Spatial and vertical distribution of organochlorine pesticides in sediments from Daya Bay, South China   总被引：3，自引：0，他引：3  

Wang Z  Yan W  Chi J  Zhang G 《Marine pollution bulletin》2008,56(9):1578-1585

The spatial and vertical distribution of organochlorine pesticides (OCPs) has been investigated in Daya Bay, China. The concentration of total OCPs in surface sediment range from 16.66 to 44.04ng/g dry weight with a mean concentration of 26.60ng/g. DDTs and HCHs were the predominant species. The ratios of (DDD+DDE)/DDT reflected a cocktail input pattern of fresh and weathered DDTs. The predominant alpha-HCH and the alpha/beta-HCH ratios indicated that the technical HCH contamination was mainly due to historical usage, although there was fresh input of lindane. The variation profiles of concentrations showed that OCPs were extensively applied between the late 1950s and early 1980s in China. A recent increasing trend in concentrations of DDTs and HCHs was found in both cores. The increasing ratios of (DDE+DDD)/DDT with corresponding decreases of DDE/DDT ratio implied that most of the DDTs deposited after their production ban were more likely "weathered" DDTs derived from soil residues.  相似文献   

Population similarity analysis of indicator bacteria for source prediction of faecal pollution in a coastal lake     

Ahmed W  Hargreaves M  Goonetilleke A  Katouli M 《Marine pollution bulletin》2008,56(8):1469-1475

Biochemical fingerprinting (BF) databases of 524 enterococci and 571 Escherichia coli isolates and an antibiotic resistance analysis (ARA) database comprising of 380 E. coli isolates from four suspected sources (i.e. dogs, chickens, waterfowls, and human sewage) were developed to predict the sources of faecal pollution in a recreational coastal lake. Twenty water samples representing four sampling episodes were collected from five sites and the enterococci and E. coli population from each site were compared with those of the databases. The degree of similarity between bacterial populations was measured as population similarity (Sp) coefficient. Using the BF-database, bacterial populations of waterfowls showed the highest similarity with the water samples followed by a sewage treatment plant (STP). Higher population similarities were found between samples from STP and water samples especially at two sites (T2 and T3) which were located near the sewerage pipes collecting wastewater from the study area. When using the ARA-database, the highest similarity was found between E. coli populations from STP and water samples at sites T2 and T4. Both faecal indicators and as well as methods predicted human faecal pollution, possibly through leakage from submerged sewerage pipes. The results indicated that the Sp-analysis of faecal indicator bacterial populations from suspected sources and water samples can be used as a simple tool to predict the source(s) of faecal pollution in surface waters.  相似文献   

Daubechies小波在射电成图降噪处理中的应用   总被引：2，自引：1，他引：1  

陈普春  张喜镇  向守平  冯珑珑  W.Reich 《天文学报》2000,41(3):327-332

在超新星遗迹的认证中,如何有效去除观测资料中的干扰噪音,突出其中的有用信号,一直是实验工作关注的焦点。小波分析法是一种新近发展超来的新的时频分析方法。与Ｆｏｕｒｉｅｒ分析方法一样,任意的能量有限函数可以用小波正交展开。与Ｆｏｕｒｉｅｒ正交基不同的是,小波正交基具有局域性好的特性,这为分离观测资料中的局部噪音。提供了一个十分不效的工具,在利用Ｄａｕｂｅｃｈｉｅｓ４离散小波时,成功地去除了射电源成图中  相似文献   

中国玛珥湖的时空分布与地质特征   总被引：34，自引：6，他引：28       下载免费PDF全文

刘嘉麒  J.F.W.Negendank  王文远  储国强  J.Mingram  郭正府  骆祥君  陈锐  刘东生 《第四纪研究》2000,20(1):78-86

自新生代以来 ,在亚洲东部大陆边缘的裂谷系和青藏高原内部及周边地区 ,火山活动频繁发生 ,形成大量火山和火山岩 ,在一些火山区还发育有大小不等、形态不一的玛珥湖 ,其中有的积水 ,有的干枯 ,它们集中分布于雷琼、东北、青藏高原等地区 ,跨越了热带、亚热带、温带和高寒地带。从中新世的山东山旺盆地 ,早更新世东北龙岗地区的龙湾 ,到雷琼地区中晚更新世的田洋、湖光岩等 ,几乎各个时代、各种类型的玛珥和玛珥湖都有 ,玛珥湖中的沉积物从几十米到一二百米厚度不等 ,记录了不同地区、不同时段气候环境演变的历史 ,对全球变化研究有着重要意义。  相似文献   

目前和将来用卫星资料作中尺度天气预报的难点及可能性          下载免费PDF全文

James F.W. Purdom  杜扬 《气象科技》1988,(2):6-9

卫星资料与其它气象信息相结合的有效使用,对当前及未来的短时预报都是一个关键问题。这种与其它气象信息相结合的有效使用,可能涉及到把资料输入到中尺度数值模式或知识库,以及按时间的函数把卫星资料与其它气象资料相结合去解释它们的产品。利用日常可以得到的地球静止气象卫星资料,气象学家能够观察到中尺度机制所导致的中尺度天气的发展。从卫星资料得到的这些见解,正在帮助实现中尺度预报和短时预报。由于日常可以从一系列栩栩如生的卫星云图以及卫星探测资料中得到大量的信息,那么如何更好地从这些资料中提取有用的信息为中尺度预报所用,是气象学家们所面临的最大难点之一。  相似文献   

沉积速率的随时间尺度变化和礁与碳酸盐台地的沉没     

周良勇 Schla.  W 《海洋地质前沿》1999,(10):11-13

浅水碳酸盐系统提供的沉积物和垂向加积的最大速率很重要,因为这一速率决定了礁或碳酸盐台地的生与死。海洋中大部分碳酸盐沉淀发生在水体的光照部分,因此大量的生产限于透光带,约在海洋１００ｍ水深以上。当台地顶部没于不透光深度时,碳酸盐的生产停止,台地将被淹没。礁或台地的生或死取决于一种平衡,就是相对海平面变化速率和碳酸盐系统加积并保持台地顶部位于透光区的最大速率间的平衡。在这个报告中,作者首次提出和评价了这个假说：礁和台地的生长潜力与碳酸盐平均生长速率遵循相同的尺度变化趋势。１　比率相关和沉积速率的比例…  相似文献   

A NEW APPROACH TO CONFIRMATION BY INFRARED SPECTROMETRY     

W.G.DE RUIG J.M.WESEMAN State Institute for Quality Control of Agricultural Products 《地理学报(英文版)》1990,(1)

In the series of analytical techniques for identification of chemical substances,infrared spectrometrypresents by far the highest information content.However,the information is most complicated too.Itconcerns a multitude of band positions,band intensities and band shapes,which,moreover,can bedisturbed by matrix and other effects.The high redundancy,however,allows conclusions to be made bya qualitative,subjective procedure.IR is often used to prove the equality between a sample and a reference material,e.g.in quality controlof a production process.In forensic control,the question to be answered is mostly not to prove equality,but whether or not the presence of a compound in a sample,e.g.a drug,can be proved.Moreover,testinghas to be performed according to objective rules.To fulfil these requirements,a new retrieval algorithm,the‘Adequate Peaks Search’,is presented.Itconcerns representing the reference spectra by sets of adequate peak positions and the sample spectrumby a set of all peak positions,whereafter the cross-sections of the sample set and the reference sets aredetermined.The concept‘adequate peak’is defined and criteria have been formulated to evaluate theresults into a positive(presence of the analyte is proved) or negative(presence is not proved)conclusion.The detection limit when the Adequate Peaks Search(APS)method was applied was four to seven timeslower than that attained by a number of experts.  相似文献   

雨生红球藻的细胞周期初探   总被引：15，自引：2，他引：13  

刘建国  殷明焱  张京浦  孟昭才  W F Bourne 《海洋与湖沼》2000,31(2):145-150

于１９９７年在青岛利用显微镜连续观察技术研究了雨生红球藻的细胞繁殖方式和动力学。结果表明,该藻细胞周期分为流动和不动２个阶段。每一阶段主要以无性生殖产生孢子的方式完成增殖。正常条件下游动细胞主要产生２、４个,偶尔产生２、４个,偶尔产生８个游动孢子,游孢子从孢子囊释放后为游动细胞。环境不适时流动细胞以及流动孢子失去鞭毛转入不动阶段。不动细胞主要形成４、８个,偶尔也能形成２０多个不动孢子,该过程不一定  相似文献   

从墨西哥南下加利福尼亚州圣罗萨莉亚盆地看加利福尼亚湾断裂系的年代     

J.W.Holt  高莉玲 《海洋地质前沿》2000,(10)

加利福尼亚湾是北美和太平洋板块间的大陆断裂作用和地壳迁移所形成的 ,这一过程可能始于１２Ｍａ左右。海湾南部海底扩张始于大约３．６Ｍａ ,通常被认为是半岛向太平洋板块迁移活动的结束。南下加利福尼亚半岛向太平洋板块迁移可能经历了３个不同的演化期 :大约１２～６Ｍａ,沿着古火山弧扩张 ;大约６～３．５Ｍａ ,转换断层和扩张盆地继续演化 ;此后 ,半岛完全迁移至太平洋板块 ,相对于北美的运动加剧。然而 ,根据此海湾扩张线性构造确定的南下加利福尼亚与北美分离的速率低于根据３．６Ｍａ以来全球板块路线推测的结果 ,表明此时半岛与…  相似文献   

兰州盆地活断层的高分辨率浅层地震勘探技术   总被引：5，自引：3，他引：2       下载免费PDF全文

卢育霞  王振明  王兰民  石玉成  Edward W.Woolery 《地震工程学报》2008,30(4):344-353

针对城市活断层浅层地震探测的一些技术问题,在兰州盆地的金城关断层和刘家堡断层沿线开展活断层浅层(50 m以内)地震勘探技术研究.主要采用纵波和横波多次覆盖共CMP点地震反射方法,获得了目标场地地震图像资料,尤其横波地震剖面更加清晰地反映出超浅层构造空间特征.以红艺村测线(HYC)和师范学校西测线(SFXX)为例,分析总结了数据采集、资料处理、剖面解释三方面浅层活断层地震探测的技术要点.结果可以为兰州市及类似复杂构造地区活断层地震调查提供技术参考.  相似文献