River Waters as a Source Of Ice Nucleating Particles
Vasenkari, Veera (2025-05-07)
River Waters as a Source Of Ice Nucleating Particles
(07.05.2025)
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
suljettu
Julkaisun pysyvä osoite on:
https://urn.fi/URN:NBN:fi-fe2025063076087
https://urn.fi/URN:NBN:fi-fe2025063076087
Tiivistelmä
Cloud-aerosol interactions are responsible for the largest uncertainties in estimates of Earth's changing energy budget. Since ice nucleating particles (INPs) are a prerequisite for primary ice formation in clouds at temperatures above -38 °C, they have a big impact on cloud phase and the radiative effect of clouds. While oceanic INPs have gained attention, freshwaters remain an underexplored INP source, despite evidence showing their INP concentrations can be up to 1000 times higher.
In this thesis, a seven-week measurement campaign was conducted at the Vanhankaupunginkoski (VKK) waterfall in the Vantaanjoki river to assess whether the VKK dam is a source of INPs. Continuous filter sampling provided airborne INP concentrations, while weekday water samples monitored river INPs. Additional data includes particle concentrations, meteorological parameters, and wind conditions. A bubble-generating chamber (BGC) was used to study INP emissions from bubble bursting under controlled conditions.
Airborne INP concentrations were slightly higher than at a comparison site and fluctuated mainly due to rain events, which likely aerosolized biological particles. Water INP concentrations were more uniform and comparable to those of other rivers, but slightly lower. Spearman’s correlation coefficient analysis linked rain events, higher flow rates, and increased INP concentrations, suggesting a watershed-derived biological INP source. BGC experiments confirmed that bubble bursting transfers INPs from water to air. In the controlled BGC setting, water INP concentrations were consistently about a million times higher than in the air as measured by filters. At the field site, variability was greater: low flow had the lowest airborne INPs, high flow resembled the controlled setting, and average flow had the highest airborne INPs, suggesting an additional INP source beyond the river. This was further supported by wind direction having little effect on airborne INP levels, indicating air masses did not transport INPs from the waterfall spray to the filters.
This project was done in collaboration with the Research Coordination group of the Finnish Meteorological Institute.
In this thesis, a seven-week measurement campaign was conducted at the Vanhankaupunginkoski (VKK) waterfall in the Vantaanjoki river to assess whether the VKK dam is a source of INPs. Continuous filter sampling provided airborne INP concentrations, while weekday water samples monitored river INPs. Additional data includes particle concentrations, meteorological parameters, and wind conditions. A bubble-generating chamber (BGC) was used to study INP emissions from bubble bursting under controlled conditions.
Airborne INP concentrations were slightly higher than at a comparison site and fluctuated mainly due to rain events, which likely aerosolized biological particles. Water INP concentrations were more uniform and comparable to those of other rivers, but slightly lower. Spearman’s correlation coefficient analysis linked rain events, higher flow rates, and increased INP concentrations, suggesting a watershed-derived biological INP source. BGC experiments confirmed that bubble bursting transfers INPs from water to air. In the controlled BGC setting, water INP concentrations were consistently about a million times higher than in the air as measured by filters. At the field site, variability was greater: low flow had the lowest airborne INPs, high flow resembled the controlled setting, and average flow had the highest airborne INPs, suggesting an additional INP source beyond the river. This was further supported by wind direction having little effect on airborne INP levels, indicating air masses did not transport INPs from the waterfall spray to the filters.
This project was done in collaboration with the Research Coordination group of the Finnish Meteorological Institute.