81. 题目: Biochar acting as an electron acceptor reduces nitrate removal in woodchip denitrifying bioreactors
期刊: Ecological Engineering
作者: Bahareh Hassanpour, Seyed Fardad Riazi, Erin G. Menzies Pluer, Larry D. Geohring, Christian D. Guzman, Tammo S. Steenhuis
摘要: Woodchip denitrifying bioreactors mitigate nitrate loading from agricultural tile effluents. Biochar is considered as an amendment to woodchips. Research findings are contradictory regarding the effect of biochar on nitrate removal. The current study is aimed at investigating the effect of biochar on the removal of nitrate in denitrifying bioreactors. For this purpose, laboratory and field experiments were carried out. In the laboratory, cylindrical up-flow bioreactors were used that were filled with woodchips and oxidized biochar at rates of 0%, 12.5%, 25%, 50% by volume. The removal of nitrate was investigated at two stages: unaged and aged for 16 weeks. The bioreactors were operated at four hydraulic retention times of 2, 4, 8, and 24 h. Additionally, we measured the concentrations of greenhouse gases in the laboratory bioreactors. In the field, nitrate removal over a 6-year period was investigated in two denitrifying bioreactors, one of which amended with 10% fresh biochar. The laboratory experiments showed that, on average, oxidized biochar (OB) amendment reduced nitrate removal by 9% in unaged and 13% in aged bioreactors while the respiration was equal or greater. This led us to conclude that oxidized biochar acted as an electron acceptor. In addition, oxidized biochar increased greenhouse gas concentrations. In the field bioreactors, fresh biochar initially increased nitrate removal. However, biochar became less effective over six years. In the final year, the biochar-amended bioreactor removed less nitrate than the woodchip bioreactor, which was ascribed to the electron-accepting ability of biochar due to aging. In sum, our study showed that biochar's electron acceptability significantly reduced denitrification in denitrifying bioreactors.
82. 题目: Molecular level characterisation of ion-exchange water treatment coupled to ceramic membrane filtration
期刊: Environmental Science: Water Research & Technology
作者: Alan J.R. Smith, Graeme Moore, Andrea Semiao, Dusan Uhrin
摘要: FT-ICR MS, NMR and ATR-FTIR were used to gain insight into the dissolved organic matter (DOM) removal process throughout a pilot water treatment system. The pilot plant under study utilises suspended ion exchange (SIX) followed by in-line coagulation with (ILCA) polyaluminium chloride and ceramic membrane filtration (CMF). MS results indicate that the SIX treatment is removing DOM irrespective of the compound type (>90% formulae similarity between SIX treated and raw water). However, the ILCA-CMF treatment substantially altered the chemical composition of the DOM by removing a high proportion of the aromatic and phenolic compounds. This was also confirmed by NMR and ATR-FTIR. An adjoining WTW plant which uses the same coagulant as the pilot plant, flocculation mixers for inline flocculation and filtration via MEMCOR® hydrophilic membranes did not show any selectivity when processing the same inlet water. Removal of aromatics/polyphenols in the pilot plant can therefore be attributed to the CMF step. Removal of aromatic/phenolic compounds is important, as these are known to react more readily with chlorine, potentially producing trihalomethanes - substances regulated in potable water.
83. 题目: The role of fluorescent dissolved organic matter on mercury photoreduction rates: a case study of three temperate lakes
期刊: Geochimica et Cosmochimica Acta
作者: Jisook Yang, Jihee Kim, Anne L. Soerensen, Woojin Lee, Seunghee Han
摘要: The formation of dissolved gaseous mercury (DGM) in lake water is mainly attributed to photochemical processes mediated by dissolved organic matter (DOM). In this study, we explored how different DOM components influence the Hg(II) photoreduction rate constant (kr) in lake surface water. For this purpose, the kr and the fluorescence properties of DOM were obtained from three Korean lakes with different trophic states. Three major fluorophores were identified by excitation-emission matrix fluorescence spectroscopy combined with a parallel factor analysis: plant-derived terrigenous humic-like DOM (C1), autochthonous DOM (C2), and soil fulvic-like DOM (C3). The principal component analysis (PCA) loading matrix demonstrated that kr increases when bulk DOM has high flavin-like and soil-derived fulvic-like fractions. The results of a Pearson's correlation agreed with the outcome of the PCA analysis: kr showed a strong positive correlation with the soil fulvic-like DOM component (r = 0.92) and the redox index (r = 0.92). This was further confirmed by a partial least squares-regression model that predicted kr (r = 0.99) using multiple DOM components. Overall, our results suggest that kr can be modeled using fluorescence intensities of diverse DOM components, which in turn has the potential to be incorporated into Hg biogeochemical models to better predict the variability of Hg redox rates across lake systems.
84. 题目: Biochar increases nitrogen use efficiency of maize by relieving aluminum toxicity and improving soil quality in acidic soil
期刊: Ecotoxicology and Environmental Safety
作者: Hao Xia, Muhammad Riaz, Mengyang Zhang, Bo Liu, Zeinab El-Desouki, Cuncang Jiang
摘要: The low nitrogen use efficiency (NUE) of fertilizers and aluminum toxicity are major limiting factors for crop development in red soil (acidic soil) of China. Biochar is a promising material for improving soil quality, alleviating aluminum and acidic toxicity. The present study was conducted on maize to evaluate the effects of biochar on NUE and soil quality under different applications of nitrogen fertilizer. Biochar was used in the following five levels in each pot; C0 (0 g), C1 (7.5 g), C2 (15 g), C3 (30 g), C4 (45 g), in combination with δ15N at two N levels: N0 (0 g kg−1) and N1 (0.2 g kg−1). The biochar increased soil nutrients, exchangeable cation, and SOM. Compared with C0, the K+, Ca2+, and Mg2+ were increased by 31.58%, 95.87%, and 463.75% while total Al3+ content of C4 treatment was decreased by 91.98%–93.30% in soil, respectively. X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) showed that Al2SiO5 was adsorbed on the surface of biochar in the soil due to the special physical structure of biochar. Besides, the results showed that root and shoot biomass increased by 44.5% and 89.6%, respectively under biochar treatment. The nitrogen utilization rate of the plant was increased by 11.08% after the amendment of biochar to soil. The δ15N content was increased from 11.97 to 21.32 for root and from 50.84 to 82.33 mg kg−1 for the shoot. The use of biochar with N fertilizer showed a more positive effect on improving NUE of maize and facilitating soil quality. Our results suggest that biochar could be used to improve soil available nutrients, alleviate aluminum toxicity and acidic toxicity. Therefore, biochar could also increase the NUE of maize by adjusting soil quality.
85. 题目: Bioavailability of dissolved organic matter in biogas slurry enhanced by catalytic ozonation combined with membrane separation
期刊: Ecotoxicology and Environmental Safety
作者: Lipeng Gu, Xin Tang, Ying Sun, Huijuan Kou
摘要: Large molecular weight pig biogas slurry (L-PBS) and small molecular weight pig biogas slurry (S-PBS) were separated from original pig biogas slurry (O-PBS) using a 100 kDa membrane. The original bioavailability and biosafety of L-PBS was very low. In order to enhance the total bioavailable dissolved organic nitrogen (TB-DON) and total bioavailable dissolved organic phosphorus (TB-DOP), optimum catalytic ozonation of L-PBS conditions were determined using Box-behnken design models (P < 0.0001) and intersection tests. The optimal values for ozone concentration, pH value, active catalyst concentration and reaction time were 2.63 mg·L−1, 6.48, 1.43 g·L−1 and 40 min, respectively. Catalytic ozonation can effectively decompose and transform 68.07% of L-PBS into S-PBS to improve content organic bioavailability, with a molecular weight distribution of 0–1 kDa (13.53%), 1–5 kDa (16.62%), 5–10 kDa (11.16%), 10–30 kDa (11.73%), 30–100 kDa (15.04%). Catalytic ozonation of L-PBS can reduce protein levels from 85.28% to 47.18%, but increases the proportion of fulvic and humic components from 10.22% to 32.67% and 4.51%–20.15%, respectively. Because catalytic ozonation changes the internal components and molecular weights of L-PBS, both saw increases in TB-DON and TB-DOP from 3.33% to 41.12% and 2.43%–37.88%, respectively, with a large number of TB-DON and TB-DOP derived from hydrophilic organic components during catalytic ozonation. These important internal mechanisms changed by catalytic ozonation can effectively reduce the ecotoxicity (IR, from 76.5% to 33.1%) and phytotoxicity (GI, enhanced from 35.4% to 70.3%) of L-PBS. Therefore, catalytic ozonation combined with membrane separation is a choice technology in improving the nutrition of biogas slurry and reduce its ecological risk.
86. 题目: Roles of non-ionic surfactant sucrose ester on the conversion of organic matters and bacterial community structure during composting
期刊: Bioresource Technology
作者: Gen Li, Qiuhui Zhu, Zhiwei Jiang, Mingqi Li, Chaofan Ma, Xintian Li, Haibo Liu, Youyan Liu, Qunliang Li
摘要: The purpose of this study was to investigate the effect of sucrose ester (SE) addition on the physico-chemical parameters, organic matter (OM) biodegradation and related bacterial communities structure in dairy manure and cassava residuals co-composting. The biodegradation rates of OM, dissolved organic matters (DOM) and lignocellulose in SE (16.34%, 44.11% and 26.73%) group were higher than those in CK (14.71%, 39.11% and 19.90%). In addition, the content of humic substances (HS) (36.34%) in SE was obviously higher than that in CK (17.68%). The relative abundance of bacterial community in SE changed, in which the abundance of Firmicutes and Actinobacteria increased, while the amount of Blastomonas decreased. Redundancy analysis indicated Bacillus and Acinetobacter were positively correlated with the temperature and OM, whereas Azomonas and Luteimonas showed a positive relation with pH. In conclusion, the amendment of SE accelerated the degradation and conversion of organic matters, enhanced the formation of HS and improved the quality of compost.
87. 题目: Evaluating performance of nitrogen and organic carbon removal in a single reactor by using A. faecalis strain NR aerobically
期刊: Bioresource Technology
作者: Bin Zhao, Dan Yang Chen, Peng Zhang, Xiao Chuan Ran, Jin Song Guo
摘要: The performance of nitrogen and organic carbon removal in a single reactor (R1) operating with A. faecalis strain NR aerobically was assessed. Under 150 mg/L influent NH4+-N, 91.3%, 71.4% and 90.9% of NH4+-N, TN and TOC were removed, presenting much higher efficiency than a control bioreactor inoculating activated sludge (R0). The amoA gene expression from strain NR in R1 was 7.8 times higher than that from activated sludge in R0, demonstrating the role of strain NR in removing NH4+. The analysis of microbial community composition revealed that strain NR was the dominant species and outcompeted ammonium oxidizing bacterium (AOB) under high organic carbon as well as ammonium. Simultaneous ammonium and organic carbon removal still maintained for a long-term operation with NH4+-N loadings of 300 and 450 mg/L in R1. Nitrogen balance showed that stripped NH3 only occupied a few percentages and aerobic denitrification played a significant role in nitrogen removal.
88. 题目: Complexation between dissolved silica and alginate molecules: Implications for reverse osmosis membrane fouling
期刊: Journal of Membrane Science
作者: Shu Wang, Xia Huang, Menachem Elimelech
摘要: Dissolved silica and organic matter are major membrane foulants in desalination of brackish water and wastewater by reverse osmosis. However, the interaction between inorganic silica species and dissolved organic molecules and their combined impact on membrane fouling are poorly understood. In this study, we have used sodium silicate and sodium alginate as model inorganic and organic foulants, respectively. Membrane fouling experiments showed a cooperative effect between the dissolved silica and alginate macromolecules, which aggravated membrane fouling. The molecular interactions between sodium alginate and sodium silicate and the properties of the formed complexes were determined by X-ray diffraction and X-ray photoelectron spectroscopy. Results show that the crystallinity of the formed complexes decreased as we increased the ratio of silica in the silica-alginate mixture, indicating the formation of amorphous complexes. Full reflection Fourier transform infrared spectroscopy also confirms new functional groups following the interaction between silica and alginate. Isothermal titration calorimetry was also employed to quantitatively determine the binding parameters by measuring the heat change during the reaction. When binding occurs between silica and alginate, the measured adsorbed or released heat is used to determine the binding constants as well as the enthalpy and entropy changes. Our results suggest that the interaction between silica and alginate is spontaneously exothermic and dominated by noncovalent bonding. Our findings provide fundamental insights into the complexation between silica and alginate in reverse osmosis membrane fouling and highlight the binding mechanism between silica and alginate molecules.
89. 题目: Impacts of organic matter on the toxicity of biosynthesized silver nanoparticles to green microalgae Chlorella vulgaris
期刊: Environmental Research
作者: Mehdi Khoshnamvand, Saeed Ashtiani, Yongsheng Chen, Jingfu Liu
摘要: The increasing production of eco-friendly nanoparticles like biosynthesized nanoparticles (BNPs) calls for study on their environmental and biological safety. Herein, the impact of natural organic matter on the toxicity of BNPs was studied. Using leaf extract of herbal plant Allium fistulosum, the Allium fistulosum-silver nanoparticles (AF-AgNPs) were synthesized with the yield of around 100% and used to explore the impacts of natural organic matter (Suwannee river humic acid) on their toxicity to green microalgae Chlorella vulgaris. The results showed that the as-prepared AF-AgNPs could decrease the end-points of biomass and chlorophyll a content of C. vulgaris in a dose-dependent manner. In addition, AF-AgNPs enhanced algal aggregation and decreased size of cells, especially at higher concentrations. However, organic matter showed an ameliorative effect on the toxicity of AF-AgNPs, and significant enhancement of biomass and chlorophyll a content (p < 0.05) were observed in media treated with higher contents of AF-AgNPs. Organic matter could also prevent more cellular aggregation and size reduction of C. vulgaris. Our results are helpful for understanding the effects of organic matter on the toxicity of BNPs to aquatic organisms.
90. 题目: Synthesized effects of proteomic and extracellular polymeric substance (EPS) revealing the enhanced hydrogen production by formed biofilm of photo-fermentative bacteria
期刊: Environment International
作者: Han-Quan Wen, Hong-Yu Ren, Guo-Jun Xie, Guang-Li Cao, De-Feng Xing, Nan-Qi Ren, Bing-Feng Liu
摘要: Photo-fermentative hydrogen production, the new energy production alternative, was greatly enhanced by formed biofilm. To understand the mechanism of enhancement, the intracellular proteome and extracellular polymeric substance (EPS)i during biofilm formation were investigated in this work. Experimental results indicated that a possible and effective altered system could transfer light to hydrogen. Proteins were significantly regulated, for example those related with nitrogenase, flagellin, EPS transportation and DNA duplication were up-regulated while those concerned photosystem were down-regulated. It revealed these changes of proteins contributed to positive activity of key enzymes, improved communication system and increased total light utilization efficiency thus leading to enhanced capacity of hydrogen production. Besides above metabolic changes inside the cells, EPS secreted by the bacteria played an important role in hydrogen production and its yield decided the release of hydrogen. When EPS descended to a lower concentration during biofilm formation, it meant carbon source for EPS synthesis was reduced, and more energy and reducing power could be transferred into hydrogen energy. More importantly, this work found that composition and structure of EPS were efficiently influenced by the formation of biofilm, such as benzene and O-H structure, secondary protein structure and the kinds of protein, which were important to stable biofilm and efficient hydrogen production. Therefore, final hydrogen yield was improved by altered protein and EPS resulted from biofilm formation. This study demonstrated that formation of biofilm is an efficient, ecological and attracting way to the future bio-hydrogen production.
91. 题目: Key factors controlling radiocesium sorption and fixation in river sediments around the Fukushima Daiichi Nuclear Power Plant. Part 1: Insights from sediment properties and radiocesium distributions
期刊: Science of the Total Environment
作者: Yukio Tachi, Tomofumi Sato, Yosuke Akagi, Makoto Kawamura, Hideji Nakane, Motoki Terashima, Kenso Fujiwara, Kazuki Iijima
摘要: In order to elucidate the radiocesium transport behaviors in natural environment, we systematically investigated sediments from the highly contaminated rivers of Ukedo and Odaka around the Fukushima Daiichi Nuclear Power Plant. We focused on determining the key factors controlling the radiocesium sorption and fixation, such as variations in the particle size, clay mineralogy, and organic matter (OM). The distribution patterns of the 137Cs concentration and particle size fractions were found to be similar for the two rivers, indicating that both clay and silt fractions contributed almost equally to the Cs sorption. The clay mineralogical composition evaluated using X-ray diffraction analysis showed that the relative contents of micaceous minerals were higher in the Ukedo River samples, whereas the relative contents of smectite and kaolinite were higher in the Odaka River samples. This implies that the sediments in both rivers were likely at different weathering stages due to the different geological settings in both catchments. The effects of OM on the sediment properties were also investigated by comparing the cation exchange capacity (CEC) and the radiocesium interception potential (RIP) of the two samples both with and without OM present. The CEC values were controlled by both the clay minerals and OM, and the RIP values increased significantly in the absence of OM. Such trends were correlated to the total organic carbon values, which may be used to understand the direct and indirect roles of OM in the sorption and fixation of Cs. These key differences in river sediment were attributed to the differences in the geological settings and weathering stages. These properties may contribute to the different sorption and fixation behaviors of radiocesium. In the second part paper, we further examined these behaviors and identified key factors by investigating their relationship to the sediment properties of both rivers.
92. 题目: Riverine nitrate source apportionment using dual stable isotopes in a drinking water source watershed of southeast China
期刊: Science of the Total Environment
作者: Xu Shang, Hong Huang, Kun Mei, Fang Xia, Zheng Chen, Yue Yang, Randy A. Dahlgren, Minghua Zhang, Xiaoliang Ji
摘要: It is crucial to quantitatively track riverine nitrate (NO3−) sources and transformations in drinking water source watersheds for preventing current and future NO3− pollution, and ensuring a safe drinking water supply. This study identified the significant contributors to riverine NO3− in Zhaoshandu reservoir watershed of Zhejiang province, southeast China. To achieve this goal, we used hydrochemistry parameters and stable isotopes of NO3− (δ15N-NO3− and δ18O-NO3−) accompanied with a Markov Chain Monte Carlo mixing model to estimate the proportional contributions of riverine NO3− inputs from atmospheric deposition (AD), chemical nitrogen fertilizer (NF), soil nitrogen (SN), and manure and sewage (M&S). Results indicated that the main form of riverine nitrogen in this region was NO3−, constituting ~60% of the total nitrogen mass on average (total organic nitrogen ~37% & ammonium ~3%). Variations in the isotopic signatures of NO3− demonstrated that microbial nitrification of NF, SN and M&S was the primary nitrogen transformation process within the Zhaoshandu reservoir watershed, whereas denitrification was minimal. A classical dual isotope bi-plot incorporating chloride concentrations suggested NF, SN and M&S were the major contributors of NO3− to the river. Riverine NO3− source apportionment results were further refined using the Markov Chain Monte Carlo mixing model, which revealed that AD, NF, SN and M&S contributed 7.6 ± 4.1%, 22.5 ± 12.8%, 27.4 ± 14.5% and 42.5 ± 11.3% of riverine NO3− at the watershed outlet, respectively. Finally, uncertainties associated with NO3− source apportionment were quantitatively characterized as: SN > NF > M&S > AD. This work provides a comprehensive approach to distinguish riverine NO3− sources in drinking water source watersheds, which helps guide implementation of management strategies to effectively control NO3− contamination and protect drinking water quality. Summary of the main finding from this works (Capsule) We utilized NO3− stable isotope analysis and a Markov Chain Monte Carlo mixing model to quantify riverine nitrate pollution sources in a drinking water source watershed in Zhejiang province, southeast China. Markov Chain Monte Carlo mixing model output showed that NF, SN and M&S were the dominant sources of riverine NO3− during the sampling period in Zhaoshandu watershed. Uncertainty analysis characterized the variation strength associated with contributions of individual nitrate sources and indicated the greatest uncertainty for SN, followed by NF, M&S and AD.
93. 题目: Key factors controlling radiocesium sorption and fixation in river sediments around the Fukushima Daiichi Nuclear Power Plant. Part 2: Sorption and fixation behaviors and their relationship to sediment properties
期刊: Science of the Total Environment
作者: Yukio Tachi, Tomofumi Sato, Chizuko Takeda, Takamitsu Ishidera, Kenso Fujiwara, Kazuki Iijima
摘要: We systematically investigated the sorption and fixation behaviors of radiocesium (137Cs) for sediments taken from the rivers of Ukedo and Odaka around the Fukushima Daiichi Nuclear Power Plant. By comparing the Cs sorption and sequential desorption results at various Cs concentrations, across a range of sediment properties, we were able to understand the different contributions at frayed edge sites (FESs) and regular exchange sites (RESs) of the clay minerals, and their relationships with the Cs concentrations and the contents of organic matter (OM). The Cs sorption and fixation were dominated by FESs at trace Cs concentrations, and by ion exchange at RES and the collapse of interlayers at higher Cs concentrations. The Cs sorption at lower Cs concentration was strongly related to radiocesium interception potential (RIP); however, Cs fixation was more related to clay mineralogy (i.e. contents of mica, vermiculite and hydroxy-interlayered vermiculite) rather than the RIP. The first-order kinetic constants for time-dependent Cs sorption at low Cs concentrations were correlated negatively to the ratio between the total organic carbon and RIP values. This implies that Cs access to FESs requires a relatively long duration that is dependent on the contents of the OM. From these results, the sorption and fixation mechanisms were confirmed to be significantly different at different Cs concentrations. Then, the prediction of Cs transport should be based on the key mechanisms that are dominant at the actual trace levels of Cs. A significant difference between the Cs fixation behaviors at the Ukedo River and Odaka River may be understood by considering the differences in their clay mineralogy, due to the different geological settings and weathering stages of both catchments.
94. 题目: The antimony sorption and transport mechanisms in removal experiment by Mn-coated biochar
期刊: Science of the Total Environment
作者: Xiaocen Jia, Jianwei Zhou, Jing Liu, Peng Liu, Lu Yu, Bing Wen, Yu Feng
摘要: A method of Mn-coated biochar production was developed, which showed great removal ability of trivalent antimony (Sb(III)) (0.94 mg g−1) and pentavalent antimony (Sb(V)) (0.73 mg g−1), and the adsorption capacity was stable under different pH. According to the adsorption kinetics and isotherm, the adsorption process of both Sb(III) and Sb(V) was chemisorption, which was both monolayer and poly layers heterogeneous chemisorption process. X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy analyses indicated that the main oxides and functional groups involved in the adsorption were manganese oxides (MnOx), carboxyl and hydroxyl groups and Sb(V) was combined with Mn-coated biochar by inner-sphere complexation. Sb(III) was oxidized by oxygen and MnOx which was both on the surface of biochar and dissolved in solution. Furthermore, X-ray absorption near-edge structure (XANES) showed that Sb(V) was the main species after Sb(III) and Sb(V) adsorbed on the Mn-coated biochar. Extended X-ray absorption fine structure (EXAFS) analysis indicated that Sb(III) and MnOx formed the monodentate mononuclear and corner-sharing complexes with a structure of Mn-O-Sb on Mn-coated biochar. While Sb(V) and MnOx formed inner-sphere complexes including edge-sharing and corner-sharing complexes. The new synthetic material can contribute to develop new remediation strategies for treating Sb-contaminated water.
95. 题目: Plastic-film mulch cropping increases mineral-associated organic carbon accumulation in maize cropped soils as revealed by natural 13C/12C ratio signature
作者: Qiu-Jin Ma, Qian Zhang, Jianbiao Niu, Xiao Gang Li
摘要: Plastic-film mulch is used for increasing soil temperature and reducing water evaporation to enhance productivity in semiarid regions worldwide; however, its effects on soil organic carbon (SOC) level and stability are not clear. We tested hypotheses that increasing soil temperature and moisture by plastic-film mulch with an increase of carbon input would increase the accumulation of heavy-fraction SOC (HFOC) and decrease the mineralization potential of HFOC. Soils were sampled at 0–45 cm depth from four treatments: (i) no mulch and no straw incorporation, (ii) mulch only, (iii) straw incorporation only, and (iv) straw incorporation plus mulch. All treatments were cultivated with C4 maize (Zea mays L.) under ridge–furrow management continuously for nine years in a field previously planted with C3 crops in a cold environment. Proportionately to the increased aboveground biomass, root biomass in the 0–20 cm depth increased under mulch compared to no mulch. Nine years later, mulch reduced both maize-derived (new) and C3-crop-derived (old) light-fraction SOC (LFOC) stocks only at 0–15 cm soil depth compared to no mulch, regardless of whether straw was incorporated or not, reflecting the increased decomposition due to increased temperature and moisture in mulched soils. Mulch increased new HFOC stock at 0–30 cm soil depth relative to no mulch. These indicated that the faster decomposition of labile LFOC with increasing plant input under mulch relative to no mulch was paralleled by an enhancement in the accumulation of stable HFOC in mulched soils. Mulch enhanced the benefits of straw incorporation in terms of increasing the accumulation of new HFOC. Over nine years, the average sequestration rate of new HFOC at 0–45 cm soil depth was 204 (±18) and 266 (±10) kg ha−1 yr−1 without and with mulch, respectively, in non-straw-incorporated plots, and 514 (±14) and 752 (±18) kg ha−1 yr−1 without and with mulch, respectively, in straw-incorporated plots. Old HFOC was unaffected by mulch or straw incorporation. Overall, mulch did not change the total SOC storage in the top 45-cm soil. Mulch decreased the mineralization potential of new HFOC under laboratory incubation compared to no mulch, indicating that the new HFOC was more decomposed in mulched soils. We concluded that increasing soil temperature and moisture by using plastic-film mulch with high plant input increases the accumulation of stable HFOC in maize croplands.
96. 题目: Molecular indicators of methane metabolisms at cold seeps along the United States Atlantic Margin
期刊: Chemical Geology
作者: Nancy G. Prouty, Pamela L. Campbell-Swarzenski, Hilary G. Close, Jennifer F. Biddle, Sabrina Beckmann
摘要: Anaerobic oxidation of methane (AOM) and the environmental conditions supporting AOM on continental margins is an essential component to global methane budgets. Diagnostic lipid biomarkers and their compound specific isotope analysis preserved in authigenic carbonates at cold seeps can serve as fingerprints to archaeal−bacterial consortia involved in AOM. However, despite the discovery of several hundreds of seeps along the United States Atlantic Margin (USAM), there are relatively few biomarker investigations of cold seep carbonates along this passive margin. A lipid biomarker, carbon isotope, and DNA marker gene study was therefore undertaken to determine the microbial origins of authigenic carbonates from two USAM seeps, Norfolk and the Baltimore Canyon seep fields. Results from this study capture a distinct archaeal lipid signature from putative methanotrophic archaea, including archaeol (I), sn-2-hydroxyarchaeol, 2,6,10,15,19-pentamethylicosane (PMI), and crocetane. The 13C-depleted AOM-related archaeal lipid samples (i.e., archaeol: −91.6‰, sn-2-hydroxyarchaeol: −129.2‰, PMI −92.8‰, and crocetane: −70.9‰) confirm the dominance of methane assimilation and isotope fractionation during AOM. These results are consistent with the detection of archaeal anaerobic methanotrophs (ANMEs) based on 16S rRNA gene sequencing. The Norfolk authigenic carbonate contained ANME-1a, -1b, 2a-2b, and 2c whereas only the ANME-2 clade was detected at Baltimore and present as the subclusters 2a-2b and -2b. The ANME-2d clade may also be present, particularly at the Baltimore seep site, given the high abundance of Candidatus Methanoperedens nitroreducens detected in the mcrA gene sequencing. The presence of terminally branched fatty acids, antesio- and iso-C15:0 components, as well as C16:1ω7 with δ13C values as low as −107.6‰, are indicative of sulfate-reducing bacteria (SRB) at the Norfolk seep site and supports syntrophy of SRB with methane-oxidizing archaea. In contrast, nitrate-driven AOM in syntrophy M. nitroreducens at the Baltimore seep site is consistent with elevated fatty acid δ13C values and lack of Deltaproteobacteria at the Baltimore seep site. Taken together, the range in lipid composition, distribution, and carbon isotopic composition observed at the Norfolk and Baltimore seep sites suggests AOM is performed by multiple archaea instead of a single species and may be paired with either or both nitrate- and sulfate-reduction. Given the heterogeneous nature of cold seep ecosystems, this study fills a critical spatial gap in our knowledge of AOM activity at two seep sites along a passive margin.
97. 题目: The effect of low-temperature biochar and its non-pyrolyzed composted biosolids source on the geochemical fractionation of Pb and Cd in calcareous river sediments
期刊: Environmental Earth Sciences
作者: Kerry Mitchell, Celeste Viridiana Mendoza-González, Magdalena Samanta Ramos-Gómez, Laura Yamamoto-Flores, Alma Lilian Guerrero-Barrera, Roberto Macias-Medrano, Francisco Javier Avelar-González
摘要: Single extraction and sequential extraction assays were used to compare the effect of low-temperature biochar and its non-pyrolyzed composted biosolids on Pb and Cd mobility in the buffered conditions of calcareous river sediments. Results showed that amendment reduced the mobility of both metals, though under higher pH conditions, the effect of the non-pyrolyzed composted biosolids on the mobility of Pb was more apparent. On the other hand, the low temperature biochar had a more significant effect on the mobility of both metals under low pH conditions. The single extraction scheme used to simulate varying physicochemical conditions confirmed that amendment decreased Pb mobility up to 49% and Cd up to 96%. Sequential extraction assays confirmed a shift in predominant metal-fraction associations; from potentially mobile fractions to the more immobile ferromanganese oxide and organic matter fractions. These results highlighted the significant impact biochar amendment can have on metal mobility even when temporarily buffered by the physicochemical conditions in the calcareous substrates.
98. 题目: Tradeoffs in soil carbon protection mechanisms under aerobic and anaerobic conditions
期刊: Global Change Biology
作者: Wenjuan Huang, Chenglong Ye, William Hockaday, Steven J. Hall
摘要: Oxygen (O2) limitation is generally understood to suppress soil carbon (C) decomposition and is a key mechanism impacting terrestrial C stocks under global change. Yet, O2 limitation may differentially impact kinetic or thermodynamic vs. physico‐chemical C protection mechanisms, challenging our understanding of how soil C may respond to climate‐mediated changes in O2 dynamics. Although O2 limitation may suppress decomposition of new litter C inputs, release of physico‐chemically protected C due to iron (Fe) reduction could potentially sustain soil C losses. To test this tradeoff, we incubated two disparate upland soils that experience periodic O2 limitation—a tropical rainforest Oxisol and a temperate cropland Mollisol—with added litter under either aerobic (control) or anaerobic conditions for one year. Anoxia suppressed total C loss by 27% in the Oxisol and by 41% in the Mollisol relative to the control, mainly due to the decrease in litter‐C decomposition. However, anoxia sustained or even increased decomposition of native soil‐C (11.0% vs. 12.4% in the control for the Oxisol and 12.5% vs. 5.3% in the control for the Mollisol, in terms of initial soil C mass), and it stimulated losses of metal‐ or mineral‐associated C. Solid‐state 13C nuclear magnetic resonance spectroscopy demonstrated that anaerobic conditions decreased protein‐derived C but increased lignin‐ and carbohydrate‐C relative to the control. Our results indicate a tradeoff between physico‐chemical and kinetic/thermodynamic C protection mechanisms under anaerobic conditions, whereby decreased decomposition of litter C was compensated by more extensive loss of mineral‐associated soil C in both soils. This challenges the common assumption that anoxia inherently protects soil C and illustrates the vulnerability of mineral‐associated C under anaerobic events characteristic of a warmer and wetter future climate.
99. 题目: Synthesis of calcite-based bio-composite biochar for enhanced biosorption and detoxification of chromium Cr (VI) by Zhihengliuella sp. ISTPL4
期刊: Bioresource Technology
作者: Arti Mishra, Bulbul Gupta, Naveen Kumar, Rashmi Singh, Ajit Verma, Indu Shekhar Thakur
摘要: The current study presents a comprehensive analysis of the potential of actinobacterium Zhihengliuella sp. ISTPL4 and different composite materials for the removal of hexavalent chromium [Cr (VI)]. Genome analysis of strain indicated the presence of several oxidoreductases which includes chromate reductase, nitrate reductase, thioredoxin, superoxide dismutase and hydrogenase are other major candidate genes. Catalytic calcite-based bio-composite material was absorbed on biochar had highest Cr removal efficiency. The main mechanism involved in Cr biosorption by this strain was explained by the Langmuir isotherm model; under equilibrium conditions the maximum adsorption was observed 49± 0.3mgg−1. Kinetic studies showed that biosorption of Cr (VI) by this strain was a rate-limiting step and followed a pseudo-second-order kinetics (R2 =0.99). SEM analysis is in line with EDX result indicating highest Cr removal by calcined biochar. MTT assay shown that the bacteria successfully convert toxic Cr (VI) to comparatively less toxic form such as Cr (III).
100. 题目: Enhanced volatile fatty acid degradation and methane production efficiency by biochar addition in food waste-sludge co-digestion: A step towards increased organic loading efficiency in co-digestion
期刊: Bioresource Technology
作者: Guneet Kaur, Davidraj Johnravindar, Jonathan W.C. Wong
摘要: This work investigated the effect of biochar addition to mitigate VFA accumulation and enhance methane production in mesophilic food waste/sludge co-digestion. Different types of biochar derived from agricultural and forestry residues at two pyrolysis temperatures were tested. Results showed that wheat straw biochar 550 °C supported the highest specific methane yield of 381.9 LCH4/kg VSadded and VS removal efficiency of 41.62% among all treatments. Degradation of propionic acid and long-chain fatty acids such as valeric, caproic and isovaleric acids was observed. This also corresponded to an increase in methanogenic favorable substrates including acetic acid (>40%) and butyric acid (~20%) over the control. Consequently, a 24% increase in overall methane production was obtained as compared to control. This demonstrated that biochar addition had positive effects on VFA degradation and methane production which could be a useful strategy to increase the organic loading in co-digestions without the fear of process failure.