19年6月18日文獻情報
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本次文獻簡報涉及海洋低氧區微生物對有機質的利用[1]，全球陸地模型估計全球土壤有機碳[2]，土壤NOM對碘的吸收[3]，微生物胞外聚合物保護細胞免受礬的結合[4]，海洋生物泵對顆粒態NOM輸移的影響[5]，不穩定NOM微生物強化水稻土中磷的動員[6]。1. 題目: High bacterial organic carbon uptake in the Eastern Tropical South Pacific oxygen minimum zone文章編號: N19061806
期刊: Biogeosciences Discussions
作者: Marie Maßmig, Jan Lüdke, Gerd Krahmann, Anja Engel
更新時間: 2019-06-18
摘要: Oxygen minimum zones (OMZs) show distinct biogeochemical processes that relate to microorganisms being able to thrive under low or even absent oxygen. Microbial degradation of organic matter is expected to be reduced in OMZs, although quantitative evidence is low. Here, we present heterotrophic bacterial production (3H leucine-incorporation), extracellular enzyme rates (leucine aminopeptidase/ß-glucosidase) and bacterial cell abundance for various in situ oxygen concentrations in the water column of the Eastern Tropical South Pacific off Peru. Bacterial heterotrophic activity in the suboxic core of the OMZ (at in situ ≤ 5 µmol O2 kg−1) ranged from 0.6 to 160 µmol C m−3 d−1 and was not significantly lower than in waters of 5–60 µmol O2 kg−1. Moreover, bacterial abundance in the OMZ was slightly and leucine aminopeptidase activity even significantly higher in suboxic waters compared to the upper oxycline suggesting no impairment of bacterial organic matter degradation in the core of the OMZ. Nevertheless, high cell-specific bacterial production and extracellular enzyme rates were observed in samples from the upper or lower oxyclines corroborating earlier findings of highly active and distinct micro-aerobic bacterial communities. To assess the impact of bacterial degradation of dissolved organic matter for oxygen loss in the Peruvian OMZ, we compared diapycnal fluxes of oxygen and dissolved organic carbon (DOC) and their microbial uptake within the upper 60 m of the water column. Our data indicate bacterial growth efficiencies of 0.5–8.6 % at the upper oxycline, resulting in a high bacterial oxygen demand that can explain up to 33 % of the observed average oxygen loss over depth. Our study therewith shows that microbial degradation of DOM has a considerable share in sustaining the OMZ off Peru.
文章二維碼:2. 題目: Comparison With Global Soil Radiocarbon Observations Indicates Needed Carbon Cycle Improvements in the E3SM Land Model文章編號: N19061805
期刊: Journal of Geophysical Research: Biogeosciences
作者: Jinsong Chen, Qing Zhu, William J. Riley, Yujie He, James T. Randerson, Susan Trumbore
更新時間: 2019-06-18
摘要: We evaluated global soil organic carbon (SOC) stocks and turnover time predictions from a global land model (ELMv1‐ECA) integrated in an Earth System Model (E3SM) by comparing them with observed soil bulk and Δ14C values around the world. We analyzed observed and simulated SOC stocks and Δ14C values using machine learning methods at the Earth System Model grid cell scale (~200 km). In grid cells with sufficient observations, the model provided reasonable estimates of soil carbon stocks across soil depth and Δ14C values near the surface but underestimated Δ14C at depth. Among many explanatory variables, soil albedo index, soil order, plant function type, air temperature, and SOC content were major factors affecting predicted SOC Δ14C values. The influences of soil albedo index, soil order, and air temperature were primarily important in the shallow subsurface (≤30 cm). We also performed sensitivity studies using different vertical root distributions and decomposition turnover times and compared to observed SOC stock and Δ14C profiles. The analyses support the role of vegetation in affecting soil carbon turnover, particularly in deep soil, possibly through supplying fresh carbon and degrading physical‐chemical protection of SOC via root activities. Allowing for grid cell‐specific rooting and decomposition rates substantially reduced discrepancies between observed and predicted Δ14C values and SOC content. Our results highlight the need for more explicit representation of roots, microbes, and soil physical protection in land models.
文章二維碼:3. 題目: Sorption of iodine in soils: insight from selective sequential extractions and X-ray absorption spectroscopy文章編號: N19061804
期刊: Environmental Science and Pollution Research
作者: Fabian Köhler, Beate Riebe, Andreas C. Scheinost, Claudia König, Alex Hölzer, Clemens Walther
更新時間: 2019-06-18
摘要: The environmental fate of iodine is of general geochemical interest as well as of substantial concern in the context of nuclear waste repositories and reprocessing plants. Soils, and in particular soil organic matter (SOM), are known to play a major role in retaining and storing iodine. Therefore, we investigated iodide and iodate sorption by four different reference soils for contact times up to 30 days. Selective sequential extractions and X-ray absorption spectroscopy (XAS) were used to characterize binding behavior to different soil components, and the oxidation state and local structure of iodine. For iodide, sorption was fast with 73 to 96% being sorbed within the first 24 h, whereas iodate sorption increased from 11–41% to 62–85% after 30 days. The organic fraction contained most of the adsorbed iodide and iodate. XAS revealed a rapid change of iodide into organically bound iodine when exposed to soil, while iodate did not change its speciation. Migration behavior of both iodine species has to be considered as iodide appears to be the less mobile species due to fast binding to SOM, but with the potential risk of mobilization when oxidized to iodate.
文章二維碼:4. 題目: Insights into interactions between vanadium (V) bio-reduction and pentachlorophenol dechlorination in synthetic groundwater文章編號: N19061803
期刊: Chemical Engineering Journal
作者: Baogang Zhang, Yutong Cheng, Jiaxin Shi, Xuan Xing, Yuling Zhu, Nan Xu, Jianxin Xia, Alistair G.L. Borthwick
更新時間: 2019-06-18
摘要: Aquifer co-contamination by vanadium (V) and pentachlorophenol (PCP) involves complicated biogeochemical processes that remain poorly understood, particularly from the perspective of microbial metabolism. Batch experiment results demonstrated that V(V) and PCP could be competitively bio-reduced, with 96.0 ± 1.8% of V(V) and 43.4 ± 4.6% of PCP removed during 7 d operation. V(V) was bio-transformed to vanadium (IV), which could precipitate naturally under circumneutral conditions, facilitating the removal of up to 78.2 ± 3.1% dissolved total V. The PCP reductive dechlorination products were mainly 2,4,6-trichlorophenol and 4-monochlorophenol with lower toxicity. High-throughput 16S rRNA gene sequencing indicated that Pseudomonas, Soehngenia, and Anaerolinea might be responsible for the two bio-transformations, with detected functional genes of nirS and cprA. Extracellular reduction by cytochrome c and intracellular conversion by nicotinamide adenine dinucleotide (NADH) occurred for both V(V) and PCP. Extracellular proteins in microbial-secreted extracellular polymeric substances (EPS) might also be involved in these enzymatic bioprocesses. EPS could protect microbial cells through V(V) binding by the chemically reactive carboxyl (COO−), and hydroxyl (–OH) groups. These findings elucidate the metabolic processes during anaerobic V(V) and PCP biotransformation, advance understanding of their biogeochemical fates, and provide a foundation on which to develop novel strategies for remediation of co-contaminated aquifers.
文章二維碼:5. 題目: Exploring the ecology of the mesopelagic biological pump文章編號: N19061802
期刊: Progress in Oceanography
作者: E.L. Cavan, E.C. Laurenceau-Cornec, M. Bressac, P.W. Boyd
更新時間: 2019-06-18
摘要: The oceans』 biological pump (BP) exports large amounts of particulate organic carbon (POC) to the mesopelagic zone (base of the euphotic zone – 1000 m depth). The efficiency at which POC is transferred through the mesopelagic zone determines the size of the deep ocean carbon store. Few observational BP studies focus on the mesopelagic, often leading to the need to oversimplify the representation of processes within this depth horizon in numerical models. In this review, we identify and describe three interlinked biological processes that act to regulate and control the transfer efficiency of POC through the mesopelagic zone; 1) direct sinking of phytoplankton cells and aggregates, 2) zooplankton community structure and 3) the microbial loop and associated carbon pump. We reveal previously unidentified relationships between planktonic community structure and POC transfer efficiency for specific regions. We also compare mesopelagic POC remineralisation depth (a proxy for POC transfer efficiency) with the permanent thermocline in different regions. Our analysis shows that even when mesopelagic POC transfer efficiency is low, such a transfer efficiency does not necessarily mean low carbon sequestration if the permanent thermocline is shallow, and we define a carbon sequestration ratio (Cseq, the remineralisation depth divided by the permanent thermocline) to highlight this. Low latitude regions typically have a higher Cseq than temperate and polar regions, and thus could be more important in transferring carbon on long timescales than previously thought. POC transfer efficiency should be regularly discussed in the context of the physical water properties such as the permanent thermocline, to truly assess an oceanic region’s ability to sequester carbon. Improved understanding of mesopelagic ecological processes and links to surface processes will better constrain ecosystem models and improve projections of the future global carbon cycle.
文章二維碼:6. 題目: Labile organic matter intensifies phosphorous mobilization in paddy soils by microbial iron (III) reduction文章編號: N19061801
期刊: Geoderma
作者: Imran Khan, Shah Fahad, Lei Wu, Wei Zhou, Peng Xu, Zheng Sun, Abdus Salam, Muhammad Imran, Mengdie Jiang, Yakov Kuzyakov, Ronggui Hu
更新時間: 2019-06-18
摘要: Iron (Fe) is one of the most abundant elements in the earth's crust and intensively interferes with the biogeochemical cycles of carbon (C) and phosphorous (P), especially in highly weathered tropical and subtropical soils. The strong affinity of phosphate to Fe oxides and hydroxides limits the P availability in paddy soils. Reductive dissolution of Fe(III) can release occluded and adsorbed P into solution and make it available for plant uptake. Such effects remain elusive, especially in highly weathered subtropical paddy soils with oscillating redox (Eh) conditions. Under submerged conditions, incomplete litter decomposition occurs and rice roots release large amounts of labile organic compounds as exudates. We investigated the role of acetate, formate, oxalate, and propionate on Fe(III) reduction, P mobilization, and CO2 efflux in two paddy soils (i.e. oxisol and ultisol) of varying organic C (OC) and Fe(II) contents. Microbial mineralization of added labile C decreased soil Eh and increased the rates of Fe(III) reduction followed by P mobilization. This indicated that microbially-mediated Fe(III) reduction was intensified by labile OC compounds, which acted as energy sources and electron donors. The release of available P via Fe reduction was accompanied by peaks in Fe(II), dissolved OC, and pH and was followed by a decrease in iron-bound P (FeP). This implied that FeP was the main source of available P in the paddy soils. The faster release of available P in the oxisol than the ultisol indicated that the higher OC and Fe(II) contents in the oxisol allowed a fast Eh decrease, leading to rapid microbial oxygen (O2) consumption and consequently faster and more intensive Fe(III) to Fe(II) reduction. This conclusion is supported by a faster Eh decrease in the oxisol than the ultisol corresponding to early P mobilization after input of labile C, and it suggests that Eh-driven Fe transformations and P mobilization are strongly modulated by labile OC mineralization.
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