13901. 题目: Uptake of phosphate by Synechocystis sp. PCC 6803 in dark conditions: Removal driving force and modeling
作者: Yun Zhou, Andrew K. Marcus, Levi Straka, Everett Eustance, YenJung Sean Lai, Siqing Xia, Bruce E. Rittmann
摘要: Rapid uptake of inorganic phosphate (Pi) by microalgae should occur through two processes operating in parallel: onto extracellular polymeric substances (EPS) and intracellular polymeric substances (IPS). Most previous studies focused only on overall Pi uptake and ignored the roles of EPS. We investigated the two-step removal of Pi by Synechocystis sp. PCC 6803 in dark conditions (i.e., without incorporation of Pi into newly synthesized biomass). We also developed a model to simulate both steps. Experimental results with Synechocystis confirmed that Pi in the bulk solution was removed by the two uptake mechanisms operating in parallel, but with different kinetics. All uptake rates decreased with time, and the Pi uptake rate by IPS was much higher than that by EPS at all times, but EPS had a larger maximum Pi-storage capacity -- 33–48 mgP/gCODEPS versus 15–17 mgP/gCODIPS. Synechocystis had a maximum Pi-storage capacity in the range of 22–28 mgP/g dry biomass. Protein in EPS and IPS played the key role for binding Pi, and biomass with higher protein content had greater Pi-storage capacity. Furthermore, biomass with low initial stored Pi had faster Pi-uptake kinetics, leading to more Pi removed from the bulk solution. This work lays the foundation for using microalgae as a means to remove Pi from polluted water and for understanding competition for Pi in microbial communities.
13902. 题目: Variations of DOM quantity and compositions along WWTPs-river-lake continuum: Implications for watershed environmental management
作者: Yulai Wang, Yunyun Hu, Changming Yang, Qiongjie Wang, Degang Jiang
摘要: Wastewater effluent makes up an increasingly large percentage of surface water supplies, but the impacts of discharge of effluent organic matter (EfOM) on receiving riverine and lacustrine dissolved organic matter (DOM) is still largely unknown. In the present study, we investigated variations of DOM quantity and quality along wastewater treatment plants (WWTPs)-river-lake continuum during drought periods, and made a tentative discussion on its implications for watershed environmental management. We used dissolved organic carbon (DOC) concentrations, UV absorption coefficients and excitation-emission-matrixs (EEMs) fluorescence spectroscopy combined with fluorescence regional integration (FRI) to characterize EfOM and riverine and lacustrine DOM along WWTPs-river-Chaohu Lake continuum. Our results showed that changes in DOM quantity and quality in receiving waterbodies were related to EfOM discharged from WWTPs and external input of DOM along inflowing river. Specifically, we found that the ratio of protein-like/humic-like notably decreased (P < 0.05), and %humic-like increased (P < 0.01) along WWTPs-river-lake continuum. Furthermore, the recent autochthonous contribution index (BIX) and the humification index (HIX) values showed that these variations of DOM composition were attributed to microbial degradations in receiving waterbodies. We concluded that the changes of DOM quantity and quality along WWTPs-river-lake continuum had important implications for DOM behaviors, and offered some novel ideas for watershed environmental management.
13903. 题目: Microbiome-Triggered Transformations of Trace Organic Chemicals in the Presence of Effluent Organic Matter in Managed Aquifer Recharge (MAR) Systems
期刊: Environmental Science & Technology
作者: Karin Hellauer, Jenny Uhl, Marianna Lucio, Philippe Schmitt-Kopplin, Daniel Wibberg, Uwe Hübner, Jörg E. Drewes
摘要: It is widely assumed that biodegradation of trace organic chemicals (TOrCs) in managed aquifer recharge (MAR) systems occurs via a cometabolic transformation with dissolved organic carbon serving as primary substrate. Hence, the composition facilitating bioavailability of the organic matter seems to have a great impact on TOrCs transformation in MAR systems. The aim of this study was to elucidate the character of effluent organic matter present in the feedwater of a simulated sequential MAR system throughout the infiltration by use of FT-ICR-MS analyses as well as spectroscopic methods. Furthermore, compositional changes were correlated with TOrCs targeted throughout the system as well as the abundance of different microbial phyla. On the basis of their behavior throughout the infiltration system in which different redox and substrate conditions prevailed, TOrCs were classified in four groups: easily degradable, redox insensitive, redox sensitive, and persistent. Masses correlating with persistent TOrCs were mainly comprised of CHNO-containing molecules but also of CHO which are known as carboxyl-rich alicyclic molecules, while CHOS and CHNOS can be neglected. Easily degradable TOrCs could be associated with CHNO-, CHO-, and CHOS-containing compounds. However, a shift of molecular compounds to mostly CHOS was observed for redox-insensitive TOrCs. Three hundred thirty eight masses correlated with removal of redox-sensitive TOrCs, but no distinct clustering was identified.
13904. 题目: Changes in long chain alkenone distributions and Isochrysidales groups along the Baltic Sea salinity gradient
期刊: Organic Geochemistry
作者: Jérôme Kaiser, Karen J. Wang, Derek Rott, Gaoyuan Li, Yinsui Zheng, Linda Amaral-Zettler, Helge W. Arz, Yongsong Huang
摘要: Isochrysidales species of the phylum Haptophyta are the exclusive producers of C37 to C42 long chain alkyl ketones, also called long chain alkenones (LCAs). While LCA distribution is known to vary with temperature and salinity, it is difficult to tease apart the direct effects of environmental parameters vs changes in the LCA-producing organisms. The Baltic Sea surface salinity gradient, which ranges from oligohaline (0.5–5 g/kg) to polyhaline (18–30 g/kg), represents a unique opportunity to study the relationships between salinity changes, species distribution and LCA biomarkers in a single ecosystem. LCA biomarkers revealed the presence of the three known Isochrysidales groups (Groups I, II and III) in Baltic Sea surface sediments, and the presence of Groups I and II were further confirmed with DNA sequencing. Group III Isochrysidales were present in the mixoeuhaline Skagerrak based on LCA signature alone. Groups I and II Isochrysidales were found for the first time in the Baltic Sea using a combination of LCAs and DNA biomarkers, solving an eighteen-year long mystery of Baltic Sea LCA-producing haptophyte identity. Group II Isochrysidales, which have a large salinity tolerance range, were spread over the Skagerrak and the complete Baltic Sea, but were characteristic for the central Baltic Sea. Oligohaline Group I Isochrysidales were representative for the northern Baltic Sea. However, evidence of Group I Isochrysidales in the central and southern Baltic Sea suggests a possible transport by surface currents since this group is typically confined to oligohaline conditions. Testing the recently developed ratio of isomeric C37 ketones (RIK37) against the Baltic Sea surface salinity gradient revealed a significant positive correlation. This may represent a salinity proxy reflecting the amount of Group I Isochrysidales relative to Group II Isochrysidales in oligohaline environments. The present study elucidates for the first time the identity and the spatial distribution of LCA producers thriving in a large and stable brackish environment.
13905. 题目: Soil tillage impact on the relative contribution of dissolved, particulate and gaseous (CO2) carbon losses during rainstorms
期刊: Soil and Tillage Research
作者: V. Chaplot, F. Darboux, M. Alexis, L. Cottenot, H. Gaillard, K. Quenea, M. Mutema
摘要: Although the impact of water erosion on soil carbon losses has been widely investigated, little is known about the relative contributions of dissolved, particulate and gaseous losses, a prerequisite for understanding the mechanisms of carbon (C) export from soils and designing mitigation procedures. The main objective of this study was to quantify the losses of dissolved organic and inorganic C (DOC, DIC), particulate organic C (POC) and soil CO2 from runoff microplots on tilled (T) and no-tilled (NT) soils. The study was performed in the Beauce region in central France under Luvisols using 45 and 80 mmh−1 artificial rains. At 45 mm h-1, T plots produced C erosion at an average of 1189.7 ± 114.8 mg C m-² h-1 with 76.9% of it being POC (915.0 ± 100.0 mg C m-² h-1), 21.7% DOC (258.3.0 ± 7.6 mg C m-² h-1), 1.4% (16.3 ± 7.2 mg C m-² h-1), DIC and 0.01% CO2. NT decreased total soil C losses by 95% (from 0.8 to 0.038 g C m-² h-1) and soil C losses were as CO2 only. At 80 mm h-1, NT surprisingly increased C erosion by 40% compared to T (from 39.4 to 55.3 g C m² h-1), with 95.5% of the C losses being POC vs 88.7% for T. These results on rainstorm-induced C fluxes from soils controlled by tillage are expected to be of future value: (1) for selecting appropriate land management that will mitigate against C losses from soils and improve soil carbon sequestration and; (2) to better understand the Global Carbon Cycle and further develop the existing models.
13906. 题目: River beads as a conceptual framework for building carbon storage and resilience to extreme climate events into river management
作者: Ellen Wohl, Katherine B. Lininger, Daniel N. Scott
摘要: River beads refer to retention zones within a river network that typically occur within wider, lower gradient segments of the river valley. In lowland, floodplain rivers that have been channelized and leveed, beads can also be segments of the river in which engineering has not reduced lateral channel mobility and channel-floodplain connectivity. Decades of channel engineering and flow regulation have reduced the spatial heterogeneity and associated ecosystem functions of beads occurring throughout river networks from headwaters to large, lowland rivers. We discuss the processes that create and maintain spatial heterogeneity within river beads, including examples of beads along mountain streams of the Southern Rockies in which large wood and beaver dams are primary drivers of heterogeneity. We illustrate how spatial heterogeneity of channels and floodplains within beads facilitates storage of organic carbon; retention of water, solutes, sediment, and particulate organic matter; nutrient uptake; biomass and biodiversity; and resilience to disturbance. We conclude by discussing the implications of river beads for understanding solute and particulate organic matter dynamics within river networks and the implications for river management. We also highlight gaps in current understanding of river form and function related to river beads. River beads provide an example of how geomorphic understanding of river corridor form and process can be used to restore retention and resilience within human-altered river networks.
13907. 题目: Restored floodplains enhance denitrification compared to naturalized floodplains in agricultural streams
作者: Brittany R. Hanrahan, Jennifer L. Tank, Martha M. Dee, Matt T. Trentman, Elizabeth M. Berg, Sara K. McMillan
摘要: Predicted changes in the timing and magnitude of storms have the potential to amplify water quality challenges associated with agricultural runoff. In agricultural streams of the Midwestern US, floodplain restoration has the potential to enhance inorganic nitrogen (N) removal by increasing the bioreactive surface area for microbially-mediated denitrification. The restoration of inset floodplains via construction of the two-stage ditch increases denitrification compared to channelized systems, however, little is known about how denitrification on restored floodplains compares to those formed naturally when stream channel management lapses. We used sacrificial microcosm incubations and membrane-inlet mass spectrometry (MIMS) to compare denitrification rates in floodplain soils collected along transects in both naturalized and restored floodplains; longitudinal transects spanned two zones in the active floodplain (near-stream, NS vs. middle, MID) and a third zone that reflected upland conditions in the riparian buffer strip (UP). Denitrification rates were 35–49% higher in the restored, inset floodplains compared to naturalized floodplains. Variation in denitrification rates were primarily explained by soil organic matter (OM) and OM was > 20% higher in restored floodplains than naturalized, highlighting the contrasts between stable, constructed floodplains with heterogeneous, depositional bars typical of naturalizing channels. Consequently, restored inset floodplains could remove > 70% more N than the naturalized floodplains during similar storm inundation events.
13908. 题目: Freeze–thaw processes and intense rainfall: the one-two punch for high sediment and nutrient loads from mid-Atlantic watersheds
作者: Shreeram Inamdar, Erin Johnson, Richard Rowland, Daniel Warner, Robert Walter, Dorothy Merritts
摘要: Large runoff, sediment, and nutrient exports from watersheds could occur due to individual extreme climate events or a combination of multiple hydrologic and meteorological conditions. Using high-frequency hydrologic, sediment, and turbidity data we show that freeze–thaw episodes followed by intense winter (February) rainstorms can export very high concentrations and loads of suspended sediment and particulate organic carbon (POC) and nitrogen (PN) from mid-Atlantic watersheds in the US. Peak suspended sediment (> 5000 mg L−1), POC (> 250 mg L−1) and PN (> 15 mg L−1) concentrations at our 12 and 79 ha forested watersheds for the February rainfall-runoff events were highest on record and the fluxes were comparable to those measured for tropical storms. Similar responses were observed for turbidity values (> 400 FNU) at larger USGS-monitored watersheds. Much of the sediments and particulate nutrients likely originated from erosion of stream bank sediments and/or channel storage. Currently, there is considerable uncertainty about the contribution of these sources to nonpoint source pollution, particularly, in watersheds with large legacy sediment deposits. Future climate projections indicate increased intensification of storm events and increased variability of winter temperatures. Freeze–thaw cycles coupled with winter rain events could increase erosion and transport of streambank sediments with detrimental consequences for water quality and health of downstream aquatic ecosystems.
13909. 题目: Road side effect on lead content in sandy soil
作者: Sarah Pariente, Zhevelev Helena, Sachs Eyal, Fragin G. Anatoly, Zilbershtein Michal
摘要: The effect of traffic load on the spatial distribution of lead concentrations in the soil at roadsides and on traffic islands was investigated along a road in Rishon LeZion, Israel. The road comprised two segments that were used during different periods: old, which was in use since 1980; and new, which was opened to traffic in 2004. Soil samples were collected from the upper 0–2 cm soil layer from the roadsides at various distances from the road, and from beneath and between shrubs on the traffic islands. The soil sampling was conducted in 2007 — a few years after the implementation of lead-free fuel — and in 2012. For each soil sample, lead concentration and soil properties associated with lead adsorption (soil organic matter and soil texture) were determined. The amounts of lead around the old road segment were higher than those around the new one. In both sampling years, the lead concentrations at the sides of both road segments were far below the maximum permissible levels for urban and agricultural areas. However, some of the sampling points on the traffic islands of the old road showed lead contamination. Small, non-significant differences in soil lead levels were found at differing distances from the road. Lead-concentration depletion rates of about 1–7 mg kg−1 yr−1 were indicated. Within the traffic islands, the samples collected beneath shrubs contained higher lead concentrations than those collected between shrubs. Soil organic matter levels of <1.5% did not affect the lead concentrations, whereas those above 1.5% showed a strong positive correlation.
13910. 题目: Implication of different humic acid fractions in soils under karst rocky desertification
作者: Xinyue Di, Baohua Xiao, Hui Dong, Shijie Wang
摘要: Karst rocky desertification, a kind of intense soil degradation, has become an urgent environmental issue in the karst region of southwest China. It was found that limestone soil, a typical soil of the karst region, is more vulnerable to karst rocky desertification than adjacent other soils although limestone soil has relatively high TOC (total organic carbon) content, but underlying mechanisms remain unclear. To investigate roles of soil properties in karst rocky desertification, three major soils, limestone soil, yellow soil and yellow brown soil, of the karst region of southwest China were sampled and their total extractable humic acid (THA) were fractionated into three sub-fractions, namely, free HA (HAf), encapsulated HA (HAe) and interacted HA (HAi), with a sequential extraction method. These soils and fractionated HA samples were systematically characterized with various analysis methods and discussed. The results showed that limestone soil had higher contents of total organic content (TOC) and THA content, but its THAC/TOC (carbon in THA to TOC) ratio (23.39%) was lower than those of yellow soil (31.44%) and yellow-brown soil (30.74%); C/N ratios and total acid contents of HAe and HAi fractions, which were physically protected by soil minerals/aggregates, were much higher than those of HAf fractions, indicating that HAe and HAi could be more active and degraded easier than HAf once exposed to microbes or/and runoff erosions. Therefore, lower HAf content and significantly lower HAfC/TOC (carbon in HAf to TOC) ratio of limestone soil may underlie the observation that limestone soil showed weak resistance to karst rocky desertification compared to other adjacent soils when the site had been artificial disturbed. We believe that roles of different HA fractions to overall quality and stability of soil deserve more attention.
13911. 题目: The impact of declining oxygen conditions on pyrite accumulation in shelf sediments (Baltic Sea)
作者: Katarzyna Łukawska-Matuszewska, Bożena Graca, Olga Brocławik, Tamara Zalewska
摘要: Deterioration of oxygen conditions in water below the halocline has been observed in the Baltic Sea. Deoxygenation is linked to the reduced frequency and volume of inflows of highly saline surface water from the North Sea (major Baltic inflows—MBIs) in the second half of the twentieth century and the increased organic matter respiration due to eutrophication. In the present study, the impact of worsening oxygen conditions on pyrite content in the Gdańsk Deep (max. depth of 118 m, southern Baltic Sea) sediments was determined. Geochemical parameters (acid volatile sulfides, pyrite sulfur, reactive iron, organic carbon, sedimentation rate and sediment age) were analyzed in relation to the variation in bottom water oxygen concentration and the occurrence of MBI. The obtained results demonstrate that pyrite content in the study area decreased after 1960. The declining pyrite content coincided with the deterioration of oxygen conditions (concentration < 2 ml l−1) in bottom water. In the same period, reactive iron concentration decreased and organic carbon increased in sediment. In the period 1616–1960, average pyrite accumulation rate was 322 µmol m−2 day−1. In the subsequent years, its average accumulation rate decreased to 210 µmol m−2 day−1. Fluctuations of oxygenation of bottom water in the study area were manifested by highly variable degree of pyritization (36 ± 11%) and particulate organic carbon to pyrite sulfur ratio (2.8–37).
13912. 题目: Spatial variability of organic matter properties determines methane fluxes in a tropical forested peatland
作者: N. T. Girkin, C. H. Vane, H. V. Cooper, V. Moss-Hayes, J. Craigon, B. L. Turner, N. Ostle, S. Sjögersten
摘要: Tropical peatland ecosystems are a significant component of the global carbon cycle and feature a range of distinct vegetation types, but the extent of links between contrasting plant species, peat biogeochemistry and greenhouse gas fluxes remains unclear. Here we assessed how vegetation affects small scale variation of tropical peatland carbon dynamics by quantifying in situ greenhouse gas emissions over 1 month using the closed chamber technique, and peat organic matter properties using Rock-Eval 6 pyrolysis within the rooting zones of canopy palms and broadleaved evergreen trees. Mean methane fluxes ranged from 0.56 to 1.2 mg m−2 h−1 and were significantly greater closer to plant stems. In addition, pH, ranging from 3.95 to 4.16, was significantly greater closer to stems. A three pool model of organic matter thermal stability (labile, intermediate and passive pools) indicated a large labile pool in surface peat (35–42%), with equivalent carbon stocks of 2236–3065 g m−2. Methane fluxes were driven by overall substrate availability rather than any specific carbon pool. No peat properties correlated with carbon dioxide fluxes, suggesting a significant role for root respiration, aerobic decomposition and/or methane oxidation. These results demonstrate how vegetation type and inputs, and peat organic matter properties are important determinants of small scale spatial variation of methane fluxes in tropical peatlands that are affected by climate and land use change.
13913. 题目: More reducing bottom-water redox conditions during the Last Glacial Maximum in the southern Challenger Deep (Mariana Trench, western Pacific) driven by enhanced productivity
期刊: Deep-Sea Research Part II: Topical Studies in Oceanography
作者: Min Luo, Thomas J. Algeo, Hongpeng Tong, Joris Gieskes, Linying Chen, Xuefa Shi, Duofu Chen
摘要: The modern southern Mariana Trench is characterized by oligotrophic surface waters, resulting in low primary productivity and well-oxygenated bottom waters. This study investigates changes in the redox conditions of bottom waters in the southern Mariana Trench during the Last Glacial Maximum (LGM) and their potential causes. We measured major, trace, and rare earth elements (REE) in three gravity cores (GC03, GC04, and GC05) and one box core (BC11) retrieved from the southern Challenger Deep at water depths from 5289 to 7118 m. The upper sediment layers of both GC05 and BC11 are dominated by valve fragments of the giant diatom Ethmodiscus rex, forming laminated diatom mats (LDMs). 14C-AMS dates of bulk organic matter show that the LDMs accumulated between 18.4 and 21.8 kyr B.P., corresponding to the LGM. Modest enrichments of U and Mo along with weak or absent Ce anomalies in the LDM point to suboxic conditions during the LGM. In contrast, non-LDM samples exhibit little to no enrichment of redox-sensitive elements as well as negative Ce anomalies, indicating deposition under oxic bottom-water conditions. The Ce anomalies are considered valid proxies for bottom-water redox conditions because REE signatures were acquired in the early diagenetic environment, as indicated by strong P-REE correlations and middle-REE enrichment associated with early diagenetic cycling of Fe-Mn oxyhydroxides in the sediment column followed by capture of the REE signal by biogenic and/or authigenic apatite. We postulate that the more reducing bottom-water conditions during the LGM were linked to increased primary productivity induced by enhanced Asian dust input. As shown in earlier studies, the increased primary productivity associated with Ethmodiscus rex blooms in the eastern Philippine Sea played a significant role in capturing atmospheric CO2 during the LGM. Consequently, the magnitude of atmospheric CO2 sequestration by giant diatom blooms during the LGM may have been greater than previously envisaged.
13914. 题目: Copper phosphide and persulfate salt: A novel catalytic system for the degradation of aqueous phase micro-contaminants
期刊: Applied Catalysis B: Environmental
作者: Charalampia Alexopoulou, Athanasia Petala, Zacharias Frontistis, Charalampos Drivas, Stella Kennou, Dimitris I. Kondarides, Dionissios Mantzavinos
摘要: The heterogeneous activation of sodium persulfate (SPS) using copper (I) phosphide (Cu3P) nanoparticles was tested in this work. The catalyst was synthesized via a two-step method involving preparation of Cu(OH)2 and subsequent low temperature phosphidation and characterized with BET, XRD, TEM/HRTEM, SEM and XPS techniques. The XRD pattern showed the existence of hexagonal Cu3P phase with mean primary crystallite size of ca. 28 nm. The XP spectra indicated the presence of residual Cu(OH)2 and Cu3(PO4)2 species on the catalyst surface, originating from the synthesis methods employed, which disappeared after exposure to reaction conditions.The activity of Cu3P was evaluated for the degradation of antibiotic sulfamethoxazole (SMX), which occurred in short reaction times. The effect of catalyst concentration (20–80 mg/L), SPS dosage (0.05–1 g/L) and SMX concentration (0.5–4.1 mg/L) on degradation was studied. Results obtained in ultrapure water (UPW) showed that SMX degradation increases with increasing catalyst content in the range 20–80 mg/L and SPS concentration in the range 0.05–0.5 g/L. In contrast, increasing SPS concentration at 1 g/L leads to lower reaction rates. Experiments were also conducted in bottled water, secondary treated wastewater, UPW spiked with bicarbonate or chloride ions, as well as UPW containing humic acid. With the use of t-butanol and methanol as radical quenching agents,SO4•- was found to be the primary radical species responsible for SMX degradation. The simultaneous use of Cu3P and solar irradiation as persulfate activators resulted in a synergistic effect in experiments performed in UPW and wastewater.From a mechanistic point of view, Cu3P acts as an electron mediator or bridge to facilitate the electron-transfer processes and this is accompanied by the intermediate formation of radicals. The catalyst remains intact, thus implying the catalytic nature of the process.
13915. 题目: Distribution, degradation and bioavailability of dissolved organic matter in the East China Sea
作者: Chong-Xiao Ji, Gui-Peng Yang, Yan Chen, Peng-Yan Zhang
摘要: Water samples were collected from the East China Sea (ECS) in October 2015 to investigate the distribution, degradation and bioavailability of organic matter. Concentrations of dissolved organic carbon (DOC), total hydrolyzable amino acids (THAAs, including dissolved free, DFAA and combined fraction, DCAA), particulate amino acids (PAAs), and total dissolved carbohydrates (TDCHO, including monosaccharides, MCHO and polysaccharides, PCHO) were measured. DOC and TCHO concentrations exhibited similar distribution patterns with high values occurring at nearshore stations, revealing the effects of terrestrial input and similar source and removal pathways of DOC and TCHO. The distributions of THAA, DCAA, and PAA displayed declining trends from the north to south of the ECS. Elevated THAA values simultaneously occurred in the center of the transect. The onboard incubation experiments with surface seawater from one station showed that the values of degradation index based on amino acids decreased with the increase of dissolved inorganic nitrogen (DIN) concentrations, indicating the mineralization of THAA to DIN during degradation process. TCHO-C% and THAA-C% are defined as the percentages of carbohydrates and amino acids in DOC, respectively. There were 21 stations suffering P limitation, implying that PO4 3− -P content was the key factor limiting the growth of phytoplankton. High TCHO-C% values were found at P-limited stations, indicating that phytoplankton preferentially produced carbohydrates when experiencing nutrient limitation. The difference of dissolved organic matter bioavailability between surface and bottom water were probably due to water stratification. Overall, the present study may have implications for the source, removal and bioavailability of organic mater in the ECS.
13916. 题目: Catalytic ozonation of 4-chloronitrobenzene by goethite and Fe2+-modified goethite with low defects: A comparative study
期刊: Journal of Hazardous Materials
作者: Lei Yuan, Jimin Shen, Pengwei Yan, Jizhou Zhang, Zhe Wang, Shengxin Zhao, Zhonglin Chen
摘要: In this study, Fe2+-modified goethite with low defects (α-Fe(Fe2+)OOH) was synthesized and characterized. Results revealed that α-Fe(Fe2+)OOH is a nano magnetic material with goethite (α-FeOOH) -type structures and has fewer Lewis acid of Fe3+ on its surface. Moreover, α-Fe(Fe2+)OOH was effective in catalytic ozonation of 4-chloronitrobenzene (4-CNB), which is a probe contaminant that cannot be efficiently removed through sole ozonation. The removal of 4-CNB increased with ozone concentration and α-Fe(Fe2+)OOH dosage, but decreased with the presence of carbonate, sulfate and phosphate. The catalytic activity of α-Fe(Fe2+)OOH also showed a dependence on solution pH. The presence of humic acid accelerated 4-CNB removal at low concentration but inhibited the removal at high concentration. In comparison with α-FeOOH, α-Fe(Fe2+)OOH significantly enhanced hydroxyl radicals generation and reduced Fe ions release in this process. The hydroxyl groups of Fe3+ on α-FeOOH and α-Fe(Fe2+)OOH surface was active site for ozone decomposition into hydroxyl radicals. Introducing Fe2+ significantly increased the density of surface hydroxyl groups relative to α-FeOOH. This enhancement significantly promoted hydroxyl radicals generation and 4-CNB degradation in the solution.
13917. 题目: Leaching of indium from end-of-life LCD panels via catalysis by synergistic microbial communities
期刊: Science of The Total Environment
作者: Yaling Xie, Shuhua Wang, Xiaochun Tian, Liming Che, Xuee Wu, Feng Zhao
摘要: Currently, a large amount of discarded liquid crystal displays (LCDs) are being produced, and the improper treatment of discarded LCDs causes serious environmental pollution problems. Indium is the most valuable metal in LCDs and is present in such devices at a concentration of over 0.025%. In this study, the bioleaching of indium from end-of-life LCD panels was comprehensively investigated through three methods: S-mediated pathway, Fe-mediated pathway and Mixed pathway of S- and Fe-mediated, which yielded maximum bioleaching efficiencies of approximately 100%, 0% and 78%, respectively. Microbial community analysis showed that the dominant functional bacteria under the S-mediated pathway were Acidithiobacillus. The Acidithiobacillus genus catalysed the leaching of indium, which was mainly achieved by indirect bioleaching. In addition, the microorganisms can secrete enzymes and extracellular polymeric substances, which also contributed to the leaching of indium. Therefore, this work provides an economical and efficient biological method for future research and practical applications in indium recovery from solid waste.
13918. 题目: Effect of production temperature on lead removal mechanisms by rice straw biochars
期刊: Science of The Total Environment
作者: Zhengtao Shen, Deyi Hou, Fei Jin, Junxian Shi, Xiaoliang Fan, Daniel C.W. Tsang, Daniel S. Alessi
摘要: Production temperature significantly affects biochar properties and consequently the removal mechanisms of heavy metals. In this study, rice straw biochars were produced at 300, 500 and 700 °C (RSB300, RSB500 and RSB700). The influence of production temperature on the adsorption characteristics and removal mechanisms of lead on this set of rice straw biochars were investigated by batch adsorption tests, micro-structural analyses and sequential metal extractions. Biochars produced at higher temperatures had significantly higher pH values and surface areas, resulting in higher metal removal capacities and faster uptake kinetics. Precipitation was a key mechanism for lead removal from solution for all biochars: lead oxalate was precipitated on RSB300, and hydrocerussite was precipitated on RSB500 and RSB700. The immobilized lead fraction on the biochars could be divided into exchangeable, acid soluble and non-available fractions. RSB300 had 11.34% of the total immobilized Pb attributed to the exchangeable fraction, whereas for RSB500 and RSB700, it was <1%. Immobilized Pb on RSB500 and RSB700 was almost exclusively attributable to the acid soluble and non-available fractions (>99%). Based on our results, RSB500 and RSB700 are likely much more appropriate for soil remediation of Pb as compared with RSB300.
13919. 题目: The effects of surfactants (sodium dodecyl sulfate, triton X-100 and cetyl trimethyl ammonium bromide) on the dewaterability of microalgae biomass using pressure filtration
期刊: Bioresource Technology
作者: Mohsen Taghavijeloudar, Junboum Park, Shervin Hashemi, Mooyoung Han
摘要: The application of pressure filtration in microalgae harvesting requires chemical pretreatment in order to reduce membrane fouling and to increase water flux. Surfactants have shown potential to enhance microalgae dewaterability by charge neutralization, bridging and releasing extracellular polymeric substances (EPS) and bound water. In this study, the effect of three surfactants including anionic sodium dodecyl sulfate (SDS), non-ionic triton X-100 and cationic cetyl trimethyl ammonium bromide (CTAB) on the dewaterability of Chlamydomonas sp. was investigated. Filtration fluxes and biomass concentrations were used to evaluate the microalgae dewaterability. Based on the results, SDS and Triton X-100 had a negative effect on the dewaterability of microalgae biomass. However, CTAB improved the dewaterability by decreasing the reversible and irreversible fouling resistance. The optimum dosage of CTAB was found to be 1500 mg/L, and resulted in 95.8% and 140% improvement on average water flux and biomass recovery efficiency, respectively.
13920. 题目: Variation in annual carbon fluxes affecting the SOC pool in hemiboreal coniferous forests in Estonia
期刊: Forest Ecology and Management
作者: Kaie Kriiska, Jane Frey, Endla Asi, Naima Kabral, Veiko Uri, Jürgen Aosaar, Mats Varik, Ülle Napa, Vladislav Apuhtin, Tiiu Timmusk, Ivika Ostonen
摘要: Estimation of soil-related carbon (C) fluxes is needed to understand the dynamics of the soil organic carbon pool, to determine changes in the carbon balance and functioning of forest ecosystems, and to support climate change policies.The objective of the study was to analyse the variation in the most dynamic soil C input (tree and understory above- and belowground litter production) and output (soil respiration) fluxes, in addition to the forest floor, understory and fine root biomass stocks, in eight different Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst) sites growing on mineral soils in Estonia. Further, the impact of soil C input and output fluxes on the soil organic carbon (SOC) pool was examined, and the net ecosystem production (NEP) of the stands was estimated.Fine root production (FRP) of the trees constituted 53% and 28% and needle litter constituted 25% and 28% of the total annual C input to the soil in the Norway spruce and Scots pine stands, respectively. The total FRP of the trees and the understory roots and rhizomes ranged from 211 to 1040 g m−2 yr−1, of which the understory comprised up to 28%. The mean annual soil respiration (Rs) rate was 5.7 ± 0.3 and 6.5 ± 0.3 Mg C ha−1 yr−1 in the pine and spruce stands, respectively, and did not differ significantly between the two groups of stands. The SOC pool of the studied stands depended significantly on both the above- and belowground C input fluxes. Tree-derived litter had the strongest effect on the SOC pool, while the Rh as the main soil C output flux showed no significant impact. The NEP ranged from 4.2 to −1.8 Mg C ha−1 yr−1 and demonstrated a strong negative correlation with stand age. The results affirm the importance of belowground as well as aboveground litter production on carbon accumulation in forest soils.