Ala Lombolo
- One of Sweden's most polluted lakes

The grain size of a sediment determines what specific surface area a sediment particle will have. This relation is described by Burden and Sims (1999) whom explain that the smaller the grain size, the larger the specific surface area of the grains will be. A large surface area will affect the physical properties of the sediment, resulting in enhanced swelling and adsorption ability as well as increased plasticity and cohesion of the sediment. Burden and Sims further describe that the smallest fractions, called colloidals, are the ones which pollutants preferably bind to. The only inorganic fraction which can be as small as colloidals (smaller than 0.001 mm) is clay. This means that fine sediments rich in colloidal clay will contain more of a pollutant than e.g. a sandy sediment exposed to the same amount of pollution.

​

The bottom sediment in Ala Lombolo is unconsolidated with a very high water content. It consists of fine grained mud with the precense of larger aggregates. This fine grain size favors the sorption of pollutants to the sediments, resulting in high concentrations of pollutants within the lake. If the lake sediments would have been corser, e.g. sandy or gravelly, the pollutants would not bind to the grains as effeciently and would instead spread over a larger area displaying lower concentrations of pollutants. The thickness of the sediments above the underlying till is estimated to 0.5-4 m which results in 425 000 cubic meters of unconsolidated lake sediments. (Kemakta, 2008)