Impacts of Pristine and Transformed Ag and Cu Engineered Nanomaterials on Surficial Sediment Microbial Communities Appear Short-Lived

Abstract

Laboratory-based studies have shown that many soluble metal and metal oxide engineered nanomaterials (ENM) exert strong toxic effects on microorganisms. However, laboratory-based studies lack the complexity of natural systems and often use "as manufactured" ENMs rather than more environmentally relevant transformed ENMs, leaving open the question of whether natural ligands and seasonal variation will mitigate ENM impacts. Because ENMs will accumulate in subaquatic sediments, we examined the effects of pristine and transformed Ag and Cu ENMs on surficial sediment microbial communities in simulated freshwater wetlands. Five identical mesocosms were dosed through the water column with either Ag(0), Ag2S, CuO or CuS ENMs (nominal sizes of 4.67 ± 1.4, 18.1 ± 3.2, 31.1 ± 12, and 12.4 ± 4.1, respectively) or Cu(2+). Microbial communities were examined at 0, 7, 30, 90, 180, and 300 d using qPCR and high-throughput 16S rRNA gene sequencing. Results suggest differential short-term impacts of Ag(0) and Ag2S, similarities between CuO and CuS, and differences between Cu ENMs and Cu(2+). PICRUSt-predicted metagenomes displayed differential effects of Ag treatments on photosynthesis and of Cu treatments on methane metabolism. By 300 d, all metrics pointed to reconvergence of ENM-dosed mesocosm microbial community structure and composition, suggesting that the long-term microbial community impacts from a pulse of Ag or Cu ENMs are limited.

Aging of Dissolved Copper and Copper‐based Nanoparticles in Five Different Soils: Short‐term Kinetics vs. Long‐term Fate

“…The CuS‐NPs were characterized previously in filtered porewater by DLS (Malvern Zetasizer Nano) and transmission electron microscopy (FEI Tecnai G2 Twin). These particles were characterized previously: the CuS‐NPs are aggregates of nonspherical particles (primary particle size of 12.4 ± 4.1 nm), and DLS confirmed that these particles exist as aggregates (185 ± 11 nm) in an aqueous suspension (Moore et al, 2016). …”

“…Copper sulfide nanoparticles (CuS‐NPs) were synthesized through the direct sulfidation of CuO‐NPs described by Moore et al (2016). In short, 1 g of ∼50 nm CuO‐NPs (Sigma Aldrich) were mixed with 2.5 g of gum arabic (Sigma Aldrich) in 900 mL of deionized water and dispersed using a sonicating probe (Branson Model 250).…”

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects—An updated review

“…Considering that non‐labile transformation end products such as AgCl and Ag 2 S are expected to be stable in the environment and to have relatively low bioavailability (Lombi et al ; Donner et al ; Doolette et al , ), the risk to terrestrial ecosystems posed by Ag NMs would appear to be low, although uncertainties related to longer‐term transformations, dosimetry, are also relevant. This conclusion has been further supported by soil‐based studies demonstrating that Ag 2 S NMs presented minimal hazard to plant–microorganism symbioses (Judy et al , ), crop plants (Doolette et al ; Wang et al ), soil microorganisms (Judy et al ; Doolette et al ; Moore et al ), and soil invertebrates (Starnes et al , ).…”

Fate of metallic engineered nanomaterials in constructed wetlands: prospection and future research perspectives

“…When an ENM is dissolved, metal ions are released from its surface. The dissolution process of ENMs has environmental relevance from the risk analysis perspective because ions are often more toxic than ENMs (Sotiriou and Pratsinis 2010;Li et al 2011;Levard et al 2013a;Moore et al 2016). However, dissolution can possibly reduce the mobility as Ag + and Ce 2+ appear to be more efficiently bound to soil/sediment than their nanoparticle counterparts (Cornelis et al 2012;Van Koetsem et al 2015).…”