Atmospheric carbonation reduces bioaccessibility of PAHs in industrially contaminated soil.

Sorptive Bioaccessibility Extraction (SBE) was used to monitor changes in accessibility of polycyclic aromatic hydrocarbons (PAHs) during storage of historically contaminated alkaline soil (Σ US EPA 16 + 2 further PAHs: 2452 ±â€¯69 mg kg-1, n = 3). While total concentrations of PAHs were rather stable during storage for 561 days at 4 °C, PAH accessibility declined by 95% due to atmospheric carbonation. The formation of carbonates was evidenced by an increase of inorganic soil carbon and by carbonate coatings on black soil particles (SEM-EDX) that could be dissolved by providing neutral to acidic soil conditions. Subjecting soil (252 days of storage) to biodegradation at pH 7 resulted in a degraded fraction of PAHs equivalent to the accessible PAH fraction of soil as received (PAHs with log Kow <5). The present study addresses important interactions and relationships between carbonation of soil, aging of PAHs in soil and related changes in PAH accessibility. A main finding was the reversibility of this retention mechanism, a changing environment (e.g. reduction of pH below 8) can result in a rise of accessible PAHs and consequently in an increase of exposure and associated risk.

Investigation of various adsorbents for their ability to bind aflatoxin B1.

The contamination of animal feed with mycotoxins represents a worldwide problem for the animal industry. The most applied method for protecting animals against aflatoxicosis is the utilization of clay minerals. In the course of a research project adsorption experiments were performed in buffer solutions in order to evaluate the ability to bind Aflatoxin B1 (AfB1) at various pH-values. In order to investigate the strength of binding, the chemisorption index was calculated. Isothermal analysis was used to determine the values for the maximum adsorption capacity. Adsorption experiments in simulated gastrointestinal fluid and real gastric juice were carried out. Furthermore binding capability of the materials regarding selected vitamins was examined. Special attention was paid to the formation of AfB2a during experimental conditions. Based on the obtainedin vitro results, highly promising sorbent materials were ranked for furtherin vivo studies. Some adsorbing bentonites were also analysed mineralogically, but the results did not indicate which smectite property influences the adsorption process for AfB1.

Adsorption of mycotoxins.

In vitro binding studies with different mycotoxins are often made to test various adsorbents for their ability to detoxify these toxins in animal feed. In this study different clays were investigated for their ability to bind aflatoxin B1, zearalenone, ochratoxin A and deoxynivalenol in two different buffer systems (pH 3 and pH 6.5). In addition chemical/physical properties like cation exchange capacity and the concentration of exchangeable Ca(2+), Na(+), Mg(2+) and K(+) ions in the adsorbents were determined to establish if there is a connection between these parameters and the capacity to bind mycotoxins. Most of the tested clays showed high adsorption rates for aflatoxin B1 in both buffer systems. Adsorption rates for ochratoxin A and zearalenone of the tested clays were in the range of 0-100%. None of the tested adsorbents had the ability to bind deoxynivalenol. In this study no correlation between the cation exchange capacity of the clays or the concentration of exchangeable Ca(2+), Na(+), Mg(2+) and K(+) ions and the ability to adsorb mycotoxins could be investigated.