Organic acid fluorescence: applications to speleothem palaeoenvironmental reconstruction
Recent advances in fluorescence spectrophotometry permit the non-destructive analysis of speleothems (secondary carbonate cave deposits) with a view to palaeoenvironmental reconstruction. The fluorescence of speleothems is derived from organic acids that have been carried by groundwater from the overlying soil, and coprecipitated with the speleothem calcite. Organic acids are formed as one of the many products of humification and their chemical structures are such that they are particularly suitable for analysis by fluorescence spectrophotometry. Numerous studies have been carried out that have demonstrated the structure and hence the fluorescence properties of organic acids to be influenced by many factors, including extraction method, concentration, source, pH, metal and inorganic ion complexing and, most importantly in the case of speleothems, soil type and climate and vegetation change. On the basis of this, recent investigations carried out on contemporary, historical and Quaternary samples have shown it to be possible to obtain palaeoenvironmental information from the fluorescence properties of organic acids in speleothems.