ASSESSING THE POTENTIAL FOR LEAD RELEASE FROM ROAD DUSTS AND SOILS

Lead release from several soil and road dust samples-obtained from var ious locations in the London Borough of Greenwich-has been investigate d as a function of acid and chloride addition. The work shows that lea d retention in dust samples is primarily dependent upon buffer capacit y, which in turn appears to be related to carbonate content. The conti nuing addition of acid eventually overcomes the buffer capacity of the system. At this point lead is rapidly released. For the soils investi gated buffer capacities appear to be small and in these cases lead is readily released. The supplementary addition of chloride to the sample s can have contrary effects upon release. For the dust samples chlorid e enhances lead release due, presumably, to the formation of chloro-le ad complexes. However for one soil sample chloride hinders lead releas e possibly by binding anionic chloro-lead complexes to anionic exchang e sites formed by the protonation of surface hydroxyl groups in the so il matrix.