Stable carbon isotope ratios of rock varnish organic matter: a new paleoenvironmental indicator

Stable carbon isotope ratios of organic matter in rock varnishes of Holocene age from western North America and the Middle East show a strong association with the environment. This isotopic variability reflects the abundance of plants with different photosynthetic pathways in adjacent vegetation. Analyses of different layers of varnish on late Pleistocene desert landforms indicate that the carbon isotopic composition of varnish organic matter is a paleoenvironmental indicator.     

Chondrites: a trace fossil indicator of anoxia in sediments

The trace fossil Chondrites, a highly branched burrow system of unknown endobenthic deposit feeders, occurs in all types of sediment, including those deposited under anaerobic conditions. In some cases, such as the Jurassic Posidonienschiefer Formation of Germany, Chondrites occurs in black, laminated, carbonaceous sediment that was deposited in chemically reducing conditions. In other cases, such as numerous oxic clastic and carbonate units throughout the geologic column, Chondrites typically represents the last trace fossil in a biotutbation sequence. This indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters.     

Copper and the role of isopods in degradation of organic matter

On an artificial substrate of filter paper, Porcellio scaber cannot extract copper from leaf litter. If one increases the copper content of the food by soaking the leaves in solutions of CuSO(4) or in organic extracts, assimilation of copper becomes possible, but only at concentrations higher than 1 microgram of copper per milligram of ash. This is too high a level for primary vegetable matter to be considered a plausible source of copper for isopods. I present evidence that in fecal material the critical level at which assimilation of copper becomes feasible is lower than in primary organic material by nearly an order of magnitude, and that isopods are obliged to switch to coprophagy in order to allow accumulation of copper in their bodies.     

Diversity of planktonic foraminifera in deep-sea sediments

The diversity of a planktonic foraminiferal assemblage on the ocean floor depends on the state of preservation of that assemblage. As dissolution progresses, species diversity (number of species in the assemblage) decreases, but compound diversity (based on relative species abundance) first increases and then decreases; species dominance first decreases and then increases. The reason for these changes is that the species most susceptible to solution deliver moresediment to the ocean floor than do species with solution-resistant shells, possibly because the more soluble tests are produced in surface waters, where growth and production are greatest.     

Metabolic activity of subsurface life in deep-sea sediments

Global maps of sulfate and methane in marine sediments reveal two provinces of subsurface metabolic activity: a sulfate-rich open-ocean province, and an ocean-margin province where sulfate is limited to shallow sediments. Methane is produced in both regions but is abundant only in sulfate-depleted sediments. Metabolic activity is greatest in narrow zones of sulfate-reducing methane oxidation along ocean margins. The metabolic rates of subseafloor life are orders of magnitude lower than those of life on Earth's surface. Most microorganisms in subseafloor sediments are either inactive or adapted for extraordinarily low metabolic activity.     

Labile organic matter as an indicator of anthropogenic evolution of gray forest soils

The change in the content of labile organic matter during anthropogenic evolution of gray forest soils of the right bank region of Nizhni Novgorod oblast has been studied. It has been established that its chemical and elemental compositions reflect the character of the biological cycle and direction of the pedogenic process in agrocenoses.     

大河口水库表层沉积物有机质特征及来源解析

为深入分析水库生态系统的污染来源和水环境的营养状况,本文对大河口水库表层沉积物中总有机碳(TOC)、总氮(TN)含量的分布特征,碳同位素(δ13C)、氮同位素(δ15N)和C/N值的组成进行分析,探讨了沉积物中有机质的来源。结果表明:大河口水库表层沉积物以远源搬运的风成沉积物为主,TOC含量在1.38%～3.52%,平均值为2.34%;TN分布范围在0.06%～0.21%,平均值为0.11%;δ~(13)C分布范围在-2.69%～-2.41%,平均值为-2.54%,δ~(15)N范围在0.19%～0.54%,平均值为0.39%。通过端元混合模型对沉积物有机质来源进行定性和半定量分析表明,陆生C3植物、土壤有机质和淡水水生植物是大河口水库沉积物有机质的3种主要来源,其中陆生C3植物贡献最大,其次是土壤有机质,个别断面有淡水水生植物来源。研究表明,大河口水库整体的初级生产力不高,有机质来源组成差异较小,有机质来源大都为外源。     

Silicate spherules from deep-sea sediments: confirmation of extraterrestrial origin

Silicate spherules produced by atmospheric melting of meteoric bodies are probably the most common form of extraterrestrial material on the earth. It has never been possible to positively identify such particles although it has been known for more than a century that silicate spherules of suspected extraterrestrial origin are present in deep-sea sediments. One such spherule has been identified as definitely extraterrestrial since its abundances of nonvolatile trace elements closely match those of primitive solar system material.     

Volcanic dust in deep-sea sediments: relationship of microfeatures to explosivity estimates

Particle size variations in a series of volcanic ash layers, deposited in high latitudes of the South Pacific during the past 2.5 million years, were earlier analyzed by using a model in which source cloud height and minimum volcanic paleoexplosivity are derived from downwind ash distribution. Examination of submicrometer morphological features of the volcanic glass shards reveals a clear relationship between what appear to be impact features on the glass surfaces and the independently derived paleoexplosivities, which suggests that this may be a simple means to characterize ash horizons and estimate relative volcanic explosivities.     

Pleistocene climates in the atlantic and pacific oceans: a comparison based on deep-sea sediments

Comparison of Pleistocene climatic records defined by variations in abundance of planktonic Foraminifera in three cores from the southeastern Pacific with similar records in cores from the Atlantic suggests that times of warm surface water in this region of the Pacific were at least partly synchronous with times of cool water in the Altantic. This conclusion opposes the Milankovitch theory of the causation of ice ages, but it harmonizes with a modified form of Simpson's hypothesis.     

Pleistocene climates in the atlantic and pacific oceans: a reevaluated comparison based on deep-sea sediments

Variations of the Globorotalia menardii complex in cores from the Indian Ocean can be interpreted as indicating climatic changes that are opposite to trends exhibited by the total planktonic fauna. The questionable value of correlations between different water masses based on a single species can be shown by Neogloboquadrina dutertrei subcretacea in cores obtained off the coast of California and Baja California. This information, in addition to previous correlations between Quaternary cores of the Atlantic and Pacific oceans, indicates that the Pleistocene history of the two oceans was parallel.     

Microbial autotrophy: a primary source of organic carbon in marine sediments

The chemoautotrophic fixation of carbon dioxide by bacteria is responsible for an appreciable component of the organic carbon in a sulfide-rich marine mud. A peak of carbon dioxide fixation (at 40 centimeters subbottom) coincides with peaks in the organic carbon content, the ratio of carbon to nitrogen, and bacterial cell counts. Stimulation of fixation by thiosulfate and inhibition by anaerobic conditions implicate the chemoautotrophic sulfur bacteria as primary producers in this environment.     

Meteorites: optical activity in organic matter

A low- amplitude, positive, Cotton effect, centered at about 340 millimicrons, has been observed in organic extracts of samples from ordinary (noncarbonaceous) chondrites. Ancillary evidence renders it likely that this optical activity derived from contamination by biologic materials on Earth.     

Volcanic eruptions: contribution to magnetism in deep-sea sediments downwind from the azores

The mean bulk magnetic susceptibility (x) and the intensity of remanent magnetization (J) of deep-sea sediments vary systematically, but in an opposite sense, for a distance of 600 kilometers downwind from the Azores. Beyond the distance both J and x diminish for at least another 600 kilometers. The dominant type of magnetic particle in the sediments is interpreted to be atmospherically transported volcanic dust.     

贵州威宁草海湿地表层沉积物有机质时空分布及其来源辨析

为探究岩溶湿地生态环境的营养状况及污染物来源,以贵州威宁草海岩溶湿地为例,通过对其不同水文期表层沉积物中总有机碳(TOC)和总氮(TN)的含量分布及其稳定碳同位素(δ¹³C)、稳定氮同位素(δ¹⁵N)和C/N的分析,探讨了沉积物有机质的分布特征及来源。结果表明:草海湿地表层沉积物丰水期TOC、TN含量变化范围分别为3.75%~32.71%和0.39%~2.90%,平均值分别为14.34%和1.52%;枯水期TOC、TN含量变化范围分别为1.26%~34.11%和0.18%~2.49%,平均值分别为12.46%和1.12%;丰水期TOC、TN含量略高于枯水期,这与丰水期大量降雨带来的陆源输入有关,同时在空间分布上二者在两个水文期均表现为西南和湖心区域大于东部和西北区域。草海湿地表层沉积物丰水期δ¹³C、δ¹⁵N分布范围分别在-2.55%~-1.97%和0.03%~0.37%,平均值分别为-2.23%和0.24%;枯水期δ¹³C、δ¹⁵N分布范围分别在-2.75%~-1.96%和0.10%~0.46%,平均值分别为-2.35%和0.30%;其中δ¹³C的空间分布特征表现为东区较西区明显偏负,说明东区污染严重,这是由于东区毗邻县城,污染物来源复杂,沉水植物遭到破坏,使得湖泊自身生产力降低。通过端元混合模型对沉积物来源进行定性和半定量分析,结果表明:草海湿地表层沉积物有机质的主要来源为土壤有机质、浮游藻类及淡水水生植物,同时由于草海岩溶湿地具有较高的初级生产力,沉积物中有机质来自内源的贡献大于来自外源的输入。     

阳宗海湖滨湿地沉积物砷和有机质对磷赋存形态的影响

以云南省阳宗海南岸湖滨湿地为研究对象,研究了沉积物中总砷(TAs)、总磷(TP)及各形态无机磷的含量及空间分布特征,并对沉积物中TAs和有机质(OM)含量与各形态磷的相关性进行了分析。结果表明:沉积物TAs含量(1.84~24.37 mg·kg~(-1))处于土壤环境质量标准Ⅲ级限值的警戒线,表层富集明显,湖滨湿地对砷具有拦截作用;沉积物TP含量受上游人为干扰方式影响,农田和农村综合干扰样带的TP含量最高(604.13 mg·kg~(-1)),表层富集明显,湖滨湿地对外源磷也有截留作用,无机磷形态中以磷石灰型(Ca_(10)-P)为主,活性磷酸二钙磷(Ca_2-P)和磷酸八钙磷(Ca_8-P)、潜在释放的磷酸铝盐(Al-P)和磷酸铁盐(Fe-P)、惰性的闭蓄态磷酸盐(O-P)含量均较低;沉积物TAs和OM含量对磷的赋存状态均存在影响,主要与砷-磷在沉积物上的竞争吸附作用以及沉积物环境因素的变化有关。     

Eolian biogenic detritus in deep sea sediments: a possible index of equatorial ice age aridity

Opal phytoliths and freshwater diatoms, transported mainly in dust to the equatorial Atlantic, are common in sediments deposited when ocean waters were cool, and sparse in those deposited when waters were warm, during the last 1.8 million years. Climate in source areas of the southern Sahara apparently was more arid during glacials and more humid during interglacials.     

三江平原耕地土壤有机质时空分布特征——以富锦市为例

以2013年三江平原富锦市实地调查和采样数据,1981年国家第二次土壤普查数据和各种辅助图件为基础,运用地统计学、统计学和GIS技术等研究方法,分析三江平原富锦市农田耕层土壤有机质(SOM)空间分布特征,探讨其32年间SOM变化的规律。结果表明,2013年富锦市SOM含量平均值为42.1 g/kg,较1981年下降了18.6%;在空间上呈现出较为明显的东南高西北低的分布格局,属于中等强度空间相关,受结构性因子和随机因子的共同作用。按照国家第二次土壤普查时富锦市SOM分级标准,1981-2013年有85.9%的农田耕层SOM发生不同程度的变化,其中有50.5%面积得到了提升,有35.4%面积有所下降。     

高原湖泊流域不同类型农村沟渠底泥氮、磷和有机质分布特征及污染评价

为揭示高原湖泊流域农村沟渠底泥氮、磷和有机质的分布特征,以云南省4种典型农村(畜禽养殖型、生态休闲型、集镇型和传统型)为研究对象,分析其全氮(TN)、全磷(TP)和有机质(OM)的含量,并应用有机指数法和单因子评价法评价底泥的污染程度。结果表明,不同类型农村之间w(TN)、w(TP)和w(OM)的空间分布差异显著,w(TN)和w(TP)均表现为畜禽养殖型集镇生态休闲型传统型,w(OM)表现为畜禽养殖型生态休闲型集镇型传统型。TN与TP呈极显著正相关,说明氮磷元素在底泥累积过程中有着较高的同步性;TP与OM呈极显著正相关,说明OM是磷元素的重要载体;TN与OM的相关性不显著,表明农村沟渠底泥氮的主要来源并不是OM的矿化与分解。各村沟渠底泥氮和有机质污染均达到了重度污染状态,磷污染程度相对较低,畜禽养殖型农村属于中度污染,集镇型和生态休闲型农村属于轻度污染,传统型农村属于清洁型。畜禽养殖业是高原湖泊流域典型农村沟渠底泥氮、磷和有机质污染的主要来源。