Modification of Soil Hydroscopic and Chemical Properties Caused by Four Recent California, USA Megafires

While it is well known that wildfires can greatly contribute to soil water repellency by changing chemical composition, the mechanisms of these changes are still poorly understood. In past decade, number, size, and intensity have increased in western USA. Recent megafires California (i.e., Dixie, Beckwourth Complex, Caldor, Mosquito fires) provided us with an opportunity characterize pre- post-fire soils study effects fires on repellency, organic constituents, connections between two. Water drop penetration time (WDPT) tests performed field showed a significant increase (from <1 s up >600 s) WDPT from soils. This after was confirmed increases apparent contact angle (ACA) 1.1 9 times unburned burned The characterization high resolution mass spectrometry abundance hydrophobic organics (e.g., PAH-like compounds molecules low number oxygen atoms) as correlation average H/C ratio aromaticity index (AI) ACA. Most likely, triggers hydrological such landslides, flooding, debris flows.