## Materials and Methods  
The study continues the preliminary characterization started on 17 iron slag smallfinds deriving from Calugareni [8]. The samples investigated in the present phase (Table 1) came from the Calugareni auxiliary fort _principia_ (headquarter building), from the Calugareni _vicus_, the civil settlement evolved next to the fort, from the _retentura_ (\"backyard\") of the principia of the Brancovenesti auxiliary fort, and one representative find from Vatava, East of the tower location. Surface macro- and micro-elemental composition of the samples was characterized by PXRF measurements carried out in three different points of the carefully cleaned finds, using an INNOV-X Alpha-6500 spectrometer (Olympus, Woburn, MA USA) (spot size 2 mm\({}^{2}\), 35 kV, 15 \(\upmu\)A, 3 mm filter, Be window, PIN Si detector, counting time 60 s in two consecutive 30 s runs). Bulk macro- and micro-elemental compositions were determined, in parallel, by PXRF and ICP-MS measurements. For the bulk PXRF measurements, the same PXRF spectrometer was used, the analysis being performed on three disc-shaped pellets (d = 1 cm) prepared from each sample by pressing \(1.00\pm 0.05\) g amounts of the finely pulverized (<63 \(\upmu\)m) material grinded in agate mill, after the external (environmentally contaminated and possibly weathered) layer removed. Despite the typical bias of the acquired data as compared to the results of the usual wet laboratory measurements, PXRF is presently a routine field analytical method for elements with medium to high atomic mass (K to U), in the concentration range of a few mg/kg to a few %. The differences can be attributed to the basically different sample preparation and measurement methodology (point-and-shoot surface measurement vs. bulk measurement on homogenized samples), chemical matrix effects (particularly at high Fe contents), matrix heterogeneity, and spectral interferences. Detection limits vary with sample matrix composition; high abundance of heavier major elements, mainly iron, negatively affects trace element detection [9]. PXRF spectrometry can't accurately quantify \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Site Location** & **Smallfind No.** & **Trench** & **Context** & **Fieldwork Year** \\ \hline Brancovenesti, _retentura_ & 9487 & A & 1 & 2012 \\  & 9454 & A & 3 & 2012 \\  & 9445 & A & 3 & 2012 \\ \hline Calugáreni, _vicus_ & 2008 & C & 2000 & 2013 \\  & 2155 & C & 2001 & 2013 \\  & 2318 & C & 2005 & 2013 \\  & 2342 & C & 2005 & 2013 \\  & 2355 & C & 2009 & 2013 \\  & 2356 & C & 2009 & 2013 \\  & 4009 & C2 & 2039 & 2014 \\  & 4137 & C1 & 2034 & 2014 \\  & 4169 & C2 & 2039 & 2014 \\  & 4222 & C1 & 2038 & 2014 \\  & 4251 & C1 & 2035 & 2014 \\  & 4264 & C1 & 2038 & 2014 \\ \hline Calugáreni, _principia_ & 10218 & A2 & 109 & 2015 \\  & 10532 & A5 & 250 & 2016 \\  & 10661 & A5 & 339 & 2016 \\  & 10673 & A & 346 & 2016 \\  & 11145 & A6 & 443 & 2017 \\ \hline Vatava, _East of the tower_ & Vat & V & 2014 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The iron slag samples. lighter elements (e.g., Na, P), nor Ti, V, Cr, Co, Ni and Ba at their typical concentrations in slag-like matrices, and its reliability is unsatisfactory in the case of the trace elements [10]. Consequently, PXRF generally can reliably provide qualitative (at best semiquantitative) data; gathering of quantitative data is problematic, particularly when the material is heterogeneous in nature. In case of iron slag samples analyzed in parallel with the PXRF method and wet chemistry, the PXRF analytical performance is defined by its \(<\)30% error, in samples containing very low or very high quantities of the analyzed element the error reaching \(>\)30% [6]. In the present study, the samples of bulk elemental composition determined by PXRF was compared with the data obtained on the same probe by ICP-MS, chosen as the wet chemical analysis method.