Indoor air quality: validation and setting up quality control for determination of anions and cations in particulate matter

In recent years, the indoor air quality has been studied more frequently due to an increasing concern within the scientific community on the effects of indoor air quality upon health. The indoor air quality studies of schools have a large impact in both health and educational performance of children since they constitute a sensitive group with higher risk than adults, particularly vulnerable to pollutants due to their undeveloped airways. A total of 14 basic schools located in Lisbon city, Portugal, were selected for sampling the total particulate matter (TPM) by passive deposition into polycarbonate filters and to assess the indoor air quality. Compared to automatic samplers, this passive sampling method represents an easier and cheaper way to assess several indoor air quality environments with no interference in the classroom activities. The procedure was performed on four different campaigns during 2009–2010. The filter loads were measured by gravimetry with a 0.1-μg sensitivity balance and, afterwards, the TPM water-soluble ions content was assessed by ionic chromatography (Cl⁻, NO₃ ⁻, PO₄ ³⁻ and SO₄ ²⁻); flame absorption (Na⁺, K⁺, Mg²⁺ and Ca²⁺). The performance characteristics of the methods, namely specificity, limit of detection, limit of quantification, working range, precision and trueness were evaluated. Measurement uncertainty was expressed in terms of precision and trueness. Precision under intralaboratory reproducibility conditions was estimated from triplicate analysis. The trueness component was estimated in terms of overall recovery using the reference material SPS-NUTR WW2 Batch 107, from Spectrapure Standards, Oslo, Norway, for anions and the certified reference material CRM 1643e, from NIST, Gaithersburg, MD for cations. Measurement uncertainty of the results obtained with the methods described in this work fulfilled the relative differences (RD) defined by the anion−cation balance in the extraction solutions of the particulate matter. Target RD values were defined: RD < 0.05.     

Study of specific ion-amino acid interactions through the use of local correlation methods

Specific ion effects, related to the hydration of ions and ion-solute interactions, play a fundamental part in many processes in chemistry and biology. Although intensively studied since the seminal studies of Franz Hofmeister and co-workers, their molecular origin has only recently started to be unveiled. In this work, we have investigated the interaction between halide anions and a selected set of amino acid residues in an attempt to identify the forces behind ion specificity. Two-dimensional potential energy surfaces have been calculated with the use of local second order M?ller-Plesset perturbation theory (LMP2), coupled with the COSMO model to describe solvent effects. The results show in great detail the impact of dispersion interactions, in particular for the heavier anions (Br(-) and I(-)). The obtained potential energy surfaces also hint at a greater mobility of iodide in the vicinity of a residue, which correlates well with its placing in the Hofmeister series.     

Dicarboxylate recognition by two macrobicyclic receptors: selectivity for fumarate over maleate

Two ditopic polyamine macrobicyclic compounds have been studied as receptors for the recognition of dicarboxylate anions of varying chain length in aqueous solution. One of the receptors consists of two tris(2-aminoethyl)amine-derived binding subunits separated by p-xylyl spacers, while the other is a heteroditopic compound, combining two different head units, a tren-derived and a 2,4,6-triethylbenzene-derived one, also separated by p-xylyl spacers. The acid-base behavior of the compounds as well as their binding ability with oxalate (oxa(2-)), malonate (mal(2-)), succinate (suc(2-)), glutarate (glu(2-)), maleate (male(2-)) and fumarate (fum(2-)) anions were studied by potentiometry at 298.2 K in aqueous solution and at ionic strength 0.10 M in KTsO. NMR studies were also performed to obtain structural information in solution on the supermolecules formed by association of the protonated macrobicycles with the dicarboxylate substrates. The results revealed that both compounds are able to form stable associations with the dianionic substrates in competitive aqueous solution, with unprecedented selectivity for fum(2-) over other dicarboxylate competitors, including its cis isomer male(2-). In addition it was found that although the selectivity pattern is unaffected by the introduction of the 2,4,6-triethylbenzene head unit, the affinity toward dicarboxylates is significantly reduced. Therefore, the comparison between the binding behavior of these two receptors showed the effect of the increased rigidity and lipophilicity of the receptor with the 2,4,6-triethylbenzene head unit in the binding properties and the selectivity pattern.     

Anti-acetylcholinesterase and antioxidant activity of essential oils from Hedychium gardnerianum Sheppard ex Ker-Gawl

Acetylcholinesterase inhibition, antioxidant and cytotoxic activities of Hedychium gardnerianum leaf essential oils from S. Miguel Island were determined. All the oils inhibited acetylcholinesterase, with IC(50) values of approximately 1 mg/mL, showing no statistical differences between collection sites. Three oils presented mixed inhibition, whilst one was almost truly competitive. This activity can be attributed to the presence of sesquiterpenes, which constituted more than 60% of the composition of the oils. Regarding the antioxidant activity as measured by the DPPH method, all the oils presented activities similar to reference compounds, although with statistical differences between collection sites. Cytotoxicity measured using Artemia salina classified these oils as moderately toxic, with LC(50) values ranging from 300 to 500 μg/mL. These results indicate a possible application of these oils in aromatherapy as coadjuvants in the treatment of cognitive diseases such as Alzheimer, since they may contribute to increase acetylcholine in cholinergic neurons and simultaneously fight deleterious oxidations responsible by neurological degeneration.     

Assessment of bioaccumulation of REEs by plant species in a mining area by INAA

Native plant species, lichens and tailings, sampled from a copper?Csulphide mining area located in southern?Ceastern Portugal, were analysed by neutron activation analysis (INAA) for determination of rare earth elements (REEs). Values of ??REEs and individual REEs concentration of tailing samples are higher than those of natural background concentrations. The higher values of REEs are found in modern slags and the mixture of oxidized gossan and sulphide disseminated country rocks when compared with the alluvial sediments contaminated by mine tailings. The total concentrations of light REEs are higher than those of heavy REEs in all tailing samples. Distribution patterns of PAAS-normalized REEs in mine tailings show slightly LREE enriched and flat HREE pattern with negative Eu anomaly. Lichens accumulated higher concentration of lanthanides than vascular plants. The elevated levels of REEs in lichen, native plant species and tailing samples reflect the contamination of REEs in S?o Domingos mining area. The Carlina corymbosa, Erica australis and Lavandula luisierra accumulated the higher amounts of La, Ce and other REEs than the other plant species grown in this mining area.     

Structure and electronic properties of a benzene-water solution

Electronic properties of benzene in water were investigated by a sequential quantum mechanical/molecular dynamics approach. Emphasis was placed on the analysis of the structure, polarization effects, and ionization spectrum. By adopting a polarizable model for both benzene and water the structure of the benzene-water solution is in good agreement with data from first principles molecular dynamics. Further, strong evidence that water molecules acquire enhanced orientational order near the benzene molecule is found. Upon hydration, the quadrupole moment of benzene is not significantly changed in comparison with the gas-phase value. We are also reporting results for the dynamic polarizability of benzene in water. Our results indicate that the low energy behaviour of the dynamic polarizability of gas-phase and hydrated benzene is quite similar. Outer valence Green's function calculations for benzene in liquid water show a splitting of the gas-phase energy levels associated with the 1e(1g)(π), 2e(2g), and 2e(1u) orbitals upon hydration. Lifting of the orbitals degeneracy and redshift of the outer valence bands is related to symmetry breaking of the benzene structure in solution and polarization effects from the surrounding water molecules.     

Simple transformation of crystalline chiral natural anions to liquid medium and their use to induce chirality

New chiral ionic liquids can be prepared simply by combining the tetra-n-hexyl-dimethylguanidinium cation with readily available chiral anions and used as an asymmetric inducing agent as demonstrated for catalytic Rh(II) carbenoid C-H insertion and Sharpless dihydroxylation.     

Characterization of Portuguese geomaterials,the clay component of <Emphasis Type="Italic">rañas</Emphasis>, as potential liners for low and intermediate radioactive disposal sites

This paper describes the development of a separation method for americium from the effluents emanating from anion exchange column, used for the recovery of plutonium from analytical waste solutions. The waste contained uranium, sodium, calcium and iron as the major impurities as estimated by ICP-AES method. ~99% pure americium was obtained by three separation steps using solvent extraction and extraction chromatography techniques. In the first step, uranium was quantitatively separated by giving five contacts of equal volumes of 30% TBP in n-dodecane. Fe and Na were separated in the next step using 0.1 M TODGA + 0.5 M DHOA as the extractant. In the last step, Am was separated from the co-extracted Ca (about 76%) using CMPO loaded extraction chromatographic column. The overall recovery was >80% with decontamination factor (D.F.) from the impurities being >3000 while the purity of the product was 99%.     

From invasion percolation to flow in rock fracture networks

The main purpose of this work is to simulate two-phase flow in the form of immiscible displacement through anisotropic, three-dimensional (3D) discrete fracture networks (DFN). The considered DFNs are artificially generated, based on a general distribution function or are conditioned on measured data from deep geological investigations. We introduce several modifications to the invasion percolation (MIP) to incorporate fracture inclinations, intersection lines, as well as the hydraulic path length inside the fractures. Additionally a trapping algorithm is implemented that forbids any advance of the invading fluid into a region, where the defending fluid is completely encircled by the invader and has no escape route. We study invasion, saturation, and flow through artificial fracture networks, with varying anisotropy and size and finally compare our findings to well studied, conditioned fracture networks.