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13221. 题目: Quantifying soil quality in a horticultural-cover cropping system
文章编号: N19060701
期刊: Geoderma
作者: Inderjot Chahal, Laura L. Van Eerd
更新时间: 2019-06-07
摘要: Understanding and interpretation of soil quality is crucial to strategize land management practices for sustaining agricultural productivity while mitigating environmental degradation. A medium-term cover crop (CC) trial, established in 2007 and repeated in 2008, at Ridgetown, Ontario was used to evaluate the comprehensive assessment of soil health (CASH), to develop a weighted soil quality index (WSQI), and to compare scores of CASH, Haney soil health test (HSHT), and WSQI in surface soil (15 cm) in 2015 and 2016 (herein referred to as site-years). Out of 25 potential soil quality indicators, 19 soil indicators were responsive to CC treatments and represented a total dataset. Using principal component analysis (PCA) of the total dataset, a minimum dataset (five indicators; pH, organic matter (OM), Solvita labile amino N (SLAN), Solvita CO2-burst, and water extractable organic C (WEOC)) was identified to calculate a WSQI. The WSQI and CASH scores were equivalent in detecting CC treatment differences in site-year 2015, but CASH detected greater magnitude (12.1%) of treatment differences than WSQI (5.7%) in site-year 2016. Cereal rye and a mixture of oilseed radish and rye (OSR + Rye) led to greater soil quality values than other tested CCs. Our results indicate the potential of CCs in significantly improving soil quality in the medium-term (6 years). This study is the first independent evaluation of CASH in a horticultural system in a humid, temperate climate, and first study to compare WSQI with commercial soil quality tests. Even though CASH and WSQI differentiated between CC treatments for soil quality evaluation in both site-years, we recommend WSQI as a valuable and practical tool (lesser number of indicators; five vs. 15), for quantifying soil quality in similar production regions and climatic conditions.
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13222. 题目: Development of CuO coated ceramic hollow fiber membrane for peroxymonosulfate activation: a highly efficient singlet oxygen-dominated oxidation process for bisphenol A degradation
文章编号: N19060614
期刊: Applied Catalysis B: Environmental
作者: Songxue Wang, Jiayu Tian, Qiao Wang, Feng Xiao, Shanshan Gao, Wenxin Shi, Fuyi Cui
更新时间: 2019-06-06
摘要: A CuO coated ceramic hollow fiber membrane with dual functionalities of membrane filtration and peroxymonosulfate (PMS) activation was successfully constructed by applying phase-inversion and dip-coating technologies. The CuO coating condition was investigated, and the optimized CuO coated ceramic hollow fiber membranes ([email protected]) exhibited excellent catalytic activity for PMS activation to depredate bisphenol A (BPA) in the presence of humic acid (HA), chloride ions (Cl-) and bicarbonate (HCO3-). Based on the scavenger experiments and electron paramagnetic resonance (EPR) analyses, the non-radical reactive oxygen species - singlet oxygen (1O2), rather than sulfate radicals (SO4•-) or hydroxyl radicals (•OH), was elucidated as the primary reactive species responsible for the oxidation of BPA in the system. The redox circles of Cu(II)/Cu(I) on the CuO surface of the [email protected] are mainly responsible for PMS activation and a possible degradation pathway of BPA was proposed. Moreover, the [email protected] exhibited excellent stability and reusability without tedious catalyst separation/recovery processes. This study is meaningful for the development of novel catalytic membrane with PMS activation functionality in water treatment.

13223. 题目: Controls on the formation of turbidity current channels associated with marine-terminating glaciers and ice sheets
文章编号: N19060613
期刊: Marine Geology
作者: Ed L. Pope, Alexandre Normandeau, Colm Ó. Cofaigh, Chris R. Stokes, Peter J. Talling
更新时间: 2019-06-06
摘要: Submarine channels, and the sediment density flows which form them, act as conduits for the transport of sediment, macro-nutrients, fresher water and organic matter from the coast to the deep sea. These systems are therefore significant pathways for global sediment and carbon cycles. However, the conditions that permit or preclude submarine channel formation are poorly understood, especially when in association with marine-terminating glaciers. Here, using swath-bathymetric data from the inner shelf and fjords of northwest and southeast Greenland, we provide the first paper to analyse the controls on the formation of submarine channels offshore of numerous marine-terminating glaciers. These data reveal 37 submarine channels: 11 offshore of northwest Greenland and 26 offshore of southeast Greenland. The presence of channels is nearly always associated with: (1) a stable glacier front, as indicated by the association with either a moraine or grounding-zone wedge; and (2), a consistent seaward sloping gradient. In northwest Greenland, turbidity current channels are also more likely to be associated with larger glacier catchments with higher ice and meltwater fluxes which provide higher volumes of sediment delivery. However, the factors controlling the presence of channels in northwest and southeast Greenland are different, which suggest some complexity about predicting the occurrence of turbidity currents in glacier-influenced settings. Future work on tidewater glacier sediment delivery rates by different subglacial processes, and the role of grain size and catchment/regional geology is required to address uncertainties regarding the controls on channel formation.

13224. 题目: The fate of litter-derived dissolved organic carbon in forest soils: results from an incubation experiment
文章编号: N19060612
期刊: Biogeochemistry
作者: Min Wang, Qiuxiang Tian, Chang Liao, Rudong Zhao, Dongya Wang, Yu Wu, Qianxi Li, Xinggang Wang, Feng Liu
更新时间: 2019-06-06
摘要: Despite being a crucial component of nutrient cycling and soil carbon (C) dynamics in forest ecosystems, there is too little information from past studies to discern whether dissolved organic carbon (DOC) exchanges with soil organic carbon or passes unaltered through soils. In this study, we added 13C-labelled litter-derived DOC into different depth soil columns in a 180-day incubation experiment to determine the fate of DOC in soils, and to monitor the changes in DOC composition when it percolates through the soil. The results showed that δ13C values increased in soil microbes, which indicated that some litter-derived DOC was immobilized by soil microbial communities. Approximately 76% of litter-derived DOC was retained in the soil (60% in topsoil and 16% in midsoil). Meanwhile, 18%, 4%, and 3% of litter-derived DOC were mineralized into CO2 in topsoil, midsoil and subsoil respectively. Only 0.04% of litter-derived DOC leached from the soil column (0–60 cm). These results indicated that DOC was mainly retained on soil, and a small portion was mineralized by microorganisms, with minimal leaching. The composition of water soluble soil organic carbon (WSOC) and leachate DOC (LDOC) were similar between the control and treatment. This indicated that the composition of WSOC and LDOC was more similar to soil C than the added DOC, which supports the previously hypothesized dynamic exchange model. These findings provide new insight by showing that most litter-derived DOC is sequestered in forest soils.

13225. 题目: Recovery of organic matter and microbial biomass after abandonment of degraded agricultural soils depends on climate
文章编号: N19060611
期刊: Land Degradation & Development
作者: Lilit Ovsepyan, Irina Kurganova, Valentin Lopes de Gerenyu, Yakov Kuzyakov
更新时间: 2019-06-06
摘要: After abandonment of agricultural lands (ongoing on 220 Mio ha worldwide), degraded arable soils undergo self‐restoration and development towards natural ecosystems. We studied the linkage between microbial properties and density fractions of soil organic matter (SOM) during post‐agricultural restoration of former arable Phaeozems and Chernozems. The chronosequence study was conducted in two contrasting bioclimatic zones of European Russia: deciduous forest (Luvic Phaeozem) and dry steppe (Calcic Chernozem). Each chronosequence included an arable soil, 3–4 soils with increasing periods after abandonment (from 7 to 35 years), and reference sites with native soils. The basal respiration (BR) and microbial biomass (Cmic) were closely correlated with the soil organic carbon (Corg) and total nitrogen (TN) content as well as SOM density fractions: free particulate organic matter (fPOM), occluded particulate organic matter (oPOM), and mineral–SOM. The greatest increase in most properties was common in the top 0–5 cm and was maximal for fPOM and oPOM fractions (by 1.5–2.5 times), Cmic (1.9 times), and BR (1.5–2.5 times). For the first time, the duration of full recovery of soil properties depending on climate were estimated. Generally, ca. 40–120 and 20–30 years in the forest and steppe, respectively, are required to restore Corg, TN, and Cmic contents in the 0–5 cm layer after the abandonment of agricultural lands. The maximal restoration rates of all properties are common in the first 15–20 years after abandonment.

13226. 题目: Effects of agricultural land use change on organic carbon and its labile fractions in the soil profile in an urban agricultural area
文章编号: N19060610
期刊: Land Degradation & Development
作者: Youlin Luo, Qiquan Li, Jie Shen, Changquan Wang, Bing Li, Shu Yuan, Bin Zhao, Huanxiu Li, Junwen Zhao, Lingke Guo, Shan Li, Yuting He
更新时间: 2019-06-06
摘要: The properties of soil organic carbon (SOC) required for carbon sequestration and nutrient availability are contradictory, and the changes in SOC caused by agricultural land use changes remain elusive. Data on the total soil organic carbon (TOC) and labile organic carbon (LOC), including easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC), of the soil profile were analysed for four typical agricultural land use scenarios in the Chengdu Plain, China. The impacts of agricultural land use changes on sequestration and nutrient availability of SOC were assessed in this urban agricultural area using the space‐for‐time substitution method. Conversion of land use from a traditional agricultural rotation to afforestation increased the MBC content and decreased the contents of EOC, DOC and TOC due to the lower input of organic matter, improved aeration of the soil profile and growth of aboveground biomass. Conversion of a traditional rotation to a rice–garlic rotation resulted in a significant increase in topsoil TOC, slight but insignificant decreases in subsoil TOC, and clear increases in LOC because of rice planting, rice straw mulch and reasonable application of chemical fertilizers. In contrast, the conversion of a traditional rotation to a rice‐leafy vegetable rotation decreased MBC due to the excessive use of chemical fertilizers that consequently increased EOC, DOC and TOC. We conclude that afforestation on paddy soil has negative consequences for soil carbon sequestration, and a rice‐leafy vegetable rotation contributes to carbon sequestration but is detrimental to soil fertility. In addition, the MBC ratio in soil could be the optimal indicator for assessing SOC stability and soil fertility, and more attention should be paid to subsoil carbon changes.

13227. 题目: Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity
文章编号: N19060609
期刊: Global Change Biology
作者: Nadia I. Maaroufi, Annika Nordin, Kristin Palmqvist, Niles J. Hasselquist, Benjamin Forsmark, Nicholas P. Rosenstock, Håkan Wallander, Michael J. Gundale
更新时间: 2019-06-06
摘要: There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free‐living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long‐term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6 and 12 kg N ha−1 yr−1) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha−1 yr−1). Our data showed that long‐term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Further, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (≤ 12 kg N ha−1 yr−1) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.

13228. 题目: Recovery of Cr(III) by using chars from the co-gasification of agriculture and forestry wastes
文章编号: N19060608
期刊: Environmental Science and Pollution Research
作者: Delfina Godinho, Miguel Nogueira, Maria Bernardo, Diogo Dias, Nuno Lapa, Isabel Fonseca, Filomena Pinto
更新时间: 2019-06-06
摘要: The aim of the present work was to assess the efficiency of biochars obtained from the co-gasification of blends of rice husk + corn cob (biochar 50CC) and rice husk + eucalyptus stumps (biochar 50ES), as potential renewable low-cost adsorbents for Cr(III) recovery from wastewaters. The two gasification biochars presented a weak porous structure (ABET = 63–144 m2 g−1), but a strong alkaline character, promoted by a high content of mineral matter (59.8% w/w of ashes for 50CC biochar and 81.9% w/w for 50ES biochar). The biochars were used for Cr(III) recovery from synthetic solutions by varying the initial pH value (3, 4, and 5), liquid/solid (L/S) ratio (100–500 mL g−1), contact time (1–120 h), and initial Cr(III) concentration (10–150 mg L−1). High Cr(III) removal percentages (around 100%) were obtained for both biochars, due to Cr precipitation, at low L/S ratios (100 and 200 mL g−1), for the initial pH 5 and initial Cr concentration of 50 mg L−1. Under the experimental conditions in which other removal mechanisms rather than precipitation occurred, a higher removal percentage (49.9%) and the highest uptake capacity (6.87 mg g−1) were registered for 50CC biochar. In the equilibrium, 50ES biochar presented a Cr(III) removal percentage of 27% with a maximum uptake capacity of 2.58 mg g−1. The better performance on Cr(III) recovery for the biochar 50CC was attributed to its better textural properties, as well as its higher cation exchange capacity.

13229. 题目: Effect of clarithromycin on the production of volatile fatty acids from waste activated sludge anaerobic fermentation
文章编号: N19060607
期刊: Bioresource Technology
作者: Xiaoding Huang, Qiuxiang Xu, Yanxin Wu, Dongbo Wang, Qi Yang, Fei Chen, You Wu, Zhoujie Pi, Zhuo Chen, Xiaoming Li, Qiong Zhong
更新时间: 2019-06-06
摘要: This study investigated the effect of Clarithromycin (CLA) on volatile fatty acids (VFAs) production during waste activated sludge (WAS) anaerobic fermentation for the first time. Experimental results showed that when CLA concentration in WAS increased from 0 to 1000 mg/kg TSS, the maximum yield of VFAs increased from 27.7 to 35.7 mg COD/g VSS (without pH pretreatment) and from 59.3 to 65.6 mg COD/g VSS (initial pH 9 pretreatment), respectively. Mechanism exploration revealed that CLA facilitated the disruption of extracellular polymeric substances, thus promoting WAS solubilization. CLA inhibited all the other anaerobic fermentation processes. However, its inhibition to acetogenesis and methanogenesis was severer than that to hydrolysis and acidogenesis, resulting in the decrease in VFAs consumption. Microbial analysis showed that CLA slightly increased the abundance of microorganisms responsible for hydrolysis and acidogenesis whereas decreased the proportion of VFAs-consuming microorganisms.
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13230. 题目: The performance of biochar-microbe multiple biochemical material on bioremediation and soil micro-ecology in the cadmium aged soil
文章编号: N19060606
期刊: Science of The Total Environment
作者: Bin Wu, Ziru Wang, Yuxing Zhao, Yuanming Gu, Ying Wang, Jiang Yu, Heng Xu
更新时间: 2019-06-06
摘要: Biochar (BC) and plant growth promoting bacteria (PGPR) have been widely applied to improve the qualities of heavy metal contaminated soil, while the synergy effect of BC and PGPR on the bioremediation of cadmium (Cd) contaminated soil was less studied. In this study, a novel PGPR strain SNB6 was isolated and then immobilized on BC as the multiple biochemical material (BCM) as well as combined with vetiver grass (Chrysopogon zizanioides L.) to form BC-PGPR-accumulator system. The promoting effects of BCM on bioremediation and soil micro-biology were comprehensively investigated. SEM and FTIR analysis indicated that the strain SNB6 was successfully fixed on BC and the functional groups between BC and SNB6 surface contributed to the immobilization effect. The BCM significantly enhanced the Cd content and bioaccumulation factor (BCF) of accumulator, about 412.35% and 403.41% higher than that of control, respectively. Meanwhile, the biomass of fresh and dry accumulator in the BCM treatment was 227.27% and 178.33% higher than that of control. In addition, the system significantly increased the proportion of HOAc-extractable Cd and soil micro-ecology. Microbial counts and soil enzyme activities in rhizosphere were both significantly improved by the interaction of BCM and C. zizanioides. Furthermore, the strain SNB6 in the rhizosphere interface was successfully colonized, and soil microbial community was evaluated to understand the microbial diversity after bioremediation. Our study indicated that the BCM could significantly enhance the bioremediation efficiency and drive the soil micro-ecology, and the BC-PGPR-accumulator system provided a feasible pathway to remediate heavy metal contaminated sites.
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13231. 题目: Effect of biochar amendment on sorption-desorption and dissipation of 17α‑ethinylestradiol in sandy loam and clay soils
文章编号: N19060605
期刊: Science of The Total Environment
作者: Zhuo Wei, Jim J. Wang, Amy B. Hernandez, Andrea Warren, Jong-hwan Park, Yili Meng, Syam K. Dodla, Changyoon Jeong
更新时间: 2019-06-06
摘要: Animal manure application in agricultural land has caused the release of steroid estrogens in the soil environment and further movement to aquatic systems. The objective of this study was to investigate the effects of biochar addition on sorption-desorption and dissipation behaviors of 17α‑ethinylestradiol (EE2) in two different textured soils. A Commerce sandy loam and a Shakey clay were selected and subjected to sterilization. Soil samples with and without sterilization were reacted with a series of EE2 solutions of different concentrations for sorption followed by desorption and quantification using HPLC-MS/MS. Long-term dissipation of EE2 in the same soils was also evaluated over a 30-d incubation. Biochar amendment increased the maximum EE2 sorption capacity but decreased its water desorption in both sandy loam and clay soils. On other hand, biochar addition increased the Koc in the clay soil which had low EE2 sorption efficiency but decreased Koc in the sandy loam which had high EE2 sorption efficiency. Biochar did significantly increase both desorbable and non-extractable fractions of EE2, while it reduced the bioavailability of EE2 to microbial degradation. The dissipation of EE2 in non-sterilized soils fit to the first-order kinetic model, whereas it was better described by zero-order kinetic for sterilized soil. Biochar increased the half-life of EE2 dissipation in non-sterilized Commerce sandy loam soil by 48% (from 3.63 to 5.37 d) and in non-sterilized Sharkey clay soil by 67% (from 2.28 to 3.81 d). Overall, this study demonstrated positive impacts of biochar on the retention of estrogen hormones in soils.
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13232. 题目: Effects of past land use on soil organic carbon changes after dam construction
文章编号: N19060604
期刊: Science of The Total Environment
作者: Ya Li, Jinming Hu, Xu Han, Yuxiang Li, Yawen Li, Baiyun He, Xingwu Duan
更新时间: 2019-06-06
摘要: A large-scale and high-dropout water-level-fluctuation zone (WLFZ) was formed by the construction of cascaded large dam in the southwest hydropower base of China. The original land use patterns changed significantly by the formation of the WLFZ, which possibly affected the soil organic carbon (SOC) stocks and local carbon cycle. However, little is known about the effects of land uses before dam construction on the SOC stocks in the WLFZ. To address this, we chose the Nuozhadu mega reservoir built in 2014 in the upper Mekong River basin as our study area. We established five sampling transects around the reservoir and sampled them in 2015. Each transect contained three vertical sampling lines representing three land-use types: natural forest, farmland, and rubber plantations. SOC stocks were determined in the WLFZ and in the infralittoral reference zone (IRZ), and the interactions among SOC, land uses, soil erosion, inundation, and other soil physicochemical properties were analyzed to establish the factors controlling SOC in the WLFZ. The average soil organic carbon density (SOCD) was not significantly different between the WLFZ and IRZ, but it differed significantly among the three types of land uses. The SOC stocks in natural forests of the WLFZ and IRZ were significantly greater than those in the other land use types. The SOCD decreased with increasing elevation in the natural forest and rubber plantation in the WLFZ, while no significant trend was found in farmland. These results indicated that the construction of a large dam in southwestern China may not lead to significant changes in regional SOC stocks, but it can result in the redistribution of SOC in the large-scale and high-dropout WLFZ. Land use before dam construction can affect the background concentrations of SOC, soil physicochemical properties, and soil erosion rate in the WLFZ, which controlled the redistribution of SOC.
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13233. 题目: Carbonation is affecting biodegradability testing of fiber cement composites
文章编号: N19060603
期刊: Science of The Total Environment
作者: Maarten Everaert, Kris Broos, Peter Nielsen, Warre Van Dun, Marijn Boone, Mieke Quaghebeur
更新时间: 2019-06-06
摘要: Fiber cement composites (FCCs) containing natural cellulosic fibres are emerging materials in the building industry. At the end of life, FCCs are often disposed of as part of the C&DW in a landfill. The production of landfill gasses in landfills needs to be kept as low as possible. Generally, leaching of total dissolved organic carbon (DOC) is used as a proxy for the biodegradability of a waste material and the subsequent production of landfill gasses, and is, therefore, used to evaluate biodegradability of waste. In this study, FCC samples with varying average diameter and varying age were subjected to both a batch leaching test (determine DOC leaching) and to a standardized biodegradability test. The batch leaching showed that the DOC leaching ranged between 520 and 1300 mg kg−1 for the tested samples, and that leaching of DOC decreases with increasing particle diameter and with increasing effects of ageing. Yet, the biodegradability results indicated that the leaching of DOC from FCCs does not result in the release of landfill gasses. This study hypothises that the DOC that leaches from the FCCs is being degraded to CO2, but that the formed CO2 is immediately captured by the material itself through the process of carbonation. An inpermeable layer is formed around the material that stops further leaching of DOC. The results of this study therefore suggest that leaching of DOC is a poor indicator for the biodegradability of FCCs.
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13234. 题目: A hydrothermal process to turn waste biomass into artificial fulvic and humic acids for soil remediation
文章编号: N19060602
期刊: Science of The Total Environment
作者: Fan Yang, Shuaishuai Zhang, Kui Cheng, Markus Antonietti
更新时间: 2019-06-06
摘要: A novel preparation protocol for synthetic, look-a-like humic substances (i.e., fulvic and humic acids) simulating geochemical processes through hydrothermal reaction is presented, with crude waste biomass as an omnipresent and universal precursor. The chemical nature of the organic scaffold and the type and abundance of oxygen-containing functional groups of the synthetic humic substances (A-FA and A-HA) are revealed by a series of examinations. Results from EA, XPS analyze, FTIR spectra and NMR technology matched well each other, suggesting high similarity on chemical structure (abundant aromatic frameworks) and contents (e.g. N and S elements) in both humic acids. Pyrolysis-gas-chromatography/mass spectrometry (Py-GC/MS) analysis is employed on the organic structure and is directly compared to extracted natural humic matter from black soils (Harbin, China). Dehydrated carbohydrates and their condensates with low molecular weight that are rich in oxygen are the main structural components of the artificial fulvic acids, while aromatic structures and aliphatic side chains are almost absent. Aromatics (7.43%) and in some cases long-chain aliphatics (7.15%) are more prominent in the A-HA sample. The combination of the diverse analytical techniques not only allows a better understanding of artificial fulvic and humic acids, but also supports the high similarity to natural humic substances in structure and morphology. As the technology can be easily scaled and is comparable cheap, the as obtained products can be discussed to rehabilitate used up farm land.
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13235. 题目: 14C characteristics of dissolved lignin along a forest soil profile
文章编号: N19060601
期刊: Soil Biology and Biochemistry
作者: Juan Jia, Xiaojuan Feng, Elisabeth Graf Pannatier, Lukas Wacker, Cameron McIntyre, Tessa van der Voort, Daniel Montlucon, Timothy Eglinton
更新时间: 2019-06-06
摘要: Lignin is a key component of soil dissolved organic carbon (DOC) and is recently suggested to track 14C-young DOC components. However, direct evidence is still lacking to prove this hypothesis in the soil. Here, utilizing molecular radiocarbon dating, we present the first 14C dataset on dissolved lignin through a Podzol soil profile. Dissolved lignin and hydroxy phenols had similar 14C content as soil organic carbon (SOC) and DOC in the surface organic layer. However, in contrast to SOC, both DOC and dissolved lignin phenols exhibited consistent and higher Δ14C values in the mineral soils. Coupled with lignin phenol concentration data, our results suggest that dissolved lignin comprises a key DOC component throughout this Podzol profile and is mainly supplied by surface leachates with young 14C ages.
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13236. 题目: Future carbon emission from boreal and permafrost lakes are sensitive to atmospheric carbon concentrations and catchment organic carbon loads
文章编号: N19060510
期刊: Journal of Geophysical Research: Biogeosciences
作者: T.K. Bayer, E. Gustafsson, M. Brakebusch, C. Beer
更新时间: 2019-06-05
摘要: Carbon storage, processing and transport in freshwater systems are important components of the global carbon cycle and sensitive to global change. However, in large‐scale modelling this part of the boundless carbon cycle is often lacking or represented in a very simplified way. A new process‐oriented lake biogeochemical model is used for investigating impacts of changes in atmospheric CO2 concentrations and organic carbon loading from the catchment on future greenhouse gas emissions from lakes across two boreal to sub‐arctic regions (Northern Sweden and Alaska). Aquatic processes represented include carbon, oxygen, phytoplankton and nutrient dynamics leading to CO2 and CH4 exchanges with the atmosphere. The model is running inside a macro‐scale hydrological model and may be easily be implemented into a land surface scheme. Model evaluation demonstrates its validity in terms of average concentration of nutrients, algal biomass, and organic and inorganic carbon. Cumulative annual emissions of CH4 and CO2, as well as pathways of CH4 emissions, also compare well to observations. Model calculations imply that lake emissions of CH4 may increase by up to 45% under the Representative Concentration Pathway 8.5 scenario until 2100, and CO2 emissions may increase by up to 80% in Alaska. Increasing organic carbon loading to the lakes resulted in a linear response in CO2 and CH4 emissions across both regions, but increases in CO2 emissions from sub‐arctic lakes in Sweden were lower than for southern boreal lakes, probably due to the higher importance of imported vegetation‐‘generated’ inorganic carbon for CO2 emission from sub‐arctic lakes.

13237. 题目: Sources of soil dissolved organic carbon in a mixed agricultural and forested watershed in Rwanda
文章编号: N19060509
期刊: CATENA
作者: Fabien Rizinjirabake, David E. Tenenbaum, Petter Pilesjö
更新时间: 2019-06-05
摘要: Dissolved organic carbon (DOC) plays a key role in linking terrestrial and aquatic carbon cycles. Most of the work on soil and water DOC has been conducted in temperate watersheds. There is still a gap in knowledge on DOC dynamics within the tropics. This study assesses water extractable organic carbon (WEOC) in topsoils and describes the relationship between WEOC and land use/land cover (LULC), slope position, curvature and soil properties using linear regression in the Rukarara River Watershed (RRW) in Rwanda. The study analyzes DOC concentration in soil percolation water (pDOC) and describes its relationship with antecedent precipitation index (API) and mean antecedent temperature (MAT) within the watershed using quadratic regression. Generalized linear model (GLM) and linear mixed effect model (LME) with site and/or LULC random effects are used to predict WEOC within the watershed. WEOC concentrations range from 124 to 855 mgC/L in the study area. The highest WEOC concentrations were observed in natural forest, followed by tree plantations, tea plantations and croplands. t-test results did not reveal a significant difference between concentrations of WEOC in valleys, upper slopes, ridges, flat, concave and convex areas in the Rukarara River Watershed (RRW). Considering the relationship between WEOC and soil properties, significant positive correlation coefficients were 0.60, 0.53, 0.50, and 0.36 respectively for the total organic carbon (TOC), the total nitrogen (TN), the cation exchange capacity (CEC), and the aluminum (Al). The best predictor WEOC as a function of soil properties was the generalized linear model (GLM) and indicated soil TOC as the overarching soil factor of WEOC in the RRW by 71%. The pDOC concentration ranges between 0.34 and 10.03 mgC/L and its relationship with both API and MAT was concave upward. APIs explained 12 to 17% of the pDOC variation in the RRW whereas MATs explained 8 to 25%, the natural forest site showing the highest values and the cropland site the lowest values. This result means that a conversion from forest to cropland within the RRW could decrease DOC in both soils and in percolation water. Also, an increase of precipitation and temperature up to respective optima in the RRW, could increase DOC in percolation water and consequently in streams. This increase of instream DOC can impact the water quality of the Rukarara River and its streams, with implications for their ecological function. Strategies of land management and water resources should be enhanced to preserve soil and water quality in the RRW.
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13238. 题目: Small altitudinal change and rhizosphere affect the SOM light fractions but not the heavy fraction in European beech forest soil
文章编号: N19060508
期刊: CATENA
作者: M. De Feudis, V. Cardelli, L. Massaccesi, S.E. Trumbore, L. Vittori Antisari, S. Cocco, G. Corti, A. Agnelli
更新时间: 2019-06-05
摘要: We evaluated the influence of the rhizosphere, soil depth, and altitude on the amount and nature of the density separated soil organic matter (SOM) pools. Samples were collected from the A and AB horizons of European beech (Fagus sylvatica L.) forest soils located at two altitudes (800 and 1000 m) along 1° of latitudinal gradient in central Italy, by using altitude as a proxy for air temperature change. Specifically, we hypothesized that: i) larger amount of labile organic matter, comprising of fresh plant and organism residues and easily degradable molecules, was allocated in the rhizosphere than in the non-rhizosphere soil, and ii) the temperature had a stronger effect on the C pools of the rhizosphere than in that of the non-rhizosphere soil. At both altitudes, we found more organic C (OC) associated with the light fractions of the rhizosphere than in those of the non-rhizosphere soil and, specifically in the rhizosphere free light fraction, larger OC concentrations were observed at 1000 m than at 800 m above sea level. These higher amounts of OC have been attributed to roots, which are one of the main source of particulate organic matter, and their activity and turnover increase when the environmental conditions become more restrictive, as it happens at higher altitude. Conversely, no effect related to rhizosphere and altitude on the OC associated to the heavy fraction was found. The recalcitrance of the OC of the heavy fraction has been ascribed both to its protection due to the tight bounds to mineral particles and to its degradation degree, as indicated by δ13C values, which were greater than those of the light fractions. The similar 14C signature and the presence of recent C in all the density fractions of rhizosphere and non-rhizosphere soil of both A and AB horizons suggested the occurrence of a rapid incorporation of fresh organic matter into the mineral horizons, followed by occlusion into aggregates and adsorption on mineral surfaces. Further, the lack of different Δ14C values between the fractions at 800 and 1000 m could indicate that a temperature change of 1 °C is not sufficient to induce marked changes in SOM cycling.

13239. 题目: Runoff, soil loss, and sources of particulate organic carbon delivered to streams by sugarcane and riparian areas: An isotopic approach
文章编号: N19060507
期刊: CATENA
作者: Taciana F. Gomes, Marijn Van de Broek, Gerard Govers, Robson W.C. Silva, Jorge M. Moraes, Plínio B. Camargo, Edmar A. Mazzi, Luiz A. Martinelli
更新时间: 2019-06-05
摘要: Soil erosion leads to land degradation and translocation of soil particles together with associated particulate organic carbon (POC) and nutrients, thereby influencing the global carbon cycle. In the present study, we estimated the contribution of POC delivered to a first-order stream from upslope sugarcane fields and a riparian forest in southeast Brazil. The results show that the amount of surface runoff and soil erosion generated in the riparian forest is significantly lower than in the upslope sugarcane field. However, the contribution of the forest to the total stream bed POC was above 70%, even though most sediments delivered to the stream originated from the upland sugarcane fields. The discrepancy between sediment and POC delivery from both land uses is a consequence of the presence of preferential runoff pathways from the agricultural fields, through the buffer strips, to the stream. This disconnection between the main sources of sediment and POC to the first-order stream is a potentially important mechanism influencing the transfer of POC from upslope areas to waterways. This mechanism should be considered in order to more reliably assess fluxes of OC from upslope areas to first-order streams in landscapes where arable land is separated from streams by a semi-natural buffer zone with permanent vegetation.

13240. 题目: Methylmercury sorption onto engineered materials
文章编号: N19060506
期刊: Journal of Environmental Management
作者: Katherine A. Muller, Craig C. Brandt, Teresa J. Mathews, Scott C. Brooks
更新时间: 2019-06-05
摘要: Four commercially available sorbents (BioChar (BC), ThiolSAMMS® (TS), SediMite (SM), and Organoclay™ PM-199 (OC-199)) were tested for their ability to sorb methylmercury (MeHg) and MeHg complexed with dissolved organic matter (DOM). Testing sorption behavior with DOM is more representative of the environmental conditions and mercury speciation expected during in-situ remediation efforts. Isotherms were fit using a robust, iterative re-weighting scheme. This fitting approach improves upon the traditionally used indirect sorption method by removing the dependence between aqueous and solid phase concentrations in isotherm fitting. Developed isotherms show that without DOM, BC, TS, and SM adsorbed similar amounts of MeHg while OC-199 sorbed substantially less MeHg. Below an equilibrium concentration of 5.6 ng L−1 BC was the best performing sorbent, between 5.6 and 20.9 ng L−1 SM sorbed the most MeHg, and above an equilibrium concentration of 20.9 ng L−1 TS outperformed the other sorbents. BC and OC-199 showed indication of MeHg sorption saturation over the tested concentration range of 3.5–680 ng L−1. With DOM, SM outperformed the other sorbents at equilibrium concentrations less than 0.98 ng L−1 and TS was the superior MeHg:DOM sorbent at higher concentrations. MeHg:DOM sorption was controlled by DOM-sorbent interactions. DOM decreased MeHg sorption onto BC and SM whereas TS exhibited similar sorption with and without DOM. OC-199 had slightly higher MeHg uptake with DOM. East Fork Poplar Creek (EFPC), an industrially Hg contaminated site, was used as a case study example to build a relationship between aqueous and fish MeHg concentrations and subsequently compare the cost of sorbent materials required to meet regulatory objectives. For this case study, SM provided the most cost-effective sorbent option for in-situ remediation efforts to reduce aqueous MeHg concentrations.

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