Micro-XRF Applications in Fluvial Sedimentary Environments of Britain and Ireland: Progress and Prospects

This chapter considers applications of micro-XRF scanning in fluvial depositional environments and presents case-studies from Britain and Ireland in three key river management areas: flood reconstruction; pollution and provenance mapping; and floodplain sediment dynamics. Although fluvial sediment archives are typically shorter and more fragmented than marine and lake sediment records, they do offer significant palaeoenvironmental potential, not least because of the sensitivity of river systems to environmental change. A major consideration in micro-XRF analysis, however, is the continuity and heterogeneity of alluvial sediments and the integrity of accretionary records once they have been subject to post-depositional processes, such as human disturbance and pedogenesis. Thus far, micro-XRF applications in fluvial environments have been limited. One research area currently being developed is the field of flood reconstruction, where elements and, in particular, element ratios (e.g. Zr/Rb, Zr/Ti) can be used as particle size proxies. Micro-XRF core scanning technologies allow for analysis at the event-scale, which hitherto has been unachievable in silt and clay sediments. The potential to build and significantly enhance our understanding of longer term flooding patterns and non-stationarity, offers considerable scope for augmenting instrumental records and providing new perspectives for contemporary river management. Rapid geochemical assessment of fluvial sedimentary deposits can also be used to support floodplain reconstruction studies and pollution investigations, but greater scope will emerge from the calibration of raw XRF count data to elemental concentration. In this paper we demonstrate the potential for using micro-XRF data in sediment provenance investigations, but improvements in error quantification and propagation need to be explored. Given that river alluvium plays an integral role in the cycling and storage of contaminants, further applications in this field would be hugely beneficial for river managers. Although sediment heterogeneity places significant challenges to the quantification of micro-XRF core scanner results, there has been little attempt to establish what these limitations mean in practical terms.