Sulphur forms in open and afforested areas of two scottish peatlands

Sulphur forms were determined at two peatland sites in Scotland, each havin g both open bog vegetation and afforested areas. Afforestation activity (in cluding initial ploughing and, in one case, active drainage) had a signific ant effect on peat physical characteristics, depending on the depth sampled , but had less influence on S chemistry. There was no significant differenc e in mean total S concentration (mean of 0.24% over the upper 100 cm peat) between the two sites or between the afforested and open areas. Organic S w as dominant with approximately 64% of the total S being C-bonded S and 27% ester sulphate S. Reduced inorganic forms (acid volatile S, elemental S and Cr-reducible S) accounted for approximately 8% of the total S. On average, only half of the Cr-reducible S could be accounted for by pyrite S as dete rmined by analysis of the Fe; the remainder was considered to be an organic S fraction. The presence of both S-oxidizing thiobacilli and sulphate-redu cing bacteria were indicative of an active oxidation/reduction cycle that r esulted in the accumulation of S at or below the mean water table. The resu lts are discussed in terms of S retention and alkalinity generation in peat lands.