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25101. 题目: Two years of aging influences the distribution and lability of metal(loid)s in a contaminated soil amended with different biochars
文章编号: N19041302
期刊: Science of The Total Environment
作者: Erkai He, Yuxi Yang, Zibo Xu, Hao Qiu, Fan Yang, Willie J.G.M. Peijnenburg, Weihua Zhang, Rongliang Qiu, Shizhong Wang
更新时间: 2019-04-13
摘要: A two-year soil incubation experiment was performed to investigate the long-term impacts of biochars (kenaf core and sewage sludge biochar (KBC and SBC) pyrolyzed at 350 °C and 550 °C) on metal(loid)s immobilization. Both KBC and SBC can immobilize Pb and Cu in contaminated soil, whereas they showed little effects on the immobilization of Zn, Cd and As. Interactions between the biochar and soil during two-year aging changed the metal species on both soil and biochar particles. KB350 formed more biochar-mineral complexes and O-containing functional groups than KB550 and thus transferred more residual metal(loid)s to their reducible species. More metal(loid)s sorbed on the KB350 than KB550 after two-year aging. However, SBC changed the acid-soluble species of metal(loid)s into the residual species during the aging process, probably due to the release of phosphate. Upon aging, SB550 exhibited a more significant increase in the residual metal amount and more sorption of metal(loid)s on the biochar particles than SB350 due to sorption of organic carbon and formation of meta-kaolinite. A key finding of our study was that different biochars have contrasting impacts on metal speciation and lability upon 2-year aging. This should be considered in assessing the actual risk of biochar-amended soils.
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25102. 题目: Assessment of sediment and organic carbon exports into the Arctic ocean: The case of the Yenisei River basin
文章编号: N19041301
期刊: Water Research
作者: C. Fabre, S. Sauvage, N. Tananaev, G. Espitalier Noël, R. Teisserenc, J.L. Probst, J.M. Sánchez Pérez
更新时间: 2019-04-13
摘要: The export of organic carbon export by the rivers to the oceans either as particulate organic carbon (POC) or dissolved organic carbon (DOC) is very sensitive to climate change especially in permafrost affected catchments where soils are very rich in organic carbon. With global warming, organic carbon export in both forms is expected to increase in Arctic regions. It should affect contemporary biogeochemical cycles in rivers and oceans and therefore modify the whole food web. This study tries to understand complex processes involved in sediment, POC and DOC riverine transport in the Yenisei River basin and to quantify their respective fluxes at the river outlet. The SWAT (Soil and Water Assessment Tool) hydrological model is used in this study to simulate water and suspended sediment transfers in the largest Arctic river. POC and DOC export have been quantified with empirical models, adapted from literature for the study case. First, the hydrological model has been calibrated and validated at a daily time step for the 2003–2008 and the 2009–2016 periods respectively, and its output has been compared with field data for water and sediment fluxes. Based on conceptualization of transfer processes, calibration on climate and soil properties has been performed in order to correctly represent hydrology and sediment transfer in permafrost basins. Second, calibration of empirical models for DOC/POC transport have been performed by comparing their output with field data, available from 2003 to 2016. Our study reveals that SWAT is capable of correctly representing hydrology, sediment transfer, POC and DOC fluxes and their spatial distribution at a daily timescale, and outlines the links between these fluxes and permafrost features. Our simulation effort results in specific sediment, POC and DOC fluxes of 2.97 t km−2 yr−1, 0.13 t km−2 yr−1 and 1.14 t km−2 yr−1 for the period 2003–2016 which are in the range of previous estimates. About 60% of the total fluxes of sediment, DOC and POC to the Arctic Ocean are exported during the two months of the freshet. Spatial analysis show that permafrost-free areas have returned higher daily organic carbon export than permafrost affected zones, highlighting the thawing permafrost effect on carbon cycle in climate change feedback.
25103. 题目: Phosphate‐limited ocean regions select for bacterial populations enriched in the carbon‐phosphorus lyase pathway for phosphonate degradation
文章编号: N19041209
期刊: Environmental Microbiology
作者: Oscar A. Sosa, Daniel J. Repeta, Edward F. DeLong, Mohammad D. Ashkezari, David M. Karl
更新时间: 2019-04-12
摘要: In tropical and subtropical oceanic surface waters phosphate scarcity can limit microbial productivity. However, these environments also have bioavailable forms of phosphorus incorporated into dissolved organic matter (DOM) that microbes with the necessary transport and hydrolysis metabolic pathways can access to supplement their phosphorus requirements. In this study we evaluated how the environment shapes the abundance and taxonomic distribution of the bacterial carbon‐phosphorus (C‐P) lyase pathway, an enzyme complex evolved to extract phosphate from phosphonates. Phosphonates are organophosphorus compounds characterized by a highly stable C‐P bond and are enriched in marine DOM. Similar to other known bacterial adaptions to low phosphate environments, C‐P lyase was found to become more prevalent as phosphate concentrations decrease. C‐P lyase was particularly enriched in the Mediterranean Sea and North Atlantic Ocean, two regions that feature sustained periods of phosphate depletion. In these regions, C‐P lyase was prevalent in several lineages of Alphaproteobacteria (Pelagibacter, SAR116, Roseobacter, and Rhodospirillales), Gammaproteobacteria, and Actinobacteria. The global scope of this analysis supports previous studies that infer phosphonate catabolism via C‐P lyase is an important adaptive strategy implemented by bacteria to alleviate phosphate limitation and expands the known geographic extent and taxonomic affiliation of this metabolic pathway in the ocean. This article is protected by copyright. All rights reserved.
25104. 题目: Spatial variability of nitrate and ammonium in Pleistocene aquifer of central Yangtze River Basin
文章编号: N19041208
期刊: Ground Water
作者: Yiqun Du, Zongjie Gan, Shuai Lu, Teng Shen, Yamin Ma, Yao Deng
更新时间: 2019-04-12
摘要: It becomes increasingly important and challenging for nitrogen pollution prevention to identify key controls for spatial variability of nitrogen in groundwater that could be affected by multiple factors, including anthropogenic input, groundwater flow and local geochemistry. This study characterized spatial variability of both nitrate and ammonium in the Pleistocene aquifer of central Yangtze River Basin and assessed the effect of various factors in controlling nitrate and ammonium levels based on multiple statistical approaches (correlation, geostatistics, multiple liner regression). The results indicate that nitrate is mostly influenced by Cl‐ that represents anthropogenic input, while Eh representing local redox state is a secondary variable influencing nitrate concentrations. The groundwater with elevated nitrate concentrations are estimated to occur mainly in areas with higher‐permeability near‐surface sediments which can facilitate more anthropogenic nitrate transport and less nitrate removal owing to more oxidized state. Ammonium is mostly correlated to Eh, followed by dissolved organic carbon (DOC), but only DOC improve significantly the accuracy of co‐kriging prediction model. The groundwater with elevated ammonium concentrations are estimated to occur mainly in areas with more organic‐rich sediments within or around the aquifer which can facilitate more ammonium release owing to natural organic matter consumption accompanying strong reducing conditions. The regional groundwater flow is not a factor significantly controlling nitrate or ammonium levels owing to flat topography and sluggish lateral flow.
25105. 题目: A mechanistic model of microbially mediated soil biogeochemical processes ‐ a reality check
文章编号: N19041207
期刊: Global Biogeochemical Cycles
作者: Simone Fatichi, Stefano Manzoni, Dani Or, Athanasios Paschalis
更新时间: 2019-04-12
摘要: Present gaps in the representation of key soil biogeochemical processes such as the partitioning of soil organic carbon (SOC) among functional components, microbial biomass and diversity, and the coupling of carbon and nutrient cycles present a challenge to improving the reliability of projected soil carbon dynamics. We introduce a new soil biogeochemistry module linked with a well‐tested terrestrial biosphere model T&C. The module explicitly distinguishes functional SOC components. Extracellular enzymes and microbial pools are differentiated based on the functional roles of bacteria, saprotrophic, and mycorrhizal fungi. Soil macrofauna is also represented. The model resolves the cycles of nitrogen, phosphorus, and potassium. Model simulations for 20 sites compared favorably with global patterns of litter and soil stoichiometry, microbial and macrofaunal biomass relations with soil organic carbon, soil respiration and nutrient mineralization rates. Long‐term responses to bare fallow and nitrogen addition experiments were also in agreement with observations. Some discrepancies between predictions and observations are appreciable in the response to litter manipulation. Upon successful model reproduction of observed general trends, we assessed patterns associated with the carbon cycle that were challenging to address empirically. Despite large site‐to‐site variability, fine root, fungal, bacteria, and macrofaunal respiration account for 33%, 40%, 24% and 3% on average of total belowground respiration, respectively. Simulated root exudation and carbon export to mycorrhizal fungi represent on average about 13% of plant net primary productivity (NPP). These results offer mechanistic and general estimates of microbial biomass and its contribution to respiration fluxes and to soil organic matter dynamics.
25106. 题目: Development of N-Cyclopropylanilines to Probe the Oxidative Properties of Triplet-State Photosensitizers
文章编号: N19041206
期刊: Environmental Science & Technology
作者: Nicholas
C. Pflug, Markus Schmitt, Kristopher McNeill
更新时间: 2019-04-12
摘要: Anilines have been shown to be especially susceptible to single-electron oxidation by excited triplet-state photosensitizers (3sens*), and thus, are good potential candidates to probe the oxidative properties of triplet-state chromophoric dissolved organic matter (3CDOM*). However, steady-state experiments tend to underestimate their rate of oxidation by 3CDOM* due to radical cation quenching (i.e., aniline•+ → aniline) by antioxidant moieties present in DOM. We envisioned the potential utility of N-cyclopropylaniline (CPA) to overcome this limitation, as it is known to undergo spontaneous, irreversible cyclopropyl ring-opening after an initial single-electron oxidation. To test this, first a set of CPA analogs was synthesized and then paired with a model sensitizer and antioxidant, or various DOM isolates, to examine their reactivity and susceptibility to antioxidant quenching during steady-state photolysis experiments. Next, time-resolved measurements of CPA and CPA analog oxidation were obtained by laser flash photolysis through direct observation of 3sens* and radical cations of CPA and CPA analogs. Finally, CPA photolysis products were isolated by semi-preparative high-performance liquid chromatography and identified by nuclear magnetic resonance spectroscopy. Outcomes of this work, including oxidation bimolecular rate constants of CPA and CPA analogs (∼9 × 108 to 4 × 109 M–1 s–1), radical cation lifetimes of CPA and its analogs (140–580 ns), and identified ring-opened products, support the usefulness of cyclopropylanilines as single-electron transfer probes in photosensitized aqueous solutions.
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25107. 题目: Strategy for phytomanagement in an area affected by iron ore dam rupture: A study case in Minas Gerais State, Brazil
文章编号: N19041205
期刊: Environmental Pollution
作者: Valéria Cristina Palmeira Zago, Nathália Corrêa das Dores, Beatriz Amanda Watts
更新时间: 2019-04-12
摘要: In 2015, the Fundão tailing dam collapsed over the district of Bento Rodrigues (Mariana, Minas Gerais, Brazil) causing deaths, hundreds of homeless families and incalculable environmental degradation. Environmentally, economically and socially sustainable strategies are needed for the recovery of the affected areas. The main goal of this study was to evaluate the development, biomass production and toxic mineral elements absorption of three species of aromatic grasses (Chrysopogon zizanioides, Cymbopogon citratus and Cymbopogon winterianus). These three species were planted on polypropylene pots filled with the iron ore tailings collected from the topsoil of the Bento Rodrigues district. The pots were fertilized with increasing doses of organic compost associated with mycorrhizae as a phytomanagement strategy. A 4 × 2 factorial scheme was used. The seedlings were fertilized with four doses of organic compost, with or without mycorrhizae. At the highest dose of the organic compost (2 kg.plant−1), the total dry matter (dry matter of the aerial part + dry matter of the roots) for C. zizanioides was 4.5 times higher than the control (tailing only). For C. winterianus and C. Citratus was 3.8 and 2.8 times higher than the control, respectively. Inoculation with mycorrhizae improved biomass production, especially in C. zizanioides. The Fe and Mn levels found in the aerial part of the plants fertilized with organic compost were lower than those just growing on the iron ore tailings for the three species, which suggest that the organic matter apparently helped the plants in the exclusion of the hazardous substances and therefore increased the tolerance to these adverse environmental conditions. C. zizanioides, associated with organic matter and mycorrhizae, would be the recommended species. The proposed phytomanagement strategy can have a significant contribution to the gradual recovery of the affected area and also serve as a source of income for the local population.
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25108. 题目: The regulation of N-acyl-homoserine lactones (AHLs)-based quorum sensing on EPS secretion via ATP synthetic for the stability of aerobic granular sludge
文章编号: N19041204
期刊: Science of The Total Environment
作者: Zhiming Zhang, Runjuan Cao, Luonan Jin, Weitang Zhu, Yatong Ji, Xiangyang Xu, Liang Zhu
更新时间: 2019-04-12
摘要: According to the relationship among microbial activity, quorum sensing (QS) and structural stability of aerobic granular sludge, the mechanism of QS regulation for microbial activity and granular stability was investigated in AGS process. Results showed that ATP content decreased sharply from 1.8 μmol/gVSS of stable granules to 0.8 μmol/gVSS of disintegrating granules, and the relative abundance of QS-activity microbes, Rhodobacter spp. and Xanthomonadaceae decreased in initially unstable granules compared with stable granules. The main AHLs were detected in this study, and C8-HSL, 3OHC8-HSL and 3OHC12-HSL decreased significantly when structure of granules changed from stability to disintegration. Accompanying with the decrease of AHLs level, the extracellular polymeric substances (EPS) content in initially unstable granules decreased sharply from 226.8 to 163.6 mg/gVSS with the ratio of extracellular protein to exopolysaccharide (PN/PS) decreasing from 3.6 to 2.2, despite EPS-secretion microbes enriched. The effect of QS on microbial activity was proved by AHL add-back study, results indicated that ATP and EPS content in sludge increased significantly (p < 0.05) with AHLs added, but EPS production was limited when ATP synthesis was disrupted. It was concluded that the AHLs-based QS favored the granular stability via the enhancement of ATP synthesis in microbes. This study provides a new perspective for QS regulation in aerobic granular sludge system, because the ATP regulated by QS could be the energy currency for cellular metabolism, such as nutrient removal, degradation of emerging pollutants, microbial growth and other aspects.
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25109. 题目: Changes in nitrogen functional genes in soil profiles of grassland under long-term grazing prohibition in a semiarid area
文章编号: N19041203
期刊: Science of The Total Environment
作者: Zilin Song, Jie Wang, Guobin Liu, Chao Zhang
更新时间: 2019-04-12
摘要: Grazing prohibition has been used to restore degraded grassland ecosystems in semiarid areas; however, the impact of this measure on soil nitrogen (N) cycling is poorly understood. Furthermore, recent studies have tended to focus on the topsoil and ignored a steep gradient of nutrient accumulation with soil depth. Here, we investigated changes in N functional genes (NFGs) involved in organic N decomposition (chiA), archaeal and bacterial ammonia oxidation (amoA-AOA and amoA-AOB), respectively, denitrification (nirK and nirS), and N fixation (nifH) in soil profiles from a chronosequence of grazing prohibition (0, 10, 15, 25, and 35 years) in the semiarid grasslands of the Loess Plateau, China. The abundance of all the investigated NFGs in grassland soils after 35 years' grazing prohibition was higher than in grazed grassland. This result suggests that microbial N turnover potential is facilitated by grazing prohibition, probably through enhanced biomass production via increases in nutrient input into the soil. The higher ratio of (chiA + nifH)/(amoA-AOA + amoA-AOB) and values of (nirK + nirS) in grazing-prohibited grasslands than in grazed grassland suggest that prohibition of grazing not only improved microbial N storage potential but also increased N gas emission potential. The abundances of NFGs varied along the soil profiles and responded differently to environmental factors. The chiA and nifH abundances decreased with soil depth and were associated with variation in aboveground biomass, NH4+-N, and organic carbon, while amoA-AOA, nirK, and nirS genes increased with depth and were more affected by soil organic carbon, moisture, and bulk density. Multivariate regression tree analysis demonstrated that aboveground biomass was the best explanatory variable for the changes in NFGs in grazed grassland, while soil organic carbon was the best in the grazing-prohibited grasslands. Our results provide new insight into the soil N cycling potential of degraded and restored semiarid grassland ecosystems.
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25110. 题目: Comparative effectiveness of different biochars and conventional organic materials on growth, photosynthesis and cadmium accumulation in cereals
文章编号: N19041202
期刊: Chemosphere
作者: Muhammad Azhar, Muhammad Zia ur Rehman, Shafaqat Ali, Muhammad Farooq Qayyum, Asif Naeem, Muhammad Ashar Ayub, Muhammad Anwar ul Haq, Akhtar Iqbal, Muhammad Rizwan
更新时间: 2019-04-12
摘要: Although biochar and conventional organic materials have been widely studied for lowering cadmium (Cd) uptake by plants but information regarding their comparative effectiveness is lacking. In this study, biochars from different feedstocks viz. rice husk biochar (RHB), cotton sticks biochar (CSB) and wheat straw biochar (WSB) were compared with conventional organic materials viz. farm manure (FM), poultry manure (PM) and press mud (PrMd) for their effectiveness to promote plant growth and to reduce Cd uptake by wheat and rice plants grown rotationally in a Cd-spiked (50 mg kg−1) soil. Each amendment was applied at the rate of 2% (w/w) in three replicates. Results showed that the application of amendments improved the soil properties and plant growth, by retaining Cd in the soil and restricting its uptake by plants. The amendments decreased the ammonium bicarbonate diethylene penta acetic acid extractable soil Cd, and improved soil organic carbon (SOC) and cation exchange capacity (CEC) as compared to only Cd-contaminated soil. The highest SOC content of 2.68 and 1.68% and CEC of 8.77 and 9.39 cmolc kg−1 were found in RHB treated post-wheat and post-rice soil, respectively. Amendments treated soil showed lower concentrations of bioavailable Cd and the maximum reduction was recorded in RHB and PrMd amended soil. Similarly, bioaccumulation of Cd was decreased with the application of all amendments; the maximum decrease was recorded in RHB and PrMd treated soil. Our results suggested that RHB and PrMd could be used for reducing the bioaccumulation of Cd in cereal grains in alkaline soils.
25111. 题目: Biochar-supported magnetic noble metallic nanoparticles for the fast recovery of excessive reductant during pollutant reduction
文章编号: N19041201
期刊: Chemosphere
作者: Shun-Feng Jiang, Kun-Fang Xi, Jing Yang, Hong Jiang
更新时间: 2019-04-12
摘要: The catalytic reduction of diverse pollutants by noble metal catalysts in the presence of reductants is a highly effective and widely used method. However, the considerable cost of noble metal catalysts impedes the practical application of this method, and the recovery of excessive reductants has not been reported previously. In this work, we prepared inexpensive biochar-supported magnetic noble metallic nanoparticles (NPs) and efficiently recovered the excessive reductants in the form of H2. The as-synthesized biochar-supported noble metallic NPs exhibited high H2 recovery during the 4-nitrophenol reduction reaction. Results showed that the catalysts with low noble metallic content have higher H2 recovery rate than commercial Pd/C, Ag/C, and Pt/C. The catalytic mechanism of magnetic biochar-supported noble metallic NPs was demonstrated to be a “synergetic effect”, where biochar and Fe3O4 acted as accelerants that enable noble metallic NPs to produce active hydrogen for the reduction reaction, and the excess active hydrogen atoms combined to form H2.
25112. 题目: Peak Chromium Pollution in Summer and Winter Caused by High Mobility of Chromium in Sediment of a Eutrophic Lake: In Situ Evidence from High Spatiotemporal Sampling
文章编号: N19041115
期刊: Environmental Science & Technology
作者: Xianfang Fan, Shiming Ding, Musong Chen, Shuaishuai Gao, Zhen Fu, Mengdan Gong, Daniel C. W. Tsang, Yan Wang, Chaosheng Zhang
更新时间: 2019-04-11
摘要: To study the mechanisms of chromium (Cr) mobilization in sediments of eutrophic lakes, monthly sampling was performed in the Meiliang Bay of Lake Taihu, China, combined with laboratory experiments. High-resolution dialysis and diffusive gradients in thin film (DGT) sampling techniques were used. Results indicated that in July 2016 and January 2017, the concentrations of soluble Cr and DGT-labile Cr(VI) in the overlying water exceeded both drinking and fishery water quality standards, resulting from the high mobility of Cr in sediments. In July (summer), the high concentration of soluble Cr (134.04 ± 7.20 μg/L) detected in the anaerobic sediments was primarily caused by the complexation of Cr(III) with dissolved organic matter (DOM). This mechanism was supported by an observed simultaneous increase of soluble Cr and DOM under simulated anaerobic conditions. In January (winter), the high concentrations of soluble Cr (97.55 ± 9.65 μg/L) and DGT-labile Cr(VI) (25.83 ± 1.25 μg/L) in aerobic sediments were primarily caused by reoxidation of Cr(III) by Mn(III/IV) oxides as evidenced by the lowest concentrations of soluble and DGT-labile Mn(II). This study sheds light on the full-year variation and mechanisms of Cr mobilization in eutrophic lake sediments and suggests the urgent need for remediation of Cr pollution especially for winter.
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25113. 题目: Factors controlling storage, sources, and diagenetic state of organic carbon in a prograding subaerial delta: Wax Lake Delta, Louisiana
文章编号: N19041114
期刊: Journal of Geophysical Research: Biogeosciences
作者: Michael R. Shields, Thomas S. Bianchi, Alexander S. Kolker, William F. Kenney, David Mohrig, Todd Z. Osborne, Jason H. Curtis
更新时间: 2019-04-11
摘要: Wax Lake Delta (WLD), southern Louisiana, is a coastal delta that formed following the dredging of a river channel in 1941 and is a field model for investigating the geomorphology, ecology, carbon dynamics, and carbon storage capacity in young prograding deltas. However, it is unknown how the transition from subaqueous to subaerial sediments affects the sources and quality of the sequestered carbon. We investigated these variations within the sediments of WLD using amino acid, lignin, and stable carbon isotope compositions of the organic matter (OM). A principal component analysis of these proxies highlighted variability in organic carbon (OC) composition with changes in elevation. The transition from subaqueous to subaerial sediments at 0 cm mean lower low water is an important component of the OM composition. In addition to the changes observed for OM source and quality, the OC loadings (OC/SA; mg C m‐2) also increase as the delta aggrades and accumulates sediments with loadings typical of delta topsets and mobile mud banks (OC/SA < 0.4) to riverine sediments (0.5 < OC/SA < 1) and eventually to highly productive regions (OC/SA > 1).
25114. 题目: Nitrogen addition shapes soil enzyme activity patterns by changing pH rather than the composition of the plant and microbial communities in an alpine meadow soil
文章编号: N19041113
期刊: Plant and Soil
作者: Xiaochen Liu, Shiting Zhang
更新时间: 2019-04-11
摘要: Aims: Increasing nitrogen (N) deposition has considerable effects on soil organic matter (SOM) decomposition mediated by soil enzyme activities. Few studies, however, have explored how N addition shapes soil enzyme activity patterns by changing plants, soils and microbes. Methods: We conducted a five-year field fertilization experiment (0, 5, 10, and 15 g N m−2 yr.−1) to study how N addition affected soil enzyme activity patterns in the topsoil (0–20 cm) and subsoil (20–40 cm) in a Tibetan alpine meadow. Enzyme activity patterns were calculated by the percentage of the sum of all measured enzyme activities. The composition of the plant and microbial communities were evaluated through measuring the abundance of plant functional groups and quantifying microbial phospholipid fatty acids (PLFAs), respectively. Soil pH and available N were also measured. Results: We found that soil N availability primarily controlled plant community composition, but pH controlled the composition of the microbial community, irrespective of soil depth. Soil enzyme activity patterns differed between two soil depths and among N addition rates. Importantly, N addition shaped soil enzyme activity patterns through the changes in soil pH rather than via the composition of the plant and microbial communities. Conclusions: Our findings indicate that N addition can affect components of plant-soil system and, in particular, weaken the linkages between plant and microbial communities and enzyme activity patterns. The work suggests that N enrichment-induced soil acidification plays a key role in SOM decomposition and nutrient cycling in the Tibetan meadow ecosystem.
25115. 题目: Microalgal–Bacterial Flocs and Extracellular Polymeric Substances: Two Essential and Valuable Products of Integrated Algal Pond Systems
文章编号: N19041112
期刊: Water, Air, & Soil Pollution
作者: Taobat A. Jimoh, M. Olajide Keshinro, Keith A. Cowan
更新时间: 2019-04-11
摘要: The integrated algal pond system (IAPS) is a passive wastewater treatment technology that can be used to remediate liquid waste from domestic, industrial and agricultural sources. The system exploits the mutualistic interaction between microalgae and bacteria to generate water of a quality suitable for discharge and/or reuse. During the treatment process, biomass in the form of microalgal–bacterial flocs (MaB-flocs) is generated, and this can be harvested and beneficiated in downstream processing. Here, we review literature on MaB-floc and extracellular polymeric substance (EPS) formation and discuss how essential microalgal–bacterial mutualism is at effecting IAPS-based wastewater treatment. Aggregation of microalgae and bacteria into MaB-flocs is clearly an outcome of EPS production by these microorganisms and arises for purposes of chemical and developmental interaction, protection, communication, aggregation and adhesion. The polymeric compounds which form the scaffold of this extracellular matrix comprise polysaccharides, proteins, uronic acid and nucleic acid. Natural EPS can be used as bioflocculant in water purification and in the dewatering and settling of sludge and is therefore an ideal natural replacement for commercially available synthetic polymers. Additionally, EPS are considered high value and can be used in many commercial applications. Thus, and to ensure sustained MaB-floc production in IAPS-based wastewater treatment plants, it is important that correct levels of EPS are maintained to facilitate settling and biomass recovery. Furthermore, it is the associated environmental and operational conditions that most impact EPS production and in turn, MaB-floc formation, and quality of the final IAPS-treated water.
25116. 题目: Variable response of inorganic carbon and consistent increase of organic carbon as a consequence of afforestation in areas with semi‐arid soils
文章编号: N19041111
期刊: Land Degradation & Development
作者: Xiaoxu Jia, Xiang Wang, Lingcao Hou, Xiaorong Wei, Yan Zhang, Ming’an Shao, Xiaoning Zhao
更新时间: 2019-04-11
摘要: Soil inorganic carbon (SIC) is the most common form of carbon in arid and semi‐arid regions, where afforestation is used to combat soil degradation. However, response of SIC to afforestation has been studied rarely, which hinders any prediction about soil carbon dynamics. To determine the response of SIC and soil organic carbon (SOC) to afforestation in semi‐arid soils and whether such responses vary with soil aggregates, soil texture and climatic conditions, we measured SIC and SOC in bulk soils and aggregate fractions under paired afforested lands and farmlands at five sites across the Loess Plateau. The relationship of these responses to soils and climatic variables was analyzed. Afforestation increased SOC at all sites, with accumulation rates of 0.21, 0.23, 0.34 and 0.09 g kg‐1 yr‐1 in bulk soils, macro‐aggregates (>0.25 mm), micro‐aggregates (0.25–0.053 mm) and silt+clay fraction, respectively, when averaged across sites and soil depths. However, the response of SIC to afforestation varied with site, with increased SIC in relatively drier sites and decreased SIC in relatively wetter sites. Change in SIC was negatively correlated with change in SOC either across or within bulk soils and aggregate fractions. The SIC decreased and SOC increased with increasing soil clay content, precipitation, temperature and site aridity index. These results indicated consistent increase in SOC, but variable response of SIC to afforestation among sites in the Loess Plateau. Such variable response of SIC should be incorporated into carbon cycle models to reduce uncertainties when predicting sequestration dynamics of soil carbon.
25117. 题目: Earthworm Lumbricus terrestris mediated redistribution of C and N into large macroaggregate-occluded soil fractions in fine-textured no-till soils
文章编号: N19041110
期刊: Applied Soil Ecology
作者: Jatta Sheehy, Visa Nuutinen, Johan Six, Ansa Palojärvi, Ossi Knuutila, Janne Kaseva, Kristiina Regina
更新时间: 2019-04-11
摘要: By processing large quantities of crop residues, earthworms enhance the mineralization of organic matter but have also been shown to stabilize soil organic carbon (SOC) into soil fractions like microaggregates (53–250 μm) within macroaggregates (>250 μm) especially in no-till soils. Our objective was to find direct evidence on the impact of an anecic, soil surface-feeding earthworm, Lumbricus terrestris L., on the redistribution of SOC and soil nitrogen (N) into macroaggregate-occluded soil fractions of boreal soils. We sampled soil (0–5 cm depth) from the middens of L. terrestris (mounds of collected residue and surface casts at the openings of its permanent burrows) and the adjacent non-midden (bulk) soil at three no-till sites in southern Finland: two clayey sites (sites 1–2) and one coarse textured site (site 3). Compared to bulk soil, the soil in L. terrestris middens featured general increase in aggregate size and content of SOC and N within the large macroaggregates (>2000 μm) at the clayey sites. The microaggregates within the large macroaggregates had accumulated more SOC and N in the midden soil especially at site 1 where 99% of the difference in total SOC between midden and bulk soil was associated with this type of SOC stabilization. At site 2, the increase in SOC found in the large macroaggregates was counteracted by a decrease in SOC in microaggregates within the small macroaggregates (250–2000 μm). No differences in SOC stored in soil fractions were found between midden and non-midden soil at the coarse soil site 3 with higher top soil decomposition rate compared to sites 1 and 2. Across the study sites, the total amount of SOC was 6% higher in midden soil compared to the bulk soil. These results suggest L. terrestris mediates the storage of SOC and N into better protected soil fractions in clay soils under boreal conditions.
25118. 题目: Cobalt-impregnated biochar produced from CO2-mediated pyrolysis of Co/lignin as an enhanced catalyst for activating peroxymonosulfate to degrade acetaminophen
文章编号: N19041109
期刊: Chemosphere
作者: Ming-Tong Yang, Yunchen Du, Wai-Chi Tong, Alex C.K. Yip, Kun-Yi Andrew Lin
更新时间: 2019-04-11
摘要: −While sulfate radical (SO4−)-based processes are useful to degrade acetaminophen (ACE), studies of using peroxymonosulfate (PMS) to degrade ACE are quite limited. In addition, although Co is validated as the most effective metal for activating PMS, very few Co catalysts have been developed and investigated for activating PMS to degrade ACE. Since carbon is a promising substrate to support Co nanoparticles (NPs) to form Co/carbon composite catalysts, most existing carbon substrates require delicate fabrications. As biochar is an easy-to-obtain but versatile carbon material, pyrolysis of Co/lignin affords an advantageous Co-impregnated biochar (CoIB) as an attractive catalyst for PMS activation. Specifically, as CO2 substitutes N2 as a reaction medium for pyrolysis of Co/lignin, the syngas production from pyrolysis can be substantially improved and a magnetic CoIB is afforded. This CoIB consists of evenly-distributed Co nanoparticles (NPs) impregnated in carbon matrices of biochar, and possesses several superior characteristics, such as high porosity, large surface area and magnetism, enabling CoIB a promising catalyst for activating PMS to degrade ACE. CoIB also shows a much higher catalytic activity of PMS activation than CoIBN2, and Co3O4 for degrading ACE. CoIB is also recyclable for activating PMS to effectively degrade ACE for multiple cycles. The ACE degradation pathway by this CoIB-activated PMS is proposed according to the degradation products. These findings validate that CoIB is assuredly an advantageous heterogeneous catalyst, which can be easily prepared from pyrolysis of Co/lignin in CO2 with concomitant enhanced syngas production for effectively activating PMS to degrade ACE.
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25119. 题目: Changes in fluorescent dissolved organic matter and their association with phytoavailable phosphorus in soil amended with TiO2 nanoparticles
文章编号: N19041108
期刊: Chemosphere
作者: Zahra Zahra, Tahir Maqbool, Muhammad Arshad, Mohsin Ali Badshah, Hyung-Kyoon Choi, Jin Hur
更新时间: 2019-04-11
摘要: This study presents the impacts of TiO2 nanoparticles (TNPs) amendment on plant growth, phosphorus (P) content, and dissolved organic matter (DOM) composition in the rhizosphere. For this work, wheat plants (Galaxy-2013) were exposed to soil amended by different amounts of TNPs (i.e., 0, 50, and 100 mg TNP/kg of soil) for 40 days and harvested. The maximum increase in the shoots and roots lengths reached 15.9 ± 0.3% and 3.8 ± 0.3% respectively, which was concurrent with improved P content in the plants. Compared with the control, the P content in the shoots and roots was enriched by 23.4% and 17.9% at 50 mg TNP/kg of soil respectively. The increased electrical conductivity (EC) and decreased pH of the rhizosphere implied that the added TNPs might induce the enhancement of the P dissolution. Fluorescence spectroscopy revealed the increase of microbial activity as depicted by the humification index (HIX) changing from 0.88 ± 0.02 to 0.92 ± 0.01, with increasing TNPs amendments. Excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) showed the presence of four fluorescent components (C1 to C4) in the rhizosphere. Three of them (C1-C3) were related to humic-like substances, while the C4 was associated with protein-like fluorescence. EEM-PARAFAC results revealed the degradation of C4, and the enhancement of the other three components, which supported the stimulation of microbial activity by the TNPs amendment. This study provided new insights into the relation between improved phytoavailble P in plants and the changes in the rhizosphere soil solution chemistry and the DOM composition upon TNPs amendments.
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25120. 题目: Ascidian spicules of Quaternary sediments from the lower slope of the Campos Basin (Brazil)
文章编号: N19041107
期刊: Quaternary International
作者: Elizabete Pedrão Ferreira, Cleber Fernandes Alves, Antonio Enrique Sayão Sanjinés, Mariana Cunha Alves
更新时间: 2019-04-11
摘要: Piston core GL-77 was collected in the lower slope of the northern Campos Basin, Brazil, and consists essentially of muds that have been deposited in turbiditic currents over the last 130 ka, at least, which corresponds to the Upper Pleistocene-Holocene interval. The identified ascidian spicules belong to the Didemnidae Family and are represented by species Micrascidites vulgaris, Bonetia brevis, Rigaudia multiradiata and Monniotia fasciculata. These species have irregular abundance and distribution, with Micrascidites vulgaris being the most common. Their occurrence is interpreted as resulting from transport to the depositional site in response to climate fluctuations (glacial and interglacial periods). The transport of ascidian spicules from a shallow-water sea is supported by the presence of terrestrial organic matter, mainly phytoclasts, sporomorphs and microphytoplankton, which were transported to the slope by the river systems. The results found in this study show that the relative frequency distribution pattern of didemnid spicules is a useful tool for monitoring sediment transport in the slope.