EVALUATING THE INFLUENCE OF SELECTED ACID PRE-TREATMENT METHODS ON C/N AND δ¹³C OF TEMPERATE INTER-TIDAL SEDIMENTS FOR RELATIVE SEA LEVEL RECONSTRUCTION

Abstract:Inter-tidal environments play a central role in relative sea level (RSL) reconstruction studies and the use of composite records developed from elemental (organic carbon, total nitrogen) and isotopie (δ¹³C) data have recently been applied in these environments. Sample pretreatment to remove inorganic carbon is a critical first step in this approach, but can distort the data. This paper presents the results of a comparative pilot study examining the performance of two acid preparation techniques (acid rinsing and acid fumigation) when applied to saltmarsh sediments from the Portmarnock and Shannon estuaries. In high marsh to supratidal settings, acid rinsing caused depletion of both C org and N tot, though no significant change to Corg/Ntot (C/N) was recorded. At lower altitudes, increased Ntot losses led to distortion of C/N ratios. Both pre-treatment methods produced comparable δ¹³C signatures in higher elevation contexts, but acid rinsing produced a depletion of 0.6‰ in low marsh and tidal flat samples. Whilst differences between pretreatment methods are observed, offsets are relatively small when compared to the range of elemental and isotopie values encountered across a saltmarsh and should not affect environmental interpretations when used for RSL reconstruction.