ASTM E1706-00e2

1.1 This test method covers procedures for testing freshwater organisms in the laboratory to evaluate the toxicity of contaminants associated with whole sediments. Sediments may be collected from the field or spiked with compounds in the laboratory.

1.1.1 Test methods are described for two toxicity test organisms, the amphipod Hyalella azteca (H. azteca) (see 13.1.2) and the midge Chironomus tentans (C. tentans) (see 14.1.2). The toxicity tests are conducted for 10 days in 300-mL chambers containing 100 mL of sediment and 175 mL of overlying water. Overlying water is renewed daily and test organisms are fed during the toxicity tests. Endpoints for the 10-day toxicity tests are survival and growth. These test methods describe procedures for testing freshwater sediments; however, estuarine sediments (up to 15 ppt salinity) can also be tested with H. azteca. In addition to the 10-day toxicity test method outlined in 13.1.2 and 14.1.2, general procedures are also described for conducting 10-day sediment toxicity tests with H. azteca (see 13.1.2) and C. tentans (see 14.1.2).

1.1.2 Guidance for conducting sediment toxicity tests is outlined in Annex A1 for Chironomus riparius, in Annex A2 for Daphnia magna and Ceriodaphnia dubia, in Annex A3 for Hexagenia spp., in Annex A4 for Tubifex tubifex, and in Annex A5 for the Diporeia spp. Guidance is also provided in Annex A6 for conducting long-term sediment toxicity tests with H. azteca by measuring effects on survival, growth, and reproduction. Guidance is also provided in Annex A7 for conducting long-term sediment toxicity tests with C. tentans by measuring effects on survival, growth, emergence, and reproduction. 1.6 outlines the data that will be needed before test methods are developed from the guidance outlined in Annex A1 to Annex A7 for these test organisms. General procedures described in Sections 17 for sediment testing with H. azteca and C. tentans are also applicable for sediment testing with the test organisms described in Annex A1 to Annex A7.

1.2 Procedures outlined in this test method are based primarily on procedures described in the United States Environmental Protection Agency (USEPA) (1-8)² and Guides E 1367, E 1391, E 1525 and E 1688.

1.3 Additional research and methods development are now in progress to: (1) evaluate additional test organisms, (2) further evaluate the use of formulated sediment, (3) refine sediment dilution procedures, (4) refine sediment toxicity identification evaluation (TIE) procedures (9), (5) refine sediment spiking procedures, (6) develop in situ toxicity tests to assess sediment toxicity and bioaccumulation under field conditions, (7) evaluate relative sensitivities of endpoints measured in tests, (8) develop methods for new species, (9) evaluate relationships between toxicity and bioaccumulation, and (10) produce additional data on confirmation of responses in laboratory tests with natural populations of benthic organisms. Some issues that may be considered in interpretation of test results are the subject of continuing research including the influence of feeding on bioavailability, nutritional requirements of the test organisms, and additional performance criteria for organism health. See Section 6 for additional detail. This information will be described in future editions of this standard.

1.4 The USEPA (1) and Guide E 1688 also describes 28-day bioaccumulation methods for the oligochaete Lumbriculus variegatus.

1.5 Results of tests, even those with the same species, using procedures different from those described in the test method may not be comparable and using these different procedures may alter bioavailability. Comparison of results obtained using modified versions of these procedures might provide useful information concerning new concepts and procedures for conducting sediment tests with aquatic organisms. If tests are conducted with procedures different from those described in this test method, additional tests are required to determine comparability of results. General procedures described in this test method might be useful for conducting tests with other aquatic organisms; however, modifications may be necessary.

1.6 Selection of Toxicity Testing Organisms:

1.6.1 The choice of a test organism has a major influence on the relevance, success, and interpretation of a test. Furthermore, no one organism is best suited for all sediments. The following criteria were considered when selecting test organisms to be described in this standard ( Table 1 and Guide E 1525). A test organism should: (1) have a toxicological data base demonstrating relative sensitivity and discrimination to a range of chemicals of concern in sediment, (2) have a database for interlaboratory comparisons of procedures (for example, round-robin studies), (3) be in contact with sediment [e.g., water column vs benthic organisms], (4) be readily available through culture or from field collection, (5) be easily maintained in the laboratory, (6) be easily identified, (7) be ecologically or economically important, (8) have a broad geographical distribution, be indigenous (either present or historical) to the site being evaluated, or have a niche similar to organisms of concern, (for example, similar feeding guild or behavior to the indigenous organisms), (9) be tolerant of a broad range of sediment physico-chemical characteristics (for example, grain size), and (10) be compatible with selected exposure methods and endpoints. The method should also be (11) peer reviewed and (12) confirmed with responses with natural populations of benthic organisms (see 1.6.8).

1.6.2 Of the criteria outlined in Table 1, a data base demonstrating relative sensitivity to contaminants, contact with sediment, ease of culture in the laboratory, interlaboratory comparisons, tolerance of varying sediment physico-chemical characteristics, and confirmation with responses of natural benthos populations were the primary criteria used for selecting H. azteca and C. tentans to be described as test methods in the current version of this standard (see Sections 13 and 14). Procedures for conducting sediment tests with organisms in accordance with Annex A1 to Annex A7 do not currently meet all the required selection criteria listed in Table 1. A similar data base must be developed before these or other test organisms can be included as standard test methods instead of as guidance in future versions of these this method.

1.6.3 An important consideration in the selection of specific species for test method development is the existence of information concerning relative sensitivity of the organisms both to single chemicals and complex mixtures. A number of studies have evaluated the sensitivity of H. azteca, C. tentans, and L. variegatus, relative to one another, as well as other commonly tested freshwater species. For example, Ankley et al (10) found H. azteca to be as, or slightly more, sensitive than Ceriodaphnia dubia to a variety of sediment elutriate and pore-water samples. In that study, L. variegatus were less sensitive to the samples than either the amphipod or the cladoceran. West et al (11) found the rank sensitivity of the three species to the lethal effects of copper in sediments from the Keweenaw Waterway, MI was (from greatest to least): H. azteca > C. tentans > L. variegatus. In short-term (48 to 96 h) exposures, L. variegatus generally was less sensitive than H. azteca, C. dubia, or Pimephales promelas to cadmium, nickel, zin