|Home||Archived October 29, 2018||(i)|
publications > paper > fertilizer-derived uranium and sulfur in rangeland soil and runoff: a case study in central Florida > results and discussion > sulfur isotopic composition of soils
4. Results and Discussion
4.3. SULFUR ISOTOPIC COMPOSITION OF SOILS
Total S in the three soil profiles has 34S of 11.9 to 20.5 (Table I). These values span the same range as most previously published S isotopic data from peat and organic soils in variably impacted areas of the northern Everglades and the highly developed Everglades Agricultural Area (EAA) (Bates et al., 2001). Data for the combined three soil profiles or for each individual profile show no obvious relation between S isotopic composition (34S) and depth (Figure 5a), or between S isotopic composition and total S (Figure 5b). The semi-native pasture (site 770) accounts for all of the highest values of 34S (34S = 15.4 to 20.5), whereas the two determinations from the pristine native grassland site (Lykes) are among the lowest values (34S = 13.1 and 13.5). 34S values for the improved and fertilized S5 site are both higher and lower than values from the native grassland site (Lykes), with only a slightly higher average value (14.1 versus 13.3).
Note that bacterial sulfate reduction can severely fractionate S isotopes. A minor role for sulfate reduction is assumed in the above discussion that considers only mixing as a control on sulfur isotope composition in uppermost surface soil layers (0-30 cm). Sulfate reduction requires anoxic conditions that are unlikely to prevail in these dry or intermittently wet surface layers. Bacterial sulfate reduction favors the lighter 32S isotope and so the remaining sulfate becomes isotopically heavier (increased 34S).
U.S. Department of the Interior, U.S. Geological Survey
This page is: http://sofia.usgs.gov/publications/papers/uranium_and_sulfur/sulfur.html
Comments and suggestions? Contact: Heather Henkel - Webmaster
Last updated: 04 September, 2013 @ 02:04 PM(KP)
|Home||Archived October 29, 2018|