Date of Award


Degree Name

Doctor of Philosophy


Environmental Science and Engineering



Second Advisor



As a hazardous waste generated in large amounts worldwide, used motor oil (UMO) is an important issue for environmental science. UMO contains the carcinogenic and mutagenic compounds Polycyclic Aromatic Hydrocarbons (PAHs). Unless properly managed and disposed of PAHs remain in the environment, principally in sediments and soil. From such environmental sinks, PAHs can migrate to watersheds contaminate drinking water, and damage ecosystems and human health.

Generators of used oil include "businesses that handle used oil through commercial or industrial operations or from the maintenance of vehicles and equipment," (United States Environmental Protection Agency (USEPA), 2013). An example of such a business is an auto repair shop that performs oil changes.

The purpose of this research is to examine the environmental impact of used motor oil generated by auto repair shops in the Ciudad Juarez-El Paso area. To quantify such impact I analyzed PAH contamination in soil samples. The working hypoThesis for this research was that the mean concentration of the EPA 16 priority PAHs present in soil samples near car repair shops is different for both El Paso and Ciudad Juarez.

The sample for the research consists of selected auto repair shops. The primary objective are threefold: (1) to survey UMO management and final disposal practices at the repair shops; (2) to perform a comprehensive analytical determination of PAHs released from UMO into soil sampled at the selected locations; and (3) to assess the impact of UMO on the environment and human health in the border region.

Through a questionnaire administered to owners or employees of automobile repair shops I gathered information from them regarding the amount of UMO generated, as well as its management and final disposal. The soil samples gathered information regarding UMO mismanagement and its possible risks for the environment and human health.

This research utilized analytical methods in extracting soil samples: ultrasonic agitation or sonication extraction method, silica-gel clean-up, and the Kuderna-Danish evaporator coupled with gas chromatography and a flame ionization detector (FID) detector for PAHs. The target compounds were the 16 PAH priority pollutants listed by the United States Environmental Protection Agency (USEPA).

The final results of the research are as follows:

The used motor oil volume generated for El Paso at the 30 car repair shops sampled was 24,522 L/month versus Ciudad Juarez 7,419 L/month, generated at the 60 shops sampled. The total PAHs in the soil samples collected in the Ciudad Juarez-El Paso area ranged from 0.01 mg kg-1 to 76.00 mg kg-1 with an average of 63.87 mg kg-1. PAH concentration in selected soil samples near the mechanic shops in the Ciudad Juarez-El Paso area exceeds the soil screening levels regulated by the USEPA and the Secretariat of the Environment and Natural Resources (SEMARNAT) in Mexico, values shown in tables 3.12 and 3.13. El Paso's most frequent PAH compound found at the soil samples was the LMW compound acenphthylene with 15.37%, the HMW compounds were: benzo(a)anthracene with 24.00%, benzo(a)pyrene 16.81%, chrysene with 13.40%, indeno(1,2,3-cd)pyrene and dibenz(a,h)anthracene with 5.66%, and Benzo(b)fluoranthene besides Benzo(k)fluoranthene 3.97%.

In Ciudad Juarez the most frequent PAH compound found was the LMW compound acenphthylene with 3.00%, the HMW compounds were: benzo(a)anthracene with 30.60 %, Benzo (a) pyrene with 26.43%, Benzo(b) fluoranthene and Benzo(k) fluoranthene 11.11%, chrysene with 8.87%, follows indeno(1,2,3-cd)pyrene and dibenz (a,h) anthracene with 5.14%. In both Ciudad Juarez and El Paso, 100% of the quantified and detected values of the HMW PAHs soil samples exceeded the EPA Regional Screening Level (RSL). Compliance or non-compliance status refers to final UMO disposal through a collector authorized by Texas Commission on Environmental Quality (TCEQ) or SEMARNAT, for the statistical analyses of the two groups, El Paso Compliance (EPC) vs. Ciudad Juarez Compliance (JZC), and Ciudad Juarez Compliance (JZC) vs. Ciudad Juarez Non Compliance (JZNC). To assess the equality of means for PAH concentration a t-test at 95% confidence was performed. Accordingly, the null hypoThesis of equal means was not rejected, and the conclusion is that no difference exists in the PAHs mean concentration from EPC and JZC, nor JZC and JZNC.

For the risk assessment the Benzo(a)pyrene equivalent (BaPeq) for EPC soil samples mean was 4.69 mg kg-1; for JZC the mean was 6.76 mg kg-1 for JZNC 7.00 mg kg-1. To assess the equality of means for BaPeq concentration a t-test at 95% confidence was performed and it is concluded that no difference exists in the mean concentration between groups. Therefore, the null hypoThesis of equal means was not rejected.

The results of this research will provide current information to hazardous waste researchers, environmental agencies and policymakers regarding the risk of PAHs posed by UMO in the Ciudad Juarez-El Paso area. Such information can contribute to local and binational management plans for soil remediation, outreach activities and proper UMO management.




Received from ProQuest

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144 pages

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