Transformation‐dissolution reactions partially explain adverse effects of metallic silver nanoparticles to soil nitrification in different soils

Abstract

Risk assessment of metallic nanoparticles (NPs) is critically affected by the concern that toxicity goes beyond that of the metallic ion. The present study addressed this concern for soils with silver nanoparticles (AgNPs) using the Ag-sensitive nitrification assay. Three agricultural soils (A, B, and C) were spiked with equivalent doses of either AgNP (diameter = 13 nm) or AgNO . Soil solution was isolated and monitored over 97 d with due attention to accurate Ag fractionation at low (∼10 μg L ) Ag concentrations. Truly dissolved (<1 kDa) Ag in the AgNO -amended soils decreased with reaction half-lives of 4 to 22 d depending on the soil, denoting important Ag-aging reactions. In contrast, truly dissolved Ag in AgNP-amended soils first increased by dissolution and subsequently decreased by aging, the concentration never exceeding that in the AgNO -amended soils. The half-lives of AgNP transformation-dissolution were approximately 4 d (soils A and B) and 36 d (soil C). The Ag toxic thresholds (10% effect concentrations, milligrams of Ag per kilogram of soil) of nitrification, evaluated at 21 or 35 d after spiking, were similar between the 2 Ag forms (soils A and B) but were factors of 3 to 8 lower for AgNO than for AgNP (soil C), largely corroborating dissolution differences. This fate and bioassay showed that AgNPs are not more toxic than AgNO at equivalent total soil Ag concentrations and that differences in Ag dissolution at least partially explain toxicity differences between the forms and among soils. Environ Toxicol Chem 2018;37:2123-2131. © 2018 SETAC.

Effects of Silver Nitrate are a Conservative Estimate for the Effects of Silver Nanoparticles on Algae Growth and Daphnia magna Reproduction

“…These observations also correspond with those in the terrestrial assay of Bollyn et al () with the same test items. In that study, 3 soils were spiked with AgNO 3 or AgNPs.…”

“…Based on preliminary experimentation, filters were conditioned with the solution to be filtered before the actual sample for analysis was taken. Preliminary experimentation showed that the optimal procedure was a single conditioning for the conventionally dissolved Ag fraction, and a double conditioning for the truly dissolved Ag fraction (Bollyn et al 2018). Filtrates were acidified with aqua regia (12% HCl/4% HNO 3 ), and an additional digestion step (2 h of heating at 100 °C on an SCP Science DigiPREP MS heating block) was applied before Ag analysis to optimize Ag recovery.…”

“…To investigate this concern and to validate a read-across approach from ionic Ag to AgNPs, the fate and effects of the smallest nanoform covered in the Ag REACH registration dossiers (with the highest specific surface area) were compared with those of Ag nitrate (AgNO 3 ), as a reference soluble Ag compound. The results of the terrestrial research requested in the Ag substance evaluation have recently been published by Bollyn et al (2018); they showed that AgNPs do not exhibit greater toxicity than AgNO 3 at equivalent total soil Ag concentrations and that differences in Ag dissolution at least partially explain toxicity differences between the forms and among soils. For the aquatic element, an algae growth assay (according to Organisation for Economic Co-operation and Development test guideline 201 [2011]) and a D. magna reproduction assay (according to Organisation for Economic Co-operation and Development test guideline 211 [2012]) were requested by the Dutch Competent Authority.…”

Dissolved Oxygen and Visible Light Irradiation Drive the Structural Alterations and Phytotoxicity Mitigation of Single-Layer Molybdenum Disulfide

“…The synthesis of chlorophyll a and intracellular ROS was also not remarkably influenced by Na 2 MoO 4 (Figure S9b,c). The above results indicated different environmental risks than those derived from released Ag ions from Ag nanoparticles . One study found that the formation of abundant surface defects was beneficial for the antibacterial activity of nanomaterials (e.g., carbon materials and metal nanoparticles) on a Gram-negative bacterium ( E. coli ), and could also strengthen the toxicity of nanomaterials to organisms (RT–W1 cells and embryos) .…”

Monoalkyl Tin Nano‐Cluster Films Reveal a Low Environmental Impact under Simulated Natural Conditions

“…The Registration, Evaluation, Authorization and Restriction of Chemicals regulation dictates that chemicals and nanoparticles (NPs) sold in the European market in volumes greater than 1 ton per year must be characterized for potential impact on aquatic ecosystems (European Commission 2006). In addition, many researches have indicated that a chemical species in nanoscale could exhibit different bioavailability and toxicity from their bulk forms, such as ions and molecules (Böhme et al 2017;Jiang et al 2017;Bollyn et al 2018;Denluck et al 2018); therefore, it is particularly important to understand the potential environmental implications before scaling up for application. The aim of the present study was to determine whether monoalkyl tin clusters are environmentally friendly materials for largescale use in the semiconductor industry.…”