Study of the unknown HONO daytime source at a European suburban site during the MEGAPOLI summer and winter field campaigns

International audienceNitrous acid measurements were carried out during the MEGAPOLI summer and winter field campaigns at SIRTA observatory in Paris surroundings. Highly variable HONO levels were observed during the campaigns, ranging from 10 ppt to 500 ppt in summer and from 10 ppt to 1.7 ppb in winter. Significant HONO mixing ratios have also been measured during daytime hours, comprised between some tenth of ppt and 200 ppt for the summer campaign and between few ppt and 1 ppb for the winter campaign. Ancillary measurements, such as NOx , O3 , photolysis frequencies, meteorological parameters (pressure, temperature, relative humidity , wind speed and wind direction), black carbon concentration , total aerosol surface area, boundary layer height and soil moisture, were conducted during both campaigns. In addition, for the summer period, OH radical measurements were made with a CIMS (Chemical Ionisation Mass Spectrometer). This large dataset has been used to investigate the HONO budget in a suburban environment. To do so, calculations of HONO concentrations using PhotoStationary State (PSS) approach have been performed, for daytime hours. The comparison of these calculations with measured HONO concentrations revealed an underestimation of the calculations making evident a missing source term for both campaigns. This unknown HONO source exhibits a bell-shaped like average diurnal profile with a maximum around noon of approximately 0.7 ppb h−1 and 0.25 ppb h−1 , during summer and winter respectively. This source is the main HONO source during daytime hours for both campaigns. In both cases, this source shows a slight positive correlation with J (NO2) and the product between J (NO2) and soil moisture. This original approach had, thus, indicated that this missing source is photolytic and might be heterogeneous occurring at ground surface and involving water content available on the ground. Published by Copernicus Publications on behalf of the European Geosciences Union. 2806 V. Michoud et al.: Study of the unknown HONO daytime sourc

Affichage environnemental des produits agricoles en France : quelle méthode pour quels objectifs ? Comparaison de deux approches d'évaluation des impacts (ACV) ou des pratiques (HVE°

Lors du Grenelle de l_environnement, l_accent a été porté dans le secteur agricole sur l_agro-écologie et la nécessité d_orienter les modes de consommation vers des produits respectueux de l_environnement. Ainsi, depuis juin 2011, une nouvelle certification volontaire a été mise en place par décret : l_agriculture à haute valeur environnementale (HVE). Cette certification a pour objectif d_harmoniser les démarches agro-environnementales existantes et repose sur un système semi-quantitatif d_évaluation des pratiques. C_est une démarche en trois niveaux d_engagements, où seul le niveau le plus exigeant autorise l_apposition du logo HVE sur les produits. En parallèle, depuis le 1 er juillet 2011, une expérimentation nationale sur l_affichage environnemental des produits de grande consommation a été lancée avec plusieurs dizaines d_entreprises et autant de projets d_affichage environnemental. L_analyse de cycle de vie (ACV) est la méthode préconisée dans ce cadre. L_objectif est d_utiliser les données d_inventaire d_ACV afin de produire des indicateurs pour l_affichage environnemental des produits agricoles. L_HVE, centrée sur les pratiques au niveau de l_exploitation agricole, et l_ACV, qui se concentre sur les impacts des filières, reposent sur deux approches bien distinctes d_analyse d_impacts environnementaux. Les informations apportées par chaque méthode peuvent s_avérer complémentaires dans le cadre de l_affichage environnemental. Cependant, les conditions pour le développement de l_ACV semblent plus favorables, étant donné que l_ACV est obligatoire tandis que l_HVE est volontaire. Ces démarches restent en construction avec encore de nombreuses interrogations méthodologiques qui pointent la difficulté à trouver un compromis entre efficacité pour la communication et rigueur scientifique. Within the frame of the French Grenelle for the environment, in the agricultural sector, the need to orient consumers toward environmental-friendly products was emphasised. In June 2011, a new certification was hence promulgated by decree: the agriculture of high environmental value (HEV). This certification aims at harmonising all agri-environmental initiatives and is based on a semi-quantitative system for the environmental impact assessment of agricultural practices. This certification consists of three levels of commitment, with only the highest level being recognised by a logo on products. At the same time, a national experimentation phase was launched (July 2011) on eco-labelling involving dozens of companies with their own labelling projects on consuming goods. Life-cycle analysis (LCA) is the recommended method within the national methodological framework for eco-labelling. It is a holistic method that quantifies environmental impacts along the product life-cycle. The certification HEV and LCA are based on very different approaches of impact assessment, which can be complementary. However, the two approaches are also likely to compete with one another in terms of visibility, implementation and potential economic added-value. LCA-based eco-labelling is becoming mandatory, whereas the HEV certification is voluntary. Development of LCA-based eco-labelling is thus more likely to develop. Both approaches remain under development and numerous methodological questions are still open. More generally, eco-labelling also raises questions on the difficulty to find a good compromise between scientific reliability and efficient communication