Volume 86, Issue 7

Definitions and terms related to bioavailability and bioaccessibility of trace metals/metalloids and organic contaminants in soil are briefly discussed and critically evaluated. Main distinguishing features of estimating the bioavailability by biological (in vivo) methods are characterized. Assessment of bioaccessibility using biomimetric (in vitro) methods and existing correlations with in vivo tests are summarized. The most promising biomimetric methods can be as follows: CaCl 2 extraction for the assessment of metals biouptake into plants; solid-phase micro extraction, supercritical fluid extraction (SFE) under mild conditions as well as Tenax and hydroxypropyl-beta-cyclodextrin (HPCD) extractions for the estimation of biouptake of persistent organic compounds (e.g., polynuclear aromatic hydrocarbons and polychlorinated biphenyls) by soil-dwelling organisms (mainly earthworms); SFE under mild conditions, HPCD and Tenax extraction for the prediction of biodegradability (microbial degradation) of organic contaminants. However, method development should be extended to further classes of substances. In addition, multidisciplinary approaches are needed for (i) standardization and round-robin studies of the most promising biomimetric methods and protocols so that the data obtained in different laboratories can be compared; (ii) further assessment and critical evaluation of correlations between in vitro and in vivo tests; application of chemometric techniques for handling sets of data obtained both by biomimetric and biological methods is of particular importance in order to evaluate new criteria for risk assessment.

A thermodynamic model is proposed, which combines the ion association and the ion interaction models using the extended database pit2010.dat for a more precise modeling of the chemical species of micro components in natural waters of varying ionic strength (fresh, saline and hyper-saline). Compared to the ion association model, the proposed combined model more adequately describes the complex character of the ionic interactions. The performance of the combined ion association/ion interaction model compared to that of the ion association model is illustrated in case studies of several Bulgarian natural water systems of different ionic strength and type of pollution. The results are interpreted in terms of the chemical behavior of the metals and of their chemical species in the water systems, which is defined by the redox potential, pH, cationic and anionic organic and inorganic composition of the water systems and by the ability of the metals to preferentially coordinate with some anions, as well as by the stability of the corresponding species. The affinity of the transition metals towards the ligands is explained by the “hardness-softness” factor and the crystal field stabilization energy (CFSE).

Uranium toxicity has been a concern for more than 100 years. The toxicology of many forms of uranium, ranging from dust of several oxides to soluble uranyl ion, was thoroughly studied during the Manhattan Project in the United States in the 1940s. The development of depleted uranium kinetic penetrators as armor-piercing incendiary weaponry produced a novel form of uranium environmental contamination, which led to greater susceptibility to the adverse health effects of the toxic heavy metal after its use in various military conflicts. The aerosol from burning uranium penetrator fragments is rapidly dissolved in biological fluids and readily absorbed from the lungs, leading to a wide range of toxic effects. We have studied some chelating agents for uranyl ion, including citrate ion and desferal (desferrioxamine B), which may be effective for minimizing the toxic effects of this insidious heavy metal. Some characteristics of the desferrioxamine complex are presented, along with information about the use of citrate as an effective chelating agent for therapy of uranium toxicity.

Surface sediments, mussels, seagrass, surface and bottom seawater samples were collected from the costal area of the southeastern Adriatic Sea and analyzed in order to determine the concentration and origin of the following elements: Fe, Mn, Zn, Ni, Cu, Ni, Co, As, Cd, Cr and Hg. The complexity of the obtained data was reduced by principal component analysis (PCA) and cluster analysis (CA), methods well known and accepted for the identification of the quality of marine environments. Both PCA and CA analysis were used to discriminate groups of samples according to the similarity of their chemical composition. The results revealed good diversity between the various samples, expressed by their distinctive positions of points in factor space. PCA indicated that the first two PC components explained about 73, 48, 43, 48, and 50 % of the total variance of the data for sediments, mussels, seagrass, and surface and bottom water, respectively. The results showed good discrimination capabilities between the samples taken from different locations, and also different seasons, which was especially evident in the surface and bottom water samples. Simultaneously, PCA/CA analysis of the amounts of trace elements found in the marine organisms could explain the manner of their bioaccumulation.

Engineered nanoparticles (ENPs) are known to possess unique size and shape dependent chemical and physical properties. As a result of their properties, ENPs have been effective in several important applications including catalysis, sensor design, photonics, electronics, medicine, and the environmental remediation of toxic pollutants. Such properties and applications have led to an increase in the manufacture of ENPs and a rise in their presence in consumer products. The increase of ENPs in consumer products presents several opportunities and challenges, and necessitates a proactive study of their health and safety. This article highlights some recent work in which we have studied the effect of exposure of well-defined ENPs to pesticides and the effect of pH and dissolved organic matter. We also summarize our work and that of others who have studied the toxicity of ENPs with microorganisms. The results provide insights on the need for green manufacturing strategies of ENPs, their use and safe disposal practices.

Novel reactive materials for catalytic degradation of chlorinated organic compounds in water at ambient conditions have been prepared on the basis of silica-supported Pd-Fe nanoparticles. Nanoscale Fe-Pd particles were synthesized inside porous silica supports using (NH 4 ) 3 [Fe(C 2 O 4 ) 3 ] and [Pd(NH 3 ) 4 ]Cl 2 or Pd acetate as reaction precursors. According to temperature programmed reduction (TPR) studies, Pd introduction decreased the reduction temperature of the supported Fe n+ species and nearly complete reduction with H 2 was observed at 400 °C. The successful surface loading with Pd was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Characterization of the samples by X-ray diffraction (XRD) and X-ray absorption near-edge structure + extended X-ray absorption fine structure (XANES + EXAFS) verified the presence of highly dispersed Pd 0 , Pd x Fe 1– x and Fe 0 phases. Reduction of the supported precursors in hydrogen resulted in materials that were highly active in perchloroethene (PCE) degradation and 2-chlorobiphenyl (2-ClBP) dechlorination. It was found that highly dispersed amorphous Fe-Pd bimetallic nanoparticles on silica support showed superior catalytic activity against PCE dechlorination in comparison to the free-standing Fe-Pd nanoparticles. For the samples with the same Fe content, the conversion of chlorinated organics as well as the stability increased with the Pd loading, e.g., the most effective degradation of PCEs and 2-ClBP was achieved at a Pd loading of 2.3–3.2 wt. %.

Nanoscience and nanotechnology have advanced in recent years followed by groundbreaking discoveries that allow a remarkable control of molecular entities in the nanoscale. Advances in the field still came in many cases without a detailed and profound understanding on the effects and impact that nanotechnology and nanomaterials can have in our future society. In this work, we have aimed to provide a short but relevant overview on the impact and risks of nanotechnogy and the possibilities to engineer safer nanomaterials for a controllable working environment.

This study was conceived to evaluate the global scientific output of secondary organic aerosol (SOA) research and to assess the characteristics of the research patterns, tendencies, and methods in the papers. Data were based on the online version of Science Citation Index Expanded from 1990 to 2013. Publications referring to SOA were assessed by distribution of the number of publications and times cited, source journals, h-index, and the most cited publications in these years. By synthetic analysis of author keywords, KeyWords Plus, titles, and abstracts, it was concluded that modeling is currently and will at least over the next decade continue to be the predominant research method to validate state-of-the-art knowledge of SOA, and that the foci of SOA research will be the key precursors terpenes, isoprene, and dicarbonyls; the mechanisms of oxidation and aqueous-phase reactions; emission inventories; and chemical composition. Recent years show growing interest for research on health effects.

The toxic and non-biodegradable nature of organic dyes necessitates the design and synthesis of novel adsorbents for their effective removal from the environment. This study reports an effective remediation behavior of surface-functionalized silica gel against water-soluble cationic dyes (up to 98 % removal). Thiol groups were functionalized at the surface of silica gel (SiO 2 –SH). The surface-tethered –SH groups were further oxidized to sulfonic acid groups to generate the negatively charged moieties at the surface of silica gel (SiO 2 –SO 3 H). The morphology of the developed adsorbents and the surface modifications were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Uptake study of three cationic dyes, namely, rhodamine B (Rh B), rhodamine 6G (Rh 6G), and crystal violet (CV) with SiO 2 –SH and SiO 2 –SO 3 H adsorbents was performed by varying the adsorbent amount, contact time, pH of solution, and temperature. The presence of negatively charged species at the surface of SiO 2 –SO 3 H results in an increased electrostatic interaction with the cationic dyes, which leads to better remediation characteristics for SiO 2 –SO 3 H as compared to SiO 2 –SH. The reusability of the developed adsorbents was also assessed by investigating adsorption/desorption of dyes. The simple fabrication process provides a facile avenue to the adsorbents with efficient remediation towards cationic dyes.

An ecotoxicological study is presented, in which three marine bivalve species ( Mytilus galloprovincialis , Callista chione , and Venus verrucosa ) living in different habitats were studied for Cd bioaccumulation, under laboratory conditions. The bivalves, originating from a relatively polluted marine area of Greece (Saronicos Gulf), were exposed to 0.5 mg Cd L –1 seawater (4.4 μmol Cd L –1 seawater) for 5, 10, 15, and 20 days. Control animals were kept in metal-free seawater as well. Three or four different parts of the organisms (gills, mantle, body, digestive system) were examined for the bioaccumulation of Cd, as well as the levels of three biomarkers (metallothioneins, acetylcholinesterase, lipid peroxidation). A depuration experiment was also carried out. During the experiment, the initial levels of Cd in the control animal tissues either decreased or remained constant and low. The organisms exhibited different behavior regarding Cd bioconcentration and biomarker responses as well as tissue distribution of Cd. After the depuration period, significant amounts of Cd remained in the organisms’ tissues, much higher than the respective levels in control animals.

In the arid and semi-arid regions, being the most water-deprived regions of the world, water scarcity is the most pressing challenge. The dry climate and the effects of the global warming are leading to increased pressure on the meager water resources causing a rapid quality degradation of chronically depleted water resources, while the use and disposal of numerous biological and chemical pollutants endangers the water bodies to a degree that part of the resources are not safe to use for human consumption, posing a health risk to the population. The degradation of water resources is magnified by the fast-growing population and the increase in domestic and irrigation water demand, which is impossible to meet from available natural resources. Such adverse development is already apparent in the Near East region (Israel, Palestine, and Jordan) where the shared water resources are already in a deteriorated state unable to satisfy the basic needs. To satisfy current and future needs, a new water resources management strategy is suggested, aiming at the sustainable use of available water resources, supplemented by the development of water reuse and desalination of brackish groundwater and seawater, cautiously considering the associated health and environmental safety, as discussed herewith.

Nitrogen-containing chiral heterocycles represent important structural elements with wide occurrence in natural and unnatural compounds exhibiting important biological activities. Herein, we describe our recent endeavors directed toward the Brønsted acid-catalyzed 1,3-dipolar cycloaddition and alkylation reactions, together with the metal/Brønsted acid relay catalytic cascade reactions to access some typical nitrogenous heterocyclic structures and natural alkaloids, including (+)-folicanthine and (+)-gliocladin C.

In this report, we present recent progress in synthetic methodologies based on three heterocyclic chiral building blocks developed from our laboratories. The potential of these chiral building block-based methods in the concise asymmetric synthesis of alkaloids and medicinally interesting molecules has been demonstrated by the total syntheses of 8-aza-prostaglandin E 1 , 11-hydroxylated analogues of the lead compounds CP-734432 and PF-04475270, (+)-castanospermine, (+)-1- epi -castanospermine, 7-deoxy-6- epi -castanospermine as well as 9- epi -sessilifoliamide J.

Naphthalimide has now become a class of most popular fluorophores for probe design, along with coumarin, fluorescein, rhodamine, BODIPY and cyanine. This account aims at the first-year graduate students as the primary audience and showcases the versatile design principles applicable to the naphthalimide fluorophore when designing a probe or label, with focused examples from the Qian research laboratory. We also provide a general synthetic scheme to naphthalimides of various substitution patterns.

The trifluoromethyl group has unique functional properties and is widely used not only in organic chemistry, but also in pharmaceutical and agrochemical science. Here we describe trifluoromethylation reactions of indoles and alkenes using Togni’s reagent. These reactions provide useful trifluoromethylated organic compounds, including heterocycles, with high efficiency.