Laktester för riskbedömning av förorenad mark

Abstract: Using leaching test is a way to get a picture of pollutants retention and leaching in a risk assessment on contaminated land. There are several different types of standardised leaching tests today, where the natural leaching processes are speeded up to make it possible to predict the leaching of pollutants. These leaching tests have been developed for waste and there are no specific guidelines on how to judge the results from the tests, when making a risk assessment on contaminated land. This work is an investigation on how to use leaching test in this type of risk assessments. The strengths and weaknesses of the different types of tests are discussed. Depending on what type of information you want from your leaching test, different types of tests are suitable. One benefit of using standardised tests is that you can easily compare results since the methods are the same. When you dispose contaminated soil, there will also be a law to make leaching tests before determining to what type of dump the waste can be classified. So if standardised leaching tests are already made during the risk assessment, it does not have to be done later if the risk assessment indicates that the soil will be disposed. A disadvantage, however, is that the standardised tests cannot reflect all the processes that will affect the leaching of pollutants. The cheapest test (batch test), which is also the most common test, does not show what will happen if parameters, such as pH and the redox potential of the soil, change. Therefore long term predictions of the effect on the environment made from this type of test are uncertain. A possible alternative to the standardised tests is a sequential test that considers leaching in a changing environment. In this work I made a case study where results from leaching test on five inorganic substances were studied. One of the parameters, which I looked specifically at, was the partition coefficient, Kd that can be calculated from the leaching test. I compared the Kd from the leaching test with literature values used in the general model when calculating guide values (tolerable total concentration) on contaminated land. The case study confirms the fact that it is hard to predict leaching from a total concentration of the pollutant. If the total concentration is high the leaching might be low, or the other way round. The study also shows that the literature Kd-value is very low compared to the Kd you get from the leaching test. From the Kd of a leaching test you can often calculate higher site-specific guide values. When doing so you have to be cautious, however, and choose one of the lowest Kd from the test. To sum up, leaching test is a good tool to predict leaching of pollutants, if you are aware of the defects and uncertainties associated with the tests.