Evaluating Iron and Manganese Reduction in Soils Using IRIS in Field and Laboratory Results
3 pm, December 4, 2024 in ANS 0408
This was a report on the cumulative project of a student for her masters' program. She is majoring in Environmental Science and Technology. This talk was a discussion of the scientific validity of a certain technique to measure iron and manganese reduction in soils. This is relevant to the speaker's focus on the effectiveness of restored lands by the Maryland State Highway Administration. First she discussed what qualifies as a wetland. The main qualifications are hydric soils, wetland hydrology saturation, and hydrophytic vegetation. She wanted to focus on the hydric soils aspect. Hydric soils are formed under conditions of saturation, flood, or ponding long enough to develop anaerobic conditions. Saturation can be measured with wells and piezometers. Anaerobic conditions can be measured by looking at soil morphology, even though this technique is flawed. Biogeochemistry of the soil is a key condition for hydric soils. This includes redox reactions, especially reduction after oxygen is no longer available. This is where the reduction of manganese and iron come in.
IRIS is the technique that she is studying. It is the Indicator of Reduction in Soils. It is a PVC pipe with painted films on top to visually show cumulative reduction. If saturation occurs enough to reduce iron and manganese, we will see a stripping of the films and the white pipe will shine through.
She considered previous research that suggested that manganese is more sensitive in cooling temps so it would be informative. Iron is less sensitive in the winter, which may not yield results. The inverse is true in warmer soil, where iron is more sensitive and manganese is less. This means that Manganese IRIS might better capture info during the growing season.
She deployed the IRIS every other month and every two weeks so there would always be some in rotation. She deployed five iron and five manganese at each site. Her results show that of the data below 11 degrees celsius (cool), the bulk of the manganese data reaches high above the 30% threshold and the bulk of the iron data is below the 30% threshold. Of the data above 11 degrees C, the bulk of the iron data is more than 30% so it meets the saturation climate and the bulk of the the manganese is much higher because it is less reliable.
This presentation was very effective. It was attractive, specific, and self-aware, and showed how much heart and work the presenter put into it. The presentation felt very fast but that is likely partially just because I was completely new to the subject. The speaker was clearly very familiar with and passionate about the subject of the talk.
The presentation had a thorough amount of critical thinking. The procedure was complex and well-considered and strategized. The overall presentation was very well structured with logical transitions deeper and deeper into the topic so that a novice at soil science can begin to understand what she worked on. She started with contextualizing and defining the key details, then focused on the definition of a wetland, then focused on the definition of hydric soils, then the technique she would analyse. Ms. Bodine described how she went out into the field to plant the devices and how she converted the visual data into quantitative data. She discussed the implications of her results, and key takeaways.
There was extensive scientific thinking employed. Ms. bodine made sure that her test sites were diverse and all around the state in wetlands of different levels of rainfall, different ages, and different sizes. The speaker defined all of the variables involved, considered statistical significance and previous research of other experts. This included comparing the chemical properties of manganese to iron to see if her results made logical sense. She also considered whether the standard optimal oxide removal threshold of 30% really held true. To determine this she compared the threshold with her own definition of a 'wetland' and the rainfall of surrounding areas. Ms. Bodine then concluded that as the weather grew warmer toward the spring and summer seasons, the threshold should be decreased to about 15% as many of her data strips did not yield evidence of reduction anywhere near 30% toward the end of her study. She considered confounding variables such as the carbon presence in the soil or the distance of the data source on the rainfall that she used to compare with her reduction results. All throughout the writing the speaker brought the talk back to the greater context of the necessity for accurate measurement techniques. Ms. Bodine then discussed a similar project that she conducted to be used as a sample. She took soil samples from the test sites, placed them into containers indoors, and placed the IRIS in those.
There were few oratory techniques used as it was a formal presentation, meant to make use of ethos and logos, with minimal pathos. She made sure to present facing the audience to engage the group. She did not read off notecards or the screen or anything because she was so familiar with the topic. She kept a steady pace and ws efficient and purposeful with her words.
Overall, this presentation was a bit too in-depth for me because I came in with no previous knowledge. Now I am more familiar with soil science and far less intimidated but far more appreciative of the hard work that must go into a masters thesis.