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26641. 题目: Biochar versus bone char for a sustainable inorganic arsenic mitigation in water: What needs to be done in future research?
文章编号: N19032408
期刊: Environment International
作者: Susan S.A. Alkurdi, Indika Herath, Jochen Bundschuh, Raed A. Al-Juboori, Meththika Vithanage, Dinesh Mohan
更新时间: 2019-03-24
摘要: Arsenic (As) is an emerging contaminant on a global scale posing threat to environmental and human health. The relatively brief history of the applications of biochar and bone char has mapped the endeavors to remove As from water to a considerable extent. This critical review attempts to provide a comprehensive overview for the first time on the potential of bio- and bone-char in the immobilization of inorganic As in water. It seeks to offer a rational assessment of what is existing and what needs to be done in future research as an implication for As toxicity of human health risks through acute and chronic exposure to As contaminated water. Bio- and bone-char are recognized as promising alternatives to activated carbon due to their lower production and activation cost. The surface modification via chemical methods has been adopted to improve the adsorption capacity for anionic As species. Surface complexation, ion exchange, precipitation and electrostatic interactions are the main mechanisms involved in the adsorption of As onto the char surface. However, arsenic-bio-bone char interactions along with their chemical bonding for the removal of As in aqueous solution is still a subject of debate. Hence, the proposed mechanisms need to be scrutinized further using advanced analytical techniques such as synchrotron-based X-ray. Moving this technology from laboratory phase to field scale applications is an urgent necessity in order to establish a sustainable As mitigation in drinking water on a global scale.
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26642. 题目: Insights into periodate oxidation of bisphenol A mediated by manganese
文章编号: N19032407
期刊: Chemical Engineering Journal
作者: Jiangkun Du, Shigang Tang, Faheem, Haibo Ling, Han Zheng, Guangfeng Xiao, Liting Luo, Jianguo Bao
更新时间: 2019-03-24
摘要: A highly efficient destruction of bisphenol A (BPA) was explored through Mn²⁺-mediated activation of periodate under ambient conditions. The conjunction of periodate with different transition metals was investigated, and Mn exhibited the best catalytic performance. The periodate oxidation of BPA could be rapidly proceeded loading with low amount of Mn²⁺ and in a wide pH range. The presence of humic acid significantly enhance the degradation efficiency due to its electron transfer characteristic. Besides, molecular oxygen played an indispensable role during the reaction, and superoxide radicals was discriminated as the leading reactive species for BPA degradation. The homogeneous periodate activation initiated by Mn²⁺ provides a feasible approach for the degradation of organic contaminants without external energy.
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26643. 题目: Marine vs freshwater microalgae exopolymers as biosolutions to microplastics pollution
文章编号: N19032406
期刊: Environmental Pollution
作者: César Cunha, Marisa Faria, Natacha Nogueira, Artur Ferreira, Nereida Cordeiro
更新时间: 2019-03-24
摘要: Microalgae can excrete exopolymer substances (EPS) with a potential to form hetero-aggregates with microplastic particles. In this work, two freshwater (Microcystis panniformis and Scenedesmus sp.) and two marine (Tetraselmis sp. and Gloeocapsa sp.) EPS producing microalgae were exposed to different microplastics. In this study, the influence of the microplastic particles type, size and density in the production of EPS and hetero-aggregates potential was studied. Most microalgae contaminated with microplastics displayed a cell abundance decrease (of up to 42%) in the cultures. The results showed that the formed aggregates were composed of microalgae and EPS (homo-aggregates) or a combination of microalgae, EPS and microplastics (hetero-aggregates). The hetero-aggregation was dependent on the size and yield production of EPS, which was species specific. Microcystis panniformis and Scenedesmus sp. exhibited small EPS, with a higher propension to disaggregate, and consequently lower capabilities to aggregate microplastics. Tetraselmis sp. displayed a higher ability to aggregate both low and high-density microplastics, being partially limited by the size of the microplastics. Gloeocapsa sp. had an outstanding EPS production and presented excellent microplastic aggregation capabilities (adhered onto the surface and also incorporated into the EPS). The results highlight the potential of microalgae to produce EPS and flocculate microplastics, contributing to their vertical transport and consequent deposition. Thus, this work shows the potential of microalgae as biocompatible solutions to water microplastics treatment.
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26644. 题目: Co-transport of phenanthrene and pentachlorophenol by natural soil nanoparticles through saturated sand columns
文章编号: N19032405
期刊: Environmental Pollution
作者: Fei Liu, Baile Xu, Yan He, Philip C. Brookes, Jianming Xu
更新时间: 2019-03-24
摘要: Mobile colloids such as nanoparticles (NPs) are often considered to affect the fate and transport of various contaminants by serving as carriers. Many studies have focused on the effect of engineered NPs on contaminant transport. To date, very little information is available on the co-transport of natural soil NPs with typical organic contaminants. This study investigated the co-transport of phenanthrene (PHE) and pentachlorophenol (PCP) by three soil NPs through saturated sand columns. Soil NPs with high organic matter and particle concentration were the most effective in transporting PHE through columns. In addition, soil NPs significantly increased the transport of low-level PHE (0.2 mg L⁻¹) but there was no obvious increase at 1.0 mg L⁻¹ PHE. This is attributed to a higher ratio of NP-associated PHE to total PHE at a low-level than at a high-level during transport. In contrast to PHE, the chemical speciation of PCP determined its mobility, which was highly dependent on solution pH. At pH 6.5, anionic PCP became dominant and soluble in the effluent. This could account for the negligible effect of soil NPs on PCP mobility. At pH 4.0, however, neutral molecular PCP dominated and, as expected, decreased mobility of PCP occurred. Soil NPs considerably enhanced the transport of neutral PCP in NP-associated forms compared to controls, due to the high hydrophobicity and sorption affinity of PCP to NPs. The mobility of soil NPs was little affected by PHE and PCP under tested conditions. This study indicated that highly mobile soil NPs may be effective carriers for organic contaminants and give a new direction to polluted site remediation by using a natural material, e.g., soil.
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26645. 题目: Variations in soil and microbial biomass C, N and fungal biomass ergosterol along elevation and depth gradients in Alpine ecosystems
文章编号: N19032404
期刊: Geoderma
作者: Parag Bhople, Ika Djukic, Katharina Keiblinger, Franz Zehetner, Dong Liu, Michael Bierbaumer, Sophie Zechmeister-Boltenstern, Rainer Georg Joergensen, Rajasekaran Murugan
更新时间: 2019-03-24
摘要: Changes in soil fungal biomass ergosterol, microbial biomass and their role in soil organic carbon (SOC) dynamics along elevation and depth gradients in the Alps are still poorly explored. We investigated changes in stocks of SOC, total N, microbial biomass C (MBC) and N (MBN) and fungal biomass ergosterol at different elevation levels (low, mid and high) in two alpine sites. These two alpine sites represent similar temperature and precipitation regimes, one on alkaline (Hochschwab) the second on acidic (Rauris) bedrock. The stocks of MBC increased with elevation in both sites ranging from 37.6 to 126.1 g m⁻², and MBN stocks from 4.1 to 19.8 g m⁻², following the changes in SOC and total N stocks, except at alkaline low elevation level. The stocks of MBC and MBN were higher at mid-elevation in alkaline than in acidic site. In contrast, MBN stocks were higher at low and high elevation level in acidic site compared to those in alkaline site. Median ergosterol stocks varied around 0.4 g m⁻² in alkaline and increased from 0.05 to 0.2 g m⁻² in acidic site. At all elevation levels, microbial biomass-C/N (MB-C/N) ratio in alkaline site increased with soil depths from 6.0 to 12.3 and remained constant in acidic site between 4.9 and 6.8. In alkaline site, the ratios of ergosterol/MBC declined from 0.6 to 1.4% at 5 cm depth to values around 0.2% at 15–25 cm depth, while this ratio varied between 0.4 and 0.1% at all soil depths in acidic site. In both sites, redundancy and variation partition analysis showed that soil microbial properties were driven by soil chemical properties rather than environmental variables. Our results suggest that environmental variables were less disruptive to soil fungal and microbial biomass and inherent soil properties drive changes in soil microbial and fungal biomass stocks and may drive changes in microbial community structure.

26646. 题目: Impact of wetting and drying cycles on soil structure dynamics
文章编号: N19032403
期刊: Geoderma
作者: Julius Diel, Hans-Jörg Vogel, Steffen Schlüter
更新时间: 2019-03-24
摘要: Soil structure is not static but undergoes continuous changes due to a wide range of biotic and abiotic drivers such as bioturbation and the mechanical disturbance by tillage. This continuous alteration of soil structure beyond the pure swelling and shrinking of some stable structure is what we refer to as soil structure dynamics. It has important consequences for carbon turnover in soil as it controls how quickly soil organic matter gets occluded from or exposed to mineralization. So far there are hardly any direct observations of the rate at which soil pores are formed and destroyed.Here we employ are recently introduced labeling approach for soil structure that measures how quickly the locations of small garnet particles get randomized in soil as a measure for soil structure dynamics. We investigate the effect of desiccation crack dynamics on pore space attributes in general and soils structure turnover in particular using X-ray microtomography for repeated wetting-drying cycles. This is explored for three different soils with a range of soil organic matter content, clay content and different clay mineralogy that were sieved to a certain aggregate size fraction (0.63–2 mm) and repacked at two different bulk density levels.The total magnitude of desiccation crack formation mainly depended on the clay content and clay mineralogy. Higher soil organic matter content led to a denser crack pattern with smaller aperture. Wetting-drying cycles did not only effect visible macroporosity (>8 μm), but also unresolved mesoporosity. The changes in macroporosity were higher at lower bulk density. Most importantly, repeated wetting-drying cycles did not lead to a randomization of distances between garnet particles and pores. This demonstrates that former failure zones are reactivated during subsequent drying cycles. Hence, wetting-drying resulted in reversible particle displacement and therefore would not have triggered the exposure of occluded carbon that was not already exposed during the previous drying event.

26647. 题目: Deep blade loosening increases root growth, organic carbon, aeration, drainage, lateral infiltration and productivity
文章编号: N19032402
期刊: Geoderma
作者: G.J. Hamilton, D. Bakker, G. Akbar, I. Hassan, Z. Hussain, A. McHugh, S. Raine
更新时间: 2019-03-24
摘要: All cultivated soils are prone to rapid reconsolidation when wet, particularly structurally unstable soils. This predisposes them to waterlogging, slow and limited infiltration, rapid drying, and poor establishment, growth and production of crops. Field-scale research was undertaken to develop soil management and/or engineering practices that will maintain a stable, loose tilth with aeration, drainage and infiltration properties that prevent waterlogging, enhance infiltration and increase crop production.The effects of deep ripping plus gypsum, permanent raised beds (PRB), deep blade loosening at 250 mm depth (DBL) and no-tillage crop establishment (NT) were studied in controlled traffic regimes on rainfed and irrigated crops. The DBL treatment severs roots at about 250 mm depth and loosens without inverting the overburden. Experiments were undertaken from 1997 to 2011 on winter waterlog-prone unstable sandy loam over clay soils in Western Australia, on an unstable fine sandy clay loam in Pakistan and on a self-mulching clay in Queensland. All sites were operated on a field scale as part of the commercial operations of collaborating farmers. Root zone soil conditions were monitored with measurements (0–400 mm) of bulk density, tilth porosity, hydraulic conductivity, perched water table depth, root mass, organic carbon, total nitrogen and moisture profiles. Irrigation applications and crop yield were also recorded.Bulk density data on all experimental sites showed reconsolidation of the tilth created by deep ripping with or without gypsum in the NT treatment occurred substantially within one growing season. The reconsolidated NT treatment in Western Australia also had low hydraulic conductivity, air-filled porosity values of only two to 4% at a soil moisture potential of −250 mm (PRB height) and suffered long duration waterlogging events. The DBL-PRB treatment on these soils remained largely unconsolidated, had larger hydraulic conductivity, an air-filled porosity at −250 mm moisture potential of ≥10%, and did not suffer waterlogging. Modelling using drainage theory showed that DBL-PRB could be as wide as three metres and easily drain saturated beds within two days, thus precluding waterlogging.Root mass in the 0–400 mm in DBL-PRB treatment was, on average, seasonally 31% greater than the NT treatment. This increase in root mass is shown to have produced increases of 48% in soil organic carbon and 34% in total soil nitrogen content, and, over 19 cropping seasons with six different types of crop, the DBL-PRB treatment produced an annual average increase in grain yield of 23% over that of the NT treatment.The DBL-PRB treatment also substantially increased the amount and rate of lateral infiltration. Irrigation wetting fronts were both measured and predicted by infiltration theory to reach the centre of 2 m wide DBL-PRB in one third to one half of the time taken in NT-PRB.DBL practice has the potential to stabilise a deepened tilth in all soil types through the conservation of the structure and mass of enhanced root growth, which increases soil organic carbon, total soil nitrogen and crop productivity, as well as preventing waterlogging and improving irrigation efficiency.

26648. 题目: Distribution and adsorption of metals on different particle size fractions of sediments in a hydrodynamically disturbed canal
文章编号: N19032401
期刊: Science of The Total Environment
作者: Shijiao Buyang, Qitao Yi, Hongbiao Cui, Keke Wan, Siliang Zhang
更新时间: 2019-03-24
摘要: Sediment resuspension widely occurs in environments with hydrodynamic disturbances, where particles are sieved into different grain size groups. The particles of different grain size exhibit heterogeneity of their physical, chemical or biological features. This research addressed the association of metals on size fractional particles sieved by sediment resuspension in a canal of Taihu basin, a highly urbanized and human-impacted area. Surface sediment samples were collected from upstream to downstream sections of the canal to analyze the concentrations and fractionation of lead (Pb), zinc (Zn), and copper (Cu). One sediment sample was sieved into five different particle size groups (50–150 μm, 30–50 μm, 10–30 μm, 5–10 μm and <5 μm) through the wet sedimentation method. The strong adsorption ability of metals on fine particles is attributed to enrichment with organic matter and iron/aluminum (Fe/Al) oxides, with the increase in Pb, Zn, and Cu concentrations from 34.2 mg/kg, 263 mg/kg, and 32.5 mg/kg of 50–150 μm size group particles to 71.4 mg/kg, 698 mg/kg, and 137 mg/kg of <5 μm size group particles, respectively. The fine particles showed stronger sorption ability on Pb than Zn and Cu, with the Freundlich isotherm constant (K_f) values of the adsorption isotherms in the <10 μm size particle group ranging from 3.7 to 5.9 g/kg for Zn and Cu versus from 11 to 18 g/kg for Pb, probably causing difference on metals accumulation and releasing risk among metals in the downstream lakes with changeable environments.
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26649. 题目: Spatial Distribution of Soil Organic Matter Related to Microtopography and NDVI Changes in Poyang Lake, China
文章编号: N19032307
期刊: Wetlands
作者: Lilin Zheng, Jinying Xu, Zhiqiang Tan, Ligang Xu, Xiaolong Wang
更新时间: 2019-03-23
摘要: The interactions between soil organic matter (SOM) and micro-topography and vegetation drive the ecology of wetland ecosystems. We investigated the distribution pattern of SOM and its relationships with elevation, slope, aspect, topographic wetness index (TWI), and normalized difference vegetation index (NDVI) in Poyang Lake, the largest freshwater lake of China. The local parameters were obtained by applying a geographically weighted regression model. Local parameter differences were analyzed between two dominant wetland types (dish-shaped pit wetland and delta wetland) and among nine land-cover types (deep water, shallow water, very shallow water, mudflat, meadow, sparse grassland, Carex-Phalaris community, Phragmites-Triarrhena community, and Artemisia-Cynodon community). The SOM response to elevation was most sensitive in the dish-shaped pit wetland and mudflat, whereas the effects of slope on SOM were more significant in the delta wetland and vegetated land-cover types. Relatively weaker correlations were observed between SOM and aspect in all study zones. Positive correlations were found between SOM and TWI, which was strongest in dish-shaped pit wetland and deep water. NDVI was positively related to SOM in most areas, but the relationships were not significant in the southern area and in the mudflat. This study helps to better understand the spatial heterogeneity of Poyang Lake.

26650. 题目: Highly efficient removal of Cr(VI) and Cu(II) by biochar derived from Artemisia argyi stem
文章编号: N19032306
期刊: Environmental Science and Pollution Research
作者: Jianyang Song, Qiulai He, Xiaoling Hu, Wei Zhang, Chunyan Wang, Rongfan Chen, Hongyu Wang, Ahmed Mosa
更新时间: 2019-03-23
摘要: In this work, a novel biochar was prepared from the Artemisia argyi stem at 300 °C (AS300), 450 °C (AS450), and 600 °C (AS600). The structural properties of these biochars were characterized with various tools. The sorption kinetic processes of Cr(VI) and Cu(II) onto these biochars were better described by the pseudo-second order. The sorption isotherm processes of Cr(VI) onto these biochars were better described by the Freundlich model while the adsorption processes of Cu(II) were consistent with the Langmuir model. Batch sorption experiments showed that AS600 had the maximum adsorption capacity to Cr(VI) and Cu(II) with 161.92 and 155.96 mg/g, respectively. AS600 was selected for the follow-up batch and dynamic adsorption experiments. Results showed that AS600 had larger adsorption capacity for Cr(VI) at lower pH while the larger adsorption capacity for Cu(II) was found at higher pH. The effect of ionic strength on the adsorption of Cu(II) by AS600 was greater than that on the adsorption of Cr(VI). Dynamic adsorption experiments showed that Cu(II) had a higher affinity for the adsorption sites on the AS600 compared with Cr(VI). The adsorption mechanisms mainly involved electrostatic attraction, ion exchange, pore filling, and chemical bonding effect.

26651. 题目: Nanostructure of Gasification Charcoal (Biochar)
文章编号: N19032305
期刊: Environmental Science & Technology
作者: Jacob W. Martin, Leonard Nyadong, Caterina Ducati, Merilyn Manley-Harris, Alan G. Marshall, Markus Kraft
更新时间: 2019-03-23
摘要: In this work, we investigate the molecular composition and nanostructure of gasification charcoal (biochar) by comparing it with heat-treated fullerene arc-soot. Using ultrahigh resolution Fourier transform ion-cyclotron resonance and laser desorption ionization time-of-flight mass spectrometry, Raman spectroscopy, and high resolution transmission electron microscopy we analyzed charcoal of low tar content obtained from gasification. Mass spectrometry revealed no magic number fullerenes such as C₆₀ or C₇₀ in the charcoal. The positive molecular ion m/z 701, previously considered a graphitic part of the nanostructure, was found to be a breakdown product of pyrolysis and not part of the nanostructure. A higher mass distribution of ions similar to that found in thermally treated fullerene soot indicates that they share a nanostructure. Recent insights into the formation of all carbon fullerenes reveal that conditions in charcoal formation are not optimal for the formation of fullerenes, but instead, curved carbon structures coalesce into fulleroid-like structures. Microscopy and spectroscopy support such a stacked, fulleroid-like nanostructure, which was explored using reactive molecular dynamics simulations.
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26652. 题目: Integrating Biolayer Interferometry, Atomic Force Microscopy, and Density Functional Theory Calculation Studies on the Affinity between Humic Acid Fractions and Graphene Oxide
文章编号: N19032304
期刊: Environmental Science & Technology
作者: Qixing Zhou, Shaohu Ouyang, Zhimin Ao, Jing Sun, Guanlan Liu, Xiangang Hu
更新时间: 2019-03-23
摘要: The interactions between nanoparticles and humic acid (HA) are critical to understanding the environmental risks and applications of nanoparticles. However, the interactions between HA fractions and graphene oxide (GO, a popular carbon nanosheet) at the molecular level remain largely unclear. Four HA fractions with molecular weights ranging from 4.6 to 23.8 kDa were separated, and the large HA fractions presented low oxygen contents and many aromatic structures. The binding constants of the large HA fractions on GO were 2.6- to 3551-fold higher than those of the small HA fractions, while the maximum adsorption capacities of the larger HA fractions onto GO were much higher. Atomic force microscopy (AFM) found that the small and large HA fractions were spread over the center and the edge of the GO nanosheets, respectively. Density functional theory (DFT) simulation and nuclear magnetic resonance spectroscopy confirmed the above phenomena (three adsorption patterns, “vs”, “ps”, and “pea”) and revealed that HA bonded to the GO nanosheets mainly through van der Waals force and π–π interactions. The integrating analysis of binding affinity, AFM, and DFT provides new insights into the environmental behavior of GO and the applications of GO in pollutant removal under exposure from HA.
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26653. 题目: Forest fires in Canadian permafrost region: the combined effects of fire and permafrost dynamics on soil organic matter quality
文章编号: N19032303
期刊: Biogeochemistry
作者: Heidi Aaltonen, Kajar Köster, Egle Köster, Frank Berninger, Xuan Zhou, Kristiina Karhu, Christina Biasi, Viktor Bruckman, Marjo Palviainen, Jukka Pumpanen
更新时间: 2019-03-23
摘要: Wildfires burn approximately 1% of boreal forest yearly, being one of the most significant factors affecting soil organic matter (SOM) pools. Boreal forests are largely situated in the permafrost zone, which contains half of global soil carbon (C). Wildfires advance thawing of permafrost by burning the insulating organic layer and decreasing surface albedo, thus increasing soil temperatures. Fires also affect SOM quality through chemical and physical changes, such as the formation of resistant C compounds. The long-term post-fire effects on SOM quality, degradability and isotopic composition are not well known in permafrost forests. We studied the effect of forest fires on the proportional sizes of SOM pools with chemical fractionation (extracting with water, ethanol and acid) of soil samples (5, 30 and 50 cm depths) collected from a fire chronosequence in the upland mineral soils of the Canadian permafrost zone. We also determined the ¹³C and ¹⁵N isotopic composition of soil after fire. In the topsoil horizon (5 cm) recent fire areas contained a smaller fraction of labile SOM and were slightly more enriched with ¹⁵N and ¹³C than older fire areas. The SOM fraction ratios reverted towards pre-fire status with succession. Changes in SOM were less apparent deeper in the soil. Best predictors for the size of recalcitrant SOM fraction were active layer depth, vegetation biomass and soil C/N ratio, whereas microbial biomass was best predicted by the size of the recalcitrant SOM fraction. Results indicated that SOM in upland mineral soils at the permafrost surface could be mainly recalcitrant and its decomposition not particularly sensitive to changes resulting from fire.

26654. 题目: The structural composition of soil phosphomonoesters as determined by solution ³¹P NMR spectroscopy and transverse relaxation (T₂) experiments
文章编号: N19032302
期刊: Geoderma
作者: Timothy I. McLaren, René Verel, Emmanuel Frossard
更新时间: 2019-03-23
摘要: In terrestrial ecosystems, a large proportion of the phosphorus (P) in soil is often found within soil organic matter. However, the majority of organic P in soil remains ‘unresolved’ and is largely observed as a ‘broad’ signal within the phosphomonoester region of a solution ³¹P nuclear magnetic resonance (NMR) spectrum on soil extracts. Our aim was to gain insight into the composition of four soils using the transverse relaxation (T₂) time of the magnetisation in solution ³¹P NMR spectroscopy as a probe of their structure. We found the broad signal within the phosphomonoester region rapidly decayed compared to the sharp signals (i.e. myo- and scyllo-inositol hexakisphosphate) across all soils, which corresponded to the former having a shorter T₂ time than the latter, and supports the existence of a broad signal due to supra-/macro-molecular structures. Furthermore, measures of the broad signal's line-width at half peak intensity based on T₂ times were found to be less than that obtained from spectral deconvolution fitting. Therefore, our results strongly suggest that the broad signal is itself comprised of more than one component. The significance of this is that the chemical nature of a large proportion of soil organic P appears to be structurally complex.
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26655. 题目: Land use change alters the radiocarbon age and composition of soil and water-soluble organic matter in the Brazilian Cerrado
文章编号: N19032301
期刊: Geoderma
作者: Jason N. James, Cole D. Gross, Pranjal Dwivedi, Tyler Myers, Fernanda Santos, Rodolpho Bernardi, Marianne Fidalgo de Faria, Iraê Amaral Guerrini, Rob Harrison, David Butman
更新时间: 2019-03-23
摘要: The Brazilian Cerrado has undergone extensive land-use change in the past century with large areas converted to agriculture and silviculture. Eucalyptus is the dominant planted tree species in Brazil, but the short rotations (6–7 years) and the associated soil disturbances can reduce soil organic matter (SOM), particularly in subsurface soil over long timeframes. SOM is critical to the continued productivity of forests and may be particularly important in Oxisol soils, which underlie much of Brazil. These soils are low in cation exchange sites and rely upon SOM for nutrient and water retention. However, the mechanisms that drive SOM loss under Eucalyptus remain unclear. This study examines both bulk soil and water-soluble organic matter chemistry deep into the soil profile (1.3 m) in paired Eucalyptus and Cerrado forest stands to identify changes in biodegradability, radiocarbon age, and functional group composition that may explain long-term declines in SOM stocks. We hypothesize that changes in litter quality associated with the conversion of Cerrado forest to Eucalyptus plantations increases the content of aliphatic functional groups in water soluble organic matter (WSOM) more quickly than bulk SOM, which drives subsoil accumulation of aliphatic organic moieties through hydrophobic interactions with soil minerals. By utilizing a suite of spectroscopic techniques (¹H nuclear magnetic resonance and Fourier transform infrared spectroscopy) alongside isotopic and incubation techniques, this study found substantial shifts toward aliphatic functional group composition in WSOM in both Eucalyptus stands and deeper soil horizons. The radiocarbon age of WSOM was younger than bulk SOM at every depth but still substantially diverged from modern in B horizons. This observation is consistent with the theory that WSOM is in dynamic equilibrium with mineral adsorbed SOM, and that old organic matter replaced on mineral surfaces by fresh inputs may be leached or further degraded by microbes. Radiocarbon age of bulk SOM was younger under Eucalyptus compared to Cerrado forest and the difference between WSOM and bulk SOM radiocarbon age was much smaller in Eucalyptus soils, which together indicate that microbes may be preferentially consuming older SOM after land-use change. The presence of Cerrado understory in Eucalyptus may be important to maintaining SOM cycling; WSOM biodegradability and microbial biomass was greatly reduced in the Eucalyptus site without any understory. Ecotones with Cerrado understory provide diversity in litter types and rooting strategies, while monoculture Eucalyptus, which is commonly found in stand interiors, may reduce the ability for microbes to maintain active nutrient recycling of organic residues.

26656. 题目: Spatiotemporal variation in environmental features and elemental/isotopic composition of organic matter sources and primary producers in the Yundang Lagoon (Xiamen, China)
文章编号: N19032222
期刊: Environmental Science and Pollution Research
作者: Xinqing Zheng, Serena Como, Paolo Magni, Lingfeng Huang
更新时间: 2019-03-22
摘要: Aquatic eutrophication is a major problem globally, leading to significant chemical-compositional changes in the first trophic levels of a food web. These will consequently affect the whole food web dynamics in eutrophic coastal ecosystems. In this study, we analyzed the spatiotemporal variation in water chlorophyll-a, total organic carbon (TOC) and TOC/Chl-a ratio, and in the elemental/isotopic (C_at/N_at, δ¹³C, δ¹⁵N) composition of particulate organic matter (POM), phytoplankton, sedimentary organic matter, benthic microalgae, U. lactuca, and decaying leaves of mangrove plants in the eutrophic, urban lagoon of Yundang (Xiamen, China). Investigations were carried out in four different sectors of the lagoon in March (dominated by Ulva lactuca) and September (dominated by phytoplankton) 2009, and the feasible contribution of potential organic matter (OM) sources to POM was assessed in each period. The results showed significant spatiotemporal variation in δ¹³C and δ¹⁵N of POM, owing to changes in its carbon sources. The POM in the diversion canal (POM_DC) of the lagoon originated mainly from terrestrial OM both in March and September, as evidenced by a C_at/N_at ratio of 12~17 and a TOC/Chl-a ratio exceeding 400, as well as depleted δ¹³C (− 27.3~− 23.7‰) and δ¹⁵N (− 2.8~0.1‰). The POM in the main canal (POM_MC) and the inner (POM_IL) and outer (POM_OL) sectors of the lagoon were largely composed of lagoon-borne phytoplankton in September. This was revealed by TOC/Chl-a values below 100 and enriched δ¹³C values (− 22.7~− 17.9‰) which are close to the values typical for fresh phytoplankton. However, these were strongly regulated by exogenous OM in March. The combined contribution of POM_MC and POM_DC to POM in March reached 64–99% in the inner lagoon and 67–88% in the outer lagoon. Non-living POM, which originates from terrestrial organic detritus, was the main contributor to POM (60.7~85.7%) both in the inner and outer sections of the lagoon. Overall, the present study demonstrates that the temporal changes in the dominance of primary producers were reflected in significant variation in the environmental features and elemental/isotopic composition of OM sources and their contribution to POM in the Yundang Lagoon. To further our understanding of the effects of eutrophication due to different primary producers on the resource partitioning in the Yundang Lagoon, additional studies on the consumers and the whole food web of the lagoon are expected.

26657. 题目: Multi-model ensemble improved the prediction of trends in soil organic carbon stocks in German croplands
文章编号: N19032221
期刊: Geoderma
作者: Catharina Riggers, Christopher Poeplau, Axel Don, Chris Bamminger, Heinrich Höper, René Dechow
更新时间: 2019-03-22
摘要: Various soil organic carbon (SOC) models and additional methods to calculate carbon (C) input to soil are used to simulate SOC stocks, e.g. for national greenhouse gas inventories. Most of the SOC models used on a regional to national scale share the principle of process-based multi-compartment models, but differ in their initialization or decomposition modifying factors. We performed a model comparison to identify the model or multi-model ensemble that best fits trends in SOC stocks of German croplands. We combined six SOC models (C-TOOL, CCB, CENTURY, ROTH-C, ICBM and YASSO07) with five C input estimation methods (bolinder, bze, ccb, ctool, ipcc-nir), producing a model set of 30 model combinations. We used data from agricultural permanent soil monitoring sites in Germany to compare modeled and measured trends of SOC stock time series. The absolute mean error (AME) of the trends for the model combinations varied between 0.01 Mg ha⁻¹ a⁻¹ and 0.86 Mg ha⁻¹ a⁻¹, with C-TOOL, CENTURY and YASSO07 generally showing smaller AME than ICBM and CCB. The scatter of the modeled trends of the 30 model combinations indicated that the choice of SOC model was more important than the choice of C input estimation method. A multi-objective criterion was used to summarize results from AME, root mean squared error (RMSE) and the probability that the measured trend lies within the confidence interval of the modeled trend. We set up a multi-model ensemble consisting of all 30 model combinations, and reduced the number of participating models until the multi-objective criterion of the ensemble was smallest. A multi-model ensemble with nine model combinations was found to be the best ensemble. The multi-model ensemble performed better than the single model combinations, with AME of 0.004 Mg ha⁻¹ a⁻¹ and RMSE of 0.56 Mg ha⁻¹ a⁻¹. Based on our results, we recommend the use of a multi-model ensemble for predicting trends in SOC stocks as it reduces structural uncertainties and solves the problem of choosing the right SOC model or C input estimation method.
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26658. 题目: A general-applicable model for estimating the binding coefficient of organic pollutants with dissolved organic matter
文章编号: N19032220
期刊: Science of The Total Environment
作者: Yi-Long Li, Wei He, Rui-Lin Wu, Baoshan Xing, Fu-Liu Xu
更新时间: 2019-03-22
摘要: The binding constant (K_doc) of organic pollutants (OPs) with dissolved organic matter (DOM) is an important parameter in determining the partitioning of OPs in the aquatic environment. Most estimation models have focused on calculating the K_doc of a specific group of OPs but failed to obtain K_doc values of different OPs effectively over the last three decades. In this study, we attempted to build a general-applicable K_doc model based on various organic compounds' K_doc values from the literature since 1973. Two multiple linear regression models, a DOM nonspecific model and an Aldrich HA model, were developed based on two solid and easy to access parameters—molecular connectivity indices (MCI) and polarity correction factors (PCF). In addition, the models' corresponding K_ow-K_doc models, which were mostly used in previous model studies, were developed for comparison. The adjusted determining coefficient (adj-R²) and standard error of the estimate (SEE) of the DOM nonspecific MCI-PCF-K_doc model were 0.815 and 0.579, respectively, whereas the adj-R² and SEE for the MCI-PCF-K_doc model of Aldrich HA reached 0.907 and 0.438, respectively. The Aldrich HA model showed higher pertinence to the nonspecific model. Furthermore, both models exhibited better fit than the K_ow-K_doc models. The dipole moment modification attempts did not significantly improve either MCI-PCF-K_doc models; hence, the two models were not altered with the dipole moment. The robustness tests by a Jackknifed method showed that the two MCI-PCF-K_doc models exhibited higher robustness than the K_ow-K_doc. Of all of the OPs, the phenols contributed the most to their robustness. Furthermore, a sensitivity analysis showed that the two MCI-PCF-K_doc models were sensitive to the robust parameters.
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26659. 题目: Iron plays an important role in molecular fractionation of dissolved organic matter at soil-water interface
文章编号: N19032219
期刊: Science of The Total Environment
作者: Zaoquan Huang, Jitao Lv, Dong Cao, Shuzhen Zhang
更新时间: 2019-03-22
摘要: Adsorption of dissolved organic matter (DOM) onto soils plays an important role in the mobility and stabilization of organic carbon in soils; however, little attention has been paid to changes in the molecular components of soil DOM during adsorption on soils. In the present study, molecular fractionation of DOM induced by adsorption on a red soil was investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The results indicated that compounds high in unsaturation or polarity or rich in oxygen had a high affinity to soil surfaces, while aliphatic compounds with few oxygenated groups and low polarity compounds were preferentially retained in solution. Among soil fractions with different particle sizes, the fine clay fraction with high iron content and surface area was the main contributor to the adsorptive fractionation of DOM. Comparison of the molecular fractionation of DOM derived from adsorption on soil with iron removed and on soil minerals with various iron contents and surface areas further indicated that iron containing minerals in the soil provided the major adsorptive sites and determined the molecular fractionation of DOM at the soil-water interface. The results provide molecular information for further understanding mechanisms underlying the persistence and mobility of organic carbon in soils.
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26660. 题目: Zinc pollution in zones dominated by algae and submerged macrophytes in Lake Taihu
文章编号: N19032218
期刊: Science of The Total Environment
作者: Musong Chen, Dan Wang, Shiming Ding, Xianfang Fan, Zengfeng Jin, Yuexia Wu, Yan Wang, Chaosheng Zhang
更新时间: 2019-03-22
摘要: Zinc (Zn) contamination in lake zones dominated by algae and macrophytes in Lake Taihu was analyzed through diffusive gradient in thin films (DGT) and dialysis (HR-Peeper) methods. It was found that in both zones Zn contamination varied by season. In July and October, dissolved Zn was present in high concentrations, and in July, high concentrations of labile Zn were found in sediments. In July, reductive dissolutions of Fe/Mn oxides likely played a key role in the release of Zn, which was confirmed by both zones having the lowest percentage of the reducible fraction of Zn in July. Complexation of dissolved organic matter (DOM) with Zn may be responsible for the observed increase in the dissolved Zn concentration in October. This conclusion was supported by noting that October had the highest percentages of Zn-DOM complexes (25.3% and 34.4%) in the algae- and macrophytes-dominated zones, respectively. However, in January, low dissolved and labile Zn contents were observed in sediments in the two zones, suggesting that the decrease of Zn in sediments was caused by the adsorption of Fe/Mn oxides.
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