ASTM E1706-20

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, (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 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) 5.6 Table 1 lists several approaches used to assess of sediment quality. These approaches include: (1) equilibrium partitioning sediment guidelines (ESGs; USEPA 2003 1.1 Relevance of Sediment Contamination—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, both organic and inorganic chemicals may 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.

1.2 Sediment Assessment Tools—Several types of information may be useful in assessing the risk, or potential risk, posed by sediment contaminants, including: (1) chemical analysis of sediment contaminants; (1.3 Strengths of Toxicity Testing of Contaminated Sediments—Directly assessing the toxicity of contaminated sediments provides some of the same advantages to sediment assessment that whole effluent toxicity testing provides to management of industrial and municipal effluents. As for effluent tests, direct testing of sediment toxicity allows the assessment of biological effects even if: (1) the identities of toxic chemicals present are not (or not completely) known; (2) the influence of site-specific characteristics of sediments on toxicity (bioavailability) is not understood; and (3) the interactive or aggregate effects of mixtures of chemicals present are not known or cannot be adequately predicted. In addition, testing the response of benthic or epibenthic organisms exposed via sediment provides an assessment that is based on the same routes of exposure that would exist in nature, rather than only through water column exposure.

1.4 Relating Sediment Exposure to Toxicity—One of the challenges with sediment assessment is that the toxicity of sediment contaminants can vary greatly with differences in sediment characteristics; a bulk sediment concentration (normalized to dry weight) may be sufficient to cause toxicity in one sediment, while the same concentration in another sediment does not cause toxicity (for example, Adams et al. 1985) 1.5 Understanding the Causes of Sediment Toxicity—While direct testing of sediment toxicity has the advantage of being able to detect the effects of any toxic chemical present, it has the disadvantage of not providing any specific indication of what chemical or chemicals are causing the observed responses. Other techniques, such as spiked-sediment toxicity tests or Toxicity Identification Evaluation (TIE) methods for sediments have been developed and are available to help evaluate cause/effect relationships (USEPA 2007) 1.6 Uses of Sediment Toxicity Tests—Toxicity tests conducted on sediments collected from field locations can be used to: (1.7 Limitations—While some safety considerations are included in this standard, it is beyond the scope of this standard to encompass all safety requirements necessary to conduct sediment toxicity tests.

1.8 This standard is arranged as follows: 

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.