12721. 题目: Seasonal freshening of NW Mediterranean surface water impacts microbial heterotrophic activity and dissolved organic matter
期刊: Estuarine, Coastal and Shelf Science
作者: Maria-Lorena Gonzalez, Stéphane Blain, Ingrid Obernosterer
摘要: The Rhone river represents the most important source of freshwater, nutrients and organic matter to the northwestern (NW) Mediterranean Sea and riverine input markedly affects biogeochemistry and ecosystem functioning in the estuarine and coastal zone. Structures of low salinity waters (LSW) originating near the river plume can also be transported along the continental shelf and offshore. The objective of the present study was to investigate the influence of LSW distant from their source, focusing on dissolved organic matter (DOM) and related microbial processes during two annual cycles (2007 and 2008) at a time series site characterized by the regular occurrence of LSW in spring (Microbial Observatory Laboratoire Arago). We observed enhanced bacterial heterotrophic production and community respiration and specific DOM features within these LSW, concurrently with low net community production. Our results suggest that LSW represent a mechanism of labile DOM supply, thereby sustaining enhanced heterotrophic microbial metabolism.
12722. 题目: Forest die-off reduces soil C and N content and increases C stability in a Mediterranean woodland
作者: Alexandra Rodríguez, Tommaso Chiti, Ana Rey, Jorge Durán
摘要: Drought-induced forest die-off is occurring worldwide and is projected to increase in coming decades. However, if and to what extent this phenomenon affects the content of carbon (C) and nitrogen (N) in soils as well as its stability is far from clear. In a Mediterranean oak forest, we found that forest die-off negatively affected soil C and N contents, and positively affected C stability. We also found that the effect of forest die-off on soil C and N content was more pronounced at the 0–5 cm than at the 5–10 cm soil layer, while the opposite was found for soil C stability. Our results highlight the importance of considering both, soil organic matter quantity and stability, along the soil profile to fully understand the effects of environmental changes on the global C and N cycle.
12723. 题目: Warming effects on carbon dynamics and microbial communities in soils of diverse texture
期刊: Soil Biology and Biochemistry
作者: Sandra F. Yanni, Bobbi L. Helgason, H. Henry Janzen, Benjamin H. Ellert, Edward G. Gregorich
摘要: Climate change may profoundly influence soil organic carbon (SOC) dynamics through effects on soil temperature and water, but the mechanisms and magnitude of those effects remain uncertain. We measured the response of residue-C and native SOC in six soils with diverse texture subjected to artificial heating after transplanting to a common field site. The soils, three from each of two climatic zones in Canada, were amended with 13C labelled oat (Avena sativa) residue to distinguish turnover of recently-applied C and native SOC. The soils were either kept at ambient temperature or heated to 5 °C above ambient and CO2 emission was monitored over two growing seasons. Temperature was the primary factor regulating soil respiration across all six soils; water content did not have any additional explanatory effect, probably because the study site conditions were generally wet and thus decomposition was not limited by water. Soil aggregation and loss of residue-C (68% after 295 days) were not affected by warming. Compared to residue-C, native-SOC was more sensitive to loss by warming. The effect of physical aggregate protection against loss of SOC under warming was not evident. Bacterial community structure (16S rRNA gene sequencing) showed that there was a strong and persistent legacy effect on microbial communities. These, differences among soils were far greater than those between heating and ambient treatments despite transplanting to a common location. Our results show that decomposition of residue-C and SOC were strongly governed by soil temperature rather than water content, even among transplanted soils with different textures and bacterial communities.
12724. 题目: Does ectomycorrhiza have a universal key role in the formation of soil organic matter in boreal forests?
期刊: Soil Biology and Biochemistry
作者: Mona N. Högberg, Ulf Skyllberg, Peter Högberg, Heike Knicker
摘要: Forest soil organic matter (SOM) is an important dynamic store of C and N, which releases plant available N and the greenhouse gases CO2 and N2O. Early stages of decomposition of recent plant litters are better known than the formation of older and more stable soil pools of N and C, in which case classic theory stated that selective preservation of more resistant plant compounds was important. Recent insights heighten that all plant matter becomes degraded and that older SOM consists of compounds proximally of microbial origin. It has been proposed that in boreal forests, ectomycorrhizal fungi (ECMF), symbionts of trees, are actively involved in the formation of slowly-degrading SOM.We characterized SOM in the mor-layer along a local soil N supply gradient in a boreal forest, a gradient with large variations in chemical and biological characteristics, notably a decline in the biomass of ECMF in response to increasing soil N supply.We found contrasting and regular patterns in carbohydrates, lignin, aromatic carbon, and in N-containing compounds estimated by solid-state 13C and 15N nuclear magnetic resonance (NMR) spectroscopy. These occurred along with parallel changes in the natural abundances of the stable isotopes 13C and 15N in both bulk SOM and extracted fractions of the SOM. The modelled “bomb-14C″ age of the lower layers studied ranged between 15 years at the N-poor end, to 70 years at the N-rich end of the gradient. On average half the increase in δ13C with soil depth (and hence age) of the mor-layer can be attributed to soil processes and the other half to changes in the isotopic composition of the plant C inputs. There was a decrease in carbohydrates (O-alkyl C) with increasing depth. This supports the classical hypothesis of declining availability of easily decomposable substrates to microorganisms with increasing soil depth and age. The observed increase in δ13C with depth, however, speaks against the idea of selective preservation of more resistant plant compounds like lignin. Furthermore, from the N-poor to the N-rich end the difference between 15N in plant litter N and N in the deeper part of the mor-layer, the H-layer, decreased in parallel with a decline in ECMF.The latter provides evidence that the role of ECMF as major sink for N diminishes, and hence their potential role in SOM stabilization, when the soil N supply increases. At the N-rich end, where bacteria dominate over fungi, other agents than ECMF must be involved in the large build-up of the H-layer with the slowest turnover rate found along the gradient.
12725. 题目: Using a mixture of microalgae, biochar, and organic manure to increase the capacity of soil to act as carbon sink
期刊: Journal of Soils and Sediments
作者: Jiajun Hu, Hongcheng Guo, Yiyun Xue, Min-tian Gao, Shiping Zhang, Yiu Fai Tsang, Jixiang Li, Ya-nan Wang, Lei Wang
摘要: Purpose: Microalgae, biochar, or organic manure (OM) can be used as soil amendments to enhance soil organic carbon (OC) content. In the present study, a mixture of all three was used to test whether they could further improve soil OC content and the soil’s ability to retain and fix carbon. Materials and methods: A laboratory incubation study was carried out to evaluate the efficacy of using microalgae, biochar, OM, or their mixture, as a soil amendment to improve OC in soil extract. Metabolic processes and soil microbial community structuring were analyzed to explore the mechanism by which the mixture increased the capacity of soil to act as a carbon sink. Results and discussion: OC increased markedly (2.9 times its initial level) following the amendment of the soil with a treatment comprising microalgae, biochar, and the highest dose of OM. Microalgal metabolites were utilized by soil microorganisms as a carbon source. Biochar reduced the concentration of extracellular polysaccharides, whereas OM increased extracellular protein concentration. These metabolites affected the relative proportions of different groups of soil microorganisms, thereby increasing the proportion of Rhodobacter and Runella, which exerted a positive synergistic effect on soil OC and increased the soil’s capacity to fix carbon. Conclusions: A mixture including microalga, biochar, and OM as a soil amendment improved the OC of soil extract, and its effect was greater than that of any of its components alone. The findings of this study can help in devising ways to increase the OC content and the CO2-fixing capacity of the soil.
12726. 题目: Coupled modelling and sampling approaches to assess the impacts of human water management on land-sea carbon transfer
期刊: Science of The Total Environment
作者: Shaoqiang Ni, Xiao Huang, Weixiu Gan, Conrad Zorn, Yuchen Xiao, Guorui Huang, Chaoqing Yu, Jifu Cao, Jie Zhang, Zhao Feng, Le Yu, Guanghui Lin, Hanna Silvennoinen
摘要: Land-sea riverine carbon transfer (LSRCT) is one of the key processes in the global carbon cycle. Although natural factors (e.g. climate, soil) influence LSRCT, human water management strategies have also been identified as a critical component. However, few systematic approaches quantifying the contribution of coupled natural and anthropogenic factors on LSRCT have been published. This study presents an integrated framework coupling hydrological modeling, field sampling and stable isotope analysis for the quantitative assessment of the impact of human water management practices (e.g. irrigation, dam construction) on LSRCT under different hydrological conditions. By applying this approach to the case study of the Nandu River, China, we find that carbon (C) concentrations originating from different land-uses (e.g. forest, cropland) are relatively stable and outlet C variations are mainly dominated by controlled runoff volumes rather than by input C concentrations. These results indicate that human water management practices are responsible for a reduction of ∼60% of riverine C at seasonal timescales, with an even greater reduction during drought conditions. Annual C discharges have been significantly reduced (e.g. 77±5% in 2015 and 39±11% in 2016) due to changes in human water extraction coupled with climate variation. In addition, isotope analysis also shows that C fluxes influenced by human activities (e.g. agriculture, aquaculture) could contribute the dominant particulate organic carbon under typical climatic conditions, as well as drought conditions. This research demonstrates the substantial effect that human water management practices have on the seasonal and annual fluxes of LSRCT, especially in such small basins. This work also shows the applicability of this integrated approach, using multiple tools to quantify the contribution of coupled anthropogenic and natural factors on LSRCT, and the general framework is believed to be feasible with limited modifications for larger basins in future research.
12727. 题目: Bio-oxidation of Elemental Mercury into Mercury Sulfide and Humic Acid-Bound Mercury by Sulfate Reduction for Hg 0 Removal in Flue Gas
期刊: Environmental Science & Technology
作者: Zhenshan Huang, Zaishan Wei, Xiaoliang Xiao, Meiru Tang, Bailong Li, Song Ming, Xiangling Cheng
摘要: Bioconversion of elemental mercury (Hg0) into immobile, nontoxic, and less bioavailable species is of vital environmental significance. Here, we investigated bioconversion of Hg0 in a sulfate-reducing membrane biofilm reactor (MBfR). The MBfR achieved effective Hg0 removal by sulfate bioreduction. 16 S rDNA sequencing and metagenomic sequencing revealed that diverse groups of mercury-oxidizing/sulfate-reducing bacteria (Desulfobulbus, Desulfuromonas, Desulfomicrobium, etc.) utilized Hg0 as the initial electron donor and sulfate as the terminal electron acceptor to form the overall redox. These microorganisms coupled Hg0 bio-oxidation to sulfate bioreduction. Analysis on mercury speciation in biofilm by sequential extraction processes (SEPs) and inductively coupled mass spectrometry (ICP-MS) and by mercury temperature programmed desorption (Hg-TPD) showed that mercury sulfide (HgS) and humic acid-bound mercury (HA-Hg) were two major products of Hg0 bio-oxidation. With HgS and HA-Hg comprehensively characterized by X-ray diffraction (XRD), excitation-emission matrix spectra (EEM), scanning electron microscopy-energy disperse spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), it was proposed that biologically oxidized mercury (Hg2+) further reacted with biogenic sulfides to form cubically crystallized metacinnabar (β-HgS) extracellular particles. Hg2+ was also complexed with functional groups −SH, −OH, −NH–, and −COO– in humic acids from extracellular polymeric substances (EPS) to form HA-Hg. HA-Hg may further react with biogenic sulfides to form HgS. Bioconversion of Hg0 into HgS was therefore achieved and can be a feasible biotechnique for flue gas demercuration.
12728. 题目: Denitrification Capacity of Hill Country Wet and Dry Area Soils as Influenced by Dissolved Organic Carbon Concentration and Chemistry
作者: Grace Chibuike, Lucy Burkitt, Marta Camps-Arbestain, Ranvir Singh, Mike Bretherton, Peter Bishop, Qinhua Shen
摘要: The quantification of the nitrate attenuation capacity of pastoral hill country wet areas, especially seepage wetlands, would aid in the proper management of hill country farms for improved water quality outcomes. This study investigated the denitrification capacity, dissolved organic carbon (DOC) concentration and chemistry of wet areas and adjacent dry areas soils in a hill country landscape in New Zealand. Soil samples were collected during spring (November 2017) from different soil depths down to 100 cm. The results showed that the mean DOC concentration in the surface 30 cm soil depth was in the order: seepage wetland (498 mg kg−1) > hillside seep (172 mg kg−1) > dry area (109 mg kg−1). The denitrification capacity of the seepage wetland within the 0–30 and 30–60 cm soil depths was 7 and 69 times greater (p ≤ 0.05), respectively, than that of the dry area. The high concentration of readily-decomposable (e.g. lower molecular weight) DOC in the seepage wetland soil could have contributed to its higher denitrification capacity. The contrasting nitrate attenuation capacities of the seepage wetland soil versus that of the dry area soil highlight the important contribution of seepage wetlands to water quality improvement in pastoral hill country landscapes.
12729. 题目: Effects of different organic wastes on soil biochemical properties and yield in an olive grove
期刊: Applied Soil Ecology
作者: Manuel Tejada, Concepción Benítez
摘要: The main objective of this work was to study the effect of three organic wastes (municipal solid waste, MSW, sheep manure, SM, and green forage vermicomposts, GFV) applied during five consecutive years to a calcaric Cambisol soil located near Córdoba (Spain). The effects of these amendments on soil biochemical properties (enzymatic activities and humus-enzymatic complexes) and olive yield were determined. At the end of the experimental period, soil enzymatic activities were highest in soils amended with GFV, followed by SM and MSW, whereas the humus-enzyme complexes were highest in soils amended with MSW, followed by SM and GFV. The application of organic matter to soil increased the levels of macro- and micronutrients in leaf. At the end of the experiment, the leaf N concentration was 49.6%, 43% and 34.1% higher in GFV, SM and MSW treatments, when compared with non-organic amended soil. Similarly, and compared with the non-organic amended soil, leaf P, K, Ca and Mg contents increased in GFV, SM and MSW-amended soils. Compared to the non-organic amended soil and at the end of the experimental period, olive yield increased 26.8% in soils amended with SM and 35.5% in soils amended with GFV. Also, the olive oil content in fruits showed only significant differences with the GFV treatment. These results suggested that the organic matter quality influenced the olive yield, suggesting that this parameter increased in soils amended with organic matter with higher fulvic acid and higher protein content and low molecular weight contents, readily degradable by soil microorganisms and assimilated by the olive tree.
12730. 题目: Effect of organic C on stable Fe isotope fractionation and isotope exchange kinetics between aqueous Fe(II) and ferrihydrite at neutral pH
期刊: Chemical Geology
作者: Piyali Chanda, Zhe Zhou, Drew E. Latta, Michelle M. Scherer, Brian L. Beard, Clark M. Johnson
摘要: Low-temperature geochemical cycling of Fe, C, nutrients, and toxic metals in nature are largely regulated by the stability and reactivity of fine-grained ferrihydrite. The presence of impurities such as C and Si in ferrihydrite structure are found to inhibit the rapid transformation of ferrihydrite to more stable iron oxides upon interaction with aqueous Fe(II). Therefore, understanding the factors controlling the reactivity of ferrihydrite, especially in the presence of C, is critical to evaluate the role of ferrihydrite in geochemical cycles. Equilibrium stable isotope fractionations are fundamental thermodynamic properties and therefore equilibrium fractionation in 56Fe/54Fe ratios reflects the nature of Fe bonding in ferrihydrite and its reactivity. In this study, we investigated stable Fe isotope fractionation between aqueous Fe(II) and ferrihydrite-organic matter coprecipitates to evaluate whether previously documented inhibition of mineralogical transformation by organic C is accompanied by changes in Fe isotope fractionation. Experiments conducted using Suwannee River natural organic matter (SRNOM) that was coprecipitated with ferrihydrite (molar C:Fe = 1.2) produced an equilibrium 56Fe/54Fe fractionation of -2.36 ± 0.26‰ between aqueous Fe(II) and ferrihydrite-SRNOM coprecipitates. This fractionation factor significantly differs from that previously determined between Fe(II)aq and pure ferrihydrite (-3.20‰) but is similar to that measured for Fe(II)aq-Si-ferrihydrite (-2.58 ± 0.14‰, molar Fe:Si = 1). Furthermore, the addition of C in the ferrihydrite structure at molar C:Fe ∼1.2 markedly increased the extent of Fe isotope exchange to a similar degree as observed with Si-ferrihydrite with molar Fe:Si ∼1. These observations suggest similar effects on both bonding and reactivity of ferrihydrite upon addition of equimolar C and Si. Due to the coexistence of ferrihydrite with organic matter in nature (e.g., wetlands), these results are important for understanding Fe isotope fractionation and exchange kinetics during mineral-fluid interactions in natural ferrihydrite-bearing systems.
12731. 题目: Aqueous Cr(VI) removal by a novel ball milled Fe0-biochar composite: Role of biochar electron transfer capacity under high pyrolysis temperature
作者: Kun Wang, Yuebing Sun, Jingchun Tang, Juan He, Hongwen Sun
摘要: A novel ball milled Fe0-biochar composite was synthesized by ball milling the mixture of biochar (pyrolyzed at 300 °C, 500 °C, and 700 °C) and micron grade iron powder. FTIR, SEM, TEM-EDS, XRD, and XPS were applied to characterize this composite. XRD results showed that iron carbide phase was formed during the ball milling process. The ability of this synthesized composited to remove aqueous Cr(VI) was tested. Removal rates of Cr(VI) (49.6%, 65.8%, and 97.8%, respectively) by ball milled Fe0-biochar composite consisting of biochar pyrolyzed at 300 °C (300BMFe0-BC), 500 °C (500BMFe0-BC), and 700 °C (700BMFe0-BC) were much higher than those (19%, 11%, and 4%, respectively) by pristine biochar pyrolyzed at 300 °C (300BC), 500 °C (500BC), and 700 °C (700BC). Cr(VI) removal rate by 700BMFe0-BC increased from 15.4% to 97.8% when prolonging ball milling time from 6 h to 48 h. Ball milling promoted the combination of Fe0 and biochar as well as reduced the hydrodynamic diameter of the composite. Acidic conditions favored Cr(VI) removal. Ball milling exposed the functional groups of biochar and improved its Cr(VI) removal rate. Raman spectra showed that the degree of graphitization in 700 °C ball milled biochar (700BMBC) was the highest. Electrochemical analysis demonstrated that 700BMBC had the highest electron transfer capacity. In the presence of Fe0, graphitized structure in 700BMBC acted as an electron conductor, facilitating electron transfer from Fe0 to Cr(VI). Ball milling also destroyed the surface iron oxide layer to regenerate the composite.
12732. 题目: Spent Ganoderma lucidum substrate derived biochar as a new bio-adsorbent for Pb2+/Cd2+ removal in water
作者: Jianning Chang, Haibo Zhang, Hongyan Cheng, Yangyang Yan, Mingchang Chang, Yanzhuan Cao, Fei Huang, Guosheng Zhang, Meng Yan
摘要: The present study firstly reports spent Ganoderma lucidum substrate derived biochars (SLBCS) for the effective removal of Pb2+/Cd2+ from water. The effects of pyrolysis temperature on the SLBCS characteristics and Pb2+/Cd2+ adsorption mechanism was studied systematically. The surface physicochemical properties of SLBCS were significantly affected by the pyrolysis temperature. The increase in pyrolysis temperature from 250 to 650 °C resulted in a drastic increase in the biochar surface area and the well development of mesoporous structure, which could provide more effective adsorption sites for Pb2+ and Cd2+ onto SLBCS. According to the Langmuir model, the obtained maximum adsorption capacity of Pb2+ onto SL650 reached 262.76 mg g−1, while that of Cd2+ reached 75.82 mg g−1. The adsorption capacities of SL650 for Pb2+ and Cd2+ were even higher than that of other modified biochars. The high adsorption capacity of SL650 for Pb2+, attributed to the precipitation supported by high temperature, benefitted the formation of carbonate minerals. Two possible mechanisms involved in Cd2+ sorption: carbonate precipitation and coordination with π electrons. Desorption of SL650 showed high efficiency for Pb2+, but slightly low efficiency for Cd2+. These results indicate that SL650 can be applied for removing heavy metals, especially Pb2+, from polluted water.
12733. 题目: Laboratory investigation of phosphorus loss with snowmelt and rainfall runoff from a Steppe wetland catchment
作者: Jing He, Zhaoyan Diao, Zhirong Zheng, Derong Su, Shihai Lyu
摘要: Phosphorus (P) losses from terrestrial soils contribute to eutrophication of surface waters. As priority non-point source pollution ways, rainfall runoff (RS1) and snowmelt runoff (RS2) are the main carrier of P loss from terrestrial ecosystem. The aim of this study was to investigate the similarities and differences between P loss with RS1 and RS2 of the same soil type. Six types of soil were used in this experiment. Results have shown that 1), Different types of soil have different P loss with RS1 and RS2 under different slope, and the changes ranged from 0.003 to 0.370 mg L−1. 2), The effects of soil type, slope and runoff type on P loss with surface runoff was not independent, both individual effects of all factors and their interaction with the other two factors effected the P loss with runoff. 3), In our experiment, some soils showed no significant difference between P content in RS1 and RS2. In some soils, P loss with RS1 was higher than that with RS2 while the opposite conclusion was showed in Bog soil (BS) which with higher soil water content. 4), The P loss with RS1 and RS2 of different soils were both mainly affected by soil water content (SW), Olsen-P content (OP) and soil organic matter content (OM). These results can help us understand the P loss with different patterns of surface runoff better and are expected to provide pertinent opinions on the analysis of P loss with runoff and its influencing factors of grassland soils.
12734. 题目: Effect of pH on effluent organic matter removal in hybrid process of magnetic ion-exchange resin adsorption and ozonation
作者: Zhiqiang Chen, Yingcai Tang, Qinxue Wen, Boxuan Yang, Yang Pan
摘要: It is essential to mitigate the risk of exposure to effluent organic matter (EfOM) in aquatic environments to ensure safe wastewater recycling. Magnetic ion-exchange (MIEX) resin adsorption combined with ozonation could provide EfOM removal. However, the poor understanding of the influences of the parameters and mechanisms in the hybrid process has restricted the applications. In this study, the response surface methodology was used to reveal the interactions of the major operation parameters. The degradation behaviour of the EfOM was investigated by using spectroscopy combined with mathematical methods. The effect of the pH on the EfOM removal was also analysed. The maximum efficiency of the removal of dissolved organic carbon (DOC) was 59.77% at the optimal MIEX resin dosage of 7.97 mL/L, ozone concentration of 8 mg/L, agitation speed of 199.84 r/min, and pH of 9.98. The ozonation was superior to resin adsorption in the removal of 1054-Da compounds, while the resin adsorption was advantageous in the removal of 4168-Da compounds. Three fluorescent components (C1, C2, and C3) were more easily subjected to external perturbation than the DOC and ultraviolet absorbance at 254 nm in the oxidation processes. The MIEX resin exhibited low efficiencies of removal of the fluorescent substances. A synchronous fluorescence analysis coupled with a two-dimensional correlation analysis revealed that the variation in EfOM followed the order of fulvic-to humic-like substances in the hybrid process of MIEX and the following ozonation. The pH was the most significant influencing factor in the hybrid process.
12735. 题目: Biochar-assisted transformation of engineered-cerium oxide nanoparticles: Effect on wheat growth, photosynthetic traits and cerium accumulation
期刊: Ecotoxicology and Environmental Safety
作者: Qumber Abbas, Guijian Liu, Balal Yousaf, Muhammad Ubaid Ali, Habib Ullah, Mehr Ahmed Mujtaba Munir, Rafay Ahmed, Abdul Rehman
摘要: The extensive use of nano-fabricated products in daily life is releasing a large volume of engineered nanoparticles (ENPs) in the environment having unknown consequences. Meanwhile, little efforts have been paid to immobilize and prevent the entry of these emerging contaminants in the food chain through plant uptake. Herein, we investigated the biochar role in cerium oxide nanoparticles (CeO2NPs) bioaccumulation and subsequent translocation in wheat (Triticum aestivum L.) as well as impact on growth, photosynthesis and gas-exchange related physiological parameters. Results indicated that CeO2NPs up to 500 mg L−1 level promoted the plant growth by triggering photosynthesis, transpiration and stomatal conductance. Higher NPs concentration (2000 mg CeO2NPs L−1) has negatively affected the plant growth and photosynthesis related processes. Conversely, biochar amendment with CeO2NPs considerably reduced (~9 folds) the plants accumulated contents of Ce even at 2000 mg L−1 exposure level of CeO2NPs through surface complexation process and alleviated the phyto-toxic effects of NPs on plant growth. XPS and FTIR analysis confirmed the role of biochar-mediated carboxylate and hydroxyl groups bonding with CeO2NPs. These findings provides an inside mechanistic understanding about biochar interaction with nano-pollutants to inhibit their bioavailability to plant body.
12736. 题目: Ferrate(VI) pre-treatment and subsequent chlorination of blue-green algae: Quantification of disinfection byproducts
期刊: Environment International
作者: Feilong Dong, Jiaqi Liu, Cong Li, Qiufeng Lin, Tuqiao Zhang, Kejia Zhang, Virender K. Sharma
摘要: Algal organic matter (AOM) from seasonal algal blooms may be an important precursor of disinfection byproducts (DBPs) in drinking water. This paper presents the effect of ferrate(VI) treatment on two blue-green algae, Chlorella sp. and Pseudanabaena limnetica, in eutrophic water. The results demonstrated that Fe(VI) removed the algal cells by causing cell death, apoptosis, and lost integrity, and decreased AOM (in terms of total organic carbon) in water via oxidation and coagulation. Chlorination of the Fe(VI) pre-oxidized algal water samples generated halogenated DBPs (including trihalomethanes, haloacetic acids, haloketones, chloral hydrate, haloacetonitriles, and trichloronitromethane), but the concentrations of DBPs were lower than those formed in the chlorinated samples without pre-treatment by Fe(VI). Higher Fe(VI) dose, longer oxidation time, and alkaline pH were beneficial in controlling DBPs. In bromide-containing algal solutions, negligible amount of bromo-DBPs were generated in the Fe(VI) pre-oxidation, and halogenated DBPs were mainly formed in the subsequent chlorination.
12737. 题目: Environmental fate and behavior of silver nanoparticles in natural estuarine systems
期刊: Journal of Environmental Sciences
作者: Penghui Li, Min Su, Xiaodan Wang, Xiaoyan Zou, Xia Sun, Junpeng Shi, Hongwu Zhang
摘要: Silver nanoparticles (AgNPs) are widely used in many consumer products, whereas their environmental behaviors in natural aquatic systems remain unknown, especially in natural brackish media. Therefore, it is urgent to investigate the environmental fate of AgNPs in natural brackish waters. Here, we investigated the stability of citrate-coated AgNPs in natural brackish water collected from 6 different sites with distinct salinities in the Xinglinwan Reservoir, located in Xiamen City, southeast China. The obtained results showed that AgNP colloids remained stable in low-salinity waters, which was mainly determined by the effects of dissolved organic matter (DOM) promoting the stability of the nanoparticles. However, the environmental fate of AgNPs in high-salinity waters was dominated by the salinity or ionic strength, especially the free ion concentrations of Cl−, SO42−, or S2−, resulting in rapid sedimentation and dissolution. In addition, both DOM and salinity contributed to the environmental behavior of AgNPs in moderate-salinity waters, ultimately resulting in either colloidal stability or sedimentation. Overall, these results may reveal that AgNPs remain relatively stable for a long period in low-salinity natural waters, and that the stability might gradually decrease as AgNPs are transferred from freshwaters through brackish waters and eventually end up in seawater along the bay. Our findings also further indicate that the toxicity and potential risks of AgNPs may present more serious threats to the environment and organisms in natural freshwaters than in natural estuarine systems or seawater.
12738. 题目: Biodegradability of hydrothermally altered deep-sea dissolved organic matter
期刊: Marine Chemistry
作者: Christian T. Hansen, Jutta Niggemann, Helge-Ansgar Giebel, Meinhard Simon, Wolfgang Bach, Thorsten Dittmar
摘要: Deep-sea dissolved organic matter (DOM) constitutes a huge carbon reservoir in the worlds' oceans that – despite its abundance – is virtually unused as a substrate by marine heterotrophs. Heating within hydrothermal systems induces major molecular modifications of deep-sea DOM. Here, we tested the hypothesis that hydrothermal heating of deep-sea DOM enhances bioavailability. Aliquots of DOM extracted from the deep North Pacific (North Equatorial Pacific Intermediate Water; NEqPIW) were re-dissolved in artificial seawater and subjected to temperatures of 100 and 200 °C (40 MPa) using Dickson-type reactors. In agreement with earlier findings we observed a temperature-related drop in dissolved organic carbon (DOC) concentration (−6.1% at 100 °C, −21.0% at 200 °C) that predominantly affected the solid-phase extractable (SPE-DOC) fraction (−18.2% at 100 °C, −51.4% at 200 °C). Fourier-transform ion cyclotron resonance mass spectrometric (FT-ICR-MS) analysis confirmed a temperature-related reduction of average molecular mass, O/C ratios, double bond equivalents (DBE) and a relative increase in aromaticity (AImod). This thermally altered DOM was added (25 μmol L−1 DOC) to deep-water samples from the South West Pacific (Kermadec Arc, RV Sonne / SO253, 32° 37.706′ S | 179° 38.728′ W) and incubated with the prevailing natural microbial community. After 16 days at 4 °C in the dark, prokaryotic cell counts in incubations containing the full spectrum of thermally-degraded DOM (extractable and non-extractable compounds) had increased considerably (on average 21× for DOM100°C and 27× for DOM200°C). In contrast, prokaryotic growth in incubations to which only solid-phase extractable thermally-altered DOM was added was not enhanced compared to control incubations. The experiments demonstrate that temperature-driven degradation of deep-sea recalcitrant DOM within hydrothermal systems turns fractions of it accessible to microbes. The thermally-produced DOM compounds that stimulate microbial growth are not retained on reversed-phase resins (SPE-DOM) and are likely low-molecular mass organic acids. Despite the comprehensive compositional modifications of SPE-DOM (SPE-DOM) through heating, it remains inaccessible to microbes at the investigated concentration levels. The microbial incubation resulted in only minor and mostly insignificant overall changes in SPE-DOM molecular composition and concentration.
12739. 题目: Seasonal variation of zooplankton community structure and trophic position in the Celtic Sea: A stable isotope and biovolume spectrum approach
期刊: Progress in Oceanography
作者: Sarah L.C. Giering, Seona R. Wells, Kyle M.J. Mayers, Hanna Schuster, Louise Cornwell, Elaine S. Fileman, Angus Atkinson, Kathryn B. Cook, Calum Preece, Daniel J. Mayor
摘要: Zooplankton on continental shelves represent an important intermediary in the transfer of energy and matter from phytoplankton to the wider ecosystem. Their taxonomic composition and trophic interactions with phytoplankton vary in space and time, and interpreting the implications of this constantly evolving landscape remains a major challenge. Here we combine plankton taxonomic data with the analysis of biovolume spectra and stable isotopes to provide insights into the trophic interactions that occur in a shelf sea ecosystem (Celtic Sea) across the spring-summer-autumn transition. Biovolume spectra captured the seasonal development of the zooplankton community well, both in terms of total biomass and trophic positioning, and matched trophic positions estimated by stable isotope analysis. In early April, large microplankton (63–200 µm) occupied higher trophic positions than mesozooplankton (>200 µm), likely reflecting the predominance of nanoplankton (2–20 µm) that were not readily available to mesozooplankton grazers. Biomass and number of trophic levels increased during the spring bloom as elevated primary production allowed for a higher abundance of predatory species. During July, the plankton assemblage occupied relatively high trophic positions, indicating important links to the microbial loop and the recycling of organic matter. The strong correlation between biomass and community trophic level across the study suggests that the Celtic Sea is a relatively enclosed and predominantly energy-limited ecosystem. The progression of the zooplankton biomass and community structure within the central shelf region was different to that at the shelf-break, potentially reflecting increased predatory control of copepods by macrozooplankton and pelagic fishes at the shelf break. We suggest that the combination of size spectra and stable isotope techniques are highly complementary and useful for interpreting the seasonal progression of trophic interactions in the plankton.
12740. 题目: Holocene sedimentation in the central part of Lake Ladoga
期刊: Quaternary International
作者: Tatyana Sapelko, Shamil Pozdnyakov, Denis Kuznetsov, Anna Ludikova, Ekaterina Ivanova, Maria Guseva, Elya Zazovskaya
摘要: New multi-proxy paleolimnological study of the sediment sequence from the central part of Lake Ladoga enabled not only reconstructing the dynamics of the Holocene paleoenvironments, but also tracing changes in the lake ecosystem productive, sedimentation conditions and sedimentation rate. The analyses included lithology, loss-on-ignition, metals, grain-size distributions, including fractions of <1 μ, pollen and diatoms. A series of radiocarbon (AMS) data was also obtained. The earlier period (prior to 9000 cal. BP) is characterized with the lowest organic matter content and highest proportion of the fine sedimentary fraction (including that of <1 μ). The transition from periglacial to forest vegetation, climate warming, and the lake level drop are inferred. In the next period (9000-4700 cal. BP) warmest climate resulted in vegetation changes, increased productivity of the Lake Ladoga ecosystem as inferred from increasing siliceous microalgae concentration and organic matter content. In the late period (4700-1000 cal. BP) climate deterioration resulted in vegetation changes. However the lake ecosystem remained highly productive as inferred from high diatom concentrations.