Risk of contamination of infiltrated water and underground soil by heavy metals within a ceramic permeable brick paving system
2020
Lin, Zizeng | Chen, Huiming | Yang, Hai
The risk of heavy metal contamination of infiltrated water and underground soil on a permeable brick paving system was investigated. The paving system was constructed as a frame structure base on top of a 1.0-m-thick clay layer with permeable ceramic brick at the surface. The concentrations of heavy metals (Zn, Cu, and Pb) in infiltrated water and soil at different underground depths under the paving system were measured. Speciation rates of Zn, Cu, and Pb at different clay depths were further determined to ascertain the probability of downward migration of the unstable forms. The results showed reduced risk of infiltrated water pollution by heavy metals due to underground soil acting as an effective trap. However, topsoil was more susceptible to heavy metal pollution, with the different pollution soil depths of Cu, Zn, and Pb mainly attributed to the different binding abilities between the heavy metals and soil. Soil Cu and Zn remained relatively stable, whereas there was a potentially high risk of Pb migration. The study found that topsoil could accumulate non-degradable heavy metals to unacceptable levels over a period of 30 years and that topsoil should therefore be replaced after 30 years to reduce the risk of soil pollution. This study fills a knowledge gap by both determining the risks of heavy metal pollution to underground soil and infiltrated water and exploring effective ways to reduce heavy metal pollution.
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