论文检索

总访问量：5360681次

总访客量：313718人

所有论文

24441. 题目: Dissolved methane concentrations and fluxes to the atmosphere from a tropical floodplain lake
文章编号: N20030302
期刊: Biogeochemistry
作者: Pedro M. Barbosa, John M. Melack, João H. F. Amaral, Sally MacIntyre, Daniele Kasper, Alicia Cortés, Vinicius F. Farjalla, Bruce R. Forsberg
更新时间: 2020-03-03
摘要: Large uncertainties in estimates of methane (CH4) emissions from tropical inland waters reflect the paucity of information at appropriate temporal and spatial scales. CH4 concentrations, diffusive and ebullitive fluxes, and environmental parameters in contrasting aquatic habitats of Lake Janauacá, an Amazon floodplain lake, measured for two years revealed patterns in temporal and spatial variability related to different aquatic habitats and environmental conditions. CH4 concentrations ranged from below detection to 96 µM, CH4 diffusive fluxes from below detection to 2342 µmol m−2 h−1, and CH4 ebullitive fluxes from 0 to 190 mmol m−2 d−1. Vegetated aquatic habitats had higher surface CH4 concentrations than open water habitats, and no significant differences in diffusive CH4 fluxes, likely due to higher k values measured in open water habitats. CH4 emissions were enhanced after a prolonged low water period, when the exposed sediments were colonized by herbaceous plants that decomposed after water levels rose, possibly fueling CH4 production. Statistical models indicated the importance of variables related to CH4 production (temperature, dissolved organic carbon) and consumption (dissolved nitrogen, oxygenated water column), as well as maximum depth, in controlling surface water CH4 concentrations.

24442. 题目: Enhancement methane fermentation of Enteromorpha prolifera waste by Saccharomyces cerevisiae: batch kinetic investigation, dissolved organic matter characterization, and synergistic mechanism
文章编号: N20030301
期刊: Environmental Science and Pollution Research
作者: Shunan Zhao, Ping Li, Hongli Fang, Liuying Song, Dunjie Li, Rutao Liu, Qigui Niu
更新时间: 2020-03-03
摘要: With the invasion of green tide, there were millions of tons of Enteromorpha prolifera (Enteromorpha) that need to be disposed of. An efficient microecological system for Enteromorpha fermentation was constructed using Saccharomyces cerevisiae (S. cerevisiae) and granular sludge at mesophilic condition (35 °C). In order to investigate the influence of S. cerevisiae dosage on fermentation, biomethane production and variations in dissolved organic matter (DOM) were investigated. The results indicated that the microecosystem with added S. cerevisiae exhibited improved fermentation capacity. Specifically, biomethane production was improved by 18%, with a maximum methane yield of 331 mL/g VS, and the time required to reach 90% methane yield was reduced by 41%. There were positive linear relationships between S. cerevisiae dosage and the efficiency of hydrolysis, acidogenesis, acetogenesis, and methanogenesis (R2 > 0.9). According to theoretical calculations, there was a positive effect of lower S. cerevisiae dosage (less than 0.93 g/g TS) on biomethane production, and excess dosage (more than 0.93 g/g TS) led to a negative effect due to volatile fatty acid (VFA) accumulation. The excitation–emission matrix (EEM) indicated that the humification index (HIX) and fulvic acid (FA) percentage of fluorescence regional integration in the system were decreased because the quinone and ketone groups of the FA accepted electrons from S. cerevisiae. These findings suggested that this microecosystem can accelerate fermentation speed (41%) and increase biomethane output (18.2%).

24443. 题目: The fate of organic carbon in marine sediments - New insights from recent data and analysis
文章编号: N20030211
期刊: Earth-Science Reviews
作者: LaRowe DE, S. Arndt, J.A. Bradley, E.R. Estes, A. Hoarfrost, S.Q. Lang, K.G. Lloyd, N. Mahmoudi, W.D. Orsi, S.R. Shah Walter, A.D. Steen, R. Zhao
更新时间: 2020-03-02
摘要: Organic carbon in marine sediments is a critical component of the global carbon cycle, and its degradation influences a wide range of phenomena, including the magnitude of carbon sequestration over geologic timescales, the recycling of inorganic carbon and nutrients, the dissolution and precipitation of carbonates, the production of methane and the nature of the seafloor biosphere. Although much has been learned about the factors that promote and hinder rates of organic carbon degradation in natural systems, the controls on the distribution of organic carbon in modern and ancient sediments are still not fully understood. In this review, we summarize how recent findings are changing entrenched perspectives on organic matter degradation in marine sediments: a shift from a structurally-based chemical reactivity viewpoint towards an emerging acceptance of the role of the ecosystem in organic matter degradation rates. That is, organic carbon has a range of reactivities determined by not only the nature of the organic compounds, but by the biological, geochemical, and physical attributes of its environment. This shift in mindset has gradually come about due to a greater diversity of sample sites, the molecular revolution in biology, discoveries concerning the extent and limits of life, advances in quantitative modeling, investigations of ocean carbon cycling under a variety of extreme paleo-conditions (e.g. greenhouse environments, euxinic/anoxic oceans), the application of novel analytical techniques and interdisciplinary efforts. Adopting this view across scientific disciplines will enable additional progress in understanding how marine sediments influence the global carbon cycle.

24444. 题目: Effect of biochar and compost on soil properties and organic matter in aggregate size fractions under field conditions
文章编号: N20030210
期刊: Agriculture, Ecosystems & Environment
作者: Jennifer Cooper, Isabel Greenberg, Bernard Ludwig, Laura Hippich, Daniel Fischer, Bruno Glaser, Michael Kaiser
更新时间: 2020-03-02
摘要: Aggregation affects soil properties crucial for sustainable soil management and productivity. However, longer-term studies (> five years) of treatments to enhance soil aggregation, such as addition of biochar with labile carbon to derive microbial binding agents, are limited, especially in temperate climates. To fill this gap, we established a field experiment with control, compost only, biochar only, and a mixed compost-biochar application (co-composted and only mixed) at low and high application rates (9–70 t ha−1) in southern Germany. After six years of agricultural use, surface (0−10 cm) and subsurface (10−30 cm) soil samples were analyzed for pH, microbial biomass carbon (Cmic), water holding capacity (WHC), and cation exchange capacity (CEC). Particulate organic matter (POM) and aggregate fractions were analyzed for organic carbon (OC) content and characterized using diffuse reflectance infrared Fourier transform spectroscopy. Biochar significantly increased OC and pH, while compost significantly increased OC, pH, Cmic, and CEC six years after application. Biochar also significantly increased OC storage in POM (10–32 times higher) and all aggregate fractions by 56–62 %, 32–47 %, and 29–32 % for the 2 - 0.25 mm, 0.25 - 0.053 mm, and < 0.053 mm fraction, respectively, while compost increased OC storage only in the 10−30 cm soil depth in the soil fractions > 0.053 mm. The proportion of reactive CO groups significantly increased in POM due to biochar and compost application, while only biochar affected the < 0.053 mm fraction. Our results suggest that six years after application, high rates of both biochar and compost are beneficial for soil properties affecting the sustainability of soil agro-ecosystems such as pH and CEC. For long lasting increase in soil C sequestration, our results indicate that only the application of biochar can be considered as a significant measure.

24445. 题目: Synchronous sequestration of organic carbon and nitrogen in mineral soils after conversion agricultural land to forest
文章编号: N20030209
期刊: Agriculture, Ecosystems & Environment
作者: Yan Zhang, Xiaolin Liao, Zhao Wang, Xiaorong Wei, Xiaoxu Jia, Mingan Shao
更新时间: 2020-03-02
摘要: Agricultural land-use change is a global issue with significant implications for global warming and ecosystem functionality. Uncertainty regarding carbon (C) and nitrogen (N) sequestration and their dynamics after land-use change hampers an accurate understanding of the C and N cycles. To address the influence of converting agricultural land to forest on organic carbon (OC) and N sequestration and their coupling relationships, we collected topsoil (0−10 cm depth) and subsurface soil (10−20 cm depth) in afforested woodlands 10, 20, and 35 yrs after the establishment of Robinia pseudoacacia in abandoned farmlands on the Loess Plateau, China. We analyzed the concentrations and stocks of OC and N in bulk soils and water-stable aggregates. We found that afforestation of farmland resulted in a relative increase of 30 % in the proportion of macroaggregates (8 – 0.25 mm) but a relative decrease of 45 % and 30 % in the proportions of microaggregates (0.25 - 0.053 mm) and silt + clay (< 0.053 mm), respectively. The respective OC and N stocks increased by 87 % and 74 % in bulk soils and by 278 % and 159 % in macroaggregates after 35 yrs of afforestation. Macroaggregates accounted for 69 % and 68 % of the OC and N stocks, respectively, in bulk soils at the 0−20 cm depth. However, the OC and N stocks in microaggregates and silt + clay were only slightly affected. These results indicated that the conversion of agricultural land to forest could sequester OC and N in both bulk soils and aggregates, mainly macroaggregates. In addition, the dynamics of OC and N were significantly correlated, implying synchronous OC and N sequestration in soils after converting agricultural land to forest.

24446. 题目: Exploring the variability of soil properties as influenced by land use and management practices: A case study in the Upper Blue Nile basin, Ethiopia
文章编号: N20030208
期刊: Soil and Tillage Research
作者: Kindiye Ebabu, Atsushi Tsunekawa, Nigussie Haregeweyn, Enyew Adgo, Derege Tsegaye Meshesha, Dagnachew Aklog, Tsugiyuki Masunaga, Mitsuru Tsubo, Dagnenet Sultan, Ayele Almaw Fenta, Mesenbet Yibeltal
更新时间: 2020-03-02
摘要: The knowledge of how soil properties vary over space and time is essential to better understand the potential of soils and their sensitivity to management interventions under different local conditions. The objective of this study was to analyze the variation in key soil properties as influenced by different land use types (cropland, grazing land, and bushland) and sustainable land management (SLM) practices (soil bund reinforced with grass, and fanya juu for croplands, and exclosures with and without trenches for grazing and bushlands) in the three contrasting agro-ecological zones of the drought-prone Upper Blue Nile basin, Ethiopia. Nine soil properties—texture, bulk density (BD), pH, electrical conductivity (EC), cation exchange capacity (CEC), total nitrogen (TN), soil organic carbon (SOC), available phosphorus (Pav), and available potassium (Kav)—were measured for topsoil (0–20 cm) samples collected from experimental plots established for monitoring runoff and soil loss rates. The results showed that seven of the nine studied soil properties significantly differed among the three land use types in the three agro-ecological zones (P < 0.05 to P < 0.001); pH, CEC, SOC, and TN values were generally lower in croplands than in others. These results imply that soil quality under crop production has been greatly deteriorated by unsustainable cropping systems practiced over centuries. Three years after the implementation of SLM practices, however, most soil parameters become within optimal ranges for supporting plant production. More particularly, sensitive soil properties (BD, SOC, TN, Pav, and Kav) showed remarkable improvement in plots where soil bunds reinforced with grass and exclosures were implemented. This improvement was primarily associated with the development of well-established vegetation cover owing to the favorable natural conditions maintained by fencing of plots and minimum tillage. These results therefore indicate that soil degradation can best be controlled through enhancing vegetation growth and reducing soil disturbance by tillage operations. We conclude that integrating land uses with suitable SLM practices is the most effective way to maintain and restore soil quality and sustain ecosystem functioning.

24447. 题目: Sludge stabilization: Characteristics of the end-products and an alternative evaluative methodology
文章编号: N20030207
期刊: Waste Management
作者: Xiaojie Mei, Jianguo Tang, Yue Zhang
更新时间: 2020-03-02
摘要: The treatment, disposal and resource recovery of sewage sludge is a major bottleneck for the water and environmental remediation efforts in China. In this paper, sixteen sludge treatment plants using anaerobic digestion and aerobic composting as stabilization procedures were investigated and analysed. The organic degradation rates varied from 0.5% to 80.2% of different plants, showing the close relationship with raw sludge property and treatment process. The increment rate of humic-like substances ranged from 19% to 81% in different cases. It has been aware of that stabilization procedures coupled the degradation of simple organics (proteins, polysaccharides, lipids) with the synthesis of complex organics (humic-like substances). Therefore, an alternative methodology, considering the content of humic-like substances (no less than 150 mg/gVS) and the fluorescence complexity index (up to 5.0) in the end-products, was proposed to evaluate the stabilization level. Humic-like substances indicate the ecological value of the end-products. Fluorescence complexity index, combining the reduction of protein-like substances with the increment of humic-like substances, can predict the humification degree. The new criterion can be the supplementary of the current ones.

24448. 题目: Insight to key diazotrophic community during composting of dairy manure with biochar and its role in nitrogen transformation
文章编号: N20030206
期刊: Waste Management
作者: Xiaotong Wu, Yu Sun, Liting Deng, Qingxin Meng, Xin Jiang, Ayodeji Bello, Siyuan Sheng, Yue Han, Haifeng Zhu, Xiuhong Xu
更新时间: 2020-03-02
摘要: Analyzing diazotrophic community may help to understand nitrogen transformation in composting and improves the final compost quality. In this study, diazotrophic community dynamics were investigated in terms of nifH gene during dairy manure and corn straw composting with biochar addition using high-throughput sequencing. Biochar decreased the diversity of diazotrophic community and altered diazotroph community structure during composting. At phylum level, Proteobacteria, Actinobacteria and Firmicutes were dominant diazotrophic communities throughout composting process. Biochar addition registered higher correlation coefficient (R) between physicochemical factors (temperature, ammonium (NH4+-N) and nitrate (NO3−-N)) and diazotroph community composition. Rhodopseudomonas and Pseudoxanthomonas was the key diazotrophic communities influencing NH4+-N transformation in control (CK) and biochar compost (BC), respectively, while for NO3−-N transformation Clostridium and Bradyrhizobium in CK, Azospira and Methylocystis in BC served as predominant factors. These results indicated that addition of biochar altered the key diazotroph communities influencing nitrogen transformation. Furthermore, some diazotrophs (e.g. Rhodopseudomonas, Bradyrhizobium and Azospira) affecting NH4+-N and NO3−-N transformation were also observed to be mediating total nitrogen (TN). Interestingly, interactions between diazotrophic communities were observed and these interactions could also influence nitrogen transformation.

24449. 题目: Chemical, physical and morphological properties of biochars produced from agricultural residues: Implications for their use as soil amendment
文章编号: N20030205
期刊: Waste Management
作者: Paloma Campos, Ana Z. Miller, Heike Knicker, Manuel F. Costa-Pereira, Agustín Merino, José María De la Rosa
更新时间: 2020-03-02
摘要: Biochar is a pyrogenous organic material resulting from the pyrolysis of organic residues, which is attracting the interest from researchers and farmers for its potential to sequester carbon and its use as soil ameliorant. Pyrolysis conditions and feedstock determine the properties of the biochars produced. In order to understand the relationship between these variables we analysed in detail the physical, chemical and surface characteristics of biochars produced from three contrasting agronomic residues abundantly generated in South Spain, such as rice husk (RH), olive pit (OP) and pruning remains of olive trees (mainly composed of olive branches and leaves; OB), using a temperature range from 350 to 600 °C and residence times from 0.5 to 4 h. High pyrolysis temperature (600 °C) and time resulted in the greatest pH and C content in the biochars. In general, elemental composition and ash content were dependent on the type of organic waste used as feedstock. 13C Nuclear Magnetic Resonance Spectroscopy and thermal (TG-DSC) analyses showed that temperatures ≥500 °C are needed to achieve a high degree of aromatization of the chars. Micro-computed tomography and field emission scanning electron microscopy revealed that the structure of RH was preserved during the pyrolysis process, favouring a greater porosity for these biochars. These data are very useful for the production of stable biochars obtained from residual biomass, maximising the value of residual biomass resources. These biochars show physical and chemical properties, such as adequate pH, high water retention capacity or high porosity, of interest for their use as soil amendments.

24450. 题目: Effects of climate warming and nitrogen deposition on subtropical montane ponds (central China) over the last two centuries: Evidence from subfossil chironomids
文章编号: N20030204
期刊: Environmental Pollution
作者: Ting Zheng, Yanmin Cao, Jia Peng, Xue Bai, Xu Chen
更新时间: 2020-03-02
摘要: Many remote montane ecosystems are experiencing biogeochemical changes driven by warming climate and atmospheric pollution. Compared with circumpolar and temperate lakes, the responses of subtropical montane lakes to these external stressors have been less investigated. Here we present sedimentary multi-proxies records (i.e. chironomids, elements and stable isotope of carbon and nitrogen) in 210Pb-dated cores from two montane ponds (central China). Before the 1900s, low biomass and the dominance of opportunistic species (e.g. Chironomus anthracinus-type) in both ponds might be in response to cold and harsh condition. Thereafter, chironomid communities in both ponds experienced pronounced shifts. Nutrient-tolerant/warm-adapted species (e.g. Chironomus sp., Polypedilum nubeculosum-type and Endochironomus impar-type) proliferated and biomass increased synchronously after the 1900s, suggestive of favorable condition for chironomid growth. Redundancy analyses revealed that changes in chironomid communities in both ponds were significantly correlated with rising temperature and δ15N depletion. Prolonged growing season and nitrogen subsidy would increase primary productivity, and hence enhancing food availability for chironomids. Catchment-mediated indirect effects of warming and nitrogen deposition, such as hydrological changes and terrestrial organic matter inputs, would impose further influences on chironomid communities. Taken together, the combined effects of climate warming and nitrogen deposition have caused significant shifts in primary consumers of these montane ponds, and imposed cascading effects on structure and function of subtropical montane aquatic ecosystems.

24451. 题目: Tillage and cropping effects on soil organic carbon: biodegradation and storage in density and size fractions
文章编号: N20030203
期刊: European Journal of Soil Science
作者: Y. Zhang, X. J. Li, E. G. Gregorich, N. B. Mclaughlin, X. P. Zhang, Y. F. Guo, Y. Gao, A. Z. Liang
更新时间: 2020-03-02
摘要: Improvements in management practices can prevent the decline of soil organic carbon (SOC) storage caused by conventional tillage practice in Northeast China. Density and size fractionation can track the transformation of plant residue into SOC and its location in soil matrix. We used a long‐term field study in China to evaluate these changes as a result of improved management involving tillage and cropping systems. Experimental treatments included no‐till (NT) and moldboard ploughing (MP) under monoculture maize (Zea mays L.) (MM) and maize‐soybean (Glycine max Merr.) rotation (MS); these were compared to the traditional management involving conventional tillage (CT) under MM. An incubation study was conducted to evaluate mineralization and the biodegradability of SOC. The soils were also physically fractionated by density (light fraction, LF) and size (sand, silt, clay). With improved management, the SOC storage in the clay showed the largest increase across all fractions. This increase was greater for MS than MM. The NTMS treatment resulted in a decline in silt‐OC storage compared to CTMM. The SOC mineralization (mg CO2‐C g−1 soil) was affected by tillage and driven by LF‐OC and was observed in the order: NTMM (2.06) > MPMM (1.72) ≈ NTMS (1.71) > CTMM (1.52) ≈ MPMS (1.41). Both cropping and depth affected the biodegradability of SOC. Considering the plough layer (0–20 cm), treatments under MM had larger proportion of biodegradable SOC than under MS. We conclude that the significant differences in SOC storage in physical fractions and SOC biodegradation were caused by differences in soil management. This article is protected by copyright. All rights reserved.

24452. 题目: Have we reached the turning point? Looking for evidence of SOC increase under conservation agriculture and cover crop practices
文章编号: N20030202
期刊: European Journal of Soil Science
作者: C. Camarotto, I. Piccoli, N. Dal Ferro, R. Polese, F. Chiarini, L. Furlan, F. Morari
更新时间: 2020-03-02
摘要: Increasing soil organic carbon (SOC) stocks in agricultural soils is currently of special interest because it can help mitigate global warming through atmospheric carbon (C) sequestration. Recommended management practices, such as conservation agriculture (CA) and conventional tillage with cover crops (CC), could have significant implications for C sequestration potential. A field experiment was carried out in Northeast Italy to compare the implementation of CA and CC with conventional agriculture (CV). The experiment began in 2010 on three farms to evaluate SOC stock variation over a 6‐yr period. Two extensive soil sampling operations were conducted in 2011 and 2017 in 240 locations, for a total of 1,440 analysed soil samples, considering the SOC stratification within a 0–50 cm profile. The results suggested that CA changed the SOC distribution rather than the total amount of SOC. Compared to CV, after the introduction of CA, a general increase in SOC (0.25 Mg C ha−1 y−1) was observed in the 0–30 cm layer, while no stock variation was observed in the 0–50 cm layer. In contrast, compared to CV, the use of CC decreased the SOC stocks by 0.74 Mg C ha−1 y−1 in the 0–50 cm layer. Over a 6‐yr period, no benefit in SOC sequestration was observed with CA and CC. However, we hypothesise that these findings could still be affected by transitory dynamics, highlighting the low soil reactivity to soil‐improving agricultural systems. A longer study period would be required to better understand the potential benefits of CA and CC on SOC sequestration. This article is protected by copyright. All rights reserved.

24453. 题目: Effect of grazing exclusion and rotational grazing on labile soil organic carbon in north China
文章编号: N20030201
期刊: European Journal of Soil Science
作者: Lei Dong, Vegard Martinsen, Yantao Wu, Ying Zheng, Cunzhu Liang, Zhongling Liu, Jan Mulder
更新时间: 2020-03-02
摘要: Overgrazing has caused serious grassland soil deterioration and significant soil organic carbon (SOC) losses. Controlled grazing is recommended for restoring grassland and enhancing SOC stocks. Studies have suggested that in particular labile organic carbon (C) is a sensitive indicator for soil degradation and SOC recovery, but few studies of the effect of different grassland management practices have been published so far. Here, we investigate the effects of long‐term grazing exclusion and short‐term rotational grazing with different grazing intensities on labile SOC, including hot water extractable organic C (HWEC) and particulate organic C (POC), as well as potential N mineralization (Nmin) rate in soils (0–10 cm) of two grasslands in Xilinhot, Inner Mongolia. Treatments include long‐term (34 years) exclusion, medium‐term (21 years) exclusion, and continuous grazing (ambient grazing) at one of the sites, whereas we investigate no grazing, light grazing, moderate grazing and high grazing intensity at the study site for rotational grazing. Our results show that grazing exclusion significantly enhances labile SOC stocks and potential Nmin rate compared to ambient grazing (e.g. POC stock at long‐ and medium‐term exclusion and ambient grazing are 5.71 ± 0.94 Mg C ha−1, 3.25 ± 0.30 Mg C ha−1 and 2.12 ± 0.38 Mg C ha−1, respectively). However, after two decades of exclusion, the potential of further C sequestration is limited. Five years of rotational grazing significantly enhances HWEC, but not POC and potential Nmin rate, when comparing the highest grazing intensity (1.88 sheep ha−1 yr−1) with grazing exclusion during the same period. We conclude that rotational grazing may be a viable alternative to exclusion, offering a more rational use of grassland without causing soil C loss. We also show that HWEC is a particularly sensitive labile SOC indicator and is tightly correlated to POC and potential Nmin rate. This article is protected by copyright. All rights reserved.

24454. 题目: Organic chemistry insights for the exceptional soil carbon storage of seagrass Posidonia australis
文章编号: N20030121
期刊: Estuarine, Coastal and Shelf Science
作者: Oscar Serrano, Mohammad Rozaimi, Paul S. Lavery, Ronald J. Smernik
更新时间: 2020-03-01
摘要: The high organic carbon (OC) stores in seagrass meadows have led to their recognition as significant Blue Carbon sinks, though the diagenetic conditions that enable OC retention in seagrass soils remain poorly understood. In this study, seagrass soils were sampled from a Posidonia australis meadow in Oyster Harbour (Albany; south-western Australia) to investigate the preservation of sedimentary OC. We analysed soil characteristics (colour, grain size and redox potential), radiocarbon age, and characterised the soil organic matter (OM) using solid state CP/MAS 13C NMR spectroscopy to examine the preservation of OM down the soil profile. There was minimal change in organic composition over 1,700 years of accumulation, indicating long-term OM preservation. Primarily, this preservation appears to be driven by the recalcitrance of seagrass detritus buried in anoxic soils. The majority (70–83%) of total sedimentary OM comprised components directly attributable to seagrass origins (lignin, carbohydrate and black carbon-like matter), while the remainder consisted mostly of protein, some of which may have been present in seagrass biomass, along with likely contributions from algae and microbes. Although black carbon originates from organic matter combustion, here we provide evidence that the 13C NMR signal identified as black carbon-like matter in our soils is possibly associated with seagrass-derived organic matter consisting of degraded lignin products or other non-pyrogenic aromatics. The increase in the relative abundance of this black carbon-like matter with aging suggests its selective preservation. The relative abundances of carbohydrates significantly decreased with age down core (i.e. they appeared to be selectively decomposed), while lignin and protein did not show any quantitative changes in relative abundance (non-selective preservation). These findings demonstrate the exceptional preservation of P. australis derived OC, which contributes to our understanding of the higher OC storage capacity of Posidonia compared to other seagrass species.

24455. 题目: MnO2 nanozyme-driven polymerization and decomposition mechanisms of 17β-estradiol: Influence of humic acid
文章编号: N20030120
期刊: Journal of Hazardous Materials
作者: Kai Sun, Qingzhu Liu, Shunyao Li, Yongbo Qi, Youbin Si
更新时间: 2020-03-01
摘要: Nanozymes, which display the bifunctional properties of nanomaterials and natural enzymes, are useful tools for environmental remediation. In this research, nano-MnO2 was selected for its intrinsic enzyme-like activity to remove 17β-estradiol (E2). Results indicated that nano-MnO2 exhibited laccase-like activity (7.22 U·mg−1) and removed 97.3 % of E2 at pH 6. Humic acid (HA) impeded E2 removal (only 72.4 %) by competing with E2 for the catalytic sites of the MnO2 nanozyme surface, and there was a good linear correlation between the kinetic constants and HA concentrations (R2 = 0.9489). Notably, the phenolic −OH of E2 interacted with HA to yield various polymeric products via radical-driven covalent coupling, resulting in ablation of phenolic −OH but increase of ether groups in the polymeric structure. Intermediate products, including estrone, E2 homo-/hetero-oligomers, E2 hydroxylated and quinone-like products, as well as aromatic ring-opening species, were identified. Interestingly, HA hindered the extent of E2 oxidation, homo-coupling, and decomposition but accelerated E2 and HA hetero-coupling. A reasonable catalytic pathway of E2 and HA involving MnO2 nanozyme was proposed. These findings provide novel insights into the influence of HA on MnO2 nanozyme-driven E2 radical polymerization and decomposition, consequently favoring the ecological water restoration and the global carbon cycle.

24456. 题目: A fast chemical oxidation method for predicting the long-term mineralization of biochar in soils
文章编号: N20030119
期刊: Science of The Total Environment
作者: Benjuan Liu, Qi Liu, Xiaojie Wang, Qicheng Bei, Yanhui Zhang, Zhibin Lin, Gang Liu, Jianguo Zhu, Tianlong Hu, Haiyang Jin, Hui Wang, Xiaoli Sun, Xingwu Lin, Zubin Xie
更新时间: 2020-03-01
摘要: Biochar stability determines the effectiveness of biochar's functions such as carbon sequestration, soil structure improvement, soil fertility enhancement and soil pollution remediation. However, a fast method for accurately predicting biochar long-term stability in soil remains elusive. Here, firstly, an incubation experiment was conducted on mineralization dynamics of different 13C-labelled biochars over 368 days to explore their actual mineralization in soils and establish their mineralization model. Thereafter, ten treatments of fast chemical oxidation methods using K2Cr2O7 (0.1 M) with different H+ concentrations and oxidation times were applied to the biochars to reveal which method best matches the mineralization of biochar in soils. Results showed that the percentage of biochar‑carbon oxidized by the solution containing 0.1 M K2Cr2O7 and 0.2 M H+ at 100 °C for 2 h was in accordance with the one that potentially would be mineralized in soils at a 100-year scale (R2 > 0.99; REMS = 2.53; RD = 15.3). The results provided a chemical oxidation method that was robust, effective, low cost and highly available for measuring the long-term stability of biochar in soils.

24457. 题目: The effect of biochar, lime and ash on maize yield in a long-term field trial in a Ultisol in the humid tropics
文章编号: N20030118
期刊: Science of The Total Environment
作者: Sarah E. Hale, Neneng L. Nurida, , Jan Mulder, Erlend Sørmo, Ludovica Silvani, Samuel Abiven, Stephen Joseph, Sarasadat Taherymoosavi, Gerard Cornelissen
更新时间: 2020-03-01
摘要: A multi-season field trial was carried out to investigate the effect of the amendment of biochar, lime, ash and washed biochar on the growth of maize. A degraded, strongly acidic Ultisol (pHKCl 3.60), with a relatively high exchangeable aluminium content (2.4 cmolc/kg) and a low exchangeable calcium content (0.99 cmolc/kg), was used. Soil was treated once at the beginning of the field trial and crop growth was monitored over seven planting seasons (PS). All treatments increased maize yield. The average increases were; seven times for biochar, five times for lime, five times for washed biochar and eight times for ash treatment, when compared to the control across all PS. The effect of biochar, lime and ash treatments on maize yield were sustained over the seven PS. Soil pHKCl was significantly increased (p < 0.05 level) following the addition of all of the amendment materials. All treatments significantly reduced the concentration of Al3+ when compared to the control (p < 0.05), with the lowest concentrations for the lime and ash treatments. The ash treatment also increased the concentration of macronutrients (K, P and Mg) to the greatest extent. Results showed that there was a clear liming effect at play. The better performance of biochar compared to lime, despite lime having the highest pH and the lowest Al3+ concentration, can be explained by the additional K, Mg and P the biochar adds to the soil. Results also showed a clear nutrient addition effect where ash added the most nutrients. Overall, this work supports the fact that small scale farmers in Indonesia should produce biochar from their waste agricultural materials. Doing so not only provides an increase in crop productivity, but also sequesters carbon resulting in the best overall environmental benefit.

24458. 题目: Lability-specific enrichment of typical engineered metal (oxide) nanoparticles by surface-functionalized microbubbles from waters
文章编号: N20030117
期刊: Science of The Total Environment
作者: Ming Zhang, Junhan Yang, Linfeng Tang, Daoyong Zhang, Xiangliang Pan
更新时间: 2020-03-01
摘要: Enrichment of metallic engineered nanoparticles (MENPs) from environmental waters is a prerequisite for their removal, reliable analyses, and environmental process interpretations. This work investigated the enrichment of typical MENPs with different degrees of lability using surface-functionalized microbbubles. During the process, the transformation/dissolution characteristics of MENPs were considered, and the impact of surfactant or coagulant dose, pH of MENP suspensions, and water matrix was systematically investigated. Results show that the colloidal gas aphrons (CGAs) were capable of enriching over 90.0% of ionic Ag(I) which ended up as AgBr and Ag2CO3 in floats when the pH of suspension was 6.0. The polyaluminum chloride-modified CGAs with positive surface charges were good at capturing the particulate ZnO-NPs (~84.8%) but failed to collect the ionic species. It should be noted that the total MENP enrichment efficiency closely related to the content proportions of different species. In the river water, both of the dissolved natural organic matter (fulvic acids) and the electrolytes might influence the enrichment process by affecting the species transformation of Ag-NPs and ZnO-NPs. For the stable TiO2-NPs, 97.1% of the nanoparticles were captured by CGAs. FAs apparently reinforced the enrichment performance since the molecules acted as bridge and facilitated the attachment between TiO2-NP and CGAs. This work contributes to establishing the robust microbubble-induced enrichment method considering the characteristics of MENP contaminants.

24459. 题目: Does submarine groundwater discharge contribute to summer hypoxia in the Changjiang (Yangtze) River Estuary?
文章编号: N20030116
期刊: Science of The Total Environment
作者: Xiaoyi Guo, Bochao Xu, William C. Burnett, Qinsheng Wei, Haiming Nan, Shibin Zhao, Matthew A. Charette, Ergang Lian, Guangquan Chen, Zhigang Yu
更新时间: 2020-03-01
摘要: The Changjiang (Yangtze) River Estuary (CJE) is one of the largest and most intense seasonal hypoxic zones in the world. Here we examine the possibility that submarine groundwater discharge (SGD) may contribute to the summer hypoxia. Spatial distributions of bottom water 222Rn suggest a hotspot discharge area in the northern section of the CJE. SGD fluxes were estimated based on a 222Rn mass balance model and were found to range from 0.002 ± 0.004 to 0.022 ± 0.011 m3/m2/day. Higher SGD fluxes were observed during summer hypoxia period. The well-developed overlap of the distribution patterns for SGD flux and dissolved oxygen (DO) implies that SGD could be an important contributor to summer hypoxia in the region off the CJE. We suggest that SGD contributes to the seasonal hypoxia either: (1) directly via discharge of anoxic groundwaters together with reducing substances; and/or (2) indirectly by delivering excess nutrients that stimulate primary productivity with consequent consumption of DO during organic matter decomposition.

24460. 题目: Soil respiration after forest conversion to tea gardens: A chronosequence study
文章编号: N20030115
期刊: CATENA
作者: Lichao Fan, Wenyan Han
更新时间: 2020-03-01
摘要: Documenting the influences of land-use change and time after conversion on soil respiration is fundamental to understanding the interplay between soil carbon sequestration and greenhouse gas emissions. We conducted fortnightly in situ measurements of soil respiration (considered herein as both total respiration [Rtotal] and root-free basal respiration [Rbasal]) along a land-use chronosequence: a native broad-leaf evergreen forest and three tea gardens (10, 40, and 100 years old) with similar characteristics of soil type and site management. Compared to the forest, soil organic carbon decreased by 7% in the 10-year-old tea garden, whereas it was similar in the 40-year-old tea garden and 18% higher in the 100-year-old tea garden; total N content increased by 35%, 44%, and 50% in the 10-, 40-, and 100-year-old tea gardens, respectively. The seasonal variation in Rtotal and Rbasal could be 62–83% and 39–69% explained by the mixed model of soil temperature and water content, respectively. The temperature sensitivity (Q10) of Rtotal increased from 1.67 in the forest to 1.98 and 1.93 in the 10- and 40-year-old tea gardens, respectively, but decreased to 1.64 in the 100-year-old tea garden. The Q10 of Rbasal increased from 1.26 in the forest to 1.58–1.95 in the tea gardens. Annual CO2 efflux of Rbasal increased ~1.5 times, but the SOC-normalized Rbasal was similar between the forest and the 100-year-old tea garden. We suggest that the loss of soil carbon storage would be compensated over a period of 40 years after the conversion of forests to tea gardens, and the time after conversion to tea gardens is an important ecological factor in mitigating the effects of land-use change.