青海湖布哈河口区表层沉积物有机质分析及其比较沉积学意义

青海湖布哈河口区与晚三叠世鄂尔多斯盆地及四川盆地具有相似的古地理特征和水体环境,对布哈河口区表层沉积物中有机质的类型和丰度进行研究具有重要的比较沉积学意义.通过对布哈河口区河流、三角洲平原、前三角洲、滨湖、浅湖及半深湖环境表层沉积物样品全岩组分、总有机碳(TOC)及有机质类型进行分析,确定布哈河口区表层沉积物中有机质主要为Ⅱ2型和少量Ⅱ1型,TOC含量不超过4.29%,其中半深湖TOC含量最高并且有机质类型较好.布哈河口区表层沉积物中TOC含量主要受黏土矿物含量、有机质生产力和水深控制,半深湖沉积物具有较高的黏土矿物含量、较高的有机质生产力、较好的有机质类型和较大的覆水深度,有利于有机质的生产和保存,为河口区最有利于烃源岩发育的环境.同时,根据前三角洲、浅湖及半深湖沉积物中TOC含量与水深存在良好的相关性,建立了利用岩石中TOC含量对古水深进行恢复的公式.     

北华北中上元古界烃源岩发育环境及其控制因素

海相烃源岩发育机理问题制约了我国油气勘探产业的发展. 中上元古界洪水庄组、铁岭组和下马岭组是北华北地区重要的烃源岩, 查清其发育环境及其控制因素具有重要的科学理论和油气勘探意义. 基于沉积学(层序地层学)、古生态及沉积地球化学探讨了烃源岩沉积古地理及其发育模式. 研究表明这些烃源岩中有机质富集的主控因素包括适宜的古地理位置、中低纬度区的生物勃发事件、水底缺氧环境、沉积物中磷组分的富集以及粘土矿物在海相碳酸盐有机质富集保存过程中的赋存驻留作用.     

中尺度流域次降雨洪水过程模拟——以太湖上游西苕溪流域为例

古近系沙河街组是阳信洼陷最重要的生烃层段.其湖盆充填具阶段性和沉积演化的旋回性,形成了由沙四段、沙三段与沙一段组成的复合生烃系统和不同的地球化学特征.利用Rock-Eval生油岩评价仪、色谱-质谱仪等实验分析技术对不同层系样品进行了地球化学特征分析研究,其中生烃潜力指标包括有机碳含量(TOC)、残余生烃潜量(S1 S2)、氢指数IH、氯仿沥青"A";成熟度指标包括热解峰温Tmax、奇偶优势参数OEP、饱和烃轻重比(C21 C22)/(C28 C29)及∑C21-/∑C22 、镜质体反射率Ro、莫烷/藿烷及甾烷生物标志物参数C29ββ(ββ αα)、C29ααα20S(20S 20R);古环境指标包括异构烷烃参数Pr/Ph、Pr/n-C17、Ph/n-C18及伽马蜡烷等.结果表明,沙四段为弱还原-还原性的半深湖沉积,沉积了一套中等厚度、分布局限的烃源岩(TOC平均为1.5%),其较深位置的烃源岩基本进入成熟阶段,多形成成熟油;沙三段属弱还原-还原性的半深湖-深湖环境,其烃源岩中有机质丰度较高(TOC平均为3.5%),大部分烃源岩处于未成熟-低成熟状态,主要形成未熟油;沙一段为湖水咸化、还原性的半深湖相环境,其烃源岩中有机质丰度高(TOC平均为5%左右),但处于未成熟阶段,主要生成生物气.     

南四湖现代沉积物中营养元素分布特征

对南四湖不同湖区20个表层沉积物和独山湖湖区沉积岩芯中营养元素进行了分析结果表明表层沉积物中南阳湖总磷最高,独山湖次之;独山湖总有机碳和总氮含量最高,南阳湖次之;而昭阳湖总有机碳、总氮和总磷含量较低.沉积岩芯中137Cs数据表明南四湖独山湖区柱状沉积物上部(0-18 cm)沉积速率为3.5mm/a;总有机碳、总氮和总磷含量主要集中在沉积岩芯0-8 cm内,并呈现一致的垂向分布规律,具有明显的三阶段分布特征,反映了流域社会经济的发展导致营养元素的释放量增加,造成了湖泊现代沉积物中营养元素的积累.碳氮比值处于7.6-11.4之间,有机质的选择性分解不明显,指示沉积物中有机质主要来自无纤维束的陆源植物.监测数据表明济宁市的城市生活污水、工农业废水排放进入南阳湖是南四湖有机质和TP富集的主要来源.     

东营凹陷波动古湖相烃源岩沉积特征

以东营凹陷牛38井为例,研究显示,该井沙河街组沙三段烃源岩的沉积特征具有明显的波动性．宏观上体现为, 构造因素控制湖盆的整体升降和沉积构造旋回,但季节性气候及其它因素的影响使湖盆呈现次级旋回的复合性沉积．微观上表现为纹层的不连续性及生物扰动构造等事件性沉积.古湖面不同幅度的波动和变化导致相对稳定的泥岩沉积的不稳定性,有机质的分布也呈现较显著的非均质性．湖泊的沉积过程影响了微量元素、有机质以及烃源物质的分布,水体较深、盐度较高的沙三段下部多数微量元素含量较高以及B／Ca、Sr／Ba呈现高值;水体较浅、盐度较低的沙三段中部各元素的分布较为稳定,B／Ca、Sr／Ba比值及Sr的含量均显著降低.波动性沉积导致烃源岩呈现明显的优劣性分布,沙三段下部中的有机质富集,为优质烃源岩;沙三段中部的有机质分布较为分散,生排烃的资源潜力有限．     

巢湖表层沉积物中生物易降解物质成分特征与分布规律

富营养化湖泊的藻类残体大量沉降到湖底,其中易降解成分的降解和转化快速消耗底层水体中的溶解氧,极易造成水土界面缺氧,影响湖泊生态系统的健康.于2014年对巢湖12个样点的表层沉积物进行周年跟踪研究,分析样品中有机质来源、总有机碳(TOC)、蛋白质、总糖、总脂以及生物聚合物碳(BPC)等成分含量,揭示易降解有机质的成分特征及在巢湖的分布规律.研究表明:巢湖表层沉积物TOC含量较高,全湖样点平均含量达到1.24%.BPC含量占TOC含量的30.99%~60.48%,有机质中易降解成分含量较高,并且在冬季和夏季时在巢湖西北部湖区有明显累积;有机质及其中的生物易降解部分均主要集中在粒径4~8μm的表层沉积物上,在应用工程技术手段处理、降解表层沉积物中的过量有机质时,更应该关注粒径为4~8μm的沉积物颗粒.     

太湖西北部表层沉积物粒度特征与沉积环境

对太湖西北部主要入湖河流、河口及近岸湖区64个表层沉积物样品进行粒度分析,结合粒度参数计算和聚类分析,探讨了表层沉积物的粒度分布特征及其沉积类型.研究结果表明:研究区沉积物平均粒径介于4.0~58.7μm之间,粒级组分为黏土、粉砂和砂,其含量的均值分别为7.19%、81.81%和11.00%.太湖西北部表层沉积物以粉砂和砂质粉砂为主;研究区粒度总体呈南粗北细的分布特征,太湖西部沿岸区距离物源区较近且水动力条件复杂,沉积物粒度较粗.太湖北部入湖河流沉积物的频率曲线峰形较宽,峰值位于细粒级;西岸入湖河道多呈单峰态,粒径偏粗;河口区沉积物粒径较河道偏粗,粗颗粒含量高.Q型聚类分析结果表明,研究区可分为4类沉积区,其中3类沉积区有典型特征:第1类沉积区主要分布在太湖西部沿岸,其沉积物粒度相对较粗;第2类沉积区主要位于入湖河流河口,沉积物粒度最粗;第3类沉积区位于蓝藻频发的梁溪河,其沉积物黏土含量极高,表明沉积物粒度特征可能与污染状况有一定的联系.     

鄱阳湖网箱养殖区沉积物有机质来源分析

通过对鱼苗时期鄱阳湖网箱养殖区沉积物、饵料及鱼粪等样品总有机碳(TOC)含量、总氮(TN)含量、碳氮比(C/N)、δ^13 C及δ^15 N的测定,分析探讨了鄱阳湖网箱养殖区沉积物有机质来源,量化了网箱养殖废物对养殖区沉积物有机质的贡献.结果表明,网箱养殖区沉积物的δ^13 C和δ^15 N值分别为-27.67‰~-25.65‰和5.19‰~7.27‰,饵料的δ^13 C和δ^15 N值分别为-24.73‰和10.28‰,鱼粪的δ^13 C和δ^15 N值分别为-26.30‰和15.54‰.网箱养殖区沉积物有机质来源主要有残饵、浮游生物及其他来源,其贡献率分别为48.3%±11.4%、25.6%±11.3%及26.0%±5.8%,而鱼粪的贡献几乎可以忽略不计.在水动力平流引起的扩散及沉积物的再悬浮的影响下,网箱养殖源有机质的扩散距离达1500 m.在鱼苗时期,鱼类网箱养殖的残饵是鄱阳湖网箱养殖区沉积物有机质的主要来源.     

高演化海相碳酸盐烃源岩地球化学综合判识--以鄂尔多斯盆地为例

针对中国海相碳酸盐岩烃源岩的成熟度高、有机质丰度低等特殊性,以鄂尔多斯盆地下古生界为例, 通过微量元素富集系数计算、稀土元素的配分模式、元素和碳同位素等的数理统计分析及三维图解等多元综合分析, 结合必要的有机参数, 反演了盆地烃源岩发育环境, 评价碳酸盐岩烃源岩及其分布. 就鄂尔多斯盆地而言, TOC为0.2%是个重要的界限值, 研究表明: 在TOC>0.2%的层段中, Ba富集,δ13Ccarb正偏移, δ13Corg<-28‰, 反映出古生产力、有机质埋藏量较高, 具较好生烃潜力, 稀土元素分异强, 指示沉降速率低, 有机质保存条件好, 利于烃源岩发育.克里摩里组、乌拉力克组具一定规模, 可视为潜在有效烃源岩. 而TOC＜0.2%的层段, Ba含量低, δ13Ccarb多为负值,δ13Corg为-24‰～-28‰,指示有机质埋藏量低,生烃潜力差,稀土元素分异弱,沉降速率较快,多属浅水高能氧化环境,不利于烃源岩发育.利用无机与有机地球化学方法综合评价高演化海相有潜力的碳酸盐岩烃源岩及分布是可行的.     

一种考虑密度因素的广义ΔlogR法预测总有机碳含量——以渤中凹陷西南部陆相深层烃源岩为例

烃源岩总有机碳含量(TOC)的预测是烃源岩有机质丰度评价的重要一环.为解决传统ΔlogR方法应用于陆相深层烃源岩误差较大的问题.本文以ΔlogR法为基础,提出了一种考虑密度因素的广义ΔlogR法预测TOC.传统ΔlogR方法是一种基于测井曲线(声波、电阻率等)和成熟度参数(LOM)的预测TOC的方法,可以获得纵向上连续的有机碳分布,并且在国内外多个地区取得了较好的效果.但是研究表明,由于陆相深层烃源岩受到压实作用等影响,传统ΔlogR方法预测的结果不理想.干酪根有机质的密度远低于烃源岩基质密度,将考虑密度因素的广义ΔlogR法预测TOC的方法应用于渤中凹陷西南部东营组和沙河街组烃源岩,对其TOC进行分段预测,并与传统ΔlogR法、敏感测井多元回归方法预测结果进行对比,结果表明,研究区使用该方法的效果要优于其他两种方法.该方法拓展了传统ΔlogR法的适用范围,为烃源岩TOC的预测提供了新的思路和方法.     

Mercury in sediments of Ulhas estuary

Hg levels in water, suspended particulate matter and sediment of the Ulhas estuary are under considerable environmental stress due to the indiscriminate release of effluents from a variety of industries including chlor-alkali plants. Concentration ranges of dissolved (0.04-0.61 micro gl(-1)) and particulate (1.13-6.43 micro gg(-1)) Hg reveal a definite enhancement of levels in the estuary. The Hg burden in sediment upstream of the weir that limits the tidal influence is low (0.08-0.19 micro gg(-1)) with low C(org) content (1.8-2.9%). The high Hg content of the sediment just below the weir varies seasonally (highest concentration recorded being 38.45 micro gg(-1)) due to incremental accretion of sediment as the fresh water flow over the weir progressively decreases. The 30 km segment of the estuary sustains markedly high levels of Hg in the sediment with an exponential decrease in the seaward direction from the weir. Higher concentrations than the expected background prevail in all the estuarine cores up to the bottom, though the overall concentration decreases from about 20 micro gg(-1) in core 7 (inner estuary) to 1 micro gg(-1) in core 31 (outer estuary). The Hg in sediment is associated with C(org), while its correlation with Al, Fe and Mn is poor. The Hg profiles in cores from the Arabian Sea (stations 34, 35 and 37) have a distinct horizon of enhanced concentration in the 5-60 cm segment. Based on 210Pb dating of core 37, the sediment at the bottom of this core is inferred to have been deposited in the year 1949, roughly two year prior to the establishment of the first chlor-alkali plant and represents the background (0.06-0.10 micro gg(-1)). The Hg profiles in the offshore cores indicate a marked increase in transfer of Hg to sediment subsequent to 1980, with a peak around 1990-1992. Based on the index of geoaccumulation it is considered that the estuarine segment between stations 4 and 23 is extremely polluted, while the sediment from the open coast is moderately polluted in the top 25-30 cm with respect to Hg. The enrichment factor of Hg in the sediment is 350-700 for core 4 and decreases to 0-7 for the open-shore cores.     

Methylation of lead in marine sediments

Results of incubation experiments with marine sediments containing added amounts of lead in various chemical forms indicated that about 0.03% of lead as Pb(NO₃)₂ underwent methylation. Tetravalent lead, as (CH₃)₃PbOAc, however, was methylated nearly quantitatively in the same time span. Experiments with sediments from four different areas of the British Columbia coastline showed little variation in methylating capacity and no relationship to total ambient lead content. The results suggest that lead contained in mine tailings in particular is not mobilized in detectable amounts by this route.     

Systematics in uranium-ionium dating of sediments

The mineral separates of a core have been systematically dated by the Io/Th chronology method. The results show that authigenic minerals, though not always completely authigenic, are suitable for dating.We give some evidence against the hypothesis of Io/²³²Th isotopic equilibrium in marine conditions and suggest that the minerals are mixtures of two components.     

Silicones in Chesapeake Bay sediments

Sediment samples from the upper reaches to the mouth of the Chesapeake Bay were analysed for extractable organic silicon (silicone) content. Organic silicon in the sediments ranged from less than 0.2 to some 36 ppm, w/w. In general, silicone tended to accumulate in high depositional areas: the northern bay, and along the shores to the south. While present, anthropogenic inputs in terms of defined source were not clear. It appears that processes in the bay act to rapidly remove silicone from the water column, probably on a function of the flocculation/precipitation of seston, especially in the northern area.     

Beryllium-10 in continental sediments

The concentration of¹⁰Be has been measured in 10 samples taken from a transect of surface sediments beginning in the Atchafalaya River and extending across the Bay 136 km into the Gulf of Mexico. If corrected for a lower retentivity of sand for Be, they have a concentration that is constant within 13%. This concentration is about an order of magnitude smaller than that of deep ocean sediments. For comparison, measurements of¹⁰Be in rainwater, in a sample of soil and in a deep ocean core were made.     

阳澄湖近代沉积物的古湖泊学研究

对阳澄湖两上短柱状样进行了地上代以及各种环境指标分析。结果表明,湖底沉积物由被长期沉积间断所分割的３个岩性层组成：下部层Ｃ属再沉积的更新世晚硬土层;中部层Ｂ为全新世沉积;上部层Ａ为近１００年以来的表层沉积。对层Ａ的详细分析显示,本世纪以来,特别是７０－８０年代以来,金属元素,营养元素和色素的沉积通量明显提高,说明湖泊重金属污染和富营养化程度的不断加重。     

Thermomagnetic evidence of native iron in sediments

The paper summarizes the results of thermomagnetic analysis concerning the distribution of metallic iron in the sediments ranging in age from Miocene to Early Cretaceous sampled from the following sections: Gams (Austria); Verkhorech’e and Sel’bukhra (the Crimea); Kvirinaki and Tetritskaro (Georgia); Aimaki, Dzhengutai, Madzhalis, and Gergebil (Ciscaucasia, Russia); Klyuchi and Teplovka (Volga region, Russia); Koshak (Kazakhstan); and Khalats and Kara-Kala (Turkmenia). Small amounts of native iron (from 10⁻⁵% to 0.05%) are identified in 521 samples of 921 studied; i.e., iron particles are almost pervasive. This fact traces the origin of these particles to cosmic dust. Some established features point to the heterogeneous character of the cosmic dust: (a) the samples clearly fall into two groups. One group comprises the rocks that contain iron particles; the rocks of the other group are iron-free. In the first group, four intervals are distinguished where the sediments are globally enriched with iron with constant nickel content (5–6%); (b) in terms of composition, the iron particles are divided into three groups. The first group contains pure iron; the particles pertaining to the second group contain iron with a minor amount of nickel typical for kamacite; and the third group comprises the particles of Fe-Ni alloy with more than 20% nickel. The first and the second groups are ubiquitous; the particles of the third group are spread locally. They bear no relation to cosmic dust and are probably associated with the meteoritic impacts.     

Trace metals in sediments of Raritan bay

Marine sediments are the ultimate recipient of nearly all trace metals introduced by man into aquatic ecosystems. This study examined the amounts and distribution of six trace metals (Cd, Cr, Cu, Ni, Pb, Zn) in sediments of Raritan Bay, apolluted estuary. The highest levels of these metals found in Raritan Bay were: Cd-15, Cr-260, Cu-1230, Ni-50, Pb-985, Zn-815. Three metals regimes within Raritan Bay are readily apparent. An area of high values extends across the Bay from the mouth of the Raritan Riverand Arthur Killinto Sandy Hook Bay. This is bounded on the south and northeast by areas of somewhat lower concentrations. An area of relatively low concentrations, near background values, occupies the region at the mouth of the Bay between Sandy Hook peninsula and Coney Island, New York. Metals values from Raritan Bay are compared with other areas and with a few exceptions, the Raritan Bay maximum levels were similar in magnitude to those of areas in Corpus Christi Harbour (U.S.A), Severn Estuary (U.K.), Deep Sea and Florida Lakes, River Blyth (U.K.), dump sites off New York City, various basins off South California, and in Long Island Sound.     

Indicative parameters of denitrification in river sediments

Denitrification is studied in sediments from two areas of the River Butrón which represent different situations with respect to their degree of pollution. Denitrification is analysed by means of the following parameters: maximum denitrification rate (V_max), Michaelis constant (K_m), denitrification rate (v), denitrification constant (k_d) and number of denitrifiers. In all the samples analysed denitrification follows a kinetic type Michaelis-Menten with respect to nitrate. V_max, K_m and number of denitrifiers are clearly superior in the polluted area when compared to the cleaner area, indicating an advantage given that denitrification suggests an alternative pathway for breaking down organic matter with low levels of dissolved oxygen. By comparison between K_m and natural nitrate concentration values we find that v follows a first order kinetic depending directly on the nitrate concentration. v also presents higher values in the area of the river where the entry of sewage is taking place than in the cleaner area. However, this difference does not have a kinetic origin but rather is given by different nitrate concentrations in their sediments. This is due to the fact that the two areas present similar efficiencies in the elimination of nitrate, which is deduced from the similar values of k_d.