Suspended Sediment Mineralogy and the Nature of Suspended Sediment Particles in Stormflow of the Southern Piedmont of the USA

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The majority of annual sediment flux is transported during storm events in many watersheds across the world. Using X-ray diffraction, we analyzed the mineralogy of grab samples of suspended sediment during different stages of storm hydrographs in the Southern Piedmont. Mineralogy of suspended sediment changes drastically from quartz-dominated during the rising limb to clay dominated during the late falling limb/baseflow. Changes in mineralogy can shed insight into turbidity relationships, suspended sediment sources, energy versus supply-limited sediment transport, and other suspended sediment parameters such as anion exchange capacity and trace element chemistry. An unexpected key finding, confirmed by X-ray diffraction and electron microscopy, is that both kaolinite and quartz are primarily transported as discrete crystalline minerals of different size classes in our watersheds; this contrasts with existing scientific literature stating that in most fluvial systems suspended sediment is transported primarily as composite particles composed of a heterogeneous mix of all particle sizes. Our findings also support existing literature that turbidity can be a good proxy for elements such as P, which are preferentially adsorbed onto iron oxide coatings thus in situ turbidity probes have great potential to provide relatively inexpensive estimates of P flux when calibrated for specific watersheds.





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River, M, and CJ Richardson (2019). Suspended Sediment Mineralogy and the Nature of Suspended Sediment Particles in Stormflow of the Southern Piedmont of the USA. Water Resources Research, 55(7). pp. 5665–5678. 10.1029/2018WR024613 Retrieved from

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Curtis J. Richardson

Research Professor of Resource Ecology in the Division of Environmental Science and Policy

Curtis J. Richardson is Professor of Resource Ecology and founding Director of the Duke University Wetland Center in the Nicholas School of the Environment. Dr. Richardson earned his degrees from the State University of New York and the University of Tennessee.

His research interests in applied ecology focus on long-term ecosystem response to large-scale perturbations such as climate change, toxic materials, trace metals, flooding, or nutrient additions. He has specific interests in phosphorus nutrient dynamics in wetlands and the effects of environmental stress on plant communities and ecosystem functions and services. The objectives of his research are to utilize ecological principles to develop new approaches to environmental problem solving. The goal of his research is to provide predictive models and approaches to aid in the management of ecosystems.

Recent research activities: 1) wetland restoration of plant communities and its effects on regional water quality and nutrient biogeochemical cycles, 2) the development of ecosystem metrics as indices of wetland restoration success, 3) the effects of nanomaterial on wetland and stream ecosystem processes, 4) the development of ecological thresholds along environmental gradients, 5) wetland development trends and restoration in coastal southeastern United States, 6) the development of an outdoor wetland and stream research and teaching laboratory on Duke Forest, 7) differential nutrient limitation (DNL) as a mechanism to overcome N or P limitations across trophic levels in wetland ecosystems, and 8) carbon sequestration in coastal North Carolina pocosins.

Richardson oversees the main analytical lab in NSOE, which is open to students and faculty. Dr. Richardson has been listed in Who's Who in Science™ annually since 1989 and was elected President of the Society of Wetland Scientists in 1987-88. He has served on many editorial review committees for peer-reviewed scientific journals, and he is a past Chair of the Nicholas School Division of Environmental Sciences and Policy. Dr. Richardson is a Fellow of the American Association for the Advancement of Science, the Society of Wetland Scientists, and the Soil Science Society of America.

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