巢湖表层沉积物中多溴联苯醚的分布和污染源解析

在巢湖不同区域采集了16个表层沉积物样品,利用气相色谱-质谱仪测定沉积物中低溴代多溴联苯醚(LPBDEs)和BDE209的含量,并对其残留、组成、空间分布和污染来源进行分析.结果表明,巢湖沉积物中共计检测到9种多溴联苯醚(PBDEs)化合物.∑LPBDEs的含量为0.001~2.75 ng/g,平均值为1.15 ng/g,平均检测率为44.83%;BDE209的含量为1.16~5.49 ng/g,平均值为2.83 ng/g,检测率为100%.与国内其他区域相比,巢湖沉积物中PBDEs含量总体处于中等水平.巢湖沉积物中各类LPBDEs和BDE209同系物含量为:西半湖东半湖湖心.巢湖沉积物中PBDEs以BDE209为主要成分,不同采样点PBDEs同系物的组成不同.相关性分析表明BDE209与LPBDEs在环境中的迁移存在相关性.     

三十年来长江中下游湖泊富营养化状况变迁及其影响因素

为弄清长江中下游通江/历史通江湖泊富营养化现状、成因及修复策略,对该区域27个大型湖泊和水库开展了4个季度的水质调查,并结合部分湖泊1988-1992年及2008年两个时段富营养化调查成果,分析近30年来长江中下游地区大型湖泊富营养化关键指标变化的特征及其驱动因素.结果表明,目前该区域绝大多数湖泊处于富营养水平,较1980s有明显加重,浮游植物叶绿素a及总磷是最主要的营养状态指数贡献因子;湖泊的富营养化状况与湖泊的江湖连通状况、换水周期等流动性状况、渔业养殖及管理、流域纳污、治理强度等人类活动方式和强度密切相关;与历史调查结果相比,氮、磷的增幅相对较小,而有机质污染程度明显加重、浮游植物叶绿素a浓度大幅增高,表明营养盐之外的其他因素,如水文节律的变化、江湖阻隔、不合理的渔业养殖活动等,对该区域湖泊的富营养化问题加剧、浮游植物生产力增高起到更为重要的作用.因此,从治理途径和策略上来看,增加湖泊的流通性、恢复部分湖泊的自然水文波动节律、优化湖泊渔业管理、提升湖泊流域营养盐的有效截留能力、实施湖泊生态修复工程是控制长江中下游湖泊富营养化、提升区域湖泊生态质量的关键.     

2002-2017年千岛湖浮游植物群落结构变化及其影响因素

为认识大型水库中浮游植物群落结构的演替特征及其驱动机制,以钱塘江流域新安江水库（下称"千岛湖"）为例,基于2002-2017年16年的水库浮游植物数据,结合同期千岛湖水质与水文气象资料,分析了千岛湖浮游植物结构及优势属的长期变化特征,探讨了影响浮游植物群落结构变化的主要因素.结果表明：2002-2017年千岛湖共鉴定出浮游植物7门93属,主要由硅藻门、绿藻门、蓝藻门及隐藻门种类组成.16年间,浮游植物年均丰度和群落结构经历了4个阶段：2008年前丰度持续低值且蓝藻不是主要类群,2009-2012年丰度较高且蓝藻成为主要类群,及2013-2015丰度降低且蓝藻占比降低,2016-2017年丰度增加且蓝藻再次成为主要类群.浮游植物门类变化的同时伴随着优势属的变化：浮游植物年优势属从2002-2008年的小环藻属（Cyclotella）、隐藻属（Cryptomonas）和蓝隐藻属（Chroomonas）转变为2009-2012年的颤藻属（Oscillatoria）、小球藻属（Chlorella）、小环藻属和蓝隐藻属,2013-2017年又转变为鱼腥藻属（Anabaena）、束丝藻属（Aphanizomenon）、小环藻属、针杆藻属（Synedra）、直链藻属（Melosira）、栅藻属（Scenedesmus）和蓝隐藻属.冗余分析表明,气温、风速、水位、入库流量等气象水文因子和总氮浓度、电导率、氮磷比、透明度等水质因子与浮游植物群落结构变化关系密切.研究结果表明,在千岛湖这种大型贫-中营养水库,浮游植物群落结构不仅受来水营养盐负荷的影响,还在很大程度上受水文、气象条件的影响,给水库藻类水华等生态风险的预测以及水库水质管理带来了挑战.     

A geological constraint on relative sea level in Marine Isotope Stage 3 in the Larsemann Hills, Lambert Glacier region, East Antarctica (31 366–33 228 cal yr BP)

In this paper we present geological evidence from the Larsemann Hills (Lambert Glacier – Amery Ice Shelf region, East Antarctica) of marine sediments at an altitude of c. 8 m a.s.l., as revealed by diatom, pigment and geochemical proxies in a lake sediment core. The sediments yielded radiocarbon dates between c. 26 650 and 28 750 ¹⁴C yr BP (31 366–33 228 cal yr BP). This information can be used to constrain relative sea level adjacent to the Lambert Glacier at the end of Marine Isotope Stage 3. These data are compared with the age and altitude of Marine Isotope Stage 3 marine deposits elsewhere in East Antarctica and discussed with reference to late Quaternary ice sheet history and eustatic sea-level change.     

The stratigraphic record and processes of turbidity current transformation across deep‐marine lobes

Sedimentary facies in the distal parts of deep‐marine lobes can diverge significantly from those predicted by classical turbidite models, and sedimentological processes in these environments are poorly understood. This gap may be bridged using outcrop studies and theoretical models. In the Skoorsteenberg Formation (South Africa), a downstream transition from thickly bedded turbidite sandstones to argillaceous, internally layered hybrid beds, is observed. The hybrid beds have a characteristic stratigraphic and spatial distribution, being associated with bed successions which generally coarsen and thicken‐upward reflecting deposition on the fringes of lobes in a dominantly progradational system. Using a detailed characterization of bed types, including grain size, grain‐fabric and mineralogical analyses, a process‐model for flow evolution is developed. This is explored using a numerical suspension capacity model for radially spreading and decelerating turbidity currents. The new model shows how decelerating sediment suspensions can reach a critical suspension capacity threshold beyond which grains are not supported by fluid turbulence. Sand and silt particles, settling together with flocculated clay, may form low yield strength cohesive flows; development of these higher concentration lower boundary layer flows inhibits transfer of turbulent kinetic energy into the upper parts of the flow ultimately resulting in catastrophic loss of turbulence and collapse of the upper part of the flow. Advection distances of the now transitional to laminar flow are relatively long (several kilometres) suggesting relatively slow dewatering (several hours) of the low yield strength flows. The catastrophic loss of turbulence accounts for the presence of such beds in other fine‐grained systems without invoking external controls or large‐scale flow partitioning and also explains the abrupt pinch‐out of all divisions of these sandstones. Estimation of the point of flow transformation is a useful tool in the prediction of heterogeneity distribution in subsurface systems.     

Effects of greenschist-facies metamorphism and related deformation on the Mobrun massive sulfide deposit,Québec,Canada

The Mobrun Zn-Cu-Ag-Au deposit in the Noranda mining camp is hosted by Archean mafic and felsic submarine volcanic rocks. The deposit comprises three massive sulfide complexes: the Main and Satellite Lenses near surface, and the 1100 orebody at depth. The rocks have been subjected to lower greenschist-facies metamorphism and related deformation, which resulted in changes in ore textures, development of shear zones and veins systems, remobilization of gold, and formation of a new mineral (electrum) within the orebodies. Both mechanical and chemical processes operated to produce secondary textures and structures resulting from brittle deformation, ductile deformation, and annealing. The specific deformation mechanisms include brittle failure and cataclastic flow, dislocation glide, dislocation creep and solution-precipitation creep. The Main and Satellite Lenses are characterized by excellent preservation of primary sulfides deposited from and reworked by synvolcanic hydrothermal fluids. These orebodies were affected to a limited degree by mechanical processes of deformation. In contrast, the 1100 orebody is characterized by a higher degree of development of textures and structures related to metamorphism and deformation, especially those formed by chemical processes. The differences may be due to the greater depth of the 1100 orebody relative to the other lenses, as regional metamorphic isograds are subhorizontal, and more extensive interaction between metamorphic fluids and the 1100 Lens.     

甘南玛曲沼泽湿地土壤微生物量、理化因子与土壤酶活的关系

对甘南玛曲沼泽湿地6个样地的微生物量与土壤酶活性及其土壤理化性质之间的关系进行了研究.结果表明:纤维素酶活性在冬季达到高峰,其余5种土壤酶活性分别在春季和秋季达到高峰;硝化细菌数量与过氧化氢酶、纤维素酶、脲酶、碱性磷酸酶有较显著的负相关关系;微生物量与酶活性之间存在极显著相关关系,其中微生物量因子中的放线菌、氨化细菌、硝化细菌和土壤酶活性因子中的酸性磷酸酶、碱性磷酸酶、中性磷酸酶是引起相关性的主要因素;酸性磷酸酶活性与土壤含水率、pH值、硝态氮含量、氨态氮含量都有密切的关系,过氧化氢酶活性可以通过有机质的含量来反映,脲酶活性可以通过土壤的含水率来反映,碱性磷酸酶活性可以通过电导率来反映.     

郑西客运专线湿陷性黄土区试验路堤的沉降观测与预测研究

郑西客运专线路堤工后容许沉降量为15 mm,湿陷性黄土区路堤地基处理的沉降控制是关键性技术难题,为此,选择湿陷性黄土代表性地段进行了不同地基处理措施路堤工程沉降观测试验研究。研究结果表明,路堤本体的压缩沉降量只有3 mm,并在路堤竣工后的15 d内趋于稳定,路堤沉降主要由地基沉降控制,而地基沉降则决定于3种不同地基处理措施层以下土层的沉降量大小。在沉降量大小、地基处理和浸水效果方面,22 m深湿陷性土层全部处理的柱锤冲扩桩区段最好,15 m深湿陷性土层的挤密桩区段较好,6 m深湿陷性土层的强夯区段最差,而且采取合理的防排水措施防止坡脚附近积水浸泡非常必要。采用双曲线法、三点法和Asaoka法预测结果的平均值作为路堤的最终沉降量,柱锤冲扩桩区段、挤密桩区段的路堤分别需要恒载预压5个月、8个月便可卸除荷载铺设无碴轨道,强夯区段路堤的预压荷载可能需要持续很长的时间。     

冀北窟窿山流纹斑岩锆石SHRIMP U-Pb年龄、地球化学特征及地质意义

冀北窟窿山流纹斑岩位于赤峰—开原断裂以南、尚义—平泉断裂带以北的华北克拉通北缘隆起带和沽源—红山子铀成矿带的西南段,主要分布于窟窿山北西部,出露面积约25 km~2。本文通过SHRIMP锆石U-Pb定年和主量元素、微量元素、稀土元素、Sr—Nd—Pb—O同位素组成测试,查明流纹斑岩形成的地质时代,探讨流纹斑岩的物质来源和形成的构造背景,分析流纹斑岩与铀矿化的关系。分析结果显示:流纹斑岩SHRIMP锆石n(~(206)Pb)/n(~(238)U)年龄为138.4±1.3 Ma(n=12,MSWD=0.25),属早白垩世早期;流纹斑岩具有高硅、富钾、钠,高FeO~T/MgO值,贫Al、Mg、Ca、P的高分异特征,属准铝质—弱过铝质高钾钙碱性系列岩石,在SiO_2—[(Na_2O+K_2O)—CaO]和SiO_2—FeO~T/(FeO~T+MgO)图解中落于A型花岗岩区;∑REE含量较低,Eu负异常明显,具轻稀土富集型稀土配分曲线特征,富集Rb、Th、U、Nb、Ta、Zr、Hf、Y等元素,亏损Sr、Ba、P、Ti等元素,10000Ga/Al=3.74～4.29(2.6),Zr+Nb+Ce+Y=374×10~(-6)～402×10~(-6)(350×10~(-6)),显示A型花岗岩微量元素的特征。流纹斑岩的[n(~(87)Sr)/n(~(86)Sr)]_i值变化范围较大(=0.690385～0.724000),ε_(Nd)(t)值较低(=-16.2～-14.9)、T_(DM2)较大(=2163～2244 Ma),Pb同位素比值较低{[n(~(206)Pb)/n(~(204)Pb)]_i=16.893～16.922、[n(~(207)Pb)/n(~(204)Pb)]_i=15.393～15.424、[n(~(208)Pb)/n(~(204)Pb)]_i=37.716～37.771},在铅同位素图解中窟窿山流纹斑岩同时带有下地壳物质和富集地幔印记;δ~(18)O_(V-SMOW)=3.5‰～4.9‰,低于正常地幔的δ~(18)O_(V-SMOW)值(=5.3‰±0.3‰),具低氧流纹岩特征。Sr—Nd—Pb—O同位素特征显示,流纹斑岩可能是源于DMM型、EMI型地幔和少量古老下地壳混合形成的年轻下地壳部分熔融的产物,而且与高温热液蚀变有关。对比表明,窟窿山流纹斑岩与中国东部绝大多数与火山岩有关的热液型铀矿的赋矿围岩时代一致,特别是与沽源—红山子铀成矿带西南段张麻井铀矿的赋矿流纹斑岩特征一致,而且在流纹斑岩的接触带内已揭露到铀矿化,指示窟窿山流纹斑岩的内、外接触带具有良好的找矿前景。