DISSOLVED ORGANIC CARBON FLUXES IN FORESTED AND URBAN WATERSHEDS

The carbon cycle has been put into stress due to climate change and land-use changes from agriculture, urbanization, and watershed modification. This study focuses on the dissolved organic carbon (DOC) aspect of the carbon cycle, in particular, the quantitative levels of DOC in an unaltered estuarine system and a forested watershed compared to an urbanized watershed. DOC, which is classified as organic carbon that passes through a filter between 0.2 µm and 0.7 µm, is an important water quality parameter. It is an indicator for the ecological productivity of a water system and also increases disinfection by-product formation potential in water and wastewater treatment plants.

Synoptic sampling of water from tidal creeks and rivers in the Charleston, SC region was conducted during the late spring and summer 2015. Sampled areas include the Frances Marion National Forest freshwater, the Ashley River brackish and saltwater, and the Charleston Harbor saltwater. Filtered and acidified water samples were analyzed for DOC concentration (mg/L) using a Total Organic Carbon (TOC) Analyzer. Basic water parameters such as dissolved oxygen, salinity, conductivity, pH, and turbidity were measured to determine possible correlation with DOC. Fecal indicator bacteria (FIB) populations in urbanized Charleston area were also compared with DOC concentrations and data showed positive correlation. Preliminary results indicate that forested watersheds have higher DOC concentrations than the urbanized watershed.

The study has provided a broad scope of the DOC levels in natural waters with varying salinity in the Charleston, SC area. The audience for this project are scientists researching DOC in other areas, land managers whose decisions may affect fate and concentration of DOC in watersheds (land use change for development, wastewater treatment plant discharge), and stakeholders who use the waterways. The main contribution of the study thus far, is detailing the current DOC levels and environmental conditions of tidal systems and the differences in urbanized portions in the Charleston, SC area. The positive correlation to the FIB shows that DOC is a potential energy source for microbiological activity. The study shows the importance of monitoring the carbon cycle because of the ever-increasing anthropogenic stressors.