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Assessing the environmental occurrence and risk of nano-silver in Hunan, China using probabilistic material flow modeling

Ding, Ru, Li, Li, Yang, Pingjian, Luo, Li, Li, Lei, Wang, Qiang
The Science of the total environment 2019 v.658 pp. 1249-1255
air, effluents, emissions, landfills, material flow analysis, metals, models, nanosilver, risk, risk characterization, sediments, sewage treatment, soil, soil pollution, surface water, wastewater treatment, water pollution, China
Using a probabilistic material flow analysis model, we investigate the mass balance and occurrence of nano-silver in the environment of Hunan, renowned as “the home to non-ferrous metals” in China. The model builds on China-specific production and environmental information and incorporates sulfidation of nano-silver in urban wastewater treatment systems. We predict that the bulk of nano-silver (>90%), primarily originating from production and consumption of nano-silver products, ends up in sewage treatment plants (STPs, 5.3t/a), followed by the landfill (4.7t/a). More than 99% of nano-silver in STPs reacts with sulfide and thus does not appear in effluents. Direct release of nano-silver from production and consumption is identified as the dominant source of nano-silver in the environment, most of which enters surface water (0.71t/a). As such, regulation of direct emissions from production and consumption of nano-silver products can be of priority for local environmental management. The modeled regional concentrations (modes) of nano-silver are 0.9ng/L in surface water, 20ng/kg in soil, 6.9μg/kg in sediment, and negligible in the air, which agree well with measurements in the modeled region. Based on the modeled concentrations, we calculate that the risk characterization ratio is <1 in the air, surface water and soil, which means that nano-silver currently poses no risk to organisms living in these environmental compartments.