论文检索

总访问量：2137825次

总访客量：105682人

所有论文

24741. 题目: The role of the anode material and water matrix in the electrochemical oxidation of norfloxacin
文章编号: N18072114
期刊: Chemosphere
作者: Salatiel W. da Silva, Emma M.O. Navarro, Marco A.S. Rodrigues, Andréa M. Bernardes, Valentín Pérez-Herranz
更新时间: 2018-07-21
摘要: The roles of the anode material, boron-doped diamond (BDD), with different boron (B) and substrate Silicon (Si) or Niobium (Nb) content, and one dimensionally stable anode (DSA ), were evaluated in the oxidation of norfloxacin (NOR) by electrochemical advanced oxidation process (EAOP). The effect of other components in real wastewater on the performance of EAOP was also studied. The anode materials were characterized by cyclic voltammetry, regarding diamond quality, electro-generation of oxidants and NOR oxidation mechanism (direct and/or indirect). The results showed that the anode material influences on the NOR oxidation pathway, due to distinct characteristics of the substrate and the coating. Apparently, low difference in diamond-sp /sp2-carbon ratio (Si/BDD100 × Si/BDD2500) does not leads to significant differences in the EAOP. On the other hand, the variation in the sp /sp2 ratio seems to be higher when Si/BDD2500 and Nb/BDD2500 are compared, which would explain the best current efficiency result for Si substrate. However, the Nb substrate presented a similar current efficiency and a 60% lower energy consumption. Dissolved organic matter (DOM) present in the real wastewater affect the EAOP-Nb/BDD due to HO and persulfate ions scavenged. However, when supporting electrolyte was added to a real wastewater spiked with NOR, the NOR decay reaches similar values found to the synthetic one. Due to the energy saving and mechanical properties, Nb substrate presents some technological advantages in relation to Si, which can facilitate the application to industrial levels.

24742. 题目: Chromium uptake by lettuce as affected by the application of organic matter and Cr(VI)-irrigation water: Implications to the land use and water management
文章编号: N18072113
期刊: Chemosphere
作者: Stavros Raptis, Dionisios Gasparatos, Maria Economou-Eliopoulos, Anastasios Petridis
更新时间: 2018-07-21
摘要: Toxic chromium [(Cr(VI)] in food chain has created an alarming situation for human life and ecosystems. The present study through a greenhouse pot experiment aims to (a) investigate the ability of organic matter in reducing Cr uptake by lettuce (Lactuca sativa L.) from a sandy loam soil irrigating with Cr(VI)-water, (b) to provide a way for the restriction of Cr transfer from contaminated soils and irrigation water to plants/crops and (c) to contribute to the better management of soil (land) and water use, without reduction of the agricultural production. Since soil and groundwater contamination by Cr is a potential risk in a worldwide scale, due to industrial activities and/or natural processes, organic carbon may play a key role in the mobility of added Cr(VI) to soil via irrigation water, in a significant way. The cultivation of lettuce, using organic matter in the form of leonardite (10 and 30 wt%) and Cr(VI)-irrigation water (100, 200 and 300 mgL 1), showed that the uptake of Cr in both shoots and roots increased with increasing concentration of Cr in the irrigation water. The highest Cr values in shoots (average = 10 mg/kg) and in roots (average = 28 mg/kg) were recorded in those plants cultivated in soil after the addition of Cr(VI)- water without organic matter, whereas the lowest Cr values in shoots (average = 0.44 mg/kg) and in roots (average = 0.7 mg/kg) were recorded in those plants cultivated in soil with addition of 30 wt% organic matter. The used leonardite as organic matter that is an oxidized form of lignite, due to its high content of humic acid is considered to be a useful organic fertilizer that provides possibilities for combining food production with soil protection. Therefore, the application of the natural organic material leonardite, as a land management technique, seems to be a cost-effective method consistent to related protocols for the protection of the soil quality.
图文摘要:

24743. 题目: Screening of biological sulfate reduction conditions for sulfidogenesis promotion using a methanogenic granular sludge
文章编号: N18072112
期刊: Chemosphere
作者: M. Mora, J. Lafuente, D. Gabriel
更新时间: 2018-07-21
摘要: Effluents containing great amounts of oxidized sulfur compounds, such as sulfate or sulfite, can be valorized as elemental sulfur from a sequential reduction-oxidation biological process. However, the most important, challenging step to be optimized is the reduction of sulfate. The present study aimed at seeking out the optimal conditions to promote sulfidogenesis instead of methanogenesis using waste carbon sources and a methanogenic granular sludge. Crude glycerol showed better results in terms of the consumed COD/S-Sulfate ratio compared with acetate, cheese whey, pig slurry, and vinasse. Then, the screening of several conditions (T, pH, and COD/S-Sulfate ratio) and the effects of air presence and dissolved sulfide inhibition on sulfate reduction was carried out. Sulfidogenesis was promoted at 35 °C, pH = 8.5, COD/S-Sulfate ratio above 7.0 g O2 g-1 S, microaerophilic conditions, and dissolved sulfide concentrations below 250 mg S2 L-1. These conditions were tested for nearly 3 months in the startup and operation of a 2 L UASB reactor. An inlet sulfate concentration of 220 mg S L-1 and an HRT of 2 h were set. Removal efficiencies of approximately 90% were obtained with less than 20% of organic matter destined for biogas production.

24744. 题目: What is driving the NF-κB response in environmental water extracts?
文章编号: N18072111
期刊: Chemosphere
作者: Peta A. Neale, Frederic D.L. Leusch, Beate I. Escher
更新时间: 2018-07-21
摘要: In vitro bioassays are increasingly applied for water quality monitoring, with assays indicative of adaptive stress responses commonly included in test batteries. The NF-κB assay is responsive to surface water and wastewater extracts, but the causative compounds are unknown and micropollutants typically found in water do not activate the NF-κB assay. The current study aimed to investigate if co-extracted organic matter and/or endotoxins could cause the NF-κB response in surface water extracts. The effect of model bacterial lipopolysaccharides (LPS) and dissolved organic carbon (DOC) was evaluated in the NF-κB assay both before and after solid-phase extraction (SPE), with 7% effect recovery for LPS and between 7 and 52% effect recovery for DOC observed. The NF-κB response, endotoxin activity, micropollutant concentration and total organic carbon concentration was measured in four surface water extracts. All water extracts showed a response in the NF-κB assay, but the detected micropollutants could not explain the effect. Comparison of predicted bioanalytical equivalent concentrations based on micropollutant, DOC and endotoxin concentrations in surface water with experimental bioanalytical equivalent concentrations suggest that co-extracted endotoxins are the most important drivers of the observed effect, with DOC only having a minor contribution. While in vitro bioassays typically detect mixtures of organic micropollutants, the current study shows that the NF-κB assay can integrate the effects of co-extracted endotoxins. Given that endotoxins can pose a risk for human health, the NF-κB assay is a valuable inclusion in bioanalytical test batteries used for water quality monitoring.
图文摘要:

24745. 题目: Influence of electrode placement for mobilising and removing metals during electrodialytic remediation of metals from shooting range soil
文章编号: N18072110
期刊: Chemosphere
作者: Kristine B. Pedersen, Pernille E. Jensen, Lisbeth M. Ottosen, John Barlindhaug
更新时间: 2018-07-21
摘要: Electrodialytic remediation was applied to a shooting range soil to investigate the influence of electrode placement on the removal and binding of metals during the treatment. The set-up was based on a 2-compartment cell, in which the cathode was separated from the soil by a cation exchange membrane and the anode was placed directly in the soil, thereby introducing protons and oxygen directly in the soil. Mobilisation of metals from less available fractions (oxidisable and residual) in the soil occurred, due to oxidation/dissolution of insoluble/soluble organic matter and possibly metal oxides in the residual fraction. The transport via electromigration out of the soil and/or re-precipitation in other fractions of the soil (oxidisable, reducible, exchangeable) depended on the metal. More than 30% of the initial content of Mn, Cd, Cu, Pb and Zn and less than 20% of the initial content of Al, Fe, K, Mg, As, Cr and Ni was transported out of the soil. By decreasing the distance between the electrodes from 3.0 to 1.5 cm, the removal of the targeted metal for remediation, Pb, was improved by more than 200%, from 14 to 31%. A similar removal could be achieved in experiments with long distance between electrodes (3.0 cm) by increasing the current intensity from 4 to 10 mA and/or the remediation time from 7 to 35 d. The experiments showed that the design and optimisation of electrodialytic remediation depends on the targeted metal and metal partitioning.

24746. 题目: Amendment of soil by biochars and activated carbons to reduce chlordecone bioavailability in piglets
文章编号: N18072109
期刊: Chemosphere
作者: M. Delannoy, S. Yehya, D. Techer, A. Razafitianamaharavo, A. Richard, G. Caria, M. Baroudi, E. Montargès-Pelletier, G. Rychen, C. Feidt
更新时间: 2018-07-21
摘要: Chlordecone (Kepone or CLD) is a highly persistent pesticide formerly used in French West Indies. Nowadays high levels of this pesticide are still found in soils which represent a subsequent source of contamination for outdoor-reared animals. In that context, sequestering matrices like biochars or activated carbons (ACs) are believed to efficiently decrease the bioavailability of such compounds when added to contaminated soils. The present study intends to test the respective efficiency of soil amendment strategies using commercial ACs or biochars (obtained by a 500 °C or 700 °C pyrolysis of 4 distinct type of wood). This study involved three experimental steps. The first one characterized specific surface areas of biochars and ACs. The second one assessed CLD-availability of contaminated artificial soils (50 μg g-1 of Dry Matter) amended with 5% of biochar or AC (mass basis). The third one assessed CLD bioavailability of those artificial soils through an in vivo assay. To limit ethically the number of animals, selections of the most promising media were performed between each experimental steps. Forty four castrated male 40-day-old piglets were exposed during 10 day by amended artificial soils according to their group (n = 4). Only treatment groups exposed through amended soil with AC presented a significant decrease of concentrations of CLD in liver and adipose tissue in comparison with the control group (p < 0.001). A non-significant decrease was obtained by amending artificial soil with biochars. This decrease was particularly high for a coconut shell activated carbon were relative bioavailability was found lower than 3.2% for both tissues. This study leads to conclude that AC introduced in CLD contaminated soil should strongly reduce CLD bioavailability.

24747. 题目: Effects of tea plantation age on soil aggregate-associated C- and N-cycling enzyme activities in the hilly areas of Western Sichuan, China
文章编号: N18072108
期刊: CATENA
作者: Shengqiang Wang, Tingxuan Li, Zicheng Zheng
更新时间: 2018-07-21
摘要: Research on the changes of soil carbon (C)- and nitrogen (N)-cycling enzyme activities within aggregate fractions is essential for improving our understanding of soil organic matter (SOM) dynamics in agricultural ecosystems. However, the short- and long-term implications of the conversion of abandoned croplands to tea (Camellia sinensis L.) plantations on enzyme activities associated with aggregate fractions remains poorly understood. In the present study, we hypothesized that (i) the concentrations of soil organic C and total N would increase as the tea plantations continued to age, and (ii) the potential of SOM decomposition would differ with the stage of tea cultivation, as there would be significant changes in the activities of soil C- and N-cycling enzymes over time. The activities of β-glucosidase, invertase, urease, and protease were analyzed in different size fractions of soil aggregates that were collected from 0 to 20 cm depth in four tea plantations with the same cultivar (Sichuan tea) of various ages (16-, 23-, 31-, and 53-years) in the hilly areas of Western Sichuan, China. The aggregates were separated using a dry-sieving procedure into four fractions, namely, large (>2 mm), medium (2–1 mm), small (1–0.25 mm) macro-aggregates, and micro-aggregates (<0.25 mm). In the early stage (in the first 23-years), tea cultivation contributed to a significant increase in organic C and total N stocks in the whole-soil, and these changes were primarily reflected in the increases of such elements stocks in the large macro-aggregates. For example, the increase in organic C stock associated with large macro-aggregates in the early stage accounted for 99.64% of the increase in organic C stock in the whole-soil. In the later stage (after 23-years), however, the increases in organic C and total N stocks in the whole-soil were primarily reflected in the increases of such elements stocks in the small macro-aggregates. Meanwhile, soil C- and N-cycling enzyme activities associated with the large macro-aggregates were significantly increased in the first 23-years of tea cultivation. These results indicated that young tea plantations in the early stage had limitations with respect to the potential for SOM sequestration; however, as the tea plantations matured under the present system of management, the SOM sequestration has improved.

24748. 题目: Ameliorating some quality properties of an erosion-prone soil using biochar produced from dairy wastewater sludge
文章编号: N18072107
期刊: CATENA
作者: Seyed Hamidreza Sadeghi, Mohammad Hossein Ghavimi Panah, Habibollah Younesi, Hossein Kheirfam
更新时间: 2018-07-21
摘要: Land degradation due to decline in soil quality and wastewater pollution is a major challenge for ecosystems sustainability, worldwide. Hence, utilizing adaptable and multi-objective strategies is essential to address environmental challenges. To this end, we produced a biochar from air-dried dairy wastewater sludge (i.e., Kalleh Dairy Company, Iran) through pyrolysis process at 300–350 °C which led to reduction in initial heavy metals contents. The produced biochar was then used to improve the soil quality of a highly degradable soil. Some important nutrients and heavy metals of dairy wastewater and produced biochar were measured by acid digestion/ICP-MS. We then spread two rates of the biochar (400 and 800 g m-2) over the surface of the small-scale boxes (0.5 × 0.5 × 0.5-m) filled by an erosion-prone soil collected from the Chalus Watershed, Northern Iran, and left for 30 days. The carbon (C), nitrogen (N) and organic matter (OM) content, and also carbon/nitrogen (C/N) ratio of treated soil were measured to assess effect of the produced biochar on soil quality improvement. The results showed that some contents of the measured heavy metals (i.e., Pb, Ni, Al, Cr, Mn, Fe and Zn) in the produced biochar significantly (p < 0.01) reduced compared to those of the raw dairy wastewater. Additionally, application of two dosages of 400 and 800 g m-2 of biochar to the study soil increased C, N, OM and C/N of the soil at tunes of 2.67–5.5; 2–3 and 2.67–5.5 times, and 22–61%, respectively, in comparison with untreated soils (control). By and large, converting the wastewater as an environmental pollution source to biochar and using it as an eco-friendly soil amendment is a multi-objective and adaptive approach for the ecosystem management.
图文摘要:

24749. 题目: Effect of vegetation type and season on microbial biomass carbon in Central Himalayan forest soils, India
文章编号: N18072106
期刊: CATENA
作者: Kiran Bargali, Vijyeta Manral, Kirtika Padalia, S.S. Bargali, V.P. Upadhyay
更新时间: 2018-07-21
摘要: Soil microbial biomass is an important component of soil organic matter constituting from 2 to 5% of the soil organic carbon and play a significant role in the cycling of nutrients and overall organic matter dynamics. The present study assessed the effects of three forest types (Banj-oak forest, Chir-pine forest and Mixed oak-pine forest) on the soil physico-chemical properties and microbial biomass Carbon in Central Himalaya, India. The soil microbial biomass carbon was determined by chloroform fumigation extraction method. In the 2 year of study period, the soil microbial biomass carbon (Cmic) was significantly higher in Mixed oak-pine forest (681 ± 1.81–763 ± 1.82 μg g-1) than in the Banj-oak (518 ± 1.50–576 ± 1.73 μg g-1) and Chir-pine forest (418 ± 1.42–507 ± 2.05 μg g-1). Though insignificant, all the forest types showed distinct seasonal variations in microbial biomass carbon with a minimum value in winter season and maximum value in rainy season. The soil microbial quotients (Cmic to Corg) were higher in Chir-pine (2.52–4.18) and Banj-oak forest (2.26–4.02) than those reported in Mixed oak-pine forest (1.44–2.24). These results indicate that Mixed oak-pine forest is better in sustaining the soil microbial biomass and soil nutrients than Banj-oak and Chir-pine forest. It recommends that nutrients rich Mixed oak-pine forest should be preferred as a forest management practice to promote microbial diversity, their activities and soil quality enhancement in Central Himalayan forests.

24750. 题目: Factors that influence soil total phosphorus sources on dam fields that are part of ecological construction programs on the Loess Plateau, China
文章编号: N18072105
期刊: CATENA
作者: Yuting Cheng, Peng Li, Guoce Xu, Zhanbin Li, Kunxia Yu, Shengdong Cheng, Binhua Zhao, Feichao Wang
更新时间: 2018-07-21
摘要: Terraces and check-dam construction are widely used to control soil and water on the Loess Plateau, China. However, it is not known whether dam fields behave as soil phosphorus sources or sinks. This study quantitatively assessed the effects of check-dam and terrace construction on soil total phosphorus (STP). It also investigated the factors that influenced STP. A total of 1010 soil samples (five land uses and five soil depths) were collected in a small watershed on the Loess Plateau. The probability density function of the Weibull distribution was used to analyze the STP sources on the dam field land. The results showed that the highest STP concentration was recorded in the dam field land. Furthermore, the STP concentration mean values for the five land-use types decreased in the following order: dam field > terraced land > grassland > forestland > sloping cropland. The highest clay content value was also recorded in the dam field land. Soil total phosphorus was significantly and positively correlated to soil organic carbon (SOC), but negatively correlated to sand content (P < 0.01) in all areas. Across the entire soil profile down to 60 cm depth, the STP levels for the five land-uses were dam field, 2.78 kg/m2; terrace, 2.86 kg/m2; grassland, 2.98 kg/m2; forestland, 2.84 kg/m2; and sloping cropland, 2.83 kg/m2. The percentage contributions made by the four land use types to the soil total phosphorus deposited in the dam field were 50% (sloping cropland), 33% (grassland) and 17% (forestland). Therefore, check dam constructions behave as a sink for soil phosphorus on the Loess Plateau, China.

24751. 题目: Soil carbon sequestration potential as affected by soil physical and climatic factors under different land uses in a semiarid region
文章编号: N18072104
期刊: CATENA
作者: Elham Alidoust, Majid Afyuni, Mohammad Ali Hajabbasi, Mohammad Reza Mosaddeghi
更新时间: 2018-07-21
摘要: Carbon (C) sequestration in soil is recognized as a possible solution for climate change mitigation. Different land uses may alter carbon sequestration in soil. In the semiarid regions of central Iran, during the last decades, land use changes from native cover to farmlands have altered the C sink role of soil to a source of CO2 emission to the atmosphere. This study was conducted to evaluate and compare changes and the potential of soil organic carbon (SOC) sequestration from 1988 to 2014, under different land uses, in western central Iran (Lordegan). The land uses included pasture, forest, rain-fed, and irrigated farmlands. Soil (450 samples) from 50 points across the study basin (390 km2) was collected in three depth increments (0–5, 5–15 and 15–30 cm) during three sampling times (June and November 2014, and June 2015). Mean SOC concentrations in the pasture, forest, rain-fed and irrigated farmlands were 10.3, 20.2, 9.2 and 10.1 g kg-1, respectively. The SOC concentration in the forest soil was significantly greater than the other land uses, and any reduction in forestland area would lead to the SOC stock decline. About 1390 Gg organic carbon was found to be stored in the top 0–30 cm depth of the study area. Comparing land use maps between 1988 and 2014 indicated an alteration in the relative contribution of each land use across the study area leading to SOC stock reduction by 100 Gg carbon during this period. The results showed that all studied soils comprised non-complexed clay, suggesting a considerable potential capacity for sequestering carbon. The results also indicated that the SOC controlling factors varied considerably among different land uses and soil depths. Mean weight diameter of aggregates (MWD), bulk density, clay and sand content, and altitude were identified as the important controlling variables by the stepwise multiple linear regression analysis.

24752. 题目: Soil surface quality assessment in rangeland ecosystems with different protection levels, central Iran
文章编号: N18072103
期刊: CATENA
作者: Azita Molaeinasab, Hossein Bashari, Mostafa Tarkesh Esfahani, Mohammad Reza Mosaddeghi
更新时间: 2018-07-21
摘要: This study aimed to evaluate the application of landscape function analysis (LFA) and some soil quality indicators for the assessment of the structure and function of Steppe rangelands in arid regions of Ghamishloo National Park, Isfahan, central Iran. Three zones with different protection levels/grazing intensities, including a national park with wild herbivores, a peripheral protected area where both livestock and wild herbivores were present, and an adjacent grazing-free area where wild herbivores were absent, were selected. Eleven soil surface indicators were assessed to measure soil stability, infiltration, and nutrient cycling indices in various zones. Eighty-seven soil samples were collected in the study area and their characteristics, including pH, electrical conductivity (EC), total nitrogen, phosphate, soil organic carbon (SOC), particulate organic matter (POM), microbial respiration, and mean weight diameter (MWD), were measured. The results showed that although structural attributes (patch area index and landscape organization index) and LFA functional attributes varied significantly between the sites with various management histories (P < 0.05), these attributes along with total patch area and number of patches per 10 m did not have significant differences between the protected and grazing-free area. Most soil quality indicators were also significantly different between the national park and grazing-free area, but MWD, SOC, and POM were not significantly different between the protected and grazing-free areas (P < 0.05). High protection level (i.e. lower grazing impact) led to more soil stability and higher proportion of macro-aggregates in the national park area compared to other areas. The methods used in this study are applicable for exploring the role of national parks in maintaining the structure and function of ecosystems in similar ecoregions.

24753. 题目: Three years of management with cover crops protecting sloping olive groves soils, carbon and water effects on gypsiferous soil
文章编号: N18072102
期刊: CATENA
作者: Blanca Sastre, Maria Jose Marques, Andrés García-Díaz, Ramón Bienes
更新时间: 2018-07-21
摘要: Soils of olive grove are usually managed by tillage, leading to organic matter depletion and soil structure degradation. Cover crops to protect soils have been revealed as a sustainable land management practice for erosion control and remediation of degraded soils, but in some cases, water competition can be a problem, all these effects (particularly soil water) are site and climate specific. A trial in a rainfed olive grove in gypsiferous soils under semiarid Mediterranean climatic conditions has been set up in Central Spain. Several parameters (plant cover, root density, organic carbon, organic nitrogen, aggregate stability, porosity, infiltration, water storage and soil penetration resistance) have been studied under different management practices: three types of cover crops, two annuals (legume and barley) and one permanent (Brachypodium distachyon); and minimum tillage. After three years of treatments, slight improvements in particulate organic carbon, aggregate stability, microporosity at 0–5 cm depth and soil water storage at 30 cm were found in cover crops; B. distachyon also increased organic carbon, and improved C/N ratio and available water. >3 years of a sustainable land management are needed to recover olive groves soil quality in gypsiferous soils under semiarid climate. In this study, cover crops facilitated carbon stratification, higher SOC content in deeper layers are important in the context of carbon sequestration.
图文摘要:

24754. 题目: Sorption of tetracycline on H3PO4 modified biochar derived from rice straw and swine manure
文章编号: N18072101
期刊: Bioresource Technology
作者: Tingwei Chen, Ling Luo, Shihuai Deng, Guozhong Shi, Shirong Zhang, Yanzong Zhang, Ouping Deng, Lilin Wang, Jing Zhang, Luoyu Wei
更新时间: 2018-07-21
摘要: Currently, the information about the sorption of tetracycline (TC) on animal manure derived biochar was rare although plant residue derived biochar showed high sorption of TC). Therefore, this study explored the sorption of TC on swine manure derived biochar, and compared with rice straw derived biochar simultaneously. Also, H3PO4 was adopted to modify both types of biochar. The sorption kinetic and isotherm data showed H3PO4 modification enhanced the sorption of TC on both types of biochar (especially swine-manure-biochar), and indicated the chemisorptions including H-bonding and π-π electron donor acceptor interaction might be the primary mechanism. Moreover, the strengthened electrostatic attraction between TC and biochars might largely explain the enhanced sorption capacity of TC along with pH increasing from 5.0 to 9.0. At the same conditions, swine manure derived biochar demonstrated lower sorption capacity of TC than rice straw biochar, but still could be good material for the sorption of TC.

24755. 题目: Assessing the metabolism of sedimentary microbial communities using the hydrogen isotopic composition of fatty acids
文章编号: N18072008
期刊: Organic Geochemistry
作者: Sandra M. Heinzelmann, Laura Villanueva, Yvonne A. Lipsewers, Danielle Sinke-Schoen, Jaap S. Sinninghe Damsté, Stefan Schouten, Marcel T.J. van der Meer
更新时间: 2018-07-20
摘要: The hydrogen isotopic composition of fatty acids (FAs) has previously been shown to reflect the metabolism of microorganisms in pure culture, but has rarely been tested in the environment. Here, we report the abundance and hydrogen isotopic composition of polar lipid derived FAs extracted from surface sediments of the saline Lake Grevelingen (The Netherlands), at two different stations and during two seasons with oxic bottom water conditions during spring and hypoxic to anoxic conditions during late summer. These data are compared with the bacterial diversity revealed by 16S rRNA gene amplicon sequencing. All measured FAs were depleted in deuterium relative to the bottom water by 103‰ to 267‰. FAs associated with heterotrophic bacteria (i-15:0 and ai-15:0) showed the smallest fractionation (–103‰ to –185‰) while those derived from pelagic photoautotrophic phytoplankton (20:5) showed the largest fractionation (–230‰ to –267‰). Overall, the hydrogen isotope fractionation reflected in the majority of the more commonly occurring FAs (14:0, 16:0, 16:1ω7) is relatively large (–172‰ to –217‰). Together with the high relative abundance of the 20:5 FA, this suggests a substantial contribution from dead pelagic biomass settling from the water column to the sedimentary polar lipid derived FA pool and not from the in situ microbial communities. Therefore, the majority of the isotope signal in the fatty acids from surface sediments might not represent the general metabolism of the active sedimentary communities. Therefore, the input of pelagic biomass into sedimentary environments may bias the information contained in the hydrogen isotopic composition of FAs.

24756. 题目: Thermodynamics of Hg(II) Bonding to Thiol Groups in Suwannee River Natural Organic Matter Resolved by Competitive Ligand Exchange, Hg LIII-Edge EXAFS and 1H NMR Spectroscopy
文章编号: N18072007
期刊: Environmental Science & Technology
作者: Yu Song, Tao Jiang, Van Liem-Nguyen, Tobias Sparrman, Erik Bj?rn, Ulf Skyllberg
更新时间: 2018-07-20
摘要: A molecular level understanding of the thermodynamics and kinetics of the chemical bonding between mercury, Hg(II), and natural organic matter (NOM) associated thiol functional groups (NOM-RSH) is required if bioavailability and transformation processes of Hg in the environment are to be fully understood. This study provides the thermodynamic stability of the Hg(NOM-RS)2 structure using a robust method in which cysteine (Cys) served as a competing ligand to NOM (Suwannee River 2R101N sample) associated RSH groups. The concentration of the latter was quantified to be 7.5 ± 0.4 μmol g–1 NOM by Hg LIII-edge EXAFS spectroscopy. The Hg(Cys)2 molecule concentration in chemical equilibrium with the Hg(II)-NOM complexes was directly determined by HPLC-ICPMS and losses of free Cys due to secondary reactions with NOM was accounted for in experiments using 1H NMR spectroscopy and 13C isotope labeled Cys. The log K ± SD for the formation of the Hg(NOM-RS)2 molecular structure, Hg2+ + 2NOM-RS– = Hg(NOM-RS)2, and for the Hg(Cys)(NOM-RS) mixed complex, Hg2+ + Cys– + NOM-RS– = Hg(Cys)(NOM-RS), were determined to be 40.0 ± 0.2 and 38.5 ± 0.2, respectively, at pH 3.0. The magnitude of these constants was further confirmed by 1H NMR spectroscopy and the Hg(NOM-RS)2 structure was verified by Hg LIII-edge EXAFS spectroscopy. An important finding is that the thermodynamic stabilities of the complexes Hg(NOM-RS)2, Hg(Cys)(NOM-RS) and Hg(Cys)2 are very similar in magnitude at pH values <7, when all thiol groups are protonated. Together with data on 15 low molecular mass (LMM) thiols, as determined by the same method (Liem-Ngyuen et al. Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory. Environ. Chem. 2017, 14, (4), 243 253.), the constants for Hg(NOM-RS)2 and Hg(Cys)(NOM-RS) represent an internally consistent thermodynamic data set that we recommend is used in studies where the chemical speciation of Hg(II) is determined in the presence of NOM and LMM thiols.
图文摘要:

24757. 题目: Optimization of integrated ultrasonic-Fenton system for metal removal and dewatering of anaerobically digested sludge by Box-Behnken design
文章编号: N18072006
期刊: Science of The Total Environment
作者: Jannatul Rumky, Mohamed Chaker Ncibi, Rutely C. Burgos-Castillo, Anjan Deb, Mika Sillanp??
更新时间: 2018-07-20
摘要: This study reveals the optimization of ultrasonic-Fenton process for the treatment of sludge taken from a local municipal wastewater treatment plant after anaerobic digestion. Box-Behnken design (BBD), a common approach of response surface methodology (RSM), was applied to evaluate and optimize the individual and interactive effects of three process variables, namely Fe2+ dose, H2O2 amount and sonication time for Fenton-ultrasonication method. Five dependent parameters including total organic carbon (TOC), extracellular polymeric substances (EPS), as LB-EPS and TB-EPS, and metals such as Zn and Cu were considered as the responses to investigate. According to the results of analysis of variances (ANOVA), five modelling equations are proposed that can be used to operate the design space with high regression coefficient R2. Modelling results suggest that Fenton parameters, such as: H2O2 and Fe2+ dosage had the significant effects on the overall removal of TOC; whereas, sonication improved the metal removal from the sludge sample. Based on response surface methodology, best performance is achievable under the following conditions: 36 mM of Fe2+, 320 mM H2O2 with 30 min of sonication respectively for all of the responses.
图文摘要:

24758. 题目: 20th century increase in body size of a hypoxia-tolerant bivalve documented by sediment cores from the northern Adriatic Sea (Gulf of Trieste)
文章编号: N18072005
期刊: Marine Pollution Bulletin
作者: Tomá? Fuksi, Adam Toma?ov?ch, Ivo Gallmetzer, Alexandra Haselmair, Martin Zuschin
更新时间: 2018-07-20
摘要: An increase in the frequency of hypoxia, mucilages, and sediment pollution occurred in the 20th century in the Adriatic Sea. To assess the effects of these impacts on bivalves, we evaluate temporal changes in size structure of the opportunistic bivalve Corbula gibba in four sediment cores that cover the past ~500 years in the northern, eutrophic part and ~10,000 years in the southern, mesotrophic part of the Gulf of Trieste. Assemblages exhibit a stable size structure during the highstand phase but shift to bimodal distributions and show a significant increase in the 95th percentile size during the 20th century. This increase in size by 2–3 mm is larger than the northward size increase associated with the transition from mesotrophic to eutrophic habitats. It coincides with increasing concentrations of total organic carbon and nitrogen, and can be related to enhanced food supply and by the tolerance of C. gibba to hypoxia.

24759. 题目: Interactions between aged biochar, fresh low molecular weight carbon and soil organic carbon after 3.5-years soil-biochar incubations
文章编号: N18072004
期刊: Geoderma
作者: Xinyu Jiang, Xiangping Tan, Jiong Cheng, Michelle L. Haddix, M. Francesca Cotrufo
更新时间: 2018-07-20
摘要: Biochar has been considered a stable additive for long-term soil carbon (C) storage and climate change mitigation. However, our understanding of the long-term interactions between aged biochar, soil organic C (SOC), and fresh low molecular weight C compounds (LMW-C) is still limited. In addition to the changes in the chemical properties of biochar and the SOC after aging, biochar stability and C sequestration potentials might be affected by the LMW-C availability. After 3.5 years of incubation, aged soils and aged soil-biochar mixtures (4 atom‰ 13C enriched grass-derived biochar, 10% addition rate) of two different soil types were used in this study, with or without the addition of LMW-C. The 13C natural abundance of the LMW-C was manipulated by mixing cane sucrose (C4) and beet sugar (C3) to make it different from or equal to the native SOC isotopic signature of the two soil types, which allowed the partitioning of the LMW-C and biochar C from the SOC in non-biochar and biochar addition treatments, respectively. We traced the 13C in the cumulative CO2, microbial biomass C (MBC), and dissolved organic C (DOC) at the beginning and the end of the 28 days of incubation. Results indicated that this aged biochar was not as effective for SOC protection as it was when fresh. Aged biochar caused significant increases in the native SOC-derived CO2 compared to non-biochar treatment during the 3.5 years of aging. Within the 28 days of incubation, aged biochar not only promoted the total CO2 emission but also did not limit the priming effect of LMW-C on native SOC mineralization. SOC-derived DOC in the aged soil-biochar mixture was significantly higher than that in the aged soil, which further increased the SOC loss. A decline in the SOC stability with aged biochar might be associated with the attenuated sorption of SOC on aged biochar, the decline in bulk density with the high biochar addition rate, and a modified microbial community. The priming of aged SOC mineralization with the addition of LMW-C might be associated with the enhanced microbial N demand in aged soils and soil-biochar mixtures. The effect of aged biochar on the soil DOC and the effect of LMW-C on the aged biochar and SOC stabilities should be further investigated in field conditions, under continuous fresh C inputs, to better evaluate the effects of biochar on long-term SOC storage.

24760. 题目: Evaluation of coastal wetland soil properties in a degrading marsh
文章编号: N18072003
期刊: Estuarine, Coastal and Shelf Science
作者: Jacob F. Berkowitz, Christine M. VanZomeren, Candice D. Piercy, John R. White
更新时间: 2018-07-20
摘要: Coastal salt marshes consist of a mosaic of vegetated and open water features, which naturally evolve and change over time. However, the rapid expansion of open water areas has been associated with marsh degradation and there is a growing need for detailed studies as coastal wetlands continue to degrade under increasing rates of sea level rise and related stressors. Yet, few studies investigate soil physicochemical and biogeochemical properties within different marsh landscape features, which could provide insight into mechanisms of the formation and expansion of open water areas. The current study compared wetland soil physical and microbial properties observed in vegetated areas with shallow open water areas called pannes, identifying a number of significant differences. Panne soils possessed lower bulk density, total C, N, P, SOC, DOC, and SRP compared with vegetated marsh areas, suggesting a shift in nutrient pools as vegetated areas transition into shallow open water features. Panne features also displayed significantly lower microbial pool sizes and processing rates than vegetated marsh soils, suggesting reduced capacity for nutrient processing in open water areas. Further, extractable NH4-N was highest in the panne soils suggesting that the absence of macrophytes decreased N uptake in open water areas. Also related to the lack of vascular plants, extractable DOC in pannes averaged less than half the concentration found in vegetated marsh areas, despite a smaller difference in soil total C. Results underscore the importance of incorporating heterogeneous landscape soil conditions when evaluating marsh degradation and considering potential restoration activities.