Table 1.
Optimized parameters of the F-ASS technique.
Table 2.
Validation parameters of the analytical method using the F-AAS technique.
Table 3.
Optimized time-temperature parameters in the GF-AAS technique.
Table 4.
Validation parameters of the analytical method using the GF-AAS technique.
Fig 1.
Distributions of daily sap volume depending on sap collection date (I-III) for young and old trees (box: 25th percentile (Q1), median and 75th percentile (Q3); whiskers: min. value within Q1-1,5*IQR and max value within Q3+1,5*IQR, circles: outliers).
Table 5.
Summary statistics for daily sap volume (dm3/24h).
Fig 2.
Distributions of the contents of minerals in birch sap for young and old trees depending on the sap collection date (box: 25th percentile (Q1), median and 75th percentile (Q3); whiskers: min. value within Q1-1,5*IQR and max value within Q3+1,5*IQR).
Fig 3.
Distributions of the contents of heavy metals in birch sap for young and old trees depending on the sap collection date (box: 25th percentile (Q1), median and 75th percentile (Q3); whiskers: min. value within Q1-1,5*IQR and max value within Q3+1,5*IQR).
Table 6.
Summary statistics for the content of minerals in birch sap (mg/dm3).
Table 7.
Summary statistics for the content of heavy metals in birch sap (μg/dm3).
Fig 4.
Effect of different factors on the content of minerals in birch sap.
Table 8.
Prediction of the content of minerals in birch sap by the GLM (mg/dm3).
Table 9.
Prediction of the content of heavy metals in birch sap by the GLM (μg/dm3).
Fig 5.
Effect of different factors on the content of heavy metals in birch sap.
Fig 6.
Implementation of daily dietary reference values (as recommended by EFSA for an adult woman) by one liter of birch sap obtained by combining the birch sap from 6 trees of one age group on successive collection dates.
Fig 7.
Concentration of heavy metals in birch sap obtained by combining the birch sap collected from 6 trees of one age group on successive collection dates, referenced to the parametric values for drinking water (horizontal line: guideline values for chemicals that are of health significance in drinking-water).