Sulfur mobility in peat

Abstract

Lead-210 chronologies, vertical S concentration gradients and δ 34S values are presented for 5 Sphagnum-dominated peat bogs located in Central Europe (Rybarenska slat and Ocean Bog; Czech Republic) and the British Isles (Thorne Moors, England; Connemara, Ireland; and Mull, Scotland). Sulfur concentrations were measured in three 40-cm deep peat cores per site, sectioned into 2-cm segments. The coefficient of variation in S concentrations was low across all depths and sites (mean of 16%), indicating a high degree of within-site homogeneity in vertical S patterns. Similar S concentration trends and similar δ 34S trends were found at all study sites. With an increasing peat depth, S concentrations first increased and then decreased. S concentrations peaked in layers which were deposited in ca. 1959, 1907, 1945, 1899 and 1799 at Rybarenska slat, Ocean, Thorne Moors, Connemara and Mull, respectively. Atmospheric S deposition peaked in 1972 in the UK and in 1987 in the Czech Republic. Due to downward S mobility in peat, S concentration maxima were found in layers 59 (±19) a older that the year of the actual peak in S input. With an increasing depth, the maturating peat substrate at all sites exhibited first a negative δ 34S shift, resulting from dissimilatory bacterial SO 4 reduction, and then a positive δ 34S shift, which may be related to advancing S mineralization. Minimum δ 34S values were detected in layers which were deposited in ca. 1988, 1982, 1945, 1940 and 1978. A comparison of historical δ 34S signatures of atmospheric S in England, measured on archived grain from the Broadbalk experiment (1845–1994), with δ 34S values of Thorne Moors peat (1830–1994) also indicated mobility of S in peat. Sulfur mobility in water-logged peat is of concern during the present period of easing industrial pollution because SO 4 released from peatlands may increase the acidity of the output.