A Study on the Influence of Environmental Factors on the Attenuation Rate of n-Propylbenzene and Isopropylbenzene in Seawater by Using Microcosm System

The attenuation characteristics of hazardous chemicals in seawater are crucial for taking targeted emergency measures after their leakage accident occurs. In order to investigate the attenuation trend of n-phenylbenzene (n-PBZ) and isopropylbenzene (i-PBZ) spilled into the sea with changes in environmental conditions, a microcosm system was used to adjust temperature, salinity, pH, light intensity, and wind speed, respectively. Based on the concentration changes of n-PBZ and i-PBZ in seawater, attenuation kinetics analysis was conducted to determine the environmental factors that had a significant impact and the adverse effects of low wind speed on their attenuation. The results showed that temperature was the factor that had the greatest impact on the attenuation of each propylbenzene with a significantly positive correlation with the attenuation rate constant (k). The k values of n-PBZ and i-PBZ at 30 ℃ were 2.11 and 1.90 times higher than those at 5 ℃, respectively. Illumination was also beneficial for the attenuation of n-PBZ and i-PBZ. The k value at light intensity of 800 μmol/(m²·s) were 1.63 and 1.57 times higher than those under dark conditions, respectively. At lower salinity, the k value increased with the increase of salinity, but remained stable at salinity ≥10. The change in seawater pH value (6~9) had no significant effect on the attenuation of propylbenzene. The low wind speed (1 m/s) commonly seen in foggy weather was very unfavorable for the attenuation of n-PBZ and i-PBZ with the k value less than 60% of those at a wind speed of 5 m/s, resulting in the accident area at medium to high ecological risks for a long period (over 20 days). Our findings demonstrated that temperature, light intensity, and wind speed are the main environmental factors affecting the natural attenuation of n-PBZ and i-PBZ in seawater.