How important are subsurface sediments to the overall function of karst aquifers?

All aquifers contain a “matrix” – the solid component through which the water flows – but karst aquifers also contain sediments that can move dynamically between mobile (readily transported) and stationary (stored) pools. Both pools of sediments can influence contaminant mobility and storage as well as hinder or enhance remediation efforts.

PROTECT Researchers & Trainees Mohammad Shokri, Dorothy Vesper, Ellen Herman, Ljiljana Rajic, Kimberly Hetrick, Ingrid Padilla, & Akram Alshawabkeh explored this phenomenon and subsequently published a paper on “Bulk Chemistry of Karst Sediment Deposits” that was presented at the 2018 Sinkhole Conference.

In this work, the team obtained information on the range of cave sediment textures and chemistry so that we can better understand sediment influence on contamination and remediation. For example, stationary sediments with high concentrations of natural organic matter are likely to attract and bond with organic contaminants, leading to long-term storage and slow release of contamination—patterns we see in the data from northern Puerto Rico. Electro kinetic remediation methods may be influenced by sediment chemistry as well. Sediments with high concentrations of iron and manganese may either limit or enhance remediation effectiveness.

Although karst sediments have been a topic of research in recent years, little attention has been focused on the characteristics and properties that relate directly to contamination and remediation. In the initial phase of this investigation we collected sediment samples from seven locations in the karst regions of TN, VA and WV and measured their physical and chemical properties. A portion of each sediment was shared with PROTECT Project 5 and incorporated into their remediation studies. In future studies we will be collecting sediment samples from caves in Puerto Rico to help us understand the effects of extreme events such as Hurricane Maria on karst sediments so stay tuned!

Nice work, PROTECT Team!