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Open AccessArticle

Aggregation, Sedimentation, and Dissolution of Copper Oxide Nanoparticles: Influence of Low-Molecular-Weight Organic Acids from Root Exudates

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Textile Pollution Controlling Engineering Center of Ministry of Environmental Protection, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
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Shanghai National Engineering Research Center of Urban Water Resources Co., Ltd., Shanghai 200082, China
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Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
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Institute of ECO-Environment and Plant Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China
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Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
*
Authors to whom correspondence should be addressed.
Nanomaterials 2019, 9(6), 841; https://doi.org/10.3390/nano9060841
Received: 24 April 2019 / Revised: 24 May 2019 / Accepted: 29 May 2019 / Published: 1 June 2019
The rhizosphere is an essential pathway for the uptake of metal-based nanoparticles (MNPs) by plant roots. However, the interaction between root exudates and MNPs is still unclear. In this study, we initially identified the major low-molecular-weight organic acids (LMWOAs) in the rice root exudates using hydroponics. Then, the individual LMWOAs were added to CuO nanoparticle suspensions to investigate their effects on the environmental behavior of the MNPs. The results showed that both the variety and the concentration of LMWOAs impacted the aggregation, sedimentation, and dissolution of CuO nanoparticles (NPs). Almost all LMWOAs except succinic acid inhibited the aggregation of CuO NPs by enhancing the electrostatic repulsive force between NPs. The presence of citric and oxalic acids rather than lactic acid greatly improved the stability of CuO NP suspensions, but other acids showed a low promoting and high inhibiting effect on NP sedimentation. Moreover, all the LMWOAs from root exudates facilitated the dissolution of CuO NPs with a positive dose-dependent correlation, especially formic acid. Notably, citric acid, as the most abundant LMWOAs in rice root exudates, largely determined the aggregation, sedimentation, and dissolution of CuO NPs. This study provides a better understanding on NP–plant interactions in the rhizosphere. View Full-Text
Keywords: root exudates; low-molecular-weight organic acids; CuO nanoparticles; aggregation; dissolution root exudates; low-molecular-weight organic acids; CuO nanoparticles; aggregation; dissolution
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Peng, C.; Tong, H.; Yuan, P.; Sun, L.; Jiang, L.; Shi, J. Aggregation, Sedimentation, and Dissolution of Copper Oxide Nanoparticles: Influence of Low-Molecular-Weight Organic Acids from Root Exudates. Nanomaterials 2019, 9, 841.

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