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17621. 题目: Photo-induced degradation and toxicity change of decabromobiphenyl ethers (BDE-209) in water: Effects of dissolved organic matter and halide ions
文章编号: N21040915
期刊: Journal of Hazardous Materials
作者: Fangyuan Cheng, Jiale He, Chao Li, Ying Lu, Ya-nan Zhang, Jiao Qu
更新时间: 2021-04-09
摘要: BDE-209 is a widely used brominated flame retardant that is ubiquitous in the aquatic environment, especially in marine water. However, photodegradation of BDE-209 in seawater is still not fully understood. In this work, the photodegradation kinetics of BDE-209 in water was studied and the effects of seawater dissolved organic matter (S-DOM) and halide ions (Cl−, Br−) were evaluated. S-DOM inhibited the degradation of BDE-209 through dynamic quenching and light shielding effect. However, with the coexistence of S-DOM, Cl− and Br−, the photodegradation of BDE-209 was significantly promoted. The promotional effect is attributed to the generation of excited triplet state S-DOM, singlet oxygen, and reactive halogen radicals. The results of density functional theory calculation showed that •Cl addition reaction on C-Br sites of BDE-209 is the main reaction pathway of BDE-209 with chlorine radical, which leads to the generation of mixed Cl/Br substituted intermediates. The acute toxicity and estrogenic effects of BDE-209 solution were enhanced during simulated sunlight irradiation. These results indicate that the environmental factors in seawater play important roles in the photodegradation of BDE-209, and contribute to the potential ecological risks of PBDEs in the marine environment.

17622. 题目: Low mobility of CuO and TiO2 nanoparticles in agricultural soils of contrasting texture and organic matter content
文章编号: N21040914
期刊: Science of The Total Environment
作者: Marie SIMONIN, Jean M.F. MARTINS, Gaëlle UZU, Lorenzo SPADINI, Aline NAVEL, Agnès RICHAUME
更新时间: 2021-04-09
摘要: The fate of nanoparticles (NPs) in soil under relevant environmental conditions is still poorly understood. In this study, the mobility of two metal-oxide nanoparticles (CuO and TiO2) in contrasting agricultural soils was investigated in water-saturated soil columns. The transport of TiO2 and CuO-NPs were assessed in six soils with three different textures (from sand to clay) and two contrasted organic matter (OM) contents for each texture. TiO2 mobility was very low in all soils, regardless of texture and OM content. Mass recoveries were always less than 5%, probably in relation with the strong homo-aggregation of TiO2-NPs observed in all soil solutions, with apparent sizes 3–6 times larger than their nominal size. This low mobility suggests that TiO2-NPs present a low risk of direct groundwater contamination in contrasted surface soils. Although their retention was also generally high (more than 86%), CuO nanoparticles were found to be mobile in all soils. This is probably related to their smaller apparent size and low capacity of homo-aggregation of CuO-NPs in all soil solutions. No clear influence of neither soil texture or soil total organic matter content could be observed on CuO transport. However, this study shows that in contrasted agricultural soils, CuO-NPs transport is mainly controlled by the solutes dissolved in soil solution (DOC and PO4 species), rather than by the properties of the soil solid phase.

17623. 题目: Impact of freeze-thaw cycles on organic carbon and metals in waters of permafrost peatlands
文章编号: N21040913
期刊: Chemosphere
作者: D.A.H.É.D.R.E.Y. PAYANDI-ROLLAND, L.I.U.D.M.I.L.A.S. SHIROKOVA, F.A.B.I.A.N. LABONNE, P.A.S.C.A.L.E. BÉNÉZETH, O.L.E.G.S. POKROVSKY
更新时间: 2021-04-09
摘要: Despite the importance of soil and surface waters freezing in permafrost landscapes, the behaviour of dissolved organic carbon (DOC), nutrients and metals during periodic freeze-thaw cycles (FTC) remains poorly known. The on-going climate warming is likely to increase the frequency of FTC in continental aquatic settings, which could modify the chemical composition of waters. In this study, we conducted 9 repetitive cycles of overnight freezing (-20 °C) and 5 hours thawing (4°C) in the laboratory using representative 0.22 μm-filtered waters from NE European permafrost peatland: leachates of vegetation and soil, and natural surface waters (depression, thermokarst lake and river). Only minor (<5% - 15%) changes of DOC concentrations, SUVA254 and molecular weight were observed in all leachates and the depression water. In contrast, several trace elements (Fe, Al, P, Mn, As, and REE) exhibited sizable variations during FTC (>10%). The leachates and the depression water were enriched in trace elements, whereas the thermokarst lake and the river demonstrated a decrease in concentration of Fe (-39 and -94 %, respectively), Al (-9 and -85 %), and Mn (-10 and -79 %) during FTC. Overall, the observations demonstrated an increase in aliphatic low molecular weight organic matter (OM), and the precipitation of Fe, Al hydroxides and organo-mineral particles. Therefore, enhanced of frequency of FTC can favour the release of metals and toxicants from acidic OM-rich surface waters and maintain stable OM-metals-colloids in large lakes and rivers, thus regulating aquatic transport of DOC and metals from soils to the Arctic Ocean.

17624. 题目: Effects of single and mixed plant types on soil carbon and nitrogen dynamics in homestead agroforestry systems in Northern Bangladesh
文章编号: N21040912
期刊: Agriculture, Ecosystems & Environment
作者: Md. Shahariar Jaman, Taofeek O. Muraina, Quockhanh Dam, Xiang Zhang, Mahbuba Jamil, Sushma Bhattarai, Ferzana Islam
更新时间: 2021-04-09
摘要: The importance of plant types and diversity have been focused for studying aboveground nutrients dynamics in the agroforestry system; however, a substantial knowledge gap remains for the belowground nutrients. We tested the effects of plant types (shrub vs. tree vs. tree-shrub) and diversity indices on soil organic carbon (SOC) and soil nitrogen (SN) dynamics in 64 homesteads in northern Bangladesh. We found that SOC, SN and soil C:N ratio were higher in the mixed plant types (tree-shrub) homesteads than single plant types (tree or shrub) homesteads. Both SOC and SN were higher in 0–10 cm than 10–20 cm soil depth in shrub homesteads (SOC: P = 0.011; SN: P = 0.023), and tree-shrub homesteads (SN: P = 0.03). In contrast, C:N ratio was consistently higher in 10–20 cm soil depth (P < 0.05) but no differences were found in bulk density (BD) (P > 0.05) across homesteads. Shannon diversity, Simpson richness and plant density positively related with SOC and SN. High plant diversity and density promoted SOC and SN more in tree-shrub homesteads than in shrub and tree homesteads, while none of the relationships differ between shrub or tree homesteads. These results indicate that mixture of plant types and their diversity elevate SOC and SN contents in homesteads. Hence, the integration of both tree and shrub under homestead agroforestry system have great potential for SOC and SN storage in the study sites and areas in other subtropical countries with substantial homestead coverage.

17625. 题目: Eco-friendly production of biochar via conventional pyrolysis: Application of biochar and liquefied smoke for plant productivity and seed germination
文章编号: N21040911
期刊: Environmental Technology & Innovation
作者: Ahmed A. Abdelhafez, Xu Zhang, Li Zhou, Min Cai, Naxin Cui, Guifa Chen, Guoyan Zou, Mohammed H.H. Abbas, Mona H.M. Kenawy, Mahtab Ahmad, Salman S. Alharthi, Mahdy H. Hamed
更新时间: 2021-04-09
摘要: Conventional pyrolysis of agricultural wastes may emit considerable amounts of greenhouse gases that affect negatively the surrounding environment. A trial was done to capture the emitted gases through connecting a small water jacket with the pyrolysis unit. This plant was then used for production of biochars from two waste materials i.e. nutshell (NS-BC) and date-palm seed (DP-BC). The biochars manufactured from the aforementioned waste materials were then evaluated for their applicability vs pig manure (each amendment was applied at rates of 1, 2.5, 5 and 10%; w/w) to improve growth of Brassica chinensis grown on a sandy soil under greenhouse conditions. Collected liquefied smokes were also tested for enhancing germination of Lactuca sativa (lettuce) seeds using different concentrations (0%–5%, v/v). Results revealed that produced biochars decreased significantly soil pH where the highest reduction (14.30%) was occurred due to addition of 10% DP-BC. Moreover, NS-BC and DP-BC decreased significantly soil salinity from 0.21 dSm −1 (control) to 0.13 and 0.14 dSm −1, respectively; on the other hand, pig manure raised significantly soil salinity (10% application rate). Residual organic matter was higher in biochar amended soils than its corresponding values in pig manure treated ones. Generally, all investigated amendments improved considerably the uptake of nitrogen, phosphorus, and potassium. Moreover, they increased chlorophyll pigments in leaves and enhanced plant growth parameters upon their application at rates up to 2.5% with superiority for NS-BC versus DP-BC. Liquefied smoke also improved lettuce seed germination and growth, but only up to 0.25% application rate. Our results highlighted the success of the adopted technique for recycling NS and DP wastes and sustaining the environment.

17626. 题目: Effect of iron nitrate modification on elimination of organic matter from landfill leachate by sludge-based activated carbon
文章编号: N21040910
期刊: Waste Management & Research: The Journal for a Sustainable Circular Economy
作者: Fan Zeng, Xiaofeng Liao, Jiawei Lu, Danping Pan, Qili Qiu, Keqiang Ding, Minghan Luo
更新时间: 2021-04-09
摘要: Sludge-based activated carbons (SACs) prepared from sewage sludge and corn straw, were modified by ferric nitrate, and the unmodified SAC and modified SAC were used as the adsorbing agent to treat the landfill leachate, the elimination capacity for chemical oxygen demand (COD) and organic matter in leachate were studied. Based on this, the physicochemical properties of SACs and the components changes in leachate were analyzed and characterized by X-ray photoelectron spectroscopy and three-dimensional fluorescence spectroscopy. The results showed that under optimal experimental conditions, the elimination capacities of SAC372 for COD, biological oxygen demand over 5 days, and NH 4 + –N in the leachate were 81.58%, 54.73%, and 69.08%, respectively; while the adsorption capacities of modified SAC for these three substances were 86.25%, 63.51%, and 79.15%, respectively. The ferric nitrate modification improved the ability of SAC to eliminate COD and organic matter from leachate slightly, and made the adsorption occurred easily. The adsorption process of unmodified SAC was dominated by multi-layer adsorption, while the adsorption process of modified SAC was dominated by monolayer adsorption. The mass fraction of Fe (2p) in modified SAC remarkably increased, from 0.70% to 26.01%, organic functional groups certain phase of Fe oxides with different valence states were generated in SAC, which provided a substrate for iron–carbon micro electrolysis. After adsorbed by unmodified SAC and modified SAC adsorption, the total fluorescence intensity of in the leachate increased by 17.01% and 116.84%, respectively. Both two SACs could decompose the humic acid-like substances into aromatic protein organic compounds, and modified SAC could further decompose the soluble microbial byproduct-like substances.

17627. 题目: Biochar and vermicompost improve the soil properties and the yield and quality of cucumber (Cucumis sativus L.) grown in plastic shed soil continuously cropped for different years
文章编号: N21040909
期刊: Agriculture, Ecosystems & Environment
作者: Fangli Wang, Xuexia Wang, Ningning Song
更新时间: 2021-04-09
摘要: Organic amendments such as biochar and vermicompost have been reported to improve soil and plant properties. However, whether the co-application of the two amendments has a synergistic effect on the alleviation of vegetable continuous cropping obstacles in plastic shed cultivation is still unclear. This study investigated the single and joint effects of biochar and vermicompost on the improvement of soil quality and cucumber yield and quality in plastic shed soil that had been continuously cultivated for 0, 5, and 20 years in northern China. The experiment was conducted in a completely randomized design with four treatments: control, without the addition of biochar (CK); 15 t/ha biochar (BC); 15 t ha−1 vermicompost (VC); and 7.5 t ha−1 biochar + 7.5 t ha−1 vermicompost (BV). The results showed that the single and joint application of biochar and vermicompost generally improved soil properties and increased cucumber yield and quality. Soil pH was most significantly increased (1.24–2.46%) by BC treatments, followed by BV treatments, which generally performed the best in decreasing soil electrical conductivity (EC) and increasing dissolved organic carbon (DOC) and the amounts of fungi and bacteria. The BV treatments also most significantly improved the fruit quality and increased cucumber yields by 29.2–56.0%. The results of structural equation modeling showed that soil pH, DOC, available phosphorus, available potassium, and the amounts of fungi and bacteria positively contributed to cucumber fruit yield and quality, whereas soil EC had a negative effect. These properties also interacted with each other (e.g., there were strong correlations among soil EC, pH, DOC, nutrients, and the amounts of fungi and bacteria), thereby indirectly affecting cucumber yield and quality. The co-application of biochar and vermicompost is therefore recommended for the alleviation of continuous cropping obstacles in plastic shed cultivation.

17628. 题目: The importance of jellyfish–microbe interactions for biogeochemical cycles in the ocean
文章编号: N21040908
期刊: Limnology and Oceanography
作者: Tinkara Tinta, Katja Klun, Gerhard J. Herndl
更新时间: 2021-04-09
摘要: Jellyfish blooms can represent a significant but largely overlooked source of organic matter (OM), in particular at the local and regional scale. We provide an overview of the current state of knowledge on the bloom‐forming jellyfish as sink and source of OM for microorganisms. In particularly, we compare the composition, concentration, and release rates of the OM excreted by living jellyfish with the OM stored within jellyfish biomass, which becomes available to the ocean's interior only once jellyfish decay. We discuss how these two stoichiometrically different jelly‐OM pools might influence the dynamics of microbial community and the surrounding ecosystem. We conceptualize routes of jelly‐OM in the ocean, focusing on different envisioned fates of detrital jelly‐OM. In this conceptual framework, we revise possible interactions between different jelly‐OM pools and microbes and highlight major knowledge gaps to be addressed in the future.

17629. 题目: Identifying key environmental factors explaining temporal patterns of DOC export from watersheds in the conterminous United States
文章编号: N21040907
期刊: Journal of Geophysical Research: Biogeosciences
作者: Xinyuan Wei, Daniel J. Hayes, Ivan Fernandez, Jianheng Zhao, Shawn Fraver, Catherine Chan, Jiaojiao Diao
更新时间: 2021-04-09
摘要: The export of dissolved organic carbon (DOC) from a watershed is a key component of the terrestrial biosphere carbon cycle. There is a need to improve our understanding of how and by how much various environmental factors are driving the temporal patterns of DOC export in order to accurately model and evaluate terrestrial carbon storage and fluxes. In this synthesis, we compiled observational data sets from 14 watersheds in the conterminous United States spanning the time period from 1981 to 2017. We used these data sets to examine the relative impacts of various climate, atmospheric deposition, and land cover factors on the temporal patterns of DOC export across watersheds of different sizes and landscape conditions, as well as the time‐series autocorrelation of DOC export. Our results suggest that the dominant factor on an annual scale was the amount of precipitation, which had a positive correlation with DOC export from a watershed. Overall increasing nitrogen deposition was coincident with increasing DOC export, and increasing sulfur deposition was coincident with declining DOC export. The seasonal pattern of DOC export was strongly regulated by air temperature, the long‐term trend was negatively influenced by increasing sulfur deposition, and no obvious autocorrelation was detected in DOC export. In addition, higher rates of DOC export were positively correlated with greater area of wetlands within a watershed, but was not found to be strongly related to any of the other land cover types.

17630. 题目: Production and Removal of Soluble Organic Nitrogen by Nitrifying Biofilm
文章编号: N21040906
期刊: Journal of Environmental Chemical Engineering
作者: Ruchi Joshi, Murthy Kasi, Tanush Wadhawan, Eakalak Khan
更新时间: 2021-04-09
摘要: This study investigated soluble organic nitrogen (sON) activity in batch reactors mimicking nitrifying moving bed biofilm reactors (MBBRs). This work was divided into two objectives focusing on the production and degradation of sON, respectively. For the first objective, a synthetic feed that did not contribute any organic nitrogen was used and results indicated that irrespective of the presence of influent organic carbon (0 versus 400mg COD/L) in the reactors, sON was contributed by the biofilm during nitrification. Although net production of sON was observed, both production and ammonification coexisted which regulated the sON concentration. For the second objective, actual wastewater was fed to the reactors to investigate sON degradation under different carbon to nitrogen (C/N) ratios. A higher concentration of sON was biodegraded in the reactor when fed with influent containing a lower C/N ratio. Overall results suggested that organic carbon bioavailability and/or ammonia concentration influenced the production and ammonification of sON. This study is the first to explore the sON activity by MBBR biofilm and findings from this work could extend the knowledge on the fixed film process with respect to sON activity to regulate and optimize reactor operation in meeting stringent total nitrogen discharge limits.

17631. 题目: Biochar and environmental sustainability: Emerging trends and techno-economic perspectives
文章编号: N21040905
期刊: Bioresource Technology
作者: Nawaz Khan, Pankaj Chowdhary, Edgard Gnansounou, Preeti Chaturvedi
更新时间: 2021-04-09
摘要: Environmental pollutants including emerging contaminants are a growing concern worldwide. Organic wastes, such as food waste, compost, animal manure, crop residues, and sludge are generally used as feedstock. The conventional treatment methodologies (primary and secondary treatment process) do not mitigate or remove pollutants effectively. Hence, an effective, low-cost, and environmentally friendly tertiary treatment process is an urgent need. Biochar finds interesting applications in environmental processes like pollutant remediation, greenhouse gas mitigation, and wastewater treatment. Studies have shown that different types of adsorbents (biochars) like, native and engineered biochar are being used in the removal or mitigation of heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, pesticides, disinfectants, polychlorinated dibenzofurans, and dibenzo-p-dioxins from contaminated sites for environmental management. The review discusses ample studieswhich can offer solutions for environmental sustenance and managementand the emerging trends and techno-economic prospectives of biochar for sustainable environmental management.

17632. 题目: Challenges and opportunities of nutrient recovery from human urine using biochar for fertilizer applications
文章编号: N21040904
期刊: Journal of Cleaner Production
作者: Abhijeet Pathy, Jyotiprakash Ray, Balasubramanian Paramasivan
更新时间: 2021-04-09
摘要: Although urine constitutes less than 1% volume of the total wastewater, it adds up 50-80% of the nutrient load [Phosphates (PO43-) and Nitrates (NO3-), Ammonium (NH4+)] in wastewater treatment plants (WWTPs). Recovery of Phosphorous (P) and Nitrogen (N) from urine diminishes the eutrophication impact as well it could act as a sustainable source of P by lessening dependence on finite phosphorite reservoirs. Due to its environmental (carbon-negative process) and economic (produced from waste) value, biochar is gaining the researcher's attention in recent years. Many studies are ongoing to introduce novel structures and modifications in the surface properties of biochar for efficient adsorption of P and N. Direct application of urine as fertilizer has been discouraged due to various hygienic pitfalls further forced to explore the alternative nutrient recovery methods. This review article explores the nutrient recovery paradigms from source-separated human urine for abridging the nutrient gap between wastewater treatment and agricultural productivity using pristine/engineered biochar. The influencing factors for P and N's adsorption process by biochar and its detailed mechanisms have been outlined. Further, it deliberates the possible strategies of engineering the biochar to enhance the recovery of P and N from human urine. Applications of nutrient-loaded biochar in an agricultural field could act as a slow-release fertilizer to releases P and N in addition to soil conditioning. This review emphasized the challenges of storage, transportation, contamination of urine, and possible difficulties in the adsorption process by pristine/engineered biochar.

17633. 题目: Hierarchical porous biochar from plant-based biomass through selectively removing lignin carbon from biochar for enhanced removal of toluene
文章编号: N21040903
期刊: Chemosphere
作者: Fengli Gan, Bowen Cheng, Ziheng Jin, Zhongde Dai, Bangda Wang, Lin Yang, Xia Jiang
更新时间: 2021-04-09
摘要: This study proposed a simple and green air oxidation (AO) method to prepare hierarchical porous biochar by selectively removing lignin carbon from biochar after the pyrolysis of plant-based biomass, based on the fact that the thermal decomposition temperature in air between lignin carbon and cellulose/hemicellulose carbon was different. Three kinds of biomass with different lignocellulose contents were used, including walnut shell, cypress sawdust and rice straw. The results found that AO treatment could effectively improve the pore structure of the three biochar. The specific surface area of WCO-4, CCO-4 and RCO-4 was 555.0 m2/g, 418.7 m2/g and 291.9 m2/g, respectively, which was significantly higher than those of WC (319.5 m2/g), CC (381.7 m2/g) and RC (69.6 m2/g), respectively. Among these, walnut shell biochar with air oxidation (WCO) had higher surface area of 555.0 m2/g and mesopore volume of 0.116 cm3/g, this was related to its high content of lignin, which could facilitate the formation of mesopores by AO treatment with high selectivity. The toluene adsorption capacity of WCO reached 132.9 mg/g, which increased by 223.4% from that without AO treatment. The kinetics study indicated that the diffusion rates of toluene molecule were improved due to the increased mesopores volume of biochar and micropores also play an important role in the adsorption of toluene. The results demonstrate that AO treatment is a promising method to develop hierarchical porous structure for lignocellulose-rich plant-based biomass with low cost and environmental-friendly, which greatly enhanced the toluene adsorption capacity.

17634. 题目: Circular Utilization of Food Waste to Biochar Enhances Thermophilic Co-Digestion Performance
文章编号: N21040902
期刊: Bioresource Technology
作者: Aaron Leininger, Zhiyong Jason Ren
更新时间: 2021-04-09
摘要: Codigestion is an emerging approach to improve wastewater sludge biogas production and valorize food waste (FW). This study explores FW-derived biochar as a codigestion amendment for the first time and reports a matrix experiment using four diverse biochar amendments (mixed food waste, pinewood, bonechar, unamended control) across four FW types (vegetable, rice, chicken, mixed). It demonstrated that biochar derived from mixed FW can greatly improve the performance of biogas production and yield relative to unamended control and other biochars. The mixed food waste (MFW) biochar amendment led to 34.5%, 35.6%, and 47.5% increase in methane production from mixed FW compared to biochars made of wood, bone and non-amendment control, and the maximum methane production rate of MFW biochar reactors could be up to 6.7-9.9 times of the control. These results suggest that a more circular utilization of FW by integrating biochar production with codigestion can bring great benefits to FW management.

17635. 题目: Enhancement of Cd(II) adsorption by rice straw biochar through oxidant and acid modifications
文章编号: N21040901
期刊: Environmental Science and Pollution Research
作者: Xian He, Zhi-neng Hong, Jun Jiang, Ge Dong, Hui Liu, Ren-kou Xu
更新时间: 2021-04-09
摘要: To develop high-efficient biochar adsorbents, the effects and mechanisms of oxidant modification and acid modification on Cd(II) adsorption by rice straw biochar were investigated. Three rice straws from Langxi in Anhui Province, Yingtan in Jiangxi Province, and Lianyungang in Jiangsu Province were collected to prepare biochars by anaerobic pyrolysis in a muffle furnace. Rice straw biochars were modified by 15% H2O2 and 1:1 HNO3/H2SO4 mixed acid, respectively, to obtain modified biochars. The untreated rice straw biochar and HCl-treated rice straw biochar with carbonate removed were used as controls. The functional groups on the surfaces of the biochars were qualitatively and quantitatively determined by Fourier transform infrared spectra and Boehm titration, respectively. The adsorption and desorption of Cd(II) onto and from the biochars and modified biochars were measured under various pH conditions. The results showed that oxidant modification with 15% H2O2 and acid modification with 1:1 HNO3/H2SO4 significantly increased the number of carboxyl functional groups on the surfaces of the biochars, and acid modification was more effective than oxidant modification in amplifying carboxyl functional groups on the surfaces of the biochars. The increase of surface functional groups effectively enhanced the specific adsorption of Cd(II) on the modified biochars. Therefore, both oxidant modification and acid modification enhanced the adsorption of Cd(II) on the biochars through increasing functional groups on the surfaces of the biochars.

17636. 题目: Influence of settling organic matter quantity and quality on benthic nitrogen cycling
文章编号: N21040815
期刊: Limnology and Oceanography
作者: Séréna Albert, Stefano Bonaglia, Nellie Stjärnkvist, Monika Winder, Bo Thamdrup, Francisco J. A. Nascimento
更新时间: 2021-04-08
摘要: Coastal sediments are major contributors to global carbon (C) mineralization and nutrient cycling and are tightly linked to processes in the pelagic environment. In this study, we aimed to investigate the regulating potential of quantity and quality of planktonic organic matter (OM) deposition on benthic metabolism, with a particular focus on nitrogen (N) cycling processes. We simulated inputs of spring (C : N 10.9) and summer (C : N 5.6) plankton communities in high and low quantities to sediment cores, and followed oxygen consumption, nutrient fluxes as well as nitrate reduction rates, that is, denitrification and dissimilatory nitrate reduction to ammonium for 10 d. Our results demonstrate the primary importance of OM quality in determining the fate of organic N once it settles to the sediment surface. Settling of N‐rich summer plankton material resulted in a ∼ twofold lower denitrification efficiency (40–56%) compared to N‐poor spring plankton (88–115%). This indicates that N‐rich plankton deposition favors recycling of inorganic nutrients to the water column over N‐loss via denitrification. OM quantity was positively related to mineralization activity, but this neither directly affected N fluxes nor denitrification activity, highlighting the complex interplay between the OM quantity and quality in regulating N cycling. In light of these new findings, we support the use of simple qualitative indicators such as C : N ratio of OM to investigate how future changes in benthic‐pelagic coupling might influence N budgets at the sediment–water interface.

17637. 题目: Scaling effects of a eutrophic river plume on organic carbon consumption
文章编号: N21040814
期刊: Limnology and Oceanography
作者: Chung‐Chi Chen, Gwo‐Ching Gong, Kuo‐Ping Chiang, Fuh‐Kwo Shiah, Chih‐Ching Chung, Chin‐Chang Hung
更新时间: 2021-04-08
摘要: The amount of fluvial input has important impacts on shelf regions. To understand how the magnitude of fluvial discharge affects plume ecosystems, particularly organic carbon consumption, data over 10 consecutive summers (2003–2012) were examined in the Changjiang River plume of the East China Sea. The area of the Changjiang River plume ranged from approximately 4.90 × 103 km2 to 94.83 × 103 km2 and varied in proportion to the freshwater discharge rate. Plankton community respiration was at the medium to high end of the values reported for coastal regions. Total organic carbon consumption over the Changjiang River plume was positively correlated with the Changjiang freshwater discharge. This scaling relationship might be associated with river flows delivering allochthonous organic carbon and dissolved inorganic nutrients into the East China Sea. However, plankton community respiration (per m3 basis) decreased as the area of the Changjiang River plume increased; this rate appeared to have been influenced by particulate organic carbon (POC) levels and/or total plankton biomass. Even though POC was dominated by phytoplankton biomass allometrically, bacteria contributed more to plankton community respiration, possibly signifying that these bacteria were more reliant on plankton‐derived organic matter. Even with high phytoplankton biomass and primary productivity, this plume ecosystem was heterotrophic, albeit close to a state of carbon balance. To support high organic carbon consumption, in addition to allochthonous sources from fluvial runoff, a large amount of organic matter might have been autochthonous and derived from plankton in the Changjiang River plume.

17638. 题目: Changes in soil phosphorus availability and associated microbial properties after chicken farming in Lei bamboo ( Phyllostachys praecox ) forest ecosystems
文章编号: N21040813
期刊: Land Degradation & Development
作者: Xu Gai, Shaocui Li, Xiaoping Zhang, Fangyuan Bian, Chuanbao Yang, Zheke Zhong
更新时间: 2021-04-08
摘要: Bamboo‐chicken farming (BCF) is a popular bamboo complex management model in Southeast Asia. However, the effects of BCF on phosphorus (P) availability and associated soil microbial communities remain poorly understood. In this study, we compared the soil properties, P fractions, phosphatase activities, and bacterial community compositions in the surface soil (0–20 cm) of a typical BCF system under different grazing densities (represented as distances of 5, 15, 25, 35, and > 60 m [control site] from the henhouse, respectively). We observed that total P (Pt) accumulation was more rapid than that of SOC and TN with increasing grazing density. Labile and moderately labile P dominated soil P accumulation under BCF. Resin‐Pi, NaHCO3‐Pi, and 1 M HCl‐Pi increased by 100–233%, 83–183% and 414–1,314%, respectively, compared with the control. The ratio of labile and moderately labile organic P to the Pt content decreased significantly with increasing grazing density from 38.54% (control) to 17.65% (5 m site). Soil phosphatase activity increased with increasing grazing density, suggesting that BCF effectively promoted the mineralization of soil Po. Inorganic P (Resin‐Pi, NaHCO3‐Pi, and 1 M HCl‐Pi) was positively correlated with Flavobacterium, Pseudomonas, and Arthrobacter but negatively correlated with Burkholderia; this highlights the different functional bacteria involved in P cycling. We conclude that BCF generally increased soil P availability and supply capacity, and the changes in P forms were closely related to changes in soil bacterial community composition. The highly labile P and low C:P ratio under high grazing density conditions may cause soil nutrient imbalance and P leaching.

17639. 题目: High-energy moisture characteristics of various low organic matter sandy soils in different land uses
文章编号: N21040812
期刊: Geoderma
作者: Arezoo Sharifi, Hossein Shirani, Ali Asghar Besalatpour, Isa Esfandiarpour-Boroujeni, Mohammad Ali Hajabbasi
更新时间: 2021-04-08
摘要: Soil structure serves as one of the most important soil physical properties influencing on water retention, aeration, plant growth as well as environmental conditions. In the current study, the effect of four land-use types on some soil structural stability indices including high-energy moisture characteristic (HEMC) at both fast and slow wetting modes, volume of the drainable pores (VDP), structural index (SI), stability ratio (SR), fractal dimensions (D) and mean weight diameter (MWD) was investigated. Jiroft County, is located in southeastern part of Kerman Province, Iran (28ο 40׳ N, 57ο 44׳ E) and characterized by soils generally high in sand and low in organic matter (OM) was selected as the study area. Land-use types included disturbed and undisturbed rangelands, protected natural forest and an artificial forest plantation. The HEMC results showed that in the slow wetting mode, undisturbed rangeland (49.6%) and protected natural forest (42.6%) indicated the highest and lowest values for near-saturated water contents, respectively. However, in fast wetting modes no significant differences was observed in case of near-saturated water content between undisturbed rangeland and disturbed rangeland and artificial forest plantation land-uses. Furthermore, the near-saturated water contents in the protected natural forest did not changed for both fast and slow wetting modes. The lowest MWD (0.05 mm) and the highest fractal dimension values (2.97) were observed for protected natural forest. The lowest values for VDP, VDP ratio (VDPR), and SI were found for undisturbed rangeland and disturbed rangeland, with the highest values obtained for protected natural forest. No significant differences were found among the land-use types in terms of SR. Furthermore, soil water retention was also low in the land use types with low aggregate formation agents like clay, OM, and calcium carbonate equivalent (CCE). Among the HEMC indices, near-saturated water content and soil water retention only indicated the structural condition. While other HEMC indices such as VDP, SI, SiR, and VDPR did not show the differences between structural and textural characteristics. This study revealed that, techniques such as measuring MWD and fractal dimension may better show the status of the soil aggregates in the studied region.

17640. 题目: Response of soil nutrient concentrations and stoichiometry, and greenhouse gas carbon emissions linked to change in land-use of paddy fields in China
文章编号: N21040811
期刊: CATENA
作者: Xuyang Liu, Josep Peñuelas, Jordi Sardans, Yunying Fang, Martin Wiesmeier, Liangquan Wu, Xiaoxuan Chen, Youyang Chen, Qiang Jin, Weiqi Wang
更新时间: 2021-04-08
摘要: The conversion of paddy cropping to vegetable production and other crops is a common agricultural practice, driven by economic benefits. However, soil carbon emissions and nutrient stoichiometric responses to this type of land-use change remain unclear. In this study, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions, Soil Organic Carbon (SOC), total nitrogen (TN), and total phosphorus (TP) concentrations and their stoichiometric relationships were measured over one year, following conversion of paddy fields to vegetable and jasmine crops 10 years ago. Soil CO2 emissions increased by 1.16 and 2.35 times after conversion to vegetable and jasmine production, respectively, and soil CH4 and N2O emissions decreased by 52 and 66%, and 12.3 and 42.5%, respectively. Global warming potential increased by 0.81 and 1.67 times, respectively; the increases in total C emissions were associated with decreases in SOC concentrations. TN decreased by 27% in jasmine soils following conversion from paddy cropping, and TP concentrations increased by 11% in vegetable soils. Carbon soil stocks increased by 19% in vegetable soils and decreased by 11% in jasmine soils, due to changes in SOC concentration and bulk density. Soil CO2 and total C emissions were negatively correlated with soil TN concentration and C:P ratio (p < 0.05), and CH4 emissions were positively correlated with SOC concentrations (p < 0.05) and soil N:P and C:P ratios (p < 0.01). Thus soil elemental stoichiometry was a good indicator of soil nutrient cycling and greenhouse gases emissions. Our findings suggest that the conversion of paddy cropping to vegetable and jasmine production increased C emissions and conversion to jasmine cropping does not lead to retention of soil nutrients, whereas TP concentration and SOC stocks increased following conversion to vegetable cropping. This study highlights that future conversion of paddy soils to vegetable or tree crops will have implications on carbon balances and global warming.