Effects of 12 years' operation of a sewage treatment plant on trace metal occurrence within a Mediterranean commercial sponge (Spongia officinalis, Demospongiae)

The present field study uses Spongia officinalis for assessing trace metals occurrence in time and space within Mediterranean rocky communities. Nine sites were selected in the Marseille area for studying spatial trends in 12 metal concentrations. Long term changes in 8 metal concentrations were assessed at sites that had been sampled before and 12 years after the opening of a treatment plant. Spongia officinalis highly concentrated all the trace metal surveyed excepted Hg and Cd. The overall contamination level registered provided a classification of the study sites which is congruent with that given by other studies on pollutant accumulation in neighbouring sandy-bottoms or benthic assemblages. Among the metals studied, Fe, Pb, Cr are those that best highlighted a pollution gradient. In the present study, only Cd concentration did not vary in space. Except for Ni, all pollutant concentrations clearly decreased between 1984 and 1999. This very impressive decrease in heavy metal concentrations within the Marseille area represents an indisputable evidence of the improvement of the seawater quality resulting from 12 years' operation of the Marseille sewage plant. Moreover, the significant decrease also recorded in the reference population at Port-Cros might reflect an overall improvement in the seawater quality of the NW Mediterranean.     

IP法几种常用电极排列的比较

激电工作使用的电极排列有多种,应根据工作目的、地质条件和需要信息量选其一种进行工作,否则不但得不到预期效果,而且浪费资金。遗憾的是有这种倾向,某种电极排列得到偏爱,不分场合照例使用,对其它电极排列的特点则考虑不多。论述各种电极排列优缺点的文章不多,虽通过模型实验结     

魁北克诺兰达地区的发现

主席先生,贵宾们,勘探工作者同事们: 过去几天里,我们有机会参加这次专题讨论会,物探和化探界的一些知名人士,回顾了各种技术在科学勘探中应用的现状。毫无疑问,在确定目标和其后的发现中,技术手段起了重要作用。地质学家与地球物理学家、地球化学家同等重要,其作用决不应被低估或忽视。本文是诺兰达地区块状硫化矿床在过去     

太古宙的微化石和“微化石状”物体——一个批判性评述

在过去15年间,已报导过格陵兰(伊苏阿上地壳群,大约3770Ma)、非洲(翁韦瓦克特群,大约3540Ma;无花果树群,大约3400Ma;维特瓦特斯兰德岩系,大约2640—2820Ma;布拉瓦约灰岩,大约2600Ma)、澳大利亚(瓦拉沃纳群,大约3520Ma;戈尔格溪群,大约3400Ma;南部克罗斯石英岩,大于2700Ma;哈默斯利群,大约2700Ma)、印度(马德拉斯片麻岩,大于3000Ma;G.R.组,大于2600Ma)、以及北美(苏丹含铁     

地理学研究中的自动化问题

新方法计算机技术与分析方法的最新发展有可能使迄今一直以人工方法处理的各项地理学科研课题实行自动化。计算机制图,计算机绘表、数字遥感、地理信息系统、空间统计以及数量空间模式等等新方法一直在不断改进。由于使用这些新方法,目前,已经能够使用数据分析的方法进行大面积的复杂的地理学课题的分析工作。而小范围的不甚复杂的课题可以广泛地运用小型计算机系统来解决。可是某些科学家、政策制订者和企业家对地理学研究在区域的、国家的与国际范围的合作项目与政策制订工作中的重要性认识不足。他们对地理学的基础研究与应用研究工作都没有给予足够的资助。     

Scale effect and calibration of contaminant transport models

The influence on solute transport of the small-scale spatial variation of aquifer hydraulic conductivity (K) was analyzed by comparing results from fine-grid (2 m by 2 m) simulations of a synthetic heterogeneous aquifer to those from coarse-grid (8 m by 4 m) simulations of an equivalent homogeneous aquifer. Realizations of the K field of the heterogeneous aquifer were generated, using the Monte Carlo approach, from a lognormal distribution with mean log K of 2 (K in m/d) and three levels of log K variance of 0.1, 0.5, and 1.0. Numerical simulation results show that the average standard deviation of point concentrations increased from 1.21 to 5.78 when the value of log K variance was increased from 0.1 to 1.0. The average discrepancy between modeled concentrations (obtained from a coarse-grid deterministic numerical simulation) and the actual mean point concentrations (obtained from fine-grid Monte Carlo numerical simulations) increased from 0.91 to 4.23 with the increase in log K variance. The results from this study illustrate the uncertainty in predictions from contaminant transport models due to their inability to simulate the effects of heterogeneities at scales smaller than the model grid.     

Detection of PAHs in seawater using surface-enhanced Raman scattering (SERS)

The laboratory characterization of a field-operable surface-enhanced Raman scattering sensor (SERS optode) is presented for the detection of aromatic hydrocarbons in seawater. The sensor has been developed for deployment with a robust underwater spectrograph. To meet the demands of the harsh seawater application, sol-gel derived SERS substrates were used. The calibration curves of six PAHs were determined to be of Langmuir adsorption isotherm type with limits of detection ranging from the microg l(-1) to ng l(-1) level. The experimentally determined adsorption constants varied strongly with the molecular weight of the analytes and correlated with their solubility. A mixture of five PAHs dissolved in seawater was investigated to demonstrate the utility of this method for screening. Emphasis was put on the interference from suspended particulate matter (SPM). The Raman measurement with backscattering configuration was shown to be immune against turbidities up to 1000 NTU. The physico-chemical interference arising from adsorption by the sediment was measured on-line by adding sediment to a PAH-spiked solution. According to the calibration curve, the PAH concentration decrease corresponded to more than 98% of the analyte being scavenged by the sediment.     

Abnormal features of Macoma balthica (Bivalvia) in the Baltic Sea: alerting symptoms of environmental adversity?

Recent studies of the Baltic clam Macoma balthica (L.) from the southern Baltic (the Gulf of Gdansk) have revealed striking morphological, histological and cytogenetic features. Strong deformation of the shell, including elongation of the posterior end and the appearance of an easily visible flexure in this part, has been recorded. The population contribution of the deformed blunt shelled ("irregular") clams ranged from 0% to 65% and tended to increase with depth. The morphologically "irregular" clams had higher accumulated tissue concentrations of trace metals (As, Ag, Cd, Pb, Cu and Zn), indicating a different metal handling ability. Adverse conditions in deeper water regions of the Gulf (e.g. hypoxia, hydrogen sulphide, elevated bioavailability of contaminants) have been suggested as inducers of the phenotypical changes (morphological deformation) in part of the population and, in parallel, of the specific physiological adaptations that result in higher metal accumulation in the "irregular" clams. Cytogenetic and histological analyses showed the presence of tumours in gill cells and digestive system of the affected clams, the prevalence of disseminated neoplasia ranging from 0% to 94% depending on the site. The disease was manifested by a modified karyotype (i.e. an abnormal number and morphology of chromosomes), a higher activity of nucleolar organizer regions (AgNORs), and tissue lesions (enlarged cells, actively proliferative with pleomorphic nuclei). Bottom sediments showed acute toxicity and have been proposed as a source of an initialising carcinogenic factor. However, none of the ecotoxicological studies provided was successful in the clear demonstration of a single (or multifactorial) agent that can account for the disseminated neoplasia.