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23461. 题目: Role of temperature on the development of hypoxia in blackwater from grass
文章编号: N19022803
期刊: Science of The Total Environment
作者: Chamindra L. Vithana, Leigh A. Sullivan, Troy Shepherd
更新时间: 2019-02-28
摘要: In eastern Australia the development of hypoxic blackwater/floodwater and its detrimental consequences are more common in summer than winter. This study examined the effect of temperature on the development of hypoxic conditions which was determined as biochemical oxygen demand (BOD) in floodwater when pasture grass (a source containing labile organic carbon) was inundated. Labile dissolved organic carbon (DOC) in blackwater is one of the main factors that contribute to the development of hypoxic conditions. Temperature plays a key role on the microbial mineralization of labile DOC and hence the development of hypoxic conditions. Prolonged flooding at different seasons (having different temperatures) was simulated in the laboratory by incubating fresh pasture grass cuttings with river water and soil at three different temperatures (20 °C, 27.5 °C and 35 °C) for 20 days. Although this study shows that elevated ambient temperatures can result in more rapid development of hypoxic conditions during the first week of flood peak, it is evident that blackwater formed at relatively moderate ambient temperatures (e.g. 20 °C) has a similar potential to deoxygenate the receiving water bodies, especially after one week's duration of flood peak.
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23462. 题目: Geochemical controls on the distribution of mercury and methylmercury in sediments of the coastal East China Sea
文章编号: N19022802
期刊: Science of The Total Environment
作者: Lu Zhao, Rui Wang, Chi Zhang, Daqiang Yin, Shouye Yang, Xiangtong Huang
更新时间: 2019-02-28
摘要: We examined the spatial and vertical distribution of total mercury (THg) in 119 surface sediment samples and 4 sediment cores from the coastal East China Sea. The THg concentrations (3.6–69.2 μg kg⁻¹, average 34.7 μg kg⁻¹) in surface sediments exhibited a decreasing trend from the inner shelf towards the outer shelf. The THg levels in sediment cores showed a significant increasing trend from the bottom to the top layer. Both the spatial and vertical distribution of THg indicates the impacts of anthropogenic inputs. The THg concentrations in the surface sediments of Yangtze River estuary were strongly correlated with sediment particle size and organic matter, governing by the Yangtze River inputs. The relatively higher THg levels in the surface sediments of southern inner shelf were attributed to the stronger binding affinity of the finer-grained sediments, the nature of organic matter, as well as local inputs. The spatial distribution of toxic methylmercury (MeHg) was distinct from THg, controlled by direct terrigenous MeHg inputs and in situ MeHg formation. The net Hg methylation potential (indicated by MeHg/THg ratio) in surface sediments were significantly influenced by both geochemical factors (DO, temperature and water depth) and the physicochemical properties of sediments (grain size, TOC, S, Fe₂O₃ and MnO), and exhibited the highest correlation with TOC, suggesting the key role of organic matter in governing net MeHg production. Moreover, sites with high MeHg/THg ratios mainly occurred within the summer hypoxia zones adjacent to the Yangtze River estuary, suggesting special attention on Hg ecological risks should be paid in this region.
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23463. 题目: Innovative drinking water treatment techniques reduce the disinfection-induced oxidative stress and genotoxic activity
文章编号: N19022801
期刊: Water Research
作者: Johan Lundqvist, Anna Andersson, Anders Johannisson, Elin Lavonen, Geeta Mandava, Henrik Kylin, David Bastviken, Agneta Oskarsson
更新时间: 2019-02-28
摘要: Disinfection of drinking water using chlorine can lead to the formation of genotoxic by-products when chlorine reacts with natural organic matter (NOM). A vast number of such disinfection by-products (DBPs) have been identified, making it almost impossible to routinely monitor all DBPs with chemical analysis. In this study, a bioanalytical approach was used, measuring oxidative stress (Nrf2 activity), genotoxicity (micronucleus test), and aryl hydrocarbon receptor (AhR) activation to evaluate an innovative water treatment process, including suspended ion exchange, ozonation, in-line coagulation, ceramic microfiltration, and granular activated carbon. Chlorination was performed in laboratory scale after each step in the treatment process in order to investigate the effect of each treatment process to the formation of DBPs. Suspended ion exchange had a high capacity to remove dissolved organic carbon (DOC) and to decrease UV absorbance and Nrf2 activity in non-chlorinated water. High-dose chlorination (10 mg Cl₂ L^-1) of raw water caused a drastic induction of Nrf2 activity, which was decreased by 70% in water chlorinated after suspended ion exchange. Further reduction of Nrf2 activity following chlorination was achieved by ozonation and the concomitant treatment steps. The ozonation treatment resulted in decreased Nrf2 activity in spite of unchanged DOC levels. However, a strong correlation was found between UV absorbing compounds and Nrf2 activity, demonstrating that Nrf2 inducing DBPs were formed from pre-cursors of a specific NOM fraction, constituted of mainly aromatic compounds. Moreover, high-dose chlorination of raw water induced genotoxicity. In similarity to the DOC levels, UV absorbance and Nrf2 activity, the disinfection-induced genotoxicity was also reduced by each treatment step of the innovative water treatment technique. AhR activity was observed in the water produced by the conventional process and in the raw water, but the activity was clearly decreased by the ozonation step in the innovative water treatment process.
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23464. 题目: Combined biochar and nitrogen fertilization at appropriate rates could balance the leaching and availability of soil inorganic nitrogen
文章编号: N19022719
期刊: Agriculture, Ecosystems & Environment
作者: Shuailin Li, Shuo Wang, Zhouping Shangguan
更新时间: 2019-02-27
摘要: Biochar has been proposed to ameliorate soil properties and plant growth. However, it remains unclear how the interaction between biochar and nitrogen (N) fertilizer impacts soil inorganic nitrogen (SIN) leaching and availability in dryland systems. Therefore, a two-year field experiment was carried out on the Loess Plateau in northern China to study the effects of biochar combined with N fertilizer on the leaching and availability of SIN. Biochar applied at 0, 20 and 40 t ha⁻¹ (B0, B1 and B2, respectively) interacted with three N fertilization levels (0, 120 and 240 kg N ha⁻¹; N0, N1 and N2, respectively). Winter wheat (Triticum aestivum L.) was cultivated in a winter wheat-summer fallow cropping system. We measured wheat aboveground biomass and residual SIN in the soil profile (0–60 cm at 10 cm intervals) using standard extraction methods (2 M KCL, shaking at 25 °C for 1 h). Additionally, to ascertain whether field-aged biochar captured SIN and to determine residual SIN availability, we also used a modified extraction method (2 M KCL, shaking at 60 °C for 2 h) and ion exchange membranes (IEMs) to extract SIN from plow layer soil (0–20 cm). Our results indicated that biochar application alone in the absence of N fertilization had no significant effect on wheat biomass or residual SIN in the soil profile. However, compared with the application of N fertilizer alone, the application of biochar at 20 t ha^-1 combined with N fertilizer not only increased wheat biomass by 12.2–13.8% but also significantly decreased residual NO₃⁻-N in the subsoil by 13.2–74.7%. Nevertheless, long-term N fertilization at 240 kg N ha^-1 led to large amounts of residual NO₃⁻-N without a significant increase in crop biomass, which inevitably increased the risk of leaching during the fallow period. Although the application of biochar at 40 t ha^-1 combined with N fertilizer more effectively decreased residual SIN in the subsoil, this approach was impractical because it decreased wheat biomass. Furthermore, the difference between NO₃⁻-N extracted via the modified method and via the standard method increased with biochar application under each N level. Thus, field-aged biochar absorbed a certain amount of NO₃⁻-N, thereby sequestering N in the soil after two years of N fertilization. Hence, biochar could reduce the residual NO₃⁻-N available for leaching during the fallow period. However, notably, overuse of biochar could reduce the amount of NO₃⁻-N available not only for leaching but also for crops. Ultimately, the application of biochar at 20 t ha^-1 combined with N fertilization at 120 kg N ha^-1 is a promising dual-win strategy for improving N availability while concurrently mitigating SIN leaching.

23465. 题目: Soil properties on sub-Antarctic Macquarie Island: Fundamental indicators of ecosystem function and potential change
文章编号: N19022718
期刊: CATENA
作者: Brian R. Wilson, Susan C. Wilson, Brian Sindel, Laura K. Williams, Kirsten L. Hawking, Justine Shaw, Matthew Tighe, Quan Hua, Paul Kristiansen
更新时间: 2019-02-27
摘要: We examined the nature and properties of soils on Australian sub-Antarctic Macquarie Island to determine key environmental factors driving their distribution, development and change. We provide the first classification of these soils using Australian and international (WRB) systems while combining elemental, stable and radio-isotope analysis to interpret processes of soil formation and key controlling environmental factors. Soil organic carbon (SOC) and total nitrogen (TN) concentrations across the island were influenced largely by elevation and topographic position with coastal soils and wetter depressions containing more SOC and TN compared with drier and higher elevation locations. Soils on the high, exposed plateau of the island contained low SOC and TN concentrations by comparison. Results suggested that soils of the coastal zone are subject to ongoing aggradation with significant inputs of nutrient, particularly extractable P (Ext P), from oceanic and especially avifauna sources. Nutrient subsidy was concentrated on coastal margins and the more sheltered eastern side of the island, diminishing significantly with increasing elevation and distance from the coast. Soils of the central plateau contained very low Ext P concentrations throughout the profile and appear to be relic if not degrading. Further comprehensive soil mapping, classification and monitoring across Macquarie Island will elucidate the important role that soils serve for healthy ecosystem function in these sub-Antarctic environments and provide early warning indicators of significant environmental change.

23466. 题目: Comparison of efficacies of peanut shell biochar and biochar-based compost on two leafy vegetable productivity in an infertile land
文章编号: N19022717
期刊: Chemosphere
作者: Bingjie Liu, Zhaohui Cai, Yuchan Zhang, Guocheng Liu, Xianxiang Luo, Hao Zheng
更新时间: 2019-02-27
摘要: The soils in northwest China are severely stressed with nutrient deficiency and water depletion, thus limiting crop production and sustainable agricultural development. Biochar-based amendments, tailored for specific soil issues, have raised great public interest for soil improvement and carbon sequestration. Peanut shell-derived biochar (PBC) and PBC-based amendment (PAD) obtained from composting were added at concentrations of 0%, 1.5%, 3%, and 5% (w/w) into light sierozem soil to compare their effects on growth of crown daisy (Chrysanthemum coronarium L.) and leaf lettuce (Lactuca sativa var longifoliaf L.). PBC had no significant effect on the yields of the two vegetables due to the second season growth, while addition of low concentrations of PAD (≤3%) significantly increased their yields by 15.8%–107%. The positive effect of PAD was primarily attributed to the improved soil qualities (e.g., water holding capacity (WHC), soil organic matter (SOM), electrical conductivity (EC)) and increased contents of available macronutrients (e.g., P and K), and micronutrients (e.g., B, Zn and Mn). However, addition of 5% PAD decreased the yield of crown daisy by 26.9% compared to that grown in untreated soil because of surplus nutrient input resulting in high EC. Overall, our findings demonstrated that the designed PAD synthesized from PBC compost had the potential to ameliorate the infertility in the soil and thus to improve vegetable yield.
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23467. 题目: Alleviation of cadmium accumulation in maize (Zea mays L.) by foliar spray of zinc oxide nanoparticles and biochar to contaminated soil
文章编号: N19022716
期刊: Environmental Pollution
作者: Muhammad Rizwan, Shafaqat Ali, Muhammad Zia ur Rehman, Muhammad Adrees, Muhammad Arshad, Muhammad Farooq Qayyum, Liaqat Ali, Afzal Hussain, Shahzad Ali Shahid Chatha, Muhammad Imran
更新时间: 2019-02-27
摘要: Due to the increase in area of cadmium (Cd)-contaminated soils worldwide, effective measures are necessary to minimize the Cd accumulation in cereals including maize (Zea mays L.) plant. A study was therefore performed to explore the effectiveness of foliar spray of zinc oxide (ZnO) nanoparticle (NPs) alone (0, 50, 75, 100 mg/L) or combined with soil application of biochar (1.0% w/w) on biomass, antioxidant enzyme activity and Cd concentrations in maize plants grown on a Cd-contaminated soil. The results depicted that ZnO NPs alone or in combination with biochar improved the height of maize plants, number of leaves, shoot and roots dry biomass, chlorophyll concentrations and gas exchange attributes. All the amendments reduced the electrolyte leakage, malondialdehyde, and hydrogen peroxide contents while improved the activities of antioxidant enzymes in leaf and roots of maize over the control. The application of 50, 75 and 100 mg/L ZnO NPs reduced the Cd contents in shoots by about 12%, 23, and 61%, and in roots by 18%, 33%, and 53%, respectively, over the control. The Cd concentrations in shoot decreased by 15%, 28%, and 68% and in roots by 14%, 35, and 55% after biochar combined with foliar spray of 50, 75 and 100 mg/L ZnO NPs, respectively. All the amendments improved the Zn concentrations in maize shoots and roots whereas reduced the soil bioavailable Cd. Overall, biochar combined with foliar spray of ZnO NPs could be recommended for safely growing the crops on Cd-contaminated soils.
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23468. 题目: Mercury bioaccumulation in tilefish from the northeastern Gulf of Mexico 2 years after the Deepwater Horizon oil spill: Insights from Hg, C, N and S stable isotopes
文章编号: N19022715
期刊: Science of The Total Environment
作者: Vincent Perrot, William M. Landing, R. Dean Grubbs, Vincent J.M. Salters
更新时间: 2019-02-27
摘要: Mercury (Hg) concentration in fish of the Gulf of the Mexico (GoM) is a major concern due to the importance of the GoM for U.S. fisheries. The Deepwater Horizon (DWH) oil spill in April 2010 in the northern GoM resulted in large amounts of oil and dispersant released to the water column, which potentially modified Hg bioaccumulation patterns in affected areas. We measured Hg species (methylmercury (MMHg) and inorganic Hg (IHg)) concentrations, and light (C, N and S) and Hg stable isotopes in muscle and liver tissues from tilefish (Lopholatilus chamaleonticeps) sampled in 2012 and 2013 along the shelf break of the northeastern GoM. Fish located close to the mouth of the Mississippi River (MR) and northwest of the DWH well-head (47 km) showed significantly lower Hg levels in muscle and liver than fish located further northeast of the DWH (>109 km), where 98% of tilefish had Hg levels in the muscle above US consumption advisory thresholds (50% for tilefish close to the DWH). Differences in light and Hg stable isotopes signatures were observed between these two areas, showing higher δ¹⁵N, and lower δ²⁰²Hg, Δ¹⁹⁹Hg and δ³⁴S in fish close to the DWH/MR. This suggests that suspended particles from the MR reduces Hg bioavailability at the base of the GoM food chains. This phenomenon can be locally enhanced by the DWH that resulted in increased particles in the water column as evidenced by the marine snow layer in the sediments. On the other hand, freshly deposited Hg associated with organic matter in more oligotrophic marine waters enhanced Hg bioaccumulation in local food webs. Comparing Hg isotopic composition in liver and muscle of fish indicates specific metabolic response in fish having accumulated high levels of MMHg.
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23469. 题目: Biotransformation of antibiotics: exploring the activity of extracellular and intracellular enzymes derived from wastewater microbial communities
文章编号: N19022714
期刊: Water Research
作者: Michael T. Zumstein, Damian E. Helbling
更新时间: 2019-02-27
摘要: Evaluating the activity of extracellular and intracellular enzymes derived from wastewater microbial communities is essential to improve our fundamental understanding of micropollutant removal during wastewater treatment. To study biotransformations with respect to enzyme biogeography, we developed a method to separate soluble extracellular, extracellular polymeric substance (EPS)-bound, and intracellular enzymes from wastewater microbial communities and assessed the protease and peptidase activity of the resulting enzyme pools. We also evaluated the biotransformation of six antibiotics (amoxicillin, ampicillin, clindamycin, daptomycin, linezolid, and vancomycin) in each enzyme pool because we expect that the kinetics, pathways, and biogeography of antibiotic biotransformations influence the selection of antibiotic resistance within wastewater microbial communities and in downstream environments. Our results demonstrated that biotransformation rate constants varied among the tested antibiotics, and that the observed rank order was consistent across three wastewater treatment plants. Importantly, many of the observed biotransformations eliminated the functional groups associated with antibiotic activity. Furthermore, we found that β-lactam hydrolysis and daptomycin hydrolysis were catalyzed by enzymes extracted from the EPS, while none of the tested antibiotics were biotransformed by soluble extracellular enzymes. Finally, our results demonstrated that the number of enzyme-catalyzed antibiotic transformations was larger for intracellular than for extracellular enzymes. Together, this study provides novel insights on the kinetics, pathways, and biogeography of antibiotic biotransformations performed by wastewater microbial communities and can be used to inform pathway prediction or the development of biodegradable chemicals.
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23470. 题目: The variation of flocs activity during floc breakage and aging, adsorbing phosphate, humic acid and clay particles
文章编号: N19022713
期刊: Water Research
作者: Mingyu Wu, Wenzheng Yu, Jiuhui Qu, John Gregory
更新时间: 2019-02-27
摘要: The mechanism of removal of humic acid, phosphate and kaolin particles by coagulation with alum and PACl or adsorption by their pre-formed precipitates was investigated, and it was found that the coagulation mechanisms for monomeric Al at neutral pH and polymeric Al₁₃ at alkaline pH were very similar. The removal of phosphate and humic acid by coagulation with alum or PACl did not change with stirring time (between 1 min and 15 min), independent of the dose and species of coagulants. However, for adsorption of these impurities by pre-formed precipitates, the results were significantly different. Both Al³⁺ and nano-sized Al₁₃ could precipitate and form aggregates at pH 7 and pH 9, respectively, and their precipitates became less active (fewer binding sites on the surface of precipitate) with the increase of shear time or shear rates before adsorbing pollutants. Thus, although the total surface area increased (the average size of flocs became smaller) at higher applied shear rates or longer shear time, the removal efficiency of humic acid and phosphate decreased. Also, from the MW distributions, it was confirmed that less humic acid was removed by the adsorption on alum precipitate pre-formed with longer shear time. Chemical groups (OH₂and OH) on the surface of precipitate determined the removal efficiency of phosphate and humic acid, and the activity of precipitate become lower as a result of higher applied shear and longer shear time. This is confirmed be due to some crystallization of the amorphous precipitate, forming inactivated hydroxyl. When kaolin was added 10 min after the alum or PACl precipitate formed, the precipitates captured kaolin particles only on their surface, whereas when alum was added to kaolin suspensions particles were trapped within the growing flocs. When alum/kaolin flocs were broken at high shear rate re-growth of flocs decreased with increasing shear time, but after a short breakage period, long aging of broken flocs had little effect on floc regrowth.
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23471. 题目: The Contribution of Biofilm to Nitrogenous Disinfection By-Product Formation in Full-Scale Cyclically-Operated Drinking Water Biofilters
文章编号: N19022712
期刊: Water Research
作者: Caroline Di Tommaso, Liz Taylor-Edmonds, Susan A. Andrews, Robert C. Andrews
更新时间: 2019-02-27
摘要: Biofiltration has been shown to be effective for disinfection by-product (DBP) precursor control, however few studies have considered its role in the potential formation of DBPs. Biofilm is composed of heterogeneous bacteria as well as extracellular polymeric substances (EPS). The objective of this study was to determine the contribution of biofilm-related materials such as EPS to form nitrogen-containing DBPs upon chloramination, and to determine the influence of cyclical (scheduled on-off) biofilter operation on DBP precursor removal. Biologically active media was sampled from a full-scale biofilter operating under cold-water conditions (3.6 ± 0.5°C) and extracted using a cation exchange resin into a phosphate buffer solution. Biomass concentrations, as determined using adenosine tri-phosphate (ATP) measurements, remained stable at 298 ± 55 ng ATP/g media over the trial period. N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN₄) formation potential (FP) tests conducted under uniform formation conditions (UFC) using extracted biofilm yielded 0.80 ± 0.27 ng NDMA/g media and 18.7 ± 3.3 ng dichloroacetonitrile (DCAN)/g media. Further analyses of extracted biofilm using fluorescence spectroscopy and liquid chromatography-organic carbon detection indicated the presence of proteins above 20 kDa and humic-like substances. Extracted proteins (93.5 ± 8.1 μg/g media) correlated well (R = 0.90) with UV 280 measurements, indicating that spectrophotometry may serve as a valuable tool to quantify proteins in extracted biofilms. While substances in biofilms can serve as NDMA and DCAN precursors, the full-scale cyclically-operated biofilter that was examined did not show release of NDMA precursors during start-up following stagnation periods of 6 hours or more. These biofilters consistently removed 6.9 ± 4.3 ng/L of NDMA precursors; the typical NDMA UFC-FP of biofilter effluent was 8.5 ± 2.6 ng/L.
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23472. 题目: Mechanistic understanding of microplastic fiber fate and sampling strategies: Synthesis and utility of metal doped polyester fibers
文章编号: N19022711
期刊: Water Research
作者: Michael Schmiedgruber, Rudolf Hufenus, Denise M. Mitrano
更新时间: 2019-02-27
摘要: The increased use of synthetic textiles in the last decades, coupled with recent emphasis on the accumulation of (micro)plastic across multiple environmental compartments, has garnered interest into how microplastic fibers are released into the environment. In particular, polyester textiles washed in the home have shown to release microplastic fibers but challenges with microplastic fiber analysis, including time and difficulty of sample preparation and measurement, has limited mechanistic studies on fiber fate and transport studies. In this study, we provide a method to synthesize fibers with an embedded metallic (In) fingerprint which can be used as a tracer for ease of analysis and show the utility of this approach to assess the affinity for heteroaggregation between microplastic fibers and other particles in a heterogeneous suspension, as well as approximate the fate of microplastic fibers in batch studies using activated sludge from a municipal wastewater treatment plant (WWTP). Total In content in the fibers was measured to be 0.2 % by weight, which was low enough to not change fiber dynamics for fate and transport studies (e.g. density, etc.) but provided sensitive detection limits by ICP-MS. Fiber length was 510 μm +/- 410 μm and 30 μm in diameter. The incorporated metal remained stable inside the polymer when suspended in water and in activated sludge, with < 0.1 % In leaching over two months. In batch experiments the majority of fibers were associated with the sludge (>99.9%), with a mass balance of > 95 % recovery achieved on average across batches. Fiber removal linearly increased with contact times of up to ten minutes, suggesting interactions between plastics and organic matter is a metric that should be considered closely in this and other environmental contexts for fate and transport.
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23473. 题目: Temperature sensitivity of biomass‐specific microbial exo‐enzyme activities and CO2 efflux is resistant to change across short‐ and long‐term timescales
文章编号: N19022710
期刊: Global Change Biology
作者: Kyungjin Min, Kate Buckeridge, Susan E. Ziegler, Kate A. Edwards, Samik Bagchi, Sharon A. Billings
更新时间: 2019-02-27
摘要: Accurate representation of temperature sensitivity (Q₁₀) of soil microbial activity across time is critical for projecting soil CO₂ efflux. Because microorganisms mediate soil carbon (C) loss via exo‐enzyme activity and respiration, we explore temperature sensitivities of microbial exo‐enzyme activity and respiratory CO₂ loss across time, and assess mechanisms associated with these potential changes in microbial temperature responses. We collected soils along a latitudinal boreal forest transect with different temperature regimes (long‐term timescale) and exposed these soils to laboratory temperature manipulations at 5, 15, and 25°C for 84 days (short‐term timescale). We quantified temperature sensitivity of microbial activity per g soil and per g microbial biomass at days 9, 34, 55, and 84, and determined bacterial and fungal community structure before the incubation and at days 9 and 84. All biomass‐specific rates exhibited temperature sensitivities resistant to change across short‐ and long‐term timescales (mean Q₁₀ = 2.77 ± 0.25, 2.63 ± 0.26, 1.78 ± 0.26, 2.27 ± 0.25, 3.28 ± 0.44, 2.89 ± 0.55 for β‐glucosidase, N‐acetyl‐β‐D‐glucosaminidase, leucine amino peptidase, acid phosphatase, cellobiohydrolase, and CO₂ efflux, respectively). In contrast, temperature sensitivity of soil mass‐specific rates exhibited either resilience (the Q₁₀ value changed and returned to the original value over time) or resistance to change. Regardless of the microbial flux responses, bacterial and fungal community structure was susceptible to change with temperature, significantly differing with short‐ and long‐term exposure to different temperature regimes. Our results highlight that temperature responses of microbial resource allocation to exo‐enzyme production and associated respiratory CO₂ loss per unit biomass can remain invariant across time, and thus that vulnerability of soil organic C stocks to rising temperatures may persist in the long‐term. Further, resistant temperature sensitivities of biomass‐specific rates in spite of different community structures imply decoupling of community constituents and the temperature responses of soil microbial activities.

23474. 题目: Kinetics of organic carbon mineralization and methane formation in marine sediments (Aarhus Bay, Denmark)
文章编号: N19022709
期刊: Geochimica et Cosmochimica Acta
作者: A.W. Dale, S. Flury, H. Fossing, P. Regnier, H. Røy, C. Scholze, B.B. Jørgensen
更新时间: 2019-02-27
摘要: Sediments were sampled at nine stations on a transect across a 7 – 10 m thick Holocene mud layer in Aarhus Bay, Denmark, to investigate the linkages between CH₄ dynamics and the rate and depth distribution of organic matter degradation. High-resolution sulfate reduction rates (SRRs) determined by ³⁵S tracer experiments decreased by several orders of magnitude down through the mud layer. The rates showed a power law dependency on sediment age: SRR (nmol cm^-3 d^-1) = 10^6.18 × Age^-2.17. The SRR data were used to independently quantify enhanced SO₄^2- transport by bioirrigation. Field data (SO₄^2–, TCO₂, T¹³CO₂, NH₄⁺ and CH₄ concentrations) could be simulated with a reaction-transport model using the derived bioirrigation rates and assuming that the power law was continuous into the methanogenic sediments below the sulfate-methane transition zone (SMTZ). The model predicted an increase in anaerobic organic carbon mineralization rates across the transect from 2410 to 3540 nmol C cm^-2 d^-1 caused by an increase in the sediment accumulation rate. Although methanogenesis accounted for only ∼1 % of carbon mineralization, a large relative increase in methanogenesis along the transect led to a considerable shallowing of the SMTZ from 428 to 257 cm. Methane gas bubbles appeared once a threshold in the sedimentation accumulation rate was surpassed.The ³⁵S-measured SRR data indicated active sulfate reduction throughout the SO₄^2- zone whereas quasi-linear SO₄^2- gradients over the same zone indicated insignificant sulfate reduction. This apparent inconsistency, observed at all stations, was reconciled by considering the transport of SO₄^2- into the sediment by bioirrigation, which accounted for 94 ± 2 % of the total SO₄^2- flux across the sediment-water interface. The SRR determined from the quasi-linear SO₄^2- gradients were two orders of magnitude lower than measured rates. We conclude that models solely based on SO₄^2- concentration gradients will not capture high SRRs at the top of the sulfate reduction zone if they do not properly account for (i) SO₄^2- influx by bioirrigation, and/or (ii) the continuity of organic matter reactivity with sediment depth or age.

23475. 题目: Biochar facilitated the phytoremediation of cadmium contaminated sediments: Metal behavior, plant toxicity, and microbial activity
文章编号: N19022708
期刊: Science of The Total Environment
作者: Xiaomin Gong, Danlian Huang, Yunguo Liu, Guangming Zeng, Sha Chen, Rongzhong Wang, Piao Xu, Min Cheng, Chen Zhang, Wenjing Xue
更新时间: 2019-02-27
摘要: Cadmium (Cd) contamination in river sediments becomes increasingly serious, and phytoremediation has been used to remediate Cd contaminated sediments, but the remediation efficiency needs to be improved. In this study, tea waste derived biochar (TB) was used to facilitate the phytoremediation of Cd contaminated sediments. Results showed that TB at 100, 500 and 1000 mg kg⁻¹ increased Cd accumulation and translocation in ramie seedlings by changing Cd speciation in sediments and altering the subcellular distribution of Cd in plant cells. TB at low contents alleviated Cd induced toxicity in ramie seedlings by promoting plant growth and mitigating the oxidative stress. In addition, the activities of urease-, phosphatase-, and catalase-producing microbes in the Cd contaminated sediments were promoted by the application of TB. These findings demonstrated that biochar at low concentrations could improve the phytoremediation efficiency and mitigating Cd-induced toxicity to plants and microbes in Cd contaminated sediments. This study herein provides a novel technological application of waste biomass in controlling and mitigating risks of heavy metals.
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23476. 题目: Mobility of chromium in sediments dominated by macrophytes and cyanobacteria in different zones of Lake Taihu
文章编号: N19022707
期刊: Science of The Total Environment
作者: Xianfang Fan, Shiming Ding, Musong Chen, Shuaishuai Gao, Zhen Fu, Mengdan Gong, Yan Wang, Chaosheng Zhang
更新时间: 2019-02-27
摘要: To study the mechanisms of chromium (Cr) mobilization in sediments of lakes with different ecotypes, seasonal sampling was performed in the macrophyte-dominated East Taihu (MDET) and cyanobacteria-dominated Meiliang Bay (CDMB) in Lake Taihu. Concentrations of labile Cr(VI) and dissolved Cr were assessed using diffusive gradients in thin films (DGT) and high-resolution dialysis passive sampling devices, respectively. Results indicated that in pore water the dissolved Cr concentrations and in sediments total Cr and Cr fractions concentrations (dissolved, exchangeable and carbonate fraction (F1), Fe-Mn oxide fraction (F2), organic/sulfide fraction (F3)) were lower in MDET than in CDMB. However, the highly toxic DGT-labile Cr(VI) concentrations were higher in MDET sediments than in CDMB sediments. In the two lake zones, the seasonal variations in concentrations of dissolved Cr and DGT-labile Cr(VI) were significant, while total Cr and Cr fractions showed negligible changes (except F1 fraction). In summer, the high mobility of dissolved Cr (MDET: 103.42 ± 10.82 μg/L; CDMB: 108.99 ± 4.24 μg/L) were mainly caused by dissolved organic matter complexing with Cr(III). In winter the high mobility of dissolved Cr (MDET: 100.27 ± 22.04 μg/L; CDMB: 102.01 ± 8.81 μg/L) and DGT-labile Cr(VI) (MDET: 28.26 ± 3.73 μg/L; CDLZ: 25.82 ± 2.26 μg/L) were primarily caused by the oxidization of Cr (III) by Mn(III/IV) oxides. This study establishes the mechanisms for seasonal variation of Cr mobilization in different lake ecological zones, highlighting the urgent need for remediation of Cr pollution, especially in macrophyte-dominated lake zones.
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23477. 题目: Geochemistry of a thermally immature Eagle Ford Group drill core in central Texas
文章编号: N19022706
期刊: Organic Geochemistry
作者: Katherine L. French, Justin E. Birdwell, Katherine J. Whidden
更新时间: 2019-02-27
摘要: The Upper Cretaceous Eagle Ford Group displays significant lateral and vertical geochemical variability. Much of the work on the Eagle Ford Group has been focused southwest of the San Marcos arch. To more fully characterize the Eagle Ford across the entire region, a thermally immature drill core was acquired north of the San Marcos arch that recovered the Pepper Shale and the Eagle Ford Group. Molecular and isotopic analyses of rock extracts were combined with bulk organic and inorganic geochemistry and mineralogy to track the variability in organic matter source and depositional environment, as well as to identify drivers of organic enrichment.The Pepper Shale received significant terrigenous organic matter in its distal deltaic or prodeltaic setting compared to the more distally deposited Eagle Ford Group that primarily hosts marine organic matter. The upper Eagle Ford contains two chemofacies. The older upper Eagle Ford chemofacies has similar mineralogy and organic matter to the underlying lower Eagle Ford, and both intervals display good to excellent source rock potential. In contrast, the younger upper Eagle Ford chemofacies has a different sterane assemblage, a larger terrigenous component, and a higher clay mineral abundance. However, anoxic to euxinic depositional conditions distinguish the lower Eagle Ford from the upper Eagle Ford, which was deposited under oxic to dysoxic conditions. Redox chemistry and organic matter source are two important variables that determine source rock quality, but they did not change in parallel during Eagle Ford deposition. Differences in organic facies explain the Tmax variability, and depositional redox conditions governed organic-richness in the Eagle Ford Group in central Texas.

23478. 题目: Sulfate Radical Induced Degradation of β₂-adrenoceptor Agonists Salbutamol and Terbutaline: Implication of Halides, Bicarbonate, and Natural Organic Matter
文章编号: N19022705
期刊: Chemical Engineering Journal
作者: Lei Zhou, Chenzhi Yan, Mohamad Sleiman, Corinne Ferronato, Jean-Marc Chovelon, Xingbao Wang, Claire Richard
更新时间: 2019-02-27
摘要: The presence of inorganic ions and organic matter in natural water would cause unpredictable consequence on the oxidation efficiency and pathways of sulfate radical (SO₄^•−) based advanced oxidation process (SR-AOPs). In this study, the impacts of water constituents, namely, halides (including chloride (Cl^-) and bromide (Br^-)), bicarbonate (HCO₃^-) and natural organic matter (NOM) on SO₄^•− induced degradation of salbutamol (SAL) and terbutaline (TBL) were evaluated systematically. Our results indicated that chloride exhibited no effect on oxidation efficiencies of SAL and TBL, while Br^-, HCO₃^- and NOM all showed inhibitory effects. Specifically, the detrimental effect of bromide was mainly attributed to the scavenging of SO₄^•− to form the less reactive species, Br₂^•−. By using laser flash photolysis (LFP), the second-order rate constants of Br₂^•− with SAL and TBL were estimated to be 2.1 and 3.9 ×10⁸ M^-1 s^-1, respectively, much smaller than those with SO₄^•− (3.7 ×10⁹ M^-1 s^-1 for SAL and 4.2 ×10⁹ M^-1 s^-1 for TBL). Moreover, bromine addition products of SAL and TBL were detected in the presence of Br^-, which were believed to be more toxic than the parent compounds. Similar to bromide, HCO₃^- could also quench SO₄^•− to generate carbonate radical (CO₃^•−), also less reactive than sulfate radical with SAL (4.8×10⁷ M^-1 s^-1) and TBL (3.2×10⁸ M^-1 s^-1). In the case of NOM, a light screening effect was regarded as the major factor responsible to the decrease of reaction rates, while sulfate radical scavenging played a very limited role. The present work would increase the awareness of secondary reactions during SR-AOPs, as more toxic products were generated in the case of bromide.
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23479. 题目: Soil microbial functions are affected by organic matter removal in temperate deciduous forest
文章编号: N19022704
期刊: Soil Biology and Biochemistry
作者: François Maillard, Valentin Leduc, Cyrille Bach, Arnaud Reichard, Laure Fauchery, Laurent Saint-André, Bernhard Zeller, Marc Buée
更新时间: 2019-02-27
摘要: A growing demand for renewable carbon (C) has led to intensified forest management resulting in the use of forest residues (e.g. canopy, bark or litter layer) as energy sources with potential modifications of soil properties and tree productivity. Because microbes mediate the recycling of C and nutrients sequestered in organic matter, we investigated the effects of organic matter (OM) removal on soil properties, root surfaces, microbial functions and abundance using a new observational forest network. We compared leaf litter and logging residue removal plots to reference plots in six beech forests located in the northern half of France. After three consecutive years of OM removal, C and nitrogen (N) pools were not affected, but OM exportation decreased the cation exchange capacity and available phosphorus (P) pool by respectively 12% and 30% in the topsoil (0–5 cm depth). Fine root surface area significantly increased by 21% in the subsoil (5–10 cm depth) in response to OM removal. Enzymatic activities involved in N and P mobilisation decreased from 12 to 38% with the manipulation of OM. Community-level profiling (CLPP) based on BIOLOG approach revealed that the metabolic potential of the microbial community strongly decreased in response to OM removal. Our results indicated that intensive forestry could affect microbial functions implicated in nutrients mobilisation. We demonstrated that soil organic matter (SOM) content is a predictor of microbial functions resistance to forest residue removal. We recommend that intensive forestry should be reduced or limited in beech forests characterised by low soil OM contents.

23480. 题目: Variations in macro and micro physicochemical properties of activated sludge under a moderate oxidation-in situ coagulation conditioning: relationship between molecular structure and dewaterability
文章编号: N19022703
期刊: Water Research
作者: Daxin Zhang, Yili Wang, Hongyu Gao, Xiaoyang Fan, Yajie Guo, Hongjie Wang, Huaili Zheng
更新时间: 2019-02-27
摘要: A moderate Mn(Ⅶ) oxidation-in situ Fe(Ⅲ) coagulation (Mn(Ⅶ)-Fe(Ⅱ)) conditioning strategy was proposed to improve sludge filterability and release the water bound in extracellular polymeric substances (EPS). During Mn(Ⅶ)-Fe(Ⅱ) conditioning, flocs disintegration and cell disruption, macro and micro physicochemical properties of activated sludge, especially of EPS, were investigated. Relationships between protein molecular structures in EPS fractions of three layers and sludge dewaterability were also determined. Besides, factor analysis was used to explain the variances of “functional” protein secondary structures, which may have an important effect on sludge dewaterability. Results showed that sludge filterability (CST₀/CST) increased by 2.40 times and partial bound water was released at 2 min oxidation of 120 mg/g KMnO₄ with subsequent FeCl₂ termination at equivalent molar ratio of 1:3. During this strategy, EPS wrapping on cells surface was disintegrated, and a limited influence occurred on cells. It was also found that CST and bound water content were strongly correlated with aggregated strands, random coil and β-turn percentages in slime (R² > 0.82, p < 0.05). Moreover, the dewaterability also presented strong negative correlations with aggregated strands, β-sheet and β-turn in TB-EPS (R² > 0.78, p < 0.05). This suggested that unfolding and despiralization of slime protein and moderate weakening rigidity of tightly bound EPS (TB-EPS) protein were beneficial for improvement of sludge dewaterability. In addition, the strong correlation between percentages of “functional” protein secondary structures and factor 1 score (R² > 0.85, p < 0.05) demonstrated that EPS migration, rather than only EPS disintegration, may have a key impact on the formation of some protein secondary structures in slime and TB-EPS. The observed protein secondary structures, which may affect sludge dewaterability, were probably derived from inner EPS.
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