论文检索

总访问量：5737727次

总访客量：393285人

所有论文

28641. 题目: Middle–Upper Ordovician (Darriwilian–Sandbian) paired carbon and sulfur isotope stratigraphy from the Appalachian Basin, USA: Implications for dynamic redox conditions spanning the peak of the Great Ordovician Biodiversification Event
文章编号: N19020304
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Nevin P. Kozik, Seth A. Young, Chelsie N. Bowman, Matthew R. Saltzman
更新时间: 2019-02-03
摘要: The Evans Ferry section from the Appalachian Basin of eastern North America has been analyzed for chemostratigraphic trends to elucidate possible causal mechanisms facilitating the Great Ordovician Biodiversification Event (GOBE). Paired stable isotope (δ¹³C and δ³⁴S) analyses were used in this carbonate-dominated locality from the Appalachian Basin to reconstruct the marine redox states during this key period of rapid biodiversification. This succession is one of the most expanded Sandbian Stage (Upper Ordovician) deposits known from North America, and it allows new high-resolution reconstructions of long-term, global carbon and sulfur cycle fluctuations. The integrated geochemical and sequence-stratigraphic investigation presented here from the Laurentian epeiric seaway allows for possible identification of the contraction and expansion of reducing water masses during the Middle–Late Ordovician that may have been linked to global-marine paleoredox dynamics. Utilizing new conodont-based ⁸⁷Sr/⁸⁶Sr isotope stratigraphy along with previous conodont biostratigraphy, we can confidently correlate our stable isotope profiles to other carbonate successions globally. Carbonate facies indicate that this area experienced partial restriction from open-marine conditions during certain intervals in the Sandbian. These semi-restricted environments record carbon (δ¹³C_carb) isotope trends that are secular in nature, as they can be correlated to other successions across Laurentia and Baltica. We identify several intervals when δ¹³C_carb and δ³⁴S_CAS (carbonate-associated sulfate) trends are decoupled. These inverse stratigraphic trends are, at times, followed by parallel positive shifts in δ¹³C_carb and δ³⁴S_CAS. Causal mechanisms for the observed decoupled δ¹³C and δ³⁴S trends may include a wide variety of factors such as more closed-system, local biogeochemical processes associated in part with diagenesis, or they could instead reflect variations in the global fluxes of organic matter and pyrite burial linked to changing marine paleoredox conditions. The positive covariation in trends presented here likely represents transient increases in organic carbon and pyrite burial in response to expansion of reducing marine environments.

28642. 题目: A blessing in disguise? Natural organic matter reduces the UV light-induced toxicity of nanoparticulate titanium dioxide
文章编号: N19020303
期刊: Science of The Total Environment
作者: Simon Lüderwald, Vera Dackermann, Frank Seitz, Elena Adams, Alexander Feckler, Carsten Schilde, Ralf Schulz, Mirco Bundschuh
更新时间: 2019-02-03
摘要: Besides their economic value, engineered inorganic nanoparticles (EINPs) may pose a risk for the integrity of ecosystems. Among EINPs, titanium dioxide (nTiO₂) is frequently used and released into surface waters in the μg range. There, nTiO₂ interacts with environmental factors, influencing its potential to cause adverse effects on aquatic life. Although factors like ultra violet (UV) light and natural organic matter (NOM) are considered as ubiquitous, their joint impact on nTiO₂-induced toxicity is poorly understood. This study addressed the acute toxicity of nTiO₂ (P25; 0.00–64.00 mg/L; ~60 nm) at ambient UV light (0.00–5.20 W UVA/m²) and NOM levels (seaweed extract; 0.00–4.00 mg TOC/L), using the immobility of Daphnia magna as response variable. Confirming previous studies, effects caused by nTiO₂ were elevated with increasing UV radiation (up to ~280 fold) and mitigated by higher NOM levels (up to ~12 fold), possibly due to reduced reactive oxygen species (ROS; measured as ^•OH radicals) formation at lower UV intensities. However, contradicting to former studies, nTiO₂-mediated ROS formation was not proportional to increasing NOM levels: lower concentrations (0.04–0.40 mg TOC/L) slightly diminished, whereas a higher concentration (4.00 mg TOC/L) promoted the ROS quantity, irrespective of UV intensity. Measured ROS levels do not fully explain the observed nTiO₂-induced toxicity, whereas increasing acetylcholinesterase and glutathione-S-transferase activities in daphnids (in presence of 8.00 mg/L nTiO₂ and elevated UV intensity) point towards neurotoxic and oxidative stress as a driver for the observed effects. Hence, despite higher ^•OH levels in the treatments where 4.00 mg TOC/L were present, NOM was still capable of reducing nTiO₂-induced stress and ultimately adverse effects in aquatic life.
图文摘要:

28643. 题目: Evaluation of Pilot-Scale Biochar-Amended Woodchip Bioreactors to Remove Nitrate, Metals, and Trace Organic Contaminants from Urban Stormwater Runoff
文章编号: N19020302
期刊: Water Research
作者: Negin Ashoori, Marc Teixido, Stephanie Spahr, Gregory H. LeFevre, David L. Sedlak, Richard G. Luthy
更新时间: 2019-02-03
摘要: Stormwater is increasingly being valued as a freshwater resource in arid regions and can provide opportunities for beneficial reuse via aquifer recharge if adequate pollutant removal can be achieved. We envision a multi-unit operation approach to capture, treat, and recharge (CTR) stormwater using low energy, cost-effective technologies appropriate for larger magnitude, less frequent events. Herein, we tested nutrient, metal, and trace organic contaminant removal of a pilot-scale CTR system in the laboratory using biochar-amended woodchip bioreactors following eight months of aging under field conditions with exposure to real stormwater. Replicate columns with woodchips and biochar (33% by weight), woodchips and straw, or woodchips only were operated with continuous, saturated flow for eight months using water from a watershed that drained an urban area consisting of residential housing and parks in Sonoma, California. After aging, columns were challenged for five months by continuous exposure to synthetic stormwater amended with 50 μg L^–1 of six trace organic contaminants (i.e., fipronil, diuron, 1H-benzotriazole, atrazine, 2,4-D, and TCEP) and five metals (Cd, Cu, Ni, Pb, Zn) frequently detected in stormwater in order to replicate the treatment unit operation of a CTR system. Throughout the eight-month aging and five-month challenge experiment, nitrate concentrations were below the detection limit after treatment (i.e., <0.05 mg N L^-1). The removal efficiencies for metals in all treatments were >80% for Ni, Cu, Cd, and Pb. For Zn, about 50% removal occurred in the woodchip-biochar systems while the other systems achieved about 20% removal. No breakthrough of the trace organic compounds was observed in any biochar-containing columns. Woodchip columns without biochar removed approximately 99% of influent atrazine and 90% of influent fipronil, but exhibited relatively rapid breakthrough of TCEP, 2,4-D, 1H-benzotriazole, and diuron. The addition of straw to the woodchip columns provided no significant benefit compared to woodchips alone. Due to the lack of breakthrough of trace organics in the biochar-woodchip columns, we estimated column breakthrough with a diffusion-limited sorption model. Results of the model indicate breakthrough for the trace organics would occur between 10,000 and 32,000 pore volumes. Under ideal conditions, this could be equivalent to decades of service assuming failure by other processes (e.g., clogging, biofouling) does not occur. These results indicate that multiple contaminants can be removed in woodchip-biochar reactors employed in stormwater treatment systems with suitable flow control and that the removal of trace organic contaminants is enhanced significantly by addition of biochar.
图文摘要:

28644. 题目: Effect of Dissolved Oxygen on Efficiency of TOC Reduction by UV at 185 nm in an Ultrapure Water Production System
文章编号: N19020301
期刊: Water Research
作者: Jeongyun Choi, Jinwook Chung
更新时间: 2019-02-03
摘要: The effect of dissolved oxygen (DO) on the degradation of methanol by ultraviolet (UV) light at 185 nm (UV-185) was examined in this study. The experiments were conducted using a bench-scale experimental apparatus that was operated under continuous conditions. In the control tests with various DO conditions, it was confirmed that UV irradiation of water without methanol produced approximately 54 μg/L of H₂O₂ and removed 15% to 90% of the DO. The production of H₂O₂ was affected by the mixing conditions within the UV reactor and the dose of UV. The degradation efficiency of methanol by UV-185 irradiation improved linearly with increasing DO concentration, with more than 90% DO consumption. The maximum total organic carbon (TOC) removal rate was observed at 100 μg/L DO and 433 mW·sec/cm², the highest DO and dosage conditions in this study. The production of H₂O₂ was also affected by DO concentration in the feed water, especially at the high UV dosage, in which lower H₂O₂ production was observed at higher DO.
图文摘要:

28645. 题目: Mutual relationships of biochar and soil pH, CEC, and exchangeable base cations in a model laboratory experiment
文章编号: N19020210
期刊: Journal of Soils and Sediments
作者: Niguss Solomon Hailegnaw, Filip Mercl, Kateřina Pračke, Jiřina Száková, Pavel Tlustoš
更新时间: 2019-02-02
摘要: Purpose: The majority of biochar studies use soils with only a narrow range of properties making generalizations about the effects of biochar on soils difficult. In this study, we aimed to identify soil properties that determine the performance of biochar produced at high temperature (700 °C) on soil pH, cation exchange capacity (CEC), and exchangeable base cation (Ca²⁺, K⁺, and Mg²⁺) content across a wide range of soil physicochemical properties. Materials and methods: Ten distinct soils with varying physicochemical properties were incubated for 12 weeks with four rates of biochar application (0.5, 2, 4, and 8% w/w). Soil pH, CEC, and exchangeable base cations (Ca²⁺, K⁺, and Mg²⁺) were determined on the 7th and 84th day of incubation. Results and discussion: Our results indicate that the highest biochar application rate (8%) was more effective at altering soil properties than lower biochar rates. Application of 8% biochar increased pH significantly in all incubated soils, with the increment ranging up to 1.17 pH unit. Biochar induced both an increment and a decline in soil CEC ranging up to 35.4 and 7.9%, respectively, at a biochar application rate of 8%. Similarly, biochar induced increments in exchangeable Ca²⁺ up to 38.6% and declines up to 11.4%, at an 8% biochar application rate. The increment in CEC and exchangeable Ca²⁺ content was found in soils with lower starting exchangeable Ca²⁺ contents than the biochar added, while decreases were observed in soils with higher exchangeable Ca²⁺ contents than the biochar. The original pH, CEC, exchangeable Ca²⁺, and texture of the soils represented the most crucial factors for determining the amount of change in soil pH, CEC, and exchangeable Ca²⁺ content. Conclusions: Our findings clearly demonstrate that application of a uniform biochar to a range of soils under equivalent environmental conditions induced two contradicting effects on soil properties including soil CEC and exchangeable Ca²⁺ content. Therefore, knowledge of both biochar and soil properties will substantially improve prediction of biochar application efficiency to improve soil properties. Among important soil properties, soil exchangeable Ca²⁺ content is the primary factor controlling the direction of biochar-induced change in soil CEC and exchangeable Ca²⁺ content. Generally, biochar can induce changes in soil pH, CEC, and exchangeable Ca²⁺, K⁺, and Mg²⁺ with the effectiveness and magnitude of change closely related to the soil’s original properties.

28646. 题目: A novel TiO₂/biochar composite catalysts for photocatalytic degradation of methyl orange
文章编号: N19020209
期刊: Chemosphere
作者: Lili Lu, Rui Shan, Yueyue Shi, Shuxiao Wang, Haoran Yuan
更新时间: 2019-02-02
摘要: A series of TiO₂/biochar composite catalysts were prepared by the hydrolysis method for the degradation of methyl orange, where biochar was obtained from the pyrolysis of waste walnut shells. The catalysts were examined by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL) and X-ray photoelectron spectroscopy (XPS), elemental analysis and ultra violet-visible diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activity results showed that the catalysts noted as CT0.1/1, CT0.2/2 and CT 0.5/1 exhibited higher catalytic activity than that of pure TiO₂. Besides, catalyst CT0.2/1 exhibited the highest catalytic activity (the decolorization efficiency of 96.88% and the mineralization efficiency of 83.23% were obtained), attributed to the synergistic effect of biochar and TiO₂, while CT1/1 possessed the lowest activity due to the shelter of light by the excess biochar. After 5 repeated use, the catalyst CT0.2/1 still exhibited rather high activity toward the degradation of MO, where the decolorization efficiency and mineralization efficiency of MO achieved 92.45% and 76.56%, and the loss of activity was negligible.

28647. 题目: Comparison of the accumulation and metabolite of fluoxetine in zebrafish larva under different environmental conditions with or without carbon nanotubes
文章编号: N19020208
期刊: Ecotoxicology and Environmental Safety
作者: Zhenhua Yan, Guanghua Lu, Hongwei Sun, Xuhui Bao, Runren Jiang, Jianchao Liu, Yong Ji
更新时间: 2019-02-02
摘要: Few studies have focused on the influence of environmental conditions on the bioavailability of pollutants interacted with nanomaterials in organisms. In this study, we primarily compared the influence of multiwalled carbon nanotubes (MWCNTs) on the bioavailability of fluoxetine in zebrafish (Danio rerio) larva under different environmental conditions: natural organic matter (NOM) and salinity. The results showed that fluoxetine accumulated in the larvae and then transformed into the metabolite norfluoxetine, with the metabolic rates from 2.8 to 3.5. Following co-exposure to MWCNTs, the accumulation of fluoxetine and norfluoxetine were further enhanced, suggesting a superior carrier of MWCNTs for fluoxetine, especially the functional MWCNTs. The consistent increase in the fluoxetine and norfluoxetine accumulation highlights the bioavailability of absorbed fluoxetine on MWCNTs in zebrafish larvae. The presence of NOM promoted the accumulation of fluoxetine and norfluoxetine in zebrafish, but alleviated the carrier effects of MWCNTs, acting as a natural antidote. Salinity negatively influenced the bioavailability of fluoxetine in the larvae, and further reversed the enhancements caused by MWCNTs. These findings provide a new insight into the influence of environmental conditions on the interactions between nanomaterials and pollutants in organisms.
图文摘要:

28648. 题目: Mercury speciation in various aquatic systems using passive sampling technique of diffusive gradients in thin-film
文章编号: N19020207
期刊: Science of The Total Environment
作者: Arne Bratkič, Katja Klun, Yue Gao
更新时间: 2019-02-02
摘要: Mercury (Hg) is one of the primary health concerns in natural and urbanised environments due to past and present natural and anthropogenic emissions. Its environmental cycle is driven by redox reactions, microbial metabolism and organic matter (OM) interactions, which may all lead to formation of bioaccumulative organic Hg species; methylmercury (MeHg), with damaging consequences for human and ecosystem health. Hence, Hg lability and bioavailability has been the focus of many investigations and assessed with a variety of chemical proxies in order to improve understanding of the conditions that lead to enhanced bioavailability of Hg and its species. We investigated Hg labile species with Diffusive Gradient in Thin-film technique (DGT) in the water column and sediment of Zenne River (Brussels, Belgium) and Gulf of Trieste (North Adriatic). They represent two contemporary important Hg-impacted areas; the former by anthropogenic urban pollution, and the latter by historic pollution from Hg mining. Hg speciation of labile inorganic and methylmercury in these two environments was not yet investigated using DGT technique. The results show labile Hg species changing with season in the water column of Zenne River, while the sediments are the source of bioavailable MeHg to the water column that is transported further creating a halo effect in the region. Values of labile Hg species for water column and sediments in Gulf of Trieste differ from previous research, highlighting the need for more investigation into Hg bioavailability. MeHg/THg ratios were compared to other sampling methods for labile Hg species.
图文摘要:

28649. 题目: High-resolution prediction of organic matter concentration with hyperspectral imaging on a sediment core
文章编号: N19020206
期刊: Science of The Total Environment
作者: Kévin Jacq, Yves Perrette, Bernard Fanget, Pierre Sabatier, Didier Coquin, Ruth Martinez-Lamas, Maxime Debret, Fabien Arnaud
更新时间: 2019-02-02
摘要: In the case of environmental samples, the use of a chemometrics-based prediction model is highly challenging because of the difficulty in experimentally creating a well-ranged reference sample set. In this study, we present a methodology using short wave infrared hyperspectral imaging to create a partial least squares regression model on a cored sediment sample. It was applied to a sediment core of the well-known Lake Bourget (Western Alps, France) to develop and validate a model for downcore high resolution LOI550 measurements used as a proxy of the organic matter. In lake and marine sediment, the organic matter content is widely used, for example, to reconstruct carbon flux variations through time. Organic matter analysis through routine analysis methods is time- and material-consuming, as well as not spatially resolved. A new instrument based on hyperspectral imaging allows high spatial and spectral resolutions to be acquired all along a sediment core. In this study, we obtain a model characterized by a 0.95 r prediction, with 0.77 wt% of model uncertainty based on 27 relevant wavelengths. The concentration map shows the variation inside each laminae and flood deposit. LOI550 reference values obtained with the loss on ignition are highly correlated to the inc/coh ratio used as a proxy of the organic matter in X-ray fluorescence with a correlation coefficient of 0.81. This ratio is also correlated with the averaged subsampled hyperspectral prediction with a r of 0.65.
图文摘要:

28650. 题目: Comparison of short-term dosing ferrous ion and nanoscale zero-valent iron for rapid recovery of anammox activity from dissolved oxygen inhibition
文章编号: N19020205
期刊: Water Research
作者: Yuan Yan, Yayi Wang, Weigang Wang, Shuai Zhou, Junjie Wang, Jianhua Guo
更新时间: 2019-02-02
摘要: As obligate anaerobes, anammox bacteria are sensitive to oxygen, which might hinder the maximization of anammox activity. However, there are very few effective strategies to rapidly recover anammox activity after its deterioration under exposure of oxygen. In this study, the activity recovery of anammox bacteria encountering dissolved oxygen (DO) exposure (0.2 and 2.0 mg L⁻¹) were compared by three strategies in short-term experiments, nZVI, Fe(II) dosing, and N₂ purging. nZVI is more effective in recovering anammox activity with a high DO exposure (2 mg L^‒1), compared to a low DO exposure (0.2 mg L^‒1). After inhibiting by 2.0 mg L⁻¹ DO, anammox activity recovery (normalized to the control) was ranked in the order of nZVI (5 mg L⁻¹) addition (63±8.2%)> Fe(II) (5 mg L⁻¹) addition (41±8.0%) >N₂ purging (39 ± 4.0%). In contrast to Fe(II) ion additions, the shell structure of nZVI combined with the buffering effect of biomass-extracellular polysaccharide (EPS) prevented the sharp pH variation and excessive dissolved Fe(II)/Fe(III) in solution. Under such circumstances, nZVI addition (5 and 25 mg L⁻¹) increased the intracellular reactive oxygen species (ROS) to a moderate level (<200%), which might be responsible for the better activity recovery of anammox than that of Fe(II) addition and N₂ purging. Specifically, 5 mg L⁻¹ nZVI dosage moderately enhanced the intracellular O₂⁻ production (∼150% of the control) after scavenging 2.0 mg L⁻¹ DO, and the anammox activity recovered better than that of both 5 and 25 mg L⁻¹ Fe(II) ions additions. However, high dosage nZVI (75 mg L⁻¹) inhibited anammox activity in spite of low or high DO exposure. Our findings elucidate that appropriate amount of nZVI (a short-term dosing) can rapidly recover anammox activity when anammox bacteria encountering oxygen exposure accidentally and could be useful in facilitating the robust operation of anammox-based processes.
图文摘要:

28651. 题目: Mycobacterial metabolic characteristics in a water meter biofilm revealed by metagenomics and metatranscriptomics
文章编号: N19020204
期刊: Water Research
作者: Junge Zhu, Ruyin Liu, Nan Cao, Jianwei Yu, Xinchun Liu, Zhisheng Yu
更新时间: 2019-02-02
摘要: Mycobacteria represent one of the most persistent bacterial populations in drinking water distribution system (DWDS) biofilm communities; however, mycobacterial in situ metabolic profiles are largely unknown. In this study, the metabolic characteristics of mycobacteria in a household water meter biofilm were unveiled using a coupled metagenomic/metatranscriptomic approach. The water meter biofilm appeared to express nitrogenase genes (nifDKH) and a full complement of genes coding for several carbon-fixation pathways, especially the Calvin cycle, suggesting the CO₂ sequestration and dinitrogen fixation potential of the biofilm. These findings indicate that it may be difficult to prevent the formation of DWDS biofilms simply by controlling the availability of organic carbon or nitrogen. The composite genome of mycobacteria (CG-M) was reconstructed based on the obtained omics data. CG-M shared similar genome phylogeny and virulence-factor profiles with Mycobacterium avium complex, suggesting that population CG-M might represent a member of mycobacteria with pathogenicity. According to the gene expression patterns, population CG-M showed the metabolic potential to assimilate CO₂ via the Calvin cycle and/or anaplerotic reactions, and even to grow autotrophically with CO as the sole carbon and energy source. This suggests that organic carbon may not be a limiting factor for mycobacterial growth in DWDSs. Moreover, our results suggest that mycobacterial aromatic degradation is primarily achieved through the catechol meta-cleavage pathway, and biofilm mycobacteria could prefer phosphate as the phosphorus source.
图文摘要:

28652. 题目: Pyrogenic carbon erosion after the Rim Fire, Yosemite National Park: the role of burn severity and slope
文章编号: N19020203
期刊: Journal of Geophysical Research: Biogeosciences
作者: Rebecca B. Abney, Timothy J. Kuhn, Alex Chow, William Hockaday, Marilyn L. Fogel, Asmeret Asefaw Berhe
更新时间: 2019-02-02
摘要: Pyrogenic carbon (PyC) is an incomplete combustion byproduct with longer soil residence times compared with non‐pyrogenic components of the soil carbon (C) pool and can be preferentially eroded in fire‐affected landscapes. To investigate geomorphic and fire‐related controls on PyC erosion, sediment fences were established in three combinations of slope (high 13.9‐37.3%; moderate 0‐6.7%) and burn severity (high; moderate) plots within the perimeter of the Rim Fire in 2013, Yosemite National Park, California, USA. After each major precipitation event following the fire, we determined transport rates of total sediment, fine and coarse sediment fractions, and C and nitrogen (N). We measured stable isotope (δ¹³C and δ¹⁵N) compositions and ¹³C‐nuclear magnetic resonance (NMR) spectra of soils and eroded sediments. The highest total and fine (<2 mm) sediment transport in high severity burned areas correlated with initial discharge peaks from an adjacent stream, while moderate burn severity sites had considerably more of the >2 mm fraction transported than high burn severity sites. The δ¹³C and δ¹⁵N values and ¹³C‐NMR analyses indicated that sediment eroded from moderate severity burn areas included fresh organic matter that was not as significantly affected by the fire, whereas sediments from high severity burn areas were preferentially enriched in PyC. Our results indicate that along a single hillslope after the Rim Fire, burn severity acted as a primary control on PyC transport post‐fire, with slope angle likely playing a secondary role. The preferential erosion of PyC has major implications for the long‐term persistence of PyC within the soil system.

28653. 题目: One-time cultivation of Chlorella pyrenoidosa in aqueous dye solution supplemented with biochar for microalgal growth, dye decolorization and lipid production
文章编号: N19020202
期刊: Chemical Engineering Journal
作者: Kannikka Behl, Surbhi Sinha, Mahima Sharma, Rachana Singh, Monika Joshi, Amit Bhatnagar, Subhasha Nigam
更新时间: 2019-02-02
摘要: Microalgae are promising bio resources that have garnered attention over the last decade due to its versatile environmental applications. For substantial biomass generation, it is imperative to relegate cost associated with algal cultivation. Biochar was synthesized and added as a component of nutrient source for cultivation of Chlorella pyrenoidosa (Cp) in an aqueous solution of Direct Red 31 (DR 31; diazo) dye to analyze its impact on biomass production, dye decolorization, and lipid generation. Effect of dye concentration, contact time, biochar dosage and pH were investigated on biochar cultivated Cp cells (Biochar-Cp). Results revealed that adjunction of biochar not only promoted algal growth but also enhanced its decolorization efficiency as well as biofuel production. Biochar-Cp cells exhibited superior DR 31 decolorization (80%) after 180 min of contact time. Mechanisms of decolorization (adsorption and biodegradation) by Biochar-Cp cells were also investigated. Lipids were obtained out from the algal biomass after dye decolorization. Fatty acid methyl esters (FAMEs) study showed hexadecanoic acid and octadecenoic acids were dominant fatty acids, major prerequisites of a competent biofuel. The study, thus revealed application of waste sawdust derived biochar as an economical component of a nutrient source in algal cultivation for versatile environmental applications.
图文摘要:

28654. 题目: Response of aggregate associated organic carbon, nitrogen and phosphorous to re-vegetation in agro-pastoral ecotone of northern China
文章编号: N19020201
期刊: Geoderma
作者: Yufei Yao, Nannan Ge, Si Yu, Xiaorong Wei, Xiang Wang, Jingwei Jin, Xuetong Liu, Mingan Shao, Yanchun Wei, Li Kang
更新时间: 2019-02-02
摘要: The agro-pastoral ecotone is an ecologically fragile transition zone and suffers from extensive human-induced land-use changes. To understand how soil organic carbon (OC) and nutrients will respond to re-vegetation practices in such an ecotone zone, we present the response of OC, nitrogen (N) and phosphorus (P) in both bulk soils and water-stable aggregates to typical re-vegetation patterns in an agro-pastoral ecotone of northern China. Three re-vegetation patterns, i.e., cropland converted to natural grassland, woodland and artificial grassland at different times (6 to 40 years), were selected. The paired croplands were also selected as the control for each re-vegetation pattern. The measured soil metrics include the proportions of each type of water-stable aggregate, the mean weight diameter and geometric mean diameter of the aggregates, and the concentrations of OC, N and P in bulk soils and each aggregate fraction. The results showed that the three re-vegetation patterns significantly increased the mass proportion of macro-aggregates, the values of mean weight diameter and geometric mean diameter, and the concentrations of OC and N in topsoils (0–10 cm). The accumulation of OC and N in bulk soils was mainly due to the accumulation in macro-aggregates. Furthermore, increases in OC and N were greater after conversion to legume vegetation than to non-legume vegetation, and were highest at approximately 20 years after the conversion. However, concentrations of P in bulk soils and aggregates were similar among the three re-vegetation patterns and the three aggregate fractions, and were minimally affected by the conversion. These results highlighted the potential of legume vegetation to increase OC and N in surface soils and aggregates, and indicated no response of soil P to re-vegetation in an agro-pastoral ecotone of northern China.

28655. 题目: Decoupled trophic responses to long‐term recovery from acidification and associated browning in lakes
文章编号: N19020114
期刊: Global Change Biology
作者: Taylor H. Leach, Luke A. Winslow, Nicole M. Hayes, Kevin C. Rose
更新时间: 2019-02-01
摘要: Increases in the concentration of dissolved organic matter (DOM) have been documented in many inland waters in recent decades, a process known as ‘browning’. Previous studies have often used space‐for‐time substitution to examine the direct consequences of increased DOM on lake ecosystems. However, browning often occurs concomitant with other ecologically important water chemistry changes that may interact with or overwhelm any potential ecological response to browning itself. Here we examine a long‐term (~20 year) dataset of 28 lakes in the Adirondack Park, New York, USA that have undergone strong browning in response to recovery from acidification. With these data, we explored how primary producer and zooplankton consumer populations changed during this time and what physical and chemical changes best predicted these long‐term ecosystem changes. Our results indicate that changes in primary producers are likely driven by reduced water clarity due to browning, independent of changes in nutrients, counter to previously hypothesized primary producer response to browning. In contrast, declines in calcium concomitant with browning play an important role in driving long‐term declines in zooplankton biomass. Our results indicate that responses to browning at different trophic levels are decoupled from one another. Concomitant chemical changes have important implications for our understanding of the response of aquatic ecosystems to browning.

28656. 题目: Characteristics of sediment affecting monomethylmercury accumulation in benthic fish of the Mekong Delta
文章编号: N19020113
期刊: Environmental Toxicology and Chemistry
作者: Hyojung Choi, Eunji Jeong, Viet Huu Nguyen, Dang Vu Bich Hanh, Nguyen Phuoc Dan, Kyung‐Hoon Shin, Seunghee Han
更新时间: 2019-02-01
摘要: The Mekong River Delta (Vietnam) is a flat, low‐lying area formed by a dense network of main tributaries of the Tien and Hau Rivers, providing a nourishing habitat for aquatic organisms. A sediment survey of the total mercury (Hg), monomethylmercury (MMHg), and geochemical variables was carried out from the coast to 131 km upriver to establish an overview of the environmental factors affecting the bioaccumulation of Hg and MMHg in delta fish. The survey results revealed that the total Hg (12–90 ng g^–1) and MMHg (0.014–1.5 ng g^–1) concentrations were in the range of uncontaminated sediment. Statistical analysis using various geochemical factors demonstrated that sediment MMHg concentrations and fractions of MMHg over total Hg in sediment were higher at sites with higher total organic carbon (TOC) and total nitrogen sites. The current levels of TOC in Mekong Delta sediment are relatively low (0.2–1.5%); however, expanding dam constructions and aquacultures related to salinity intrusion are reinforcing the carbon burial rate by increasing the fine fractions. Based on the positive relationship found between MMHg and TOC in sediment, proper management efforts are necessary to reduce MMHg production in the Mekong River Delta sediment. Environ Toxicol Chem 2018;9999:1–8. © 2018 SETAC

28657. 题目: Simultaneous adsorption and immobilization of As and Cd by birnessite-loaded biochar in water and soil
文章编号: N19020112
期刊: Environmental Science and Pollution Research
作者: Hong-Yan Wang, Peng Chen, Yong-Guan Zhu, Kuang Cen, Guo-Xin Sun
更新时间: 2019-02-01
摘要: A novel biochar was prepared by loading birnessite to improve its capability to simultaneously adsorb As(III), As(V), and Cd(II) in water and soil. Layer sheet–structured birnessite was successfully loaded onto the biochar surface with increased functional groups. SEM, XRD, and FTIR combining with XPS analysis were utilized to characterize birnessite-loaded biochar and its adsorption mechanisms for As and Cd(II). The saturated adsorption capabilities of the birnessite-loaded biochar (BRB) for As(III), As(V), and Cd(II) were as large as 3543, 2412, and 9068 mg/kg (calculated by Langmuir isotherm model), much higher than for the corresponding non-loaded biochar (no adsorption of As, 4335 mg/kg for Cd). Adsorption of Cd and As onto BRB was controlled by multi mechanisms; Cd(II) appeared to coordinate to vacant sites of birnessite, while As formed surface complex with functional groups. Furthermore, BRB showed higher abilities for co-adsorption of As(III) and Cd or As(V) and Cd, which may be due to the formation of Cd₃(AsO₄)₂ surface precipitate as well as synergistic reaction between anions and cations. After conditioning to soil, BRB showed potential for Cd and As remediation under both flooded and unflooded conditions. These results suggested that BRB can be used as an effective sorbent for simultaneous immobilization of heavy metals, especially As and Cd, in environmental and agricultural systems.

28658. 题目: Effects of biochar addition on the NEE and soil organic carbon content of paddy fields under water-saving irrigation
文章编号: N19020111
期刊: Environmental Science and Pollution Research
作者: Shihong Yang, Xiao Sun, Jie Ding, Zewei Jiang, Junzeng Xu
更新时间: 2019-02-01
摘要: The addition of biochar has been reported as a strategy for improving soil fertility, crop productivity, and carbon sequestration. However, information regarding the effects of biochar on the carbon cycle in paddy fields under water-saving irrigation remains limited. Thus, a field experiment was conducted to investigate the effects of biochar addition on the net ecosystem exchange (NEE) of CO₂ and soil organic carbon (SOC) content of paddy fields under water-saving irrigation in the Taihu Lake region of China. Four treatments were applied: controlled irrigation (CI) without biochar addition as the control (CA), CI with biochar addition at a rate of 20 t·ha⁻¹ (CB), CI with biochar addition at a rate of 40 t·ha⁻¹ (CC), and flooding irrigation (FI) with biochar addition at a rate of 40 t·ha⁻¹ (FC). Biochar addition increased rice yield and irrigation water use efficiency (IWUE) by 24.0–36.3 and 33.4–42.5%, respectively, compared with the control. In addition, biochar addition increased the NEE of CI paddy fields. The average NEE of paddy fields under CB and CC was 2.41 and 30.6% higher than that under CA, respectively. Thus, the increasing effect of biochar addition at a rate of 40 t·ha⁻¹ was considerably better than those of the other treatments. Apart from biochar addition, irrigation mode was also identified as an influencing factor. CI management increased the NEE of paddy fields by 17.6% compared with FI management. Compared with CA, CB increased total net CO₂ absorption by 10.0%, whereas CC decreased total net CO₂ absorption by 13.8%. Biochar addition also increased SOC, dissolved organic carbon, and microbial biomass carbon contents. Therefore, the joint regulation of biochar addition and water-saving irrigation is a good technique for maintaining rice yield, increasing IWUE, and promoting soil fertility. Furthermore, when amended at the rate of 20 t·ha⁻¹, biochar addition will be a good strategy for sequestering carbon in paddy fields.

28659. 题目: Identification of toxicants from a highly C10–C40 contaminated sediment influenced by the wood industry: Petroleum hydrocarbons or biogenic organic compounds?
文章编号: N19020110
期刊: Environmental Toxicology and Chemistry
作者: Mari Dahl, Suvi Survo, Pia Välitalo, Grit Kabiersch, Olga‐Sofia Alitalo, Olli‐Pekka Penttinen, Anna‐Lea Rantalainen
更新时间: 2019-02-01
摘要: Sediment from a log pond located in south Finland contained 15,000 to 50,000 mg/kg dw of C₁₀–C₄₀ hydrocarbons. It was unclear whether they originated from the hydraulic fluid of the log hoist or the wood extractives. In the present study, methods of effect‐directed analysis were used for the identification of toxicants. A combination of fractionation, biotesting and chemical analyses revealed that the key toxicant of log pond sediment was retene, a dialkyl‐substituted phenanthrene derived from wood resin acids. Additionally, the most toxic fraction included three other wood‐originated diterpenic compounds. Typical wood extractives such as sesquiterpenes and odd‐carbon number alkanes in the range C₂₁–C₃₃ were identified in the fraction, which showed minor genotoxic potency. The most polar fraction contained triterpenes and showed estrogenic activity. No evidence for the presence of hydraulic fluid in sediment was found. The study also indicated that in cases where the organic matter content of sediment or soil is high, using the results of standard mineral oil analysis in risk management can lead to incorrect actions, because standard methods do not differentiate petroleum hydrocarbons from biogenic hydrocarbons. This article is protected by copyright. All rights reserved

28660. 题目: Organic matter quantity and quality across salinity gradients in conduit‐ vs. diffuse flow‐dominated subterranean estuaries
文章编号: N19020109
期刊: Limnology and Oceanography
作者: Andrea J. Pain, Jonathan B. Martin, Caitlin R. Young, Laibin Huang, Arnoldo Valle‐Levinson
更新时间: 2019-02-01
摘要: Submarine groundwater discharge (SGD) is a source of water and bioreactive solutes to coastal zones but may be modified by organic matter (OM) remineralization dynamics within subterranean estuaries (STEs). We hypothesize that bioreactive solute fluxes should depend on water residence time in STEs, but links between OM transformations and residence time in STEs are poorly characterized. To test this hypothesis, we compare dissolved OM (DOM) quantity and quality in two hydrologically distinct STE systems: a reef lagoon on the east coast of the Yucatan Peninsula, Mexico, where semidiurnal mixing in submarine springs of a carbonate karst aquifer results in short residence times, and a barrier lagoon on the east coast of Florida, where slow flow through siliciclastic sediments results in long residence times. We measured dissolved organic carbon concentrations and characterized colored DOM (CDOM) with ultraviolet spectroscopy and fluorescence combined with Parallel Factor Analysis. Both sites exhibit similar shifts in OM quality with salinity and reflect a marine source of labile OM to the STEs. Nonconservative mixing and CDOM production occurs at all sites but the long water residence times in the siliciclastic STEs cause orders of magnitude greater production than the carbonate STE. Consistent CDOM production across sites with disparate characteristics indicates that STEs are common sources of CDOM to surface water. However, observed variation in the magnitudes of CDOM production indicates that estimating global, and even regional, solute fluxes associated with SGD will be complicated by hydrologic control on extents of OM remineralization.