A δ34S isoscape of total sulphur in soils across Northern Ireland

A map of the spatial variation in isotopic composition of a substrate, or isoscape, provides a tool to address a range of research questions, such as the use of isotope fingerprinting to identify the origin of compounds. The focus of this study was to establish a soil S isotope map for Northern Ireland in order to investigate spatial variability within the isotopic composition of total soil sulphur (S). The sample resolution was about one sample every 141 km(2).delta S-34 values were grouped based on soil type and soil parent material. Total soil S delta S-34 data were grouped according to soil type, to evaluate whether a soil's characteristics affect its isotopic composition. Gleyed soils had a mean delta S-34 value of +6.3 +/- 6.1 parts per thousand, lower than the means for other soil types. A trend towards higher delta(34)s values (mean delta S-34 of +13.8 +/- 6.0 parts per thousand) was observed in soils with a high organic matter content. No trends in delta S-34 value were observed for other soil types. There were no discernible correlations between total soil S delta S-34 and soil parent material, with the exception of shale and mudstones. The majority of soils derived from shale and mudstones had delta S-34 values at or close to the mean of +4.9 parts per thousand. A spatially coherent pattern of relatively high soil total S delta S-34 values in the west and north, and low in the SE, is discernible in Northern Ireland. Based on the observed spatial distribution, it has been concluded that the quantity and source (anthropogenic or marine) of wet atmospheric S deposition is a controlling factor on regional variation of soil delta S-34 in Northern Ireland. This S isoscape will assist studies of S cycling in Northern Ireland and may assist in the creation of an 'isotopic fingerprint' for a potential 'input' source needed to interpret data in traceability studies. (C) 2011 Elsevier Ltd. All rights reserved.