S-35-sulphate reduction and transformation in peat

The incorporation of S-35-labelled sulphate into reduced inorganic forms an d into organic S has been studied in pear samples from two contrasting site s, a deep blanket pear and a shallow hill blanket pest. During anaerobic in cubation, S-35 was rapidly incorporated into AVS (acid volatile sulphide), elemental S and Cr-reducible S but these pools showed evidence of rapid rec ycling, In the longer term, S-35 was found in the ester sulphate pool and i n a residual S pool, taken to be principally C-bonded organic S. Incorporat ion was more rapid in the deep pear than in the hill peat, in peat from wet areas more than dry areas and in subsurface (10-20 cm) peat more than in s urface (0-10 cm) peat. Incorporation in the hill peat under aerobic incubat ion into either reduced inorganic or organic forms was very limited. Mean s ulphate reduction rates at the temperature of incubation (26 degreesC) were estimated to be in the range 60-12,000 mug S kg(-1) wet weight peat d(-1) while mean turnover times of reduced S were 17 and 550 d for the deep and h ill peats, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved .