Recent Talks

Wed, 18 May 2011 12:46:23 -0600

At the beginning of this month, I attended the National Ground Water Association’s Annual Summit in Baltimore, MD to present my research. The file below is my slide deck for the NGWA presentation. As it turns out, they liked my talk and I won the NGWA’s Len Assante Scholarship Fund’s Farvolden Award. It’s a nice little chunk of change! :)

Click on the file below to view the slide deck of my talk at Washington and Lee. This talk breaks down my research to the very basics and the motivation behind the project.

Chlorinated Solvent Contamination

Mon, 4 Jan 2010 13:41:57 -0700

Wow, it’s been a while since I’ve worked on this site. Now that I’m back in the lab spending time collecting data, I have time to work on this once again. I will pick up where I left off.

According to the US EPA’s DNAPL information website, chlorinated solvents such as Trichloroethene are the most prevalent organic contaminants at Superfund Sites. The United States Air Force’s Center for Engineering and the Environment reports that 50% of the U.S. Department of Defense’s contaminated waste sites consist of chlorinated solvents. So as you can see, these pesky little contaminants are quite prevalent in the environment.

In particular, tetrachloroethene (PCE) (the contaminant in which I am working with for my research) is ranked number 33 on the US EPA’s rank of concern for environmental contaminants. The breakdown products of PCE include Trichloroethene (TCE), ranked 16, Dichloroethene (DCE), ranked 79, and vinyl chloride (VC), ranked 4. Therefore, it’s rather imperative to develop and fully understand the most efficient remedial technologies in order to clean up these contaminated groundwater sites across the country, and the rest of the world.

Next Up: An In-Depth Look at PCE and it’s affect on humans.

Chlorinated Solvents and DNAPLS

Fri, 13 Mar 2009 12:15:29 -0600

The focus of my PhD research is on a class of chemicals called chlorinated solvents. (Other names for these chemicals are organochlorides or chlorocarbons.) They consist of chloride atoms and carbon atoms. In order to introduce the chemicals and their importance, I’ll start with a little background of the production and use of chlorinated solvents.

A little history:
According to Pankow and Cherry (1996), chlorinated solvents were first produced in Germany in the 19th century and in the United States in 1906. They were not heavily used until World War II. It was not until the 1970’s that environmental contamination was recognized as a concern. Historically and today, a wide range of industries use chlorinated solvents. The three largest contributors to their use and their release into the environment are the electronic, instrument manufacturing, and the aerospace industries (Pankow and Cherry, 1996). Smaller sources include dry cleaning, machine, photographic processing, and printing shop industries.

Chlorinated solvents are produced as a liquid called a Non-Aqueous Phase Liquid (NAPL). These liquids are ones that do not dissolve in water (think oil and water). The term NAPL was coined in 1981 in order to differentiate between a dense liquid found to be hazardous waste leaching from a landfill in NJ and the surrounding groundwater (Pankow and Cherry, 1996). There are two different types of NAPLs: Light NAPLS (LNAPLs) and Dense NAPLS (DNAPLs). LNAPLs are less dense than water and will float on the top of the water surface. Picture spilling gasoline on a lake while refueling a boat before water-skiing and the shiny sheen that can be seen on the surface of the water. DNAPLs are more dense than water and will penetrate the water surface and will continue flowing beneath the water table until it reaches an impenetrable barrier. Chlorinated solvents fall into the DNAPL category.

However, at the risk of confusing you, the definition that NAPLs are immiscible (don’t dissolve) in water is a bit misleading. The constituents of the NAPL will, with time, slowly move from the NAPL phase to the surrounding water until the water is fully saturated with that molecule. For example, if you left a cup of water and oil sitting out for years, the water would slowly become a bit murky, or cloudy, because the molecules that make up that oil are slowly leaving the oil and going into the water.

Combine the very slow dissolution and the usually large volumes of DNAPL released to the ground and these chemicals become long-term sources of pollution. The chemicals dissolved from the DNAPL phase are usually found in water supplies on the order of micrograms/liter (ppb) or as much as miligrams/liter (ppm) concentrations. To put this in perspective, the U.S. Environmental Protection Agency (EPA) places limits on concentrations for varying chemicals (called maximum concentration limits, mcls) and the limits for these chemicals are on the order of 1-10 micrograms/liter. They are usually odorless and tasteless at typical concentrations -- which made their detection impossible until methods were developed to detect those low concentrations.

Despite their widespread use during the 1940’s, the first significant study of the behavior of NAPLs in the subsurface (in the ground) did not occur until the late 1960’s/early 1970’s. Friedrich Schwille studied NAPLs in Germany but his research did not make it over to the United States until the late 1980’s. Therefore, many decades of use and release into the environment had occurred before we even started to gain some understanding of their behavior. It turns out that these chemicals are quite difficult to find, characterize, and clean-up in the environment (will discuss in later posts.)

Common chlorinated solvents consist of tetrachloroethene (picture seen above), trichloroethene, dichloromethane, chloroform, carbon tetrachloride, chlorobenzene. The molecule above, tetrachloroethene (other name: perchloroethene, PCE), consists of two carbon atoms (dark gray) and four chloride ions (green). PCE is the chemical that I will be working with for the purpose of this research project.

Next up: The prevalence of chlorinated solvent contamination in the environment, specifically in the United States.

Back to basics

Thu, 12 Mar 2009 14:00:48 -0600

After talking with my brother, Patrick, this morning, I realized that I need to start from the beginning and the basics of what I am researching. It is important for scientific information be accessible and understandable by all - other scientists as well as non-scientists (I don’t believe there are really any non-scientists -- anyone who wonders about things, problem solves, informally seeks answers to the natural world, etc. can be considered a scientist -- so when I say non-scientist from this point forward I am referring to the folks who do not list a form of science as their profession.)

So, my plan is to start from the beginning and work my way up to current research. This will take time and will consist of several posts. My goal is to break it down so folks can know what I’m talking about because my research affects everyone. Everyone has to have water to drink, right?

Water quality is an ever-growing concern and accessible clean drinking water is a novelty in a growing number of places. Our water supply is vulnerable to all sorts of contamination from the rising number of pharmaceuticals in human waste to some sort of awful biological attack on our country (or other countries!). It is imperative that folks understand the issues involved in providing quality water to the public, including the efforts to clean up the vast amount of contaminated water.

According to the Gallup Poll present above and sent to me by my brother, Parker, water quality is a large issue on the minds of many people. So, I figure it’s only appropriate for me to do my part and present my research in the area contaminant hydrology and make it accessible to anyone who’s interested. Which, according to the poll above, is a lot of people.

Up Next: Type of contaminant I’m researching and why it matters.

Grad Students

Sun, 15 Feb 2009 13:28:12 -0700

My research partner sent this video to me in the midst of tediously analyzing 25 samples from our tracer experiment. Each sample took 5 minutes to analyze. I have three more tracer test samples to analyze. That’s a couple days of sitting in a lab, mindlessly analyzing samples while waiting for five minutes in between each one. Five minutes is not long enough to get involved in a task but too long to just sit and wait. It’s times like that when I very much appreciate the humor in the above YouTube video.