4. Conclusions
This study demonstrates the low plant availability of Ag from
soil amended with biosolids containing environmentally relevant
Ag 2 S-NPs at realistic Ag concentrations (PT1). Silver sulfide NPs that
were applied directly to soil were less bioavailable than Ag 2 S-NPs
borne biosolids.
Our results show that commonly used fertilisers (thiosulfate and
KCl) can increase the plant uptake of Ag released from Ag 2 S-NPs and
AgNPs
(PT2). This increase may be due to complexation of Ag + by
thiosulfate and chloride ligands, which act to stabilise Ag + in soil
solution thereby increasing Ag mobility and bioavailability. Con-
versely, soil application of H 2 O 2 and phosphate fertiliser (MAP) was
found to decrease the plant uptake of Ag from soil amended with
Ag 2 S-NPs, AgNPs or Ag + . Future studies should seek to understand
the effect of applying more than one fertiliser type, as this is the
likely scenario in agricultural settings.
This study suggests that the potential risk of AgNPs to terrestrial
plants is very low. Under the conditions used in this study, the concentration of Ag in edible plant parts was