A δ³⁴S isoscape of total sulphur in soils across Northern Ireland
2011
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 141km². δ³⁴S values were grouped based on soil type and soil parent material. Total soil S δ³⁴S data were grouped according to soil type, to evaluate whether a soil’s characteristics affect its isotopic composition. Gleyed soils had a mean δ³⁴S value of +6.3±6.1‰, lower than the means for other soil types. A trend towards higher δ³⁴S values (mean δ³⁴S of+13.8±6.0‰) was observed in soils with a high organic matter content. No trends in δ³⁴S value were observed for other soil types. There were no discernible correlations between total soil S δ³⁴S and soil parent material, with the exception of shale and mudstones. The majority of soils derived from shale and mudstones had δ³⁴S values at or close to the mean of+4.9‰. A spatially coherent pattern of relatively high soil total S δ³⁴S 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 δ³⁴S 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.
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