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QUESTION: 



Besides conducting biological tests on marine organisms to evaluate the 

 toxicity of the material, what other test do you conduct? Overall, how 

 effective is the biological testing? 



ANSWER: 



A range of physical, chemical and biological tests may be performed as part 

 of a dredged material evaluation, as follows: 



Physical tests, such as grain size, total organic carbon, settling rates, may 

 be conducted to evaluate the possibility for physical effects at the disposal 

 site. This information is also useful for determining the potential for 

 transport of material away from the disposal site during disposal or 

 resuspension and transport after deposition. Physical test results are also 

 important in the interpretation of chemical and biological results. 



Chemical tests are used to develop a list of contaminants of concern for the 

 project. Bulk sediment chemistry can be used in a screening mode to predict 

 release of contaminants to the water column (assumes all contaminant is 

 release to water column during disposal) or uptake by marine organisms 

 (using equilibrium partitioning theory). An elutriate may be evaluated as a 

 more realistic prediction for release of contaminants to the water column. 

 Prediction of release to the water column is done to determine if the project 

 will violate water quality criteria. At the present time, except for 

 determining compliance with water quality criteria, bulk sediment chemistry 

 data alone cannot be used for determining the suitability of a project for 

 ocean dumping. 



Biological tests have been used in the ocean dumping program for decision 

 making since 1977. These tests are used to determine the potential for the 

 whole sediment to cause toxic impacts in the water column and on the 

 seafloor, and the potential for individual contaminants to move from the 

 sediment to living organisms. In biological tests, animals are exposed to the 

 whole sediment (or an elutriate of the sediment in the case of water column 

 bioassays) and observed to determine if the sediment has an effect on them. 

 Biological tests have the advantage of integrating the effects of all 

 contaminants, without having to conduct individual chemical analyses; this 

 minimizes the risk of overlooking a particular chemical and addresses 

 chemicals for which sediment criteria have not been developed. Monitoring 

 results have demonstrated that biological tests are predictive of effects at 

 the disposal site. 



