EVALUATING THE STORM EVENT EXPORT OF DISSOLVED ORGANIC CARBON FROM AN URBAN ENVIRONMENT TO THE KALAMAZOO RIVER, ALBION, MI

In order to evaluate the anthropogenic impact on freshwater ecosystems it is important to assess the export of biogeochemical solutes from the urban environment to the adjacent streams. We can investigate this relationship by developing our understanding of one of these solutes, dissolved organic carbon (DOC). This solute is the primary form of carbon found in freshwater systems. Freshwater DOC is a combination of organic carbon derived from organic sources such as fallen leaves, grass, etc. This is important to measure because it’s a key control on water quality and the ecology of stream networks, including influencing the control of nutrient cycles, food webs, and drinking water quality. There are presently few studies regarding the amount of DOC exported to stream systems from urban environments. Storm drains in urban watersheds act as a fast track to streams in comparison to the much slower process of infiltration through soils. Infiltration through soils allows for solutes such as DOC to sorb to soil particles and provides ample time for microbial processing of said solutes. Conversely, storm drains may convey solutes from the terrestrial landscape to the stream on a time scale orders of magnitude faster than the much slower process of infiltration. In this study, we assessed the quantity of DOC that was transferred from a relatively small portion of the urban landscape on the Albion College campus to the North Branch Kalamazoo River. We sampled across gutters, storm drains, and puddles on campus, as well as at the outflow storm drain, within the stream, and the groundwater for 9 precipitation events across a section of Albion College’s campus. For these sampling events we measured the total concentration of DOC. Using a City of Albion map of the city stormwater sewer system we determined the flow path to the stream. The area of campus assessed is approximately 0.07769964 km² with 47.60% developed as impervious surfaces. In this sampling we found that DOC on campus ranged from < 2 mg/L up to 329mg/L as compared to stream baseflow DOC concentrations consistently below 9 mg/L. Additionally, we found that stream DOC nearly doubled to 18 mg/L, a value comparable to that found in the storm drains during precipitation events.