Environ. Sci. Technol. 2007, 41, 66-73
Platinum, Palladium, and Rhodium in Fresh Snow from the Aspe Valley (Pyrenees Mountains, France) M A R I E L L A M O L D O V A N , * ,† SOPHIE VESCHAMBRE,† DAVID AMOUROUX,† B R U N O B EÄ N E C H , ‡ A N D OLIVIER F. X. DONARD† Laboratoire de Chimie Bio-Inorganique et Environnement, CNRS UMR 5034, Universite´ de Pau et des Pays de l’Adour, Helioparc Pau Pyre´ne´es, 2 avenue du Pre´sident Angot, 64053 Pau Cedex 9, France, and Laboratoire d’Aerologie, Centre de Recherches Atmosphe´riques, CNRS UMR 5560, Universite´ Paul Sabatier, Campistrous, 65300 Lannemezan, France
Platinum, palladium, and rhodium have been measured in fresh snow samples from 14 locations within the Aspe Valley (Pyrenees Mountains, France) during two winter seasons, February 2003 and March 2004. Ultraclean procedures were employed for the sampling, sample treatment, and analysis in order to reduce sample contamination. Possible spectral interferences on platinum group element (PGE) analysis by inductively coupled plasma mass spectrometry (ICP-MS) were controlled and corrected. The detection limits obtained were 0.05, 0.45, and 0.075 pg g-1 for Pt, Pd, and Rh, respectively. PGE content in fresh snow from the Pyrenees Mountains range from 0.20 to 2.51 pg g-1 for Pt, 1.45-14.04 pg g-1 for Pd, and 0.24-0.66 pg g-1 for Rh. The higher PGE concentration, generally measured in sites located close to road traffic, exhibit potential resuspension of PGE-enriched particles emitted locally from the car exhaust, although no direct relationship could be observed with the number of vehicles. Measured atmospheric synoptic conditions allowed identification of the origin of air masses reaching the Aspe Valley and therefore provided information about the possible sources of platinum group elements. Higher PGE concentrations measured in 2004 samples, compared to the ones collected in 2003, indicate the influence of atmospheric synoptic conditions on the studied area. Fresh snow samples collected in 2003 could not be linked to a specific source, whereas 2004 samples could be influenced by PGE emissions from European vehicle fleet and Russian PGE-containing mining activities.
Introduction The uptake of solid, liquid, and gas-phase impurities by snow includes both organic (1, 2) and inorganic (3, 4) compounds. Snow contributes as an effective scavenger to the removal of pollutants from the atmosphere. As a result the snow* Corresponding author phone: +34-985105005; fax: +34985103125; e-mail:
[email protected]. Present address: Department of Physical and Analytical Chemistry; University of Oviedo, Julia´n Claverı´a, 8; 33006-Oviedo, Spain. † Universite ´ de Pau et des Pays de l’Adour. ‡ Universite ´ Paul Sabatier. 66
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 41, NO. 1, 2007
bound pollutants will be transferred to the adjacent environment (aquatic systems, soil, vegetation, etc.) during melting. Therefore, the determination of pollutants in snow represents an interesting approach for the evaluation of the impact of anthropogenic pollution, especially in mountain ecosystems. In recent years there has been a growing interest in the environmental release of platinum, palladium, and rhodium (platinum group elements, PGE) as a result of their use as main active components in automotive catalytic converters (5-9). The amount and rate of PGE released from the autocatalyst surface through exhaust fumes is affected by several factors such as the type and age of the catalytic converter, the type of engine, the condition and speed of the vehicle, the driving habits, and meteorological conditions (10). Although emitted PGE were initially believed to remain in the roadside environment, recent studies suggest that fine PGE-containing particles can be transported and distributed at regional and long-range levels (11). For instance, atmospheric regional transport of fine PGE-containing particles has been studied in Alpine ice cores (12, 13) and a peat bog (14). Long-range transport has been suggested for Greenland snow and ice (15, 16). Automotive catalytic converters and Russian smelter activities are PGE potential sources, although long-range transport mechanisms and dynamics are largely unresolved. The Pyrenees Mountains are situated in southwest Europe, forming a natural border between France and Spain. The Aspe Valley, located on the Pyrenees National Park (Atlantic Pyrenees) extends over an area of 490 km2 and is bisected by the French national road RN134. Agriculture and mountain tourism, together with aluminum manufacturer industry, represent the main local economic activities. Aspe Valley is about 65 km long, with altitudes between 300 and 2600 m. Aspe Valley can be divided in two areas: the lower part in the North with the lowest altitude from 350 to 1000 m above the sea level (named hereafter low valley), and the highest part of the valley in the South, bordering Spain, with the highest altitude from 1000 to 2600 m above sea level (named hereafter high valley). Additionally, the geomorphological structure of the low valley shows a U profile, whereas a V profile is observed in the high valley. Therefore, it is expected that the narrowing profile of the high valley could strongly influence the movement of local air masses and, as a result, the dispersion of local atmospheric pollution. Information concerning air quality in the Pyrenees Mountains is very scarce. Until very recently, the Aspe Valley was considered a pristine area due to the low traffic density, which represents only about 1% of the transborder road transport. However, the opening of the Somport Tunnel on 17 January 2003, connecting France and Spain, is expected to increase road traffic density. As a result, up to 2400 vehicles per day, especially heavy-duty trucks, are expected, raising vehicle emissions in local mountain environments such as the Aspe Valley (17). For that reason, starting in 2002, a multidisciplinary research project has been set up to study the impact of road transport pollutants (trace metals and platinum group elements) in the Aspe Valley by measuring their content in four environmental matrices (fresh snow, bulk wet deposition, air particles, and epiphytic lichens) (18, 19). The geomorphological characteristics of the valley, limited industry, and traffic density make the Aspe Valley a useful area for environmental field studies. 10.1021/es061483v CCC: $37.00
2007 American Chemical Society Published on Web 12/02/2006
FIGURE 1. Fresh snow spot sampling sites in the Aspe Valley. The present study shows data on the PGE content in fresh snow samples collected during two important snowfall events widespread in the whole valley, February 2003 and March 2004, at 14 different locations within the Aspe Valley. Ultraclean procedures were employed for the sampling, sample treatment, and analysis. Analyses were carried out with high-sensitivity techniques. Atmospheric synoptic conditions, measured with the help of a VHF (very high frequency) radar wind profiler, have been used to identify the origin of air masses over the Aspe Valley in order to determine the source of air. The main purposes of the present work are (i) to expand the knowledge on spatial and temporal air monitoring of the Pyrenees Mountains by determining the PGE content in fresh snow, (ii) to contribute to the database on snow PGE in mountain regions, and, (iii) to contribute to a better understanding of the transport of PGE-containing particles at regional and global scales.
Experimental Section Sampling Strategy and Sample Treatment. Significant snowfalls occurred during the 2-3 days prior to the sampling day. Spot sampling of fresh snow was carried out on 13 February 2003 and 3 March 2004 at 14 sites selected along the Aspe Valley (Figure 1). Sampling sites were selected as far away as possible from possible direct anthropogenic pollution sources, from trees and rocks. Sampling sites were classified in three groups depending on their Euclidean distance to road RN134 as (i) remote sites (>350 m), (ii) intermediate sites (150-350 m), and (iii) close sites (
