Early development of Chondrus ocellatus Holm （Gigartinaceae, Rhodophyta）

1 INTRODUCTION Red algae C. ocellatus lives in temperate zone of coastal area, and inhabits at substrates from high tide to low tide regions. Its life history is composed of three phases: tetrasporophyte, gametophyte and carposporophyte. Chondrus is one o…     

小叶锦鸡儿(Caragana microphylla)群落蒸散发模拟

基于2016、2017年生长季原位气象监测数据,利用Shuttleworth-Wallace(S-W)模型模拟了科尔沁沙地主要固沙植物小叶锦鸡儿(Caragana microphylla)群落的蒸散发,对蒸散组分进行了拆分,并利用涡度相关系统对模拟蒸散发值进行了验证。结果表明:2016、2017年生长季小叶锦鸡儿群落蒸散发量分别为345.4、325.2 mm,土壤蒸发量分别为93.8、83.8 mm,植被蒸腾量分别为251.6、241.4 mm,土壤蒸发占总蒸散发分别为27.2%、25.8%。30 min尺度上模拟值与实测值一致性较高,模拟精度大体表现为晴天>阴天>雨天。持续干旱和降水后,小叶锦鸡儿蒸腾耗水规律明显不同,持续干旱时期小叶锦鸡儿保持较低的蒸腾耗水,且具有明显的"午休"现象,连续降水后小叶锦鸡儿"午休"消失,蒸腾耗水增强。饱和水汽压差是影响小叶锦鸡儿蒸散发的主要因子。     

Responses of primary productivity to current and climate changes in the mud area to the southwest of Cheju Island during the past 800 years

The biogenic silica (BSi), total organic carbon (TOC), total nitrogen (TN) and grain size were analyzed with a gravity core (3250-6) collected from the mud area in the north East China Sea. The average deposition rate of the upper core was about 0.078 cm yr^?1 based on the results of ²¹⁰Pb_ex. The mean grain size increased with depth in general. The frequency distribution of grain size showed that two marked changes of deposition environment occurred at 30 cm and 50 cm depths (about 1550 AD and 1300 AD, respectively). The variations of BSi and TOC indicated two distinct major periods of primary productivity over the past 800 years: a stage of low primary productivity corresponding to weak upwelling and low nutrient input below 30 cm depth (about 1200–1550 AD), and a stage of high primary productivity with strong currents and upwelling above 30 cm depth (about 1550–1950 AD). The stage with high primary productive appeared to be due to the northward-expanded muddy area caused by strong Asian Winter Monsoon and enhanced Yellow Sea Warm Current in winter. In conclusion, the BSi and TOC in the muddy sediments, the symbols of marine primary productivity, can be then used to investigate the evolution history of currents and relative climate change in the offshore areas.     

Effects of agricultural practices on nitrogen distribution in unsaturated soils

Nitrogen fertilizer consumption is very common in the agricultural practices. Nitrogen application could be an important source of groundwater N pollution. Normally, nitrogen can pass through the unsaturated zone to pollute the groundwater. Different agricultural practices have different cultivation methods, accordingly different fertilization and irrigation techniques. Hence, the agricultural practice determines the environment of the unsaturated zone, which subsequently determines the extent of groundwater N pollution. To verify the pollution modes and transformation mechanisms of nitrogen, both in situ and laboratory tests were conducted at four different sites to study the effects of agricultural practices on nitrogen distribution in unsaturated zones. The inorganic nitrogen in soil is extracted by potassium chloride solution, and the soil utilization form and pollution type are identified by δ¹⁵N by comparing with the known standard values. The experimental results indicate that continual fertilization and sewage irrigation in these agricultural regions were the primary sources of nitrogen in the unsaturated zone. In the soils planted with rice, δ¹⁵N–NH₄ ⁺ was relatively elevated due to ammonium volatilization. In the unsaturated zone of rice–wheat rotation fields, NO₃ ^?–N and δ¹⁵N were both elevated because of manure fertilizer. Meanwhile, denitrification also occurred in the hypoxic environment due to the high soil water content.     

Holocene and Eemian climatic optima in the Korean Peninsula based on textural and carbon isotopic records from the stalagmite of the Daeya Cave,South Korea

Textural and stable isotopic records from the absolute-dated stalagmite of the Daeya Cave (DY-1) provide new insights into the climatic evolution of the Korean Peninsula during the Holocene and Eemian climatic optima. The stalagmite yielded ages of 8572 ± 227 to 5907 ± 158 and 1,23,456 ± 535 to 1,19,837 ± 1089 years, which coincide with the Holocene and Eemian climatic optima, respectively. The stalagmite’s δ¹³C record closely resembles previously reported Chinese speleothem δ¹⁸O data. Thus it can be suggested that textural and geochemical results of the DY-1 reflect East Asian monsoon intensity, which is forced by summer insolation patterns in the northern hemisphere. Lighter carbon isotopic compositions, well-developed fibrous calcite crystals, and their relatively faster growth rate in the stalagmite sample are interpreted to reflect the warmest and wettest climate conditions of the Holocene and Eemian interglacials. Both climatic optima took place when insolation was decreasing from its maximum level, temperature in Greenland was highest, and sea level approached its maximum level. These climatic optima also coincide with decreasing Antarctic temperatures. Compared the DY-1 data to other proxies, it is suggested that the Holocene and Eemian climatic optima developed through a balance among boreal insolation, monsoon intensity, and sea level (also continental ice volume), which are the main climatic forcing factors in the northern hemisphere. These trends also follow the bi-polar seesaw mechanism as previously described.     

U-Pb age of detrital zircons from neoproterozoic placers of the Erementau-Niyaz massif as a reflection of stages of Precambrian tectono-magmatic evolution of northern Kazakhstan

A typical feature of the Precambrian complexes of the Kokshetau, Ishkeolmess, Erementau-Niyaz, and Aktau-Dzhungaria massifs of Northern and Central Kazakhstan is the presence of the end Mesoproterozoic-beginning of the Neoproterozoic quartzite-schist sequences in these sections. The lower and upper parts of these sequences are mostly composed of schists with interlayers of quartzites and marbles and of quartzitic sandstones, respectively. It is suggested that the quartzite-schist sequences represent the sub-platform cover of a large continental block and were formed in the regressive basin with widely abundant facies of submarine deltas and a littoral shoal. The presence of horizons and the lenses enriched in zircon-rutile heavy concentrate with the amount of accessory minerals of 10-70% characterizes the quartzite-schist sections of the Kokshetau and Erementau-Niyaz massifs. The U-Pb age of zircons from one such locality in the central part of the Erementau-Niyaz massif was analyzed by LA-ICP-MS. The Concordia ages of zircons are in the intervals 1041 ± 13-1519 ± 14, 1623 ± 14-1931 ± 14, and 2691 ± 14-2746 ± 14 Ma. One age was 2850 ± 14 Ma. The age distribution is characterized by clear peaks of 1.08, 1.20. 1.34, 1.46, 1.65, 1.89, and 2.70 Ga and weak peaks of 1.13 and 1.68 Ga. The age of the majority of zircons ranges from 1309 ± 14 to 1519 ± 14 Ma. Our data indicate that mostly Neoproterozoic rocks with a subordinate role of Paleoproterozoic and Neoarchean complexes served the feeding sources for the quartzite-schist sequence of the Erementau-Niyaz massif. The Mesoproterozoic and Paleoproterozoic events identified for the detrital zircons of the Erementau-Niyaz massif are completely manifested only in Laurentia. In the first approximation, these events coincide with the assembly and breakup of the Columbia/Nuna supercontinent (～1650–1580 and 1450–1380 Ma) and assembly of the Rodinia supercontinent (1300–900 Ma).     

Least Square Finite Element Method for Viscous Splitting of Unsteady Incompressible Navier–Stokes Equations

In order to solve unsteady incompressible Navier–Stokes(N–S) equations, a new stabilized finite element method,called the viscous-splitting least square FEM, is proposed. In the model, the N–S equations are split into diffusive and convective parts in each time step. The diffusive part is discretized by the backward difference method in time and discretized by the standard Galerkin method in space. The convective part is a first-order nonlinear equation.After the linearization of the nonlinear part by Newton's method, the convective part is also discretized by the backward difference method in time and discretized by least square scheme in space. C~0-type element can be used for interpolation of the velocity and pressure in the present model. Driven cavity flow and flow past a circular cylinder are conducted to validate the present model. Numerical results agree with previous numerical results, and the model has high accuracy and can be used to simulate problems with complex geometry.     

General geological characteristics of a certain mixed-type asbestos deposit,Shaanxi Province

As is evidenced from the mode of occurrence, mineralogy, and features of asbestos minerals and the types of veins, as well as the fibrous characters, it is recognized that the asbestos deposit studied in this paper is different in origin from either the serpentine type associated with ultrabasic rocks or that related to dolomitic limestone or dolomite, and can be assigned to a gradation between the two types