To study the stability of NPs in the water, 50 nm and 100 nm citrate capped AgNPs and 60 nm 100 nm tannic-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 environmental waters were showed in Fig. 9 (a)–(b).