Summary of Summer Research

A requirement to graduate from the WM geology department is to complete a senior research project. Many students decide to conduct research over the summer before their senior year to get ahead and focus strictly on research before the business of classes start. I’m so thankful that I did as it has allowed me to learn so much and get through 2/3 of my research.

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Sampling Lake Cores from Norway

The goal of my research is to compare lead concentrations from a mid-latitude lake and a high latitude lake. Lake Matoaka served as my mid-latitude lake at 37 degrees North. For my high latitude lake I’m looking at Lake Ostadvatnet in Northern Norway, which lies at 68 degrees North. The Matoaka core was taken in the spring of 2016 by a former William and Mary Geology student for her thesis. The Ostadvatnet core was taken in May of 2017. Below are images taken from Google earth showing where the lake is located in Norway. The second image although blurry shows the shape of Ostadvatnet, marked by the yellow pin. The red circle surrounds the Viking Museum, where a Viking Longhouse existed around 800AD. The core from Ostadvatnet goes back around 5000 yrs. Which means it contains a 5000 year record of lake sedimentation and lead concentrations. We are interested to see if we can see a spike in lead concentration around where we believe 800AD is located on the core.

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First Set of Samples Processed

I have now finished sampling and digesting all the samples from the Lake Matoaka core and have run them all through the ICP. My graph follows the basic pattern of a Pb concentration graph with depth. My professor Jim Kaste and I were very interested in what looks like a double peak in my data around 20cm. If you look closely you can see there are two recorded Pb concentrations for the depth of 20-21cm. This is because I did some duplicates of randomly chosen depths so that I could compare their values to see if there was error with either the ICP or during the digestion processes. The first 20-21cm sample has a Pb concentration of 110 Micrograms of Pb/ gram of sediment and the second of 133 Micrograms of Pb/ gram of sediment. This is a huge margin of error and causes my data to appear to have a double peak. My professor and I discussed reasons for the large error and we believe that the burn step, where the samples go in the furnace for 6hrs, could be the issue. We are now in the processes of resampling a few samples around the peak and alleviating the burn step, and replacing it with an overnight peroxide step to dissolve out the organic matter that way instead. This method could also have a greater return on Pb concentrations as we believe our values are a bit low.

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Learning the Ropes of Pb Digestions

Coming into this summer I didn’t know exactly what to expect. I knew what I would be doing based on reading numerous papers and theses, but I admit I couldn’t fully visualize the step by step process I would be going through. After getting situated in Williamsburg, I headed to the lab in McGlothlin St. Hall to meet with my advisor Jim Kaste. Over the next couple weeks I got situated and comfortable with the equipment and procedures. I learned early on that the research I was conducting required fine motor skills and a lot of patience.

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Abstract: How the Latitude of a Lake Affects Lead Concentrations in Sediment Cores

Lead is a toxin that is known to affect many major organs in the human body if ingested. This summer and into the fall I will be conducting research comparing total lead concentrations in various lake sediment cores. The lead composition in the stratigraphy of the cores can reflect different anthropogenic lead sources such as coal combustion, ore smelting, and combustion of gasoline containing lead. In the 1970’s the United States’ Congress passed legislation banning the sale of the gasoline containing lead. This resulted in lower rates of atmospheric lead deposition. However, once lead goes into the atmosphere it can travel thousands of miles before being removed and deposited on the Earth’s surface, which is one reason it can be observed in lake cores across the globe. The actual extent that the lead from these sources traveled is unknown. Therefore; first, I want to see if lead can be found in lake sediment cores located at high latitudes, and second, assuming lead will be found, see if the concentrations seem to match up proportionally to those of cores at lower latitudes. The first core I will be looking at will be taken from a lake on Vestvagoy Island, which is one of the Lofoten Islands located in northern Norway at about 68 degrees north latitude. The second core will be taken from Lake Matoaka on William and Mary’s campus located at 37 degrees north latitude. For each core I’m going to take samples down the core and let them dry out in an oven, so I can grind them into a fine powder. Then I will ash them at 475 degrees Celsius for 6 hours. The ash residue will be digested in 10 ml of a 1:1 by volume solution of nitric acid, and then be filtered and diluted to 60ml with deionized water. Next I will use a plasma emission spectroscopy to analyze the diluted digestion for lead content. The recovery of lead should be greater than 90 percent, which is the high purity standard. I expect the plotted stratigraphy from the Norway core to resemble that of the Matoaka core, but for there to be a lower lead concentration observed overall. This would lead to the conclusion that lead concentration decreases with increased latitude.