赤铁矿与磁铁矿混合比例对磁性参数的影响

本文通过将磁铁矿与赤铁矿进行人工混合,其中磁铁矿含量固定为0.3%,而赤铁矿含量则变化于0%～9%,并根据磁铁矿颗粒大小分为两个系列(纳米级磁铁矿+赤铁矿,系列1;假单畴磁铁矿+赤铁矿,系列2),探讨了磁性参数对上述磁性矿物混合比例的响应关系,结果显示:退磁参数S比值和Hcr/Hc不仅与磁铁矿和赤铁矿混合比例相关,同时也受到磁铁矿颗粒大小的影响,对于系列1而言,S比值对赤铁矿含量小于2%的混合样品较敏感,随着赤铁矿含量增加显著下降;Hcr/Hc则在赤铁矿含量大于3%时变化较大,通常用于指示亚铁磁性矿物颗粒大小的参数XARM/X与XARM/SIRM,也受到磁铁矿与赤铁矿混合比例的影响,对于磁铁矿颗粒较细的系列1而言,当赤铁矿含量小于3%时,XARM/SIRM随着赤铁矿含量增加存在较为显著的下降现象,上述结果表明,当使用磁性参数进行环境解释时,需要同时考虑磁性矿物颗粒大小以及不同矫顽力矿物混合比例的影响,特别是磁铁矿以超顺磁颗粒为主的样品.     

磁铁矿的低温磁学性质研究进展

磁铁矿(Fe3O4)是自然界沉积物和岩石天然剩磁的最主要载磁矿物.本文主要评述低温条件下(2\|300K)磁铁矿的晶体结构特征、Verwey相变以及磁晶各向异性等,重点介绍了两种重要的剩磁随温度变化曲线.最后简单地介绍磁铁矿的低温磁学研究在地学中的应用以及氧化和超顺磁效应对低温磁学性质的影响.     

有机质对城市污染河道沉积物铵态氮吸附-解吸的影响

采集污染程度不同的城市河道沉积物(通吕运河、濠河和通甲河),在分析H2O2对沉积物有机质和铵态氮影响的基础上,分析沉积物在去除有机质前后铵态氮释放动力学和吸附热力学过程,研究城市污染河道沉积物有机质对铵态氮吸附-解吸的影响.结果表明:单位体积H2O2对有机质去除率随H2O2使用量增多而降低;去除有机质后,沉积物铵态氮含量显著增加,通吕运河、濠河和通甲河铵态氮最大含量分别是有机质去除前的4.16、3.55和2.85倍;沉积物对铵态氮的饱和吸附量随有机质含量减少而下降;沉积物铵态氮释放过程均表现为先快速释放,后减缓至平衡过程;去除有机质后,随着有机质含量的减少,沉积物铵态氮的最大释放量呈增大趋势;沉积物有机质和铵态氮含量是影响沉积物铵态氮释放的主要因素.     

三峡库区土地利用对河流溶解性有机质的多时空尺度影响

三峡库区拥有目前世界上规模最大的水利枢纽工程,自投入使用以来,为长江流域提供了丰富的水源及电力,促进了经济的发展,但同时也对该区域的生态环境造成了严重的冲击。澎溪河流域作为三峡库区长江流域干流的典型回水区和消落带,是众多学者研究三峡库区生态环境变化的重点区域。为探究不同时空尺度下土地利用对河流溶解性有机质（DOM）的影响,以澎溪河流域为研究对象,基于紫外-可见光谱分析和三维荧光光谱矩阵-平行因子分析,结合河段缓冲区、河岸带缓冲区及子流域3种空间尺度的二级土地利用类型,解析了旱雨季水体DOM的组成及来源特征,并采用相关分析和冗余分析方法探讨了3种空间尺度下土地利用方式对旱雨季水体DOM的多时空尺度影响。结果表明：（1）旱季水体DOM荧光组分以陆源类腐殖质所占比例更大,雨季水体DOM荧光组分以富里酸贡献为主。（2）流域内陆源输入和内源产生对水体DOM丰度均有贡献,雨季较旱季水体DOM的陆源性更强,自生源特征较弱。（3）土地利用在雨季和子流域尺度下对水体DOM的影响更显著,其中,雨季子流域尺度下,土地利用指数对水体DOM参数的解释率为90.35%。（4）不同土地利用方式对水体DOM产生的影响...     

云南阳宗海表层沉积物有机质组成结构对磷赋存形态特征的影响

利用连续提取分级的方法定量分析阳宗海表层沉积物磷赋存形态,阐明了沉积物C、N、H和O组成及溶解有机质(DOM)紫外-可见光谱特征,探讨沉积物元素组成及DOM组成结构对不同形态磷含量的影响.结果表明:(1)沉积物潜在可移动磷含量在68.67~124.70 mg/kg之间变化,平均占总磷含量的9.81%,表现为BD-PNa OH-nr PNH_4Cl-P;沉积物稳定磷含量在496.73~908.28 mg/kg之间变化,平均占总磷含量的60.86%.(2)沉积物C、N含量和疏水性DOM光谱参数A_(240-400)表现出北部高、南部低的变化趋势,但H/C、O/C和(N+O)/C摩尔比和亲水性DOM光谱参数A_(240-400)变化趋势则与之恰好相反.(3)沉积物NH4Cl-P含量与C、N和H含量之间呈显著正相关,但与H/C、O/C、(N+O)/C摩尔比和亲水性DOM光谱参数E_2/E_3值之间呈显著负相关;NaOH-rP和BD-P+NaOH-rP含量均与O含量及O/H摩尔比呈显著负相关;NaOH-rP、BD-P+NaOH-rP和HCl-P均与疏水性DOM光谱参数A_(240-400)值之间呈显著正相关.因此,天然有机质元素组成及官能团结构是影响沉积物磷赋存形态的重要因素.     

鄱阳湖水体溶解有机质分子量分布、荧光特征及对重金属分布的影响

溶解有机质(DOM)在环境水体中广泛存在,具有连续的分子量分布特征,并可显著影响水体中污染物的迁移转化和归趋行为.于2019年春季采集鄱阳湖全湖水样,采用超过滤技术将DOM样品分为低分子量(LMW,<1 kDa)和高分子量(HMW,1 kDa～0.45μm)组分,通过三维荧光光谱结合平行因子分析(EEM-PARAFAC)和ICP-MS分析不同分子量区间有机组分和重金属含量.结果表明,鄱阳湖水体DOM中LMW-DOM占比为43%～55%,HMW-DOM占比为45%～57%.平行因子模型提取出3个相互独立的荧光组分,分别为类富里酸组分C1、C2和类腐殖酸组分C3. 60%～73%的C1分布在LMW中,77%～93%的C2分布在HMW中,而C3几乎平均分布在LMW-和HMW-DOM中,可能与C1、C2、C3组分分别含有的传统荧光峰有关.通过对荧光参数FIX(<1.4)、BIX(<0.8)的计算发现鄱阳湖DOM陆源特征显著,且HMW组分具有比LMW组分更高的陆源特征和芳香度.重金属检测结果表明Cr、Mn、Fe、Pb则主要分布在HMW中(63%～94%),As、Cd、Ba、Se...     

超压对有机质热演化的差异抑制作用及层次

有机质热演化由一系列平行而连续的反应构成. 不同热演化反应具有不同的活化能分布、产物浓度变化速率和体积膨胀效应, 其对超压的响应程度可以明显不同, 决定了超压对不同热演化反应和不同成熟度指标的差异抑制作用和层次. 通过对莺歌海盆地、琼东南盆地和渤海湾盆地东濮凹陷不同压力系统有机质热演化的综合对比分析, 识别出超压抑制有机质热演化的4个层次: (1) 超压抑制了有机质热演化的各个方面, 包括不同干酪根组分的热降解(生烃作用)和烃类的热演化; (2) 超压仅抑制了烃类的热演化和富氢干酪根组分的热降解, 而对贫氢干酪根组分的热演化不产生重要影响, 因此镜质体反射率未受到抑制; (3) 超压抑制了烃类的热裂解, 而对干酪根的热降解未产生明显影响; (4) 超压对有机质热演化的各个方面均未产生可识别的影响. 超压抑制有机质热演化的各个方面是源岩早期超压(超压在有机质成熟度较低时开始发育)和长期保持封闭流体系统的结果. 超压发育过晚、超压强度低、超压流体频繁释放等都可能导致超压对有机质热演化的各个方面均不产生可识别的影响. 在很多情况下, 超压对有机质热演化的抑制作用属于第2和第3层次, 需要用多种参数识别超压抑制作用.     

泥质沉积物和泥岩中有机质的赋存形式与富集机制

运用多学科的、系统的分析方法, 研究泥质沉积物和泥岩中有机质赋存形式与富集机制的差异性. 黏土粒级的有机碳和氯仿沥青A含量明显高于其他粒级, 说明黏土矿物对富集有机质具重要作用; 其中氯仿沥青A含量增加尤为显著, 表明黏土矿物富集的主要是可溶有机质. 热重(TG)和差热分析(DTA)结果显示, 有机质富集和赋存形式具明显的多样性, 除在黏土粒级中主要富集可溶有机质外, 在其他粒级中见大量的生物碎屑和无定形有机质的存在, 在DTA曲线上表现为多个放热峰的出现. 泥岩样经不同方法预处理后, 进行X射线衍射(XRD)和DTA分析. 在XRD曲线上黏土矿物层间距随温度变化, DTA曲线上的有机质放热峰也随温度变化. 在350℃附近黏土矿物层间距与有机质放热峰的变化具有一致性, 且极其稳定, 这是有机质进入黏土矿物层间形成有机黏土复合体的显著特征. 由此可见, 有机质与黏土矿物结合并不完全是简单的表面吸附, 部分有机质进入到黏土矿物的层间, 形成非常稳定的有机质黏土复合体. 有机质在沉积物和泥岩中的保存形式和富集机制的研究对于深入理解全球碳循环过程和通量, 以及评价有机质的生烃过程具有重要意义.     

鄱阳湖湿地溶解性有机质的光化学属性对水体光活性中间体(PPRIs)季节性变化的影响

湿地的水文和水化学在时空尺度上会呈现显著差异,进而会引发光化学反应的变化,光活性中间体(PPRIs)是水体间接光反应的产物,具有极强的氧化性,对水环境中有机物和污染物的归驱具有重要的影响,因此迫切需要探究湿地中PPRIs的产生过程。本研究通过捕获剂法监测了鄱阳湖湿地4个季节水体中3种PPRIs(¹O₂、·OH及³CDOM^*)的产生速率和稳态浓度的变化,并通过紫外吸收光谱、三维荧光光谱、以及傅立叶变换离子回旋共振质谱等技术对水体中可溶性有机质(DOM)组分的化学特征进行分析,揭示了鄱阳湖湿地不同季节水体中的DOM的光化学反应特性及与PPRIs产生的相关性。结果发现:鄱阳湖夏季和秋季水体的pH值、溶解有机碳(DOC)浓度较高,相反,硝酸盐、亚硝酸盐浓度在夏季和秋季较低。夏季和秋季的DOM中芳香族化合物丰度较高,并且木质素丰度明显高于冬季和春季。不同季节鄱阳湖水体有色可溶性有机物产生能力依次为秋季>夏季>冬季>春季。夏季和秋季水体中¹O₂和·OH产生速率和稳态浓度显著高于春季和冬季水体。pH、DOC、E2/E3、脂类、蛋白类及木质素类与PPRIs产生速率展现出了良好的正相关关系,尤其是其中的DOC与木质素类组分;另外在三维荧光指标结果中,荧光指数(FI)和新鲜度指数(β/α)与PPRIs呈现负相关关系,证明FI值越低即DOM陆源性越高、非新生DOM比例越高,则PPRIs产生速率越高。综上,PPRIs的光化学产生与植物源DOM密切相关。与春季和冬季相比,夏季和秋季鄱阳湖水体的有机质高,而其中DOM组分中芳香族化合物丰度较高,主要来自陆生植物和土壤有机质,其有机质的腐殖化水平较高,而在春季和冬季水体有机质主要来自湖泊本身和微生物产生的有机质,属于内源。淹水植物残体降解过程释放的有机组分,对夏、秋季DOM的来源和组成有着极易被忽视的影响和作用,而其中光化学活性较强的有机组分如木质素是造成其PPRIs产率更高的主要原因。     

藻源性有机质对高原深水湖泊沉积物矿化作用的激发效应

湖泊营养水平提升,浮游植物快速增殖,大量藻类碎屑沉降到沉积物表面。藻屑作为新生不稳定有机质,对湖泊沉积物有机质(SOM)产生激发效应,影响湖泊沉积物碳循环过程。本文以深水湖泊抚仙湖南湖心沉积物为研究对象,采用优势种水华束丝藻(Aphanizomenon flos-aquae),进行不同浓度藻屑添加(×1倍组、×5倍组和×10倍组)的培养实验。应用碳同位素在线监测仪,探究藻屑添加对于SOM矿化作用的激发效应并预测可能产生的环境效应。结果表明：(1)添加的藻屑对上覆水和间隙水发光性溶解性有机质(CDOM)组成和性质产生影响,前期CDOM中类蛋白组分含量显著增加,但后期CDOM腐殖化程度升高。同时,藻屑的添加使二氧化碳(CO₂)释放量增大,蛋白酶活性和转化酶活性增强;(2)3个不同浓度的藻屑添加组均检测到不同程度激发效应,其中×1倍组和×5倍组对SOM矿化过程前期体现为正激发效应,最大值分别达到(12.18±0.65)和(26.60±9.14)μg/(mL ws),后期两个组别都转为负激发效应;×10倍组则在整个实验过程中均表现为负激发效应;(3)藻屑的添加使得间隙水易...     

Effect of organic matter on splash detachment and the processes involved

The influence of organic matter on splash detachment was investigated using soils with grass and peat treatments. The relationship between organic matter and aggregate stability to water disruption was positive for soils with grass treatment while it was negative for those with peat treatment. Organic matter from both treatments, however, reduced splash detachment by rainfall. Soils with grass did this by increasing aggregate stability while peat acted as a mulch on the soil surface. This implies that though organic matter always reduces splash detachment, different processes may be involved, depending on the form of the organic material. Because of the different processes involved, both negative and positive relationships between splash detachment and aggregate stability as reported in literature were obtained for the soils with grass and peat respectively.     

Tolerance of Brazilian brain coral Mussismilia braziliensis to sediment and organic matter inputs

In Brazil, where reefs occur in markedly turbid environments, the relationship between sedimentation/organic matter and corals is poorly known. Thus, the ex situ effects of sediment with and without organic matter over the ΔF/Fm and physical state of Mussismilia braziliensis were analyzed. The ΔF/Fm and coral physical state, evaluated through the susceptibility index to sedimentation (SI), were measured in seven colonies exposed to sedimentation (0–450 mg cm⁻² day⁻¹) free of organic matter after 45 days of exposure, and in 12 colonies exposed to sedimentation (0–500 mg cm⁻² day⁻¹) with organic matter content (10%), in which case ΔF/Fm was measured after 72 h and SI after 120 h. In both cases there were effects of increasing sedimentation on the SI with no effect on ΔF/Fm. Despite the tolerance to high sedimentation rates shown by this coral, we noted that the presence of organic matter might reduce its tolerance to sedimentation stress.     

The contribution of bacteria to organic matter in coal-measure source rocks

On the basis of GC–MS analysis, a suite of nine coal-measure source rocks(Ro 0.51%–0.63%) from the southern margin of Junggar basin was found to contain many biomarkers for bacterially-generated hydrocarbons:hopane, sesquiterpene, C₂₃+ monomethyl alkanes(even carbon predominance), and C₂₄+ alkyl cyclohexane.Rock–eval and microscope analysis indicate that vitrinite(especially desmocollinite and homocollinite) plays a significant role in the generation of hydrocarbons in coalmeasure source rocks. Vitrinite performs this role by absorbing ultramicroscopic organic matter, generally in the form of resins or bacterial plastids. C₂₃+ monomethyl alkanes(even carbon predominance) and C₂₄+ alkyl cyclohexane series compounds are derived from bacterial metabolites of higher plants. The ultramicro organic matter adsorbed by vitrinite source rocks in the study area is probably ultramicro bacterial plastids. Because the organic matter of higher plants with low hydrogen content has been transformed into organic matter rich in hydrogen by bacteria, the hydrocarbon generation capacity of source rocks is greatly improved. In other words, in coal-measure source rocks, bacteria play an important role in hydrocarbon generation.     

An isotopic model for the origin of autochthonous organic matter contained in the bottom sediments of a reservoir

Geochemical analysis of surface sediment samples collected in 2005 and 2006 was used to evaluate the potential sources of the organic matter present in sediments of southeast Poland's Solina Reservoir.Statistical analysis of sediment variables(carbon to nitrogen ratio, and the carbon 13 and nitrogen 15 isotope ratios) determined for the organic fraction indicated significant spatial variability with respect to sources of organic matter. A binary mixing model was developed from literature sources to predict the relative contributions of allochthonous and autochthonous production to sediment organic matter.Autochthonous production was shown to account for 60-75% of bulk sedimentation in the lacustrine parts of the reservoir, near the dam. In contrast, autochthonous production accounted for only 25% of sedimentation in the riverine zone receiving stream inputs. Statistical analysis identified the δ~(15)N of organic matter as the best predictor of the source of organic matter. Multiple regression analysis indicated that two water-quality variables(nitrate and dissolved silica) were significantly related to the δ~(15)N signature of organic matter. This led to a conclusion that limnetic nitrate and dissolved silica concentrations were regulating organic matter production in the Solina Reservoir.     

Individual and population indicators of Zostera japonica respond quickly to experimental addition of sediment-nutrient and organic matter

A manipulative field experiment was designed to investigate the effects of sediment-nutrients and sediment-organic matters on seagrasses, Zostera japonica, using individual and population indicators. The results showed that seagrasses quickly responded to sediment-nutrient and organic matter loading. That is, sediment-nutrients positively impacted on seagrasses by increasing N content of leaves and roots, leaf length and belowground biomass. Sediment-organic matter loading lowered N content of seagrass leaves and belowground biomass. Negative effects of organic matter loading were aggravated during nutrient loading, by decreasing N content of leaves, P content of roots, leaf width, shoot number in the middle period of the experiment, increasing C/N ratio of leaves, C/P and N/P ratio of roots and above to belowground biomass ratio of seagrasses. Consequently, Z. japonica could be considered as a fast indicator to monitor seagrass ecosystem status in the eutrophic areas and facilitate to interpreting the response of seagrasses to multiple stressors.     

基于脂质生物标志物评估河道型水库表层沉积物有机质来源

水电开发导致河岸生境破碎化程度加剧和水库沉积物截留问题日益突出,而目前关于河道型水库有机质(OM)溯源及分布特征的研究较少,进而造成OM在水库复杂环境介质中迁移机理尚不清楚。本研究将脂质生物标志物分析方法应用于大渡河瀑布沟水库表层沉积物,经过气相色谱-质谱法对沉积物OM脂质组分进行了分析,将其量化并分为自然、成岩、热源和污水标志物4种来源。结果表明:OM平均含量坝前(10.7%±4.8%)>坝后(7.3%±0.9%)>库中(6.7%±1.8%),说明水库对沉积物OM的截留有显著影响。可提取脂质组分主要来源于自然标志物(45.9%±13.9%),碳偏好指数、陆源/水生比和陆生与水生植物输入比显示OM主要来源于陆生高等植物,占自然定量分子的70.5%±9.1%。此外,坝前汉源城镇下游D6和D7点位人为标志物(44.6%±25.1%)分子明显比自然标志物(24.2%±3.7%)含量高,并进一步通过比例研究强调了污水标志物的贡献率较为突出(31.6%±12.8%),这与该地住宅区生活污水处理设施覆盖率较低相关,表明OM污染源组成变化与水库滞留效应的耦合作用有关。     

Characterization of organic matter in marine sediments to estimate age offset of bulk radiocarbon dating

Radiocarbon dating of Arctic marine sediment is often challenging due to the low availability of calcareous fossils. Consequently, bulk organic matter dating has at times been used to establish sediment core chronologies. Yet, radiocarbon dates based on bulk organic matter often appear to deviate vastly from dates based on fossils, mainly caused by input of allochthounous carbon, including terrigenous organic matter. In this study, we aim to examine the link between the composition of the bulk organic matter and the age offsets between the bulk radiocarbon dates and those obtained from calcareous foraminiferal tests. All samples are taken from the marine sediment core AMD14-204C from offshore Upernavik (eastern Baffin Bay). The radiocarbon dates for bulk organic matter are on average ∼3000 years older than the radiocarbon dates based on foraminifera, but with changing age offsets throughout the record. To investigate the cause of this age offset and its variations over time, we applied core scanning, X-ray Fluorescence analysis, stable isotopes, organic pyrolysis and microscopic organic petrology to examine the distribution and characterization of the organic matter. The results show that the older organic matter includes clastic input of reworked sedimentary rocks potentially originating from West Greenland and/or the Canadian Arctic Archipelago. Changes in the input of contemporary marine algal produced organic matter versus both terrigenous input and reworked ancient organic matter appear to control the age offsets between the bulk and foraminifera dates. A low Hydrogen Index and low δ¹³C_org values together with a high Oxygen Index, indicative of high influence of terrigenous organic matter, seem to correspond to samples with the largest age offsets; 1000–2000 years greater than in other samples. To examine the cause of the variations in the age offsets, a new quantification of the autochthonous organic matter as a fraction of the TOC was calculated. This shows that samples with the largest age offsets contained the lowest fraction (as low as ∼12%) of autochthonous organic matter in the TOC.     

Erodibility of soil and organic matter: independence of organic matter resistance to interrill erosion

The enrichment of organic matter in interrill sediment is well documented; however, the respective roles of soil organic matter (SOM) and interrill erosion processes for the enrichment are unclear. In this study, organic matter content of sediment generated on two silts with almost identical textures, but different organic matter contents and aggregations, was tested. Artificial rainfall was applied to the soils in wet, dry and crusted initial conditions to determine the effects of soil moisture and rainfall and drying history on organic matter enrichment in interrill sediment. While erosional response of the soils varied significantly, organic matter enrichment of sediment was not sensitive to initial soil conditions. However, enrichment was higher on the silt with a lower organic matter content and lower interrill erodibility. The results show that enrichment of organic matter in interrill sediment is not directly related to either SOM content or soil interrill erodibility, but is dominated by interrill erosion processes. As a consequence of the complex interaction between soil, organic matter and interrill erosion processes, erodibility of organic matter should be treated as a separate variable in erosion models. Further research on aggregate breakdown, in particular the content and fate of the organic matter in the soil fragments, is required. Copyright © 2007 John Wiley & Sons, Ltd.     

The degree of metamorphism of organic matter in sedimentary rocks as a paleo-geothermometer,applied to the Upper Rhine Graben

The subsidence of sedimentary layers implies increasing temperature downwards within the sedimentary column, so that the degree of coalification of organic matter increases continually. Apart from temperature, the slowly reacting chemical compounds of the organic matter strongly depend on time, too.It is shown that the coal rank is proportional to the integral of temperature and time of burial (t) for the Tertiary sedimentary rocks of the Upper Rhine Graben. This relationship is used to calculate paleogeothermal gradients (gradT) for some boreholes in the Upper Rhine Graben, from which the rate of burial during geological history (z(t)) is known. The degree of coalification is measured by its mean optical reflectivity (R _m), so that the relationship between coalification and geothermal history isR _m ² gradT z(t) dt.The results show high heat flow during Lower Tertiary and a decrease during Upper Tertiary at some locations of the Upper Rhine Graben. The recent high heat flow is not detectable in coalification. The young thermal anomaly is perhaps caused by ascending pore fluid and/or by heat conduction from a heat source in the lower crust.