Metal contents and Pb isotopes in road-side dust and sediment of Japan

Abstract

In order to elucidate the sources of metals in urbanized areas, metal contents and Pb isotope ratios were determined in road-side dust and sediments samples collected from Tokyo, Osaka and Kyoto. The samples were leached using 1% HNO3 for metal concentrations and Pb isotopes analysis. Metal (Pb, Cd, Zn, As, Cr and Ni) concentrations and Pb isotopes (206Pb, 207Pb and 208Pb) in the solutions were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The extent of anthropogenic contribution to road-side dust was assessed by comparing the metal concentration values in road-side dust of the sample sites to those of Okinawa, an unpolluted road-side dust site due to low traffic density. Considering a Pb background of 21.0ppm measured in the Okinawan road-side dust, Pb in road-side dust of Tokyo was found to be about twelve times higher which may indicate Pb pollution in the streets of Tokyo. The contaminated road-side dust can be transported into pond and river sediments during runoff and rainfall events. The concentrations of anthropogenic Pb in road-side dust and sediment were compared to those of other metals (Cd, Zn, As, Cr and Ni). There was a positive correlation found between Pb with Cd, Ni and Zn concentrations in sediment which suggests a common origin. The range of the Pb isotope ratios in road-side dust agreed well to that in the sediments (207Pb/206Pb=0.8644–0.8688 and 208Pb/206Pb=2.1044–2.170) suggesting that sediments may be contributed and transported by mean of road-side dust. Moreover, Pb isotope ratios (208Pb/206Pb and 207Pb/206Pb) confirmed that Pb pollution in the road-side dust and sediments was contributed the combination of battery and solder products.