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24601. 题目: Persulfate activation with sawdust biochar in aqueous solution by enhanced electron donor-transfer effect
文章编号: N19071213
期刊: Science of The Total Environment
作者: Juan He, Yao Xiao, Jingchun Tang, Hongkun Chen, Hongwen Sun
更新时间: 2019-07-12
摘要: In addition to its strong adsorption capacity, the biochar-induced catalytic degradation of contaminants has attracted considerable attention recently. However, the mechanism and influential factors are poorly understood. This study investigated the persulfate (PS) activation performance of sawdust biochar (SBC) pyrolyzed at different temperatures (SBC-300 to SBC-700, respectively.) in acid orange 7 (AO7) degradation and found the main activation mechanism of it. The results demonstrated the degradation efficiency of PS/SBC system increased with the increasing SBC pyrolysis temperature. Moreover, the degradation rates of AO7 in the system could be even increased from 7% (SBC-300) to over 90% (SBC-700) under the optimum dosage of PS (9 mmol/L) and SBC (1.5 g/L). The reaction mainly took place in the pore and near the surface of SBC which was defined as graphite electron donor-transfer complex in this study, and graphite holes played a decisive role in the reaction. Besides, SO₄⁻ and OH were the active radicals participating in the reaction. It was found that comparing with the oxygen function groups and persistent free radicals (PFRs) of SBC, the electrical conductivity and electron donor ability were playing the main roles in enhancing PS activation with biochar pyrolyzed at high temperature for AO7 degradation.
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24602. 题目: Eco-efficient treatment of ion exchange spent brine via electrodialysis to recover NaCl and minimize waste disposal
文章编号: N19071212
期刊: Science of The Total Environment
作者: Maryam Haddad, Laurent Bazinet, Benoit Barbeau
更新时间: 2019-07-12
摘要: Natural organic matter (NOM) is removed from potable water for aesthetic, operational and indirect health concerns. NOM removal via ion exchange (IX) resins is receiving increasing attention owing to its simple operation. However, production of a spent brine during IX regeneration is the main drawback due to strict discharge regulations and limited and costly brine management options. In this study, the viability of desalinating the IX brine was assessed via electrodialysis (ED). ED desalination of the IX brine led to the production of highly pure NaCl and NOM-rich solutions which can be used for the IX regeneration and agricultural applications, respectively. Of particular interests were the impacts of the membrane permselectivity and implementation of pulsed electric field (PEF) on membrane fouling, desalination, purity of the NaCl solution and energy consumption. Our results demonstrated that ED desalination with monovalent ion permselective membranes consumed approximately 2 Wh per g of produced NaCl, achieved 88.8% desalination, produced pure NaCl solution with negligible membrane fouling. Furthermore, for the first time, we demonstrated that the PEF-ED intensified the process and decreased membrane fouling only when the conventional ion-exchange membranes were used; while no significant difference was detected when the PEF-ED was operated with the monovalent ion permselective membranes.
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24603. 题目: Degradation of propranolol by UV-activated persulfate oxidation: Reaction kinetics, mechanisms, reactive sites, transformation pathways and Gaussian calculation
文章编号: N19071211
期刊: Science of The Total Environment
作者: Tiansheng Chen, Jingshuai Ma, Qianxin Zhang, Zhijie Xie, Yongqin Zeng, Ruobai Li, Haijin Liu, Yang Liu, Wenying Lv, Guoguang Liu
更新时间: 2019-07-12
摘要: Contamination with β-blockers such as propranolol (PRO) poses a potential threat to human health and ecological system. The present study investigated the kinetics and mechanisms of PRO degradation by UV-activated persulfate (UV/PS) oxidation. Here, the experimental results showed that the degradation of PRO followed pseudo-first-order reaction kinetics, the degradation rate constant (k_obs) was increased dramatically with increasing PS dosage or decreasing initial PRO concentration. And increasing the initial solution pH could also enhance the degradation efficiency of PRO. Radical scavenging experiments demonstrated that the main radical species was sulfate radicals (SO₄^•−), with hydroxyl radicals (HO·) playing a less important role. Meanwhile, the second-order rate constants of PRO degradation with SO₄^•− and HO· were determined to be 1.94 × 10¹⁰ M⁻¹ s⁻¹ and 6.77 × 10⁹ M⁻¹ s⁻¹, respectively. In addition, the presence of natural organic matter (NOM) and nitrate anion (NO₃⁻) showed inhibitory effect on PRO degradation, whereas bicarbonate anion (HCO₃⁻) and chlorine anion (Cl⁻) greatly enhanced the degradation of PRO. Moreover, the transformation products of PRO were identified by applying ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) technique. Molecular orbital calculations were used to estimate the reaction site of PRO with radicals, simultaneously. Hence, the transformation pathways including hydroxylation, dehydration, naphthalene ring opening, and the cleavage of aldehyde groups were proposed. This work enriches the mechanism of PRO degradation under UV/PS system on the basis of results obtained by experimental characterization and Gaussian theoretical calculation.
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24604. 题目: Activated biochar with iron-loading and its application in removing Cr (VI) from aqueous solution
文章编号: N19071210
期刊: Colloids and Surfaces A: Physicochemical and Engineering Aspects
作者: Rao He, Xingzhong Yuan, Zhongliang Huang, Hou Wang, Longbo Jiang, Jing Huang, Mengjiao Tan, Hui Li
更新时间: 2019-07-12
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24605. 题目: Driving factors of soil organic carbon fractions over New South Wales, Australia
文章编号: N19071209
期刊: Geoderma
作者: Jonathan Gray, Senani Karunaratne, Thomas Bishop, Brian Wilson, Manoharan Veeragathipillai
更新时间: 2019-07-12
摘要: We modelled and mapped the distribution of three principal soil organic carbon (SOC) fractions across New South Wales and gained insights into the factors controlling their distribution. Carbon fractions are important for modelling soil carbon dynamics for carbon accounting, and as a potential indicator of soil quality. We considered particulate organic carbon (POC), humic organic carbon (HOC) and resistant organic carbon (ROC), which represent fractions of increasing bio-chemical stability. A dataset of 427 NSW profiles with mid-infrared (MIR) derived carbon fractions and a set of 16 predictor variables were applied. Random Forest and multiple linear regression techniques were applied, for depth intervals to 30 cm.The derived models and maps were of moderate strength, with validation results revealing Lin's concordance values for the 0–30 cm depth interval of 0.79 for total SOC stocks and 0.60 to 0.74 for the fraction stocks. Maps of mean stocks, and upper and lower 95% prediction intervals are presented. Absolute stocks (in Mg ha⁻¹) of each fraction have a strong linear relationship with total SOC and are controlled by similar environmental and land management factors, normally increasing in a systematic way with increasingly moist climate (considering rainfall and temperatures), increasing mafic lithology (associated with more fertile, clay rich soils) and less disturbed land uses with higher vegetation cover.The environmental factors influencing the relative proportions of each fraction (% of total SOC) are more complex, but climate and lithology appear to be dominant, in addition to depth in profile. An SOC vulnerability index is mapped over the State, identifying areas where the stored carbon is most vulnerable to land management or environmental change. Our findings add to the understanding of factors driving the distribution of soil carbon and its fractions, which may ultimately contribute to more effective climate change mitigation programs.
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24606. 题目: Synergic effects of biochar and polyacrylamide amendments on the mechanical properties of silt loam soil under coastal reclamation in China
文章编号: N19071208
期刊: CATENA
作者: Hongde Wang, Dongli She, Yuanhang Fei, Shengqiang Tang
更新时间: 2019-07-12
摘要: Recent surveys have reported severe erosion and slope collapse caused by a combination of the poor structure of silt loam and heavy rainfall in reclaimed areas of China. Biochar and polyacrylamide (PAM) have been widely used as amendments to protect soil from degradation and enhance plant growth. However, few studies have focused on their synergic effects on soil mechanical properties. In this study, biochar and PAM were incorporated into silt loam at rates of 0%, 2%, and 5% and 0‰, 0.4‰, and 1‰, respectively, to investigate the extent to which biochar and PAM additions affect soil consistency limits and shear strength and to evaluate the slope reliability under natural conditions. The results show that the plastic limit (PL) and liquid limit (LL) were significantly enhanced by amendments of 5% biochar and 1‰ PAM. Soil consistency limits were significantly correlated with the soil 3D fractal dimension (FD), μ-CT porosity and electrical conductivity (EC). Amendment of coastal silt loam soil with biochar resulted in decreased cohesion. The application of PAM reduced the negative effect of biochar on cohesion and considerably increased the cohesion value of the silt loam. The results of the slope stability analysis were closely related to the shear strength parameters. Biochar-amended silt loam soil in the coastal area exhibited a much lower factor of safety (FS) compared with the control soil, irrespective of the level of the water and the slope angle within the slope system. A PAM amendment in coastal silt loam soil increased the FS significantly (P < 0.05) and minimized the negative effects on the FS that was caused by the biochar amendment. Therefore, biochar and PAM could be applied to silt loam soil together to improve soil quality to enhance the slope stability under coastal reclamation in China.

24607. 题目: Morphology and pedogenesis of placic horizons in podzolic Ultisols with high clay content in humid subtropical forests
文章编号: N19071207
期刊: Geoderma
作者: Zeng-Yei Hseu, Sen-Po Wu, Shih-Hao Jien, Wen-Shu Huang, Zueng-Sang Chen
更新时间: 2019-07-12
摘要: Placic (Bsm) horizons are commonly found in different types of soils worldwide, but are very rare in Ultisols. The formation of Bsm horizon and podzolization are different processes in pedogenesis. This study collected five podzolic Ultisols containing Bsm horizons from the subalpine forests in Taiwan to illustrate the morphological characteristics and genesis of the Bsm horizons in these soils with both clay illuviation and podzolization. The distinctive Bsm horizons were 3 to 10 mm thick and had abrupt and wavy boundaries with overlying albic (E) and underlying argillic (Bt) horizons. All Bsm horizons contained over 35% of clay fraction which significantly increased from E horizon to B horizons in the pedons. The Bsm horizons showed much higher bulk density than adjacent horizons above or below them, elucidating that such iron pans were relatively impermeable to water and plant roots. The maximum contents of pedogenic Fe occurred in the Bsm horizons mainly cemented by poorly crystalline Fe oxides associated with high amounts of organic matter and epiaquic conditions. Pedogenic Al appeared to be accumulated in the Bt horizons where spodic materials were identified according to the oxalate-extractable amount of Fe and Al. The polygenetic processes of these podzolic Ultisols with Bsm horizons were proposed as three stages. Firstly, clay illuviation predominantly occurred to form Bt horizon in the interglacial periods during the mid to late Pleistocene. Then, podzolization gradually became a major process to accumulate spodic materials in the Bt horizon because of the coniferous forest formation under the cool and humid climates close to the late Pleistocene; however, water was perched at the soil surface due to poor drainage and abrupt textural change between E and Bt horizons after the Holocene. Eventually, the reduced iron from E horizon was gradually re-oxidized and precipitated on the top of Bt horizon where exhibited oxidizing condition to form Bsm horizon until today. Because of the occurrence of Bsm horizon in these Ultisols, a new subgroup Placic Epiaquults, was therefore proposed to the keys to Soil Taxonomy.

24608. 题目: Vertical distribution of isoprenoid GDGTs in suspended particles from the East China Sea shelf and implications for sedimentary TEX86H records
文章编号: N19071206
期刊: Organic Geochemistry
作者: Yaoyao Wang, Da-Wei Li, Julian P. Sachs, Jingwen Hu, Yali Cao, Li Li, Hailong Zhang, Meixun Zhao
更新时间: 2019-07-12
摘要: The TEX86H (or TEX₈₆) paleothermometer has been widely applied for reconstructing water temperature in marine settings, particularly in marginal seas which often archive paleoclimate records with high temporal resolution. Yet debate remains regarding the water depth at which the TEX86H signal is imparted in these settings. In this study, East China Sea (ECS) surface sediments and suspended particulate matter (SPM) from different water depths (0–60 m) were analyzed for lipid biomarkers to better constrain the depth to which the sedimentary TEX86H signal corresponds. Our data showed divergent vertical distributions between archaeal lipids and phytoplankton lipids. The maximum concentration of core lipid isoprenoid glycerol dialkyl glycerol tetraethers (core iGDGTs) appeared in bottom waters (2–5 m above the sea floor) at all sites, whereas phytoplankton lipids showed highest abundance in surface waters (0 m). Consistent with the maximum core iGDGTs concentration in bottom waters, the best correlation was observed between SPM TEX86H values and 2–4 weeks averaged water temperatures from the bottom waters. Moreover, the SPM core iGDGTs content was higher in bottom waters than in surface sediments, implying that in situ production rather than sediment resuspension leads to the maximum concentration of core iGDGTs in bottom waters. By compiling published surface sediment data from water depths < 100 m we find that the correlation of TEX86H with bottom water temperature (BWT) exceeds that with sea surface temperature (SST). Therefore, it is proposed that sedimentary TEX86H is a BWT proxy in the shallow ECS.

24609. 题目: Real-time monitoring of the membrane biofouling based on spectroscopic analysis in a marine MBBR-MBR (moving bed biofilm reactor-membrane bioreactor) for saline wastewater treatment
文章编号: N19071205
期刊: Chemosphere
作者: Zhengyu Yu, Weiguo Li, Songwen Tan
更新时间: 2019-07-12
摘要: A MBBR-MBR system has been developed with marine microorganisms enriched for saline wastewater treatment in this work, showing high COD and NH₃–N removals. The behaviour of fouling-related components (EPS and SMP) has been studied as functions of operating time (40–90 days), salinity (0–30 g/L NaCl) and backflow ratio (0–300%, from MBR to MBBR). High biodegradability of the MBBR-MBR at optimal conditions can induce more biodegradation of humic acid-like (λ_ex/λ_em: 350nm/430 nm) and fulvic acid-like (260nm/445 nm) molecules to soluble microbial by-product-like molecules (275nm/325 nm), reducing the membrane biofouling rate. The biodegradation process is suggested by the excitation-emission matrix (EEM) images. In the study of sudden salinity shock, results show that real-time monitoring the concentration of biofoulants is more effective (operative time extended by 60%) than monitoring the transmembrane pressure (operative time extended by 33%) to prevent membrane fouling. Due to an early warning from the real-time monitoring, the coming membrane-fouling is predictable and the operating conditions, such as backflow ratio, can be changed to minimize the biofouling rate.

24610. 题目: Mechanisms on the impacts of humic acids on persulfate/Fe²⁺-based groundwater remediation
文章编号: N19071204
期刊: Chemical Engineering Journal
作者: Xiaodong Li, Bin Wu, Qian Zhang, Duanping Xu, Yuqin Liu, Fujun Ma, Qingbao Gu, Fasheng Li
更新时间: 2019-07-12
摘要: Persulfate (PS) has been increasingly applied for in situ chemical oxidation of organic contaminants in groundwater, while the impacts of humic acids (HAs) on the efficiency of persulfate/Fe²⁺-based remediation are not well understood. This study examined the effects of HAs originating from different places, including three commercial HAs and two soil HAs, on 2,4-dinitrotoluene (DNT) degraded by PS/Fe²⁺. DNT degradation by PS/Fe²⁺ was dependent on the types and concentrations of HAs and pH in solution. The positive correlation between the first order kinetic rate constant of DNT degradation by PS/Fe²⁺/HAs and the conditional stability constant (K_M) indicates that the complexation of HAs with Fe³⁺ was beneficial to the degradation of DNT. The first order kinetic rate constant of DNT degradation by PS/Fe²⁺/HAs correlated well with their absorbance intensity of HAs at 465 or 665 nm. High positive correlation coefficients indicated that π-electrons of HAs strongly influenced DNT degradation, which was consistent with the results provided by solid-state ¹³C NMR spectra. Two-dimensional correlation spectroscopy (2DCOS) analysis confirmed that the fulvic-like fraction of HAs is prior to the humic-like fraction complexed with Fe³⁺.
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24611. 题目: Reductive dissolution of jarosite by a sulfate reducing bacterial community: Secondary mineralization and microflora development
文章编号: N19071203
期刊: Science of The Total Environment
作者: Kun Gao, Mengge Jiang, Chuling Guo, Yufei Zeng, Cong Fan, Junhui Zhang, John R. Reinfelder, Weilin Huang, Guining Lu, Zhi Dang
更新时间: 2019-07-12
摘要: Jarosite is an iron-hydroxysulfate mineral commonly found in acid mine drainage (AMD). Given its strong adsorption capacity and its ability to co-precipitation with heavy metals, jarosite is considered a potent scavenger of contaminants in AMD-impacted environments. Sulfate-reducing bacteria (SRB) play an important role in the reductive dissolution of jarosite; however, the mechanism involved has yet to be elucidated. In this study, an indigenous SRB community enriched from the Dabaoshan mine area (Guangdong, China) was employed to explore the mechanism of the microbial reduction of jarosite. Different cultures, with or without dissolved sulfate and the physical separation of jarosite from bacteria by dialysis bags, were examined. Results indicate that the reduction of jarosite by SRB occurred via an indirect mechanism. In systems with dissolved sulfate, lactate was incompletely oxidized to acetate coupled with the reduction of SO₄²⁻ to S²⁻, which subsequently reduced the Fe³⁺ in jarosite, forming secondary minerals including vivianite, mackinawite and pyrite. In systems without dissolved sulfate, jarosite dissolution occurred prior to reduction, and similar secondary minerals formed as well. Extracellular polymeric substances secreted by SRB appeared to facilitate the release of sulfate from jarosite. Structural sulfate in the solid phase of jarosite may not be available for SRB respiration. Although direct contact between SRB and jarosite is not necessary for mineral reduction, wrapping jarosite into dialysis bags suppressed the reduction to a certain extent. Microbial community composition differed in direct contact treatments and physical separation treatments. Physical separation of the SRB community from jarosite mineral supported the growth of Citrobacter, while Desulfosporosinus dominated in direct contact treatments.
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24612. 题目: Nutrient enrichment induces a shift in dissolved organic carbon (DOC) metabolism in oligotrophic freshwater sediments
文章编号: N19071202
期刊: Science of The Total Environment
作者: F.L. Brailsford, H.C. Glanville, P.N. Golyshin, M.R. Marshall, C.E. Lloyd, P.J. Johnes, D.L. Jones
更新时间: 2019-07-12
摘要: Dissolved organic carbon (DOC) turnover in aquatic environments is modulated by the presence of other key macronutrients, including nitrogen (N) and phosphorus (P). The ratio of these nutrients directly affects the rates of microbial growth and nutrient processing in the natural environment. The aim of this study was to investigate how labile DOC metabolism responds to changes in nutrient stoichiometry using ¹⁴C tracers in conjunction with untargeted analysis of the primary metabolome in upland peat river sediments. N addition led to an increase in ¹⁴C-glucose uptake, indicating that the sediments were likely to be primarily N limited. The mineralisation of glucose to ¹⁴CO₂ reduced following N addition, indicating that nutrient addition induced shifts in internal carbon (C) partitioning and microbial C use efficiency (CUE). This is directly supported by the metabolomic profile data which identified significant differences in 22 known metabolites (34% of the total) and 30 unknown metabolites (16% of the total) upon the addition of either N or P. ¹⁴C-glucose addition increased the production of organic acids known to be involved in mineral P dissolution (e.g. gluconic acid, malic acid). Conversely, when N was not added, the addition of glucose led to the production of the sugar alcohols, mannitol and sorbitol, which are well known microbial C storage compounds. P addition resulted in increased levels of several amino acids (e.g. alanine, glycine) which may reflect greater rates of microbial growth or the P requirement for coenzymes required for amino acid synthesis. We conclude that inorganic nutrient enrichment in addition to labile C inputs has the potential to substantially alter in-stream biogeochemical cycling in oligotrophic freshwaters.
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24613. 题目: Effects of different long-term tillage systems on the composition of organic matter by ¹³C CP/TOSS NMR in physical fractions in the Loess Plateau of China
文章编号: N19071201
期刊: Soil and Tillage Research
作者: Lili Gao, Bisheng Wang, Shengping Li, Ya Han, Ximei Zhang, Daozhi Gong, Mingchao Ma, Guopeng Liang, Huijun Wu, Xueping Wu, Dianxiong Cai, Aurore Degré
更新时间: 2019-07-12
摘要: The adoption of conservation tillage is promising for soil management system in the Loess Plateau of China; however, how conservation tillage influences the molecular structure contributes and long-term stabilization of soil organic matter (SOM) is still not clear in this area. In this study, experimental plots were continually cultivated with winter wheat (Triticum aestivum L.) and soil samples were collected in September 2009 and September 2015, 10 and 16 years after the experiment was initiated, respectively. Four treatments were applied: reduced tillage (RT), no tillage (NT), sub-soiling (SS) and conventional tillage (CT). Soil samples were physically fractionated into five fractions: free light fraction (FLF), occluded light fraction (OLF), coarse sand particulate organic matter (c-POM), fine sand particulate organic matter (f-POM) and mineral associated organic matter + silt + clay (m-SOM). The soil organic carbon (SOC) stocks were analysed in SOM fractions and bulk soil (BS). Solid state ¹³C cross polarization/total sideband suppression nuclear magnetic resonance (¹³C CP/TOSS NMR) spectroscopy was applied to determine the abundance of different forms of carbon (C) (carboxyl C, O/N-alkyl C, aromatic C and alkyl C) in the soil physical fractions.The SOC stocks in the 0–30 cm layer were influenced by the tillage systems. Although there were no significant differences in SOC stocks among these four treatments in the 0–10 and 10–20 cm layers in first 10 years, after 16 years, the SOC stocks were highest in the SS and NT treatments in the 0–10 cm layer. As the duration of the experiment increased from 2009 to 2015, the SOC content of m-SOM-C fraction under RT and CT also increased. As determined by ¹³C NMR, in the light fractions (FLF to OLF), the abundance of aromatic C increased when the abundance of O/N-alkyl C declined and there was a higher aromatic C/O/N-alkyl C ratio. A gradual increase in the abundance of alkyl C of heavy fractions was accompanied by a decrease in aromatic C, which might be due to the microbial by-products deposited on mineral surface in the soils. In addition, a higher SOM preservation were shown in conservation tillage (NT and SS) by our NMR data. Particular interesting were the results of the light and c-POM fractions, in which conservation tillage showed a higher abundance of O/N-alkyl C and a lower aromatic C/O/N-alkyl C ratio in these two fractions compared with conventional tillage (RT and CT).However, these changes were not evident in the heavy fractions. The changes in the chemical structures of the light and c-POM fractions were possibly due to the retention of crop residues and low levels of soil disturbance. In conclusion, long-term conservation tillage affected the fractions and the chemical functional groups of SOM and could be ideal to preserve SOC in the Loess Plateau.

24614. 题目: Temperature sensitivity of SOM decomposition governed by aggregate protection and microbial communities
文章编号: N19071107
期刊: Science Advances
作者: Shuqi Qin, Leiyi Chen, Kai Fang, Qiwen Zhang, Jun Wang, Futing Liu, Jianchun Yu, Yuanhe Yang
更新时间: 2019-07-11
摘要: Temperature sensitivity ( Q 10 ) of soil organic matter (SOM) decomposition is a crucial parameter for predicting the fate of soil carbon (C) under global warming. However, our understanding of its regulatory mechanisms remains inadequate, which constrains its accurate parameterization in Earth system models and induces large uncertainties in predicting terrestrial C-climate feedback. Here, we conducted a long-term laboratory incubation combined with a two-pool model and manipulative experiments to examine potential mechanisms underlying the depth-associated Q 10 variations in active and slow soil C pools. We found that lower microbial abundance and stronger aggregate protection were coexisting mechanisms underlying the lower Q 10 in the subsoil. Of them, microbial communities were the main determinant of Q 10 in the active pool, whereas aggregate protection exerted more important control in the slow pool. These results highlight the crucial role of soil C stabilization mechanisms in regulating temperature response of SOM decomposition, potentially attenuating the terrestrial C-climate feedback.

24615. 题目: Drivers of carbon export efficiency in the global ocean
文章编号: N19071106
期刊: Global Biogeochemical Cycles
作者: Stephanie Henson, Fred Le Moigne, Sarah Giering
更新时间: 2019-07-11
摘要: The export of organic carbon from the surface ocean forms the basis of the biological carbon pump, an important planetary carbon flux. Typically, only a small fraction of primary productivity (PP) is exported (quantified as the export efficiency: export/PP). Here we assemble a global data synthesis to reveal that very high export efficiency occasionally occurs. These events drive an apparent inverse relationship between PP and export efficiency, which is opposite to that typically used in empirical or mechanistic models. At the global scale, we find that low PP, high export efficiency regimes tend to occur when macrozooplankton and bacterial abundance are low. This implies that a decoupling between PP and upper ocean remineralisation processes can result in a large fraction of PP being exported, likely as intact cells or phytoplankton‐based aggregates. As the proportion of PP being exported declines, macrozooplankton and bacterial abundances rise. High export efficiency, high PP regimes also occur infrequently, possibly associated with non‐biologically mediated export of particles. A similar analysis at a biome scale reveals that the factors affecting export efficiency may be different at regional and global scales. Our results imply that the whole ecosystem structure, rather than just the phytoplankton community, is important in setting export efficiency. Further, the existence of low PP, high export efficiency regimes imply that biogeochemical models that parameterise export efficiency as increasing with PP may underestimate export flux during decoupled periods, such as at the start of the spring bloom.

24616. 题目: Linking dissolved organic matter composition and bacterioplankton communities in an Amazon floodplain system
文章编号: N19071105
期刊: Limnology and Oceanography
作者: Michaela L. de Melo, Dolly N. Kothawala, Stefan Bertilsson, João Henrique Amaral, Bruce Forsberg, Hugo Sarmento
更新时间: 2019-07-11
摘要: Dissolved organic matter (DOM) is the main substrate for aquatic prokaryotes, fuelling their metabolism and controlling community composition. Amazonian rivers transport and process large fluxes of terrestrial DOM, but little is known about the link between DOM composition and heterotrophic bacteria in the Amazon basin. The aims of this study were to characterize DOM composition and investigate the coupling between DOM and bacterial community composition (BCC) during a complete hydrological cycle in an Amazon floodplain system (lake Janauacá). Our study revealed a clear seasonal pattern in DOM composition through the flood pulse, which affected the amounts of autochthonous and allochthonous inputs and consequently the extent of humification, molecular weight, and aromaticity of the DOM. BCC was tightly coupled to DOM fluorescence, which was also driven by differences over the hydrological cycle, with distinct components and operational taxonomic units being simultaneously more abundant and correlating with a specific season. This coupling was particularly well reflected for three of the four identified fluorescence components, two terrestrial humic‐like components (C1 and C3) and an autochthonous component (C4). Despite clear changes in DOM composition, dissolved organic carbon concentrations tended to be relatively stable throughout the year. Overall, our results suggest that BCC shifts were associated with DOM quality but not with its quantity (that remains relatively constant throughout the year), and that bacteria preferably use labile and freshly produced DOM in lake Janauacá.

24617. 题目: Fractal features of sandy soil particle-size distributions during the rangeland desertification process on the eastern Qinghai-Tibet Plateau
文章编号: N19071104
期刊: Journal of Soils and Sediments
作者: Xiao Feng, Jianjun Qu, Lihai Tan, Qingbin Fan, Qinghe Niu
更新时间: 2019-07-11
摘要: Purpose: Fractal theory has been frequently applied to quantify soil particle-size distributions (PSDs) and evaluate soil degradation. Eolian desertification occurring on the eastern Qinghai-Tibet Plateau is threatening the ecological environment. It is essential to investigate the desertification process by adopting the concept of space as a substitute for time. Here, the fractal features of soil PSDs and their relationships with selected soil properties and wind erosion and deposition were studied. Materials and methods: The tested soil samples were collected from rangelands with four different degrees of desertification (light, medium, severe, and extremely severe). Soil particle sizes were measured by a laser diffraction particle-size analyzer. Soil moisture and soil bulk density were determined by the soil weight difference before and after oven-drying for 8 h. Soil organic carbon was determined by the K₂Cr₂O₇-H₂SO₄ oxidation method and soil total nitrogen was analyzed using the Kjeldahl digestion procedure. Wind tunnel experiments were conducted to simulate wind erosion and deposition during the desertification process. Values of the fractal dimension of soil PSDs were calculated using the volume-based fractal model. ANOVA with an LSD test and Pearson correlation analysis were used to analyze whether different parameters used in the fractal model influenced the results of the fractal dimensions and were reasonable to be applied. Results and discussion: Different parameters, including the arithmetic mean size and the upper sieve size of two successive sieve sizes, values of R_min, and the number of data points used in the fractal model, rarely influenced the results of the fractal dimensions (p > 0.05). The D values showed a significantly positive correlation with the clay and silt contents and a strong negative correlation with the sand contents. Along the degrees of desertification from light to extremely severe, the contents of clay, silt, and very fine sand decreased while the fine sand contents increased, and the D values decreased accordingly. Rangelands with heavier desertification and lower D values were more easily exposed to wind erosion, relating to the further loss of soil organic carbon, soil total nitrogen, and soil moisture and increased soil bulk density. The soil depth could affect soil PSDs and the selected soil properties of rangelands under light and medium degrees of desertification but rarely influenced those of severely and extremely severely desertified lands. Conclusions: Different parameters, including the arithmetic mean size, the upper sieve size, values of R_min, and the number of data points used in the fractal model, had no impacts on the results of the fractal dimensions, and were reasonable to be applied. We suggest the fractal dimension as an effective indicator to evaluate soil environment changes induced by desertification.

24618. 题目: Chemical and microbiological responses of heavy metal contaminated sediment subject to washing using humic substances
文章编号: N19071103
期刊: Environmental Science and Pollution Research
作者: Jia Wen, Lang Xing, Yongxu Wang, Guangming Zeng
更新时间: 2019-07-11
摘要: Washing of contaminated soils or sediments using humic substances (HS) extracted either from source-rich materials or compost has been tested effective to remove various heavy metals. Nevertheless, the remaining chemical fractionation of metals and post-washing biological responses were not discussed in previous research. In this study, we used a HS extracted from green waste compost to wash off Cd, As, and Ni from a contaminated sediment, and evaluated the washing effect on sediment microbes by measuring a series of indexes with regard to microbial biomass and enzyme activities. Results showed that HS washing was more effective in removing the cationic metals Cd and Ni than the anionic metal As. The highest HS dose of 2000 mg L⁻¹ resulted in 24.5-, 33.1-, and 12-fold increases of removal for Cd, Ni, and As, respectively. The remaining Cd and As were found to migrate to less stable fractions, whereas the remaining Ni was dominantly found in the residual fraction. Increases of metal removal efficiency, microbial biomass, and dehydrogenase activity were found to correlate with the increase of HS concentrations. Increasing doses of HS slightly altered sediment pH to the lower range but did not cause any significant effect on microbial activities. The study proves that HS washing is indeed a more environmental-friendly strategy than many existing washing agents which have exerted various side effects on soil properties.

24619. 题目: Soil and water conservation using biochar and various soil moisture in laboratory conditions
文章编号: N19071102
期刊: CATENA
作者: Leila Gholami, Nabiyeh Karimi, Ataollah Kavian
更新时间: 2019-07-11
摘要: Some organic and inorganic conditioners have extraordinary potential in reducing runoff and soil erosion. On the other hand, the initial soil moisture is one of the most efficient factors in changing runoff and soil erosion. In this work, the applicability of biochar from sewage sludge at three concentrations (0.4 (B₁), 0.8 (B₂) and 1.6 (B₃) t ha⁻¹) in controlling erosion of soils with four initial moisture contents (10 (M₁), 15 (M₂), 20 (M₃), and 30 (M₄) percent) was conducted under rainfall simulator in a lab experiment. The results showed that biochar at all treatments had a suitable role in soil and water conservation by increasing the time to runoff, reducing the runoff and soil erosion at all the moisture treatments. The decreased runoff coefficient in initial soil moistures of 10, 15, 20 and 30% was 40, 55, 24 and 8% (for B₁), 52, 63, 36 and 24% (for B₂) and 23, 27, 46 and 59% (for B₃), respectively; the soil erosion rate for the same initial soil moistures was 80, 79, 71 and 83% (for B₁), 89, 82, 77 and 86% (for B₂) and 91, 85, 85 and 88% (for B₃), respectively. The maximum reduction in soil erosion was observed in 1.6 t ha⁻¹ biochar and 10% moisture. Therefore, the application of this biochar is affordable, useful and safe method in reducing runoff, soil erosion and sediment concentration as well as decreasing the environmental pollutants.

24620. 题目: In-situ multi-sensor characterization of soil cores along an erosion-deposition gradient
文章编号: N19071101
期刊: CATENA
作者: Martin Leue, Carsten Hoffmann, Wilfried Hierold, Michael Sommer
更新时间: 2019-07-11
摘要: Soil landscape research is faced with wide-ranging questions of soil erosion, precision farming, and agricultural risk management. Digital Soil Morphometrics is a powerful tool to provide respective answers or recommendations but requires soil data from the pedon-to-field scale with high horizontal and vertical resolutions, including the subsoil. We present an efficient sampling and measurement method for easily obtainable soil driving cores with low-destructive preparation. Elemental contents and soil organic and mineral matter composition were measured rapidly and in large numbers using a multi-sensor approach, i.e., visible and near-infrared (Vis-NIR), diffuse reflectance infrared Fourier transform (DRIFT), and X-ray fluorescence (XRF) spectroscopy. The suitability of the approach with respect to three-dimensional soil landscape models was tested using soils along a slope representing different stages of erosion and deposition in a hummocky landscape under arable land use (Calcaric Regosols, Calcic Luvisols, Luvic Stagnosols, Gleyic-Colluvic Regosols). The combination of soil core sampling, pedological description, and three spectroscopic techniques enabled rapid determination and interpretation of horizontal and vertical spatial distributions of soil organic carbon (SOC), soil organic and mineral matter composition, as well as CaCO₃, Fe, and Mn contents. Depth profiles for SOC, CaCO₃, and Fe contents were suitable indicators for site-specific degrees of erosion and matter transport processes at the pedon-to-field scale. Fe and Mn profiles helped identifying zones of reductive and oxic domains in subsoils (gleyzation). Further methodical developments should implement plant-availability of nutrients, characterization of Fe-oxides, and calibration of the spectroscopic techniques to field-moist samples.