EFFECTS OF CRUSHED LIMESTONE APPLICATION ON PLANT UPTAKE OF TRACE ELEMENTS IN AN ACIDIC SEEP

To determine plant tolerances to contamination and pH, this study examined soil conditions, plant growth, and trace element uptake for plants growing in an acidic seep at the reclaimed Green Valley coal mine site in western Indiana. The physicochemical conditions in the seep have resulted in death of plant species in the central portion of the seep with decreased growth and plant diversity along the seep margins. During the summer of 2004, a layer of 1-4 cm diameter crushed limestone was placed over part of the seep to neutralize soil acidity and enhance plant growth. Over 100 points were sampled in limed and non-limed areas of the seep to determine the overall impact of liming on soil pH, plant growth, and plant uptake of trace elements. At each point, soil pH was measured and a 15-cm deep soil core was collected for chemical analysis of trace elements by ICPMS and for soil nutrients (NH₄⁺, NO₃^-, and plant-available P) by automated colorimetric methods. Plants (trees, shrubs, grasses, and forbs) were clipped and separated into stems/leaves, seeds, and flowers for trace element analysis by ICPMS.

Soil pH in the seep area ranged from 3.5 to 6.3, and contrary to the original intentions, mean soil pH below the lime layer (pH 4.4) did not vary significantly from non-limed seep areas (pH 4.6). Preliminary results show that some plants in the seep area contained higher levels of some trace elements than plants collected outside the seep area as background. In general, tree seedlings contained higher concentrations of trace elements than either forbs or grasses. In addition, trace elements appear to be more concentrated in some plant parts. For example, much higher trace element concentrations were detected in the seeds of a grass, Festuca pratensis, as compared to the stems and leaves. Further analysis is being conducted to evaluate seasonal changes in plant uptake of trace elements.