CHARACTERIZING THE MOLECULAR COMPOSITION OF EXTRACTABLE HUMIC MATERIAL IN A FARM SOIL AND LAKE DREDGED SEDIMENTS

Eutrophication is an ongoing environmental problem for the Lake Erie watershed. Over the last 20 years, the region has seen an increase in harmful algal blooms (HABs) of toxic cyanobacteria. The Maumee watershed discharging at the Western Lake Erie Basin (WLEB) is contributing to the HABs in part due to nutrient pollution and sediment erosion from intensive (50-80%) agricultural land use in the region. Sedimentation in the WLEB causes the need for frequent dredging of shipping channels in Toledo, OH, with over 800,000 cubic yards of dredged sediments (DS) removed annually to maintain the channels. Previous research has indicated that DS are beneficial as a farm soil amendment, as they are enriched in phosphate (PO₄^-3), nitrate (NO^3-), and soil organic matter (SOM). The largest component (>60%) of SOM is humic substances, which play a role in nutrient sorption and release and contribute to soil and plant health. The research objective of this study is to characterize the humic substances in farm soil and DS to gain insights on the relationship between PO₄^-3 and NO^3- sorption and the molecular composition of different humic fractions. SOM from farm soil and DS will be extracted using Humeomics, a sequential chemical extraction process. The extracted fractions will be characterized using FTIR, fluorescence spectroscopy, and Parallel Factor analysis (PARAFAC). Preliminary results from DS characterized with fluorescence spectroscopy showed the presence of several components including terrestrial humic-like and fulvic-like, and protein and tryptophan-like microbial compounds.