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26001. 题目: Potential Alterations in the Chemical Structure of Soil Organic Matter Components during Sodium Hydroxide Extraction
文章编号: N19110312
期刊: Journal of Environment Quality
作者: Xi Chen, Mengcan Jin, Yujun Xu, Wenying Chu, Daniel C. Olk, Jingwei Hu, Yanyu Jiang, Jingdong Mao, Hongjian Gao, Michael L. Thompson
更新时间: 2019-11-03
摘要: The use of alkaline solutions, especially 0.1 to 0.5 M NaOH solutions, for the extraction of humic substances (HS) from soils is controversial because of the potential for chemical and physical alteration of the organic materials in soils. Therefore, it is important to investigate the effects of NaOH extraction on the chemical structure of natural organic matter (NOM) in terrestrial ecosystems. By using solid-state nuclear magnetic resonance, we investigated the impact of NaOH and water extractions on the chemical structure of insoluble and extractable fractions of three model components of NOM: cellulose, van Soest lignin, and peat. We found both sp2–hybridized and carboxyl C groups occurred in the NaOH-extractable cellulose fraction relative to the bulk cellulose. Compounds solubilized from the lignin by treatment with 0.1 M NaOH were dominated by aromatic C-O, aromatic C, and OCH3 functional groups, indicating that some free phenolic monomers were extracted by the alkaline solution. Compared with the bulk peat, the concentration of COO/NCO and sp2–hybridized C in NaOH-reconstituted peat sample increased by 40 and 5%, respectively, whereas the concentration of carbohydrate C decreased by 14%. In summary, the chemical structures of cellulose, van Soest lignin, and the peat were altered to some extent by the 0.1 M NaOH extraction. These observations provide useful context in the consideration of potential alterations in chemical composition when one interprets results of HS extractions employing NaOH solutions. Future research will establish the proportion of these alterations that may result from an alternative, slower procedure for acidifying solutions after NaOH extraction.
26002. 题目: Lasting Effects of Wildfire on Disinfection By-Product Formation in Forest Catchments
文章编号: N19110311
期刊: Journal of Environment Quality
作者: Alex T. Chow, Kuo-Pei Tsai, Timothy S. Fegel, Derek N. Pierson, Charles C. Rhoades
更新时间: 2019-11-03
摘要: Severe wildfires often have dramatic short-term effects on water quality, although there is increasing evidence that in some catchments their effects can persist for many years. Forest recovery after the 2002 Hayman Fire burned catchments that supply drinking water to over a half million users in Denver, CO, has been extremely slow and has caused persistent water quality concerns. To evaluate whether postfire water quality changes increase the potential to form undesirable by-products of water disinfection, we compared stream water from eight burned catchments within the Hayman Fire and five adjacent unburned catchments. We tested dissolved organic carbon (DOC) concentrations and the formation of disinfection by-products (trihalomethanes [THMs], haloacetonitriles [HANs], chloral hydrate [CHD, and haloketones [HKTs]) in stream water monthly during 2014 and 2015. Stream DOC, THMs, and CHD and specific ultraviolet absorbance at 254 nm (SUVA254) were elevated in catchments with a moderate extent of high-severity wildfire (8–46% of catchment area) relative to catchments that were unburned and those that burned more extensively (>74% of catchment area) 14 yr after the fire. In contrast, formation of highly toxic but unregulated nitrogenous HANs increased linearly with wildfire extent. Although these findings should not raise concern regarding drinking water safety, they highlight the long-term influences of high severity wildfire on source water C content, composition, and treatability.
26003. 题目: Supramolecular Answers to the Organic Matter Controversy
文章编号: N19110310
期刊: Journal of Environment Quality
作者: Martha J. M. Wells
更新时间: 2019-11-03
摘要: The foundation of separation science is the division or deconvolution of a mixture into constituent parts. To do so greatly informs our understanding of complex systems. Equally important is consideration of the behavior of a mixture as a whole—to consider if the whole is the sum of the parts or if individual components interact synergistically or antagonistically when combined. Application of separation science has seldom assumed greater importance than in consideration of the controversy surrounding the traditional and emergent views of the complex chemical system of natural organic matter (NOM). Analyses of simulated and actual environmental water samples using noninvasive separation techniques including flow field-flow fractionation (flow FFF), excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor (PARAFAC) analyses, and dynamic light scattering (DLS) are discussed. The data are used to explore whether a distinct chemical category of humic (diagenetic) substances exists in NOM; whether separation of organic matter into fulvic and humic extracts has relevant meaning translatable to actual environmental water samples; whether extraction procedures alter the chemistry of NOM extracts; and, if humic and fulvic acids exist, what physicochemical property or properties make humic substances unique among other forms of NOM. A fluorescence-based nonoperational definition of humic substances is introduced. The underexplored role of supramolecular, self-assembled aggregation is presented as a NOM conceptual model. Responses are provided to questions raised in the great NOM debate within a supramolecular context.
26004. 题目: Using Humic Fractions to Understand Natural Organic Matter Processes in Soil and Water: Selected Studies and Applications
文章编号: N19110309
期刊: Journal of Environment Quality
作者: D. C. Olk, P. R. Bloom, M. De Nobili, Y. Chen, D. M. McKnight, M. J. M. Wells, J. Weber
更新时间: 2019-11-03
摘要: Natural organic matter (NOM) plays key environmental roles in both aquatic and soil systems. A long-standing approach for evaluating NOM composition and activity is to extract soils with alkali solutions to obtain humic substances, namely humic acids (HA), and fulvic acids (FA), or to briefly expose isolated fractions of dissolved organic matter to alkali. Critics have claimed these methods create laboratory artifacts and are thus unsuitable for studying NOM behavior in field conditions. In response, we describe case studies in which humic fractions were analyzed to identify significant processes in environmental or agricultural issues. Specifically, humic fractions played a key role in maintaining toxic levels of arsenic (As) in drinking water supplies in South and Southeast Asia. Elsewhere, binding reactions of FA and HA with prions were shown to provide a plausible mechanism for variable persistence of prion infectivity across soil types. Humic substances were also shown to enhance iron (Fe) uptake by plants in solution culture and field conditions. Their specific binding sites for mercury (Hg) as determined in laboratory conditions enabled accurate modeling of soil Hg binding under varying conditions. A young HA fraction reproduced in controlled conditions the capacity of animal manure to maintain potassium (K) availability in strongly K-fixing field soils, leading to development of a commercially successful humic-K fertilizer. Humic fractions accurately represented NOM across multiple settings and research objectives while providing novel opportunities for advanced analyses. The study of humic fractions has helped resolve scientific and practical issues in aquatic and soil systems.
26005. 题目: First Quantification of the Controlling Role of Humic Substances in the Transport of Iron Across the Surface of the Arctic Ocean
文章编号: N19110308
期刊: Environmental Science & Technology
作者: Luis Miguel Laglera, Camila Sukekava, Hans A Slagter, Javier Downes, Alberto Aparicio-Gonzalez, Loes J. A. Gerringa
更新时间: 2019-11-03
摘要: One of the main reasons behind our current lack of understanding of iron cycling in the oceans is our inability to characterize the ligands that control iron solubility, photosensitivity, reactivity, and bioavailability. We currently lack consensus about the nature and origin of these ligands. Here, we present the first field application of a new methodological development that allows the selective quantification of the fraction of Fe complexed to humic substances (HS). In the HS-rich surface Arctic waters, including the Fe-rich Transpolar Drift (TPD), we found that HS iron binding groups were largely occupied by iron (49%). The overall contribution of Fe–HS complexes to DFe concentrations was substantial at 80% without significant differences between TPD and non-TPD waters. Stabilization and transport of large concentrations of DFe across the surface of the Arctic Ocean are due to the formation of high concentrations of Fe–HS complexes. Competition of Arctic Fe–HS complexes with desferrioxamine and EDTA indicated that their stability constants are considerably higher than the stability constants previously found for riverine HS in temperate estuaries and HS standard material. This is the first case of identification of the ligand-dominating iron speciation over a specific region of the global ocean.
26006. 题目: Physiological responses of three mono-species phototrophic biofilms exposed to copper and zinc
文章编号: N19110307
期刊: Environmental Science and Pollution Research
作者: Emilie Loustau, Jessica Ferriol, Shams Koteiche, Léo Gerlin, Joséphine Leflaive, Frédéric Moulin, Elisabeth Girbal-Neuhauser, Jean-Luc Rols
更新时间: 2019-11-03
摘要: In freshwater ecosystem, phototrophic biofilms play a crucial role through adsorption and sequestration of organic and inorganic pollutants. However, extracellular polymeric substance (EPS) secretion by phototrophic biofilms exposed to metals is poorly documented. This work evaluated the physiological responses of phototrophic biofilms by exposing three microorganisms (cyanobacterium Phormidium autumnale, diatom Nitzschia palea and green alga Uronema confervicolum) to 20 and 200 μg L−1 of Cu or 60 and 600 μg L−1 of Zn, both individually and in combination. Analysis of metal effects on algal biomass and photosynthetic efficiency showed that metals were toxic at higher concentrations for these two parameters together and that all the strains were more sensitive to Cu than to Zn. U. confervicolum was the most impacted in terms of growth, while P. autumnale was the most impacted in terms of photosynthetic efficiency. In consequence to metal exposure at higher concentrations (Cu200, Zn600 and Cu200Zn600), a higher EPS production was measured in diatom and cyanobacterium biofilms, essentially caused by an overproduction of protein-like polymers. On the other hand, the amount of secreted polysaccharides decreased during metal exposure of the diatom and green alga biofilms. Size exclusion chromatography revealed specific EPS molecular fingerprints in P. autumnale and N. palea biofilms that have secreted different protein-like polymers during their development in the presence of Zn600. These proteins were not detected in the presence of Cu200 despite an increase of proteins in the EPS extracts compared to the control. These results highlight interesting divergent responses between the three mono-species biofilms and suggest that increasing protein production in EPS biofilms may be a fingerprint of natural biofilm against metal pollutants in freshwater rivers.
26007. 题目: Integration of field observation and air quality modeling to characterize Beijing aerosol in different seasons
文章编号: N19110306
期刊: Chemosphere
作者: Jiu-meng Liu, Peng-fei Wang, Hong-liang Zhang, Zhen-yu Du, Bo Zheng, Qin-qin Yu, Guang-jie Zheng, Yong-liang Ma, Mei Zheng, Yuan Cheng, Qiang Zhang, Ke-bin He
更新时间: 2019-11-03
摘要: Fine particulate matter (PM2.5) pollution in Beijing was investigated based on field observation and air quality modeling. Measurement results showed that when using elemental carbon (EC) as the reference component, concurrent increases were observed in the relative abundances of sulfate, nitrate, organic carbon (OC) and water-soluble organic carbon (WSOC) when RH exceeded ∼65% during winter. The observed increases could not be explained by variations of primary biomass burning emissions, instead they likely pointed to heterogeneous chemistry and presumably indicated that formation of secondary inorganic and organic aerosols might be related during winter haze events in Beijing. Large gaps were found in winter when comparing the observational and modeling results. In summer, RH exhibited little influence on the observed sulfate/EC, OC/EC or WSOC/EC, and the observed and modeled results were in general comparable for the concentrations of sulfate, EC and OC. This study suggests that distinct yet poorly-understood atmospheric chemistry may be at play in China’s winter haze events, and it could be a substantial challenge to properly incorporate the related mechanisms into air quality models.
26008. 题目: Rapid and distinct responses of particulate and mineral-associated organic nitrogen to conservation tillage and cover crops
文章编号: N19110305
期刊: Geoderma
作者: Andrea Jilling, Daniel Kane, Alwyn Williams, Anthony C. Yannarell, Adam Davis, Nicholas R. Jordan, Roger T. Koide, David A. Mortensen, Richard G. Smith, Sieglinde S. Snapp, Kurt A. Spokas, A. Stuart Grandy
更新时间: 2019-11-03
摘要: Particulate organic matter (POM) is considered an “active” source of nitrogen (N) in cultivated soils, responding readily to management and being more physically accessible to decomposers than mineral-associated forms of organic matter. However, there is increasing evidence that mineral-associated organic matter (MAOM) can also exhibit short-term changes to management that may impact plant and microbial N dynamics. In this study, we investigated how N within soil organic matter fractions responded to three years of tillage and cover crop treatments. We collected soils from a row-crop (maize-soybean rotation) field experiment replicated across three sites in the north central and mid-Atlantic United States: a high-soil organic matter site (3.1% soil organic carbon) in Illinois (IL) and two sites in Michigan (MI) and Pennsylvania (PA) with lower soil organic matter content (1.0% and 1.4% soil organic carbon, respectively). Management treatments included two levels of tillage (chisel plow and ridge tillage) and two levels of cover crop (with and without rye cover crop). Using an optimized sonication method coupled with particle size separation, we isolated and analyzed for N content free POM, occluded POM, a coarse silt fraction, and MAOM. Using partial least squares regression, we also explored broad cross-site relationships between soil organic matter (SOM) fractions, soil N availability, and crop performance.Both particulate and fine fractions responded to tillage and cover crop treatments, but patterns varied by site and fraction. In the low-SOM MI and PA soils, ridge tillage and cover cropping both increased N within POM fractions. The response to ridge tillage was most pronounced, with a 76% and 24% increase in occluded POM N content in MI and PA, respectively. In contrast, at the IL site (high-SOM), the inclusion of cover crops led to higher N, specifically within the fine fractions (coarse silt and MAOM). Cover cropping increased MAOM N content in IL by 24%. When analyzing all sites together, variables associated with fine fractions were more closely associated with N mineralization and crop performance. MAOM can be responsive to short-term management practices and, along with POM, may also be potential sources of N for crops.
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26009. 题目: Resource recovery and biochar characteristics from full-scale faecal sludge treatment and co-treatment with agricultural waste
文章编号: N19110304
期刊: Water Research
作者: Benedict C. Krueger, Geoffrey D. Fowler, Michael R. Templeton, Berta Moya
更新时间: 2019-11-03
摘要: Unsafe disposal of faecal sludge from onsite sanitation in low-income countries has detrimental effects on public health and the environment. The production of biochar from faecal sludge offers complete destruction of pathogens and a value-added treatment product. To date, research has been limited to the laboratory. This study evaluates the biochars produced from the co-treatment of faecal sludge from septic tanks and agricultural waste at two full-scale treatment plants in India by determining their physical and chemical properties to establish their potential applications. The process yielded macroporous, powdery biochars that can be utilised for soil amendment or energy recovery. Average calorific values reaching 14.9 MJ/kg suggest use as solid fuel, but are limited by a high ash content. Phosphorus and potassium are enriched in the biochar but their concentrations are restricted by the nutrient-depleted nature of septic tank faecal sludge. High concentrations of calcium and magnesium led to a liming potential of up to 20.1% calcium carbonate equivalents, indicating suitability for use on acidic soils. Heavy metals present in faecal sludge were concentrated in the biochar and compliance for soil application will depend on local regulations. Nevertheless, heavy metal mobility was considerably reduced, especially for Cu and Zn, by 51.2–65.2% and 48.6–59.6% respectively. Co-treatment of faecal sludge with other carbon-rich waste streams can be used to influence desired biochar properties. In this case, the addition of agricultural waste increased nutrient and fixed carbon concentrations, as well as providing an additional source of energy. This study is a proof of concept for biochar production achieving full-scale faecal sludge treatment. The findings will help inform appropriate use of the treatment products as this technology becomes more commonly applied.
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26010. 题目: The performance and mechanism of simultaneous removal of fluoride, calcium, and nitrate by calcium precipitating strain Acinetobacter sp. H12
文章编号: N19110303
期刊: Ecotoxicology and Environmental Safety
作者: Jun feng Su, Han Zhang, Ting lin Huang, Xiao fen Hu, Chang lun Chen, Jia ran Liu
更新时间: 2019-11-03
摘要: A calcium precipitating and denitrifying bacterium H12 was used to investigate the F− removal performance and mechanism. The results showed that the strain H12 reduced 85.24% (0.036 mg·L−1·h−1) of F−, 62.43% (0.94 mg·L−1·h−1) of Ca2+, and approximately 100% of NO3− over 120 h in continuous determination experiments. The response surface methodology analysis demonstrated that the maximum removal efficiency of F− was 88.98% (0.062 mg·L−1·h−1) within 72 h under the following conditions: the initial Ca2+ concentration of 250.00 mg·L−1, pH of 7.50, and the initial C4H4Na2O4·6H2O concentration of 800.00 mg·L−1. The scanning electron microscopy images, the X-ray photoelectron spectroscopy, and X-ray diffraction results suggested the following removal mechanism of F−: (1) the bacteria, as the nucleation site, were encapsulated by bioprecipitation to form biological crystal seeds; (2) Biological crystal seeds adsorbed F− to form Ca5(PO4)3F and CaF2; (3) Under the induction of bacteria, calcium, fluoride and phosphate coprecipitated to form Ca5(PO4)3F and CaF2. In addition, the gas chromatography data indicated that F− had little or no effect on the gas composition during denitrification, and the fluorescence spectroscopy analysis also proved that the extracellular polymeric substance (protein) is the site of bioprecipitation nucleation.
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26011. 题目: Characterizing the interactions between copper ions and dissolved organic matter using fluorescence excitation–emission matrices with two-dimensional Savitzky–Golay second-order differentiation
文章编号: N19110302
期刊: Ecotoxicology and Environmental Safety
作者: Shu Liu, Hiroaki Shirai, Jinxing Zuo, Xiaolong Yang, Xiaomin Li, Mohammed Kamruzzaman, Wenhong Fan
更新时间: 2019-11-03
摘要: Monitoring dissolved organic matter (DOM) content in aquatic environments is crucial for not only understanding the dynamics of heavy metals but also predicting their bioavailability. Fluorescence spectroscopy is typically employed to characterise DOM. Here, the interaction between DOM and trace metals was investigated by combining excitation–emission matrix (EEM) quenching with two-dimensional Savitzky–Golay second-order differentiation (2D-SG-2nd-df) analysis. The 2D-SG-2nd-df analysis decomposed the EEM spectra of commercial humic acid (HA) samples into six separate fluorescence peaks, which agreed with the results obtained through conventional parallel factor (PARAFAC) analysis. Compared with PARAFAC modeling, the 2D-SG-2nd-df approach provided more valid and reliable results when the dataset contained distinct samples. Moreover, since the results obtained from 2D-SG-2nd-df for each sample are independent, shifts in the peak wavelength can be reproduced more efficiently using this method. Triplicate titration experiments showed clear differences in HA–copper interactions for samples with different HA composition and molecular weight. The binding strength between copper and low-molecular-weight DOM in water was weaker than that observed for high-molecular-weight DOM. The results obtained in this study will serve as a basis for applying 2D-SG-2nd-df not only to DOM but also to other samples studied using EEM measurements.
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26012. 题目: In situ fluorescence measurements of dissolved organic matter: A review
文章编号: N19110301
期刊: Science of The Total Environment
作者: Elfrida M. Carstea, Cristina L. Popa, Andy Baker, John Bridgeman
更新时间: 2019-11-03
摘要: There is a need for an inexpensive, reliable and fast monitoring tool to detect contaminants in a short time, for quick mitigation of pollution sources and site remediation, and for characterization of natural dissolved organic matter (DOM). Fluorescence spectroscopy has proven to be an excellent technique in quantifying aquatic DOM, from autochthonous, allochthonous or anthropogenic sources. This paper reviews the advances in in situ fluorescence measurements of DOM and pollutants in various water environments. Studies have demonstrated, using high temporal-frequency DOM fluorescence data, that marine autochthonous production of DOM is highly complex and that the allochthonous input of DOM from freshwater to marine water can be predicted. Furthermore, river measurement studies found a delayed fluorescence response of DOM following precipitation compared to turbidity and discharge, with various lags, depending on season, site and input of dissolved organic carbon (DOC) concentration. In addition, research has shown that blue light fluorescence (λemission = 430–500 nm) can be a good proxy for DOC, in environments with terrestrial inputs, and ultraviolet fluorescence (λemission = UVA–320–400 nm) for biochemical oxygen demand, and also E. coli in environments with sanitation issues. The correction of raw fluorescence data improves the relationship between fluorescence intensity and these parameters. This review also presents the specific steps and parameters that must be considered before and during in situ fluorescence measurement session for a harmonized qualitative and quantitative protocol. Finally, the strengths and weaknesses of the research on in situ fluorescence are identified.
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26013. 题目: Lignin Contribution to Aliphatic Constituents of Humic Acids through Fungal Degradation
文章编号: N19110215
期刊: Journal of Environment Quality
作者: Seyyedhadi Khatami, Ying Deng, Ming Tien, Patrick G. Hatcher
更新时间: 2019-11-02
摘要: To investigate how fungi transform lignin in soil during humification, a naturally brown-rotted wood was subjected to additional fungal degradation by the white-rot fungus Phanerochaete chrysosporium. Both Fourier transform infrared spectroscopy and ultrahigh resolution mass spectrometry showed that fungal degradation, an integral part of the soil humification process, transformed lignin-derived aromatic molecules and simultaneously created many new aliphatic molecules. The majority of these new aliphatic molecules were chemically different from aliphatic molecules already existent in the lignin precursor extract and in the P. chrysosporium biomass. Our results strongly suggest that humification by white-rot fungi in soil transforms lignin to humic substances with a predominant aliphatic character. This challenges the concept that only aromatic structures are expected from humification of lignin by fungi. This finding also reverses current views that aliphatic constituents of soil humic materials are not principally derived from lignin.
26014. 题目: Current Understanding of the Use of Alkaline Extractions of Soils to Investigate Soil Organic Matter and Environmental Processes
文章编号: N19110214
期刊: Journal of Environment Quality
作者: Tsutomu Ohno, Nancy J. Hess, Nikolla P. Qafoku
更新时间: 2019-11-02
摘要: A better understanding of soil organic matter (SOM) biogeochemistry is critical to meeting the environmental challenges that we face currently with the changing climate. Humic substances obtained from alkaline extractions of soils have played a predominant role in developing our knowledge of SOM chemistry and behavior during the 20th century. Recently, there have been new important developments that, according to some researchers, may be used to argue against the existence of the humic substances in soils as they are presently defined. A debate on the definition and continued use of the term humic substances has been taking place at conferences and in the scientific literature. However, because a consensus has not been reached on this important topic, the use of the term humic substances in this special issue conforms to the current existing definition of this term. This special issue of the Journal of Environmental Quality includes 10 papers on the subject of Alkaline Extraction of Soils and Natural Waters to Understand Environmental Processes and contributes to the ongoing assessment of the role of humic substances in current and future soil, environmental, and ecological studies. The contributed papers are grouped into three broad subject headings: (i) chemistry of humic substances, (ii) humic substances in environmental processes, and (iii) case studies and reviews of humic substances. Continued progress in understanding SOM and C biogeochemistry is essential to achieve long-term ecological, environmental, and agricultural sustainability through the development of management strategies that conserve soil C and reduce the reliance on chemical inputs for meeting crop nutrient needs.
26015. 题目: Do Fulvic, Humic, and Humin Carbon Fractions Represent Meaningful Biological, Physical, and Chemical Carbon Pools?
文章编号: N19110213
期刊: Journal of Environment Quality
作者: Lucretia A. Sherrod, Merle F. Vigil, Catherine E. Stewart
更新时间: 2019-11-02
摘要: Humic fractions have been used to characterize soil organic matter chemistry and to identify different carbon (C) pools. The relevance of alkaline fractionation is questioned because of probable artifacts created by the extraction. Fractionation using water-soluble organic C (WSOC), soil microbial biomass C (SMBC), permanganate-oxidizable C (POX-C), and particulate organic matter C (POM-C) methodologies are sensitive to C changes. Mineral-associated organic C (MAOC) includes WSOC and other C fractions that are not all passive C. We measured 15 proficiency soils ranging in texture, mineralogy, pH, and soil organic C (SOC) to isolate C pools with differing turnover times. We define WSOC, SMBC, POX-C, and fulvic acid (FA) as fast pools. Slow cycling pools include POM-C and humic acid (HA) fractions, whereas passive pools include MAOC minus WSOC (PMAOC) and humin C (HC). Data showed FA was correlated with POX-C (r = 0.84) as a fast C pool but was slightly more correlated with PMAOC (r = 0.86), a passive pool. Slow C pools of HA and POM-C were not strongly correlated (r = 0.49). All alkaline fractions of C showed highest correlations to PMAOC, followed by POX-C, and all showed poor correlations with POM-C. The conventional first extraction fraction (A) yielded 70% recovery of the total FA extracted, whereas only 45% of HA was obtain. Acid soils on average had higher total FA. The regression model using physical fractionation was the best (SOC = WSOC + POM-C + PMAOC, R2 0.98). Only the HA fraction was a significant parameter in the regression of SOC = FA + HA + HC (p = 0.0029).
26016. 题目: Evidence for the Existence of Humic Acids in Peat Soils Based on Solid-State C NMR
文章编号: N19110212
期刊: Journal of Environment Quality
作者: Patrick G. Hatcher, Derek C. Waggoner, Hongmei Chen
更新时间: 2019-11-02
摘要: Humic extracts, in particular humic acids, of organic-rich peat soils were examined by solid-state 13C nuclear magnetic resonance (NMR) and shown to be integral components of the peat, contrary to recent suggestions that humic materials are artifacts of alkali extraction. The authenticity of humic substances is demonstrated by recombining the various humic fractions and comparing the NMR spectrum of the recombined peat with the original untreated peat sample. Even though significant NMR-determined structural differences exist between humic acids and the insoluble humin fractions, the recombination reproduces the original unextracted peat quite well. Applying a biopolymer mixing model to the spectra shows that humic acids have a high proportion of char-like material that is interpreted as being derived from noncombustion polymerization or secondary synthesis during humification, a process that has been challenged by a recent soil formation model.
26017. 题目: Humic Acid Buildup Increases Carbon Dioxide Emissions from Redox-Oscillating Upland Soils while Catalyzing Iron(III) Reduction and Phosphorus Desorption
文章编号: N19110211
期刊: Journal of Environment Quality
作者: Jared L. Wilmoth, Alan J. Sexstone, Louis M. McDonald
更新时间: 2019-11-02
摘要: Humic substances comprise chemically and physically complex forms of organic C that are recognized to be involved in the catalytic cycling of electrons in diverse biogeochemical reactions. Recent investigations have indicated that humic substances existing in redox-dynamic terrestrial environments, such as intermittently wet soils, may be uniquely important for regulating greenhouse gas emissions. However, many relevant studies have relied on the use of commercially available humic substances and/or synthetic humic analogs. In the present study, during a 42-d anoxic incubation, we investigated the regulatory and catalytic effects of increasing concentrations of site-specific (i.e., native) humic acid (HA) in an Appalachian upland soil known to experience redox-oscillating conditions in the field. Extracted native HA was characterized using 13C nuclear magnetic resonance (13C-NMR), Fourier transformed infrared (FT-IR), and total CHNS elemental analyses. We found that native HA was relatively enriched in aromatic and amino acid C. Increasing concentrations of native HA added at the start of soil incubations led to higher rates of CO2 emission and microbial Fe(III) reduction, indicating that a buildup of soil HA allows for a greater number of electrons to shuttle between Fe(III) reducers and Fe(III) electron acceptors during microbial oxidation of organic C. Treatments with native HA were also compared against a synthetic HA-analog treatment containing 0.2 g anthraquinone-2,6-disulfonic acid (AQDS) kg−1 dry soil to investigate catalytic electron cycling by native HA and AQDS. Our data suggest that the buildup of native humic substances, which are relatively rich in aromatic and amino acid C, leads to globally relevant increases in CO2 emissions, the redox cycling of Fe, and the availability of organic P after transition to anaerobic conditions in upland soils.
26018. 题目: Combination of Humic Substances and Arbuscular Mycorrhizal Fungi Affecting Corn Plant Growth
文章编号: N19110210
期刊: Journal of Environment Quality
作者: Nadia Quevedo Pinos, Ricardo Luis Louro Berbara, Sael Sanchez Elias, Tadeu Augusto van Tol de Castro, Andrés Calderín García
更新时间: 2019-11-02
摘要: This study evaluates the interaction effects on corn (Zea mays L.) growth between intact humic substances (HS) extracted in an alkaline medium from three different origins (an Organosol [HS-Org], an Andisol [HS-And], and vermicompost [HS-Vc]) and the arbuscular mycorrhizal fungus (AMF) Dentiscutata heterogama. The HS were characterized by spectroscopic techniques, and different biochemical, morphological, nutritional, and AMF colonization parameters were evaluated in corn plants. The experiment was conducted in a greenhouse, and low-fertility soils sterilized after solarization were used as the substrate. Hybrid corn BR-3025 was planted, and the HS concentrations used were 5, 10, and 20 mg carbon L−1 for HS-And, HS-Vc, and HS-Org, respectively, applied 15, 25, and 45 d after emergence close to the roots. The results show that HS application and D. heterogama inoculation significantly stimulated the biomass in relation to the treatments without AMF. Carbohydrate and protein content were stimulated by HS–AMF interaction. A higher leaf content of nutrients was observed in the AMF- and HS-inoculated plants. The HS-Vc application and AMF inoculation resulted in intense stimulation, which was confirmed with a high mycorrhizal efficiency. The spore density and glomalin content were also stimulated by the three different HS applications independently of their source. The HS-Vc has intermediate structural chemical characteristics in terms of polarity and aromaticity compared with HS-Org and HS-And. The HS-Vc more strongly stimulated the plant physiological parameters when combined with the AMF inoculation. These results may indicate that the HS formed in soil and characterized by structures that are more balanced may function more effectively.
26019. 题目: Association of metals with geochemical phases in wetland soils of a Ramsar site in India
文章编号: N19110209
期刊: Environmental Monitoring and Assessment
作者: B. Anjan Kumar Prusty, Rachna Chandra, P. A. Azeez
更新时间: 2019-11-02
摘要: Mobilization of metals in wetland ecosystems is a function of the behaviour of a specific metal species and is dependent largely on the prevailing micro-environmental conditions. Apparently, five different chemical forms of metals are known with varying affinity to binding sites, mobility, bioavailability and toxicity. Quantification of these forms of metals in the soils is imperative in predicting their biogeochemical fate and toxicity. In this context, we examined the association of Cu, Pb and Zn, with various geochemical phases in the soil profile of wetland system of Keoladeo National Park, a Ramsar site in India. The assessment covered the soil profile until 100 cm depth at every 25-cm intervals. Different operationally defined geochemical phases in the soil at different depths were examined during the study for respective metal concentrations. Hydrous oxides of Fe-Mn were the major carrier for all the three metals and the fraction associated with exchangeable phase was the least. The low organic matter content in the soil seems to be influencing the metal association with the organic matter (OM-S) phase, which was also a less preferred carrier for metals. For Cu (5.8–78.4%) and Pb (33.5–88.5%), Fe-Mn hydroxide phase was an important binding site and for Zn (31.02–79.03%), it was the silicate mineral matrix (RES phase). This suggests the importance of micro-environmental conditions in the wetland bed such as redox and pH in mobilization of metals. As metals such as Pb have high eco-toxicological potential, an assessment of fractional concentrations of metals provides insights into their mobility and bioavailability in aquatic ecosystems. This aids wetland managers to develop appropriate strategy to maintain quality of inflow water, the single most crucial factor for a wetland ecosystem, and thus controls the micro-environmental conditions.
26020. 题目: Modeling organic carbon accumulation rates and residence times in coastal vegetated ecosystems.
文章编号: N19110208
期刊: Journal of Geophysical Research: Biogeosciences
作者: E. Fay Belshe, Jose Sanjuan, Carmen Leiva‐Dueñas, Nerea Piñeiro‐Juncal, Oscar Serrano, Paul S. Lavery, Miguel Angel Mateo
更新时间: 2019-11-02
摘要: Coastal vegetated 'blue carbon' ecosystems can store large quantities of organic carbon (OC) within their soils; however, the importance of these sinks for climate change mitigation depends on the OC accumulation rate (CAR) and residence time. Here we evaluate how two modeling approaches, a Bayesian age‐depth model alone or in combination with a two‐pool OC model, aid in our understanding of the timelines of OC within seagrass soils. Fitting these models to data from Posidonia oceanica soil cores, we show that age‐depth models provided reasonable CAR estimates but resulted in a 22% higher estimation of OC burial rates when ephemeral rhizosphere OC was not subtracted. This illustrates the need to standardize CAR estimation to match the research target and time frames under consideration. Using a two‐pool model in tandem with an age‐depth model also yielded reasonable, albeit lower, CAR estimates with lower estimate uncertainty, which increased our ability to detect among‐site differences and seascape‐level trends. Moreover, the two‐pool model provided several other useful soil OC diagnostics, including OC inputs, decay rates, and transit times. At our sites, soil OC decayed quite slowly both within fast‐cycling (0.028± 0.014,yr‐1) and slow‐cycling (0.0007± 0.0003,yr‐1) soil pools, resulting in OC taking between 146 and 825,yrs to transit the soil system. Further, an estimated 85% to 93% of OC inputs enter slow‐cycling soil pools, with transit times ranging from 891 to 3115,yrs, substantiating the importance of P. oceanica soils as natural, long‐term OC sinks