Physical-chemical characterization of CeO2 nanoparticles before and after interactions with roots of barley in hydroponic conditions Mattiello A.(1), Marchiol L.(1), Lynch I.(2) (1) Dipartimento di Scienze Agrarie e Ambientali – Università di Udine (2) School of Geography, Earth and Environmental Sciences – University of Birmingham Rationale Engineered nanoparticles (ENPs) are used increasingly in industrial and agricultural applications, consumer products and a variety of medical applications.[1-3] They are thus expected to enter the environment unintendedly and via various pathways, acting in an unknown manner on biota in soils and waters[4] (fig .1). Factors such as pH, ionic strength, light, temperature, water hardness, microorganisms, and natural organic matter (NOM) can influence the physical-chemical and biological transformation of the nanostructures and, on the other side, ENPs affect the organisms present in the accumulation compartment.[5] The physical-chemical characteristics of ENPs affecting both their toxicity and bioavailability to the organisms are: dissolution, agglomeration/aggregation state and size.[6]
Barley plants (Hordeum vulgare L.) were grown in a hydroponic system (fig. 2) with 50% Hoagland solution + 50 or 100 ppm of CeO2 nanoparticles (CeNPs) + 10 ppm gum arabic (GA) for 7 and 14 days by changing (C) or by leaving (NC) the treatment solution. The treatment solutions were analyzed by Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS) and differential Centrifugal Sedimentation (DCS) systems in order to check if their physical characteristics change and how these influence the uptake by inductively coupled plasma optical emission spectrometry (ICP-OES).
Figure 1: Estimated global mass flow of ENPs (t year-1) from production to disposal or release (Keller et al., 2014).
DLS CeNPs 100
16 14
Sol T0=825
12
Intensity (Percent)
Experimental Design
Sol T7=531
Pot T7=342
10
Pot T14 C=342
8
Sol T14=396
Pot T14 NC=342
6 4 2 0 10
100
Size (d.nm)
1000
10000
DCS CeNPs 100
100
Sol T0=260
Figure 2: Barley plants in hydroponic system into a climate chamber.
Results The DLS and DCS characterization data of the treatment solutions with CeNPs at 50 ppm are not displayed because they did not show differences between the treatment solutions in contact with the plants (Pot) and not in contact with them (Sol), on the contrary the treatment solutions at 100 ppm show differences between them (fig. 3). • DLS Treatment solution Sol the CeNPs tend to form smaller aggregates over time (T0= 825 nm, T7= 531 nm and T14= 396 nm); • DCS Treatment solution Sol the CeNPs tend to form bigger aggregates over time (T0= 260 nm, T7= 298 nm and T14= 326 nm); • DLS Treatment solution Pot the CeNPs remain stable over time (T7= 342 nm, T14 C= 342 nm and T14 NC= 342 nm); • DCS Treatment solution Pot the CeNPs tend to form smaller aggregates over time (T7= 260 nm, T14 C= 220 nm and T14 NC= 212 nm). The AFM and ICP-OES CeNPs data are not displayed because the analyses are still in progress.
Alessandro Mattiello Università di Udine Dipartimento di Scienze Agrarie e Ambientali (DiSA), Via delle Scienze, 206
Relative Light Absorption
90 80
Sol T7=298
Pot T7=260
70 Pot T14 C=220
60 50
Pot T14 NC=212
Sol T14=326
40 30 20 10 0 10
100
1000
10000
Particle Diameter (nm)
Figure 3: DLS and DCS data solutions characterization not in contact (Sol) and in contact (Pot) with plants.
Conclusions and Expected results In conclusion the preliminary results could demonstrate the capacity of the barley plants to keep the CeNPs more stable and avoid their agglomeration. This could be have an subsequent effect on the uptake of the CeNPs by plants.
References [1] F. Gottschak et al., 2014, Environ. Sci. Tech., 43:9216-9222. [2] H.H. Liu and Y. Cohen, 2014, Environ. Sci. Tech., 48:3281-3292. [3] B. Nowack et al., 2012, Environ. Toxicol. Chem., 31:50-59. [4] G.E. Schaumann et al., 2015, Sci. Total Environ., 535:3-19. [5] F. Mohd Omar et al., 2014, Sci. Total Environ., 468-469:195-201. [6] T. J. Baker et al., 2014, Environ. Pollut., 186:257-271
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