An evaluation of wet chemical methods for quantifying sulfur fractions in freshwater wetland peat1

Abstract

The specificity and efficiency of procedures for fractionating total S into inorganic and organic constituents were evaluated by analyzing a series of known standards. Acid volatilization was specific for FeS. Chromium reduction recovered over 90% of the S from FeS, S0, and FeS2. Acetone extraction followed by chromium reduction of the filtrate was specific for S0. Hydriodic acid reduction recovered > 90% of the S from FeS, SO42−, and p‐nitrophenyl sulfate, an organic aryl ester sulfate analog. The Zn‐HCl reduction procedure is of questionable value, only partially recovering S from SO42−, S0, and FeS2. None of these procedures affected l‐methionine. Analyses were performed on both moist and oven‐dried peat from Big Run Bog, West Virginia. Oven‐drying of peat samples increased estimates of ester sulfate S and SO42−‐S and decreased estimates of carbon‐bonded S, which was calculated by difference.

Determination and fractionation of sulphur in a contaminated dredged sediment1

“…The following procedures for quantifying sulphur fractions involved the reduction of sulphur to H 2 S in an Johnson-Nishita apparatus 26 and trapping the evolved H 2 S in Zn-acetate solutions. Acid-volatile, Zn-HClreducible, chromium-reducible, acetone-soluble and hydriodic-acid-reducible sulphur were determined as described by Wieder et al 27 The sample (50 mg for the hydriodic-acid-reducible sulphur and 500 mg for the other fractions) was added to the reaction flask and the system was purged with N 2 at a bubbling rate in the Zn-acetate traps of 1-2 bubbles per second for 10 min before the introduction of reagents.…”

“…For the determination of HIreducible S, a solution of 50% hypophosphorous acid, 90% formic acid and 57% hydriodic acid in a proportion of 4:2:1 was prepared daily. 20 instead of 8 mL 27 of that solution were brought in the reaction flasks. After 10 minutes, the suspension was heated to boil during 90 minutes.…”

“…Acid-volatile sulphur (AVS) is mostly sulphide S. 27,29 In the reduced sediment, 70% of total sulphur was sulphide S. AVS was quantitatively converted during drying and oxidation of the sediment ( Table 2). The formation and accumulation of inorganic sulphur fractions is typical for polluted sediments and is related to a large influx of sulphur compounds, protons and metals.…”

“…30 Landers et al 25 used the Zn-HCl distillation procedure for the determination of inorganic non-sulphate sulphur but warned for incomplete recovery of pyrite when present in reduced soils or sediments. Wieder et al 27 found the procedure of questionable value because sulphur from S 0 , FeS 2 and SO 4 2-was only partially recovered.…”

“…This may result from sulphates in the oxidised sediments, that are partially determined as well. 27 Wieder et al 27 determined extraction/distillation efficiencies by analysing pure sulphur compounds with the different methods. They found that 15.5 to 24.0 % of the added sulphate was determined as Zn-HCl S. Assuming a recovery of 20%, then 1.24 g of Zn-HCl S should have originated from sulphates present in the oxidised sediment Table 1 Table 3 Table 2 (6.2 g).…”