Dry deposition of nitrogen compounds (NO2, HNO3, NH3), sulfur dioxide and ozone in west and central African ecosystems using the inferential method 1Laboratoire d'Aérologie, UMR5560, CNRS/UPS, Toulouse, France
22 Nov 2013
2Laboratoire de Physique de l'Atmosphère, Université Félix Houphouët-Boigny de Cocody, Abidjan, Côte d'Ivoire
3International Centre for Theoretical Physics, Trieste, Italy
4Geographic Information Science Center of Excellence, South Dakota State University, Brookings, USA
Received: 12 Mar 2013 – Published in Atmos. Chem. Phys. Discuss.: 02 May 2013 Abstract. This work is part of the IDAF program (IGAC-DEBITS-AFRICA) and is based on
the long-term monitoring of gas concentrations (1998–2007) established at
seven remote sites representative of major African ecosystems. Dry
deposition fluxes were estimated by the inferential method using on the one hand
surface measurements of gas concentrations (NO2, HNO3, NH3,
SO2 and O3) and on the other hand modeled exchange rates. Dry
deposition velocities (Vd) were calculated using the big-leaf model of
Zhang et al. (2003b). The bidirectional approach is used for NH3
surface–atmosphere exchange (Zhang et al., 2010). Surface and meteorological
conditions specific to IDAF sites have been used in the models of
deposition. The seasonal and annual mean variations of gaseous dry
deposition fluxes (NO2, HNO3, NH3, O3 and SO2) are
Revised: 01 Oct 2013 – Accepted: 12 Oct 2013 – Published: 22 Nov 2013
Along the latitudinal transect of ecosystems, the annual mean dry deposition
fluxes of nitrogen compounds range from −0.4 to −0.8 kg N ha−1 yr−1
for NO2, from −0.7 to −1.0 kg N ha−1 yr−1 for HNO3 and
from −0.7 to −8.3 kg N ha−1 yr−1 for NH3 over the study period
(1998–2007). The total nitrogen dry deposition flux
(NO2+HNO3+NH3) is more important in forests (−10 kg N ha−1 yr−1)
than in wet and dry savannas (−1.6 to −3.9 kg N ha−1 yr−1).
The annual mean dry deposition fluxes of ozone
range between −11 and −19 kg ha−1 yr−1 in dry and wet savannas,
and −11 and −13 kg ha−1 yr−1 in forests. Lowest O3 dry
deposition fluxes in forests are correlated to low measured O3
concentrations, lower by a factor of 2–3, compared to other ecosystems.
Along the ecosystem transect, the annual mean of SO2 dry deposition fluxes
presents low values and a small variability (−0.5 to −1 kg S ha−1 yr−1).
No specific trend in the interannual variability
of these gaseous dry deposition fluxes is observed over the study period.
Citation: Adon, M., Galy-Lacaux, C., Delon, C., Yoboue, V., Solmon, F., and Kaptue Tchuente, A. T.: Dry deposition of nitrogen compounds (NO2, HNO3, NH3), sulfur dioxide and ozone in west and central African ecosystems using the inferential method, Atmos. Chem. Phys., 13, 11351-11374, doi:10.5194/acp-13-11351-2013, 2013.