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The rainfall effect onto solidification and stabilization of heavy metal-polluted sediments
Yan Sun1, Daofang Zhang1, Feipeng Li1
1Institute of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China.
Royal Society Open Science
|September 3, 2020
Summary
Rainfall slightly reduces the strength of solidified sediments, but does not significantly affect heavy metal leaching during curing. Simulated acid rain, however, impacts leaching, though cement stabilization remains effective with low heavy metal mobility.
Area of Science:
- Environmental Engineering
- Geotechnical Engineering
- Materials Science
Background:
- Solidification/stabilization (S/S) is crucial for managing contaminated sediments.
- Rainfall can influence the integrity and long-term safety of solidified matrices.
- Understanding rainfall effects is vital for effective waste management strategies.
Purpose of the Study:
- To investigate the impact of rainfall on the solidification/stabilization (S/S) process of sediments.
- To evaluate the effects of simulated acid rain on the leaching behavior of heavy metals from S/S materials.
- To assess the long-term safety and effectiveness of S/S treatment under environmental exposure.
Main Methods:
- Rainfall tests were conducted on S/S sediment samples.
- Unconfined compressive strength (UCS) and Toxicity Characteristic Leaching Procedure (TCLP) were used for characterization.
- Semi-dynamic leaching tests with simulated acidic leachants (pH 2.0, 4.0, 7.0) were performed.
- Diffusion coefficients (D) and leachability index (LX) were calculated to evaluate S/S effectiveness.
Main Results:
- UCS decreased with a maximum deterioration rate of 34.23% after 7 days of rainfall, and 7.98% after 28 days.
- Rainfall had minimal impact on heavy metal leaching during the curing process.
- Simulated acid rain significantly affected heavy metal leaching behaviors.
- Cumulative leached heavy metals were below 2.0%, indicating good cement stabilization.
- Calculated diffusion coefficients for Cd, Cu, and Pb indicated low mobility of heavy metals in S/S sediments.
Conclusions:
- While rainfall can reduce the strength of solidified sediments, its effect on heavy metal leaching during curing is limited.
- Simulated acid rain poses a greater risk to the leaching characteristics of heavy metals.
- The S/S treatment demonstrated good stabilization of heavy metals, with low mobility observed.
- Further research into long-term durability under various environmental conditions is warranted.
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