Analysis analysed.

Recently, it has become apparent that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate and that bioavailability of contaminants is a better measure of potential exposure. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. In this study, phenanthrene extractability using hydroxypropyl-beta-cyclodextrin (HPCD) and desorption kinetics using butan-1-ol (BuOH) were determined in three dissimilar spiked soils. The soils were extracted after 1 d, 40 d and 80 d of soil-compound contact time. The amount of phenanthrene extracted by HPCD was compared to the rapidly desorbed fraction removed by BuOH. Further experiments using the same soils and extraction methods to assess the relative extractability of phenanthrene, pyrene and benzo(a)pyrene were conducted. Overall, the extraction methods used in this study had different extraction efficiencies. Results suggest that as compound hydrophobicity increased, BuOH became a more exhaustive extractant with respect to HPCD, especially for soils with high clay and organic matter content. These results are important as they highlight differences between two contrasting non-exhaustive extraction techniques both of which have been suggested to be appropriate in the assessment of bioavailability.

Chemistry Techniques, Analytical↗

PubMed2005

Optimization of a pressurization methodology for extracting pore-water.

Sediment toxicity can be assessed by conducting pore-water toxicity assays with standard water column organisms. Several methods have been developed for sampling pore-water. Centrifugation and pressurization methods are recommended when large volumes of pore-water are required to perform toxicity assays. Nevertheless, these methods involve sediment transportation and storage in laboratory, which can alter sediment toxicity. Therefore, an extraction method for large volumes that could be employed in the field site would be highly desirable. This study aimed to optimize and further evaluate an existing sediment pressurizing device with low construction costs, easy to carry and operate in the field, and presenting minimal chemical reactivity. The latter characteristic was achieved by lining the device interior with Teflon, by using large pore filters (50 microm), and by using an inert gas (nitrogen). Pore-water extraction efficiency and the toxicities of pore-water samples obtained by pressurization and by refrigerated centrifugation were compared. An artificial sediment (70% sand, 20% kaolin and 10% alpha-cellulose) spiked with an alcohol (phenol), a surfactant (SDS), a metal (copper), an organophosphate pesticide (parathion), and a natural sediment contaminated with acid mine drainage, were assayed for toxicity using Microtox assays. Sediment pressurization was found to be as efficient to extract pore-water as centrifugation, being more cost effective and adequate for field use.

Chemistry Techniques, Analytical↗