Thesis Proposal

The City of El Paso is situated on the western most edge of the State of Texas. The city is made up of approximately 624,000 inhabitants and spreads over an area of 250 square miles. Other sizable metropolitan areas in the region include the City of Las Cruces, NM and Ciudad Juarez, CHIH. In total, there are approximately 2.3 Million residents within the tri-state region[i].

A large workforce coupled with El Paso’s geographical location and a major rail line running through the city have all been factors in attracting industry to the area. These new industrial operations brought with them economic development and improvements in the quality of life, however, along with those benefits came pollution and contamination issues whose impacts have long been understudied or ignored altogether. Due to increases in industrial activity and vehicle usage, certain areas within the city have been contaminated with heavy metals (HM). The EPA has issued a memorandum discussing the issue and has sited past research showing contamination near industrial areas within El Paso[ii]. The EPA has also assigned the El Paso region the status of Non-Attainment for particulate matter less than 10 microns in diameter (PM₁₀).

The fact is that we have many environmental issues within our region. These are complicated by the fact that pollution has contributed to the individual cities over state and international boundaries. Instead of discussing the wide range of environmental issues facing the area, this study will focus on how HM enter the environment and are deposited as street dust, and how that contamination may be a public health concern when re-suspended as particulate matter. Although both heavy metals and particulate matter have been individually studied in depth, there is not much literature showing what possible inhalation hazards may be present when particulate matter contains fractions of heavy metals.

2.0 Motivations and Objectives

The driving motivations behind this research stem from an interdisciplinary perspective that includes, among others, environmental engineering, aeolian science, and public health. The study will investigate dust particles that have been deposited on road surfaces through natural and anthropogenic mechanisms. The basic premise that ties deposited road sediments with public health is the resuspension of particles into the atmosphere when disturbed. Various studies discuss the resuspension of street dusts by vehicles, when small or light weight dust particles are resuspended they essentially revert in particulate matter. The size of the particulate (aerodynamic diameter) then determines the amount of time the particulate will stay suspended in air. A study performed within the El Paso region showed that the emissions factor, or amount of resuspended dusts, was related to both the vehicle weight and speed[iii].

A large amount of research has also been conducted that studied the concentrations of HM within street sediments. These studies found that in most cases elevated concentrations of HM could be attributed to anthropogenic sources such as high traffic density[iv] and industrial pollution[v]. The results from a few of these studies are noteworthy within this context because the Middle East and the El Paso region have similar features in terms of climate, rainfall, and weather patterns. Both regions are in arid locations that receive the majority of their rainfall within a compressed period of time during the year. The driest season for both Jordan and the El Paso region is the summer months of April thru early July. The population of Amman, approximately 2.5 Million (in 2007), is also comparable to that of the El Paso region as a whole.

Therefore, the objectives of this research will be to characterize the street sediment samples collected for size distribution and amount of HM present. The size fractions of the dust samples are needed in order to determine if the dust is within the size range that is classified as Particulate Matter. Furthermore the main research interest of the study is to determine if street dusts are within the respirable fraction (<2.5 microns). This is the size fraction that has been determined to be able to reach the inner lung tissue of the human body and cause adverse health effects to a person. The Heavy Metals that will be analyzed for will be the RCRA 8 metals (As, Ba, Ca, Cr, Pb, Hg, Se, Si) and Vanadium (V). The reasons why these specific metals were chosen for chemical identification will be discussed within the Methodology section below. Taken together, respriable particles that contain a large concentration of HM would be a worst case scenario and pose the greatest risk to the general public.

3.0 Scope of Work

The proposed scope of work for this project will consist of two phases. Phase I will include a pilot study on the main campus of the University of Texas at El Paso (UTEP). The purpose of the pilot study will be to fine tune the collection methods and analytical techniques that will be used during phase II of the study. Phase II will consist of sampling and analysis of road sediments from Interstate 10. Results and comparisons from both the pilot and main studies will be included within the final thesis report.

3.1 Pilot Study

The pilot study will consist of sample collection at predetermined sites throughout the UTEP campus. Figure I shows the sampling sites throughout the campus. Sampling sites include traffic intersections as well as areas where traffic normally does not decelerate or stops. The different sampling sites will allow a comparison of results in order to investigate the amount of road sediments that are deposited from disintegrating brake parts.

3.1.1 Sampling Procedures

Sampling of road dusts will take place with a standard vacuum as well as with a plastic broom and dust pan. The vacuum will be outfitted with a special High Efficiency Particulate Air (HEPA) filter bag. A HEPA filter is defined as a filter that stops 99.97 % of particulates larger than 0.3 microns in size. Therefore, a HEPA vacuum bag will trap 99.97% of particulates larger than 0.3 microns. Considering that the study will focus on particulates between 2.5 and 10 microns, the HEPA bags will work well in capturing road sediments of interest to this study. A particle size comparison will be made between those samples taken with the vacuum and with the broom in order to determine if broom and dust pan sampling allows fine particles to escape during sampling. A composite sample of the two sides of the road as well as the middle of the road will be taken in order to obtain an average of the contamination found within the sediments throughout the entire area.

3.1.2 Sample Analysis

The collected samples will be analyzed for particle size fractions and for chemical composition. Particle sizes will be determined by properly preparing the samples for analysis through a particles sizing machine that will list the size fractions within a given sample. The chemical composition of the samples will be determined by analysis with an Inductively Coupled Plasma- Optical Emission Spectrometer (ICP-OES).

Samples preparation for the chemical analysis will follow the procedure outlined in Manno et at (2006) and will include placing 0.1 g of dried sample into a digestive mixture consisting of a ratio of 3:2:1 of HNO3–HClO4–HF[vi]. The sample will be digested through a Microwave digestion process before being run through the ICP-OES.

3.2 Main Study

The purpose of the pilot study discussed above is to fine tune the analytical and collection procedures that will be needed for the main study. This study will focus on collecting and analyzing the same type of samples as in the pilot study, only the sampling area for this work portion of the thesis will consist of Interstate 10 (I-10) within the boundaries shown in Figure II. A large amount of coordination with the Texas Department of Transportation (TxDOT) will need to occur in order to carry out this type of study on a functioning interstate.

The sampling procedure and sample analysis will be the same as those outlined for the pilot study. Any deficiencies and/or changes made due to the experience from the pilot study will be discussed within the Thesis report. The specific amount of sample that needs to be collected will also be determined during the pilot study.

4.0 Data Analysis

4.1 Descriptive Statistics

The analytical data from the sampling will be sorted and described through standard analytical methods. The data will be analyzed in order to prove or disprove the study’s two null hypothesis:

4.2 Data Correlations

The collected data will be analyzed for any correlations that may used to determine possible sources of HM. Studies have shown that certain metals can be used as indicators of HM sources. Therefore, the study’s metals analysis will include specific metals that are known to be found within vehicle mechanical breakdown. Analysis will also include relationships between particle size distribution and HM concentrations.

5.0 Proposed Timeline

Cited Literature

[i] City of El Paso Website, Statistics Section, http://www.ci.el-paso.tx.us/quickfacts.asp

[ii] EPA Memorandum (2002) Request for Removal Action at the El Paso County Metals Survey site, El Paso, El Paso County, Texas

[iii] Gillies, J.A. , V. Etyemezian, H. Kuhns, D.A. Gillette, and D. Nikolic. "Effect of vehicle characteristics on unpaved road dust emissions." Atmospheric Environment. 39(2005): 2341–2347.

[iv] Al-Khashman, O. (2007) Environmental Geochemical Health 29:1–10

[v] Al-Khashman, O. (2004) Atmospheric Environment, 38: 6803-6812

[vi] Emanuela Manno, Daniela Varrica, Gaetano Dongarra, “Metal distribution in road dust samples collected in an urban area close to a petrochemical plant at Gela, Sicily.” Atmospheric Environment 40 (2006) 5929–5941.