Objectives of the work package: WP5 will assess the effects of MNP and MesoP alone (SO4) and combined with other stressors (SO5) on soil quality as indicated by physical and chemical properties, and by crop growth dynamics and yield. Analysis will be performed at the CSS, at samples collected from pot and field experiments described in T4.1 (complementing WP4) (SO2) and at samples from targeted experiments providing answers to specific scientific questions. A series of research tasks will (a) assess impact on soil physical properties (T5.1); (b) model impact on MNP preferential flow and soil matrix (T5.2) (SO6); (c) assess impacts on soil chemical properties (T5.3); (d) assess the impact on plant physiology and crop production (T5.4); and (e) determine NP plant uptake and assess the risk for food trophic chain. To study the impact of MNP on selected soil types, WP5 will collaborate with the monitoring plan compiled in WP2 and definition of methods of soil sampling and soil analysis in collaboration with WP3 (sampling sites selection). Data obtained in WP5 will be stored in an online database (T2.4) accessible to all project partners and farmers included in the project. Unified soil sampling strategies and experimental design with WP3, WP4 and WP6 will be used.
Task 5.1 Assessment of the impact of MNP and other stressors on soil physical properties: Task leader: UL | Participant(s): WU, CDEUB, UCSC | Timing: M12-48, The focus of T5.1 will be on soil physical properties related to soil water. The impact of the type of plastic additives, plastic particle size and their concentration, with and without other stressors on soil physical properties will be determined in pot and field experiments described in T4.1 and shared with WP4. Selected soil physical properties will be assessed in both experimental scales including: (a) soil aggregate stability, aggregate size distribution (UCSC); and (b) texture structure, bulk density, pore size distribution, hydraulic conductivity, infiltration, soil water retention, and soil water repellency (UL). Measurements of soil water content (dielectric sensors), tension, and simulation of the soil water availability for plants will be performed on selected treatments of experimental platforms (T4.1) and targeted lab and pot experiments (UL). Results will contribute to other WP5 tasks and to WP4, WP6 and WP7.
Task 5.2 Modelling transport of MNP and other stressors in the soil profile: Task leader: CDEUB | Participant(s): UL, WU, CSS partners | Timing: M12-48, This task will measure and model advanced physical properties (e.g. soil water dynamics) in combination with soil biota reaction and activity on representative soils types from selected fields (CSS). We will investigate the degree of preferential flow qualitatively (CDEUB, UL) (e.g., using dye tracer experiments) (T6.1) and quantitatively by analysing the amount of MNP in the soil columns in the laboratory (WU) (T6.3), examining adsorption by tomography at the aggregate scale, and modelling at the profile scale. The aim is to improve understanding of NP transport in soils and to gain insights into the principal physicochemical mechanisms as well as the experimental conditions (e.g. degree of saturation, flow rate, particle concentration, and size) governing their mobility and retention. Modelling (CDEUB) of NP will be done using two different models: (i) a transfer model based on fractionation of water into mobile and immobile fractions coupled with the attachment/detachment model; and (ii) Hydrus 1D. Modeling results will be validated against data generated in T6.3. Our outcomes will contribute to T5.3, T5.4, T4.4, T6.3, and WP7.
Task 5.3 Assessment of the impact of MNP and other stressors on soil chemical properties: Task leader: WU | Participant(s): AGES, CDEUB, UL, NVM | Timing: M12-54, The focus of T5.3 will be on understanding how MNP will interfere in soil biogeochemical processes (C, N, P cycles), supporting WP4 on the interpretation of data regarding effects on soil functional microbial groups involved in nutrient cycling (T4.2), and soil chemical properties as pH, EC or nutrients availability, which might be affected by MNP with/without organic stressors. Effects will be determined at different experimental scales in accordance with T4.1 description as follows: Pot experiments: soil chemical properties which might affect or be affected by the soil biota group targeted will be determined (i.e. NH4, NO3 levels – AOM, Denitrifiers; Phosphorus, EC – AMF; pH – all biota groups) (WU, CDEUB, UL, NVM); Field experiments: soil chemical parameters that will allow to give a complete picture about the fate and effects of MNP in agricultural soils and support WP4 on interpretation of effects on the soil biota (UBERN-CDEUB) (i.e. pH, EC, NH4, NO3 SO4 levels etc). Results will contribute to the T5.4, WP4, WP6, and WP7.
Task 5.4 Assessment of the impact of MNP and other stressors on crop physiology and productivity: Task leader: FiBL-CH | Participant(s): AGES, UL, UCSC, NVM | Timing: M12-54, This task aims to analyse the response of selected crop plants (highest coverage in CSS) to MNP. This will be addressed in pot and field experiments described in T4.1, regarding: (i) crop growth dynamics: crop parameters that are potentially responding to increasing loads of MNP in soils and analyse plant growth from the germination to the cropping phase will be measured; (ii) crop plants physiology: critical MNP loads for plant growth at physiological level (e.g. throughout plant life cycle) will be identified, to be used as input parameters in field experiments. Additional Pot experiments will be carried out to assess “multi-stress” combinations (i. e. MNP in addition with drought) on plant performance (UCSC). This task will combine information from WP4, WP5 and WP6 and prepare a thorough assessment of MNP impact on the crop dynamics and crop growth in relation to soil health and fertility. Results will contribute to the Task 5.5, WP6 and WP7.
Task 5.5 NP plant uptake and risk characterization for the human food chain: Task leader: GIUB | Participant(s): UCSC, | Timing: M12-54, The uptake of NP by plants will be analysed to link NP – plant interaction to physiology. Nanoparticles can be taken up via the root or via the leaves but are little translocated in the plant. Fluorescence-labelled and metal-labelled NP will be added to the soil in targeted pot experiments and applied to the leaves (to simulate NP deposition) in the experiments used in task 5.4 to assess plant physiological parameters. The transfer of NP into plants and the risk for food chain transfer will be assessed from NP uptake in edible plant parts (GIUB, USCS). Results will contribute to the WP6 and WP7.
Deliverable 5.1: Effects of the MNP on the soil physical properties related to soil water [M48, UL, R, PU] Deliverable 5.2: Report of modelling transport of MNP in soil [M48, CDEUB, R, PU] Deliverable 5.3: Effects of MNP on the soil chemical properties [M54, WU, R, PU] Deliverable 5.4: Impact of MNP on crop productivity and plant physiology [M54, FiBL-CH, R, PU] Deliverable 5.5: NP plant uptake and transfer to the food chain – Calculation of threshold values for health risk [M54, GIUB, R, PU]