Leaching Behavior of Heavy Metals and Transformation of Their Speciation in Polluted Soil Receiving Simulated Acid Rain

Abstract

Heavy metals that leach from contaminated soils under acid rain are of increasing concern. In this study, simulated acid rain (SAR) was pumped through columns of artificially contaminated purple soil. Column leaching tests and sequential extraction were conducted for the heavy metals Cu, Pb, Cd, and Zn to determine the extent of their leaching as well as to examine the transformation of their speciation in the artificially contaminated soil columns. Results showed that the maximum leachate concentrations of Cu, Pb, Cd, and Zn were less than those specified in the Chinese Quality Standards for Groundwater (Grade IV), thereby suggesting that the heavy metals that leached from the polluted purple soil receiving acid rain may not pose as risks to water quality. Most of the Pb and Cd leachate concentrations were below their detection limits. By contrast, higher Cu and Zn leachate concentrations were found because they were released by the soil in larger amounts as compared with those of Pb and Cd. The differences in the Cu and Zn leachate concentrations between the controls (SAR at pH 5.6) and the treatments (SAR at pH 3.0 and 4.5) were significant. Similar trends were observed in the total leached amounts of Cu and Zn. The proportions of Cu, Pb, Cd, and Zn in the EXC and OX fractions were generally increased after the leaching experiment at three pH levels, whereas those of the RES, OM, and CAR fractions were slightly decreased. Acid rain favors the leaching of heavy metals from the contaminated purple soil and makes the heavy metal fractions become more labile. Moreover, a pH decrease from 5.6 to 3.0 significantly enhanced such effects.

Using time of flight secondary ion mass spectrometry and field emission scanning electron microscopy with energy dispersive X-ray spectroscopy to determine the role of soil components in competitive copper and cadmium migration and fixation in soils

“…In addition, these authors, together with Cerqueira et al (2011a), indicated that the lability of the sorbed Cd 2+ was higher than Cu 2+ . Several authors, such as Vega et al (2009a) and Zheng et al (2012), also noted the high level of mobility of Cd 2+ in soils, especially in those with the lowest pH, and they found that the sorption of Cd 2+ is affected by pH and by the presence of other cations. Adriano (2001) also showed that the mobility of Cd 2+ is preferably regulated by pH.…”

Biosynthesis of Multicomponent Nanoparticles with Extract of Mortiño (Vaccinium floribundum Kunth) Berry: Application on Heavy Metals Removal from Water and Immobilization in Soils

“…Acidic liquids reacting with soils are more aggressive initiating accelerated leaching of heavy metals [47,48]. At pH < 5, the mobility of metals is improved as a result of the higher concentration of competing protons [49,50].…”

Cypermethrin exposure and effects on the reproductive male system: a literature review

“…Another form of environmental contamination occurs by leaching that is a process which residues from pesticides are transferred from the place of application to another medium, usually liquid, such as water (ZHENG et al, 2012). In this way, these compounds promote the contamination of these soils and can also cause contamination of groundwater.…”