Studies of forest floor biological activities in an area previously damaged by sulphur dioxide emissions

Abstract

As part of an environmental control program aimed to assess possible future effects of air contaminants from a new destruction plant for hazardous chemical residuals in Central Sweden, a study was undertaken the year before the plant went into operation to collect base-line information on biological activities in the soils of the surrounding forests. Measurements were made of N-mineralization, respiration, phosphatase-, dehydrogenase-, and nitrogenase activity on sieved samples from the forest floor (0 to 3 cm).

The results were evaluated in relation to a previous contamination of the area by air pollutants from a plant for oil production. This plant produced oil from the local alun shale between 1942 and 1966. During these years somewhere between 6 × 10⁵ and 1.2 × 10⁶ tonne of S, mainly in the form of SO₂, were released into the atmosphere.

The results showed that the forest floor was not especially acid when compared to similar sites in locally unpolluted areas. The concentration of Cu, however, was five times higher than expected. No disturbances could be detected as regards N-mineralization, respiration or phosphatase activity. Dehydrogenase- and nitrogenase activity were much more difficult to evaluate. A suppression of dehydrogenase activity was indicated on the study plots closest to the previous plant. In the case of nitrogenase activity no appropriate reference material was available to judge whether disturbances existed.