Microtox 생물검정법을 이용한 은 이온과 은 나노입자의 수용액과 토양에서의 독성 비교 평가

초록

This study was conducted to assess the microbial toxicity of ionic silver solution (Ag+N) and silver nanoparticle suspension (Ag0NP) based on the Microtox bioassay. In this test, the light inhibition of luminescent bacteria was measured after 15 and 30 min exposure to aqueous solutions and soils spiked with a dilution series of Ag+N and Ag0NP. The resulting dose-response curves were used to derive effective concentration (EC25, EC50, EC75) and effective dose (ED25, ED50, ED75) that caused a 25, 50 and 75%inhibition of luminescence. In aqueous solutions, EC50 value of Ag+N after 15 min exposure was determined to be < 2 mg L-1 and remarkably lower than EC50 value of Ag0NP with 251 mg L-1. This revealed that Ag+N was more toxic to luminescent bacteria than Ag0NP. In soil extracts, however, ED50value of Ag+N with 196 mg kg-1 was higher than ED50 value of Ag0NP with 104 mg kg-1, indicating less toxicity of Ag+N in soils. The reduced toxicity of Ag+N in soils can be attributed to a partial adsorption of ionic Ag+ on soil colloids and humic acid as well as a partial formation of insoluble AgCl with NaCl of Microtox diluent. This resulted in lower concentration of active Ag in soil extracts obtained after 1 hour shaking with Ag+N than that spiked with Ag0NP. With longer exposure time, EC and ED values of both Ag+N and Ag0NP decreased, so their toxicity increased. The toxic characteristics of silver nanomaterials were different depending on existing form of Ag (Ag+, Ag0), reaction medium (aqueous solution, soil), and exposure time.

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