THE METAL ACCUMULATION IN FOUR FINNISH DUMPS LOCATED IN MIRES

Rauni Varkia, Laboratory of Physical Geography, Siltavuorenpenger 20 A, PL9, 00014 University of Helsinki.

Study areas are four dumps in Southem Finland. All dumps are located in mires and they have been used for dumping communal and industrial wastes. They are considered as risk dumps in Finnish risk dump study. Two of them are still in use (Iitti & Askola) and two are closed (Mäntsälä & Sotunki). Metals (heavy) are used as indicators of pollution distribution area. The aim is to define where the metals accumulate and if they do are there any similarities in metal accumulation. Another question is can you use the metal accumulation and distribution data in concluding how big environmental risk are the dumps located in mires. Peat core samples were taken from the surface to the bottom of the mire in different distances from the dump. Also some water, plant and ditch side samples have been taken. I use atomic absorption spectrophotometry (AAS) to analyze metal concentrations. Also a PCA- analysis was done(principal component analysis) to clarify if there are some similarities in metal accumulation between different dumps and locations.

Study areas:

Mäntsälä dump is located in the edge of mire Ollilansuo which is ditched and drainaged. The bottom of the mire is clay and in the westem side and under the dump there is some sand and gravel formations. Dump waters are absorbed in to the surroundind ground. Waters from the mire flow in small rivulets to river Mäntsälän joki. The dump area is now under construction and landscaping.

Sotunki dump is located in Vantaa mire Stormossen. in the southern side of the dump area is a nature conservation area. Soil in the mire surroundings is moraine and clay . Some bedrock formations are also visible. Dump waters flow from small rivulet to the bay Bölsfjärden. The soil under the peat is clay.

Askola dump is located in northem edge of mire Suurisuo. The mire is draineged. The soil in the surrounding area consists of sand and gravel fonnations and moraines. Under the mire there is clay. Obviously the clayey bottom is in lenses, because there was some groundwater flow under the clayey lens.

Iitti dump is in Kausala in the southem side of the mire Veittoistensuo and it is still in use. Waters from dump and mire are flowing in to Leininselkä.

Analysis and Results:

Samples have been dried, wet digested (HNO₃, HCIO₄, H2SO₄ in relation 10:2:1) and analysed with flame atomic absorption spectrometry.

Normally peat contains metals such as Ca, Mg, Na. Clay in the other hand has an enormous cation exchange capacity which in turns affects to the metal adsorption to clay particles. There seems to be metal accumulation in the surface of the mire and in the bottom in transition zone between peat and bottom clay. The peat samples between bottom and surface do not show any significant metal accumulation. Highest metal concentrations in surface samples were in the muddy and clayey ditch sides. Metal contents were guite low in moss and water samples despite some exceptions. Concentrations are higher near the dump sides and diminish outwards. It seems that metals move in surface and also in the bottom of the mire.

In the future conductivity measurements will be done to clarify how far the dump influences can be observed.