Short Communication Competitive diesel engine emissions of sulphur and nitrogen species A. Dur an a, * , M. Carmona a , R. Ballesteros b a Department of Chemical Engineering, Escuela T ecnica Superior de Ingenieros Industriales, University of Castilla-La Mancha, Avda. Camilo Jos e Cela 3, 13071 Ciudad Real, Spain b Department of Mechanical Engineering, Escuela T ecnica Superior de Ingenieros Industriales, University of Castilla-La Mancha, Avda. Camilo Jos e Cela 3, 13071 Ciudad Real, Spain Received 17 October 2002; received in revised form 25 March 2003; accepted 31 March 2003 Abstract NO x ,nitrateandsulphateemissionsfromatypicalEuropeanpassengercardieselenginehavebeenmeasuredtesting eight different fuels under five steady operating conditions (reproducing modes of the European transient urban/ extraurbancertificationcycle).Itisconfirmedthatnitrogenspeciescompetewithsulphurcompoundstobeadsorbedby diesel particulate matter (DPM) before being emitted into the atmosphere. This competition is found to increase with engineload,andisexplainedonthebasisofthedifferentspecificsurfaceandadsorptioncapacityofsootparticlesunder different operating modes. When a high specific surface is available, as occurs in low load modes, both nitrates and sulphates are adsorbed by soot particles. On the contrary when a small surface is accessible, like in high load modes, sulphatesareselectivelyadsorbed.Thisisspeciallyimportantsincesulphatesareresponsibleforhydrocarbonretention in DPM due to the scrubbing effect. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Adsorption; Emissions; NO x ; Soot; Sulphates 1. Introduction Requirementsforfuelstoreduceengineemissionsare becomingmoresevere(Singaietal.,1999).Furthermore, diesel engines are currently designed to stay within emissions certification limits. Among pollutants, NO x can be emitted into the atmosphere either as a direct gaseous emission or it can be transformed into a salt (nitrates and nitrites) and then be adsorbed by soot particles to become a component of the final diesel particulate matter (DPM). During the adsorption pro- cess in soot particles, nitrates and nitrites may compete with sulphates and hydrocarbons, so that the specific surface of the soot will influence the relative adsorption of each species. It is known that the amount of sulphates adsorbed is responsible for the mass of hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs), retained in the particles and emitted into the atmosphere due to the so-called scrubbing effect (Wall and Hoekman, 1984). Thus, the competition between N and S species is important in order to determine particle composi- tion. On the other hand, the engine operating mode influences soot characteristics, so that competition be- tween N and S species is also influenced by this pa- rameter. Chemosphere 52 (2003) 1819–1823 www.elsevier.com/locate/chemosphere * Corresponding author. Tel.: +34-926-295300x3814; fax: +34-926-295361. E-mail address: antonio.duran@uclm.es (A. Dur an). 0045-6535/03/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0045-6535(03)00387-4