氮源对番茄灰霉病菌菌丝生长的影响

选用15种常见氮源,应用固体和液体培养方法,筛选适宜番茄灰霉病菌生长的氮源营养物质.结果表明:在固体培养中,病菌对氮源的利用以蛋白胨为最好,其次为酵母膏.在液体培养中,病菌对氮源的利用以酵母膏为最好,其次为(NH4)2SO4.     

浑善达克沙地东段风沙源治理模式初步研究——以内蒙古克什克腾旗为例

针对浑善达克沙地东段的自然经济条件和沙漠化危害特点,因地制宜地营建农防林与牧防林相结合,防护林与经济林相结合,沙漠化治理与沙产业开发相结合的综合防护体系6667hm2。防护体系建立后,区域内生态环境明显改善,维护了首都的生态安全。     

宁夏西海固地区农业生态环境面源污染调查研究

农业生态环境面源污染控制与保护已成为区域农业和社会协调发展的重大问题。通过调查分析,西海固地区的农业面源污染源主要有化肥、农药、地膜、土壤侵蚀、牲畜禽粪便污染、有污染的灌溉水源与农村生活污水和农村固体废弃物等,并对西海固地区农业面源污染现状及其成因进行了分析。基于农业生态环境面源污染具有污染发生的广泛性、复杂性和治理难度大等特点,提出了防治农业面源污染与保护农业生态环境的对策及建议。     

Ineffectiveness of pruning to control citrus huanglongbing caused by <Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter americanus

The huanglongbing (HLB) disease of citrus trees, caused by Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, was first reported in Brazil in March, 2004. The presence of the disease has caused serious concerns among growers. Pruning experiments were conducted to determine if removal of symptomatic branches or the entire canopy (decapitation) would eliminate infected tissues and save HLB-affected trees. Pruning was done in five blocks on a total of 592 3- to 16 year-old ‘Valência’, ‘Hamlin’ or ‘Pêra’ sweet orange trees showing no symptoms or with two levels of symptom severity. Ten decapitated trees per block were caged and all trees were treated with insecticides to control the psyllid vector, Diaphorina citri. Mottled leaves reappeared on most symptomatic (69.2%) as well on some asymptomatic (7.6%) pruned trees, regardless of age, variety, and pruning procedure. Presence of the pathogen (Ca. Liberibacter americanus) in all symptomatic trees was confirmed by PCR. In general, the greater the symptom severity before pruning the lower the percentage of trees that remained asymptomatic after pruning.     

栽培防病措施对防治小麦白粉病的重要作用

为了解栽培措施对防治小麦白粉病的作用,通过不同栽培措施对病情产生不同影响的大量田间调查,明确了小麦早播、密播,过量水、肥条件下的旺苗和种植高度感病品种,都会加重小麦秋苗带菌量。短期播种、合理密植、视墒灌水、配方施肥、培育小麦壮苗及避免种植高感品种等均能减轻小麦秋苗带菌量。小麦秋苗带菌量大,则翌春病菌越冬菌源量也大。种植高感品种在田间有发病中心的作用。应把栽培防病措施规范化、科学化、制度化,以充分发     

淡水环境中可溶有机质研究进展

论述了淡水环境中可溶有机质(DOM)在分离与分析方法、来源与特征,以及环境意义等方面的研究进展。指出了在分离方法上,从XAD树脂分离到反渗透膜分离已经发展出各种分离技术;在分析方法上,现代波谱分析技术得到了广泛应用。DOM是由在来源、年龄、存在状态、后生改造等方面存在巨大差异的不同有机质混合构成的,因而呈现出十分复杂的非均质结构。DOM通过其自身的生物可利用性、改变有机污染物和重金属的生物可利用性及其耗氧能力影响环境质量,而且其自身的一些地球化学特征也能用来反映环境的变化特点。最后简述了湿地淡水环境中DOM的研究趋势和展望。     

车内噪声分析与控制研

利用互易性原理,提出了一种空气声传播路径实验方法.首先测得各声源对于车内噪声的传递函数,进而得到各声源对于车内噪声的贡献度.根据声源识别结果,对汽车车身进行吸声、隔声设计,结果表明,车内地板隔声量从前向后分别提高了1.83～9.74 dB(A),汽车车内噪声下降了4.7 dB(A).     

Decreasing shrimp (Pandalus borealis) sizes off Newfoundland and Labrador – environment or fishing?

During the 1990s, carapace length statistics including minimum size caught (L_min), mean male and female lengths, size at sex transition (L₅₀) and maximum size (L_max) of northern shrimp (Pandalus borealis) decreased in commercial and survey catches off Newfoundland and Labrador. Decreased growth rates caused by decreases in per‐capita food availability due to large population increases, exacerbated by increased metabolic demands from higher water temperatures in the mid‐1990s, appear to be the main cause of the size decrease. Fishing could have had an accelerating effect on environmentally driven decreases in shrimp growth and size by ‘cropping’ the largest shrimp from the population. The greatest decreases in shrimp size occurred in Hudson Strait and the adjacent northern shelf, the area which also has the highest densities and largest shrimp. We hypothesize that the greater size decrease here resulted from decreased primary production from decreased nutrient flux into the euphotic zone, caused by increased atmospheric warming, freshwater runoff and stratification during the warming trend of the 1990s.     

苦水玫瑰产地土壤重金属污染评价与溯源解析

探明特色农产品产地土壤重金属污染特征及其污染来源可促进特色农作物产业的健康有序发展,对于助力乡村振兴和发展乡村特色产业具有重要意义。该研究以苦水玫瑰产地土壤为研究对象,应用内梅罗综合污染指数法、污染负荷指数法和改进物元可拓模型来量化土壤重金属As、Cd、Cr、Cu、Hg、Ni、Pb和Zn的污染水平并进行对比分析,还利用正定因子矩阵模型(positive matrix factorization, PMF)进行土壤重金属溯源解析。结果表明:1)研究区土壤除Hg和Cr的均值低于兰州市和甘肃省土壤背景值之外,其余As、Cd、Cu、Ni、Pb和Zn的均值都高于二者的背景值,但所有元素的测定值均低于《土壤环境质量农用地土壤污染风险管控标准(试行)(GB 15 618-2018)》(pH值大于7.5)的筛选值。2)内梅罗综合污染指数和污染负荷指数分别处于0.71～2.02和0.64～1.48之间,均值为1.41和1.17,土壤总体上为轻度污染。改进物元可拓模型评价结果显示研究区土壤总体上处于尚清洁状态,与内梅罗综合污染指数与污染负荷指数评价结果基本一致,但改进物元可拓模型的评价结果更具有实际指导意...     

Spatio-temporal distribution of sergestid shrimp Acetes intermedius in the coastal waters of southwestern Taiwan

SUMMARY: Spatio-temporal variation of the sergestid shrimp Acetes intermedius in the coastal waters of southwestern Taiwan was investigated based on 1546 samples collected by 13 commercial fishing vessels from July to October 1996. Adult sergestid shrimp started a down-estuary migration with the increased river discharge associated with heavy summer rainfall. Fishing season for this species was to commence after that. In July, the shrimp stock was found on the shallow continental shelf off Tungkang and Fangshan. They mainly aggregated in Kaoping Canyon off Tungkang during August and September occurring at very high densities. In October, the shrimp returned to the coastal waters off Tungkang and Fangshan at lower densities. The heavy rainfall is a factor that triggers the shrimps to make a down-estuary migration that could reduce competition for food between adults and their offspring during the period of high river discharge. When the northeast monsoon prevailed, the sergestid shrimp moved back to the estuaries and the fishing season was terminated.