus accelerating the electron transfer process. The high-valent Mn species (Mn(V)) also contributed to BPA removal in BBC350/PMS process. Overall, this study uncovered the origin of synergistic effect between BC700 and Fe/Mn minerals by exploring the electron transfer regime, which might provide new insights into PMS activation in practical applications.

407. 题目: Comprehensive assessment of dissolved organic matter processing in the Amazon River and its major tributaries revealed by positive and negative electrospray mass spectrometry and NMR spectroscopy
文章编号: N22102309
期刊: Science of the Total Environment
作者: Siyu Li, Mourad Harir, Philippe Schmitt-Kopplin, Michael Gonsior, , David Bastviken, Juliana Valle, Fausto Machado-Silva, Norbert Hertkorn
更新时间: 2022-10-23
摘要:

Rivers are natural biogeochemical systems shaping the fates of dissolved organic matter (DOM) from leaving soils to reaching the oceans. This study focuses on Amazon basin DOM processing employing negative and positive electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI[±] FT-ICR MS) and nuclear magnetic resonance spectroscopy (NMR) to reveal effects of major processes on the compositional space and structural characteristics of black, white and clear water systems. These include non-conservative mixing at the confluences of (1) Solimões and the Negro River, (2) the Amazon River and the Madeira River, and (3) in-stream processing of Amazon River DOM between the Madeira River and the Tapajós River. The Negro River (black water) supplies more highly oxygenated and high molecular weight compounds, whereas the Solimões and Madeira Rivers (white water) contribute more CHNO and CHOS molecules to the Amazon River main stem. Aliphatic CHO and abundant CHNO compounds prevail in Tapajos River DOM (clear water), likely originating from primary production. Sorption onto particles and heterotrophic microbial degradation are probably the principal mechanisms for the observed changes in DOM composition in the Amazon River and its tributaries.

408. 题目: Molecular tracers for characterization and distribution of organic matter in a freshwater lake system from the Lesser Himalaya
文章编号: N22102308
期刊: Biogeochemistry
作者: Diptimayee Behera, Sharmila Bhattacharya, Abdur Rahman, Sanjeev Kumar, Ambili Anoop
更新时间: 2022-10-23
摘要:

The knowledge of distribution and sources of organic matter (OM) in aquatic systems is important to understand the biogeochemical cycling of carbon in terrestrial environments. In this study, we have evaluated quantitative contributions of OM sources and their distribution using bulk geochemical parameters (TOC and δ13Corg), n-alkane indices and source specific biomarkers (C20 highly branched isoprenoid (HBI)) in Renuka Lake in Lesser Himalaya. The principal sources of OM in the sediments were aquatic productivity with minor input from terrestrial plants, which varied from littoral to central part of the lake. The microbial community in Renuka Lake were established using short chain n-alkanes and C20 HBI, whereas pristane/phytane (Pr/Ph) depicts depositional condition of the lake system. The land use/land cover changes and grain size analysis were used to investigate the multiple reasons and processes that govern the spatial heterogeneity of the distribution of sedimentary OM. The results show that human activities and alterations of the aquatic landscape can significantly affect the composition and distribution of OM in aquatic systems. The present study shows that elucidating the sources and distribution of OM in an aquatic system is crucial for constraining the ecological status and aiding conservation measures.

409. 题目: Organic carbon and microbial activity in Umbric Rhodic Ferralsol soils under green cane relative to pre-harvest burning of sugarcane
文章编号: N22102307
期刊: Journal of Soils and Sediments
作者: N P Mkhonza, P Muchaonyerwa
更新时间: 2022-10-23
摘要:

Purpose

Pre-harvest burning of sugarcane for easier harvesting and increase sucrose recovery, due to trash removal, may reduce soil quality particularly for Umbric Rhodic Ferralsols that have naturally high concentrations of soil organic carbon (SOC). Harvesting without burning (green cane) retains large quantities of biomass on the surface, which may be an alternative to improve carbon (C) sequestration and microbial activity. In the current study, we examined the effects of green cane relative to burnt cane on SOC concentration and stock, microbial biomass carbon (MBC) and β-d-glucosidase enzyme activity.

Materials and methods

Soils under green cane were compared with adjacent burnt cane fields. The soils were sampled, in March 2021, from the 0–5, 5–10, 10–20, 20–30, 30–40, 40–50, 50–60, 60–80 and 80–100 cm depths, using micropits in the top 10 cm and using augers for deeper layers. The soils were analysed for SOC, MBC and β-d-glucosidase activity. In addition, soil microbial quotient (SMQ) was calculated.

Results and discussion

The SOC concentration and stock, MBC, SMQ and β-d-glucosidase activity were significantly higher under green cane than under burnt cane. The SOC under green cane was 24% higher than that under burnt cane. The MBC under green cane and burnt cane constituted 3.52 and 1.25% of the total SOC, respectively. The concentration of all the parameters decreased with an increase in soil depth. The SMQ was not affected by soil profile depth. The β-d-glucosidase enzyme activity was higher under green cane than under burnt cane in the top 5 cm depth but not at deeper layers. The β-d-glucosidase activity was positively correlated to the bulk SOC and MBC.

Conclusions

These findings imply that green cane production increases SOC storage, and microbial activity, when compared with the burnt cane on Umbric Rhodic Ferralsols.

410. 题目: Colloidal organic phosphorus in the South China Sea
文章编号: N22102306
期刊: Marine Chemistry
作者: Chih-Ping Lee, Liang-Saw Wen
更新时间: 2022-10-23
摘要:

Phosphorus (P) is a growth-limiting nutrient that controls primary producers in marine environments. Recent studies suggested that dissolved organic P (DOP) may promote microbial production in the euphotic zone of the oligotrophic ocean. The characteristics of dissolved organic P (DOP) are crucial because it affects microbial utilization of P in the organic pool. Here we provide evidence of colloidal organic P (high-molecular-weight [HMW]-DOP, 1 kDa – 0.45 μm) in the South China Sea (SCS) and highlight the importance of size fractionations in the marine P cycle. Both soluble reactive phosphorus and DOP exhibited geographic variations, indicating that P cycling is strongly affected by hydrography and water mixing. DOP accounted for >90% of the P in the surface water of the SCS. A positive correlation between DOP and chlorophyll-a concentrations suggested that primary producers played a crucial role in DOP production. HMW-DOP comprised 75% of the surface DOP. The enrichment of P in the colloidal fraction compared with its low-molecular-weight (LMW, <1 kDa) counterpart suggested that HMW-DOP is a significant inventory to promote microbial growth. HMW-DOP depth profiles indicated surface enrichment, whereas LMW-DOP exhibited low variation throughout the water column. The difference in the features of these depth profiles indicated that P has different recycling pathways for the two size fractions. Overall, the size distribution of DOP reveals information on DOP characteristics and reactivity, which further provide insight into microbial P utilization in the ocean.

411. 题目: Enhanced Fluoride Adsorption on Aluminum-Impregnated Kenaf Biochar: Adsorption Characteristics and Mechanism
文章编号: N22102305
期刊: Water, Air, & Soil Pollution
作者: Moon-Yeong Choi, Chang-Gu Lee, Seong-Jik Park
更新时间: 2022-10-23
摘要:

In this study, kenaf, a fast-growing plant, was pyrolyzed to biochar, and the biochar was impregnated with aluminum to improve its fluoride adsorption capacity. The Al-impregnated kenaf biochar (Al-KNF-BC) was pyrolyzed at temperatures of 300–700 °C, where the specimen treated at 300 °C (Al-KNF-300) demonstrated the highest fluoride adsorption capacity. The kinetics and equilibrium adsorption of fluoride by Al-KNF-300 followed the pseudo-second-order and Langmuir models, respectively. According to the Langmuir model, the maximum fluoride adsorption capacity of Al-KNF-300 was 13.93 mg/g. The enthalpy and entropy of fluoride adsorption by Al-KNF-300 were 37.80 kJ/mol and 124.1 J/mol K, respectively. Fluoride adsorption by Al-KNF-300 was favorable at pH values as low as 3, and the effect of anion competition followed the order HCO3 > SO42− > NO3 > Cl. A maximum adsorption efficiency of 99.23% was obtained at an adsorbent concentration of 16.67 g/L, at which point the fluoride concentration decreased from 100 to < 1.5 mg/L (the drinking water standard). Based on these results, Al-KNF-300 can be considered an effective and inexpensive adsorbent for removing fluoride from contaminated water to meet drinking water standards.

412. 题目: Biochar and Eisenia fetida (Savigny) promote sorghum growth and the immobilization of potentially toxic elements in contaminated soils
文章编号: N22102304
期刊: Applied Soil Ecology
作者: Matteo Garau, Giovanni Garau, Tom Sizmur, Sean Coole, Paola Castaldi, Maria Vittoria Pinna
更新时间: 2022-10-23
摘要:

Biochar is a soil amendment capable of influencing plant growth and potentially toxic elements (PTEs) bioavailability in soils. At the same time Eisenia fetida (Savigny) is able to interact with biochar influencing its performance. As such they could constitute a resource for assisted phytostabilisation of PTE-polluted soils. To this end, a softwood-derived biochar was added at 2 and 5 % (w/w) rate, with and without E. fetida, to a soil contaminated with Cd, Pb, Zn, As, and Sb, to evaluate the PTE phytostabilisation potentials when combined with Sorghum vulgare. The combination of sorghum, 5 % biochar, and earthworms reduced the mobility of most PTEs in soil (e.g., up to 65 % and 60 % for Pb and Zn), while sorghum biomass was greatly increased (i.e., ~3- and 2-fold for roots and shoots, respectively).

Biochar addition alone reduced the PTE uptake by plants, while the presence of earthworms slightly increased it. Overall, the joint action of biochar and earthworms increased the PTE removal efficiency by S. vulgare compared to control plants (e.g., the amount of root As, Pb and Sb was ~5-, 4- and 3-fold higher, respectively). Although 2 % biochar didn't affect E. fetida fitness, the highest biochar rate (5 %) exhibited toxic effects (the survival rate reduced by ~2-fold; weight loss increased by ~3-fold). Taken together, these results indicated that S. vulgare, in combination with softwood biochar and E. fetida, could be used for the assisted phytostabilisation of PTEs contaminated soils.

413. 题目: Enhanced sludge dewaterability by ferrate/ferric chloride: The key role of Fe(IV) on the changes of EPS properties
文章编号: N22102303
期刊: Science of the Total Environment
作者: Wei Lin, Junmin Guo, Jie Zeng, Renglu Chen, Huu Hao Ngo, Jun Nan, Guibai Li, Jun Ma, An Ding
更新时间: 2022-10-23
摘要:

The complex characteristics of extracellular polymeric substances (EPS) seriously affect the improvement of sludge dewaterability. Ferrate (Fe(VI))/ferric chloride (Fe(III)) was applied through its strong oxidability to effectively enhance sludge dewaterablity by changing the properties of EPS in this study. Results confirmed that water content (WC), specific resistance to filtration (SRF) and capillary suction time (CST) fell from 82.8 %, 9.3 × 1010 s2/g and 35.1 s to 76.1 %, 2.6 × 1010 s2/g and 16.2 s, respectively, when adding 12 mg Fe(VI)/g VSS and 12 mg Fe(III)/g VSS with the dosing interval of 5 min. Investigations of the mechanism strongly suggested that Fe(VI) was successfully catalyzed by Fe(III), promoting the generation of methyl phenyl sulfone (PMSO2) and facilitating the electron transfer, with Fe(IV) having the major role in the oxidation process. Furthermore, sludge water-holding capacity and hydrophilicity waned after oxidation due to the destruction of EPS structure, which promoted the decrement of bound water to enhance the discharge of sludge water, so as to improve the efficiency of dewatering.

414. 题目: Divergent effects of moderate grazing duration on carbon sequestration between temperate and alpine grasslands in China
文章编号: N22102302
期刊: Science of the Total Environment
作者: Zhenchao Zhang, Ting Hua, Yanhua Zhao, Yanpeng Li, Yi Wang, Fei Wang, Juan Sun, Jian Sun
更新时间: 2022-10-23
摘要:

Moderate grazing has been widely proven to improve ecosystem functioning and have profound effects on the carbon cycling and storage in grassland ecosystems, which highly depend on grazing duration and grassland type. However, the effects of moderate grazing durations on carbon sequestration with different grassland types over broad geographic scales across China remain underexplored in the context of striving for carbon neutrality. Here, we explored the probably different responses of carbon sequestration to moderate grazing duration for temperate and alpine grasslands based on 129 published literatures regarding the China's grasslands. The results showed the soil organic carbon stocks were significantly increased during short-term (<5 years) grazing duration, while significantly decreased during medium- (5–10 years) and long-term (≥ 10 years) grazing durations in temperate grasslands. However, the soil organic carbon stocks were significantly decreased during short-term grazing duration, while showed no significant changes during medium- and long-term grazing durations in alpine grasslands. The changes in soil organic stock were significantly positively correlated with the changes in belowground biomass, root:shoot, and microbial biomass carbon (P < 0.05). These findings suggest that the temperate grasslands change from carbon sink to carbon source with moderate grazing duration increasing, while the alpine grasslands present an opposite change pattern from carbon source to carbon sink, regulated by grazing-altered carbon input and microbial activities. Our study might have significant implications for future sustainable management practices for carbon sequestration of China's grasslands.

415. 题目: Humic fractions from Amazon soils: Lifetime study and humification process by fluorescence spectroscopy
文章编号: N22102301
期刊: Applied Geochemistry
作者: Amanda M Tadini, Gustavo Nicolodelli, Houssam Hajjoul, DéboraM.B.P. Milori, Stephane Mounier
更新时间: 2022-10-23
摘要:

The Amazon Forest is an important and primordial ecosystem, as it controls the dynamics of soil organic matter (SOM) and is considered one of the crucial carbon reservoirs in the world. Based on that, this study evaluated the molecular properties of humic (HA) and fulvic (FA) acid from Amazon soil, with and without Cu(II) ions, by Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) and Fluorescence Spectroscopy (FS). Fluorescence excitation-emission matrix (EEM) was obtained by FS, and EEM spectra were treated by canonical polyadic/parallel factor analysis (EEM-CP/PARAFAC). The results showed that the humification index (A465nm) determined by FS is directly dependent on fluorophores’ CII/CI ratio in these soils with depth (r = 0.89), especially for HA samples in deep horizons, which demonstrated that the CII consists more complex and humified structure of the SOM. The lifetime decay showed the presence of static quenching in the humic fractions. From the lifetime data provided by TRLFS and the different correlations with carbon content and A465nm, it can be suggested that the fluorescence suppression modifies the molecular properties of the humic fractions with the addition of Cu(II) ions, such as altering the mobility and availability of the metal in the complexation reactions in these Amazonian Spodosols, mainly for the fulvic fraction.

416. 题目: Distribution and export of particulate organic carbon in East Antarctic coastal polynyas
文章编号: N22102212
期刊: Deep Sea Research Part I: Oceanographic Research Papers
作者: Lavenia Ratnarajah, Viena Puigcorbé, Sébastien Moreau, Montserrat Roca-Martí, Julie Janssens, Matthew Corkill, Luis Duprat, Cristina Genovese, Jan Lieser, Pere Masqué, Delphine Lannuzel
更新时间: 2022-10-22
摘要:

Polynyas represent regions of enhanced primary production because of the low, or absent, sea-ice cover coupled with the proximity of nutrient sources. However, studies throughout the Southern Ocean suggest elevated primary production does not necessarily result in increased carbon export. Three coastal polynyas in East Antarctica and an off-shelf region were visited during the austral summer from December 2016 to January 2017 to examine the vertical distribution and concentration of particulate organic carbon (POC). Carbon export was also examined using thorium-234 (234Th) as a proxy at two of the polynyas. Our results show that concentrations and integrated POC stocks were higher within the polynyas compared to the off-shelf sites. Within the polynyas, vertical POC concentrations were higher in the Mertz and Ninnis polynyas compared to the Dalton polynya. Similarly, higher carbon export was measured in the diatom-dominated Mertz polynya, where large particles (>53 μm) represented a significant fraction of the particulate 234Th and POC (average 50% and 39%, respectively), compared to the small flagellate-dominated Dalton polynya, where almost all the particulate 234Th and POC were found in the smaller size fraction (1–53 μm). The POC to Chlorophyll-a ratios suggest that organic matter below the mixed layer in the polynyas consisted largely of fresh phytoplankton at this time of the year. In combination with a parallel study on phytoplankton production at these sites, we find that increased primary production at these polynyas does lead to greater concentrations and export of POC and a higher POC export efficiency.

417. 题目: Microbial properties determine dynamics of topsoil organic carbon stocks and fractions along an age-sequence of Mongolian pine plantations
文章编号: N22102211
期刊: Plant and Soil
作者: Yansong Zhang, De-Hui Zeng, Zeyong Lei, Xin Li, Guigang Lin
更新时间: 2022-10-22
摘要:

Purpose

Afforestation is increasingly recognized as an effective measure to mitigate elevated atmospheric carbon (C) dioxide and combat climate change. While afforestation can increase C sequestration by biomass production with tree growth, little is known about whether and how tree growth affects soil organic carbon (SOC) stocks and stability. Here, we aimed to explore mechanisms underlying changes in SOC stocks and fractions with stand development from the perspective of tree-microbe-mineral interactions.

Methods

We measured aboveground plant input, soil pH and exchangeable base cations, microbial biomass, hydrolytic and oxidative enzymes, and SOC stocks and fractions along an age-sequence of Mongolian pine (Pinus sylvestris var. mongolica) plantations with six age classes ranging from 15- to 61-year-old and adjacent grasslands in the Keerqin Sandy Lands, Northeast China.

Results

We found that afforestation of grasslands did not significantly affect 0–100 cm SOC stocks. Ecosystem C stocks linearly increased with stand development, and this C accretion was mainly attributed to tree biomass C sequestration. Topsoil (0–10 cm soil layer) mineral-associated C (MAOC) stocks and absolute phenol oxidase activities increased, and particulate organic C (POC) stocks and absolute β-glucosidase activities decreased with increasing stand age, but these changes disappeared in the 61-year-old stand. Structural equation model revealed that topsoil MAOC stocks were directly related to bacterial biomass and absolute β-glucosidase and phenol oxidase activities, and topsoil POC stocks were directly related to absolute β-glucosidase activities.

Conclusions

Our findings suggest that soil microbes play a central role in mediating the dynamics of SOC stocks and stability along stand development.

418. 题目: Source and quality of dissolved organic matter in streams are reflective to land use/land cover, climate seasonality and pCO2
文章编号: N22102210
期刊: Environmental Research
作者: Liuqing Zhang, Y Jun Xu, Siyue Li
更新时间: 2022-10-22
摘要:

Sources and quality of dissolved organic matter (DOM) in streams may be largely controlled by the landscape and season. In this study, we attempted to answer three critical questions: 1) Do land use/land cover (LULC) types affect DOM characteristics 2) Is there seasonal fluctuation in DOM components 3) How do DOM quality and LULC types influence aqueous carbon dioxide partial pressure (pCO2). To achieve this, we investigated the fluorescence characteristics of DOM and its implication for pCO2 in three streams draining land with different urban intensities under distinctive dry and wet seasons. Four fluorescence components were identified, including two terrestrial humic-like components, one protein-like component and one microbial humic-like component. We found a significant positive relationship of the maximum fluorescence intensity (Fmax) of four components and fluorescence index (FI370) with urbanization intensity in both the dry and wet seasons. The mean Fmax, biological index (BIX) and FI370 all exhibited an increasing trend from upstream to downstream in the stream with highest proportions of urban and cropland. The fluorescence characteristics were negatively related to proportion of forested land in the both seasons. The terrestrial humic-like DOM was dominating in the studied streams. Moreover, the seasonality altered the DOM composition, with protein-like component emerging only in stream waters during the dry season, while microbial humic-like component exclusively occurred during the wet season. pCO2 values were positively related to terrestrial humic-like and biological protein-like components, and urban land. The dry season had much higher pCO2 than the wet season. Results from the Partial Least Squares Path (PLS-PM) models further indicated that LULC types were important in mediating FDOM whilst pCO2 was more sensitive to the direct effect from FDOM dynamics. We conclude that DOM source and quality in streams are reflective to LULC and climate seasonality, and are good indicators of pCO2 via source tracer and quality of fluorescence components.

419. 题目: Distribution of Mn Oxidation States in Grassland Soils and Their Relationships with Soil Pores
文章编号: N22102209
期刊: Environmental Science & Technology
作者: Alexandra N Kravchenko, Jocelyn A Richardson, Jin Ho Lee, Andrey K Guber
更新时间: 2022-10-22
摘要: Manganese (Mn) is known to be an active contributor to processing and cycling of soil organic carbon (C), yet the exact mechanisms behind its interactions with C are poorly understood. Plant diversity in terrestrial ecosystems drives feedback links between plant C inputs and soil pores, where the latter, in turn, impact the redox environment and Mn. This study examined associations between soil pores (>36 μm Ø) and Mn within intact soils from two grassland ecosystems, after their >6-year implementation in a replicated field experiment. We used μ-XRF imaging and XANES spectroscopy to explore spatial distribution patterns of Mn oxidation states, combined with X-ray computed microtomography and 2D zymography. A high plant diversity system (restored prairie) increased soil C and modified spatial distribution patterns of soil pores as compared to a single species system (monoculture switchgrass). In switchgrass, the abundance of oxidized and reduced Mn oxidation states varied with distance from pores consistently with anticipated O2 diffusion, while in the soil from restored prairie, the spatial patterns suggested that biological activity played a greater role in influencing Mn distributions. Based on the findings, we propose a hypothesis that Mn transformations promote C gains in soils of high plant diversity grasslands.

420. 题目: Initial soil organic carbon stocks govern changes in soil carbon: reality or artifact?
文章编号: N22102208
期刊: Global Change Biology
作者: Eric W Slessarev, Allegra Mayer, Courtland Kelly, Katerina Georgiou, Jennifer Pett-Ridge, Erin E Nuccio
更新时间: 2022-10-22
摘要: Changes in soil organic carbon (SOC) storage have the potential to affect global climate; hence identifying environments with a high capacity to gain or lose SOC is of broad interest. Many cross-site studies have found that SOC-poor soils tend to gain or retain carbon more readily than SOC-rich soils. While this pattern may partly reflect reality, here we argue that it can also be created by a pair of statistical artifacts. First, soils that appear SOC-poor purely due to random variation will tend to yield more moderate SOC estimates upon resampling, and hence will appear to accrue or retain more SOC than SOC-rich soils. This phenomenon is an example of regression to the mean. Second, normalized metrics of SOC change—such as relative rates and response ratios—will by definition show larger changes in SOC at lower initial SOC levels, even when the absolute change in SOC does not depend on initial SOC. These two artifacts create an exaggerated impression that initial SOC stocks are a major control on SOC dynamics. To address this problem, we recommend applying statistical corrections to eliminate the effect of regression to the mean, and avoiding normalized metrics when testing relationships between SOC change and initial SOC. Careful consideration of these issues in future cross-site studies will support clearer scientific inference that can better inform environmental management.

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