Tube-based field-portable x-ray fluorescence (FPXRF) as a qualitative screening tool for resource conservation and recovery act (RCRA) metals in children’s products and comparison to total metals analyses to predict hazardous waste metals toxicity characteristic

This research was performed to assess the efficacy of tube-based field portable x-ray fluorescence (FXPXRF) devices to evaluate RCRA heavy metal concentrations in children\u27s products and determine potential hazardous waste toxicity characteristics by comparative analysis to inductively coupled plasma (ICP) yields per SW6010B. Sample sets consisting of wood, plastic, rubber, bulk, plated/coated, and metal matrices were purchased, size-reduced as necessary and directly analyzed three-times for 120 seconds each via FPXRF operated in the Consumer Goods/Test All mode. Subsequently, the same samples were prepared in accordance to SW3050B and analyzed via ICP at an accredited contract laboratory. Side-by-side results analysis indicates that FPXRF consistently exhibits positive bias compared to standard laboratory methods in the majority of matrices due to XRFs abilities to estimate total metallic analyte concentrations versus extract-labile substances only. Instances in which FPXRFs positive bias was absent were believed attributed to suboptimal sample homogeneity or limited sample area compared to total sample volume of SW3050B extraction. Though FPXRFs overestimation of metallic analyte concentrations does not directly correlate to SW6010B ICP yields without application of correction factors, it does provide a better indication of total versus liberated analyte presence

Spatial variation in carbon source use and trophic position of ringed seals across a latitudinal gradient of sea ice

Anthropogenic climate change is causing changes to the Arctic sea-ice system with implications for the magnitude and timing of Arctic pelagic and ice-associated (sympagic) primary production that influences food web interactions. Ringed seals (Pusa hispida) are generalist predators that, as a species experience vastly different icescapes from low to high-Arctic latitudes. Quantifying spatial variation in their diet can help us understand how changes in sea-ice dynamics affect trophic interactions in Arctic marine food webs. However, multiple complementary analytical tools to examine variation in carbon source use and trophic dynamics in the diet of ringed seals have not yet been applied across their latitudinal range in the Arctic. We conducted stable isotope analysis (δ13C and δ15N) and measured highly branched isoprenoid diatom lipid biomarkers of ringed seals from the low, intermediate, and high Arctic (from 61.1°N to 77.5°N) to investigate spatial variation in their carbon source use and trophic position in relation to sea-ice dynamics. Both δ13C and highly branched isoprenoids indicated that ringed seals from higher latitudes had more sympagic carbon in their diet (liver δ13C: −18.3 ± 0.2 ‰, HBI: 89.9 ± 2.08 %) than ringed seals at lower latitudes (liver δ13C: −21.1 ± 0.1 ‰, HBI: 22.0 ± 2.73 %). Ringed seal trophic position increased from the low (3.78 ± 0.02) to high (4.76 ± 0.03) Arctic, suggesting increased fish consumption or a different trophic structure coinciding with the latitudinal change in carbon source. Ringed seals demonstrated a clear shift from low to high Arctic in the relative contribution of phytoplanktonic vs sympagic primary production. These patterns are likely linked to the vastly different icescapes in these environments and demonstrate that shifts in primary producer composition and Arctic food webs can be identified in ringed seal diets. Information on these prey and energy shifts over large spatial scales also provides insights into potential future changes to Arctic ecosystem function with continued sea-ice decline