Chemical element concentrations in black locust (Robinia pseudoacacia L.) and green ash (Fraxinus pennsylvanica Marsh.) leaves at the reclaimed Green Valley coal Mine, Indiana, USA

摘要

The Green Valley Mine in Indiana was abandoned in 1963 after 15 years of coal mining. Reclamation began in 1994 and ended in 1999 with the dense planting of twelve different tree species. By 2006, only green ash (Fraxinus pennsylvanica Marsh.) and black locust (Robinia pseudoacacia L.) had survived in any significant numbers. Given the acid mine drainage found at the site, we sought to determine whether element toxicity originating from mine waste was responsible for the extirpation of the trees. Leaf samples taken from 125 mine trees and 29 control trees were acquired and assayed for 41 element concentrations using inductively coupled plasma mass spectrometry (ICPMS). Except for sodium, there was no compelling evidence to indicate that toxic elemental levels were responsible for the widespread tree deaths. In addition to sodium toxicity, we suspect that micronutrient deficiency was a primary factor explaining the extirpation of trees at the mine.