Aerosol deposition is an important pathway for the delivery of bioactive trace elements (TE) to the open ocean. Quantifying the solubility of aerosol TE is essential to our understanding of the impacts of atmospheric deposition on marine productivity, yet is confounded by uncertainties with regard to sample storage (time and conditions) and how best to measure solubility. Short-term solubility experiments may not capture some less-reactive fractions that could become soluble over longer time scales in the ocean. The use of an extended seawater leaching scheme requires a supply of fresh, clean surface ocean seawater and is limited to those TE that can be quantified on small volumes of seawater. We will present data on the use of hot, dilute acetic acid (4.5 M) amended with 0.02M hydroxylamine (aka "Berger Leach") to quantify the solubility of a broad suite of TE from aerosol samples collected on the US GEOTRACES North Atlantic Zonal Transect and from Bermuda. The samples were stored both frozen and thawed for up to five years. Solubility from frozen filters using ultrapure water was tested over a 14-month period showing no significant loss of solubility. The Berger Leach was applied to frozen filters (stored 2-5 years) and thawed filters (stored up to 5 years) and showed no significant loss of solubility regardless of storage time or conditions. We conclude that the ultrapure water leach provides a lower limit estimate for aerosol TE solubility while the Berger Leach provides an upper limit estimate, thereby helping to constrain ocean biogeochemical models that include aerosol solubility.

Dissolved black carbon (DBC) is an important component in the global carbon cycle, and constitutes a significant portion of dissolved organic carbon (DOC) in aquatic systems. While global fluxes of DBC may be well understood, little is known about systematic processing of this carbon pool in fluvial systems. Similar to DOC, DBC composition may change as it moves throughout a river continuum before it is eventually deposited into the ocean. This is especially important for large river systems that are major sources of DOC to the ocean and may have significant impacts on ocean biogeochemistry and carbon cycling. To better understand variations in DBC dynamics throughout a large fluvial system, DBC was quantified using the benzene polycarboxylic acid method (BPCA) in three major tributaries of the Amazon River, each with varying biogeochemical characteristics. In some rivers, light availability appeared to influence both DBC quantity and composition. Higher concentrations of DBC characterized by a larger, more aromatic DBC pool was found in the Rio Negro, a black water river with high levels of chromophoric dissolved organic matter and low light penetration. In the Rio Tapajos, a clear water river with higher light penetration, lower DBC concentrations characterized by higher abundances of the less polycondensed DBC pool provided evidence of photodecomposition under such conditions. The Rio Madeira is characterized as a white water river with high suspended sediment yields rich in mineral clays and metals, such as iron. This river had the lowest DBC concentrations and also had less polycondensed DBC, suggesting a preferential adsorption of the more polycondensed DBC components onto clay particles or selective coprecipitation of high molecular weight DBC with iron oxides.

Furfural is considered one of the platform chemicals derived from the dehydration of xylose from biomass.  Selective transformations of furfural can lead to products relevant to biofuel as well as fine chemical industries.  Our work investigated the selective transformation furfural and furfuryl alcohol to ether and hydrogenation products in the liquid phase using light alcohol solvents.  The selectivity is attributed to a synergistic interaction between the supported Pd/C catalyst with metal halide additives acting as Lewis acids.  This presentation will hightlight our results from both ambient and high pressure conditions. By optimizing the reaction conditions, highly selective processes were identified.