Effect of the type of contamination and land use on soil enzymatic activities. Results of the French 'Bioindicator program'

Since many decades, enzymatic activities are used to assess the effects of land use changes, agricultural practices and soil contamination on soil functioning. A lot of studies point out contradictory results depending notably on the methodology used, as well as soil characteristics… To overcome the lack of consensus concerning indicators available to assess soil quality and functioning, the national research programme “Bioindicator” (overseen by ADEME) was set up in France to develop and assay biological indicators (2006–2012). We aimed at standardizing and emphasizing the number of biochemical measurements, and developed miniaturized colorimetric methods to obtain a great enzymatic dataset. Thirteen activities (from three laboratories) were measured within this programme, in 47 modalities of 13 experimental sites differing in terms of land use (Corine land cover), contamination type – Polycyclic Aromatic Hydrocarbures or metals – and pollution levels (Vibrisse 8th decile). This dataset allows an analysis of the effect of atmospheric or added contamination gradients on the enzymatic activities. Our objectives are to point out the sensitivity of enzymes for each type of pollution and land use, to offer the most appropriate panel for a sensible analysis. Data were analysed for the all datasets, each site and each land use. Our main conclusions are as follows: enzymes are more sensitive to metallic contamination than to organic ones; enzymes are good indicators of metal bioavailability; Alkaline phosphatase and Arylamidase are the most relevant enzymes to assess the effect of soil contamination