during the growing season , comparisons were made of the leaf surface microflora of ( i ) two groups of mature oak trees , one in the vicinity of a smelting complex contaminated by heavy metals and the other at a relatively uncontaminated site , and ( ii ) two groups of oak saplings at the uncontaminated site , one of which was sprayed with zinc , lead , and cadmium to simulate the heavy metal pollution from the smelter without the complicating effects of other pollutants .
C0006632
cadmium
C0347988
heavy metal