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24621. 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.

24622. 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.

24623. 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.

24624. 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.

24625. 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.

24626. 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.

24627. 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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24628. 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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24629. 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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24630. 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.

24631. 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.

24632. 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.

24633. 题目: Pretreatment of macroalgal Laminaria japonica by combined microwave-acid method for biohydrogen production
文章编号: N18072905
期刊: Bioresource Technology
作者: Yanan Yin, Jianlong Wang
更新时间: 2018-07-29
摘要: Suitable pretreatment can effectively enhance the fermentative hydrogen production from algae biomass. In this study, combined microwave-acid pretreatment was applied to disintegrate the biomass of macroalgae L. japonica, and dark fermentation in batch mode was conducted for hydrogen production. The results showed that combining microwave pretreatment at 140°C and 2450 MHz with 1% H₂SO₄ for 15 min could effectively disrupt macroalgal cells and release the organic matters, and soluble chemical oxygen demand (SCOD) concentration increased by 1.92-fold and achieved 5.12 g/L. During the fermentation process, both polysaccharides and proteins were consumed. Hydrogen production process was dominated by acetate-type fermentation, and the dominance of genus Clostridium contributed to more efficient hydrogen production. After the pretreatment, hydrogen yield increased from 15 mL/g TS_added to 28 mL/g TS_added, and energy conversion efficiency increased from 9.5% to 23.8%. Combined microwave-acid pretreatment is potential in enhancing hydrogen production from the biomass of L. japonica.

24634. 题目: Performance and toxicity assessment of nanoscale zero valent iron particles in the remediation of contaminated soil: A review
文章编号: N18072904
期刊: Chemosphere
作者: Wenjing Xue, Danlian Huang, Guangming Zeng, Jia Wan, Min Cheng, Chen Zhang, Chanjuan Hu, Jing Li
更新时间: 2018-07-29
摘要: Nanoscale zero valent iron (nZVI) particles have been studied in recent years as a promising technology for the remediation of contaminated soil. Although the potential benefits of nZVI are considerable, there is a distinct need to identify possible risks after environmental exposure to nZVI. This work firstly introduced the remediation of nZVI for heavy metals and chlorinated organic compounds in contaminated soil. And the corresponding stabilization mechanisms were discussed. We also highlighted the factors affecting nZVI reactivity, including nZVI surface area, nZVI stabilizers, soil pH, soil organic matter and soil types. In addition, this review shows a critical overview of the current understanding of toxicity of nZVI particles to soil bacteria and fungi. The toxicity mechanisms, cellular defenses behaviors and the factors affecting the toxicity of nZVI were summarized. Finally, the remaining barriers to be overcome in materials development for environment application are also discussed.
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24635. 题目: Tryptophan-like fluorescence as a measure of microbial contamination risk in groundwater
文章编号: N18072903
期刊: Science of The Total Environment
作者: Saskia Nowicki, Dan J. Lapworth, Jade S.T. Ward, Patrick Thomson, Katrina Charles
更新时间: 2018-07-29
摘要: Microbial water quality is frequently assessed with a risk indicator approach that relies on Escherichia coli. Relying exclusively on E. coli is limiting, particularly in low-resource settings, and we argue that risk assessments could be improved by a complementary parameter, tryptophan-like fluorescence (TLF). Over two campaigns (June 2016 and March 2017) we sampled 37 water points in rural Kwale County, Kenya for TLF, E. coli and thermotolerant coliforms (total n = 1082). Using three World Health Organization defined classes (very high, high, and low/intermediate), risk indicated by TLF was not significantly different from risk indicated by E. coli (p = 0.85). However, the TLF and E. coli risk classifications did show disagreement, with TLF indicating higher risk for 14% of samples and lower risk for 13% of samples. Comparisons of duplicate/replicate results demonstrated that precision is higher for TLF (average relative percent difference of duplicates = 14%) compared to culture-based methods (average RPD of duplicates ≥ 26%). Additionally, TLF sampling is more practical because it requires less time and resources. Precision and practicality make TLF well-suited to high-frequency sampling in low resource contexts. Interpretation and interference challenges are minimised when TLF is measured in groundwaters, which typically have low dissolved organic carbon, relatively consistent temperature, negligible turbidity and pH between 5 and 8. TLF cannot be used as a proxy for E. coli on an individual sample basis, but it can add value to groundwater risk assessments by improving prioritization of sampling and by increasing understanding of spatiotemporal variability.
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24636. 题目: Photocatalytic degradation of bisphenol A over a ZnFe₂O₄/TiO₂ nanocomposite under visible light
文章编号: N18072902
期刊: Science of The Total Environment
作者: Thanh Binh Nguyen, C.P. Huang, Ruey-an Doong
更新时间: 2018-07-29
摘要: A ZnFe₂O₄-TiO₂ nanocomposite combining p-type ZnFe₂O₄ and n-type TiO₂ was successfully fabricated. The ZnFe₂O₄-TiO₂ nanocomposite greatly enhanced the bisphenol A (BPA) photodegradation under visible light irradiation at 465 ± 40 nm. Loading TiO₂ with 1 wt% of ZnFe₂O₄ produced high photocurrent and low charge transfer resistance. The photodegradation rate of BPA by ZnFe₂O₄-TiO₂, which was highly dependent on the water chemistry including pH, anions, and humic acid, was 20.8–21.4 times higher than that of commercial TiO₂ photocatalysts. Chloride and sulfate ions enhanced BPA photodegradation mostly due to the production of more radical species; whereas nitrate, dihydrogen phosphate, and bicarbonate ions decreased the photodegradation rate of BPA due to the scavenge of hydroxyl radicals. The photoactivity and recyclability of ZnFe₂O₄-TiO₂ in lake water was also assessed. A near complete BPA removal from lake water was observed under visible light irradiation. Furthermore, >90% of photocatalytic activity toward BPA degradation was achieved in 5 cycles of continuous addition of BPA to the lake water. The BPA degradation intermediates were identified by HPLC/MS/MS and possible reaction pathways were proposed. Results clearly demonstrate the excellent visible-light-sensitive photocatalytic degradation of BPA over ZnFe₂O₄-TiO₂ composite which has a great application potential for the decomposition of emerging contaminants in impaired waters.
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24637. 题目: Bioactivity of humic substances and water extracts from compost made by ligno-cellulose wastes from biorefinery
文章编号: N18072901
期刊: Science of The Total Environment
作者: R. Spaccini, V. Cozzolino, V. Di Meo, D. Savy, M. Drosos, A. Piccolo
更新时间: 2018-07-29
摘要: The ligno-cellulose residues from biorefinery production of bio-ethanol were used as woody structuring material within an on-farm composting system, with the aim to obtain bioactive water soluble and humic fractions from composted materials. The molecular characterization of initial biomasses and final products revealed a transformation towards more stable compounds during composting and showed the selective incorporation of specific phenolic derivatives of ligno-cellulose in both bulk samples and corresponding extracts. While the use of the stable bulk composts as organic fertilizer resulted in a decrease of nitrogen and phosphorous assimilation in maize tissues, a bio-stimulation was shown by water soluble organic compounds and humic substances in germination tests and pot experiments, respectively. The differential responses obtained in maize seedlings and plants were related to the molecular composition and concentration of the applied water extracts and humic substances, thus suggesting a role of phenols and lignin derivatives in the stimulation of maize roots and shoots and the enhancement of P uptake. The results confirm that ligno-cellulose residues may be effectively recycled as composting additives in order to enrich mature compost in aromatic and lignin compounds. A preliminary knowledge on the molecular characteristics and biological properties of composted materials is an essential requirement to select the most suitable derivatives from composted ligno-cellulose wastes in sustainable agricultural practices.
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24638. 题目: Fluorescence Quenching and Energy Transfer Phenomena Associated with the Interactions of Terbium Ion and Humic Acid
文章编号: N18072804
期刊: Aquatic Geochemistry
作者: Mingquan Yan, Gregory V. Korshin, Marc F. Benedetti, Chi-Wang Li
更新时间: 2018-07-28
摘要: Fluorescence of the hydrophobic acid fraction (HPOA) of Suwannee River natural organic matter and Tb³⁺ excitation spectra were measured in tandem using the instantaneous and time-resolved emission modes. The intensity of HPOA fluorescence decreased in the presence of Tb³⁺, while the intensity of the emission from Tb³⁺ cations bound by HPOA increased by up to several orders of magnitude due to energy transfer (ET) from HPOA to Tb³⁺ ions. To determine intrinsic ET and fluorescence quenching (FQ) coefficients, NICA–Donnan modeling was carried. It showed that phenolic groups in HPOA dominated both the ET and FQ processes and that the binding of Tb³⁺ by HPOA could be described using the non-ideality parameter n_Tb, median binding constant log K_Tb for the phenolic sites and intrinsic ET and FQ coefficients (denoted as η_TbΦ and α_TbΦ), and were 0.48, 8.5, 1385 and 0.12, respectively. The high value of the energy transfer coefficient of Tb³⁺ ions bound by the phenolic groups in HPOA is indicative of both the match between the electronic levels of the donor and acceptor, and the short distance between them. The deviation of the data of Nica–Donnan modeling of the ET and FQ dependence of versus [Tb]_total for a 1.0 M ionic strength highlights the need to quantify the distribution of donor–acceptor distances in HPOA molecules in more detail.

24639. 题目: Effects of altered dry-season length and plant inputs on soluble soil carbon
文章编号: N18072803
期刊: Ecology
作者: Peter M Homyak, Joseph C Blankinship, Eric W Slessarev, Sean M Schaeffer, Stefano Manzoni, Joshua P Schimel
更新时间: 2018-07-28
摘要: Soil moisture controls microbial activity and soil carbon cycling. Because microbial activity decreases as soils dry, decomposition of soil organic matter (SOM) is thought to decrease with increasing drought length. Yet, microbial biomass and a pool of water‐extractable organic carbon (WEOC) can increase as soils dry, perhaps implying microbes may continue to break down SOM even if drought stressed. Here, we test the hypothesis that WEOC increases as soils dry because exoenzymes continue to break down litter, while their products accumulate because they cannot diffuse to microbes. To test this hypothesis we manipulated field plots by cutting‐off litter inputs and by irrigating and excluding precipitation inputs to extend or shorten the length of the dry season. We expected that the longer the soils would remain dry, the more WEOC would accumulate in the presence of litter, whereas shortening the length of the dry season, or cutting off litter inputs, would reduce WEOC accumulation. Lastly, we incubated grass roots in the laboratory and measured the concentration of reducing sugars and potential hydrolytic enzyme activities, strictly to understand the mechanisms whereby exoenzymes break down litter over the dry season. As expected, extending dry season length increased WEOC concentrations by 30% above the 108 μg C g⁻¹ measured in untreated plots, whereas keeping soils moist prevented WEOC from accumulating. Contrary to our hypothesis, excluding plant litter inputs actually increased WEOC concentrations by 40% above the 105 μg C g⁻¹ measured in plots with plants. Reducing sugars did not accumulate in dry senesced roots in our laboratory incubation. Potential rates of reducing sugar production by hydrolytic enzymes ranged from 0.7 to 10 μmol g⁻¹ hr⁻¹ and far exceeded the rates of reducing sugar accumulation (~0.001 μmol g⁻¹ hr⁻¹). Our observations do not support the hypothesis that exoenzymes continue to break down litter to produce WEOC in dry soils. Instead, we develop the argument that physical processes are more likely to govern short‐term WEOC dynamics via slaking of microaggregates that stabilize SOM and through WEOC redistribution when soils wet up, as well as through less understood effects of drought on the soil mineral matrix.

24640. 题目: Rapid oxidation of iodide and hypoiodous acid with ferrate and no formation of iodoform and monoiodoacetic acid in the ferrate/I⁻/HA system
文章编号: N18072802
期刊: Water Research
作者: Xianshi Wang, Yulei Liu, Zhuangsong Huang, Lu Wang, Yicheng Wang, Yanting Li, Juan Li, Jingyao Qi, Jun Ma
更新时间: 2018-07-28
摘要: Toxic and odorous iodinated disinfection byproducts (I-DBPs) could form in the chemical oxidation of iodine-containing water. A critical step for controlling the hazardous I-DBPs is to convert the iodine species into stable and harmless iodate (IO₃⁻) while inhibiting the accumulation of highly reactive hypoiodous acid (HOI). Herein, the oxidation of I⁻ and HOI with ferrate was investigated, and the formation profile of HOI during the oxidation of I⁻ was determined based on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) coloring method through a stopped-flow spectrophotometer. The second-order rate constants (k_app) of ferrate with HOI decreased from 1.6 × 10⁵ M⁻¹s⁻¹ to 8.3 × 10² M⁻¹s⁻¹ as the solution pH varied from 5.3 to 10.3, which were 7.5, 7.2 and 13.8 times higher than that of ferrate with I⁻ at pH 6.0, 7.0 and 8.0, respectively. Compared with other oxidants such as ozone, hypochlorous acid, chloramine and potassium permanganate, ferrate would swiftly oxidize HOI formed in the I⁻ oxidation process. For the ferrate oxidation of I-containing water, HOI was swiftly oxidized to IO₃⁻ from pH 5.0 to 9.0. Phosphate buffer promoted the oxidation of I⁻ while inhibited the oxidation of HOI with ferrate. When 5 mgC/L of humic acids (HA) existed in the solution, no formation of iodoform and monoiodoacetic acid (MIAA) was observed in the oxidation of iodide (20 μM) with ferrate (from 10 μM to 80 μM). These results have important implications for the control of I-DBPs in water treatment.
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