Standard Test Method for Measuring the Toxicity of Sediment-Associated Contaminants with Freshwater Invertebrates

Importancia y uso:

5.1 Sediment provides habitat for many aquatic organisms and is a major repository for many of the more persistent chemicals that are introduced into surface waters. In the aquatic environment, most anthropogenic chemicals and waste materials including toxic organic and inorganic chemicals can accumulate in sediment, which can in turn serve as a source of exposure for organisms living on or in sediment. Contaminated sediments may be directly toxic to aquatic life or can be a source of contaminants for bioaccumulation in the food chain.

5.2 The objective of a sediment test is to determine whether chemicals in sediment are harmful to or are bioaccumulated by benthic organisms. The tests can be used to measure interactive toxic effects of complex chemical mixtures in sediment. Furthermore, knowledge of specific pathways of interactions among sediments and test organisms is not necessary to conduct the tests. Sediment tests can be used to: (1) determine the relationship between toxic effects and bioavailability, (2) investigate interactions among chemicals, (3) compare the sensitivities of different organisms, (4) determine spatial and temporal distribution of contamination, (5) evaluate hazards of dredged material, (6) measure toxicity as part of product licensing or safety testing, (7) rank areas for clean up, and (8) estimate the effectiveness of remediation or management practices.

5.3 Results of toxicity tests on sediments spiked at different concentrations of chemicals can be used to establish cause and effect relationships between chemicals and biological responses. Results of toxicity tests with test materials spiked into sediments at different concentrations may be reported in terms of a LC50 (median lethal concentration), an EC50 (median effect concentration), an IC50 (inhibition concentration), or as a NOEC (no observed effect concentration) or LOEC (lowest observed effect concentration). However, spiked sediment may not be representative of chemicals associated with sediment in the field. Mixing time, aging and the chemical form of the material can affect responses of test organisms in spiked sediment tests (10.6).

5.4 Evaluating effect concentrations for chemicals in sediment requires knowledge of factors controlling their bioavailability. Similar concentrations of a chemical in units of mass of chemical per mass of sediment dry weight often exhibit a range in toxicity in different sediments (Di Toro et al. 1990 (4), 1991 (2)). Effect concentrations of chemicals in sediment have been correlated to interstitial water concentrations, and effect concentrations in interstitial water are often similar to effect concentrations in water-only exposures. The bioavailability of nonionic organic compounds and metals in sediment is often inversely correlated with the organic carbon concentration; moreover, the bioavailability of metals in sediment are often inversely correlated with acid volatile sulfide. Whatever the route of exposure, these correlations of effect concentrations to interstitial water concentrations indicate that predicted or measured concentrations in interstitial water can be used to quantify the exposure concentration to an organism. Therefore, information on partitioning of chemicals between solid and liquid phases of sediment is useful for establishing effect concentrations (DiToro et al. 1990 (4), 1991 (2); Wenning et al. 2005 (19)).

5.5 Field surveys can be designed to provide either a qualitative reconnaissance of the distribution of sediment contamination or a quantitative statistical comparison of contamination among sites. Surveys of sediment toxicity are usually part of more comprehensive analyses of biological, chemical, geological, and hydrographic data (USEPA 2002a, b, and c) (20-22). Statistical correlations may be improved and sampling costs may be reduced if subsamples are taken simultaneously for sediment tests, chemical analyses, and benthic community structure.

5.6 Table 1 lists several approaches used to assess of sediment quality. These approaches include: (1) equilibrium partitioning sediment guidelines (ESGs; USEPA 2003 (23), 2005 (24); Nowell et al. 2016 (25)), (2) empirical sediment quality guidelines (for example, probable effect concentrations, PECs; MacDonald et al. 2000 (26), Ingersoll et al. 2001 (27)), (3) tissue residues, (4) interstitial water toxicity, (5) whole-sediment toxicity with field-collected sediment tests and with sediment-spiking tests, (6) benthic community structure, and (7) sediment quality triad integrating data from sediment chemistry, sediment toxicity and benthic community structure (Burton 1991 (28), Chapman et al. 1997 (29), USEPA 2002a, b, and c (20-22)). The sediment assessment approaches listed in Table 1 can be classified as numeric (for example, ESGs), descriptive (for example, whole-sediment toxicity tests), or a combination of numeric and descriptive approaches (for example, PECs). Numeric methods can be used to derive chemical-specific effects-based sediment quality guidelines (SQGs). Although each approach can be used to make site-specific decisions, no one single approach can adequately address sediment quality. Overall, an integration of several methods using the weight of evidence is the most desirable approach for assessing the effects of contaminants associated with sediment (USEPA 2002a, b, and c (20-22), Wenning et al. 2005 (19), Guide E1525, Guide E3163). Hazard evaluations integrating data from laboratory exposures, chemical analyses, and benthic community assessments (the sediment quality triad) provide strong complementary evidence of the degree of pollution-induced degradation in aquatic communities (Burton 1991 (28), Chapman et al. 1997 (29)). Importantly, the weight of the evidence needed to make a decision (number of methods used) should be determined based on the weight (cost) of the decision.

Subcomité:

E50.47

Referida por:

E0729-23E01, E0724-21, E1391-03R23, E2122-22, E2591-22, E2455-25, E1676-12R21, E1022-22, E1850-04R19, E2552-23, E1192-23, E1023-23, E1688-19, E1611-21, E1525-02R23, E1295-22, E1563-21A, E2172-22, E3163-24, E1562-22, E1439-12R19, E2186-02AR23, E1367-03R23

Volúmen:

11.09

Número ICS:

07.100.20 (Microbiology of water)

Palabras clave:

amphipod; bioavailability; Chironomus dilutus; Chironomus riparius; contamination; Hexagenia spp; Hyalella azteca; invertebrates; mayfly; midge; mussel; oligochaete; sediment; toxicity; Tubifex tubifex;