Molecular understanding of salt-induced selective aggregation and selective sorption of dissolved organic matter to natural and engineered particles
EMSL Project ID
50211
Abstract
Salt-induced aggregation and sorption of dissolved organic matter (DOM) to natural and engineered nanomaterial (NNM and ENM) surfaces occur widely in aquatic and terrestrial systems. Since DOM consists of a mixture of thousands of molecules, it may undergo fractionation upon salt-induced aggregation and/or sorption to NMs. Few studies have analyzed the bulk chemical properties of DOM molecules that remain in solution after aggregation or sorption to NMs. These studies provide valuable insights into the principle mechanisms of DOM aggregation by analyzing the bulk chemistry of DOM. However, detailed molecular-level composition and structural properties (e.g., degree of saturation, oxygen content, sulfur, and nitrogen) of DOM molecules susceptible to salt-induced aggregation and sorption by NMs remain scarce. Such detailed information on individual DOM molecules will greatly further our understanding of their resistance to coagulation or sorption to NNMs and ENMs. Such understanding is currently hampered by the high diversity and complexity of DOM and the limited resolution of the available mass spectrometers. Therefore, the overall aim of this proposed research is to determine DOM environmental behaviors by identifying DOM compounds susceptible to salt-induced aggregation and sorption to NNMs and ENMs as a function of DOM composition, salt type and NNM and ENM properties. This aim will be achieved by characterizing the molecular composition and properties of DOM molecules in solution (that is <10 kDa) before and after mixing with salts of Ca2+, Mg2+, Al3+, and Fe3+, and natural clay and metal and metal (Ag, Pt, Ti, Fe, Mn, Al, and Si) oxide NM using 21 T Electrospray ionization ultrahigh resolution-Fourier transform-ion cyclotron resonance-mass spectrometry (ESI-FT-ICR-MS) and nuclear magnetic resonance spectroscopy (NMR). The effect of DOM sorption on NM surface properties will be determined by X-ray photoelectron spectroscopy (XPS) and high resolution-transmission electron microscopy (HR-TEM) coupled with electron energy loss spectroscopy (EELS). The experimental data will be further underpinned by numerical simulations DOM-DOM molecules and DOM-NM interactions to explain 1) which DOM molecules selectively undergo aggregation and sorption, 2) why does these molecules undergo selective aggregation and sorption; that is what are the mechanisms determining these interactions, and 3) how does the selectively sorbed molecules impact NM surface properties.The requested analytical resources (e.g., ESI-FT-ICR-MS, and NMR) are necessary to achieve the proposed research objectives due to the complexity of DOM, which requires ultrahigh resolution mass spectroscopy techniques that are not available for the principal investigator at the University of South Carolina.
The outcome of the proposed research will significantly improve our understanding of numerous environmental and biological processes such as DOM environmental fate and transport, and consequently, the global geochemical cycle of carbon and contaminants with high affinity to DOM, carbon sequestration in soils, and effect of DOM of ENM environmental fate, uptake and toxicity. Furthermore, DOM selective sorption to ENM will significantly improve our understanding of the effect of DOM on NM surface properties (e.g., oxidation state, formation of core-shell particles), environmental interaction (e.g., aggregation and dissolution), and biological interactions (e.g., uptake and toxicity).
Project Details
Start Date
2018-05-01
End Date
2018-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Sikder, M.; Wang, J.; Poulin, B. A.; Tfaily, M. M.; Baalousha, M., Nanoparticle size and natural organic matter composition determine aggregation behavior of polyvinylpyrrolidone coated platinum nanoparticles. Environmental Science: Nano 2020, 7, (11), 3318-3332.