Chemical forms of cadmium and lead in some contaminated soils

Lead contamination in smelting and mining environments and variations in chemical forms and bioavailability

“…Such differences depend on the source of the metal, the environmental conditions it is subjected to and the amount of time that has elapsed since the lead was exposed to the environment. Several authors have stated the importance of the chemical form of contaminant metals in assessing their bioavailability and toxicity (Barltrop et al, 1975;Biggins and Harrison, 1980;Khan and Frankland, 1983;Gibson and Farmer, 1984;Wixson and Davies, 1994).…”

Metal Removal

“…World-wide population was alerted by the case of paddy fields irrigated by mining drainage (Zn mines) where significant quantities of Cd were traced in rice. This rice consumption by farmers and local populations caused adverse health impacts (disease named as "itaT-itai") (Kobayashi 1978).…”

“…Direct oral ingestion of contaminated soils and dust by children is the principal cause of lead absorption (Healy et al 1982;Xintaras 1992). Lead is one of the heavy metals with relatively lower mobility and a tendency to adsorb to organic matter, clays and oxide/hydroxide complexes by forming precipitates (Khan and Frankland 1983) such as Pb carbonates (PbCO 3 , 2PbCO 3 Pb(OH) 2 , 4PbCO 3 .2Pb(OH) 2 ) (Mercier et al 2002a;Zimdahl and Skogerboe 1977), orthophosphates of Pb, primary pyromorphites and plumbogummites (last three formed in anaerobic environment) (Nriagu 1974). The Pb contamination primarily originates from recycling sites and battery dumpyards municipal incinerator ashes, shooting range where it is present in different forms as PbCO 3 , PbSCX PbO and PbO 2 (Hessling et al 1990;Nedwed and Clifford 1997).…”

“…Thus, speciation of heavy metals in soils was the theme of several studies (Khan and Frankland 1983;Brown et al 1986;Gibson and Farmer 1986;Calvet et al 1990;Van Beschoten et al 1997;Galvez-Cloutier and Dube 1998;Papassiopi et al 1999). The speciation of metals has significant effects on their water solubility, transport, toxicity, and treatment (Calmano et al 2005).…”

Assessment of lead availability in soils contaminated by mine spoil

“…Moreover, such strong complexing agents usually extract more than 50% of the total metal present in the soil (Davies et al, 1987;Khan and Frankland, 1983) -an amount which is several orders of magnitude higher than that taken up by plants during a single growing s e a s o n .…”