ENRICHMENT OF N2 AND AR IN THE ATMOSPHERE OF CO2-CONSUMING SOILS

The phenomenon of unexplained N2/Ar-enrichment in soil air is quite fr equently to be encountered in soil air studies on anthropogenically in fluenced sites. In the present study two anthropogenic deposits and a calcareous fluvisol were investigated for their soil air composition. While in the alkaline deposits extreme enrichments of N2 and Ar (N2 Ar: up to 99%, v/v) were found as persistent site characteristics, the fluvisol showed only slight (about 1%, v/v) transient N2/Ar-enrichmen ts in summer. All sites, which did not show substantial vertical seepa ge percolation, exhibited enhanced CO2-Solubility either due to strong calcite precipitation or dissolution. So, it was concluded that inten sive continuous depletion Of CO2 was responsible for the subsequent co nvective influx of atmospheric air. From the results obtained it was c oncluded that an encasement of the concerned soil volume rather imperm eable to gas transport as well as intense dissolution of CO2 in the po re water are prerequisites for substantial N2/Ar-enrichments in soil a ir.