Evaluation of nano-silver concentrations using multi-media fate and transport models with different spatial resolutions.

Due to the complexity of the environmental matrix and the limitation of the detection level, it is important to use models to evaluate environmental exposure to nanomaterials. Based on this, this research established two multi-media fate and transport models of silver nanoparticles (AgNPs) with respective coarse and fine spatial resolutions. Using the case of the spatial distribution of AgNPs in the Xiangjiang River, China, we compared how the spatial resolution of a model impacts modeling results. The results show that the process of heterogeneous aggregation has the greatest impact on the modeled concentration of AgNPs in water, and the heterogeneous aggregation of free AgNPs with natural colloids and settling down to sediments is the dominant mechanism responsible for the loss of AgNPs. In addition, the use of different spatial resolutions gives similar trends in the modeled AgNPs concentration, despite the difference in absolute levels. Our work also shows that the reliability and accuracy of the rate constant of heterogeneous aggregation has a great influence on the modeled AgNPs concentrations.

Enzyme digestion combined with SP-ICP-MS analysis to characterize the bioaccumulation of gold nanoparticles by mustard and lettuce plants.

Plants can absorb and accumulate engineered nanomaterials (ENMs) through water and soil, providing a potential way for nanoparticles to be enriched in humans through the food chain. In this paper, a combination of enzymatic digestion method and SP-ICP-MS analysis was used to quantitatively characterize the enriched AuNPs in mustard and lettuce plants. The results showed that Macerozyme R-10 enzyme can extract AuNPs from plants without obvious aggregation/dissolution. Both mustard and lettuce plants can absorb and enrich the complete AuNPs to the above-ground organs, and the particle number concentrations detected are 1.24 × 107 particles L-1 and 4.39 × 107 particles L-1, respectively. With different exposure level of AuNPs(0.5 mg L-1,), a particle number concentration of 2.32 × 107 particles L-1 was detected in the stems of lettuce plants, while the mustard failed to transport AuNPs to the above-ground organs. The transport efficiency of Au ions by plants is higher than that of AuNPs, and the plants have stronger bioavailability for ions.

Quantitative detection of gold nanoparticles in soil and sediment.

Ever-growing application of engineering nanoparticles in many sectors of the society requires efficient methods to extract them from soil and sediment, for the sake of environmental protection. In this study, we develop a new method which uses sodium pyrophosphate solution (TSPP, Na4P2O7) as extratant to extract gold nanoparticle (AuNPs) from soil and sediment under optimized parameters through vortexing, water bath oscillation, ultrasonic bath and precipitation. SP-ICP-MS was used for the detection of number concentration, mass concentration and size distribution of AuNPs in soil. UV irradiation was innovatively used to directly degrade soil organic matter to improve the recovery of AuNPs due to their low recovery rate in rich organic soils. It could be found that the mass fraction recovery increased from 36% (without UV digestion) to 83% (with 48h UV digestion). The extraction method is versatile for different coating layers and wide-ranging particle sizes in real soil and sediment. Therefore, the rapid and efficient characterization and quantification of AuNPs in soil and sediment are achieved, and the researches on the extraction method of AuNPs and their behavior and toxicity assessment in soil environment can be enriched.