When conducting a study on heavy metal content in sediments, it is important not to rely on the total content measured, but account for the diffirent sedimentary parameters. This is to be able to compare diffirent settings without making wrongful assumptions based on the fact that the properties of the soils differ. Grain size for example is one sediment parameter that plays a major role in determening how much pollutants is held in a sediment. Generally heavy metals and other pollutants show an inverse correlation to grain size, making it difficult to compare a sandy soil and a clay just based on the total content of pollutants. 

 

Another reason to account for other parameters than just the total content is that some metals detected are part of the natural minerals making up the sediment, meaning they are not polluting the environment and should not be included in the assesment. Other metals bind strongly to certain sediment making it less likely to effect sorrounding environment. The method used for ruling out the later parameters mentioned, is to test for the mobility of metals and pollutants in the sediment rather than total content. One way of doing that is by a  BCR three-step sequential extraction procedure, that was used on soil samples from the industrial area of Uddevalla in the study by Carlström, 2012. This study will be used as an example of the effects sedimentery parameters can have on the assesment of ground pollution.