OHNO2 - The origin of nitrous acid (HONO) emissions from northern soils and linkages to nitrogen cycle processes

Principal investigator: Assoc. Prof. Marja Maljanen

Funding period: Finnish Academy, 2016-2020

The main goal of the project is to study the unknown HONO (nitrous acid) emissions from northern ecosystems. The principal scientist of this project is Associate professor Marja Maljanen from biogeochemistry group. The other bgc group members involved in the project are University researcher Hannu Nykänen, Post Doc researcher Maarit Liimatainen and PhD student Hem Raj Bhattarai. This study is made in co-operation with the Department of Applied Physics (Pasi Yli-Pirilä and Jorma Joutsensaari).

HONO is a significant photochemical precursor for hydroxyl radical (OH), which is one of the main agents removing e.g. methane from the atmosphere. Recently it was found that soils can be sources of HONO, but the mechanisms of HONO production in soils are still unknown as well as HONO emission rates from different ecosystems.

In this project we explore the mechanisms and environmental factors affecting HONO emissions from northern soils and try to understand the mechanisms and conditions favoring HONO production in soils. We hypothesize that all soils with high N2O emissions emit also HONO at high rate (e.g. drained peatlands, N-fertilized agricultural soils). Our hypothesis is that NO2- formed in nitrification (ammonium oxidation) is the key microbial process for the HONO production but also denitrification can be source of NO2-. Also the environmental conditions (moisture, pH) can affect HONO production. Field measurements and laboratory experiments will be carried out to achieve the goals.