Determination of Total Sulfur in Tidal Marsh Soils by X-ray Spectroscopy
1977
Darmody, R. G. | Fanning, D. S. | Drummond, W. J. | Foss, J. E.
Two X-ray spectroscopy techniques, called additions and corrections, were developed for total S analysis of soils. The techniques are especially applicable to tidal marsh soils because of the wide range in organic matter contents of these soils and the importance of S in their genesis, classification, and management. Both methods involve basically the same equation: %S = (Sample counts/sec)/(counts/sec per %S), where c/sec is the sulfur Kα counts/sec (peak minus background). In the additions technique, the c/sec per %S is estimated by adding a known concentration of S as thiourea to a powdered soil sample and determining c/sec with and without addition. In the corrections technique, the c/sec per %S is based on the soil organic matter content, since c/sec per %S increases in a regular manner with increasing organic matter content. Results by the additions technique agreed well with values from Na₂CO₃ fusion analyses of tidal marsh soils and with Leco furnace analyses of powdered rock samples, and analyses by the corrections technique agreed well with those by the additions technique. When compared with National Bureau of Standards values for standard coals, however, total S contents were underestimated by the additions technique as employed, apparently at least partly related to a pyritic S form in the coals. Pyritic S gives less c/sec per %S than thiourea. An organoleptic “whiff” (aroma) method for field estimation of S in marsh soils is also described. “Whiff” values gave a highly significant correlation (r = 0.53) with surface soil S content as measured by the X-ray additions technique. Maryland tidal marsh soils examined contained 0.10 to 96% organic matter and 0.02 to 5.44% total S.
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