论文检索

总访问量：6124580次

总访客量：492073人

所有论文

22821. 题目: Changes in soil organic carbon and total nitrogen in apple orchards in different climate regions on the Loess Plateau
文章编号: N20110201
期刊: Catena
作者: Yuanhong Zhang, Rui Wang, Xingxing Peng, Yujiao Zhang, Fang Ning, Zonggui Xu, Qian Wang, Zhaoyang Dong, Guangcan Jia, Li Wei, Jun Li
更新时间: 2020-11-02
摘要:

The Loess Plateau is the largest high-quality apple-producing area in China. However, the responses of soil organic carbon (SOC) and total nitrogen (TN) concentrations and stocks to long-term cultivation in apple orchards under different climate regions remain unclear. We conducted soil sampling in apple orchards distributed throughout the main apple-production area on the Loess Plateau. A total of 28 soil samples (max depth 500 cm) from stands of different ages at 7 soil sampling sites were collected to evaluate the changes in SOC and TN concentrations and stocks; furthermore, C:N ratios across apple orchards in different climate regions were evaluated. Compared with those in the semihumid region, SOC concentration and stock in the 0–500 cm soil profile were 6.6% and 32.1% lower, respectively, in the semiarid region. Furthermore, over the entire soil profile, TN concentration and stock were 12.1% and 38.4% lower, respectively, in the semiarid region than in the semihumid region. However, the C:N ratios in the semiarid region were higher than those in the semihumid region. SOC and TN concentrations generally decreased with increasing soil depth, and those in the 0–120 cm soil layer were significantly higher than those at the other soil depths in both climate regions. The most important factors, which control the variability of SOC and TN, were precipitation, plantation age, topographical properties (altitude and landform of apple orchards) and soil type. These results not only provide information on the effects of changes in SOC and TN concentrations and stocks and C:N ratios but also provide regional-level information that can aid the sustainable development of apple orchards on the Loess Plateau.

22822. 题目: Boron speciation and extractability in temperate and tropical soils: a multi-surface modeling approach
文章编号: N20110104
期刊: Applied Geochemistry
作者: Elise Van Eynde, Liping Weng, Rob N.J. Comans
更新时间: 2020-11-01
摘要:

Boron is an essential micronutrient for plants, but can also be toxic when present in excess in the soil solution. A multi-surface geochemical model was used to assess the important processes that affect the distribution of the geochemically reactive B in soils over the solution and solid phase. The multi-surface model was based on the adsorption of B on dissolved and solid humic acids, representing reactive organic matter, ferrihydrite, representing the Fe and Al (hydr)oxides, and clay mineral edges. In addition, the performance of previously proposed extraction methods for measuring reactive B was evaluated. Based on B measured in 0.01 M CaCl₂ soil extracts (7-85 μmol kg^-1 soil), we calculated the reactive boron concentration for 5 temperate and 5 tropical soils (8-106 μmol kg^-1 soil). We found that extractions with 0.43 M HNO₃ or with 0.2 M mannitol + 0.1 M triethanolamine buffer extract on average 240 and 177 % of the reactive B predicted by the model, thus releasing additional B that is assumed to be not or only very slowly available for exchange with the soil solution. Reactive B calculated by the model corresponded best to the B measured in a 0.05 M KH₂PO₄ (pH 4.5) extraction. In general, the multi-surface modeling showed that 68 % or more of reactive boron was present in the solution phase for the soils in this study and that the adsorption was dominated by oxides in the tropical soils, while solid organic matter was the main adsorbent in the temperate soils. When changing the soil pH(CaCl₂), B concentration was found to decrease with increasing pH, and both experimental data and modelling suggests that this effect is mainly due to increased binding of B to organic matter.

22823. 题目: V V Reduction by Polaromonas spp. in Vanadium Mine Tailings
文章编号: N20110103
期刊: Environmental Science & Technology
作者: Xiaoxu Sun, Lang Qiu, Max Kolton, Max Häggblom, Rui Xu, Tianle Kong, Pin Gao, Baoqin Li, Chengjian Jiang, Weimin Sun
更新时间: 2020-11-01
摘要: Vanadium (V) is an important metal with critical industrial and medical applications. Elevated V contamination, however, can be a threat to the environment and human health. Microorganisms can reduce the more toxic and mobile VV to the less toxic and immobile VIV, which could be a detoxification and energy metabolism strategy adopted by V-reducing bacteria (VRB). The limited understanding of microbial responses to V contamination and the mechanisms for VV reduction, however, hamper our capability to attenuate V contamination. This study focused on determining the microbial responses to elevated V concentration and the mechanisms of VV reduction in V tailings. The bacterial communities were characterized and compared between the V tailings and the less contaminated adjacent mineral soils. Further, VV-reducing enrichments indicated that bacteria associated with Polaromonas, a genus belonging to the family Burkholderiaceae, were potentially responsible for VV reduction. Retrieved metagenome-assembled genomes (MAGs) suggested that the Polaromonas spp. encoded genes (cymA, omcA, and narG) were responsible for VV reduction. Additionally, Polaromonas spp. was metabolically versatile and could use both organic and inorganic electron donors. The metabolic versatility of Polaromonas spp. may be important for its ability to flourish in the V tailings.

22824. 题目: Converting alfalfa pasture into annual cropland achieved high productivity and kept soil organic carbon in a semiarid area
文章编号: N20110102
期刊: LAND DEGRADATION AND DEVELOPMENT
作者: Xu‐Long Zhang, Yang‐Yang Zhao, Wen‐Juan Gao, Xin Song, Xin‐Tan Zhang, Xiao‐Yan Shi, Feng‐Min Li
更新时间: 2020-11-01
摘要:

Converting alfalfa (Medicago sativa L.) into cropland (rotated cropland, RC) is a common way of land use to reuse degraded alfalfa pasture. However, it is a big challenge for RC to achieve high productivity and maintain high soil organic carbon (SOC) achieved by previous alfalfa. We converted a long‐term alfalfa pasture into RC in 2010, and study the effects of fertilization on soil moisture, crop productivity, and SOC in RC and continuous cropland (CC), both under plastic film mulching, from 2010 to 2018. Before the conversion, alfalfa pasture had higher SOC (12.3%) and total N (7.7%) compared to CC. However, it not only occurred severe soil desiccation, but the available P and inorganic‐N were only about 39.4% and 25.1% of CC. After the conversion, soil moisture in RC at 0‐0.6 m restored up to CC only after one year, and restored to 95.3% and 69.2% of CC at 0.6‐2 and 2‐5 m throughout nine‐years. Crop yield and biomass in RC with fertilization were not significant to CC since the third year due to the increased available P and inorganic‐N, and sufficient soil moisture restoration at 0‐0.6 m. SOC in RC without fertilization decreased by 8.1% throughout nine‐years, while RC with fertilization consistently kept SOC up with previous alfalfa due to the increased biomass, inorganic‐N, and total N. These findings help to eliminate concerns about the continuously low production and rapid decline of SOC in croplands converted from alfalfa and support for sustainable high‐productivity and high SOC sequestration in dryland farming.

This article is protected by copyright. All rights reserved.

22825. 题目: Enhanced adsorption of tetracycline by an iron and manganese oxides loaded biochar: Kinetics, mechanism and column adsorption
文章编号: N20110101
期刊: Bioresource Technology
作者: Xin Zhang, Yaru Li, Mengru Wu, Yao Pang, Zhenbing Hao, Mian Hu, Rongliang Qiu, Zhihua Chen
更新时间: 2020-11-01
摘要:

A Fe/Mn oxides loaded biochar (FeMn-BC) was prepared to enhance the adsorption of tetracycline (TC). γ-Fe₂O₃ and MnO₂ were assigned to the Fe and Mn oxides, respectively. The enhanced adsorption of TC was dominated by the loaded γ-Fe₂O₃ and MnO₂. According to Akaike-Information-Criteria evaluation, Elovich kinetic and Langmuir isotherm models could best describe the adsorption with a maximum capacity of 14.24 mg/g. During adsorption process, the γ-Fe₂O₃ and MnO₂ hydrolyzed into hydroxides (FeOOH and MnOOH) which acted as bases to complex with TC²⁻ ion under alkaline condition (pH = 11). After the adsorption, the concentrations of leached Fe and Mn could meet the requirements PRC standards GB13456-2012 and GB8978-1996, respectively. The FeMn-BC had ~24% on TC removal (initial concentration of 20 mg/L) after four-cycles regeneration. The FeMn-BC was also available for TC adsorptions in column tests and actual wastewater.

22826. 题目: Reviews and syntheses: The mechanisms underlying carbon storage in soil
文章编号: N20103103
期刊: Biogeosciences
作者: Isabelle Basile-Doelsch, Jérôme Balesdent, Sylvain Pellerin
更新时间: 2020-10-31
摘要: Soil organic matter (OM) represents a key C pool for climate regulation but also an essential component for soil functions and services. Scientific research in the 21st century has considerably improved our knowledge of soil organic matter and its dynamics, particularly under the pressure of the global disruption of the carbon cycle. This paper reviews the processes that control C dynamics in soil, the representation of these processes over time, and their dependence on variations in major biotic and abiotic factors. The most recent advanced knowledge gained on soil organic matter includes the following. (1) Most organic matter is composed of small molecules, derived from living organisms, without transformation via additional abiotic organic polymerization; (2) microbial compounds are predominant in the long term; (3) primary belowground production contributes more to organic matter than aboveground inputs; (4) the contribution of less biodegradable compounds to soil organic matter is low in the long term; (5) two major factors determine the soil organic carbon production yield from the initial substrates: the yield of carbon used by microorganisms and the association with minerals, particularly poorly crystalline minerals, which stabilize microbial compounds; (6) interactions between plants and microorganisms also regulate the carbon turnover time and therefore carbon stocks; (7) among abiotic and biotic factors that regulate the carbon turnover time, only a few are considered in current modeling approaches (i.e., temperature, soil water content, pH, particle size, and sometimes C and N interactions); and (8) although most models of soil C dynamics assume that the processes involved are linear, there are now many indications of nonlinear soil C dynamics processes linked to soil OM dynamics (e.g., priming). Farming practices, therefore, affect soil C stocks not only through carbon inputs but also via their effect on microbial and organomineral interactions, yet it has still not been possible to properly identify the main mechanisms involved in C loss (or gain). Greater insight into these mechanisms and their interdependencies, hierarchy and sensitivity to agricultural practices could provide future levers of action for C sequestration in soil.

22827. 题目: Complex interactions of in-stream DOM and nutrient spiralling unravelled by Bayesian regression analysis
文章编号: N20103102
期刊: Biogeosciences
作者: Matthias Pucher, Peter Flödl, Daniel Graeber, Klaus Felsenstein, Thomas Hein, Gabriele Weigelhofer
更新时间: 2020-10-31
摘要: Uptake and release patterns of dissolved organic matter (DOM) compounds and nutrients are entangled, and the current literature does not provide a consistent picture of the link between DOM composition, nutrient concentrations, and effects on their cycling. We performed two plateau addition experiments for each of five different, realistic, complex DOM leachates in a small stream, heavily enriched in nitrate but not phosphate or DOM due to diffuse agricultural pollution. By including cow and pig dung as well as corn, leaves and nettles leachates, the study used a wide range of different DOM qualities. We measured changes in nutrient concentrations and determined DOM fractions by fluorescence measurements and parallel factor (PARAFAC) decomposition. To assess influences from hydrological transport processes, we used a 1-D hydrodynamic model. We propose a non-linear Bayesian approach to the nutrient spiralling concept, the Interactions in Nutrient Spirals using BayesIan REgression (INSBIRE) approach. This approach can disentangle complex and interacting biotic and abiotic drivers in nutrient uptake metrics, show their variability and quantify their error distribution. Furthermore, previous knowledge on nutrient spiralling can be included in the model using prior probability distributions. We used INSBIRE to assess interactions of compound-specific DOM and nutrient spiralling metrics the data of our experiment. The uptake processes of different DOM fractions were linked to each other. We observed stimulating and dampening effects of DOM fractions on each other and the overall DOM uptake. We found saturation effects for dissolved organic carbon (concentration of C, DOC) uptake, as rising concentrations of a DOM fraction dampened its uptake. The degradation of a humic DOM component of terrestrial origin was stimulated by other DOM fractions, pointing to priming effects. We also found an influence of the wetted width on the uptake of soluble reactive phosphorus (SRP) and a microbially derived humic substance, which indicates the importance of the sediment-water interface for P and humic C cycling in the studied stream. Interestingly, we found no interactions between DOM uptake and nitrate or SRP concentrations, or any effect of the added DOM leachates on nitrate uptake, indicating that the increase in DOC concentrations and SRP concentrations were not sufficient to affect the relatively steady nitrate uptake during the experiments. Overall, we show that bulk DOC is a weak predictor of DOC uptake behaviour for complex DOM leachates and that individual DOM compound uptake, nitrate uptake and SRP uptake are controlled very differently within the same aquatic ecosystem. We also found effects of hydromorphology on the uptake of one humic fluorophore and SRP. We conclude that cycling of different C fractions, their interaction and interactions with N and P uptake in streams is a complex, non-linear problem, which can only be assessed with advanced non-linear approaches, such as we present with INSBIRE.

22828. 题目: Significant increase of assimilable organic carbon (AOC) levels in MBR effluents followed by coagulation, ozonation and combined treatments: Implications for biostability control of reclaimed water
文章编号: N20103101
期刊: Frontiers of Environmental Science & Engineering
作者: Xiaojie Shi, Zhuo Chen, Yun Lu, Qi Shi, Yinhu Wu, Hong-Ying Hu
更新时间: 2020-10-31
摘要: As water reuse development has increased, biological stability issues associated with reclaimed water have gained attention. This study evaluated assimilable organic carbon (AOC) in effluents from a full-scale membrane biological reactor (MBR) plant and found that they were generally stable over one year (125-216 µg/L), with slight increases in warmer seasons. After additional tertiary treatments, the largest increases in absolute and specific AOCs were detected during ozonation, followed by coagulation-ozonation and coagulation. Moreover, UV₂₅₄ absorbance is known to be an effective surrogate to predict the AOC changes during ozonation. Applying coagulation prior to ozonation of MBR effluents for removal of large molecules was found to reduce the AOC formation compared with ozonation treatment alone. Finally, the results revealed that attention should be paid to seasonal variations in influent and organic fraction changes during treatment to enable sustainable water reuse.

22829. 题目: Formation of carbonaceous and nitrogenous iodinated disinfection byproducts from biofilm extracellular polymeric substances by the oxidation of iodide-containing waters with lead dioxide
文章编号: N20103003
期刊: Water Research
作者: Jun Hu, Yiran Xu, Ying Chen, Jiang Chen, Huiyu Dong, Jianming Yu, Zhimin Qiang, Jiajia Qu, Jianmeng Chen
更新时间: 2020-10-30
摘要:

Lead dioxide (PbO₂) is an important form of lead mineral scales in drinking water pipes. Iodide (I⁻) widely presents in source waters and can be thermodynamically oxidized by PbO₂ to the reactive iodine species (I₂/HOI). Biofilm extracellular polymeric substances (EPS) are nonnegligible precursors of disinfection byproducts (DBPs). The aim was to study the oxidation of I⁻ by PbO₂ and formation of iodinated DBPs (I-DBPs) from EPS. At a high molar ratio of PbO₂ to I⁻ (> 100), the observed rate constants of I⁻ oxidation decreased as pH increased from 6.0 to 9.0 with an H⁺ dependence of 0.79, and the rate constant (k) was 1.6 × 10¹¹ M^−2.79 s⁻¹. Most of formed I₂/HOI (> 92%) was transformed to organic iodine in the presence of EPS. EPS had a lower formation potential (FP) of carbonaceous I-DBPs (C-IDBPs), while a higher that of nitrogenous I-DBPs (N-IDBPs) than HA, resulting in a higher Chinese Hamster Ovary cell cytotoxicity. Generally, the formation of I-DBPs decreased with the increase of pH due to the reduction of surface positive charge and electrochemical driving force. PbO₂ dose and I⁻ concentration also had a significant effect on the I-DBPs formation. EPS proteins had a higher FP of both C- and N-IDBPs than polysaccharides on account of more electrophilic sites and higher nitrogen content. In proteins, aspartic acid was the main contributor to triiodomethane and iodoacetic acids formation, whereas aspartic acid, asparagine and tyrosine were the major precursors of diiodoacetonitrile and diiodoacetamide. The study helps to improve the control strategy of I-DBPs when biofilm outbreaks in lead-containing water pipes.

22830. 题目: Characterising organic carbon sources in Anthropocene affected Arctic upland lake catchments, Disko Island, West Greenland
文章编号: N20103002
期刊: Biogeosciences
作者: Mark A. Stevenson, Suzanne McGowan, Emma J. Pearson, George E. A. Swann, Melanie J. Leng, Vivienne J. Jones, Joseph J. Bailey, Xianyu Huang, Erika Whiteford
更新时间: 2020-10-30
摘要: The Arctic is rapidly changing, disrupting biogeochemical cycles and the processing, delivery and sedimentation of carbon (C), in linked terrestrial-aquatic systems. In this investigation, we coupled a hydrogeomorphic assessment of catchment soils, sediments and plants with a recent lake sediment sequence to understand the source and quality of organic carbon present in three Arctic upland lake catchments on Disko Island, located just south of the Low-High Arctic transition zone. This varied permafrost landscape has exposed soils with less vegetation cover at higher altitudes, and all lakes received varying extent of glacial meltwater inputs. We provide improved isotope and biomarker source identifications for palaeolimnological studies in high latitude regions, where terrestrial vegetation is at or close to its northerly and altitudinal range limit. The poorly developed catchment soils lead to lake waters with low dissolved organic carbon (DOC) concentrations (≤ 1.5 mg L⁻¹). Sedimentary Carbon / Nitrogen (C / N) ratios, the C isotope composition of organic matter (δ¹³C_org) and biomarker ratios (n-alkanes, n-alkanols, n-alkanoic acids and sterols) showed that sedimentary organic matter (OM) in these lakes is mostly derived from aquatic sources (algae and macrophytes). We used a 210 Pb dated sediment core to determine how carbon cycling in a lake-catchment system (Disko 2) had changed over recent centuries. Recent warming since the end of the Little Ice Age (LIA ~1860 AD), which accelerated after ca. 1950, led to melt of glacier ice and permafrost releasing nutrients and DOC to the lake, stimulating pronounced aquatic algal production, as shown by a > 10 fold increase in β-carotene, indicative of a major regime shift. Our findings highlight that in Arctic lakes with sparsely developed catchment vegetation and soils, recent Anthropocene warming results in pronounced changes to in-lake C processing and the deposition of more reactive, predominately autochthonous C, compared with extensively vegetated low Arctic systems.

22831. 题目: Microbial inputs at the litter layer translate climate into altered organic matter properties
文章编号: N20103001
期刊: GLOBAL CHANGE BIOLOGY
作者: Lukas Kohl, Allison Myers‐Pigg, Kate A. Edwards, Sharon A. Billings, Jamie Warren, Frances Podrebarac, Susan E. Ziegler
更新时间: 2020-10-30
摘要:

Plant litter chemistry is altered during decomposition but it remains unknown if these alterations, and thus the composition of residual litter, will change in response to climate. Selective microbial mineralization of litter components and the accumulation of microbial necromass can drive litter compositional change, but the extent to which these mechanisms respond to climate remains poorly understood. We addressed this knowledge gap by studying needle litter decomposition along a boreal forest climate transect. Specifically, we investigated how the composition and/or metabolism of the decomposer community varies with climate, and if that variation is associated with distinct modifications of litter chemistry during decomposition. We analyzed the composition of microbial phospholipid fatty acids (PLFA) in the litter layer and measured natural abundance δ¹³C_PLFA values as an integrated measure of microbial metabolisms. Changes in litter chemistry and δ¹³C values were measured in litterbag experiments conducted at each transect site. A warmer climate was associated with higher litter nitrogen concentrations as well as altered microbial community structure (lower fungi:bacteria ratios) and microbial metabolism (higher δ¹³C_PLFA). Litter in warmer transect regions accumulated less aliphatic‐C (lipids, waxes) and retained more O‐alkyl‐C (carbohydrates), consistent with enhanced ¹³C‐enrichment in residual litter, than in colder regions. These results suggest that chemical changes during litter decomposition will change with climate, driven primarily by indirect climate effects (e.g. greater nitrogen availability and decreased fungi:bacteria ratios) rather than direct temperature effects. A positive correlation between microbial biomass δ¹³C values and ¹³C‐enrichment during decomposition suggests that change in litter chemistry is driven more by distinct microbial necromass inputs than differences in the selective removal of litter components. Our study highlights the role that microbial inputs during early litter decomposition can play in shaping surface litter contribution to soil organic matter as it responds to climate warming effects such as greater nitrogen availability.

22832. 题目: Cutting oil-water emulsion wastewater treatment by microwave assisted catalytic wet peroxide oxidation
文章编号: N20102906
期刊: Separation and Purification Technology
作者: Alicia L. Garcia-Costa, Angela Luengo, Juan A. Zazo, Jose A. Casas
更新时间: 2020-10-29
摘要:

Cutting-oil in water emulsions (COWE) suppose an environmental threat due to their high volume, stability and low biodegradability (BOD₅/COD: 0.07). So far, these effluents have been treated by physical methods which merely transfer the pollutants into another phase. In this work, Microwave-assisted Catalytic Wet Peroxide Oxidation (MW-CWPO) is used for the first time in the degradation of COWE 0.5%w, using graphite as catalyst. Working at pH₀: 9, graphite: 10 g/L, 15.7 g/L H₂O₂, at MW power of 800 W by pulsation method, complete demulsification and 82% Total Organic Carbon (TOC) removal is achieved in only 10 min. Furthermore, the remaining TOC in solution is mainly ascribed to malonic, acetic and formic acids, which results in readily biodegradable effluents (BOD₅/COD: 0.93). The degradation mechanism is a complex combination of H₂O₂-mediated adsorption of the pollutants onto the graphite's surface and its subsequent oxidation mediated by hot-spots induced by MW radiation. This work also studies the influence of pH₀, catalyst load and H₂O₂ dosage in COWE degradation. Finally, catalyst stability upon 3 consecutive cycles was tested and various techniques are proposed and examined for catalyst regeneration.

22833. 题目: Biomarker constraints on Mediterranean climate and ecosystem transitions during the Early-Middle Miocene
文章编号: N20102905
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Aura C. Salocchi, Julia Krawielicki, Timothy I. Eglinton, Chiara Fioroni, Daniela Fontana, Stefano Conti, Vincenzo Picotti
更新时间: 2020-10-29
摘要:

Paleoenvironmental and paleoclimatic variations experienced by the Mediterranean region during the mid-Miocene Burdigalian-Langhian interval have been investigated through analysis of biomarker signals (n-alkanes and glycerol dialkyl glycerol tetraethers, GDGTs) from slope mudstones of the northern Apennines (Marne di Vicchio Fm). Terrestrial signatures in marine sediments reflected by preserved long-chain n-alkanes with a identifiable odd-over-even carbon number predominance attest to the thermal immaturity of the sedimentary rock. Abundances of n-C₂₇, n-C₂₉ and n-C₃₁ alkanes, coupled with the carbon isotopic signatures of the n-C₃₁ homologue suggest that Mediterranean vegetation crossed a transition phase adapting to arid conditions that may favored a shift from woodland to wooded grassland during the Middle Miocene. This ecosystem evolution could have been favored by the passage from warm humid conditions to a warm drier climate, as indicated by GDGT-based TEX₈₆ and BIT indexes. Strong similarities between these Mediterranean biomarker records and those from the Atlantic (DSDP Sites 94, 516, 608) imply a constant connection of the western Mediterranean to the Atlantic Ocean from ~19 Ma to ~14.5 Ma.

22834. 题目: Making the Biotic Ligand Model kinetic, easier to develop, and more flexible for deriving water quality criteria
文章编号: N20102904
期刊: Water Research
作者: Wen-Qing Liang, Minwei Xie, Qiao-Guo Tan
更新时间: 2020-10-29
摘要:

In aquatic environments, the ecological risks posed by metals are greatly affected by water chemistry, thereby creating challenges for water quality management. Biotic ligand models (BLMs) have become the most widely used tools to interpret and predict water chemistry effects. Traditional BLM development methods require a large number of toxicity tests and organisms, and model predictions are limited to certain toxicity statistics (e.g., 48-h median effective concentration, 48-h EC₅₀), to which the models were calibrated. To address these limitations, we propose a new method to develop BLMs by integrating them into the toxicokinetic-toxicodynamic (TK-TD) framework. Metal bioaccumulation was predicted from metal exposure and water chemistry using the BLM-type toxicokinetics, whilst metal toxicity was predicted from metal bioaccumulation using the toxicodynamics. Using the new method, we developed a kinetic BLM of cadmium for Daphnia magna with only six toxicity tests and 1540 daphnids; this represents a 60−80% reduction compared to the traditional methods. The model was validated in the presence of commercial dissolved organic matter (DOM) and in natural waters sampled from 12 lakes. The kinetic BLM was able to accurately simulate the protective effects of the commercial DOM by employing the Stockholm humic model, whilst the complexation capabilities of some natural DOM were overestimated. We further used the model to predict Cd EC₅₀ and no-effect concentrations for different waters, generating predictions close to the effect concentrations reported in the literature. Overall, our method requires fewer resources and presents an easier approach to develop BLMs; the kinetic BLM is more flexible and can serve as a useful tool for developing water quality criteria.

22835. 题目: Let more big fish sink: Fisheries prevent blue carbon sequestration--half in unprofitable areas
文章编号: N20102903
期刊: Science advances
作者: Gaël Mariani, William W. L. Cheung, Arnaud Lyet, Enric Sala, Juan Mayorga, Laure Velez, Steven D. Gaines, Tony Dejean, Marc Troussellier, David Mouillot
更新时间: 2020-10-29
摘要: Contrary to most terrestrial organisms, which release their carbon into the atmosphere after death, carcasses of large marine fish sink and sequester carbon in the deep ocean. Yet, fisheries have extracted a massive amount of this blue carbon, contributing to additional atmospheric CO2 emissions. Here, we used historical catches and fuel consumption to show that ocean fisheries have released a minimum of 0.73 billion metric tons of CO2 (GtCO2) in the atmosphere since 1950. Globally, 43.5% of the blue carbon extracted by fisheries in the high seas comes from areas that would be economically unprofitable without subsidies. Limiting blue carbon extraction by fisheries, particularly on unprofitable areas, would reduce CO2 emissions by burning less fuel and reactivating a natural carbon pump through the rebuilding of fish stocks and the increase of carcasses deadfall.

22836. 题目: The effects of temperature on soil phosphorus availability and phosphatase enzyme activities: a cross-ecosystem study from the tropics to the Arctic
文章编号: N20102902
期刊: Biogeochemistry
作者: Alanna N. Shaw, Cory C. Cleveland
更新时间: 2020-10-29
摘要: Earth system models predict large increases in global terrestrial net primary productivity (NPP) over the next century, largely reflecting positive effects of climate change and increasing atmospheric carbon dioxide concentrations on plant growth. However, while theory predicts that soil phosphorus (P) availability may keep pace with P demand as the climate warms, we lack experimental evidence to support this prediction. Here, using a set of laboratory experiments and incubations, we measured both the effect of temperature on the mechanism of biochemical P mineralization—phosphatase (Ptase) enzyme activities—and on rates of soil P mineralization in soils from a range of ecosystem types from the tropics to the Arctic. Consistent with temperature effects on soil nitrogen (N) mineralization, we found that both Ptase activities and P availability in soil increased with temperature following macromolecular rate theory (MMRT) based kinetics. However, across all sites and temperatures, there was no relationship between Ptase activity and mineralized P, indicating that the potential responses of P mineralization with warming vary among ecosystems. The lack of relationship between Ptase and P availability with increasing temperature is consistent with previous work showing that P mineralization rates are also strongly affected by other biotic and abiotic factors, including organic P substrate availability and the geochemical properties of soil. However, our results indicate that the use of Ptase temperature kinetics alone as a proxy for soil P mineralization in terrestrial ecosystems is insufficient to predict future P availability accurately, and modeling efforts that do so will likely overestimate the effects of temperature on soil P availability.

22837. 题目: The Bioavailability Of Dissolved, Particulate, And Adsorbed Organic Carbon In Groundwater Systems
文章编号: N20102901
期刊: Ground Water
作者: Francis H. Chapelle
更新时间: 2020-10-29
摘要:

Dissolved organic carbon (DOC) is the smallest amount of organic carbon present in aquifer systems and is typically dwarfed by amounts of particulate organic carbon (POC) and adsorbed organic carbon (AOC). Research conducted over the last half century, however, has shown that these dissolved, particulate, and adsorbed compartments interact dynamically with each other. That suggests the hypothesis that the bioavailability of DOC in groundwater may indicate the bioavailability of the associated POC and AOC compartments as well. If that proves to be the case, it would greatly simplify the process of evaluating the bioavailability of total organic carbon present in groundwater systems. That hypothesis was examined by (1) comparing DOC bioavailability between two aquifers receiving modern atmospheric recharge, but with the recharge passing through POC/AOC sources of substantially different geologic ages, and (2) measuring POC/AOC bioavailability in sediments in from two aquifers before and after injection with bioavailable DOC consisting of dissolved sugars and emulsified vegetable oil. The results of both comparisons are consistent with the hypothesis that DOC bioavailability in groundwater reflects the bioavailability of the associated POC and AOC compartments and vice versa. Thus, DOC bioavailability may be a useful indicator of an aquifer's potential to drive reduction/oxidation processes that affect the chemical quality of groundwater.

This article is protected by copyright. All rights reserved.

22838. 题目: Engineering porous biochar for capacitive fluorine removal
文章编号: N20102810
期刊: Separation and Purification Technology
作者: Qi Dong, Dongxu Yang, Liang Luo, Qiang He, Fangheng Cai, Si Cheng, Yi Chen
更新时间: 2020-10-28
摘要:

Chronic accumulation of fluoride (F⁻) threats human health and eventually brings about skeletal fluorosis, dental fluorosis and joint deformation, which has aroused global attention. As an emerging technique, electrosorption presented great potential in wastewater purification. The key role in electrosorption is the exploitation of economical, environmentally-friendly and efficient electrode material. Nowadays, many existing investigations on the preparation of porous carbon material focused on the introduction of extra dopant and activation reagent. However, the information concerning the preparation of pure porous biochar and the inherent environmental significance is neglected. Here, a win–win strategy, named conversion waste biomass into porous biochar, has been applied in capacitive fluorine removal. The results indicated that the capacity of porous biochar electrode was 1.28 mg/g, which was improved by 48.8% in contrast to activated carbon electrode. Furthermore, competition experiments revealed concentration-dependence interference in the present of foreign ions. Electrosorption cycle experiment manifested excellent stability of the biochar electrodes. The electrode was regenerated without consuming any chemicals and could produce current for energy recovery. More importantly, continuous-flow experiment showed that the removal efficiency of F⁻ was 91.98% at the synthetic wastewater. High specific capacitance, low internal resistance and appropriate pore distribution were responsible for the F⁻ removal mechanism. Overall, this work would pioneer a facile method in the preparation of low-price electrode material and their potential applications in environmental remediation.

22839. 题目: Combined effects of rice straw-derived biochar and water management on transformation of chromium and its uptake by rice in contaminated soils
文章编号: N20102809
期刊: Ecotoxicology and Environmental Safety
作者: Wendan Xiao, Xuezhu Ye, Zhiqiang Zhu, Qi Zhang, Shouping Zhao, De Chen, Na Gao, Jing Hu
更新时间: 2020-10-28
摘要:

Chromium (Cr) pollution in soil is a global problem owing to its wide industrial use. The mobility, toxicity, and crop uptake of Cr depends on its valence state. Cr(VI) is highly mobile and toxic whereas Cr(III) is generally considered immobile and less toxic. We performed a pot experiment to investigate the combined effects of rice straw-derived biochar and water management on transformation of Cr and its uptake by rice in contaminated soils. The main plots had water management treatments of alternating wetting and drying (AWD) and continuous flooding (CF), and the subplots had three levels of straw biochar (0, 5, and 10 g kg⁻¹). The results showed that water management and the addition of biochar had a significant effect on the dynamics of soil redox potential (Eh), pH, dissolved organic carbon (DOC), and Fe(II) concentration. As these parameters are important factors affecting Cr transformation in paddy soils, the dynamics of the Cr(III) and Cr(VI) concentrations were clearly different under different treatments. The highest reduction of Cr(VI) was observed in the treatment with CF water management in combination with 10 g kg⁻¹ of biochar amendment, which resulted in a 62% reduction of Cr(VI) to Cr(III) in soil. The alterations in the oxidation state of Cr greatly affected its accumulation in the rice grains. The CF combined with 10 g kg⁻¹ of biochar treatment, caused the Cr concentration in rice grains to be 66.2% lower compared with that of the unamended control under AWD water management. Possibly owing to the reduction in phytotoxic effects of Cr(VI), the combined treatment showed an improvement in rice grain weight. In conclusion, the combination of 10 g kg⁻¹ of biochar amendment and CF water management may potentially be used in Cr-contaminated soil to mitigate the impacts of Cr contamination on rice production.

22840. 题目: Nanoscale zerovalent iron, carbon nanotubes and biochar facilitated the phytoremediation of cadmium contaminated sediments by changing cadmium fractions, sediments properties and bacterial community structure
文章编号: N20102808
期刊: Ecotoxicology and Environmental Safety
作者: Xiaomin Gong, Danlian Huang, Yunguo Liu, Dongsheng Zou, Xi Hu, Lu Zhou, Zhibin Wu, Yang Yang, Zhihua Xiao
更新时间: 2020-10-28
摘要:

Environment functional materials have been widely used, but whether their effects on the contaminated environment could facilitate phytoremediation is not yet well understood. In this study, starch stabilized nanoscale zerovalent iron (SN), multiwall carbon nanotubes (MW) and tea waste derived biochar (TB) were used to facilitate the phytoremediation of cadmium (Cd) contaminated sediments by Boehmeria nivea (L.) Gaudich. Results showed that 100 mg/kg SN, 500 mg/kg MW and 500 mg/kg TB facilitated phytoremediation, as evidenced by increasing Cd accumulation and/or promoting plant growth. These concentrations of materials increased the reducible fraction of Cd by 9–10% and decreased the oxidizable proportion of Cd by 48–52%, indicating the improvement of Cd bioavailability through converting the oxidizable Cd into reducible form. The activities of urease, phosphatase and catalase, which related to nutrient utilization and oxidative stress alleviation, increased by 20–24%, 25–26%, and 8–9% in the sediments treated with 500 mg/kg MW and 500 mg/kg TB, respectively. In addition, the 16S rRNA gene sequence results showed that these concentrations of materials changed the bacterial diversity. The abundance of Acidobacteria, Actinobacteria, Nitrospirae and Firmicutes were increased by some of the applied materials, which could promote plant growth, change Cd bioavailability and reduce Cd toxicity. These findings indicated that the applied environment functional materials could facilitate the phytoremediation of Cd contaminated environment by changing Cd fractions, sediments properties and bacterial community structure.