Fluorescence spectroscopic studies of natural organic matter fractions

Because of the well-known molecular complexity and heterogeneity of natural organic matter (NOM), an aquatic bulk NOM was fractionated into well-defined polyphenolic-rich and carbohydrate-rich subfractions. These fractions were systematically characterized by fluorescence emission, three dimensional excitation-emission matrices, and synchronous-scan excitation spectroscopy in comparison with those of the reference International Humic Substances Society soil humic acid and Suwannee River fulvic acid. Results indicate that fluorescence spectroscopy can be useful to qualitatively differentiate not only NOM compounds from varying origins but also NOM subcomponents with varying compositions and functional properties. The polyphenolic-rich NOM-PP fraction exhibited a much more intense fluorescence and a red shift of peak position in comparison with the carbohydrate-rich NOM-CH fraction. Results also indicate that synchronous excitation spectra were able to provide improved peak resolution and structural signatures such as peak positioning, shift, and intensity among various NOM components as compared with those of the emission and excitation spectra. In particular, the synchronous spectral peak intensity and its red shift in the region of about 450-480 nm may be used to indicate the presence or absence of high molecular weight and polycondensed humic organic components, or the multicomponent nature of NOM or NOM subcomponents.     

Persistent organochlorine contaminants in hair samples of Northern Poland population, 1968-2009

The European regulation on chemicals, REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals), came into force on 1 June 2007. With pre-registration complete in 2008, data for these substances may provide an overview of the expected chemical space and its characteristics. In this paper, using various in silico computation tools, we evaluate 48 782 neutral organic compounds from the list to identify hazardous and safe compounds. Two different classification schemes (modified Verhaar and ECOSAR) identified between 17% and 25% of the compounds as expressing only baseline toxicity (narcosis). A smaller portion could be identified as reactive (19%) or specifically acting (2.7%), while the majority were non-assigned (61%). Overall environmental persistence, bioaccumulation and long-range transport potential were evaluated using structure-activity relationships and a multimedia fugacity-based model. A surprisingly high proportion of compounds (20%), mainly aromatic and halogenated, had a very high estimated persistence (>195 d). The proportion of compounds with a very high estimated bioconcentration or bioaccumulation factor (>5000) was substantially less (6.9%). Finally, a list was compiled of those compounds within the applicability domain of the models used, meeting both persistence and bioaccumulation criteria, and with a long-range transport potential comparable to PCB. This list of 68 potential persistent organic pollutants contained many well-known compounds (all halogenated), but notably also five fluorinated compounds that were not included in the EINECS inventory. This study demonstrates the usability of in silico tools for identification of potentially environmentally hazardous chemicals.     

A survey of Pb,Cu, Zn,Cd, Cr,As, and Se in earthworms and soil from diverse sites

Earthworms and soils were collected from 20 diverse sites in Maryland, Pennsylvania, and Virginia, and were analyzed for Pb, Cu, Zn, Cd, Cr, As, and Se. Correlation coefficients relating concentrations of the elements in earthworms to concentrations in soil were low (–0.20<r<+0.57). Species differences and ecological variables contributed to the variability in concentrations of these elements in earthworms. The maximum concentrations of Pb (2100 ppm), Zn (1600 ppm), Cd (23 ppm) and Se (7.6 ppm) detected in earthworms were in the range reported to be toxic to animals fed diets containing these elements; however, even in the absence of any environmental contamination, some species of earthworms may contain high concentrations of Pb, Zn, and Se. Earthworms of the genus Eisenoides, for example, were exceptional in their ability to concentrate Pb. When earthworms are used as indicators of environmental contamination, it is important to identify the species, to report the soil characteristics, and to collect similar earthworms from very similar but uncontaminated soil.