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25961. 题目: Sodium hypochlorite assisted membrane cleaning: Alterations in the characteristics of organic foulants and membrane permeability
文章编号: N18073112
期刊: Chemosphere
作者: Shu Zhai, Weiming Zhang, Ting Li, Wenbin Zhang, Lu Lv, Bingcai Pan
更新时间: 2018-07-31
摘要: Chemical cleaning is an important approach for alleviating severe fouling in membrane separation processes. In this study, lysozyme (LYS) was exposed to sodium hypochlorite (NaClO) with varied concentrations (0–2000 ppm) to understand the changes in the physicochemical properties and functional groups as well as the variations in membrane permeabilities. The results showed that membrane filterability exhibited an obvious ‘U-shaped’ trend, and the valley existed when the ratio of Cl/C (the ratio of NaClO and TOC concentrations in feed water) is among 1.35–3.09. Upon exposure to low dose NaClO, three-dimensional fluorescence excitation-emission matrix (3D-EEM) spectra showed that tryptophan protein substances were transformed to more hydrophobic humic-like substances. Fourier transform infrared (FTIR) analysis further confirmed that exposure to low dose NaClO promoted the breakage of aromatic substituents, leading to the formation of hydrophobic condensed aromatic substances. On the contrary, at high NaClO loads, protein structures were destroyed completely and almost no obvious fluorescent intensities could be detected, which promoted the recovery of membrane filterabilities. Notably, the chemical cleaning mechanisms of fouled membranes with NaClO were understood in depth in this study. These results provide new information about the oxidation products of LYS and the cleaning efficiency upon exposure to NaClO.
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25962. 题目: Dynamic changes of polychlorinated biphenyls (PCBs) degradation and adsorption to biochar as affected by soil organic carbon content
文章编号: N18073111
期刊: Chemosphere
作者: Shengyan Huang, Jianping Bao, Mingjuan Shan, Hua Qin, Hailong Wang, Xuejun Yu, Junhui Chen, Qiufang Xu
更新时间: 2018-07-31
摘要: Biochar amendment constitutes an effective soil remediation strategy for organic contaminants, but how the soil organic carbon (SOC) content affects polychlorinated biphenyls (PCBs) degradation and adsorption to biochar remains unclear. A 120-day biochar amendment experiment was conducted to investigate the dynamic effects of SOC on PCBs degradation in soil and adsorption to biochar. Biochar in low-SOC (LSOC) soils adsorbed a significantly higher amount of PCBs than did that in high-SOC (HSOC) soils. PCBs degradation was also greatly enhanced in LSOC soils when compared with that in HSOC soils after 30 days of biochar amendment. Degradation of di- and tri-chlorobiphenyls (CBs) were significantly enhanced in the LSOC soils than in the HSOC soils, while the biochar in the LSOC soil tended to adsorb significantly higher amount of tetra- and penta-CBs. Compared to biochar adsorption, microbial degradation contributed significantly to soil PCBs removal. Soil bacterial 16S rDNA abundance increased concomitantly with soil PCBs degradation. Regardless of SOC, soil bacterial communities and PCB congener compositions changed significantly after 30 days of biochar amendment. The abundance of Actinobacteria and Firmicutes were negatively correlated with the soil PCBs removal, while Gemmatimonadetes and Proteobacteria were positively correlated. The results of this study revealed that, compared with that to HSOC soils, biochar amendment to LSOC soils may have a greater positive effect on both soil PCB degradation and biochar adsorption. Therefore, the application of bamboo biochar to LSOC soils could be more effective than that to HSOC soils with respect to the remediation of PCBs contamination.

25963. 题目: Effects of freeze-thaw cycles on aggregate-associated organic carbon and glomalin-related soil protein in natural-succession grassland and Chinese pine forest on the Loess Plateau
文章编号: N18073110
期刊: Geoderma
作者: Lie Xiao, Yang Zhang, Peng Li, Guoce Xu, Peng Shi, Yi Zhang
更新时间: 2018-07-31
摘要: Glomalin-related soil protein (GRSP) is a hydrophobic glycoprotein that can protect soil organic carbon (SOC) from decomposition by promoting the formation of soil aggregates. Few studies, however, have evaluated the response of aggregate-associated SOC and GRSP to freeze-thaw cycles (FTs) under different patterns of vegetation restoration. Soil samples were collected from three typical natural-succession grasslands (dominated by Artemisia capillaris, A. sacrorum, and Bothriochloa ischaemum) and a Chinese pine (Pinus tabuliformis) forest before and after natural FTs during a winter-spring season on the Loess Plateau in China. The soil aggregate stability and concentrations of SOC, easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) in different aggregate fractions were measured. The FTs decreased the proportion of >5.0 mm wet-sieved fractions, increased the proportion of <0.25 mm wet-sieved fractions, and decreased the mean weight diameters by 8.7, 9.5, 2.9, and 9.4% in the soils of A. capillaris, A. sacrorum, B. ischaemum, and P. tabuliformis, respectively. The SOC, T-GRSP, and EE-GRSP concentrations in each aggregate fraction generally decreased after FTs in the four vegetation types. The SOC, T-GRSP, and EE-GRSP concentrations did not differ significantly in the larger aggregate fractions before the FTs in the soils for B. ischaemum and P. tabuliformis, but their concentrations were significantly higher for B. ischaemum than P. tabuliformis after FTs. The SOC and GRSP concentrations were significantly and linearly correlated in most aggregate fractions both before and after the FTs. These results indicated that the FTs decreased SOC by decreasing the GRSP concentration in each aggregate fraction and that SOC was more sensitive to FTs in forest than in natural-succession grassland.

25964. 题目: Universal Biomarker Analysis: Aromatic hydrocarbons
文章编号: N18073109
期刊: Organic Geochemistry
作者: Clifford C. Walters, Frank C Wang, Meytal B. Higgins, Marlene E. Madincea
更新时间: 2018-07-31
摘要: Universal Biomarker Analysis is a GC×GC-ToFMS method that provides absolute quantification and non-targeted pseudo MS-MS for all resolved hydrocarbon components in petroleum and rock extracts. This is achieved by merging two chromatographic datasets obtained under field ionization (FI), which provides molecular ions, and electron impact (EI), which provides diagnostic fragment ions. We recently demonstrated this technique for the analysis of saturated biomarkers (Walters et al., 2018. Org. Geochem. 115, 57). Here, we show its application to aromatic biomarkers. Universal Biomarker Analysis is compared to conventional GC-MS for frequently analyzed aromatic hydrocarbons, such as the alkylated naphthalenes and biphenyls, mono- and tri-aromatic steroidal hydrocarbons to illustrate where this new method provides demonstrated advantages. The technique is well suited for the analysis of rare species not commonly analyzed in targeted GC-MS/MS analyses. This is illustrated by the tentative identification of A/B-ring C₂₆-C₂₉ diaromatic steroidal hydrocarbons in a crude oil, compounds that have been previously identified as minor components of immature rock extracts, and indications of previously unknown C₂₆ methyl-triaromatic steroidal hydrocarbons.

25965. 题目: Comparisons of NOM fouling and cleaning of ceramic and polymeric membranes during water treatment
文章编号: N18073108
期刊: Separation and Purification Technology
作者: Mohammad T. Alresheedi, Benoit Barbeau, Onita D. Basu
更新时间: 2018-07-31
摘要: This research examines the effect of various NOM fractions on ceramic and polymeric UF membranes performance in terms of fouling and cleaning. Fouling experiments were performed using five model solutions, humic acid, protein as bovine serum albumin (BSA), alginate with and without calcium, and a combined NOM mixture. Two chemical agents were selected: an oxidant (NaOCl) and caustic (NaOH). Fouling and cleaning behavior were assessed using the resistance in series (RIS) model, membrane permeability, carbon mass balance, and fluorescence excitation and emission matrix (FEEM) analysis. The results demonstrated that NOM fouling order of the ceramic UF was similar to polymeric UF with the following trend: NOM mixture ≈BSA > alginate ±Ca⁺² > humic acid. However, the backwash efficiency was 1.5×–2× higher for the ceramic UF in comparison to the polymeric UF, indicating a much higher hydraulic reversibility for the ceramic UF. A carbon mass balance in compliment with FEEM plots determined that NOM removal by the ceramic UF was ≈ 10% higher than the polymeric UF. Chemical cleaning was found to be effective for both membrane types. Thus, it was not possible to conclude, that the ceramic membrane demonstrated an advantage for chemical cleaning under the conditions studied.

25966. 题目: Structure and activity of soil microbial communities in three Mediterranean forests
文章编号: N18073107
期刊: Applied Soil Ecology
作者: Felicia Grosso, Paola Iovieno, Anna Alfani, Flavia De Nicola
更新时间: 2018-07-31
摘要: The effect of plant cover on soil microbial community structure and activity was investigated in forest ecosystems dominated by holm oak (Quercus ilex), Turkey oak (Quercus cerris) and beech (Fagus sylvatica), in two seasons (autumn and early summer). Microbial community structure was investigated by phospholipid fatty acid (PLFA) profile and ergosterol determination. Microbial community activity was assessed by fluorescein diacetate hydrolisys, β-glucosidase and cellulase activities. The Turkey oak forest showed the lowest soil microbial biomass, both as total and specific PLFA markers. PLFA profile showed a different microbial community structure among forest soils, mainly between the two oak systems. Enzyme activities were affected by soil organic carbon content, with the lowest values measured in Turkey oak. A seasonal effect both on microbial biomass and on enzyme activity was generally observed. Among the investigated forest systems, the beech forest appeared to store more carbon both in aboveground biomass and in soil.
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25967. 题目: Short- and long-term warming alters soil microbial community and relates to soil traits
文章编号: N18073106
期刊: Applied Soil Ecology
作者: Hongying Yu, Quanhui Ma, Xiaodi Liu, Zhenzhu Xu, Guangsheng Zhou, Yaohui Shi
更新时间: 2018-07-31
摘要: Climatic warming abnormally alters the structure and function of terrestrial ecosystems. It is vital to understand the response of belowground biota such as soil microbial communities to warming regimes, especially in native arid areas. The present in situ experiment was established to determine the effects of climatic warming regimes on soil microbe communities and the relationships between soil microbial groups and soil physicochemical features in a desert grassland ecosystem. Two warming regimes—long-term moderate warming (T1) and short-term acute warming (T2)—were established to simulate different climatic change scenarios. Soil from each plot was collected in 2014 at the late stage of the experiment, and phospholipid fatty acid (PLFA) profiling analysis was performed to assess the composition of the soil microbial communities. It was found that warming induced a severe water deficit stress. The T2 warming regime significantly increased the ratio of bacteria to fungi (B/F), and the ratio of Gram-positive to Gram-negative bacteria (GP/GN) in August. Belowground biomass (BGB) and soil organic carbon (SOC) were significantly correlated with all of the soil microbial groups in August. The changes in B/F and GP/GN ratios might indirectly induce changes in microbial structure. It was concluded that alterations in the structure of soil microbial communities may strongly depend on growing seasons and that soil nutrient status might have a profound impact on soil microbial communities’ responses to climatic warming.

25968. 题目: The response of metal leaching from soils to climate change and land management in a temperate lowland catchment
文章编号: N18073105
期刊: CATENA
作者: Marcel van der Perk, Maria Stergiadi, Ton C.M. de Nijs, Rob N.J. Comans, Marc F.P. Bierkens
更新时间: 2018-07-31
摘要: Changes in soil hydrology as a result of climate change or changes in land management may affect metal release and leaching from soils. The aim of this study is to assess the cascading response of SOM and DOC levels and metal leaching to climate change in the medium-sized lowland Dommel catchment in the southern part of the Netherlands. We implemented the CENTURY model in a spatial setting to simulate SOM, DOC, and water dynamics in topsoils of the Dutch portion of the Dommel catchment under various climate and land management scenarios. These CENTURY model outputs were subsequently used to calculate changes in the topsoil concentrations, solubility, and leaching of cadmium (Cd) and zinc (Zn) for current (1991–2010) and future (2081–2100) conditions using empirical partition-relations. Since the metal leaching model could not be evaluated quantitatively against measured values, we focus mainly on the trends in the projected metal concentrations and leaching rates for the different scenarios. Our results show that under all climate and land management scenarios, the SOM contents in the topsoil of the Dommel catchment are projected to increase by about 10% and the DOC concentrations to decrease by about 20% in the period from present to 2100. These changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates under the climate change scenarios. Our scenario calculations show a considerable decrease in topsoil Cd concentrations in the next century as a result of increased percolation rates. Zinc, however, shows an increase due to agricultural inputs to soil via manure application. These trends are primarily controlled by the balance between atmospheric and agricultural inputs and output via leaching. While SOM and DOC are important controls on the spatial variation in metal mobility and leaching rates, climate-induced changes in SOM and DOC only have a minor influence on metal concentrations and leaching rates. The climate-induced changes in metal concentrations in both the topsoil and the soil leachate are primarily driven by changes in precipitation and associated water percolation rates.

25969. 题目: Soil structure formation and organic matter distribution as affected by earthworm species interactions and crop residue placement
文章编号: N18073104
期刊: Geoderma
作者: Joana Frazão, Ron G.M. de Goede, Yvan Capowiez, Mirjam M. Pulleman
更新时间: 2018-07-31
摘要: Earthworms play an important role in soil organic matter (SOM) dynamics and soil structure formation, including soil porosity and aggregate stability. Earthworms feed on organic inputs such as crop residues (CR) which are displaced by mouldboard ploughing. In a 61-day mesocosm experiment, we investigated the effects of CR placement (surface-applied vs. incorporated) and different earthworm species (combinations) on: 1) the survival and biomass of the earthworm species Lumbricus terrestris, L. rubellus, and Aporrectodea caliginosa, representing anecic, epigeic and endogeic ecological groups, respectively; and 2) earthworm-mediated soil structure formation. Earthworms were present either as single species or as species mixtures combining anecics with each of the other groups. Incorporating CR reduced biomass of surface-feeders (L. terrestris: −30% of initial body weight vs. −9% when CR were surface-applied; L. rubellus: −74% vs. −24%, respectively). L. rubellus survival was also lower when CR were incorporated (50%) than when CR were surface-applied (92%). In surface-applied CR treatments, the amount of particulate organic matter (POM) > 250 μm in the soil profile was positively affected by L. terrestris in the soil upper 20 cm by 16.5%. A similar but weaker effect was found when CR were incorporated (9% increase). Large water-stable macroaggregates (>2000 μm) increased in the upper 20 cm soil only when CR were surface-applied and L. terrestris was present (from 2.7 to 13.1 g kg⁻¹). Small water-stable aggregates increased with functional groups interactions at all soil depths, irrespective of the CR placement. Surface-applied CR increased soil porosity at 2.5–10 cm depth. Large water-stable macroaggregate formation by earthworms was hampered through the incorporation of CR, although CR incorporation increased porosity between 2.5 and 30 cm soil depth despite reduced earthworm biomass. Furthermore, small macroaggregate formation was hampered by single species, whereas combining functional groups stimulated their formation. Under field conditions residue incorporation might result in trade-offs between the contribution of surface-feeding earthworms to soil porosity and i) their fitness, as surface-feeding earthworms' body weight loss was larger than when crop residues were surface-applied; as well as ii) large water-stable macroaggregates formation, as no increase in those was found when CR was incorporated.

25970. 题目: Release of nutrients and organic carbon in different soil types from hydrochar obtained using sugarcane bagasse and vinasse
文章编号: N18073103
期刊: Geoderma
作者: Lucas Raimundo Bento, Antônio Joel Ramiro Castro, Altair Benedito Moreira, Odair Pastor Ferreira, Márcia Cristina Bisinoti, Camila Almeida Melo
更新时间: 2018-07-31
摘要: Hydrothermal carbonization of byproducts from the sugarcane industry generates a solid material (hydrochar) rich in carbon and nutrients with the potential to be used as a soil conditioner. In this context, the objective of this work was to evaluate the nutrient release process from hydrochar with the aim of improving soil quality. To do this, experiments were performed evaluating the concentration of NO₃⁻, PO₄⁻³, K, Ca, Mg, Fe and total organic carbon leached from a column filled with soil and different hydrochar proportions during one month. The proportions of hydrochar were 1 and 4% (w/w) applied to sand, ultisol, and oxisol. Nitrogen and phosphorus were immobilized in the soils due to the high organic carbon released that increase microbial activity and to the presence of iron and aluminum oxides, respectively. The oxisol retains part of the carbon released by the hydrochar due to its high content of silt and clay. Only part of the carbon and nutrients of the hydrochar was released, indicating a recalcitrant material. The prepared hydrochar provided nutrients and organic carbon depending on the soil type to which it was applied. This study shows that hydrochar, if applied in the appropriate proportion, can enhance the soil fertility.

25971. 题目: The Crvenka loess-paleosol sequence: A record of continuous grassland domination in the southern Carpathian Basin during the Late Pleistocene
文章编号: N18073102
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Slobodan B. Marković, Pál Sümegi, Thomas Stevens, Randall J. Schaetzl, Igor Obreht, Wei Chu, Björn Buggle, Michael Zech, Roland Zech, Christian Zeeden, Milivoj B. Gavrilov, Zoran Perić, Zorica Svirčev, Frank Lehmkuhl
更新时间: 2018-07-31
摘要: In this study, we compare two independent paleoenvironmental proxies for a loess sequence in northern Serbia, in the southern Carpathian Basin: novel n-alkane biomarkers and traditional land snail assemblages. Both are associated with other, more widely used proxy data for loess sections, such as environmental magnetism, grain size, and geochemical indices. Together, these paleoenvironmental proxy records provide evidence for the continued dominance of grasslands during the Late Pleistocene in the Southern Carpathian Basin. It is contrary to other European loess provinces, which are characterized by high diversity of Late Pleistocene environments (ranging from tundra-like to deciduous forest habitats). These findings highlight the southeastern part of Carpathian Basin as an important, but still insufficiently investigated, biogeographical refugium, and biodiversity preservation zone. The reason for this is a mostly stable paleoclimate for much of the Late Pleistocene.

25972. 题目: Changes in vegetation type on the Chinese Loess Plateau since 75 ka related to East Asian Summer Monsoon variation
文章编号: N18073101
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Jiangsi Liu, Thomas J. Algeo, Huan Yang, Jinjiang Pan, Changyan Tang, Junhua Huang, Shucheng Xie
更新时间: 2018-07-31
摘要: Floral communities in terrestrial habitats such as steppes are highly sensitive to regional climate changes. Here, we generated carbon and nitrogen isotope profiles for soil organic matter (SOM) in the Weinan loess-paleosol section in order to investigate changes in floral communities on the Chinese Loess Plateau (CLP) and their relationship to climate variation since 75 ka. δ¹³C_SOM at Weinan ranges from −23.6 to −18.0‰ and δ¹⁵N_SOM ranges from +3.4 to +5.5‰. Modeling based on the δ¹³C_SOM record suggests that the proportion of C4 plants (%C4) has varied from lower during cold intervals (with minima of 24–32% at 73.1 ka, 20.9 ka (LGM), and 0.6 ka) to higher during warm intervals (with maxima of 62–64% at 53.0 ka and 8.2 ka). The δ¹³C_SOM and δ¹⁵N_SOM profiles are strongly correlated (r = +0.82; p(α) <0.001), suggesting that the N-isotope composition of SOM was also largely controlled by inputs of C4 versus C3 plants, consistent with known patterns of N-isotope variation among modern plants. The %C4 profile exhibits significant covariation with reconstructed mean annual temperatures (MAT) (r = +0.42; p(α) <0.001), mean annual precipitation (MAP) (r = +0.42; p(α) <0.001), and summer monsoon intensity (r = +0.50; p(α) <0.001), suggesting that paleovegetation was controlled by each of these climate variables to a degree. Comparing the Weinan record to SOM profiles across the CLP region, we identified three zones of varying monsoonal influence, with the East Asian Summer Monsoon (EASM) exerting the strongest influence on the southeastern margin of the CLP, and the East Asian Winter Monsoon (EAWM) greater influence on its northwestern margin. This paper provides new insights into deciphering paleovegetation patterns and their links to paleoclimate change on the basis of paired C- and N-isotope records.

25973. 题目: ADM1 based mathematical model of trace element precipitation/dissolution in anaerobic digestion processes
文章编号: N18073007
期刊: Bioresource Technology
作者: Bikash Chandra Maharaj, Maria Rosaria Mattei, Luigi Frunzo, Eric D. van Hullebusch, Giovanni Esposito
更新时间: 2018-07-30
摘要: Due to the complex biogeochemistry of trace elements (TEs, e.g. Fe, Ni and Co) in anaerobic digestion processes, their role and fate is poorly understood. Challenging, time consuming and low detection limits of analytical procedures necessitate recruitment of mathematical models. A dynamic mathematical model based on anaerobic digestion model no.1 (ADM1) has been proposed to simulate the effect of TEs. New chemical equilibrium association/dissociation and precipitation/dissolution reactions have been implemented to determine TE bioavailability and their effect on anaerobic digestion. The model considers interactions with inorganic carbonate (HCO₃⁻ and CO₃²⁻), phosphate (PO₄³⁻, HPO₄²⁻, H₂PO₄⁻) and sulfide (HS⁻ and S²⁻). The effect of deficiency, activation, inhibition and toxicity of TEs on the biochemical processes has been modelled based on a dose-response type inhibition function. The new model can predict: the dynamics of TEs (among carbonate, sulfide and phosphate); the starvation of TEs; and the effect of initial sulfur-phosphorus ratio in an in-silico batch anaerobic system.

25974. 题目: TEX₈₆ in sinking particles in three eastern Atlantic upwelling regimes
文章编号: N18073006
期刊: Organic Geochemistry
作者: Eunmi Park, ens Hefter, Gerhard Fischer, Gesine Mollenhauer
更新时间: 2018-07-30
摘要: Seasonal variations in fluxes of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) and the estimated temperatures based on TEX₈₆ were examined in sinking particles collected using moored sediment traps in the eastern Atlantic upwelling regions. In the equatorial Guinea Basin, GDGT fluxes show a correlation with opal fluxes, implying that GDGTs are mainly transported via aggregation with diatoms. The flux-weighted temperatures derived from particles collected both at 853 m and 3,921 m depth correspond to the water temperature (24.1 °C) of ca. 50 m depth, where nitrate concentration starts to increase. This suggests that nutrient concentrations may affect the depth habitat of Thaumarchaeota, thereby influencing the TEX₈₆-derived water temperatures. In the coastal upwelling off Namibia, TEX_86H temperatures are similar to satellite-derived sea surface temperature (SST) during the warm season, but the record derived from the trap is delayed relative to the SST by approximately 26 days. Warm biases, however, occur during the cold season. Higher TEX₈₆ values have been found within the oxygen minimum zones (OMZs) in the water column of coastal upwelling regions. Thus, contributions from GDGTs produced in OMZs might explain the warmer temperature estimates during the cold season in regions where OMZs are pronounced. This scenario could explain the observed warm bias off Namibia. We, therefore, suggest that in the eastern Atlantic upwelling systems, nutrient depth distribution and GDGTs produced in OMZs can be potential environmental factors influencing TEX₈₆ in sinking particles. In paleoenvironmental records of TEX₈₆, non-thermal signals have to be considered on regional scales.

25975. 题目: Systematic optimization approach for the efficient management of the photo-Fenton treatment process
文章编号: N18073005
期刊: Science of The Total Environment
作者: Francesca Audino, Gerard Campanyà, Montserrat Pérez-Moya, Antonio Espuña, Moisès Graells
更新时间: 2018-07-30
摘要: The photo-Fenton process is a photochemical process that has proved to be highly efficient in degrading new potentially harmful contaminants. Despite of this, scarce attention has been paid to the development of systematic procedures and optimisation strategies to efficiently operate such a process. The present work aims at investigating the effectiveness of a model-based approach in carrying out the dynamic optimisation of the recipe of a photo-Fenton process, performed in fed-batch mode (reactant dosage).
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25976. 题目: Identification of sources and transformations of nitrate in the Xijiang River using nitrate isotopes and Bayesian model
文章编号: N18073004
期刊: Science of The Total Environment
作者: Cai Li, Si-Liang Li, Fu-Jun Yue, Jing Liu, Jun Zhong, Zhi-Feng Yan, Ruo-Chun Zhang, Zhong-Jun Wang, Sen Xu
更新时间: 2018-07-30
摘要: Coupled nitrogen and oxygen isotopes of nitrate have proven useful in identifying nitrate sources and transformation in rivers. However, isotopic fractionation and low-resolution monitoring limit the accurate estimation of nitrate dynamics. In the present study, the spatio-temporal variations of nitrate isotopes (¹⁵N and ¹⁸O) and hydrochemical compositions (NO₃⁻ and Cl⁻) of river water were examined to understand nitrate sources in the Xijiang River, China. High-frequency sampling campaigns and isotopic analysis were performed at the mouth of the Xijiang River to capture temporal nitrate variabilities. The overall values of δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ ranged from +4.4‰ to +14.1‰ and from −0.3‰ to +6.8‰, respectively. The results of nitrate isotopes indicated that NO₃⁻ mainly originated from soil organic nitrogen (SON), chemical fertilizer (CF), and manure and sewage wastes (M&S). The negative correlation of nitrate isotopic values with NO₃⁻/Cl⁻ ratios suggested the importance of denitrification in NO₃⁻ loss. The results of Bayesian model with incorporation of isotopic fractionation during the denitrification showed that SON and CF contributed to the most (72–73%) nitrate in the wet season; whereas approximately 58% of nitrate was derived from anthropogenic inputs (M&S and CF) in the dry season. The nitrate flux was 2.08 × 10⁵ tons N yr⁻¹ during one hydrologic year between 2013 and 2014, with 86% occurring in the wet season. Long-term fluctuations in nitrate flux indicated that nitrate export increased significantly over the past 35 years, and was significantly correlated with nitrate concentrations. The seasonal pattern of nitrate dynamics indicated the mixing of nitrified NO₃⁻ and denitrified NO₃⁻ between surface flow and groundwater flow under different hydrological conditions. Overall, the present study quantitatively evaluates the spatio-temporal variations in nitrate sources in a subtropical watershed, and the high-frequency monitoring gives a better estimate of nitrate exports and proportional contributions of nitrate sources.
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25977. 题目: Carbon emissions induced by land-use and land-cover change from 1970 to 2010 in Zhejiang, China
文章编号: N18073003
期刊: Science of The Total Environment
作者: Enyan Zhu, Jingsong Deng, Mengmeng Zhou, Muye Gan, Ruowei Jiang, Ke Wang, AmirReza Shahtahmassebi
更新时间: 2018-07-30
摘要: Land-use and land-cover change (LUCC) is a crucial factor affecting carbon emissions. Zhejiang Province has witnessed unprecedented LUCC concomitant with rapid urbanization from 1970 to 2010. In this study, remote sensing, geographic information system (GIS) and the Intergovernmental Panel on Climate Change (IPCC) method were combined to quantify changes in both vegetation carbon storage and soil organic carbon (SOC) storage resulting from LUCC during 1970–1990 and 1990–2010. For both 1970–1990 and 1990–2010, the results showed successive decrease in farmlands (2.8 × 10⁵ ha or −9.15% and 5.9 × 10⁵ ha or −20.49%, respectively) and grasslands (3.4 × 10⁴ ha or −10.73% and 1.5 × 10⁵ ha or −54.1%, respectively), and continuous increase in forests (2.0 × 10⁴ ha or 0.33% and 1.7 × 10⁵ ha or 2.81%, respectively) and built-up lands (2.07 × 10⁵ ha or 78.41% and 6.49 × 10⁵ ha or 137.8%, respectively). From 1970 to 1990, approximately 8.3 Tg of the total carbon sink declined, including a 0.4 Tg reduction in vegetation carbon and a 7.9 Tg reduction in SOC. While from 1990 to 2010, approximately 17.5 Tg of carbon storage declined, comprising a 2.8 Tg of carbon accumulated by vegetation, and a 20.3 Tg reduction in SOC. Overall, LUCC has resulted in huge amount of carbon emissions in Zhejiang from 1970 to 2010. Efficient planning for LUCC and gradual mitigation of carbon emissions are indispensable for future urban development in China under increasing pressure from global warming.
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25978. 题目: Estimation of unsaturated shear strength parameters using easily-available soil properties
文章编号: N18073002
期刊: Soil and Tillage Research
作者: Elham Amiri Khaboushan, Hojat Emami, Mohammad Reza Mosaddeghi, Ali Rrza Astaraei
更新时间: 2018-07-30
摘要: Unsaturated soil shear strength is an important parameter in soil erosion and management. Measurement of unsaturated shear strength at field scale is difficult, time-consuming, and very costly. This study was conducted to investigate the relationship between unsaturated shear strength parameters and soil properties, and to predict the unsaturated shear strength parameters (effective cohesion, c', angle of effective internal friction, φ' and angle of internal friction related to matric suction, φ^b) using multiple-linear regression (MLR). Direct shear tests were performed at combinations of three normal stresses of 25, 50 and 100 kPa, and four matric suctions of 0, 10, 30 and 50 kPa (i.e., 12 tests per each soil) to determine the shear strength parameters in 14 soils. Soil properties including particle size distribution (sand, silt, and clay percentages or geometric mean diameter, d_g and geometric standard deviation, σ_g), organic matter content (OM), calcium carbonate content (CaCO₃), compactness indices (bulk density, ρ_b and, relative bulk density, ρ_b-rel), and mean weight diameter of aggregates (MWD_dry, MWD_wet), structural stability indices (aggregate stability, AS, stability index, SI and index of crusting, I_c) were determined and used as predictors in MLR models. Strong negative correlations were found between c' and φ'. The c' positively correlated with clay content. Significant negative correlation was observed between c' and sand fractions and d_g. Significant positive correlation was obtained between φ' and fractions of sand and d_g. The φ' negatively correlated with clay, fine silt content (FSi), MWD_dry, and AS. The φ^b had no significant correlation with soil properties, indicating that φ^b is independent of soil properties and basically is affected by matric suction. Clay, coarse sand (CS) and very fine sand (VFS) were applied in the model for predicting c'. Clay had a positive and, CS and VFS had negative effects on c'. Pedotransfer functions (PTFs) using the fine sand (FS) and VFS as predictor could estimate the φ' accurately, so that they entered to PTFs with positive signs. In addition, the φ^b was predicted by parameter I_c only, so that it had negative effect on φ^b. Overall, better prediction models were developed for φ' than for c' and φ^b.

25979. 题目: Improving understanding of soil organic matter dynamics by triangulating theories, measurements, and models
文章编号: N18073001
期刊: Biogeochemistry
作者: Joseph C. Blankinship, Asmeret Asefaw Berhe, Susan E. Crow, Jennifer L. Druhan, Katherine A. Heckman, Marco Keiluweit, Corey R. Lawrence, Erika Marín-Spiotta, Alain F. Plante, Craig Rasmussen, Christina Schädel, Joshua P. Schimel, Carlos A. Sierra, Aaron Thompson, Rota Wagai, William R. Wieder
更新时间: 2018-07-30
摘要: Soil organic matter (SOM) turnover increasingly is conceptualized as a tension between accessibility to microorganisms and protection from decomposition via physical and chemical association with minerals in emerging soil biogeochemical theory. Yet, these components are missing from the original mathematical models of belowground carbon dynamics and remain underrepresented in more recent compartmental models that separate SOM into discrete pools with differing turnover times. Thus, a gap currently exists between the emergent understanding of SOM dynamics and our ability to improve terrestrial biogeochemical projections that rely on the existing models. In this opinion paper, we portray the SOM paradigm as a triangle composed of three nodes: conceptual theory, analytical measurement, and numerical models. In successful approaches, we contend that the nodes are connected—models capture the essential features of dominant theories while measurement tools generate data adequate to parameterize and evaluate the models—and balanced—models can inspire new theories via emergent behaviors, pushing empiricists to devise new measurements. Many exciting advances recently pushed the boundaries on one or more nodes. However, newly integrated triangles have yet to coalesce. We conclude that our ability to incorporate mechanisms of microbial decomposition and physicochemical protection into predictions of SOM change is limited by current disconnections and imbalances among theory, measurement, and modeling. Opportunities to reintegrate the three components of the SOM paradigm exist by carefully considering their linkages and feedbacks at specific scales of observation.

25980. 题目: Manure amendment reduced plant uptake and enhanced rhizodegradation of 2,2′,4, 4′-tetrabrominated diphenyl ether in soil
文章编号: N18072906
期刊: Biology and Fertility of Soils
作者: Leilei Xiang, Yang Song, Yongrong Bian, Guangxia Liu, Anna Herzberger, Chenggang Gu, Xin Jiang, Fang Wang
更新时间: 2018-07-29
摘要: To test whether manure amendment in soil reduces plant uptake of persistent organic pollutants, carrot (Daucus carota L.) was used as a model plant and 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) was selected as a model persistent organic pollutant to conduct a pot experiment with contaminated soil amended by composted pig manure. The results showed that the concentration and bioconcentration factors (BCFs) of BDE-47 in the edible part of carrot significantly decreased from 229.7 ± 28.2 to 43.4 ± 20.4 ng g⁻¹ and from 1.86 ± 0.5 to 0.15 ± 0.03, respectively, with increasing composted pig manure dose from 0 to 4%. Organic matter (OM) derived from composted pig manure played a dominant role in reducing persistent organic pollutant bioavailability in soil. Composted pig manure amendment and carrot cultivation jointly altered the bacterial community composition in soil, especially the rhizosphere. Rhizodegradation of BDE-47 was enhanced from 8.6 to 28.5% with increasing composted pig manure dose from 0 to 4%, corresponding to increased soil microbe diversity and polybrominated diphenyl ether-degrading bacteria (Sphingomonas, etc.) abundance in the rhizosphere. This study is the first, to the best of our knowledge, to provide an effective agronomic strategy of manure amendment to reduce plant uptake and simultaneously enhance rhizodegradation of persistent organic pollutants in soil, and thus potentially reduce human health risks through dietary intake.