Search Results (5)

The impact of hydrocarbon spills in the unsaturated zone is a significant environmental concern, particularly in locations where contamination arises from leaks in underground fuel storage tanks (USTs). This paper presents the outcomes achieved through the utilization of VLEACH, a finite-difference numerical model, to assess the concentrations of organic contaminants in the solid, liquid, and gas phases within the vadose zone. Additionally, it evaluates the mass transfer of pollutants to the aquifer as part of an environmental assessment for the placement of a forthcoming service station. The study encompasses an analysis of 18 scenarios under realistic conditions based on actual field data. These scenarios were constructed, taking into account various factors, including the nature of the leak (one-time or permanent), the depth of the phreatic level, and the soil conditions and properties. The results highlight the potential environmental consequences of a permanent leak as compared to those resulting from a specific accident. The findings further emphasize the substantial influence of soil moisture on transport phenomena within the vadose zone. Variations in soil moisture significantly alter hydraulic conductivity, impact magnitudes, transport velocities, and even the predominant transport mechanism. Consequently, precise delineation of soil moisture becomes a crucial parameter in such simulations. Additionally, it has been observed that each component of BTEX (benzene, toluene, ethylbenzene, and xylene) experiences varying transport velocities through the vadose zone. Benzene, having a greater propensity to concentrate in the liquid and gas phases, exhibits the swiftest movement through the vadose zone. The detection of benzene in aquifers can serve as an indicator of the potential future arrival of the remaining BTEX compounds. Full article

The spill pressure of the contaminant source is an important factor affecting the amount, location, form, and behavior of the dense non-aqueous phase liquids (DNAPLs) that plume in a contaminated subsurface environment. In this study, perchloroethylene (PCE) infiltration, distribution and, remediation via a surfactant-enhanced aquifer remediation (SEAR) technique for a PCE spill event are simulated to evaluate the effects of the spill pressure of the contaminant source on the DNAPLs’ behavior in two-dimensional homogeneous and heterogeneous aquifers. Five scenarios with different spill pressures of contamination sources are considered to perform the simulations. The results indicate that the spill pressure of the contaminant source has an obvious influence on the distribution of DNAPLs and the associated efficiency of remediation in homogeneous and heterogeneous aquifers. As the spill pressure increases, more and more contaminants come into the aquifer and the spread range of contamination becomes wider and wider. Simultaneously, the remediation efficiency of contamination also decreases from 93.49% to 65.90% as the spill pressure increases from 33.0 kPa to 41.0 kPa for a heterogeneous aquifer with 200 realizations. The simulation results in both homogeneous and heterogeneous aquifers show the same influence of the spill pressure of the contaminant source on PCE behaviors in the two-dimensional model. This study indicates that the consideration of the spill pressure of the contaminant sources (such as underground petrol tanks, underground oil storage, underground pipeline, and landfill leakage) is essential for the disposal of contaminant leakage in the subsurface environment. Otherwise, it is impossible to accurately predict the migration and distribution of DNAPLs and determine the efficient scheme for the removal of contaminant spills in groundwater systems. Full article

Petroleum spills and land contamination are becoming increasingly common around the world. Polycyclic aromatic hydrocarbons (PAHs) and other pollutants found in petroleum are constantly migrating underground, making their migration in soil a hot research topic. Therefore, it is of great significance to evaluate the migratory process of petroleum hydrocarbons in petroleum-polluted soil to clarify its ecological and environmental risks. In this study, Phenanthrene (PHE) was used as a typical pollutant of PAHs. The soil was gathered from three typical oilfields in China, and a soil column apparatus was built to simulate the vertical migration of PHE in the soil. The migration law and penetration effect of PHE in various environmental conditions of soil were investigated by varying the ionic strength (IS), pH, particle size, and type of soil. According to the literature, pH has no discernible effect on the migration of PHE. The migration of PHE was adversely and positively linked with changes in IS and soil particle size, respectively. The influence of soil type was mainly manifested in the difference of organic matter and clay content. In the Yanchang Oilfield (YC) soil with the largest soil particle size and the least clay content, the mobility of PHE was the highest. This study may reveal the migration law of PAHs in soils around typical oilfields, establish a new foundation for PAH migration in the soil, and also provide new ideas for the management and control of petroleum pollution in the soil and groundwater. Full article

This article shows the interesting results of a pioneer effort by IAG/USP researchers to use ground-penetrating radar (GPR) for humanitarian purposes, guiding the rescue of victims in the tragedy of Brumadinho. The tailings Dam I at the Córrego do Feijão iron ore mine, located in the Brumadinho complex, Minas Gerais State, Brazil, collapsed on 25 January 2019. About 11.7 million m³ of mining mud was spilled from the dam, burying bodies, equipment, structural buildings, buses, and cars along a length of 8.5 km up to the Paraopeba River. Additionally, the contaminated mud traveled more than 300 km along the bed of the Paraopeba River toward the São Francisco River. This work shows the results of a geophysical investigation using the GPR method 17 days after the event. To carry out the geophysical survey, an excavator was used for soil compaction. The data acquisition was performed on the tracks left by the excavator chain using SIR-4000 equipment and antennas of 200 and 270 MHz (GSSI). The GPR studies aimed to map bodies, structural buildings, and equipment buried in the mud. The location of the profiles followed preferably the edge of the slope due to the higher probability of finding buried bodies and objects. The GPR results allowed the detection of subsoil structures, such as concentrations of iron ore and accumulations of sand from the dam filter. The GPR was effective because the iron ore sludge in the mixing process became porous and the pores were filled with air, which provided penetration and reflection of the GPR electromagnetic waves up to a depth of 3.5 m. The results were surprising. Although no bodies or underground equipment were found, the results of this research served to eliminate the studied areas from future excavations, thus redirecting the rescue teams and optimizing the search process. These important results can serve as an additional motivation for the use of GPR in future humanitarian work in areas of tragedies. Full article

Drinking water production facilities are designed to filter contaminants that are ever-present in raw water. These facilities, however, pose risks of tap water contamination or water supply discontinuation in the event of a massive chemical spill. A managed aquifer recharge (MAR) offers the advantage of purifying surface water as well as maintaining water underground for extended periods of time, thus securing sufficient time for a response to contaminant infiltration and dramatically increasing consumer safety. However, contaminated aquifers are difficult to recover; accordingly, it is important that MAR sites engage in preemptive responses to chemical spills in order to protect their aquifers. This study assesses potential risks in order to quantify the detrimental impacts of chemical spills in cities located in river basins on drinking water supply facilities. The targets of analysis are two MAR sites in South Korea. The potential risk analysis offers grounds upon which aggressive basin management can be implemented to ensure water supply facility operation safety. The lack of data for available for analysis is addressed using a stochastic methodology that ranks cities in which MAR sites are endangered based on the cities’ potential risk probability distributions. The results of the analysis show that water supply facilities surrounded by larger cities have relatively higher potential risks, and would, therefore, need to handle more management targets to prevent chemical spills. Furthermore, the proposed methodology contributes not only to potential risk management of existing water supply facilities, but also to MAR site selection. Full article