DOI: 10.17604/x1n6-r149
title: Total and soluble iron concentrations and particle size distributions from the Cumbre Vieja and La Soufriere volcanic eruptions

description: The file called Sample Total and Soluble Iron Concentrations.csv contains total iron content (by weight) and soluble iron content (presented both by weight and as nmol iron per gram material) in aerosol samples collected from three different volcanic eruptions and one mineral dust storm. This file also includes a column reporting the fractional solubility of iron in the samples. 
Particle size data for volcanic ash aerosol samples is reported in four different .csv files. Each file represents data collected using different methodology. 
The file called 30 Micron Aperture Particle Size Data.csv reports particle size measured with a Multisizer 4e Coulter Counter (Beckman Coulter) after samples were suspended in ISOTON II electrolyte, using a 30 µm aperture (accurate for the 0.69-17.9 µm size range) after a pre filtration step through a 20 µm nylon net filter. 
The file called 100 Micron Aperture Particle Size Data.csv reports particle size measured with the Coulter Counter after samples were suspended in ISOTON II electrolyte, using a 100 µm aperture (accurate for the 2.4-59.8 µm size range) after a pre filtration step through a 80 µm nylon net filter. 
The file called 200 Micron Aperture Particle Size Data.csv reports particle size measured with the Coulter Counter after samples were suspended in ISOTON II electrolyte, using a 200 micron aperture (accurate for the 4-120 µm size range) after no pre filtration step. Particle size for each sample in the three data files containing Coulter Counter data is reported as counts in size bins, averaged for triplicate measurements of each sample and blank sample. Blank samples consisted of ISOTON II electrolyte that had been pre filtered according to the sample pre filtration procedure. Standard error on the triplicate runs for each sample is also reported. 
The file called Nanoparticle Tracking Analysis Particle Size Data.csv contains particle size data for volcanic ash aerosol measured using Nanoparticle Tracking Analysis with a NanoSight™ LM10 (NanoSight Ltd., Amesbury, UK), which is reports sizes in the 1-973.9 nm size range. For this analysis, aerosol particles were suspended in MilliQ (18 MΩ ∙ cm) water and pre filtered through a 1.2 µm nylon membrane filter. Particle size is reported as particles per mL water in size bins. Replicate analysis completed on two different days were averaged for both samples and blanks. MilliQ served as a blank. Standard error for replicate analysis of the volcanic ash is also reported for both days of analysis.
description: This data includes total and soluble Fe concentrations in aerosol samples and particle size data for aerosol samples using a Coulter Counter or Nanoparticle Tracking Analysis from the manuscript “Composition and plume gas interaction control iron fractional solubility more than particle size in volcanic ash: Implications for fertilization of the North Atlantic”
Deposition of volcanic ash is thought to impact marine biogeochemical cycling by adding soluble iron (Fe) to the surface ocean. The magnitude of this input is a function of the amount of ash deposited, the total Fe content in the ash, and ash-derived Fe’s fractional solubility. However, the relative importance of chemical composition, acidic processing by the volcanic plume, and ash particle size in determining solubility is unclear. We paired an aerosol leach meant to provide an upper limit for fractional Fe solubility with chemical analyses of ash from the Cumbre Vieja and La Soufrière eruptions, which both impacted the North Atlantic in 2021. Fe in the ash samples is <6% soluble, but Fe fractional solubility in Cumbre Vieja ash is approximately triple that of La Soufrière ash. Compared to La Soufrière, a larger proportion of the Fe in Cumbre Vieja ash is in silicate rather than oxide minerals, which release more soluble Fe. Elevated levels of surficial fluorine (F) also suggest that Cumbre Vieja ash was subjected to a more fluorine-rich eruption plume and underwent more acidic processing. Particle size does not appear to be a primary control on Fe release. We estimate that the Cumbre Vieja eruption had a much larger impact on dissolved Fe (DFe) concentration in the surface ocean than the La Soufrière eruption due to differences in soluble Fe content and particle deposition velocity. These differences may help explain why some eruptions elicit a biological response in the ocean while others do not.  

This data is associated with the article: Elliott, H.E., Blades, E., Royer, H.M., Buck, C., Kollman, C., Kukkadapu, R., China, S., Cheng, Z., Lata, N.N., Engelhard, M., Bowden, M., Lahiri, N., Parham, R.L., Meagher, L., Angstman, B., Ault, A.P., Hornby, A., Dayton, K., Gazel, E., Gaston, C.J. Composition and plume gas interaction control iron fractional solubility more than particle size in volcanic ash: Implications for fertilization of the North Atlantic