& Roe, H. M. (2019). An evaluation of methodologies for calibrating Itrax X-ray fluorescence counts with ICP-MS concentration data for discrete sediment samples. Chemical Geology.

Arcellinida (testate lobose amoebae), a group of benthic protists, were examined from 46 sediment-water interface samples collected from oligotrophic Oromocto Lake, New Brunswick, Canada. To assess (1) assemblage homogeneity at a sub-meter spatial scale and (2) the necessity for collecting samples from multiple stations during intra-lake surveys; multiple samples were collected from three stations (quadrats 1, 2, and 3) across the north basin of Oromocto Lake, with quadrat 1 (n = 16) being the furthest to the west, quadrat 2 (n = 15) situated closer to the center of the basin, and quadrat 3 (n = 15) positioned 300 m south of the mouth of Dead Brook, an inlet stream. Results from cluster analysis and non-metric multidimensional scaling (NMDS) analysis identified two major Arcellinida assemblages, A1 and A2, the latter containing two sub-assemblages (A2a and A2b). Redundancy analysis and variance partitioning results indicated that seven statistically significant environmental variables (K, S, Sb, Ti, Zn, Fe, and Mn) explained 41.5% of the total variation in the Arcellinida distribution. Iron, Ti and K, indicators of detrital runoff, had the greatest influence on assemblage variance. The results of this study reveal that closely spaced samples (~ 10 cm) in an open-water setting are comprised of homogenous arcellinidan assemblages, indicating that replicate sampling is not required. The results, however, must be tempered with respect to the various water properties and physical characteristics that comprise individual lakes as collection of several samples may likely be necessary when sampling multiple sites of a lake basin characterized by varying water depths (e.g., littoral zone vs. open water), or lakes impacted by geogenic or anthropogenic stressors (e.g., eutrophication, or industrial contamination).

No abstract

XRF core scanning has evolved to become a standard analytical technique for the rapid assessment of elemental, density and textural variations in a wide range of sediments and other materials, with applications ranging from palaeoceanography, paleoclimatology, geology, and environmental forensics to environmental protection. In general, scanning provides rapid, non-destructive acquisition of elemental and textural variations at sub-millimetre resolution for a wide range of materials. Numerous procedural adaptations have been developed for the growing number of applications, such as analyses of unconsolidated, water-rich sediments, powdered soil samples, or resin bags. Here, practical expertise and guidance from the Itrax community, gained over 15 years, is presented that should provide insights for new and experienced users.

A novel geomatics methodology is presented for locating optimal lake coring sites to potentially capture evidence of paleo-storms. One hundred sediment-water interface samples collected from Harvey Lake, NB, Canada (45° 43′ 45″ N; 67° 00′ 25″ W) were analyzed using: end member mixing analysis (EMMA), which can be used to recognize modal grain size distributions derived from sediment resuspension during major storms; and Itrax X-ray fluorescence core scanningderived Ti, an indicator of catchment runoff, which is enhanced during major storm events. Simple geospatial models based on lake bathymetric and historical wind speed data (Fredericton INTL A climatological station; 1953-2015) were used to determine lake bottom areas susceptible to wave base sediment resuspension. EMMA End Member (EM) 02 (mode = 40 μm) was widely distributed in areas > 4.4 m water depth, which have been unimpacted by wave base remobilization since 1953. Deposition of EM 02 in deeper water areas was interpreted to be of major storm derivation, the result of fallout of resuspended sediments from the water column. This EM was most concentrated in the central part of the lake at >6 m water depth, as well as at the z-max (~ 11 m), and in Herbert's Cove (3-6 m). The main source of runoff derived Ti into the lake was through Sucker Brook, with the highest concentrations in Herbert's Cove and the central part of the lake, including the lake z-max. This assessment indicates that the best undisturbed sedimentary record of paleo-storms is mostly likely in the central part of the lake north of the z-max at water depths of > 6 m, as well as deeper water areas of Herbert's Cove.