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24581. 题目: Removal of atrazine by biochar-supported zero-valent iron catalyzed persulfate oxidation: Reactivity, radical production and transformation pathway
文章编号: N20022005
期刊: Environmental Research
作者: Zhao Jiang, Jiaojiao Li, Duo Jiang, Yan Gao, Yukun Chen, Wei Wang, Bo Cao, Yue Tao, Lei Wang, Ying Zhang
更新时间: 2020-02-20
摘要: Atrazine is a widely used herbicide whose presence poses a potential threat to agriculture and human living environment. This work studied the degradation performances and mechanisms of zero-valent iron and biochar composite (ZVI/BC) activated persulfate (PS) for atrazine. The results showed that the removal percentage of atrazine reached 73.47% within 30 min. Furthermore, the optimal parameters (175 mg/L ZVI/BC, 2 mM PS and initial pH of 3) were obtained through response surface methodology. Meanwhile, the high atrazine removal percentage (83.77%) was obtained under the optimal conditions. Radical quenching studies and electron spin resonance revealed that active substances produced during PS activation, as well as that SO₄^·− and HO^· were dominant active species for the atrazine degradation. According to iron corrosion products and XPS analysis, the reaction mechanism of ZVI/BC-PS system was proposed as that ZVI loaded on the composites further activated PS to produce SO₄^·− and HO^· which accompany with the valent changing of iron and finally causing degradation of atrazine. In addition, the degradation pathways of atrazine in ZVI/BC-PS system included dealkylation, alkyl oxidation and dechlorination-hydroxylation by the results of GC-MS and LC-MS. These findings demonstrated that ZVI/BC activated persulfate may be an efficient technique for the degradation of atrazine.
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24582. 题目: Microstructural and biochemical diversity of forest soil organic surface layers revealed by density fractionation
文章编号: N20022004
期刊: Geoderma
作者: Jörg Prietzel, Sigrid Hiesch, Gertraud Harrington, Svenja Müller
更新时间: 2020-02-20
摘要: Particularly on sites with shallow, nutrient-poor soils, forest soil organic surface layers (O layers) are important for the storage of plant-available nutrients and water, and thus for forest vitality and productivity. O layers can contain up to 70 mass percent of inorganic compounds (minerals) which may be spatially separated from or closely associated with soil organic matter (SOM). O layer SOM may differ in biochemical properties and resistance against mineralization, depending on the extent of organo-mineral association. Moreover, type and intensity of SOM-mineral mixing in O layers conveys information about biological activity. Here, for the first time we present detailed density fractionation results to distinguish SOM constituents in O layers with different chemical properties and likely also different degrees of organo-mineral association. Additionally, we characterized spatial association patterns of the SOM fractions. We investigated samples of Of (Oe) and Oh (Oa) horizons of temperate forest soils with different parent materials (basalt, gneiss, andesite, Pleistocene gravel, dolomite). The samples were distinguished into six density fractions (ρ < 0.8 g cm⁻³; 0.8–1.0 g cm⁻³; 1.0–1.2 g cm⁻³; 1.2–1.4 g cm⁻³; 1.4–1.6 g cm⁻³; >1.6 g cm⁻³) by sequential treatment with deionized H₂O (ρ = 1.0 g cm⁻³), 1-propanol (ρ = 0.8 g cm⁻³), and sodium polytungstate (SPT) solution of increasing density (ρ = 1.2, 1.4, 1.6 g cm⁻³). The procedure is characterized by a mass recovery of 93 ± 5% and an organic carbon (OC) recovery of 90 ± 9%. In each fraction, we analyzed the concentrations of C, N, metal cations (Fe, Al, Ca, Mg), C speciation (¹³C NMR spectroscopy), as well as abundances of ¹³C and ¹⁵N. For selected fractions, we additionally determined the radiocarbon age and acquired microscopic images. From the Of to the Oh horizons, the contribution of heavy fractions (>1.4 g cm⁻³) to total soil mass and total SOC increased, indicating augmented organo–mineral association with progressive SOM decomposition state. Compared to bulk soil, heavier fractions >1.4 g cm⁻³ were characterized by smaller SOC concentrations, whereas concentrations of Al and Fe were increased for fractions >1.4 g cm⁻³ in the of and >1.6 g cm⁻³ in the Oh horizon. The SOM in the heavy fractions was enriched in N, carboxyl C, and alkyl C, but depleted in O/N-alkyl C and aryl C. Smaller mean particle sizes and C/N ratios as well as increased alkyl C / O/N-alkyl C ratios and ¹³C and ¹⁵N abundances indicate an advanced SOM decomposition state and enrichment of microbial-derived SOM in heavier fractions. However, according to its ¹⁴C signature, in contrast to high-density (ρ > 1.6 g cm⁻³) SOM in the mineral soil, forest floor SOM with high density is a rapidly cycling SOM pool with a turnover time <50 years.
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24583. 题目: Irreversible fouling in hollow-fiber PVDF MF/UF membranes filtering surface water: Effects of precoagulation and identification of the foulant
文章编号: N20022003
期刊: Journal of Membrane Science
作者: Katsuki Kimura, Keita Kume
更新时间: 2020-02-20
摘要: In this study, microfiltration (MF) and ultrafiltration (UF) of surface water were compared in terms of irreversible fouling and effective pretreatment. Hollow-fiber MF/UF membranes made from the same polymer (polyvinylidene fluoride (PVDF)) were examined with multiple samples of surface water used for drinking water production. Experiments were carried out in a realistic style: with a constant flow rate and periodic backwashing. Regardless of the source of the feed water, evolution of fouling was less significant in the case of UF. In the case of MF, anion exchange followed by coagulation using poly-aluminium chloride (PACl) efficiently mitigated membrane fouling, whereas PACl coagulation alone was sufficient for UF. Artificial alteration of the composition of natural organic matter (NOM) in the feed water was carried out by MF/UF with different pore sizes, and it was revealed that different fractions of NOM were responsible for evolution of irreversible fouling in MF and UF: large biopolymers and small biopolymers were responsible for irreversible fouling in MF and UF, respectively. The mechanism of fouling mitigation by coagulation was also investigated. Cake (coagulated flocs) deposited on the membrane surface mitigated irreversible fouling in UF, whereas it did not affect irreversible fouling in MF. It was postulated that advection flow caused by membrane filtration made more adsorption sites available inside the flocs for removal of small biopolymers (i.e., UF foulants).
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24584. 题目: Two-year study of biochar: Achieving excellent capability of potassium supply via alter clay mineral composition and potassium-dissolving bacteria activity
文章编号: N20022002
期刊: Science of The Total Environment
作者: Mengyang Zhang, Muhammad Riaz, Bo Liu, Hao Xia, Zeinab El-desouki, Cuncang Jiang
更新时间: 2020-02-20
摘要: At present, there has been renewed interest in biochar research, but most of them were focused on the short-term effects of biochar and the information of long-term application of biochar is still lacking. In addition, the nutrient mechanism of biochar has rarely been the subject of research. This research explored the effect of potassium (K) nutrient and the response of bacterial communities to biochar in yellow-brown soil based on two-year experiment. In this study, we used peanut shell biochar obtained by pyrolysis at 400 °C, and at the same time, 0%, 20%, 40%, 100% conventional potassium fertilizer were used. The results indicated that the effective improvement of biochar on acidic soil was long-term and 2% biochar replaced 40% conventional potassium fertilizer. Biochar accelerated the conversion of slowly-available K to available K by changing the composition of clay minerals and promoting the growth of K-dissolving bacteria. From the perspective of bacterial community, biochar significantly increased the relative abundance of Sphingomonas, Gaiella, and Elev-16S-1332, which improved the potential ability of soil to degrade pollutants and inhibit pathogens. The pH, organic matter, cation exchange capacity (CEC), and available phosphorus and potassium were important environmental factors that caused significant effects in the bacterial community of yellow-brown soil. Overall, the study demonstrates that biochar is not only an effective alternative to potash fertilizer but also improves soil bacterial communities.
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24585. 题目: The impact of biodegradable carbon sources on nutrients removal in post-denitrification biofilm reactors
文章编号: N20022001
期刊: Science of The Total Environment
作者: Artur Mielcarek, Joanna Rodziewicz, Wojciech Janczukowicz, Joanna Struk-Sokołowska
更新时间: 2020-02-20
摘要: Wastewater from households wastewater treatment plants (HWWTP) is discharged to the ground or to the surface waters. Special consideration should be given to the improvement of HWWTP effectiveness, particularly in relation to nutrients. The addition of biodegradable carbon sources to biofilm reactor, can enhance microbial activity but may also lead to filling clogging. The study aimed to compare 3 different organic substrates: acetic acid (commonly applied)and two untypical - citric acid and waste beer, under the same operational conditions in a post-denitrification biofilm reactor. The study investigated the impact of a type of organic substrate, low pH and time on: (1) biofilm growth, (2) the characteristics of extracellular polymeric substances (EPS), (3) the kinetics of nutrients removal and (4) reactor clogging. Results were referred to (5) the effectiveness of nutrients removal. The study demonstrated that low pH assured the development of a thinbiofilm. Citric acid ensured the lowest biomass volume, being by 53% lower than in the reactor with acetic acid and by as much as 61% lower than in the reactor with waste beer. The soluble EPS fraction prevailed in the total EPS in all reactors. The content of the tightly bound EPS fraction ranged from 26.93% (citric acid) to 36.32% (waste beer). Investigations showed also a high ratio of exoproteins to polysaccharide in all fractions, which indicated a significant role of proteins in developing a highly-proliferating biofilm. The treated wastewater met requirements of Polish regulations concerning COD and nitrogen concentrations.
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24586. 题目: Water quality changes and organic matter removal using natural bank infiltration at a boreal lake in Finland
文章编号: N20021907
期刊: Hydrogeology Journal
作者: M. Jylhä-Ollila, H. Laine-Kaulio, P. Niinikoski-Fusswinkel, J. Leveinen, H. Koivusalo
更新时间: 2020-02-19
摘要: Managed aquifer recharge (MAR) refers to intentional infiltration of surface water to an aquifer for facilitating natural water treatment and storage. MAR is often used as a treatment to remove natural organic matter from water in drinking water production. The sustainability of MAR depends on how the aquifer capacity to remove organic matter will evolve over the long term. This report explores the behavior of MAR systems by using a natural lake–aquifer system as a surrogate. Natural infiltration of lake water to groundwater has been going on for millennia at the research site in Finland chosen for this study. According to the measurements, the mean concentration of total organic carbon (TOC) in lake water was 3.0 mg/L. Within the distance of 3 m from the lake bank (retention time 7–15 days), already 46% of TOC was removed. At greater distances along the flow paths within the aquifer, 80–90% of TOC was removed. The observed TOC removal in the aquifer was slightly higher than the reported values at MAR sites, indicating that MAR can be an effective solution to the problem of removing natural organic matter in the long term. Signs of accumulation of organic matter were not observed in the aquifer, which suggests that biodegradation was the main removal method, and the role of sorption was minor. Several processes had an impact on oxygen levels in the aquifer, which led to spatial and seasonal changes in the redox conditions and in the iron and manganese concentrations in groundwater.

24587. 题目: Nitrifier adaptation to low energy flux controls inventory of reduced nitrogen in the dark ocean
文章编号: N20021906
期刊: Proceedings of the National Academy of Sciences
作者: Yao Zhang, Wei Qin, Lei Hou, Emily J. Zakem, Xianhui Wan, Zihao Zhao, Li Liu, Kristopher A. Hunt, Nianzhi Jiao, Shuh-Ji Kao, Kai Tang, Xiabing Xie, Jiaming Shen, Yufang Li, Mingming Chen, Xiaofeng Dai, Chang Liu, Wenchao Deng, Minhan Dai, Anitra E. Ingalls, David A. Stahl, Gerhard J. Herndl
更新时间: 2020-02-19
摘要: Ammonia oxidation to nitrite and its subsequent oxidation to nitrate provides energy to the two populations of nitrifying chemoautotrophs in the energy-starved dark ocean, driving a coupling between reduced inorganic nitrogen (N) pools and production of new organic carbon (C) in the dark ocean. However, the relationship between the flux of new C production and the fluxes of N of the two steps of oxidation remains unclear. Here, we show that, despite orders-of-magnitude difference in cell abundances between ammonia oxidizers and nitrite oxidizers, the two populations sustain similar bulk N-oxidation rates throughout the deep waters with similarly high affinities for ammonia and nitrite under increasing substrate limitation, thus maintaining overall homeostasis in the oceanic nitrification pathway. Our observations confirm the theoretical predictions of a redox-informed ecosystem model. Using balances from this model, we suggest that consistently low ammonia and nitrite concentrations are maintained when the two populations have similarly high substrate affinities and their loss rates are proportional to their maximum growth rates. The stoichiometric relations between the fluxes of C and N indicate a threefold to fourfold higher C-fixation efficiency per mole of N oxidized by ammonia oxidizers compared to nitrite oxidizers due to nearly identical apparent energetic requirements for C fixation of the two populations. We estimate that the rate of chemoautotrophic C fixation amounts to ∼1 × 10 13 to ∼2 × 10 13 mol of C per year globally through the flux of ∼1 × 10 14 to ∼2 × 10 14 mol of N per year of the two steps of oxidation throughout the dark ocean.

24588. 题目: Advanced landfill leachate biochemical effluent treatment using Fe-Mn/AC activates O 3 /Na 2 S 2 O 8 process: process optimization, wastewater quality analysis, and activator characterization
文章编号: N20021905
期刊: Environmental Science and Pollution Research
作者: Zhanmeng Liu, Liang Pan, Fengping Hu, Yunqi Hu
更新时间: 2020-02-19
摘要: A novel catalyst of Fe-Mn/AC was prepared and used as a heterogeneous catalyst to activate O₃/Na₂S₂O₈ for landfill leachate biochemical effluent treatment. The experimental results indicated that the highest COD (84%) and color (98%) removal was obtained at Fe-Mn/AC dosage 1.2 g/L, O₃ concentration 1.2 g/L, Na₂S₂O₈ dosage 6 g/L, initial pH 10, and reaction time 100 min. Three-dimensional and excitation emission matrix (3D-EEM) fluorescence spectrometry, Fourier transform infrared spectroscopy (FTIR), and gas chromatography mass spectrometry (GC/MS) of wastewater samples before and after treatment demonstrated that the leachate biochemical effluent contained a large amount of humic and fulvic acid organic compounds. After treatment with this coupling system, both the pollution level of dissolved organic matter (DOM) and the fluorescence intensity declined. The micro morphology of Fe-Mn/AC was characterized using scanning X-ray diffraction patterns (XRD), electron microscope spectra (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. It can be concluded that the microscopic morphology of the catalyst is porous. The main active components are amorphous MnO₂ and multivalent iron oxides. Furthermore, the Fe-Mn/AC catalyst showed great reusability; the removal efficiency of COD was only reduced from 84% to 79% at the fourth reaction. Moreover, the COD removal efficiency could recover to 81% after catalyst regeneration.

24589. 题目: Effect of Fe–Mn–Ce modified biochar composite on microbial diversity and properties of arsenic-contaminated paddy soils
文章编号: N20021904
期刊: Chemosphere
作者: Guogang Zhang, Xuewei Liu, Minling Gao, Zhengguo Song
更新时间: 2020-02-19
摘要: In this study, we investigated the mechanism of decrease in arsenic (As) bioavailability after addition of biochar (BC) supplemented with iron (Fe)- manganese (Mn)- cerium (Ce) oxide (FMCBC) to As-contaminated paddy soil. We explored the effects of these composites on the oxidation, reduction, microbial community, and soil enzyme activity of As-contaminated paddy soil. Results showed that FMCBCs improve soil pH, significantly improve the redox capacity of soil, and reduce bioavailable forms of As. FMCBCs can convert As from a specifically or non-specifically bound form into amorphous hydrous oxide bound- and crystalline hydrous oxide bound form. The application of FMCBCs increased soil enzyme activity (urease, catalase, alkaline phosphatase, and peroxidase), and greatly influenced the relative abundance of certain microorganisms (Proteobacteria, Acidobacteria, and Gemmatimonadetes), which improved soil enzyme heavy metal tolerance and prevented their denaturation. Thus, FMCBCs can not only change the form and distribution of As in soil but also create an environment suitable for microbial growth, consequently affecting the geochemical cycling of As in soil.

24590. 题目: Reviews and syntheses: The mechanisms underlying carbon storage in soil
文章编号: N20021903
期刊: Biogeosciences
作者: Isabelle Basile-Doelsch, Jérôme Balesdent, and Sylvain Pellerin
更新时间: 2020-02-19
摘要: Scientific research in the 21st century has considerably improved our knowledge of soil organic matter and its dynamics, particularly under the pressure of the global disruption of the carbon cycle. This paper reviews the processes that control C dynamics in soil, the representation of these processes over time, and their dependence on variations in major biotic and abiotic factors. The most recent advances in soil organic matter knowledge are:

24591. 题目: Characterizing the interactions between sediment dissolved organic matter and zinc using multispectroscopic techniques
文章编号: N20021902
期刊: Environmental Pollution
作者: Weiwei Lü, Xin Yao, Haoyu Ren, Huanguang Deng, Min Yao, Baohua Zhang
更新时间: 2020-02-19
摘要: Sediment dissolved organic matter (DOM) was collected in November 2018 from Lake Dongping, China. The lake was divided into the entrance of the Dawen River, the open region of the lake, the tourism district and the macrophyte-dominated region based on principal component analysis (PCA) of 9 DOM-related parameters. Multispectroscopic tools were used to investigate the binding of zinc (Zn) with four kinds of DOM collected from the entrance of the Dawen River (EDOM), the open area of the lake (ODOM), the macrophyte-dominated area (mainly dominated by Potamogeton crispus L.) (PDOM) and the tourism district (TDOM). Three fluorescent components, the humic-like (components 1 and 3) and protein-like (component 2) components, were found by excitation-emission matrix spectra with parallel factor analysis. The EDOM, ODOM and TDOM were controlled by protein-like components, and the PDOM was controlled by humic-like components. Different components respond differently to Zn addition. The binding order of the tyrosine-like fraction > the tryptophan fraction > the humic-like fraction was identified by Synchronous fluorescence (SF) spectra and two-dimensional correlation spectroscopy (2D-COS). The fluorescence intensity of the protein-like component was suppressed, and the humic-like component was enhanced with the addition of Zn. The effective quenching constants (log K) of the protein-like component in PDOM were clearly higher than those in the EDOM, ODOM and TDOM, indicating higher metal binding potential in PDOM than in other kinds of DOM in Lake Dongping. The %F_max (the amounts of each component measured as % of the total fluorescence maxima for the three components) of the humic-like components exhibited a gradual increase in all kinds of DOM with the addition of Zn, suggesting that the addition of Zn increased the humification of DOM.
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24592. 题目: Influence of granular activated carbon media properties on natural organic matter and disinfection by-product precursor removal from drinking water
文章编号: N20021901
期刊: Water Research
作者: D.M. Golea, P. Jarvis, B. Jefferson, G. Moore, S. Sutherland, S.A. Parsons, S.J. Judd
更新时间: 2020-02-19
摘要: Operational and financial constraints challenge effective removal of natural organic matter (NOM), and specifically disinfection by-product (DBP) precursors, at remote and/or small sites. Granular activated carbon (GAC) is a widely used treatment option for such locations, due to its relatively low maintenance and process operational simplicity. However, its efficacy is highly dependent on the media capacity for the organic matter, which in turn depends on the media characteristics.The influence of GAC media properties on NOM/DBP precursor removal has been studied using a range of established and emerging media using both batch adsorption tests and rapid small-scale column tests. DBP formation propensity (DBPFP) was measured with reference to trihalomethanes (THMs) and haloacetic acids (HAAs). All GAC media showed no selectivity for specific removal of precursors of regulated DBPs; DBP formation was a simple function of residual dissolved organic carbon (DOC) levels.UV₂₅₄ was found to be a good surrogate measurement of DBPFP for an untreated water source having a high DOC. Due to the much-reduced concentration of DBP precursors, the correlation was significantly poorer for the coagulation/flocculation-pretreateed water source.Breakthrough curves generated from the microcolumn trials revealed DOC removal and consequent DBP reduction to correlate reasonably well with the prevalence pores in the 5–10 nm range. A 3–6 fold increase in capacity was recorded for a 0.005–0.045 cm³/g change in 5–10 nm-sized pore volume density. No corresponding correlation was evident with other media pore size ranges.
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24593. 题目: Mechanisms of Pb and/or Zn adsorption by different biochars: Biochar characteristics, stability, and binding energies
文章编号: N20021804
期刊: Science of The Total Environment
作者: Man Zhao, Yuan Dai, Miaoyue Zhang, Can Feng, Baojia Qin, Weihua Zhang, Nan Zhao, Yaying Li, Zhuobiao Ni, Zhihong Xu, Daniel C.W. Tsang, Rongliang Qiu
更新时间: 2020-02-18
摘要: Biochar has been widely studied as an amendment for use in remediation of water and soil contaminated with heavy metals such as Pb²⁺ and Zn²⁺, but the effects of biochar characteristics, including stability, on the competitive adsorption of Pb²⁺ and Zn²⁺ by biochars from various sources are incompletely understood. In this work, biochars from three different feedstocks, including rice straw (RS), chicken manure (CM), and sewage sludge (SS), were prepared at two pyrolysis temperatures, 550 and 350 °C, and tested to investigate the influence of their stabilities and other characteristics on their adsorption of Pb²⁺ and Zn²⁺ in both single- and binary-metal systems. RS biochar had the highest carbon and hydrogen contents, greatest number of functional groups (e.g., OH and C=C/C=O), highest pH, most negative surface charge, and highest physical stability, and thus the highest adsorption capacity for Pb²⁺ and Zn²⁺. Pyrolysis at the higher temperature resulted in a slight decrease in aromatic functional groups on biochar surfaces but higher adsorption capacities for Pb²⁺ and Zn²⁺ due to the decreased biochar particle size and increased specific surface area. FTIR, XRD, and XPS analyses indicated that Pb²⁺ and Zn²⁺ were absorbed on the biochars primarily via chemical complexation with aromatic functional groups. Quantum chemistry calculations confirmed that these functional groups (e.g., –OH and-COOH) tended to bind more strongly with Pb²⁺ than with Zn²⁺ due to the former's lower binding energies, which also accounted for the notable decrease in adsorption of Zn²⁺ in the presence of Pb²⁺. In addition, compared to carboxyl groups, hydroxyl groups had smaller binding energies and stronger metal complexation. These findings provide a theoretical basis for improved understanding of potential applications of biochars in environmental remediation.
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24594. 题目: Monitoring dissolved organic carbon by combining Landsat-8 and Sentinel-2 satellites: Case study in Saginaw River estuary, Lake Huron
文章编号: N20021803
期刊: Science of The Total Environment
作者: Jiang Chen, Weining Zhu, Yong Q. Tian, Qian Yu
更新时间: 2020-02-18
摘要: Dissolved organic carbon (DOC) in aquatic environments is an important cycled pool of organic matter on the Earth. Satellite remote sensing provides a useful tool to determine spatiotemporal distribution of water quality parameters. Previous DOC remote sensing studies in inland water suffered from either low spatial resolution or low temporal frequency. In this study, we evaluated the potential of jointly using Landsat-8 and Sentinel-2 with high spatial resolution to estimate DOC concentrations in Saginaw River plume regions of Lake Huron. Firstly, CDOM (colored dissolved organic matter) was estimated from images using the known models and then DOC can be derived in terms of the good correlations between DOC and CDOM. The results show that Landsat-8 and Sentinel-2 had acceptable accuracy and good consistency in DOC estimation so that jointly using them can improve the observation frequency. In different seasons from 2013 to 2018, DOC was typically higher in spring and autumn but lower in summer. Monthly spatiotemporal variations of DOC in 2018 were also observed. The image-derived DOC spatiotemporal variations show that DOC was covaried with Saginaw River discharge (r = 0.82) and also weakly and negatively correlated with water temperature (r = −0.6). This study demonstrated that using Landsat-8 and Sentinel-2 together can offer the potential applications for monitoring DOC and water quality dynamic in complex inland water.
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24595. 题目: Terrestrial loads of dissolved organic matter drive inter-annual carbon flux in subtropical lakes during times of drought
文章编号: N20021802
期刊: Science of The Total Environment
作者: Chih-Yu Chiu, John R. Jones, James A. Rusak, Hao-Chi Lin, Keisuke Nakayama, Timothy K. Kratz, Wen-Cheng Liu, Sen-Lin Tang, Jeng-Wei Tsai
更新时间: 2020-02-18
摘要: Lentic ecosystems are important agents of local and global carbon cycling, but their contribution varies along gradients of dissolved organic matter (DOM) and productivity. We investigated how contrasting summer and autumn precipitation can shape annual and inter-annual variation in ecosystem carbon (C) flux (gross primary production (GPP), ecosystem respiration (ER), and CO₂ efflux) in two subtropical lakes differing substantially in trophic state and water color. Instrumented buoys recorded time series of free-water DO, terrestrial DOM (tDOM), chlorophyll a, water temperature profiles, and meteorological measurements over five years (2009–2011 and 2014–2015). Reduced precipitation caused immediate and prolonged effects on C flux in both lakes. During the drought year (2014) GPP and ER declined by 60 to 80% and both lakes were either CO₂ sinks or neutral. In the subsequent wet year (2015), GPP and ER increased by 40 to 110%, and both lakes shifted to strong net CO₂ emitters. Higher ecosystem R resulted from larger GPP while higher tDOM contributed to a dramatic increase in dissolved inorganic carbon, which intensified CO₂ emission in both lakes. C flux was more responsive in the clear mesotrophic lake, declining by approximately 40% in the cumulative GPP and ER, and increasing by >400% in CO₂ efflux whereas changes in the oligotrophic colored lake were more modest (approximately 30% and 300% for metabolic declines and efflux increases, respectively). Temporal variation and magnitude of C flux were governed by tDOM-mediated changes in epilimnetic nutrient levels and hypolimnetic light availability. This study demonstrated terrestrial loads of DOM strongly influence the inter-annual response and sensitivity of ecosystem C flux to variation in inter-annual precipitation. Our findings have important implications for predicting the trend, magnitude, duration, and sensitivity of the response of C flux in subtropical lakes/reservoirs to future changes in precipitation patterns under altered climatic conditions.
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24596. 题目: Sterol, fatty acid, and lignin biomarkers identify the response of organic matter accumulation in Englebright Lake, California (USA) to climate and human impacts
文章编号: N20021801
期刊: Organic Geochemistry
作者: Christina R. Pondell, Elizabeth A. Canuel
更新时间: 2020-02-18
摘要: Climate change is one of the biggest challenges facing humankind. Higher temperatures and changes in precipitation will lead to greater frequency of drought, wildfire, and intense storms that will threaten systems already vulnerable to climate and anthropogenic change. These threats will transform carbon delivery across the terrestrial–aquatic interface. This study investigated how anthropogenic activities and climate influence organic carbon delivery using Englebright Lake, a reservoir in California, as a model system. Organic carbon accumulation in three depositional settings (bottomset, foreset, topset) was analyzed using fatty acid, sterol and lignin biomarkers and compared to records of watershed events to determine responses to dam construction, mining impacts and flood events. Concentrations of long chain saturated fatty acids, plant sterols, epi-brassicasterol/brassicasterol and lignin biomarkers increased by an order of magnitude in foreset deposits in response to flood events (p < 0.007 for each biomarker). Hydraulic mining for gold was recorded as near-zero concentrations of terrigenous biomarkers in topset deposits, whereas decreases in diacids coincident with increases in aquatic sterols in bottomset deposits reflected the response to dam construction (p < 0.007 for each biomarker). Organic carbon accumulation was controlled by event magnitude and duration, and climate-driven event signals were up to an order of magnitude larger than anthropogenic-driven event signals. These data demonstrate the importance of understanding the depositional environment because the ability to characterize three different depositional settings in Englebright Lake enabled us to identify the smaller anthropogenic signals that would have been obscured by the much larger response to climate events.

24597. 题目: Characterization of water-insoluble oxidative potential of PM2.5 using the dithiothreitol assay
文章编号: N20021702
期刊: Atmospheric Environment
作者: Dong Gao, James A. Mulholland, Armistead G. Russell, Rodney J. Weber
更新时间: 2020-02-17
摘要: Both water-soluble and insoluble components of ambient particulate matter (PM) have been shown to contribute to the oxidative potential (OP) of PM. In this study, we used the dithiothreitol (DTT) assay to assess the water-soluble (OPWS−DTT) and total OP (OPtotal−DTT) of ambient fine particles (PM2.5), with water-insoluble OP (OPWI−DTT) determined by difference. Ambient PM2.5 filter samples were collected daily during 2017 in urban Atlanta and were analyzed for OP and major PM components. Results from measurements suggested a measurable contribution of water-insoluble components to OPDTT, which comprised on average 20% of total PM OP. Strong seasonal trends were observed in both volume- and mass-normalized OPtotal−DTT and OPWI−DTT, with higher values in the winter than in the summer, possibly driven by biomass burning emission seasonality. Correlation analysis indicated that all forms of OPDTT measurements were related to organic species and metals. OPtotal−DTT and OPWI−DTT were correlated with brown carbon (BrC) and total metals, especially total crustal elements. A multivariate regression model was developed for OPtotal−DTT based on particle composition data. The model suggested that the variability of OPtotal−DTT was primarily affected by BrC, followed by EC, total Cu and an antagonistic interaction between BrC and total Cu.

24598. 题目: Co-transport behavior of ammonium and colloids in saturated porous media under different hydrochemical conditions
文章编号: N20021701
期刊: Environmental Science and Pollution Research
作者: Jingqiao Li, Wenjing Zhang, Yunqi Qin, Xiaofei Li, Shengyu Wu, Juanfen Chai, Shanghai Du
更新时间: 2020-02-17
摘要: To investigate co-transport behavior of ammonium and colloids in saturated porous media under different hydrochemical conditions, NH₄⁺ was selected as the target contaminant, and silicon and humic acid (HA) were selected as typical organic and inorganic colloids in groundwater. Column experiments were then conducted to investigate the transport of NH₄⁺ colloids under various hydrochemical conditions. The results showed that because of the different properties of colloidal silicon and HA after combining with NH₄⁺, the co-transport mechanism became significantly different. During transport by the NH₄⁺–colloid system, colloidal silicon occupied the adsorption sites on the medium surface to promote the transport of NH₄⁺, while humic acid (HA) increased the number of adsorption sites of the medium to hinder the transport of NH₄⁺. The co-transport of NH₄⁺ and colloids is closely related to hydrochemical conditions. In the presence of HA, competitive adsorption and morphological changes of HA caused NH₄⁺ to be more likely to be transported at a higher ionic strength (IS = 0.05 m, CaCl₂) and alkalinity (pH = 9.3). In the presence of colloidal silicon, blocking action caused the facilitated transport to be dependent on higher ionic strength and acidity (pH = 4.5), causing the recovery of NH₄⁺ to improve by 7.99%, 222.25% (stage 1), and 8.63%, respectively. Moreover, transport increases with the colloidal silicon concentrations of 20 mg/L then declines at 40 mg/L, demonstrating that increased concentrations will lead to blocking and particle aggregation, resulting in delayed release in the leaching stage.

24599. 题目: Spatially Resolved Organomineral Interactions across a Permafrost Chronosequence
文章编号: N20021607
期刊: Environmental Science & Technology
作者: Tyler D. Sowers, Rucha P. Wani, Elizabeth K Coward, Matthew H.H. Fischel, Aaron R. Betts, Thomas A. Douglas, Owen W. Duckworth, Donald L. Sparks
更新时间: 2020-02-16
摘要: Permafrost contains a large (1700 Pg C) terrestrial pool of organic matter (OM) that is susceptible to degradation as global temperatures increase. Of particular importance is syngenetic Yedoma permafrost containing high OM content. Reactive iron phases promote stabilizing interactions between OM and soil minerals and this stabilization may be of increasing importance in permafrost as the thawed surface region (active layer) deepens. However, there is limited understanding of Fe and other soil mineral phase associations with OM carbon (C) moieties in permafrost soils. To elucidate the elemental associations involved in organomineral complexation within permafrost systems, soil cores spanning a Pleistocene permafrost chronosequence (19,000, 27,000, and 36,000 years old) were collected from an underground tunnel near Fairbanks, Alaska. Subsamples were analyzed via scanning transmission X-ray microscopy–near edge X-ray absorption fine structure spectroscopy at the nano- to microscale. Amino acid-rich moieties decreased in abundance across the chronosequence. Strong correlations between C and Fe with discrete Fe(III) or Fe(II) regions selectively associated with specific OM moieties were observed. Additionally, Ca coassociated with C through potential cation bridging mechanisms. Results indicate Fe(III), Fe(II), and mixed valence phases associated with OM throughout diverse permafrost environments, suggesting that organomineral complexation is crucial to predict C stability as permafrost systems warm.

24600. 题目: Valorization of biomass waste to engineered activated biochar by microwave pyrolysis: Progress, challenges, and future directions
文章编号: N20021606
期刊: Chemical Engineering Journal
作者: Shin Ying Foong, Rock Keey Liew, Yafeng Yang, Yoke Wang Cheng, Peter Nai Yuh Yek, Wan Adibah Wan Mahari, Xie Yi Lee, Chai Sean Han, Dai-Viet N. Vo, Quyet Van Le, Mortaza Aghbashlo, Meisam Tabatabaei, Christian Sonne, Wanxi Peng, Su Shiung Lam
更新时间: 2020-02-16
摘要: Biomass waste represents the promising surrogate of fossil fuels for energy recovery and valorization into value-added products. Among thermochemical conversion techniques of biomass, pyrolysis appears to be most alluring owing to its low pollutant emission and diverse products formation. The current pyrolysis applications for valorization of biomass waste is reviewed, covering the key concepts, pyrolysis mode, operating parameters and products. To date, existing types of pyrolysis include conventional pyrolysis (poor heat transfer due to non-selective heating), vacuum pyrolysis (lower process temperature because of vacuum), solar pyrolysis (entirely “green” with solar-powered), and a newly touted microwave pyrolysis. In microwave pyrolysis of biomass, the heat transfer is more efficient as the heat is generated within the core of material by the interaction of microwave with biomass. The plausible mechanisms of microwave heating are dipole polarization, ionic conduction and interfacial polarization. The lack of top-tier reactor design is identified as the main obstacle that impedes the commercialization of microwave pyrolysis in biomass recycling. Based on the existing works, it is surmised that microwave pyrolysis of biomass produces solid biochar as a main product. To confront the great market demand of activated biochar, it is proposed that the solid char could be upgraded into engineered activated biochar with desirable properties for wide application in pollution control, catalysis and energy storage. Hence, the production of engineered activated biochar from microwave pyrolysis process and its applications are reviewed and explicitly discussed to fill the research gap, and the key implications for future development are highlighted.
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