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Production Mechanism and Emissions of CO2 in Water Networks of an Agricultural Watershed during Drainage Period 排水期农业流域水网中的二氧化碳生成机制和排放量
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-07-03 DOI: 10.1021/acsearthspacechem.4c00077
Xia Li, Kaiming Liu, Hai Zhang, Xinyi Dong, Li Bai, Xiaolong Liu, Jun Li, Mingguo Wang
Growing evidence shows that water networks in agricultural watersheds, including rivers, paddy fields (PFs), and ditches (DCs), are hotspots of aquatic greenhouse gas emissions globally. However, the knowledge of the role of natural processes and anthropogenic activities, including agricultural practices, in promoting CO2 production and emissions still remains unclear. In this study, sampling and analysis of different surface waters during the agricultural drainage period were conducted to clarify the production mechanism and emission of CO2. The results showed that all of the surface waters in the Nongjiang River (NJR) watershed acted as sources with respect to atmospheric CO2, while a few in the Honghe Wetland and the estuary acted as CO2 sinks. Longitudinal variations of CO2 in mainstreams of the NJR indicated that fertilizer application, manure, and sewage discharges stimulated the CO2 production, while those in the Yalu River (YLR) were mainly affected by the natural wetlands. The accumulation of carbon and nitrogen in waters of PF and DC have enhanced CO2 emissions during drainage periods. The high ratio of ΔCO2/ΔO2 revealed the important role of the extensive respiration in CO2 production in the NJR. Furthermore, the correlation between dissolved oxygen and CO2 demonstrated that respiration and photosynthesis dominated CO2 production and consumption in all types of water bodies. This study implied that agricultural water networks might be vague sources for aquatic systems, and effort is still urgently needed to quantitatively assess the CO2 emissions in the context of wetland–farmland shifts regionally and worldwide.
越来越多的证据表明,农业流域的水网,包括河流、水田(PFs)和沟渠(DCs),是全球水生温室气体排放的热点。然而,人们对自然过程和人为活动(包括农业实践)在促进二氧化碳产生和排放方面所起作用的认识仍不清楚。本研究对农业排水期的不同地表水进行了采样和分析,以明确二氧化碳的产生和排放机制。结果表明,邕江流域的所有地表水都是大气二氧化碳的源,而红河湿地和河口的少数地表水则是二氧化碳的汇。长江干流二氧化碳的纵向变化表明,施肥、粪便和污水排放刺激了二氧化碳的产生,而鸭绿江干流则主要受天然湿地的影响。在排水期,PF 和 DC 水体中碳和氮的积累增加了 CO2 排放。ΔCO2/ΔO2的高比值揭示了广泛的呼吸作用在南京江河二氧化碳生成中的重要作用。此外,溶解氧与 CO2 之间的相关性表明,在所有类型的水体中,呼吸作用和光合作用都主导着 CO2 的产生和消耗。这项研究表明,农业水网可能是水生系统的模糊来源,目前仍迫切需要努力定量评估区域和全球湿地-农田转变过程中的二氧化碳排放量。
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引用次数: 0
Better use the following title: Pathways to Interstellar Amides via Carbamoyl (NH2CO) Isomers by Radical-Neutral Reactions on Ice Grain Mantles 最好使用以下标题通过冰粒表面的辐射-中性反应,通过氨基甲酰基(NH2CO)异构体获得星际酰胺的途径
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-07-03 DOI: 10.1021/acsearthspacechem.4c00106
Gabriela Silva-Vera, Giulia M. Bovolenta, Namrata Rani, Sebastian Vera, Stefan Vogt-Geisse
Explaining the formation pathways of amides on ice-grain mantels is crucial to understanding the prebiotic chemistry in an interstellar medium. In this computational study, we explore different radical-neutral formation pathways for some of the observed amides (formamide, acetamide, urea, and N-methylformamide) via intermediate carbamoyl (NH2CO) radical precursors and their isomers. We assess the relative energy of four NH2CO isomers in the gas phase and evaluate their binding energy on small water clusters to discern the affinity that the isomers present to an ice model. We consider three possible reaction pathways for the formation of the carbamoyl radicals, namely, the OH + HCN, CN + H2O, and NH2 + CO reaction channels. We computed the binding energy distribution for the HCN and CH3CN precursors on an ice model consisting of a set of clusters of 22 water molecules each to serve as a starting point for the reactivity study on the ice surface. The computations revealed that the lowest barrier to the formation of an NH2CO isomer corresponds to the NH2 + CO reaction (12.6 kJ mol–1). The OH + HCN reaction pathway results in the exothermic formation of the N-radical form of carbamoyl HN(C═O)H with a reaction barrier of 26.7 kJ mol–1. We found that the CN + H2O reaction displays a high energy barrier of 70.6 kJ mol–1. Finally, we also probed the direct formation of the acetamide radical precursor via the OH + CH3CN reaction and found that the most probable outcome on interstellar ices is the H-abstraction reaction to yield CH2CN and H2O. Based on these results, we believe that including alternative reaction pathways, leading to the formation of amides via the N-radical form of carbamoyl, would provide an improvement in the prediction of the amide abundances in astrochemical models, especially regarding the chemistry of star-forming regions.
解释冰粒幔上酰胺的形成途径对于理解星际介质中的前生物化学至关重要。在这项计算研究中,我们通过中间氨基甲酰基(NH2CO)自由基前体及其异构体,探索了一些观测到的酰胺(甲酰胺、乙酰胺、脲和 N-甲基甲酰胺)的不同自由基中性形成途径。我们评估了四种 NH2CO 异构体在气相中的相对能量,并评估了它们与小水团簇的结合能,以确定这些异构体对冰模型的亲和力。我们考虑了形成氨基甲酰基的三种可能反应途径,即 OH + HCN、CN + H2O 和 NH2 + CO 反应途径。我们计算了 HCN 和 CH3CN 前体在冰模型上的结合能分布,冰模型由一组各含 22 个水分子的簇组成,作为冰表面反应性研究的起点。计算显示,NH2CO 异构体形成的最低障碍对应于 NH2 + CO 反应(12.6 kJ mol-1)。OH + HCN 反应途径导致氨基甲酰基 HN(C═O)H 的 N-自由基形式的形成放热,反应势垒为 26.7 kJ mol-1。我们发现,CN + H2O 反应显示出 70.6 kJ mol-1 的高能垒。最后,我们还探测了通过 OH + CH3CN 反应直接形成乙酰胺自由基前体的情况,发现在星际冰上最有可能发生的结果是 H-萃取反应生成 CH2CN 和 H2O。基于这些结果,我们认为,将通过氨基甲酰基的 N-自由基形式形成酰胺的替代反应途径包括在内,将改进天体化学模型中对酰胺丰度的预测,特别是对恒星形成区化学的预测。
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引用次数: 0
Ethynyl Radical Hydrogen Abstraction Energetics and Kinetics Utilizing High-Level Theory 利用高层理论研究乙炔基自由基析氢能量学和动力学
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-07-03 DOI: 10.1021/acsearthspacechem.4c00040
Laura N. Olive, Alexandra D. Heide, Justin M. Turney, Henry F. Schaefer, III
The ethynyl radical, C2H, is found in a variety of different environments ranging from interstellar space and planetary atmospheres to playing an important role in the combustion of various alkynes under fuel-rich conditions. Hydrogen-atom abstraction reactions are common for the ethynyl radical in these contrasting environments. In this study, the C2H + HX → C2H2 + X, where HX = HNCO, trans-HONO, cis-HONO, C2H4, and CH3OH, reactions have been investigated at rigorously high levels of theory, including CCSD(T)-F12a/cc-pVTZ-F12. For the stationary points thus located, much higher levels of theory have been used, with basis sets as large as aug-cc-pV5Z and methods up to CCSDT(Q), and core correlation was also included. These molecules were chosen because they can be found in either interstellar or combustion environments. Various additive energy corrections have been included to converge the relative enthalpies of the stationary points to subchemical accuracy (≤0.5 kcal mol–1). Barriers predicted here (2.19 kcal mol–1 for the HNCO reaction and 0.47 kcal mol–1 for C2H4) are significantly lower than previous predictions. Reliable kinetics were acquired over a wide range of temperatures (50–5000 K), which may be useful for future experimental studies of these reactions.
乙炔基 C2H 存在于各种不同的环境中,从星际空间和行星大气到在燃料丰富的条件下各种炔烃的燃烧过程中都发挥着重要作用。在这些截然不同的环境中,乙炔基常见的是氢原子抽离反应。本研究采用严格的高水平理论(包括 CCSD(T)-F12a/cc-pVTZ-F12)研究了 C2H + HX → C2H2 + X 反应,其中 HX = HNCO、反式-HONO、顺式-HONO、C2H4 和 CH3OH。对于由此定位的静止点,使用了更高水平的理论,基集大至 aug-cc-pV5Z,方法高达 CCSDT(Q),还包括核相关性。之所以选择这些分子,是因为它们可以在星际环境或燃烧环境中找到。为了使静止点的相对焓收敛到亚化学精度(≤0.5 kcal mol-1),还加入了各种附加能量修正。此处预测的障碍(HNCO 反应为 2.19 kcal mol-1,C2H4 反应为 0.47 kcal mol-1)明显低于之前的预测。我们在很宽的温度范围(50-5000 K)内都获得了可靠的动力学数据,这可能对今后这些反应的实验研究有所帮助。
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引用次数: 0
Seawater Redox Conditions in the Late Paleoproterozoic: Insight from the North China Craton 晚古生代海水氧化还原条件:来自华北克拉通的启示
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-07-01 DOI: 10.1021/acsearthspacechem.4c00061
Qing Ma, Yaoqi Zhou, Aubrey Zerkle, Mengchun Cao
The “Boring Billion” (BB, ∼1800–800 Ma) is characterized by the perceived stasis of carbon isotopes within the geological record of that time. However, geochemical data obtained from global Paleo-Mesoproterozoic strata indicate heterogeneity and complexity of oxygen contents in the oceans, which hinder paleoenvironmental reconstructions from this period. Furthermore, there has been a dearth of studies focused on the Paleoproterozoic strata in the western and southern parts of the North China Craton (NCC). In this paper, we report elemental abundances and Fe speciation data from the Huangqikou Formation in the Ordos Basin, western NCC, and the Dagushi, Bingmagou, Baicaoping, and Puyu Formations in the Xiong’er Basin, southern NCC. Our latest findings, integrated with prior research, indicate that sedimentary environments in these parts of the NCC in the late Paleoproterozoic were uniformly anoxic and ferruginous. During a marine transgression, we see limited evidence of oxic surface waters entering the sedimentary water and resulting in intermittent oxygenation events in the Ordos Basin. However, microbial respiration of oxygen and/or limited oxygen replenishment under sluggish circulation in the basin might have caused the consistently anoxic conditions in the Xiong’er Basin during the late Paleoproterozoic.
Boring Billion"(BB,1800-800 Ma)时期的特点是该时期地质记录中的碳同位素被认为是静止的。然而,从全球古中生代地层中获得的地球化学数据表明,海洋中氧含量的异质性和复杂性阻碍了这一时期古环境的重建。此外,针对华北克拉通(NCC)西部和南部地区古近纪地层的研究一直很缺乏。本文报告了华北克拉通西部鄂尔多斯盆地黄旗口地层和华北克拉通南部熊耳盆地大孤石地层、兵马沟地层、白草坪地层和蒲峪地层的元素丰度和铁标本数据。结合之前的研究,我们的最新发现表明,在古近纪晚期,北中国大陆这些地区的沉积环境是一致的缺氧和铁质环境。在海相侵蚀期间,我们看到有限的证据表明,含氧地表水进入沉积水体,导致鄂尔多斯盆地出现间歇性富氧事件。然而,在盆地循环不畅的情况下,微生物对氧气的呼吸作用和/或有限的氧气补充可能造成了熊耳盆地在古近代晚期持续缺氧的状况。
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引用次数: 0
Seasonal Contrasts in Dissolved Selenium Dynamics in Subarctic Thaw Lakes 亚北极解冻湖泊溶解硒动态的季节对比
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-07-01 DOI: 10.1021/acsearthspacechem.4c00041
Audrey Laberge-Carignan, Martin Pilote, Dominic Larivière, Florence Mercier, Diogo Folhas, Raoul-Marie Couture
Thermokarst ponds (thaw lakes) are ubiquitous in northern landscapes. They are hotspots for the biogeochemical processing of elements, such as carbon (C), nitrogen (N), sulfur (S), iron (Fe) and manganese (Mn). In turn, those elementary cycles may control the mobility of selenium (Se), an essential micronutrient. To unravel these coupled biogeochemical cycles and identify processes controlling Se mobility, we studied four thermokarst ponds in a subarctic peatland valley influenced by permafrost thaw. The data set comprises of water column and sediment porewater concentration profiles collected during both summer and winter. Physicochemical parameters and dissolved concentrations of major elements, nutrients, and Se were measured and used to model fluxes at the sediment–water interface and to calculate Se speciation. The results suggest that the proximity of the pond from the permafrost structures influenced their biogeochemical dynamics. In the ponds close to permafrost, Se concentrations are 2-fold higher in winter compared to summer, accompanied by an increase in sediment fluxes from 13 to 149 pmol cm–2 yr–1 between summer and winter. The combination of comparatively older dissolved organic matter and of oxygenated conditions explain the seasonal variation in Se concentrations. In the ponds further from the permafrost, Se concentrations are higher, remain unchanged in the water column across seasons, and are linearly correlated with both DOC (R2 = 0.64, p < 0.01, n = 50) and Fe (R2 = 0.60) concentrations. Thermodynamic calculations show that Se(IV) dominates Se speciation in the porewater at all sites, while the water column reaches saturation with respect to elemental zerovalent Se, suggesting that precipitation of elemental Se could mediate dissolved Se concentrations. Collectively, our results point to the strong control that redox conditions exert on Se mobility, via DOC and Fe, and to the linkages between landscape features, pond physicochemistry, and Se dynamics.
热卡斯特池塘(解冻湖)在北方地貌中无处不在。它们是碳(C)、氮(N)、硫(S)、铁(Fe)和锰(Mn)等元素进行生物地球化学处理的热点。反过来,这些基本循环可能会控制硒(Se)这种必需微量元素的流动性。为了揭示这些耦合的生物地球化学循环并确定控制硒流动性的过程,我们研究了受永久冻土融化影响的亚北极泥炭地山谷中的四个恒温池塘。数据集包括夏季和冬季采集的水体和沉积物孔隙水浓度剖面图。测量了主要元素、营养物质和硒的物理化学参数和溶解浓度,并将其用于模拟沉积物-水界面的通量和计算硒的种类。结果表明,池塘与永久冻土结构的距离影响了池塘的生物地球化学动态。在靠近永久冻土层的池塘中,冬季的硒浓度是夏季的 2 倍,同时夏季和冬季之间的沉积物通量从 13 pmol cm-2 yr-1 增加到 149 pmol cm-2 yr-1。相对较老的溶解有机物和富氧条件共同解释了硒浓度的季节性变化。在离永久冻土较远的池塘中,硒浓度较高,水体中的硒浓度在不同季节保持不变,并且与溶解有机物(R2 = 0.64,p < 0.01,n = 50)和铁(R2 = 0.60)浓度呈线性相关。热力学计算表明,Se(IV)在所有地点的孔隙水中都占主导地位,而水体中的零价硒元素则达到饱和状态,这表明元素硒的沉淀可能会影响溶解硒的浓度。总之,我们的研究结果表明,氧化还原条件通过 DOC 和铁对硒的移动性有很强的控制作用,同时也说明了地貌特征、池塘物理化学和硒动态之间的联系。
{"title":"Seasonal Contrasts in Dissolved Selenium Dynamics in Subarctic Thaw Lakes","authors":"Audrey Laberge-Carignan, Martin Pilote, Dominic Larivière, Florence Mercier, Diogo Folhas, Raoul-Marie Couture","doi":"10.1021/acsearthspacechem.4c00041","DOIUrl":"https://doi.org/10.1021/acsearthspacechem.4c00041","url":null,"abstract":"Thermokarst ponds (thaw lakes) are ubiquitous in northern landscapes. They are hotspots for the biogeochemical processing of elements, such as carbon (C), nitrogen (N), sulfur (S), iron (Fe) and manganese (Mn). In turn, those elementary cycles may control the mobility of selenium (Se), an essential micronutrient. To unravel these coupled biogeochemical cycles and identify processes controlling Se mobility, we studied four thermokarst ponds in a subarctic peatland valley influenced by permafrost thaw. The data set comprises of water column and sediment porewater concentration profiles collected during both summer and winter. Physicochemical parameters and dissolved concentrations of major elements, nutrients, and Se were measured and used to model fluxes at the sediment–water interface and to calculate Se speciation. The results suggest that the proximity of the pond from the permafrost structures influenced their biogeochemical dynamics. In the ponds close to permafrost, Se concentrations are 2-fold higher in winter compared to summer, accompanied by an increase in sediment fluxes from 13 to 149 pmol cm<sup>–2</sup> yr<sup>–1</sup> between summer and winter. The combination of comparatively older dissolved organic matter and of oxygenated conditions explain the seasonal variation in Se concentrations. In the ponds further from the permafrost, Se concentrations are higher, remain unchanged in the water column across seasons, and are linearly correlated with both DOC (<i>R</i><sup>2</sup> = 0.64, <i>p</i> &lt; 0.01, <i>n</i> = 50) and Fe (<i>R</i><sup>2</sup> = 0.60) concentrations. Thermodynamic calculations show that Se(IV) dominates Se speciation in the porewater at all sites, while the water column reaches saturation with respect to elemental zerovalent Se, suggesting that precipitation of elemental Se could mediate dissolved Se concentrations. Collectively, our results point to the strong control that redox conditions exert on Se mobility, via DOC and Fe, and to the linkages between landscape features, pond physicochemistry, and Se dynamics.","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141515261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Effect of Nitrogen on the Structure and Composition of Primordial Organic Matter Analogs 氮对原始有机物模拟物的结构和组成的影响
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-06-28 DOI: 10.1021/acsearthspacechem.3c00311
Pauline Lévêque, Clémence Queffelec, Christophe Sotin, Carlos Afonso, Olivier Bollengier, Adriana Clouet, Erwan Le Menn, Yves Marrocchi, Isabelle Schmitz, Bruno Bujoli
Organic molecules are ubiquitous in primitive solar system bodies such as comets and asteroids. These primordial organic compounds may have formed in the interstellar medium and in protoplanetary disks (PPDs) before being accreted and further transformed in the parent bodies of meteorites, icy moons, and dwarf planets. The present study describes the composition of primordial organics analogs produced in a laboratory simulator of the PPD (the Nebulotron experiment at the CRPG laboratory) with nitrogen contents varying from N/C < 0.01 to N/C = 0.63. We present the first Fourier transform ion cyclotron resonance mass spectrometry analysis of these analogs. Several thousands of molecules with masses between m/z 100 and 500 are characterized. The mass spectra show a Gaussian shape with maxima around m/z 250. Highly condensed polyaromatic hydrocarbons (PAH) are the most common compounds identified in the samples with lower nitrogen contents. As the amount of nitrogen increases, a dramatic increase of the chemical diversity is observed. Nitrogen-bearing compounds are also dominated by polyaromatic hydrocarbons (PANH) made of 5- and 6-membered rings containing up to four nitrogen atoms, including triazine and pyrazole rings. Such N-rich aromatic species are expected to decompose easily in the presence of water at higher temperatures. Pure carbon molecules are also observed for samples with relatively small fractions of nitrogen. MS peaks compatible with the presence of amino acids and nucleobases, or their isomers, are detected. When comparing these Nebulotron samples with the insoluble fraction of the Paris meteorite organic matter, we observe that the samples with intermediate N/C ratios bracketing that of the Paris insoluble organic matter (IOM) display relative proportions of the CH, CHO, CHN, and CHNO chemical families also bracketing those of the Paris IOM. Our results support that Nebulotron samples are relevant laboratory analogs of primitive chondritic organic matter.
有机分子在彗星和小行星等太阳系原始天体中无处不在。这些原始有机化合物可能在星际介质和原行星盘(PPD)中形成,然后在陨石、冰卫星和矮行星的母体中吸积并进一步转化。本研究描述了在原行星盘实验室模拟器(CRPG 实验室的 Nebulotron 实验)中产生的原始有机物类似物的组成,氮含量从 N/C < 0.01 到 N/C = 0.63 不等。我们首次对这些类似物进行了傅立叶变换离子回旋共振质谱分析。对质量介于 m/z 100 和 500 之间的数千个分子进行了表征。质谱显示出高斯形状,最大值在 m/z 250 左右。在含氮量较低的样品中,最常见的化合物是高度缩合的多芳烃(PAH)。随着含氮量的增加,化学多样性也急剧增加。含氮化合物还主要是由含有多达四个氮原子的五元环和六元环组成的多芳烃(PANH),包括三嗪环和吡唑环。在较高温度下,这些富含氮的芳香族化合物在有水的情况下很容易分解。在含氮相对较少的样品中也能观察到纯碳分子。检测到的 MS 峰与氨基酸和核碱基或其异构体的存在相符。在将这些星云样品与巴黎陨石有机物的不溶部分进行比较时,我们观察到,具有与巴黎不溶性有机物(IOM)相当的中间氮/碳比的样品显示出 CH、CHO、CHN 和 CHNO 化学族的相对比例,也与巴黎 IOM 的比例相当。我们的研究结果表明,Nebulotron 样品是原始软玉有机物的相关实验室类似物。
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引用次数: 0
Role of Source, Mineralogy, and Organic Complexation on Lability and Fe Isotopic Composition of Terrestrial Fe sources to the Gulf of Alaska 阿拉斯加湾陆地铁源的来源、矿物学和有机络合作用对其稳定性和铁同位素组成的影响
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-06-27 DOI: 10.1021/acsearthspacechem.3c00338
Linqing Huang, Sarah M. Aarons, Bess G. Koffman, Wenhan Cheng, Lena Hanschka, Lee Ann Munk, Jordan Jenckes, Emmet Norris, Carli A. Arendt
Iron (Fe) is a key trace nutrient supporting marine primary production, and its deposition in the surface ocean can impact multiple biogeochemical cycles. Understanding Fe cycling in the subarctic is key for tracking the fate of particulate-bound sources of oceans in a changing climate. Recently, Fe isotope ratios have been proposed as a potential tool to trace sources of Fe to the marine environment. Here, we investigate the Fe isotopic composition of terrestrial sources of Fe including glacial sediment, loess, volcanic ash, and wildfire aerosols, all from Alaska. Results show that the δ56Fe values of glaciofluvial silt, glacial dissolved load, volcanic ash, and wildfire aerosols fall in a restricted range of δ56Fe values from −0.02 to +0.12‰, in contrast to the broader range of Fe isotopic compositions observed in loess, −0.50 to +0.13‰. The Fe isotopic composition of the dissolved load of glacial meltwater was consistently lighter compared to its particulate counterpart. The ‘aging’ (exposure to environmental conditions) of volcanic ash did not significantly fractionate the Fe isotopic composition. The Fe isotopic composition of wildfire aerosols collected during an active fire season in Alaska in the summer of 2019 was not significantly fractionated from those of the average upper continental crust composition. We find that the δ56Fe values of loess (<5 μm fraction) were more negative (−0.32 to +0.05‰) with respect to all samples measured here, had the highest proportion of easily reducible Fe (5.9–59.6%), and were correlated with the degree of chemical weathering and organic matter content. Transmission electron spectroscopy measurements indicate an accumulation of amorphous Fe phases in the loess. Our results indicate that Fe isotopes can be related to Fe lability when in the presence of organic matter and that higher organic matter content is associated with a distinctly more negative Fe isotope signature likely due to Fe-organic complexation.
铁(Fe)是支持海洋初级生产的一种关键微量营养元素,它在表层海洋的沉积会影响多种生物地球化学循环。了解亚北极地区的铁循环是追踪气候变化中海洋微粒源命运的关键。最近,有人提出用铁同位素比值来追踪海洋环境中铁的来源。在这里,我们研究了阿拉斯加州冰川沉积物、黄土、火山灰和野火气溶胶等陆地铁源的铁同位素组成。结果表明,冰川淤泥、冰川溶解负荷、火山灰和野火气溶胶的 δ56Fe 值范围有限,从 -0.02 到 +0.12‰,而在黄土中观察到的铁同位素组成范围更广,从 -0.50 到 +0.13‰。冰川融水溶解负荷的铁同位素组成一直比颗粒负荷轻。火山灰的 "老化"(暴露在环境条件下)并没有明显改变铁同位素组成。2019 年夏季阿拉斯加火灾活跃期收集的野火气溶胶的铁同位素组成与平均上部大陆地壳组成相比没有明显分馏。我们发现,黄土(<5 μm部分)的δ56Fe值与本文测量的所有样本相比更负(-0.32至+0.05‰),易还原铁的比例最高(5.9-59.6%),并且与化学风化程度和有机物含量相关。透射电子显微镜测量结果表明,黄土中积累了无定形的铁相。我们的研究结果表明,铁同位素与有机质存在时的铁易变性有关,有机质含量越高,铁同位素特征越明显,这可能是由于铁-有机络合造成的。
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引用次数: 0
The Capture of Cadmium from Solution during the Replacement of Calcite by Apatite 磷灰石置换方解石过程中从溶液中捕获镉的过程
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-06-27 DOI: 10.1021/acsearthspacechem.4c00031
Maude Julia, Christine V. Putnis, Lorena H. Filiberto, Max Winkler
The capture of cadmium (Cd) from phosphate-containing solutions during the replacement of CaCO3 by phosphate phases such as hydroxylapatite (HAP) and tricalcium phosphate (TCP) has been studied under high and low temperature and pressure conditions using atomic force microscopy, scanning electron microscopy equipped with an X-ray spectrometer and a backscattered electron detector, Raman spectroscopy, and microprobe analysis. Starting with cubes of Carrara Marble (polycrystalline calcite) and single crystals of calcite, a new solid phosphate phase was observed to incorporate Cd from solution, formed under different pressure and temperature conditions tested. Results showed that Cd precipitated in a new phase on the surface of all samples tested. In Carrara Marble, pseudomorphic replacement of CaCO3 is restricted possibly due to kinetic limitation caused by the adsorption of Cd complexes formed in solution at reactive surface sites and the variation of fluid composition inside the sample. However, on the sample surface, this kinetic limitation is less influential, so the new phase could incorporate higher amounts of Cd faster. Furthermore, this reaction at room temperature was found to have similar and/or better Cd-uptake efficiency as HAP and CaCO3 in pure Cd solution through the precipitation of Cd-containing phosphate crystals on the sample surface. Both reactions were able to capture Cd in the precipitating phase structure and could provide a mechanism for simultaneous Cd and phosphate removal from solutions contaminated with both, in industrial or natural settings.
在高温、低温和高压条件下,使用原子力显微镜、配备 X 射线光谱仪和背散射电子探测器的扫描电子显微镜、拉曼光谱和微探针分析,研究了羟基磷灰石(HAP)和磷酸三钙(TCP)等磷酸盐相置换 CaCO3 的过程中从含磷酸盐溶液中捕获镉(Cd)的情况。从卡拉拉大理石(多晶方解石)立方体和方解石单晶体开始,观察到一种新的固体磷酸盐相从溶液中析出镉,并在不同的压力和温度条件下形成。结果表明,镉以一种新的相沉淀在所有测试样品的表面。在卡拉拉大理石中,CaCO3 的拟态置换受到限制,这可能是由于溶液中形成的镉络合物在反应表面位点的吸附以及样品内部流体成分的变化造成的动力学限制。然而,在样品表面,这种动力学限制的影响较小,因此新相可以更快地掺入更多的镉。此外,通过在样品表面沉淀含镉磷酸盐晶体,发现室温下的这种反应与纯镉溶液中的 HAP 和 CaCO3 具有相似和/或更高的镉吸收效率。这两种反应都能在沉淀相结构中捕获镉,可为在工业或自然环境中同时从受到镉和磷酸盐污染的溶液中去除镉和磷酸盐提供一种机制。
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引用次数: 0
Adaptive Changes in Bacterial and Archaeal Community Structures and Functions Occur under Primordial Conditions 原始条件下细菌和古细菌群落结构与功能的适应性变化
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-06-26 DOI: 10.1021/acsearthspacechem.4c00089
Xiao-Tong Wu, Yu-Qin He, Min Qiu, Guo-Xiang Li, Xiao-Bin Ou, Yi-Bo Wu, Peng Bao
The microorganisms responsible for driving the Anammox and Sammox processes may have ancient origins and remain poorly understood. In this research, we enriched the microorganisms from paddy soils and marine sediments under Anammox and Sammox conditions to investigate the shifts in their structure and functions. The community structure showed significant differences between enrichment cultures of paddy soils and marine sediments under the Anammox and Sammox conditions. Among samples from paddy soils, Proteobacteria, Nitrospirota, Verrucomicrobiota, Gemmatimonadata, and Euryarchaeota accounted for a larger proportion under Anammox culture conditions, while Firmicutes, Bacteroidota, Chloroflexi, Planctomycetota, Acidobacteriota, Crenarchaeota, and Nanoarchaeota accounted for a larger proportion under Sammox culture conditions. Among samples from marine sediments, Proteobacteria, Bacteroidota, and Euryarchaeota accounted for a larger proportion in the Anammox culture conditions, while Firmicutes, Chloroflexi, Crenarchaeota, and Nanoarchaeota accounted for a larger proportion in Sammox culture conditions. Genes associated with assimilatory sulfate reduction, nitrate reduction, and denitrification pathways were more abundant under Anammox culture conditions, whereas genes related to dissimilatory sulfate reduction and nitrification pathways were more prevalent under Sammox culture conditions. These findings provide valuable insights into the ecological conditions and microbial species of the primordial era and may aid in the searching for extraterrestrial life.
负责驱动 Anammox 和 Sammox 过程的微生物可能起源于远古,但人们对其了解甚少。在这项研究中,我们在 Anammox 和 Sammox 条件下富集了水稻田土壤和海洋沉积物中的微生物,以研究其结构和功能的变化。在 Anammox 和 Sammox 条件下,水稻田土壤和海洋沉积物富集培养物的群落结构有明显差异。在水稻田土壤样品中,变形菌群、硝化菌群、蛭石微生物群、革囊菌群和极毛藻生物群在 Anammox 培养条件下所占比例较大;而在 Sammox 培养条件下,固相菌群、类杆菌群、绿菌群、平面菌群、酸性菌群、Crenarchaeota 和 Nanoarchaeota 所占比例较大。在海洋沉积物样本中,变形菌群、类杆菌群和极毛藻群在 Anammox 培养条件下所占比例较大,而在 Sammox 培养条件下,固相菌群、绿僵菌群、Crenarchaeota 和 Nanoarchaeota 所占比例较大。在 Anammox 培养条件下,与硫酸盐同化还原、硝酸盐还原和反硝化途径相关的基因更为丰富,而在 Sammox 培养条件下,与硫酸盐异化还原和硝化途径相关的基因更为普遍。这些发现为了解原始时代的生态条件和微生物物种提供了宝贵的信息,可能有助于寻找地外生命。
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引用次数: 0
Water Uptake and Release of Nitrate Salt Mixtures of Relevance to the Atacama Desert and Mars 与阿塔卡马沙漠和火星有关的硝酸盐混合物的吸水和释放
IF 3.4 3区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY Pub Date : 2024-06-25 DOI: 10.1021/acsearthspacechem.3c00371
M. S. Fernanders, R. V. Gough, V. F. Chevrier, D. Boy, J. Boy, C. E. Carr, M. A. Tolbert
Understanding the behavior of water in extreme environments is crucial in assessing its habitability potential. This study investigates the water uptake and release of nitrate and nitrate salt mixtures under Martian and Atacama Desert-like conditions. The Atacama serves as a Mars analogue due to its hyper-arid climate and shared salt composition. This study determines deliquescence and efflorescence relative humidities (DRH and ERH, respectively) for pure magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) as a function of temperature and perchlorate/nitrate mixtures at various ratios at 248 K. Finally, the effects of magnesium sulfate anhydrous (MgSO4) on Mg(NO3)2·6H2O are also investigated. Pure Mg(NO3)2 DRH varied with temperature (80% RH at 223 K to 63% at 268 K), while ERH remained constant at 24% RH across temperatures. When mixed with perchlorate, the DRH values were lowered, reaching values close to 40% RH. The less deliquescent MgSO4 had minimal impact on Mg(NO3)2 water uptake when mixed in equimolar ratios. The laboratory DRH conditions did not align with conditions found on Mars, indicating that the salt mixtures are unlikely to deliquesce under Martian conditions found at Gale Crater. However, the warmer temperatures of the Atacama may favor water uptake. Therefore, the DRH and ERH data were applied to two sites in the Atacama. Conditions in the Atacama support water uptake by nitrates in the fall/winter seasons, allowing for the possibility of metastable brines persisting for extended periods. Thus, although nitrates may enhance habitability in the Atacama, they may play less of a role in habitability on Mars.
了解水在极端环境中的行为对于评估其宜居潜力至关重要。本研究调查了硝酸盐和硝酸盐混合物在类似火星和阿塔卡马沙漠条件下的吸水和释水情况。阿塔卡马沙漠因其超干旱气候和相同的盐成分而成为火星的类似物。本研究确定了纯净的六水硝酸镁(Mg(NO3)2-6H2O)在 248 K 温度下的潮解相对湿度(DRH)和渗出相对湿度(ERH)与温度以及不同比例的高氯酸盐/硝酸盐混合物的函数关系,最后还研究了无水硫酸镁(MgSO4)对 Mg(NO3)2-6H2O 的影响。纯 Mg(NO3)2 的 DRH 随温度的变化而变化(从 223 K 时的 80% 相对湿度到 268 K 时的 63%),而 ERH 在不同温度下保持不变,为 24% 相对湿度。与高氯酸盐混合后,DRH 值降低,接近 40% 相对湿度。等摩尔比混合时,潮解性较低的 MgSO4 对 Mg(NO3)2 吸水的影响微乎其微。实验室 DRH 条件与火星上的条件并不一致,这表明在盖尔陨石坑的火星条件下,盐混合物不太可能潮解。然而,阿塔卡马地区较高的温度可能有利于水的吸收。因此,在阿塔卡马的两个地点应用了 DRH 和 ERH 数据。阿塔卡马地区的条件有利于硝酸盐在秋冬季节吸收水分,从而使可稳定存在的卤水有可能长期存在。因此,虽然硝酸盐可能会提高阿塔卡马地区的宜居性,但它们在火星宜居性方面所起的作用可能较小。
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ACS Earth and Space Chemistry
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