盲样考核浓度预判及稀释方法——以原子荧光法测定水中砷为例

以原子荧光法测定水中砷为例,探讨了实验室盲样考核浓度预判及稀释方法.分析了3个砷盲样考核实例,归纳了“直接稀释法”“系列稀释法”“最大稀释法”3种方法,分别适用于盲样浓度范围窄、适中、宽3种情况,检测人员可根据考核机构给定的浓度范围合理选用.     

PSO和SVM混合算法确定太湖入湖河流水质主要影响因子

以影响太湖入湖河流水质的24个因子值为研究对象,将PSO算法与SVM算法相结合。PSO算法用于优化SVM算法的参数c和g,以利于快速、高效地确定c和g的全局最优值;SVM算法基于最优的c和g,分别以24,21,18,15,12,9和6个因子作为特征向量预测水质的污染程度。结果表明,当特征向量为9个影响因子时预测率最高。其参数c=18.56,g=1.35,对应的预测率为：全局预测率92.59%,重度污染水质预测率88.89%,轻度污染水质预测率94.45%。因此,通过PSO和SVM混合算法,可以确定影响太湖入湖河流水质的主要因子,利用这些主要因子对水质进行预测预警,不但可以节省时间,而且可以得到精确的结果。     

3种杀菌剂及其复配剂对斑马鱼的急性毒性

采用"半静态法"测定了3种农药及其复配剂对斑马鱼的24 h、48 h、72 h和96 h急性毒性,根据我国《化学农药环境安全评价实验准则》中毒性等级划分标准来划分它们对斑马鱼的毒性等级,发现35%精甲霜灵悬浮种衣剂的24 h、48 h、72 h和96 h-LC_(50)均超过10 a.i.mg·L~(-1),属"低毒"级,而25 g·L~(-1)咯菌腈悬浮种衣剂的24 h、48 h、72 h和96 h-LC_(50)分别为0.704 mg·L~(-1)、0.514 mg·L~(-1)、0.424 mg·L~(-1)、0.262 mg·L~(-1),根据0.100 a.i.mg·L~(-1)LC_(50)(96 h)≤1.00 a.i.mg·L~(-1)划分,属"高毒"级,80%嘧菌酯水分散粒剂的24 h、48 h、72 h和96 h-LC_(50)分别为9.803 mg·L~(-1)、5.175 mg·L~(-1)、4.328 mg·L~(-1)、2.326 mg·L~(-1),根据1.00 a.i.mg·L~(-1)LC_(50)(96 h)≤10.00 a.i.mg·L~(-1)划分,属于"中毒"级。11%精甲霜灵-咯菌腈-嘧菌酯悬浮种衣剂的24 h、48 h、72 h和96 h-LC_(50)分别为2.267 mg·L~(-1)、2.073 mg·L~(-1)、1.620 mg·L~(-1)、1.280 mg·L~(-1),根据1.00 a.i.mg·L~(-1)LC_(50)(96 h)≤10.00 a.i.mg·L~(-1)划分,属于"中毒",虽然11%精甲霜灵-咯菌腈-嘧菌酯悬浮种衣剂和80%嘧菌酯水分散粒剂同属"中毒",但比较具体数值,发现11%精甲霜灵-咯菌腈-嘧菌酯悬浮种衣剂毒性相对更大,原因是其中含有"高毒"的咯菌腈。     

中国耕地非农化压力时空格局的演变分析

社会经济和资源禀赋的区域差异导致耕地非农化压力表现出明显的空间异质性。开展耕地非农化压力测算并揭示其时空格局演变,是实现土地资源优化配置的基础。从经济因素、社会因素、产业结构和资源禀赋4个方面构建耕地非农化压力指数评价指标体系,采用熵值法计算各指标权重,继而计算1990~2014年中国31省的耕地非农化压力指数,并在此基础上开展了耕地非农化压力的时空格局分析。结果表明:(1)从空间格局分布来看,中国耕地非农化压力空间分布呈现明显的地理梯度,总体上呈现从东到西依次递减的态势。(2)从时间变化趋势来看,不同地区各省份之间的耕地非农化压力指数变化呈现多元化趋势。东部沿海地区,山东、浙江、江苏的耕地非农化压力指数处于上升阶段,上海、福建的压力指数变化趋势逐渐趋稳,广东的压力指数呈现下降趋势。中部地区,河南、河北、山西、江西的耕地非农化压力指数趋稳,陕西、湖北以及四川、重庆等西南地区省份的压力指数呈上升趋势。西部沿边3省(云南、西藏、新疆)的耕地非农化压力呈现了一致的下降趋势。(3)从时空格局结合来看,耕地非农化压力不同的省份其变化趋势呈现出截然不同的走向。在耕地非农化压力较大的地区,耕地非农化经历了从制度驱动向发展推动的阶段,经济增长的倒"U"型轨迹明显,经济增长与耕地非农化之间的关系逐渐脱钩。在耕地非农化压力居中或较小的地区,产业发展滞后,土地比较收益较低,耕地的社会保障作用、生态作用对耕地非农化的影响较大,从而增加了部分省份的耕地非农化压力。     

Production and characterization of biodiesel from Eriobotrya Japonica seed oil: an optimization study

Biodiesel is now-a-days recognized as a real potential alternative to petroleum-derived diesel fuel due to its number of desirable characteristics. However, its higher production cost resulting mainly due to use of costly food-grade vegetable oils as raw materials is the major barrier to its economic viability. Present work is an attempt to explore the potential of Eriobotrya japonica seed oil for the synthesis of biodiesel using alkali-catalyzed transesterification. Optimization of production parameters, namely molar ratio of alcohol to oil, amount of catalyst, reaction time and temperature, was carried out using Taguchi method. Fatty acid composition of both oil and biodiesel was determined using GC and H¹ NMR. Alcohol to oil molar ratio of 6:1, catalyst amount of 1% wt/wt, 2 h reaction time and 50 ^°C reaction temperature were found to be the optimum conditions for obtaining 94.52% biodiesel. Highest % contribution was shown by the ‘amount of catalyst’ (67.32%) followed by molar ratio of alcohol to oil (25.51%). Major fuel properties of E. japonica methyl esters produced under optimum conditions were found within the specified limits of ASTM D6751 for biodiesel, hence it may be considered a prospective substitute of petro-diesel.     

乌鲁木齐市不同区域大气降尘中重金属污染及来源分析

为进一步了解城市不同区域间大气降尘中重金属含量及其差异性,沿城市走向梯度布设降尘采样点采集样品。采用电感耦合等离子体原子发射光谱(ICP-AES)仪测定样品中Cu、Cr、Mn、Fe、Ni、Zn、Cd、Pb和As等重金属含量,并计算富集因子来判断不同区域间的污染源类型,通过因子分析方法探讨污染的来源。结果显示,所测重金属元素中除Mn外,均受到人为源的影响,且十分严重。从贡献率来看,不同区域间第一因子的贡献率虽有差异,但均为来自土壤的风沙扬尘造成;第二因子的贡献率也不尽相同,主要是燃煤产生的污染;第三因子出现了差异,市南区和市北区主要是受金属冶炼的影响,而市中区的影响可能来自垃圾焚烧;市南区未出现第四因子,而市中区和市北区的污染源也不相同。分析表明,城市大气降尘污染依然严重,做好防控风沙和建筑扬尘,减少煤炭消耗,调整能源结构和产业布局是整体减少大气降尘的关键。     

餐厨垃圾高温厌氧消化产沼气的试验研究

探究了温度、含固率、pH及接种率对餐厨垃圾厌氧消化产沼量的影响,并设计L9(34)正交试验进行厌氧发酵工艺优化研究。结果表明,在温度为55℃、含固率为8%(质量分数)、pH为7.00、接种率为90%(质量分数)时,厌氧发酵累积产沼量为809.0mL/g(以挥发性固体计);各影响因素对产沼量的影响大小为温度pH接种率含固率。     

一种基于预测法的电磁兼容设计方法

文章以数模混合电路设计实践为基础,介绍了一种基于预测法的电磁兼容设计方法。先以电磁兼容测试理论为基础介绍数模混合电路设计中的电磁兼容方法,在以此方法建立电磁兼容设计模型,并通数模混合电路实践来检验和改进设计模型。     

大港油田苦咸再生水反渗透工艺自动控制研究

分析了大港油田污水回用深度处理工程苦咸再生水反渗透工艺仪表配置及自动控制方式,介绍了苦咸再生水反渗透系统亟待解决的各类问题。着重论述了仪表设置、余氯控制、结垢污堵控制、微生物污堵控制的实际运行方式,探讨了苦咸再生水反渗透工艺的技术可行性和可靠性。     

Cesium-137 contamination of oak (Quercus petrae Liebl.) from sub-mediterranean zone in South Bulgaria

This study focuses on the cesium-137 (¹³⁷Cs) contamination in grass and in different compartments of oak trees growing in ecosystems, located in the zone with sub-mediterranean climate in South Bulgaria, characterized with high summer temperatures, low precipitation and often periods of drought. In 2008, three experimental sites - PP1, PP2, PP3 - were sampled in oak ecosystems from Maleshevska Mountain at 900 m above sea level. Samples from grass species and oak tree leaves, branches with different diameter, wood disks and bark were analyzed for ¹³⁷Cs activity with γ-spectrometry. The soil-to-plant transfer factor (TF) values for ¹³⁷Cs were estimated differentiating different tree compartments. Our findings showed relatively high activity concentrations of ¹³⁷Cs in oak trees even 22 years after the Chernobyl accident. The grass under oak was less contaminated compared with the oak trees. The different organs of oak trees could be distinguished according to the ¹³⁷Cs contamination as follows: bark > branches (d < 1 cm) > leaves > branches (d > 3 cm) > wood. The relatively higher contamination of bark compared with the new-formed biomass suggested that a significant part of ¹³⁷Cs was accumulated as a result of direct adsorption at the time of the main contamination event. The TF values obtained and the presence of ¹³⁷Cs in the branches, leaves and in the wood formed after 1986 confirmed that 22 years after the contamination, the main mechanism of ¹³⁷Cs entrance in tree biomass was the root uptake.