Impacts of antropogenic contaminants on vegetation and groundwater chemistry in a fen complex (IL)

Residential development within the watershed of a fen complex has resulted in encroachment of ground-water borne anthropogenic contaminants into 3 high quality fens. Groundwater samples were collected from peat and marl and analyzed for inorganic constituents. Height and density of Typha angustifolia L. and Scirpus acutus Muhl. were recorded in belt transects coincident with ground-water samples. Contaminant plumes from septic systems of houses near the fens had higher Na, Cl, NO[sub 3], and TDS levels than uncontaminated areas of the fens. Typha density increased significantly as Na, Cl, CL/SO[sub 4], and TDS levels increased; Scirpus occurred only where pH [ge] 7.1 (X[sub 2]=11.656, sl=.02). Scirpus density was generally independent of other water chemistry levels. In one fen Scirpus density declined significantly as Typha density increased (r[sub 2]=25.86). Contamination appears to favor Tvpha invasion, which subsequently leads to displacement of Scirpus.