Preliminary Validation of Persulfate Delivery Through Porous Pipe in the Vadose Zone: A Two-Dimensional Sandbox Experiment

ABSTRACT

When remediating contamination in the vadose zone, which is a potential source of continuous groundwater and surface water pollution, technical challenges are often encountered. In this study, the feasibility of delivering sodium persulfate (SPS) oxidant to unsaturated soils was explored by integrating porous pipes, commonly used in agriculture, with in-situ chemical oxidation (ISCO). An evaluation of the operating characteristics of the pipe determined a recommended influent rate of < 0.1 L min⁻¹ and an initial influent water pressure < 20 kPa to prevent percolation pore enlargement. Two-dimensional sandbox experiments revealed that pulse infiltration at an influent rate of 0.05 L min⁻¹ was effective in creating matrix flow and lateral movement, minimizing preferential flow induced by continuous infiltration. Application of SPS (10% by wt.) under these conditions resulted in approximately 90% wetting of the sandbox area SPS flow at the experimental time that infiltrated from the pipe. After a 14-d post infiltration resting state, residual SPS concentrations ranged from 6,000 -12,000 mg/kg in soil, with soil pH levels of 3–4, ORP around 600 mV, and 40–60% decreases in soil organic carbon. This developed method helps retain the oxidant and promote chemical reactions, making ISCO a viable option for remediating unsaturated soil contamination.

KEYWORDS:

• In situ chemical oxidation (ISCO)
• unsaturated soil
• soil remediation
• sodium persulfate
• matrix flow

Acknowledgments

This study was funded by the National Science and Technology of Taiwan under Project No. 111-2221-E-005-032-MY2. The authors acknowledge John F. Miano for valuable discussion and proofread of this manuscript.

Disclosure statement

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Chenju Liang reports financial support was provided by National Science and Technology Council of Taiwan.

Supplemental material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15320383.2024.2386616

Data availability statement

The data that support the findings of this study are available on request from the corresponding author, Chenju Liang.

Additional information

Funding

The work was supported by the National Science and Technology Council of Taiwan [111-2221-E-005-032-MY2].