2.7. Measurement of total silver content in plant tissues and soil Total Ag concentrations of plant tissues (shoots and roots) were determined using a closed vessel microwave-assisted digestion
procedure and analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and ICP-mass spectrometry (ICP-
MS,Agilent 7500ce). Further details of analysis methods and Ag
recoveries are given in S1.3. The limit of quantification (LOQ) for Ag concentrations in plant tissues and soils was 0.02 mgAg/kg. Prior to ICP-MS analysis, shoot samples from PT1 required
pre-concentration due to low Ag concentrations. This method decreased the LOQ to 0.01 mg Ag/kg (S1.3).
Total Ag concentrations in roots from PT2 were corrected for the presence of Ag bound to soil on root surfaces using a chromium
(Cr) correction method. This method assumes that no soil Cr was
Taken up by the plant (S1.4). On average, 14 ± 3% of the Ag that was
Detected in root samples was attributable to the presence of soil Ag in the root sample (S1.4).
Pot trial 2 soils were extracted with ammonium nitrate (NH 4 NO 3 ) (ISO 19730) [34] to estimate the potentially bioavailable fraction of Ag, w Ag (?g Ag/kg) (S1.5).