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25901. 题目: Sulfur controlled cadmium dissolution in pore water of cadmium-contaminated soil as affected by DOC under waterlogging
文章编号: N19092206
期刊: Chemosphere
作者: Guoxi Wang, Zhengyi Hu, Songyan Li, Yan Wang, Xiaolei Sun, Xiangru Zhang, Meng Li
更新时间: 2019-09-22
摘要: Cadmium (Cd) precipitation and dissolution in pore water is associated with dissolved organic carbon (DOC)-induced reduction-oxidation of sulfur (S) under waterlogging and is vital for controlling the bioavailability in paddy soil. A 120-day soil incubation experiment, including application of sulfur (S, 30 mg kg−1) and wheat straw (W, 1.0%) alone or in combination (W + S) into Cd-contaminated paddy soil under waterlogging, was conducted to investigate the dynamic of dissolved Cd and its relationship with DOC, S2−, Fe2+, pH, Eh and pe + pH in soil pore water. The results showed that the lowest dissolved Cd concentration was observed in the W + S-treated soil pore water among all treatments when the soil Eh remained at lower values during the period of 15–60 days of incubation, which could be attributed to CdS precipitation and/or co-precipitation of Cd absorbed by FeS2 because of the reduction in sulfur. The application of S resulted in a Cd rebound in the pore water irrespective of W addition when the Eh began to increase from its lowest values during the period of 45–75 days of incubation, and SOB genera were observed in the S added soil. This could be attributed to re-dissolution of the precipitated Cd in soils under the SOB-driven oxidation of sulfide such as CdS and FeS2. In conclusion, DOC-driven reduction-oxidation of sulfur controls Cd dissolution in the pore water of Cd-contaminated paddy soil under waterlogging conditions. Further studies are required to investigate the interaction of sulfur and SOM-induced DOC on Cd bioavailability in rice-planted paddy soils.
25902. 题目: Low-molecular-weight organic acids enable biochar to immobilize nitrate
文章编号: N19092205
期刊: Chemosphere
作者: Natalie Heaney, Emem Ukpong, Chuxia Lin
更新时间: 2019-09-22
摘要: Batch experiments were conducted using two biochar materials produced from different feedstocks to examine the behavior of solution-borne nitrate in the presence and absence of three model low-molecular weight organic acids (LMWOAs). The results showed that the biochar materials alone were not able to remove the solution-borne nitrate. LMWOAs caused protonation of the biochar surfaces and consequently enabled the biochar materials to adsorb nitrate from the solution. Different types of LMWOA had different capacities to immobilize solution-borne nitrate. Over 80% of the solution-borne nitrate could be removed within 72 h in the presence of citric acid or malic acid. By comparison, removal rate of nitrate was lower in the presence of oxalic acid, possibly due to competition of oxalate ion with nitrate for the available adsorption sites on the biochar surfaces. Nitrate adsorption onto the MSP700 biochar in the presence of all three-LMWOAs followed first order and second order kinetics, suggesting that the immobilization of nitrate involved complex interplay of physisorption and chemisorption. Nitrate adsorption onto RH700 biochar in citric and malic acid treatment systems followed second order kinetics. In the presence of oxalic acid for both biochar materials, nitrate adsorption showed perfect correlation R2 = 1 for both models.
25903. 题目: pH dependence of the binding interactions between humic acids and bisphenol A - A thermodynamic perspective
文章编号: N19092204
期刊: Environmental Pollution
作者: Li-hong Gan, Zi-run Yan, You-fei Ma, Yu-ying Zhu, Xiu-yan Li, Juan Xu, Wei Zhang
更新时间: 2019-09-22
摘要: The wide application of bisphenol A (BPA) leads to the emergence of BPA residuals in natural water environments. Dissolved organic matter (DOM) existed in water can bind with BPA, hence influencing the migration and transformation of BPA in aquatic environments. pH is a crucial factor governing the binding interactions between DOM and BPA. However, the mechanisms driven the binding process under different pH conditions are still unclear. In this study, the interactions between BPA and humic acids (HA), a primary component of DOM, are investigated over a wide pH range of 3–12 by integrating fluorescence quenching, dynamic light scattering and microcalorimetry. pH dependence of the binding interactions between HA and BPA are interpreted from a thermodynamic perspective. The results indicate that HA can spontaneously interact with BPA to form a stable HA-BPA complex. With the increasing pH, the binding interactions change from entropy driven to entropy-enthalpy co-driven. Hydrophobic force dominate the binding interactions under acidic condition. The synergy of hydrophobic force and hydrogen bond promotes the binding process under neutral condition. Under alkaline condition, electrostatic repulsion participates the binding process in addition to hydrophobic force and hydrogen bond, weakening the binding strength. Therefore, neutral pH is favorable for HA to bind with BPA, consequently enhancing the dissolution of BPA in natural water bodies. The results are beneficial to better understand the pH dependent distribution of BPA in aquatic environments.
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25904. 题目: Sludge dewaterability: The variation of extracellular polymeric substances during sludge conditioning with two natural organic conditioners
文章编号: N19092203
期刊: Journal of Environmental Management
作者: Marie Christine Amie Sene Faye, Kai Kai Zhang, Sun Peng, Yanrong Zhang
更新时间: 2019-09-22
摘要: To assess the characteristics of Extracellular Polymeric Substances during natural organic conditioners for sludge treatment, Moringa oleifera (MO) and chitosan (CTS) were used as conditioners. The findings of this study show that despite the high EPS content due to the fact that this component is not destroyed upon conditioning, sludge conditioned with MO and CTS displayed efficient and improved dewaterability. MO and CTS showed the same mechanism of action by protonation of the negatively charged EPS and reduction of electrostatic repulsions between sludge flocs, thus enhancing sludge filterability by neutralizing and settling. The effect of MO and CTS on EPS lies in their ability to neutralize EPS, settling them. MO and CTS neutralize and aggregate the EPS, hence improving sludge dewaterability. The results indicate that CTS can impact the EPS quantity and quality while MO impacts the EPS quality. Understanding the impact of MO and CTS on sludge EPS can help elucidate the mechanism of their dewaterability efficiency.
25905. 题目: Composition change and adsorption performance of EPS from Bacillus vallismortis sp. induced by Na2S
文章编号: N19092202
期刊: Ecotoxicology and Environmental Safety
作者: Qiuhua Li, Weifeng Song, Mengge Sun, Jiayao Li, Zefeng Yu
更新时间: 2019-09-22
摘要: Sodium sulfide (Na2S) was used as an inducer to regulate the components of Bacillus vallismortis sp. EPS (Extracellular Polymeric Substances). The main objective of this study was to improve the content of sulfhydryl protein and the adsorption property of EPS to Zn (Ⅱ) that as an typical heavy metal. The results showed that the maximum EPS production of 105.58 mg/g VSS coupling with doubled increase in protein in which the contant of -SH increased by 48.2% from 104.15 to 154.36 μmol/L were recorded in the presence of 20 mg/L Na2S. Under this condition, the adsorption capacity of S-EPS (EPS with added exogenous Na2S) for Zn (Ⅱ) was highest. The kinetics of the adsorption process of Zn (Ⅱ) by the S-EPS can be well fitted by the Langmuir isotherm model and the theoretical maximum adsorption amount of 979.09 mg/g EPS could be obtained. The results of 3D-EEM and FTIR analyses, illustrated that -SH, CO, and N-H/C-N played major roles in the removal of Zn (Ⅱ) by S-EPS. The results obtained in this study demonstrated that the addition of sulfur source could increase the content of sulfhydryl protein, and effectively regulate the content of chemical composition, expecially for the sulfhydryl of EPS, and thereby greatly improving the removal efficiency of heavy metals, which showed a great application prospect in the prevention and control of heavy metal pollution.
25906. 题目: Magnetic Biochar Derived from Biosolids via Hydrothermal Carbonization: Enzyme Immobilization, immobilized-enzyme kinetics, environmental toxicity
文章编号: N19092201
期刊: Journal of Hazardous Materials
作者: He Zhang, Anthony G. Hay
更新时间: 2019-09-22
摘要: Magnetic and nonmagnetic biochar (MBC & BC) were produced from biosolids under hydrothermal conditions and characterized in order to understand surface chemistry impacts on enzyme immobilization and activity. Peak surface pore size of MBC was 180 nm and that of BC was 17 nm. Despite similar surface area (≈ 49 m2/g) MBC immobilized more laccase (99 mg/g) than biochar (31 mg/g). For horseradish peroxidase (HRP), the two biochars had similar immobilization capacity (≈ 65 mg/g). Laccase and HRP on MBC had 47.1 and 18.0% higher specific activity than on BC, respectively. The matrix activity of MBC-laccase (33.3 U/mg support) was 3.7-fold higher than BC-laccase (8.8 U/mg support) and higher than the same amount of free laccase (30.2 U) at pH 3.0 (P < 0.05). Although MBC had its own peroxide oxidation activity (104.1 and 165.9 U/mg biochar at pHs 5&6) this only accounted for 16.7 and 20.4 % of the total MBC-HRP activity respectively. After 10 wash cycles, MBC still retained 79.3% and 60.3% of laccase and HRP activity, respectively. Additionally, MBC had lower acute toxicity, suggesting that it is relative benign from an environmental perspective.
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25907. 题目: Photodegradation of Fludioxonil and Other Pyrroles: The Importance of Indirect Photodegradation for Understanding Environmental Fate and Photoproduct Formation
文章编号: N19092106
期刊: Environmental Science & Technology
作者: Jennifer N Apell, Nicholas C. Pflug, Kristopher McNeill
更新时间: 2019-09-21
摘要: Fludioxonil is a pyrrole-containing pesticide whose registration as a plant protection product is currently under review in the United States and Europe. There are concerns over its potential persistence and toxicity in the aquatic environment; however, the pyrrole moiety represents a potential reaction site for indirect photodegradation. In this study, the direct and indirect photodegradation of fludioxonil, along with pyrrole, 3-cyanopyrrole, and 3-phenylpyrrole, were investigated. Results showed that pyrrole moieties are capable of undergoing direct photoionization and sensitized photooxidation to form radical cation species, which then likely deprotonate and react with dissolved oxygen. Additionally, pyrrole moieties can undergo reactions with singlet oxygen (1O2). Furthermore, the presence of electron-withdrawing or -donating substituents substantially impacted the reaction rate with 1O2 as well as the one-electron oxidation potential of the pyrrole that dictates reactions with triplet states of dissolved organic matter (3CDOM*). For fludioxonil, which can undergo both direct and indirect photodegradation, the reaction rate constant with 1O2 alone resulted in a predicted t1/2 < 2 days in waters under sunlit near-surface conditions, suggesting it will not be persistent in aquatic systems. These results are useful for evaluating the environmental fate of fludioxonil as well as other pyrrole compounds.
25908. 题目: Spectral characteristics of soil dissolved organic matter: Long-term effects of exogenous organic matter on soil organic matter and spatial-temporal changes
文章编号: N19092105
期刊: Chemosphere
作者: N.Y. Musadji, L. Lemée, L. Caner, G. Porel, P. Poinot, C. Geffroy-Rodier
更新时间: 2019-09-21
摘要: The aim of this study was to evaluate the long-term effect of urban and green waste compost exogenous organic matter (EOM) on soil dissolved organic matter (DOM). A luvic cambisol was amended 7 years before the study. DOM was investigated along a soil profile down to 1 m depth regarding seasonal variations (autumn and spring). DOM sampled by suction cups was characterized using dissolved organic carbon (DOC) content and excitation emission matrix (EEM) fluorescence. The variability of DOM concentrations was pronounced but no major change in composition was determined. The results obtained, reinforced by statistical analysis, showed that the DOM quality was mainly influenced by soil management (organic matter amendment) whereas the quantity mainly depended on the season (heavy precipitation event). DOM humic characteristics were strongly dependent on amendment and changed with depth but was not affected by the season. Long term effect of compost organic matter was highlighted after a 7-years amendment.
25909. 题目: Competitive adsorption of tylosin, sulfamethoxazole and Cu(II) on nano-hydroxyapatitemodified biochar in water
文章编号: N19092104
期刊: Chemosphere
作者: Zhen Li, Zhaoyan Wang, Xiaona Wu, Miao Li, Xiang Liu
更新时间: 2019-09-21
摘要: Antibiotics and heavy metals are frequently detected simultaneously in water environment. In this study, the competitive adsorption behavior of tylosin (TYL) and sulfamethoxazole (SMX) on nano-hydroxyapatite modified biochar (nHAP@biochar) in accordance with Cu(II) in single, binary and ternary systems was investigated. The specific surface area of nHAP@biochar was 566.056 m2/g. The adsorption of TYL on nHAP@biochar reduced by 13.36%–41.04% or 9.92%–38.69% with Cu(II) and SMX in the solution, respectively. The suppression of SMX was stronger than Cu(II) on the adsorption of TYL when the SMX or Cu(II) was constant. The adsorption of SMX increased by 2.01–3.56 times in the present of Cu(II), while suppressed by TYL up to 42.30%. Due to the bridging of TYL or SMX between the nHAP@biochar and Cu(II) and destroying of bound water surrounded, the adsorption of Cu(II) increased to a greater extent. Electrostatic interaction and H-bond were the two main interactions between TYL, SMX and Cu(II) and nHAP@biochar. π-π interactions was also interaction between the SMX and nHAP@biochar.
25910. 题目: Effects of pH and gallic acid on the adsorption of two ionizable organic contaminants to rice straw-derived biochar-amended soils
文章编号: N19092103
期刊: Ecotoxicology and Environmental Safety
作者: Ying He, Ting Yao, Shuo Tan, Bingqi Yu, Kailin Liu, Lifeng Hu, Kun Luo, Min Liu, Xiangying Liu, Lianyang Bai
更新时间: 2019-09-21
摘要: The existing form of ionizable organic contaminants (IOCs) could affect their adsorption characteristics to soil and biochar. In this study, 2 IOCs, namely, sulfadiazine and imazalil, were selected to study their adsorption by rice straw-derived biochar-amended soils, as well as the effect of pH and gallic acid on their adsorption. The results showed that the soil adsorption isotherms of the two ionizable organic contaminants could be fitted well by a linear equation and the Freundlich equation, and r2 was more than 0.80. The adsorption coefficient (Kd) in the three kinds of soil ranged from 0.262 to 4.07 L kg−1 for sulfadiazine and from 3.11 to 96.5 L kg−1 for imazalil. After the addition of biochar, the adsorption of sulfadiazine and imazalil in the soil increased. The adsorption of sulfadiazine by biochar gradually decreased with the increase in pH; the adsorption of imazalil increased when the pH increased from 2 to 5 and then gradually decreased with increasing pH. Gallic acid enhanced the adsorption of the two IOCs to pure soil and biochar-amended soil.
25911. 题目: Binding characteristics of cadmium and zinc onto soil organic matter in different water managements and rhizosphere environments
文章编号: N19092102
期刊: Ecotoxicology and Environmental Safety
作者: Jiajun Wen, Zhongwu Li, Ninglin Luo, Mei Huang, Xiang Ding, Xianrong Bu, Ming Chen
更新时间: 2019-09-21
摘要: Soil organic matter (SOM) could immobilize most of metals, but it could promote the migration of a small part of metals in special environments. Heavy rainfall and drought makes wetlands affected by the alternation of drought and flood, altering the mobility of metals. Few studies have been conducted on the changes of binding characteristics of metals onto SOM which derived from different water conditions and rhizospheric environments. The objective of this paper was to explore the sequential differences of spectral variations of fluorescent groups and UV–Vis groups of metals onto SOM which derived from different water managements and rhizospheric environments. The method adopted was mainly two-dimensional correlation analysis (2DCOS). The results showed that flooding samples contained more aromatic substances compared to draining samples, which could promote metal binding. The binding characteristics were shown in the following: (1) Cd2+ and Zn2+ could react with aromatic substances, react with functional groups in SOM, and promote the formation of new groups such as carboxyl; (2) both Zn2+ and Cd2+ could bind with functional groups on proteins but relatively reductive environment can weaken the binding ability of Cd2+; (3) the protein-like or fulvic-like groups gave the fastest responses and then came the amide and carboxyl groups in nearly all flooding samples; (4) in flooding samples, Cd2+ was most easily to bind with fulvic-like groups, while Zn2+ was most easily to bind with protein-like groups. This work is conducive to the long-term management of heavy metal pollutants in wetlands.
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25912. 题目: Are the n-alkane carbon isotopic profiles of South Australian coastal asphaltites indicative of their extent of weathering?
文章编号: N19092101
期刊: Organic Geochemistry
作者: David M. McKirdy, Se Gong, Alexander J. Corrick, P. Anthony Hall, Christine Trefry, Andrew S. Ross
更新时间: 2019-09-21
摘要: Asphaltic bitumen (asphaltite) found on the ocean beaches of South Australia is considered to be a product of an adjacent, but as yet unlocated, submarine oil seep. Four large asphaltites recently stranded on three different beaches were sub-sampled (n = 5–6). Samples were analysed to determine if their n-alkane δ13C profiles displayed systematic variation along a transect from the centre to the outer rim of the specimen. Previously reported 13C-enrichment in n-alkanes isolated from the outer portions of similar archival asphaltites was attributed to weathering. With one notable exception, these new specimens exhibited no unidirectional enrichment from interior (fresh) to exterior (weathered), although in every instance n-alkanes in the intermediate and outermost sub-samples were for the most part isotopically heavier than the same homologues in the central interior of the specimen. To be a viable measure of the extent of weathering in a population of coastal asphaltites, and hence also their relative exposure time in the ocean, this analytical protocol requires the specimens to have remained physically intact during their transit from the parent seep to shore. Whether this requirement has been met is impossible to determine, thereby limiting the effectiveness of the method to those specimens in which there is a consistent pattern of internal variation in their n-alkane carbon isotope profiles.
25913. 题目: Exploring the upper particle size limit for field flow fractionation online with ICP-MS to address the challenges of water samples from the Taihu Lake
文章编号: N19092011
期刊: Analytica Chimica Acta
作者: Jingjing Yang, Ping Tan, Tianyin Huang, Volker Nischwitz
更新时间: 2019-09-20
摘要: Regular algal blooms are occurring in Taihu lake, which may be triggered by resuspension of sediments containing relevant amounts of phosphorus. Therefore, our study aims at quantification of phosphorus concentrations bound to suspended particulate matter in Taihu water samples to investigate this hypothesis. A field flow fractionation (FFF) method online with ICP-MS detection was developed to achieve an overview on particulate fractions of phosphorus and related elements including Fe, Al and C from the low nanometer to the low micrometer size range. Mass balance of dissolved and particulate elemental contents was established for quality control purpose and indicated low recovery of Fe, Al and P. Complementary determination of volume based particle size distribution by dynamic imaging analysis showed a majority of particle volume and thus mass in particles with size >5 μm. In order to address this challenge, the upper particle size limit of FFF online with ICP-MS was for the first time investigated in detail using well characterised monodisperse latex particles as model for organic matter in the low micrometer size range including microalgae. The effect of pre-filtration of the sample as well as the contribution of sample introduction via three different interfaces including micromist nebuliser/spray chamber, direct injection nebulisation and APEX with heated spray chamber and solvent removal by condensation on the particulate carbon recovery was studied by ICP-MS detection. The same instrumental setup was also applied for the characterisation of particulate elemental contents in the Taihu water samples as far as possible. Significant improvement of the detected particulate fraction in Taihu water samples was achieved by increasing the membrane pore size for pre-filtration and by using the APEX for introduction of the eluate from FFF into ICP-MS.
25914. 题目: Linkages between flow regime, biota, and ecosystem processes: Implications for river restoration
文章编号: N19092010
期刊: Science
作者: Margaret Palmer, Albert Ruhi
更新时间: 2019-09-20
摘要: River ecosystems are highly biodiverse, influence global biogeochemical cycles, and provide valued services. However, humans are increasingly degrading fluvial ecosystems by altering their streamflows. Effective river restoration requires advancing our mechanistic understanding of how flow regimes affect biota and ecosystem processes. Here, we review emerging advances in hydroecology relevant to this goal. Spatiotemporal variation in flow exerts direct and indirect control on the composition, structure, and dynamics of communities at local to regional scales. Streamflows also influence ecosystem processes, such as nutrient uptake and transformation, organic matter processing, and ecosystem metabolism. We are deepening our understanding of how biological processes, not just static patterns, affect and are affected by stream ecosystem processes. However, research on this nexus of flow-biota-ecosystem processes is at an early stage. We illustrate this frontier with evidence from highly altered regulated rivers and urban streams. We also identify research challenges that should be prioritized to advance process-based river restoration.
25915. 题目: Aided phytostabilisation over two years using iron sulphate and organic amendments: Effects on soil quality and rye production
文章编号: N19092009
期刊: Chemosphere
作者: Teresa Fresno, Jesús M. Peñalosa, Maren Flagmeier, Eduardo Moreno-Jiménez
更新时间: 2019-09-20
摘要: An outdoor macrocosm experiment using Fe-based and organic amendments over 2 years was set up to evaluate the effectiveness of aided-phytostabilisation. For that, a soil contaminated with As- and Cu-rich waste material (∼13000 mg As kg−1 and ∼500 mg Cu kg−1) was treated with combinations of iron sulphate (Fe) with lime, paper mill sludge (PS), holm-oak biochar (BC), olive mill waste compost (OMWC) or green waste compost (GWC). Rye (Secale cereale L.) was grown in the treated and non-treated soils 16 months after addition of the amendments. Arsenic and Cu dynamics in soil were assessed throughout the experiment and soil quality parameters (soil nutrients, organic matter and soil biology) were measured almost two years after addition of the amendments. All treatments resulted in a reduction of soluble and extractable Cu during the experiment and, despite the increase in soil pH (from 5 to 68) and DOC (from 10 up to 50 mg DOC L−1) provoked by the amendments, As was not significantly mobilised in the treated soils. Treatments combining Fe sulphate with the organic materials, especially biochar and both composts, resulted in an increase in soil available nutrients and enhanced rye growth. In this semi-field scale experiment, the combination of Fe sulphate with holm-oak biochar showed the most promising results in terms of soil fertility (nutrient availability), plant As and Cu uptake and soil C sequestration. Further research should focus on monitoring long-term effects of the soil amendments on crops, following repeated applications.
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25916. 题目: Biochar synthesis from sweet lime peel for hexavalent chromium remediation from aqueous solution
文章编号: N19092008
期刊: Journal of Environmental Management
作者: Amita Shakya, Avelino Núñez-Delgado, Tripti Agarwal
更新时间: 2019-09-20
摘要: Sweet lime (Citrus limetta) peel biochar was obtained by slow pyrolysis of raw biomass at 450 °C with 5 °C/min heating rate. Proximate and ultimate analysis, physico-chemical characterization of the biochar was done. Batch adsorption experiments for Cr(VI) removal were performed with varying pH, biochar dose, contact time and initial Cr(VI) concentrations. It took 8–24 h to reach the equilibrium at 30 °C for varying Cr(VI) concentrations. The biochar was found to possess higher adsorption capacity (100 mg/g) than the adsorbents reported in several previous studies. Langmuir adsorption isotherm and pseudo second order model best explained the experimental data, suggesting monolayer adsorption as the dominant mechanism. Chemical interaction, ion exchange of solute and sorbate ions and physical adsorption also contributed into Cr(VI) adsorption process. Further, Cr(VI) adsorption was found to be a multistep process. The findings suggested that sweet lime peel biochar can be utilized as a low cost and efficient alternative for Cr(VI) removal, which could be useful for aqueous solutions, as well as to promote overall protection against soil and water degradation and pollution.
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25917. 题目: Investigation of polycyclic aromatic hydrocarbons in soils from Caserta provincial territory, southern Italy: Spatial distribution, source apportionment, and risk assessment
文章编号: N19092007
期刊: Journal of Hazardous Materials
作者: Pengzhi Qi, Chengkai Qu, Stefano Albanese, Annamaria Lima, Domenico Cicchella, David Hope, Pellegrino Cerino, Antonio Pizzolante, Huang Zheng, Jiji Li, Benedetto De Vivo
更新时间: 2019-09-20
摘要: The concentrations of polycyclic aromatic hydrocarbons (PAHs) in soils from Caserta provincial territory, southern Italy, were systematically investigated along with their correlations with soil properties and health risk. The concentrations of ∑16PAHs ranged from 10.0 to 4191 ng/g, with a median (1 st quartile, Q1; 3rd quartile, Q3) of 28.5 (17.5–65.0) ng/g; Four-ring PAHs were the most abundant and contributed an average of ∼50.2% of the ∑16PAHs. Significant differences in the spatial distributions of PAHs in soil were observed, with higher levels of PAH contamination found in Caserta city and the surrounding areas. According to the positive matrix factorization (PMF) model, three sources were identified: chemical production and metal smelting, vehicle emissions, and coal/biomass combustion. Soil total organic carbon was significantly correlated with the concentration of total PAHs and the concentrations of PAHs with three-, four-, and five-rings. In contrast, only the concentration of ∑4DBPs (dibenzo(a,e)pyrene, dibenzo(a,h)pyrene, dibenzo(a,i)pyrene, dibenzo(a,l)pyrene) was well correlated with population density. The soil mass inventory of ∑16PAHs was estimated to be 6.87 metric tons (geometric mean). The ecological risks posed by PAHs in the study are negligible; however, health risks of exposure to soil-borne PAHs were identified based on a probabilistic risk model.
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25918. 题目: Unravelling the influences of sewer-dosed iron salts on activated sludge properties with implications on settleability, dewaterability and sludge rheology
文章编号: N19092006
期刊: Water Research
作者: Sohan Shrestha, Keshab Sharma, Zhongwei Chen, Zhiguo Yuan
更新时间: 2019-09-20
摘要: Although the beneficial impacts of iron dosing to sewer on activated sludge unit's performance, especially in relation to phosphate removal, have been reported, the extent of impacts on different sludge properties affecting the operation and performance of the activated sludge unit are not fully understood. In this study, we investigated the influences of iron salt dosing to sewer on both settleability and dewaterability of downstream activated sludge unit. We also examined, based on the comparative assessment of different key activated sludge properties, possible underlying factors responsible for the changes in sludge settleability and dewaterability. For this, iron chloride was dosed to a sewer reactor of integrated laboratory sewer-bioreactor system. The activated sludge samples were obtained from two separate reactors, an experimental sequencing batch reactor (SBR-E) downstream of sewer reactor receiving iron dosing and a control SBR (SBR-C) downstream of a sewer reactor without any iron dosing. Iron-conditioned sludge showed improved settleability and dewaterability over the unconditioned activated sludge. Mean differences in settleability and dewaterability between two sludges were 22.5 ± 7.8 mL/g (p < 0.05) and 7.8 ± 1.2% (p < 0.05), respectively. Iron-conditioned sludge showed lower contents of soluble extracellular polymeric substances (EPS) fractions, protein and polysaccharide contents, and monovalent-to-divalent (M+/D++) cations ratio, but higher humification index as compared to the unconditioned sludge. Iron-conditioned sludge exhibited marginal increment in mean particle size (Dv50) and settleable particle size classes (100–400 μm) but reduction in supracolloidal particle size classes (1–100 μm). In terms of sludge rheology, iron-conditioned sludge exhibited relatively lower relative sludge network strength, viscosity, yield stress, elastic/viscous/complex moduli (G′/G′′/G*), and damping factor tan(δ) but increased shear compliance (J) and shear strain (%) with time.The iron-conditioned sludge therefore exhibited relatively weaker deformation resistance and sludge elasticity. Based on the foregoing results, we posit the combined synergistic effect of favourable changes to the key sludge properties, might be responsible for the observed improvement in settleability and dewaterability of iron-conditioned sludge.
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25919. 题目: Optical properties, source apportionment and redox activity of humic-like substances (HULIS) in airborne fine particulates in Hong Kong
文章编号: N19092005
期刊: Environmental Pollution
作者: Yiqiu Ma, Yubo Cheng, Xinghua Qiu, Gang Cao, Binyu Kuang, Jian Zhen Yu, Di Hu
更新时间: 2019-09-20
摘要: Humic-like substances (HULIS) account for a considerable fraction of water-soluble organic matter (WSOM) in ambient fine particulates (PM2.5) over the world. However, systemic studies regarding the chemical characteristics, sources and redox activity of HULIS are still limited. In this study, the mass concentration, optical properties, and reactive oxygen species (ROS)-generation potential of HULIS were investigated in PM2.5 samples collected in Hong Kong during 2011–2012, and they all showed higher levels on days under regional pollution than on days under long range transport (LRT) pollution and local emissions. Positive matrix factorization (PMF) analysis was conducted regarding the mass concentration and dithiothreitol (DTT) activity of HULIS. Four primary sources (i.e. marine vessels, industrial exhaust, biomass burning, and vehicle emissions), and two secondary sources (i.e. secondary organic aerosol formation and secondary sulfate) were identified. Most sources showed higher contributions to both the mass concentration and DTT activity of HULIS on regional days than on LRT and local days, except that marine vessels had a higher contribution on local days than the other two synoptic conditions. Secondary processes were the major contributor to HULIS (54.9%) throughout the year, followed by biomass burning (27.4%) and industrial exhaust (14.7%). As for the DTT activity of HULIS, biomass burning (62.9%) and secondary processes (25.4%) were found to be the top two contributors. Intrinsic ROS-generation potential of HULIS was also investigated by normalizing the DTT activity by HULIS mass in each source. HULIS from biomass burning were the most DTT-active, followed by marine vessels; while HULIS formed through secondary processes were the least DTT-active. For the optical properties of HULIS, multiple linear regression model was adopted to evaluate the contributions of various sources to the light absorbing ability of HULIS. Biomass burning was found to be the only source significantly associated with the light absorbing property of HULIS.
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25920. 题目: Nutrients and heavy metals mediate the distribution of microbial community in the marine sediments of the Bohai Sea, China
文章编号: N19092004
期刊: Environmental Pollution
作者: Meiqing Lu, Xin Luo, Jiu Jimmy Jiao, Hailong Li, Xuejing Wang, Jingyan Gao, Xiaolang Zhang, Kai Xiao
更新时间: 2019-09-20
摘要: The Bohai Sea, one of the largest marginal seas in China, is extensively influenced by human and industrial activities. The pollutant loads from anthropogenic activities have induced severe ecological problems. The study investigates the physicochemical characteristics of seawater and sediments in Bohai Bay and Laizhou Bay of the Bohai Sea. The diversity and composition of microbial community in sediments are analyzed by 16S rRNA gene amplicon sequencing. The sequencing results present 16 phyla and 31 classes from the samples. Proteobacteria constituted a dominant phylum, of which the classes of Gamma-, Delta-, and Epsilon-are predominant sub-divisions. Nitrogen, phosphorus, and sulfur cycling related microbes present high abundance in both bays. The metabolism of organic matters is the main factor that influences the distribution of microbial communities in Bohai Bay, while the inflow of Yellow River is the dominant factor that influences the distribution of microbial communities in Laizhou Bay. Sulfur oxidizing process is expected to be positively influenced by heavy metals, while ammonia (NH4+) oxidizing process is prone to be negatively affected by heavy metals in both bays. Microbial communities in the offshore sediments of Laizhou Bay and the majority microbial communities in Bohai Bay sediments are subject to similar predominant controlling factors. This phenomenon is likely ascribed to ocean circulation. The results of this study can provide constructive guidelines on ecosystem management of marginal seas in Bohai and elsewhere.
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