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32241. 题目: Moderate thinning increases soil organic carbon in Larix principis-rupprechtii (Pinaceae) plantations
文章编号: N18062511
期刊: Geoderma
作者: Junyong Ma, Fengfeng Kang, Xiaoqin Cheng, Hairong Han
更新时间: 2018-06-25
摘要: Forest thinning management practices such as thinning play a major role in the process of soil organic carbon (SOC) sequestration, however, the mechanism for SOC variations is still unclear. The objectives of this study were to estimate SOC stock and its active chemical components following a short term density adjustment of stand woods. Three treatments, low intensity thinning (removal of 15% of the trees, three 25 25 m repeated plots), moderate thinning (30% removal), and heavy intensive thinning (50% removal) were compared to control plots with no thinning three years before sampling of soil carbon composition. A number of carbon components (i.e. SOC; soil total nitrogen, TN; permanganate oxidizable C, POXC; dissolved organic carbon, DOC; microbial biomass carbon, MBC) were measured in five soil layers within the Larix principis-rupprechtii plantation throughout the growing seasons of 2015 and 2016. Results indicated both SOC content and its active component, POXC content, were maximized under the moderate density adjustment (p < 0.01). Density adjustment significantly affected POXC/SOC ratio (p < 0.001), with maximum POXC content per unit SOC content also under moderate density adjustment. However, density adjustment hardly had any impact on DOC or MBC, both of which showed more obvious seasonal dynamics than SOC, TN and POXC. Summer affected SOC storage by altering the POXC, TN and MBC. Our results suggest that effects of density adjustment on POXC drive variation in SOC.

32242. 题目: No-tillage with continuous maize cropping enhances soil aggregation and organic carbon storage in Northeast China
文章编号: N18062510
期刊: Geoderma
作者: Yan Zhang, Xiujun Li, Edward G. Gregorich, Neil B. McLaughlin, Xiaoping Zhang, Yafei Guo, Aizhen Liang, Ruqin Fan, Bingjie Sun
更新时间: 2018-06-25
摘要: In Northeast China, conventional tillage practices involve removal of crop residue after harvest and prior to moldboard plowing; this has been shown to cause a decline of soil organic carbon (SOC) and degradation of soil structure. No-tillage has been suggested to be an effective way to increase SOC storage but its effectiveness in some soils and climates has been questioned. Different cropping systems also influence SOC storage. Hence, we established an experiment to evaluate how a combination of different tillage and cropping systems could improve soil aggregation and organic carbon storage. We included five treatments: a) NTMS: no tillage with maize (Zea mays L.)-soybean (Glycine max Merr.) (MS) rotation; b) MPMS: moldboard plowing with maize-soybean rotation; c) NTMM: no tillage with continuous maize (MM); d) MPMM: moldboard plowing with continuous maize; e) CTMM: conventional tillage with continuous maize (the conventional farming practice in Northeast China). All crop residues were returned to the soil except in the CTMM treatment. Returning residue to the soil significantly increased SOC storage in all tillage/cropping systems with NTMM having the highest increase in rate of SOC storage at 0.80 Mg C ha 1 yr 1 relative to the start of the experiment. The CTMM depleted SOC storage at rate of 0.52 Mg C ha 1 yr 1 relative to the start of the experiment. Soil under NTMS exhibited a significant SOC decline deep in the soil (5–30 cm) but overall SOC storage in 0–30 cm profile was equal to that under MPMS. The NTMM had the highest SOC storage and the highest proportion and associated organic carbon (OC) in occluded micro-aggregates (53–250 μm, inside of 250 μm aggregates) across all experimental treatments. The OC in occluded micro-aggregates was much higher than that associated with unprotected micro-aggregates (53–250 μm, outside of 250 μm aggregates). The effects of tillage on aggregate size and OC concentration occurred mainly in the surface layer (0–5 cm) whereas the effect of cropping system on aggregate size and OC concentration occurred at deeper depths. The MS cropping system increased the proportion of silt-clay (<53 μm, outside of 250 μm aggregates) over MM while occluded silt-clay (<53 μm, inside of 250 μm aggregates) in MM was greater than in MS in all layers. The NTMM treatments improved SOC storage and aggregation over the other treatments.

32243. 题目: Physicochemical surface properties of different biogenic silicon structures: Results from spectroscopic and microscopic analyses of protistic and phytogenic silica
文章编号: N18062509
期刊: Geoderma
作者: Daniel Puppe, Martin Leue
更新时间: 2018-06-25
摘要: The significance of biogenic silicon (BSi) for Si cycling in terrestrial biogeosystems has been acknowledged since decades. Its importance originates from the fact that BSi generally is more soluble than silicate minerals and thus i) controls Si fluxes from terrestrial to aquatic ecosystems and ii) plays an important role as source of readily- or plant-available Si (i.e., H4SiO4) in soils. In this context, physicochemical surface properties of BSi structures determine their dissolution kinetics. We applied transmission Fourier transform infrared (FTIR) spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) microscopy, and confocal laser scanning microscopy (CLSM) to investigate physicochemical surface properties of different biogenic silica structures. Using these techniques we were able to detect differences on a molecular level (FTIR, DRIFT) and in surface roughness parameters (CLSM) between BSi synthesized by protists (testate amoebae, diatoms) and BSi synthesized by plants (phytoliths) as well as between fresh (extracted from plants) and aged (extracted from soils) phytoliths. While fresh phytoliths showed organic impurities that can be assigned to occluded organic matter, aged phytoliths showed additional impurities of mineral origin. This is due to the fact that the used non-destructive gravimetric extraction of phytoliths is unsuitable for a distinct differentiation between biogenic silica (phytoliths) and non-biogenic (minerogenic or microcrystalline) Si forms in general. We recommend DRIFT microscopy for analyses of phytoliths extracted from soils because this technique allows measurements of selected, single siliceous phytoliths (as well as other BSi structures). Surface roughness parameters of aged phytoliths decreased compared to the ones of fresh phytoliths indicating a decrease of specific surface areas available for dissolution processes. Physicochemical surface properties will help us to better understand the BSi status (BSi quality and quantity) of soils with implications for Si availability in soils and thus Si cycling in terrestrial biogeosystems.

32244. 题目: Sensitivity of peatland litter decomposition to changes in temperature and rainfall
文章编号: N18062508
期刊: Geoderma
作者: Michael C. Bell, Jonathan P. Ritson, Anne Verhoef, Richard E. Brazier, Michael R. Templeton, Nigel J.D. Graham, Chris Freeman, Joanna M. Clark
更新时间: 2018-06-25
摘要: Changes to climate are projected over the next 50 years for many peatland areas. As decomposition of peat-forming vegetation is likely to be intrinsically linked to these changes in climate, a clear understanding of climate-peat dynamics is required. There is concern that increased temperature and decreased precipitation could increase the rate of decomposition and put the carbon sink status of many peatlands at risk, yet few studies have examined the impact of both climatic factors together. To better understand the sensitivity of peatland decomposition to changes in both temperature and precipitation and their interaction, we conducted a short-term laboratory experiment in which plant litters and peat soil were incubated, in isolation, in a factorial design. Treatments simulated baseline and projected climate averages derived from the latest UK climate change projections (UKCP09) for Exmoor, a climatically marginal peatland in SW England. Regular carbon dioxide flux measurements were made throughout the simulation, as well as total mass loss and total dissolved organic carbon (DOC) leached. The largest effect on carbon loss in this multifactor experiment was from substrate, with Sphagnum/peat releasing significantly less C in total during the experiment than dwarf shrubs/graminoids. Climate effects were substrate specific, with the drier rainfall treatment increasing the DOC leaching from Calluna, but decreasing it from Sphagnum. Partitioning between CO2 and DOC was also affected by climate, but only for the peat and Sphagnum samples, where the future climate scenarios (warmer and drier) resulted in a greater proportion of C lost in gaseous form. These results suggest that indirect effects of climate through changes in species composition in peatlands could ultimately turn out to be more important for litter decomposition than direct effects of climate change from increased temperatures and decreased rainfall.

32245. 题目: Small-scale spatial patterns of soil organic carbon and nitrogen stocks in permafrost-affected soils of northern Siberia
文章编号: N18062507
期刊: Geoderma
作者: Alevtina Evgrafova, Tilman René de la Haye, Ina Haase, Olga Shibistova, Georg Guggenberger, Nikita Tananaev, Leopold Sauheitl, Sandra Spielvogel
更新时间: 2018-06-25
摘要: The vulnerability of soil organic matter (SOM) sequestered in permafrost-affected soils to climate change plays one of the key roles in the global carbon (C) cycle. However, it still remains unclear how changing soil and site-specific factors, associated with the changing depth of the permafrost table due to thawing, influence the spatial distribution and variability of soil organic carbon (SOC) and total nitrogen (N) stocks in high-latitude mineral soils. The relationships between the spatial variation of SOC and N stocks (0–30 cm) and active layer (AL) thickness, thickness of the organic layer (OL), soil acidity, Al and Fe hydroxides as well as plant- and microbial-derived C inputs were studied using ordinary statistics and geostatistics within six landscape patches (16 m2) in the Siberian forest-tundra ecotone underlain by warm and discontinuous permafrost. At deeper permafrost table, SOC and N stocks (0–30 cm) were lower and, according to the semivariogram analysis, an overall homogenization of SOC and N distribution at the analyzed scale occurred. Total N and SOC stocks were spatially independent from root-derived organic matter distribution (i.e. the concentration of suberin-derived monomers) at shallow AL patches, whereas there was a significant positive spatial correlation within deep AL and non-permafrost soils. Hence, the development of root systems and an increase in rooting depth, leading to “hot spots” of SOM accumulation at intensively rooted soil patches, was observed as a result of deeper AL. Total N and SOC stocks within deeper AL and non-permafrost subsoils were also positively spatially correlated with the concentration of Fe and Al hydroxides, demonstrating the importance of organo-mineral associations for SOM stabilization in soils with lower permafrost table. This study confirmed that deepening of the AL in boreal forest ecosystems may lead to an overall homogenization of SOM distribution and simultaneous development of distinct mechanisms of SOM accumulation and stabilization.

32246. 题目: Soil organic carbon prediction based on scale-specific relationships with environmental factors by discrete wavelet transform
文章编号: N18062506
期刊: Geoderma
作者: Hongfen Zhu, Wei Hu, Yaodong Jing, Yi Cao, Rutian Bi, Wude Yang
更新时间: 2018-06-25
摘要: The spatial distribution of soil organic carbon (SOC) is vital to agricultural and environmental management, and its variation is influenced by environmental factors operating at different scales and intensities. The objective of this study was to explore the scale-dependent effects of environmental factors on SOC distribution and to predict SOC based on their scale-specific relationships using wavelet transform. The spatial data of SOC, slope, soil water content (SWC), soil bulk density (SBD), sand, silt, and Landsat 8 remote sensing reflectance (Rrs) were extracted at 330 m interval along three transects in the arable land of Taiyuan basin, China. The spatial series of SOC and environmental variables along each of three transects were separated into six detail components and one approximation representing different scales using wavelet decomposition. The specific scale of each detail component was identified by Hilbert transform. The SOC variances over the entire basin were mainly explained (54%–86%) by scales of 12.70 and 21.12 km. Compared with the relationships between SOC and environmental factors at sampling scale, their multiscale correlations were better at larger scales. The SOC estimation using wavelet reconstruction based on predicted SOC at all scale components outperformed its prediction using stepwise multiple linear regression (SMLR) based on the original sampling data. The major contributing scale to SOC prediction was 12.70 km over the entire basin. In the prediction of overall SOC, Rrs was the major predictor in the upstream and downstream portions, whereas soil texture was the major contributor in the midstream portion. In this study, the SOC prediction using wavelet transform based on scale-dependent relationships with environmental variables generated new insights in soil properties estimation, and wavelet transform has potential for determining the multiscale relationships of soil properties with influencing factors.

32247. 题目: Spatial point pattern analysis of piping erosion in loess-derived soils in Golestan Province, Iran
文章编号: N18062505
期刊: Geoderma
作者: Mohsen Hosseinalizadeh, Narges Kariminejad, Giandiego Campetella, Alireza Jalalifard, Mohammad Alinejad
更新时间: 2018-06-25
摘要: Point pattern analysis of collapsed pipes as a subsurface erosion in natural and manmade conditions plays an important role to understand their landforms/features, predisposing factors, and for prevention and forecasting purposes. Thus, the present study aimed to evaluate the spatial pattern and the associated land factors of piping erosion in loess-derived soils in a semiarid climate in Golestan Province, Iran by applying numerical summary statistics. To this end, a 105 ha area with homogeneous environmental conditions (gentle slope and loess-derived soil) was selected and the maps related to 101 collapsed pipes and their features were obtained by the aerial photos provided by an unmanned aerial vehicle (UAV) with a 50 cm resolution and field survey. The mean of spatial distances between pipe locations was 309 m, and the frequency of pipes per hectare was 0.97. Moreover, soil samples of the pipe locations were collected and physical-chemical soil properties were measured in laboratory. Approximately 95% simulation envelopes were selected using the 5th-lowest and 5th-highest values of 199 Monte Carlo simulations of the null model of homogeneous complete spatial randomness. Based on the results of univariate pair correlation function, the significant aggregation of 101 collapsed pipes was observed at a scale of 0–50 m in both rangeland and agricultural land use types. The bivariate pair correlation function, which is considered to be the most informative second-order summary characteristic, was used for analyzing the statistical correlations between collapsed pipes and linear phenomena including distance from drainage networks, ridges, and roads. Based on bivariate summary statistics, collapsed pipes had positively been affected by both the distribution of drainage networks and ridges. However, the negative statistical correlations occurred between pipes and roads at the scales of 1–50 m. Also, the correlations of soil characteristics (silt content, exchangeable sodium percentage (ESP), the weight of soil in a given volume (bulk density), soil electrical conductivity (EC), and organic matter (O.M.)) of neighboring collapsed pipes were evaluated by mark correlation function. Based on mark correlation function k mm (r), a significantly positive correlation was found between the pipes density and silt content, ESP, and bulk density, when they are more than overall average. In addition, less values of EC and O.M. were positively related to the aggregation of collapsed pipes. Similar to the results of summary statistics, the maps confirmed all statistical correlations. Consequently, the outcome of this study highlights the spatial pattern of collapsed pipes and their associations in the study area.

32248. 题目: Sugarcane yield and soil carbon response to straw removal in south-central Brazil
文章编号: N18062504
期刊: Geoderma
作者: Ricardo de Oliveira Bordonal, Lauren Maine Santos Menandro, Leandro Carneiro Barbosa, Rattan Lal, Débora Marcondes Bastos Pereira Milori, Oriel Tiago Kolln, Henrique Coutinho Junqueira Franco, Jo?o Luís Nunes Carvalho
更新时间: 2018-06-25
摘要: Understanding the impacts of straw removal on quantity and quality of soil organic carbon (SOC) is crucial for sustaining or improving soil functions and producing economically viable sugarcane yields. Field experiments were carried out on commercial farms to quantify effects of straw removal on sugarcane yields, SOC stocks and the degree of soil organic matter (SOM) humification under three diverse edaphoclimatic conditions (Quirinópolis-GO, Chapad o do Céu-GO and Quatá-SP) in Brazil, while considering the effects of cover crop on sugarcane yields during two harvest seasons. Three straw removal rates (0, 50, and 100%) were arranged in a randomized block design with four replications within two paired areas, one seeded with Crotalaria spectabilis (cover crop–CC) and the other kept under bare fallow (BF) during the sugarcane-replanting period. Sugarcane yields were measured annually using an instrumented truck equipped with load cells, and soil samples were collected to a depth of 40-cm two years after establishing the trials. Straw removal for two years did not significantly influence cane yields in Quatá-SP, but in Chapad o do Céu-GO and Quirinópolis-GO, complete straw removal resulted in cumulative yield losses of up to 28 and 62 Mg ha 1 respectively. The inclusion of Crotalaria spectabilis within sugarcane cropping cycle increased two-year cumulative yields by 25 and 27 Mg ha 1 in Chapad o do Céu-GO and Quirinópolis-GO respectively. SOC response to straw removal was highly site-specific after two years. In fine-textured soils, straw removal rates did not significantly affect SOC stocks in Chapad o do Céu-GO, but in Quirinópolis-GO complete straw removal favored the depletion of SOC stock relative to partial or no straw removal in both soil layers (0–10 and 0–40 cm) of the BF area, while within the CC area SOC depletion was observed in the 0–40 cm layer. For sandy soil (Quatá-SP), complete straw removal decreased SOC stock only in the top 10 cm of the CC area. Laser-Induced Fluorescence Spectroscopy showed high degree of SOM humification in soils with depleted SOC stock, indicating that excessive straw removal was degrading soil quality by reducing the amount of labile C in the SOM. Conclusions drawn from this study indicate that, even on a short-term basis, complete straw removal already began to modify the quantity and quality of SOC, while both moderate or complete removals adversely affected sugarcane yields.

32249. 题目: Riverine particulate C and N generated at the permafrost thaw front: case study of western Siberian rivers across a 1700...
文章编号: N18062503
期刊: Biogeosciences
作者: Ivan V. Krickov, Artem G. Lim, Rinat M. Manasypov, Sergey V. Loiko, Liudmila S. Shirokova, Sergey N. Kirpotin, Jan Karlsson, and Oleg S. Pokrovsky
更新时间: 2018-06-25
摘要: In contrast to numerous studies on the dynamics of dissolved (<0.45 m) elements in permafrost-affected high latitude rivers, very little is known of the behavior of river suspended (>0.45 m) matter (RSM) in these regions. In order to test the effect of climate, permafrost and physio-geographical landscape parameters (bogs, forest and lake coverage of the watershed) on RSM and particulate C, N and P concentration in river water, we sampled 33 small and medium size rivers (10–100000km2 watershed) along a 1700km N–S transect including both permafrost-affected and permafrost-free zones of Western Siberian Lowland (WSL). The concentration of C and N in RSM decreased with the increase in river watershed size, illustrating (i) the importance of organic debris in small rivers which drain peatlands and (ii) the role of mineral matter from bank abrasion in larger rivers. The presence of lakes in the watershed increased C and N but decreased P concentrations in RSM. The C:N ratio in the RSM reflected the source from deep rather than surface soil horizon, similar to that of other Arctic rivers. This suggests the export of peat and mineral particles through suprapermafrost flow occurring at the base of the active layer. There was a maximum of particulate C and N concentration at the beginning of permafrost appearance (a sporadic and discontinuous zone, 62–64°N). This presumably reflected the organic matter mobilization from newly thawed organic horizons in soils at the active latitudinal thawing front. The results suggest that a northward shift of permafrost boundaries and an increase in active layer thickness may increase particulate C and N export by WSL rivers to the Arctic Ocean by a factor of 2, while P export may remain unchanged. In contrast, within a long-term climate warming scenario, the disappearance of permafrost in the north, the drainage of lakes and transformation of bogs to forest may decrease C and N concentration in RSM by 2 to 3 times.

32250. 题目: Quantification of lignin oxidation products as vegetation biomarkers in speleothems and cave drip water
文章编号: N18062502
期刊: Biogeosciences
作者: Inken Heidke, Denis Scholz, and Thorsten Hoffmann
更新时间: 2018-06-25
摘要: Here we present a sensitive method to analyse lignin oxidation products (LOPs) in speleothems and cave drip water to provide a new tool for paleo vegetation reconstruction. Speleothems are valuable climate archives. However, compared to other terrestrial climate archives, such as lake sediments, speleothems contain very little organic matter. Therefore, very few studies on organic biomarkers in speleothems are available. Our new sensitive method allows to use LOPs as vegetation biomarkers in speleothems. Our method consists of acid digestion of the speleothem sample followed by solid phase extraction (SPE) of the organic matter. The extracted polymeric lignin is degraded in a microwave assisted alkaline CuO oxidation step to yield monomeric LOPs. The LOPs are extracted via SPE and finally analysed via ultrahigh-performance liquid chromatography (UHPLC) coupled to electrospray ionisation (ESI) and high-resolution orbitrap mass spectrometry (HRMS). The method was applied to stalagmite samples with a sample size of 3–5g and cave drip water samples with a sample size of 100–200mL from the Herbstlabyrinth-Advent-Cave in Germany. In addition, fresh plant samples, soil water and powdered lignin samples were analysed for comparison. The concentration of the sum of eight LOPs (Σ8) was in the range of 20–84ngg 1 for the stalagmite samples and 230–440ngL 1 for the cave drip water samples. The limits of quantification for the individual LOPs ranged from 0.3–8.2ng per sample. Our method represents a new and powerful analytical tool for paleo vegetation studies and has great potential to identify the pathways of lignin incorporation into speleothems.

32251. 题目: Fodder radish seed cake biochar for soil amendment
文章编号: N18062501
期刊: Environmental Science and Pollution Research
作者: Wendel Paulo Silvestre, Paula Lúcia Galafassi, Suelem Daiane Ferreira, Marcelo Godinho, Gabriel Fernandes Pauletti, Camila Baldasso
更新时间: 2018-06-25
摘要: In this work, fodder radish seed cake (FRSC) was pyrolyzed in a rotary kiln reactor at 0, 3, and 6 rpm, at final temperature of 500 °C. Maximum biochar yield was observed at 0 rpm (≈ 26 wt.%). Increase of the rotary speed decreased the volatile matter content and increased the ash content of the biochars. Biochars exhibited alkaline pH (≈ 9.0), low electrical conductivity (< 105.6 dS m 1), and high cation exchange capacity (69 to 78 cmolc kg 1), as well as high nitrogen contents (≈ 80 g kg 1). FTIR analysis presented biochars with similar spectra, with carboxyl and carbonyl groups within the structure, along with aromatic rings and nitrogen containing functions (amides). Biochar incubation experiments in an acrisol at different biochar doses (5 g L 1 soil to 40 g L 1 soil) were performed in order to evaluate changes in soil fertility parameters caused by FRSC biochar application. Results indicated that most of macro (N, P, K, Ca, Mg) and micronutrients (S, Cu, Zn, Mn, B, Na) increased with increase of the dosage, along with the decrease in Al and H+ Al contents. An increase in pH (from 4.25 to 5.33) was also observed, in electric conductivity (from 30.0 to 45.7 dS m 1), and a decrease in soil real density (from 3.67 to 2.99 kg L 1) at the dosage of 40 g char L 1 soil.

32252. 题目: Influence of aggregation on nanoscale titanium dioxide (nTiO2) deposition to quartz sand
文章编号: N18062405
期刊: Chemosphere
作者: Zhong Tang, Tao Cheng, Leanne M. Fisher-Power
更新时间: 2018-06-24
摘要: Although extensive research has been conducted to investigate nTiO2 aggregation and deposition, effects of aggregation on concurrent/subsequent deposition of nTiO2, which has important implications to the fate and transport of nTiO2 in groundwater, has received only limited attention. The objective of this study was to investigate how pH, dissolved organic matter (DOM), and valence of background solution cation influence aggregation and concurrent/subsequent deposition of nTiO2. Experiments were performed to examine nTiO2 aggregation and deposition onto quartz sand with co-present illite, kaolinite, and montmorillonite colloids under various geochemical conditions. Results showed that nTiO2 formed hetero-aggregates (i.e., nTiO2-clay aggregates) at low pH when nTiO2 and clay colloids carried opposite charges, and the hetero-aggregates may either deposit or remain suspended depending on their interactions with quartz sand and Fe/Al oxyhydroxide coatings. Deposition of nTiO2 and/or nTiO2-clay aggregates occurred as a result of electrostatic attraction, secondary minimum, and potentially Mg2+ bridging. Humic acid prevented nTiO2 aggregation and deposition under most conditions. In MgCl2 solutions, however, it facilitated deposition by adsorbing to nTiO2 and Fe/Al oxyhydroxides, thereby enabling Mg2+ bridging. This study demonstrated the important and complex roles of pH, DOM, cation valence, and clay colloids in controlling aggregation and subsequent deposition of nTiO2.

32253. 题目: Identifying localized and scale-specific multivariate controls of soil organic matter variations using multiple wavelet coherence
文章编号: N18062404
期刊: Science of The Total Environment
作者: Ruiying Zhao, Asim Biswas, Yin Zhou, Yue Zhou, Zhou Shi, Hongyi Li
更新时间: 2018-06-24
摘要: Environmental factors have shown localized and scale-dependent controls over soil organic matter (SOM) distribution in the landscape. Previous studies have explored the relationships between SOM and individual controlling factors; however, few studies have indicated the combined control from multiple environmental factors. In this study, we compared the localized and scale-dependent univariate and multivariate controls of SOM along two long transects (northeast, NE transect and north, N transect) from China. Bivariate wavelet coherence (BWC) between SOM and individual factors and multiple wavelet coherence (MWC) between SOM and factor combinations were calculated. Average wavelet coherence (AWC) and percent area of significant coherence (PASC) were used to assess the relative dominance of individual and a combination of factors to explain SOM variations at different scales and locations. The results showed that (in BWC analysis) mean annual temperature (MAT) with the largest AWC (0.39) and PASC (16.23%) was the dominant factor in explaining SOM variations along the NE transect. The topographic wetness index (TWI) was the dominant factor (AWC = 0.39 and PASC = 20.80%) along the N transect. MWC identified the combination of Slope, net primary production (NPP) and mean annual precipitation (MAP) as the most important combination in explaining SOM variations along the NE transect with a significant increase in AWC and PASC at different scales and locations (e.g. AWC = 0.91 and PASC = 58.03% at all scales). The combination of TWI, NPP and normalized difference vegetation index (NDVI) was the most influential along the N transect (AWC = 0.83 and PASC = 32.68% at all scales). The results indicated that the combined controls of environmental factors on SOM variations at different scales and locations in a large area can be identified by MWC. This is promising for a better understanding of the multivariate controls in SOM variations at larger spatial scales and may improve the capability of digital soil mapping.
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32254. 题目: Identifying the reducing capacity of biomass derived hydrochar with different post-treatment methods
文章编号: N18062403
期刊: Science of The Total Environment
作者: Yan Yan, Xianlong Ma, Weimin Cao, Xiaolei Zhang, Jizhi Zhou, Qiang Liu, Guangren Qian
更新时间: 2018-06-24
摘要: In this study, hydrochar was prepared from wheat straw (WS) and Spartina alterniflora (SA) biomass by hydrothermal carbonization, and further treated with HCl and NaOH washing, HNO3 oxidization and low temperature thermal heating. The reducing capacity (RC) of sample was quantified by I2 titration to explore how these modification methods affected the redox properties of hydrochar. The results indicated HNO3 and thermal oxidization increased the RC of hydrochar by 2–5 folds while NaOH washing had the negative effect on samples' RC. By analyzing the excitation-emission matrix (EEM) fluorescence of alkaline extraction solution of sample, humic acid like substances generated from various methods were identified as one of the major sources for electron donating. HNO3 oxidization could significantly increase the RC in hydrochar, which was likely resulting from the generation of alkali-soluble small molecule organic compounds. However, excessive oxidation by nitric acid with prolonged duration led to the gradual decrease in hydrochar's RC. Heating treatment caused a significant increase in the content of redox-active oxygen-containing functional groups and persistent free radicals (PFRs) in hydrochar. Even though both could donate electrons in the redox reaction with I2, the former was considered a greater contributor for the RC of hydrochar. From this study, the origin of RC of hydrochar can be identified as: oxygen-containing functionality, humic-like matter and PFRs. By employing different modification methods, the RC of hydrochar could be tuned by regulating the above sources. This study provided fundamental knowledges and simple routes to manipulate the redox properties of hydrochar for different environmental applications.
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32255. 题目: Responses of microbial carbon metabolism and function diversity induced by complex fungal enzymes in lignocellulosic waste composting
文章编号: N18062402
期刊: Science of The Total Environment
作者: Zhuotong Zeng, Xueying Guo, Piao Xu, Rong Xiao, Danlian Huang, Xiaomin Gong, Min Cheng, Huan Yi, Tao Li, Guangming Zeng
更新时间: 2018-06-24
摘要: Composting is an economic and effective technology for solid waste treatment, which is an essential method to promote the biogeochemical cycle of contaminants. However, the application of this technology was limited by the bio-degradative recalcitrance of lignin and other kind of phytotoxic substances release. The combination with microorganisms and enzymes is a popular and efficient way to enhanced composting. This study, referring to metabolic mechanisms, fungal molecular and biogeochemical cycles, was performed to investigate the effects of lignin degradation, carbon metabolic diversity, as well as the related changes induced by these two kinds of complex enzymes in composting. The biological diversity is important indicator in ecosystem, which concerns the environmental applicability of one technology. The carbon metabolism diversity reflected the biogeochemical cycles of organic matter, which was also an essential input to analyze the effects of composting. The changes on the diversity characteristics of carbon are essential to comprehensively understand the deep mechanisms of this process, and extended the application of complex enzymes in the field of enhanced composting. The analysis of Biolog revealed that the utilization of pyruvic acid methyl ester, α-Cyclodextrin, d-Mannitol, d-Galacturonic, Itaconic acid and l-asparagine were deeply promoted, and that of d, l-α-Glycerol-phosphate, l-Threonine, Glycyl-l-Glutamic acid and putrescine were depressed by adding the complex enzyme in composting. Moreover, according to the data, the addition of complex enzymes improved the degradation efficiency and the metabolic capacity of carbon in composting. These findings undoubtedly contribute to the development of enzyme-based technologies and the applications of complex enzymes in composting, which is of great benefit to eliminate the limitation and extend the application of composting.
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32256. 题目: Structural response of humic acid upon binding with lead: A spectroscopic insight
文章编号: N18062401
期刊: Science of The Total Environment
作者: Nuzahat Habibul, Wei Chen
更新时间: 2018-06-24
摘要: Lead (Pb) is a widespread heavy metal that can cause damage to the ecosystem, and the ubiquitously existing dissolved organic matter (DOM) can significantly affect the environmental behavior of Pb. The present work explores the interaction process of Pb with humic acid (HA) through integration of synchronous fluorescence and log-transformed UV–vis absorption spectroscopy coupled with spectral slope calculation and two-dimensional correlation analyses. The spectral slope calculation results show that the carboxylic and phenolic groups in HA were the predominant binding sites to Pb, and the interaction process was highly dependent on solution pH. Correlation analyses confirmed a superior binding affinity of carboxylic groups in HA over phenolic groups. Integration of spectral slope calculation with two-dimensional correlation spectroscopy is a promising tool for better understanding the molecular structure of Pb-DOM complexes and the characteristics of Pb binding to DOM, which may provide new insights into the prevention, control, and remediation of Pb contamination in environment.
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32257. 题目: Quinone group enhances the degradation of levofloxacin by aqueous permanganate: Kinetics and mechanism
文章编号: N18062303
期刊: Water Research
作者: Ke Xu, Huiyu Dong, Mengkai Li, Zhimin Qiang
更新时间: 2018-06-23
摘要: Quinone group is an important fraction of humic acid. The pseudo-first-order rate constant (k obs) of levofloxacin (LF) degradation by permanganate (MnO4 ) significantly increased from 0.010 (without benzoquinone, BQ) to 0.042–0.443 min-1 at [BQ]o:[MnO4 ]o (molar ratio) = 0.03–0.25 at pH 7.5, and an acidic pH facilitated LF degradation. In the presence of BQ, MnO4 was first reduced to Mn(II). Then, Mn(II) reacted with BQ to produce Mn(III) and semiquinone radical, which was promoted under acidic conditions. With dissolved oxygen available, Mn(III) further oxidized semiquinone radical to produce singlet oxygen (1O2) and superoxide radical (O2 ) as well as regenerate BQ. In addition, MnO4 could also react with Mn(II) to produce Mn(III), whose complexation with semiquinone radical in turn promoted this reaction. Due to the predominant scavenging of O2 by BQ, 1O2 and Mn(III) mainly contributed to the accelerated LF degradation, with a notable formation of hydroxyl, ketone and endoperoxide groups in the degradation byproducts. This study helps better understand the role of natural organic matter in the degradation of organic micropollutants by MnO4 in water treatment.
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32258. 题目: Carbon dioxide, methane and nitrous oxide emissions from the human-impacted Seine watershed in France
文章编号: N18062302
期刊: Science of The Total Environment
作者: Audrey Marescaux, Vincent Thieu, Josette Garnier
更新时间: 2018-06-23
摘要: Greenhouse gas (GHG) emissions from rivers and lakes have been shown to contribute significantly to global carbon and nitrogen cycling. In temperate and human-impacted regions, simultaneous carbon dioxide, methane and nitrous oxide emissions from aquatic systems are poorly documented. We estimated carbon dioxide (CO2) concentrations in the Seine hydrosystem (71,730 km2, France) using direct measurements, and calculations of CO2 partial pressures from 14 field campaigns conducted between 2010 and 2017, and compared them to methane (CH4) and nitrous oxide (N2O) concentrations. In the main stem of the Seine River, CO2 showed the same spatial gradient as N2O and CH4 with peaks in concentration downstream from the arrival of effluents from wastewater treatment plants enriched in organic matter, thus favoring mineralization. It is likely that high CO2 concentrations upstream were due to organic carbon inputs from soils and enriched CO2 groundwater discharges, whereas high N2O and CH4 upstream values were likely due to denitrification in riparian wet areas and anoxic decomposition of organic matter-rich wetlands, respectively. In addition, seasonal variations in all three GHGs were observed with higher concentrations in summer when higher temperatures promote mineralization and low water reduces the dilution of organic matter mainly originating from WWTP effluents. GHG emissions were calculated and compared with agricultural and nonagricultural (urban, transport) fluxes in the basin. In the Seine River network, CO2 emissions dominated riverine GHG emissions, reaching 95.3%, while N2O and CH4 emissions accounted for 4.4% and 0.3%, respectively. These indirect emissions from the hydrosystem were estimated to account for 3.7% of the total GHG emissions from the basin that amounted to 61,284 Gg CO2eq yr-1. Comparatively, direct agricultural and nonagricultural GHG emissions were estimated at 23.3% and 73.0%., respectively.
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32259. 题目: Mapping soil organic matter in the Baranja region (Croatia): Geological and anthropic forcing parameters
文章编号: N18062301
期刊: Science of The Total Environment
作者: Igor Bogunovic, Sebastiano Trevisani, Paulo Pereira, Vesna Vukadinovic
更新时间: 2018-06-23
摘要: Spatial mapping of soil organic matter (SOM) and evaluation of the related natural and anthropic influencing factors are crucial to monitor the extent of degraded land and the evolution of soil functions. The objective of this work is to study the spatial distribution of SOM in a highly exploited agricultural area in the Baranja Region (Croatia). The spatially dense dataset available (4825 top-soil samples from 0 to 30 cm) allowed to produce reliable SOM maps using geostatistical interpolation kriging algorithms and to study the relationships with possible influencing factors. The interpolation has been conducted by means of two approaches. In one approach, the overall data set is considered for computing a global variogram and performing a direct interpolation of SOM values. In the second approach, the data are stratified according to two different geological and morphogenetic domains, Holocene Domain (HD) and Pleistocene Domain (PD), and a distinct geostatistical analysis is performed in each domain. The results showed that average SOM in the studied region was 2.29%, indicating a future need for adopting sustainable soil management practices in this region. SOM was significantly higher in HD (2.64%) than PD (1.97%) domain. SOM in PD generally had a much lower global variability. Global dataset analysis reveals that regional intrinsic factors prevail over local intrinsic and extrinsic factors in determining SOM spatial patterns. In contrast, the stratified approach can filter the effect of regional variability related to the main geological and geomorphological setting. The structural spatial correlation in PD is weaker than in HD, as manifested by spatial patches of low and high SOM content with smaller extension in PD with respect to HD. The strong relationships between SOM spatial patterns and geological/geomorphological factors suggest the possibility of adopting finer subdivision criteria in future research.
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32260. 题目: A model assessment of the role played by the carbonate (CO3?) and dibromide (Br2?) radicals in the photodegradation of glutathione in sunlit fresh- and salt-waters
文章编号: N18062204
期刊: Chemosphere
作者: Davide Vione
更新时间: 2018-06-22
摘要: Glutathione (GLU) is a peptidic thiol that plays important anti-oxidant roles in organisms and that occurs in both freshwater and seawater, where it can undergo both bio- and photodegradation. Recent results have elucidated the role played by OH, 1O2, H2O2 and other yet unidentified transients in GLU photochemistry, but very little is known of the role of CO3 -. This is an important gap because CO3 - is usually very reactive towards electron-rich compounds including thiols and mercaptans. Very little is also known on the environmental importance of the reaction between GLU and Br2 -, which could account for the literature finding that GLU phototransformation is enhanced in simulated seawater compared to freshwater. By means of a photochemical model approach based on the APEX software (Aqueous Photochemistry of Environmentally-occurring Xenobiotics), here we provide an assessment of the role that several photoreactants, including most notably CO3- and Br2 -, have in the photodegradation of GLU (both the whole substance and the separate neutral and mono-anionic species) under representative fresh- and saltwater conditions. Our model suggests that CO3 - would dominate the photodegradation of GLU in low-DOC and high-pH freshwater, which are the only freshwater conditions that really ensure GLU photodegradation to be competitive with biotransformation. This result supports the potential key importance of CO3 - in the environmental photochemistry of GLU. In surface seawater and in brackish water, GLU phototransformation might be dominated by the Br2 - reaction (the role of additional halogen species such as Cl2- and ClBr - is still unknown).
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