Despite most regulatory constraints being based on physico-chemical analysis, the hazard toward the natural environment represented by a contaminated solution or matrix cannot simply be assessed on the basis of the single analytical approach. The latter supposes that the contaminants can all be identified and are not too numerous (which is not always the case), but moreover, the chemical concentration does not provide any information about phenomena of synergy or antagonism between pollutants, and does not provide information about the toxicity towards living organisms (criterion H14 of the European Directive 91/689). Biological methods can do so (ADEME, 1999). The purpose of these methods is to assess the eco-toxicological danger of solutions and matrix. They are carried out in vitro on biological species chosen for their sensitivity to pollution (Ramade, 2000).
Eco-toxicity tests can also be carried out from solids thanks to extraction techniques (see Section 7.6.1 on leaching and percolation, above).
Biological test analyses range between classical tests on organisms measuring survival to tests on cells and enzymatic activity.
Water from different parts of the road pavements and embankments and their surrounding environment may be analysed for toxicity to plants, animals, fish and humans. The methods used for collection of the water for this purpose will be as for collection for analyses for chemical compounds. It is, however, especially important that the water quality does not change during the toxicity test. Therefore, it must be kept cool and in dark, and quickly transported to the laboratory (see Section 7.4.6).
The classical tests for deciding toxicity, biological degradation and bioaccumulation are tests according to international standards (OECD Guidelines, ISO). The tests use living micro and macro-organisms (plants, animals) or cell cultures to characterise the toxicity of tested single chemical compounds or mixtures of compounds. In vitro methods use cells or enzymes and proteins for the testing of single compounds or complex mixtures.
When assessing the environmental effects, the test solution is often subjected to several test organisms such as algae, crustaceans and fish to search for differences in the sensitivity of organisms at different trophic levels of the ecosystem.
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Table 7.4 Some examples on standard toxicity tests
Codes refer to OECD (Organisation for Economic Co-operation & Development) and ISO (International Standards Organisation) test procedures |
Eco-toxicity tests (Table 7.4) may be classified as acute tests or chronic tests. Acute tests are tests with effects showing within a short time. A classical acute test is the measurement of the survival of organisms. The results are recorded as the concentration at which half the number of test organisms survive/die during the test period (LC50, Lethal Concentration). If the test period is 96 h the concentration referred to will be 96 h LC50. The chronic tests are conducted during a longer period at lower test compound concentrations. The end point is not death, but some secondary sub-lethal effect.
This chapter presents a general overview of water and soil sampling and analysis in the road environment. The main principles of data collection and storage, and methodologies for sampling design are presented. Furthermore, water and soil sampling procedures as well as in-situ and laboratory measurements and analyses methods are described, with an elucidation about their usefulness, potentialities and fields of application.
It is intended that the information presented in this chapter, as well as the bibliographic material that is referenced at its end, can provide a sufficient and valuable base from which the reader can consider the best choices for contaminant sampling and analysis methodologies, accordingly to the purpose of his/her investigation, and considering the abilities of available methods and tools as presented above.
