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Bone matrix formation and mineralization are two closely related, yet separated processes. Matrix formation occurs first, mineralization is a second step strictly dependent on the dietary intake of calcium and phosphorus (P). However, mineralization is commonly used as diagnostic parameter for bone-related diseases. In this context, bone loss, often characterized as a condition with reduced bone mineral density, represents a major burden for human health, for which increased dietary mineral intake is generally recommended. Using a counterintuitive approach, we use a low-P diet followed by a sufficient-P intake to increase bone volume. We show in zebrafish by histology, qPCR, micro-CT, and enzyme histochemistry that a two-months period of reduced dietary P intake stimulates extensive formation of new bone matrix, associated with the upregulation of key genes required for both bone matrix formation and mineralization. The return to a P-sufficient diet initiates the mineralization of the abundant matrix previously deposited, thus resulting in a striking increase of the mineralized bone volume as proven at the level of the vertebral column, including vertebral bodies and arches. In summary, bone matrix formation is first stimulated with a low-P diet, and its mineralization is later triggered by a sufficient-P dietary intake. In zebrafish, the uncoupling of bone formation and mineralization by alternating low and sufficient dietary P intake significantly increases the bone volume without causing skeletal malformations or ectopic mineralization. A modification of this approach to stimulate bone formation, optimized for mammalian models, can possibly open opportunities to support treatments in patients that suffer from low bone mass. Lay Summary: Bone loss, typically associated to bone fragility, represents a major burden for human health. Bone is constituted by an organic collagen scaffold undergoing mineralization. In physiological conditions, the ratio between mineral content and collagen matrix ensures optimal bone properties. An increased mineral amount compared to the deposited matrix results in bone loss and fragility. Stimulating the formation of new bone matrix prior its mineralization will increase the collagen scaffold volume, paving the way for increased bone volume upon mineral deposition. In this context, we show that in zebrafish reduced dietary phosphorus intake for a limited time stimulates the formation of large amounts of non-mineralized bone matrix. The newly formed bone matrix resumes mineralization upon sufficient dietary phosphorus intake, thus resulting in significantly increased mineralized bone volume. The modulation of phases of different dietary phosphorus intake, when optimized on mammalian models, has the potential to unlock new strategies in the treatment of bone diseases, as it could eventually help to increase the bone volume in patients without, or in addition to, pharmacological intervention. Graphical Abstract [ABSTRACT FROM AUTHOR]

Biogenic volatile organic compounds (BVOCs) are emitted by vegetation and react with other compounds to form ozone and secondary organic matter (OM). In regional air quality models, biogenic emissions are often calculated using a plant functional type approach, which depends on the land use category. However, over cities, the land use is urban, so trees and their emissions are not represented. Here, we develop a bottom-up inventory of urban tree biogenic emissions in which the location of trees and their characteristics are derived from the tree database of the Paris city combined with allometric equations. Biogenic emissions are then computed for each tree based on their leaf dry biomass, tree-species-dependent emission factors, and activity factors representing the effects of light and temperature. Emissions are integrated in WRF-CHIMERE air quality simulations performed over June–July 2022. Over Paris city, the urban tree emissions have a significant impact on OM, inducing an average increase in the OM of about 5 %, reaching 14 % locally during the heatwaves. Ozone concentrations increase by 1.0 % on average and by 2.4 % during heatwaves, with a local increase of up to 6 %. The concentration increase remains spatially localized over Paris, extending to the Paris suburbs in the case of ozone during heatwaves. The inclusion of urban tree emissions improves the estimation of OM concentrations compared to in situ measurements, but they are still underestimated as trees are still missing from the inventory. OM concentrations are sensitive to terpene emissions, highlighting the importance of favoring urban tree species with low-terpene emissions. [ABSTRACT FROM AUTHOR]

The composition of soil dust aerosols derives from the mineral abundances in the parent soils that vary across dust source regions. Nonetheless, Earth system models (ESMs) have traditionally represented mineral dust as a globally homogeneous species. The growing interest in modeling dust mineralogy, facilitated by the recognized sensitivity of the dust climate impacts to composition, has motivated state-of-the-art ESMs to incorporate the mineral speciation of dust along with its effect upon the dust direct radiative effect (DRE). In this work, we enable the NASA Goddard Institute for Space Studies ModelE2.1 to calculate the shortwave (SW) DRE accounting for the regionally varying soil mineralogy. Mineral–radiation interaction at solar wavelengths is calculated according to two alternative coupling schemes: (1) external mixing of three mineral components that are optically distinguished, one of which contains embedded iron oxides; (2) a single internal mixture of all dust minerals with a dynamic fraction of iron oxides that varies regionally and temporally. We link dust absorption to the fractional mass of iron oxides based on recent chamber measurements using natural dust aerosol samples. We show that coupled mineralogy overall enhances the scattering by dust, and thus the global cooling, compared to our control run with globally uniform composition. According to the external mixing scheme, the SW DRE at the top of atmosphere (TOA) changes from -0.25 to -0.30Wm-2 , corresponding to a change in the net DRE, including the longwave effect, from -0.08 to -0.12Wm-2. The cooling increase is accentuated when the internal mixing scheme is configured: the SW DRE at the TOA becomes -0.34Wm-2 with a net DRE of -0.15Wm-2. The varying composition modifies the regional distribution of single scattering albedo (SSA), whose variations in specific regions can be remarkable (above 0.03) and significantly modify the regional SW DRE. Evaluation against the AErosol RObotic NETwork (AERONET) shows that explicit representation of soil mineralogy and its regional variations reduces the low bias of model dust SSA while improving the range of variability across stations and calendar months. Despite these improvements, the moderate spatiotemporal correlation with AERONET reveals remaining modeling challenges and the need for more accurate measurements of mineral fractions in soils. [ABSTRACT FROM AUTHOR]

Mineral dust aerosol is an important contributor to the Earth climate system and the correct representation of its size distribution is fundamental for shaping the current state and the evolution of climate. Despite many observational dust size data are available in the literature, using this body of information to proper guide the development and validation of climate models and remote sensing retrievals remains challenging. This is due to the diverse nature of different data, both in terms of measurement methods, diameter definitions, sampled concentrations and data treatments, leading to inherent heterogeneities. In this study we collect, evaluate, harmonize, and synthetize 58 size distribution data from the past 50 years of in situ field observations with the aim of providing a consistent dataset to the community to use for constraining the representation of dust size across its lifecycle. Four levels (LEV) of data treatment are defined, going from original data (LEV0), data interpolated and normalized on a standardized diameter path (LEV1), and data in which original particle diameters are converted into a common geometrical definition under both spherical (LEV2a) and aspherical (LEV2b) assumptions. Size distributions are classified to be representative of emission/source (SOURCE, <1 day from emission; number of datasets in this category, N=12), mid-range transport (MRT, 1-4 days of transport; N=36) and long-range transport (LRT, >4 days of transport; N=10). The harmonized dataset shows consistent features in the shape of the dust size distribution suggesting the conservation of airborne particles with time: a main mode located at ~10 µm (in volume) is observed for SOURCE dust, decreasing to ~5 µm and ~2 µm for MRT and LRT conditions, respectively, for which an additional mode becomes evident below 0.4 µm. Data for the three levels (LEV1, LEV2a, LEV2b) and the three categories (SOURCE, MRT, LRT), together with statistical metrics (mean, median, 25% and 75% percentiles, and standard deviation) are made available as: SOURCE (https://doi.org/10.57932/58dbe908-9394-4504-9099-74a3e77140e9; Formenti and Di Biagio, 2023a); MRT (https://doi.org/10.57932/31f2adf7-74fb-48e8-a3ef-059f663c47f1; Formenti and Di Biagio, 2023b); LRT (https://doi.org/10.57932/17dc781c-3e9d-4908-85b5-5c99e68e8f79; Formenti and Di Biagio, 2023c). [ABSTRACT FROM AUTHOR]