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12461. 题目: Fenton oxidation of municipal secondary effluent: comparison of Fe/Ce-RGO (reduced graphene oxide) and Fe 2+ as catalysts
文章编号: N18090810
期刊: Environmental Science and Pollution Research
作者: Zhong Wan, Jianlong Wang
更新时间: 2018-09-08
摘要: The advanced treatment of municipal secondary effluent by heterogeneous and homogeneous Fenton processes using Fe/Ce-RGO (reduced graphene oxide) and Fe2+ as catalysts was studied and compared. Sulfamethazine (SMT) was spiked in the effluent to examine the effectiveness of the emerging contaminant removal. The Fe/Ce-RGO catalyst was characterized using a scanning electron microscope (SEM) and cycle voltammetry curves. The removal of dissolved organic carbon (DOC), soluble chemical oxygen demand (SCOD), SMT, and ultraviolet-visible spectroscopy in 254 nm (UV254) of municipal secondary effluents was examined. The DOC removal efficiency of secondary effluent (without addition of SMT) was 36.30% and 11.74% using Fe/Ce-RGO and Fe2+ as catalysts, respectively. The removal efficiency of DOC, SCOD, and SMT in heterogeneous Fenton process was higher than that in homogeneous Fenton process. The changes of three-dimensional excitation-emission matrix (3DEEM) fluorescence, soluble microbial products (SMPs), humic acids, and UV254 were determined, and the results indicated that UV254, aromatic proteins, and humic acids decreased rapidly in both processes; however, polysaccharides and protein-like substances were difficult to degrade. Although some toxic substances produced after Fenton-like treatment, the biodegradability of the treated effluent was enhanced.

12462. 题目: Effects of waste lime and Chinese medicinal herbal residue amendments on physical, chemical, and microbial properties during green waste composting
文章编号: N18090809
期刊: Environmental Science and Pollution Research
作者: Lu Zhang, Xiangyang Sun
更新时间: 2018-09-08
摘要: Traditional composting is time-consuming and often results in a low-quality product. The objective of this study was to determine the effects of waste lime (WL; at 0, 2.5, and 3.5%) and/or Chinese medicinal herbal residues (CMHRs; at 0, 10, and 20%) as amendments on the two-stage composting of green waste (GW). The combination of WL and CMHRs improved compost particle-size distribution and pH, decreased nitrogen loss, and increased cation exchange capacity (CEC), nutrient content, and microbial numbers. The combination of WL and CMHRs also accelerated organic matter humification and lignocellulose degradation and therefore increased the germination index of the final compost. Relative to the non-amended compost, the optimal amendment (2.5% WL and 20% CMHRs) increased the percentage of particles of ideal size from 23.8 to 66.9%, the pH from 6.69 to 7.17, the CEC from 52 to 169 cmol/kg, the humic acid to fulvic acid ratio from 1.32 to 2.49, the hemicellulose degradation rate from 42 to 87%, and the cellulose degradation rate from 20 to 61%. The treatment with addition of 2.5% WL and 20% CMHRs to GW required only 21 days to generate the highest quality compost product.

12463. 题目: Impacts of different biochar types on hydrogen production promotion during fermentative co-digestion of food wastes and dewatered sewage sludge
文章编号: N18090808
期刊: Waste Management
作者: Gaojun Wang, Qian Li, Mawuli Dzakpasu, Xin Gao, Chaosui Yuwen, Xiaochang C. Wang
更新时间: 2018-09-08
摘要: Pyrolysis and anaerobic digestion are two important strategies for waste management that may be combined for clean energy production. This article investigates the effects of 12 types of biochars derived from four feedstocks at three pyrolysis temperatures on H2 production via fermentative co-digestion of food wastes and dewatered sewage sludge. The results show that feedstock type and pyrolysis temperature significantly influence biochar properties such as pH, specific surface area and ash contents. Despite the wide range of BET specific surface areas (1.2–511.3 m2/g) and ash contents (5.3–73.7(wt%)) of biochars produced, most biochars promoted the VFAs production process and altered the fermentative type from that of acetate type to butyrate type, which seemed to have a higher efficiency for H2 production. Moreover, fitting of the results to the modified Gompertz model shows that biochar addition shortens the lag time by circa 18–62% and increases the maximum H2 production rate by circa 18–110%. Furthermore, the biochar derived at higher pyrolysis temperatures enhances H2 production dramatically over those derived at low temperatures. Principal components analysis demonstrated that the pH buffering capacity of biochar was critical to the promotion of fermentative H2 production by mitigating the pH decrease caused by VFAs accumulation. Consequently, a sustainable integrated waste management strategy combining pyrolysis and anaerobic digestion is proposed for the efficient treatment of various bio-wastes.

12464. 题目: Pyrolysis behavior and economics analysis of the biomass pyrolytic polygeneration of forest farming waste
文章编号: N18090807
期刊: Bioresource Technology
作者: Sunwen Xia, Haoyu Xiao, Ming Liu, Yingquan Chen, Haiping Yang, Hanping Chen
更新时间: 2018-09-08
摘要: The pyrolysis behavior of Chinese chestnut and Jatropha curcas shells (CNS and JCS, respectively) were investigated to determine the optimum operating temperature for biomass pyrolytic polygeneration systems. At low temperatures (250–450 °C), CO2 was the main component of the pyrolytic gas, and high acidity oil was obtained. When the temperature increased to 550–650 °C, phenol-enriched oil and high LHV biochar (∼26 MJ/kg) were obtained; H2 and CO yields increased. At high temperatures (750–950 °C), heavy-oil and high LHV pyrolytic gas (∼15 MJ/m3) were obtained. Meanwhile, the biochar showed a highly condensed aromatic ring system and low H/C (∼0.1) and O/C (∼0.05) ratios. CNS and JCS biochars showed different tendencies with regard to their structure evolution. An economic analysis was performed, which suggested that the optimum operating temperatures were 450 °C for CNS and 350 °C for JCS.
图文摘要:

12465. 题目: An overview of the effect of pyrolysis process parameters on biochar stability
文章编号: N18090806
期刊: Bioresource Technology
作者: Lijian Leng, Huajun Huang
更新时间: 2018-09-08
摘要: Biochar produced from biomass pyrolysis is becoming a powerful tool for carbon sequestration and greenhouse gas (GHG) emission reduction. Biochar C recalcitrance or biochar stability is the decisive property determining its carbon sequestration potential. The effect of pyrolysis process parameters on biochar stability is becoming a frontier of biochar study. This review discussed comprehensively how and why Biomass compositions and physicochemical properties and biomass processing conditions such as pyrolysis temperature and reaction residence time affect the stability of biochar. The review found that relative high temperature (400-700 oC), long reaction residence time, slow heating rate, high pressure, the presence of some minerals and biomass feedstock of high-lignin content with large particle size are preferable to biochar stability. However, challenges exist to mediate the trade-offs between biochar stability and other potential wins. Strategies were proposed to promote the utilization of biochar as a climate change mitigation tool.
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12466. 题目: Degradation kinetics, mechanism and toxicology of tris(2-chloroethyl) phosphate with 185 nm vacuum ultraviolet
文章编号: N18090805
期刊: Chemical Engineering Journal
作者: Yujia Chen, Jinshao Ye, Ya Chen, Han Hu, Hongling Zhang, Huase Ou
更新时间: 2018-09-08
摘要: Organophosphorus esters (OPEs), a series of high production volume chemicals, receive increasing concerns due to their occurrence in worldwide aquatic environment and resistance to conventional biological water treatment processes. Degradation of tris(2-chloroethyl) phosphate (TCEP) was tested with 185 + 254 nm ultraviolet irradiation treatment. Transformation of TCEP followed a pseudo-first order kinetics with an apparent rate constant at 1.65 × 10−3 s−1 when [TCEP]0 = 3.51 μM, 185 vacuum ultraviolet (VUV) irradiation intensity = 0.24 mW cm−2. Degradation experiments with wavelength screening, radical scavenging and kinetic calculation revealed that the radical-based oxidation induced by 185 nm VUV was the dominant mechanism with a reaction rate constant kOH-TCEP at (3.2 ± 0.3) × 108 M−1 s−1. Radical-based addition and substitution of TCEP generated intermediate products with phosphate backbone at early stage (0–20 min). Based on the toxicology analysis including reactive oxygen species and apoptosis of Escherichia coli, these early stage products have lower toxicity than TCEP or their further small molecule products. Variable pH value and natural organic matters/anions affected the efficiency of VUV, while intrinsic VUV screening and radicals scavenging were two key inhibition mechanisms. VUV induced a radical-based oxidation of TCEP, and it will be a promising treatment method for transforming and detoxifying micro-pollutants from water.
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12467. 题目: A facile and green pretreatment method for nonionic total organic halogen (NTOX) analysis in water – Step I. Using electrodialysis to separate NTOX and halides
文章编号: N18090804
期刊: Water Research
作者: Yulin Zhang, Yinan Bu, Jiarui Han, Yan Liu, Baiyang Chen, Xiangru Zhang, Mengting Yang, Yueting Sui
更新时间: 2018-09-08
摘要: Adsorbable organic halogen (AOX) is a bulk organic parameter conventionally used to indicate all adsorbable halogenated organic disinfection byproducts formed in disinfected water. Analytically, AOX is determined by three sequential steps: 1) concentration and separation of AOX from halides with activated carbon, 2) conversion of AOX into halides with pyrolysis, and 3) quantification of halides via microcoulometry or ion chromatography (IC). Because the approach is relatively costly and cannot effectively recover non-adsorbable compounds, we herein proposed a facile and green pretreatment tool to measure the nonionic portion of total organic halogen (NTOX) with a new three-step approach: 1) separation of NTOX and halides with electrodialysis (ED), 2) conversion of NTOX into halides with ultraviolet, and 3) analysis of halides with IC. To verify this proposal, this study presented the efficiency of ED in separating halides and NTOX under a variety of operational and environmental conditions. The results showed that ED removed ≥98.5% of fluoride, chloride, bromide, and iodide from all tested waters (up to 1000 mg-X/L) within 1.5 h. Meanwhile, ED recovered an average of 87.9% of fourteen small molecular weight model compounds with each at 100 μg/L. By using electrospray ionization-triple quadrupole mass spectrometry, the whole pictures of high molecular weight compounds in a chlorinated drinking water before and after ED pretreatment were compared, which revealed 79.7% and 83.6% recoveries of overall polar chlorinated and brominated compounds, respectively. In addition, the quantity and property of the dissolved organic matter were largely maintained by ED, and the retained organics may be used for later characterization. The study hence presents a novel use of ED as a pretreatment tool to enable subsequent NTOX measurement.
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12468. 题目: Thermo-activated peroxydisulfate oxidation of indomethacin: Kinetics study and influences of co-existing substances
文章编号: N18090803
期刊: Chemosphere
作者: Ruobai Li, Meixuan Cai, Haijin Liu, Guoguang Liu, Wenying Lv
更新时间: 2018-09-08
摘要: The widespread occurrence of non-steroidal anti-inflammatory drugs (NSAIDs) (e.g., Indomethacin) in the ambient environment has attracted growing concerns due to their potential threats to ecosystems and human health. Herein, we investigated the degradation of indomethacin (IM) by thermo-activated peroxydisulfate (PDS). The pseudo first-order rate constant (kobs) of degradation of IM was increased significantly with higher temperatures and PDS doses. Moreover, when the initial pH value was raised from 5 to 9 the IM degradation was initially decreased and then increased. Basic conditions were favorable for the removal of IM in the thermo-activated peroxydisulfate system. A response surface methodology based on the Box-Behnken design (BBD) was successfully employed for the optimization of the thermo-activated peroxydisulfate (PDS) system. The presence of chlorine ions manifested a dual effect on the degradation of IM, while bicarbonate and SRFA (as a NOM model) reduced it. Radical scavenging tests and electron spin resonance (ESR) revealed that the dominant oxidizing species were SO4 and OH at pH 9. Furthermore, the TOC removal efficiency attained 28.8% and the release of Clwas 38.5% at 60 °C within 24min, while the mineralization rate of IM were 85.5% with the PDS concentration up to 20 mM at 2 h oxidation. To summarize, thermo-activated PDS oxidation is a promising technique for the remediation of IM-contaminated water.
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12469. 题目: Increased microbial uptake and plant nitrogen availability in response to simulated nitrogen deposition in alpine meadows
文章编号: N18090802
期刊: Geoderma
作者: A.C. Simpson, D. Zabowski, R.M. Rochefort, R.L. Edmonds
更新时间: 2018-09-08
摘要: As global industry and intensive agriculture increase in response to an expanding human population, oligotrophic ecosystems such as alpine and subalpine habitats are increasingly vulnerable to transported atmospheric nitrogen (N) pollution. Even at low levels, N deposition can alter soil chemistry via changes in decomposition rates and mineralization of N from soil organic matter. We used fertilization to mimic N deposition in three National Park alpine meadow ecosystems in the Pacific Northwest (PNW) of the United States (an area of low ambient N deposition) over a 3-year period. Our sites were two moist heath meadow ecosystems in the western Cascade Mountains and one dry meadow ecosystem in the eastern Olympic Mountains. We assessed alpine soil chemistry and N cycling responses to simulated N deposition, using soil inorganic N availability to plants as a critical loads indicator. Soil solution inorganic N supply as measured by resin probes increased in response to N treatment at all sites by Year 3 in plots fertilized at the 10 kg N ha−1 yr−1 treatment level. At the heath meadow sites, we observed increased soil NO3-N during the summer and decreased extractable organic carbon (C) during the fall in response to applied N. We also observed seasonal increases in the proportion of soil N contained in microbial biomass in response to treatment. These data indicate season-specific increases in microbial N uptake and mineralization in response to fertilizer treatment. The carbon-rich, fine-ash volcanic soils of the North Cascades were the most sensitive to N treatment with low microbial N uptake. From those soils, we derived an empirical critical load of 6 kg N per ha−1 yr−1 for increased soil N availability. However, alpine meadow soils in the Western Cascades undergo N limitation in the fall and may have less potential for N leaching with fall rains. In contrast, soils at the dry meadow site had much greater potential for N mineralization, and are temperature- and moisture-limited rather than N limited. Changes in soil chemistry in response to N deposition were site-specific and resulted from differences in plant uptake and soil N mineralization capacity, indicating two very different regimes for response to N deposition for N-limited alpine meadows vs moisture-limited alpine meadows.
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12470. 题目: Bioremediation of chromium contaminated water by diatoms with concomitant lipid accumulation for biofuel production
文章编号: N18090801
期刊: Journal of Environmental Management
作者: Abolghasem Hedayatkhah, Mariana Silvia Cretoiu, Giti Emtiazi, Lucas J. Stal, Henk Bolhuis
更新时间: 2018-09-08
摘要: Hexavalent chromium compounds such as chromate and dichromate, commonly designated as Cr (VI) compounds, are widely used heavy metals in different industries and are considered highly toxic to most life forms. Unfortunately, they have become a major pollutant of groundwater and rivers around dichromate using industries. Bioremediation is widely used to decrease the amount of dichromate in wastewater but requires large amounts of precious fresh water. Here we tested two marine micro-algal species, Phaeodactylum tricornutum strain CCY0033 and Navicula pelliculosa strain CCMP543, for their ability of dichromate bioremediation and concomitantly producing lipids that can serve as biofuel. Dichromate tolerance of the strains was investigated under different growth conditions in order to obtain high biomass yields, high lipid accumulation and high dichromate removal from the medium. Both algal strains grew well and produced high biomass in media containing up to 1 mg of dichromate per liter. Variations in growth conditions revealed that dichromate removal from the medium correlated positively with biomass yield. Dichromate removal using living cells was in the same order of magnitude as with autoclaved dead cells or when using extracted extracellular polymeric substances (EPS). This suggests biosorption of dichromate to cell-associated polymeric substances as the major mechanism of the bioremediation process. For both strains, optimal dichromate removal and lipid production were achieved at a light intensity of 55 μmol m−2s−1 and at a sodium nitrate concentration of 3 mM. The optimal temperature for dichromate removal and lipid production was 23 °C for P. tricornutum and 27 °C for N. pelliculosa. Compared to P. tricornutum strain CCY0033, N. pelliculosa strain CCMP543 produced an overall higher lipid yield under these conditions.

12471. 题目: The characteristics of carbonaceous aerosol in Beijing during a season of transition
文章编号: N18090720
期刊: Chemosphere
作者: Jiu-meng Liu, Zhen-yu Du, Mark Gordon, Lin-lin Liang, Yong-liang Ma, Mei Zheng, Yuan Cheng, Ke-bin He
更新时间: 2018-09-07
摘要: Carbonaceous aerosol was measured during fall of 2010 in Beijing. Daily variation of organic carbon (OC) was found to coincide with that of relative humidity (RH), and the OC to elemental carbon (EC) ratios were more than doubled during the more humid periods (RH above 0.75) compared to other conditions. This large increase in OC/EC could not be explained by the variations of primary biomass burning emissions but was accompanied by a five-fold increase in the sulfate to EC ratio. It was then inferred that secondary organic aerosol (SOA) formation was enhanced under the more humid conditions, presumably through aqueous-phase processes. This enhanced SOA formation might be partially associated with particles externally mixed with black carbon, as indicated by the RH-dependent relationships between aerosol optical attenuation and EC loading. In addition, organic aerosols exhibited different properties between the more humid and the other periods, such that they were less volatile and charred more significantly during thermal-optical analysis in the former case. These differences coincided with the evidence of enhanced SOA formation under the more humid conditions. This study highlights the necessity of incorporating aqueous-phase chemistry into air quality models for SOA.

12472. 题目: Environmental parameters, and not phylogeny, determine the composition of extracellular polymeric substances in microbial mats from extreme environments
文章编号: N18090719
期刊: Science of The Total Environment
作者: Yolanda Blanco, Luis Alfonso Rivas, Elena González-Toril, Marta Ruiz-Bermejo, Mercedes Moreno-Paz, Víctor Parro, Arantxa Palacín, Ángeles Aguilera, Fernando Puente-Sánchez
更新时间: 2018-09-07
摘要: The ability to establish biofilms is a key trait for microorganisms growing in extreme environments. The extracellular polymeric substances (EPS) present in biofilms provide not only surface attachment, but also protection against all kinds of environmental stressors, including desiccation, salinity, temperature or heavy metal pollution. The acquisition of suitable biofilm characteristics might thus be an important process mediating the adaptation of microorganisms to novel environmental conditions. In this work we have characterized the EPS of 20 phylogenetically diverse biofilms collected in situ from five contrasting extreme environments, including two geothermal areas (Copahue, Argentina; Seltun, Iceland), two cold areas (Pastoruri glacier, Peru; Byers Peninsula, Antarctica) and one extremely acidic river (Río Tinto, Spain). Biofilms were subjected to biochemical characterization, glycan profiling and immunoprofiling with an antibody microarray. Our results showed that environmental conditions strongly influence biofilm characteristics, with microorganisms from the same environment achieving similar EPS compositions regardless of the phylogeny of their main species. The concentration of some monosaccharides in the EPS could be related to environmental conditions such as temperature or heavy metal toxicity, suggesting that in some cases stress resistance can be mediated by specific sugars. Overall, our results highlight the existence of conserved EPS compositional patterns for each extreme environment, which could in turn be exploited to engineer ecological adaptations in genetically modified microorganisms.
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12473. 题目: Significantly depleted 15N in suspended particulate organic matter indicating a strong influence of sewage loading in Daya Bay, China
文章编号: N18090718
期刊: Science of The Total Environment
作者: Zhixin Ke, Yehui Tan, Liangmin Huang, Jiaxing Liu, Chenhui Xiang, Chunyu Zhao, Jingping Zhang
更新时间: 2018-09-07
摘要: The influence of anthropogenic nutrient loading on the stable isotopic signatures (δ13C and δ15N) in the suspended particulate organic matter (SPOM) is still not fully understood. Water quality and the values of δ13C and δ15N in the SPOM were investigated in the surface water of Daya Bay during the spring of 2016 and 2017. The results indicated that the Dan'ao River is the main point source of nutrient pollution in Daya Bay. The δ15NPOM was very low in the Dan'ao River. The distribution pattern for this parameter in Daya Bay was determined chiefly by Dan'ao River discharge. Variations in δ15NPOM were ascribed mostly to the input of 15N-depleted DIN assimilated by the estuarine phytoplankton in Daya Bay. Extremely high NH4+ level in the river discharge should be responsible for the low δ15NPOM in the river water. The distribution of δ13CPOM in Daya Bay was regulated mainly by the input of 13C-depleted riverine SPOM. In the present study, the influence of phytoplankton growth on the δ13CPOM was not significant. Moreover, episodic rain events significantly influenced the temporal and spatial variations in water quality and isotopic signature in Daya Bay. The relatively depleted SPOM 15N in 2016 may have been correlated with the strong El Niño events of 2015–2016. Increases in the frequency and volume of rainfall associated with El Niño may have enhanced nutrient loading and the risk of algal red tide in the Daya Bay. In general, significant 15N depletion in SPOM could be the characteristic of hypereutrophic riverine waters. This study suggested that δ15NPOM may be an effective indicator of the strength of riverine nutrient loading in Daya Bay.
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12474. 题目: Predicting cadmium concentration in soils using laboratory and field reflectance spectroscopy
文章编号: N18090717
期刊: Science of The Total Environment
作者: Xia Zhang, Weichao Sun, Yi Cen, Lifu Zhang, Nan Wang
更新时间: 2018-09-07
摘要: Visible and near-infrared spectroscopy (VNIRS, 350–2500 nm) is a promising alternative to rapidly investigate soil contamination by heavy metals. To explore the possibility of predicting heavy metal concentration in soils using laboratory and field reflectance spectroscopy and examine transferability of the prediction method, 46 soil samples from a mining area, 42 soil samples from an agricultural land, and the corresponding two sets of field soil spectra were collected. Cadmium (Cd) was taken as an example in this study. The collected soil samples were air-dried, ground, sieved, and then used for laboratory spectral measurement and chemical analysis. Soil reflectance spectroscopy associated with organic matter was extracted from the VNIRS and used to predict Cd concentration based on strong sorption and retention of Cd on soil organic matter. Genetic algorithm (GA) was adopted for band selection, and the selected bands were used to calibrate the prediction model with partial least squares regression (PLSR). Compared with the prediction using entire VNIR region, the ratio of prediction to deviation (RPD) and the coefficient of determination (R2) were improved from 1.473 and 0.508 to 2.997 and 0.881 for laboratory spectra and 1.437 and 0.484 to 1.992 and 0.731 for field spectra by using spectral bands associated with organic matter in the mining area. The RPD and R2 values were improved from 1.919 and 0.707 to 3.727 and 0.923 for laboratory spectra and 1.057 and 0.036 to 1.747 and 0.646 for field spectra by the prediction method in the agricultural land. The improvement was further revealed by prediction of Cd concentration with a selected subset of soil samples from the mining area. The results suggest that predicting Cd concentration in soils with GA-PLSR using reflectance spectroscopy associated with organic matter is feasible and the prediction method could have the potential to be applied to field conditions.
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12475. 题目: Nitrogen and phosphorus enrichment accelerates soil organic carbon loss in alpine grassland on the Qinghai-Tibetan Plateau
文章编号: N18090716
期刊: Science of The Total Environment
作者: Ruyi Luo, Jianling Fan, Weijin Wang, Jiafa Luo, Yakov Kuzyakov, Jin-Sheng He, Haiyan Chu, Weixin Ding
更新时间: 2018-09-07
摘要: Anthropogenic activities have substantially increased soil nutrient availability, which in turn affects ecosystem processes and functions, especially in nutrient-limited ecosystems such as alpine grasslands. Although considerable efforts have been devoted to understanding the responses of plant productivity and community composition to nitrogen (N) and phosphorus (P) enrichment, the nutrient enrichment effects on soil organic carbon (SOC) and microbial functions are not well understood. A four-year field experiment was established to evaluate the influence of continuous N and P enrichment on plant growth and SOC content in an alpine grassland of the Qinghai-Tibetan Plateau. The study included four treatments: Control without addition, N addition, P addition, and N plus P addition. N addition strongly increased aboveground plant biomass and decreased species richness by promoting growth of the dominant grasses species. In contrast, N and P enrichment significantly decreased SOC, especially the recalcitrant organic C content in the surface layer (0–10 cm) by reducing the slow C pool and enlarging the active C pool. Microbial biomass and activities of C-degrading enzymes (β-glucosidase, cellulase and polyphenol oxidase) and an N-degrading enzyme (chitinase) increased with nutrient inputs. The CO2 emissions during a 300 d incubation period were positively correlated with the cellulase and chitinase activities, while the slow C pool was negatively correlated with the cellulase and polyphenol oxidase activities. Consequently, N and P enrichment accelerated decomposition of the recalcitrant C by stimulating microbial growth and increasing enzyme activities, leading to negative impacts on soil C sequestration. Overall, the results indicate that alpine grassland soils of the Qinghai-Tibetan Plateau may be changing from a C sink to a C source under increasing N and P availability, and improvement of alpine grassland management through nutrient inputs should consider not only the aboveground biomass for grazing, but also the soil C sequestration and ecosystem functioning.
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12476. 题目: Cu and Co nanoparticles co-doped MIL-101 as a novel adsorbent for efficient removal of tetracycline from aqueous solutions
文章编号: N18090715
期刊: Science of The Total Environment
作者: Jiahui Jin, Zhaohui Yang, Weiping Xiong, Yaoyu Zhou, Rui Xu, Yanru Zhang, Jiao Cao, Xin Li, Chengyun Zhou
更新时间: 2018-09-07
摘要: Chromium metal-organic framework (MIL-101(Cr)) has been widely studied for removing organic contaminants from aqueous solutions due to its excellent water stability and giant pore size, but its low adsorption capacity limits the application. In this study, a new adsorbent MIL-101 loaded with CuCo bimetallic nanoparticles (CuCo/MIL-101) was successfully fabricated and applied in removal of tetracycline (TC) from aqueous solutions. The adsorption capacity of CuCo/MIL-101 for TC increased by 140% compared with that of pure MIL-101, which may be attributed to the chemical bonding between Cu and Co BNPs in MIL-101 and TC molecules. The effects of pH, ionic strength, humic acid and contact time on the adsorption were also discussed in detail. The results showed that the removal efficiency of TC solution with high concentration (100 mg L−1) by CuCo/MIL-101 was still as high as 82.9%. The data of adsorption kinetics and isotherms could be well fitted by Elovich model and Freundlich model, respectively. According to the fitting parameters, the maximum adsorption capacity of CuCo/MIL-101 reached up to 225.179 mg g−1. Additionally, the adsorption process of TC onto CuCo/MIL-101 was spontaneous and endothermic. Electrostatic interactions could play an important role in the adsorption process. The enhanced adsorption capacity, excellent reusability and water stability demonstrated the potential of CuCo/MIL-101 composite as a novel adsorbent for the removal of TC from aqueous solutions.
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12477. 题目: Synthesis of soil carbon losses in response to conversion of grassland to agriculture land
文章编号: N18090714
期刊: Soil and Tillage Research
作者: Shiming Tang, Jianxin Guo, Shucheng Li, Jiahuan Li, Shu Xie, Xiajie Zhai, Chengjie Wang, Yujuan Zhang, Kun Wang
更新时间: 2018-09-07
摘要: The conversion of grassland to cropland is one of the major changes in land use, and it accelerates both soil erosion and the loss of soil organic carbon (SOC). However, the general patterns of SOC loss after grassland cultivation are rarely assessed, and the potential mechanisms remain unclear. Here, a meta-analysis of 81 case studies was performed to show that SOC decreased with soil depths of 0–60 cm after grassland conversion, but no significant differences were found at depths >60 cm. SOC also declined significantly with the duration of grassland conversion. The response ratio of SOC changes tended to reach equilibrium after 20 years of grassland cropping. Our results indicate that reduction in SOC mainly depended on changes in precipitation, soil physical-chemical properties and soil microbes. These conclusions highlight the importance of improving the accuracy of predictions on SOC losses and on the global carbon cycle in the face of land-use changes worldwide.

12478. 题目: Anticyclonic eddy edge effects on phytoplankton communities and particle export in the northern South China Sea
文章编号: N18090713
期刊: Journal of Geophysical Research: Oceans
作者: Lei Wang, Bangqin Huang, Edward A. Laws, Kuanbo Zhou, Xin Liu, Yuyuan Xie, Minhan Dai
更新时间: 2018-09-07
摘要: We examined response of phytoplankton total chlorophyll a (TChl a) and community composition to three coherent anticyclonic eddies (ACEs) observed during a cruise to the northern South China Sea on July 28‐August 7, 2007. Photosynthetic pigments were measured to estimate the contribution of nine phytoplankton groups to TChl a. Although the water column integrated TChl a inventory in the upper 100 m was very similar among the three ACEs (17.6–18.9 mg m–2) we observed during the cruise, there were remarkable enhancements in biomasses at the eddy edges. TChl a inventory was 20.8 ± 3.0 mg m–2 at the edge, which was 33% or 60% higher than at the center and reference. The greatest enhancement of the TChl a at edge was attributed to haptophyte‐8, which was 1.6 and 2.2 times the analogous concentrations at the center and reference sites. The Prochlorococcus Chl a was ~50% greater at the edge relative to the reference and was intermediate at the center. Diatom Chl a at the edge was ~2.5 times the concentrations at the center and reference sites. The positive correlation between particulate organic carbon (POC) flux and haptophyte‐8 Chl a at the edge implied an important role of haptophyte‐8 in particle export productivity. It is interesting to note that there occurred higher fluxes of biogenic Si at the center of the ACEs due likely to lateral transport of diatoms from the edge. The phenomenon of higher TChl a at the edge but higher export at the center may have been the combined result of vertical convection and lateral transport within the eddies.

12479. 题目: Organic matter and nutrient inputs from large wildlife influence ecosystem function in the Mara River, Africa
文章编号: N18090712
期刊: Ecology
作者: Amanda L. Subalusky, Christopher L. Dutton, Laban Njoroge, Emma J. Rosi, David M. Post
更新时间: 2018-09-07
摘要: Animals can be important vectors for the movement of resources across ecosystem boundaries. Animals add resources to ecosystems primarily through egestion, excretion and carcasses, and the stoichiometry and bioavailability of these inputs likely interacts with characteristics of the recipient ecosystem to determine their effects on ecosystem function. We studied the influence of hippopotamus excretion/egestion and wildebeest carcasses, and their interactions with discharge, in the Mara River, Kenya. We measured nutrient dissolution and decomposition rates of wildlife inputs, the influence of inputs on nutrient concentrations and nutrient limitation in the river and the influence of inputs on biofilm growth and function in both experimental streams and along a gradient of inputs in the river. We found that hippopotamus excretion/egestion increase ammonium and coarse particulate organic matter in the river, and wildebeest carcasses increase ammonium, soluble reactive phosphorus, and total phosphorus. Concentrations of dissolved carbon and nutrients in the water column increased along a gradient of wildlife inputs and during low discharge, although concentrations of particulate carbon decreased during low discharge due to deposition on the river bottom. Autotrophs were nitrogen-limited, and heterotrophs were carbon-limited and nitrogen- and phosphorus- co-limited, upstream of animal inputs, but there was no nutrient limitation downstream of inputs. In experimental streams, hippo and wildebeest inputs together increased biofilm GPP and R. These results differed in the river, where low concentrations of hippo inputs increased gross primary production (GPP) and respiration (R) of biofilms, but high concentrations of hippo inputs in conjunction with wildebeest inputs decreased GPP. Our research shows that inputs from large wildlife alleviate nutrient limitation and stimulate ecosystem metabolism in the Mara River, and that the extent to which these inputs subsidize the ecosystem is mediated by the quantity and quality of inputs and discharge of the river ecosystem. Thus, animal inputs provide an important ecological subsidy to this river, and animal inputs were likely important in many other rivers prior to the widespread extirpation of large wildlife. This article is protected by copyright. All rights reserved.

12480. 题目: Characterization of spatially variable riverbed hydraulic conductivity using electrical resistivity tomography and induced polarization
文章编号: N18090711
期刊: Hydrogeology Journal
作者: Sien Benoit, Gert Ghysels, Kevin Gommers, Thomas Hermans, Frederic Nguyen, Marijke Huysmans
更新时间: 2018-09-07
摘要: The spatial distribution of hydraulic conductivity (K) in riverbeds is essential to understand and model river–groundwater interactions. However, K in riverbeds varies over several orders of magnitude and its spatial distribution is closely linked to complex geological and fluvial processes. Investigating the local distribution and spatial heterogeneity of K is therefore a challenging task. The use of direct current (DC) and time-domain-induced polarization (IP) geoelectrical methods to map qualitatively the spatial distribution of K within riverbeds is described. The approach is demonstrated for a test site situated in a typical lowland river in Belgium. Inverted geophysical parameters (resistivity, chargeability and normalized chargeability) are compared with estimates of K obtained through slug tests. In general, high values of K are observed in the middle of the river and lower values towards the banks, while the opposite is true for chargeability and normalized chargeability. Therefore, there exists an inverse correlation between K and IP geophysical parameters. Furthermore, geostatistical analyses using variograms show that all parameters have ranges of similar magnitudes. The strong correlation between K and chargeability or normalized chargeability can be explained by the fact that all three parameters are mainly controlled by clay and organic matter content.

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