Tracking the Transport of Silver Nanoparticles in Soil: a Saturated Column Experiment

Karrar N M Mahdi,Coen Ritsema,Ruud Peters,Violette Geissen,Martine Van Der Ploeg

doi:10.1007/s11270-018-3985-9

Karrar N M Mahdi, Coen Ritsema + Show 3 more

Open Access

https://doi.org/10.1007/s11270-018-3985-9

Copy DOI

Abstract

Silver nanoparticles (AgNPs) can enter the environment when released from products containing them. As AgNPs enter soil, they are often retained in the soil profile and/or leached to the groundwater. This research assessed the transport of AgNPs in their “particle form” through the soil profile using a series of columns. Three soil types were put into soil columns: LSH (loam with high organic matter (OM)), LSL (loam with low OM), and Sand (no OM). The results showed that AgNP transport and retention in soil as well as particle size changes are affected by soil organic matter (OM) and the cation exchange capacity (CEC) of soil. OM affected the transport and retention of AgNPs. This was evident in the LSH columns where the OM concentration was the highest and the AgNP content the lowest in the soil layers and in the effluent water. The highest transported AgNP content was detected in the Sand columns where OM was the lowest. CEC had an impact on the particle size of the AgNPs that were retained in the soil layers. This was clear in columns packed with high CEC-containing soils (LSL and LSH) where AgNP particle size decreased more substantially than in the columns packed with sand. However, the decrease in AgNP sizes in the effluent water was less than the decrease in particle size of AgNPs transported through but retained in the soil. This means that the AgNPs that reached the effluent were transported directly from the first layer through the soil macropores. This work highlights the ability to track AgNPs at low concentrations (50 μg kg−1) and monitor the changes in particle size potential as the particles leach through soil all of which increases our knowledge about AgNP transport mechanisms in porous media.

Highlights

Silver nanoparticles (AgNPs) are a metallic nanomaterial consisting of spherically shaped particles ranging in size from 1 to 100 nm (Helmlinger et al 2016)
This study focused on tracking the transport and the changes in particle size of AgNPs, as they moved through 16-cm-long columns filled with different soils and in the effluent eventually leached from these columns
In the columns packed with LSH, there was very limited AgNP transport after 24 h as less than 1 μg AgNPs was detected in each of the soil layers 2 and 3 and almost none in layer 4 while 20 μg of the initially applied AgNPs remained in layer 1

Summary

Introduction

Silver nanoparticles (AgNPs) are a metallic nanomaterial consisting of spherically shaped particles ranging in size from 1 to 100 nm (Helmlinger et al 2016). Previous studies have researched the potential toxicity of AgNPs to humans and the environment (EC 2017). The increase in the production of AgNPs and the number of applications that use these AgNPs has raised concerns about the potential release of these materials into the environment. AgNPs can reach the soil through plant strengthening agents (Lorenz et al 2011; Prasad et al 2014; Thuesombat et al 2014), slag from incinerators (Holder et al 2013), and contaminated sludge from sewage treatment plants (Lombi et al 2013). Previous studies have shown that there is a large variation in the concentration and the particle size of the AgNPs that are used in consumer products which means that the different particle sizes and concentrations of AgNPs released into soil and water have different toxic effects. Once AgNPs are introduced to the soil environment, the AgNPs can be transported to deeper layers in the soil and to the groundwater (Sagee et al 2012; Cornelis et al 2013; Liang et al 2013a) as well as transported with surface water runoff (Kaegi et al 2010; Tian 2010; Mahdi et al 2017)

Methods

Results

Conclusion