Increased use of engineered nanoparticles (ENPs) in agriculture may lead to the contamination of fresh produce along with potential health risks. Therefore, a better understanding of agriculturally-relevant ENP behaviour upon exposure to chemical sanitizers commonly used in produce processing is key to evaluating and developing strategies for their removal. This study aimed to examine the temporal changes of silver nanoparticles (AgNPs) when exposed to commercially applicable chlorine concentrations in simulated lettuce wash water. Aggregation and dissolution of AgNPs (5 mg/L) at three different chlorine concentrations (2, 50 and 100 mg/L) were evaluated in the presence and absence of dissolved lettuce extract (DLE, 0.1%), with 5 mg/L AgNPs in deionized water used as the control. Particle size (diameter, nm), zeta potential (mV) and dissolved Ag concentration (mg/L) were measured initially and then after 2, 6, 12, 24 h and 4, 7 and 10 days at 4°C. Particle size increased with time at all chlorine levels tested in the presence (89 to 168 nm) and absence (49 to 431 nm) of DLE as compared to the control (58 to 60 nm) (<i>P</i> &lt; 0.05) indicating greater aggregation of AgNPs with chlorine and DLE. Lower dissolved Ag concentrations and increasingly negative zeta potentials were found in the presence of chlorine (0.01 to 0.03 mg/L and -39 to -95 mV) and DLE (0.01 to 0.14 mg/L and -28 to -32 mV), as compared to the control (0.54 to 0.8 mg/L and -10 to -20 mV) (<i>P</i> &lt; 0.05). These results indicate that the fate of AgNPs is greatly impacted by both chlorine and organic matter in lettuce wash water. A clear understanding of these interactions as well as sorption of AgNPs to leafy greens is needed to optimize wash water conditions for effective removal of ENPs from fresh produce.

Fate of silver nanoparticles in lettuce wash water as impacted by chlorine and organic matter

2019 Fall National Meeting

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