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23341. 题目: Assessing soil organic carbon stock of Wisconsin, USA and its fate under future land use and climate change
文章编号: N19030915
期刊: Science of The Total Environment
作者: Kabindra Adhikari, Phillip R. Owens, Zamir Libohova, David M. Miller, Skye A. Wills, Jason Nemecek
更新时间: 2019-03-09
摘要: Carbon stored in soils contributes to a variety of soil functions, including biomass production, water storage and filtering, biodiversity maintenance, and many other ecosystem services. Understanding soil organic carbon (SOC) spatial distribution and projection of its future condition is essential for future CO₂ emission estimates and management options for storing carbon. However, modeling SOC spatiotemporal dynamics is challenging due to the inherent spatial heterogeneity and data limitation. The present study developed a spatially explicit prediction model in which the spatial relationship between SOC observation and seventeen environmental variables was established using the Cubist regression tree algorithm. The model was used to compile a baseline SOC stock map for the top 30 cm soil depth in the State of Wisconsin (WI) at a 90 m × 90 m grid resolution. Temporal SOC trend was assessed by comparing baseline and future SOC stock maps based on the space-for-time substitution model. SOC prediction for future considers land use, precipitation and temperature for the year 2050 at medium (A1B) CO₂ emissions scenario of the Intergovernmental Panel on Climate Change. Field soil observations were related to factors that are known to influence SOC distribution using the digital soil mapping framework. The model was validated on 25% test profiles (R²: 0.38; RMSE: 0.64; ME: −0.03) that were not used during model training that used the remaining 75% of the data (R²: 0.76; RMSE: 0.40; ME: −0.006). In addition, maps of the model error, and areal extent of Cubist prediction rules were reported. The model identified soil parent material and land use as key drivers of SOC distribution including temperature and precipitation. Among the terrain attributes, elevation, mass-balance index, mid-slope position, slope-length factor and wind effect were important. Results showed that Wisconsin soils had an average baseline SOC stock of 90 Mg ha⁻¹ and the distribution was highly variable (CV: 64%). It was estimated that WI soils would have an additional 20 Mg ha⁻¹ SOC by the year 2050 under changing land use and climate. Histosols and Spodosols were expected to lose 19 Mg ha⁻¹ and 4 Mg ha⁻¹, respectively, while Mollisols were expected to accumulate the largest SOC stock (62 Mg ha⁻¹). All land-use types would be accumulating SOC by 2050 except for wetlands (−34 Mg C ha⁻¹). This study found that Wisconsin soils will continue to sequester more carbon in the coming decades and most of the Driftless Area will be sequestering the greatest SOC (+63 Mg C ha⁻¹). Most of the SOC would be lost from the Northern Lakes and Forests ecological zone (−12 Mg C ha⁻¹). The study highlighted areas of potential C sequestration and areas under threat of C loss. The maps generated in this study would be highly useful in farm management and environmental policy decisions at different spatial levels in Wisconsin.
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23342. 题目: Degradation of sulfamethoxazole by ionizing radiation: Kinetics and implications of additives
文章编号: N19030914
期刊: Science of The Total Environment
作者: Run Zhuan, Jianlong Wang
更新时间: 2019-03-09
摘要: Sulfamethoxazole (SMX) is a widespread and persistent antibiotic pollutant in the aquatic environment. In this paper, SMX was degraded by gamma irradiation, and various influencing factors were explored. The experimental results revealed that after 1.5 kGy irradiation, 20 mg/L SMX could be completely decomposed. Kinetics studies suggested that the radiation-induced degradation process of SMX conformed first-order kinetic. The pH value had influence on the decomposition efficiency through changing the species of reactive radicals and the existing form of SMX molecules and their distribution. Additionally, the effect of inorganic anions (CO₃²⁻, HCO₃⁻, NO₃⁻, SO₄²⁻, Cl⁻, HPO₄²⁻) and organic matters (peptone, glucose, humic acid) on SMX degradation was evaluated, which had negative influence on SMX degradation. The degradation efficiency of SMX decreased in the effluent water of WWTP in comparison with that in deionized water, suggesting that the components in the effluent inhibited the radiation-induced decomposition of SMX. The mineralization of SMX by ionizing radiation was also evaluated. These results revealed that ionizing radiation is a promising technology to degrade SMX in aqueous solution as well as in wastewater.
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23343. 题目: Mercury speciation, bioavailability, and biomagnification in contaminated streams on the Savannah River Site (SC, USA)
文章编号: N19030913
期刊: Science of The Total Environment
作者: Xiaoyu Xu, Albert L. Bryan, Gary L. Mills, Alexis M. Korotasz
更新时间: 2019-03-09
摘要: Water, sediment, and biota from two streams on the Savannah River Site were sampled to study mercury (Hg) biogeochemistry. Total and methyl- Hg (MHg) concentrations were measured for all samples, speciation models were used to explore Hg speciation in the water, and Diffusive gradients in thin films (DGT) were applied to indicate the vertical profiles of labile Hg (DGT-Hg). Trophic position (δ¹⁵N) was estimated for biota and used to establish MHg biomagnification model. The speciation model indicated Hg methylation in the water occurred on settling particles and the most bioavailable Hg species to bacteria were complexes of inorganic Hg and labile organic ligands. Correspondingly, dissolved organic carbon concentrations were positively related to MHg concentrations in the water. In the sediment, the sharp increase of DGT-Hg around the sediment water interface underscores the importance of this interface, which determines the differences in the accumulation and generation of labile Hg among different waterbodies. The positive correlation between sediment MHg and sulfate concentrations suggested possible methylation reaction by dissimilatory sulfate reducing bacteria in the sediment. The food web magnification factors of MHg were 9.6 (95% CI: 4.0–23.4) and 4.4 (95% CI: 2.5–7.7) for the two streams established with trophic data of biofilm, invertebrates, and fish. Meanwhile, DGT-Hg concentrations in the water were positively correlated to biofilm Hg concentrations, which can be combined with the MHg biomagnification model to generate a modified biomagnification model that estimate MHg bioaccumulation with only labile Hg concentrations in the water. With this approach, Hg accumulation in abiotic and biotic environmental compartments was connected and the different bioaccumulation patterns of Hg in different waterbodies were explained with both geochemical and biological factors.
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23344. 题目: Biogeochemical fate of ferrihydrite-model organic compound complexes during anaerobic microbial reduction
文章编号: N19030912
期刊: Science of The Total Environment
作者: Dawit N. Wordofa, Dinesh Adhikari, Sarrah M. Dunham-Cheatham, Qian Zhao, Simon R. Poulson, Yuanzhi Tang, Yu Yang
更新时间: 2019-03-09
摘要: Associations of organic carbon (OC) with iron (Fe) oxide minerals play an important role in regulating the stability of OC in soil environments. Knowledge about the fate and stability of Fe-OC complexes is impaired by the heterogeneity of OC. Additional biogeochemical variables in soil environments, such as redox conditions and microbes, further increase complexity in understanding the stability of mineral-associated soil OC. This study investigated the fate and stability of model organic compounds, including glucose (GL), glucosamine (GN), tyrosine (TN), benzoquinone (BQ), amylose (AM), and alginate (AL), complexed with an Fe oxide mineral, ferrihydrite (Fh), during microbial reduction. During a 25-d anaerobic incubation with Shewanella putrefaciens CN32, the reduction of Fe followed the order of Fh-BQ > Fh-GL > Fh-GN > Fh-TN > Fh-AL > Fh-AM. In terms of OC released during the anaerobic incubation, Fh-GN complexes released the highest amount of OC while Fh-AM complexes released the lowest. Organic carbon regulated the reduction of Fe by acting as an electron shuttle, affecting microbial activities, and associating with Fh. Benzoquinone had the highest electron accepting capacity, but potentially can inhibit microbial activity. These findings provide insights into the roles of different organic functional groups in regulating Fe reduction and the stability of Fh-bound OC under anaerobic conditions.
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23345. 题目: Agricultural soil organic carbon stocks in the north-eastern Iberian Peninsula: Drivers and spatial variability
文章编号: N19030911
期刊: Science of The Total Environment
作者: Inmaculada Funes, Robert Savé, Pere Rovira, Roberto Molowny-Horas, Josep M. Alcañiz, Emilio Ascaso, Ignasi Herms, Carmen Herrero, Jaume Boixadera, Jordi Vayreda
更新时间: 2019-03-09
摘要: Estimating soil organic carbon (SOC) stocks under agriculture, assessing the importance of their drivers and understanding the spatial distribution of SOC stocks are crucial to predicting possible future SOC stocks scenarios under climate change conditions and to designing appropriate mitigation and adaptation strategies. This study characterized and modelled SOC stocks at two soil depth intervals, topsoil (0–30 cm) and subsoil (30–100 cm), based on both legacy and recent data from 7245 agricultural soil profiles and using environmental drivers (climate, agricultural practices and soil properties) for agricultural soils in Catalonia (NE Spain). Generalized Least Square (GLS) and Geographical Weighted Regression (GWR) were used as modelling approaches to: (i) assess the main SOC stock drivers and their effects on SOC stocks; (ii) analyse spatial variability of SOC stocks and their relationships with the main drivers; and (iii) predict and map SOC stocks at the regional scale. While topsoil variation of SOC stocks depended mainly on climate, soil texture and agricultural variables, subsoil SOC stocks changes depended mainly on soil attributes such us soil texture, clay content, soil type or depth to bedrock. The GWR model revealed that the relationship between SOC stocks and drivers varied spatially. Finally, the study was only able to predict and map topsoil SOC stocks at the regional scale, because controlling factors of SOC stocks at the subsoil level were largely unavailable for digital mapping. According to the resulting map, the mean SOC stock value for Catalan agriculture at the topsoil level was 4.88 ± 0.89 kg/m² and the total magnitude of the carbon pool in agricultural soils of Catalonia up to 30 cm reached 47.9 Tg. The present study findings are useful for defining carbon sequestration strategies at the regional scale related with agricultural land use changes and agricultural management practices in a context of climate change.
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23346. 题目: Advancing soil ecological risk assessments for petroleum hydrocarbon contaminated soils in Canada: Persistence, organic carbon normalization and relevance of species assemblages
文章编号: N19030910
期刊: Science of The Total Environment
作者: Amy Gainer, Karl Bresee, Natacha Hogan, Steven D. Siciliano
更新时间: 2019-03-09
摘要: Sediment toxicity studies and ecological risk assessments on organic contaminants routinely apply organic carbon normalization to toxicity data; however, no studies examine its potential for use in soils with petroleum hydrocarbon (PHC) contamination. Limited studies in soil ecotoxicology assess the influence of species assemblages used in species sensitivity distribution construction on the resulting guideline designated to of soil dwelling organisms. Canadian regulations utilize more conservative approaches to deriving guidelines with soil ecotoxicology data compared to the rest of the world, so we investigated the impact of these on soil invertebrates in a variety of field soils. In addition to toxicity, the persistence of a medium PHC mixture was also assessed in the field soils to determine the duration of toxic effects. We found organic matter influenced PHC toxicity to soil invertebrates, but persistence was influenced more by soil cation exchange capacity. Incorporating organic carbon normalization into species sensitivity distribution curves provided a higher level of protection to soil dwelling receptors in low organic matter soils as well as reduce the variability of PHC soil toxicity data. Soil remediation guidelines derived for protection of soil dwelling organisms using a diverse species assemblage provided similar levels of protection as guidelines developed with test species specific for remote, forested land uses in Canada. We conclude that: (i) Canadian hazard concentration values for PHC contamination of soils should be revisited as they may not be protective and (ii) that soil PHC guidelines for protection of soil dwelling organisms should be expressed as carbon normalized values.
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23347. 题目: Effects of different land uses on soil physical and chemical properties in Odeda LGA, Ogun State, Nigeria
文章编号: N19030909
期刊: Environmental Earth Sciences
作者: A. A. Alabi, A. O. Adewale, B. Adebo, A. S. Ogungbe, J. O. Coker, F. G. Akinboro, Giwa Bolaji
更新时间: 2019-03-09
摘要: The study investigated the effect of different land use systems on soil physical and chemical properties in Odeda Local Government Area, Ogun State, Nigeria. A total number of nine composite samples were collected each from the sampling locations at three depths (0–10, 10–20 and 20–30 cm) using a soil auger from three different locations; abattoir wastewater area, farmland area, and automobile workshop area. Some physicochemical properties that reflect soil nutrients content and fertility status (Ca²⁺, Mg²⁺, Na⁺, K⁺, C, N, P, pH, ECEC, particle size, electrical conductivity, and hydrocarbon content) were determined using standard physicochemical techniques. Results from the oil-spill affected (Automobile workshop) and non-oil affected soil were compared. The result shows that land use type affects soil properties differently; bulk density was low in farmland due to the penetration of roots into the soil, but was high at abattoir because of the abattoir effluent on soil that decomposed and reduced the pore space in the soil. The bulk density also high at the mechanic workshop because of the movement of vehicles which vary from light to heavy. Chemical properties like organic matter were more in mechanic village and abattoir than farmland because of the abattoir effluent, which decomposed to increase the organic matter in the soil and the presence of organic compounds from vehicles at mechanic village increased the level of organic matter in the soil. The organic matter was present in large quantity in the farmland, but was reduced by consumption by the plant.

23348. 题目: Comparison of plant and microbial communities between an artificial restoration and a natural restoration topsoil in coal mining subsidence area
文章编号: N19030908
期刊: Environmental Earth Sciences
作者: Ying Liu, Shaogang Lei, Chuangang Gong
更新时间: 2019-03-09
摘要: Increased attention has been paid to the influences of coal mining subsidence on the ecological environment. The revegetation of former mining areas is critical to restore the ecological balance. The subsidence area in the Shendong mining area, located in the semiarid region of China, has been restored from 2003, using five different plant species. In July 2017, we compared the plant and microbial communities of artificial restoration areas (AR) and naturally regenerated areas (NR). Based on our results, restoration planting was somehow successful, but the sites did not reach a level similar to that prior to mining. Higher plant species richness, canopy coverage, and bacterial community diversity were observed in AR. However, these features have lower similarity compared with those in NR sites. Soil factors such as pH, moisture content, total carbon content, organic matter, nitrogen level, and bulk density have a greater impact on soil bacterial community structure and diversity. In the ecological restoration of mining areas, attention should be paid to the restoration of soil properties. This study provides a scientific basis for the successful ecological restoration or highly damaged mining areas.

23349. 题目: Biochemical changes of polysaccharides and proteins within EPS under Pb(II) stress in Rhodotorula mucilaginosa
文章编号: N19030907
期刊: Ecotoxicology and Environmental Safety
作者: Jianjie Li, Zhongquan Jiang, Shasha Chen, Tong Wang, Liu Jiang, Mengxiao Wang, Shimei Wang, Zhen Li
更新时间: 2019-03-09
摘要: Microorganisms have been widely applied to heavy metal adsorption due to their strong secretion of extracellular polymeric substances (EPS). This study explored the responses of Rhodotorula mucilaginosa (R1, a red yeast with substantial EPS supply) under Pb stress. The maximum sorption of Pb cations by R1 was ~650 mg/L. In particular, despite the declined microbial biomass, the total Pb sorption after incubation was actually elevated in the solution with high Pb concentration. At 0–1000 mg/L Pb(NO₃)₂ level, the longitudinal sizes of the yeast capsules increased from 2.04 to 2.90 µm. At 1500 mg/L, however, the survived yeast started to lose the membrane integrity of the cells. Meanwhile, the percentages of organic carbon contents of EPS decreased from 40% to 33% when the Pb(NO₃)₂ concentration raised to 2500 mg/L, confirming the incorporation of Pb²⁺ cations into the fungal EPS during the sorption. For the survived R1 cells, function of polysaccharides to resist Pb toxicity only worked at extremely high Pb(NO₃)₂ levels (>= 1500 mg/L). In contrast, proteins showed continuously enhanced ability to resist Pb toxicity, consistent with their increasing content (per cell) in the EPS. Moreover, ATR-IR spectra showed that the intensity of amide II peak at 1540 cm⁻¹ was significantly increased, indicating elevated glutathione (GSH) in EPS. This suggested that GSH could be the critical Pb-binding component in EPS proteins. This study hence elucidated roles of polysaccharides and proteins in EPS under the toxicity caused by heavy metals.

23350. 题目: Effects of Vertical Hydrodynamic Mixing on Photomineralization of Dissolved Organic Carbon in Arctic Surface Waters
文章编号: N19030906
期刊: Environmental Science: Processes Impacts
作者: Angang Li, Antoine Aubeneau, Tyler King, Rose M. Cory, Bethany Neilson, Diogo Bolster, Aaron Packman
更新时间: 2019-03-09
摘要: Photomineralization, the transformation of dissolved organic carbon (DOC) to CO₂ by sunlight, is an important source of CO₂ in arctic surface waters. However, quantifying the role of photomineralization in inland waters is limited by understanding of hydrologic controls on this process. To bridge this gap, this study evaluates mixing limitations, i.e., whether and by how much vertical mixing limits the depth-integrated photomineralization rate, in freshwater systems. We developed a conceptual model to qualitatively assess mixing limitations across the range of light attenuation and hydrologic conditions observed in freshwaters. For the common case of exponential light attenuation over depth, we developed a mathematical model to quantify mixing limitation, and used this model to assess a range of arctic freshwater systems. The results demonstrate that mixing limitations are important when there is significant light attenuation by suspended sediment (SS), which is the case in some arctic, boreal and temperate waters. Mixing limitation is pronounced when light attenuation over depth is strong and when the photomineralization rate at the water surface exceeds the vertical mixing rate. Arctic streams and rivers have strong vertical mixing relative to surface photomineralization, such that model results demonstrate no mixing limitation regardless of how much SS is present. Our analysis indicates that well-mixed assumptions used in prior work are valid in many, but not all, arctic surface waters. The effects of mixing limitations in reducing the photomineralization rate must be considered in arctic lakes with high SS concentrations.

23351. 题目: Nutrient retention by different substrates from an improved low impact development system
文章编号: N19030905
期刊: Journal of Environmental Management
作者: Junjie Zhou, Xinqiang Liang, Shengdao Shan, Dawei Yan, Yanfeng Chen, Chunke Yang, Yuanyuan Lu, Christophe Niyungeko, Guangming Tian
更新时间: 2019-03-09
摘要: The reuse of water in agriculture has become more common in water management worldwide. However, there is very limited information about nutrient retention in water reclamation management. In this study, an improved low impact development (LID) practice was constructed to investigate the synergistic effects of three substrates amendment on nitrogen (N) and phosphorus (P) retention under two irrigation modules: spray and drip irrigation. The orthogonal combination of the three substrates was controlled during four leaching events, with polyacrylamide (PAM), peat soil, and straw biochar application rates of 1, 2, and 4 g kg⁻¹; 5, 10, and 20 g kg⁻¹; and 10, 20, and 40 g kg⁻¹, respectively. Results showed that the optimum treatments for N and P were 2 g kg⁻¹ of PAM; 2 g kg⁻¹ of PAM, 10 g kg⁻¹ of peat soil, and 40 g kg⁻¹ of straw biochar, respectively. The highest amounts of N and P retention under spray and drip irrigation were 83.12 mg N kg⁻¹ and 50.09 mg N·kg⁻¹, and 11.88 mg P·kg⁻¹ and 7.47 mg P·kg⁻¹, respectively. The analysis of variance indicated that PAM, biochar, and peat soil affected the retention of leachate, N, and P differently. PAM application could not only improve the water, N, P retention capacity of soil, but also significantly increase the content of ＞2 mm water-stable soil aggregate (WSA) (p＜0.05), and there is an advisable linear relation between N, P retention and the content of ＞2 mm WSA (R² = 0.79, 0.67, respectively). Overall, this study concludes that a combined application of PAM and biochar could reduce P loss and increase the ＞2 mm WSA under leaching condition.

23352. 题目: Post – Mining soil as carbon storehouse under polish conditions
文章编号: N19030904
期刊: Journal of Environmental Management
作者: Agnieszka Placek-Lapaj, Anna Grobelak, Krzysztof Fijalkowski, Bal Ram Singh, Åsgeir R. Almås, Malgorzata Kacprzak
更新时间: 2019-03-09
摘要: The main aim of these studies was to determine the potential for carbon sequestration in brown coal open-cast mine by phytoremediation using scots pine (Pinus sylvestris L.) and giant miscanthus (Miscanthus x giganteus) plants. This paper presents relationships between soil organic carbon (SOC) sequestration and carbon phytosequestration in waste dump associated with open-cast lignite mine in Central Poland. The research is the continuation of previously carried out experiments, but was conducted in field conditions. In reclamation of post-mining landscapes, during field experiment, an effect of sewage sludge, compost and lake chalk amendments and in combination of plants was investigated. The impact of soil amendments on carbon stock, CO₂ emission reduction, plant biomass production and carbon content in shoots and roots was studied. The highest SOC stock was found in soil treated with sewage sludge (33 Mg*ha⁻¹) and compost (45 Mg*ha⁻¹) stabilized by lake chalk. These fertilizer combinations also contributed the most in relation to CO₂ emission reduction through SOC stock (83 Mg*ha⁻¹ and 127 Mg*ha⁻¹ respectively). In addition, greater amounts (60–100%) of soil organic matter was converted into humic acids fraction. This phenomenon could be the initial stage of the progressive process of organic matter deposition and carbon sequestration in post-mining area. Carbon phytosequestration was determined through carbon bound in plant tissues. The highest carbon content (60%) in both plant species was recorded in treatments with sewage sludge and compost with lake chalk. Stabilization of compost by lake chalk application was good method to improve the efficiency of carbon sequestration in soil and carbon phytosequestration. Improving the efficiency of these two processes, through skillfully selected soil additives and plant species, may be used on a larger scale in the future as an alternative to the storage of carbon dioxide, especially in degraded areas.

23353. 题目: Clay-biochar composites for sorptive removal of tetracycline antibiotic in aqueous media
文章编号: N19030903
期刊: Journal of Environmental Management
作者: K.S.D. Premarathna, Anushka Upamali Rajapaksha, Nadeesh Adassoriya, Binoy Sarkar, Narayana M.S. Sirimuthu, Asitha Cooray, Yong Sik Ok, Meththika Vithanage
更新时间: 2019-03-09
摘要: The focus of this research was to synthesize novel clay-biochar composites by incorporating montmorillonite (MMT) and red earth (RE) clay materials in a municipal solid waste (MSW) biochar for the adsorptive removal of tetracycline (TC) from aqueous media. X-ray Fluorescence Analysis (XRF), Fourier Transform Infrared Spectroscopy (FTIR), Powder X-ray Diffraction (PXRD) and Scanning Electron Microscopy (SEM) were used for the characterization of the synthesized raw biochar (MSW-BC) and clay-biochar composites (MSW-MMT and MSW-RE). Results showed that minute clay particles were dispersed on biochar surfaces. The FTIR bands due to Si-O functional group vibrations in the spectra of the clay-biochar composites provided further evidence for successful composite formation. The kinetic TC adsorption data of MSW-MMT were well fitted to the Elovich model expressing high surface activity of biochar and involvement of multiple mechanisms in the adsorption. The kinetic TC adsorption data of MSW-BC and MSW-RE were fitted to the pseudo second order model indicating dominant contribution of chemisorption mechanism during the adsorption. The adsorption differentiation obtained in the kinetic studies was mainly due to the structure of the combined clay material. The adsorption isotherm data of all the adsorbents were well fitted to the Freundlich model suggesting that the adsorption of TC onto the materials occurred via both physisorption and chemisorption mechanisms. In comparison to the raw biochar and MSW-RE, MSW-MMT exhibited higher TC adsorption capacity. Therefore, MSW-MMT clay-biochar composite could be applied in the remediation of TC antibiotic residues in contaminated aqueous media.
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23354. 题目: Microbial groups and their functions control the decomposition of coniferous litter: A comparison with broadleaved tree litters
文章编号: N19030902
期刊: Soil Biology and Biochemistry
作者: Weiwei Zhang, Kai Yang, Zhitang Lyu, Jiaojun Zhu
更新时间: 2019-03-09
摘要: The conversion of secondary forests to pure coniferous plantations leads to a decrease in soil quality partly because of the slow decomposition rate of coniferous litter. Microbial decomposers directly regulate the decomposition process. However, little is known about how litter type and microbial communities including both bacteria and fungi interact to affect decomposition rates. A field experiment was performed consisting of seven treatments (i.e., four tree litters: Quercus mongolica, Juglans mandshurica, Acer mono, and Larix gmelinii) in which either monospecific litters or mixtures of larch litter with each broadleaved tree litter (mass ratio was 1:1) were placed into litterbags, and the microbial community composition and enzyme activities were measured. The results showed that in monospecific litters, the highest mass loss was observed in Acer litter, followed by Quercus, Juglans, and Larix litters. Furthermore, synergistic non-additive mixture effects were found in the Larix-Acer and Larix-Quercus mixtures. Most of the abundant bacterial taxa and potential functional genes encoding the hydrolytic enzymes were not significantly affected by the litter type. In contrast, each litter type was characterized by a specific fungal community, as well as different patterns of extracellular enzyme activity. The most abundant fungal decomposers in Larix litter during the first 540 days of decomposition, such as Meria, Lambertella, Venturia, and Ochroconis, were negatively correlated with most of the enzymatic activities, which possibly explains the slower decomposition rate of Larix litter. In conclusion, mixing Larix litter with broadleaved litters could change the microbial community composition, and accelerate the decomposition of hemicelluloses, and lignin. Introducing broadleaved tree species with fast litter turnover rates by allowing natural regeneration and planting broadleaved tree species in pure larch plantations may be an effective way to restore soil quality in temperate forest regions.

23355. 题目: Methane levels in five shallow lakes in China: Effect of lake paludification
文章编号: N19030901
期刊: Quaternary International
作者: Lingling Li, Shuchun Yao, Bin Xue, Longjuan Cheng, Renhua Yan
更新时间: 2019-03-09
摘要: Understanding methane dynamics in lakes is relevant for assessing the natural source of greenhouse gases. Paludification is one of the most common phenomena of lake degeneration, which would have significant influence on CH₄ dynamics. However, the actual variety of CH₄ dynamics by lake paludification is not yet clear. We investigated CH₄ concentrations and production potentials in five shallow lakes located in the east China. The CH₄ concentrations and production potentials were significantly higher (approximately 5–10 times) in the lakes with greater paludification degrees and had no significant difference among other lakes with low and similar paludification indexes. High CH₄ levels in the paludificated lakes can be associated with the increase of sediment organic matter content and decrease of water depth due to the accelerated sedimentation and outspread of macrophytes during the lake paludification. Similarly, organic matter supply might be a limitation for CH₄ production in the lakes with low paludification degrees. These results indicate that lake paludification is probably a main reason for the significant CH₄ differences among the studied lakes. This study draws attention to lakes with paludification tendency when making CH₄ emission budgets in shallow lakes.

23356. 题目: Significant organic carbon accumulation in two coastal acid sulfate soil wetlands
文章编号: N19030819
期刊: Geophysical Research Letters
作者: Dylan R. Brown, Scott G. Johnston, Isaac R. Santos, Ceylena J. Holloway, Christian J. Sanders
更新时间: 2019-03-08
摘要: Restoring degraded freshwater wetlands may help to maximize soil carbon sequestration. In this study, we use eighteen ²¹⁰Pb‐dated sediment cores to determine the organic carbon (OC) accumulation rates from two hydrologically restored freshwater coastal acid sulfate soil (CASS) wetlands. Recent OC accumulation rates (from ~1980 to present) were estimated to be 251 ± 26 g m^‐2 yr^‐1 in the seasonally inundated CASS and 227 ± 50 g m^‐2 yr^‐1 in the permanently inundated CASS. The average OC accumulation during the previous century (190 ± 20 g m^‐2 yr^‐1) was within the range of blue carbon ecosystems (saltmarshes, mangroves and seagrasses). Considering their large area and carbon accumulation rate, we estimate that Australian CASS wetlands sequester approximately 7.8 ± 0.8 Tg of carbon annually which is equivalent to ~8% of the CO₂ emission from fossil fuels in Australia. Hence, preserving or restoring CASS may be a good climate change mitigation strategy.

23357. 题目: Land inundation and cropping intensity influences on organic carbon in the agricultural soils of Bangladesh
文章编号: N19030818
期刊: CATENA
作者: M.J. Uddin, Peter S. Hooda, A.S.M. Mohiuddin, Mike Smith, Martyn Waller
更新时间: 2019-03-08
摘要: Land inundation is a common occurrence in Bangladesh, mainly due to the presence of two major river systems – the Brahmaputra and the Ganges. Inundation influences land use and cropping intensity. However, there is little information on the influences of the extent of flooding and cropping intensity has on soil organic carbon (SOC), particularly at the landscape level. To investigate these influences, we collected 268 surface (0–30 cm) soil samples from 4 large sites within the two alluviums deposits (the Brahmaputra river and the Ganges river), on a regular grid (1600 m). The findings show that SOC levels are generally low, reflecting the intensity of agriculture and land management practices. SOC variability was higher across the medium high land (MHL) and medium low land (MLL) sites than in the high land (HL) and low land (LL) sites. The relatively low SOC levels and variability in the HL sites indicate soils here might have reached to equilibrium levels due to higher land use intensity. Topographically higher lands (HL and MHL), due to less of inundation, had higher cropping intensities and lower SOC's than lower lands (MLL and LL), which had lower cropping intensities, as they remain inundated for longer periods of time. The findings clearly demonstrate the intrinsic influence of land inundation in driving cropping intensity, land management practices and SOC levels.

23358. 题目: Effects of peat decomposition on δ¹³C and δ¹⁵N depth profiles of Alpine bogs
文章编号: N19030817
期刊: CATENA
作者: Simon Drollinger, Yakov Kuzyakov, Stephan Glatzel
更新时间: 2019-03-08
摘要: Decomposition of organic substances is one of the main processes responsible for the signatures of stable carbon and nitrogen isotopes (δ¹³C and δ¹⁵N) in soils and peats. However, the applicability of δ¹³C and δ¹⁵N signatures at the natural abundance level as indicators of the degree of peat decomposition is still debatable. We evaluated δ¹³C and δ¹⁵N depth patterns of peat cores sampled at nine sites in two nearby Alpine peat bogs with varying degree of organic matter degradation. Based on water table depths and past drainage intensities, the peat cores were divided into three degradation classes. We found similar overall depths patterns of δ¹³C and δ¹⁵N across the nine depth profiles and distinct differences between aerobic and anaerobic peat layers. Considerable differences in stable C and N isotope signatures of same depths were detected between profiles of the three classes, whereas depth profiles of peat cores with similar degree in peatland degradation were nearly identical. In the aerobic peat layers, δ¹³C and δ¹⁵N increased with depths at all study sites from 2.6‰ to 4.9‰ for δ¹³C and 3.2‰ to 7.0‰ for δ¹⁵N compared to the initial signatures of the plant biomass. Standardised δ¹³C of aerobic layers differ distinctly between slightly degraded peats at the open peat bog area, intermediately degraded peats at the tree-covered edge areas and strongly degraded peats at the former peat-cutting site. δ¹³C signatures of aerobic layers of strongly degraded peats were markedly more negative compared to the slightly degraded peats because of the selective ¹²C losses by microbial respiration. δ¹⁵N were more positive at strongly degraded than at slightly degraded sites in both, aerobic and anaerobic peat layers. The uniform stable isotope ratios in the anaerobic layers deeper than the local maxima of the isotopic signatures support the assumption that minor ¹³C fractionation occurs under anaerobic conditions. δ¹³C slightly declining with depth in the waterlogged layers of strongly degraded peat reflects the preferential utilisation and loss of labile organic compounds enriched in ¹³C. δ¹⁵N of strongly degraded peats was higher compared to well-conserved peat. The close relationship between the measured δ¹⁵N to δ¹⁵N modelled based on C:N ratios and bulk densities supports the assumption that the δ¹⁵N signature is the result of isotopic fractionation by peat decomposition. We conclude that peat decomposition strongly affects the δ¹³C and δ¹⁵N depth profiles of peat bogs and most likely overrides other factors, such as differences between plant species, litter components, atmospheric δ¹³C shift during peat formation, temperature effects, or type of mycorrhizal symbiosis.

23359. 题目: Biochar amendment and Calamagrostis angustifolia plantation affect sources and production pathways of N2O in agricultural ditch systems
文章编号: N19030816
期刊: Environmental Science: Processes Impacts
作者: Qianding Cheng, Hongguang Cheng, Zhenzhen Wu, Xiao Pu, Lu Lu, Jian Wang, Jinbo Zhao, Aihua Zheng
更新时间: 2019-03-08
摘要: Nitrous oxide (N₂O) from agricultural ditches is a non-negligible source of anthropogenic greenhouse gas (GHG) emissions, but few studies have addressed this topic in depth. On the other hand, although there are numerous reports that biochar application can affect N₂O emissions from soil, the understanding of the process and source of changes is still incomplete. To examine the effect of biochar and Calamagrostis angustifolia on N₂O emissions, we conducted experiments with constructed ditches where corn stalk biochar (pyrolysis temperature of 450℃) was applied at a rate of 16.77 Mg ha^-1 and C. angustifolia was planted. The sources (native sediment versus exogenous inorganic N) and production pathways (nitrification versus denitrification) of N₂O emissions were discriminated using the ¹⁵N isotope tracer method. We observed that biochar application reduced the cumulative total N-N₂O emissions from the native sediment by 10.8-18.7% and reduced the cumulative ¹⁵N-N₂O emissions from the exogenous ¹⁵N-labelled inorganic N by 25.7-68.6%; C. angustifolia planting reduced these cumulative N₂O emissions by 48.8-53.3% and 93.3-92.4%, respectively. The results showed that biochar stimulated nitrification and nitrification-derived ¹⁵N-N₂O emissions, but reduced denitrification-derived ¹⁵N-N₂O emissions in bare sediment microcosms; C. angustifolia effectively reduced both nitrification-derived and denitrification-derived ¹⁵N-N₂O emissions. Therefore, we concluded that the effect of biochar application on N₂O emissions may depend on its dominant N₂O production pathway and biochar application plus C. angustifolia plantation could be beneficial for the mitigation of N₂O emissions in agricultural ditch systems.

23360. 题目: A critical review of clay-based composites with enhanced adsorption performance for metal and organic pollutants
文章编号: N19030815
期刊: Journal of Hazardous Materials
作者: Huawen Han, Muhammad Khalid Rafiq, Tuoyu Zhou, Rong Xu, Ondřej Mašek, Xiangkai Li
更新时间: 2019-03-08
摘要: Adsorption techniques offer unique advantages owing to the use of synthetic (e.g., nanosized metal oxides and polymer-functionalized nanocomposites) and natural (e.g., clay and biochar) materials for pollutant removal. Although the most widely used adsorbent is activated carbon, extensive studies have highlighted the promising potential of modified clay minerals and biochar for removing heavy metal and organic pollutants from industrial, drinking, and eutrophic wastewater, due to their low cost and easy accessibility. However, clay modification using acids, calcination, polymers, or surfactants exhibits relatively low absorption/regeneration ability towards antibiotics, aromatics, and various dyes. The coexistence of numerous contaminants in industrial wastewater inhibited the performance of adsorbents, which accelerated the development of novel modified clay composites such as clay-biochar, organo-bentonite/sodium alginate beads, and enhanced biochar. This review summarizes recent studies and absorption mechanisms concerning clay composites based on various modification methods and component materials. The comparison of clay composites used for the removal of organic and inorganic contaminants provides valuable insight into real wastewater treatment. Knowledge gaps, uncertainties, and future challenges involved in the fabrication and regeneration of modified clay composites are also identified.
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