Geoscience Reference
In-Depth Information
Fig. 12.26 Breakthrough curves for AgNPs in different soil mixtures a coarse: soil fraction of
250-1,000 lm, medium: 70 wt. % of the 250-1,000 lm and 30 % of the \250 lm diameter
fraction, and fine: containing equal weights of the two fractions; Darcy velocity 0.66 cm/min.
Average aggregate size is in the order coarse [ medium [ fine. b Breakthrough curves for
bromide in the same soil mixtures coarse, medium, and fine, and for AgNPs in pure quartz (Darcy
velocity 0.66 cm/min) (Sagee et al.
2012
). Reprinted from Sagee et al. (
2012
). Copyright 2012
with permission from Elsevier
These results indicate that the AgNPs interact with the soil, influencing both
retention and rate of transport. Another indication of AgNP-soil interactions is
seen in Fig.
12.27
, where AgNP transport in solutions with and without humic acid
is compared. The presence of humic acids increases the concentration of eluting
AgNPs from less than 50 to *75 % of the initial concentration. This increase
suggests that humic acids act as surfactants that stabilize nanoparticles in solution
