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24481. 题目: Ferrihydrite Growth and Transformation in the Presence of Ferrous Iron and Model Organic Ligands
文章编号: N19111410
期刊: Environmental Science & Technology
作者: Laurel K. ThomasArrigo, Ralf Kaegi, Ruben Kretzschmar
更新时间: 2019-11-14
摘要: Ferrihydrite (Fh) is a poorly crystalline Fe(III)-oxyhydroxide found in abundance in soils and sediments. With a high specific surface area and sorption capacity at circumneutral pH, ferrihydrite is an important player in the biogeochemical cycling of nutrients and trace elements in redox-dynamic environments. Under reducing conditions, exposure to Fe(II) induces mineral transformations in ferrihydrite; the extent and trajectory of which may be greatly influenced by organic matter (OM). However, natural OM is heterogeneous and comprises a range of molecular weights (MWs) and varied functional group compositions. To date, the impact that the chemical composition of the associated OM has on Fe(II)-catalyzed mineral transformations is not clear. To address this knowledge gap, we coprecipitated ferrihydrite with model organic ligands selected to cover a range of MWs (25 000–50 000 vs <200 Da) as well as carboxyl content (polygalacturonic acid (PGA) > citric acid (CA) > galacturonic acid (GA)). Coprecipitates (C:Fe ≈ 0.6) were reacted with 1 mM 57Fe(II) for 1 week at pH 7, with time-resolved solid-phase analysis (via X-ray diffraction, X-ray absorption spectroscopy, and electron microscopy) revealing that all ligands inhibited Fe(II)-catalyzed ferrihydrite mineral transformations and the formation of crystalline secondary mineral phases compared to a pure ferrihydrite. For carboxyl-rich coprecipitates (Fh-PGA and Fh-CA), mineral transformations were less inhibited than in the carboxyl poor Fh-GA, and a crystalline lepidocrocite shell was formed surrounding the residual ferrihydrite core. However, Fe isotope analysis revealed that all coprecipitates underwent near complete atom exchange. Collectively, our results highlight that ferrihydrite is indeed an active mineral phase in redox-dynamic environments, but that its stability under reducing conditions, and thus capacity for nutrient and trace element retention, depends on the chemical characteristic of the associated OM, specifically OM-induced changes in the particle surface charge and the distribution of organic functional groups.
24482. 题目: The interactions between biochar and earthworms, and their influence on soil properties and clover growth: A 6-month mesocosm experiment
文章编号: N19111409
期刊: Applied Soil Ecology
作者: Stanislav Garbuz, Marta Camps-Arbestain, Alec Mackay, Brian DeVantier, Maria Minor
更新时间: 2019-11-14
摘要: A six-month mesocosm experiment was conducted to investigate the joined effect of biochar and earthworms on soil properties and plant (white clover) growth in two contrasting soils – a dystric Cambisol and a sil-andic Andosol, both soils with pH-H2O < 6. Treatments were (i) biochar amendment (1% weight basis), (ii) a positive control (lime added at the liming equivalence of the biochar application), and (iii) a negative control (no amendment). Each treatment had two variants: with or without earthworms (Aporrectodea caliginosa). Soil chemical and biological properties were measured before the start of the experiment and after 6 months of incubation. Earthworms were associated with higher ammonium-N and nitrate-N concentrations, lower pH, higher fungi:bacteria ratio, higher abundance of Collembola, and higher clover biomass in mesocosms. The influence of biochar on plant productivity was overshadowed by earthworm activity, yet a significant positive effect of biochar on clover biomass was observed in the absence of earthworms; this effect was not related to the liming potential of biochar. Synergistic effects of biochar and earthworms were observed for increasing abundance of Collembola and soil fungal biomass. The interaction between biochar and earthworms was soil-type specific – for example, on their own, biochar and earthworms increased clover growth more in the Cambisol, while the positive synergistic effect of biochar and earthworms on soil biochemical processes and clover growth was more evident in the Andosol. Combined use of biochar and earthworms has good productivity potential for acidic soils, and can be part of sustainable soil management.
24483. 题目: Promoting the granulation process of aerobic granular sludge in an integrated moving bed biofilm-membrane bioreactor under a continuous-flowing mode
文章编号: N19111408
期刊: Science of The Total Environment
作者: Chencheng Dai, Liying Bin, Bing Tang, Ping Li, Shaosong Huang, Fenglian Fu, Qian Yin
更新时间: 2019-11-14
摘要: This investigation demonstrated that aerobic granular sludge (AGS) could be cultivated rapidly in a single continuous-flowing membrane bioreactor (MBR) by introducing freely moved bio-carriers with a filling ratio of 10%. By operating the bioreactor for 28 days, AGS was successfully cultivated and kept stable for >2 months with a compact structure and clear shape, in which, extracellular polymeric substances played a key role in maintaining the stability of granular sludge structure. The microbial composition between AGS and attached biofilm was quite different, which indicated that the introduced bio-carriers improved the biodiversity within the bioreactor. Additionally, an explicit internal circulation was formed by the introduced bio-carriers, which was the main reason leading to the rapid formation of AGS. This is an interesting discovery and a novel approach to promote the rapid granulation of biomass in an MBR. Moreover, combining the biodegradation of AGS and filtration of membrane module, the bio-reactor achieved an excellent performance in removing CODCr (>90%) and TN (>85%) during the whole process.
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24484. 题目: Coagulation mechanisms of humic acid in metal ions solution under different pH conditions: A molecular dynamics simulation
文章编号: N19111407
期刊: Science of The Total Environment
作者: Yuejie Ai, Chaofeng Zhao, Lu Sun, Xiangke Wang, Lijun Liang
更新时间: 2019-11-14
摘要: Humic acid (HA) exerts a variety of significant environmental and geochemical influences on the soils, sediments and aqueous environments. The interaction with metal ions induces strong HA-metal complexation, thus effecting the transport of the toxic metals as well as the colloidal aggregation of HA. In the present work, we systematically report and analyze the aggregation mechanisms of HAs in solutions filled with different heavy cations (Ag+, Cd2+ and Cr3+) or common metal ions (Na+, Ca2+ and Al3+) under neutral and low pH conditions by using molecular dynamic simulations. We aim to explore the effects of pH, metal ions type and other possible weak interactions on the aggregation capabilities of HA. Scrutiny of the simulation results showed that the aggregation of HAs under neutral condition was driven by the HA-metal complexation which combined the effects of electrostatic attraction and inter-molecular bridging between cations and COO– groups. Larger extent of aggregation was found in heavy metal ions compared with the common ones. On the other hand, under low pH condition, due to the protonation states of carboxyl and phenolic group, the aggregation of HAs was stabilized mainly by weak forces, such as hydrogen bonds between different functional groups. In addition, other weak interactions such as the hydrophilic and hydrophobic effects, the cation-π interactions have also been proposed to be progressive effects on the coagulation behavior. Our computational studies give supplement to the experimental observation and provide insights into the intrinsic mechanisms of the aggregation behavior of HAs and their complexation with metal ions. Such computational modelling supplied a highly effective tool for qualitatively evaluating their roles in environmental remediation.
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24485. 题目: Effect of potassium on nitrate removal from groundwater in agricultural waste-based heterotrophic denitrification system
文章编号: N19111406
期刊: Science of The Total Environment
作者: Haishuang Wang, Chuanping Feng, Yang Deng
更新时间: 2019-11-14
摘要: Heterotrophic denitrification based on solid carbon sources has been widely investigated for nitrogen removal in recent years. In this study, the response of the heterotrophic denitrification process under different K+ concentrations was clarified. Additionally, the denitrification enhancement mechanism was revealed and resource utilization of agricultural waste was achieved. A series of batch tests were conducted to study the effect of different K+ concentrations on the denitrification performance, dissolved organic matter (DOM) dissolution and microbial community structure. Results demonstrate that the threshold of K+ concentration for the NO3−-N and NO2−-N reduction rates were 229.78 ± 25.80 and 159.10 ± 24.60 mg-K/L, respectively. Excitation-emission matrix (EEM) analysis identified the main DOM components associated with tyrosine-like, tryptophan-like and humic-like substances, as well as illustrated the evolutionary behavior and utilization of DOM. High throughput 16S rRNA gene sequencing indicates that a K+ concentration of 229.78 ± 25.80 mg-K/L exhibited the highest diversity of functional species associated with fermentation and denitrification. The genera Pseudomonas and Thiobacillus were the unique denitrifiers at this K+ concentration. The correlation of K+ concentration, DOM dissolution of different regions and microorganism structure were analyzed using correlation matrix and PCA, and the appropriate K+ concentration of different functional microorganisms survival was optimized by this analysis method.
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24486. 题目: Biochar addition to forest plantation soil enhances phosphorus availability and soil bacterial community diversity
文章编号: N19111405
期刊: Forest Ecology and Management
作者: Chuifan Zhou, Kate Heal, Mulualem Tigabu, Lidan Xia, Huaying Hu, Danyang Yin, Xiangqing Ma
更新时间: 2019-11-14
摘要: Depletion of soil nutrients is a major cause of decline in productivity of forest plantations in successive rotations. Biochar amendment in agricultural systems has been shown to yield various beneficial effects, including increasing soil phosphorus (P) availability. However, the direct and indirect effects of biochar addition on forest soil P dynamics have largely been unexplored. The objective of this study was to examine how biochar produced from harvest residue (leaves and woodchips) affect the P dynamics in second rotation Cunninghamia lanceolata (Chinese fir) plantation soil. An incubation experiment which involved mixing of forest soil with 1% or 3% w/w leaf or woodchip biochar, pyrolyzed at 300 °C or 600 °C, was conducted for 80 days at 20 °C. After 7, 40 and 80 days of incubation, soil samples were analyzed for total and available P, inorganic and organic P pools, and soil phosphatase activity. At the end of the incubation period, bacterial community composition and diversity were analyzed by 16S rDNA sequencing. The leaf biochar produced at both pyrolysis temperatures was more alkaline and had significantly higher soluble P, nitrogen and calcium contents than the woodchip biochar. Soil total and available P increased significantly in all leaf biochar treatments after 80 days incubation compared to the untreated control soil, but the woodchip biochar treatments had no significant effects. At the end of the experiment, Al-P content was significantly lower and Ca10-P content higher in soil amended with both biochar types compared to the control soil, and Fe-P content was significantly higher in the leaf biochar treatments. Contrary to expectations, acid and alkaline phosphatase enzyme activities were significantly lower in some of the biochar treatments after 80 days incubation compared to the control soil. Nevertheless, the diversity of the bacterial community was higher in leaf biochar-amended forest soil than the woodchip biochar-amended and untreated soil at the end of the experiment. In particular, the abundance increased in the leaf biochar soil treatments of P-solubilizing bacteria, such as Burkholderia-Paraburkholderia, Planctomyces, Sphingomonas and Singulisphaera, which can indirectly improve P availability in soil. Thus, conversion of tree harvest residues, particularly leaves, into biochar and recycling back into the soil could be a viable option to boost P availability and help to conserve nutrients or reduce nutrient losses for the next rotation. Before recommending plantation management with biochar, long-term studies are required assessing the life cycle of biochar under field conditions and its promoting effect on growth of C. lanceolata.
24487. 题目: The changes in functional marker genes associated with nitrogen biological transformation during organic-inorganic co-composting
文章编号: N19111404
期刊: Bioresource Technology
作者: Huiyong Yu, Beitao Xie, Rayyan Khan, Huifeng Yan, Guoming Shen
更新时间: 2019-11-14
摘要: In this article, the changes in the functional marker genes associated with nitrogen biological transformation during the organic-inorganic co-composting process with adding biochar or not were studied. Results showed that the addition of biochar increased the abundance of ureC, AOA amoA and AOB amoA gene while decreased the abundance of nirK gene. The addition of 10% biochar by weight ratio was better for the optimization of nitrogen biological transformation process. The correlation analysis showed that the ureC gene was highly correlated with NH4+-N concentration while the AOA amoA and AOB amoA genes were moderately correlated with NH4+-N concentration. Similarly, the nirK gene was moderately correlated with NO3−-N concentration. This work would contribute to understanding the mechanisms underlying in the nitrogen bio-transformation further at the molecular level during organic-inorganic co-composting.
24488. 题目: Biochar facilitated bioprocessing and biorefinery for productions of biofuel and chemicals: A review
文章编号: N19111403
期刊: Bioresource Technology
作者: Xiao Sun, Hasan K. Atiyeh, Mengxing Li, Yan Chen
更新时间: 2019-11-14
摘要: Biochar is traditionally used to improve soil properties in arable land and as adsorbent or precursor of activated carbon in wastewater treatment. Recent advances have shown biochar potentials in enhancing productions of biofuels and chemicals such as bio-ethanol, butanol, methane, hydrogen, bio-diesel, hydrocarbons and carboxylic acids. The properties of biochar such as high levels of porosity, functional groups, cation exchange capacity, pH buffering capacity, electron conductivity, and macro-/micro- nutrients (Na, K, Ca, Mg, P, S, Fe, etc.) provide appropriate conditions to relieve physicochemical stresses on microorganisms through pH buffering, detoxification, nutrients supply, serving as electron carrier and supportive microbial habitats. This paper critically reviewed biochar production and characteristics, biochar utilization in anaerobic digestion, composting, microbial fermentation, hydrolysate detoxification, catalysis in biomass refinery and biodiesel synthesis. This review provides novel vision of biochar application, which could guide future research towards cleaner and more economic production of renewable fuels and bio-based chemicals.
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24489. 题目: Characterizing property and treatability of dissolved effluent organic matter using size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors
文章编号: N19111402
期刊: Chemosphere
作者: Min-Hui Cai, Ya-Ping Wu, Wen-Xiang Ji, Yu-Ze Han, Yan Li, Ji-Chun Wu, Chen-Dong Shuang, Gregory V. Korshin, Ai-Min Li, Wen-Tao Li
更新时间: 2019-11-14
摘要: In this study, size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors was used for characterizing property and treatability of effluent organic matter (EfOM) from 12 wastewater treatment plants. According to their apparent molecular weight (AMW), EfOM fractions were assigned to biopolymers (>20 kDa), humic substances that comprise sub-fractions of humic-like acids (HA-I & HA-II, 2.3–7.0 kDa) and fulvic-like acids (FA, 1.5–2.3 kDa), building blocks (0.55–1.5 kDa) and low molecular weight neutral substances (<550 Da). The fractions of biopolymers and low molecular weight neutral substances didn't show humic-like fluorescence, while the fractions of HA-II, FA and building blocks usually had signatures of both humic-like and protein-like fluorescence. Humic substances generally contributed the largest proportion of dissolved organic carbon and nitrogen (DOC & DON) in effluents. Coagulation removed EfOM fractions following the order of biopolymers > HA subfraction > FA subfraction > building blocks, while little removal of protein-like fluorescence in HA-II and FA subfractions was detected. Anion exchange treatment could effectively reduce DOC and DON concentrations; the sequence of the treatment efficiency was humic substances > biopolymers > building blocks. Increasing O3 doses caused DOC and DON of EfOM to be gradually transformed from large AMW fractions into small AMW fractions, while chromophores and fluorophores in HA subfractions were relatively more refractory than those in the other fractions. Size exclusion chromatography with multiple detectors are suggested to be an informative technique for estimating treatability of EfOM by advanced wastewater treatment processes.
24490. 题目: Fate and transport processes of nitrogen in biosorption activated media for stormwater treatment at varying field conditions of a roadside linear ditch
文章编号: N19111401
期刊: Environmental Research
作者: Dan Wen, Diana Ordonez, Amy McKenna, Ni-Bin Chang
更新时间: 2019-11-14
摘要: Roadside drainage networks can result in changes to watershed hydrology and water quality. By acting as hydrological links between urban development, agricultural fields, and natural streams, roadside ditches may be modified by filling in some green sorption media to control nitrogen pollution. Biosorption activated media (BAM), one of the green sorption media, are composed of sand, tire crumb, and clay, which can remove nitrogen from stormwater and groundwater through integrated hydrological, chemophysical, and microbial processes. The fate and transport processes of interest are complicated by internal microbial processes including ammonification, nitrification, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA), each of which is controlled by different microbial species in addition to some varying field conditions. In this study, BAM was tested in a suite of columns to address site-specific physical, chemical and biological concerns driven by in situ traffic compaction, carbon availability, and animal impact (such as gopher turtles, moles, and ants) all of which impose different impacts on nitrogen fate and transport processes that may be signified by changing dissolved organic nitrogen species (DONs). The traffic compaction condition resulted in the most suitable hydraulic retention time in the hydrological process, which is beneficial for the assimilation of DONs in a long-term carbon rich environment due to biofilm expansion. Denitrifiers were the most predominant microbial population and the microbial species of DNRA were the second most predominant one in all three field conditions. However, the relationship of denitrifiers and DNRA in BAM can be shifted from commensalism to competition or even inhibition after carbon addition in microbial ecology.
24491. 题目: Systematic variation in marine dissolved organic matter stoichiometry and remineralization ratios as a function of lability
文章编号: N19111315
期刊: Global Biogeochemical Cycles
作者: Emily J. Zakem, Naomi M. Levine
更新时间: 2019-11-13
摘要: Remineralization of organic matter by heterotrophic organisms regulates the biological sequestration of carbon, thereby mediating atmospheric CO2. While surface nutrient supply impacts the elemental ratios of primary production, stoichiometric control by remineralization remains unclear. Here we develop a mechanistic description of remineralization and its stoichiometry in a marine microbial ecosystem model. The model simulates the observed elemental plasticity of phytoplankton and the relatively constant, lower C:N of heterotrophic biomass. In addition, the model captures the observed decreases in DOC:DON and the C:N remineralization ratio with depth for more labile substrates, which are driven by a switch in the dominant source of labile DOM from phytoplankton to heterotrophic biomass. Only a model version with targeted remineralization of N‐rich components is able to simulate the observed profiles of preferential remineralization of DON relative to DOC and the elevated C:N of bulk DOM. The model suggests that more labile substrates are associated with C‐limited heterotrophic growth and not with preferential remineralization, while more recalcitrant substrates are associated with growth limited by processing rates and with preferential remineralization. The resulting patterns of variable remineralization stoichiometry mediate the extent to which a proportional increase in carbon production resulting from changes in phytoplankton stoichiometry can increase the efficiency of the biological pump. Results emphasize the importance of understanding the physiology of both phytoplankton and heterotrophs for anticipating changes in biologically driven ocean carbon storage.
24492. 题目: Effect of sheep manure-derived biochar on colloidal phosphorus release in soils from various land uses
文章编号: N19111314
期刊: Environmental Science and Pollution Research
作者: Seyed Hamid Hosseini, Xinqiang Liang, Christophe Niyungeko, He Miaomiao, Fayong Li, Sangar Khan, Kamel Mohamed Eltohamy
更新时间: 2019-11-13
摘要: Colloidal phosphorus (CP) as an additional route of P mobilization in soil solution has gained much attention. A batch experiment was conducted to investigate the effect of sheep manure-derived biochar (SMB) on CP release from various land uses (paddy, vegetable, tea, and citrus) at a rate of 0% as a control treatment (CK), 1% as a low (L) level, 2% as a middle (M) level, and 4% as a high (H) level of SMB application. The CP and MRPcoll in the solution increased from 30.58 to 88.97% and from 2.45 to 55.54% of total P (TP), respectively. The SMB enhanced CP release in all the soils and all the treatments (except CK and L levels in tea soil; CK, L, and M levels in vegetable soil; and L and M levels in citrus soil). Multiple linear regression revealed a significant correlation between CP and MRPcoll and between colloidal iron, aluminum, calcium, and total organic carbon (Fecoll, Alcoll, Cacoll, and TOCcoll) and pH, which may play an important role as CP carriers that could depend on the pH. This study suggests that the application of SMB in the soil at an appropriate rate of 1 and 2% for tea and vegetable soils, respectively, could be beneficial to avoid the risk of CP release in water bodies.
24493. 题目: Conversion of organic carbon from decayed native and invasive plant litter in Jiuduansha wetland and its implications for SOC formation and sequestration
文章编号: N19111313
期刊: Journal of Soils and Sediments
作者: Jianfang Yan, Lei Wang, Yiu Fai Tsang, Liwei Qian, Xiaohua Fu, Ying Sun, Pengfei Wu
更新时间: 2019-11-13
摘要: Purpose: It is still controversial which type of plant litter is conducive to soil organic carbon (SOC) formation. Here we are to explore the conversion of organic carbon (OC) from decayed plant litter in soil and its influence on final SOC sequestration. Materials and methods: In situ investigation combined with laboratory soil incubation experiments were conducted in mixing zones dominated by halophytes of Phragmites communis and Spartina alterniflora in the Jiuduansha wetland of the Yangtze River estuary to investigate differences in conversion patterns of OC from two decayed plant litters of different characteristics using traditional physicochemical indicators and stable isotope tracing. Additionally, the mechanism of biotransformation was investigated through analysis of soil microbial community structure. Results and discussion: Due to the higher content of lignin and cellulose in P. communis litter, the associated soil microbial community was more conducive to the formation of soil humus (HS). By contrast, more easily decomposable S. alterniflora litter induced its related soil microbial community more amenable to mineralization. Consequently, OC from decayed S. alterniflora litter remained in soil for less time than that from decayed P. communis, and the lost OC was more readily converted into CO2. OC from decayed P. communis was degraded very slowly during the early stage of conversion (November), and its longer duration in soil was favorable for HS formation. Conclusions: Analysis of the conversion of intermediates derived from different types of decayed plants can provide insight into plant litter input and SOC formation, and indicate the whereabouts of lost OC. From the perspective of plant biomass and conversion of plant litter-derived OC, P. communis is more conducive to soil carbon sequestration than S. alterniflora.
24494. 题目: Increased lateral transfer of soil organic carbon induced by climate and vegetation changes over the southeast coastal region of China
文章编号: N19111312
期刊: Journal of Geophysical Research: Biogeosciences
作者: Yuyan Liu, Xiaoyuan Wang, Yawen Wang, Chuang Tong, Wenping Yuan
更新时间: 2019-11-13
摘要: Soil erosion and the subsequent lateral movement of soil carbon profoundly affect the spatial pattern of carbon sources and sinks in terrestrial ecosystems. The eight river basins of Fujian Province considered in this study are an important part of the southeastern coastal river basin of the ninth‐largest river system in China. In recent years, the erosion of soil and soil organic carbon in the southeast coastal region of China is not ideal owing to the high and concentrated rainfall, natural vegetation destruction, and other reasons. In this study, the soil organic carbon erosion and deposition rates related to erosion in the eight river basins of Fujian Province are quantified, and their spatial distribution characteristics are extracted. Based on the soil erosion rate from two national soil erosion surveys and topsoil carbon content from the Harmonized World Soil Database, we estimated that the lateral soil organic carbon erosion increased from 7.53 g C m‐2 yr‐1 to 26.75 g C m‐2 yr‐1 in eight river basins of Fujian Province from 1995–1996 to 2010–2012. The soil organic carbon erosion rate in the eight river basins increased by 2.6 times, while the soil organic carbon erosion rate for the whole of China decreased by 44% during the same period. The increase in torrential rain and decrease in vegetation cover in the southeastern coastal areas largely contributed to the erosion of soil and soil organic carbon. The lateral transfer rate of soil organic carbon may be further exacerbated by the increase of torrential rain in the southeastern coastal areas of China.
24495. 题目: Response of density stratification, aquatic chemistry, and methylmercury to engineered and hydrologic forcings in an endorheic lake (Great Salt Lake, U.S.A.)
文章编号: N19111311
期刊: Limnology and Oceanography
作者: Shu Yang, William P. Johnson, Frank J. Black, Ryan Rowland, Christine Rumsey, Andrew Piskadlo
更新时间: 2019-11-13
摘要: Elimination of limited flow through the earthen railroad causeway separating the north and south arms of Great Salt Lake, Utah, U.S.A., in late 2013 destratified this meromictic endorheic lake and effectively eliminated previous elevated methylmercury (40–90 ng L−1) in deep waters. Reestablishment of north–south flow in late 2016 offered the opportunity to understand the drivers of density stratification, which in turn drive geochemical conditions supporting mercury methylation at depth. Both engineered (causeway flow reopening) and hydrologic (snowmelt) forcings were observed to initiate meromixis (stratification). Return to meromixis drove anoxia at depth with increased sulfide and methylmercury concentrations. However, shallow brine oxygen concentrations were lower under destratified relative to meromictic conditions, and brief periods of anoxia and elevated sulfide and methylmercury occurred at depth even under destratified conditions, demonstrating oxygen demand by underlying sediment organic matter. Mercury demethylation in deep waters was observed only under destratified conditions when oxygen reached bottom waters. These findings indicate that the deep brine layer acts as a cap that prevents oxygen from the overlying mixolimnion from coming into contact with sediment organic matter and drives accumulation of methylmercury in deep waters under meromictic (stratified) conditions.
24496. 题目: Changes in food characteristics reveal indirect effects of lake browning on zooplankton performance
文章编号: N19111310
期刊: Limnology and Oceanography
作者: Laetitia Minguez, Erik Sperfeld, Stella A. Berger, Jens C. Nejstgaard, Mark O. Gessner
更新时间: 2019-11-13
摘要: Browning caused by colored dissolved organic matter is predicted to have large effects on aquatic ecosystems. However, there is limited experimental evidence about direct and indirect effects of browning on zooplankton in complex field settings. We used a combination of an ecosystem‐scale enclosure experiment and laboratory incubations to test how prolonged browning affects physiological and life‐history traits of the water flea Daphnia longispina, a key species in lake food webs, and whether any such effects are reversible. Daphnids and water were collected from enclosures in a deep clear‐water lake, where the natural plankton community had been exposed for 10 weeks to browning or to control conditions in clear water. Daphnid abundance was much lower in the brown than in the clear enclosure. Surprisingly, however, daphnids continuously kept in brown enclosure water in the laboratory showed increased metabolic performance and survival, and also produced more offspring than daphnids kept in clear enclosure water. This outcome was related to more and higher‐quality seston in brown compared to clear water. Moreover, daphnids transferred from clear to brown water or vice versa adjusted their nucleic acid and protein contents, as indicators of physiological state, to similar levels as individuals previously exposed to the respective recipient environment, indicating immediate and reversible browning effects on metabolic performance. These results demonstrate the importance of conducting experiments in settings that capture both indirect effects (i.e., emerging from species interactions in communities) and direct effects on individuals for assessing impacts of browning and other environmental changes on lakes.
24497. 题目: Microbial community composition and functional potential in Bothnian Sea sediments is linked to Fe and S dynamics and the quality of organic matter
文章编号: N19111309
期刊: Limnology and Oceanography
作者: Olivia Rasigraf, Niels A. G. M. van Helmond, Jeroen Frank, Wytze K. Lenstra, Matthias Egger, Caroline P. Slomp, Mike S. M. Jetten
更新时间: 2019-11-13
摘要: The Bothnian Sea is an oligotrophic brackish basin characterized by low salinity and high concentrations of reactive iron, methane, and ammonium in its sediments, enabling the activity and interactions of many microbial guilds. Here, we studied the microbial network in these sediments by analyzing geochemical and microbial community depth profiles at one offshore and two near coastal sites. Analysis of 16S rRNA gene amplicons revealed a distinct depth stratification of both archaeal and bacterial taxa. The microbial communities at the two near coastal sites were more similar to each other than the offshore site, which is likely due to differences in the quality and rate of organic matter degradation. The abundance of methanotrophic archaea of the ANME‐2a clade was shown to be related to the presence of methane and varied with sediment iron content. Metagenomic sequencing of sediment‐derived DNA from below the sulfate–methane transition zone revealed a broad potential for respiratory sulfur metabolism via partially reduced sulfur species. The potential for nitrogen cycling was dominated by reductive processes via a truncated denitrification pathway encoded exclusively by bacterial lineages. Gene‐centric fermentative metabolism analysis indicated a potential importance for acetate, formate, alcohol, and hydrogen metabolism. Methanogenic/‐trophic pathways were dominated by Methanosaetaceae, Methanosarcinaceae, Methanomassiliicoccaceae, Methanoregulaceae, and ANME‐2 archaea. Our results indicated flexible metabolic capabilities of core microbial community taxa, which could adapt to changing redox conditions, and with a spatial and depth distribution that is likely governed by the quality and input of available organic substrates and, for ANME‐2, of iron oxides.
24498. 题目: Co-pyrolysis of lignocellulosic and macroalgae biomasses for the production of biochar - A review
文章编号: N19111308
期刊: Bioresource Technology
作者: Fakayode Olugbenga Abiola, Elmuez Alsir Ahmed Aboagarib, Cunshan Zhou, Haile Ma
更新时间: 2019-11-13
摘要: Biochar properties are significantly influenced and controlled by biomass feedstock type and pyrolysis operating conditions, and the development of multiple biochar properties for various applications has necessitated the need for blending different feedstocks together. Co-pyrolysis as a potential technology has been proposed to improve the overall performance of biomass pyrolysis and has proved effective in improving biochar properties. Consequently, the combination of lignocellulosic and macroalgae biomasses has been targeted for biochar production and improvement of biochar properties through co-pyrolysis. This paper therefore presents a critical review of biochar production from co-pyrolysis of lignocellulosic and macroalgae biomass (CLMB). It discusses the biomass feedstock selection, characterization, pre-processing and suitability for thermal processing; and analyzes biochar production, characterization and reactor technologies for CLMB. Furthermore, the potential and economic viability of biochar production system from CLMB are explored; and finally, the current state and future directions of biochar production from CLMB are extensively discussed.
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24499. 题目: Effect of biochar and bacterial inoculum additions on cow dung composting
文章编号: N19111307
期刊: Bioresource Technology
作者: Mukesh Kumar Awasthi, Yumin Duan, Sanjeev Kumar Awasthi, Tao Liu, Zengqiang Zhang
更新时间: 2019-11-13
摘要: The present study evaluates the effectiveness of different types of biochar additives and bacterial inoculation on gaseous emission, nutrient preservation, and relevant functional bacterial community during cow manure composting. The result revealed that biochar and bacterial consortium inoculation effectively inhibited gaseous emission and improved carbon and nitrogen sequestration, remarkably enriching the abundance of the functional bacteria community. Notably, superior efficacy was found in 12% wheat straw biochar and bacterial consortium amendment composting of T6 with the lowest cumulative CO2-C and NH3-N (308.02 g and 12.71 g, respectively), minimal total C and N losses, and the highest bacterial population. Additionally, gaseous emission exhibited a strong correlation between physicochemical properties with intersection of 66.78% and a unique substrate utilizing bacterial communities. Consequently, the integrated application of biochar and bacterial consortium inoculation was suggested as an efficient method to adjust microbial activity and facilitate cellulose-rich waste degradation, enabling efficient management of organic waste from cow manure and wheat straw by composting.
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24500. 题目: The influence of thermal maturity on the stable isotope compositions and concentrations of molybdenum, zinc and cadmium in organic-rich marine mudrocks
文章编号: N19111306
期刊: Geochimica et Cosmochimica Acta
作者: Alexander J. Dickson, Erdem Idiz, Donald Porcelli, Sander H.J.M. van den Boorn
更新时间: 2019-11-13
摘要: The concentrations and isotopic compositions of molybdenum (Mo), zinc (Zn) and cadmium (Cd) in organic-rich marine mudrocks may be used to characterize ocean chemistry in the geological past. These approaches rely on the rarely tested assumption that the geochemical signatures of these metals are not affected by the thermal maturation of the organic matter with which they are associated. We have conducted a series of artificial maturation experiments on two well-known immature organic-rich mudrocks, the Kimmeridge Blackstone Band (Late Jurassic age), and the Posidonia Shale (Early Jurassic age). These pyrolysis experiments allow us to trace changes in the composition of organic matter through varying stages of maturation, and the concentration and isotopic compositions of metals in rock residues and evolved organic fluids. Our results indicate that the thermal maturation of organic matter does not result in significant alteration of the isotopic compositions of Mo, Zn and Cd in the rock residues, which thus retain primary palaeodepositional information. Systematic increases in the concentrations of Mo, Zn and Cd in rock residues with progressively higher thermal maturity are attributed to the loss of substrate mass in the form of fluids released during pyrolysis-induced cracking of kerogen, and to the relatively low concentrations of Mo, Zn and Cd in these fluids. The Mo-isotope compositions of fluids produced during pyrolysis are isotopically similar to the bulk rock; in contrast the isotopic composition of Zn in organic fluids is ∼0.4–0.6 ‰ lighter than the bulk rock. The progressive loss of organic matter from rock residues during maturation coupled with the increases in metal concentrations leads to an increase of metal/TOC ratios, which may be up to double their original (syn-depositional) value in thermally mature rocks. This observation must be taken into account when using metal/TOC ratios as proxies for oceanic metal inventories throughout geological time. Finally, calculations using the mass of asphaltenes recovered during the pyrolysis experiments suggest that organically bound Mo, Zn and Cd account for several percent of the total rock metal inventory.