IMPACTS OF FOREST FIRE ON STREAM SEDIMENT: A CHEMICAL ANALYSIS OF THE 16 MILE FIRE IN DELAWARE STATE FOREST, PENNSYLVANIA, USA

Wildfires, which will occur naturally or be produced from anthropogenic activities, are known to have significant impacts in most terrestrial and aquatic ecosystems such as streams. Following a wildfire, burning of soil and vegetation to ash can potentially lead to the input of contaminants such as trace elements into nearby aquatic streams. For this study, stream sediments were examined from the 16-Mile Fire that occurred in April 2016 at the Delaware State Forest, Pennsylvania, USA to determine major and trace elements present. While major and trace elements have been previously examined in soil from the 16-Mile Wildfire, stream sediments have not been extensively studied, particularly tributaries within and outside the fire perimeter. Sediment cores were collected from five streams both within the burned area of the 16-Mile Fire and outside the fire zone to compare results. Inductively coupled plasma mass spectroscopy (ICP-MS) was conducted for major, trace, and rare earth elements (REE) concentrations of the samples to determine the presence of fire signatures identified previously. Particle sizes were analyzed to understand the distribution of sediment in each sample. The presence of charcoal fragments was also found in all stream sediment samples four years after the 16-Mile Fire. Trace elements such as V, Co, Ni, Cu, Rb, Sr, Zr, and Ba were in higher concentrations outside the fire than inside. A digital elevation model helped to determine the watershed areas impacted by the 16-Mile Fire. Results indicate that only one stream (BK_5) did not intersect the fire and was more concentrated in signature element than samples taken from fire-intersected watersheds. Possible reasons for within-fire element depletion in stream sediments, compared to surrounding areas, include a combination of rapid loss following the fire, sequestering in the soil, or uptake into new vegetation (on land or in water). The data reported here are the first results on stream sediment chemistry in the 16-Mile Fire research, which provides an important understanding where fire signatures reside and their impact on aquatic environments.