四川稀土矿（氟碳铈矿）稀土总量的测定方法

氟碳铈矿矿样经高氟酸分解、脱硅后,稀土元素以氢氧化物和草酸盐形成进行沉淀与干扰元素分离,氢氧化物沉淀使稀土与钙、镁分离,草酸盐沉淀,使稀土与铁、铝、锆、钛等元素分离。适应矿石稀土含量１％～７４％的含量测定。该方法用于氟硕铈矿稀土总量的测定,方法简便、快速、准确。     

UNIQUE ASPECTS OF MODELING IRRIGATI0N-INDUCED SOIL EROSION

llNTRODUCTIONIrrigationisimp0rtanttof00dpr0ducti0nthr0ughoutthew0rld.Irrigati0nisused0naboutl5theworld'scropland(KendalIandPimentel,l994)and5%ofthew0rld'sfoodproductionland,whichincludesrangelandandpermanentcr0pland(FAO,l998).However,irrigatedlandproducesmorethan30%ofthew0rld'sf0od(Tribe,1994),whichis2l/2timesasmuchperunitareacomparedt0n0n-irrigatedproducti0n(KendallandPimentel,1994).IntheUnitedStates,approximatelyl5theharvestedcr0plandisirrigated,butalmost40thet0talcr0pvalue…     

Microcosm experiments on the effect of nutrient enrichment and a soil layer on the development of freshwater plankton

We investigated the response of phytoplankton and zooplankton to experimental alteration of nitrate and phosphate levels in outdoor enclosures. Experiments were conducted in summer and winter and in the absence and presence of a layer of soil. The tubs (12 in all) except the two plain water controls were manured initially with a mixture of fresh cowdung (50g 1⁻¹), mustard oil cake (25 g l⁻¹) and poultry wastes (25 g l⁻¹; mostly excreta), prior to enrichment. Water samples were collected from the experimental tubs twice a week to measure selected physico-chemical and biological variables. Water temperature in the summer experiments ranged from 20–30 °C and during the winter experiments from 11–15 °C. The pH values ranged from 8.0 to 9.5 and the dissolved oxygen levels from 8.2–10.0 mg l⁻¹. The levels of soluble reactive phosphorus and nitrate nitrogen ranged from undetectable levels to 1800 μg l⁻¹ and 6000 μg l⁻¹, respectively. The increase in chlorophyll-a following enrichment was rapid (3–7 days) during summer, but slower in winter (7–14 days). The predominant phytoplankton species observed in the tubs belong to the genera Sphaerocystis, Chlorella, Scenedesmus, Cosmarium, Ulothrix, Zygnema, Gonium and Pandorina. The rotifer species observed were Brachionus calyciflorus, Rotaria neptunia, Lecane bulla, L. luna, L. unguitata, Euchlanis dilatata, Asplanchna intermedia, Pseudoharringia spp., Eosphora spp., Lepadella ovalis, Epiphanes brachionus, Hexarthra mira and Cephalodella gibba. The cladocerans observed were Macrothrix spp. and Alona spp.     

Grazing experiments and model simulations of the role of zooplankton in Phaeocystis food webs

A combined empirical and modelling study was conducted to further examine the potential importance of grazing by zooplankton in pelagic food webs in which Phaeocystis is a significant or dominant component. Laboratory experiments were designed to measure ingestion of Phaeocystis and other potential prey items which co-occur with Phaeocystis. Grazers included copepods and ciliates, and prey included Phaeocystis colonies and solitary cells, diatoms, ciliates, bacteria, and detritus. These data were expressed in the model currency of nitrogen units, and fit to hyperbolic tangent equations which included minimum prey thresholds. These equations and literature data were used to constrain a food web model whose purpose was to investigate trophic interactions rather than to mimic actual events. Nevertheless, the model output was similar to the general pattern and magnitude of development of Phaeocystis–diatom communities in some environments where they occur, e.g. north Norwegian waters. The model included three forms of nitrogen, three phytoplankton groups, bacteria, two zooplankton groups, and detritus, with detailed flows between compartments. An important component of the model was inclusion of variable prey preferences for zooplankton. The experiments and model simulations suggest several salient conclusions. Phaeocystis globosa colonies were eaten by a medium-sized copepod species, but ingestion appeared to be strongly dependent upon a proper size match between grazer and prey. If not, colonies were eaten little if at all. Phaeocystis solitary cells were ingested rapidly by ciliate microzooplankton, in agreement with prior literature observations. In contrast, detritus was eaten comparatively slowly by both ciliates and copepods. Both types of zooplankton exhibited apparent minimum prey thresholds below which grazing did not occur or was inconsequential. Model simulations implied that transitions between life cycle stages of Phaeocystis may potentially be important to phytoplankton–zooplankton interactions, and that relative rates of ingestion of Phaeocystis by various zooplankton may have significant impacts upon material fluxes through and out of Phaeocystis–diatom ecosystems. Indirect effects of trophic interactions appear to be equally significant as direct effects.     

α-1,4-葡聚糖裂解酶的动力学性质研究

红藻中的α-1,4-葡聚糖裂解酶是红藻淀粉的降解酶,除了 红藻淀粉外,它还可以作用于多种底物。文中分别以PNPG和可溶性淀粉作底物,以龙须菜的 几个品系作为材料,研究了该酶促反应的动力学方面的性质。以 PNPG作为底物,该酶在60m in内酶促反应速度与保温时间成线性关系;在野生型龙须菜品系中该酶的最适反应温度是50 ℃,在两种突变型品系中是40℃;最适pH范围在4.4～5.5;底物浓度是4mmol/L时达到最大反 应速度;葡萄糖对该酶促反应有明显的抑制作用。以可溶性淀粉作为底物,在反应60 min内 酶反应速度与保温时间成线性关系;最适反应温度为50℃;最适pH范围在5.0～5.8;底物浓 度是8mg/mL时达到最大反应速度;葡萄糖对可溶性淀粉的抑制作用比对PNPG的弱。     

A brief introduction to recent applications of several sediment-analysis techniques in palaeolimnological studies-dry bulk density and water content, mineral magnetism, carbonate content, and content of total organic carbon, nitrogen content and c

ChalacteriStics of lacustrine sediments are often capable of ~ring the hydrological regales of the lakeand its environment and human achvihes in itS catclunent during the sedimentahon of these sedimentS.Therefore, by identifying these characteristics of sedimentS, it is likely to postUlate the physicalconditions in and around the lake during geological periods. Such reconstrUction of palaeoenvironmentshas become an increasingly important branch of ear sciences as there has been an expanded n…     

Study of Water Motion at the Dissolved Oxygen Minimum Layer and Local Oxygen Consumption Rate from the Lagrangian Viewpoint

By using the Euler-Lagrangian method, we examine water movements within the layer of minimum oxygen concentration and estimate local oxygen consumption rates for 15 regions of the global ocean. To do this, a number of labeled particles (which represent water parcels) are deployed at the center of a grid with 15 depth levels and tracked backward in time for 50 years in a three-dimensional velocity field. We assume that a particle picks up oxygen when it encounters the point of maximum oxygen concentration along the 50 years segment of its path. We introduce a contribution rate from waters distributed throughout the global ocean to the oxygen concentration of a local layer under consideration. Water parcels which are assumed to pick up oxygen within the oxygen minimum layer of an oceanic region under consideration make a very small contribution to the overall oxygen concentration of this layer. In addition, these parcels move out of the layer and water parcels from the upper layers take their place. The averaged Lagrangian local oxygen consumption rate is 0.033 ml/l/yr for the depth of the oxygen minimum layer, 0.20 ml/l/yr at 100 m depth (euphotic layer), 0.043 ml/l/yr for layers from 150 m to 800 m depth and 0.012 ml/l/yr for deep layers from 800 m to 3000 m. The present Lagrangian numerical experiment produces a maximum difference between observed and calculated concentrations of oxygen and, therefore, a maximum oxygen consumption rate. Although the present method has an ambiguity as to how oxygen is picked up, we nevertheless were able to identify regions in which the water parcels pick up oxygen of maximum concentration. We found that the South Equatorial Current (SEC) transports oxygen of higher concentration to the middle latitude regions of both the North Atlantic and the North Pacific across the equator.     

长江口北槽口外悬沙浓度垂线分布的数学模拟

利用垂向一维悬沙运动模型,对长江口北槽口外大、小潮悬沙浓度垂线分布进行模拟,模拟结果同“六点法”实测值拟合较好,表明影响悬沙浓度垂线分布的主要因素为悬沙垂向扩散及絮凝沉降作用。     

Total lipid and fatty acid composition of eight strains of marine diatoms

Fatty acid composition and total lipid content of 8 strains of marine diatoms (Nitzschia frustrula, Nitzschia closterium, Nitzschia incerta, Navicula pelliculosa, Phaeodactylum tricornutum, Synedra fragilaroides) were examined. The microalgae were grown under defined conditions and harvested at the late exponential phase. The major fatty acids in most strains were 14∶0 (1.0%–6.3%), 16∶0 (13.5–26.4%), 16∶1n−7 (21.1%–46.3%) and 20∶5n−3 (6.5%–19.5%). The polyunsaturated fatty acids 16∶2n−4, 16∶3n−4, 16∶4n−1 and 20∶4n−6 also comprised a significant proportion of the total fatty acids in some strains. The characteristic fatty acid composition of diatoms is readily distinguishable from those of other microalgal groups. Significant concentration of the polyunsaturated fatty acid 20∶5n−3 (eicosapentaenoic acid) was present in each strain, with the highest proportion in B222 (19.5%). Project supported by the Hi-Tech “863” Programs of the China Ministry of Science and Technology (863-819-02-01).     

河北沧州市臭氧质量浓度与气象因子的关系分析

利用2014—2020年河北沧州逐小时气象与环境监测数据,对沧州市臭氧(O₃)污染加剧现状及其与气象因子的关系进行分析。结果表明：(1)沧州地区O₃污染呈加剧态势,且O₃已上升为该地区首要污染物;O₃污染集中出现在5—9月,O₃质量浓度日变化呈单峰单谷型,最大浓度出现在16:00前后;(2)5—9月O₃日最大8 h平均质量浓度(简称“O₃-8 h”)所处时段,平均气温、最高气温、相对湿度、总辐射辐照度与O₃质量浓度的相关性较好,本站气压、水汽压和平均风速与O₃质量浓度的相关性未通过显著性检验;(3)5—9月O₃-8 h时段,当同时满足8 h平均气温高于30.9℃、最高气温高于32.7℃、平均相对湿度低于42.1%、平均总辐射辐照度高于505.8 W·m^-2时,出现O₃污染的概率达84%;(4)气象因子不是O₃