Acid volatile sulfide approach

An approach similar to that in soils can be applied to metal-contaminated sediments, where sulfides, measured as acid-volatile sulfides (AVS), have been demonstrated as being the predominant factor controlling metal mobility and toxicity in anaerobic sediments. The difference or ratio between SEM (simultaneous extracted metals) and AVS (SEM-AVS) is used to predict toxicity. In cases where SEM does not exceed the AVS, this approach has been shown to consistently predict the absence of toxicity (Allen et al. 1993 Ankley et al. 1996 DiToro, Hansen et al. 2001b). When SEM exceeds the AVS, toxicity is predicted, but the appearance and extent of toxicity may be determined by other binding phases (e.g., organic carbon) in the pore water. Luoma and Fisher (1997) stated that the association of metal bioavailability with AVS in sediments is not, however, straightforward in all cases and should be treated with caution. 

The most widely used approach to model metal bioavailability in sediments is based on the tendency of many toxic metals (Cd, Cu, Pb, Ni, and Zn) to form highly insoluble metal sulfides in the presence of acid-volatile sulfide. Metals are predicted... 

The acid volatile sulfide (AVS) approach to calculate the dissolved (pore water) fraction of metals in sediments, again for comparison with the water EQS (Di Toro et al. 1990). 

Gas chromatography (GC) with an infrared (IR) detector was introduced as a method to detect volatile radiolytic products, some of which were hypothesized to be responsible for the bad smells emanating from irradiated drugs. Thiocyanic acid was held responsible, for example, for the sulfurous smell in irradiated ampicillin. The head-space (HS) injection technique for GC and the on-line MS detection allowed new approaches to detect radiosterilization [12]. Many volatile radiolytic products were identified from the mass spectral libraries. Some ofthe compounds identified such as aldehydes, esters and sulfides were quite malodorous. A few of the volatile radiolytic products came from the degradation of drug molecules by the ionizing radiation, whereas residual solvents played a key role in the formation of other volatile radiolytic products. 

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