Changes in litter near an aluminum reduction plant

Abstract

Litter was collected from eight sites at distances as far as 33 km from an Al reduction plant in western Tennessee. As a result of an accumulation of fine litter (<4.75 mm) the weight of the litter per unit area was abnormally high at the two sites within 2 km of the plant. Compared to litter collected far from the plant, it had a lower fiber content, was more sapric, and was less acid. Fluoride emissions from the plant were suggested as the probable cause of litter changes. Concentrations of water-extractable and acid-extractable F − in the litter, the 0- to 5-cm soil layer, and the 5- to 15-cm soil layer were strongly correlated with distance from the plant. Total acid-extractable F − in the litter and upper 15 cm of soil was about 41 times as much at the closest site (700 mg/kg) as at the most distant sites (12 and 16 mg/kg). In a bioassay of litter from our study sites, woodlice ( Porcellio scaber Latr.) had an abnormally high mortality in litter that contained 440 mg/kg or more of acid-extractable F − . However, when F − was added as NaF to litter, a significant increase in mortality was observed only in treatments exceeding 800 mg/kg. The decrease in the rate of decomposition of the litter might eventually induce a deficiency of soil macronutrients, but none was detected.