Quantitative expression of LNAPL pollutant concentrations in capillary zone by coupling multiple environmental factors based on random forest algorithm.

The capillary zone plays a crucial role in migration and transformation of pollutants. Light nonaqueous liquids (LNAPLs) have become the main organic pollutant in soil and groundwater environments. However, few studies have focused on the concentration distribution characteristics and quantitative expression of LNAPL pollutants within capillary zone.

Spatial distribution characteristics and degradation mechanism of microorganisms in n-hexadecane contaminated vadose zone.

The damage caused by petroleum hydrocarbon pollution to soil and groundwater environment is becoming increasingly significant. The vadose zone is the only way for petroleum hydrocarbon pollutants to leak from surface into groundwater. The spatial distribution characteristics of indigenous microorganisms in vadose zone, considering presence of capillary zones, have rarely been reported.

The collaborative monitored natural attenuation (CMNA) of soil and groundwater pollution in large petrochemical enterprises: A case study.

A large in-service petrochemical enterprises in Northeast China was taken as the research object, and the Collaborative Monitored Natural Attenuation (CMNA) for soil and groundwater pollution was carried out to remedy combined pollution and reduce environmental risks. The pollutants distributions were obtained based on detailed regional investigation (Mar. 2019), and feature pollutants in soil and groundwater were then screened.

Microwave-induced steam distillation (MISD) remediation in petroleum hydrocarbon-contaminated sites: From process improvement to pilot application.

The process improvement, a pilot remediation test and the decontamination mechanism of microwave-induced steam distillation (MISD) for petroleum hydrocarbons (PHs) removal were conducted. Processes of multistage steam distillation and carbon reinforcement were compared to determine the best remediation process. Pilot project was then carried out to explore the applicability of MISD in site-scale remediation.

Construction, application and validation of a new algorithm for determining light nonaqueous-phase liquid fluxes in unsaturated zones.

An analytical algorithm coupling free-phase migration, precipitation, and natural attenuation through volatilization and biodegradation (FPVB) was developed to calculate the flux of light nonaqueous-phase liquid (LNAPL) leaking from unsaturated zone to groundwater. Sandbox and soil column experiments were performed to identify the LNAPL migration characteristics and states to provide data to establish and verify FPVB algorithm. For free-phase migration, the Kinematic Oily Pollutant Transport (KOPT) model was used to determine LNAPL movement velocity and leakage time.

Response relationship of environmental factors caused by toluene concentration during leaching of capillary zone.

Due to the leaching of capillary water, the petroleum pollutants initially trapped in vadose zone may migrate to lower aquifer, thus increasing the risk of groundwater pollution. In order to explore the effect of capillary leaching on toluene-contaminated soil and the relationship between toluene concentration (TC) and environmental factors (EFs) during the leaching process, the sterilized and non-sterilized soil column experiments were designed. The EFs were used to estimate TC.

Analysis of the LNAPL Migration Process in the Vadose Zone under Two Different Media Conditions.

This study focused on the processes of free infiltration, precipitation displacement, and natural attenuation of the LNAPL under the condition of near-surface leakage. Sandbox experiments were performed to explore the migration characteristics of LNAPL in the vadose zone with two media structures and the influences of the soil interface on the migration of LNAPL. The results indicate that the vertical migration velocity of the LNAPL infiltration front in medium and coarse sand was 1 order of magnitude higher than that in fine sand and that the LNAPL accumulated at the coarse-fine interface, which acted as the capillary barrier.

Response of environmental factors to attenuation of toluene in vadose zone.

Contaminated groundwater migrates in reverse direction under capillary force in vadose zone, and the attenuation process of pollutant adsorption and microbial degradation changes the environment of vadose zone. In this study, the response of toluene to environmental factors during reverse migration and attenuation of toluene from aquifer to vadose zone was studied by column experiment and experimental data analysis. The changes of environmental factors, including potential of hydrogen (pH), dissolved oxygen (DO), and oxidation-reduction potential (ORP), and toluene concentration were monitored by soil column experiment under sterilized and non-sterilized conditions.