Indexed on: 29 Sep '18Published on: 29 Sep '18Published in: Environmental Science & Technology
Ice-nucleating particles (INPs) associated with fresh waters are a neglected, but integral component of the water cycle. Abundant INPs were identified from surface waters of both the Maumee River and Lake Erie with ice nucleus spectra spanning a temperature range from -3°C to -20°C. The majority of river INPs were sub-micron in size and attributed to biogenic macromolecules, inferred from the denaturation of ice-nucleation activity by heat. In a watershed dominated by row-crop agriculture, higher concentrations of INPs were found in river samples compared to lake samples. Further, ice-nucleating temperatures differed between river and lake samples, which indicated different populations of INPs. Seasonal analysis of INPs that were active at warmer temperatures (≧ -10°C; INP]) showed their concentration to correlate with river discharge, suggesting a watershed origin of these INPs. A terrestrial origin for INPs in the Maumee River was further supported by a correspondence between the ice-nucleation signatures of river INPs and INPs derived from the soil fungus Mortierella alpina . Aerosols derived from turbulence features in the river carry INP, although their potential influence on regional weather is unclear. INP contained within aerosols generated from a weir spanning the river, ranged in concentration from 1-11 INP m, which represented a fold-change of 3.2 over average INP concentrations sampled from aerosols at control locations.