Street Dust: Source and Sink of Heavy Metals To Urban Environment

S Ayrault,L Bordier,O Boudouma,M Catinon,M Tissut,G Agnello,S Reynaud,Nicola Pirrone

doi:10.1051/e3sconf/20130120001

Abstract

Air-transferred solid material accumulated for 40 years in different places in an urban area, Grenoble city, France. An appropriate fractionation procedure allowed to separate: 1) a coarse inorganic fraction, 2) a coarse organic fraction, 3) a slowly depositing organo-clay fraction and 4) very fine particles. The composition of each fraction was determined for 20 elements and for isotopic lead signature. The organo-clay fraction was especially rich in Ag, Cd, Co, Cr, Ni and Ti. The sand fraction showed very high concentrations specifically in Cu, Pb and Fe. In contrast, Cd and Zn were mainly accumulated in the coarse organic fraction. The SEM-EDX study of the coarse inorganic fraction showed the presence of red particles associating Pb and Fe, black particles rich in Cu and typical fly ashes originating mostly from iron industry. This sand fraction is suspected to contribute to the contamination of the organo-clay fraction through adsorption. The Pb-Fe contamination likely originates from the neighbouring road surface contaminated by car traffic for several decades. The 206 Pb/ 207 Pb ratio showed that these street dust samples may contain up to 50% of lead originated from leaded gasoline additives, twelve years after their prohibition. All these features clearly differ from the composition found for the deposit on tree bark in the same place. These results demonstrate that the deposition over several decades is a very complex phenomenon which requires multi-techniques investigations to be understood thoroughly. They also show that large dense particles which can only be transported on a limited distance by high magnitude events may play a major role in the long-term contamination of urban soils.

Highlights

Atmospheric contamination by diverse components of natural or anthropogenic origins is a subject of great concern (e.g., Zereini et al, 2005), as is the case for water pollution (e.g., Mondal et al, 2010), and especially for particulate metals in urban environment (e.g., Harrison et al, 1997)
Due to their high heavy metal concentration shown by inductively coupled plasma – mass spectrometry (ICP-MS) coupled to the presence of pure crystals of these metals as shown by Scanning Electron Microscope (SEM)-Energy Dispersive X-ray (EDX) analysis, we concluded that the source of the dense particles seems obviously anthropogenic and located for one part at a limited distance from the studied place
When considering the elements content of the dust and comparing it to the deposit on tree bark of the same age, several elements show that the street dusts are significantly enriched in Pb, Cd, Cu, Co, Zn and As

Summary

Introduction

Atmospheric contamination by diverse components of natural or anthropogenic origins is a subject of great concern (e.g., Zereini et al, 2005), as is the case for water pollution (e.g., Mondal et al, 2010), and especially for particulate metals in urban environment (e.g., Harrison et al, 1997). A second type of danger may exist for different kinds of living beings, which depends on the uptake, through several ways, of a mixture of particles of atmospheric origin deposited on the earth surface. Such an exposure occurs mainly through transcutaneous transfer or digestive uptake (Laidlaw and Filippelli, 2008). It is crucial to identify such contaminated places, try to suppress the emission of the involved pollutants and use remediation strategies (Kidd et al, 2009)

Methods

Results

Conclusion