Detection and quantitative analysis of polychlorinated biphenyls in tilapia from Hawaiian waters

The purpose of this study was to investigate polychlorinated biphenyls (PCBs) contamination in tilapia (Oreochromis mossambicus) collected from the Manna stream and Ala Wai Canal of O'ahu, an island of the geographically isolated Hawaiian archipelago. Our results show that the average concentrations of PCBs varied from 51.90 to 89.42 ng g(-1) lipid weight for the sampling sites. Relative toxic potencies (RTPs) and toxic equivalencies (TEQs) were determined to be 20.38-40.60 ng TCDD g(-1) lipid weight and 2.89-4.17 ng TEQ g(-1) lipid weight by 7-ethoxy-resorufin-O-deethylase (EROD) activity analysis and calculation of PCB concentrations based on toxic equivalency factors (TEFs), respectively. Penta-chlorinated congeners were found to be predominant, which revealed that Aroclor 1254 was a possible major source of PCBs in our fish samples. PCB 118, an indicator PCBs, constituted more than 55% and 30% of the total PCBs and TEQs, respectively. In addition, PCB 118 was found to have a linear correlation to the total PCBs (R = 0.975) and TEQs (R = 0.782). Detection of concentrated PCBs in Hawaiian waters suggests a potentially adverse impact of this pollutant on human health, as well as ecological systems, and suggests the necessity of environmental monitoring and hazard assessment of PCBs within the Hawaiian Islands. (c) 2008 Published by Elsevier Ltd.

Detection of polybrominated diphenyl ethers in tilapia (Oreochromis mossambicus) from O'ahu, Hawai'i

Polybrominated diphenyl ethers (PBDEs) have been detected for the first time at a range from 231.58 to 685.61 ng g(-1) lipid weight in the muscles of tilapia ( Oreochromis mossambicus) collected from O'ahu, an island of the geographically isolated Hawaiian archipelago.

包头稀土工业区土壤中钍的环境化学行为

本论文分为两部分：1. 综述部分（第一章和第二章），介绍了我国包头地区稀土工业区钍污染概况，对稀土工业生产造成的放射性生态环境污染进行了分析和归纳；评述了土壤和沉积物中放射性核素污染生态物理化学研究和进展；说明了本研究课题的背景、意义和技术路线。2. 实验部分（第三章至第六章），包括以下几方面内容：土壤样品和高铁矿渣样品中钍的分析方法的建立；对土壤和矿渣样品中钍的形态进行定量分析，考察了土壤性质对土壤中钍形态分布的影响；模拟自然环境，研究钍在土壤-植物系统之间的迁移积累和钍形态的植物可利用性；土壤样品对钍的吸附-解吸行为及其影响因素。 我国包头稀土工业在稀土矿浮选和稀土精矿湿法冶炼过程中产生了大量含放射性钍的废渣、废水和粉尘，对当地生态环境造成严重的破坏和放射性污染。 采用合适内标，ICP-MS法对样品中钍分析，考察了基体干扰、记忆效应和质谱干扰，比较了不同的样品消解方法对钍测定的影响，并用标准土壤样品和标准加入法对方法的准确性进行了评价。分别采用Tessier、BCR和Martínez-Aguirre形态萃取方法对土壤和样品中钍的形态进行分析，通过对总量的回收率和萃取剂选择性比较，选择了Martínez-Aguirre连续萃取法定量样品中钍的形态，并对其进行了优化和评价。考察了土壤性质影响着钍的形态分布。 通过盆栽实验，考察了小麦对根际土壤中钍形态分布以及的在不同生长期对钍的吸收影响。利用相应的材料人工模拟了土壤中钍的形态，对模拟的钍各形态的植物可利用性和植物吸收贡献指数进行评估分析。利用不同的磷酸盐对土壤进行培养处理，考察了磷酸盐的加入对土壤中钍的生物可利用性影响。 实验了土壤样品对钍的吸附-解吸过程，通过吸附容量、分配系数和吸附百分比等参数考察土壤对钍吸附能力，并考察了被土壤吸附钍的解吸行为。通过吸附机理的分析，土壤对钍的吸附作用主要是通过Th(IV)的表面水解吸附模式进行。根据实验结果，土壤样品对溶液中钍的吸附热力学可以用Freundlich方程式来描述，吸附的动力学过程可用Elovich方程描述，并对吸附方式和吸附过程进行论述。实验发现，吸附-解吸条件、土壤性质、外源稀土元素和施肥等对土壤吸附钍有一定影响。

Evaluation of a sequential extraction for the speciation of thorium in soils from Baotou area, Inner Mongolia

Sequential extraction procedures were widely applied for speciation of radioactive elements. In this study, the sequential extraction procedure developed by Martinez-Aguirre was employed for quantification of different chemical forms of thorium in the soil. The total amount of thorium in contaminated soil was much higher by four-fold than the local background value. The soil properties affect the amount of thoriurn and distribution of fractions in contaminated soil. Results showed that the proportion of thorium in soils from Baotou was found as the residual fraction (F5 + F6) > absorbed fraction (F3), coprecipitated fraction (F4) > carbonates fraction (172) and exchangeable fraction (F1) that could be available to plants. The recovery, calculated by ratio of the sum of the six fractions to the pseudo-total content of thorium, was in the range from 96% to 110%. A comparison was carried out between the sequential extraction and the single extraction to evaluate the selectivity of the extractants. It was found that the amount of thorium of absorbed fraction (H) was higher in the single extraction than that estimated in the sequential extraction, possibly duo to transform of the labile form. While for non-residual fraction analysis, the single extraction scheme was a desirable alternative to the sequential extraction procedure.

Thioreduction of cyclopentanone and hydrodesulfurization of dibenzothiophene over sulfided nickel or cobalt-promoted molybdenum on alumina catalysts

Two series of sulfided Ni or Co promoted Mo/alumina catalysts, having different Ni or Co loadings, were characterized by their activities for the transformation of cyclopentanone into cyclopentanethiol (flow reactor, 220 degrees C, atmospheric pressure) and for the hydrodesulfurization of dibenzothiophene (flow reactor, 340 degrees C, 3 MPa hydrogen pressure). The addition of the promoter increased significantly the activity of the Mo/alumina catalyst for both reactions, up to a maximum obtained with the catalysts having a (promoter)/(promoter+Mo) molar ratio equal to 0.3-0.4. This increase in activity was due in part to an increase in the hydrogenating properties of the Mo/alumina catalyst. However, an additional modification of the catalyst (basic and nucleophilic properties) must be considered to account for the spectacular effect of the promoter on the rate of the dibenzothiophene direct desulfurization reaction. (C) 1999 Elsevier Science B.V. All rights reserved.