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23921. 题目: Effect of UV/TiO2 pretreatment on fouling alleviation and mechanisms of fouling development in a cross-flow filtration process using a ceramic UF membrane
文章编号: N18102717
期刊: Chemical Engineering Journal
作者: Tao Yang, Houfeng Xiong, Fen Liu, Qiyong Yang, Bingjie Xu, Changchao Zhan
更新时间: 2018-10-27
摘要: In the application of ultrafiltration (UF) for removal of natural organic matter (NOM) from water, membrane fouling has always been considered a big issue. The influence of UV/TiO2 photocatalysis as pretreatment to mitigate cross-flow ceramic UF membrane fouling caused by humic acid (HA) and the involved mechanisms of fouling development were investigated. The characterization of dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA), excitation-emission matrix (EEM), molecular weight (MW), hydrophilicity, fouling resistance, scanning electron microscopy (SEM) and model fitting using Hermia blocking models were performed. The dominant membrane fouling patterns can be predicated by the initial intermediate pore blocking, transition fouling and the final stage of limited cake growth. With extended UV/TiO2 pretreatment time, a significant reduction of cake filtration coefficients and a slight decrease in pore blocking coefficients were observed. Longer UV/TiO2 pretreatment achieved the remarkable effect of reversible fouling elimination as a result of reaching the final stage of limited cake growth earlier and aggregation forming a porous cake layer by TiO2 particles mixed with more hydrophilic (HPI) and high MW (>50 kDa) humic-like substances. However, photocatalytic pretreatment exhibited a slight effect on the mitigation of irreversible fouling that was mainly dominated by HPI fractions, especially tryptophan-like protein (5–50 kDa) organics attaching to and/or blocking the membrane pores.
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23922. 题目: Attribution of crop yield responses to application of organic amendments: A critical review
文章编号: N18102716
期刊: Soil and Tillage Research
作者: Corinne Celestina, James R. Hunt, Peter W.G. Sale, Ashley E. Franks
更新时间: 2018-10-27
摘要: Soil organic matter affects soil physical, chemical and biological properties and is thus agronomically important because these factors affect crop yields. Organic amendments such as manures, composts and plant residues are frequently used in crop production systems as alternatives to inorganic fertilizers, to restore degraded soils and ameliorate physicochemical constraints. Crop yield responses to the application of organic amendments can be due to the amelioration of soil constraints, plant nutrients contained in the amendment, or both factors acting in concert. Because of the way in which many organic amendment experiments are conducted, these factors can be confounded due to poor experimental design leading to difficulties in accurately ascribing crop yield responses to these different factors. In this review we consider three scenarios where organic amendments are used as fertilizers, soil restorative agents and soil ameliorants to highlight common limitations of these experiments that prevent attribution of crop yield response. To overcome these limitations, we provide guidelines for the design, conduct and analysis of organic amendment experiments which will allow the attribution of yield responses to nutrition, alleviation of physicochemical constraints, or other factors. To achieve these aims, field experiments must (1) identify a genuine constraint to crop yield at the experimental site; (2) incorporate proper treatments to control for the effects of nutrient content and method of placement; (3) use appropriate sampling protocols to assess treatment differences; (4) carry out suitable soil and plant analyses; and (5) be conducted over several sites and years. Controlled environment experiments and modelling approaches may also be used to overcome some of the limitations of field experiments and provide a detailed mechanistic understanding of the crop yield response.
23923. 题目: Membrane fouling in aerobic granular sludge (AGS)-membrane bioreactor (MBR): effect of AGS size
文章编号: N18102715
期刊: Water Research
作者: Wenxiang Zhang, Feng Jiang
更新时间: 2018-10-27
摘要: The main goal of the current study was to investigate the membrane fouling mechanism of aerobic granular sludge (AGS) from a self-cultivated AGS membrane bioreactor (MBR) with various AGS sizes. In this regard, AGSs were sieved into 6 levels: 0∼0.5, 0.5∼0.7, 0.7∼1, 1∼1.2, 1.2∼1.7 mm and larger than 1.7 mm, then filtrated by a small filtration cell. Interestingly, there appeared a critical AGS size (1∼1.2 mm) for membrane fouling. Above 1.2 mm, flux increased and fouling reduced with size, due to the loose cake layer and high permeability caused by larger AGS. Below 1 mm, for smaller AGS, higher flux and lower fouling appeared, because less extracellular polymeric substance (EPS) formed and adhered onto AGS foulants. In the critical size, membrane fouling was serious to the most extent, on account of the dual role of the compact structure of cake fouling layer and the adhesion of EPS. Moreover, this critical AGS size also possessed the highest cake layer, pore blocking and irreversible fouling, which generally existed in various operational conditions. Besides, the results of SEM, AFM, hydrophilicity and ATR-FTIR also proved that the existence of the maximum membrane fouling at the critical AGS size. This study provides a deep understanding of the membrane fouling mechanisms of AGS in MBR and is beneficial for developing a new membrane fouling mitigation strategy by terms of regulating AGS size.
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23924. 题目: Application of fractional-order derivative in the quantitative estimation of soil organic matter content through visible and near-infrared spectroscopy
文章编号: N18102714
期刊: Geoderma
作者: Yongsheng Hong, Yaolin Liu, Yiyun Chen, Yanfang Liu, Lei Yu, Yi Liu, Hang Cheng
更新时间: 2018-10-27
摘要: The spectral preprocessing method has become an integral component of soil analysis through visible and near-infrared (Vis-NIR) spectroscopy. Various spectral pretreatment techniques are applied to improve model accuracy by removing undesired side effects, such as spectral noise, baseline shift, and light scattering, and by accentuating spectral features. Conventional integer-order derivatives (i.e., first and second derivatives), which represent specific cases of fractional-order derivatives (FODs), may neglect some detailed spectral information related to target variables. The objective of this study was to compare the performance of FOD in the estimation of soil organic matter (SOM) with that of conventional first and second derivatives. A total of 258 soil samples (180 for calibration and 78 for validation) were collected from Jianghan Plain, Central China. The reflectance spectra and SOM concentrations of the samples were obtained in the laboratory. Two regression techniques, namely, partial least squares (PLS) and PLS–support vector machine (PLS–SVM), and eight FOD transformation processes for spectral data were combined and compared. Results indicated that as the derivative order increased, the details of the FOD spectra changed and the spectral resolution of reflectance curves improved; the intensity of the spectral signals, however, weakened. The correlation between SOM and FOD spectra was enhanced at some specific wavelengths (e.g., the absolute value of the best one-dimensional correlation coefficient of the 1.25-order derivative spectra could reach 0.65 but that of the original reflectance spectra was only 0.47). In most cases, the PLS–SVM models performed better in SOM estimation than the PLS models. The PLS–SVM model with the 1.25-order derivative spectra exhibited the best model performance and provided the validation R2 and ratio of performance to an interquartile range of 0.79 and 3.03, respectively. FOD offers greater advantages in balancing the spectral resolution and the magnitude of spectral strength than traditional integer-order derivatives. Furthermore, the FOD algorithm has strong application potential in soil Vis-NIR spectroscopy and other types of spectroscopy.
23925. 题目: Disentangling temperature effects on leaf wax n-alkane traits and carbon isotopic composition from phylogeny and precipitation
文章编号: N18102713
期刊: Organic Geochemistry
作者: Jia Wang, Yunping Xu, Liping Zhou, Minrui Shi, Ergu Axia, Yufu Jia, Zixun Chen, Jiazhu Li, Guoan Wang
更新时间: 2018-10-27
摘要: Leaf wax n-alkanes are terrestrial plant biomarkers that have characteristics that are widely employed as proxies for climatic conditions. Understanding the relation of different environmental factors to the amounts and types of leaf wax n-alkanes in modern plants is crucial for the application of these proxies to paleoenvironmental reconstructions. However, the effects of climate conditions on plant wax characteristics remain complicated due to the interactions among temperature, precipitation and phylogeny. To evaluate the effect of temperature with minimized interfering factors, we collected 106 Artemisia plants across a 15 °C mean annual temperature gradient along the 400 mm isohyet in China. Both total n-alkane concentration (∑alk) and carbon preference index (CPI) varied greatly but did not correlate with temperature. Average chain length (ACL) increased with temperature, especially summer temperature (TJJA, June–August), indicating that ACL could be used as proxy for temperature. The stable carbon isotope compositions of n-C27, n-C29 and n-C31 were very similar in each plant (−38.2‰ to −30.0‰, −39.0‰ to −30.2‰, −38.7‰ to −30.5‰, respectively), which reflects a similar biosynthetic process for all three n-alkane homologues of Artemisia. There was a positive relation between δ13C of bulk leaf tissues (δ13Cbulk) and of n-alkanes (δ13Calk), and the average offset of δ13C29 relative to δ13Cbulk (εC29/bulk) was −7.1‰. Increasing trends in both δ13Cbulk and δ13C29 were found with temperature. However, correlation of δ13Cbulkwith temperature (R2 = 18%) was much weaker than that of δ13C29 with temperature (R2 = 60%). Therefore, δ13C29 appears to be a better proxy of paleotemperature than δ13Cbulk.
23926. 题目: Pore water geochemistry and diagenesis of estuary sediments—an example of the Zrmanja River estuary (Adriatic coast, Croatia)
文章编号: N18102712
期刊: Journal of Soils and Sediments
作者: Željka Fiket, Tomislav Fiket, Maja Ivanić, Nevenka Mikac, Goran Kniewald
更新时间: 2018-10-27
摘要: Purpose: The geochemistry of pore waters from sediments deposited in the semi-enclosed bay of the Zrmanja River estuary, encompassing two small interconnected basins, the Novigrad Sea and the Karin Sea, was investigated. The conducted research aimed to identify diagenetic processes occurring in surficial bottom sediments and to assess the impact of these reactions on trace element concentrations in the overlying water. Materials and methods: Sediment pore waters were extracted from sediment cores in a nitrogen atmosphere. Multielemental analysis of prepared samples was performed by high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). All samples were analysed for the total concentration of 15 elements (As, Ba, Co, Cr, Fe, Li, Mn, Mo, Ni, Rb, Sb, Sr, Ti, U and V). Results and discussion: Results indicate enrichment of sediment pore waters in the majority of measured elements relative to the estuary water. Degradation of organic matter and dissolution of Mn-Fe-oxyhydroxides under suboxic and anoxic conditions were identified as principal sources of dissolved cations in the studied pore waters. While sediments from the Novigrad Sea act as a permanent geochemical sink, the estimated fluxes for the Karin Sea sediments indicate transfer of certain elements from the sediment back to the water column, amounting to ~ 0.3 μg m−2 day−1 for Co, Ti and U; ~ 0.7 μg m−2 day−1 for As; between 1 and 5 μg m−2 day−1 for Mo, Ni and Ba; and ~ 70 μg m−2 day−1 for Fe and Mn. Conclusions: In the Zrmanja River estuary, the observed differences in the sediment pore water geochemistry and the role of the sediments in terms of mass exchange at the sediment-water interface could not be solely attributed to the sediment particle characteristics, but are considered to be a combined effect of organic matter input and local hydrogeological setting.
23927. 题目: Longitudinal discontinuities in riverine greenhouse gas dynamics generated by dams and urban wastewater
文章编号: N18102711
期刊: Biogeosciences
作者: Hyojin Jin, Tae Kyung Yoon, Most Shirina Begum, Eun-Ju Lee, Neung-Hwan Oh, Namgoo Kang, and Ji-Hyung Park
更新时间: 2018-10-27
摘要: Surface water concentrations of CO2, CH4, and N2O have rarely been measured simultaneously in river systems modified by human activities, contributing to large uncertainties in estimating global riverine emissions of greenhouse gases (GHGs). Basin-wide surveys of the three GHGs were combined with a small number of measurements of C isotope ratios in dissolved organic matter (DOM), CO2, and CH4 in the Han River basin, South Korea, to examine how longitudinal patterns of the three gases and DOM are affected by four cascade dams along a middle section of the North Han River (hereafter termed middle reach
) and treated wastewater discharged to the lower Han River (lower reach
) traversing the Seoul metropolitan area. Monthly monitoring and two-season comparison were conducted at 6 and 15 sites, respectively, to measure surface water gas concentrations and ancillary water quality parameters including concentrations of dissolved organic carbon (DOC) and optical properties of DOM. The basin-wide surveys were complemented with a sampling cruise along the lower reach and synoptic samplings along an urban tributary delivering effluents from a large wastewater treatment plant (WWTP) to the lower reach. The levels of pCO2 were relatively low in the middle reach (51–2465µatm), particularly at the four dam sites (51–761µatm), compared with those found in the largely forested upper basin with scattered patches of croplands (163–2539µatm), the lower reach (78–11298µatm), and three urban tributaries (2120–11970µatm). The upper and middle reaches displayed generally low concentration ranges of CH4 and N2O, with some local peaks influenced by agricultural runoff and impoundments. By comparison, the lower reach exhibited exceptionally high concentrations of CH4 (1.2–15766nmolL−1) and N2O (7.5–1396nmolL−1), which were significantly correlated with different sets of variables such as DO and PO43− for CH4 and NH4+ and NO3− for N2O. Downriver increases in the levels of DOC and optical properties such as fluorescence index (FI) and protein-like fluorescence indicated an increasing DOM fraction of anthropogenic and microbial origin. The concentrations of the three GHGs and DOC were similar in magnitude and temporal variation at a WWTP discharge and the receiving tributary, indicating a disproportionate contribution of the WWTP effluents to the tributary gas and DOC exports to the lower reach. The values of δ13C in surface water CO2 and CH4 measured during the sampling cruise along the lower reach, combined with δ13C and Δ14C in DOM sampled across the basin, implied a strong influence of the wastewater-derived gases and aged DOM delivered by the urban tributaries. The downstream enrichment of 13C in CO2 and CH4 suggested that the spatial distribution of these gases across the eutrophic lower reach may also be constrained by multiple concomitant processes including outgassing, photosynthesis, and CH4 oxidation. The overall results suggest that dams and urban wastewater may create longitudinal discontinuities in riverine metabolic processes leading to large spatial variations in the three GHGs correlating with different combinations of DOM properties and nutrients. Further research is required to evaluate the relative contributions of anthropogenic and in-stream sources of the three gases and DOM in eutrophic urbanized river systems and constrain key factors for the contrasting impoundment effects such as autotrophy-driven decreases in pCO2 and in-lake production of CH4 and N2O.
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23928. 题目: Porous biochar composite assembled with ternary needle-like iron-manganese-sulphur hybrids for high-efficiency lead removal
文章编号: N18102710
期刊: Bioresource Technology
作者: Fan Yang, Shuaishuai Zhang, Dong-Wan Cho, Qing Du, Jingpeng Song, Daniel C.W. Tsang
更新时间: 2018-10-27
摘要: Hierarchical porous biochar derived from corn straw containing ternary needle-like iron-manganese-sulphur composites (Fe-Mn-S@HCS) are fabricated, and their physicochemical characteristics and performance for Pb removal were examined in detail. Introduction of Mn (transition metal) into Fe-biochar composites can effectively alter the chemical state of Fe; simultaneous doping with S can enhance cation exchange for Pb removal. High uptake of Pb by Fe-Mn-S@HCS in a short time period was observed with the adsorption capacity of 181.5 mg g-1 and the pseudo-second-order rate constant of 0.075 g mg-1 h-1. Complexation, reduction, and precipitation were found to be involved in the Pb removal by Fe-Mn-S@HCS based on the results of HRTEM, XPS, and XRD analyses. This study demonstrated the feasibility of Fe-Mn-S biochar composites for high-efficiency Pb removal from aqueous solution.
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23929. 题目: The stability mechanism for organic carbon of aggregate fractions in the irrigated desert soil based on the long-term fertilizer experiment of China
文章编号: N18102709
期刊: CATENA
作者: Yanjun Chai, Xibai Zeng, Shengzhe E, Zongxian Che, Lingyu Bai, Shiming Su, Yanan Wang
更新时间: 2018-10-27
摘要: Soil samples from the Hexi Corridor located in the arid regions of Northwestern China were collected from a 24–year–old field experiment. The distribution of organic carbon (OC) in the different size water stable aggregate (WSA) fractions and the stability mechanism of OC in WSA size fractions were studied. The results showed that long-term application of solo organic manures or in combination with inorganic N fertilizer significantly increased the OC concentrations of different size WSA fractions compared to the CK, while long-term application of solo N fertilizer had no significant effect. After fertilization for 24 years, the OC concentrations of 0.25–2 mm WSA fraction was significantly positively correlated with the percentages of this WSA fraction, while the OC concentrations of >2 mm, 0.053–0.25 mm and <0.053 mm were not significantly correlated with their corresponding percentages of WSA fractions (P > 0.05). In addition, the OC concentrations of loosely, stably and tightly bound humus in 0.25–2 mm WSA fraction were significantly higher than those in other size WSA fractions, which were also significantly correlated with the corresponding chemical components, e.g. different forms of calcium, in 0.25–2 mm WSA fraction (P < 0.05). It could be explained that affinities of OC to chemical components in 0.25–2 mm WSA fraction were stronger than those in other size WSA fractions. The results of NMR analysis also showed that the aromaticity and alkyl/O-alkyl ratio for the 0.25–2 mm WSA fractions were significantly lower than those for other size WSA fractions (P < 0.05). These results demonstrated that the 0.25–2 mm WSA fraction played an important role in stabilizing soil OC and protecting OC from degradation in the irrigated desert soil.
23930. 题目: Effects of water temperature and light intensity on the performance of gravity-driven membrane system
文章编号: N18102708
期刊: Chemosphere
作者: Senlin Shao, Danting Shi, Yueqi Li, Yang Liu, Zhiying Lu, Zheng Fang, Heng Liang
更新时间: 2018-10-27
摘要: The selection of favorable environmental conditions for gravity-driven membrane (GDM) systems is crucial to their widespread application. In this study, GDM systems operated under different light intensities (illuminance levels of 0, 200, and 3000 Lux) and water temperatures (10, 20, and 30 °C) were investigated for their performance and fouling layer characteristics. The results showed that indoor light (200 Lux) had limited effects on the performance of the GDM system. However, full daylight (3000 Lux) led to algal growth; these algae increased fouling resistance and deteriorated permeate water by releasing algogenic organic matter, although they could also enhance the heterogeneity of the biofouling layer by increasing the microbial activity. Water temperature rarely influenced the total organic matter removal. The fouling layers had different thicknesses and heterogeneity, but the same level of EPS; therefore, the hydraulic resistances of these fouling layer were almost the same at different water temperatures. These findings suggest that GDM system could be operated at low water temperature and indoor light conditions, and that strong light should be avoided during the operation of GDM systems.
23931. 题目: Aryl hydrocarbon receptor mediates the cardiac developmental toxicity of EOM from PM2.5 in P19 embryonic carcinoma cells
文章编号: N18102707
期刊: Chemosphere
作者: Tao Chen, Hongmei Jin, Huimin Wang, Yugang Yao, Stanley Aniagu, Jian Tong, Yan Jiang
更新时间: 2018-10-27
摘要: Ambient fine particulate matter (PM2.5) has been found to be associated with congenital heart defects, but the molecular mechanisms remain to be elucidated. Our previous study revealed that extractable organic matter (EOM) from PM2.5 exerted cardiac developmental toxicity in zebrafish embryos. The aim of the current study is to explore the effects of EOM on cardiac differentiation of P19 mouse embryonic carcinoma stem cells. We found that EOM at 10 μg/ml (a non-cytotoxic dose level) significantly reduced the proportion of cardiac muscle troponin (cTnT) positive cells and the percentage of spontaneously beating embryoid bodies, indicating a severe inhibition of cardiac differentiation. Immunofluorescence and qPCR data demonstrated that EOM increased the expression levels of the aryl hydrocarbon receptor (AhR) and its target gene Cyp1A1 and diminished the expression level of β-catenin. Furthermore, EOM treatment significantly upregulated cell proliferation rate and elevated the percentage of γH2A.X positive cells without affecting apoptosis. It is worth noting that the EOM-induced changes in gene expression, cellular proliferation and DNA double strain breaks were attenuated by the AhR antagonist CH223191. In conclusion, our data indicate that AhR mediates the inhibitory effects of EOM (from PM2.5) on the cardiac differentiation of P19 cells.
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23932. 题目: Novel and high-performance biochar derived from pistachio green hull biomass: Production, characterization, and application to Cu(II) removal from aqueous solutions
文章编号: N18102706
期刊: Ecotoxicology and Environmental Safety
作者: Haniyeh Jalayeri, Francesco Pepe
更新时间: 2018-10-27
摘要: In recent years, biochar is being widely considered as an effective and low cost biosorbent in water and wastewater treatment processes. Various biomasses can be effectively used for biochar production, and this study investigates the use of a novel biochar derived from pistachio green hull to remove Cu(II) from aqueous solutions. The biochar was analyzed by FTIR, SEM-WDX, and SEM-EDX. The efficacy of several experimental factors was investigated in a number of batch adsorption experiments. The sorption kinetics of copper on the biochar were satisfactorily described by a pseudo–second order model. The adsorption isotherms were well described by the Langmuir model. The analysis of experimental results suggested that the Cu(II) sorption onto biochar could mainly be ascribed to cation exchange, surface precipitation, and surface complexation with oxygen-containing functional groups. Overall, it can be concluded that biochar derived from pistachio green hull is valuable as a green cost-effective sorbent for Cu(II) removal from water.
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23933. 题目: Effect of pyrolysis temperature on characteristics, chemical speciation and risk evaluation of heavy metals in biochar derived from textile dyeing sludge
文章编号: N18102705
期刊: Ecotoxicology and Environmental Safety
作者: Xingdong Wang, Chunxing Li, Zhiwei Li, Guangwei Yu, Yin Wang
更新时间: 2018-10-27
摘要: Textile dyeing sludge (TDS) was pyrolyzed at temperature ranging from 300 to 700 °C to investigate characteristics and to evaluate the risk of heavy metals (Zn, Cu, Cr, Ni, Cd, and Mn) in biochar derived from the TDS. The analyzation of characteristics and potential environmental risk evaluation of heavy metals were conducted by the BET-N2, FTIR, and BCR sequential extraction procedure. The results showed that the pyrolysis treatment of the TDS contributed to the improvement of the pH value and specific surface areas with increasing pyrolysis temperature. Conversion of the TDS to biochar significantly decreased the H/C and O/C ratios, resulting in a far stronger carbonization and a higher aromatic condensation for the TDS derived biochar. The total contents of Zn, Cu, Cr, Ni and Mn in biochar increased with pyrolysis temperature owing to the thermal decomposition of organic matter in the TDS; but for Cd, the portion distributed in the biochars decreased significantly when the temperature increased up to 600 °C. However, using BCR sequential extraction procedure and analysis, it was found that pyrolysis process promoted changes in the chemical speciation and biochar matrix characteristics, leading to reduce bio-available fractions of heavy metals in the biochars. The potential environmental risk of heavy metals decreased from considerable risk in the TDS to low risk or no risk in biochar after pyrolysis above 400 °C. This work demonstrated that the pyrolysis process was a promising method for disposing of the TDS with acceptable environment risk.
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23934. 题目: Monitoring biofouling based on aerobic respiration in reverse osmosis system
文章编号: N18102704
期刊: Journal of Environmental Sciences
作者: Youngjae Yu, Keun-Young Park, Jaehyun Jung, Wonjung Song, Jaehyuk Kim, Junhee Ryu, Harshad Lade, Jihyang Kweon
更新时间: 2018-10-27
摘要: A monitoring method of biofouling in reverse osmosis (RO) system was proposed based on the fluorescent signal of resorufin, which is reduced by nicotinamide adenine dinucleotide released from viable cells during aerobic respiration. The fluorescent signal of resorufin reduced by planktonic cells and microorganisms of biofilm showed linearity, indicating its feasibility to monitor biofouling in a RO system. For the application of the method to the lab-scale RO system, the injection concentration of resazurin and the injection flow rate were optimized. Biofilm on RO membranes continuously operated in a lab-scale RO system was estimated by resorufin fluorescence under optimized detection condition. As a result, resorufin fluorescence on RO membrane showed a significant increase in which the permeability of RO system decreased by 30.48%. Moreover, it represented the development of biofilm as much as conventional biofilm parameters such as adenosine triphosphate, extracellular polymeric substances, and biofilm thickness. The proposed method could be used as a sensitive and low-cost technology to monitor biofouling without autopsy of membranes.
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23935. 题目: The enantioselective environmental behavior and toxicological effects of pyriproxyfen in soil
文章编号: N18102703
期刊: Journal of Hazardous Materials
作者: Hui Liu, Xiaotong Yi, Jiawei Bi, Peng Wang, Donghui Liu, Zhiqiang Zhou
更新时间: 2018-10-27
摘要: We synthesized nine pyriproxyfen (PYR) metabolites and developed a chiral residual analysis method for PYR with its metabolites in five soils using ultra performance liquid chromatography-tandem mass spectrometer/tandem mass spectrometer (UPLC-MS/MS). Soil degradation research showed that higher organic matter content and bigger soil particle size were conducive to the degradation of PYR and metabolites. Metabolite A 4'-OH-PYR was mainly found in five soils. PYR and metabolite A performed enantioselective degradation in soil with half-lives ranging from 2.11 d to 9.69 d and 2.80 d and 13.30 d, respectively. The activity of dehydrogenase, sucrase were inhibited and catalase activity was promoted under the disturbance of PYR. Urease was more sensitive to PYR with uncertain influences. Most soil enzymes were not restored to their initial active state after 120 d. The toxicity of metabolites to earthworms was greater than that of the parent compound PYR. This study provides the basic degradation and toxicity data of chiral pesticide PYR and its main metabolites in soil ecosystem, which is of great significance for guiding safe use and comprehensive evaluation of PYR on environmental risk.
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23936. 题目: Characterization and quantification of structure and flow in multichannel polymer membranes by MRI
文章编号: N18102702
期刊: Journal of Membrane Science
作者: S. Schuhmann, J.W. Simkins, N. Schork, S.L. Codd, J.D. Seymour, M. Heijnen, F. Saravia, H. Horn, H. Nirschl, G. Guthausen
更新时间: 2018-10-27
摘要: Polymeric multichannel hollow fiber membranes were developed to reduce fiber breakage and to increase the volume-to-membrane-surface ratio and consequently the efficiency of filtration processes. These membranes are commonly used in ultrafiltration and are operated in in-out dead-end mode. However, some of the filtration details are unknown. The filtration efficiency and flow in the multichannel membranes depend on filtration time and are expected to vary along spatial coordinates. In the current work, in-situ magnetic resonance imaging was used to answer these questions. Velocities were quantified in the feed channels to obtain a detailed understanding of the filtration process. Flow and deposits were measured in each of the seven channels during filtration of sodium alginate, which is a model substance for extracellular polymeric substances occurring in water treatment. Volume flow and flow profiles were calculated from phase contrast flow images. The flow in z-direction in the center channel was higher than in the surrounding channels. Flow profiles variate depending on the concentration of Ca2+, which changes the filtration mechanism of aqueous solutions of sodium alginate from concentration polarization to gel layer filtration.
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23937. 题目: Decomposition of cyanobacterial bloom contributes to the formation and distribution of iron-bound phosphorus (Fe-P): Insight for cycling mechanism of internal phosphorus loading
文章编号: N18102701
期刊: Science of The Total Environment
作者: Zhicong Wang, Shun Huang, Dunhai Li
更新时间: 2018-10-27
摘要: Lake eutrophication and the resulting cyanobacterial blooms have become a global water environment problem. These eutrophic lakes usually have relatively high internal phosphorus loading such as Fe-P to support the formation of cyanobacterial blooms. In order to reveal the mechanisms and processes of phosphorus cycling in lake sediments, in this study, Lake Chaohu was selected as the research area, and the effects of cyanobacterial bloom decomposition on the horizontal distribution pattern of Fe-P was studied by field investigation and laboratory simulations. According to the phosphorus fractions in the sediments, Lake Chaohu can be divided into three lake areas, and the Fe-P content in western Chaohu is the highest (908.6 ± 54.9 mg kg−1). The contents and proportions of Fe-P were significantly positively correlated with cyanobacterial pigments in sediments, but they negatively correlated with undegraded chl-a, especially when the Fe-P content was <400 mg kg−1. Based on these statistical analyses, we proposed a hypothesis that the settled cyanobacterial organic matters (COM) could promote the formation of Fe-P. This hypothesis was proved by the simulation experiments of adding COM to the oligotrophic lakeshore clay. The results suggested that the content and proportion of Fe-P in sediments were significantly increased by the COM addition, and also, they were significantly positively correlated with the decomposition of the COM. The formation processes of Fe-P were further confirmed by the analysis of Fourier transform infrared (FT-IR) spectra. Microbial community analysis suggested that the bacterial species including FeOB and genus Pseudomonas might play an important role in the formation of Fe-P. This study suggested that the settled COM could enhance the eutrophication of sediments through a positive feedback cycle. Therefore, it is necessary to carry out bloom removal and sediment dredging simultaneously, and only then the cyanobacterial bloom can be effectively controlled.
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23938. 题目: Generality of hydrologic transport limitation of watershed organic carbon flux across ecoregions of the United States
文章编号: N18102613
期刊: Geophysical Research Letters
作者: Jay P. Zarnetske, Martin Bouda, Benjamin W. Abbott, James Saiers, Peter A. Raymond
更新时间: 2018-10-26
摘要: Though the flux of dissolved organic carbon (DOC) through freshwaters is nearly equivalent to the net carbon uptake of all terrestrial ecosystems, uncertainty remains about how source processes (carbon production and location) and transport processes (hydrologic connectivity and routing) interact to determine DOC flux across flow conditions and ecoregions. This limits our ability to predict the fluvial carbon flux responses to changes in climate and land‐use. We used DOC concentration and discharge patterns with ensemble modelling techniques to quantify DOC flux behavior for 1006 United States watersheds spanning diverse climate and land cover conditions. We found that DOC flux was transport‐limited (concentration increased with discharge) in 80% of watersheds and that this flux behavior spanned ecoregions and watershed sizes. The generality of transport limitation demonstrates how coupling discharge models with widely available watershed properties could allow DOC flux to be efficiently integrated into landscape and earth system models.
23939. 题目: Can SOC modelling be improved by accounting for pedogenesis?
文章编号: N18102612
期刊: Geoderma
作者: Peter Finke, Emmanuel Opolot, Jerôme Balesdent, Asmeret Asefaw Berhe, Pascal Boeckx, Sophie Cornu, Jennifer Harden, Christine Hatté, Elizabeth Williams, Sebastian Doetterl
更新时间: 2018-10-26
摘要: Recent findings suggest that soil organic carbon mineralization and stabilization depend to a substantial degree on the soil geochemistry and the degree of weathering. We hypothesized that this dependence can be translated to decay rate modifiers in a model context, and used data from the Merced chronosequence (CA, U.S.A., 100 yr–3 Myr), representing a weathering sequence, to test, on a 1000-year time scale for model spin-up, a simple soil organic carbon (SOC) model based on the RothC26.3 model concepts. Model performance was tested for four levels of information: (1) known decay rates for each model SOC pool at individual chronosequence locations, obtained by calibrating the model to measured SOC-fractions and measured site-specific C-inputs; (2) average decay rates for each SOC-pool, corrected per location with rate modifiers based on geochemical proxies and measured site-specific C-inputs; (3) uncorrected average decay rates per SOC-pool and measured site-specific C-inputs; (4) uncorrected average decay rates per SOC-pool and averaged C-inputs. A lumped root mean square error (RMSE) statistic was calculated for each information level. We found that using local measurements of fresh C-input led to a decrease in RMSE of near 15% relative to information level (4). Applying geochemical rate modifiers led to a further reduction of 20%. Thus, we conclude that there is a benefit of including geochemical rate modifiers in this SOC-model. We repeated this analysis for a five-pool and a four-pool SOC model that either included or excluded an inert organic matter pool. In terms of the lumped RMSE both models performed similarly, but by comparing measured and simulated percentage Modern Carbon (pMC) for bulk SOC we concluded that measured pMC was best approximated using a four-pool SOC model (without an Inert Organic Matter pool). Furthermore, it is likely that a five-pool model including a very slowly decaying pool would further improve model performance.
23940. 题目: The potential use of natural vs commercial biosorbent material to remediate stream waters by removing heavy metal contaminants
文章编号: N18102611
期刊: Journal of Environmental Management
作者: Samia Richards, Julian Dawson, Marc Stutter
更新时间: 2018-10-26
摘要: The presence of high level of heavy metals in aquatic environment is a cause of ecological and environmental concern and thus their removal from water courses is environmentally essential. Four natural inexpensive biosorbents: macro algae (Fucus vesiculosus), crab shells (Cancer pagurus), wood chippings and iron-rich soil were tested for copper (Cu2+) and zinc (Zn2+) removal from aqueous solutions. Batch equilibrations were performed at 1:100 w/v with different initial metal concentrations. Three macro algae pre-treatments (unmodified (UM algae), chemically treated (Ca-T algae) and thermally treated (T-T algae)) were additionally investigated for performance. The sorption capacities were compared with the commercial material biochar and activated carbon. The maximum level of the sorbents for Cu2+ uptake at 15.7 mM/l was attained by the natural material of UM algae (72.37 ± 0.37 mg/g) > Ca-T algae (66.77 ± 0.19 mg/g) > T-T algae (63.06 ± 0.82 mg/g), followed by the commercial material activated carbon (36.71 ± 2.20 mg/g). The maximum level of the sorbents for Zn2+ uptake at 15.3 mM/l was also achieved by the natural material of UM algae (52.40 ± 0.80 mg/g) > Ca-T algae (48.83 ± 2.01 mg/g) > T-T algae (39.57 ± 0.80 mg/g) followed by the commercial material activated carbon (20.78 ± 1.63 mg/g) and biochar (18.07 ± 1.09 mg/g). The results demonstrated that Cu2+ and Zn2+ were effectively removed by these biosorbents at all concentrations. However, at high metals concentrations, the natural material macro algae had greater Cu2+ and Zn2+ sorption capacity than the conventional sorbent activated carbon, and the affinity of these natural biosorbents were greater for Cu2+ than Zn2+. Hence, inexpensive natural and readily available materials showed potential as biosorbents to remediate polluted stream water of toxic metal contaminants.