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8121. 题目: Land use and climate change effects on soil organic carbon in North and Northeast China
文章编号: N18081002
期刊: Science of The Total Environment
作者: Yin Zhou, Alfred E. Hartemink, Zhou Shi, Zongzheng Liang, Yanli Lu
更新时间: 2018-08-10
摘要: Soil is recognized as the largest carbon reservoir in the terrestrial ecosystem. Soil organic carbon (SOC) is vulnerable to changes in land use and climate. For a better understanding of the SOC dynamics and its driving factors, we collected data of the 1980s and 2000s in the North and Northeast China and conducted the digital soil mapping for spatial variation of SOC for the respective period. In the 1980s, 585 soils were sampled and the area was resampled in 2003 and 2004 (1062 samples) in a 30-km grid. The main land use in the area was cropland, forest and grassland. The random forest was used to predict the SOC concentration and its temporal change using land use, terrain factors, vegetation index, vis-NIR spectra and climate factors as predictors. The average SOC concentration in 1985 was 10.0 g kg−1 compared to 12.5 g kg−1 in 2004. The SOC variation was similar over the two periods, and levels increased from south to north. The estimated SOC stock was 1.68 Pg in 1985 and 1.66 Pg in 2004, but the SOC changes were different under different land uses. Over the twenty-year period, average temperatures increased and large areas of forests and grassland were converted to cropland. SOC under cropland was increased by 0.094 Pg (+9%) whereas 0.089 Pg SOC was lost under forests (−25%) and 0.037 Pg in the soils under grassland (−25%). It is concluded that land use is the main drivers for SOC changes in this area while climate change had different contributions in different regions. SOC loss was remarkable under the land use conversion while cropland has considerable potential to sequester SOC.
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8122. 题目: Dissolved organic carbon in snow cover of the Chinese Altai Mountains, Central Asia: Concentrations, sources and light-absorption properties
文章编号: N18081001
期刊: Science of The Total Environment
作者: Yulan Zhang, Shichang Kang, Tanguang Gao, Julia Schmale, Yajun Liu, Wei Zhang, Junming Guo, Wentao Du, Zhaofu Hu, Xiaoqing Cui, Mika Sillanpää
更新时间: 2018-08-10
摘要: Dissolved organic carbon (DOC) in snow plays an important role in river ecosystems that are fed by snowmelt water. However, limited knowledge is available on the DOC content in snow of the Chinese Altai Mountains in Central Asia. In this study, DOC in the snow cover of the Kayiertesi river basin, southern slope of Altai Mountains, was investigated during November 2016 to April 2017. The results showed that average concentrations of DOC in the surface snow cover (1.01 ± 0.52 mg L−1) were only a little higher than those in glaciers of the Tibetan Plateau, European Alps, and Alaska, but much higher than in Greenland Ice Sheet. Depth variations of DOC concentrations from snowpack profiles indicated higher values in the surface layer. During the observation period, scavenging efficiency for DOC in snow cover is estimated to be 0.15 ± 0.10, suggesting that DOC in snow can be affected more by the meltwater during ablation season than during accumulation season. The average mass absorption cross section at 365 nm and the absorption Ångström exponent of DOC were 0.45 ± 0.35 m2 g−1 and 2.59 ± 1.03, respectively, with higher values in March and April 2017. Fraction of radiative forcing caused by DOC relative to black carbon accounted for about 10.5%, implying DOC is a non-ignorable light-absorber of solar radiation in snow of the Altai regions. Backward trajectories analysis and aerosol vertical distribution images from satellites showed that DOC in the snow of the Altai Mountains was mainly influenced by air masses from Central Asia, Western Siberia, the Middle East, and some even from Europe. Biomass burning and organic carbon mixed with mineral dust contributed significantly to the DOC concentration. This study highlights the effects of DOC in the snow cover for radiative forcing and the need to study carbon cycling for evaluation of quality of the downstreams ecosystems.
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8123. 题目: Indirect Photochemical Formation of Carbonyl Sulfide and Carbon Disulfide in Natural Waters: Role of Organic Sulfur Precursors, Water Quality Constituents, and Temperature
文章编号: N18080918
期刊: Environmental Science & Technology
作者: Mahsa Modiri Gharehveran, Amisha D. Shah
更新时间: 2018-08-09
摘要: Carbonyl sulfide (COS) and carbon disulfide (CS2) are volatile sulfur compounds that are critical precursors to sulfate aerosols, which enable climate cooling. COS and CS2 stem from the indirect photolysis of organic sulfur precursors in natural waters, but currently the chemistry behind how this occurs remains unclear. This study evaluated how different organic sulfur precursors, water quality constituents, which can form important reactive intermediates (RIs), and temperature affected COS and CS2 formation. Nine natural waters ranging in salinity were spiked with cysteine, cystine, dimethylsulfide (DMS), or methionine and exposed to simulated sunlight over varying times and water quality conditions. Results indicated that COS and CS2 formation increased up to 11× and 4×, respectively, after 12 h of sunlight, while diurnal cycling exhibited varied effects. COS and CS2 formation was also strongly affected by the DOC concentration, organic sulfur precursor type, O2 concentration, and temperature, while salinity differences and CO addition did not play a significant role. Overall, important factors in forming COS and CS2 were identified, which may ultimately impact their atmospheric concentrations.
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8124. 题目: Solar Photocatalysis with Modified Titanium Dioxide Photocatalysts: Effects on Natural Organic Matter and Disinfection Byproduct Formation Potential
文章编号: N18080917
期刊: Environmental Science: Water Research & Technology
作者: Stephanie Leah Gora, Aleksandra Sokolowski, Melisa Hatat-Fraile, Robert Liang, Y. Norman Zhou, Susan Andrews
更新时间: 2018-08-09
摘要: Solar photocatalysis with titanium dioxide (solar/TiO2) is an advanced oxidation process (AOP) for drinking water treatment that has the potential to provide concurrent disinfection and contaminant degradation with minimal energy input. In this study, a suite of photocatalytic TiO2 nanomaterials modified with nitrogen, boron, or silver to improve their performance under solar irradiation was evaluated for use in solar drinking water treatment applications. The effect of solar/TiO2 treatment with each material on natural organic matter (NOM) in synthetic and real river water was determined by tracking the change in dissolved organic carbon (DOC) and UV absorbance at 254 nm (UV254) over a range of irradiation times comparable to solar/TiO2 disinfection studies. The samples were subsequently chlorinated and the concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs), two commonly regulated disinfection byproducts (DBPs) were measured. In almost all cases, the DBP formation potential (DBPfp) of both water sources decreased due to NOM’s adsorption to the TiO2 nanomaterials. However, DBPfp increased upon simulated solar irradiation at low UV doses before decreasing upon further solar irradiation to provide higher UV doses. Additionally, changes in SUVA, THMfp/DOC, and HAAfp/DOC indicate that the overall reactivity of the NOM towards chlorine was increased by solar/TiO2 treatment. The results of this study suggest that small but significant increases in DBPfp are likely to occur at TiO2 and UV doses typically used in solar/TiO2 disinfection studies. The results also suggest that modifications made to nanomaterials to improve their performance in solar applications can have unexpected impacts on their chemical and physical properties that hinder their treatment efficacy.

8125. 题目: Vulnerability of DNA hybridization in soils is due to Mg2+ ion induced DNA aggregation
文章编号: N18080916
期刊: Soil Biology and Biochemistry
作者: Xiaofang Wang, Hyojin Kweon, Seokho Lee, Hyejin Shin, Beelee Chua, Mark R. Liles, Ming-kuo Lee, Ahjeong Son
更新时间: 2018-08-09
摘要: The NanoGene assay is an inhibitor-resistant gene quantification assay based on magnetic bead and quantum dot nanoparticles. It employs a set of probe and signaling probe DNAs to capture target DNA via hybridization. Using simple DNA preparation that bypasses conventional DNA extraction, it was able to detect and quantify specific bacterial genes in environmental sample. In this study, the vulnerability of the NanoGene assay to the presence of various environmental factors was investigated. A total of 43 soil samples were inoculated with 109 CFU/mL of Pseudomonas putida prior to DNA isolation without purification. Subsequently, the NanoGene assay was performed for quantitative detection of P. putida with respect to 12 soil properties including pH, moisture, humic acids, organic matter, sand, silt, clay, cation exchange capability, sodium, potassium, magnesium, and calcium. Using multiple linear regression, the NanoGene assay was found to be particularly vulnerable to the presence of Mg2+, which was selected as a major variable (P = 0.001). The vulnerability of the NanoGene assay to Mg2+ was further explored by atomic force microscopy, which indicated significant Mg2+-mediated DNA aggregation. The inhibition of the NanoGene assay from some soil samples as a consequence of DNA aggregation could therefore be prevented by the use of Mg2+ chelators such as EDTA, enabling application of this method across diverse soil types.
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8126. 题目: Efficiency and surface characterization of different plant derived biochar for cadmium (Cd) mobility, bioaccessibility and bioavailability to Chinese cabbage in highly contaminated soil
文章编号: N18080915
期刊: Chemosphere
作者: Saqib Bashir, Qaiser Hussain, Muhammad Shaaban, Hongqing Hu
更新时间: 2018-08-09
摘要: Cadmium (Cd) contamination in red soil has become a serious environmental concern due to its toxic effects on organisms and the food chain. Possible eco-friendly solutions for Cd immobilization were required to reduce its mobility through biochar. This study evaluated the comparative efficiency of rice straw (RSB), rice hull (RHB) and maize stover (MSB) derived biochar (BC) on Cd mobility and its accumulation in Chinese cabbage (Brassica chinensis L.), which is highly Cd accumulating crop. Results showed that the soil chemical properties (pH, organic carbon and nutrients) significantly increased with increasing the biochar application rate from 1.5% to 3%. Concentration of Cd decreased in CaCl2 extract by 58.6, 39.7 and 46.49% and in toxicity characteristics leaching test (TCLP) by 42.9, 32.7 and 36.7% for RSB, RHB and MSB, respectively at 3% application rate. The simple bioaccessibility extraction test (SBET) techniques showed a significant decrease in Cd by 30.5, 20.6 and 27.5% for RSB, RHB and MSB, respectively at the 3% application rate. Moreover, the Cd contents in the cabbage shoots decreased by 25, 21.3 and 23.1% for RSB, RHB and MSB at a 3% application rate and in the roots by 31.3, 23.9 and 26.5% for RSB, RHB and MSB at a 3% application rate, respectively. Bioaccumulation (BCF) and translocation factors (TF) were significantly decreased upto 26.5% and 11%, respectively among all biochar types. Overall, RSB demonstrated positive results as soil amendments for Cd immobilization and thereby, reducing its bioavailability in the Cd contaminated soil to mitigate food security risks.

8127. 题目: Mercury contamination of stream sediments in the North Bohemian Coal District (Czech Republic): Mercury speciation and the role of organic matter
文章编号: N18080914
期刊: Chemosphere
作者: Dominik Vöröš, Mercedes DíazSomoano, Eva Geršlová, Ivana Sýkorová, Isabel Suárez-Ruiz
更新时间: 2018-08-09
摘要: Industrial expansion in the North Bohemian Coal District over the past decades has had an adverse effect not only on stream sediments but also on the freshwater system. So far mercury occurrence has not been properly investigated in the area. In response to this situation, the present study applies mercury quantification and speciation in order to predict the possible mobility of mercury. The enrichment factor (EF) and sediment quality guidelines (SQGs) were used to calculate the degree of mercury contamination. An automatic mercury analyser was employed to detect the total mercury content (Hg-T) and Thermal Desorption technique was used to identify mercury species. All the sediment samples were assessed with the contamination degree which increased to very severe in stream sediments in the middle section of the river course. Mercury species identified were chiefly the insoluble forms Hg-FeS2 and HgS. Lignite components and combustion residues were identified as the primary source of Hg contamination in the area.
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8128. 题目: Large catchment-scale spatiotemporal distribution of soil organic carbon
文章编号: N18080913
期刊: Geoderma
作者: V. Kunkel, G.R. Hancock, T. Wells
更新时间: 2018-08-09
摘要: There are a dearth of studies globally examining soil organic carbon (SOC) at large catchment scales. Here we assess the catchment scale climate and geomorphic controls on SOC. The study was conducted on the east coast of New South Wales, Australia and focussed on a 562 km2 (Krui River) catchment sampled in 2006 and 2015 and a 606 km2 (Merriwa River) catchment sampled in 2015. Both catchments have similar soils, topography and landuse. There was no significant difference in SOC between 2006 and 2014 data sets, indicating that SOC was temporally stable over the intervening 8 years (Krui catchment), despite the seasonal variability in climate such as rainfall. SOC concentration was also shown to have no significant difference between Krui catchment and Merriwa catchment, indicating that SOC is spatially stable for catchments of similar land-use, climate and geomorphology. SOC concentrations from all three data sets were compared to a range of terrain attributes. Similar with other studies, elevation, as a surrogate for orographic rainfall, was found to have the strongest significant control on SOC % at the large catchment scale. Confirmation of the use of elevation as a surrogate for rainfall was made by comparing SOC with rainfall obtained from a network of weather stations across the study sites. Relationships between SOC and other terrain attributes found inconsistent relationships. The findings demonstrate that for catchments with similar soils, topography and climate that SOC can be reliably predicted using simple topographic variables. The methods here provide a robust tool which can be used for SOC assessment at other sites as well as assist in understanding SOC distribution and controls for longer term and regional scales.

8129. 题目: Integrated graptolite-conodont biostratigraphy and organic carbon chemostratigraphy of the Llandovery of Kallholn quarry, Dalarna, Sweden
文章编号: N18080912
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Natalia Walasek, David K. Loydell, Jiří Frýda, Peep Männik, Robert F. Loveridge
更新时间: 2018-08-09
摘要: A revised graptolite and conodont biostratigraphy together with new organic carbon isotope data for the middle Aeronian to lower Telychian (Llandovery, lower Silurian) of Kallholn quarry, central Sweden, are presented. The base of the section is marked by an unconformity between the Ordovician Boda Limestone and Aeronian shales with limestone nodules belonging to the Pribylograptus leptotheca Biozone. These are overlain by strata assigned to the lower Lituigraptus convolutus Biozone. The Stimulograptus sedgwickii Biozone, previously recorded from the section, is absent and marked by an unconformity which is overlain by radiolarian-rich graptolitic shales belonging to the Stimulograptus halli Biozone. The overlying Telychian strata are assigned to the Spirograptus guerichi, Spirograptus turriculatus and Streptograptus crispus biozones. Conodonts indicate that the boundary between the Distomodus staurognathoides Biozone and Pterospathodus eopennatus Superzone lies within the Sp. turriculatus Biozone, as it does also in the Ohesaare core, Estonia. The δ13Corg record shows mostly minor fluctuations but with a distinct twin-peaked positive excursion in the upper Sp. turriculatus Biozone, close to the boundary with the overlying Streptograptus crispus Biozone. The excursion in the Kallholn section may correlate with the earliest positive shift in δ13C values at the onset of the excursion associated with the Valgu Event or it may represent a new excursion (provisionally named the Kallholn excursion) preceding this. Many more bentonites (36) occur in the section than previously recorded – geochemical studies are needed to confirm whether the Osmundsberg bentonite (which may or may not be equivalent to the “O” bed in Estonia and Latvia) is present.

8130. 题目: Biochar presence in soil significantly decreased saturated hydraulic conductivity due to swelling
文章编号: N18080911
期刊: Soil and Tillage Research
作者: Lukáš Jačka, Lukáš Trakal, Petr Ouředníček, Michael Pohořelý, Václav Šípek
更新时间: 2018-08-09
摘要: The application of biochar on two contrasting soils was tested in order to assess its effects on soil hydraulic properties (SHP) and study the interaction between water and the biochar surface (e.g., the swelling effect).Two contrasting soil types were enriched with 0, 2 and 5% (wt.) doses of grape stalks biochar in order to prepare soil samples for a 14-days continually saturated laboratory experiment. H2O bonds to the biochar surface were detected using FTIR spectroscopy.Results show that water molecules were bound through polar hydrogen bonds to OH and COH, and these interactions caused (i) intensive swelling, which decreased the bulk density and enhanced the water holding capacity (up to 5% in the case of sandy loam and 5% biochar dose), and (ii) significantly decreased Ks in both soils (with a maximum difference of 82.6%).The results of this laboratory experiment provide useful information about the significant effect of presented biochar in two contrasting soils, and its application appears to be an potential option for addressing drought (especially in coarser soils). Nevertheless, these findings must be verified under field conditions where the presence of biota and long-term effects can be taken into account.
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8131. 题目: Influence of pH and redox on mobilization of inositol hexakisphosphate from oligotrophic lake sediment
文章编号: N18080910
期刊: Biogeochemistry
作者: Kasper Reitzel, Henning S. Jensen, Benjamin L. Turner, Charlotte Jørgensen
更新时间: 2018-08-09
摘要: It has been suggested that inositol hexakisphosphate (IP6) contributes to the release of phosphorus (P) from lake sediments, but a mechanistic understanding remains elusive. We investigated the potential mobilization and mineralization of myo- and scyllo-IP6 from the sediment of an oligotrophic Danish lake known to contain high concentrations of inositol phosphates. Solution 31P NMR spectroscopy was used to determine changes in myo- and scyllo-IP6 in laboratory microcosms incubated under either oxic or anoxic conditions. In addition, we incubated sediment slurries adjusted to pH between 4.9 and 6.6, with and without addition of myo-IP6, and induced redox changes by adding starch and sulfate. We observed no significant changes in myo- or scyllo-IP6 after 1 year of incubation under anaerobic conditions. A sequential extraction procedure revealed that one half of the added myo-IP6 was recovered in the humic acid fraction (acid-insoluble organic matter) and the other half in the fulvic acid fraction (acid-soluble organic matter). Reduction in redox potential by starch addition did not mobilize myo-IP6, but myo-IP6 bound to humic acids was released to the pore water when the pH was increased to ≥ 5.8. This pH-induced mobilization of IP6 occurred in parallel with increases in dissolved iron and organic matter, suggesting the release of IP6 bound to humic acids through metal bridges. We conclude that myo-IP6 mobilization from this oligotrophic lake sediment is driven by changes in pH rather than by changes in the redox potential.

8132. 题目: Agricultural loess soils along a climosequence evidenced different susceptibility to acidification by simulated N-fertilization
文章编号: N18080909
期刊: CATENA
作者: Laura Antonela Iturri, Daniel Eduardo Buschiazzo
更新时间: 2018-08-09
摘要: Agricultural loess soils of the central region of Argentina show acidification evidences linked to both climatic conditions and N-fertilization. Because of that, simulations to estimate the future acidification trends under continuing N-fertilization, considering the different neutralization capacities of the soils in this region, were performed. An equivalent number of protons to that produced by a constant application of 180 kg urea ha−1 year−1 (84 kg N ha−1 year−1) during 1, 10, 30 and 50 years of fertilization, was added to unfertilized topsoil samples of agricultural Haplustolls, Hapludolls and Argiudolls. Mostly proton additions did not modify neither CEC nor the contents of both amorphous and crystalline Al, Mn and Fe oxides. However, the Hapludolls, located in the transition zone of the climosequence, showed decreases in their phyllosilicates crystallinity with the most acidifying treatments equivalent to 30 and 50 years of N-fertilization. This effect was less pronounced in those soils placed in both the driest (Haplustolls) and the moist (Argiudolls) environments, due to the amount and composition of the substances and/or systems with acid neutralizing capacity that prevailed. Thus, the Haplustolls were the less affected soils by acidification due to their high amount of free lime- and soil organic matter (SOM) as well as the smectitic mineralogy of their fine mineral fractions, clay and silt. The Argiudolls were the soils with stronger neutralizing mechanisms given by both their high SOM and fine mineral fractions contents, though illitic. Therefore, the Hapludolls were the most susceptible soils to being acidified if N-fertilization continues, according to the low quantity of SOM and fine mineral fractions of illitic mineralogy. From these results, the development and validation of mathematical models were assessed in order to predict the soil buffer capacity and the future pH of the soils. The soil buffer capacity was explained 78% by both the cation exchange and dissolution reactions of minerals accumulated in clays and silts, while pH values were explained 75% by the cation exchange capacity as well as by the SOM, free-lime and clay and silt contents. The pH that the soils would have in the future was predicted with an accuracy of 75% by the outcomes of the simulations, and in a 57% by the pH values of no-tilled and urea fertilized soils.

8133. 题目: Alteration of bioaccumulation mechanisms of Cu by microalgae in the presence of natural fulvic acids
文章编号: N18080908
期刊: Chemosphere
作者: Wen Shi, Xiaoman Fang, Xingfei Wu, Gaoxiang Zhang, Weiyan Que, Feili Li
更新时间: 2018-08-09
摘要: The impact of natural fulvic acids (FAs) on the toxicity and bioaccumulation of Cu by Chlorella pyrenoidosa was studied. FAs extracted from Taihu Lake were separated into three fractions using dialysis bags: F1 (<500 Da), F2 (500–1000 Da) and F3 (>1000 Da). The results showed that the F3 fraction with a larger molecular weight contained less acidic groups and unsaturated aliphatic structures than F1 and F2, and it showed stronger alleviation of the toxicity of Cu to algae. In the presence of F1∼F3, the bioaccumulation curve of Cu in algae intersected with the straight line in the binary system of Cu-algae at approximately 5.3 × 10−3-6.0 × 10−3 mM of Cu equilibrium concentration, showing an inhibition of bioaccumulation of Cu in lower concentrations but an enhancement in higher Cu concentrations. The ratio of {Cu}ads/{Cu}int was used to clarify the transformation mechanism on adsorption; the transition interval occurred at a ratio of 3.5–4.4. This ratio indicated a shift from a mechanism of slow trending to equilibrium to a mechanism with rapid increase, which may be due to the bridging action of Cu to form a ternary complex of FA-Cu-algae and the occurrence of multilayer adsorption. The promotion order of F1> F3> F2 was consistent with percentages of the carboxyl group in total acidic functional groups in the FAs. This research is helpful for improving the accuracy of present models for the prediction of heavy metal risks in aqueous environments.
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8134. 题目: Graphene oxide triggers mass transfer limitations on the methanogenic activity of an anaerobic consortium with a particulate substrate
文章编号: N18080907
期刊: Chemosphere
作者: J. Iván Bueno-López, J. Rene Rangel-Mendez, Felipe Alatriste-Mondragón, Fátima Pérez-Rodríguez, Virginia Hernández-Montoya, Francisco J. Cervantes
更新时间: 2018-08-09
摘要: Graphene oxide (GO) is an emerging nanomaterial widely used in many manufacturing applications, which is frequently discharged in many industrial effluents eventually reaching biological wastewater treatment systems (WWTS). Anaerobic WWTS are promising technologies for renewable energy production through biogas generation; however, the effects of GO on anaerobic digestion are poorly understood. Thus, it is of paramount relevance to generate more knowledge on these issues to prevent that anaerobic WWTS lose their effectiveness for the removal of pollutants and for biogas production. The aim of this work was to assess the effects of GO on the methanogenic activity of an anaerobic consortium using a particulate biopolymer (starch) and a readily fermentable soluble substrate (glucose) as electron donors. The obtained results revealed that the methanogenic activity of the anaerobic consortium supplemented with starch decreased up to 23-fold in the presence of GO compared to the control incubated in the absence of GO. In contrast, we observed a modest improvement on methane production (>10% compared to the control lacking GO) using 5 mg of GO L−1 in glucose-amended incubations. The decrease in the methanogenic activity is mainly explained by wrapping of starch granules by GO, which caused mass transfer limitation during the incubation. It is suggested that wrapping is driven by electrostatic interactions between negatively charged oxygenated groups in GO and positively charged hydroxyl groups in starch. These results imply that GO could seriously hamper the removal of particulate organic matter, such as starch, as well as methane production in anaerobic WWTS.

8135. 题目: Effects of elevated production of autochthonous dissolved organic matter on the freely dissolved concentration of cadmium
文章编号: N18080906
期刊: Environmental Science: Processes Impacts
作者: Qianqian Dong, Feng Wang, Yihua Xiao, Penghui Li, Qinghui Huang
更新时间: 2018-08-09
摘要: Eutrophication enhances the production of autochthonous dissolved organic matter (DOM), which is a major driving factor behind the impairment of many aquatic ecosystems. In a mesocosm study, we investigated the effects of the abundance and composition of DOM on the potential bioavailability of cadmium (Cd) caused by eutrophication, using three-dimensional excitation–emission matrix fluorescence spectroscopy integrated with tangential flow ultrafiltration technology. The complexing capacity of DOM–Cd and the sorption distribution coefficient between DOM and the bulk solution was calculated based on a 1 : 1 complexation model. The fluorescent DOM was decomposed into three components (one protein-like and two humic-like substances) by parallel factor analysis (PARAFAC). The fluorescence intensity of the protein-like substance was significantly correlated with the concentration of chlorophyll a (Chl-a), indicating that the protein-like substance mainly originated from the release or decomposition of algal cells. The complexing capacity of DOM–Cd decreased from 997 μmol Cd per gram dissolved organic carbon (DOC) to 884 μmol Cd per gram DOC with an increase in the proportion of autochthonous protein-like substances. However, the total Cd-complexing capacity of DOM was still high during the algal bloom due to the increase of DOM abundance. The proportion of freely dissolved concentration of Cd to total Cd concentration decreased from 50% to 20%, suggesting that the potential bioavailability of Cd was reduced.
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8136. 题目: Spectral fusion by Outer Product Analysis (OPA) to improve predictions of soil organic C
文章编号: N18080905
期刊: Geoderma
作者: Fabrício S. Terra, Raphael A. Viscarra Rossel, José A.M. Demattê
更新时间: 2018-08-09
摘要: Soil organic carbon (C) is an important indicator of agricultural and environmental quality. It improves soil fertility and helps to mitigate greenhouse gas emissions. Soil spectroscopy with either vis–NIR (350–2500 nm) or mid-IR (4000–400 cm−1) spectra have been used successfully to predict organic C concentrations in soil. However, research to improve predictions of soil organic C by simply combining vis–NIR and mid-IR spectra to model them together has been unsuccessful. Here we use the Outer Product Analysis (OPA) to fuse vis–NIR and mid-IR spectra by bringing them into a common spectral domain. Using the fused data, we derived models to predict soil organic C and compared its predictions to those derived with vis–NIR and mid-IR models separately. We analyzed 1259 tropical soil samples from surface and subsurface layers across agricultural areas in Central Brazil. Soil organic C contents were determined by a modified Walkley-Black method, and vis–NIR and mid-IR reflectance spectra were obtained with a FieldSpec Pro and a Nicolet 6700 Fourier Transformed Infrared (FT-IR), respectively. Reflectances were log-transformed into absorbances. The mean content of soil organic C was 9.14 g kg−1 (SD = 5.64 g kg−1). The OPA algorithm was used to emphasize co-evolutions of each spectral domain into the same one by multiplying the absorbances from both sets of spectra to produce a matrix with all possible products between them. Support Vector Machine with linear kernel function was used for the spectroscopic modeling. Predictions of soil organic C using vis–NIR, mid-IR, and fused spectra were statistically compared by the Tukey's test using the coefficient of determination (R2), root mean squared error (RMSE), and ratio of performance to interquartile distance (RPIQ). Absorbances in vis–NIR and mid-IR were emphasized in the common spectral domain presenting stronger correlations with soil organic C than individual ranges. Soil organic C predictions with the OPA fused spectra were significantly better (R2 = 0.81, RMSE = 2.42 g kg−1, and RPIQ = 2.87) than those with vis–NIR (R2 = 0.69, RMSE = 3.38 g kg−1, and RPIQ = 2.08) or mid-IR spectra (R2 = 0.77, RMSE = 2.90 g kg−1, and RPIQ = 2.43). Fusing vis–NIR and mid-IR spectra by OPA improves predictions of soil organic C.

8137. 题目: Apparent electrical conductivity predicts physical properties of coarse soils
文章编号: N18080904
期刊: Geoderma
作者: Mallika A. Nocco, Matthew D. Ruark, Christopher J. Kucharik
更新时间: 2018-08-09
摘要: Precision agriculture informed by electromagnetic induction surveys could reduce groundwater withdrawals and nitrogen leaching from coarse soils. However, coarse, nonsaline soils often have extremely narrow ranges of mapped apparent electrical conductivity (ECa) and the efficacy of ECa for predicting soil physical properties is uncertain in this context. For this reason, it is also uncertain as to whether electromagnetic induction surveys are valuable for guiding precision agriculture on coarse, nonsaline soils. Additionally, the need to ground-truth electromagnetic induction surveys for individual agricultural fields with soil sampling and statistical model development hampers adoption of precision agriculture at the regional scale. Our research objectives were to quantify the variation in mapped ECa and develop statistical relationships between ECa and soil physical properties both within and across several agricultural fields in the Wisconsin Central Sands, a distinct hydropedological region with coarse, glaciolacustrine soils. We used nonparametric correlation analyses to identify associations and quantile regression, a statistical approach with no assumptions of normality or homoscedasticity, to identify predictive relationships between ECa and soil physical properties. We found strong, significant (p < 0.05) correlative and predictive relationships between ECa and topsoil (0–0.3 m) particle size fraction, organic matter content, and field capacity within and across several fields. Yet, we did not observe many significant relationships between ECa and subsoil (0.5–0.6 m) physical properties, which we attribute to heterogeneous soil layering and the low depth resolution of our soil sampling approach. Our findings demonstrate that proximal sensing of ECa can identify intrafield variability in soil properties under extremely narrow observed ECa ranges (0–11 mS m−1). Moreover, we found that interfield quantile regression models predicted soil physical properties across several agroecosystems. Heteroscedasticity was present in interfield ECa relationships with physical properties, which resulted in the need for different quantile regression models across the conditional distribution. The flexibility for accommodating heteroscedasticity in soils and simplicity of modeled functions make quantile regression a promising approach for developing interfield or regional models of ECa to predict soil physical properties in distinct, hydropedological regions with coarse soils.

8138. 题目: Profiling microbial communities in a watershed undergoing intensive anthropogenic activities
文章编号: N18080903
期刊: Science of The Total Environment
作者: Hehuan Liao, Kai Yu, Yanhua Duan, Zigong Ning, Binrui Li, Leiyu He, Chongxuan Liu
更新时间: 2018-08-09
摘要: In lotic ecosystems highly susceptible to anthropogenic activities, the influences of environmental variables on microbial communities and their functions remain poorly understood, despite our rapidly increasing sequencing ability. In this study, we profiled the microbial communities in the hyporheic sediments of a watershed undergoing intensive anthropogenic activities via next-generation sequencing of 16S rRNA V4–V5 hypervariable regions on Illumina MiSeq platform. Tidal impacts on microbial communities were investigated via co-occurrence networks. In addition, the influences of physicochemical variables including salinity, and the concentrations of nutrients, organic matter and heavy metals on the microbial communities were explored via canonical correspondence analyses. The sediment samples were collected from 19 sites covering the whole main river stem of the target watershed (n = 19; Maozhou river watershed, Shenzhen, China). The samples were sub-divided in the field for microbiological analyses and measurements of physicochemical variables. The results indicated that core microbiome was associated with archaea methanogens and bacteria members from Proteobacteria, Chloroflexi, Bacteroidetes, Acidobacteria, Synergistetes and Firmicutes, among which, gram-negative and anaerobic bacteria genera contributing to the cycling of carbon, nitrogen and sulfur were predominant. Site-specific microbiomes were revealed that may serve as indicators of local environmental conditions (e.g., members affiliated to Oceanospirillales were abundant at sites with salt intrusion). Distinct microbial co-occurrence networks were identified for non-tidal, inter-tidal and tidal sites. Major environmental factors influencing microbial community composition included the concentrations of nitrate and bicarbonate in river water, pore water concentrations of sulfate, dissolved organic carbon and electrical conductivity, as well as manganese concentrations associated with the solid sediment. Collectively, the results of this study provide fundamental insights into the influence of environmental perturbations on microbial community composition in a lotic system, which may aid in the design of effective remediation and/or restoration strategies in the target watershed and beyond.
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8139. 题目: Multiple stressor effects on biodiversity and ecosystem functioning in a Mediterranean temporary river
文章编号: N18080902
期刊: Science of The Total Environment
作者: Evangelia Smeti, Daniel von Schiller, Ioannis Karaouzas, Sofia Laschou, Leonidas Vardakas, Sergi Sabater, Elisabet Tornés, Luis Simón Monllor-Alcaraz, Nuria Guillem-Argiles, Elena Martinez, Damià Barceló, Miren López de Alda, Eleni Kalogianni, Arturo Elosegi, Nikolaos Skoulikidis
更新时间: 2018-08-09
摘要: The hydrological and biological complexity of temporary rivers as well as their importance in providing goods and services is increasingly recognized, as much as it is the vulnerability of the biotic communities in view of climate change and increased anthropogenic pressures. However, the effects of flow intermittency (resulting from both seasonal variations and rising hydrological pressure) and pollution on biodiversity and ecosystem functioning have been overlooked in these ecosystems. We explore the way multiple stressors affect biodiversity and ecosystem functioning, as well as the biodiversity-ecosystem functioning (B-EF) relationship in a Mediterranean temporary river. We measured diversity of benthic communities (i.e. diatoms and macroinvertebrates) and related ecosystem processes (i.e. resource use efficiency-RUE and organic matter breakdown-OMB) across a pollution and flow intermittency gradient. Our results showed decreases in macroinvertebrate diversity and the opposite trend in diatom assemblages, whereas ecosystem functioning was negatively affected by both pollution and flow intermittency. The explored B-EF relationships showed contrasting results: RUE decreased with higher diatom diversity, whereas OMB increased with increased macroinvertebrate diversity. The different responses suggest contrasting operating mechanisms, selection effects possibly driving the B-EF relationship in diatoms and complementarity effects driving the B-EF relationship in macroinvertebrates. The understanding of multiple stressor effects on diversity and ecosystem functioning, as well as the B-EF relationship in temporary rivers could provide insights on the risks affecting ecosystem functioning under global change.
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8140. 题目: Effect of sulfur-iron modified biochar on the available cadmium and bacterial community structure in contaminated soils
文章编号: N18080901
期刊: Science of The Total Environment
作者: Chuan Wu, Lizheng Shi, Shengguo Xue, Waichin Li, Xingxing Jiang, Manikandan Rajendran, Ziyan Qian
更新时间: 2018-08-09
摘要: Cadmium contamination in paddy soils has aroused increasing concern around the world, and biochar has many positive properties, such as large specific surface areas, micro porous structure for the heavy metal immobilization in soils. However there are few studies on sulfur-iron modified biochar as well as its microbiology effects. The purpose of this study was to evaluate the Cd immobilization effects of sulfur or sulfur-iron modified biochar and its related microbial community changes in Cd-contaminated soils. SEM-EDX analysis confirmed that sulfur and iron were loaded on the raw biochar successfully. Sulfur-modified biochar (S-BC) and sulfur-iron modified biochar (SF-BC) addition increased pH value and the content of soil organic matter, and also decreased DTPA-extractable Cd. There was a negative significant correlation between organic matter content and the available Cd (P < 0.05). During a 45-d incubation period, the fractions of Cd are mainly with the exchangeable (25.16–35.79%) and carbonate (22.01–25.10%) fractions. Compared with the control, the concentrations of exchangeable Cd in soil were significantly (P < 0.05) decreased by 12.54%, 29.71%, 18.53% under the treatments of BC, S-BC, SF-BC respectively. The S-BC and SF-BC treatments significantly (P < 0.05) increased Chao1, observed, Shannon and Simpson diversity indices compared with the control and biochar treatments. Meanwhile, the relative abundance of Proteobacteria, Bacteroidetes, and Actinobacteria increased, whereas the abundance of Acidobacteria and Germmatimonadetes decreased.Capsule: Sulfur-modified and sulfur-iron modified biochar applications decreased the available Cd and changed the microbial community.
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