Transport of silver nanoparticles in intact columns of calcareous soils: The role of flow conditions and soil texture

Abstract

A B S T R A C TGrowing production of manufactured nanomaterials has increased the possibility of contamination of groundwater resources and soils by nanoparticles (NPs). It is crucial to study the fate of NPs in subsurface porous media in order to evaluate and control their risks to ecosystems and human health. Hence, this study was conducted to investigate the transport and retention of polyvinylpyrrolidone (PVP) stabilized silver nanoparticles (AgNPs, a diameter of 40 nm) under saturated and unsaturated conditions in intact columns of two calcareous sandy loam (TR) and loam (ZR) soils. Furthermore, similar experiments were conducted using sand quartz as a reference medium. A pulse of the AgNP suspension with an input concentration (C 0 ) of 50 mg L −1 was injected into the columns for 3 pore volumes. The transport of bromide (Br), as a non-reactive inert tracer, was also examined. High mobility of AgNPs was observed through the sand columns due to unfavorable conditions for AgNP deposition on the quartz sand surfaces. Nearly all AgNPs introduced into the columns of both soils were retained in the soil. Percentages of AgNPs leached out of the columns were < 1% of the total injected mass in both soils. Hyperexponential retention profiles (RPs) were observed in both soils and maximum concentrations of 100-130 mg kg −1 were determined near the columns' inlet. However, slightly stronger retention of AgNPs and greater maximum retained concentrations on the solid phase (S max ) in the ZR soil compared with the TR soil may be attributed to smaller grain sizes of the ZR soil. Hydrodynamic forces adjacent to the solid surfaces near the column inlet can provide a viable explanation for the hyperexponential shape of RPs. The one-site kinetic attachment model in HYDRUS-1D, which accounted for time-and depth-dependent retention, was successfully used to analyze the retention of AgNPs. The results showed that the degree of saturation had little effect on the mobility of AgNPs through undisturbed soil columns. Our results suggested the limited transport of AgNPs in neutral/alkaline calcareous soils under both saturated and unsaturated conditions.

Impact of Titanium Dioxide Nanoparticles on Nutrient and Contaminant Reduction in Wastewater Treatment Wetlands

“…Choi et al (2018) [31] found that municipal waste throughout the year contained between 22 and 319 μg/L titanium dioxide, and 20-212 μg/L zinc oxide. Wetlands also have high concentrations of dissolved organic matter, which may encourage sorption and retention of large quantities of MENPs [32], [33] . Plants are also a potential significant compartment for MENPs in wetlands.…”

Transport and retention of engineered silver nanoparticles in carbonate-rich sediments in the presence and absence of soil organic matter

“…However, only few studies on engineered nanoparticle transport through carbonate-dominated material exist. Rahmatpour et al (2018) compared polyvinylpyrrolidone (PVP)-coated AgNP transport through pure quartz sand and two calcareous topsoils with considerable clay content (sandy loam and loam). They found that their two topsoils retained around 99% of the injected PVP-AgNPs, whereas pure quartz sand retained about 11%.…”

“…Laumann et al (2013) showed that the mobility of polydisperse nano zero-valent iron strongly decreases with increasing carbonate content in crushed limestone. These authors attributed retention of negatively charged nanoparticles in limestone to cation bridging and elimination of the energy barrier to attachment by charge heterogeneity and/or near neutral zeta potentials (Laumann et al, 2013;Dong et al, 2017;Rahmatpour et al, 2018), as well as to the morphology of the limestone (Bayat et al, 2014(Bayat et al, , 2015. Systematic studies considering predefined unconsolidated mixtures of carbonate-and quartzbased sands as well as natural carbonate-rich aquifer material do not exist in the literature to the knowledge of the authors.…”

Tailoring Highly Thermal Conductive Properties of Te/MoS2/Ag Heterostructure Nanocomposites Using a Bottom‐Up Approach

“…[22] The second is that the effective transfer of electrons is limited, as the electrons move laterally along the layered structure of the MoS 2 nanosheet, resulting in poor electrical conductivity of the MoS 2 . [26,27] Yao et al fabricated Ag NP-decorated SiC NWs/epoxy nanocomposite paper and achieved a high in-plane thermal conductivity of 34.0 W m −1 K −1 . [23] Therefore, considering all these factors, an effective way to improve the thermal conductivity and electrical conductivity is to deposit highly thermally conductive and highly reactive materials on the MoS 2 substrate.…”

“…Metallic Ag shows a high thermal conductivity of 418 W m −1 K −1 at room temperature, which is considered as a strong candidate to further improve the thermal conductivity. So far, physical methods (including evaporation, sputtering, and laser ablation), wet chemical reduction, electrochemical, microemulsion, photoreduction, and other chemical methods have been developed to prepare the Ag NPs . Yao et al fabricated Ag NP‐decorated SiC NWs/epoxy nanocomposite paper and achieved a high in‐plane thermal conductivity of 34.0 W m −1 K −1 .…”