Standard Guide for Conducting Whole Sediment Toxicity Tests with Amphibians

Importancia y uso:

5.1 While federal criteria and state standards exist that define acute and chronic “safe” levels in the water column, effects levels in the sediment are poorly defined and may be dependent upon numerous modifying factors. Even where USEPA recommended Water Quality Criteria (WQC, (49)) are not exceeded by water-borne concentrations, organisms that live in or near the sediment may still be adversely affected (50). Therefore, simply measuring the concentration of a chemical in the sediment or in the water is often insufficient to evaluate its actual environmental toxicity. Concentrations of contaminants in sediment may be much higher than concentrations in overlying water; this is especially true of hydrophobic organic compounds as well as inorganic ions that have a strong affinity for organic ligands and negatively-charged surfaces. Higher chemical concentrations in sediment do not, however, always translate to greater toxicity or bioaccumulation (51), although research also suggests that amending sediment with organic matter actually increases the bioaccumulation of contaminant particles (52, 53). Other factors that can potentially influence sediment bioaccumulation and toxicity include pH mineralogical composition, acid-volatile sulfide (AVS) grain size, and temperature (54-56). Laboratory toxicity tests provide a direct and effective way to evaluate the impacts of sediment contamination on environmental receptors while providing empirical consideration of all of the physical, chemical and biological parameters that may influence toxicity.

5.2 Amphibians are often a major ecosystem component of wetlands around the world, however limited data are available regarding the effects of sediment-bound contaminants to amphibians (39, 41, 43, 55, 57, 58). Laboratory studies such as the procedure described in this standard are one means of directly assessing sediment toxicity to amphibians in order to evaluate potential ecological risks in wetlands.

5.3 Results from sediment testing with this procedure may be useful in developing chemical-specific sediment screening values for amphibians.

5.4 Sediment toxicity test can be used to demonstrate the reaction of test organisms to the specific combination of physical and chemical characteristics in an environmental medium. The bioavailability of chemicals is dependent on a number of factors, which are both site-specific and medium-specific. Although many of these factors can be estimated using equilibrium partitioning techniques, it is difficult to account for all the physical and chemical properties which could potentially affect bioavailability. Sediment toxicity tests may be particularly applicable to evaluating hydrophobic compounds which may not readily partition into the water column. See Table 1 for a summary of advantages and disadvantages associated with sediment toxicity tests.

Subcomité:

E50.47

Volúmen:

11.09

Número ICS:

13.060.70 (Examination of water for biological properties)

Palabras clave:

amphibian; bioavailability; Bufo spp.; hydric soils; Lithobates spp.; Lithobates pipiens; risk assessment; sediment; toxicity; wetland;