Probing Interactions at the Organic-Inorganic Interface of Biomass Burning Aerosol: Reactivity of Organic Tracer Species with Different Iron Oxide Mineral Phases.

As wildfire events become more frequent, there is a need to better understand the impact of smoke on the environment and human health. Smoke, or biomass burning aerosol (BBA), can undergo atmospheric processing changing its chemical and optical properties. We examined the interactions between four lignin pyrolysis products (catechol, syringol, syringic acid, and vanillic acid) and three BBA-relevant iron oxide mineral phases (hematite, maghemite, and magnetite) using attenuated total reflectance-Fourier transform infrared spectroscopy and dissolved iron measurements to better understand how atmospheric processing changes concentrations of soluble iron, iron oxidation state, and brown carbon abundance.

Role of Source, Mineralogy, and Organic Complexation on Lability and Fe Isotopic Composition of Terrestrial Fe sources to the Gulf of Alaska.

Iron (Fe) is a key trace nutrient supporting marine primary production, and its deposition in the surface ocean can impact multiple biogeochemical cycles. Understanding Fe cycling in the subarctic is key for tracking the fate of particulate-bound sources of oceans in a changing climate. Recently, Fe isotope ratios have been proposed as a potential tool to trace sources of Fe to the marine environment.

Estimating Excreted Nutrients to Improve Nutrient Management for Grazing System Dairy Farms.

Improving nutrient management in grazing system dairy farms requires determining nutrient flows through animals, the placement of cows within farms and potential for collection, and the re-use and loss of nutrients. We applied a model incorporating data collected at a range of temporal and spatial scales to quantify nutrient excretion in all locations that lactating herds visited on five days over a year on 43 conventional and organic grazing system dairy farms. The calculated nutrient loads excreted by cows in different places were highly skewed; while N, P and K deposited loads were consistent across the year, S, Ca and Mg loads varied between sampling times and seasons.

Titanium isotopes constrain a magmatic transition at the Hadean-Archean boundary in the Acasta Gneiss Complex.

Plate subduction greatly influences the physical and chemical characteristics of Earth's surface and deep interior, yet the timing of its initiation is debated because of the paucity of exposed rocks from Earth's early history. We show that the titanium isotopic composition of orthogneisses from the Acasta Gneiss Complex spanning the Hadean to Eoarchean transition falls on two distinct magmatic differentiation trends. Hadean tonalitic gneisses show titanium isotopic compositions comparable to modern evolved tholeiitic magmas, formed by differentiation of dry parental magmas in plume settings.