Retention of Sterically and Electrosterically Stabilized Silver Nanoparticles in Soils
2014
Hoppe, Martin | Mikutta, Robert | Utermann, Jens | Duijnisveld, Wilhelmus | Guggenberger, Georg
The current study investigated the interaction of sterically stabilized OECD standard Ag ENP (AgNM-300k) and silver ions (Ag⁺) in 25 German arable soils with varying properties (organic carbon concentration of 0.4–25 mg g–¹ and clay content of <0.1–392 mg g–¹) in 24 h batch retention experiments. A soil subset (n = 8) was investigated to test the soil interactions with citrate-stabilized Ag ENP (AgCN30). The adsorption of Ag⁺ was consistent with the Freundlich model with high KF values (mean KF = 2553 L kg–¹, n = 25), which suggested a high retention of Ag⁺. The retention of AgNM-300k followed a linear partitioning model and generally exhibited a low retention for the majority of the investigated soils (group 1, mean Kᵣ, ₗᵢₙₑₐᵣ = 3.7 L kg–¹, n = 19), and was correlated with the clay content (relation to log₁₀(Kᵣ, ₗᵢₙₑₐᵣ), r² = 0.40, n = 19). Soils showing a high retention of AgNM-300k (group 2, mean Kᵣ, ₗᵢₙₑₐᵣ = 1048 L kg–¹, n = 6) either had a low (<5.1) or high pH (>7.0) and generally contained >200 mg g–¹ clay. For the sample subset tested, AgCN30 and AgNM-300k were retained in similar dimensions regarding the same soils. The results suggest that the highest risk of long-term ENP mobilization exists when Ag ENP are applied to agricultural soils with low clay contents (<130 mg g–¹) and slightly acidic conditions.
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