Zahra Khodaparast

Many Portuguese pastures face a risk of desertification, but including biochar may enhance the soil sponge function and help mitigate this threat. This study examines biochar's climate change mitigation potential as a climate-smart management strategy. It examines its effects on GHG emissions and soil properties in hardsetting Portuguese pasture soil under current and projected rainfall conditions. Biochar was incorporated to a depth of 20 cm at a 3% gravimetric concentration in October 2022. The field site is a biodiverse sown pasture at the Quinta da França farm in Covilhã, Portugal. The two-factor experiment, i.e. biochar amendment and rainfall reduction, has four treatments: i) no biochar 100% rainfall; ii) no biochar 50% rainfall; iii) biochar 100% rainfall; iv) biochar 50% rainfall. The plots are installed in a random block design with five replicates (20 plots of 3 m × 3 m). GHG emissions, soil temperature, and soil moisture were monitored during the peak of the growing season in April 2024. The GHG emissions of N2O, CH4 and CO2 were monitored weekly in addition to the recorded data of soil temperature at +12 cm, soil surface and -6 cm (via TOMST sensor in each plot) and soil moisture up to -20 cm (via SENTEK sensor in each plot) at the day of the GHG sampling. The vegetation biomass was measured by sampling a random quadrant of the vegetation per plot. Overall, biochar and rainout shelters reduce CH₄ emissions compared to the control, though differences are not statistically significant. While both biochar application and reduced precipitation decrease CH₄ emissions, reduced precipitation has a larger effect than biochar. Reduced precipitation decreases soil moisture, slowing microbial activity and nitrogen transformations that can reduce NH₄ emissions from soil. Biochar-treated soils generally emitted less CO2 than control soils, with more considerable reductions observed on 17th and 24th April. Applying biochar reduced CO2 emissions by up to ≈26% (24th April). Biochar-treated soils generally emitted less N₂O than control soils, with more considerable reductions observed on the 17th and 24th of April. Applying biochar reduced N₂O emissions by up to ≈93.9% (24th April). However, responses varied, with bochar 100% rainfall occasionally showing smaller reductions or slight increases (30th April). Biochar can disrupt the processes of nitrification and denitrification that generate N₂O, making biochar an effective strategy for mitigating greenhouse gas emissions. The data analysis is underway to determine the correlation between GHG and temperature and soil moisture. This work is part of the TRUESOIL project, True SOC sequestration: understanding trade-offs and dynamic interactions between SOC stocks and GHG emissions for climate-smart agri-soil management. Thus, the sequestered soil organic carbon (SOC) and the C locked in the biomass (NEE) will be analysed.

Climate change models indicate that pastoral land use in many parts of Iberia will no longer be feasible from 2050 due to rainfall decreases and desertification, thereby negatively affecting soil functioning, food security and rural livelihoods. Amending agricultural soils with biochar (carbon-based product of biomass pyrolysis) has been shown to potentially increase crop yield, mainly by improving soil pH, soil structure, water storage and exchange. The aim of this study was to quantify how biochar may alter the soil sponge function under current (100% rainfall) and future (50% rainfall.The collaborative work between ongoing projects SOILCOMBAT, POLLINATE and TRUESOIL, aims to sustainably engineer the soil-water regulation function of Portuguese pasture soils, while minimizing detrimental effects on other soil quality parameters through the use of biochar for soil amendment. Our approach was a random block design field-trial in a real-world scenario at the Quinta da França farm (Terraprima, Portugal), a non-irrigated sown biodiverse pasture on a dystric Cambisol. The four treatments are: control 100% rainfall; control 50% rainfall; biochar (3% gravimetric) 100% rainfall; biochar (3% gravimetric) 50% rainfall; N=20). Biochar-amendment-treatments were applied at 0-20 cm depth keeping the 20-60 cm depth unaltered. It is five times replicated. Plots were equipped with soil climate sensors (volumetric moisture and temperature) recording at six depths, namely -5, -15, -25, -25, -45 & -55 cm depth (N=120).The first 2 years of the on-going field trial at Quinta da França showed that for the treated 0-20 cm depth with 50% rainfall, the biochar plots kept 15% more moisture than the control ones, while for 100% rainfall conditions, biochar plots kept 23% more moisture. The results for deeper soil water storage (20-60 cm depth) showed that for the 50% rainfall, the biochar plots have 24% less moisture than the control ones, while for natural rainfall conditions, biochar plots have 19% less moisture than the control ones. This could indicate that the 0-20 cm depth biochar-amended soil layer, keep more water in surface (0-20 cm depth) than non-amended surface soil. Seasonal effects will be explored further.We conclude that biochar amendments improve the soil-water regulation functions of this pasture. The results are expected to contribute to the UN Sustainable Development Goals (SDG) #13 and #15, namely sustainable food production and climate adaptation of pastoral ecosystems, while combating desertification. AcknowledgementsWe acknowledge the Portuguese Foundation for Science and Technology FCT/MCTES for the funding of CESAM (UIDP/50017/2020+UIDB/50017/2020+LA/P/0094/2020) through national funds, as well as of projects SOILCOMBAT (https://doi.org/10.54499/PTDC/EAM-AMB/0474/2020), POLLINATE (https://doi.org/10.54499/PTDC/EAM-AMB/1509/2021), and of authors F. Verheijen (https://doi.org/10.54499/CEECIND/02509/2018/CP1559/CT0004), A.C. Bastos (art. 23º DL57/2016 of 29 Aug amended by DL 57/2017 of 19 July, OE), P. Quinteiro (CEEC/00143/2017), B. Gholamahmadi’s (PhD grant2020.04610.BD), L Simões (PhD grant 2022.09866.BD). We also acknowledge the European Commission Joint Programme SOIL for the funding of project TRUESOIL (https://doi.org/10.54499/EJPSoils/0001/2021) and the La Caixa Foundation in collaboration with CESAM for the funding of A. Jelinčić(LCF/BQ/DI22/11940011).

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a method with high potential to visualize the distribution of elements in different samples, including a variety of organisms. This study aimed to demonstrate the broad application of LA-ICP-MS in nanomaterial-biota fate studies as a high throughput bioimaging tool and to broaden the choice of standard organism models in material-biota interaction research. In this study, operation parameters of LA-ICP-MS were optimised on one organism, woodlice Porcellio scaber. Subsequently, the scanning conditions were tested on a range of aquatic (Girardia tigrina, Lumbriculus variegatus, and Oncorhynchus mykiss), terrestrial organisms (Lumbricus rubellus, Porcellio scaber) and one plant (Triticum aestivum) upon exposure to Ag₂S nanoparticles (NPs) and silver nitrate (AgNO₃). Model organisms were exposed in aquatic or terrestrial mesocosm experiments where nominal concentrations of Ag were 10 μg Ag per L of water and 10 mg Ag per kg of soil, respectively. The results showed that both sample preparation and LA-ICP-MS imaging conditions, as optimized on the selected organism (65 μm laser diameter, scan rate 100 μm s⁻¹, measuring duration 35 min), are applicable on different tissues. These LA-ICP-MS imaging conditions enable recognition of the main biological structures and biodistribution of elements of interest. By using fast-screening LA-ICP-MS, we confirmed the presence of Ag₂S NPs on the body surface or in the gut lumen (adsorbed and retained), but not in other internal parts of organisms, which is consistent with our previous toxicokinetic studies. The presence of Ag was also confirmed in some parts of wheat roots. The advantage of this technique is the possibility of sequential use of fast- and slow-scanning steps to optimise the duration of analysis and data processing, whilst also improving cost-effectiveness without compromising the quality of results.

Quantification of the uptake and elimination of nanomaterials (NMs) by organisms is key in assessing the environmental risks of NMs. For this, uptake models for conventional solutes may be used, although no consensus exists on their applicability for NMs. In this critical review therefore, conventional modelling approaches are scrutinised for their applicability for NMs. Statically derived accumulation factors, like BCF or BAF based on measured concentrations, are considered to be flawed because NMs are thermodynamically not stable, an important assumption for this approach. Dynamically derived accumulation factors, based on kinetic exposure experiments, may be applicable because no equilibrium between the organism and exposure medium is needed. Currently there is no full understanding of the passive uptake of NMs, which hampers assessment of the applicability of biotic ligand models. Passive uptake, however, is generally considered to be very limited, which would imply a limited applicability of BLMs for NMs. Physiologically based pharmacokinetic (PBPK) models, or biodynamic models, have successfully been applied in uptake studies with NMs. Their underlying assumptions can be met in experiments addressing NMs and case studies presented in this review demonstrate their applicability to model NM-form specific kinetics, integrated with environmental fate models, including relevant physiological processes. Their application requires the a priori definition of the major mechanisms driving the uptake kinetics and the quantification of the associated kinetic rate constants. This limits their application to those mechanisms for which the kinetic rate constants can actually be quantified. Within these limitations, PBPK models have been shown to be applicable and provide a promising general approach to improve modelling of NM-accumulation in organisms.