Isotopic Analysis of CMNH Herbarium Samples

Since the late 1700s, coal mining played an important role in sustaining Pittsburgh’s economy. In 1875, steel production began in Pittsburgh and became the main driver of economic success in the area. Steel production flourished until the Great Depression when the industry began to decline. By the 1980s, more than 75 percent of steel production in Pittsburgh had stopped. Pittsburgh’s long history of air pollution as a result of industry has caused environmental changes in the area over the years. Studying the nutrient chemistry in preserved specimens can provide information about the environmental conditions at the time that the species were collected. Studies using pressed specimen have been done in Rhode Island and Monterey Bay, and the findings have provided information about how the environment in those areas has changed over the years. My research will focus on studying how air pollution levels in Allegheny County and the surrounding areas affected the chemistry of carbon and nitrogen found in woody and non-woody plant specimen preserved and stored in the herbarium at the Carnegie Museum of Natural History. I sub-sampled herbarium specimen of both woody (Red Maple, Acer rubrum) and non-woody (Ground Ivy, Glechoma hederaceae L.) plants found in urban and rural areas during two different time periods to see how pollution level, location, and plant type effect the C-N concentrations and isotopic composition (13C, 15N) of plant tissue. The time periods I took samples from were pre-1950 and post 1990. The study includes 40 total samples comprised of 20 from urban areas and 20 from rural areas. Within each set of urban and rural samples, 5 samples from each species were sub-sampled from specimens collected before 1950 and after 1990. I expect that there will be differences in the C-N concentrations and isotopic composition in the plant tissues based on location, as this was the case in similar studies in other regions. I also expect that there will be a difference in the nutrient concentrations based on the type of plant and time period, as different species accumulate nutrients in different ways.

I will be completing my research alongside Dr. Emily Elliott, Dr. Daniel Bain, and Dr. Josef Werne, Professors at the University of Pittsburgh. Mason Heberling, Assistant Curator and Botany Co-chair of Collections at the Carnegie Museum of Natural History assisted in the sampling process and helped guide the study design.

I believe that this project could lead to very interesting discoveries that could be expanded upon in the future. Pressed plants offer a unique look into the past that could provide important information about the environment and how it responds to effects of anthropogenic activities. The specimen preserved in herbarium collections such as the one at the Carnegie Museum of Natural History could be applied to various aspects of environmental science research. The findings from my research project could lead to a variety of important discoveries about the environment in Pittsburgh and its surrounding communities.

My name is Sarah Worthington, and I am a senior environmental science major and studio arts minor. I am the engineering director at Pitt’s radio station and have had the chance to work on many interesting projects and learn so many new skills over the past couple of months. I am also a DJ at the radio station and have been hosting shows since my freshman year at Pitt. I enjoy art and music and hope to pursue both of these passions after graduation. I also hope to do more research in the future regarding climate change and the natural environment.

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