The effects of heat on physical and hydraulic properties of oil shale were investigated. The porosity and water absorption of oil shale increased with increasing pyrolysis temperature. The porosity increased by 19.048% and water absorption increased by 0.76% when oil shale was heated to 500 °C. Thus, originally impermeable oil shale was converted to a permeable rock formation, facilitating interactions between surrounding groundwater and oil. Heated oil shale was immersed in water, which showed strong alkaline properties. The content of Ca²⁺ remained stable and a slight decrease in SO₄²⁻ content was observed. Hydrocarbon content in the water samples reached maximum concentration within three days.

Peroxodisulfate (PDS), peroxymonosulfate (PMS), and hydrogen peroxide (H₂O₂) might coexist in a persulfate system. It leads to the mutual interference in concentration determination due to their similar structures. Simultaneous detection of the three peroxides involves limited reporting. Herein, a multi-step iodometry was established to simultaneously determine the concentrations of PDS, PMS, and H₂O₂ coexisting in a solution. Firstly, molybdate–NaHCO₃-buffered iodometry was proposed to uplift the overall detection of peroxides since the recovery rate of H₂O₂ was unexpectedly lower in the peroxide mixture than in the single H₂O₂ solution with reported NaHCO₃-buffered iodometry. Then, multi-step iodometry was proposed based on the established molybdate–NaHCO₃-buffered iodometry using the combination with catalase and revised acetate-buffered iodometry (pH 3). The multi-step iodometry determined the coexisting PMS, PDS, and H₂O₂ with the recovery rate of 95–105% and a standard deviation of ≤7% of two replicates at the individual centration of 13–500 μmol∙L⁻¹. The recovery rates of peroxides were within 95–105% at pH 3–11 and within 90–110% in the presence of Cl⁻ (0–150 mg∙L⁻¹), F⁻ (0–1.5 mg∙L⁻¹), SO₄²⁻ (0–150 mg∙L⁻¹), or NO₃⁻ (0–20 mg∙L⁻¹). The recovery rate of H₂O₂ was lowered down to 91% or 87% in the sample containing 100 mg/L Ca²⁺ or Mg²⁺, respectively, but was lifted up to 100% or 93% once pretreated by adding 0.11–1.06 g∙L⁻¹ Na₂CO₃. In the background of tap water, surface water, and ground water, peroxides were all detected in 90–110%, which indicates the applicability of multi-step iodometry in real waters.