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25961. 题目: Methylmercury production in a paddy soil and its uptake by rice plants as affected by different geochemical mercury pools
文章编号: N19060105
期刊: Environment International
作者: Jinling Liu, Jianxu Wang, Yongqiang Ning, Shaochen Yang, Pengcong Wang, Sabry M. Shaheen, Xinbin Feng, Jörg Rinklebe
更新时间: 2019-06-01
摘要: The formation of neurotoxic methylmercury (MeHg) in paddy fields and its accumulation by rice plants is of high environmental concern. The contribution of different geochemical mercury (Hg) pools in paddy soils to MeHg production and its accumulation by rice seedlings is not well-studied up to now. Therefore, we investigated the impact of different inorganic Hg forms, including HgCl2, nano-particulated HgS (nano-HgS), Hg bound with dissolved organic matter (Hg-DOM), β-HgS, and α-HgS, at levels of 5 mg Hg/kg soil and 50 mg Hg/kg soil, on the production of MeHg in the soil during rice growing season. Further, we studied the uptake of MeHg by the roots, stalks, leaves, and grains of rice in the tillering, panicle formation, and ripening growth stages, and compared these treatments to a non-polluted soil (control). MeHg contents in HgCl2 polluted soil were the highest, and were 13.5 times and 36.1 times higher than control in 5 and 50 mg/kg Hg treatments, respectively. MeHg contents in α-HgS, β-HgS, nano-HgS, and Hg-DOM polluted soil were 3.9, 2.6, 2.4, and 1.7 times, and 4.4, 15.1, 6.7, and 10.9 times higher than control in 5 and 50 mg/kg Hg treatments, respectively, suggesting the mobilization and methylation of these Hg complexes. The ratio of MeHg to total Hg in the pore water (indication of methylation potential) in HgCl2 and β-HgS treatments were higher than in Hg-DOM, α-HgS, and nano-HgS treatments. HgCl2 treatment resulted in significantly higher MeHg contents in the root, stalk, leaf, and brown rice than nano-HgS, Hg-DOM, β-HgS, and α-HgS treatments both in 5 and 50 mg/kg Hg polluted soils. Rice grain in HgCl2 treatment showed a potential hazard to human health, as indicated by high health risk index (HRI > 1) of MeHg. Current results improve our understanding of MeHg production in soil polluted with different Hg forms, and the assessment of human health risks from consumption of MeHg-laden rice grain at Hg polluted sites with different Hg forms in soils.
25962. 题目: Metal pollution in surface sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro, Brazil): Toxic effects on marine organisms
文章编号: N19060104
期刊: Environmental Pollution
作者: Mariana Vezzone, Ricardo Cesar, Denis Moledo de Souza Abessa, Aline Serrano, Rodrigo Lourenço, Zuleica Castilhos, Ana Paula Rodrigues, Fernando Cesar Perina, Helena Polivanov
更新时间: 2019-06-01
摘要: The Rodrigo de Freitas Lagoon (RFL - Rio de Janeiro, RJ, Brazil) is a highly polluted and eutrophic lacustrine system, which has been often used for the practice of aquatic sports, including during the 2016 Summer Olympic Games. This study proposes the evaluation of metal concentrations in surface sediments from the RFL before and after urban interventions performed for the 2016 Olympics, as well as their toxicity to the benthic amphipod Tiburonella viscana and embryos of the sea-urchin Echinometra lucunter. Metal concentrations determined in 2017 were significantly higher than those obtained in 2015 (especially Cu, Cd and Ni), suggesting that the interventions performed to fulfill the requirements of the Olympics increased metal contents in sediments. The sediments from the northern sector of the RFL were muddier, more organically enriched, exhibited higher metal concentrations and were more toxic to T. viscana when compared to the sediments collected in the southern sector. This fact is particularly important since the practice of sports, including during the 2016 Olympics, has been preferably performed in the northern sector. Metal distribution was strongly correlated with organic matter and mud contents. The toxicity to E. lucunter embryos was high for both northern and southern sediments; most of the samples led to 100% lack or abnormal embryonic development. The integration of physical, chemical and ecotoxicological data indicates that the mortality to T. viscana was correlated with metal contents, whereas the toxicity to E. lucunter was apparently related to the release of ammonia from the sediment to water column. Finally, high metal concentrations and the toxicity to aquatic organisms evidence the ecological risks to the biota from RFL.
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25963. 题目: Initial microaggregate formation: Association of microorganisms to montmorillonite-goethite aggregates under wetting and drying cycles
文章编号: N19060103
期刊: Geoderma
作者: Lars Krause, Danh Biesgen, Aaron Treder, Steffen A. Schweizer, Erwin Klumpp, Claudia Knief, Nina Siebers
更新时间: 2019-06-01
摘要: There is an intimate relationship between microorganisms and the formation and stability of soil microaggregates, realized by the immobilization and occlusion of microorganisms. Little is known about the initial aggregate formation phase and the role of microorganisms in this process under the impact of environmental changes such as wetting and drying. We investigated this initial aggregate formation process of montmorillonite and goethite in combination with two bacterial strains, Pseudomonas protegens strain CHA0 and Gordonia alkanivorans strain MoAcy 2, in the presence or absence of stress conditions in form of wetting and drying cycles for up to eight days. Montmorillonite and goethite formed microaggregates instantaneously, the size of these aggregates being enhanced in the presence of microorganisms, resulting in up to twofold larger aggregates. This increase in aggregate size was strain-dependent. However, the aggregates that developed during the first 48 h broke into smaller structures later on. A microscopic analysis of the microaggregates revealed that notably the larger microaggregates harbored bacteria and that microaggregates had a sheltering effect on living cells, especially when exposed to desiccation stress. Additionally, aggregate formation was analyzed in the presence of a Pseudomonas protegens mutant strain (CHA211) with increased production capability of extracellular polymeric substances (EPS). About fivefold higher survival rates of culturable cells were observed after desiccation for this EPS overproducing mutant strain in comparison to the wild-type. Our results hint at an aggregate formation process characterized by a rapid occlusion of mineral compounds, and, after the addition of microorganisms, the bacterial colonization of small microaggregates, leading to an increase in aggregate size. The further development of the aggregate size distribution varied depending on the presence of microbial taxa and was modulated by environmental conditions like desiccation events.
25964. 题目: Multifunctional Pd/Fe-biochar composites for the complete removal of trichlorobenzene and its degradation products
文章编号: N19060102
期刊: Journal of Environmental Management
作者: Lu Han, Jingchun Yan, Linbo Qian, Wenying Zhang, Mengfang Chen
更新时间: 2019-06-01
摘要: To elucidate the effect of structure and property of biochar on the structure-activity relationship among the composites of biochar supported Pd/Fe and 1,2,4-trichlorobenzene (1,2,4-TCB) and its dechlorination products, biochar supported Pd/Fe nanoparticles with different mass ratios were investigated for the enhanced removal of 1,2,4-TCB (52 μmol/L) and its dechlorination products. 1,2,4-TCB was removed through the electrochemical dechlorination by Pd/Fe and adsorption by biochar simultaneously. As the mass ratio of CS700 to Pd/Fe was 0.1:1, biochar within the Pd/Fe-CS7000.1 system played a significant role in the adsorption of 1,2,4-TCB. However, there is little adsorption to biochar for dechlorination products due to strong competition by 1,2,4-TCB. As the mass ratio of CS700 to Pd/Fe was increased to 5:1, 1,2,4-TCB was completely removed from the solution by the composites within 0.5 h. The dechlorination products (1,2-DCB, MCB, benzene and trace 1,3-DCB) were completely sequestered on solid phase but absent in aqueous solution. However, the excessive biochar increased the inaccessibility of 1,2,4-TCB or decreased the reactive sites of Pd/Fe leading to the less dechlorination of 1,2,4-TCB. The alkaline biochar did not influence the chemical reactivity of Pd/Fe in the composites and buffered the acid and alkaline solutions with pH being maintained at neutral conditions under initial pH ranging from 3.07 to 10.03. The highly hydrophobicity of biochar could maintain the affinity of the composite for the chlorinated compounds even if the concentration of 1,2,4-TCB was up to 80.9% of its aqueous solubility. This study provides efficient synergistic removal support for the treatment of TCB affected groundwater.
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25965. 题目: Insight into the interaction mechanism of iron ions with soil humic acids. The effect of the pH and chemical properties of humic acids
文章编号: N19060101
期刊: Journal of Environmental Management
作者: Patrycja Boguta, Valeria D'Orazio, Nicola Senesi, Zofia Sokołowska, Katarzyna Szewczuk-Karpisz
更新时间: 2019-06-01
摘要: The main aim of this work was to study the mechanisms of interaction between iron(II) ions and humic acids as a function of pH, iron concentration and various humic acids chemical properties, including the degree of humification, elemental composition, aromaticity and content of acidic functional groups. The results indicated that iron was bound by humic acids at pH 7 in amounts ∼2 times higher than at pH 5 (averaged capacities: 117 and 57 cmol/kg, respectively). Iron binding at pH 7 increased with increasing the total carboxylic and phenolic groups content and the degree of humification of humic acids (R-coefficients: 0.99 and 0.95, respectively). The stability of humic acid-iron complexes at pH 7 were only slightly lower than at pH 5 due to iron hydroxides formed at pH > 5 (averaged stability constants: 5.18 and 5.26, respectively). Iron coordination mode varied depending on pH: at pH 5, the bidentate (chelate) mode dominated, whereas at pH 7 the bridging mode appeared prevalent. The total amount of bound iron was much smaller than the content of the carboxylic and phenolic groups in humic acids, on average by ∼80 (pH 7) and ∼90.1% (pH 5) indicating the occurrence of steric effects in humic acid structure i.e. the reduction of the complexation capacity of free functional groups by adjacent groups occupied by iron and/or the formation of intramolecular aggregates with iron hindering the access of further metal ions. At pH 5 the complexes were soluble in the iron concentration range positively correlated to carboxylic and phenolic groups content, showing the protective nature of negatively charged functional groups on the stability of the solution. At this pH, the destabilization of the system was governed by the neutralization of humic acid charged structures by metal cations and the compression of the double electric layer. At pH 7 the stability of the humic acid-iron solution was largely determined by the form of iron, mainly by the precipitation of metal hydroxides acting as a flocculant destabilizing the solution by co-precipitation of humic acid-iron complexes.
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25966. 题目: Biochar-Mediated Anaerobic Oxidation of Methane
文章编号: N19053106
期刊: Environmental Science & Technology
作者: Xueqin Zhang, Jun Xia, Jiaoyang Pu, Chen Cai, Gene W. Tyson, Zhiguo Yuan, Shihu Hu
更新时间: 2019-05-31
摘要: Biochar was recently identified as an effective soil amendment for CH4 capture. Corresponding mechanisms are currently recognized to be from physical properties of biochar, providing a favorable growth environment for aerobic methanotrophs which perform aerobic methane (CH4) oxidation. However, our study shows that the chemical reactivity of biochar can also stimulate anaerobic oxidation of CH4 (AOM) by anaerobic methanotrophic archaea (ANME) of ANME-2d, which proposes another plausible mechanism for CH4 mitigation by biochar amendment in anaerobic environments. It was found that, by adding biochar as the sole electron acceptor in an anaerobic environment, CH4 was biologically oxidized, with CO2 production of 106.3 ± 5.1 μmol g–1 biochar. In contrast, limited CO2 production was observed with chemically reduced biochar amendment. This biological nature of the process was confirmed by mcr gene transcript abundance as well as sustained dominance of ANME-2d in the microbial community during microbial incubations with active biochar amendment. Combined FTIR and XPS analyses demonstrated that the redox activity of biochar is related to its oxygen-based functional groups. On the basis of microbial community evolution as well as intermediate production during incubation, different pathways in terms of direct or indirect interactions between ANME-2d and biochar were proposed for biochar-mediated AOM.
25967. 题目: Does the element composition of soils of restored wetlands resemble natural wetlands?
文章编号: N19053105
期刊: Geoderma
作者: Guodong Wang, Marinus L. Otte, Ming Jiang, Ming Wang, Yuxiang Yuan, Zhenshan Xue
更新时间: 2019-05-31
摘要: The main goal of this study was to assess if wetland restoration changes soil biogeochemistry, here measured as organic matter content (OM) and element concentrations of the soils, back to its original state. We selected nine sampling sites in the Sanjiang Plain, China, that had two or three of the wetland types ‘undisturbed/natural’, ‘restored’, and ‘paddy field’ close to each other. The paddy fields were originally established on natural wetlands, and the original wetland soils would therefore have been similar. We analyzed the soils for element composition, OM, as well as electrical conductivity (EC) and pH. Distinct differences between undisturbed wetlands, restored wetlands and paddy fields existed in terms of element composition, OM, and EC, with most values for restored wetlands in-between those of undisturbed wetlands and paddy fields. Ordination analysis of the element concentrations by RDA identified that OM explained most variance (23.9% of 34.4% of total). OM correlated positively with N and S, negatively with most metals. Disturbance of wetland soils by agricultural activities most likely depleted OM of the soils, which in turn altered the concentrations of most elements. Restoration, even if only a few years ago, recovered the OM and changed the element contents in the direction of a natural condition to some extent. This information is important for restoration of wetlands, because to be successful, not only hydrology and biodiversity need to be restored but also the soil composition and biogeochemistry. It further can be used for assessment of success of wetland restoration.
25968. 题目: Soil organic carbon stock on the Majorca Island: Temporal change in agricultural soil over the last 10 years
文章编号: N19053104
期刊: CATENA
作者: José Antonio y Rodríguez Martín, Jorge Álvaro-Fuentes, Jose Luis Gabriel, Carmen Gutiérrez, Nikos Nanos, Miguel Escuer, José Joaquín Ramos-Miras, Carlos Gil, Diana Martín-Lammerding, Rafael Boluda
更新时间: 2019-05-31
摘要: For quite a long time, soil organic carbon stock (SOCS) has reduced from reconverting forest areas into agricultural land or by inadequate agronomic practices. However in recent decades in Mediterranean areas, abandonment of agricultural areas due to lack of economic profits and to promoting tourism has fostered a change in land use that has impacted soil carbon. In line with this, the Majorca Island (Spain) could be a good study area to evaluate temporary changes in carbon stocks in soils in areas with a Mediterranean climate. The present study analysed the spatial distribution of SOCS and evaluated the temporal changes over 11 years in agricultural soils in relation to the influence of land use and land management’. The global carbon budget (estimated at 30 cm depth) on the Majorca Island was estimated at 31.23 Tg C, and showed wide spatial variability. As expected, SOCS was higher in the forest areas of the Tramuntana Mountain Range (>100 Mg ha−1), while the lowest contents were found in agricultural use (79.3 Mg ha−1), located mainly in the centre and south of this island.The total C stored from 2006 to 2017 increased by 2.62 Tg C (15%) in agricultural areas on the island. We noted a major increase in SOCS in the agricultural zones on mountain slopes (>2-fold higher), associated with abandoned crops in terrace cultivation, but grassland systems also increased. Nonetheless, the present study shows a sharp drop in SOCS in the centre and south of this island. This decrease was more pronounced in annual crops (−14.5%), which could be attributed to intensive soil management and increased irrigated land. Land abandonment has been indicated as the main potential to carbon sequestration in soil, but this potential for carbon sequestration is a finite process. Certain changes in agricultural practices on Majorca, and in rural Mediterranean areas in general, are necessary to avoid carbon loss in cropland soils. Adoption of conservation agriculture practices, e.g. cover crops, crop rotation, organic additions and reduced tillage techniques, can help increase SOC levels in rural Mediterranean areas.
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25969. 题目: Degradation of tris-(2-chloroisopropyl) phosphate via UV/TiO2 photocatalysis: kinetic, pathway, and security risk assessment of degradation intermediates using proteomic analyses
文章编号: N19053103
期刊: Chemical Engineering Journal
作者: Xiaolong Yu, Hua Yin, Jin Shao Ye, Hui Peng, Guining Lu, Zhi Dang
更新时间: 2019-05-31
摘要: As a class of emerging organic contaminants (EOCs), organophosphate flame retardants (OPFRs) have been raising concern due to their persistence, bioaccumulation and toxicity. Therefore, it is urgent need to develop environmental-friendly and high-efficient techniques to remove OPFRs. The degradation kinetics and mechanism of tris-(2-chloroisopropyl) phosphate (TCPP), a representative OPFRs, by UV/TiO2 photocatalytic degradation were explored in current research. It was found that degradation reaction was well documented by first-order kinetics with a kobs of 0.3146 min−1, and hydroxyl radical was identified as a dominating contributor for the TCPP elimination. Simultaneously, six steady intermediate products were generated with the release of Cl− and PO43− as photocatalytic reaction further proceeded. The degradation efficiency can be interfered by natural organic matters, anions and pH value, implying that an incomplete mineralization of TCPP could be ubiquitous in heterogeneous water matrix. Combining the proteomics analysis with KEGG metabolism networks analysis, the process of transmembrane transport and energy generation in Escherichia coli altered by intermediates has proved that the intermediates could be transported and utilized through cellular metabolism. Moreover, the diminution of stress resistance suggested that the toxicity of degradation products through UV/TiO2 photocatalytic degradation was lower than that of intact TCPP. To sum up, environmental safety of degrading intermediate products and the satisfactory detoxification effect of TCPP were identified under appropriate mineralization, indicating that UV/TiO2 photocatalysis technique was safe and high-efficient for TCPP control.
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25970. 题目: Interaction with low molecular weight organic acids affects the electron shuttling of biochar for Cr(VI) reduction
文章编号: N19053102
期刊: Journal of Hazardous Materials
作者: Zibo Xu, Xiaoyun Xu, Xinyi Tao, Chengbo Yao, Daniel C.W. Tsang, Xinde Cao
更新时间: 2019-05-31
摘要: Biochar can act as “electron shuttle” in soil redox reactions. It is possible that biochar accepts the electrons from low molecular weight organic acids (LMWOAs) in soil and then transfer them to the acceptors, e.g., Cr(VI). This study evaluated the interaction between seven soil LMWOAs and peanut shell biochar (BC) as well as its effect on the electron shuttling of biochar for Cr(VI) reduction. Both redox reactions and sorption process occurred during the interaction of biochar and LMWOAs, which altered the contents of Cr(VI) reduction-relevant groups (i.e., C–O and –C = O) on the surface of biochar. The redox reactions were more important to the electron transfer between biochar produced at 400℃ (BC400) and LMWOAs due to the repeated cycle of reduction-oxidation of surface functional groups. The reduction rate of Cr(VI) by LMWOAs mediated by BC400 was 1.10-7.09 × 10-3 h-1, among which tartaric acid had the best reduction efficiency due to its highest reducing capability. For biochar produced at 700℃ (BC700), the sorption process of LMWOAs was the key factor to the direct electron shuttling process through the conjugated structure of biochar. The reduction rate of Cr(VI) by LMWOAs mediated by BC700 was significantly higher and ranged 7.40-864 × 10-3 h-1, with the oxalic acid having the best reduction efficiency due to its highest sorption capacity by BC700. The results obtained from this study can help to establish the linkage between biochar and LMWOAs in soil electron network, which better explains the multifunctional roles of biochar during the redox processes such as Cr(VI) reduction in soil.
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25971. 题目: Organic matter variations and links to climate across the early Toarcian oceanic anoxic event (T-OAE) in Toyora area, southwest Japan
文章编号: N19053101
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: David B. Kemp, Viktória Baranyi, Kentaro Izumi, Roger D. Burgess
更新时间: 2019-05-31
摘要: Marked climate warming during the early Toarcian oceanic anoxic event (T-OAE, ~182 Ma) has been shown to have had a significant effect on the global carbon cycle and biosphere. There is also emerging evidence that a primary short-term consequence of this warming was a marked increase in hydrological cycling. In this study, we have investigated local environmental responses to T-OAE climate change by conducting a palynofacies analysis through an expanded Panthalassic margin record of the event exposed in southwestern Japan (Nishinakayama Formation, Toyora area). Palynomorphs are poorly preserved and rare in the studied interval. A pronounced increase in terrestrial phytoclast abundance coeval with the peak of the T-OAE can be linked to increased fluvial supply driven by enhanced hydrological cycling that occurred in response to early Toarcian warming. Broader scale trends in phytoclast abundance through the studied interval may be linked to longer-term sea-level changes. Nitrogen-isotopes, commonly used to elucidate basin redox changes, are found to correlate with changes in the relative abundance of phytoclasts. In contrast, carbon-isotope data are probably not significantly influenced by changes in organic matter type through the succession. However, thermal maturity indicators demonstrate that the succession is overmature, and this likely suppresses the magnitude of the well-known T-OAE carbon-isotope excursion in this succession.
25972. 题目: Impact of light and Suwanee River Fulvic Acid on O 2 and H 2 O 2 Mediated Oxidation of Silver Nanoparticles in Simulated Natural Waters
文章编号: N19053011
期刊: Environmental Science & Technology
作者: Hongyan Rong, Shikha Garg, T. David Waite
更新时间: 2019-05-30
摘要: In this work, we investigate the impact of natural organic matter (NOM) and light on silver nanoparticle (AgNP) dissolution kinetics with particular emphasis on determining the (i) mechanism via which NOM affects the oxidative dissolution of AgNPs, (ii) the role of photogenerated organic radicals and reactive oxygen species (ROS) in oxidative dissolution of AgNPs, and (iii) the mechanism of formation of AgNPs in NOM solution under dark and irradiated conditions. We measured the oxidation of citrate stabilized AgNPs by O2 and hydrogen peroxide (H2O2) in the dark and in irradiated Suwannee River fulvic acid (SRFA) solutions at pH 8.0. Results show that the reactivity of AgNPs toward O2 and H2O2 in the dark decreased in the presence of SRFA as a result of blocking of AgNP surface sites through either steric or electrostatic effects. Irradiation promoted dissolution of AgNPs by O2 and H2O2 in the presence of low concentrations (≤20 mg·L–1) of SRFA as a result of contribution from photogenerated H2O2 formed on irradiation of SRFA as well as photofragmentation of AgNPs. Furthermore, our results show that photogenerated superoxide can induce formation of AgNPs by reducing Ag(I) ions. Based on our experimental results, we have developed a kinetic model to explain AgNP transformation by O2 and H2O2 in the dark and in irradiated SRFA solutions with this model of use in predicting the transformation and fate of AgNPs in natural waters.
25973. 题目: Dissolved organic matter composition in a marsh‐dominated estuary: Response to seasonal forcing and to the passage of a hurricane
文章编号: N19053010
期刊: Journal of Geophysical Research: Biogeosciences
作者: Maria L. Letourneau, Patricia M. Medeiros
更新时间: 2019-05-30
摘要: Dissolved organic matter (DOM) is a large and complex mixture of compounds with source inputs that differ with location, season and environmental conditions. Here, we investigated drivers of DOM composition changes in a marsh‐dominated estuary off the southeastern U.S. Monthly water samples were collected at a riverine and estuarine site from September 2015 to September 2016, and bulk, optical, and molecular analyses were conducted on samples before and after dark incubations. Results showed that river discharge was the primary driver changing the DOM composition at the mouth of the Altamaha River. For discharge higher than ~ 150 m3 s‐1, DOC concentrations and the terrigenous character of the DOM increased approximately linearly with river flow. For low discharge conditions, a clear signature of salt marsh‐derived compounds was observed in the river. At the head of Sapelo Sound, changes in DOM composition were primarily driven by river discharge and possibly by summer algae blooms. Microbial consumption of DOC was larger during periods of high discharge at both sites, potentially due to the higher mobilization and influx of fresh material to the system. The Georgia coast was hit by Hurricane Matthew in October 2016, which resulted in a large input of carbon to the estuary. The DOC concentration was ~ 2 times higher and DOM composition was more aromatic with a stronger terrigenous signature compared to the seasonal maximum observed earlier in the year during peak river discharge conditions. This suggests that extreme events notably impact DOM quantity and quality in estuarine regions.
25974. 题目: Evaluation of bacterial glycerol dialkyl glycerol tetraether and 2H-18O biomarker proxies along a Central European topsoil transect
文章编号: N19053009
期刊: Biogeosciences
作者: Johannes Hepp, Imke K. Schäfer, Verena Lanny, Jörg Franke, Marcel Bliedtner, Kazimierz Rozanski, Bruno Glaser, Michael Zech, Timothy I. Eglinton, and Roland Zech
更新时间: 2019-05-30
摘要: Molecular fossils, like bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs), and the stable isotopic composition of biomarkers, such as δ2H of leaf wax-derived n-alkanes (δ2Hn-alkane) or δ18O of hemicellulose-derived sugars (δ18Osugar) are increasingly used for the reconstruction of past climate and environmental conditions. Plant-derived δ2Hn-alkane and δ18Osugar values record the isotopic composition of plant source water (δ2H/δ18Osource-water), which usually reflects mean annual precipitation (δ2H/δ18Oprecipiation), modulated by evapotranspirative leaf water enrichment and biosynthetic fractionation. Accuracy and precision of respective proxies should be ideally evaluated at a regional scale. For this study, we analysed topsoils below coniferous and deciduous forests, as well as grassland soils along a Central European transect in order to investigate the variability and robustness of various proxies, and to identify effects related to vegetation. Soil pH-values derived from brGDGTs correlate reasonably well with measured soil pH-values, but systematically overestimate them (ΔpH = 0.6 ± 0.6). The branched vs. isoprenoid tetraether index (BIT) can give some indication whether the pH reconstruction is reliable. Temperatures derived from brGDGTs overestimate mean annual air temperatures slightly (∆TMA = 0.5 °C ± 2.4). Apparent isotopic fractionation (εn-alkane/precipitation and εsugar/precipitation) is lower for grassland sites than for forest sites due to "signal damping", i.e. grass biomarkers do not record the full evapotranspirative leaf water enrichment. Coupling δ2Hn-alkane with δ18Osugar allows to reconstruct the stable isotopic composition of the source water more accurately than without the coupled approach (Δδ2H = ~-21 ‰ ± 22 and Δδ18O = ~-2.9 ‰ ± 2.8). Similarly, relative humidity during daytime and vegetation period (RHMDV) can be reconstructed using the coupled isotope approach (ΔRHMDV = ~-17 ± 12). Especially for coniferous sites, reconstructed RHMDV values as well as source water isotope composition underestimate the measured values. This can be likely explained by understory grass vegetation at the coniferous sites contributing significantly to the n-alkane pool but only marginally to the sugar pool in the topsoil. The large uncertainty likely reflect the fact that biosynthetic fractionation is not constant, as well as microclimate variability. Overall, GDGTs and the coupled δ2Hn-alkane-δ18Osugar approach have great potential for more quantitative paleoclimate reconstructions.
25975. 题目: Biochar from extracted marine Chlorella sp. residue for high efficiency adsorption with ultrasonication to remove Cr(VI), Zn(II) and Ni(II)
文章编号: N19053008
期刊: Bioresource Technology
作者: Muhammad Amin, Pakamas Chetpattananondh
更新时间: 2019-05-30
摘要: The biochar BC-450 derived from the extracted marine Chlorella sp. residue (EMCR) had high surface area (266 m2/g) and was rich in ash and O-functional groups. Its characteristics are suitable for heavy metal adsorption. The adsorption parameters were investigated to optimize the removal efficiency of Cr(VI), Zn(II) and Ni(II) from aqueous solution by conventional adsorption (CA) and by ultrasonication adsorption (UA). The adsorption was fit by Langmuir isotherm and by pseudo-second-order model. The equilibrium times were 10, 8, 15 minutes and 40, 60, 80 minutes for removal of Cr(VI), Zn(II) and Ni(II) with UA and CA, respectively. The maximum adsorption capacities of Cr(VI), Zn(II) and Ni(II) for CA and UA were 15.94, 17.62 and 24.76 mg/g and 18.86, 21.31 and 27.45 mg/g, respectively. UA presented 1.1-1.3 times greater removal efficiencies than CA in much shorter time. The EMCR is a promising feedstock for producing low cost and high efficiency adsorbents.
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25976. 题目: Extracellular polymeric substances extraction and recovery from anammox granules: Evaluation of methods and protocol development
文章编号: N19053007
期刊: Chemical Engineering Journal
作者: Cuijie Feng, Tommaso Lotti, Yuemei Lin, Francesca Malpei
更新时间: 2019-05-30
摘要: Selection of appropriate extraction methods of extracellular polymeric substances (EPSs) is crucial, affecting the yield, composition and the properties of EPSs. However, there is still a lack of standard methods for EPS extraction. In this study, seven methods were compared to extract EPS from anaerobic ammonium oxidation (anammox) granules, and the effectiveness and cell lysis of these methods were evaluated. The heating-Na2CO3 based method obtained a higher EPS yield with limited cell lysis. Proteins (PN) and polysaccharides (PS) were predominant in extractable EPSs. Particularly, PN-related substances were substantially enriched and high PN/PS ratios resulted in most methods. Different methods resulted in EPSs with a different size distribution. By analysis of Attenuated total reflectance-Fourier transform infrared spectra (ATR-FTIR), amide- and polysaccharide-associated bands were dominant. ATR-FTIR and fluorescence density of excitation-emission matrix spectra indicated EPS compositions and structures varied with the extraction methods. Moreover, the extraction/recovery protocol based on the heating-Na2CO3 method was remarkably improved, by varying heating time and using a centrifugal filter device with membrane (CFDM) to replace concentration and purification steps. Eventually, the thermal method with an extraction time of 45 mins was identified to be most effective. The application of CFDM was demonstrated as an alternative approach to concentrate and purify for EPS recovery. To our best knowledge, this is the first original study to systematically evaluate the different EPS extraction methods from anammox granules.
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25977. 题目: Risk evaluation of biochars produced from Cd-contaminated rice straw and optimization of its production for Cd removal
文章编号: N19053006
期刊: Chemosphere
作者: Zhengtao Shen, Xiaoliang Fan, Deyi Hou, Fei Jin, David O'Connor, Daniel C.W. Tsang, Yong Sik Ok, Daniel S. Alessi
更新时间: 2019-05-30
摘要: Based on the “waste-treat-waste” concept, biochars were produced from cadmium (Cd)-contaminated rice straw (CRSBs) at 300, 500, and 700 °C (CRSB300, CRSB500, and CRSB700). The risks of the Cd remaining in CRSBs were evaluated and the optimal biochar pyrolysis temperature for Cd removal was investigated. It was observed that 41% of the total Cd in the raw rice straw was exchangeable, which may poses significant risks to crops and humans. Pyrolyzing at 300 °C did not significantly alter the Cd fractions, while the exchangeable fraction of Cd greatly dropped to 5.79% at 500 °C and further to 2.12% at 700 °C. Increasing the highest pyrolysis temperature resulted in CRSB with higher pH values, greater surface area, and smaller pore sizes, thus providing more rapid and efficient removal of Cd from aqueous solutions. For Cd removal tests, increasing pyrolysis temperature (300–700 °C) increased the total (24.8–55.1 mg/g) and non-exchangeable (18.9–52.8 mg/g) Cd concentrations immobilized on the CRSBs and significantly decreased the exchangeable Cd fraction (23.7%–4.85%). It is suggested based on the study from aqueous solutions that CRSB700 was the most suitable for the remediation of Cd contaminated soil on site due to the lowest risks of remained Cd from feedstock, fastest and highest Cd removal, and most stable immobilization of Cd.
25978. 题目: Ozonation reactivity characteristics of dissolved organic matter in secondary petrochemical wastewater by single ozone, ozone/H2O2, and ozone/catalyst
文章编号: N19053005
期刊: Chemosphere
作者: Liya Fu, Changyong Wu, Yuexi Zhou, Jiane Zuo, Guangqing Song, Yu Tan
更新时间: 2019-05-30
摘要: Advanced oxidation methods (e.g., ozonation systems) are used for control of recalcitrant pollutants in secondary petrochemical wastewater. For the selection of the optimal wastewater treatment method, we compared the reactivity characteristics of dissolved organic matter (DOM) in three common ozone treatment processes: single ozone, ozone/H2O2, and ozone/catalyst. The raw and ozonated DOM were fractionated into six fractions using ion exchange resins. Fluorescence spectroscopy and size exclusion chromatography were employed to characterize the fractions. The results showed that the single ozone system transformed hydrophobic components into hydrophilic components, but exhibited low mineralization ability. By contrast, the increase in hydrophilic acid fractions transformed from other fractions in the ozonation process were further mineralized in the ozone/H2O2 and ozone/catalyst systems. Ozone/H2O2 preferentially reduced hydrophobic bases, whereas ozone/catalyst preferentially reduced hydrophilic neutral components. However, ozone/H2O2 exhibited low selectivity in degrading organic compounds of different molecular weights. The highest total organic carbon (TOC) removal efficiency was achieved in the ozone/catalyst system, which promoted the transformation from fulvic acid- and humic acid-like substances into aromatic proteins and soluble microbial by-product-like substances. The single ozone system transformed high-molecular-weight compounds into low-molecular-weight compounds, resulting in an unsatisfactory TOC removal efficiency. By contrast, the ozone/catalyst system selectively removed the residual low-molecular-weight compounds in the reaction with ozone. This might have contributed to the high TOC removal efficiency of the ozone/catalyst treatment. These results can be used by other researchers and engineers to inform the selection of optimal ozone treatment based on wastewater characteristics.
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25979. 题目: Characterisation of dissolved organic matter in fermentation industry effluents and comparison with model compounds
文章编号: N19053004
期刊: Chemosphere
作者: Jeraz Cooper, Alice Antony, Audrey Luiz, John Kavanagh, Amir Razmjou, Vicki Chen, Greg Leslie
更新时间: 2019-05-30
摘要: Advanced organic characterisation methods were used to investigate the suitability of lab-based model compounds as surrogates to mimic the dissolved organic matter (DOM) of both first and second generation fermentation industry effluents. Comparisons to both humic acid and synthetic melanoidin revealed the limitations of using these model organic compounds in treatment studies of biorefinery effluent. Rapid resin fractionation (RRF) of effluent from yeast cultivated on molasses suggests that 64% of the dissolved organic matter is present in the form of very hydrophobic acid (VHPhoA) compounds. Molecular weight distribution by size exclusion chromatography (LC-OCND) and fluorophore specific intensity by fluorescence excitation and emission matrix (FEEM) of the yeast effluent was comparable to signatures from humic acid. This indicates that humic acid would be a suitable model compound for oxidation, adsorption and filtration studies. Differences among the fermentation industry effluents were found to be inherently dependent on both the biochemistry of yeast and processes used. RRF and FEEM spectra of effluent from bioethanol production on cellulosic feed highlighted a preponderance of neutral compounds with fluorophore specific intensity characteristic of non-humic compounds with a higher fraction of neutral compounds (41%) relative to VHPhoA (38%), SHPhoA (16%) and HPhi (5%) moieties. Findings were not consistent with commercial humics, synthetic melanoidins or other cellulosic and lignocellulosic based effluents from Kraft and Thermomechanical pulp mills since the actual pollutants are heavily dependent on the pre-treatment process. This suggests further work is required to develop a model compound for treatment studies of effluent from second generation bio-refineries.
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25980. 题目: Disentangling the effects of parent material and litter input chemistry on molecular soil organic matter composition in converted forests in Western Europe
文章编号: N19053003
期刊: Organic Geochemistry
作者: Olaf Brock, Annemieke Kooijman, Klaas G.J. Nierop, Bart Muys, Karen Vancampenhout, Boris Jansen
更新时间: 2019-05-30
摘要: By storing carbon in the soil, forests contribute to climate change mitigation. Edaphic (soil related) factors, such as soil pH, as well as tree species affect forest carbon cycles, but are difficult to disentangle. We studied how conversion of deciduous stands to mono-culture spruce plantations affected the soil organic matter (SOM) composition along a lithological gradient in the Mullerthal (Luxembourg) and Gaume (south-east Belgium) regions. Parent materials in these regions range from decalcified sands to calcareous marls. A twin plot setup of adjacent deciduous and coniferous stands on the same parent material was used to evaluate the effect of edaphic factors versus litter input differences on SOM composition and soil organic carbon (SOC) stocks. Lignin and cutin/suberin molecular proxies were identified with thermally assisted hydrolysis and methylation (THM), to distinguish litter sources (coniferous vs deciduous and leaf litter vs roots) in the studied stands. In this study, SOC stocks were influenced more by parent material than by forest type. Lignin yield, composition and degradation state were influenced both by litter input chemistry and edaphic context. There appear to be important interaction effects between the two, as the relative importance of parent material and litter quality was site specific. We therefore advice that carbon stock models include data on both vegetation history as well as edaphic context.
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