论文检索

主页 | 软件工具 | 课题库 | 公众号
:



总访问量:1074378

总访客量:36313

关键词:
Organic Matter |
DOM |
POM |
Soil OM |
Sediment OM |
Organic Carbon |
Organic Nitrogen |
Biomarker |
Humic Substances |
Fulvic Substances |
Humins |
Biochar |
Black Carbon |
GDGT |
Lignin |
Free Radical |
...
最新文章  | 
昨日文章 | 
前日文章
期刊:
Agriculture, Ecosystems & Environment |
Agricultural Water Management |
Applied Geochemistry |
Applied Soil Ecology |
Aquatic Geochemistry |
Atmospheric Research |
Biogeochemistry |
Biogeosciences |
Biology and Fertility of Soils |
Bioresource Technology |
CATENA |
Chemical Engineering Journal |
Chemical Geology |
Chemosphere |
CLEAN - Soil, Air, Water |
Colloids and Surfaces A: Physicochemical and Engineering Aspects |
Deep Sea Research Part II: Topical Studies in Oceanography |
Earth-Science Reviews |
Ecological Engineering |
Ecology Letters |
Ecology |
Ecotoxicology and Environmental Safety |
Environment International |
Environmental Earth Sciences |
Environmental Geochemistry and Health |
Environmental Monitoring and Assessment |
Environmental Pollution |
Environmental Research |
Environmental Science & Technology |
Environmental Science and Pollution Research |
Environmental Science: Processes Impacts |
Environmental Science: Water Research & Technology |
Environmental Toxicology and Chemistry |
Estuarine, Coastal and Shelf Science |
European Journal of Soil Science |
Forest Ecology and Management |
Geochimica et Cosmochimica Acta |
Geoderma |
Geophysical Research Letters |
Global Change Biology |
Global Biogeochemical Cycles |
Groundwater |
Harmful Algae |
International Journal of Coal Geology |
Journal of Environmental Chemical Engineering |
Journal of Environmental Management |
Journal of Environmental Sciences |
Journal of Geophysical Research: Biogeosciences |
Journal of Geophysical Research: Oceans |
Journal of Hazardous Materials |
Journal of Membrane Science |
Journal of Soils and Sediments |
Land Degradation & Development |
Limnology and Oceanography |
Marine Chemistry |
Marine Pollution Bulletin |
Nature Communications |
Nature Geoscience |
Ocean Science Journal |
Oikos |
Organic Geochemistry |
Palaeogeography, Palaeoclimatology, Palaeoecology |
Plant and Soil |
Progress in Oceanography |
Quaternary International |
Science of The Total Environment |
Sedimentary Geology |
Separation and Purification Technology |
Soil and Tillage Research |
Soil Biology and Biochemistry |
Waste Management |
Water Research |
Water, Air, & Soil Pollution |
Wetlands |
...

所有论文

17321. 题目: Short-term land-use change from grassland to cornfield increases soil organic carbon and reduces total soil respiration
文章编号: N18100201
期刊: Soil and Tillage Research
作者: Ikabongo Mukumbuta, Mariko Shimizu, Ryusuke Hatano
更新时间: 2018-10-02
摘要: Land-use change between grasslands and croplands has a significant influence on soil organic carbon (SOC) and soil respiration (RS). However, the response of the different components of RS to land-use changes and variations in temperature and moisture regimes is poorly understood. This study investigated the responses of RS, heterotrophic respiration (RH) and root respiration (RR) to changes of soil temperature, moisture and nitrogen (N), and changes in SOC, accompanying with land-use changes for 11 years. The study was conducted in a >30-year old permanent grassland (OG; 2005–2009), that was ploughed and converted to a cornfield (2010–2012) and then converted to a new grassland (NG; 2013–2015). Three treatments, chemical fertilizer and manure, chemical fertilizer only, and unfertilized control, were assessed. Fluxes of RS and RH were measured using the closed chamber method. SOC was monitored at 0–15 and 15–30 cm soil depth.On average, RS decreased by 25–43% after conversion from OG to cornfield and then increased by 21–33% after the change from cornfield to NG. Contrary to RS, RH increased by more than 30% following land-use change from OG to cornfield and declined by at least 20% after converting cornfield to NG. The contribution of RH to RS was significantly higher in cornfield (60–100%) than in OG (38–60%) and NG (47–80%). The different trends of RS and RH following land-use change calls for a clear distinction of the CO2 source when reporting its emissions from soil. The influence of soil temperature, moisture and N on RS and RH differed among the land-uses. The conversion of grassland to cornfield significantly increased SOC, especially in the manure-amended plot. This increase in SOC in the first 1–3 years of conversion indicates that conversion or ploughing of grassland is important to turn plant litter/applied manure into actual soil carbon. These results call for a rethink of the commonly held notion that conversion of grassland to cropland depletes SOC, as the conversion could be beneficial if done for shorter time periods.
图文摘要:

17322. 题目: Total mercury in surficial bottom sediments of Volga River’s reservoirs in Central Russia
文章编号: N18100104
期刊: Environmental Earth Sciences
作者: Yury G. Udodenko, Viktor T. Komov, Viktor V. Zakonnov
更新时间: 2018-10-01
摘要: The total mercury content of the surface layer (0–5 cm) of different types of bottom sediment in Gorky and Cheboksary reservoirs was determined. The content of mercury in bottom sediments varied within a wide range, 0.001–0.234 mg/kg. In spite of large industrial enterprises near the watersheds, which are potential sources of mercury in the environment, the content is comparable to background values. Depending on the sediment type, the metal concentration rises within a sequence: sand and loamy sand > sandy loams > clay and silt. The content of mercury positively correlates with the amount of organic matter in bottom sediments (r = 0.49–0.86, p ≤ 0.001) and the proportion of clay silt particles (r = 0.55–0.76, p ≤ 0.001). This relationship indicates the presence of two forms of mercury: sorbed on fine particle surfaces and as part of complex compounds. A negative correlation between Hg concentration and the flow velocity in the reservoir was revealed (r = − 0.40 to − 0.58, p ≤ 0.05). This relationship is due to the effect of pulsating discharge and wind currents on sedimentation conditions, and thus on the accumulation of mercury. The rate of accumulation was calculated as 15 kg/year in Gorky reservoir and 9 kg/year in Cheboksary, with average concentrations of 0.057 and 0.046 mg/kg, respectively, in the surface layer of bottom sediments.

17323. 题目: Mercury Isotopic Fractionation during Pedogenesis in a Tropical Forest Soil Catena (French Guiana): Deciphering the Impact of Historical Gold Mining
文章编号: N18100103
期刊: Environmental Science & Technology
作者: S. Guédron, D. Amouroux, E. Tessier, C. Grimaldi, J. Barre, S. Berail, V. Perrot, M. Grimaldi
更新时间: 2018-10-01
摘要: We used natural mercury (Hg) stable isotopes to investigate the Hg cycle in a rainforest soil catena (French Guiana) partially gold-mined during the early 1950s. Litterfall showed homogeneous Δ199Hg values [−0.18 ± 0.05‰, i.e., a modern gaseous elemental Hg (GEM) isotopic signature]. After litter decomposition, Hg bound to organic matter (OM) is mixed with Hg from pristine (−0.55 ± 0.22‰) or gold-mined (−0.09 ± 0.16‰) mineral materials. Negative Δ199Hg values in deep pristine mineral horizons (−0.60 ± 0.16‰) suggest the transfer of Hg bound to dissolved OM depleted in odd isotopes due to mass-independent fractionation during Hg abiotic reduction. Perennial palm tree leaves collected above gold-mined and pristine soil recorded contrasting Δ199Hg signatures likely resulting from GEM re-emission processes from soils and leaf surfaces. Upslope, soil δ202Hg signatures showed a negative shift (ε ∼ −1‰) with depth attributed to mass-dependent fractionation during Hg sorption and complexation onto iron oxides and dissolved OM. Downslope, higher δ202Hg values in soils resulted from hydromorphy [lower humification, greater Hg(II) reduction, etc.]. The unique Hg isotopic signatures of Amazonian soils probably result in multistep fractionation processes during pedogenesis (millions of years) and in a potentially different Hg isotopic signature of preanthropogenic background GEM.
图文摘要:

17324. 题目: Effects of light and temperature on Mg uptake, growth, and calcification in the proxy climate archive Clathromorphum compactum
文章编号: N18100102
期刊: Biogeosciences
作者: Siobhan Williams, Walter Adey, Jochen Halfar, Andreas Kronz, Patrick Gagnon, David Bélanger, and Merinda Nash
更新时间: 2018-10-01
摘要: The shallow-marine benthic coralline alga Clathromorphum compactum is an important annual- to sub-annual-resolution archive of Arctic and subarctic environmental conditions, allowing reconstructions going back >600 years. Both Mg content, in the high-Mg calcitic cell walls, and annual algal growth increments have been used as a proxy for past temperatures and sea ice conditions. The process of calcification in coralline algae has been debated widely, with no definitive conclusion about the role of light and photosynthesis in growth and calcification. Light received by algal specimens can vary with latitude, water depth, sea ice conditions, water turbidity, and shading. Furthermore, field calibration studies of Clathromorphum sp. have yielded geographically disparate correlations between MgCO3 and sea surface temperature. The influence of other environmental controls, such as light, on Mg uptake and calcification has received little attention. We present results from an 11-month mesocosm experiment in which 123 wild-collected C. compactum specimens were grown in conditions simulating their natural habitat. Specimens grown for periods of 1 and 2 months in complete darkness show that the typical complex of anatomy and cell wall calcification develops in new tissue without the presence of light, demonstrating that calcification is metabolically driven and not a side effect of photosynthesis. Also, we show that both light and temperature significantly affect MgCO3 in C. compactum cell walls. For specimens grown at low temperature (2°C), the effects of light are smaller, with a 1.4mol% MgCO3 increase from low-light (mean = 17lx) to high-light conditions (mean = 450lx). At higher (10°C) temperature there was a 1.8mol% MgCO3 increase from low to high light. It is therefore concluded that site- and possibly specimen-specific temperature calibrations must be applied, to account for effects of light when generating Clathromorphum-derived temperature calibrations.
图文摘要:

17325. 题目: Development of a novel chem-bio hybrid process using biochar supported nanoscale iron sulfide composite and Corynebacterium variabile HRJ4 for enhanced trichloroethylene dechlorination
文章编号: N18100101
期刊: Water Research
作者: Honghong Lyu, Jingchun Tang, Boxiong Shen, Tariq Siddique
更新时间: 2018-10-01
摘要: A sequential chem-bio hybrid process was developed using a novel biochar supported carboxymethyl cellulose-stabilized nanoscale iron sulfide (CMC-FeS@biochar) as a chemical remover and Corynebacterium variabile HRJ4 as a biological agent for trichloroethylene (TCE) degradation. Compared with CMC-FeS, FeS@biochar600, bare FeS and biochar600, the CMC-FeS@biochar600 composite displayed better physiochemical properties (smaller hydrodynamic diameter and higher stability) and demonstrated excellent removal capacity for TCE from aqueous phase. A facultative bacterial strain, Corynebacterium variabile HRJ4, growing well in the presence of CMC-FeS@biochar (added up to 0.25 g L-1), further enhanced TCE removal after chemical treatment. The dechlorination pathway proposed based on the gas chromatography–mass spectrometry (GC-MS) analysis revealed that TCE was dechlorinated to cis-1,2-dichloroethene (cis-DCE) and acetylene via hydrogenolysis and β-elimination, respectively within 12 h by CMC-FeS@biochar. Addition of HRJ4 strain into the reaction system effectively enhanced the degradation of the residual TCE, cis-DCE and acetylene to ethylene. Acetylene was the main product in chemical process, whereas ethylene was the main product in biological process as strain HRJ4 could reduce acetylene to ethylene effectively. The results of this study signify the potential application of CMC-FeS@biochar600/HRJ4 chem-bio hybrid system for complete degradation of TCE in the anaerobic environment.
图文摘要:

17326. 题目: Estimation of chlorophyll a content in inland turbidity waters using WorldView-2 imagery: a case study of the Guanting Reservoir, Beijing, China
文章编号: N18093010
期刊: Environmental Monitoring and Assessment
作者: Xing Wang, Zhaoning Gong, Ruiliang Pu
更新时间: 2018-09-30
摘要: Complex optical properties, such as non-pigment suspension and colored dissolved organic matter (CDOM), make it difficult to achieve accurate estimations of remotely sensed chlorophyll a (Chla) content of inland turbidity. Recent attempts have been made to estimate Chla based on red and near-infrared regions where non-pigment suspension and CDOM have little effect on water reflectance. The objective of this study is to validate the applicability of WV-2 imagery with existing effective estimation methods from MERIS when estimating Chla content in inland turbidity waters. The correlation analysis of measured Chla content and WV-2 imagery bands shows that the Chla sensitive bands of WV-2 are red edge, NIR 1, and NIR 2. The coastal band is designed for seawater Chla detection. However, the high correlation with turbidity data and low correlation with Chla made coastal band unsuitable for estimating Chla in inland waters. The high-resolution water body images were extracted by combining the spectral products (NDWI) with the spatial morphological products (sobel edge detection). The estimation results show that the accuracy of the single band and NDCI is not as good as the two-band method, three-band method, stepwise regression algorithm (SRA) and support vector machines (SVM). The SVM estimation accuracy was the highest with an R2, RMSE, and URMSE of 0.8387, 0.4714, and 19.11%, respectively. This study demonstrates that the two-band and three-band methods are effective for estimating Chla in inland water for WV-2 imagery. As a high-precision estimation method, SVM has great potential for inland turbidity water Chla estimation.

17327. 题目: Forms and buffering potential of aluminum in tropical and subtropical acid soils cultivated with Pinus taeda L
文章编号: N18093009
期刊: Journal of Soils and Sediments
作者: Antonio Neri Azevedo Rodrigues, Antonio Carlos Vargas Motta, Vander Freitas Melo, Gabriel Democh Goularte, Stephen A. Prior
更新时间: 2018-09-30
摘要: Purpose: Several interactions between Al and the solid phase of soil influence Al buffering in soil solution. This work evaluated soils cultivated with Pinus taeda L. to determine Al forms in organic and mineral horizons using various extraction methods and to relate acidity with clay mineralogy. Materials and methods: Organic and mineral horizons of 10 soil profiles (up to 2.1 m deep) in southern Brazil were sampled. Organic horizons were separated into fresh, aged, and fermented/humified litter. The following Al extraction methods were utilized: 0.5 mol L−1 pH 2.8 CuCl2–Al complexed in organic matter; 1.0 mol L−1 KCl–exchangeable Al; water–Al soluble in soil solution; HF concentrated + HNO3 concentrated + H2O2 30% (v/v)–total Al. Six sequential extractions were carried out to isolate different forms of amorphous minerals that can buffer Al on soil solution: 0.05 and 0.1 mol L−1 sodium pyrophosphate; 0.1 and 0.2 mol L−1 ammonium oxalate; 0.25 and 0.5 mol L−1 NaOH. Samples of clay were also analyzed by XRD. Results and discussion: There was a clear effect of litter age on increasing total Al concentration. In the aged litter and fermented and/or humified litter, levels of total Al were 1.4 to 3.8 and 1.5 to 7.8 times greater than in fresh litter, respectively. The CuCl2 method had higher Al extraction capacity than the KCl method for litter. The lowest Al–pyrophosphate values were observed in the Oxisol, which also had a predominance of gibbsite and the lowest levels of Al–KCl and Al–CuCl2. There was an inverse relationship between degree of soil weathering and soluble and exchangeable Al in soils. Available Al increased with higher Si proportion in minerals of the clay fraction (2:1 > 1:1 > 0:1). Conclusions: The worst scenario was soils with the combination of high soluble and exchangeable Al levels and high concentrations of amorphous forms of Al minerals. The best predictors of Al accumulation in the youngest litter horizon were extractions of amorphous minerals with pyrophosphate and NaOH. These extractors are normally used to predict the level of Al buffering in soils. Organic matter had less influence on Al dynamics in soils.

17328. 题目: Biotransformation of trace organic chemicals in the presence of highly refractory dissolved organic carbon
文章编号: N18093008
期刊: Chemosphere
作者: Karin Hellauer, Sara Martínez Mayerlen, Jörg E. Drewes, Uwe Hübner
更新时间: 2018-09-30
摘要: Previous studies demonstrated that the transformation of trace organic chemicals (TOrCs) in managed aquifer recharge (MAR) systems is favored under carbon-limited and oxic redox conditions especially, if the dissolved organic carbon (DOC) serving as primary substrate has a refractory character. Since co-metabolism is suggested to be the dominant removal mechanism, it is hypothesized that TOrCs transformation is controlled by the concentration of the refractory carbon under oxic redox conditions. A laboratory-scale soil column experiment mimicking MAR was established to investigate the influence of two different concentrations of highly refractory carbon sources on TOrCs transformation, namely drinking water (DW) and drinking water augmented with humic acid (DW+HA). Oxic redox conditions and carbon-limitation were present in both systems (ΔDOCDW+HA ≈ 0.6 - 0.7 mg/L; ΔDOCDW ≈ 0.1 mg/L). Of the 12 TOrCs investigated seven exhibited moderate to efficient transformation in both systems with only one compound (diclofenac) showing significantly enhanced (co-metabolic) biotransformation by adding humic acids as primary growth substrate. It is postulated that transformation of some TOrCs is characterized by metabolic degradation under starving conditions (ΔDOC ≤ 0.1 mg/L). By comparing the transformation efficiency of selected TOrCs with previous studies operated under carbon-limited and oxic conditions, an inconsistent behavior of some compounds was observed. These results demonstrate that key factors triggering the transformation of TOrCs are still poorly understood and thus, further investigations regarding the biodegradation pathways of TOrCs, upregulation of key enzymes by the microbial community but also more detailed analysis of the composition of the biodegradable DOC are needed.

17329. 题目: Elimination kinetics and detoxification mechanisms of microcystin-LR during UV/Chlorine process
文章编号: N18093007
期刊: Chemosphere
作者: Xinran Zhang, He Jun, Shuqi Xiao, Xin Yang
更新时间: 2018-09-30
摘要: Microcystin-LR (MC-LR), a toxin produced by cyanobacteria, is very toxic and poses a threat to public health when entering water treatment works. In this study, UV/chlorine process, as an advanced oxidation process (AOP), has been demonstrated for effective elimination of MC-LR levels and associated toxicity. At a chlorine dose of 3.0 mg L−1 and UV fluence of 125 mJ cm−2, MC-LR (initial concentration 1.0 μM) was reduced by 92.5%, which was much higher than 20.3% removal under UV irradiation alone and 65.1% removal during dark chlorination. Enhanced degradation was attributed by hydroxyl radicals (HO) and reactive chlorine species (RCS), mainly Cl2- and ClO. Increasing chlorine doses or lowering pH favored MC-LR removal. Increased bicarbonate and natural organic matter concentrations inhibited MC-LR removal, but bromide ions enhanced MC-LR removal instead. MC-LR elimination rates in natural waters were roughly two times smaller than those in ultrapure water. The reactive radicals promoted hydroxylation of both diene of Adda moiety and double bond of Mdha moiety in MC-LR. UV exposure enhanced the dechlorination of chloro-MC-LR via the cleavage of CCl bond. The toxicity was evaluated by a protein phosphatase (PP2A) inhibition assay. At a chlorine dose of 3.0 mg L−1 and UV fluence of 125 mJ cm−2, the toxicity of the treated water was reduced by 75.0%, which was also higher than 25.7% and 46.7% removal under UV irradiation alone and during dark chlorination, respectively. These results highlight UV/chlorine is an efficient AOP for MC-LR degradation and detoxification.
图文摘要:

17330. 题目: Formation and redox reactivity of ferrihydrite-organic carbon-calcium co-precipitates
文章编号: N18093006
期刊: Geochimica et Cosmochimica Acta
作者: Dinesh Adhikari, Tyler Sowers, Jason W. Stuckey, Xilong Wang, Donald L. Sparks, Yu Yang
更新时间: 2018-09-30
摘要: Complexation with minerals plays a critical role in regulating the stability of organic matter. The presence of cations is assumed to be important for the complexation between organic matter and minerals, but there is still limited direct analysis for the formation and reactivity of mineral-organic matter-cation ternary complexes, as well as governing factors for the fate of minerals and organic matter in the complexes. In order to close this knowledge gap, we investigated the formation and reactivity of ferrihydrite (Fh)-organic carbon (OC)-calcium (Ca) ternary co-precipitates. We performed microbial anaerobic Fe reduction using Shewanella putrefaciens CN32 on synthesized Fh-OC-Ca co-precipitates and characterized OC and Fe minerals using various spectroscopic and wet chemistry techniques. We found that Ca incorporated into the co-precipitate was a function of OC/iron (Fe) ratio, but OC incorporation was not impacted by the Ca content. During reduction, the presence of Ca favored the formation of green rust but decreased the formation of magnetite and siderite in co-precipitates with high OC content. The reduction of Fe and reductive release of Fe-bound OC were controlled primarily by the C/Fe ratio, rather than Ca/Fe ratio. Phenolic OC was preferentially released or degraded during the reduction compared to aromatic and carboxylic OC. Collectively, C/Ca incorporation data, Fe K-edge extended x-ray absorption fine structure (EXAFS) analysis for co-precipitates before and after reduction, and the reductive release of Ca and OC suggest the formation of Fh-OC-Ca ternary co-precipitates, likely with OC as bridges. The reduction of Fe and reductive release of OC were primarily controlled by the C/Fe ratio, whereas the presence of Ca affected the mineral phase transformation for Fh during the reduction of Fe. Hence, our results provide novel understanding for the formation and reactivity of Ca-based ternary co-precipitates, which can be valuable for building up process-based models for cycles of carbon and metals.

17331. 题目: The roles of mycorrhiza and Penicillium inoculants in phosphorus uptake by biochar-amended wheat
文章编号: N18093005
期刊: Soil Biology and Biochemistry
作者: Aikaterini Efthymiou, Birgit Jensen, Iver Jakobsen
更新时间: 2018-09-30
摘要: Biochar (BC) application to soil can potentially replace mineral P fertilizers and its effectiveness as fertilizer can be improved by plant inoculation with the phosphate-solubilizing microorganism Penicillium aculeatum (Pa). Arbuscular mycorrhiza (AM) fungi are important in plant P nutrition and may possibly act synergistically with Pa to improve the uptake of BC-P. Responses in wheat to inoculation with Pa and the AM fungus Rhizophagus irregularis were studied in a pot experiment at two levels of BC fertilization. Pots contained a mesh-enclosed, root free compartment with 33P-labelled soil for assessment of the AM contribution to P uptake and for studying if Pa would affect P uptake by the AM fungal hyphae. AM application suppressed wheat growth, albeit AM pathway had a major role in total P uptake at the two lowest P levels (nil or 20 mg BC-P kg−1 soil). Moreover, AM contribution had similar magnitudes in the presence and absence of Pa. Rhizosphere and bulk soil were actively colonized by Pa, both in the presence and absence of AM. The application of Pa or BC at a low rate increased AM-colonized root lengths. Although this was not translated to increased P uptake by wheat, the results suggest that AM and Pa can be combined without showing antagonistic interactions. However, more work is needed to understand how AM and Pa can be combined to increase plant growth.

17332. 题目: Broadcast woody biochar provides limited benefits to deficit irrigation maize in Colorado
文章编号: N18093004
期刊: Agriculture, Ecosystems & Environment
作者: M. Ramlow, E.J. Foster, S.J. Del Grosso, M.F. Cotrufo
更新时间: 2018-09-30
摘要: Biochar soil amendments have been widely promoted for their ability to improve soil fertility in degraded tropical soils, and irrigation and fertilizer use efficiency in fertile temperate agricultural systems. Here, we evaluate if a woody biochar can produce both agronomic and environmental benefits in deficit irrigation systems by ameliorating water stress, improving crop N uptake and mitigating greenhouse gas emissions. To evaluate these responses, we established a maize field trial in northern Colorado under deficit irrigation treatments with a woody biochar amendment. Irrigation treatments included recommended irrigation (Full), recommended irrigation except during non-essential growth phases (Limited) and 50% of recommended irrigation (Drought). We measured crop biomass, grain yield, grain N uptake, mineral N availability, soil water content, soil field capacity, soil C sequestration and N2O emissions. Drought treatments reduced both grain and biomass yield while Limited irrigation showed no significant yield reduction relative to Full irrigation. Biochar amendments did not provide any yield improvements. Biochar also did not alter mineral N availability within the soil profile or grain N uptake. Biochar amendments increased gravimetric soil water content by 9.7% over the field season and increased water retention by 7.4%. However, these increases failed to alleviate the water stress coefficient, an index of how much the water content has dropped below the maximum soil water depletion acceptable between irrigation applications, which was correlated with yield. Biochar sequestered C primarily as coarse biochar particles with significant losses, likely a result of erosion. Across irrigation treatments biochar treatments trended towards a lower mean cumulative N2O emissions over the growing season, but such effect was not significant due to high spatial variability in N2O fluxes. Both biochar amendments and Limited irrigation treatments did not significantly impact yield-scaled cumulative N2O emissions or irrigation water-use efficiency. This research highlights the importance of targeting the deficit irrigation treatment timing and amount to maximize biochar’s improved water retention in order to reduce crop water stress. It also confirms the diminished biochar N2O emission reductions in the field relative to most lab incubations due to drier field conditions and crop N uptake.

17333. 题目: Digital mapping of soil properties using multiple machine learning in a semi-arid region, central Iran
文章编号: N18093003
期刊: Geoderma
作者: Mojtaba Zeraatpisheh, Shamsollah Ayoubi, Azam Jafari, Samaneh Tajik, Peter Finke
更新时间: 2018-09-30
摘要: Knowledge about distribution of soil properties over the landscape is required for a variety of land management applications and resources, modeling, and monitoring practices. The main aim of this research was to conduct a spatially prediction of the top soil properties such as soil organic carbon (SOC), calcium carbonate equivalent (CCE), and clay content using digital soil mapping (DSM) approaches in Borujen region, Chaharmahal-Va-Bakhtiari province, central Iran. To achieve this goal, a total of 334 soil samples were collected from 0 to 30 cm depth. Three non-linear models including Cubist (Cu), Random Forest (RF), Regression Tree (RT) and a Multiple Linear Regression (MLR) were used to link environmental covariates and the studied soil properties. The environmental covariates were obtained from a digital elevation model (DEM) and satellite imagery (Landsat Enhanced Thematic Mapper; ETM). The model was calibrated and validated by the 10-fold cross-validation approach. Root mean square error (RMSE) and coefficient of determination (R2) were used to determine the performance of the models, and relative RMSE (RMSE%) was used to define prediction accuracy. According to the RMSE and R2, Cu and RF resulted in the most accurate predictions for CCE (R2 = 0.30 and RMSE = 9.52) and clay contents (R2 = 0.15 and RMSE = 7.86), respectively, while both of RF and Cu models showed the highest performance to predict SOC content (R2 = 0.55). Results showed that remote sensing covariates (Ratio Vegetation Index and band 4) were the most important variables to explain the variability of SOC and CCE content, but only topographic attributes were responsible for clay content variation. According to RMSE% results, it could be concluded that the best model is not necessarily able to make the most accurate estimation. This study recommended that more observations and denser sampling should be carried out in the entire study area. Alternatively, stratified sampling by elevation in homogeneous sub-areas was recommended. The stratified sampling probably will increase the performance of models.

17334. 题目: Impact of chlorine exposure time on disinfection byproduct formation in the presence of iopamidol and natural organic matter during chloramination
文章编号: N18093002
期刊: Journal of Environmental Sciences
作者: Nana Osei B. Ackerson, Alexis H. Killinger, Hannah K. Liberatore, Thomas A. Ternes, Michael J. Plewa, Susan D. Richardson, Stephen E. Duirk
更新时间: 2018-09-30
摘要: Chloramines, in practice, are formed onsite by adding ammonia to chlorinated drinking water to achieve the required disinfection. While regulated disinfection byproducts (DBPs) are reduced during chloramine disinfection, other DBPs such as iodinated (iodo-) DBPs, that elicit greater toxicity are formed. The objective of this study was to investigate the impact of prechlorination time on the formation of both halogen-specific total organic halogen (TOX) and iodo/chlorinated (chloro-) DBPs during prechlorination/chloramination in source waters (SWs) containing iopamidol, an X-ray contrast medium. Barberton SW (BSW) and Cleveland SW (CSW) containing iopamidol were prechlorinated for 5–60 min and afterwards chloraminated for 72 hr with ammonium chloride. Chlorine contact time (CCT) did not significantly impact total organic iodine (TOI) concentrations after prechlorination or chloramination. Concentrations of total organic chlorine (TOCl) formed during prechlorination did not significantly change regardless of pH and prechlorination time, while TOCl appeared to decrease after 72 hr chloramination period. Dichloroiodomethane (CHCl2I) formation during prechlorination did not exhibit any significant trends as a function of pH or CCT, but after chloramination, significant increases were observed at pHs 6.5 and 7.5 with respect to CCT. Iodo-HAAs were not formed during prechlorination but were detected after chloramination. Significant quantities of chloroform (CHCl3) and trichloroacetic acid (TCAA) were formed during prechlorination but formation ceased upon ammonia addition. Therefore, prechlorination studies should measure TOX and DBP concentrations prior to ammonia addition to obtain data regarding the initial conditions.
图文摘要:

17335. 题目: Pre-ozonation of source water: assessment of efficacy against Giardia duodenalis cysts and effects on natural organic matter
文章编号: N18093001
期刊: Chemosphere
作者: Liane Yuri Kondo Nakada, Regina Maura Bueno Franco, Vagner Ricardo da Silva Fiuza, Luciana Urbano dos Santos, Nilson Branco, José Roberto Guimarães
更新时间: 2018-09-30
摘要: The protozoan Giardia duodenalis is one of the parasites of primary concern in drinking water treatment plants, due to its resistance to chlorination. Another matter of concern regarding chlorination of drinking water is the formation of disinfection by-products in the presence of precursors such as natural organic matter (NOM). In this study, the effects of ozonation (5 mg L−1) on G. duodenalis cysts in raw surface water from a drinking water treatment plant were evaluated, and the presence and alteration of NOM were assessed, as an indicative of the potential to prevent total organic halogen (TOX) formation during post-chlorination. Following ozone treatment, the presence of damaged cysts was observed by direct immunofluorescence assay (IFA) and confirmed by the molecular approach propidium monoazide-polymerase chain reaction (PMA-PCR). Using an animal model, analysis of the intestinal tissues revealed that 80% of the animals inoculated with ozonated water were positive for trophozoites. This study shows that analysis of intestinal fragments is imperative to accurately assess animal infection following inoculation of treated cysts. More importantly, considering the low infective dose of Giardia cysts in susceptible hosts, an ozone dosage usually applied in drinking water treatment plants did not completely inactivate G. duodenalis cysts in surface water. Nonetheless, the results suggest that competitive reactions with NOM have occurred, and the applied ozone dosage has proven useful to remove NOM reactivity, and thus prevent halogenated DBP formation during post-chlorination.
图文摘要:

17336. 题目: The fate of carbon and nutrients exported out of the Southern Ocean
文章编号: N18092907
期刊: Global Biogeochemical Cycles
作者: Judith Hauck, Andrew Lenton, Clothilde Langlais, Richard Matear
更新时间: 2018-09-29
摘要: Southern Ocean (SO) nutrient export via mode and intermediate waters is known to affect global biological production. The accompanying effects on the CO2 flux outside the SO are less certain. We performed idealized model simulations to separate the transient effects of SO carbon pumps on nutrients, primary production and CO2 flux outside the SO. The SO biological carbon pump (BCP) leads to DIC and nutrient reduction at the surface and in the exported water masses, and to a DIC increase at depth through the sinking of organic matter. When primary production is suppressed in the Southern Ocean, only 30% of SO export, 43% of SO net primary production and 50% of biologically‐driven SO CO2 flux are compensated outside the SO on a 200‐year time‐scale. In contrast, when the abiotically‐driven CO2 flux is suppressed, 90% of CO2 outgassing in the SO is compensated by air‐sea CO2 exchange outside the SO. The longer sequestration time‐scale of the BCP can be explained by incomplete compensation of primary production. This is a result of almost complete compensation of diatom productivity and no compensation of nanophytoplankton productivity due to feedbacks in phytoplankton community composition. The longer sequestration time‐scale is further sustained by the sinking and remineralization of particles in the deep ocean that are not in contact with the atmosphere over the 200‐year time‐scale considered. As SO biologically‐driven CO2 flux is only partly compensated outside the SO, potential future changes in SO productivity may have an important impact on the global carbon cycle.

17337. 题目: Effect of treated wastewater on growth and secondary metabolites production of two Eucalyptus species
文章编号: N18092906
期刊: Agricultural Water Management
作者: Aya Maaloul, Serge Michalet, Ezzeddine Saadaoui, Naziha Ghzel, Jalila Bekir, Chokri Ben Romdhane, Mohamed Mars, Marie-G. Dijoux-Franca, Mehrez Romdhane
更新时间: 2018-09-29
摘要: The use of Treated Waste Water (TWW) as an alternative to limit water use in agriculture practices in the context of global warming is of particular importance, especially in countries where water resources are limited. In this study, we assessed the effect of TWW irrigation on two Eucalyptus species (E. camaldulensis and E. occidentalis) in their early stages of growth (up to one year after seedling and transplantation) in pot experiment and compared to Well-Water (WW) irrigation. Changes in plant growth traits/ characteristics including plant height, stem diameter, number of leaves and Leaf Mass per Area (LMA) were analysed as well as the modification of root and leaves secondary metabolic profiles and total phenolic contents. Soil physico-chemical parameters were also measured before and after the experiment.Our results showed that both species do not have the same response to TWW irrigation: while most growth recorded parameters were most affected in E. camaldulensis after one year of growth with TWW, E. occidentalis had its leaf number significantly increased with TWW after seven months. Leaves were lighter and smaller than the ones obtained with WW irrigation after four months but the reduction of weight and area was proportional in such a way that LMA was not affected and this effect was transitory. Such effect was not observed with E. camaldulensis.Concerning root and leaf secondary metabolite profiles, changes in both plant part extract compositions were observed according to irrigation type, though these were weak compared to plant species identity. Common metabolic patterns following TWW irrigation could be showed in both species like for example the increase of quercetin glucosinnapate in leaf extracts or the decrease of two peduncalagin isomers detected as major compounds in the same extracts. Though some differences were also observed, particularly, E. occidentalis had more compounds decreased in its roots than E. camaldulensis when irrigated with TWW while in leaves the tendency was inverted. Total phenolic content was decreased in both species and for both plant parts, but this diminution was more pronounced in E. occidentalis roots. We also noticed modifications in soil parameters after TWW exposure and some were dependant on the species of Eucalyptus like for example soil organic matter content which increased with TWW in the case of E. occidentalis, whereas it decreased for E. camaldulensis. All these results let us hypothesize that E. occidentalis possess better adaptation capabilities to TWW irrigation than E. camaldulensis and that these might be related to changes in root metabolism.

17338. 题目: Increased rice yield in long-term crop rotation regimes through improved soil structure, rhizosphere microbial communities, and nutrient bioavailability in paddy soil
文章编号: N18092905
期刊: Biology and Fertility of Soils
作者: Sheng Lu, Joe Eugene Lepo, Hai-Xing Song, Chun-Yun Guan, Zhen-Hua Zhang
更新时间: 2018-09-29
摘要: Soil in short-term crop rotation systems (STCR) is still in the initial development stage of farmland soil, whereas after long-term crop rotation treatment (LTCR), soil properties are significantly different. This study compares STCR (4 years) and LTCR (30 years) rice-rice-fallow, rice-rice-rape rotation practices under the same soil type background and management system. To reveal ecosystem mechanisms within soils and their effects on rice yield following LTCR, we analyzed the physical, chemical, and microbiological properties of soils with different rotations and rotation times. Relative to STCR, LTCR significantly reduced soil water-stable aggregate (WSA) content in the < 0.053-mm range, while > 2 mm WSA content significantly increased. Soil organic matter increased in fields under LTCR, mainly in > 2 mm, 2–0.25 mm, and < 0.053 mm soil WSA in 0–10 cm soil layer. LTCR was associated with significantly increased total soil organic matter, at the same time being associated with increasing the amount of active organic matter in the 0–20 cm soil layer. The two crop rotation regimes significantly differed in soil aggregate composition as well as in soil N and P, microbial biomass, and community composition. Relative to STCR, LTCR field soils had significantly higher soil organic matter, active organic matter content, soil enzyme activities, and overall microbial biomass, while soil WSA and microbial community composition was significantly different. Our results demonstrate that LTCR could significantly improve soil quality and rice yield and suggest that length of rotation time and rice-rice-rape rotation are critical factors for the development of green agriculture.

17339. 题目: Facet-Mediated Adsorption and Molecular Fractionation of Humic Substances on Hematite Surfaces
文章编号: N18092904
期刊: Environmental Science & Technology
作者: Jitao Lv, Yuexia Miao, Zaoquan Huang, Ruixia Han, Shuzhen Zhang
更新时间: 2018-09-29
摘要: Interactions between dissolved organic matter (DOM) and iron oxyhydroxides have important environmental and geochemical implications. The present study employed two hematite nanocrystals to investigate the adsorption and molecular fractionation of two typical humic substances (HSs) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). Hematite with a predominant exposure of {100} facets induced more pronounced adsorption and molecular fractionation of HSs than {001} facets, indicating that the interfacial adsorptive fractionation process of HSs was mediated by exposed facets of hematite. Further exploration of the surface OH groups of the two hematite nanocrystals confirms that the facet-mediated molecular fractionation of HSs was attributable to the abundance of singly iron-atom coordinated −OH sites on the hematite surfaces. Molecules with a high oxidation state and high aromaticity such as oxidized black carbon, polyphenol-like, and tannic-like compounds preferentially formed ligand-exchange complexes with singly coordinated −OH groups on the hematite surfaces, inducing the selective binding and molecular fractionation of HSs at the mineral–water interface. These results demonstrate that singly iron-atom coordinated −OH sites determine DOM adsorption and mediate molecular fractionation on hematite surfaces, and this contributes substantially to our understanding of the molecular mechanisms of iron oxyhydroxide-mediated molecular exchange of DOM in soils and/or sediments.
图文摘要:

17340. 题目: Treatment train for tailings pond water using Opuntia ficus-indica as coagulant
文章编号: N18092903
期刊: Separation and Purification Technology
作者: Jing Wan, Tulip Chakraborty, Chunbao (Charles) Xu, Madhumita B. Ray
更新时间: 2018-09-29
摘要: In this study, the mucilage of Opuntia ficus-indica, a type of cactus was used as a bio-coagulant to treat tailings pond water (TPW) from the oil sands process industry. The performance of Opuntia ficus-indica was compared with conventional coagulants such as alum and ferric chloride for the removal of turbidity and dissolved organic carbon (DOC). Albeit at a higher dose of 900 mg/L, compared to that of alum (190 mg/L) and ferric chloride (104 mg/L), Opuntia ficus-indica could remove 98% of the turbidity of tailings pond water. The DOC removal was low for all coagulants and ranged from 15-28%, but acidification of TPW effluent improved DOC removal significantly. FTIR analysis showed the presence of oxidized napthenic acids and carboxylic groups on the surface of the TPW solids and flocs. The settling velocity of the flocs was 6.28 cm/min, 4.54 cm/min, and 3.01 cm/min generated by Opuntia ficus-indica, alum, and ferric chloride, respectively. Of several heavy metals present in TPW, Opuntia ficus-indica showed higher arsenic removal (64%) compared to alum and ferric chloride, while alum and ferric chloride showed significantly higher phosphorous removal compared to Opuntia ficus-indica. Activated carbon was used as the final treatment step for removal of residual organics; Opuntia ficus-indica treated TPW showed about 1.8 times greater adsorption capacity for activated carbon than that treated with alum.

 共 18774 条记录  本页 20 条  本页从 17321-17340 条  867/939页  首页 上一页  862 863 864 865 866 867 868 869 870 871 872  下一页  末页   

本数据库数据来源自各期刊,所有权归属各期刊。数据仅供分享学习,不作商业用途,特此申明。