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24541. 题目: Evaluation of lacustrine organic δ13C as a lake-level indicator: A case study of Lake Qinghai and the satellite lakes on the Tibetan Plateau
文章编号: N19071808
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Xiangzhong Li, Weiguo Liu, Liming Xu
更新时间: 2019-07-18
摘要: In recent years, the sedimentary δ13Corg values have been recognized to be indicative of lake-level changes in lakes on the Tibetan Plateau (TP). However, the sensitivity of sedimentary δ13Corg to lake-level changes and the potential relationship between lake-level variations and climatic forces are still unknown in this particular region. Here, we systematically evaluate sedimentary δ13Corg as a proxy of lake-level changes in lakes with different sizes on the TP. Consistent with previous studies, the total organic matter of sediments was mainly contributed by aquatic plants in lakes on the TP. In the studied lakes, sedimentary δ13C values mainly reflect lake-level changes, as the species of aquatic plants with different δ13Corg values strongly respond to lake level. However, sedimentary δ13C values are much more sensitive to lake-level changes in a moderate-depth lake (~ 10 m) than those in a deep lake (~ 27 m) or a shallow lake (<3–5 m). In other words, the sedimentary δ13Corg may not effectively record lake-level changes on the TP when the lakes are deep (not sensitive) or shallow (only submerged plants). This relationship can be clearly seen in the case study in cores HY15 and GH02. The sedimentary δ13Corg trend in core HY15 was well correlated with the observed lake-level changes over the past 50 yr in Lake Qinghai. Based on the hypothesis that δ13Corg is indicative of lake-level changes, the lake-level change showed obvious millennial-scale oscillations in Lake Gahai (moderate lake) during the Holocene, but there were no obvious lake-level oscillations in Lake Qinghai (deep lake). In addition, the variation in the TOC/ON ratio suggested that sedimentary δ13Corg was often influenced by the contribution of terrestrial plants in Lake Gahai during the Holocene. Therefore, although δ13Corg was a very sensitive proxy of lake-level changes in lakes with maximum water depths ranging from 5 m to 20 m in lakes on the northeastern TP, we should consider the possible contribution of terrestrial plants when the sedimentary δ13Corg value is used as indicator of lake-level changes.
24542. 题目: Molecular and isotopic behavior of Insoluble Organic Matter of the Orgueil meteorite upon heating
文章编号: N19071807
期刊: Geochimica et Cosmochimica Acta
作者: Laurent Remusat, Jean-Yves Bonnet, Sylvain Bernard, Arnaud Buch, Eric Quirico
更新时间: 2019-07-18
摘要: Organic matter contained in carbonaceous chondrites may have evolved due to aqueous and/or thermal evolution on the parent body. The thermal behavior of the insoluble organic matter (IOM) of the Orgueil meteorite was investigated. The evolutions of structural and molecular properties were assessed by Raman, infrared and XANES spectroscopies, the H- and N-isotopic compositions by NanoSIMS. The starting IOM is a disordered organic macromolecule presenting a high degree of cross-linking. Hydrogen and Nitrogen isotope distributions are heterogeneous with the occurrence of numerous micron-sized hot spots enriched in heavy isotopes of H or N. After 1 hour at 300°C, there is subtle modification of the structural ordering and the isotopic compositions. After 1 hour at 500°C, the structure evolves toward condensation. Indeed, FTIR and XANES data are consistent with a continuous evolution of the molecular structure toward an increase of aromatization, starting at 300°C and becoming more intense at 500°C. The bulk D-enrichment is significantly reduced and D-rich hot spots are lost at 500°C. The experimental evolution of the δD is consistent with observations of IOM isolated from lightly altered carbonaceous chondrites. In contrast, the 15N-rich hot spots seem insensitive to high temperature up to 500°C and bulk δ15N remains constant. The thermal evolution of H- and N- isotopes is decoupled, indicating that the D-rich and 15N-rich moieties exhibit different thermal recalcitrance.
24543. 题目: Modern and late Pleistocene particulate organic carbon transport by the Amazon River: Insights from long-chain alkyl diols
文章编号: N19071806
期刊: Geochimica et Cosmochimica Acta
作者: Christoph Häggi, Enno Schefuß, André O. Sawakuchi, Cristiano M. Chiessi, Stefan Mulitza, Dailson J. Bertassoli, Jens Hefter, Matthias Zabel, Paul A. Baker, Stefan Schouten
更新时间: 2019-07-18
摘要: The relative abundance of the C32 1,15 long-chain alkyl diol (LCD) is an emerging proxy for the input of riverine aquatic particulate organic carbon (POC) into coastal oceans. This compound has the potential to complement other established proxies reflecting riverine terrestrial POC input and allows for a more nuanced assessment of riverine POC export to coastal seas. The current understanding of this proxy is, however, limited. In this study, we compare different indices for riverine sediment input to coastal marine waters (i.e. C32 1,15-LCD, BIT index and Fe/Ca ratio) in a source-to-sink assessment in the Amazon River drainage system and the northeast South American continental margin, and we test their down-core applicability in a marine gravity core containing late Pleistocene fluvial Amazonian sediments. We show that the relative abundance of the C32 1,15-LCD is highest in water bodies with low flow velocity and low turbidity such as the downstream portion of lowland tributaries and floodplain lakes. Relative C32 1,15-LCD abundance is lowest in Andean white water tributaries where autotrophic productivity is hindered by high turbidity and high flow velocity. We also find that suspended particulate matter from all major tributaries during the extreme 2015 dry season has a similar LCD distribution to that of floodplain lakes. This indicates that the chemical composition of the tributaries is less relevant for the LCD distribution than their physical properties such as flow velocity and turbidity. Results from marine surface sediments offshore the Amazon River estuary show significant positive correlations between all three studied proxies. In contrast, we find that the relative C32 1,15-LCD abundance in the down-core record is anti-correlated to the BIT index and Fe/Ca ratio. While BIT index and Fe/Ca ratio show high (low) values during Heinrich stadials (Dansgaard-Oeschger interstadials), the C32 1,15-LCD proxy shows the opposite signal. BIT values are also higher during Marine Isotope Stage (MIS) 2 than during MIS 3, in contrast to trends in the C32 1,15-LCD proxy. We posit that this pattern arises from a reduction in relative C32 1,15-LCD abundance and total LCD productivity in the Amazon River during MIS 2 when less-humid conditions and lower sea level led to reduced area of floodplains. During Heinrich stadials, Andean sediment input increased and led to higher turbidity that resulted in lower C32 1,15-LCD production. Our study shows that major changes in water discharge, sediment transport and river morphology can lead to discrepancies between the BIT index and the relative abundance of the C32 1,15-LCD. Thus, we suggest that Amazonian aquatic and terrestrial POC pools had contrasting responses to changes related to both climate (e.g. increased Andean precipitation) and river morphology (e.g. steeper along-channel slope due to falling and low stand sea level).
24544. 题目: Effects of biochar amendment on nitrogen mineralization in black soil with different moisture contents under freeze-thaw cycles
文章编号: N19071805
期刊: Geoderma
作者: Qiang Fu, Jiawen Yan, Heng Li, Tianxiao Li, Renjie Hou, Dong Liu, Yi Ji
更新时间: 2019-07-18
摘要: Freeze-thaw cycles (FTCs) affect the nitrogen cycling process in the non-growing season. To explore the effects of biochar application combined with soil moisture on nitrogen mineralization under FTCs, a laboratory FTC test of simulated soil columns was conducted. In this laboratory study, black soil from the Songnen Plain, China, was subjected to different biochar application rates (0%, 2% and 4%), moisture contents (15%, 20% and 25%) and numbers of FTCs (each FTC consisted of freezing at −20 °C for 48 h and thawing at 10 °C for 48 h). We explored the changes in soil moisture and aggregates as well as the effects of biochar application and different moisture contents on nitrogen availability under FTCs. The results showed that FTCs promoted the fragmentation and decomposition of soil aggregates, processes that are also related to the moisture content and biochar application rate. Moreover, the application of biochar increased the soil water holding capacity. The ammonium nitrogen and nitrate nitrogen contents in the soil first increased and then decreased during the FTCs and peaked after the third FTC. However, influenced by transfer and transformation processes, the inorganic nitrogen contents were higher than the initial levels after freezing and thawing. In addition, the content of ammonium nitrogen increased with increasing initial soil moisture content but decreased with increasing biochar application rate. However, the content of nitrate nitrogen increased with increasing initial soil moisture content and biochar application rate. Analysis of variance showed that FTCs and moisture content are the major driving factors that affect nitrogen mineralization (p < 0.05). This study provides guidance for the regulation of farmland soil nitrogen and the efficient utilization of agricultural resources in areas with seasonally frozen soil.
24545. 题目: Sources of black carbon in the atmosphere and in snow in the Arctic
文章编号: N19071804
期刊: Science of The Total Environment
作者: Ling Qi, Shuxiao Wang
更新时间: 2019-07-18
摘要: We systematically identify sources of black carbon (BC) in the Arctic, including BC in the troposphere, at surface and in snow, using tagged tracer technique implemented in a 3D global chemical transport model GEOS-Chem. We validate modeled BC sources (fossil fuel combustion versus biomass burning) against carbon isotope measurements at Barrow (Alaska), Zeppelin (Norway), Abisko (Sweden), Alert (Canada) and Tiksi (Russia) in the Arctic. The model reproduces the observed annual mean fraction of biomass burning (fbb, %) at the five sites within 20% and the observed and modeled monthly fbb values agree within a factor of two. Model results suggest that fossil fuel combustion is the major source of BC in the troposphere (50–94%, vary with sub-regions), at surface (55–68%) and in snow (58–69%) in the Arctic as annual mean, but biomass burning dominates at certain altitudes (600–800 hPa) and during periods of time between April to September. The model shows that BC in the troposphere, in deposition and in snow in different Arctic sub-regions have distinctively different sources and source regions. We find that long-range transport of Asian emissions has a stronger influence on BC in the atmosphere than on BC deposition. In contrast, contributions from Russian and European emissions are larger for BC deposition than for BC in the atmosphere. Specifically, Asian fossil fuel combustion emissions dominate BC loading in all Arctic sub-regions in both winter (Oct.–Mar., 35–54%) and summer (Apr.–Sep., 34–56%). For BC deposition, Siberian fossil fuel emissions are the largest contributors in Russia both in winter (62%) and summer (44%), and European fossil fuel emissions dominate in Ny-Ålesund (44% in winter) and Tromsø (71% in winter and 46% in summer). For BC deposition in the North American sector, Asian fossil fuel emissions are the largest contributors in winter (25–38%) and North American biomass burning emissions (38–72%) dominate in summer.
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24546. 题目: The distribution of arsenic fractions and alkaline phosphatase activities in different soil aggregates following four months As(V) ageing
文章编号: N19071803
期刊: Chemosphere
作者: Guannan Lu, Haixia Tian, Ziquan Wang, Huayong Li, Megharaj Mallavarapu, Wenxiang He
更新时间: 2019-07-18
摘要: Soil as a heterogeneous mass is composed of different size aggregates. The distribution of different arsenic (As) fractions in soil aggregates is vital to assess the potential risk of As pollution. In this study, soil samples were aged for 4 months with different arsenate [As(V)] concentrations. Dry sieving method was used to obtain five different size aggregates and the content of As in these fractions was determined. The results showed that P4 (0.1–0.25 mm) contained the highest organic matter (OM) than other size aggregates. After 4 months of ageing, available phosphorus (AP) content increased with the increase of As(V) concentration among 5 aggregates. The distribution of different arsenic fractions among 5 aggregates was similar. The relative contents of water-soluble (F1), exchangeable (F2) and carbonate (F3) fractions increased with the increase in As concentration, while the residual fraction (F7) decreased sharply. Humic-bound (F4), and Fe and Mn oxide bound fractions (F5) were about 35% and 20% respectively, after 4 months of As(V) ageing. Generally, the alkaline phosphatase (ALP) activities of P4 were lowest among five aggregates under each concentration of As(V). Moreover, F2 and F3 exhibited a strong inhibition of ALP activity. This study demonstrates that not only water-soluble and exchangeable arsenic but also humic-bound fraction should be considered when assessing As bioavailability and toxicity.
24547. 题目: Epiphytic bacterial community shift drives the nutrient cycle during Potamogeton malaianus decomposition
文章编号: N19071802
期刊: Chemosphere
作者: Bing Han, Felix Gyawu Addo, Xiaoying Mu, Lisha Zhang, Songhe Zhang, Xiaoyang Lv, Xin Li, Peifang Wang, Chao Wang
更新时间: 2019-07-18
摘要: Epiphytic bacteria on submerged macrophytes play important roles in the nutrient cycle in freshwater ecosystems. However, little is known about the composition and role of epiphytic bacteria during the decomposition of submerged macrophytes. In this study, the alterations in epiphytic bacterial composition, abundances of nitrogen cycle-related genes and nutrient release were investigated in a 56-day decomposition process of Potamogeton malaianus. The total reduced biomass was positively related to the contents of carbon, nitrogen and phosphorus released from plant residues. Nutrient released from plant litter showed a positively effect on the concentrations of carbon, nitrogen and phosphorus in the overlying water (p < 0.01). The carbon, phosphorus and nitrogen decreased with decomposition process in both plant debris and overlying water. Humic acid-like substances were the main component of dissolved organic matter in the conditioning stage, whereas fulvic acid-like substances dominated in the fragmentation stage. Results from network analysis and canonical correspondence analysis showed dominant bacterial clades changed with decomposition process. Bacteroidetes was the most abundant phylum in the leaching stage and Spirochaetes, Chlorobi, and Bacteroidetes dominated in the conditioning stage, while Chlorobi dominated in the fragmentation stage. The highest abundance of cnorB and nosZ were detected in the leaching and fragmentation stage, respectively. Bacterial denitrification contributed to nitrogen removal and might be promoted by high ORP and DOC concentration. Our results indicate that epiphytic bacterial community shift drived the metabolism of nutrients C, N, and S during the decomposition of P. malaianus.
24548. 题目: Biochar enabled syntrophic action: Solid state anaerobic digestion of agricultural stubble for enhanced methane production
文章编号: N19071801
期刊: Bioresource Technology
作者: Kunwar Paritosh, Vivekanand Vivekanand
更新时间: 2019-07-18
摘要: In this study, effect of hardwood biochar on solid state anaerobic digestion of wheat straw has been investigated. The concentration of biochar was 5, 10, 15, 20, 25 and 30 g/L and added in inoculum along with wheat straw for anaerobic action. Results showed that 10 g/L of hardwood biochar led to 2-fold increment in methane yield (223 L/kg VS) compared to the control (110 L/kg VS). However, increasing the concentration of hardwood biochar did not help in significant increase in methane yield and raised pH and alkalinity up to 8.3 and 24.3 g/L respectively. Principal component analysis showed that methane yield is positively correlated with volatile solid reduction while biochar loading is directly correlated with pH as well as alkalinity and inversely correlated with total volatile fatty acid. This study revealed that biochar may help to maintain syntrophy in the anaerobic reactor and enhance methane yield significantly.
24549. 题目: pH Dependence of Arsenic Oxidation by Rice-Husk-Derived Biochar: Roles of Redox-Active Moieties
文章编号: N19071721
期刊: Environmental Science & Technology
作者: Delai Zhong, Yi Jiang, Zezhou Zhao, Linling Wang, Jing Chen, Shupeng Ren, Zhenhua Liu, Yanrong Zhang, Daniel C. W. Tsang, John C. Crittenden
更新时间: 2019-07-17
摘要: Biochars have demonstrated great potential for water decontamination and soil remediation; however, their redox reactivity toward trace contaminants and the corresponding redox-active moieties (RAMs, i.e., phenolic −OH, semiquinone-type persistent free radicals (PFRs), and quinoid C═O) remain poorly understood. Here we investigated the roles of the RAMs on biochar in oxidation of As(III) under varying pH and O2 conditions. The results showed that the promoted oxidation of As(III) by the RAMs is strongly pH dependent. Under acidic and neutral conditions, only the oxidation of As(III) by •OH and H2O2 produced from activation of O2 by phenolic −OH and semiquinone-type PFRs occurred. In contrast, the oxidation by semiquinone-type PFRs, quinoid C═O, and H2O2 (if O2 was introduced) appeared under alkaline conditions. This pH-dependent oxidation behavior was attributed to the varying redox activities of RAMs, as confirmed by multiple characterization and validation experiments using biochar with tuned RAMs compositions, as well as thermodynamics evaluation. Our findings provide new insights into the roles of the RAMs on biochar in the promoted oxidation of trace As(III) over a broader pH range under both anoxic and oxic conditions. This study also paves a promising way to oxidize As(III) with biochar.
24550. 题目: An effective biochar-based slow-release fertilizer for reducing nitrogen loss in paddy fields
文章编号: N19071720
期刊: Journal of Soils and Sediments
作者: Da Dong, Cheng Wang, Lukas Van Zwieten, Hailong Wang, Peikun Jiang, Minmin Zhou, Weixiang Wu
更新时间: 2019-07-17
摘要: Purpose: As a carbon sequestration material, biochar has attracted much attention due to its potential to enhance rice productivity and nitrogen retention in paddy fields. However, little information is available about the impacts of rice straw-derived biochar on coating materials of slow-release fertilizers especially with bentonite, starch, and humic acid. Materials and methods: In this study, a biochar-based slow-release fertilizer was developed and evaluated at field scale. An orthogonal experimental design was applied to investigate the blending ratios of biochar, humic acid, and bentonite with three adhesives, and how these influenced N release. Results and discussion: The optimum coating combination was 25% biochar, 4% bentonite, and 10% humic acid with modified cornstarch as the adhesive (herein referred to as CF10). The product not only decreased N leaching and runoff losses at the seeding and tillering stages but also supplied more nutrients to the rice at the heading and maturing stages. The SEM and FT-IR observations revealed that an effective dense layer was formed that slowed N release from the granule. Conclusions: Laboratory- and field-scale studies showed that biochar has played a crucial role in developing a slow-release coating for the compound fertilizer based on its structural properties, porosity, and chemical interaction with other coating ingredients. We conclude that biochar-based slow-release fertilizer is a promising alternative N fertilizer for rice production.
24551. 题目: The contrasting roles of aquatic fungi and oomycetes in the degradation and transformation of polymeric organic matter
文章编号: N19071719
期刊: Limnology and Oceanography
作者: Hossein Masigol, Seyed Akbar Khodaparast, Jason Nicholas Woodhouse, Keilor Rojas‐Jimenez, Jeremy Fonvielle, Forough Rezakhani, Reza Mostowfizadeh‐Ghalamfarsa, Darshan Neubauer, Tobias Goldhammer, Hans‐Peter Grossart
更新时间: 2019-07-17
摘要: Studies on the ecological role of fungi and, to a lesser extent, oomycetes, are receiving increasing attention, mainly due to their participation in the cycling of organic matter in aquatic ecosystems. To unravel their importance in humification processes, we isolated several strains of fungi and oomycetes from Anzali lagoon, Iran. We then performed taxonomic characterization by morphological and molecular methods, analyzed the ability to degrade several polymeric substrates, performed metabolic fingerprinting with Ecoplates, and determined the degradation of humic substances (HS) using liquid chromatography‐organic carbon detection. Our analyses highlighted the capacity of aquatic fungi to better degrade a plethora of organic molecules, including complex polymers. Specifically, we were able to demonstrate not only the utilization of these complex polymers, but also the role of fungi in the production of HS. In contrast, oomycetes, despite some morphological and physiological similarities with aquatic fungi, exhibited a propensity toward opportunism, quickly benefitting from the availability of small organic molecules, while exhibiting sensitivity toward more complex polymers. Despite their contrasting roles, our study highlights the importance of both oomycetes and fungi in aquatic organic matter transformation and cycling with potential implications for the global carbon cycle.
24552. 题目: Ocean acidification alters meiobenthic assemblage composition and organic matter degradation rates in seagrass sediments
文章编号: N19071718
期刊: Limnology and Oceanography
作者: Chiara Ravaglioli, Claudio Lardicci, Antonio Pusceddu, Eleonora Arpe, Silvia Bianchelli, Emanuela Buschi, Fabio Bulleri
更新时间: 2019-07-17
摘要: Seagrass meadows are an important organic matter (OM) reservoir but, are currently being lost due to global and regional stressors. Yet, there is limited research investigating the cumulative impacts of anthropogenic stressors on the structure and functioning of seagrass benthic assemblages, key drivers of OM mineralization and burial. Here, using a 16‐month field experiment, we assessed how meiobenthic assemblages and extracellular enzymatic activities (as a proxy of OM degradation) in Posidonia oceanica sediments responded to ocean acidification (OA) and nutrient loadings, at CO2 vents. P. oceanica meadows were exposed to three nutrient levels (control, moderate, and high) at both ambient and low pH sites. OA altered meiobenthic assemblage structure, resulting in increased abundance of annelids and crustaceans, along with a decline in foraminifera. In addition, low pH enhanced OM degradation rates in seagrass sediments by enhancing extracellular enzymatic activities, potentially decreasing the sediment carbon storage capacity of seagrasses. Nutrient enrichment had no effect on the response variables analyzed, suggesting that, under nutrient concentration unlikely to cause N or P imitation, a moderate increase of dissolved nutrients in the water column had limited influence on meiobenthic assemblages. These findings show that OA can significantly alter meiobenthic assemblage structure and enhance OM degradation rates in seagrass sediments. As meiofauna are ubiquitous key actors in the functioning of benthic ecosystems, we postulated that OA, altering the structure of meiobenthic assemblages and OM degradation, could affect organic carbon sequestration over large spatial scales.
24553. 题目: Testing various scenarios to improve circulation in Golden Horn: A case study
文章编号: N19071717
期刊: Marine Pollution Bulletin
作者: Tarkan Erdik, Olgay Şen, İzzet Öztürk
更新时间: 2019-07-17
摘要: The Golden Horn (GH), as a consequence of heavy domestic and industrial discharges from Alibeykoy and Kagithane creeks, was heavily polluted for more than 50 years. As a result, the upstream area was filled with debris and organic solids, which produced unbearable odour in the past due to anaerobic decomposition of the organic matter in the sedimented zone. Istanbul Metropolitan Municipality (IBB) decided to develop new strategies of estuary management and pollution reduction. To this end, Golden Horn Environment Protection Project (GHEPP) was developed to transport 3m3/s of clean Black Sea water into GH through a diversion tunnel to keep circulation ongoing throughout the year. In this study, the performance of GHEPP is assessed by developing various scenarios. The relationship between Black Sea diversion flow (BSDF) and residence time is derived. The numerical tests highlight that BSDF is effective in reducing the residence time in the upstream, while in the downstream, exchange flows with the Bosphorus Strait (BS) is effective. Besides, the current patterns in the GH and exchange flow discharges with the BS are determined for three unique flow conditions occurring in the strait: (1) two-layer flow pattern, (2) one-layer flow patterns in the southern direction, and (3) one-layer flow pattern in the northern direction.
24554. 题目: Composition variations and spatiotemporal dynamics of dissolved organic matters during the occurrence of green tide (Ulva prolifera blooms) in the Southern Yellow Sea, China
文章编号: N19071716
期刊: Marine Pollution Bulletin
作者: Xiuzhu Li, Conghe Li, Ying Bai, Xiaoyong Shi, Rongguo Su
更新时间: 2019-07-17
摘要: Seawater samples were collected from April 6 to September 6, 2017 in the Southern Yellow Sea, China where green tides often occurred, and analyzed for nutrients, dissolved organic carbon (DOC), and fluorescent dissolved organic matter (FDOM). The DOC concentrations increased significantly in the green tide areas by approximately 1.2 times compared to those in the non-green tide areas. From the large-scale outbreak to the complete dissipation of the green tide, the fluorescence intensities of the four FDOM fluorescent components identified in the green tide areas were significantly higher than those in the non-green tide areas. During the extinction period, the fluorescence intensities of the three humus-like components and one protein-like component were approximately 1.8 and 1.3 times higher than those in the non-green tide areas, respectively. These findings suggested that the outbreak of green tide could release DOM into water and affect the biogeochemical cycle in green tide regions.
24555. 题目: Lipid biomarker temperature proxy responds to abrupt shift in the bacterial community composition in geothermally heated soils
文章编号: N19071715
期刊: Organic Geochemistry
作者: Cindy De Jonge, Dajana Radujković, Bjarni D Sigurdsson, James T. Weedon, Ivan Janssens, Francien Peterse
更新时间: 2019-07-17
摘要: Specific soil bacterial membrane lipids, branched glycerol dialkyl glycerol tetraethers (brGDGTs), are used as an empirical proxy for past continental temperatures. Their response to temperature change is assumed to be linear, caused by physiological plasticity of their, still unknown, source organisms. A well-studied set of geothermally warmed soils (Iceland) shows that the brGDGT fingerprint only changes when the soil mean annual temperature is warmer than 14 °C. This sudden change in brGDGT distribution coincides with an abrupt shift in the bacterial community composition in the same soils. Determining which bacterial OTUs are indicative for each soil cluster shows that Acidobacteria are possible brGDGT producers, together with representatives from the Actinobacteria, Chloroflexi, Gemmationadetes and Proteobacteria. Projecting the lipid fingerprint of the cold and warm bacterial communities onto the global soil calibration dataset creates two distinct soil clusters, in which brGDGTs respond differently to temperature and, especially, soil pH. We show that, on a local scale, a community effect rather than physiological plasticity can be the primary driver of the brGDGT-based paleothermometer along large temperature gradients. This threshold response needs to be taken into account when interpreting brGDGT-based paleo-records.
24556. 题目: Biogeochemical evidence for environmental changes of Pleistocene Lake Olduvai during the transitional sequence of OGCP core 2A that encompasses Tuff IB (~1.848 Ma)
文章编号: N19071714
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Andrea M. Shilling, Devon E. Colcord, Jonathan Karty, Angela Hansen, Katherine H. Freeman, Jackson K. Njau, Ian G. Stanistreet, Harald Stollhofen, Kathy D. Schick, Nicholas Toth, Simon C. Brassell
更新时间: 2019-07-17
摘要: Olduvai Gorge is renowned for discoveries of hominin fossils and tools in a well-resolved sedimentary context, representing one of the foremost sites in East Africa that has afforded critical evidence of hominin evolution. In 2014, the Olduvai Gorge Coring Project (OGCP) recovered the first deep sediment cores from this location. These cores provide the first opportunity to examine an extensive stratigraphic record from one location and independent of the weathering and related degradation typical of outcrop samples. Samples from these cores have been correlated to Bed I tuffs and basalt marker beds that are well characterized from outcrops within the gorge. This study focuses on the biogeochemical investigation of a ~10 m segment from OGCP sediment core 2A, where age constraints indicate deposition occurred over ~50,000 years (from 1.8055 ± 0.003 Ma to 1.8551 ± 0.013 Ma). The segment includes Tuff IB and IF, which were deposited at a time that prior research indicates represents marked changes in the paleoenvironment at Olduvai, with indications that Paleolake Olduvai may have been completely desiccated by the time Tuff IF was deposited. This environmental change is recorded by the composition of sedimentary organic matter (OM) in terms of bulk organic geochemical properties observed as a decrease in % TOC and δ13Corg. In addition, temporal variations in source-specific biomarkers (n-alkanes, phytane, steradienes, A-norsteranes and alkenones) reflect a shift from a deeper lake setting with a prevalence of aquatic-sourced OM combined with input from terrestrial plant waxes to a more shallow, perennial lake where evidence of burrows and erosional surfaces is associated with microbially degraded OM and intermittent aquatic biomarkers. Thus, variations in biogeochemical proxies complement the sedimentological evidence confirming increased periods of prolonged desiccation of Paleolake Olduvai beginning around the time of Tuff IB deposition.
24557. 题目: Characterization of biocomposite using coconut oil impregnated biochar as latent heat storage insulation
文章编号: N19071713
期刊: Chemosphere
作者: Jisoo Jeon, Ji Hun Park, Seunghwan Wi, Sungwoong Yang, Yong Sik Ok, Sumin Kim
更新时间: 2019-07-17
摘要: Objective of this research was to characterize properties of the latent heat storage biocomposite (LHSBC) as a novel material that can be employed as a latent heat storage insulation by using biochar. Biochars produced from waste material pine cone, pine saw dust, and paper mill sludge were vacuum impregnated with a bio-based phase change material (PCM), coconut oil, to prepare LHSBCs. In particular, this paper analyzed the chemical stability, latent heat storage performance, thermal conductivity, and thermal stability of LHSBCs based on results of fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), laser flash method and thermogravimetric analysis (TGA). As a result, the LHSBCs showed a maximum latent heat storage capacity of 74.6 J/g and a low thermal conductivity of 0.030 W/mK at the maximum, confirming that LHSBCs have a high latent heat storage capacity and thermal insulation performance. With a maximum specific heat of 1.69 J/gK, a high, sensible heat storage was confirmed. In addition, all LHSBCs were found to be thermally and chemically stable. The LHSBC could be employed as a material with good thermal insulation performance and heat storage characteristics.
24558. 题目: Metal oxyanion removal from wastewater using manganese-oxidizing aerobic granular sludge
文章编号: N19071712
期刊: Chemosphere
作者: Zhanfei He, Zhen Wei, Qingying Zhang, Jinte Zou, Xiangliang Pan
更新时间: 2019-07-17
摘要: As, Sb, and Cr are redox-sensitive and toxic heavy metal(loid)s, and redox reactions are usually involved in the treatment of substrates containing these elements. In this study, manganese-oxidizing aerobic granular sludge (Mn-AGS) was obtained by continuously adding Mn(II) to the sludge in a sequencing batch reactor (SBR). Morphological observations, and analyses of extracellular polymeric substances (EPS), Mn valence-states, and microbial communities were performed on the resulting sludge. After 50 days of cultivation, biogenic Mn(III,IV) oxides (bio-MnOx) accumulated up to approximately 25 mg Mn/g suspended solids (SS). X-ray photoelectron spectroscopy (XPS) revealed that the percentage of Mn(III,IV) was 87.6%. The protein (PN) component in EPS increased from 80.3 to 87.8 mg/g volatile suspended solids (VSS) during cultivation, which might be favorable for sludge granulation and heavy metal(loid) removal. Batch experiments showed that Mn-AGS was better at oxidizing As(III)/Sb(III) into less toxic As(V)/Sb(V) than traditional AGS. Remarkably, the results indicated that Mn-AGS did not oxidize Cr(III) but was able to reduce Cr(VI) into relatively harmless Cr(III). This work provided a new promising method with which to treat As(III), Sb(III), and Cr(VI) in wastewaters.
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24559. 题目: Adsorption site-dependent transport of diclofenac in water saturated minerals and reference soils
文章编号: N19071711
期刊: Chemosphere
作者: Chenglong Yu, Erping Bi
更新时间: 2019-07-17
摘要: Use of reclaimed water for irrigation is a main way for pharmaceutical compounds such as diclofenac getting into the soil environment. However, the role of minerals, especially iron oxides, in the diclofenac adsorption to soils with low soil organic matter (SOM) is still in the lack of evaluation. In this study, adsorption of diclofenac onto six minerals (five nature minerals-hematite, goethite, magnetite, kaolinite and aluminium oxide and one engineered mineral-activated aluminia) and five reference soils was investigated by column chromatography. Adsorption of diclofenac onto minerals and soils was totally reversible and interactions such as H-bonding were the primary mechanisms. Adsorption affinity of iron oxides was much higher than that of nature silicon and aluminum oxides. Diclofenac tended to be adsorbed by mineral surface -OH groups with high thermodynamic stability, which were dehydroxylated at high temperature. Compared with the SOM-dominated sorption of naphthalene, adsorption of diclofenac onto soils was controlled by bonding with surface -OH groups of iron oxides. Adsorption coefficients of diclofenac onto soils can be well predicted by contents of extracted Fe by diethylenetriamine pentaacetic acid (DTPA) instead of total iron oxides contents, suggesting that the bonding was adsorption site-dependent. These findings highlighted the importance of iron oxides in the adsorption of diclofenac (an anionic pharmaceutical compound) in soils with relatively low SOM (e.g., 1.03-3.45%). It also indicated that contents of effective surface -OH groups and DTPA-Fe were the promising parameters to develop the predictive models for diclofenac adsorption onto minerals and soils, respectively.
24560. 题目: Loss of soil organic carbon following natural forest conversion to Chinese fir plantation
文章编号: N19071710
期刊: Forest Ecology and Management
作者: Zhijie Yang, Shidong Chen, Xioafei Liu, Decheng Xiong, Chao Xu, Mary A. Arthur, Rebecca L. McCulley, Sihong Shi, Yusheng Yang
更新时间: 2019-07-17
摘要: China manages the largest area of forest plantations on the globe, with most of them converted from natural forests. Establishment and management of forest plantations often involves severe human disturbances such as slash burning and intense site preparation which could lead to rapid and substantial soil organic carbon (SOC) losses and affect long-term SOC recovery. In this study we examined SOC dynamics and soil microbial respiration following the conversion of natural secondary forest to a Chinese fir plantation with slash burning in southern China. SOC decreased by 28% in the first year after forest conversion, with more than 40% of the decrease due to volatilization from slash burning. Slash burning also increased soil microbial respiration in the first five months following forest conversion. SOC of the Chinese fir plantation did not recover to the pre-burning level in 40-years, indicating that the loss of SOC is a long-term phenomenon in forest conversion. We found that soil microbial respiration was largely controlled by photosynthesis in the natural secondary forest; however, both newly formed photosynthates and SOC were important C sources for soil microorganisms in the young Chinese fir plantation. The intensive burning of harvest residue not only induced direct SOC losses through volatilization, but may also have accelerated the decomposition of SOC in the first few years after forest conversion. We conclude that slash burning is the primary, initial pathway by which SOC is lost in these subtropical forest plantations, and that the recovery of SOC in this subtropical forest system will likely be a slow process, requiring centuries or more. Replacing natural forest with Chinese fir plantations using slash burning is likely to substantially deplete C stored in the soil for many years and may negatively affect long-term SOC sequestration potential.