Molecular characterization of dissolved organic matter components facilitating the transport and transformation of mercury
EMSL Project ID
50352
Abstract
Browning of surface water has been observed across the northeastern United States and northern Europe. This trend has generally been attributed to increases in dissolved organic matter following the onset of recovery from acid deposition, but some investigators have suggested that it could also be a manifestation of changing climate. In addition to acidification from acid deposition, remote forest ecosystems also experience mercury contamination originating from atmospheric mercury deposition. At Honnedaga Lake, located in the southwestern region of the Adirondack State park in New York, a watershed scale lime addition was conducted to accelerate the recovery of a chronically acidic tributary. Following this addition, significant increases in dissolved organic matter and specific ultraviolet absorbance at 254nm (SUVA) have been observed. These changes in dissolved organic matter have implications for the mobility and bioavailability of mercury. Dissolved organic matter is an important ligand influencing the transport of inorganic mercury and the transformation of inorganic mercury into methylmercury, the form which strongly bioaccumulates and biomagnifies up food webs. With this study, we aim to determine how changes in dissolved organic matter composition following lime addition reflect natural recovery from acid deposition at a molecular level. Quantification of changes in the quality of dissolved organic matter on a molecular level will help improve understanding of the dynamics of ecosystem function as larger less labile forms of dissolved organic matter limit the bioavailability of inorganic and methyl mercury. Given the complex nature of dissolved organic matter, advanced analytical techniques are necessary to determine compositional changes. Electrospray ionization (ESI) Fourier transform ion cyclotron resonance-mass spectrometry (FTICR-MS) has proven to be a superior analytical platform for this analysis because of its high resolution power and mass accuracy. By analyzing soil and water samples from lime-treated and reference watersheds, we hope to detect differences in the composition of dissolved organic matter and potentially identify complexes containing mercury. Identifying the changes in dissolved organic matter and mercury-dissolved organic matter complexes would inform policy decisions and mitigation strategies as acid-impacted ecosystems recover from chronic acidification from historical acid deposition but experience ongoing effects of atmospheric mercury deposition.
Project Details
Project type
Exploratory Research
Start Date
2018-10-21
End Date
2019-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members