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28561. 题目: Modelling of iohexol degradation in a Fe(Ⅱ)-activated persulfate system
文章编号: N19022308
期刊: Chemical Engineering Journal
作者: Jing-Ping Zhu, Yi-Li Lin, Tian-Yang Zhang, Tong-Cheng Cao, Bin Xu, Yang Pan, Xi-Tong Zhang, Nai-Yun Gao
更新时间: 2019-02-23
摘要: Iohexol can hardly be removed in conventional wastewater treatment processes due to its non-biodegradable and hydrophilic characteristics. In this study, a kinetic model was established to describe iohexol degradation in Fe (Ⅱ) - activated persulfate system. The developed model can well predict iohexol degradation and evolution of sulfate radical with various initial iohexol and oxidant (ferrous iron and persulfate) concentrations under various water matrix. The rate constant of iohexol reacting with sulfate radical was calculated as (1.83±0.10) ×10⁹ M^-1s^-1. The effects of the two most common components in natural water bodies, chloride ion and natural organic matter (NOM) on iohexol degradation, were also studied. Both experimental data and model results showed that the low concentration of chloride ion promoted iohexol degradation while high concentration inhibited it, and NOM slightly inhibited iohexol degradation. Besides, radical quenching tests were employed to identify the main radicals formed in the system and further verified the model accuracy. The model is also capable of predicting the atrazine degradation with the correlation coefficients between the experimental data and predicted results above 0.97, suggesting the applicability of the established model for some other recalcitrant contaminant degradation in the Fe2+/PS system.
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28562. 题目: Efficient degradation of carbamazepine by organo-montmorillonite supported nCoFe₂O₄-activated peroxymonosulfate process
文章编号: N19022307
期刊: Chemical Engineering Journal
作者: Junxue Wu, Giovanni Cagnetta, Bin Wang, Yuezong Cui, Shubo Deng, Yujue Wang, Jun Huang, Gang Yu
更新时间: 2019-02-23
摘要: Carbamazepine (CBZ) is one of most frequently detected pharmaceutical contaminants in water ecosystem, which cannot be removed efficiently by traditional techniques. Degradation of CBZ by peroxymonosulfate (PMS) activated with organo-montmorillonite supported nCoFe₂O₄ (nCoFe₂O₄/OMt) was investigated in this study. The degradation efficiency of CBZ (5 mg L^-1) was 93% within 60 min in the presence of 0.4 g L^-1 nCoFe₂O₄/OMt and 0.5 mM PMS at pH 6.8 and 25°C, following a pseudo-first order kinetics. High PMS concentration and low initial pH could enhance CBZ degradation. The presence of Cl^-, NO₃^- and HCO₃^- showed marked enhancement, slight suppression and obvious inhibition of CBZ degradation, respectively. High concentration of humic acid could decrease the CBZ degradation. X-ray photoelectron spectroscopy of nCoFe₂O₄/OMt before and after reaction revealed that both Co²⁺/Co³⁺ and Fe²⁺/Fe³⁺ were involved in PMS activation during the CBZ degradation. Electron paramagnetic resonance and radical scavenger experiments confirmed that both ^•OH and SO₄^•- played a predominant role on the CBZ degradation. The degradation products were identified by LC-MS/MS to understand the possible pathways.
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28563. 题目: Performance of microaeration hydrolytic acidification process in the pretreatment of 2-butenal manufacture wastewater
文章编号: N19022306
期刊: Journal of Hazardous Materials
作者: Guangqing Song, Yin Yu, Tao Liu, Hongbo Xi, Yuexi Zhou
更新时间: 2019-02-23
摘要: The performance of the microaeration hydrolytic acidification (MAHA) process and microbial community were investigated under different organic loading rates (OLRs) for the pretreatment of 2-butenal manufacture wastewater (2-BMW). Results indicated that OLRs had different impact on the performance of MAHA process. More than 23.7 ± 2.3% of the chemical oxygen demand (COD) removal and the highest acidification degree (20.9 ± 3.1%) were obtained when OLRs were less than 4.0 ± 0.1 kgCOD/m³ d. However, further increasing OLRs to 6.1 ± 0.1 kgCOD/m³ d subsequently led to the significant reductions of COD removal and acidification degree. In addition, it could be preliminarily inferred that 2H-pyran-2-one tetrahydro-4-(2-methyl-1-propen-3-yl), 5-formyl-6-methyl-4,5-dihydropyran and ethyl sorbate were the main refractory and toxic organics for microorganisms in the wastewater. The soluble microbial product (SMP) and extracellular polymeric substance (EPS) contents (protein, polysaccharide, nucleic acid) had obvious changes under different OLRs. With parallel factor (PARAFAC) model, four fluorescent components were identified. The F_max of protein-like substances in SMP significantly decreased with increasing OLRs to 6.1 ± 0.1 kgCOD/m³ d, which might attribute to fluorescence quenching. Illumina MiSeq sequencing revealed that Pseudomonas, Longilinea, T78, Clostridium, WCHB1-05, Acinetobacter, SHD-231 and Oscillospira were dominant genera at different OLRs.
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28564. 题目: Enhanced adsorption of bisphenol A and sulfamethoxazole by a novel magnetic CuZnFe₂O₄–biochar composite
文章编号: N19022305
期刊: Bioresource Technology
作者: Jiyong Heo, Yeomin Yoon, Gooyong Lee, Yejin Kim, Jonghun Han, Chang Min Park
更新时间: 2019-02-23
摘要: The widespread occurrence of endocrine-disrupting compound and pharmaceutical active compounds such as bisphenol A (BPA) and sulfamethoxazole (SMX) in natural freshwater resources can cause serious environmental problems even at low exposure levels. In this work, in order to remove BPA and SMX from aqueous solutions, a novel biochar-supported magnetic CuZnFe₂O₄ composite (CZF–biochar) was synthesized by a facile one-pot hydrothermal process. After characterization studies, the key factors affecting BPA and SMX adsorption on CZF–biochar were comprehensively investigated. The primary mechanisms for BPA and SMX adsorption included charge-assisted H-bonding, hydrophobic, and π-π electron donor-acceptor interactions. In summary, considering the fast kinetics, high adsorption properties, easy magnetic separation, and recyclability for multiple reuses, the CZF–biochar composite has potential for the removal of BPA, SMX, and potentially other emerging organic contaminants from contaminated soil and water.
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28565. 题目: A Modified Method for Enhancing Adsorption Capability of Banana Pseudostem Biochar towards Methylene Blue at Low Temperature
文章编号: N19022304
期刊: Bioresource Technology
作者: Sen Liu, Jihui Li, Shuang Xu, Mengzhen Wang, Yucang Zhang, Xinghua Xue
更新时间: 2019-02-23
摘要: A phosphomolybdic acid promoted oxidative pyrolysis was described for preparation of banana pseudostem biochar. The strategy succeeded to introduce oxygen-containing groups onto the biochar surface at low temperature. In addition, pore channels were created, demonstrated by the SEM images of biochar prepared at 200 ^oC. Adsorption experiments showed that the biochar pyrolyzed at 200 ^oC exhibited much better adsorption capability than others pyrolyzed at higher temperatures for methylene blue (MB). The adsorption capability of biochar prepared at 200 ^oC was enhanced from 87.28 to 146.23 mg/g at 45 ^oC with phosphomolybdic acid modification. The enhancement of adsorption capacity could be ascribed to the increase of surface oxygen-containing functional groups and pore channels. In-situ generated carboxylic groups during adsorption and desorption played an important role in removal of MB. Adsorption of MB was mainly attributed to hydrogen bonding, electrostatic interactions and cation exchanges.
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28566. 题目: The isotopic composition and fluxes of particulate organic carbon exported from the eastern margin of the Tibetan Plateau
文章编号: N19022303
期刊: Geochimica et Cosmochimica Acta
作者: Jin Wang, Robert G. Hilton, Zhangdong Jin, Fei Zhang, Alexander L. Densmore, Darren R. Gröcke, Xiaomei Xu, Gen Li, A. Joshua West
更新时间: 2019-02-23
摘要: Erosion of organic carbon from the terrestrial biosphere and sedimentary rocks plays an important role in the global carbon cycle across a range of timescales. Over geological timescales (>10⁴ years), erosion and burial of particulate organic carbon (POC) from the terrestrial biosphere (POC_biosphere) is an important CO₂ sink, while oxidation of organic carbon derived from sedimentary rocks (petrogenic, POC_petro) releases CO₂ to the atmosphere. Over decadal to millennial timescales, the balance between POC_biosphere production and degradation affects atmospheric CO₂ concentrations. To better constrain the controls on erosional carbon transfers, here we quantify POC_biosphere and POC_petro fluxes in a mountain range with relatively low runoff, the Longmen Shan, which drains the eastern margin of the Tibetan Plateau. We measure total organic carbon content ([OC_total]) and the carbon isotopic compositions (¹³C/¹²C expressed as δ¹³C; ¹⁴C/¹²C expressed as fraction modern or F_mod) of organic matter in suspended sediments collected from six gauging stations on the Min Jiang, a tributary of the Yangtze River, from 2005 to 2012. We find that POC_petro has a large range of δ¹³C, from -26.2‰ to -13.2‰. This POC_petro mixes with POC_biosphere to set the δ¹³C of POC in river sediments. Binary mixing models reveal the possibility of aged POC_biosphere at two gauging stations which drain the high elevations of the eastern Tibetan Plateau, with modelled F_mod values of 0.82 ± 0.09 and 0.84 ± 0.08. This is consistent with prior suggestions of aged biospheric carbon being eroded from the Plateau.The annual POC_petro yields range from 0.04 ± 0.02 tC km^-2 yr^-1 to 1.69 ± 0.56 tC km^-2 yr^-1 across the five study catchments, with basin average yield that appears to be linked to catchment average slope as a likely proxy for erosion rate. Here, the variability in the petrogenic organic carbon content of rocks masks the signal of the weathering and oxidation of this rock-derived organic carbon. The annual POC_biosphere yields range from 0.21 ± 0.04 tC km^-2 yr^-1 to 3.33 ± 0.57 tC km^-2 yr^-1. These values are towards the lower end of those measured in mountain ranges around the world, which we suggest not only reflects the relatively low erosion rates of the Longman Shan, but also the low annual runoff (<1 m yr^-1). Across this region, the river POC_biosphere discharge is related to the intensity of runoff events. Our data suggest that a wetter (and/or stormier) climate could increase the erosional export of POC_biosphere in this tectonically-active mountain range. Depending on the fate of POC_biosphere downstream in larger river systems, this could act as carbon-cycle climate feedback over geological timescales.

28567. 题目: Conversion of sewage sludge into environmental catalyst and microbial fuel cell electrode material: A review
文章编号: N19022302
期刊: Science of The Total Environment
作者: Md Manik Mian, Guijian Liu, Biao Fu
更新时间: 2019-02-23
摘要: At present, environmentally friendly and cost-effective disposal of sewage sludge (SS) is the major challenge of wastewater treatment that prompted the concept of sludge valorization. A recent technology, SS conversion into biochar as an efficient catalyst for environmental application, shows great promise to sludge valorization. This review presents the literature and advances of sludge biochar-based catalysts (SBCs), including their synthesis route, physiochemical characteristics, catalytic applications, reaction mechanisms, chemical stability, feasibility, and future aspects. Two major applications of SBCs such as organic pollutants degradation and employing as an electrode material in a microbial fuel cell (MFC) were summarized. The literature has indicated that carbonization of raw or organic/ inorganic-laden sludge produces various metal phase structure and surface functional groups which perform various catalytic reaction such as Fenton-like reaction, ozonation, H₂O₂/ persulfate activation, and photoreaction in the organic pollutants degradation tests. The degradation efficiency and chemical stability of SBCs have found very satisfying. Moreover, catalysts are highly recyclable, separable, and ensure negligible metal leaching. Secondly, high-temperature carbonized sludge exhibits excellent electrical conductivity which is suitable to use as MFC electrodes. The low-cost sludge biochar-based electrodes (SBEs) performance is comparable to many commercial electrodes. This new technology is concurrently advantageous for environmental pollution remediation, energy production, and harmful metals immobilization, which offer a new route towards SS valorization.
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28568. 题目: Effect of Bovine Serum Albumin on Stability and Transport of Kaolinite Colloid
文章编号: N19022301
期刊: Water Research
作者: Chaorui Yan, Tao Cheng, Jianying Shang
更新时间: 2019-02-23
摘要: The stability and transport of clay colloids in groundwater are strongly influenced by colloid interactions with dissolved organic matter (DOM). Protein is an important DOM component that is ubiquitous in natural water, reclaimed water, and soil solutions. To date, the interactions between clay colloids and proteins have not been fully studied. The objective of this study was to examine the effect of bovine serum albumin (BSA), a representative protein, on the stability, aggregation, and transport of kaolinite colloids under neutral pH conditions. Hydrodynamic diameter and ζ-potential measurements, stability tests, and column transport experiments were performed in salt solutions with a range of ionic strengths and different BSA concentrations at pH 7. Additionally, BSA-kaolinite colloid interactions were studied using TEM and batch adsorption experiments. The experimental results showed that BSA prevented colloid aggregation and increased the stability and transport of colloids, especially at high ionic strength, even though the charges of kaolinite colloids were less negative in the presence of BSA. Theoretical calculation of the interaction energies indicated that XDLVO theory, in which the steric force is considered due to BSA adsorption, could correctly quantify the interaction energies in the presence of BSA. This study demonstrated that the role of protein needs to be determined in order to better predict the overall effect of DOM on particle aggregation and transport in the soil environment.
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28569. 题目: BIOCHAR IMMOBILIZES AND DEGRADES 2,4,6‐TRICHLOROPHENOL IN SOILS
文章编号: N19022203
期刊: Environmental Toxicology and Chemistry
作者: Liqiang Cui, Chuntao Yin, Tianming Chen, Guixiang Quan, James A. Ippolito, Benzhi Liu, Jinlong Yan, Qaiser Hussain
更新时间: 2019-02-22
摘要: Soil contamination by chlorophenol compounds, such as 2,4,6‐trichlorophenol (2,4,6‐TCP), is of great concern because they are environmentally persistent, difficult to degrade, and can lead to cancer. Thus, means of degrading these compounds in‐situ are desperately needed. Biochar was investigated as a material to sequester, reduce downward transport, and aid in soil 2,4,6‐TCP degradation. In two column studies, wheat straw (Triticum aestivum L.)‐derived biochar (pyrolyzed at 450 ^°C) application to soil (up to 5% by wt.) improved soil water and soil organic carbon (SOC) content. Biochar reduced 2,4,6‐TCP downward transport, likely due to improved soil water mobility and retention allowing 2,4,6‐TCP to be more easily transported and sorbed to organic functional groups on biochar, leading to enhanced degradation. The 2,4,6‐TCP was rapidly degraded into a combination of benzene derivatives and low molecular weight organic compounds in the first two months following biochar application. This study provides evidence that biochars can be used to improve environmental quality by lessening the downward transport and enhancing the degradation of the organochlorine compounds such as 2,4,6‐TCP. This article is protected by copyright. All rights reserved

28570. 题目: Ecotoxicological assessments of biochar additions to soil employing earthworm species Eisenia fetida and Lumbricus terrestris
文章编号: N19022202
期刊: Environmental Science and Pollution Research
作者: Tom Elliston, Ian W. Oliver
更新时间: 2019-02-22
摘要: Biochar is the degradation-resistant product generated by the pyrolysis of organic materials and is produced for the intended use of land application in order to promote carbon sequestration and soil improvement. However, despite the many potential benefits biochar application offers, it is important to quantify any ecological impacts that may result from soil amendment in order to avoid potentially causing negative effects upon soil biota which are crucial in the many ecosystem services provided by soil. Any impacts on earthworms in particular are important to evaluate because of their pivotal role in organic matter breakdown, nutrient cycling and soil formation. In this study, we conducted a series of ecotoxicological assays to determine lethal and sublethal (avoidance, mass change and moisture content) effects of heavy biochar applications that reflect levels that may be used in soil restoration efforts. Two earthworm species, Eisenia fetida, an epigeic species, and Lumbricus terrestris, an anecic species, were utilised as test organisms. Two types of biochar, produced from wheat straw and rice husk feedstocks, respectively, were applied to OECD artificial soil and to a natural soil (Kettering loam) at rates of up to 20% w/w. The influence of biochar application on soil porewater chloride, fluoride and phosphate concentrations was also assessed. The biochar applications induced only a subtle level of avoidance behaviour while effects on survival over a 4-week exposure period were inconsistent. However, death and physical damage to some individual earthworms at high biochar application rates were observed, the mechanisms and processes leading to which should be investigated further. Earthworm development (mean mass change over time) proved to be a more sensitive measure, revealing negative effects on L. terrestris at 10% and 20% (w/w) wheat biochar applications in OECD soil and at 20% (w/w) applications of both biochars in Kettering loam. The moisture content of E. fetida remained remarkably consistent across all treatments (~ 82%), indicating that this is not a sensitive measure of effects. The high rates of biochar application resulted in increased chloride (2 to 3-fold) and phosphate (100-fold) concentrations in simulated soil porewaters, which has important implications for soil fertility and production but also for environmental management.

28571. 题目: Combined use of biochar and zinc oxide nanoparticle foliar spray improved the plant growth and decreased the cadmium accumulation in rice ( Oryza sativa L.) plant
文章编号: N19022201
期刊: Environmental Science and Pollution Research
作者: Shafaqat Ali, Muhammad Rizwan, Shamaila Noureen, Sarwat Anwar, Basharat Ali, Muhammad Naveed, Elsayed Fathi Abd_Allah, Abdulaziz A. Alqarawi, Parvaiz Ahmad
更新时间: 2019-02-22
摘要: The contamination of large areas of arable land with cadmium (Cd) is a serious concern worldwide and environmentally feasible amendments are necessary to minimize Cd accumulation in cereals such as rice (Oryza sativa L.). A pot study was, therefore, conducted to evaluate the efficiency of foliar spray of different levels (0, 50, 75, 100 mg/L) of zinc oxide nanoparticles (ZnO NPs) alone or combined with biochar (1.0% w/w) on Cd content in rice plants grown on an aged Cd-polluted soil. The results showed that ZnO NPs alone or combined with biochar improved the biomass and photosynthesis of rice plant. The ZnO NPs significantly diminished the Cd concentration and enhanced the Zn concentrations in shoots and roots either alone or in combination with biochar. Foliar spray of 100 mg/L ZnO NPs significantly diminished the Cd content in rice shoot and rice roots by 30% and 31%, respectively. The Cd concentrations in rice shoot and root diminished by 39% and 38% after 100 mg/L ZnO NPs combined with biochar, respectively. The ZnO NPs in combination with biochar increased the soil pH from 8.03 to 8.23 units. Soil AB-DTPA-extractable Cd significantly reduced with the amendments applied over the control. Foliar spray of ZnO NPs combined with biochar could be used to grow rice plants especially in areas where Cd concentration is high and Zn deficiency is high.

28572. 题目: Modeling the seasonal cycle of iron and carbon fluxes in the Amundsen Sea Polynya, Antarctica
文章编号: N19022109
期刊: Journal of Geophysical Research: Oceans
作者: P. St-Laurent, P. L. Yager, R. M. Sherrell, H. Oliver, M. S. Dinniman, S. E. Stammerjohn
更新时间: 2019-02-21
摘要: The Amundsen Sea Polynya (ASP) is distinguished by having the highest net primary production per unit area in the coastal Antarctic. Recent studies have related this high productivity to the presence of fast‐melting ice shelves but the mechanisms involved are not well understood. In this study we describe the first numerical model of the ASP to represent explicitly the ocean‐ice interactions, nitrogen and iron cycles, and the coastal circulation at high resolution. The study focuses on the seasonal cycle of iron and carbon and the results are broadly consistent with field observations collected during the summer of 2010–2011. The simulated biogeochemical cycle is strongly controlled by light availability (dictated by sea ice, phytoplankton self‐shading and variable sunlight). The micronutrient iron exhibits strong seasonality, where scavenging by biogenic particles and remineralization play large compensating roles. Lateral fluxes of iron are also important to the iron budget, and our results confirm the key role played by inputs of dissolved iron from the buoyancy‐driven circulation of melting ice shelf cavities (the ‘meltwater pump’). The model suggests that westward‐flowing coastal circulation plays two important roles: it provides additional iron to the ASP, and it collects particulate organic matter (POM) generated by the bloom and transports it to the west of the ASP. As a result, maps of vertical POM fluxes show highest fluxes in shelf regions located west of the productive central ASP. Overall, these model results improve our mechanistic understanding of the ASP bloom, while suggesting testable hypotheses for future field efforts.

28573. 题目: The role of algae in fine sediment flocculation: In-situ and laboratory measurements
文章编号: N19022108
期刊: Marine Geology
作者: Zhirui Deng, Qing He, Zeinab Safar, Claire Chassagne
更新时间: 2019-02-21
摘要: The precise interactions between organic and inorganic particles in the context of flocculation is an on-going topic of research. The suspended particulate matter (SPM) found in estuaries is composed of both organic and inorganic particles with specific particle size distributions (PSD's). These PSD's are a function of the hydrodynamic conditions, suspended sediment concentration (SSC), organic matter composition, salinity and seasonal variations. A field campaign was carried out in August 2015 in the turbidity maximum zone of the Yangtze Estuary, where the SPM dynamics were recorded. The concentration of algae in the water column was indirectly measured through the chlorophyll-a concentration (CC). We show that there is a strong correlation between SSC and CC in the whole water column, for the whole tidal cycle. Additional flocculation experiments in the laboratory confirm that the largest observed flocs are predominantly organic-based, and that salinity alone could not induce the flocculation of the Yangtze mineral particles. A key parameter for the maximal floc size is the algae concentration to sediment concentration ratio. When this ratio is high, the D50 is high and vice-versa.

28574. 题目: Tropical tree height and crown allometries for the Barro Colorado Nature Monument, Panama: a comparison of alternative hierarchical models incorporating interspecific variation in relation to life history traits
文章编号: N19022107
期刊: Biogeosciences
作者: Isabel Martínez Cano, Helene C. Muller-Landau, S. Joseph Wright, Stephanie A. Bohlman, Stephen W. Pacala
更新时间: 2019-02-21
摘要: Tree allometric relationships are widely employed for estimating forest biomass and production and are basic building blocks of dynamic vegetation models. In tropical forests, allometric relationships are often modeled by fitting scale-invariant power functions to pooled data from multiple species, an approach that fails to capture changes in scaling during ontogeny and physical limits to maximum tree size and that ignores interspecific differences in allometry. Here, we analyzed allometric relationships of tree height (9884 individuals) and crown area (2425) with trunk diameter for 162 species from the Barro Colorado Nature Monument, Panama. We fit nonlinear, hierarchical models informed by species traits – wood density, mean sapling growth, or sapling mortality – and assessed the performance of three alternative functional forms: the scale-invariant power function and the saturating Weibull and generalized Michaelis–Menten (gMM) functions. The relationship of tree height with trunk diameter was best fit by a saturating gMM model in which variation in allometric parameters was related to interspecific differences in sapling growth rates, a measure of regeneration light demand. Light-demanding species attained taller heights at comparatively smaller diameters as juveniles and had shorter asymptotic heights at larger diameters as adults. The relationship of crown area with trunk diameter was best fit by a power function model incorporating a weak positive relationship between crown area and species-specific wood density. The use of saturating functional forms and the incorporation of functional traits in tree allometric models is a promising approach for improving estimates of forest biomass and productivity. Our results provide an improved basis for parameterizing tropical plant functional types in vegetation models. ]]>

28575. 题目: Krill faecal pellets drive hidden pulses of particulate organic carbon in the marginal ice zone
文章编号: N19022106
期刊: Nature Communications
作者: A. Belcher, S. A. Henson, C. Manno, S. L. Hill, A. Atkinson, S. E. Thorpe, P. Fretwell, L. Ireland, G. A. Tarling
更新时间: 2019-02-21
摘要: The biological carbon pump drives a flux of particulate organic carbon (POC) through the ocean and affects atmospheric levels of carbon dioxide. Short term, episodic flux events are hard to capture with current observational techniques and may thus be underrepresented in POC flux estimates. We model the potential hidden flux of POC originating from Antarctic krill, whose swarming behaviour could result in a major conduit of carbon to depth through their rapid exploitation of phytoplankton blooms and bulk egestion of rapidly sinking faecal pellets (FPs). Our model results suggest a seasonal krill FP export flux of 0.039 GT C across the Southern Ocean marginal ice zone, corresponding to 17–61% (mean 35%) of current satellite-derived export estimates for this zone. The magnitude of our conservatively estimated flux highlights the important role of large, swarming macrozooplankton in POC export and, the need to incorporate such processes more mechanistically to improve model projections.

28576. 题目: The Effects of Tree Species on Soil Organic Carbon Content in South Korea
文章编号: N19022105
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ji‐Yeon Cha, Yoon‐Kyung Cha, Neung‐Hwan Oh
更新时间: 2019-02-21
摘要: The effects of tree species on soil organic carbon (SOC) content have been evaluated in many studies, but only with a relatively small number of sample plots, resulting in ambiguous conclusions. Here we used a total of 595 forest plots in South Korea to investigate the role of four grouped tree species—pines, oaks, other conifers, and other deciduous trees—in the forest SOC content in both forest floors and mineral soils. Significant differences were observed in SOC content among the groups. Pines contained 7.12 Mg C ha^‐1 of organic carbon in forest floors, whereas oaks and other deciduous trees contained 5.39 and 5.41 Mg C ha^‐1, respectively. In contrast, oaks and other deciduous trees contained ~66 Mg C ha^‐1 of organic carbon each in mineral soils (0‐30 cm depth), whereas pines contained 49.50 Mg C ha^‐1. The total SOC content including both forest floors and mineral soils was the largest under oaks and the smallest under other coniferous trees, due to SOC being approximately an order of magnitude higher in mineral soils than in forest floors. The effects of tree species on SOC storage became apparent for the forest stands with >20‐year‐old trees, which suggests that the observed differences in the SOC content are likely due to the current stands rather than remnants of previous stands. The decomposition rates of organic materials could be a controlling factor affecting SOC storage, rather than inputs of photosynthesized products to soils.

28577. 题目: Ligands representing important functional groups of natural organic matter facilitate Fe redox transformations and resulting binding environments
文章编号: N19022104
期刊: Geochimica et Cosmochimica Acta
作者: Amrita Bhattacharyya, Michael P. Schmidt, Eli Stavitski, Behrooz Azimzadeh, Carmen Enid Martínez
更新时间: 2019-02-21
摘要: Functional groups in natural organic matter have the potential to interact with and stabilize iron (Fe) redox species (ferric, ferrous) through complexation reactions. In this study, iron complexes with cysteine, arginine and histidine are used to investigate the extent to which specific functional groups present in these amino acids might hinder the oxidation of Fe²⁺ or promote the reduction of Fe³⁺. Iron complexes are synthesized by addition of ferrous or ferric salts to cysteine, arginine and histidine solutions at pH 7. The Fe-amino acid complexes are analysed using X-ray Absorption Spectroscopy (XAS), theoretical CTM4XAS (Charge Transfer Multiplet for XAS) calculations, and vibrational spectroscopy (FTIR and Raman). In addition, oxidation of the amino acids is determined by linear sweep voltammetry and chemical equilibrium modeling is used to predict the speciation of Fe in complexes with the amino acids. It is observed the extent of Fe redox transformation is affected by the electron donating capability of the ligand with which Fe reacts. In particular, the extent of Fe³⁺ reduction is related to the oxidation of the ligand with 80, 14 and 0 % Fe³⁺ reduction by cysteine, arginine and histidine, respectively. Conversely, Fe²⁺ is preserved by cysteine (80%) > arginine (77%) > histidine (62%). The chemical forms of Fe in these mixed Fe oxidation-state systems include Fe-organic complexes and Fe precipitates. XAS and vibrational spectroscopy indicate thiol-S and amino-N bind Fe in complexes with cysteine. While amino-N and guanidyl-N functional groups of arginine bind Fe, carboxylate-O binding and the formation of Fe precipitates are only observed when Fe³⁺ is the predominant redox species. Whereas Fe precipitates seem to prevail in Fe(III)-histidine, distinct organic (Fe-O/N-C) and mineral (Fe-O-Fe) or mixed organic-mineral (Fe(O/N-C)_x(O-Fe)_y) coordination environments occur in Fe(II)-histidine with ∼60% Fe²⁺; in either case, Fe-N(imidazole) binding is not evident. The ligand atoms to which Fe binds and the inherent reduction capacity of the ligand appear to mediate Fe redox transformations. The proportion of ferric iron (Fe³⁺) seems to determine whether a precipitate forms. Consistent with spectroscopic data, chemical equilibrium modeling using experimental solution conditions and fractional Fe²⁺ and Fe³⁺ concentrations obtained from CTM4XAS predict the formation of Fe(II)- and Fe(III)- amino acid complexes and hydrolyzed Fe species; these calculations however also predict the formation of Fe oxide precipitates in all Fe complexes. The results presented in this study help to explain the co-occurrence of Fe²⁺ and Fe³⁺ in natural environments where organic matter is present. They also highlight the role specific organic functional groups play on the formation and stabilization of Fe(II,III)-organic complexes and precipitates, and thus on the Fe redox cycle which affects Fe bioavailability and mobility in terrestrial and subsurface environments.

28578. 题目: Responses of soil organic carbon decomposition to warming depend on the natural warming gradient
文章编号: N19022103
期刊: Geoderma
作者: Wenfang Xu, Wenping Yuan, Lilun Cui, Minna Ma, Fenguo Zhang
更新时间: 2019-02-21
摘要: Inconsistent responses of soil organic carbon (SOC) decomposition to climate warming have been observed in field experiments. Responses vary with the duration of experimental warming; however, even the longest warming experiment could not account for possible future climate-driven changes in SOC decomposition. Here, we investigated the responses of SOC decomposition to natural warming in soil samples (at soil depths of 0–10, 10–20, and 20–30 cm) collected at two altitudes (lower-elevation, warm points; higher-elevation, cool points) with an approximate 1 °C difference in mean soil temperature, representing an infinite natural warming duration in the Qinghai–Tibetan Plateau. We incubated these soil samples at three temperatures (i.e., 5, 10, and 15 °C) and analyzed the CO₂ emission rate to assess the responses of SOC decomposition to warming. The results revealed higher CO₂ emission rates from topsoil (0–10 and 10–20 cm) samples collected at lower-elevation (warm points) than higher-elevation (cool points). By contrast, subsoil (20–30 cm) samples showed higher CO₂ emission rates at higher-elevation points. Soil microbial biomass carbon (MBC) exhibited similar patterns in topsoil and subsoil, indicative of the regulation SOC decomposition by MBC. Overall, CO₂ emission rates were higher in subsoil, possible the result of the high vulnerability of carbon and decreased microbial carbon use efficiency in subsoil. For all sampling points, the largest CO₂ emission rates and MBC increases were observed at 5 °C incubation temperature, demonstrating that cold-tolerant microbes may undergo adaptations that enable their tolerance to cold conditions. Taken together, our findings provide evidence of the natural warming gradient using a climosequence approach to illustrate the importance of microbial-mediation in controlling SOC decomposition. Moreover, models should consider different mechanisms of soil carbon dynamics in topsoil and subsoil when predicting carbon–climate feedback.

28579. 题目: From peat swamp forest to oil palm plantations: The stability of tropical peatland carbon
文章编号: N19022102
期刊: Geoderma
作者: Hannah V. Cooper, Christopher H. Vane, Stephanie Evers, Paul Aplin, Nicholas T. Girkin, Sofie Sjögersten
更新时间: 2019-02-21
摘要: Accurate assessment of tropical peatland carbon dynamics is important to (a) determine the size of the active carbon pool, (b) estimate the scale of transfers of peat-derived greenhouse gases (GHGs) to the atmosphere resulting from land use change, and (c) support carbon emissions reduction policies. To date, information on the quality of tropical peatland organic matter and its sensitivity to increases in global temperatures is limited, particularly in the context of land conversion. The aim of this work is therefore to determine peat quality and temperature response of potential GHG emissions under flooded conditions from tropical peatland sites. Whilst reflecting the process of conversion from forest to oil palm plantation. Four land use types that represent the stages of conversion from peat swamp forest to oil palm were chosen: (i) secondary ‘forest’, (ii) recently ‘drained’ but not cleared forest (iii) cleared and recently planted ‘young oil palm’ plantation and (iv) ‘mature oil palm’ plantation. Overall, surface peat carbon was more labile than deeper peats. The largest labile pool was measured at forest sites. In the later stages of land conversion, the labile carbon had been lost and the relative abundance of recalcitrant organic material increased. Potential GHG fluxes were greatest in surface peats compared to deeper peats and declined as labile carbon was depleted following land conversion. Higher temperatures resulted in higher potential GHG emissions at all stages of conversion, but the magnitude of the temperature response depended on organic matter lability. For CO₂ fluxes, the temperature response was most pronounced at forest sites. This reflects the greater peat lability at this land use. In contrast, for CH₄ emissions, there were increased emissions both at forest and converted land types with higher temperatures. This suggests that increasing temperatures in response to climate warming may drive higher CH₄ emissions from sites dominated by degraded organic matter. Collectively, this study demonstrates that during conversion from peat swamp forest to oil palm plantation, the enhanced decomposition and reduced litter input rates is reflected eventually in reduced potential gross CO₂ emissions from peat. Nonetheless higher temperature resulting from climate warming may maintain high GHG emissions at plantation sites.

28580. 题目: Removal of Cyanotoxins by Potassium Permanganate: Incorporating Competition from Natural Water Constituents
文章编号: N19022101
期刊: Water Research
作者: Juliana R. Laszakovits, Allison A. MacKay
更新时间: 2019-02-21
摘要: In recent years, harmful algal blooms capable of producing toxins including microcystins, cylindrospermopsin, and saxitoxin have increased in occurrence and severity. These toxins can enter drinking water treatment plants and, if not effectively removed, pose a serious threat to human health. The work here investigated the efficacy of permanganate oxidation as a treatment strategy, with a focus on incorporating competition by cyanobacterial cells and dissolved organic matter (DOM). We report rate constants of 272 ± 23 M^-1 s-for the reaction between permanganate and microcystin-LR, 0.26 ± 0.05 M^-1 s^-1 for the reaction between permanganate and cylindrospermopsin, and, using chemical analogues, estimate a maximum rate constant of 2.7 ± 0.2 M^-1 s^-1 for the reaction between permanganate and saxitoxin. We conclude that permanganate only shows potential to remove microcystins. No pH (6-10) or alkalinity (0-50 mM) dependence was observed for the rate of reaction between microcystin-LR and permanganate; however, a temperature dependence was observed and can be characterized by an activation energy of 16 ± 5 kJ mol^-1. The competition posed by cyanobacterial cells was quantified by an apparent second order rate constant of 2.5 ± 0.3 x 10-6 L μg chl-a^-1 s^-1. From this apparent second order rate constant, it was concluded that cyanobacterial cells are not efficient scavengers of permanganate within typical contact times but this second order rate constant can be used to accurately predict microcystin degradation in algal-impacted waters. The competition posed by DOM depended on both the amount of DOM present (as measured by TOC) and its electron donating capacity (as predicted by SUVA-254 or E2/E3 ratio). DOM was concluded to scavenge permanganate efficiently and we forward that this should be considered in permanganate dosing calculations.
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