Mining has a very long-lasting impact in landscapes. This may manifest as topographic transformation that affects runoff generation, flood wave timing, and inundation. It may also involve the introduction of sediment-bound pollutants that undergo biogeochemical transformation to more toxic forms under hydrologic conditions that are suitable for certain bacterial communities. The 19th C. Gold Rush generated both physical and chemical legacies of great consequence to California. The industrial-scale process of hydraulic mining in the Sierra Nevada foothills displaced 1.1 billion m3 of sediment, filling river valleys, and creating anthropogenic fans composed of mine tailings that grade all the way to the Central Valley.

We are studying the complex set of processes linking the physical, chemical, and biological environment to better understand the mechanisms and processes by which Hg enters food webs in watersheds. This work has illustrated the importance of river corridors as key locations in the landscape where Hg is converted from inorganic to more hazardous organic forms, from which it is bioavailable to food webs.

Projects on this research theme include:

Establishing process links between streamflow, sediment transport/storage, and biogeochemical processing of mercury. Funded by National Science Foundation Geomorphology and Land-use Dynamics, M. Singer (PI), J.D. Blum, M. Marvin-DiPasquale, 2013-2016

Tracking hydraulic mining sediments from the Sierra Piedmont into flood bypasses of the Sacramento Valley, CA. Funded by National Science Foundation Geography and Spatial Sciences, M. Singer (PI), L.A. James, R. Aalto, T. Dunne, 2005-2008

Publications on this research theme include:

Washburn, S.J., Blum, J.D., Donovan, P.M., Singer, M.B. (2019); Isotopic evidence of methyl- and inorganic mercury photoreduction and retention on particles in surface waters of Central California, USA, Science of the Total Environment, 674:451-461, doi: 10.1016/j.scitotenv.2019.04.145. pdf

*Nakamura T., Singer M.B., Gabet E. (2018); Remains of the 19th Century: Deep storage of contaminated hydraulic mining sediment along the Lower Yuba River, California, Elementa: Science of the Anthropocene, 6(1):70, doi: 10.1525/elementa.333. pdf

Donovan, P.M., Blum, J.D., Singer, M.B., Marvin-DiPasquale, M., Tsui, M.T.K. (2016); Methylmercury degradation and exposure pathways in streams and wetlands impacted by historical mining, Science of the Total Environment, 568:1192-1203, doi: 10.1016/j.scitotenv.2016.04.139. pdf

Singer, M.B., Harrison, L.R., Donovan, P.M., Blum, J.D., Marvin-DiPasquale, M. (2016); Hydrologic indicators of hot spots and hot moments of mercury methylation potential along river corridors, Science of the Total Environment, 568:697-711, doi: 10.1016/j.scitotenv.2016.03.005. pdf

Donovan, P.M., Blum, J.D., Singer, M.B., Marvin-DiPasquale, M., Tsui, M.T.K. (2016); Isotopic composition of inorganic and methylmercury downstream of historical gold mining, Environmental Science and Technology, 50(4):1691–1702, doi: 10.1021/acs.est.5b04413. pdf

Singer, M.B., Aalto, R., James, L.A., *Kilham, N.E., *Higson, J.L., Ghoshal, S. (2013); Enduring legacy of toxic fans via episodic redistribution of California gold mining debris. Proceedings of the National Academy of Sciences (PNAS), 110(46):18436-18441, doi: 10.1073/pnas.1302295110. pdf

Donovan, P.M, Blum, J.D., Yee, D., Gehrke, G.E., Singer, M.B. (2013); An isotopic record of mercury in San Francisco Bay sediment. Chemical Geology, 349–350:87-98, doi: 10.1016/j.chemgeo.2013.04.017. pdf

*Springborn, M., Singer, M.B., Dunne, T. (2011); Sediment-adsorbed total mercury flux through Yolo Bypass, the primary floodway and wetland in the Sacramento Valley, California. Science of the Total Environment, 412-413:203-213, doi: 10.1016/j.scitotenv.2011.10.004. pdf

James, L.A., Singer, M.B. (2009), *Ghoshal, S., Megison, M.; Historical channel changes in the lower Yuba and Feather Rivers, California: Long-term effects of contrasting river-management strategies. Geological Society of America Special Paper, 451:57-81, doi: 10.1130/2008.2451(04). pdf