Mobile sediment in an urbanizing karst aquifer: implications for contaminant transport

Here we investigate geochemical characteristics of sediment in different co mpartments of a karst aquifer and demonstrate that mobile sediments in a ka rst aquifer can exhibit a wide range of properties affecting their contamin ant transport potential. Sediment samples were collected from surface strea ms, sinkholes, caves, wells, and springs of a karst aquifer (the Barton Spr ings portion of the Edwards (Balcones Fault Zone) Aquifer, Central Texas) a nd their mineralogy, grain-size distribution, organic carbon content, and s pecific surface area analyzed. Statistical analysis of the sediments separa ted the sampling sites into three distinct groups: (1) streambed, sinkholes , and small springs; (2) wells; and (3) caves. Sediments from the primary d ischarge spring were a mix of these three groups. High organic carbon conte nt and high specific surface area gives some sediments an increased potenti al to transport contaminants; the volume of these sediments is likely to in crease with continued urbanization of the watershed.