Long-range transport and deposition on the Arctic snowpack of nuclear contaminated particulate matter

The primary environmental concern related to nuclear power is the production of radioactive waste hazardous to humans and the environment. The main scientific and technological problems to address this are related to the storage and disposal of the nuclear waste and monitoring the dispersion of radioactive species into the environment. In this work, we determined an anomalously high ¹⁴C activity, well above the modern natural background, on surface and seasonal snow sampled in early May 2019 on glaciers in the Hornsund fjord area (Svalbard). Due to the lack of local sources, the high snow concentrations of ¹⁴C suggest long-range atmospheric transport of nuclear waste particles from lower latitudes, where nuclear power plants and treatment stations are located. The analysis of the synoptic and local meteorological data allowed us to associate the long-range transport of this anomalous ¹⁴C concentration to an intrusion event of a warm and humid air mass that likely brought pollutants from Central Europe to the Arctic in late April 2019. Elemental and organic carbon, trace element concentration data, and scanning electron microscopy morphological analysis were performed on the same snow samples to better constrain the transport process that might have led to the high ¹⁴C radionuclide concentrations in Svalbard. In particular, the highest ¹⁴C values found in the snowpack (> 200 percent of Modern Carbon, pMC) were associated with the lowest OC/EC ratios (< 4), an indication of an anthropogenic industrial source, and with the presence of spherical particles rich in iron, zirconium, and titanium which, altogether, suggest an origin related to nuclear waste reprocessing plants. This study highlights the role of long-range transport in exposing Arctic environments to human pollution. Given that the frequency and intensity of these atmospheric warming events are predicted to increase due to ongoing climate change, improving our knowledge of their possible impact to Arctic pollution is becoming urgent.

Development of graphitization method for low carbon aerosol filter samples with Automated Graphitization System AGE-3

The wide applications of the radiocarbon (¹⁴C) approach in environmental, archeological, and geological research often necessitates the analysis of microgram-sized samples. The ability to measure low carbon samples is particularly relevant for aerosol particle filters, especially for samples from pristine environments. For this purpose, we investigated the sample dilution method for graphitization of low-carbon samples (20-200 μg C) with an Automated Graphitization System (AGE-3), and applied a mass balance equation for the calculation of ¹⁴C values. Materials with known ¹⁴C values (standards NIST-OXII and IAEA-C7) were diluted with ¹⁴C-free phthalic anhydride (PhA) until sufficient mass (500 μg C) for graphitization with the AGE-3 system was acquired. Reliable ¹⁴C values were obtained for samples with carbon amount in the range of 40-200 μg. Next, we adapted the dilution method for estimation of aerosol sample ¹⁴C values. Using it, we attained a precision of 0.71 ± 0.83 pMC for ¹⁴C measurements of aerosol samples containing 40-200 μg C. A shift of radiocarbon values to 5.07 pMC (average 3.08 ± 1.7 pMC) was observed for samples with low carbon content (<20 μg C). We determined that a precision of 2-3 pMC is acceptable for aerosol particle source apportionment studies. Using the sample dilution method, graphitization with AGE-3 of aerosol samples with carbon content >40 μg becomes a viable and efficient way of sample preparation for ¹⁴C analysis.