论文检索

总访问量：5737918次

总访客量：393318人

所有论文

28601. 题目: The adsorption, regeneration and engineering applications of biochar for removal organic pollutants: A review
文章编号: N19020606
期刊: Chemosphere
作者: Yingjie Dai, Naixin Zhang, Chuanming Xing, Qingxia Cui, Qiya Sun
更新时间: 2019-02-06
摘要: In recent years, with the continuous development of industry and agriculture, the content of organic pollutants in the environment has been increasing, which has caused serious pollution to the environment. Adsorption has proven to be an effective and economically viable method of removing organic contaminants. Since biochar has many advantages such as various types of raw materials, low cost, and recyclability, it can achieve the effect of turning waste into treasure when used for environmental treatment. This paper summarizes the source and production of biochar, points out its research status in the removal of organic pollutants, expounds its adsorption mechanism on organic pollutants, introduces the relevant adsorption parameters, summarizes its regeneration methods, studies its application of engineering, and finally analyses of benefits and describes the development prospects.

28602. 题目: Can polyethylene passive samplers predict polychlorinated biphenyls (PCBs) uptake by earthworms and turnips in a biochar amended soil?
文章编号: N19020605
期刊: Science of The Total Environment
作者: Ludovica Silvani, Sigurbjörg Hjartardottir, Lucie Bielská, Lucia Škulcová, Gerard Cornelissen, Luca Nizzetto, Sarah E. Hale
更新时间: 2019-02-06
摘要: A pot experiment was carried out in which aged polychlorinated biphenyls (PCBs) contaminated soil was amended with biochar, and three phases: earthworms, turnips and polyethylene (PE) passive samplers, were added simultaneously in order to investigate changes in bioavailability of PCB following biochar amendment. Two biochars were used: one made from rice husk in Indonesia using local techniques and the other made from mixed wood shavings using more advanced technology. The biochars were amended at 1 and 4% doses. The overall accumulation of PCBs to the phases followed the order: earthworm lipid > PE > turnip. The rice husk biochar reduced PCB accumulation to a greater degree than the mixed wood biochar for all phases, however there was no effect of dose for either biochar. Earthworm uptake was reduced between 52% and 91% for rice husk biochar and by 19% to 63% for mix wood biochar. Turnip uptake was not significantly reduced by biochar amendment. Phase to soil accumulation factors (PSAF) were around 0.5 for turnips, approximately 5 for PE and exceeded 100 for earthworms. This study demonstrates that both biochars can be a sustainable alternative for in situ soil remediation and that PE can be used as tool to simulate the uptake in earthworms and thus remediation effectiveness.
图文摘要:

28603. 题目: Temperature dependence of characteristics of organic precursors, bromide, and disinfection byproduct formation
文章编号: N19020604
期刊: Science of The Total Environment
作者: Chih-Hsuan Huang, Chia-Yang Chen, Gen-Shuh Wang
更新时间: 2019-02-06
摘要: This study characterized the potential effects of elevated water temperature on source water quality and corresponding disinfection byproduct (DBP) formation. Results of laboratory simulations showed that although DBP formation increased with temperature, both the concentrations of dissolved organic carbon (DOC) and DBP formation decreased when water was incubated at higher temperatures (35 °C) prior to chlorination, probably due to increased microbial activity leading to greater degradation of organic precursors that affects DBP formation. However, the effect of incubation temperature prior to chlorination on final DBP formation varies with the characteristics of source water. When bromide was present, the ratio of Br-DBPs increased. The concentrations of total trihalomethanes (THMs) and haloacetonitriles (HANs) also increased when levels of bromide increased. This trend was not substantial for total haloacetic acids (HAAs). The hydrophobic organic precursors of THMs and HANs can be effectively removed by coagulation and filtration processes, and the effects of higher incubation temperature may thus be compromised. However, no apparent changes were observed for HAAs. The effects of bromide may also be more apparent in HAA and HAN formation after coagulation and filtration treatments.
图文摘要:

28604. 题目: Response of chromophoric dissolved organic matter dynamics to tidal oscillations and anthropogenic disturbances in a large subtropical estuary
文章编号: N19020603
期刊: Science of The Total Environment
作者: Yongqiang Zhou, Yuan Li, Xiaolong Yao, Wenhao Ding, Yibo Zhang, Erik Jeppesen, Yunlin Zhang, David C. Podgorski, Chunmei Chen, Yi Ding, Huawu Wu, Robert G.M. Spencer
更新时间: 2019-02-06
摘要: Estuaries support the livelihood of ~75% of the world's population and maintain high primary production in coastal waters, which are often subjected to strong tides and anthropogenic disturbances. There is a paucity of information on how the optical composition and bioavailability of chromophoric dissolved organic matter (CDOM) are influenced by tidal oscillations in estuaries with highly urbanized surrounding areas. We examined the semi-diurnal Qiantang Bore, one of the Earth's three most predominant tide bores, and found that dissolved organic carbon (DOC), CDOM absorption a(254) and terrestrial humic-like C1, tryptophan-like C2 and C5, fulvic-like C3, and microbial humic-like C4 decreased markedly with increasing salinity. This suggests that physical mixing of riverine freshwater and saltwater can shape the optical composition of CDOM in the estuary. This was supported by the semi-diurnally and hourly observations at Zhijiang (salinity ~0.1‰, upstream of the estuary) that DOC, bioavailable DOC (BDOC), C1–C2, and C4–C5 increased markedly with decreasing tidal level, while DOC and C1–C5 increased notably with increasing salinity. We further found δ¹⁸O was enriched with increasing tidal level, while tryptophan-like C2 and C5, and fulvic-like C3 decreased significantly with increasing tidal level at Zhapu (salinity ~7‰, downstream of the estuary). Furthermore, DOC, BDOC, C1, and C4 decreased, while δ¹⁸O and C3 increased markedly with increasing salinity. Further evidences come from the notably lower mean first principal component (PC1) scores at Zhijiang and Zhapu, both positively associated with anthropogenic tryptophan-like inputs, were observed during ebb than during flood tides, and PC1 at Zhijiang increased notably with increasing salinity. We conclude that anthropogenic inputs contributed primarily to the CDOM pool in the estuary and are mediated by the physical mixing of riverine freshwater and seawater, and ebb tides are often associated with enhanced anthropogenic CDOM with relatively high bioavailability.
图文摘要:

28605. 题目: Phosphorus speciation and bioavailability of sewage sludge derived biochar amended with CaO
文章编号: N19020602
期刊: Waste Management
作者: Qiang Liu, Zheng Fang, Yuan Liu, Yangyang Liu, Yunfeng Xu, Xiuxiu Ruan, Xiaolei Zhang, Weimin Cao
更新时间: 2019-02-06
摘要: In this study, biochar samples were prepared from the co-pyrolysis of sewage sludge (SS) and CaO to explore the transformation of P speciation in sample. The potential of these biochar as a fertilizer to promote the growth of the plant was also evaluated. The result indicated that CaO addition can greatly facilitate the conversion of non-apatite inorganic phosphorus (NAIP) to apatite inorganic phosphorus (AP, mainly Ca₃(PO₄)₂ and Ca₃Mg₃(PO₄)₄). The addition of 10% CaO in feedstock is sufficient to convert SS inherent P into more bioavailable AP. Under such a dosage, AP content in biochar increased by 21.2–33.6% in contrast to CaO free sample at pyrolysis temperature of 500–800 °C, and water-soluble phosphorus (WSP) content decreased to less than 1% of TP. The addition of CaO can also apparently reduce Zn, Mn leaching from biochar. Additionally, hydroponics assay showed that CaO amended SS biochar can promote the growth of rice seedling. The results of this study indicate that preparing CaO amended SS biochar is a technically feasible strategy to utilize P resource in SS.

28606. 题目: Fate and removal of trace pollutants from an anion exchange spent brine during the recovery process of natural organic matter and salts
文章编号: N19020601
期刊: Water Research
作者: Elisabeth Vaudevire, Farzaneh Radmanesh, Annemieke Kolkman, Dennis Vughs, Emile Cornelissen, Jan Post, Walter van der Meer
更新时间: 2019-02-06
摘要: The results of this sampling campaign on pilot scale processes aim to evaluate the occurrence and behavior of trace organic micro-pollutants and metal elements during anion exchange treatment of surface water and the subsequent treatment of generated spent brine with two types of electrodialysis membrane pairs. This knowledge is relevant to assess the quality and reusability of secondary products created during brine treatment; specifically the excess of sodium chloride to be recycled onsite and the natural organic matter, mostly consisting of humic substances, which find multiple applications in the agricultural industry. This study highlights that (1) the attachment mechanism of organic micro-pollutants to anion exchange resin occurs through electrostatic interaction and the subsequent transfer through ion exchange membranes is restricted by size exclusion; and (2) the complexation of trace metals compounds with the natural organic matter partly explains their removal by anion exchange. Complexes remain stable during treatment of the brine with electrodialysis.
图文摘要:

28607. 题目: Significance of acetate as a microbial carbon and energy source in the water column of Gulf of Mexico: implications for marine carbon cycling
文章编号: N19020511
期刊: Global Biogeochemical Cycles
作者: Guang-Chao Zhuang, Tito D. Peña-Montenegro, Andrew Montgomery, Joseph P. Montoya, Samantha B. Joye
更新时间: 2019-02-05
摘要: Acetate is a key intermediate of organic matter mineralization but its metabolism remains largely unconstrained in the pelagic ocean. We conducted an integrated biogeochemical study to investigate microbial acetate cycling in the northern Gulf of Mexico with the goal of elucidating the importance of acetate as a carbon and energy source. Acetate was used primarily as an energy source, as evidenced by observed oxidation rates (rate constant k: 0.06−0.22 d−1) that varied between 42%−96% of total biological acetate uptake (i.e., assimilation + oxidation; k: 0.06−0.34 d−1). The assimilation of acetate into biomass (k: 0.01−0.20 d−1) illustrated the potential significance of acetate as a biomass carbon source, particularly in nutrient‐rich coastal waters. No relationship between acetate assimilation or oxidation and environmental factors, such as chlorophyll and nutrients, was observed. However, elevated acetate uptake in reduced oxygen waters characterized by particulate organic carbon (POC) mineralization suggests that acetate metabolism may be a good proxy for POC breakdown. Molecular genetic analysis revealed that SAR11 Alphaproteobacteria were the most abundant heterotrophic bacteria and suggests they may utilize acetate. At some sites, acetate carbon may have accounted for up to 50.4% of the bacterial carbon production. These results suggest acetate may serve as an important carbon and energy source for heterotrophic bacteria thus revealing a potentially significant role of acetate for dissolved organic carbon cycling in the ocean.

28608. 题目: Urbanization-induced glomalin changes and their associations with land-use configuration, forest characteristics, and soil properties in Changchun, Northeast China
文章编号: N19020510
期刊: Journal of Soils and Sediments
作者: Qiong Wang, Wenjie Wang, Xingyuan He, Wei Zhou, Chang Zhai, Peijiang Wang, Ze Tang, Chenhui Wei, Bo Zhang, Lu Xiao, Hongyuan Wang
更新时间: 2019-02-05
摘要: Purpose: Glomalin-related soil protein (GRSP), produced by arbuscular mycorrhizal fungi, plays crucial roles in the global carbon cycle and improves soil quality. However, information on GRSP and its contribution to the soil organic carbon (SOC) pool in the process of urbanization is limited. Materials and methods: In this study, easily extracted GRSP (EE-GRSP) and total GRSP (T-GRSP) were analyzed in an urban-rural gradient, and a detailed survey of greenspace characteristics (soil properties: pH, electric conductivity [EC], bulk density, temperature, and SOC; forest characteristics: tree density, tree size, tree species, and arbor and shrub richness; land use: road, building, greenspace, and wetland and water) in 306 plots was undertaken. Results and discussion: EE-GRSP/SOC and T-GRSP/SOC decreased significantly by 10% in urban plots when compared with the rural plots. From the rural to urban plots, decrease in pH and increases in SOC, EC, tree height, and under branch height (p < 0.01) were found in this study. These changes in greenspace characteristics were responsible for variation in GRSP, while their relative explanatory power differed (soil properties: 43.8%, forest characteristics: 25.7%, and land use: 18.6%). Forward selection analysis identified that EC, greenspace proportion, pH, shrub richness, diameter at breast height, wetland and water proportion, bulk density, and under branch height had significant explanatory power for the variation in GRSP (all: p < 0.05). Conclusions: Our findings indicate that urbanization greatly affects the contribution of GRSP to the SOC pool. The changes in greenspace characteristics played key roles in regulating the pattern of GRSP, especially soil properties. The results of this study may be used as a reference for the exploration of GRSP in urban environments and implementation of soil improvement practices by regulating GRSP.

28609. 题目: Distribution and preservation of root and shoot derived carbon components in soils across the Chinese‐Mongolian grasslands
文章编号: N19020509
期刊: Journal of Geophysical Research: Biogeosciences
作者: Tian Ma, Guohua Dai, Shanshan Zhu, Dima Chen, Litong Chen, Xiaotao Lü, Xiaobo Wang, Juntao Zhu, Yangjian Zhang, Wenhong Ma, Jin‐Sheng He, Yongfei Bai, Xingguo Han, Xiaojuan Feng
更新时间: 2019-02-05
摘要: The relative contribution of roots versus shoots to soil organic carbon (SOC) is a long‐debated topic related to soil carbon formation and dynamics. However, the variation of root and shoot derived carbon in natural soils remains poorly constrained due to limited tools to separate them. Here we overcome the difficulty by analyzing biomarkers for root (suberin) and shoot (cutin) in grassland soils spanning >7,000 km on the Qinghai‐Tibetan and Mongolian Plateaus. Coupled with a comprehensive list of climatic, edaphic and vegetation variables, we assess their inputs, distribution and preservation patterns. We find that while suberin was a root‐specific tracer, cutin biomarkers that occurred only in trace amount in roots also had a minor but non‐negligible contribution from belowground sources due to the massive root mass in the alpine grasslands. Both components had higher SOC normalized concentrations in the alpine than temperate grasslands, along with a higher preservation percentage against net primary productivity and a lower degradation parameter, suggesting a better preservation of these plant derived lipid components in the alpine region. Moreover, while cutin and suberin abundances were affected by plant inputs and other SOC constituents, the root mass normalized incorporation efficiency of suberin was only positively correlated to SOC in both regions with a steeper slope in the alpine grasslands and also negatively correlated to root mass in the alpine soils. These results imply that root carbon incorporation is sensitive to environmental variations in the cold region, suggesting potentially more dynamic alterations to root carbon sequestration with environmental changes.

28610. 题目: Pyrolyzed municipal sewage sludge ensured safe grain production while reduced C emissions in a paddy soil under rice and wheat rotation
文章编号: N19020508
期刊: Environmental Science and Pollution Research
作者: Qianqian Shao, Yanyan Ju, Wenjie Guo, Xin Xia, Rongjun Bian, Lianqing Li, Wenjian Li, Xiaoyu Liu, Jufeng Zheng, Genxing Pan
更新时间: 2019-02-05
摘要: Safe recycling of the growing amounts of municipal sewage sludge containing toxic metals had been critically challenged with the fast urbanization. In this study, we investigated soil amendment of municipal wastewater treatment (MSS) converted biochar for its recycling in agricultural soils. In a field experiment, unpyrolyzed (USS) and pyrolyzed municipal sewage sludge (PSS) was amended at 20 t ha⁻¹ on dry base to a rice paddy before rice plantation, with a control without amendment. Grain yield and emission of non-CO₂ potent greenhouse gases were examined as well as topsoil metal mobility and plant uptake determined throughout a rice-wheat rotation year. Compared to USS treatment, addition of PSS caused a significantly increased grain yield of rice by 35% but no change in grain yield of wheat following the rice season. No distinct difference was observed in grain concentration of major nutrients of N, P, and K between USS and PSS treatments. Compared to USS treatment, PSS treatment reduced CH₄ emissions by 91.6% from soil and by 78.5% from ecosystem during rice-growing season. Whereas, PSS treatment led to a reduction of ecosystem N₂O emissions by 70.8% relative to USS treatment during wheat-growing season. While both USS and PSS treatments slightly but insignificantly increased soil total content of heavy metals, PSS treatment reduced CaCl₂-extractable Cd pool by 33~40% over USS treatment. Grain contents of Cd and Pb and Cd/Zn were markedly reduced under PSS over USS, without exceeding the Chinese state guideline limit. Carbon emission intensity was considerably (by over 20%) reduced for soil and ecosystem but unchanged for wheat soil, under PSS over USS. Thus, soil amendment of pyrolyzed sewage sludge could be a measure for climate smart soil and for safe grain production in rice agriculture. It deserves further study if repeated amendment could exert sustainable impacts on soil health and food security in the paddy.

28611. 题目: Preliminary studies about the role of physicochemical parameters on the organotin compound dynamic in a South American estuary (Bahía Blanca, Argentina)
文章编号: N19020507
期刊: Environmental Monitoring and Assessment
作者: Pamela Y. Quintas, Eleonora M. Fernández, Carla V. Spetter, Andrés H. Arias, Mariano Garrido, Jorge E. Marcovecchio
更新时间: 2019-02-05
摘要: This work provides a preliminary study of the destination, mobility, and availability of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) in contaminated sediments and water column within Puerto Rosales Port, located in the middle zone of the Bahía Blanca Estuary (Argentina). Therefore, this study presents the first comprehensive results of the role of several physicochemical parameters (temperature, pH, Eh, salinity, turbidity, organic matter, chlorophyll, and macronutrients) in behavior of organotin compounds (OTCs) in a marine-coastal ecosystem. The samples were collected seasonally in May, August, and November during 2014. Levels of OTCs were determined in sediments and water column samples by means of gas chromatography–mass spectrometry analysis. Degradation index analyses suggested not recent inputs of TBT at the area of study. However, results submitted a continuous input of TBT into the column water; further, its distribution and degradation pattern were shown to be influenced by salinity, turbidity, particulate organic matter, chlorophyll, and nitrates. These last two parameters, chlorophyll and nitrates, also were very important for sediment samples. Chlorophyll together with high temperatures recorded in the surface sediments triggers biodegradation process of TBT and DBT resulting in high MBT levels while nitrates seemed to promote debutylation process. Furthermore, pH appeared to influence drastically the adsorption/desorption activity of TBT and DBT in sediment. Finally, the Eh obtained suggested a degradation of TBT thanks to the presence of Fe (III) in this compartment. In addition, in fact, the results outlined a possible MBT additional input that contributes to the pollution observed in the study area.

28612. 题目: A laboratory study of the presence and transformation of dissolved Mn(III) across the sediment–water interface of an anoxic freshwater body
文章编号: N19020506
期刊: Environmental Earth Sciences
作者: Lei Chen, Junjie Zhang, Xilai Zheng
更新时间: 2019-02-05
摘要: Dissolved Mn(III) has been verified to be an important component of Mn cycling in a natural water system. However, the existence and stability of dissolved Mn(III) and its interactions with environmental factors, such as pH, dissolved oxygen (DO), oxidation–reduction potential (ORP) and dissolved organic carbon (DOC) in freshwater body are still not clear. In this paper, the dynamic characteristics of dissolved Mn (Mn_diss), Mn(III), pH, DO, ORP and DOC across the sediment–water interface of anoxic freshwater environment (Wangjuan Reservoir of Qingdao City) were studied through laboratory experiments. The correlations between Mn_diss and these key environmental factors, as well as between Mn(III) and environmental factors were quantitatively analyzed. The results indicated that concentration gradient was the main driving force of Mn_diss and Mn(III) of each layer overlying water, and there were obvious differences between the concentrations of Mn_diss and Mn(III) of overlying and pore water. In sediment pore water, dissolved Mn(III) concentrations were as high as 9.35 mg/L and constituted up to 23% of the total dissolved Mn pool, indicating that dissolved Mn(III) could stably exist in anoxic freshwater body and mainly came from the reduction process of Mn oxides in sediment. According to data analysis results, both the concentrations of Mn_diss and Mn(III) of pore water had significant correlations with the values of pH, ORP, and DOC of sediment pore water. The correlation coefficients of Mn_diss with the three factors were − 0.861, − 0.882 and − 0.934, respectively, while, the correlation coefficients of Mn(III) with them were − 0.836, − 0.671 and − 0.851, respectively.

28613. 题目: Adsorption capacity of phenanthrene and pyrene to engineered carbon-based adsorbents produced from sewage sludge or sewage sludge-biomass mixture in various gaseous conditions
文章编号: N19020505
期刊: Bioresource Technology
作者: Paulina Godlewska, Anna Siatecka, Magdalena Kończak, Patryk Oleszczuk
更新时间: 2019-02-05
摘要: Adsorption of phenanthrene (PHE) and pyrene (PYR) by engineered carbon-based adsorbents produced from sewage sludge in an atmosphere of nitrogen (N₂) or carbon dioxide (CO₂) at temperatures of 500, 600, and 700°C was investigated. The addition of willow to the SSL decreased the biochar adsorption capacity. However, there was an increase in the adsorption capacity after changing N₂ to CO₂. The addition of willow to SSL and the type of carrier gas affected the mechanism of adsorption. The adsorption of PHE and PYR on the SSL-derived adsorbents produced in N₂ occurred through pore filling. The adsorption on the SSL-derived adsorbents with willow followed the mechanism of π-π electron-donor-acceptor (EDA) interactions and hydrophobic interactions. A similar mechanism was observed with regard to the biochars produced from SSL in atmosphere of CO₂. For the SSL-derived adsorbents with willow in CO₂, the adsorption mechanism was observed to vary between PHE and PYR.
图文摘要:

28614. 题目: Precipitation of molybdenum from euxinic waters; role of organic matter
文章编号: N19020504
期刊: Chemical Geology
作者: George R. Helz, Trent P. Vorlicek
更新时间: 2019-02-05
摘要: Molybdenum preserved in organic-rich shales is a key archive employed in studying Earth's past oxygenation and Life's evolution. In these shales, positive correlations between Mo and C_org are common and have been attributed to Mo scavenging from seawater by organic shuttles. Here, we argue that known organic ligands are too weak or too scarce to capture more than minor amounts of Mo from seawater, especially in competition with sulfide. Alternatively, we demonstrate that Mo-C_org correlations can arise simply from microbially mediated oxidation of C_org by SO₄²⁻. This process produces sulfide and lowers pH, triggering precipitation of FeMoS₄, which soon transforms irreversibly to FeMoS₂(S₂). In euxinic basins, the extent of sulfate reduction progress increases with depth and can be modeled as an empirical function of biological productivity and water replacement time. The response of dissolved Mo to sulfate reduction progress occurs in three stages identified by a thermodynamic model. In Stage I, progress is too small to precipitate Mo from waters that are only mildly sulfidic. In Stage II, the flux of Mo to sediments is promoted by sulfate reduction progress, giving rise to positive Mo-C_org correlations in sediments due to fluctuations in biological productivity. In some cases, precipitation in this stage begins before MoS₄²⁻ becomes the predominant dissolved Mo species, in which case FeMoS₄ with negative δ⁹⁸Mo can be produced. In Stage III, the flux of Mo becomes independent of further sulfate reduction progress and Mo-C_org correlations degrade, as reported in extremely C_org-rich shales. Even though the model omits a number of potentially important processes, its predicted Mo profiles in waters of several modern euxinic basins are qualitatively reasonable and are consistent with observed reduction of Mo^VI in water to Mo^IV in sediments. According to the model, spikes in atmospheric P_CO2 will markedly increase Mo accumulation and lower δ⁹⁸Mo in euxinic basin sediments. This appears to have occurred repeatedly during the Phanerozoic and may be commencing now as a result of fossil fuel combustion. Minimal deposition of Mo in organic-rich shales during the Archean has been attributed to low MoO₄²⁻ in seawater but seems more likely to be due to low SO₄²⁻.
图文摘要:

28615. 题目: New U-Pb zircon age and carbon isotope records from the Lower Silurian Longmaxi Formation on the Yangtze Platform, South China: Implications for stratigraphic correlation and environmental change
文章编号: N19020503
期刊: Chemical Geology
作者: Yanfang Li, Tongwei Zhang, Deyong Shao, Baojian Shen
更新时间: 2019-02-05
摘要: The Ordovician–Silurian (O–S) transition was a period of dramatic climatic, environmental, and biological change. Numerous studies have documented the Late Ordovician glacial or mass extinction interval, but the Early Silurian has received significantly less attention. This study presents a U-Pb zircon age data and organic carbon isotope (δ¹³C_org) records from the Upper Ordovician to Lower Silurian succession of South China to better constrain carbon isotope perturbations and to evaluate their possible causes and relationships to paleoenvironmental change during Early Silurian time. A volcanic ash bed located at the top of the organic-rich Lower Silurian Longmaxi Formation yields a ²⁰⁶Pb/²³⁸U zircon age of 440 ± 3 Ma (MSWD = 1.4), which is consistent with the Rhuddanian–Aeronian (R–A) boundary age. The newly acquired age is similar to that documented an ash bed in Scotland (439.57 ± 1.13 Ma) perhaps indicating synchronous volcanism. The δ¹³C_org values show a negative excursion in the organic-rich lower Longmaxi Formation that is interrupted by a positive excursion in the organic-lean upper part of the unit. The positive excursion begins immediately above the dated ash bed thus assigning it to the R–A boundary. The documented δ¹³C_org trend is comparable to those of other sections throughout the world, and is suggestive of a global perturbation of carbon cycle. The negative δ¹³C_org excursion of the Rhuddanian stage was coeval with deposition of organic-rich shale under anoxic/euxinic conditions, whereas the subsequent positive δ¹³C_org excursion coincided with a change to suboxic conditions that could have diminished organic matter preservation. We propose that the negative δ¹³C_org excursion could be considered as the defining isotopic characteristic of the Rhuddanian oceanic anoxic event (Rhuddanian OAE). Results of the present study in tandem with published age data from the Guanyinqiao Bed immediately below the base of the Longmaxi Formation suggest that the negative δ¹³C_org excursion and associated Rhuddanian OAE persisted for approximately 3 Myr. This relatively long-lived event reflects a sustained addition of isotopically light carbon into the atmosphere-ocean system, possibly related to the release of volcanic CO₂. The enhanced burial of organic carbon in association with the Rhuddanian OAE could have removed the substantial ¹²C from the carbon reservoir and lowered atmospheric pCO₂ thus resulting in a subsequent positive δ¹³C excursion and global cooling at the R-A boundary.

28616. 题目: Hypoxic water mass in the highly turbid well-mixed macrotidal Rokkaku River Estuary, Ariake Sea, Japan
文章编号: N19020502
期刊: Estuarine, Coastal and Shelf Science
作者: Yuichi Hayami, Minoru Wada, Yu Umezawa, Naoki Fujii, Akito Nakamura, Fumiaki Mori
更新时间: 2019-02-05
摘要: Hypoxic water masses are usually formed in the bottom layer of stratified water columns. However, we found that hypoxia was formed throughout the water column in a well-mixed macrotidal estuary, the Rokkaku River Estuary, Japan. There was a spring-neap variation in the dissolved oxygen (DO) concentration where hypoxia developed during spring tides. Minimum DO concentration was observed 1 or a few days after the spring tide. When hypoxia developed, all the water column from bottom to surface became hypoxic (<2 mg l⁻¹ or < 30% saturation). The hypoxic water mass was associated with the estuarine turbidity maximum (ETM). Oxygen demand of water in this area was very large (>2 mg l⁻¹ day⁻¹). Potential oxygen consumption by microorganisms was positively correlated with turbidity. Concentration of suspended solid (SS) at the ETM exceeded 1000 mg l⁻¹. Furthermore, particulate organic carbon (POC) concentration in the estuary increased in spring tides. C/N ratio and δ¹³C of organic matter suggested that POC was transported from the sea into the estuary. These results suggest that the active resuspension of organic matter caused by the strong tidal current during spring tides enhanced the respiratory activity of microorganisms and the main source of the organic matter was detrital material from the sea. Such a large amount of organic matter should fuel microbial respiration effectively. Since microbial oxygen consumption was larger than the oxygen supply from the water surface even in the well mixed condition, a hypoxic water mass was formed in this estuary.

28617. 题目: Extreme weather events modulate processing and export of dissolved organic carbon in the Neuse River Estuary, NC
文章编号: N19020501
期刊: Estuarine, Coastal and Shelf Science
作者: Alexandria G. Hounshell, Jacob C. Rudolph, Bryce R. Van Dam, Nathan S. Hall, Christopher L. Osburn, Hans W. Paerl
更新时间: 2019-02-05
摘要: As the interface between riverine and coastal systems, estuaries play a key role in receiving, transporting, and processing terrestrial organic carbon prior to export to downstream coastal systems. Estuaries can switch from terrestrial organic carbon reactors under low river flow to pipelines under high flow, but it remains unclear how estuarine terrestrial organic carbon processing responds to the full spectrum of discharge conditions, which are bracketed by these high and low discharge events. The amount of terrestrial dissolved organic carbon and colored dissolved organic matter imported, processed, and exported was assessed for riverine discharge events spanning from 4th to 99th flow quantiles in the Neuse River Estuary, North Carolina, USA using spatially and temporally (July 2015–December 2016) resolved measurements. The extent of dissolved organic matter processing in the estuary under various flow conditions was estimated using a non-steady state box model to calculate estuary-wide terrestrial dissolved organic carbon and colored dissolved organic matter source & sink terms. Under mid-range riverine discharge conditions (4th to 89th flow quantiles), the Neuse River Estuary was a sink for terrestrial dissolved organic carbon, retaining and/or processing (i.e., flocculation; photochemical and microbial degradation) on average ∼29% of terrestrial dissolved organic carbon. Following floods due to extreme precipitation events (99th flow quantile), however, over 99% of the terrestrial dissolved organic carbon loaded from the riverine end-member was exported directly to the downstream coastal system. Following such extreme weather events, the estuary acts as a pipeline for direct export of terrestrial dissolved organic carbon, drastically altering the amount and quality of dissolved organic carbon loaded to downstream coastal systems. This has important implications under future climate scenarios, where extreme weather events are expected to increase.
图文摘要:

28618. 题目: Hydrochars produced with by-products from the sucroenergetic industry: a study of extractor solutions on nutrient and organic carbon release
文章编号: N19020409
期刊: Environmental Science and Pollution Research
作者: Daniely Reis Santos, Otávio da Mata Cunha, Márcia Cristina Bisinoti, Odair Pastor Ferreira, Altair Benedito Moreira, Camila Almeida Melo
更新时间: 2019-02-04
摘要: Hydrothermal carbonization transforms biomass into value-added material called hydrochar. The release of nutrients (P, N, Ca, Mg, and K) and organic carbon (TOC) from hydrochar in different extractive solutions was investigated in this study. Two sets of hydrochar were produced: (i) hydrochar prepared from sugarcane bagasse and vinasse mixture (BV-HC) and (ii) hydrochar prepared by the addition of H₃PO₄ to this mixture (BVA-HC). Both hydrochar types released significative amounts of nutrient and organic carbon, mainly Ca (5.0 mg g⁻¹) in the mixture (KCl, K₂SO₄, NaOH, 1:1:1) extractive solution and TOC (72.6 mg g⁻¹) in the NaOH extractive solution, for BV-HC. Nutrient release was influenced by pH and ionic strength. The release of P, Ca, and Mg was affected by the presence of insoluble phosphate phases in BVA-HC. The release of nutrients P, N, Ca, Mg, and K and organic carbon demonstrated that hydrochar has potential for soil application purposes.

28619. 题目: Enhanced adsorption for Pb(II) and Cd(II) of magnetic rice husk biochar by KMnO 4 modification
文章编号: N19020408
期刊: Environmental Science and Pollution Research
作者: Chen Sun, Tong Chen, Qunxing Huang, Jun Wang, Shengyong Lu, Jianhua Yan
更新时间: 2019-02-04
摘要: Novel KMnO₄-treated magnetic biochar (FMBC) was successfully synthesized by addition of Fe(NO₃)₃ during carbonization and KMnO₄ treatment following for Pb(II) and Cd(II) adsorption. SEM-EDS, XPS, and ICP-AES were used to evaluate the FMBC and magnetic biochar (FBC) on surface morphology, surface chemistry characteristics, surface functional groups, and Pb(II) and Cd(II) adsorption behavior. Results showed that the Langmuir maximum adsorption quantity of FMBC reached 148 mg/g for Pb(II) and 79 mg/g for Cd(II), nearly 7 times of that of FBC. The enhancement of FMBC for heavy metal adsorption was due to the successful load of manganese oxides and the increased oxygen functional groups consistent with XPS and FTIR results. The adsorption capacities of FMBC were maintained over 95% when the pH value was higher than 2.5 and 3.5 for Pb(II) and Cd(II), respectively. The adsorption performances of both heavy metals by FMBC were hardly influenced by ionic strength and humid acid. The adsorption capacities of FMBC could maintain over 50% and 87% after four cycles for Pb(II) and Cd(II), respectively. The saturation magnetization of FMBC was about 11.5 emu/g, which did not change after adsorption. This work proposed a new method to fabricate a magnetic biochar with high adsorption capacities of heavy metals Pb(II) and Cd(II).

28620. 题目: Characterization of goethite-fulvic acid composites and their impact on the immobility of Pb/Cd in soil
文章编号: N19020407
期刊: Chemosphere
作者: Qianjun Liu, Xiang Li, Jiepeng Tang, Yangmei Zhou, Qintie Lin, Rongbo Xiao, Min Zhang
更新时间: 2019-02-04
摘要: The coprecipitation of organic matter (OM) and minerals is a relatively common phenomenon in soil, and it has a significant influence on the surface properties and reactivity of minerals. In turn, the fate of pollutants in soil is greatly affected by the organic-mineral composites. In this study, goethite-fulvic acid (Ge-FA) composites with varying FA mass ratios in the range of 0–15% were synthesized by coprecipitation. The sample properties were studied using XRD, FTIR, SEM-EDS and N₂ gas adsorption techniques. The influence of Ge-FA on the mobility of Pb/Cd in soil was investigated. The crystal forms of Ge-FA changed from goethite (FA≤4%) to hematite (FA≥5%), and the FA affected the FeO bond vibrations. These results demonstrated that FA was successfully introduced into the iron oxide. Ge-FA changed from a filamental morphology to an aggregate as the FA ratio increased. The coprecipitation resulted in blockages of iron oxides, thereby decreasing the specific surface area and pore volume. The adsorption amount of Pb(II) on Ge-FA increased as the FA ratio increased, but no significant change was observed for Cd(II). With the application of Ge-FA, the exchangeable concentrations of Pb and Cd in contaminated soil decreased by 42.4%–93.6% and 15.8%–43.7%, respectively. The exchangeable and carbonate bound fractions of Pb and Cd decreased and were transformed into the FeMn bound and residual fractions.
图文摘要: