Archive for the category: Feature Presentation

Marijn BAUTERS^1,2, Hans VERBEECK², Landry CIZUNGU³ and Pascal BOECKX¹

¹ Isotope Bioscience Laboratory – ISOFYS, Ghent University, Coupure Links 653, 9000 Gent, Belgium

² CAVElab, Computational and Applied Vegetation Ecology, Department of Applied Ecology and Environmental Biology, Ghent University, Coupure Links 653, 9000 Gent, Belgium

³ Faculty of Agronomy, Université Catholique de Bukavu, Avenue de la mission, BP 285, Bukavu, DR Congo.

^Ϯ E-mail: Pascal.Boeckx@UGent.be

Abstract

Recent data analyses and modelling activities have shown that the CO₂ uptake by terrestrial ecosystems strongly depends on site fertility, i.e. nutrient availability. Accurate projections of future net forest growth and terrestrial CO₂ uptake thus necessitate an improved understanding on nutrient cycles and how these are coupled to the carbon cycle. This holds especially for tropical forests, since they represent about 40–50% of the total carbon that is stored in terrestrial vegetation. Central African forests are very poorly characterized and their role in global change interactions shows distinct knowledge gaps. Research in the Congo Basin region should combine assessments of both carbon stocks and the underlying nutrient cycles, which directly impact the forest productivity. We set up a monitoring network for carbon stocks and nitrogen fluxes in different forest types in the Congo Basin, which is now operative. Preliminary data show an atmospheric N deposition of 20-30 kg N ha^-1 yr^-1 with N mainly derived from fires and different N dynamics in mixed vs. mono-dominant forests, whereby the N economy of ectomycorrhizal fungi is likely the driving force for establishment mono-dominant forest ecosystems and nitrate leaching.

Saumya Singh*, Anshu Sharma* and U.C. Kulshrestha*

*School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067 INDIA

Abstract

Atmospheric emissions of reactive nitrogen (Nr) species namely NH₃ and NO_x are at high levels in India in recent years, but only a few studies have employed nitrogen (N) deposition monitoring for gaseous and particulate N depositions together to evaluate total dry N deposition.  In the present study, gaseous N pollutants (NH₃ and NO₂) and related ionic species (NH₄⁺, NO₃^–) were determined in water-soluble fine particulates at an agricultural site in the Indo-Gangetic Plain (IGP) during July-Sept,2013 with the aim of estimate the relative contribution of respective species to total dry N deposition. The NH₃ and NO₂ levels were recorded as 30.41µg/m³ and 4.0 ±2.3 µg/m³. Aerosol NH₄⁺ and NO₃^–concentrations were measured at 0.37 µg/m³ and 1.43 µg/m³.These values are at a relatively higher scale which might be due to high fertilizer use and biomass burning. Contribution of reduced for and oxidized form of nitrogen was also calculated.

Jeffrey L. Collett, Jr.¹, Yi Li¹, Bret A. Schichtel², John T. Walker³, Donna B. Schwede³, Xi Chen³, Christopher M.B. Lehmann⁴, Melissa A. Puchalski⁵, and David A. Gay⁴

¹Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA, collett@atmos.colostate.edu
²National Park Service, Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, Colorado, USA
³U.S. Environmental Protection Agency, Office of Research and Development, Research Triangle Park, North Carolina, USA
⁴National Atmospheric Deposition Program, University of Illinois Urbana-Champaign, Champaign, Illinois, USA
⁵U.S. Environmental Protection Agency, Clean Air Markets Division, Washington D.C., USA.

Abstract

U.S. reactive nitrogen emissions increased greatly in the last century due to rapid increases in fossil fuel combustion and development of agriculture.  One result was excess nitrogen deposition to many natural ecosystems. Successful policies in the last two decades to reduce nitrogen oxides emissions have substantially decreased nitrate wet deposition. Levels of wet ammonium deposition, however, have increased in many regions. Overall, the balance between oxidized and reduced nitrogen deposition has shifted from a nitrate-dominated situation in the 1980s to an ammonium-dominated situation today. Although gaseous ammonia has not historically been routinely measured in the U.S., a recent expansion in observations, combined with ongoing measurements of nitric acid and fine particle ammonium and nitrate, provides new insight into the balance of oxidized and reduced nitrogen in the total (wet + dry) U.S. nitrogen deposition budget. Observations reveal that reduced nitrogen contributes approximately 65 percent, on average, of the total inorganic nitrogen deposition budget. Dry deposition of ammonia plays an especially key role in nitrogen deposition.  While U.S. emissions of nitrogen oxides are expected to continue to decline in the foreseeable future, ammonia emissions are projected to grow.  Continued progress toward reducing U.S. nitrogen deposition will be increasingly difficult without new efforts to reduce ammonia emissions.

Galy-Lacaux¹, C. Delon¹, K. Pienaar², M. Adon^1,3, V. Yoboué³, B. Diop⁴, L. Sigha⁵, D. Laouali⁶, A. Akpo⁷

1 Laboratoire d’Aérologie, Université de Toulouse, CNRS, Toulouse, France, mailto:lacc@aero.obs-mip.fr

2 School of Physical and Chemical Sciences, North-West University, Potchefstroom, South Africa

3 Université de Cocody, Abidjan, Côte d’Ivoire

4 Université de Bamako, Mali

5 Université de Yaoundé CRH IRGM, Yaoundé, Cameroun

6 Université de Niamey, Niger

7 Université Abomey Calavi, Cotonou, Benin

Abstract

Atmospheric nitrogen concentrations depend on land surface exchanges of nitrogen compounds. In Africa, deposition and emission fluxes of nitrogen compounds are poorly quantified, and are likely to increase in the near future due to land use change and anthropogenic pressure. This work is part of the long term deposition monitoring project IDAF initiated in the 1990s. IDAF (IGAC/DEBITS/Africa) is the African contribution to study deposition in the IGAC/DEBITS programme and contributes to the WMO-GAW programme. This work proposes an estimate of an atmospheric N compounds budget in Africa, along an ecosystem transect, from dry savanna to wet savanna and forest, for the years 2000 to 2007. The budget takes into account: (1) gaseous dry deposition fluxes estimated by considering N compounds concentrations at the monthly scale and modeling of deposition velocities at the IDAF sites, (2) wet deposition fluxes calculated from measurements of ammonium and nitrate chemical content in precipitations and (3) N emission sources taking into account simulated NO biogenic emission from soils, NH₃ emission by volatilization and NOx and NH₃ emission from biomass burning and domestic fires. This regional N emission deposition budget should give the present status at the scale of the main African ecosystems and should help to quantify the processes that may contribute to the changing levels of N deposition.

Wim de Vries^1,2, Johannes Kros²

¹ Alterra Wageningen University and Research Centre, PO Box 47, 6700 AA Wageningen, the Netherlands, www.wageningenur.nl, wim.devries@wur.nl

² Environmental Systems Analysis Group, Wageningen University, PO Box 47, 6700 AA Wageningen, the Netherlands.

Abstract

The intensification of  European agriculture, including large inputs of nitrogen (N) to soil by fertilizers and manure, has led to an increase in crop growth but also in various adverse effects. This includes: (i) loss of biodiversity in natural terrestrial ecosystems due to increased emission and deposition of ammonia (NH₃), (ii) eutrophication of surface waters due to increased N runoff and (iii) increased nitrate (NO₃) levels in drinking water reservoirs due to elevated N leaching. In this study we identified agricultural regions where current N inputs exceed critical N inputs at a high spatial resolution for the entire European Union using the INTEGRATOR model. Critical N inputs were derived on the basis of critical N losses, which in turn were based on critical levels of NH₃ emission and critical N concentrations in leaching to ground water or runoff to surface water in view of the adverse impacts listed above. Results show that at EU-27 level, current N inputs slightly exceed critical N inputs in view of eutrophication by 15% for aquatic ecosystems and 25% for terrestrial ecosystems. We identified those places where there is a need to lower N losses to acceptable levels by increasing the nitrogen use efficiency (NUE).