论文检索

总访问量：5926771次

总访客量：428904人

所有论文

26101. 题目: The role of ¹⁵N in tracing N dynamics in agro-ecosystems under alternative systems of tillage management: A review
文章编号: N19110901
期刊: Soil and Tillage Research
作者: Christopher J. Smith, Phillip M. Chalk
更新时间: 2019-11-09
摘要: Cultivation has led to a substantial loss of soil organic matter in the surface soil layers. The use of no-till (or zero-till) has been promoted as a practice that maximises the retention on organic residues to reverse or slow the loss of soil organic matter. However, the terms are misnomers because sowing the crop disturbs the soil. The definitions of conservation tillage systems should be used, including quantifying the mass of residue return to the system. Over 116 research papers that used ¹⁵N natural abundance, ¹⁵N depleted or ¹⁵N enriched isotopic techniques were reviewed to quantify the impact of tillage, especially no-till, on the N dynamics of cropping systems. The negative effects of no-till on crop yields at low fertiliser N applications were reported in numerous studies that had operated for short periods, with a few conducted on a long-term basis (>10-15 years). Based on the cumulative research, we concluded that no-till had little impact on ¹⁵N fertiliser recovery, or the accumulation of N released from the mineralisation of “native” soil organic matter. In most studies, the impact of no-till on N dynamics is confounded by soil water and soil temperature differences. Often the positive response to no-till was attributed to greater plant available water during the growing season. Soil moisture was the main determinant of the gross N transformation rate and the potential for N mineralisation was not different between conventional and no-till systems. The effect of no-till is restricted to the surface soil. Although differences exist in the surface soil, we were unable to confirm from the ¹⁵N studies that no-till increased organic N sequestration. Net N mineralisation of the large unlabelled soil organic N pool in the root zone dilutes the effect of increased organic N accumulation and N mineralised in the surface layers of no-till systems. Tillage systems did affect the percentage of legume N derived from the atmosphere. Nitrogen fixation was greater under no-till compared to conventional cultivation when (i) mineral N was lower, and (ii) plant available water status was better due to suppression of weeds.

26102. 题目: Soil Organic Matter and Phosphate Sorption on Natural and Synthetic Fe Oxides under in Situ Conditions
文章编号: N19110816
期刊: Environmental Science & Technology
作者: Kristof Dorau, Lydia Pohl, Christopher Just, Carmen Höschen, Kristian Ufer, Tim Mansfeldt, Carsten W. Mueller
更新时间: 2019-11-08
摘要: Iron (Fe) oxides in soils are strong sorbents for environmentally important compounds like soil organic matter (SOM) or phosphate, while sorption under field conditions is still poorly understood. We installed polyvinyl chloride plastic bars which have been coated either with synthetic Fe or manganese (Mn) oxides for 30 days in a redoximorphic soil. A previous study revealed the formation of newly formed (natural) Fe oxides along the Mn oxide coatings. This enables us to differentiate between sorption occurring onto the surfaces of synthetic versus natural Fe oxides. After removal of the bars, they were analyzed by nanoscale secondary ion mass spectrometry (NanoSIMS) to study the distribution of Fe (56Fe16O–), SOM (12C14N–), and phosphorus (31P16O2–) at the microscale. Image analysis of individual Fe oxide particles revealed a close association of Fe, SOM, and P resulting in coverage values up to 71%. Furthermore, ion ratios between sorbent (56Fe16O–) and sorbate (12C14N– and 31P16O2–) were smaller along the natural oxides when compared with those for synthetic Fe oxides. We conclude that both natural and synthetic Fe oxides rapidly sequester SOM and P (i.e., within 30 days) but that newly, natural formed Fe oxides sorbe more SOM and P than synthetic Fe oxides.

26103. 题目: Mineralogical control on the fate of continentally derived organic matter in the ocean
文章编号: N19110815
期刊: Science
作者: T. M. Blattmann, Z. Liu, Y. Zhang, Y. Zhao, N. Haghipour, D. B. Montluçon, M. Plötze, T. I. Eglinton
更新时间: 2019-11-08
摘要: First-order relationships between organic matter content and mineral surface area have been widely reported and are implicated in stabilization and long-term preservation of organic matter. However, the nature and stability of organomineral interactions and their connection with mineralogical composition have remained uncertain. In this study, we find that continentally derived organic matter of pedogenic origin is stripped from smectite mineral surfaces upon discharge, dispersal, and sedimentation in distal ocean settings. In contrast, organic matter sourced from ancient rocks that is tightly associated with mica and chlorite endures in the marine realm. These results imply that the persistence of continentally derived organic matter in ocean sediments is controlled to a first order by phyllosilicate mineralogy.

26104. 题目: Distribution character of localized iron microniche in lake sediment microzone revealed by chemical image
文章编号: N19110814
期刊: Environmental Science and Pollution Research
作者: Zhihao Wu, Shengrui Wang, Ningning Ji
更新时间: 2019-11-08
摘要: DGT (diffusive gradients in thin films) technique and LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) for heterogeneous distribution of the soluble labile iron (Fe) at submillimeter resolution in lake sediment porewater are reported. The soluble labile Fe species include ion and labile organic complexes. The chemical images in two dimensions (2D) for DGT concentration of Fe (C_DGT(Fe)) are investigated for Fe remobilization character. There are 902 C_DGT(Fe) values between 1000 and 2000 μg L⁻¹, 463 values between 2000 and 3000 μg L⁻¹, and 112 values over 3000 μg L⁻¹ in all chemical maps. Based on the linear correlation relationships between C_DGT (Fe) and total Fe (TFe), total organic carbon (TOC), acid-volatile sulfide (AVS), Eh, concentrations of the soluble reactive phosphorus (P) (SRP), and soluble labile trace metals (Zn, Cu, Pb, and Zn) in a vertical 1D profile of sediment or porewater, Fe release mechanisms are mainly due to the reductive Fe release from iron oxyhydroxides and the decomposition of organic matter in algae biomass and deep sediment layer. It can be used to explain the formation mechanisms of Fe microniches in chemical maps with heterogeneous character to a great extent. C_DGT(Fe) peak flux in the center of Fe microniche and the low C_DGT (Fe) at the edge of a microniche are due to the formation of the insoluble iron sulfide and the abundant acid-volatile sulfide (AVS) in sediment. The verified co-remobilization of the soluble labile Fe and trace metals or SRP in sediment porewater can be used to predict their simultaneous release from Fe microniches with the large C_DGT (Fe) peaks. The different kinds of Fe microniche zones and hot spots from sediment/water interface (SWI) to deep sediment correspond to the formation mechanisms of microniches mentioned above. Moreover, some narrow Fe microniche zones with the large C_DGT (Fe) across chemical maps are due to the desorption of Fe(II) from the freshly formed oxide on Myriophyllum verticiilatur roots, which are located at sites of microniche zones.

26105. 题目: TEMPERATURE SENSITIVITY OF DECOMPOSITION OF SOIL ORGANIC MATTER FRACTIONS INCREASES WITH THEIR TURNOVER TIME
文章编号: N19110813
期刊: Land Degradation & Development
作者: Yufu Jia, Yakov Kuzyakov, Guoan Wang, Wenbing Tan, Biao Zhu, Xiajuan Feng
更新时间: 2019-11-08
摘要: Soil organic carbon (SOC) is an indicator of soil fertility. Global warming accelerates SOC decomposition, consequently, resulting in land degradation. Characterization of the response of SOC decomposition to temperature is important for predicting land development. A simulation model based on temperature sensitivity (Q₁₀) of SOC decomposition has been used to predict SOC response to climate warming. However, uncertain Q₁₀ leads to substantial uncertainties in the predictions. A major uncertainty comes from the interference of rainfall. To minimize this interference, we sampled surface (0‐5cm) soils along an isohyet across a temperature gradient in the Qinghai‐Tibet Plateau. The Q₁₀ of bulk soil and the four soil fractions: Light fraction (LightF), particulate organic matter (POM), hydrolyzable fraction (HydrolysF), and recalcitrant fraction (RecalcitF), was studied by ¹⁴C dating. Turnover time (TT) follows the order: LightF < POM < bulk soil < HydrolysF < RecalcitF. The Q₁₀ follows the order: LightF (1.0) = POM (1.0) < HydrolysF (3.63) < bulk soil (5.93) < RecalcitF (7.46). This indicates that stable fractions are much more sensitive to temperature than labile fractions. We also suggest that protection mechanisms rather than molecular composition regulate SOC turnover. A new concept ‘protection sensitivity’ of SOC decomposition was proposed. Protection sensitivity relates to protection type and primarily controls Q₁₀ variation. A simulation model based on the Q₁₀ of individual fractions predicted SOC change and land development in the Qinghai‐Tibet Plateau in the next 100 years much effectively as compared to simulations based on one‐pool model (Q₁₀ = 2) or bulk soil (Q₁₀ = 5.93).

26106. 题目: A Global Analysis on the Impact of No‐Tillage on Soil Physical Condition and Organic Carbon Content, and Plant Root Response
文章编号: N19110812
期刊: Land Degradation & Development
作者: Surajit Mondal, Debashis Chakraborty, K.K. Bandyopadhyay, Pramila Aggarwal, D.S. Rana
更新时间: 2019-11-08
摘要: Food security involves the sustainable utilization of soil and land resources. No‐tillage (NT) practice is a proponent of better resource utilization, to improve soil physical condition, and a potential sink to atmospheric carbon. However, the impact varies across climates, over the NT history, cropping systems and soil depths. A meta‐analysis was performed, based on 4131 paired data from 522 studies spread globally, to evaluate the effect of NT in comparison to conventional tillage (CT), on soil physical condition (bulk density, BD; mean weight diameter of aggregates, MWD; field capacity water content, FC; and steady‐state infiltration rate, IR), soil organic carbon (SOC) content, and the root response (root length density, RLD). No‐tillage significantly improved MWD and FC at surface and sub‐surface layers by 19‐58% and 6‐16% respectively, and resulted in no change in BD in either of the layers, but IR increased by 66%. Surface 0‐5 and 5‐10 cm layers had significantly higher SOC content under NT, while in other layers, the SOC content either reduced or did not change, resulting in a small and insignificant variation in the SOC stock (~1.1%) in favour of NT. The RLD improved by ~35% in NT only at 0‐ to 5‐cm soil depth. Effect of climate, soil type or cropping system could not be broadly recognized, but the impact of NT certainly increased over time. Improvements in soil aggregation and hydraulic properties are highly convincing with the adoption of NT, and therefore this practice leads to the better and sustainable use of soil resources.

26107. 题目: Effect of forest land use change on carbohydrates, physical soil quality and carbon stocks in Moroccan cedar area
文章编号: N19110811
期刊: Journal of Environmental Management
作者: Hafida Zaher, Mohamed Sabir, Hassan Benjelloun, Hounzandji Paul-Igor
更新时间: 2019-11-08
摘要: The present work was conducted to evaluate the carbon storage potential of Moroccan cedar forest and its vulnerability to transformations through deforestation and overgrazing. The present study took place in the Middle Atlas where is the most beautiful of Moroccan cedar forest (Cedrus atlantica). We considered three levels of degradation (Natural cedar, degraded cedar and cleared area). For each land use, we estimated carbon stocks in four reservoirs, i.e., aboveground biomass (trees, shrubs and herbaceous plants), belowground biomass (roots), necromass (litter and deadwood) and the soil. Various physico-biochemical characteristics (structural stability, bulk density, soil organic carbon and carbohydrates (neutral and uronic sugars)) were also evaluated. Carbon stocks were 395.37 Mg ha⁻¹ for the natural cedar and 76.05 Mg ha⁻¹ for the cleared area. Analysis of the ecosystem carbon stock distribution revealed that soil was the largest reservoir. The soil carbon stock varies from 46.4% to 93.5%, that of the biomass (aboveground and belowground) fluctuate between 4.3% and 52.7% and in the necromass it is between 0.8 and 2.2%. The conversion of natural forest into cleared area resulted in a deterioration of the soil physical quality (decrease of the percentage of water-stable aggregate by 36% and increase of bulk density by 57%). Also, natural forests have 25% and 50% more neutral sugars and uronic sugars respectively than the cleared area. The correlations established between carbohydrates and carbon stocks of the different reservoirs considered showed that the increase in neutral sugars is more explained by the aboveground biomass (R² = 79%, P = 0.0013) and necromass (R² = 85%, P = 0.0004). Otherwise, the soil carbon stock explained the most increase in uronic sugars (R² = 99%, P = 0.0001). Neutral sugar can be an indicator of soil physical quality. Neutral sugars were responsible for 85% of the highly significant increase in soil structural stability and over 79% of the highly significant decrease in bulk density. Moreover, uronic sugars appear to be a good indicator of the richness in organic carbon of soils sampled since the increase of these sugars justified more than 90% of the increase in the soil organic carbon content.
图文摘要:

26108. 题目: New insights into CO₂ sorption on biochar/Fe oxyhydroxide composites: Kinetics, mechanisms, and in situ characterization
文章编号: N19110810
期刊: Chemical Engineering Journal
作者: Xiaoyun Xu, Zibo Xu, Bin Gao, Ling Zhao, Yulin Zheng, Jinsheng Huang, Daniel C.W. Tsang, Yong Sik Ok, Xinde Cao
更新时间: 2019-11-08
摘要: Despite its importance, chemical process has been often overlooked in CO₂ sorption on carbon based oxyhydroxide composites. In this study, pristine and ball-milled biochar/Fe oxyhydroxide composites were fabricated for CO₂ sorption at 25 °C. The composites, particularly the ones with high Fe content, were effective sorbents for CO₂ with the capacities of up to 160 mg g⁻¹. The primary mechanism of CO₂ sorption on biochar composites with low Fe content was physical adsorption. When the Fe content increased, biochar/Fe oxyhydroxide composites showed enhanced CO₂ sorption capacities, but the sorption kinetics became slower. This is because the governing CO₂ sorption mechanism was shifted from physical adsorption to chemical reaction between Fe oxyhydroxides and CO₂. The formed (oxy)hydroxycarbonate could be decomposed at a temperature between 50 and 125 °C. Furthermore, ball milling could speed up CO₂ mineralization rate on the composites, especially for those with high Fe content, to favor the relative significance of chemical sorption. Both physical and chemical CO₂ sorption mechanisms were verified by different characterization methods including in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Findings of this study not only demonstrate the importance of chemical sorption, but also provide new insights on CO₂ capture by low-cost and environmentally benign biochar/Fe oxyhydroxide composites. Besides, the low regeneration temperature of chemically-sorbed CO₂ gives biochar/Fe oxyhydroxide composite a competitive edge over other CO₂ sorbents, which often need a high regeneration temperature or are not regenerable.
图文摘要:

26109. 题目: Interfacial oxygen nanobubbles reduce methylmercury production ability of sediments in eutrophic waters
文章编号: N19110809
期刊: Ecotoxicology and Environmental Safety
作者: Xiaonan Ji, Chengbin Liu, Gang Pan
更新时间: 2019-11-08
摘要: Eutrophication can induce hypoxia/anoxia and rich organic matter at the sediment-water interface in surface waters. When eutrophic waters are impacted with mercury (Hg) pollution, methylmercury (MeHg) production ability (MPA) of surface sediment would increase and more MeHg might be produced. To tackle this risk, this study firstly collected samples of surface sediment and overlying water from a typical eutrophic lake—Taihu Lake. Then from a sediment-water simulation system, we demonstrated that eutrophic waters were able to methylate Hg spontaneously, and that sediment is the major Hg sink in the system. After the addition of HgCl₂ solution (approximately 1 mg L⁻¹ in the slurry), MeHg concentrations in the sediment increased by 11.7 times after 48 h. The subsequent column experiments proved that O₂ nanobubbles could significantly decrease the MPA of surface sediment, by up to 48%. Furthermore, we found that O₂ nanobubbles could remediate anoxia mainly by increasing dissolved oxygen (from 0 to 2.1 mg L⁻¹), oxidation-reduction potentials (by 37% on average), and sulfate (by 31% on average) in the overlying water. In addition, O₂ nanobubbles could also help decrease organic matter concentration, as was revealed by the decline of dissolved organic carbon in the overlying water (by up to 57%) and total organic carbon in surface sediment (by up to 37%). The remediation of anoxia and reduction of organic matter could contribute to the decrease of hgcA gene abundance (by up to 86%), and thus result in the reduction of MPA after the addition of O₂ nanobubbles. This study revealed the risk of MeHg production in case Hg pollution occurs in eutrophic waters and proposed a feasible solution for MeHg remediation.
图文摘要:

26110. 题目: Quantification of different silicon fractions in broadleaf and conifer forests of northern China and consequent implications for biogeochemical Si cycling
文章编号: N19110808
期刊: Geoderma
作者: Xiaomin Yang, Zhaoliang Song, Changxun Yu, Fan Ding
更新时间: 2019-11-08
摘要: The terrestrial biogeochemical silicon (Si) cycle significantly contributes to maintaining the functions and sustainability of terrestrial ecosystems. Over the short term, the biogeochemical Si cycle can be strongly influenced by dissolved Si, organic bound Si, Si adsorbed to pedogenic oxides/hydroxides, and biogenic and pedogenic amorphous Si. However, quantitative studies about these relatively soluble Si fractions are rare. In this study, we quantified different Si fractions in the 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm and 40–50 cm soil layers of broadleaf forests (Betula forest and Quercus forest) and conifer forests (Larix forest and Pinus forest) in northern China using a sequential chemical extraction scheme optimized for these Si fractions. The results showed that the total Si (Si_t) in the soil layers consisted of 97.7–98.5% crystalline Si (Si_cry) and 1.5–2.3% non-crystalline Si (Si_noncry) fractions. Within the Si_noncry fraction, the proportions of dissolved Si (Si_dis), organic matter bound Si (Si_org), pedogenic oxides/hydroxides chemisorbed Si (Si_sorb), and amorphous Si (Si_amor) were 3.4–6.7%, 5.5–8.9%, 6.3–8.5%, and 77.7–84.8%, respectively. Although the Si_dis fraction was the least abundant component, it is at the center of the interconversion processes among the different Si_noncry fractions. The Si_amor fraction was the largest component of Si_noncry and was composed of 37.7–71.9% biogenic amorphous Si (Si_bio-amor) and 28.1–62.3% pedogenic amorphous Si (Si_ped-amor). Our study indicated that i) Si_ped-amor fraction is more easily influenced by soil pH comparing to Si_bio-amor fraction; ii) the Si_bio-amor fraction contributes more to the biogeochemical Si cycle in broadleaf forests, whereas the Si_ped-amor fraction contributes more in conifer forests; and iii) soil pH, soil organic matter, and plant community differences can influence the vertical distribution of the different Si_noncry fractions and thus affect the multiple transformation processes among these Si fractions in studied forests.

26111. 题目: Land‐use change with pasture and short‐rotation eucalypts impacts the soil C emissions and organic C stocks in the Cerrado biome
文章编号: N19110807
期刊: Land Degradation & Development
作者: Rafael da Silva Teixeira, Ricardo Cardoso Fialho, Daniela Cristina Costa, Rodrigo Nogueira de Sousa, Rafael Silva Santos, Ana Paula Mendes Teixeira, Thalles Guimarães Reis, Ivo Ribeiro da Silva
更新时间: 2019-11-08
摘要: The expansion of short‐rotation eucalypt plantations in low soil organic matter (SOM) sandy soils may offers an alternative to improve soil C sequestration. The goal of this study was to estimate the changes in C stocks and emissions in different SOM fractions following conversion of the native Cerrado to pasture and then to eucalypt plantation. Therefore, we studied soils under native Cerrado, planted pasture (cultivated for 34‐years following the clearing of the Cerrado) and eucalypt plantation (4‐years). The C and N stocks in particulate organic matter (POM) and mineral‐associated organic matter (MAOM) were determined 4‐years after eucalypt planting. Soil CO₂‐C, CH₄‐C fluxes and CO₂‐C concentrations in soil profile were measured in different seasons over four years. Variation in the natural abundance of ¹³C was used to partition the SOM‐C. The soil CO₂‐C and CH₄‐C fluxes were influenced by soil surface moisture (r = 0.185^o and r = 0.430^**, respectively), while only the soil CH₄‐C fluxes correlated with soil surface temperature (r = 0.355^**). The highest soil CO₂‐C flux in soil under eucalypt occurred after 4‐years of eucalypt planting (2.5 kg ha^‐1 h^‐1, approximately 70%). The pasture soil acted as a CH₄‐C source to the atmosphere. The pasture MAOM‐C losses in the 0.0‐1.0‐m soil layers were not compensated by the new eucalypt C inputs (MAOM‐C lost ~ 9.6 Mg ha^‐1). In summary, the recent worldwide expansion of short‐rotation eucalypt plantations should be carefully considered, particularly under pasture degraded soil sandy soils, since land‐uses able to increase SOM are priorities.

26112. 题目: Improved oxidation of refractory organics in concentrated leachate by a Fe 2+ -enhanced O 3 /H 2 O 2 process
文章编号: N19110806
期刊: Environmental Science and Pollution Research
作者: Zheqing Huang, Zhepei Gu, Ying Wang, Aiping Zhang
更新时间: 2019-11-08
摘要: Concentrated leachate from membrane processes, which contains a mass of refractory organics and salt, has become a new problem for wastewater engineers. In this study, removal of organic contaminants in concentrated landfill leachate was investigated by applying the ferrous ion (Fe²⁺) catalyzed O₃/H₂O₂ process. The maximum chemical oxygen demand (COD) and absorbance at 254 nm (UV₂₅₄) removal efficiencies under the optimal conditions (initial pH = 3.0, Fe²⁺ dosage = 6.500 mM, H₂O₂ dosage = 18.8 mM and O₃ dosage = 52.65 mg min⁻¹) were 48.82% and 63.59%, respectively. These were higher than those achieved using the Fe²⁺/O₃, O₃/H₂O₂, and O₃ processes, and biodegradability of the leachate was improved significantly. Moreover, compared with other processes, the Fe²⁺ had a stronger catalytic effect. Molecular distribution analysis and three-dimensional excitation and emission matrix analysis both indicated that the fulvic acid and humic acid in the concentrated leachate were greatly degraded. Ultraviolet-visible spectra showed that the Fe²⁺/O₃/H₂O₂ process mainly destroyed unsaturated bonds and decreased the aromatic degree of the leachate. The reaction mechanism of the Fe²⁺/O₃/H₂O₂ process mainly was attributed to three factors: (1) O₃ and H₂O₂ reacting to produce ^•OH; (2) H₂O₂ and O₃ decomposing into ^•OH through the oxidation of Fe²⁺ to Fe³⁺; and (3) coagulation by Fe (OH)₃. The ^•OH can rapidly degrade recalcitrant organics, and coagulation also increases the removal of organic matter. Therefore, the Fe²⁺/O₃/H₂O₂ process was an effective method for treating concentrated landfill leachate.

26113. 题目: Influence of the properties of 7 micro-grain activated carbons on organic micropollutants removal from wastewater effluent
文章编号: N19110805
期刊: Chemosphere
作者: Ronan Guillossou, Julien Le Roux, Romain Mailler, Catherine Morlay, Emmanuelle Vulliet, Fabrice Nauleau, Vincent Rocher, Johnny Gasperi
更新时间: 2019-11-08
摘要: Most studies dedicated to organic micropollutants (OMPs) removal from wastewater effluents by adsorption onto activated carbon (AC) only consider a few conventional AC properties. The link between OMPs removal and these properties is often missing, which limits the understanding of the adsorption process and the interpretation of the results. The chemical, physical and textural properties of seven newly commercialized micro-grain activated carbons (μGACs) were determined to assess their influence on the removal of 28 OMPs. Conventional batch tests with wastewater effluent showed that a high percentage of microporous volume (>65%) was detrimental for the removal of 10 OMPs, probably due to a higher blockage of micropores by dissolved organic matter (DOM). The removal of 5 OMPs was correlated with μGACs surface chemistry properties (i.e. charge) which were potentially modified by DOM adsorption or inorganic species, thus favoring the adsorption of positively-charge compounds. A combination of OMPs properties including their charge, hydrophobicity and minimal projection area could explain their removal. Correlations were found between the removal of several OMPs and UV₂₅₄ and dissolved organic carbon, suggesting that DOM and OMPs interacted with each other or followed similar adsorption mechanisms. A decrease in μGACs particle size had a positive impact on UV₂₅₄ removal under continuous-flow conditions in columns representative of a large-scale pilot due to better expansion.
图文摘要:

26114. 题目: Absorbance and EEM fluorescence of wastewater: Effects of filters, storage conditions, and chlorination
文章编号: N19110804
期刊: Chemosphere
作者: Massimiliano Sgroi, Erica Gagliano, Federico G.A. Vagliasindi, Paolo Roccaro
更新时间: 2019-11-08
摘要: Aim of this study was to delineate sample handling procedures for accurate fluorescence and UV absorbance measurements of wastewater organic matter. Investigations were performed using different wastewater qualities, including primary, secondary and tertiary wastewater effluents, and a wastewater-impacted surface water. Filtration by 0.7 μm glass microfiber filter, 0.45 μm polyvinylidene fluoride (PVDF) membrane, 0.45 μm cellulose nitrate membrane, and 0.45 μm polyethersulfone (PES) syringe filter released manufacture impurities in water that affected fluorescence measurements. However, pre-washing of filter by Milli-Q water was able to eliminate these interferences. Different storage conditions were tested, including storage of filtered and unfiltered samples under different temperatures (25 °C, 4 °C, −20 °C). According to the obtained results, the best practice of wastewater samples preservation was sample filtration at 0.7/0.45 μm immediately after collection followed by storage at 4 °C. However, the time of storage that assured changes of these spectroscopic measurements that do not exceed the 10% of the original value was dependent on water quality and selected wavelengths (i.e., selected fluorescing organic matter component). As a general rule, it is advisable to perform fluorescence and UV absorbance measurements as soon as possible after collection avoiding storage times of filtered water longer than 2 days. Finally, addition of chlorine doses typical for wastewater disinfection mainly affected tryptophan-like components, where changes that exceed the 10% of the fluorescence intensity measured in the unchlorinated sample were observed even at very low doses (≥1 mg/L). On the contrary, tyrosine-like and humic-like components showed changes <10% at chlorine doses of 0.5–5 mg/L.
图文摘要:

26115. 题目: Effect of suspended particles with different grain sizes on the bioaccumulation of PAHs by zebrafish (Danio rerio)
文章编号: N19110803
期刊: Chemosphere
作者: Yawei Zhai, Xinghui Xia, Haotian Wang, Hui Lin
更新时间: 2019-11-08
摘要: The physicochemical characteristics are different for suspended particles (SPS) with different sizes in rivers. Here, we studied the effect of SPS (1 g L⁻¹) with three different sizes (63–106 μm, 20–63 μm, and <20 μm) on the bioaccumulation of deuterated polycyclic aromatic hydrocarbons (phenanthrene-d10, anthracene-d10, fluoranthene-d10 and pyrene-d10) in zebrafish using passive dosing devices to maintain the freely dissolved concentrations of PAHs-d10 constant in water. The results showed that all the three grain size SPS could be ingested by zebrafish, and there was no significant difference in the amount of ingested SPS among the three grain sizes. The concentrations (lipid-normalized or not) of PAHs-d10 in zebrafish were promoted in the presence of the three different size SPS, and the PAH-d10 concentrations in zebrafish increased with decreasing particle size. Compared with the systems without SPS, the lipid-normalized concentrations of PAHs-d10 increased by 12%–72%, 34%–130%, and 60%–196%, respectively in zebrafish in systems with 63–106 μm, 20–63 μm, and <20 μm of SPS after exposure for 20 h. The stronger effect of SPS with smaller grain sizes was probably due to their lower organic carbon content, lower ratio of black carbon to organic carbon content, smaller particle size, and higher dissolved organic matter contents, which could promote the desorption of PAHs-d10 from ingested SPS and bioaccessibility of PAHs-d10 to zebrafish. This study suggests that in addition to SPS concentration, the suspended particle size should be considered in ecological risk assessment for hydrophobic organic compounds in aquatic environment.

26116. 题目: Microbial processing of organic matter drives stability and pore geometry of soil aggregates
文章编号: N19110802
期刊: Geoderma
作者: Sheikh M.F. Rabbi, Budiman Minasny, Alex B. McBratney, Iain M. Young
更新时间: 2019-11-08
摘要: The formation and stability of aggregates are crucial for soil function. Here we seek to understand the influence of microbial processing on the formation of aggregates in a structurally homogeneous microcosm, treated with two different types of organic matter - glucose and cellulose. The results demonstrated that decomposition of organic matter triggered the formation of water stable macro-aggregates and the carbon (C) that cemented the aggregates was derived primarily from microbial source. The porosity and pore connectivity of the newly formed aggregates in the glucose amended soils provided evidence of the development of physically stable aggregates rendered by the cementation process.

26117. 题目: Tracing water mass fractions in the deep western Indian Ocean using fluorescent dissolved organic matter
文章编号: N19110801
期刊: Marine Chemistry
作者: Jeonghyun Kim, Yeseul Kim, Hyoun-Woo Kang, Suk Hyun Kim, TaeKeun Rho, Dong-Jin Kang
更新时间: 2019-11-08
摘要: The meridional distributions of fluorescent dissolved organic matter (FDOM) and various hydrologic properties were investigated along 67°E in the western Indian Ocean. Our results showed that the highest fluorescence of the humic FDOM (FDOM_H) was discovered in the Indian Deep Water (IDW), and relatively lower values were observed in the intruding water masses from the upper layer (e.g., Circumpolar Deep Water (CDW), Antarctic Intermediate Water (AAIW), and South Indian Central Water (SICW)). The deep FDOM_H was robustly correlated with apparent oxygen utilisation (AOU), as suggested by previous studies. In particular, the slopes of the regression line AOU on FDOM_H varied for different water masses and the two humic components. In this study, to identify the factor inducing the variations of the slope, we estimated the relative water mass fraction of different water masses using a three-end-member mixing model with a salinity-FDOM_H diagram. The distribution of water mass fractions was in good agreement with water mass distribution from the conventional method from temperature and salinity distribution and previous studies. The FDOM_H components were positively correlated with the aged water mass fraction (i.e., IDW; r = 0.93) and negatively correlated with fresher ones originating from the upper water (r = −0.93, −0.51, and − 0.95 for CDW, AAIW, and SICW, respectively). The fluorescence ratio between the two FDOM_H components was also observed to be linked to the water mass fractions. The results indicate that the distribution of FDOM_H is attributed to the mixing of various deep-water masses during the global ocean circulation.

26118. 题目: Photochemical Production of Sulfate and Methanesulfonic Acid from Dissolved Organic Sulfur
文章编号: N19110716
期刊: Environmental Science & Technology
作者: Rachele Ossola, Julie Tolu, Baptiste Clerc, Paul Ragnar Erickson, Lenny H. E. Winkel, Kristopher McNeill
更新时间: 2019-11-07
摘要: Photodegradation processes play an important role in releasing elements tied up in biologically refractory forms in the environment, and are increasingly being recognized as important contributors to biogeochemical cycles. While complete photo-oxidation of dissolved organic carbon (to CO2) and dissolved organic phosphorous (to PO43–) has been documented, the analogous photoproduction of sulfate from dissolved organic sulfur (DOS) has not yet been reported. Recent high-resolution mass spectrometry studies showed a selective loss of organic sulfur during photodegradation of dissolved organic matter, which was hypothesized to result in the production of sulfate. Here, we provide evidence of ubiquitous production of sulfate, methanesulfonic acid (MSA), and methanesulfinic acid (MSIA) during photodegradation of DOM samples from a wide range of natural terrestrial environments. We show that photochemical production of sulfate is generally more efficient than the production of MSA and MSIA, as well as volatile S-containing compounds such as CS2 and COS. We also identify possible molecular precursors for sulfate and MSA, and we demonstrate that a wide range of relevant classes of DOS compounds (in terms of S oxidation state and molecular structure) can liberate sulfate upon photosensitized degradation. This work suggests that photochemistry may play a more significant role in the aquatic and atmospheric fate of DOS than currently believed.

26119. 题目: Oscillating redox conditions in the Middle–Late Jurassic Alpine Tethys: Insights from selected geochemical indices and ⁵⁷Fe Mössbauer spectroscopy
文章编号: N19110715
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Krzysztof Bąk, Marta Bąk, Jacek Gatlik, Artur Błachowski
更新时间: 2019-11-07
摘要: The Middle–Late Jurassic greenhouse conditions included CO₂ levels that have been estimated to be four to five times higher than they are presently. By analysing the pattern of selected trace elements as redox proxies (V, U, and Mo) and the variations in the chemical state of iron using ⁵⁷Fe Mössbauer spectroscopy, we demonstrate the occurrence of major changes in sediment redox conditions from the Late Bajocian through the Late Oxfordian in the pelagic environment of the Alpine Tethys in its Carpathian domain. Our interpretation is based on analysis of siliceous limestones rich in radiolarians intercalated with red nodular limestones of Ammonitico Rosso-type facies from the Krížna Nappe in the eastern part of the Tatra Mountains, Poland. The presented redox potential (Eh values) shows its changeable pattern along the section (from −0.74 V to 0.16 V). The low values of Eh (from −0.74 V to −0.4 V) create the long-term (ca. 7 Myr) trend of the medium-scale fluctuations comprising the Upper Bajocian through the Lower Oxfordian interval of predominately grey and green radiolarian siliceous limestones. This interval comprises the three short-term (less than 0.5 Myr) periods of slightly increasing Eh (from −0.35 V to −0.17 V) observed in the uppermost Bajocian, lower Bathonian, and lower Callovian, as well as the significant changes in sediment redox conditions from oxic to dysoxic in the Upper Bajocian. The overlying succession corresponding to the Middle–Upper Oxfordian (ca. 4 Myr) is characterized by red radiolarian siliceous limestones with positive Eh values that indicate deposition under more oxic conditions than those during any other period in the study section. The negative values of Eh, attributed to the upwelling periods, coincide with the decreasing sea surface water temperature (SST) and increasing organic matter flux. The largest negative shift is noted in the Upper Callovian, which coincided with the cool climatic phase. The positive Eh values indicate oxic conditions due to the lowering of organic matter input, coinciding with an increased SST caused by surface water stratification. Based on the observed long-term variation in the redox, we postulate thermally driven east–west atmospheric circulation along the equatorial Tethys Ocean, caused by the sharp contrast in sea surface temperature, similar to the Walker Circulation operating across the modern Pacific. This phenomenon would have been the dominant periodical mode over the tropics and subtropics regions of the NW Tethys during the Middle–Late Jurassic. Global warming reduces the long-term strength of the mean tropical atmospheric circulation, leading to sea water stratification near the surface and consequently lowering the organic matter flux. However, additional seaways of heat transport could also exist, as they are associated with the opening/closing of the Hispanic Corridor.
图文摘要:

26120. 题目: A Mississippian black shale record of redox oscillation in the Craven Basin, UK
文章编号: N19110714
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Joseph F. Emmings, Simon W. Poulton, Christopher H. Vane, Sarah Davies, Gawen R.T. Jenkin, Michael H. Stephenson, Melanie J. Leng, Angela Lamb, Vicky Moss-Hayes
更新时间: 2019-11-07
摘要: Early diagenetic redox oscillation processes have been rarely recognised in the ancient rock record but potentially exert an important control on mineral authigenesis, hydrocarbon prospectivity and supply of metals and/or reduced S as part of associated mineral systems. The upper unit of the Mississippian Bowland Shale Formation is a candidate record of diagenetic redox oscillation processes because it was deposited under a relatively high sediment accumulation rate linked to a large delta system, and under dominantly anoxic and intermittently sulphidic bottom-water conditions. In order to characterise the syngenetic and early diagenetic processes, sedimentological and geochemical data were integrated through the Upper Bowland Shale at three sites in the Craven Basin (Lancashire, UK). Organic matter (OM) comprises a mixture of Type II, II-S, II/III and III OM. ‘Redox zones’ are defined by patterns of Fe-speciation and redox-sensitive trace element enrichment and split into two groups. ‘Sulphidic’ zones (EUX, AN-III, AN-I and AN-IT) represent sediments deposited under conditions of at least intermittently active sulphate-reduction in bottom-waters. ‘Non-sulphidic’ zones (OX-RX, OX-F and OX) represent sediments deposited under non-sulphidic (oxic to ferruginous anoxic) bottom-waters. Operation of a shelf-to-basin ‘reactive Fe’ (Fe_HR) shuttle, moderated by sea level fluctuation and delta proximity, controlled the position and stability of redoxclines between zones of Fe and sulphate reduction, and methanogenesis. Early diagenetic redoxclines were capable of migration through the shallow sediment column relatively quickly, in response to sea level fluctuation. Preservation of syngenetic and early diagenetic geochemical signals shows redoxclines between Fe and sulphate reduction, and the upper boundary of sulphate-methane transition zone, were positioned within decimetres (i.e., 10s cm) of seabed. Falling sea level and increasing Fe_HR supply is recognised as a switch from zones EUX (high sea level), AN-III and ultimately AN-I and AN-IT (low sea level). Zone AN-I defines the operation of ‘redox oscillation’, between zones of Fe and sulphate reduction in shallow porewaters, associated with enhanced degradation of OM and complete dissolution of primary carbonate. Preservation of OM and carbonate, in this system, was a function of changing bottom and pore water redox processes. Redox oscillation operated in a siliciclastic, prodeltaic environment associated with a relatively high sediment accumulation rate and high loadings of labile organic matter and metal oxides. These findings are important for understanding Late Palaeozoic black shales in the context of hydrocarbon and mineral systems.