Abstract. Low concentrations of 106Ru were detected across Europe
at the turn of September and October 2017. The origin of 106Ru
has still not been confirmed; however, current studies agree that
the release occurred probably near Mayak in the southern Urals. The
source reconstructions are mostly based on an analysis of concentration
measurements coupled with an atmospheric transport model. Since reasonable
temporal resolution of concentration measurements is crucial for proper
source term reconstruction, the standard 1-week sampling interval
could be limiting. In this paper, we present an investigation of the
usability of the newly developed AMARA (Autonomous Monitor of Atmospheric Radioactive Aerosol) and CEGAM (carousel gamma spectrometry) real-time monitoring
systems, which are based on the gamma-ray counting of aerosol filters and allow for determining the moment when 106Ru arrived at the monitoring site within approx. 1 h and detecting activity concentrations as low as several mBq m−3 in 4 h intervals.
These high-resolution data were used for inverse modeling of the 106Ru
release. We perform backward runs of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) atmospheric transport
model driven with meteorological data from the Global Forecast System
(GFS), and we construct a source–receptor sensitivity (SRS) matrix
for each grid cell of our domain. Then, we use our least squares with
adaptive prior covariance (LS-APC) method to estimate possible locations
of the release and the source term of the release. With Czech monitoring
data, the use of concentration measurements from the standard regime
and from the real-time regime is compared, and a better source reconstruction
for the real-time data is demonstrated in the sense of the location
of the source and also the temporal resolution of the source. The
estimated release location, Mayak, and the total estimated source
term, 237±107 TBq, are in agreement with previous studies. Finally,
the results based on the Czech monitoring data are validated with
the IAEA-reported (International Atomic Energy Agency) dataset with a much better spatial resolution, and
the agreement between the IAEA dataset and our reconstruction is demonstrated. In addition, we validated our findings also using the FLEXPART (FLEXible PARTicle dispersion) model coupled with meteorological analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF).