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Copper (Cu) stress is one of the predominant crop yield-reducing factors in agriculture. Application of carbon nanomaterials (CNMs) could have promotive effects on crop growth; however, their effects on alleviation of Cu stress for plants have rarely been documented. In this study, we investigated the comparative role of carbon nanotubes (CNTs) and carbon nanoparticles (CNPs) in corn (Zea mays) seed germination, seedling growth as well as Cu stress alleviation. The results showed that CNTs and CNPs stimulated corn seed germination by significantly increasing germination rate (GR), shortening the mean germination time (MGT), and increasing overall germination index (GI). They also significantly elongated seedling length and increased fresh biomass with optimal application rates ranging from 50 to 100 mg L -1 . Principle component analysis (PCA) confirmed that seed germination indexes and seedling growth were positively affected by CNTs or CNPs, but inversely influenced by high levels of Cu stress (> 20 mg L -1 ). Furthermore, higher Cu accumulation and anti-oxidative enzyme activity (SOD, POD, CAT) were observed in plants co-exposed to Cu 2+ and either CNTs or CNPs compared to plants exposed to Cu 2+ alone. CNPs had stronger improvement on plant growth and Cu stress alleviation than CNTs, which suggest they may be cost-effective agriculture amendments to improve plant growth under heavy metal stress., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Increasing applications of nanoparticles (NPs) in agriculture have raised potential risks to soil and aquatic ecosystems. A comparative study examining the transport of commonly used NPs in porous media is of critical significance for their application and regulation in agroecosystems. In this study, laboratory column leaching experiments were conducted to investigate the transport and retention of polysuccinimide NPs (PSI-NPs) in two saturated porous media with different grain sizes, as compared with multi-walled carbon nanotubes (MWCNTs), nano-Ag and nano-TiO 2 . Zeta potential of the NPs was negative at pH 6.3 and decreased in an order of PSI-NPs > nano-TiO 2  > MWCNTs > nano-Ag. The coarse and fine sands used in this study had negative charges with similar zeta potentials. The movement of NPs was affected by grain size, with larger sizes facilitating mobility while finer sizes favoring retention of NPs in the porous matrix. The retention profile significantly varied between the two sand columns, with more NPs transported to deeper layers in the coarse sand than the fine sand. The relative percentage of NPs detected in leachate was found to be positively correlated with the zeta potential of NPs (r = 0.931). Among the NPs, nano-Ag had the most negative zeta potential, and therefore was the most mobile, followed by MWCNTs and nano-TiO 2 . Having the least negative zeta potential, PSI-NPs had the lowest mobility, as compared with other NPs regardless of matrix grain size. This work reveals grain size and zeta potential of NPs are major factors that influence transport of NPs along the vertical porous profile, as well as demonstrating the relative unimportance of NP composition, which could serve as important guideline in nanomaterials application, risk assessment, and waste management in agroecosystems., (Copyright © 2021 Elsevier B.V. All rights reserved.)