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28941. 题目: A field-deployable surface-enhanced Raman scattering (SERS) method for sensitive analysis of silver nanoparticles in environmental waters
文章编号: N18111001
期刊: Science of The Total Environment
作者: Huiyuan Guo, Leigh C. Hamlet, Lili He, Baoshan Xing
更新时间: 2018-11-10
摘要: The proliferation of silver nanoparticles (AgNPs) in the environment and resultant transport into aquatic systems have raised concerns regarding their potential toxicity to various organisms. These environmental and ecological concerns demand reliable AgNP detection methods which can measure environmentally relevant quantities of AgNPs in real aquatic systems. This study developed a method that couples a rapid vacuum filtration technique with a portable Raman spectrometer to achieve on-site detection of ultra-low levels of AgNPs in typical and complex aquatic systems. To extract and detect AgNPs, aluminum chloride and ferbam were added for AgNP aggregation and labelling, respectively. The AgNP aggregates were filtered through a membrane, and their presence and quantity were determined based upon the surface-enhanced Raman scattering (SERS) peak intensity of ferbam. Under the optimized conditions, the extraction efficiencies are 99 ± 0.001% in ultrapure water and 98 ± 0.025% in marine water for 1 mg/L AgNPs. This method enables simple volume adjustment and improves the consistency of AgNP distribution on the membrane. The performance of the method was evaluated in different environmental waters, including marine water, fresh waters (pond water, river water, and reservoir outlet water) and drinking waters (municipal tap water and well water), with highest signal intensity in marine water and lowest signals in fresh waters. The signal intensity difference was suggested to be caused by the amount of natural organic matter (NOM) in these environmental waters. Using pond water as an example, the interference was minimized by changing the aggregating salt from AlCl3 to MgCl2, and AgNPs as low as 5 μg/L were reliably detected with a volume of 100 mL. At the same volume, the developed method was sensitive enough to detect 1 μg/L AgNPs in marine water and also holds promise for assessing the time-dependent transformation of AgNPs.
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28942. 题目: Genetic Structure and Haplotype Pattern of Marine Planktonic Ostracod (Porroecia spinirostris) from South China Sea Based on Mitochondrial COI Gene
文章编号: N18110913
期刊: Ocean Science Journal
作者: Lei Xu, Hong Li, Lianggen Wang, Feiyan Du
更新时间: 2018-11-09
摘要: Ostracods (Crustacea, Ostracoda) are small bivalved crustaceans, contributing to the marine zooplankton community. They are widely distributed and are relatively abundant components of the marine mesozooplankton worldwide, playing an important role in the transport of organic matter to deep layers. By analysing the mitochondrial COI gene, we explored the population genetic structure and haplotype pattern of Porroecia spinirostris which is the dominant ostracod in the South China Sea. We investigated the population genetic structure of ostracods at medium spatial scales in the absence of physical barriers. Our data provides evidence of the importance of both long-distance dispersal as well as genetic isolation in determining the seascape genetic structure of this species. Our data suggest that P.spinirostris can achieve long distance dispersal and specific haplotypes were successful in colonizing habitats from the Xisha to the Nansha area. A total of 36 haplotypes were defined from 85 individuals with most of these haplotypes occurring only once. The dominant haplotype was found in twelve sampling sites. The largest distance between two sampling sites harbouring this haplotype is more than 700 km. Our findings of long distance dispersal in the South China Sea combined with mild genetic differentiation among fifteen sampling sites (average ΦST = 0.167) are in line with a scenario where population genetic structure is strongly impacted by colonization patterns. The seascape genetic structure of P.spinirostris in the South China Sea reflects both the importance of long distance dispersal as well as of reduced levels of gene flow, likely caused by colonization events followed by demographic expansions.
28943. 题目: Geochemical and micropaleontological impacts caused by the 2011 Tohoku-oki tsunami in Matsushima Bay, northeastern Japan
文章编号: N18110912
期刊: Marine Geology
作者: Toshiaki Irizuki, Osamu Fujiwara, Kaoru Yoshioka, Atsushi Suzuki, Yuichiro Tanaka, Masayuki Nagao, Shungo Kawagata, Shigenori Kawano, Osamu Nishimura
更新时间: 2018-11-09
摘要: We present stratigraphic, geochemical (CNS elemental analysis), and micropaleontological (ostracode assemblages) evidence for the 2011 Tohoku-oki tsunami impact in Matsushima Bay, northeastern Japan, and examine the recovery process after the impact to the bay environment using short sediment cores from two different topographic settings at a water depth of approximately 4 m. At both sites, tsunami deposits are composed of two sedimentary layers that recorded the first tsunami run-up and backwash. At the western site near the channel that connects the bay with the Pacific Ocean, the first tsunami wave eroded the bay floor sediments and left the tsunami deposits composed of medium sand rich in shell fragments, but with sparse numbers of meiobenthic ostracodes. By contrast, at the eastern site, which is surrounded by many small islands, the first wave eroded very little of the bay floor sediments and left tsunami deposits consisting of sandy mud, rich in exotic ostracodes, such as phytal species, shallow marine sand dwelling species, and brackish water species. Overlying post-tsunami deposits are composed mainly of organic-rich mud in which organic matter was derived primarily from marine plankton. Ostracode assemblages in the tsunami deposits lack the offshore species that live in water depths >50 m and are dominated by the species from Matsushima Bay and its adjacent nearshore, upper sublittoral areas, and brackish water environments. The distance from deep-water offshore areas to the core sites is too far to transport ostracode valves by tsunami waves.
28944. 题目: Spatial simulation of soil-water content in dry and wet conditions in a hectometer-scale alpine meadow
文章编号: N18110911
期刊: Land Degradation & Development
作者: Xu-Chao Zhu, Rui-Xue Cao, Ming-An Shao
更新时间: 2018-11-09
摘要: Soil‐water content (SWC) is a key factor in restoring degraded vegetation in alpine‐meadow ecosystems, but it has rarely been spatially simulated on a hectometer scale. We simulated SWC for typical dry and wet days in an alpine meadow using multivariate linear regression and autoregressive state‐space equations based on SWC and other soil, terrain and vegetation parameters to evaluate the efficiency of these two methods in dry and wet soil moisture conditions. SWC measured on a typical dry day (SWC‐D) and a wet day (SWC‐W) increased and decreased with depth, respectively and SWC‐D was similar to SWC‐W at a depth of 50 cm. Both SWC‐D and SWC‐W were significantly correlated with soil bulk density (BD), capillary porosity (CP), silt content (Silt), gravel and stone content (GSC), pH and organic carbon density (OCD), and both SWC‐D and SWC‐W were significantly auto‐correlated and cross‐correlated with BD, Silt, GSC, pH and OCD at more than one lag distance. Multivariate linear regression using three variables in both dry and wet conditions had the highest accuracy, and the accuracy was generally higher for dry conditions than it was for wet conditions. The bivariate state‐space model was the most accurate for both dry and wet soil conditions, but the expression variables were totally different, with pH and OCD for dry day and BD and Silt for wet day. The conditions of soil moisture should thus be considered when choosing variables with which to simulate SWC, instead of only considering the relationships between SWC and other variables.
28945. 题目: The use of biochar and crushed mortar in treatment wetlands to enhance the removal of nutrients from sewage
文章编号: N18110910
期刊: Environmental Science and Pollution Research
作者: Tanveer Saeed, Nilufar Yasmin, Guangzhi Sun, Ariful Hasnat
更新时间: 2018-11-09
摘要: An experimental study was carried out using in pilot-scale constructed wetland systems, operated in parallel to treat raw sewage. Each system consisted of a vertical flow (VF) unit that was filled with biochar as the main media, followed by a horizontal flow (HF) unit filled with crushed cement mortar. Hydraulic loading (HL) ranged 340–680 mm/day was applied on the VF wetland units, where high total nitrogen (TN) mass removal rate (20–23 g N/m2 d) was obtained, demonstrating that biochar media had a beneficial effect on the degradation of nitrogenous pollutants. Total phosphorus (TP) removal percentage (concentration based) was ≥ 86% in HF wetlands packed with mortar materials. In one system, the flow direction of the sewage was directed by the deployment of downflow pipes and vertical baffles, aiming to facilitate the formation of aerobic and anaerobic zones in the wetland matrices. The effects of such arrangement were analyzed by comparing pollutant removal efficiencies in the two systems. On average, 99, 96, 93, and 86 percentage removals were obtained for ammonia (NH4-N), TN, biochemical oxygen demand (BOD), and TP, respectively, during the experiments. Biochar and crushed mortar proved to be a highly effective combination as media in subsurface flow constructed wetlands for wastewater treatment.
28946. 题目: Efficiency of sequential UV/H 2 O 2 and biofilm process for the treatment of secondary effluent
文章编号: N18110909
期刊: Environmental Science and Pollution Research
作者: Peng-Fei Yan, Shoujun Yuan, Wei Wang, Zhen-Hu Hu, Yang Mu, Han-Qing Yu
更新时间: 2018-11-09
摘要: In response to the shortage of water resources, multiple processes have been applied to turn wastewater secondary effluent (SE) into potable water. However, trace organic contaminants (TOrCs) and high concentrations of organic matter contained in SE pose a significant challenge to the reclamation. In this manuscript, combined UV-based and biofilm processes were used to treat the SE spiked with ibuprofen (IBU) and clofibric acid (CA). The efficiency of these sequential treatments was characterized in terms of changes in dissolved organic carbon (DOC), absorbance at 254 nm (A254), fluorescence excitation-emission matrix (FEEM), the concentration of IBU and CA, and molecular weight of SE. Parallel factor (PARAFAC) was applied as the analysis method for FEEM of the samples and two fluorescent components were successfully identified: humic-like substances (C1) and protein-like matter (C2). Large reductions in A254, C1, C2, IBU, and CA were observed during the UV-based processes, especially with the addition of H2O2. Nearly 50% of A254, 80% of the component C1 were decreased and almost complete removal of the component C2 and TOrCs was achieved by UV/2.0 mM H2O2 after 90-min treatment. During the oxidation processes, the formation of lower molecular weight (LMW) compounds was detected, and the biodegradability of the organic matters was greatly increased. Although no significant DOC reduction was obtained in UV-based processes, an obvious further DOC reduction (30~60%) was achieved by biofilm treatment following UV-based processes, especially after UV/H2O2 treatments. In the meantime, large amounts of LMW were removed in the biofilm treatment process. This manuscript provides an effective advanced treatment of SE for the removal of DOC and TOrCs, facilitating the wastewater reclamation.
28947. 题目: Stability of Ferrihydrite–Humic Acid Coprecipitates under Iron-Reducing Conditions
文章编号: N18110908
期刊: Environmental Science & Technology
作者: Jacqueline Mejia, Shaomei He, Yu Yang, Matthew Ginder-Vogel, Eric E. Roden
更新时间: 2018-11-09
摘要: Recent studies have suggested the potential for release of iron (hydr)oxide-bound organic carbon (OC) during dissimilatory iron oxide reduction (DIR). However, the stability of iron (hydr)oxide-bound OC in the presence of a natural microbial consortium capable of driving both OC metabolism and DIR has not been resolved. Pure ferrihydrite (Fhy) and Fhy–humic acid coprecipitates (Fhy-HA) were inoculated with a small quantity of freshwater sediment and incubated under anoxic conditions in the presence and absence of H2 or glucose as electron donors for DIR. H2 promoted DIR led to release of ca. 1 mM dissolved organic carbon (DOC). However, comparable amounts of DOC were released from both pure Fhy and Fhy-HA, similar to DOC levels in mineral-free, inoculum-only controls. These results suggest that the observed DOC release during H2-promoted DIR originated from OC contained in the inoculum as opposed to the much larger pool (ca. 38 mM) of OC in the Fhy-HA. Thus, DIR preferentially released sorbed OC with low aromaticity (inoculum OC) versus highly aromatic OC (HA) coprecipitated with iron oxide. Our findings provide new insight into the extent and mechanisms by which DIR is likely to influence aqueous/solid-phase OC partitioning in anoxic soils and sediments.
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28948. 题目: Fern, Dicranopteris linearis, derived phytoliths in soil: morphotypes solubility and content in relation to soil properties
文章编号: N18110907
期刊: European Journal of Soil Science
作者: M. N. Nguyen, A. Meharg, M. Carey, S. Dultz, F. Marone, S. B. Cichy, C. T. Tran, G. H. Le, N. T. Mai, T. T. H. Nguyen
更新时间: 2018-11-09
摘要: Ferns are among the most popular groups of plants in the tropics and subtropics, and their role as carbon sequestrators has been widely recognized. However, there is little understanding of the silicaceous structures (phytoliths) of ferns, rate of phytolith turnover, the consequences for organic matter sequestered in phytoliths and consequences for other soil properties. In the study reported here, high resolution X‐ray tomographic microscopy and chemical characterization were applied to examine the traits of phytoliths of the fern Dicranopteris linearis (Burm.f.) Underw. (D. linearis), with a focus on their dissolution properties and accumulation in northern Vietnamese soils in relation to soil properties. Tomographic images revealed an inter‐embedding structure of silica and organic matter, especially in leaf derived material. We propose that organic matter and silica can preserve each other against decomposition. In batch experiments, there was a relatively small rate of dissolution of phytoliths with dry ashing and subsequent H2O2 treatment. Silicon (Si) dissolution for D. linearis phytolith samples was much less than that for rice phytoliths. Despite the fact that the aluminum (Al) content was large in D. linearis leaves, batch dissolution data did not confirm a relation between Al and the slow rate of phytolith dissolution. The soil phytolith content varied from 0.9 to 7.5 g kg–1 in the topsoil across the mountainous areas in northern Vietnam, whereas it tended to be smaller in the subsoil. The data indicate a relation between phytolith and soil organic matter, clay content, oxalate‐soluble Al and electrical conductivity, suggesting that these soil properties are among the important factors affecting the size of the soil phytolith Si pool.
28949. 题目: Soil properties and distribution in the riparian zone: the effects of fluctuations in water and anthropogenic disturbances
文章编号: N18110906
期刊: European Journal of Soil Science
作者: F. Ye, M. H. Ma, S. J. Wu, Y. Jiang, G. B. Zhu, H. Zhang, Y. Wang
更新时间: 2018-11-09
摘要: China’s Three Gorges Dam has generated a large riparian zone around the reservoir that has changed the natural fluctuation in water level (FWL) and intensity of anthropogenic disturbance (AD, i.e. human activities triggering pollutant input). Knowledge about how riparian soil properties respond to such changes remains limited. The aims of this study were to identify the distribution of soil properties in the riparian zone and to determine which types of factors, local‐scale FWL or regional‐scale AD, have a larger effect on the soil properties. A total of 144 composite soil samples, collected from two riparian areas in four sampling surveys, were investigated. Multivariate regression tree analysis indicated that the variation in soil properties was mainly controlled by FWL (40.1%) compared with the minor role of AD (2.1%). Soil total carbon, total nitrogen and organic matter were mainly affected by AD, whereas FWL had a major influence on soil pH, ammonium and nitrate. Along the elevation gradient (150–175 m), the soil properties were determined mainly by the sampling elevation, accounting for 67.6% of the variation, followed by short‐term (5.6%) and long‐term flooding (3.3%). The 167.5‐m elevation was proposed to be the threshold that divides the riparian zone into two different response zones. Soil below 167.5 m was mainly affected by local‐scale FWL, whereas that above 167.5 m was largely affected by regional‐scale AD. This proposed threshold suggests that riparian soil management around the Three Gorges Reservoir should consider both local‐ and regional‐scale factors and that different approaches and strategies for ecological restoration need to be applied along an elevation gradient.
28950. 题目: Formation kinetics of disinfection byproducts in algal-laden water during chlorination: A new insight into evaluating disinfection formation risk
文章编号: N18110905
期刊: Environmental Pollution
作者: Rui Huang, Zhiqi Liu, Boyin Yan, Jingjing Zhang, Dongmei Liu, Yongpeng Xu, Peng Wang, Fuyi Cui, Zhiquan Liu
更新时间: 2018-11-09
摘要: It is necessary and important to investigate the formation of disinfection byproducts (DBPs) in water treatment systems for the management of disinfection formation risk. In the present study, the formation potential of trichloromethane (TCM) and haloacetic acids in different algal metabolites were compared, and the formation kinetics of these DBPs were investigated. The results indicated that DBP formation potential, the traditional index widely used to evaluate the disinfection formation risk, can represent neither the total precursors of DBPs nor the possible generated amounts of DBPs in drinking water systems. Kinetic analyses showed that the formation of DBPs could be well described by a classical second-order reaction kinetic model and that the actual concentrations of DBPs during chlorination were predictable with the model. The formation of DBPs in drinking water treatment systems was highly dependent on the total precursors of DBPs in water and the formation rate of DBPs with chlorine; the latter is usually underestimated in previous studies. Because of their high reactivity, TCM in hydrophilic extracellular organic matter and trichloroacetic acid in all algal metabolites should be serious considerations in the management of disinfection formation risk.
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28951. 题目: Micrometer scale imaging of sedimentary climate archives – sample preparation for combined elemental and lipid biomarker analysis
文章编号: N18110904
期刊: Organic Geochemistry
作者: Susanne Alfken, Lars Wörmer, Julius S. Lipp, Jenny Wendt, Heidi Taubner, Arndt Schimmelmann, Kai-Uwe Hinrichs
更新时间: 2018-11-09
摘要: Mass spectrometry imaging (MSI) can be used for the µm scale mapping of target molecules on intact sample surfaces. Recently we demonstrated that MSI of non-disturbed sediments can be used for paleoenvironmental studies; using matrix-assisted laser desorption/ionization coupled to Fourier transform-ion cyclotron resonance-mass spectrometry we visualized the spatial distributions of archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids. There is a pressing need for implementing sample preparation procedures that allow exploiting the full potential of sediment MSI. Here we present a suite of sample preparation steps, optimized for the analysis of GDGTs in marine sediments. It considers the crucial requirements for successful MSI and optional combination with elemental imaging via micro X-Ray Fluorescence Spectroscopy (µ-XRF). Preservation of the sediment’s spatial distribution is achieved with freeze-drying and subsequent embedding in a mixture of gelatin and carboxymethyl cellulose. This enables sectioning the sample into sequential slices from 20–500 µm thickness. Thinner sections showed enhanced signal intensity in MSI, but elemental mapping by µ-XRF is more accurate for thicker sections; 100 µm thick slices provide satisfactory results for both analyses and are recommended for congruent elemental and biomarker imaging. When applied to the uppermost ∼5 cm of marine sediment from a Santa Barbara Basin box core, the optimized sample preparation yields reproducible ultra-high-resolution GDGT records from sequential slices, thus demonstrating the robustness of the method. Congruent µ-XRF results aid the establishment of a contextual framework regarding supply of terrigenous and marine detritus as well as the assignment of molecular data to annual layers.
28952. 题目: Clade-dependent size response of conodonts to environmental changes during the late Smithian extinction
文章编号: N18110903
期刊: Earth-Science Reviews
作者: Marc Leu, Hugo Bucher, Nicolas Goudemand
更新时间: 2018-11-09
摘要: In contrast to the benthos whose taxonomic recovery was lagging way behind that of the nekton, highly diverse Smithian conodont and ammonoid faunas were profoundly decimated during the late Smithian, ca. 2 Myr after the Permian-Triassic boundary mass extinction. As body size reduction is a common evolutionary response to heavy environmental stress, we investigate how the size of the P1 elements of different conodont clades responded during the late Smithian crisis based on three sections from the northern Indian Margin. A major and world-wide positive carbon excursion is also a consistent signature of the late Smithian time interval. Where adequate ammonoid biochronological control is lacking (i.e., Kashmir), a new carbonate carbon isotope record provides an independent age proxy for correlations with southern Tibet and the Salt Range. Assuming a positive correlation between the size of P1 elements and body size, we confirm that segminate conodonts underwent a size decrease during the late Smithian. However, segminiplanate conodonts consistently displayed a substantial size increase during the same time interval, thus highlighting clade specific, diverging answers and precluding any simplistic generalization of size responses to the same stress event. Additionally, a moderate but consistent size increase during the early Spathian is documented for both clades, thus obscuring any simple general relation between temperature stress and size among conodonts. Comparison of size time series with the oxygen isotopic composition of conodonts (a proxy for sea-water temperature) suggests that only the size of segminate P1 elements may correlate positively with temperature. Although at a slower pace, the size of segminiplanate P1 elements continued to increase during the early Spathian, when temperature rose again after the late Smithian cooling event. Therefore, temperature alone cannot explain the size variations of segminiplanate conodonts. The late Smithian was also a time of increasing burial of organic matter on continental shelves, but lateral variations of this factor also obscure any relation with the documented size changes. Last but not least, the stratigraphically more comprehensive study in Nammal reveals a segminiplanate gap during the middle Smithian thermal high. The biogeographical expansion of this clade towards the low latitudes during the Griesbachian, the early Smithian, the late Smithian and the early Spathian apparently occurred during the coolest intervals of the Early Triassic, in agreement with their supposed cooler habitat.
28953. 题目: Organic loading rate (OLR) regulation for enhancement of aerobic sludge granulation: Role of key microorganism and their function
文章编号: N18110902
期刊: Science of The Total Environment
作者: Zhiming Zhang, Jianxiang Qiu, Ronghao Xiang, Haitian Yu, Xiangyang Xu, Liang Zhu
更新时间: 2018-11-09
摘要: According to unique growth characteristics of various environmental microorganism specially with different substrates and their levels, aerobic sludge granulation are studied under different operation mode of influent organic loading rate (OLR), and the EPS component, sludge surface characters and functional microbes are analyzed to achieve a novel process for stable sludge granulation. Results showed that activated sludge cultivated under gradient influent OLR decreasing from 5.5 to 3.5 kgCOD m−3 d−1 achieved complete granulation with average size of 438 μm and exopolysaccharide (PS) to protein (PN) ratio over 2.0. Meanwhile, these granules had excellent flocculability and hydrophobicity with Zeta potential and contact angle of −15 mV and 110°, respectively. Principal component analysis (PCA) illustrated that microbes with function of EPS secretion enriched with decreased OLR regulation for their suitable specific growth characteristics, then promoted other microbes aggregation and sludge granulation along with the improvement of cellular surface characters and microbial niche.
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28954. 题目: The role of Fe(III) in soil organic matter stabilization in two size fractions having opposite features
文章编号: N18110901
期刊: Science of The Total Environment
作者: Beatrice Giannetta, Claudio Zaccone, César Plaza, Matthew G. Siebecker, Pere Rovira, Costantino Vischetti, Donald L. Sparks
更新时间: 2018-11-09
摘要: Soil organic matter (SOM) protection, stability and long-term accumulation are controlled by several factors, including sorption onto mineral surfaces. Iron (Fe) has been suggested as a key regulator of SOM stability, both in acidic conditions, where Fe(III) is soluble, and in near-neutral pH environments, where it precipitates as Fe(III) (hydr)oxides. The present study aimed to probe, by sorption/desorption experiments in which Fe was added to the system, the mechanisms controlling Fe(III)-mediated organic carbon (C) stabilization; fine silt and clay (FSi + Cl) and fine sand (FSa) SOM fractions of three soils under different land uses were tested. Fe(III) addition caused a decrease in the organic C remaining in solution after reaction, indicating an Fe-mediated organic C stabilization effect. This effect was two times larger for FSa than for FSi + Cl, the former fraction being characterized by both low specific surface area and high organic C content. The organic C retained in the solid phase after Fe-mediated stabilization has relatively low sensitivity to desorption. Moreover, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy indicated that Fe-mediated organic C stabilization can be mainly ascribed to the formation of complexes between carbohydrate OH functional groups and Fe oxides. These results demonstrate that the binding of labile SOM compounds to Fe(III) contributes to its preservation, and that the mechanisms involved (flocculation vs. coating) depend on the size fractions.
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28955. 题目: Impact of pH on Iron Redox Transformations in Simulated Freshwaters Containing Natural Organic Matter
文章编号: N18110810
期刊: Environmental Science & Technology
作者: Shikha Garg, Chao Jiang, T. David Waite
更新时间: 2018-11-08
摘要: The impact of the pH of natural waters on the various pathways contributing to the formation and decay of Fe(II) in the presence of Suwannee River Fulvic Acid (SRFA) is investigated in this study. Our results show that thermal Fe(III) reduction occurs as a result of the presence of hydroquinone-like moieties in SRFA with the rate of Fe(III) reduction by these entities relatively invariant with change in pH in the range 6.8–8.7. The Fe(II) oxidation rate in the dark is controlled by its interaction with O2 and increases with increase in pH with the overall outcome that the steady-state Fe(II) concentration in the dark is strongly affected by solution pH. On irradiation, a portion of the hydroquinone-like moieties present are oxidized to form semiquinones that are capable of reducing Fe(III) and/or oxidizing Fe(II) under circumneutral pH conditions. The extent of photogeneration of semiquinones on irradiation of SRFA and the persistence of these radicals increases significantly with decrease in pH. Due to the higher concentration and longevity of these organic moieties under low pH conditions, the impact of pH on steady-state Fe(II) concentration is less pronounced in previously irradiated SRFA solution compared to that observed in dark SRFA solution. Under irradiated conditions, the rates of Fe transformation (including both Fe(II) oxidation and Fe(III) reduction) are nearly independent of pH. While ligand-to-metal charge transfer (LMCT) is the dominant pathway for photochemical Fe(III) reduction, Fe(II) oxidation under irradiated conditions mainly occurs as a result of interaction with O2, semiquinones and other short-lived oxidants. Overall, our data supports the conclusion that, as a result of the contribution from photogenerated organic moieties to Fe redox transformations, the steady-state Fe(II) concentration in irradiated surface waters containing natural organic matter may not be impacted significantly by changes in pH.
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28956. 题目: Two-decade long fertilization induced changes in subsurface soil organic carbon stock vary with indigenous site characteristics
文章编号: N18110809
期刊: Geoderma
作者: Feng Liang, Jianwei Li, Shuiqing Zhang, Hongjun Gao, Boren Wang, Xiaojun Shi, Shaoming Huang, Minggang Xu
更新时间: 2018-11-08
摘要: Soil organic carbon (SOC) sequestration at subsurface layers (i.e. >20 cm) remains unclear under long-term fertilization practices. Based on long-term datasets of fertilization experiments in four typical Chinese croplands, representing soils with high fertility at Gongzhuling (GZL, black soil) and Chongqing (CQ, purple soil), and low fertility at Zhengzhou (ZZ, aquatic Chao soil) and Qiyang (QY, red soil), we calculated SOC storage, its change relative to initial condition (ΔSOC) in 0–20, 20–40 and 40–60 cm. We also obtained annual organic C inputs (OCI; stubble, roots and manure amendment) and derived soil C sequestration efficiency (CSE: the ratio of ΔSOC over OCI) in 0–20 cm and 0–60 cm. The fertilization treatments include cropping with no fertilization (CK), chemical nitrogen, phosphorus and potassium fertilizers (NPK) and combined chemical fertilizers and manure (NPKM). Results showed SOC stock significantly increased with fertilizations (i.e. initial, CK < NPK < NPKM). Relative to initial condition, surface (0–20 cm) and subsurface (20–60 cm) SOC stocks significantly decreased under CK at all sites except GZL, a site with elevated SOC stocks under all fertilizations and depths. Subsurface SOC stocks significantly increased at high fertility soils (i.e., GZL and CQ) but remained no change or significantly decreased at low fertility soils (i.e., ZZ and QY) under NPK and NPKM. Accordingly, CSE derived in 0–60 cm was consistently higher than that in 0–20 cm in high fertility soils but lower in low fertility soils. These results demonstrated that subsurface soils (20–60 cm) remained as C sinks in indigenously high fertility sites but experienced substantial C depletions in low fertility sites. This study informed the need to account for subsurface soil carbon changes for accurate estimates of soil C sequestration capacity under long-term fertilization.
28957. 题目: Floating aquatic plants for total nitrogen and phosphorus removal from treated swine wastewater and their biomass characteristics
文章编号: N18110808
期刊: Journal of Environmental Management
作者: Sartika Indah Amalia Sudiarto, Anriansyah Renggaman, Hong Lim Choi
更新时间: 2018-11-08
摘要: In this study, the removal of nitrogen and phosphorus from the effluent of treated swine wastewater by Eichhornia crassipes, Pistia stratiotes, Limnobium laevigatum, and Lemna sp. was investigated. This study also aimed to quantify the potential biomass production and lignocellulosic composition of the floating plants cultured in the effluent. Plants were grown in treated swine wastewater effluent or Hoagland's solution. Pistia stratiotes showed the highest total nitrogen removal of 63.15% from the treated effluent. Lemna sp. showed the highest phosphorus removal of 36.15% from the treated effluent. However, Lemna sp. could not be further utilized because the plants could only be cultured for 13 days. The effluent likely had properties that inhibited the growth and nutrient uptake by the plants; further studies would be required to verify these properties. Pistia stratiotes and Eichhornia crassipes have higher tolerance than Lemna sp. to grow in treated swine wastewater. Eichhornia crassipes produced the highest biomass of 5.19 g dry weight/m2/day. Cellulose and lignin contents were higher in the Hoagland's solution treatment when compared with the effluent. However, based on an independent T-test analysis, the cellulose contents of plants grown in different media were not significantly different. Hemicellulose content was significantly different for Pistia stratiotes (p < 0.05). Finally, lignin content was significantly different for Eichhornia crassipes and Lemna sp (p < 0.05). The nutrient composition and available plant nutrients as well as other substances present in the effluent might have influenced the plant cell wall composition.
28958. 题目: Copper toxicity to blue mussel embryos (Mytilus galloprovincialis): The effect of natural dissolved organic matter on copper toxicity in estuarine waters
文章编号: N18110807
期刊: Science of The Total Environment
作者: Rebecca Zitoun, Susan J. Clearwater, Christel Hassler, Karen J. Thompson, Anathea Albert, Sylvia G. Sander
更新时间: 2018-11-08
摘要: Copper (Cu) is a naturally occurring micronutrient of eco-toxicological concern in aquatic ecosystems. Current knowledge of Cu-speciation and bioavailability in natural saline environments is insufficient to adequately inform environmental protection policy for estuarine systems. We assessed the combined effect of two of the main drivers of metal bioavailability, salinity and natural dissolved organic carbon (DOC), on Cu-speciation and associated Cu-toxicity to blue mussel (Mytilus galloprovincialis) embryos in a standard 48-h bioassay. We placed special emphasis on measurement of Cu-speciation rather than modelling. Cu-toxicity was found to be a function of DOC and salinity. The varying protective effect of different DOC-types suggests that estuarine DOC is more protective against Cu-toxicity than oceanic DOC. Salinity was negatively correlated with [Cu48-h-EC50], indicating a salinity-induced alteration in the physiology of the exposed mussel embryos and/or Cu-DOC-reactivity. These two assumptions were supported by (1) the relative uniformity of bioavailable copper ([Cu′]) across similar salinity treatments despite considerable variation in [Cu48-h-EC50] and DOC-concentrations, and (2) the fact that Cu-toxicity and [Cu′] were slightly higher in the 35 salinity treatment compared to the 25 salinity treatment. Stripping voltammetry studies determined the presence of only one strong Cu-binding ligand class (i.e., L1), either actively or passively released by the exposed embryos. [L1] was found to be proportional to the total dissolved Cu-concentration ([CuT]), suggesting a protective effect of Cu-binding-ligands, in addition to the protective effect of DOC. There was also a strong positive correlation between [L1] and [Cu48-h-EC50], implying that electrochemically defined ligand concentrations along with measurements of [Cu′], DOC-quality, and salinity can be used as proxies for 48-h-EC50 Cu-values in estuarine waters, which may result in a significant improvement to risk assessments of Cu in estuarine systems.
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28959. 题目: Characteristics of organic nitrogen fractions in sediments of the water level fluctuation zone in the tributary of the Yangtze River
文章编号: N18110806
期刊: Science of The Total Environment
作者: Junjie Lin, Yujiao Tang, Dan Liu, Shuai Zhang, Bo Lan, Liping He, Zhiguo Yu, Shuang Zhou, Xi Chen, Yanhua Qu
更新时间: 2018-11-08
摘要: The contents of different organic nitrogen (N) fractions, their contributions to total N (TN) and the relationship between their mineralizable N (MN) and different organic N fractions in sediments of the water level fluctuation (WLF) zone were investigated. The contents of TN, acid hydrolyzable N (AHN), and nonhydrolyzable N (NHN) decreased in sediments from the lower altitudes of the WLF zone. The AHN and NHN accounted for 70.56 to 82.89% and 17.11 to 29.44% of TN, respectively. The AHN was the main organic N fraction, indicating that these sediments might promote greater water eutrophication in the Three Gorges tributaries. The distribution of amino-acid N (AAN), ammonium N (AN), amino-sugar N (ASN) and hydrolyzable unidentified N (HUN) in the WLF zone was found to be 170 m > 160 m > 150 m. AAN, AN, ASN, and HUN accounted for 34.70, 20.25, 15.52 and 29.24% of AHN, respectively. HUN and ASN were the main contributors of MN to N release.
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28960. 题目: Achieving completely anaerobic ammonium removal over nitrite (CAARON) in one single UASB reactor: Synchronous and asynchronous feeding regimes of organic carbon make a difference
文章编号: N18110805
期刊: Science of The Total Environment
作者: Zheng-Zhe Zhang, Ya-Fei Cheng, Bing-Qian Zhu, Ying-Yi Liu, Qian Zhang, Ren-Cun Jin
更新时间: 2018-11-08
摘要: At least 11% of total nitrogen (TN) remains in the anammox effluent, making it difficult to meet increasingly stringent discharge standards. To overcome this bottleneck, an innovative process to achieve completely anaerobic ammonium removal over nitrite (CAARON) in one single up-flow anaerobic sludge blanket reactor was proposed in this study. The synchronous feeding of acetate at a C/N (nitrite) ratio of 0.6 significantly reduced the nitrogen removal capacity of anammox reactor by limiting the abundance and metabolism of anammox bacteria. In contrast, the asynchronous feeding of acetate optimized the partition of the reactor column into two specific compartments: the lower half favoring anammox and the upper half dominated by DEAMOX (DEnitrifying AMmonium Oxidation). A high TN removal efficiency of 96.2 ± 0.4% and a low effluent TN concentration of 9.3 ± 0.9 mg L−1 were obtained under a high TN loading rate of 9.0 kgN m−3 d−1. The dominant functional microbes in the CAARON process were identified as Candidatus Kuenenia and Thauera, which were responsible for the anammox and denitratation reactions, respectively. Overall, the results in this study provide valuable insight into the coupling of anammox with denitratation, which is a cost-efficient approach for treating ammonium-rich wastewaters.
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