## 3 Results and Discussion
### Climatic Conditions and Mobility
Furthermore, these two (from \(-\)5.8% to \(-\)6.5%) and six (from \(-\)9.8% to \(-\)10.2%) individuals, which presented oxygen isotopic values outside of Edessa's range (\(-\)7.4% to \(-\)9.5%) probably consumed drinking water from other sources and lived in other places. One possible explanation for the high \(\delta^{18}\)O\({}_{\text{ap}}\) values (\(-\)6.5% to \(-\)5.8%) is that these two individuals originated from an area characterized by a warmer climate or lived closer to the sea. The low \(\delta^{18}\)O\({}_{\text{ap}}\) values (\(-\)10.2% to 9.8%) of the six individuals from Edessa probably indicate that they lived at higher altitudes or latitudes. However, the \(\delta^{18}\)O\({}_{\text{ap}}\) value of consumed water is related not only to the region where they lived, but also to the region's altitude, which is a factor that has to be examined before concluding about the climatic conditions of the studied periods and differentiating local and nonlocal individuals. Additionally, the population of an ancient city could get water from sources of different altitudes; therefore, the \(\delta^{18}\)O\({}_{\text{w}}\) of water springs were correlated to the climate data and the geographic spread of ancient cities in order to define the isotopic fingerprint of the areas. The annual precipitation rate for the area of Edessa (Agras and the city of Edessa) is 500 mm, with a mean annual temperature of 12 \({}^{\circ}\)C; however, it exceeds 750 mm in regions of higher altitude ( mountainous areas: Vermio and Voras-Kaimaktsalan Massif reach 2000 m and 2500 m, respectively). In order to take into consideration the relationship between \(\delta^{18}\)O\({}_{\text{w}}\) and altitude, an oxygen isotopic analysis was conducted for water sources (eight springs in the area near Agras and Edessa) at different altitudes of the regions (\(\delta^{18}\)Ow) (Figure 4) and the results were combined with those presented in Dotsika [19]. The local/specific gradient of oxygen isotope value versus altitude (\(\delta^{18}\)O\({}_{\text{w}}\) = a \(\times\) Altitude + b) is:  
\[\delta^{18}\text{O}_{\text{w}}=-\ 0.0030\ \times\text{Altitude}-6.3. \tag{1}\]  
Figure 4: The \(\delta^{18}\)O\({}_{\text{w}}\) (v-SMOW) isotopic values of spring waters from the area near Agras and Edessa versus altitude. The open circles are from [19] and the filled ones from this work. The linear regression line has a slope equal to \(-\)0.0030 and \(r^{2}\) = 0.83. This correlation can, potentially, provide a valuable explanation for the measured \(\delta^{18}\)O\({}_{\text{ap}}\) range of unknown samples both contemporary and archaeological. Hence, if we apply the isotopic gradient (Equation (1), 0.3%\(\cdot\)/100 m) and attribute the maximum isotopic \(\delta^{18}\)O\({}_{\text{ap}}\) difference between the samples to the different altitude of the drinking water, the difference of 1.2% for Agras corresponds to a hypsometrical difference of \(\sim\)400 m, while for Edessa the difference is 48% and 3.75% for males and females, respectively, and the corresponding hypsometrical difference is \(\sim\)1000 m. If we exclude the more positive and negative samples (E/T23, E/T27B, E/T32, E/T4B, E/T4A, E/T24, E/T25, and E/T29), the difference is 2.18% and corresponds to a hypsometrical difference of \(\sim\)700 m. Considering the mountainous topography of the area, the consumed water could have originated from springs with a different recharge altitude, but this altitude difference is too high to correspond to different sources of drinking water originating from reservoirs of the local groundwater for Edessa. However, if we assume that the altitudinal distribution of population could be \(\pm\)100 m, that is to say a total of 200 m, which means 480 \(\pm\) 100 m for Agras city and 350 \(\pm\) 100 m for Edessa city, the accepted oxygen isotopic difference between the populations of the same region is 0.68%.