关于底部大空间结构中墙梁的计算方法初探

作者根据设计经验详细论述了底部大空间结构中的墙梁的具体计算方法和设计原则。对从事该专业的技术人员具有一定的参考价值。     

Otolith geochemistry in young‐of‐the‐year peacock bass Cichla temensis for investigating natal dispersal in the Rio Negro (Amazon – Brazil) river system

This study examined otolith geochemistry as a natural marker of natal origins in young‐of‐the‐year (YOY) Cichla temensis in the Negro River Basin of Brazil. We analysed trace element and isotopic composition of otoliths of YOY collected off spawning nests from the main stem and major tributaries. These were compared with regional bedrock geologic composition to explore underlying mechanisms of differences in otolith geochemistry. Our results suggest that spatial differences in otolith geochemistry can be used to distinguish natal origins based on ⁸⁷Sr/⁸⁶Sr, Sr/Ca and Ba/Ca ratios. This approach allowed us to correctly classify 99% of juvenile fish to their natal streams using cross‐validation in a linear discriminant function analysis (LDFA). Patterns of otolith isotopic composition correspond with patterns in regional geology as expected based on previously demonstrated correlations, although some fine‐scale spatial differences cannot be accounted for by available geologic information. These results demonstrate that otolith chemistry is valuable as a natural marker of natal origins in this system and suggest that inferences from geologic maps may be useful for interpreting movements based on otolith geochemical signatures. This information provides the basis for future work to investigate the early life history and spatial ecology of this important cichlid.     

黄土丘陵区不同地貌类型地球化学分布特征

根据宁夏南部黄土丘陵区彭阳古城乡黄土梁峁—茹河河谷剖面和西吉城郊乡黄土梁峁—葫芦河河谷剖面土壤样品地球化学测试的结果,分别对不同地貌部位的常量元素、微量元素和微量元素有效态的含量进行了对比研究。大多数常量元素比较稳定,K+、Na+在河谷阶地区富集,在黄土梁峁及边坡流失;CaO和Fe2O3由于土壤水的作用和氧化还原条件的不同,其含量在河谷阶地区较少;大多数微量元素在土壤中比较稳定,Ti、P、V、Zn和Ba等元素的含量:黄土丘陵梁峁顶部<河谷阶地;B在土壤中的含量:黄土丘陵梁峁顶部>黄土丘陵梁峁边坡>河谷阶地;微量元素的有效态含量:河谷阶地>黄土丘陵梁峁顶部>黄土丘陵梁峁边坡。     

基于土壤类型和微量元素辅助信息的土壤属性空间模拟

为探讨大尺度区域土壤属性空间化的方法,以吉林省为例,研究土壤养分（pH值、有机质、速效磷、速效钾和碱解氮）和地形地貌、微量元素等变量之间的关系;并在考虑土壤类型基础上,将相关性较高的变量作为协因子进行土壤养分的Cokriging插值研究。结果表明,pH值与经度、有效铁、锰和速效氮的相关系数分别高达-0.66、-0.71、-0.70和-0.67;有机质与经度、pH值、有效钙、锰的相关系数分别为0.55、-0.58、0.56和0.52;碱解氮与经度、纬度、pH值、有效铁、锌的相关系数分别为0.57、-0.57、-0.67、0.56、0.54;速效磷与速效钾、有效锌的相关系数分别为0.67和0.64。分析发现以相关性较高的微量元素作为协因子进行Cokriging插值精度均优于采用地形变量作为协因子的Cokriging插值。交叉检验和检验站验证结果表明,与普通Kriging相比,基于土壤类型和微量元素的Cokriging插值在增加估值精度方面有所提高。     

微量元素间及其与营养素之间的协同与拮抗作用

本文综述了微量元素间及其与营养素之间的协同与拮抗作用,矿物元素发生协同与拮抗作用的机理。     

Conditions related to solubility of rare and minor elements in forest soils

Soil solutions expelled by high‐speed centrifugation (13900 g) of intact soil sample cores at field moisture from 30 forest topsoils (A horizons of mainly Dystric and Eutric Cambisols, according to the FAO‐Unesco system) low in clay were subjected to analysis of 60 elements, using ICP‐MS and ICP‐AES. Concentrations measured were related to soil and soil solution properties assumed to be important for the solubility of elements, using stepwise regression analysis. On an average two thirds of the variability in soil solution concentration of elements were accounted for by, in particular, organic C concentrations, pH and/or nitrate concentrations of the solutions, varying among elements from 19 to 90 %. Concentrations of elements strongly positively related to soil solution acidity were Al, Be, Ge, Li, Ni, Pb, and Zn, strongly negatively related to acidity were Ca, Mo, and W. Most positively related to nitrate concentrations in soil solutions were B, Ba, Cd, Mg, Mn, and Sr; negatively were Nb, Ta, and Ti. Concentrations of organic C in the soil solutions correlated positively, often quite closely, with most of the other elements studied, including La, all the lanthanides, and with Ag, Br, Cr, Fe, Ga, Hf, Hg, In, P, Th, U, Y, and Zr. Soluble organic compounds were apparently ’︁carriers’ of these elements in the soil solution. The concentrations of elements in HNO₃ digests of the soils usually accounted for just little or no statistical variability of their soil solution concentrations.     

农产品及产地环境中微量元素检测研究进展

农产品及产地环境中微量元素高效、准确检测是农产品政府监管、保障消费安全、促进粮油产业高质量发展的重要手段。本文评述了近几年农产品及产地环境中微量元素的检测技术,比较分析了光谱、质谱、色谱和电化学等方法的原理和特点,及其在微量元素检测实际应用中的优缺点,以期为农产品及产地环境中微量元素检测技术研究提供参考,为粮油产业高质量发展与农产品质量安全提供技术支撑。     

森林草原交错区沟塘草甸土壤微量元素分析

为研究森林草原交错区不同坡向沟塘草甸土壤化学计量特征,以内蒙古阿尔山市的沟塘草甸为研究区域,通过野外调查与室内实验相结合的方法,对阴坡阳坡不同深度土层有效微量元素(Fe,Mn,Cu,Zn)含量及有机C,全N,全P含量进行比较分析,探究沟塘草甸土壤化学计量特征。结果表明:1)阴坡阳坡土壤有效Fe和有效Mn含量均随着土层深度增加呈现先增后减趋势,而有效Cu含量随着土层深度变化差异不显著;2)阴坡阳坡土壤有效微量元素含量均呈现Fe>Mn>Zn>Cu趋势;3)土壤有效微量元素含量与pH值无相关性,有效Fe含量与有效Mn、有效Cu、有效Zn含量相关性(P<0.01)极为显著;4)同一坡向不同深度土层C∶N,N∶P差异均不显著,而C∶P差异显著;5)土壤pH在不同坡向不同深度土层均无显著差异。研究结果为沟塘草甸土壤微量元素分析提供数据支持。     

原子吸收光谱法测定野生樱桃李中微量元素

[目的]建立野生樱桃李中微量元素含量的测定方法.[方法]采用干灰化法对野生樱桃李进行样品前处理,原子吸收光谱法对野生樱桃李中Fe、Zn、Ca、Mg、K、Na、Cu和Mn等8种微量元素进行测定.[结果]用火焰原子吸收光谱法测定野生樱桃李中微量元素的含量,加标回收率为95.0;～102.5;,变异系数≤2.41;,检出限为0.009～0.052 μg/mL.不同类型的野生樱桃李微量元素含量有所不同,NO10的钾、钠、铁的含量最高,NO2的钙、镁的含量最高,NO9的铜、锌含量最高,NO13的锰含量最高.[结论]该方法操作简便、数据准确可靠,精密度高,适合于测定野生樱桃李中微量元素含量,可为进一步开发利用野生樱桃李奠定基础.     

茶叶及其茶水中铁、铜、锰的含量测定

为了解不同产地茶叶微量元素的含量变化,采用火焰原子吸收光谱法(FAAS)对信阳毛尖(不发酵茶)、福建铁观音(半发酵茶)、云南普洱(发酵茶)3种茶叶及茶水样品中的微量元素铁、铜、锰分别进行了测定。结果表明,3种茶叶及其相应茶水中微量元素的含量均为Mn>Fe>Cu,同种元素在不同茶叶中的含量有一定差别;从微量元素溶出率的大小看,元素的溶出与元素总量无关。Cu、Fe和Mn的回收率分别为97.0%~105.5%、81.9%~97%和83%~93%。