CHARACTERIZATION OF SULFUR RETAINED BY SOILS EXPOSED TO SULFUR-DIOXIDE

Soils have substantial capacity for sorption of sulfur dioxide (SO2) but little is known about the nature of the sorbed S. Three surface soils varying in pH, organic matter, CaCO3 equivalent and surface area were exposed to air containing 5% SO2 and subsequently analyzed by ten different procedures to characterize the sorbed S. Most of the sulfur retained by soils after exposure to SO2 could be recovered as CaCl2-extractable S, Ca(H2PO4)2-extractable S, or S released as H2S by hydriodic acid (HI). Only small amounts of sulfur could be recovered as tetrachloromercurate (TCM)-extractable S, S released as SO2 by HCl, or S released as H2S by HCl + Zn, HCl + Sn, or Raney Ni and NaOH. However, large amounts of S released as SO2 by HCl were recovered from the air-dry Webster and the moist Storden soils indicating that SO2 sorption is influenced by organic matter in air-dry soils and by CaCO3 in moist soils.