The application of persulfate (PS) for the remediation of petroleum hydrocarbon contamination is among the most widely employed in situ chemical oxidation (ISCO) techniques, and it has received widespread attention due to its limited impact on soil integrity. This study employed a FeSO4-activated PS oxidation method to investigate the feasibility of remediating soil contaminated with total petroleum hydrocarbons (TPHs). The factors tested included the TPH concentration, different PS:FeSO4 ratios, the reaction time for remediation, soil physical and chemical property changes before and after remediation, and the effect of soil before and after remediation on soybean growth. The TPH degradation rate in soil was highest for high-, medium-, and low-TPHs soils-81.5%, 81.4%, and 72.9%, respectively, with minimal disruption to the soil's physicochemical properties-when PS:FeSO4 = 1:1. The remediation verification results indicated that the condition of the soybeans was optimal when PS:FeSO4 = 1:1. Under this condition, the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate all remained high. Therefore, the best remediation effect was achieved with PS:FeSO4 = 1:1, which also minimized the damage to the soil and the effects on crop growth.

To investigate the efficacy and strength properties of Fe2+-activated persulfate remediation for 1,2-dichlorobenzene-contaminated soil with varying persulfate concentrations, we conducted degradation, microscopic, particle size, liquid-plastic limit, unconfined compressive strength (UCS), and undrained shear tests. The results indicate that adding 15.0% Fe2+-activated persulfate achieves a 92.59% removal rate of 1,2-dichlorobenzene. Furthermore, the reaction produces sodium sulfate, calcium sulfate, and ferric hydroxide. Small amounts of sodium sulfate and calcium sulfate fill the pores between soil particles, leading to a denser soil structure. However, the expansive effect of excessive sodium sulfate crystals weakens the inter-particle cohesion, leading to soil loosening. After remediation, the clay content increases, while the silt and sand content decreases. The liquid limit, the plastic capacity and the plastic index increase, while the plastic limit decreases with the increase of the persulfate dosage. The UCS and the maximum shear stress decrease with the increase of the persulfate dosage. The UCS of the soil treated by 10.0% persulfate is 310.75 kPa, 20.34% higher than the strength of untreated soil. The maximum deviator stress at shear failure is 142.73 kPa.

The mixing of black carbon (BC) with secondary materials is a major uncertainty source in assessing its radiative forcing. However, current understanding of the formation and evolution of various BC components is limited, particularly in the Pearl River Delta, China. This study measured submicron BC-associated nonrefractory ma-terials and the total submicron nonrefractory materials using a soot particle aerosol mass spectrometer and a high-resolution time-of-flight aerosol mass spectrometer, respectively, at a coastal site in Shenzhen, China. Two distinct atmospheric conditions were also identified to further explore the distinctive evolution of BC-associated components: polluted period (PP) and clean period (CP). Comparing the components of two particles, we found that more-oxidized organic factor (MO-OOA) prefers to form on BC during PP rather CP. The formation of MO-OOA on BC (MO-OOABC) was affected by both enhanced photochemical processes and nocturnal heterogeneous processes. Enhanced photo-reactivity of BC, photochemistry during the daytime, and heterogeneous reaction at nighttime were potential pathways for MO-OOABC formation during PP. The fresh BC surface was favorable for the formation of MO-OOABC. Our study shows the evolution of BC-associated components under different at-mospheric conditions, which should be considered in regional climate models to improve the assessment of the climate effects of BC.