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25841. 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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25842. 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.

25843. 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.

25844. 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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25845. 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.

25846. 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.

25847. 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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25848. 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.

25849. 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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25850. 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.

25851. 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 (EC_a) and the efficacy of EC_a 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 EC_a and develop statistical relationships between EC_a 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 EC_a and soil physical properties. We found strong, significant (p < 0.05) correlative and predictive relationships between EC_a 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 EC_a 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 EC_a can identify intrafield variability in soil properties under extremely narrow observed EC_a 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 EC_a 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 EC_a to predict soil physical properties in distinct, hydropedological regions with coarse soils.

25852. 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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25853. 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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25854. 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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25855. 题目: Identification of a novel C₃₃ botryococcane and C₃₃ botryococcanone in the Maoming Basin, China
文章编号: N18080817
期刊: Organic Geochemistry
作者: Jing Liao, Hong Lu, Qiao Feng, Youping Zhou, Quan Shi, Ping'an Peng, Guoying Sheng
更新时间: 2018-08-08
摘要: A novel C₃₃ botryococcane in a sedimentary sample from the Maoming Basin in China was found to have a methyl group positioned β to the quaternary carbon C-10 in its structure based on IR, MS and NMR analyses and Lindeman-Adams modelling. This structure is inconsistent with the prediction from the currently accepted botryococcene biosynthetic pathway and different from the skeleton for the C₃₃ botryococcanes suggested in the literature. A C₃₃ botryococcan-24-one with the same carbon skeleton as the C₃₃ botryococcane was also found to co-occur in the sediment sample. The location of the carbonyl group at C-24 is different from that of a previously reported botryococcenone from an Australian collection of race B of Botryococcus braunii where it is positioned at C-15. We propose a biogeochemical pathway to explain the occurrence of this unique skeleton in the Maoming Basin sediment. The biochemical component of the pathway involves electrophilic or nucleophilic attack between two farnesyl diphosphates (FPPs) leading to direct or indirect formation of a C₃₀ botryococcene via a cyclobutane ring intermediate (1′-2-3-2′ cyclisation). A Retro-Prins reaction and subsequent methylation gives rise to C₂₉ and C₃₃ botryococcenes in sequence. The geochemical component involves first in-water-column (photo)-oxidation of the alkene to a C₃₃ botryococcanone and subsequent reduction (hydrogenation) to stabilize the ketone as an alkane.

25856. 题目: Significant chemical fluxes from natural terrestrial groundwater rival anthropogenic and fluvial input in a large-river deltaic estuary
文章编号: N18080816
期刊: Water Research
作者: Xin Luo, Jiu Jimmy Jiao, Willard S. Moore, John A. Cherry, Ya Wang, Kun Liu
更新时间: 2018-08-08
摘要: The shores of the Pearl River estuary are home to 35 million people. Their wastes are discharged into the large river delta-front estuary (LDE), one of the most highly polluted systems in the world. Here we construct a radium reactive transport model to estimate the terrestrial groundwater discharge (TGD) into the highly urbanized Pearl River LDE. We find the TGD comprises only approximately 0.9% in term of water discharge compared to the river discharge. The TGD in the Pearl River LDE delivers significant chemical fluxes to the coast, which are comparable to the fluvial loadings from Pearl River and other world major rivers. Of particular importance is the flux of ammonium because of its considerable role in Pearl River estuary eutrophication and hypoxia. Unlike the ammonium in many other aquifers, the ammonium in the Pearl River aquifer system is natural and originated from organic matter remineralization by sulfate reduction in the extremely reducing environment. The TGD derived NH₄⁺ is as much as 5% of the upstream Pearl River fluvial loading and 42% of the anthropogenic inputs. This high groundwater NH₄⁺ flux may greatly intensify the eutrophication, shift the trophic states, and lead to alarming hypoxia within the affected ecosystems in the Pearl River LDE. The large TGD derived chemical fluxes will lead to deterioration of water and will potentially affect human health.

25857. 题目: Erosion-induced carbon losses and CO₂ emissions from Loess and Black soil in China
文章编号: N18080815
期刊: CATENA
作者: Xin Gao, Yaxian Hu, Qiqi Sun, Lanlan Du, Pengfei Duan, Lunguang Yao, Shengli Guo
更新时间: 2018-08-08
摘要: Soil erosion influences both lateral soil organic carbon (SOC) re-distribution and vertical soil CO₂ emissions. While potential SOC mineralization during transport and the burial effects of SOC at depositional sites have been addressed in previous reports, erosion induced on-site CO₂ emissions are still under-studied. In this study, two soils (Loess soil and Black soil) with similar texture but contrasting aggregate structure and SOC content were subject to a set of 60-min long simulated rainfall events. There were two different rainfall intensities (30 and 90 mm h⁻¹) at three slope gradients (5°, 15° and 25°). Runoff and sediment from erosion plot were collected at 10-min intervals over 60 min. Soil CO₂ emissions from eroding slopes, SOC and particle size distribution of the eroding soil were measured after the erosion events. The results show that the runoff rates from the two soils were comparable, but the sediment rates from the Loess soil roughly three times that from the Black soil. In general, the SOC erosion from the Loess soil was 1.8 times that from the Black soil, even though the SOC concentration in the original Black soil was 56% higher than the Loess soil. The cumulative soil CO₂ emissions from the eroding slopes of the Loess soil ranged from 15.4 to 19.7 g C m⁻², which was doubled on the Black soil (from 28.1 to 59.6 g C m⁻²). When the rainfall intensity raised from 30 mm h⁻¹ to 90 mm h⁻¹, the cumulative soil CO₂ emissions from the Black soil decreased by 38.2%, but only declined by 10.0% on the Loess soil. When the slope gradient increased from 5° to 25°, the cumulative soil CO₂ emissions decreased by 23.8% on the Black soil but by 12.6% on the Loess soil. Therefore, our observations suggest that the soil CO₂ emissions on the Black soil was much more sensitive to the variations of rainfall intensity and slope gradients than the Loess soil. Greater SOC erosion should not be directly translated to less on-site soil CO₂ emissions. The selective depletion/enrichment of SOC and the lability of individual components must be fully understood when accounting for slope-scale carbon balances.

25858. 题目: Spatial variation of heavy metals in sediments within a temperate mangrove ecosystem in northern New Zealand
文章编号: N18080814
期刊: Marine Pollution Bulletin
作者: Ujwal Bastakoti, John Robertson, Andrea C. Alfaro
更新时间: 2018-08-08
摘要: Spatial dynamics of heavy metals (Cd, Cu, Fe, Pb, and Zn) and metalloid As were investigated along the sedimentary column, inside and outside mangrove stands, and within the upper, middle, and lower Mangawhai Estuary, New Zealand. Organic matter contents (1.89 to 17.15%) were 10 times higher inside versus outside mangroves, and decreased sharply with depth to 30 cm. Cu, Fe, and Zn were highest in the upper estuary and Pb was highest close to a road (lower estuary), reflecting road run-off. A mangrove island (lower estuary; high energy) had lowest heavy metal and highest As concentrations (resulting from high absorption of As by the carbonate rich sediments). Most of the analysed sediment parameters in our study were higher inside versus outside mangroves, suggesting the accumulation of organic matter and build up capacity to buffer pollutants. Our results show that mangrove stands tend to accumulate heavy metals and may act as natural filters of pollution of coastal waterways.

25859. 题目: Role of extracellular polymeric substances in efficient chromium(VI) removal by algae-based Fe/C nano-composite
文章编号: N18080813
期刊: Chemosphere
作者: Jun Wu, Lin-Lin Ma, Raymond J. Zeng
更新时间: 2018-08-08
摘要: Subsequent application of the obtained algae by chemical coagulation (e.g. Fe(III) addition) presents a challenge because of various iron compounds in algae. In this study, algae obtained by chemical coagulation were carbonized to yield an algae-based Fe/C nano-composite with a high capacity for hexavalent chromium (Cr(VI)) removal (236.9 mg/g), which is attributed to the high reductive Fe content (e.g., FeS, Fe(0), and FeO) and specific surface area. The optimal conditions—that is, 100 mg/L Fe(III) addition and 800 °C—were determined. Moreover, the role of extracellular polymeric substances (EPS) in carbonization was examined as it affected the product composition and efficiency of Cr(VI) removal, owing to the stabilizing property effect of EPS in algae. Algal EPS induced the homogeneous distribution of Fe compounds on the surface of the algae, and the generated α-FeOOH nanoparticles were wrapped in organic carbon matrix, resulting in a sufficient reaction between Fe compounds and organic carbon during carbonization. X-ray photoelectron spectroscopy showed that reduction and adsorption contributed 83.44% and 16.56% to Cr(VI) removal, respectively. This study provides a new insight into the role of EPS in the efficient Cr(VI) removal by algae-based Fe/C nano-composite and presents a promising application of this Fe/C nano-composite in environmental remediation.

25860. 题目: Insight into mechanism of aged biochar for adsorption of PAEs: Reciprocal effects of ageing and coexisting Cd²⁺
文章编号: N18080812
期刊: Environmental Pollution
作者: Fanqi Jing, Saran P. Sohi, Yuyan Liu, Jiawei Chen
更新时间: 2018-08-08
摘要: Biomass derived biochar is a stable carbon-rich product with potential for soil amendment. Introduced into the natural environment, biochar will naturally experience ‘ageing’ processes that are liable to change its physicochemical properties and the mobility of sorbed pollutants over the longer term. To elucidate the reciprocal effects of biochar ageing and heavy metal adsorption on the affinity of biochar for organic pollutants, we systematically assessed the adsorption of diethyl phthalate (DEP), representative of phthalic acid esters (PAEs), to fresh and aged biochars with and without coexistence of Cd²⁺. Long-term oxidative ageing was simulated using 5% H₂O₂ and applied to biochar samples made from corn cob, maize straw and wheat straw made by pyrolysis at both 450 °C and 650 °C. Our results showed that biochar made at lower temperature (450 °C) and from straw exhibited the higher adsorption capacity, owing to their greater polarity and abundance of O-containing functional groups. The adsorption of DEP onto fresh biochars was found to be driven by van der Waals force and H-bonding. Biochar made at the higher temperature (650 °C) displayed higher carbon stability than that produced at lower pyrolysis temperature. Oxidized biochar showed lower adsorption capacity than fresh biochar owing to the formation of three-dimensional water clusters on biochar surface, which blocked accessible sites and decreased the H-bonding effect between DEP and biochars. The coexistence of Cd²⁺ suppressed the sorption of DEP, via competition for the same electron-rich sites. This indicates that cation/π-π EDA interactions are the primary mechanism for PAE and Cd²⁺ stabilization on biochar. Our study sheds light on the mechanism of organic pollutant sorption by biochar, as well as the potential susceptibilities of this sorption to ageing effects in the natural environment.
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