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25681. 题目: Enhanced Cd removal from aqueous solution by biologically modified biochar derived from digestion residue of corn straw silage
文章编号: N19041911
期刊: Science of The Total Environment
作者: Qi Tao, Yixuan Chen, Junwen Zhao, Bing Li, Yuhao Li, Shiyi Tao, Meng Li, Qiquan Li, Qiang Xu, Yiding Li, Huanxiu Li, Bin Li, Yulan Chen, Changquan Wang
更新时间: 2019-04-19
摘要: Biologically modified biochars derived from digestion residue of corn straw silage at different pyrolysis temperature (300–700 °C) were prepared for removing Cd from water. Compared with the pristine biochar derived from corn straw (CB), transabdominal transformation of corn straw silage (TCB) significantly increased surface area (4.24–56.58 m² g⁻¹), oxygen-containing functional group (COC, MgO, SiO) and mineral components (CaCO₃, KCl). The sorption isotherms could be well described by Langmuir model, the kinetic data was best fitted by the Pseudo second order model. The maximum sorption capacity (Qm) obtained from Langmuir model for TCB700 (175.44 mg g⁻¹) was 3 times of CB700 (56.82 mg g⁻¹). Precipitation with minerals, ion exchange and complexation with oxygen-containing functional groups were the main mechanisms of Cd(II) sorption on TCB. These results imply that biologically modified biochar derived from digestion residue of corn straw silage at ≥600 °C is an effective sorbent for Cd removal from water.
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25682. 题目: Combining bulk characterization and benzene polycarboxylic acid molecular markers to describe biochar properties
文章编号: N19041910
期刊: Chemosphere
作者: Zhaofeng Chang, Luping Tian, Jun Zhang, Qing Zhao, Fangfang Li, Min Wu, Bo Pan
更新时间: 2019-04-19
摘要: The physicochemical properties of biochar determined its sorption of organic contaminations, and the environmental aging process changed the biochar properties. However, the correlation between biochar heterogeneous properties and their sorption characteristics is unclear. In this study, peanut shell biochars were produced at 200–700 °C, and HNO₃/H₂SO₄ was used to oxidize 400 °C biochar for 2–10 h to simulate the enhanced aging process of biochar in the environment. Benzene polycarboxylic acid (BPCA) molecular markers, and bulk characterization were analyzed to describe biochar physicochemical properties and to further predict the sorption characteristics to bisphenol A (BPA). For pristine biochars, the mellitic acid/BPCAs (B6CA/BPCAs) increased with the raise of pyrolysis temperature and the H/C atomic ratio was positively correlated with benzenepentacarboxylic acid/B6CA (B5CA/B6CA) (P < 0.01), which indicated the increased aromatic condensation. After HNO₃/H₂SO₄ treatment, the aromaticity (H/C ratio) decreased while the highly condensed components in biochars were enriched (increased B6CA/BPCAs values). Multiple regression models were adopted to establish a quantitative relationship between biochar heterogeneous properties and their sorption of BPA. Both nonlinearity coefficient N values (N = 0.08 + 0.103 B5CA/B6CA + 0.721 (O + N)/C, R² = 0.985) and single-point sorption coefficients log K_d (log K_d = 1.236 + 0.006 BPCAs + 1.449 (O + N)/C, R² = 0.936) could be estimated combining molecular markers and polarity parameters for biochars.

25683. 题目: Cu(II) adsorption onto ammonia-oxidizing bacteria and archaea
文章编号: N19041909
期刊: Geochimica et Cosmochimica Acta
作者: Drew Gorman-Lewis, Willm Martens-Habbena, David A. Stahl
更新时间: 2019-04-19
摘要: Nitrogen cycling is dependent on ammonia-oxidizing bacteria and archaea transforming ammonia to nitrite. Copper is an essential cofactor for ammonia monooxygenase in ammonia-oxidizing archaea and bacteria. Copper is also essential for several electron carriers in ammonia-oxidizing archaea. Hence, copper acquisition is a critical step for complete enzyme maturation and metabolic function. In this work, we describe copper adsorption onto the bacterial species Nitrosococcus oceani C-107 and Nitrosomonas europaea C-31 and archaeal species Nitrosopumilus maritimus SCM1 (N. maritimus). Surface complexation models described copper adsorption onto bacterial species with one reaction, while (N. maritimus required two reactions to adequately describe adsorption. Enthalpies of copper adsorption derived from isothermal titration calorimetry combined with surface complexation modeling revealed slightly exothermic enthalpies for N. maritimus and thermoneutral to endothermic enthalpies for the bacterial species. Entropies of copper adsorption were positive and indicative of entropy-driven inner-sphere complexation reactions. Thermodynamic parameters describing copper adsorption onto N. maritimus are consistent with adsorption onto a mixture of phosphorous-bearing anionic oxygen and thiol ligands. Thermodynamic parameters describing Cu(II) adsorption onto N. oceani and N. europaea were consistent with Cu(II) adsorption onto phosphorous-bearing anionic oxygen ligands. Modeling competitive copper complexation between N. maritimusand two organic acids, to mimic dissolved organic carbon, showed that N. maritimus could compete with nitrilotriacetic acid and triethylenetetramine under conditions similar to experimental measurements of copper adsorption. These results suggest that selectivity of the N. maritimus surface may confer some advantage in low-copper environments.

25684. 题目: Nitrogen turnover and N₂O/N₂ ratio of three contrasting tropical soils amended with biochar
文章编号: N19041908
期刊: Geoderma
作者: Bernard Fungo, Zhe Chen, Klaus Butterbach-Bahl, Johannes Lehmannn, Gustavo Saiz, Víctor Braojos, Allison Kolar, Tatjana F. Rittl, Moses Tenywa, Karsten Kalbitz, Henry Neufeldt, Michael Dannenmann
更新时间: 2019-04-19
摘要: Biochar has been reported to reduce emission of nitrous oxide (N₂O) from soils, but the mechanisms responsible remain fragmentary. For example, it is unclear how biochar effects on N₂O emissions are mediated through biochar effects on soil gross N turnover rates. Hence, we conducted an incubation study with three contrasting agricultural soils from Kenya (an Acrisol cultivated for 10-years (Acrisol10); an Acrisol cultivated for over 100-years (Acrisol100); a Ferralsol cultivated for over 100 years (Ferralsol)). The soils were amended with biochar at either 2% or 4% w/w. The ¹⁵N pool dilution technique was used to quantify gross N mineralization and nitrification and microbial consumption of extractable N over a 20-day incubation period at 25 °C and 70% water holding capacity of the soil, accompanied by N₂O emissions measurements. Direct measurements of N₂ emissions were conducted using the helium gas flow soil core method. N₂O emissions varied across soils with higher emissions in Acrisols than in Ferralsols. Addition of 2% biochar reduced N₂O emissions in all soils by 53 to 78% with no significant further reduction induced by addition at 4%. Biochar effects on soil nitrate concentrations were highly variable across soils, ranging from a reduction, no effect and an increase. Biochar addition stimulated gross N mineralization in Acrisol-10 and Acrisol-100 soils at both addition rates with no effect observed for the Ferralsol. In contrast, gross nitrification was stimulated in only one soil but only at a 4% application rate. Also, biochar effects on increased NH₄⁺ immobilization and NO₃⁻consumption strongly varied across the three investigated soils. The variable and bidirectional biochar effects on gross N turnover in conjunction with the unambiguous and consistent reduction of N₂O emissions suggested that the inhibiting effect of biochar on soil N₂O emission seemed to be decoupled from gross microbial N turnover processes. With biochar application, N₂ emissions were about an order of magnitude higher for Acrisol-10 soils compared to Acrisol-100 and Ferralsol-100 soils. Our N₂O and N₂ flux data thus support an explanation of direct promotion of gross N₂O reduction by biochar rather than effects on soil extractable N dynamics. Effects of biochar on soil extractable N and gross N turnover, however, might be highly variable across different soils as found here for three typical agricultural soils of Kenya.
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25685. 题目: Photosynthate-¹³C allocation in the plant-soil system after ¹³C–pulse labeling of Phragmites australis in different salt marshes
文章编号: N19041907
期刊: Geoderma
作者: Chen Wang, Rong Xiao, Yuan Cui, Ziwen Ma, Yutong Guo, Qian Wang, Yujiao Xiu, Mingxiang Zhang
更新时间: 2019-04-19
摘要: Photosynthetic carbon is an integral part of carbon cycle in plant-soil system, also is an important source of soil organic carbon. In this study, ¹³C labeling was used for exploring allocation of photosynthate-¹³C in Phragmites australis -soil system undergoing the salt marsh restoration project by freshwater pumping in Yellow River Estuary (YRE), China. Samples were collected from T₀ (before labeling) to 90 days after labeling (T₄), in natural salt marsh, 5-, 10- and 15-year freshwater pumping areas, respectively. The photosynthate-¹³C contents of soil were gradually decreased to 0 mg/g at T₄ in most areas, while it was 2.21 mg/g in 15-year pumping area, higher than other areas at the last sampling time (T₄). And the allocation of photosynthate-¹³C in soil was increased from 3.58% at T₂ to 44.46% at T₃ in natural salt marsh, while no significant change was found in other areas from T₂ to T₃, followed by the significantly higher photosynthate-¹³C proportion in soils of 15-year pumping area at T₄. EC (R² = 0.5972) and small macro-aggregates proportion of soil (R² = 0.4829) had positive correlations with Δ photosynthate-¹³C (the value of photosynthate-¹³C in underground part minus that in soil); silt and clay fractions proportion of soil (R² = 0.7044) had negative correlation with Δ photosynthate-¹³C. Distribution and transportation of photosynthetic carbon in the underground were affected by soil physical and chemical properties.

25686. 题目: Late Vistulian and Holocene development of litho-morpho-pedogenic processes in the southern Baltic coastal zone: A case study from Dębina, northern Poland
文章编号: N19041906
期刊: Geoderma
作者: Jerzy Jonczak, Wacław Florek, Bogusława Kruczkowska, Joanna Gadziszewska, Monika Niska, Łukasz Uzarowicz
更新时间: 2019-04-19
摘要: The study aimed to reconstruct major phases of the litho-morpho-pedogenic processes in the southern Baltic coastal zone near Dębina in northern Poland. Five profiles of fossil soils in the coastal cliff were described, sampled and analysed using standard procedures. The studied outcrop covers a sequence of deposits, including the basal till of the Świecie Stadial (MIS 4) of the Vistula Glaciation, the ablation till of the Pomeranian Phase (MIS 2) of the Vistula Glaciation, the thin cover of glacilimnic sand, the lacustrine sediments filling the palaeolake basin, and aeolian deposits of varied age. A sequence of paleosols developed successively within these deposits during the Late Vistulian and Holocene (MIS 1). The initialization of soil-forming processes occurred under the influence of periglacial environment and pioneer tundra vegetation. Endostagnic Podzols (Abruptic, Epiarenic, Endoloamic, Endodensic) developed within the plateau, and they have some features typical for periglacial environments (e.g. the presence of a cryoilluvial horizon, the poor humification of soil organic matter, the low abundance in N and P, and the vertical displacement of P). The basin of a small lake has been filled successively with sediments and Dystric Endocalcaric Katostagnic Fluvisols (Arenic, Humic, Endolimnic) developed from these sediments during the Late Vistulian and Early Holocene. The previously mentioned soils were buried by sandy cover in the Early Subatlantic due to intensification of aeolian processes. Ortsteinic Podzols (Pantoarenic) developed within a newly formed sandy cover. A fossil fireplace preserved in the top of these soils constitutes evidence of human activity dating back almost 2000 years. Ortsteinic Podzol (Pantoarenic) are dissected by a dry valley that developed as a result of some fluvial episode, perhaps induced by human activity. It was subsequently filled with aeolian sands, and Dystric Arenosols (Aeolic, Ochric) developed within them. Ortsteinic Podzol (Pantoarenic) and Dystric Arenosols (Aeolic, Ochric) were buried approximately five centuries ago. Our findings for the studied cliff section correlate well with results of other authors concerning the postglacial dynamics of morphogenetic processes. The studies provide significantly enriched geomorphological knowledge related to the formation of relief in the study area, with pedological aspects.

25687. 题目: Impact of andosolization on pedogenic Fe oxides in ferrallitic soils
文章编号: N19041905
期刊: Geoderma
作者: E. Van Ranst, F. Mees, E. De Grave, L. Ye, J.-T. Cornelis, B. Delvaux
更新时间: 2019-04-19
摘要: The accumulation of soil organic matter (SOM), poorly crystalline Fe oxides and metal-humus complexes is a trait of non-allophanic Andosols. The process of andosolization, which may occur in ferrallitic soils with high organic matter content, can involve transformation from well crystallized Fe oxides to poorly crystallized Fe oxides and Fe-humus complexes. This study investigates such changes in pedogenic Fe mineral associations for a soil toposequence between 1500 and 2260 m altitude along the southern flank of the volcanic Bambouto Mountains, Western Cameroon. The soils consist of highly weathered material, dominated by kaolinite, gibbsite and Fe oxides, grading to Protoandic Umbrisols at high altitude, recording an increase in SOM content with increasing altitude. As revealed by selective extraction analysis, the relative amount of poorly crystalline Fe oxides is low in the Bt and Bo horizons of low-altitude pedons, as well as in deep subsurface horizons of the high-altitude pedons. In contrast, it is significantly higher in the A and Bw horizons of the high-altitude pedons, with a clear increase with increasing altitude. Mössbauer spectroscopy analysis of B horizon samples identifies goethite as the dominant Fe oxide phase in nearly all pedons, with higher hematite contents in a mid-altitude zone marked by lower annual rainfall than in other parts of the toposequence. The Mössbauer spectra also reveal the presence of dissolved organic matter (DOM)-ferrihydrite, whose abundance is greatest in the Bw horizon of the high-altitude pedons, with an increase in relative abundance with increasing altitude. The observed patterns are attributed to dissolution-reprecipitation of Fe oxides that initially formed through ferrallitic weathering of volcanic parent materials that were roughly uniform along the toposequence. At high altitude, coupled hematite dissolution and DOM-ferrihydrite formation are favoured by high organic matter contents and low pH, related to cool humid environmental conditions and their effect on the vegetation and organic matter cycling.

25688. 题目: Estimating forest soil organic carbon content using vis-NIR spectroscopy: Implications for large-scale soil carbon spectroscopic assessment
文章编号: N19041904
期刊: Geoderma
作者: Shangshi Liu, Haihua Shen, Songchao Chen, Xia Zhao, Asim Biswas, Xiaolin Jia, Zhou Shi, Jingyun Fang
更新时间: 2019-04-19
摘要: Large-scale soil organic carbon (SOC) stock assessment is expensive as a large number of samples must be collected and then their time-consuming measurements must be made in the laboratory. Previous studies have shown that visible-near-infrared reflectance (vis-NIR) spectroscopy can quickly predict SOC content at a low cost. However, the application of this method at the large scale remains challenging due to the high spatial heterogeneity of SOC and the spatially dependent relationships of soil spectra and SOC content. Here, we conducted large-scale soil sampling across China's forests and established the Chinese forest soil spectral library (CFSSL) by measuring SOC content and scanning the vis-NIR reflectance of 11, 213 soil samples. Compared with the traditional global partial least squares regression (PLSR) modeling method (R² = 0.75, RPIQ = 1.95), the clustering by fast research and find of density peak in combination with the Cubist model significantly improved the prediction ability of SOC content (R² = 0.96, RPIQ = 5.83). This study provided a cost-efficient spectroscopic methodology, including measurement and prediction modeling, for large-scale SOC estimation.

25689. 题目: Effects of passivators on antibiotic resistance genes and related mechanisms during composting of copper-enriched pig manure
文章编号: N19041903
期刊: Science of The Total Environment
作者: Xun Qian, Jie Gu, Wei Sun, Xiaojuan Wang, Haichao Li
更新时间: 2019-04-19
摘要: Due to the intensive use of feed additives in livestock farming, animal manure has become a hotspot for antibiotics, heavy metals, and antibiotic resistance genes (ARGs). Unlike antibiotics, heavy metals cannot be degraded during composting and thus could pose a persistent co-selective pressure in the proliferation of antibiotic resistance. Passivators are commonly applied to immobilize metals and improve the safety of compost. However, little is known about the effects of various passivators on ARGs and mobile genetic elements (MGEs) during composting and the underlying mechanisms involved. Thus, three typical passivators (biochar, fly ash, and zeolite) were applied during the composting of copper-enriched pig manure, and their effects on ARGs, copper resistance genes, MGEs, and the bacterial communities were examined. Compared to the control, all passivator treatments reduced the abundances of at least six ARGs (tetC, tetG, tetQ, tetX, sul1, and ermB) by 0.23–1.09 logs and of two MGEs (intI1 and ISCR1) by 26–85% after composting. Biochar and fly ash also significantly reduced the abundances of intI2 and Tn914/1545. In contrast, abundances of copper resistance genes were not reduced by passivators, implying that the decreased co-selective pressure may not be a major contributor to ARG reductions in this study. Procrustes analysis and redundancy analysis demonstrated that shifts in the bacterial community determined the changes in the abundances of ARGs, and the variation in MGEs and DTPA-Cu can also partially explain the ARG variance. Overall, all of three passivators can be used to reduce the health risks associated with ARGs in livestock manure, and biochar performed the best at reducing ARGs and MGEs.
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25690. 题目: Effects of copper ions on removal of nutrients from swine wastewater and on release of dissolved organic matter in duckweed systems
文章编号: N19041902
期刊: Water Research
作者: Qi Zhou, Xiang Li, Yan Lin, Chunping Yang, Wenchang Tang, Shaohua Wu, Dehao Li, Wei Lou
更新时间: 2019-04-19
摘要: High concentration of Cu²⁺ in swine wastewater raises concerns about its potential adverse effects on nutrient removal by aquatic plants like duckweed. In this work, the effects of copper ions on nutrient removal and release of dissolved organic matter (DOM) were investigated in duckweed systems. Results showed that the removal performance of ammonia nitrogen (NH₃-N) and total phosphorus (TP) increased at 0.1–1.0 mg/L of Cu²⁺, while dropped at 2.0–5.0 mg/L of Cu²⁺. A novel kinetic model in which Cu²⁺ was taken into account was then developed which was used to optimize Cu²⁺ concentration at 0.96 mg/L for nutrient removal in duckweed systems. NADH, detected in DOM by the parallel factor (PARAFAC) analysis, exhibited high capacities of binding copper ions, so it played an important role on the decrease of Cu²⁺ concentrations in duckweed systems. The principle component analysis (PCA) showed that the dominant DOM were lower molecular weight compounds at 1.0 mg/L of Cu²⁺ and higher molecular weight compounds at 2.0–5.0 mg/L of Cu²⁺. The bonds of C−H (humic-like), N=O (NO₃⁻) and Ar-H (tyrosine) in DOM were responsible for not only the fastest binding with Cu²⁺ from the result of the two-dimensional Fourier transform infrared correlation spectroscopy (2D-FTIR-CoS) but also the variations of DOM conformations at a critical concentration of 0.5 mg/L Cu²⁺ from the perturbation correlation moving window two-dimensional (PCMW2D) analysis. These findings lead to a better understanding on the environmental behaviors and mechanisms of Cu²⁺ in duckweed systems.
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25691. 题目: Comparative study on the pretreatment of algae-laden water by UV/persulfate, UV/chlorine, and UV/H₂O₂: Variation of characteristics and alleviation of ultrafiltration membrane fouling
文章编号: N19041901
期刊: Water Research
作者: Ying Wan, Pengchao Xie, Zongping Wang, Jiaqi Ding, Jingwen Wang, Songlin Wang, Mark R. Wiesner
更新时间: 2019-04-19
摘要: In this study, ultraviolet based advanced oxidation processes (UV-AOPs) including UV/persulfate (UV/PS), UV/chlorine, and UV/H₂O₂ were employed to alleviate ultrafiltration membrane fouling during the treatment of algae-laden water. The results show that UV/PS pretreatment exhibited the best performance on fouling control, followed by the UV/H₂O₂ pretreatment. The fouling mitigation performance improved with the increase of oxidant dose. However, UV/chlorine pretreatment aggravated membrane fouling, and the irreversible fouling resistance increased by five times compared with that of raw water. The dissolved organic carbon (DOC) in the algae-laden solution was reduced after UV/PS pretreatment, while either UV/chlorine or UV/H₂O₂ pretreatment had little influence on the DOC of feed water. UV/PS and UV/H₂O₂ pretreatments were effective in the degradation of fluorescent compounds, thus reducing the deposition of organic matter on the membrane surface. Additionally, the decreased concentration of hydrophobic organics, algal cells, and debris in feed water after UV/PS pretreatment was also contributed to the fouling alleviation. The aggravated irreversible fouling after UV/chlorine pretreatment was probably ascribed to the increased accumulation of hydrophobic fractions in the membrane pores. Modeling result indicates that membrane fouling during the filtration of raw algae-laden water was dominated by intermediate blocking and cake filtration mechanisms. Both UV/PS and UV/H₂O₂ pretreatments transformed the combined fouling mechanism into standard blocking, while UV/chlorine pretreatment aggravated the pore blocking in the initial filtration period.
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25692. 题目: Spatial distribution and stoichiometry of soil carbon, nitrogen and phosphorus along an elevation gradient in a wetland in China
文章编号: N19041808
期刊: European Journal of Soil Science
作者: C. Hu, F. Li, Y. H. Xie, Z. M. Deng, Z. Y. Hou, X. Li
更新时间: 2019-04-18
摘要: Despite extensive studies on how environmental factors influence plant nutrient distribution and stoichiometry, it remains unclear how elevation affects soil distribution and stoichiometry. Here, patterns of the spatial distribution and stoichiometry of soil carbon (C), nitrogen (N) and phosphorus (P) were studied (with 123 soil samples) along a small‐scale elevation gradient in the wetland of East Dongting Lake, China. Plant nutrient concentrations (C, N and P), soil stoichiometry (C:N, C:P and N:P ratios) and their relations with other soil properties were analysed. In addition, the spatial distributions of plant nutrient concentrations and stoichiometry were evaluated geostatistically with regression kriging, entailing estimation of regression parameters by generalized least squares and ordinary kriging of the residuals. Soil C, N and P concentrations and stoichiometry had moderate to strong spatial dependence, and the ratios of C:P and N:P had similar patterns of distribution to soil organic carbon (SOC) and total nitrogen (TN). The SOC, TN, C:N, C:P and N:P ratios increased with increasing elevation, whereas total phosphorus (TP) showed no marked change. Furthermore, SOC, TN, C:N, C:P and N:P decreased considerably with increasing duration of submergence, soil moisture and pH. Therefore, elevation appeared to influence the distribution of plant nutrients and stoichiometry as a result of changing soil moisture and duration of submergence.

25693. 题目: Water‐soluble phenolic metabolites in lichens and their potential role in soil organic matter formation at the pre‐vascular stage
文章编号: N19041807
期刊: European Journal of Soil Science
作者: A.G. Zavarzina, T.N. Nikolaeva, V.V. Demin, P.V. Lapshin, M.I. Makarov, A.A. Zavarzin, N.V. Zagoskina
更新时间: 2019-04-18
摘要: Soil organic matter (SOM) is the largest reservoir of organic carbon in the biosphere. However, little is known about the processes of its formation at the pre‐vascular stage. Lichens are among the pioneer colonizers on mineral substrates and are possible early land flora. This study is the first report on the identification and quantification of water‐soluble phenolic compounds (PCs), potential precursors of humic substances, in epigeyic lichens from two systematic groups. Results show (Folin–Denis assay) that cyanobiont‐containing lichens (order Peltigerales) possess three to five times more total soluble PCs than Lecanoralean lichens (Cladonia, Cetraria spp.) and mosses. Soluble PCs in lichens occur in the conjugated form. Alkali‐hydrolysable compounds (esters) predominate over acid‐hydrolysable ones (glycosides). Phenolic complexes with N‐containing compounds or reducing sugars, or both, have been identified by thin layer chromatography (TLC). Benzoic acid derivatives were most common among PCs, detected in lichens by reversed‐phase high pressure liquid chromatography (RP‐HPLC). Phenolic acids occur in the order (μg 100 g^‐1): p‐hydroxybenzoic (327–1007) > syringic (87–361) > salycilic (135–210) > vanillic acid (12–19) (Peltigeralean lichens); salicylic (53–102) > p‐hydroxybenzoic (45–54) > caffeic (29) > syringic (18) > vanillic acid (9–13) (Lecanoralean lichens). Protocatechuic, caffeic and p‐coumaric acids were rare, ferulic acid was not detected. Syringyl and vanillyl aldehydes and ketones occur in much larger amounts than acids. Methoxy‐substituted and ortho‐substituted phenols, detected in lichens, are known for their high reactivity in soils under lignified vegetation, suggesting their important roles in SOM formation under a cryptogam cover.

25694. 题目: K_d distributions in freshwater systems as a function of material type, mass-volume ratio, dissolved organic carbon and pH
文章编号: N19041806
期刊: Applied Geochemistry
作者: Wirginia Tomczak, Patrick Boyer, Mohamed Krimissa, Olivier Radakovitch
更新时间: 2019-04-18
摘要: The contamination of freshwater systems by metals is a worldwide problem due to their toxicity, abundance and persistence in the environment. One of the main processes affecting their residence time in freshwater systems is their solid-liquid fractionation, often modeled by the K_d approach defined as the concentration ratio between the particulate and dissolved phases under the assumptions of reversibility, equilibrium and trace conditions. Because K_d is an empirical parameter that depends on several environmental factors, its variability can cover orders of magnitude for a single element. Such variability is unknown for most case studies, but the modelers need it to evaluate the uncertainty of their calculations. In order to fill this gap, this paper presents statistical K_d distributions for in situ suspended matters as a function of suspended load, dissolved organic carbon and pH. They were obtained using a database containing 8564 K_d values from 50 elements, classified as a function of three exchange conditions (adsorption, desorption and in situ) and two environmental components (suspended and deposited sediments). These distributions and relations can be used to reduce of several order of magnitudes the global variability of K_d values in the case where in situ data are not available.

25695. 题目: Soil organic carbon stocks in fluvial and isolated tropical wetlands from Colombia
文章编号: N19041805
期刊: CATENA
作者: Jonathan Pérez-Rojas, Flavio Moreno, Julio César Quevedo, Jorge Villa
更新时间: 2019-04-18
摘要: Freshwater tropical wetlands are valuable sinks of carbon (C) on the global scale. While much attention has been paid to forested peatlands, little is known about C stored in tropical freshwater mineral soil wetlands dominated by herbaceous and macrophyte vegetation, specially its spatial variability at the ecosystem level. Here we study the soil organic carbon of two tropical lowland wetlands (fluvial and isolated), located in the interandean valley of the Magdalena river in Colombia. Soil cores were extracted from 11 sampling zones distributed in the two wetlands, including the dryland adjacent to each wetland. They were sectioned into 2 cm-depth increments that were analyzed for C content. The average bulk density was higher (P < 0.001) in the fluvial wetland (0.87 ± 0.3 g cm⁻³) than in the isolated one (0.45 ± 0.3 g cm⁻³), the concentration of C (% Cr) was higher (P < 0.001) in the isolated wetland (11.1 ± 6.8%) than in the fluvial one (1.9 ± 1.1%) as well as the average soil organic carbon (6.4 ± 2.6 and 2.9 ± 1.1 t C ha⁻¹ cm⁻¹, respectively). Per unit area, the fluvial wetland had about twice as much storage capacity of C as the dryland, while in the isolated wetland the ratio was up to five times higher. Hydrogeomorphology was an important factor for the C storage in these ecosystems. The fluctuating hydrodynamics of the fluvial wetland seems to favor aerobic conditions and thus the prevalence of aerobic over anaerobic decomposition, lowering accumulation of C. This study makes an important contribution towards the understanding of C dynamics in different types of tropical wetlands and brings data to support their conservation.

25696. 题目: Consumption and alteration of different organic matter sources during remediation of a sandy sulfuric soil
文章编号: N19041804
期刊: Geoderma
作者: Angelika Kölbl, Franziska Bucka, Petra Marschner, Luke Mosley, Rob Fitzpatrick, Stefanie Schulz, Tillmann Lueders, Ingrid Kögel-Knabner
更新时间: 2019-04-18
摘要: Saturated acid sulfate soils with hypersulfidic material are productive wetland soils, but when they dry, they generate large amounts of sulfuric acid due to oxidation of pyrite to form sulfuric material (pH <4) and consequently sulfuric soils. After re-saturation of sulfuric soils and thus the re-establishment of reduced conditions, activity of sulfate reducing bacteria (SRB) can lead to a renewed formation of Fe sulfides and pH increase. Many SRB are heterotrophic and require sufficient available organic matter; however, little is known about OC consumption and changes of the composition of organic substrates during the amelioration process. To investigate remediation of a sandy, OC-poor sulfuric soil (initial pH = 2.5), short-term anoxic incubation experiments over a period of approx. 10 weeks were conducted after re-submerging under controlled laboratory conditions. We tested different organic matter quantities between 10% up to 200% of the native soil OC content. Besides wheat straw, we used lactate additions to test if this selectively promotes the activity of SRB, and thus, accelerates sulfate reduction and pH neutralization. The results showed that OC additions of ≥50% of native soil OC content and pre-adjustment of pH to values ≥5.0 were necessary to subsequently enable microbial reduction reactions to occur, which increased the pH to values ≥5.5. OC additions of ≥100% instead of 50% of native soil OC as wheat straw led to quicker changes of redox and pH values, to slightly higher microbial activity as indicated by CO₂ release, and to higher proportions of newly-formed mineral-associated OC. The addition of OC as lactate solution to promote specifically SRB was only successful in combination with wheat straw addition. Here, the presence of lactate led to the quickest changes of pH and redox values and resulted in pH ≥7 and redox values ≤ −300 mV due to an active microbial population. Our results indicate that a diverse microbial community is more important for successful remediation than a selective promotion of SRB.

25697. 题目: Adsorption of Organic Micropollutants to Biosolids-Derived Biochar: Estimation of Thermodynamic Parameters
文章编号: N19041803
期刊: Environmental Science: Water Research & Technology
作者: Yiran Tong, Brooke K Mayer, Patrick McNamara
更新时间: 2019-04-18
摘要: This research quantified thermodynamic parameters to better understand the use of wastewater biosolids-derived biochar as an adsorbent to remove micropollutants. The objective of this research was to quantify adsorption capacity; isosteric heat; and change of enthalpy, entropy, and free energy characterizing adsorption reactions between biochar and micropollutants. Adsorption isotherms were developed using a range of temperatures for the micropollutants benzyldimethyldecylammonium chloride (BAC-C10), carbamazepine (CBZ), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), and triclosan (TCS). The thermodynamic parameters derived from the isotherm data were used to assist in characterizing binding affinity, spontaneity, and mechanisms of adsorption. More polar compounds such as BAC-C10 and CBZ exhibited linear adsorption, indicating weak interactions with more polar amorphous moieties on the biochar surface. For the micropollutants that were present predominantly in the neutral form at pH 7 (CBZ, E2, EE2, and TCS), increasing hydrophobicity increased the extent of adsorption. The enthalpy change of adsorption and the positive correlation between hydrophobicity and change of entropy (R2=0.8) both suggest that hydrophobic interaction was the dominant adsorption mechanism for neutral compounds. Increases in adsorption with increasing temperature, together with the estimated thermodynamic parameters, indicated that the reactions were endothermic, meaning that higher temperatures should offer improved removal via adsorption. The negative free energy changes observed suggested that adsorption was spontaneous and that adsorption rates outcompete desorption rates. Under multi-solute conditions, the adsorption capacities for all compounds were suppressed to varying extents; however, the magnitude of changes in enthalpy and entropy were not affected by competitive multi-solute adsorption.

25698. 题目: Biochar/struvite composite as a novel potential material for slow release of N and P
文章编号: N19041802
期刊: Environmental Science and Pollution Research
作者: Pan Hu, Yihe Zhang, Leipeng Liu, Xinke Wang, Xinglong Luan, Xi Ma, Paul K. Chu, Jichao Zhou, Pengda Zhao
更新时间: 2019-04-18
摘要: For soil and environmental remediation, biochar/struvite composites are prepared by the crystallization-adsorption method. The recovery rates of N, P, and Mg in the solution increase to 99.02%, 97.23%, and 95.22%, respectively, by forming 10% biochar/struvite composite. X-ray diffraction (XRD) patterns acquired from the 10% biochar/struvite composite show a crystalline structure of MgNH₄PO₄·6H₂O (PDF no. 15-0762) and release of the main nutrient elements (N, P, Mg) from the 10% biochar/struvite composite increases significantly compared to struvite. The solubility of the biochar/struvite composite is the highest in 0.5 mol/L HCl, second in 20 g/L citric acid, and lowest in water. The power function equation describes more precisely the cumulative release of N, P, and Mg from the biochar/struvite composite in distilled water, whereas it follows the simple Elovich equation in 20 g/L critic acid and first-order kinetics equation in 0.5 mol/L HCl. Leaching experiments are performed on the biochar/struvite composite in soil, and the results indicate that the biochar/struvite composite has a longer cycle of release of nutrients than traditional chemical fertilizers and has large potential as a slow-release fertilizer.

25699. 题目: Assessing the role of different dissolved organic carbon and bromide concentrations for disinfection by-product formation using chemical analysis and bioanalysis
文章编号: N19041801
期刊: Environmental Science and Pollution Research
作者: Peta A. Neale, Frederic D. L. Leusch
更新时间: 2019-04-18
摘要: Concerns regarding disinfection by-product (DBP) formation during drinking water treatment have led water utilities to apply treatment processes to reduce the concentration of DBP precursor natural organic matter (NOM). However, these processes often do not remove bromide, leading to high bromide to dissolved organic carbon (DOC) ratios after treatment, which can increase the formation of more toxic brominated DBPs. In the current study, we investigated the formation and effect of DBPs in a matrix of synthetic water samples containing different concentrations of bromide and DOC after disinfection with chlorine. Trihalomethanes and haloacetic acids were analysed by chemical analysis, while effect was evaluated using in vitro bioassays indicative of the oxidative stress response and bacterial toxicity. While the addition of increasing bromide concentrations did not alter the sum molar concentration of DBPs formed, the speciation changed, with greater bromine incorporation with an increasing Br:DOC ratio. However, the observed effect did not correlate with the Br:DOC ratio, but instead, effect increased with increasing DOC concentration. Water samples with low DOC and high bromide did not exceed the available oxidative stress response effect-based trigger value (EBT), while all samples with high DOC, irrespective of the bromide concentration, exceeded the EBT. This suggests that treatment processes that remove NOM can improve drinking water quality, even if they are unable to remove bromide. Further, iceberg modelling showed that detected DBPs only explained a small fraction of the oxidative stress response, supporting the application of both chemical analysis and bioanalysis for monitoring DBP formation.

25700. 题目: Contrasting vegetation states do not diverge in soil organic matter storage: evidence from historical sites in tundra
文章编号: N19041710
期刊: Ecology
作者: Sari Stark, Dagmar Egelkraut, Kjell‐Åke Aronsson, Johan Olofsson
更新时间: 2019-04-17
摘要: Ecosystems where severe disturbance has induced permanent shifts in vegetation and soil processes may represent alternative stable states. To date, little is known on how long‐lasting changes in soil processes are following such disturbances, and how the changes in plant and soil processes between the alternative states eventually manifest themselves in soil organic matter (SOM) storage. Here, we analyzed plant density, the shrub:forb –ratio, microbial respiration, extracellular enzyme activities and SOM stocks in soils of subarctic tundra and historical milking grounds, where reindeer herding induced a vegetation transition from deciduous shrubs to graminoids several centuries earlier but were abandoned a century ago. This provides the possibility to compare sites with similar topography, but highly contrasting vegetation for centuries. We found that enzymatic activities and N:P stoichiometry differed between control and disturbed sites, confirming that culturally induced vegetation shifts exert lasting impacts on tundra soil processes. Transition zones, where shrubs had encroached into the historical milking grounds during the past 50 years, indicated that microbial activities for N and P acquisition changed more rapidly along a vegetation shift than those for microbial C acquisition. Although plant and soil processes differed between control and disturbed sites, we found no effect of historical vegetation transition on SOM stock. Across the study sites, soil SOM stocks were correlated with total plant density but not with the shrub:forb ratio. Our finding that SOM stock was insensitive to a centennial difference in plant community composition suggests that, as such, grazing‐induced alternative vegetation states might not necessarily differ in SOM sequestration.