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Fly bioash (FBA) as a by-product of biomass-fuelled facilities exhibits alkaline properties and is enriched with phytonutrients, thereby offering the potential to effectively ameliorate acidic and nutrient-deficient soils. However, concerns about health risks due to a potential FBA radioactive contamination are still not well studied, notably under field conditions. This study examined pH changes and concentrations of natural (238U, 232Th, 226Ra, 40K) and anthropogenic (137Cs) radionuclides after application of very alkaline (pH > 12) FBA in: (i) highly acid (pHKCl = 4.1) Luvisol and (ii) sunflower (Helianthus annuus L.) seeds, grown in organic farming and rain-fed conditions. FBA (originated from a modern cogeneration, fuelled on certified deciduous forest wood chips) was applied at increasing doses; 0, 4.5, 8.6, 13, and 17.2 t/ha. After 54 months of application, FBA significantly increased soil pHKCl by up to 1.8 unit and the seed yield by 15%, compared with no amended Control, without compromising soil electrical conductivity (salinity). The activity concentrations (Ac) of all observed radionuclides, measured using high-resolution gamma-ray spectrometry, were not altered under FBA application, neither in the surface (0–30 cm) Luvisol horizon nor in the sunflower seed. Moreover, the Ac of 238U, 232Th, and 137Cs in the seed were below detection limit, whereas the Ac of 40K and 226Ra were lower by up to 2.6 and 61 times, respectively, than their corresponding Ac in the soil treatments. The radiological footprint of FBA exhibited lower Ac for most of the observed radionuclides compared with both (i) Croatian non-arable topsoils (with reductions of 238U 3.6 times, 232Th 1.8 times, 226Ra 1.7 times, and 137Cs 1.5 times) and (ii) widely used mineral N/P/K fertilisers in conventional agroecosystems (with reductions of 238U 12.5 times; 226Ra 1.3 times, and 40K 2.4 times). Our findings provide evidence that the application of FBA as a soil conditioner does not pose radiological health or environmental risks, contributing to more sustainable agri-food production and circular bioeconomy. However, it is essential to conduct further studies to comprehensively investigate the effects of FBA application on soil and crop quality across diverse environmental conditions and extended spatiotemporal scales. [ABSTRACT FROM AUTHOR]

One of negative side-effects of usage of bio-renewables might be generation of mineral (ash) material, potential source of environmental pollution. A hypothesis was that bottom ash (BA; from biomass cogeneration facility) could be efficiently (re) used in soil chemical conditioning similarly to widely-used dolomite-based soil conditioner (DO; from Croatian Dinaric-coastal region) which we tested by: i) physicochemical characterisation of BA and DO, and ii) bioassay with Raphanus sativus cultivated in acidic soil amended with BA or DO. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) confirmed complex chemical/physical structures and morphology between amendments, X-ray diffraction (XRD) showed their distinctive mineralogy with predominantly dolomite (in DO) vs. quartz and calcite (in BA), while secondary ion mass spectrometry (SIMS) revealed their diverse elemental/isotopic composition. The BA or DO amendments ameliorated soil acidity, increased available P, K and most other nutrients, but not Cd. The BA or DO amendments improved vegetative growth and edible hypocotyl yield. However, both amendments also increased Cd accumulation in all radish tissues, which was unexpected given the alkaline matrix of bio-ash and dolomite that would be likely to facilitate retention and immobilisation of toxic Cd. Thus, thorough characterisation and evaluation of BA- and/or DO-based materials and relevant soils (with an emphasis on metal sorption/immobilisation) prior to application in (agro) ecosystems is crucial for producing food clean of toxic metals. Unlabelled Image • Biomass bottom ash (BA) & dolomite (DO) are very alkaline (pH KCl = 10.2–11.2) matrices. • BA & DO ameliorated soil acidity quickly (by >1.5 pH units) & nutrient availability. • BA & DO improved radish vegetative growth & nutrition accumulation. • BA & DO increased Cd uptake and accumulation in all radish tissues. [ABSTRACT FROM AUTHOR]

Biomass-fuelled facilities generate alkaline and mineral-/nutrient-enriched co-product (ash) that has to be appropriately managed, and preferably reused. The assumption that wood biomass fly ash (BFA) could be used in chemical amelioration of soil acidity and fertility was tested by: i) physicochemical characterisation of BFA and ii) bioassay with maize grown in acidic (pH KCl 4.68) hydromorphic soil amended with BFA (0–10% w/w). Scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction revealed non-homogeneous (ir)regular spherical/porous agglomerated particle morphology and distinctive distribution of Si-/Ca-/K-based minerals, while secondary ion mass spectrometry, for the first time, confirmed their isotopic (six Ca, three Si/Mg and two K isotopes) diversity. BFA addition strongly shifted soil pH KCl (up to 9.1), raised salinity (by > 8.2-fold) and the content of most phytonutrients (up to 5.4-fold); however, BFA amendments at >1.25% restricted the maize root and shoot growth, likely due to alkaline stress as indicated by necrotic/chlorotic symptoms at >5.0% rate. The BFA amendments increased total concentration of metals in soil (without exceeding the levels recognised as contamination); however, phytoextraction of Cd, Zn, Mn, Cu and Mo was significantly supressed (Cd by almost 12-fold), confirming that BFA improved soil-plant metal immobilisation, shifting rhizosphere biogeochemistry towards chemisorption/precipitation reactions. Even though results revealed a strong liming and P–K–Ca–Mg–Zn–Mn–Cu enrichment potential of BFA, to avoid possible negative environmental implications (saline/alkaline stress, metal contamination, adverse effects on soil microbiome), quantitative and qualitative ex ante evaluation of the BFA/soil matrix combinations is essential before application to ameliorate suboptimal (acidic, low-nutrient) or metal-contaminated soils. Image 1 • Wood biomass fly ash (Bio-ash) is alkaline (pH water eluate >12.5) inorganic matrix. • Bio-ash increased pH (by > 2 units) of acidic hydromorphic soil. • Bio-ash is a potential inorganic nutrient- and mineral-rich soil conditioner. • Bio-ash at ≤1.25% w/w enhanced maize growth and at 5–10% w/w induced alkaline stress. • Bio-ash immobilised Cd, Cu and Zn in acidic hydromorphic soil. [ABSTRACT FROM AUTHOR]

Erosion has been reported as one of the top degradation processes that negatively affect agricultural soils. The study objective was to identify hydropedological factors controlling soil water dynamics in erosion-affected hillslope vineyard soils. The hydropedological study was conducted at identically-managed Jastrebarsko (location I), and Jazbina (II) and (III) sites with Stagnosol soils. Soil Hydraulic Properties (SHP) were estimated on intact soil cores using Evaporation and WP4C methods; soil hydraulic functions were fitted using HYPROP-FIT software. For Apg and Bg/Btg horizons, uni- and bimodal soil hydraulic models could be well fitted to data; although, the bimodal model performed better in particular cases where data indicated non-uniform pore size distribution. With these SHP estimations, a one-year (2020) water flow scenario was simulated using HYDRUS-1D to compare water balance results obtained with uni- and bimodal hydraulic functions. Simulation results revealed relatively similar flux distribution at each hillslope position between the water balance components infiltration, surface runoff, and drainage. However, at the bottom profile at Jastrebarsko, bimodality of the hydraulic functions led to increased drainage. Soil water storage was reduced, and the vertical movement increased due to modified soil water retention curve shapes. Adequate parameterization of SHP is required to capture the hydropedological response of heterogenous erosion-affected soil systems. [ABSTRACT FROM AUTHOR]