To study the stability of NPs in thewater, 50 nmand 100 nmcitratecapped
AgNPs and 60 nm 100 nmtannic-capped AuNPs were spiked in
the filtered natural water and effluent water respectively, and the NPs
were investigated during a ten-day incubation period. The average diameters
of AgNPs and AuNPs after first day were presented in the
Table 7. Table SI-3 showed particle number concentration recoveries
of AuNPs and AgNPs spiked into filtered HuNan University effluent
and Xiangjiang River after first day. It indicated that silver and gold
nanoparticles in complex matrix were stable at the first day which
were in accordance with Telgmann's study (Telgmann et al., 2014).
The variations of silver and gold nanoparticles in the environmentalwaters
were showed in Fig. 9 (a)–(b). The particle diameters of AgNPs decreased
approximately 10% during a ten-day period in both of the
naturalwater and effluentwater (Fig. 9(a)). It indicated that dissolution
occurred when AgNPs were dispersed in environmental water at low
number concentration. This was consistentwith the results of Furtado's
study (Furtado et al., 2014). The interactions between particleswere infrequent
at low concentrations limiting the rate of homoagglomeration
(Furtado et al., 2015). Ag+ was then released into solution through the
oxidation and dissolution of AgNPs (Li and Lenhart, 2012). Dissolution
happened when AgNPs were dispersed in synthetic water (Table SI-3).
As for AuNPs, both of the 60 nm and 100 nm AuNPs spiked into the