title: Leaching of cadmium, chromium, copper, lead, and zinc from two slag dumps with different environmental exposure periods under dynamic acidic condition.
abstract: Over the past few decades, zinc smelting activities in Guizhou, China have produced numerous slag dumps, which are often dispersed on roadsides and hill slopes throughout the region. During periods of acid rain, these exposed slags release heavy metals into surface water bodies. A column leaching study was designed to test the potential release of the heavy metals cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) under simulated acid rain events. Two slags with varying environmental exposure periods were packed in columns and subjected to leaching solutions of pH 3.5, 5.5, or DI H2O at intervals of 1, 7, 14, 28, 56d. Pulse concentrations of Cd in leachate were found above 5μg/L, Cr, Pb, and Zn >10μg/L, whereas, Cu reached 10μg/L. After five leaching events, the leachability (percentage of cumulative heavy metal leached after five leaching events as in its respective total concentration in slags) of Cd was 0.05 percent and 0.035 percent from the old and young slag, respectively. Cr (0.035 percent and 0.05 percent) was greater than Cu (0.002 percent and 0.005 percent) and Zn (0.006 percent and 0.003 percent), while the lowest leachability was observed for Pb (0.0005 percent and 0.0002 percent) from the old and young slags, respectively. Reaction rates (release amount of heavy metals in certain period of leaching) of heavy metals in the leachates demonstrated the sequence of Zn>Cr>Cd, Cu>Pb. Leaching release of heavy metals was jointly affected by the pH of leaching solution and mineral composition of slags (including chemical forms of Cd, Cr, Cu, Pb, and Zn). Environmental exposure period of slags, resulting in the alteration of minerals, could affect the release process of heavy metals in leaching as well.
authors.affiliation: Institute of Geochemistry, Chinese Academy of Sciences, 46 Guanshui Road, Guiyang City, Guizhou Province 550002, China.
authors.forename: Zhisheng
authors.initials: Z
authors.lastname: Jin
authors.affiliation: Institute of Geochemistry, Chinese Academy of Sciences, 46 Guanshui Road, Guiyang City, Guizhou Province 550002, China.
authors.forename: Taoze
authors.initials: T
authors.lastname: Liu
authors.affiliation: University of Georgia, AESL, 2300 College Station Road, Athens, GA 30602, USA. Electronic address: yangyuangen@hotmail.com.
authors.forename: Yuangen
authors.initials: Y
authors.lastname: Yang
authors.affiliation: University of Georgia, AESL, 2300 College Station Road, Athens, GA 30602, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Jackson
mesh_terms: D015258:Acid Rain; D002681:China; D004781:Environmental Exposure; D004784:Environmental Monitoring; D064371:Hazardous Waste Sites / Q000706:statistics & numerical data*; D007220:Industrial Waste / Q000032:analysis*; D019216:Metals, Heavy / Q000032:analysis / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*
chemical_list: D015258:Acid Rain; D007220:Industrial Waste; D019216:Metals, Heavy; D012989:Soil Pollutants
keywords: Column leaching; Exposure periods of slag; Heavy metals; Mineral composition