Isotopes in teeth and a cryptic population of coastal freshwater seals

Human activities threaten the biodiversity of aquatic mammals across the globe. Conservation of these species hinges on the ability to delineate movements and foraging behaviors of animals, but gaining such insights is hampered by difficulties in tracing individuals over their lives. We determined isotope ratios in teeth (⁸⁷Sr/⁸⁶Sr, ¹³C/¹²C, and ¹⁸O/¹⁶O) to examine lifelong movement and resource-use patterns of a unique freshwater population of a wide-ranging pinniped species (harbor seal [Phoca vitulina]) that resides in Iliamna Lake, Alaska (U.S.A.). This population's potentially unique migratory behavior and use of different trophic resources are unknown. The isotope ratios we measured in teeth showed that seals were born in the lake, remained lifelong residents, and relied principally on resources produced from in the lake, even when seasonally abundant and nutrient-dense spawning anadromous fish (i.e., sockeye salmon [Oncorhynchus nerka]) were available in the lake. Our results illustrate how serial isotope records in teeth, particularly ⁸⁷Sr/⁸⁶Sr ratios, can be used to quantify how coastal mammal populations exploit both freshwater and marine ecosystems. Understanding lifelong patterns of habitat and resource use is essential information when designing effective conservation plans for threatened coastal mammals. We present the Iliamna Lake harbor seals as a unique case study into how isotope records within teeth can help reveal the cryptic ecology of such a population residing in an intact ecosystem. The results also provide critical baseline information for the Kvichak River system, which is facing an uncertain future due to proposed large-scale industrial development and a rapidly changing climate.     

小麦生长周期中土壤Cu的迁移转化实验研究

通过盆栽试验,研究了不同土壤Cu添加浓度下,在小麦生长不同时期,小麦根区土壤与非根区土壤中总量Cu和有效态Cu的浓度,以此揭示其迁移转化特征。研究发现:小麦生长可以对土壤中的Cu进行吸收,拔节期小麦吸收能力最强;Cu添加有利于小麦对土壤中Cu的吸收,在试验水平下,添加浓度越高促进作用越明显,在200 mg/kg Cu添加浓度下,成熟期土壤中Cu含量较幼苗期减少了79%;小麦生长使土壤中有效态Cu占总量Cu的比重增加,并且使非根区土壤中Cu向根区土壤迁移。     

扰动和加藻共同作用下太湖沉积物中形态磷变化规律

为了阐明反复扰动下,不同初始浓度藻对沉积物中各形态磷释放的影响.以太湖梅梁湾沉积物和上覆水作为研究材料,探讨了扰动和藻类共同作用下沉积物中各形态磷的变化规律.结果表明,无扰动状态下,NH4Cl-P和Res-P均有所降低,而Fe/Al-P和Ca-P则有所增加.其中,Ca-P随藻类初始浓度增加而增加,分别增加48%、66%、74%.但是,扰动状态下,NH4Cl-P和Res-P也明显降低.Fe/Al-P明显增加,其占总磷的百分比为66.2%(3组试验的平均值)高于不扰动状态(53.4%,3组试验的平均值);此外,Ca-P占总磷的百分比为24.1%(3组扰动试验的平均值)明显低于不扰动状态(33.0%,3组试验的平均值).这暗示了扰动和藻类共同作用下促进了Fe/Al-P的形成,而无扰动下藻类却促进了Ca-P的形成.     

煤矸石-土壤混合基质对小白菜生长的影响及Pb迁移规律

盆栽试验研究了施用不同量煤矸石(0%、13%、26%、40%、53%)对贫瘠土壤改良的效果和对小白菜生长品质的影响。结果表明:(1)混合基质中Pb的迁移能力较差,小白菜中Pb积累量与植物体生物量具有正相关关系;(2)小白菜的发芽率、根系长度、地面以上株高和生物量等均在煤矸石施入比例为26%时达到最佳,发芽率、地面以上株高和干重分别增加23%、23.05%和20.62%;施入煤矸石超过40%时将导致各项指标有所下降;(3)采用单因子污染指数法进行食品质量评价,加入煤矸石量分别为0%、13%和26%时,产品污染指数分别为0.69、0.79和0.93,属于清洁水平;而加入煤矸石量为40%和53%时,污染指数分别为1.12(轻污染水平)和1.38(轻污染水平)。煤矸石可增加植物生长过程所需营养物质而作为贫瘠土壤的改良剂,实现煤矸石资源化并改善矿区生态环境。     

Fast method for simulation of radionuclide chain migration in dual porosity fracture rocks

In fractured rocks with a porous rock matrix such as granites, radionuclides will flow with the water in the fracture network. The nuclides will diffuse in and out the rock matrix where they can sorb and be considerably retarded compared to the water velocity. A water parcel entering the network will mix and split at the fracture intersections and parts of the original parcel will traverse a multitude of different fractures. The flowrates, velocities, sizes and apertures of the fractures can vary widely. Normally one must solve the transport equations for every fracture and use the effluent concentration as inlet condition to the next fracture and so on. It is shown that under some weakly simplified conditions it suffices to determine one single parameter group containing information on the flow wetted surface that a water parcel contacts along the entire path. It is also shown how this can be obtained. Then, solving the transport equations only once for time and location along the path gives the concentration and nuclide flux of every nuclide in the chain everywhere along a path. The same solution actually is valid for every path in the network. This dramatically reduces the computation effort. The same approach can be used for models based on streamtubes.     

Using Local Knowledge as a Research Tool in the Study of River Fish Biology: Experiences from the Mekong

River fisheries are extremely important for food-security among the rural poor in many tropical countries. The growing populations and rapid industrialisation of these countries require that appropriate action should be taken to sustain the resources for future generations. However, an incomplete understanding of river fisheries biology, at the managerial level, often hampers proper planning and management. This is partly due to the difficult access to large parts of such river basins, the complex nature of the fisheries, and in many cases a severe lack of research funds. In contrast, the thousands, or often millions of people who live along the shores of the rivers and rely on the fishery for their daily survival, have a very intimate knowledge of the behaviour and biology of the fish. In this situation, gathering the knowledge of the fishers may provide politicians or planners with baseline knowledge in a relatively quick and cheap way.This paper discusses two years of research using local knowledge in the study of fish migration and spawning in the Lower Mekong Basin. The study involves semi-structured interviews with 355 expert fishermen in four countries along 2,400 km of the Mekong mainstream. By piecing together information from fishermen in different areas, we were able to construct migration maps, and provide rough estimates of the spawning period for 50 fish species. We conclude that river fisheries research can benefit significantly from local knowledge as the basis for future research.     

Coupled modeling of cement/claystone interactions and radionuclide migration

The interactions between cement and a clayey host-rock of an underground repository for intermediate-level radioactive waste are studied with the reactive transport code HYTEC for supporting performance assessment. Care is taken in using relevant time scales (100,000 years) and dimensions. Based on a literature review, three hypotheses are considered with respect to the mineralogical composition of the claystone and the neo-formed phases. In the long term, the pH is buffered for all hypotheses and important mineral transformations occur both in cement and the host-rock. The destruction of the primary minerals is localized close to the cement/claystone interface and is characterized by the precipitation of secondary phases with retention properties (illite, zeolite). However, beyond the zone of intense mineral transformations, the pore water chemistry is also disturbed over a dozen meters due to an attenuated but continuous flux of hydroxyl, potassium and calcium ions. Four interdependent mechanisms control the profile in the whole system: diffusion of the alkaline plume, mineralogical buffering, ion exchange and clogging of the pore space at the cement/claystone interface. The migration of a selected group of radionuclides (Cs, Ra, Tc and U) is explicitly integrated in the simulations of the strongly coupled system. Theoretical profiles of distribution coefficient (Kd) and solubility limit values are derived from the simulations, and their sensitivity with respect to the system evolution is estimated.     

可压密煤层瓦斯运移方程与数值模拟研究

建立了非均质可压密煤层瓦斯运移方程和数值模拟方程,通过计算机数值模拟解,并运用相似理论,得到了煤层瓦斯压力分布曲线和煤（孔）壁瓦斯涌出衰减曲线方程。采掘面围岩中的集中应力峰值点存在高瓦斯压力和压力梯度,克林伯格效应和煤体排放瓦斯后的应力释放对钻孔瓦斯流量有明显的增长作用     

城市街道峡谷空气质量的初步研究

介绍了街道峡谷的定义及特征,通过对其空气质量进行初步研究,分析影响街道峡谷空气质量的因素,选择采样点位及监测技术,探讨了污染物迁移扩散的规律,提出今后街道峡谷研究的方向.