Terrestrial Origin for Abundant Riverine Nanoscale Ice-Nucleating Particles.

Area of Science:

• Environmental Science
• Atmospheric Science
• Hydrology

Background:

• Ice-nucleating particles (INPs) are crucial for cloud formation and precipitation.
• Freshwater INPs are understudied despite their integral role in the water cycle.
• Agricultural watersheds may significantly contribute to freshwater INP concentrations.

Purpose of the Study:

• To quantify and characterize INPs in the Maumee River and Lake Erie.
• To investigate the origin and seasonal variability of freshwater INPs.
• To assess the potential role of terrestrial sources, like soil fungi, in freshwater INPs.

Main Methods:

• Collected surface water samples from the Maumee River and Lake Erie.
• Analyzed INP concentrations and ice nucleation spectra across a temperature range (-3 to -15 °C).
• Used heat denaturation to infer the biogenic nature of INPs and compared signatures with soil fungus Mortierella alpina.

Main Results:

• Abundant INPs were found in both river and lake waters, with higher concentrations in the river.
• River INPs were predominantly submicron, biogenic macromolecules, active at warmer temperatures (INP_-10).
• INP_-10 concentrations correlated with river discharge, indicating a watershed origin, and were found in river aerosols.

Conclusions:

• The Maumee River watershed is a significant source of freshwater INPs, particularly biogenic macromolecules.
• Terrestrial sources, including soil fungi, likely contribute to the INP population in freshwater systems.
• Further research is needed to clarify the atmospheric transport and regional weather impact of INPs from freshwater aerosols.