Pollution characteristics and migration law of petroleum hydrocarbons in an industrial site in the intertidal zone of the river estuary

Taking an industrial site in the intertidal zone of the river estuary as the research object, the total petroleum hydrocarbons (TPHs) of soil and groundwater samples were collected and investigated, and the migration law of TPHs in the soil and groundwater of the industrial site in the intertidal zone and the influence of tide on it were analyzed and discussed. The results showed that the groundwater level in the area along the river of the site fluctuated obviously by tide, the average permeability coefficient of the aquifer was 1.40 m/d, and the permeability of aquifer near the river was better. The maximum exceeding multiple of TPHs in the soil of the site was 1.39 times. The pollution was mainly distributed in the core production area, mainly neared the junction between the first two different lithological layers. The vertical distribution of TPHs in soil was significantly influenced by stratum structure and tidal effect. When the water level decreased, TPHs migrated downward and part of TPHs remained in vadose zone, while when the water level rose, it led to the opposite process. The maximum exceeding multiple of TPHs in the groundwater of the site was 95.23 times, the pollution plume center was consistent with the main areas of soil TPHs pollution, and the groundwater flow field had a significant impact on the migration and distribution of pollutants. The tidal effect expanded the range of TPH pollution plume. The fluctuation of groundwater level with no long-term stable flow direction made TPHs redistribute countless times between soil and groundwater, so that its migration law was not obvious. This study revealed to a certain extent that the long-term fluctuation of the intertidal groundwater level caused by the tidal effect had a significant impact on the migration law of pollutants in the soil and groundwater, which could provide a scientific guidance for the effective control and restoration of similar contaminated sites