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41. 题目: Interactions between biochar and clay minerals in changing biochar carbon stability
文章编号: N21102306
期刊: Science of The Total Environment
作者: Fanqi Jing, Yuqing Sun, Yuyan Liu, Zhonghao Wan, Jiawei Chen, Daniel C.W. Tsang
更新时间: 2021-10-23
摘要: The science-informed design of stable carbonaceous materials as ‘green’ soil amendment will be indispensable for improving the soil fertility and carbon sequestration ability. In this study, a series of biochars were prepared from mineral-rich cellulosic corn straw (C), lignocellulosic pine wood (P), and lignin-rich walnut shell (W) at 500 or 700 °C. Their change of carbon stability after 90-day interaction with two typical soil clay minerals (i.e., kaolinite or montmorillonite) under a field-relevant condition (mass ratio of biochar to soil clay at 1:5) was evaluated as carbon loss (%) determined by the K2CrO7-H2SO4 oxidation method. The spectroscopic analyses demonstrated that the highly graphitized and microporous W-biochars exhibited a high carbon stability (35.6–40.2% C loss) that could be further enhanced in the presence of kaolinite or montmorillonite. This promotion was probably ascribed to the transformation from the aromatic CC/CC functionality to the ester CO and methyl CH configurations on the biochar surface forming stable organo-mineral complexes (i.e., COAl) with the clay minerals. In contrast, a substantial level of labile C fraction was observed in the C- and P-biochars (e.g., 94.8% C loss of P700-M) after incubation with the clay minerals, especially for montmorillonite with high CEC, swelling capacity, and week interlayer bonding. This adverse impact was possibly attributed to the aliphatic CC/CC bonding with low oxidation resistance after co-precipitation with the clay minerals. The results of this study can provide deeper insight into the evolution of physicochemical properties, porous structure, and carbon interactions during long-term biochar application for carbon sequestration and sustainable development.

42. 题目: Comparing the effects of algae and macrophyte residues' degradation on biological nitrogen fixation in freshwater lake sediments
文章编号: N21102305
期刊: Science of The Total Environment
作者: Linqi Tian, Helong Jiang, Na Song, Shangwei He, Farasat Ali
更新时间: 2021-10-23
摘要: The degradation and mineralization of organic residues are important factors that drive biochemical processes in lake ecosystems. However, the effect of organic matter's degradation on biological nitrogen fixation (BNF) in freshwater lake sediments remains poorly understood. This study investigated the response of sediment nitrogen fixation to the degradations of algae and macrophyte residues through continuous flow mesocosms combined with nifH sequencing analysis and isotope tracing. The results suggested that the active nitrogen fixation of sediments only occurred in the first two weeks of the rapid degradation of organic residues. Degradation of algae and macrophytes residues quickly increased the nifH abundance and the nitrogenase activity (NA) in sediments; however, the maximum NA triggered by algae's degradation (658.2 ± 16.8 ng g−1 day−1) was six times higher than that induced by the degradation of macrophytes residues. There was no significant difference in NA of sediments with the degradation of Potamogeton and Phragmites. Redundancy analysis (RDA) showed that the variation of diazotrophic community in sediment was significantly (p < 0.01) correlated with the concentrations of SO42− and NH4+ in overlying water and the Fe(II) content and Eh in sediment. Overall, the BNF of sediments can quickly respond to the degradation of organic residues, and the degradation of algae has a stronger promoting effect on the nitrogen fixation in sediments than that of macrophyte residues.

43. 题目: Light absorption properties and molecular compositions of water-soluble and methanol-soluble organic carbon emitted from wood pyrolysis and combustion
文章编号: N21102304
期刊: Science of The Total Environment
作者: Ranran Zhao, Qixing Zhang, Xuezhe Xu, Wenjia Wang, Weixiong Zhao, Weijun Zhang, Yongming Zhang
更新时间: 2021-10-23
摘要: Organic carbon (OC) emitted from biomass burning (BB) plays an important role in the global radiation budget. In this work, primary OC emitted from wood pyrolysis and combustion under nitrogen (N2) and air conditions in a tube furnace was investigated. The absorption spectra, chemical functional groups, and molecular compositions of OC were analyzed using UV–Vis-NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. The light absorption properties showed that the mass absorption efficiency at 365 nm (MAE365) of methanol-soluble OC (MSOC) is 3.1–3.8 times higher than that of water-soluble OC (WSOC). Moreover, the MAE365 values derived from the N2 pyrolysis atmosphere are higher than that from the air atmosphere for both MSOC and WSOC. These results indicated that OC extracted by methanol has higher light absorption, especially for the OC emitted from the N2 pyrolysis atmosphere. Although the FTIR spectra showed identical functional groups for the OC from the air and N2 conditions, molecular compositions from the FT-ICR MS analysis presented significant differences. The molecular weight (MW), double bonds equivalent (DBE), DBE/C, and modified aromaticity index (AImod) of extracted OC showed higher values in MSOC than those in WSOC, and higher values under the N2 atmosphere than those under the air atmosphere. In addition, MAE365 showed positive correlations with MW (r = 0.94), DBE (r = 0.88), DBE/C (r = 0.96), and AImod (r = 0.97), whereas negative correlations with H/C (r = −0.97), O/C (r = −0.90), N/C (r = −0.88), and S/C (r = −0.93). These results indicated that molecules with larger MW and a high level of unsaturation and aromaticity present higher light absorption, while molecules with high elemental ratios of H/C, O/C, N/C, and S/C are adverse to light absorption.

44. 题目: Poorly conductive biochar boosting extracellular electron transfer for efficient volatile fatty acids oxidation via redox-mediated mechanism
文章编号: N21102303
期刊: Science of The Total Environment
作者: Gaojun Wang, Yao Xing, Guohao Liu, Yuxi Chu, Gaofei Yao, Qian Li, Rong Chen
更新时间: 2021-10-23
摘要: This study explored the performances, and associated mechanisms of biochar promoting volatile fatty acids (VFA) oxidation via extracellular electron transfer (EET) pathway. It was found that in a bioelectrochemical system, adding biochar suspension remarkably enhanced electricity generation whatever acetate or propionate used as an electron donor. The maximum current density in biochar-assisted groups reached 1.6–2.2 A/m2, which were 69.2–220.0% higher than that of control groups. The lower electrical resistance of anode in biochar-assisted groups was potentially attributed to the formed biofilm dominated by electro-active Geobacteraceae, and the electron donor type depending on dominant genus. In specific, with biochar assistance, Desulfuromonas enriched from 1.1% to 25.0% when acetate as an electron donor, and the relative abundance of Geobacter increased from 4.6% to 31.7% as dominant genus in propionate-add group. Electrochemical analysis uncovered that biochar hardly elevated sludge electrical conductivity, while the excellent redox-based electron exchange transfer capacity likely made biochar as a transient electron acceptor, which is more accessible than anode to support the metabolism of electroactive bacteria in the initial stage. Meanwhile, the porous surface area of biochar particle likely provided a “bridge” between suspended sludge and anode, to support a more directional evolution of electroactive bacteria on anode. This dual-function of biochar achieved a sustainable VFA oxidation via EET-based pathway.

45. 题目: Natural organic matter under human‐influenced environments: Implication in future environmental quality research
文章编号: N21102302
期刊: Journal of Environmental Quality
作者: Alex T Chow
更新时间: 2021-10-23
摘要: Many recent researches have confirmed that anthropogenic materials including microplastics and nanomaterials have been integrated into soil and dissolved organic matter in the environments. These pools of organic matter could be geochemically processed through different pathways and have different chemical and physical characteristics than the pools of natural organic matter (NOM). However, environmental scientists and engineers currently refer any organic matter collected in soil, water and sediments as NOM. Since “real” NOM pools are rapidly dissipated due to losses in natural landscapes, the shift from NOM into human influenced-organic matter (Hi-OM) pools could have huge ecological impacts on the environment. Future environmental quality research should highlight the differences between Hi-OM from NOM.

46. 题目: Factors controlling the spatial variability of soil aggregates and associated organic carbon across a semi-humid watershed
文章编号: N21102301
期刊: Science of The Total Environment
作者: Pingping Zhang, Yunqiang Wang, Lan Xu, Hui Sun, Ruijie Li, Jingxiong Zhou
更新时间: 2021-10-23
摘要: Soil aggregates (SA) play crucial roles in soil organic carbon (SOC) sequestration. Different SA fractions contribute differently to the sequestration of SOC. However, few studies have examined the factors controlling SA fractions and associated SOC contents across a watershed. Soil samples were collected at 0–10 cm (surface layer) and 10–20 cm (subsurface layer) from 88 sites across a semi-humid watershed (1.1 km2) on the Loess Plateau, China. These samples were separated into macroaggregates (MA), microaggregates (MI), and silt + clay fractions (SC) by wet-sieving, and SOC content of each fraction was determined. The objectives were to: 1) investigate the spatial variability of SA fractions and associated SOC contents as well as their main controls across an entire watershed, and 2) explore the linkages between soil aggregation and SOC sequestration. The bulk and aggregate SOC contents of all SA fractions showed moderate variability, with coefficient of variations of 23.3–31.9%. Geostatistical analysis indicated that the spatial patterns of SA fractions and SOC content varied with aggregate size. From combined Spearman's correlation analysis and structural equation modelling, we found that soil texture was an important control on the spatial variability of all SA fractions and associated SOC contents. Vegetation dynamics and management practices associated with land use were also important controls on MA and MI and their associated SOC contents, especially in the surface layer. However, SC and its associated SOC content were more sensitive to eco-hydrological processes related to topography. Among the land uses, grassland had the greatest SOC sequestration potential. The fine roots of herbs can wrap MI in MA and increase SOC content within MA, which is the primary mechanism responsible for SOC sequestration in grasslands. These results indicate that using vegetation with fine root systems for restoration is a good strategy to increase SOC sequestration in this region.

47. 题目: Living, dead, and absent trees ‐ How do moth outbreaks shape small‐scale patterns of soil organic matter stocks and dynamics at the Subarctic mountain birch treeline?
文章编号: N21102216
期刊: Global Change Biology
作者: Nele Meyer, Yi Xu, Katri Karjalainen, Sylwia Adamczyk, Christina Biasi, Lona van Delden, Angela Martin, Kevin Mganga, Kristiina Myller, Outi‐Maaria Sietiö, Otso Suominen, Kristiina Karhu
更新时间: 2021-10-22
摘要: Mountain birch forests (B. pubescens Ehrh. ssp. czerepanovii) at the subarctic treeline not only benefit from global warming, but are also increasingly affected by caterpillar outbreaks from foliage-feeding geometrid moths. Both of these factors have unknown consequences on soil organic carbon (SOC) stocks and biogeochemical cycles. We measured SOC stocks down to the bedrock under living trees and under two stages of dead trees (12 and 55 years since moth outbreak) and treeless tundra in northern Finland. We also measured in-situ soil respiration, potential SOC decomposability, biological (enzyme activities, microbial biomass), and chemical (N, mineral N, pH) soil properties. SOC stocks were significantly higher under living trees (4.1±2.1 kg m²) than in the treeless tundra (2.4±0.6 kg m²), and remained at an elevated level even 12 (3.7±1.7 kg m²) and 55 years (4.9±3.0 kg m²) after tree death. Effects of tree status on SOC stocks decreased with increasing distance from the tree and with increasing depth, i.e. a significant effect of tree status was found in the organic layer, but not in mineral soil. Soil under living trees was characterized by higher mineral N contents, microbial biomass, microbial activity, and soil respiration compared with the treeless tundra; soils under dead trees were intermediate between these two. The results suggest accelerated organic matter turnover under living trees but a positive net effect on SOC stocks. Slowed organic matter turnover and continuous supply of deadwood may explain why SOC stocks remained elevated under dead trees, despite the heavy decrease in aboveground C stocks. We conclude that the increased occurrence of moth damage with climate change would have minor effects on SOC stocks, but ultimately decrease ecosystem C stocks (49% within 55 years in this area), if the mountain birch forests will not be able to recover from the outbreaks.

48. 题目: Distribution, behavior and budget of Pb in suspended particles in the Changjiang Estuary and adjacent east China sea
文章编号: N21102215
期刊: Chemosphere
作者: Yu Yu, Sun Junchuan, Li Bing, Dong Xiaoyu, Ren Yichao
更新时间: 2021-10-22
摘要: Content, isotopes and budget of Pb in suspended particulate matter (SPM) in the Changjiang Estuary and adjacent East China Sea (ECS) were determined to investigate the biogeochemical cycling of particulate Pb in coastal sea. The content of particulate Pb ranged from 11.3 to 669.4 μg/g in February (winter) and from 20.1 to 79.4 μg/g in August (summer). Except in surface water, particulate Pb content in August is higher than that in February. In lower water, particulate Pb and Th and SPM all decreased gradually from the estuary towards the sea, indicating their lithogenic origin from the Changjiang River. Particulate Pb displayed abnormally high concentration in February surface water, resulting from the atmospheric deposition of anthropogenic Pb in winter. 208Pb/206Pb and 207Pb/206Pb in surface water north to the estuary were higher than background values, suggesting anthropogenic disturbance of Pb. Particulate Pb content in the Changjiang River and the estuary had increased by 77–78% from the 1980s to 2016 due to pollution. Pb was also scavenged by organic matter, leading to higher Pb content in waters with high productivity. Budget of particulate Pb in the northern ECS was established. The Changjiang River contributed 97.0% and 58.1% of particulate Pb input in summer and winter half year, respectively. 88.8% of particulate Pb was deposited in the estuary and adjacent coastal sea in summer but 88.7% was exported with southward coastal currents in winter.

49. 题目: Iron-coated biochar alleviates acid accumulation and improves methane production under ammonium enrichment conditions
文章编号: N21102214
期刊: Science of The Total Environment
作者: Yuanfang Deng, Jun Xia, Rui Zhao, Jiaxing Xu, Xiaoyan Liu
更新时间: 2021-10-22
摘要: The high stress of ammonia-nitrogen in swine manure anaerobic digestion (SMAD) negatively impacts methane yields. Here, the effects of iron-coated biochar in SMAD under different ammonium stresses were investigated. Iron-coated biochar prepared at 500 °C (500BC@Fe) had a large specific surface area (123.2 cm3/g) and an acceptable ammonium adsorption capacity (5.25 mg/g). In SMAD, 500BC@Fe addition effectively broke the thermodynamic barrier from butyrate to acetate and accelerated propionate degradation. It acted as a temporary electron acceptor to promote direct interspecies electron transfer in the initial SMAD stage. As the ammonium stress sharply increased from 400 mg/L to 4000 mg/L, the methanogenesis efficiency decreased from 94.3% to 94.0% and the biochemical methane potential decreased from 189.7 NmL/g VS to 176.1 NmL/g VS. A kinetic analysis showed that the predictive value of SMAD may be calculated more accurately using the Logistic function than the Modified Gompertz equation. This study provides basic theoretical data and important kinetic parameters for the intensive production of iron-coated biochar and its large-scale application in SMAD.

50. 题目: Legacy of plaggen agriculture: High soil organic carbon stocks as result from high carbon input and volume increase
文章编号: N21102213
期刊: Geoderma
作者: Livia Urbanski, Peter Schad, Karsten Kalbitz, Jan van Mourik†, Ernst Gehrt, Ingrid Kögel-Knabner
更新时间: 2021-10-22
摘要: Plaggic Anthrosols are anthropogenic soils formed by former plaggen agriculture in north-western continental Europe. Here, we present an inventory of organic carbon (OC) concentrations and stocks of Plaggic Anthrosols and of reference soils in the vicinity without plaggen fertilization history from eight sites in northwest Germany (Lower Saxony, North Rhine-Westphalia) and the eastern parts of The Netherlands (North Brabant, Overijssel). To evaluate the enrichment of Plaggic Anthrosols with OC and the implications for OC stocks, soils were analysed for basic soil properties (bulk density, pH, OC − and nitrogen (N) concentrations), texture, and acid oxalate-(FeOX) and dithionite-citrate-bicarbonate-extractable iron (FeDCB) concentrations. Organic C stocks and plant-available water capacity (PAWC) were calculated. The plaggic topsoils are characterized by high OC concentrations (6.5–36.9 mg g−1) and a thickness of 53–124 cm, in contrast to the modern cultivated ∼30 cm thick topsoils of the reference soils with 10.6–24.0 mg g−1 OC concentration. The plaggen agriculture formed a soil with improved properties and conditions for plant growth. The addition of plaggen material to the topsoils induced a volume increase as well as higher OC concentrations in the Ap horizons, resulting in significantly higher OC stocks in the Plaggic Anthrosols (6.3–14.5 kg m−2) compared to the reference soils (4.9–10.5 kg m−2). The additional soil volume amounted to 30–56% to the total soil profile depth (1.0 to 1.6 m) and comprised 25–62% of the total OC stocks. Compared to the reference soils, the volume increase of the plaggic topsoil increased the PAWC in the effective rooting zone by 1.6 to 3.4 times. Plaggic Anthrosols represent a relic of historical farming with preserved high OC concentrations and improved storage capacity for plant-available water, causing higher nutrient availability and an increase in yields, which in turn result in higher in-situ OM input, additionally contributing to high OC stocks. The results of this study demonstrate the potential of soil melioration practices similar to the former plaggen management to induce high OC concentrations and increase OC stocks in sandy agricultural soils.

51. 题目: Enhanced biodegradation of dissolved organic carbon in the western boundary Kuroshio Current when intruded to the marginal South China Sea
文章编号: N21102212
期刊: Journal of Geophysical Research: Oceans
作者: Xiaolin Li, Kai Wu, Shuai Gu, Peng Jiang, Huifang Li, Zhanfei Liu, Minhan Dai
更新时间: 2021-10-22
摘要: The advective supply of allochthonous dissolved organic carbon (DOC) from open ocean to marginal seas through western boundary current intrusion influences the regional carbon inventory and microbial activities. However, there is limited observation about this process and its biogeochemical impacts on marginal seas. In this study, we investigated the biodegradation of allochthonous DOC carried by the intrusion of the Kuroshio Current into South China Sea (SCS). Using an isopycnal mixing model, the exchange and biodegradation processes of Kuroshio-intruded DOC were quantified. We estimated that approximate 10% of the surface DOC was remineralized due to the enhanced biodegradation in the SCS. This result was supported by the on-deck bioassay experiments were also conducted under different environmental contexts. The results of modeling and on-deck incubations indicate that DOC biodegradation was enhanced by the sharp gradient of environment factors, including nutrients supply, microbial species, and bio-lability of DOC in the frontal zone during the surface water mass mixing. The amount of carbon and nitrogen released from the enhanced DOC degradation by Kuroshio intrusion was estimated to be approximately equal to 8.6 Tg C yr-1. The amount of nitrogen could contribute 0.19 - 0.70 mmol N m-2 d-1 to the surface of SCS which is comparable to the total supply from deeper water and nitrogen fixation. This study suggests that the enhanced biodegradation of DOC during the western boundary currents intrusion could serve as an important sink of oceanic DOC, and thus provide an additional nutrient source to marginal seas.

52. 题目: Do grassland management practices affect soil lignin chemistry by changing the composition of plant-derived organic matter input?
文章编号: N21102211
期刊: Plant and Soil
作者: Aliia Gilmullina, Cornelia Rumpel, Katja Klumpp, Abad Chabbi
更新时间: 2021-10-22
摘要: Background and aims Grassland management practices alter plant litter input into soil in terms of quantity and quality via defoliation, nutrient input and trampling. These alterations may impact litter decomposition and soil organic matter (SOM) quality and quantity. Here, we aimed to investigate the effect of four grassland management practices (unmanaged, low and high intensity grazing, and mowing) on organic matter (OM) input quality and its relation with SOM composition. Methods We considered three types of OM input: aboveground and belowground material from living plants and partly degraded aboveground litter. We assessed their quality based on their elemental (C and N) contents, their stable carbon isotope (13C) and their lignin composition. Results The results showed that C/N ratios differed among plant-derived OM input types but did not vary among treatments. In contrast, lignin biogeochemistry and lignin/N ratios of plant tissues were differentiated according to input type and treatment. High grazing intensity resulted in the lowest lignin/N ratios of aboveground litter. Lignin chemistry of all plant OM input types under grazing treatments indicated low maturity stage. Despite the similar lignin contribution to soil carbon under all grassland management practices, soil lignin was more degraded under mowing than under the other practices. Conclusions We conclude that grassland management may have an impact on SOM composition by altering plant OM input composition rather than its stoichiometry.

53. 题目: Biotic responses of deep-sea benthic foraminifera in the equatorial Indian Ocean during the Quaternary: Influence of the ballasting effect on organic matter by calcareous plankton skeletons
文章编号: N21102210
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Hiroyuki Takata, Jin Hyung Cho, Jeongwon Kang, Hirofumi Asahi, Hyoun Soo Lim, Yu-Hyeon Park, Sangmin Hyun
更新时间: 2021-10-22
摘要: We investigated Quaternary benthic foraminifera in core GPC1803 in the eastern equatorial Indian Ocean since ~740 ka to examine the relationship between benthic foraminiferal fauna and ballasting of particulate organic matter (POM) by calcareous plankton skeletons. Because plankton skeletons affect POM sinking in the water column as ballasts, ballasting of POM by biominerals may play an important role to linkage between the surface and deep-sea paleoceanography. We consider this scheme, based on faunal analysis of benthic foraminifera. From multidimensional scaling (MDS) of fossil benthic foraminifera, we recognized two MDS axes. Based on the scores of MDS axis 1, we subdivided our study period into five intervals and identified two major faunal transitions at ~370 ka and ~ 210 ka. After ~210 ka, the food supply to the seafloor increased with an increase in the past flux of calcareous plankton skeletons. A positive correlation between the benthic foraminifera accumulation rate and the carbonate mass accumulation rate existed during ~600–370 ka and after ~210 ka. It is reasonable to suppose that the increase in calcareous plankton skeletons stimulated more efficient vertical transport of POM through the water column due to the positive ballasting effect on POM. The ~370–210 ka period seemed to represent a transitional phase in food supply. Prior to ~370 ka, alternations among three seasonal food supply-related species were generally observed along with glacial–interglacial variations probably under lower food supply, compared with the after ~210 ka period; however, alternations among these three species became obscure and intermittent after ~370 ka. The nearly continuous common occurrences of these seasonal food supply-related species before ~370 ka might have been enhanced by a lower past flux of calcareous plankton skeletons. Scenario of ballasting of POM by biomineral might explain long-term changes of carbonate corrosivity in the Indian Ocean, similarly in the Atlantic and eastern equatorial Pacific Oceans, during the mid-Brunhes dissolution interval.

54. 题目: Binding strength of mercury (II) to different dissolved organic matter: The roles of DOM properties and sources
文章编号: N21102209
期刊: Science of The Total Environment
作者: Yuqin Wang, Jiang Liu, Van Liem-Nguyen, Shanyi Tian, Siqi Zhang, Dingyong Wang, Tao Jiang
更新时间: 2021-10-22
摘要: Dissolved organic matter (DOM) influences the environmental fate and toxic effects of trace metals such as mercury (Hg). However, because of limits in DOM analytical techniques and lack of sample diversity in past studies, it remains unclear whether the binding strength of DOM complexed with Hg(II) is related to the DOM properties. In this study, different DOM isolates (n = 26) from various sources were used to determine the conditional stability constant (logK) of DOM-Hg complexes using the equilibrium dialysis ligand exchange (EDLE) method. UV–Vis and fluorescence spectrometry was used to evaluate the correlation between logK values and DOM properties, such as chromophoric moieties, aromaticity, and molecular weight. Results demonstrated that the DOM from different sources presented a large range of binding strengths to Hg(II), because of their heterogeneous properties. Moreover, DOM chromophores, including aromaticity and molecular weight, are critical indicators of the DOM-Hg affinity in ambient-relevant circumstances. Especially, higher terrestrial DOM led to greater DOM-Hg affinity. Additionally, this study supports that UV–Vis and fluorescence spectroscopy can be used to estimate DOM composition and its binding strength with Hg(II). Furthermore, the observed relationship between logK and DOM properties provided a possible pathway of explanation for the spatial co-variations between Hg(II) concentrations and DOM characters observed in previous field investigations.

55. 题目: Response of global farmland soil organic carbon to nitrogen application over time depends on soil type
文章编号: N21102208
期刊: Geoderma
作者: Haowei Ni, Chaoyang Liu, Bo Sun, Yuting Liang
更新时间: 2021-10-22
摘要: Carbon (C) and nitrogen (N) are closely coupled to regulate the cycle of soil organic carbon (SOC) and its feedback to climate change in terrestrial ecosystem. However, the response of SOC content to N input in different soil types on time scales is still less understood. Here, we did a meta-analysis by collecting global farmland data across 60 years based on soil taxonomy, as well as our long-term field agricultural experiment from 2006 to 2019 (total number of observations, n = 301). The results showed that N addition promoted the increase of SOC content on an average of 9.1% in agrosystem, but varied considerably in different soil types (5.2%–12.0%). The SOC content of Alfisols and Mollisols soils showed a significant increasing response along the time scale. Furthermore, random forest model and structural equation model analysis indicated that climate factors and soil types indirectly affect the temporal response of SOC to N application through soil properties such as TN and C:N. This study emphasizes that the temporal response of SOC content to long-term N addition depends on soil type, with an scale-up effect in soil types with relative high SOC content (like Alfisols and Mollisols), which provides a new perspective for better understanding the C sequestration as the consequence of coupling effect of C and N in farmland system under long-term human activities.

56. 题目: Removal of Cyanobacteria using Novel Pre-pressurized Coagulation: The Effect of Cellular Properties and Algogenic Organic Matter Characteristics
文章编号: N21102207
期刊: Separation and Purification Technology
作者: Lili Li, Tongbo Yu, Shaozhe Cheng, Jing Li, Chengxuan Li, Gaohong Wang, Daoyong Tan, Lin Li, Haiyang Zhang, Xuezhi Zhang
更新时间: 2021-10-22
摘要: Pressurization pretreatment is reported as a novel pretreatment method for the coagulation removal of Microcystis sp. from eutrophicated water, as less coagulant is required than without pressurization. However, how cellular properties and algogenic organic matter (AOM) characteristics change with pressurization pretreatment and thus reduce the coagulant dose are still not understood. Using Microcystis flos-aquae in Lake Taihu, this study analyzed the changes in cellular morphology, size distribution, and charge density, as well as the changes in concentration and composition of cell-based protonated functional groups. Coagulation experiments using different combinations of cells and AOM with/without pressurization pretreatment showed that the changes in cell surface properties played a bigger role in coagulation enhancement than AOM. The enhancement of the coagulation efficiency of M. flos-aquae with pressurization pretreatment is related to the rupture of the mucilaginous sheath and subsequent exposure of cells with more active functional groups, the content of phosphodiester, carboxyl and phosphoryl functional groups on the surface of M. flos-aquae cells increased by 55%, 29% and 203%, respectively. Thus increasing the binding sites between M. flos-aquae cells and cationic polyacrylamide (CPAM). As a result, with pressurization pretreatment, the dose of CPAM was reduced from 5 mg L-1 to 0.8 mg L-1 for the same removal efficiency of 90%. These results may help us understand the mechanism by which pressurization treatment impacts M. flos-aquae coagulation and thus provide a new perspective for the low-cost and sustainable removal of cyanobacterial blooms.

57. 题目: Interactive effects of salinity and SOM on the ecoenzymatic activities across coastal soils subjected to a saline gradient
文章编号: N21102206
期刊: Geoderma
作者: Y. Dong, R. Chen, E. Petropoulos, B. Yu, J. Zhang, X. Lin, M. Gao, Y. Feng
更新时间: 2021-10-22
摘要: Salinity and soil organic matter (SOM) are key edaphic factors that exert substantial influence on soil microbial activity. To understand the interactive effects of both factors on microbial activity, nine ecoenzymes involved in C, N, P and S cycling were assayed across a saline gradient (coastal areas of the Bohai Gulf, CN). The electrical conductivity (EC) of the soils ranged from 0.14 to 13.65 dS m−1. The response of the ecoenzymatic activities (EEAs) to salinity followed a nonlinear relationship due to the interaction of SOM and salinity on EEAs. The nonlinear response demonstrated divergent patterns below and above an EC of 2 dS m−1. Specifically, when EC < 2 dS m−1, no correlation between EEAs and conductivity was observed and EEAs had a positive correlation with SOM; when EC > 2 dS m−1, the EEAs were negatively correlated with conductivity and no correlation with SOM was observed. Substrate amendment at EC < 2 dS m−1 significantly improved EEAs that reached the levels similar to those of non-saline soils, while EEAs remained unrecovered when EC > 2 dS m−1. This EC value may stand as critical (threshold) salinity. Under higher EC conditions, EEAs are mainly affected by salinity while SOM has no critical role. This becomes reversed when salinity (as EC) drops below the critical value. This study provides with a numerical salinity reference for the potential of the land ‘to be reclaimed by organic matter addition’ and assists in defining strategies for soil reclamation based on the proposed salinity threshold.

58. 题目: The influence of organic alkalinity on the carbonate system in coastal waters
文章编号: N21102205
期刊: Marine Chemistry
作者: Daniel E. Kerr, Peter J. Brown, Anthony Grey, Brian P. Kelleher
更新时间: 2021-10-22
摘要: Total alkalinity (TA) is one of the four main carbonate system variables and is a conventionally measured parameter used to characterise marine water carbonate chemistry. It is an important indicator of a waterbody's buffering capacity and a measure of its ability to resist acidification, a matter of growing concern in the marine environment. Although TA is primarily associated with the inorganic components of seawater such as bicarbonate, there is a growing consensus that dissolved organic matter (DOM) can significantly contribute to TA in coastal waters. This organic fraction of TA (OrgAlk) is typically deemed negligible and is not accounted for in conventional TA expressions. However, omission of OrgAlk can lead to the propagation of errors in subsequent carbonate system calculations and to misinterpretation of key carbonate chemistry descriptors such as calcium carbonate saturation states. Here we provide an overview of OrgAlk contributions to TA and investigate the implications of its omission in carbonate system studies conducted in coastal waters. We examine the prevalence of OrgAlk across both coastal and pelagic waters using publicly available carbonate system data products, such as GLODAP and GOMECC. Current measures to account for, incorporate and characterise the contribution of OrgAlk to TA are also critically examined.

59. 题目: Fate of Cr(VI) during aging of ferrihydrite-humic acid co-precipitates: Comparative studies of structurally incorporated Al(III) and Mn(II)
文章编号: N21102204
期刊: Science of The Total Environment
作者: Lin Zhang, Fenglian Fu, Guangda Yu, Guangzhao Sun, Bing Tang
更新时间: 2021-10-22
摘要: Ferrihydrite-humic acid co-precipitates have impacts on the adsorption and reduction of Cr(VI) in the natural environment. Besides, ferrihydrite-humic acid co-precipitates usually coexist with foreign metal cations like Al(III) and Mn(II), which may change the properties of ferrihydrite and affect the fate of Cr(VI). In this work, structurally incorporated Al(III) or Mn(II) in ferrihydrite-humic acid co-precipitates with Cr(VI) (Fh-HA-Cr-Al or Fh-HA-Cr-Mn) were prepared, and the behavior and phase transformation of co-precipitates were explored via the characterization analyses of samples during aging for 10 days. This study showed that partial adsorbed Cr(VI) was reduced to Cr(III) in the presence of humic acid, thereby reducing the toxicity of Cr(VI). Interestingly, two different results occurred because of the incorporation of Al(III) and Mn(II). Al(III) hindered the transformation of ferrihydrite and changed the aging products by inhibiting the dissolution of ferrihydrite, which decreased Cr to incorporate iron minerals. By contrast, doping of Mn(II) accelerated the phase transformation of co-precipitates, and was more conducive to the encapsulation and fixation of Cr. The results of this study can facilitate the understanding of the effects of Al(III) and Mn(II) on Cr(VI) fixation during the aging of Fh-HA-Cr.

60. 题目: Soil and organic carbon redistribution in a recently burned Mediterranean hillslope affected by water erosion processes
文章编号: N21102203
期刊: Geoderma
作者: Julian Campo, Erik L.H. Cammeraat, Eugenia Gimeno-García, Vicente Andreu
更新时间: 2021-10-22
摘要: Forest fires cause many changes in the physical, chemical and biological soil properties such as aggregation and soil organic carbon contents (SOC) as well as on soil hydrology and erosion processes. Most studies on post-fire soil erosion in Mediterranean environments have been plot-based and research at hillslope or broader scale is scarce. Understanding SOC nature, distribution and modifications, as produced by forest fires and erosion, has become crucial to model and define the role of soil erosion as source or sink of C, and to sustainably manage ecosystem services related to the soil resource. This research provides data about the loss and redistribution of soil and SOC in a Mediterranean forest hillslope burned with high severity, at the Natural Park of Sierra de Espadán, Spain. Soil was sampled in coupled hillslopes (ca. 0.25 ha) (BU: burned, CO: control) at bottom (depositional), middle (transport) and top positions (eroding) at two depths (0–2 cm, 2–5 cm), and under two environments (UC: under canopy soil, BS: bare soil). Sediments were collected after each erosive event along one year, and yields were calculated. Samples were analysed to assess aggregate stability (AS), size and density fractionations, SOC contents and stocks. The main hypothesis is that fire affects soil characteristics related to aggregation and SOC stabilization and, together with erosion processes, may modify SOC distribution within aggregates and the burned hillslope. Soils were in general very stable, but some differences in the results of the methods used were observed. Significant differences were found for the environment (under canopy vs bare) and soil depth but not for slope position. SOC content was high both at BU and CO with no significant differences. In the BU hillslope, a homogenization of SOC contents was observed along the hillslope, while in the CO, a higher SOC content was measured in the depositional and transport sites than in the eroding one. Similar trends were observed for SOC stocks. Only four erosive rain events were registered in this study, which generated no sediment yields in CO hillslope. In the BU one, sediment yields were measured (0.05–0.58 Mg ha−1, total 0.925 Mg ha y−1), which mobilised OC amounts ranging between 0.005 and 0.04 MgC ha−1. When samples were fractioned, changes were observed in the mass distribution of soil and sediment aggregates by size and density, and in the OC content between density fractions of BU soils with regard to sediment and CO soils. According to the results, effective post-fire management should be oriented to control and reduce the erosion of aggregates < 2 mm, which present the highest SOC content and are very prone to be transported off-site. This fraction should include all the partially burned biomass (free light material), which acts as a first mulching and contains high amounts of OC that should be kept within the burned hillslope to increase soil fertility, promote vegetation recovery and act as a C sink. In the BU hillslope, eroded free light material might be buried at the depositional site and if the conditions are favourable for its conservation, SOC accumulation would be promoted, which may have implications for its stabilization, and the role of soil erosion as a C sink.

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