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| Titel |
Reactive nitrogen fluxes and gas-aerosol interactions above a semi-natural forest in the Po Valley, Italy |
| VerfasserIn |
Marsailidh Twigg, Chiara Di Marco, Ben Langford, Benjamin Loubet, Giacomo Gerosa, Angelo Finco, Mark Sutton, Eiko Nemitz |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148018
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| Publikation (Nr.) |
 EGU/EGU2017-12243.pdf |
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| Zusammenfassung |
| The Po Valley, Italy, is known to be a nitrogen hotspot through the co-emissions of nitrogen
oxides (NOx) and ammonia (NH3) due to intensive agriculture and industry within the
region. Due to the regions poor air quality there have been a number of studies to understand
the atmospheric composition and the tropospheric chemistry. Studies on the deposition of
reactive N to the local ecosystems are however limited due to the complexities of measuring
species such as NH3. The following study presented took place above an oak-hornbeam
forest “Bosco Fontana” near Mantova, situated in the Po Valley, Italy with the aim to
determine the importance of individual N species to the dry deposition budget and
understand the impact of the chemical interactions and changes in the gas-aerosol
partioning.
Water soluble gases (NH3, HONO and HNO3) and their counter-part aerosol species
(NH4+ and NO3−) were measured using an online wet chemistry instrument called the
GRadient of Aerosols and Gases Online Registration (GRAEGOR, ECN, NL). The fluxes
were calculated using a modified gradient method, with concentration measurements at 2
heights. In addition, NH4+ and NO3− species were also measured by eddy covariance using
an aerosol mass spectrometer (AMS, Aerodyne Inc.). Eddy Covariance was also used to
measure NO fluxes.
Nitric acid (HNO3) as expected had the fastest deposition rate (Vd) of 18.80 mm s−1 of
all the N species measured. The study however did demonstrate that the deposition of
NH4+ and NO3− was greatly enhanced during the day due to the evaporation during
deposition close to the surface of the canopy, which resulted in the Vd of HNO3 to be
reduced.
Overall, the largest deposition flux over the forest was from NH3, with an average of
-253.42 ng m−2 s−1, which accounted for 75% of the total N deposition budget during the
period presented. The aerosols (NH4+ and NO3−) combined accounted for 19% and HNO3
contributed just 5% to the total N deposition budget. Taking this budget, measured over 2
weeks, an inferred annual budget of 75 Kg N ha−1 yr−1, which is greater than
previously measured at the same site using a throughfall method for N deposition. |
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