HEAVY METAL AND GRAIN-SIZE ANALYSIS OF A SEDIMENT CORE FROM THE LITTLE TALLAPOOSA RIVER FLOODPLAIN, PIEDMONT PHYSIOGRAPHIC PROVINCE, GEORGIA, USA

Here we present heavy metal and grain size analysis of a 3.6 m sediment core of fine-grained Holocene floodplain alluvium obtained using the Vibracore method. This analysis is part of a larger, ongoing study on the University of West Georgia campus examining hydrogeology and sedimentology of a riparian wetland on the floodplain of the Little Tallapoosa River in the Piedmont Physiographic Province, Carroll County, Georgia. The core consists of generally fining-upward fluvial sediments. The base of the core consists of apparent channel-deposited sand and gravel; the remainder of the core consists of apparent channel-fill, natural levee and backswamp deposits. There is an apparent buried soil horizon at 2.7 m. The core was analyzed at 10 cm intervals for grain size (percent sand, silt, clay) using the hydrometer method. The same intervals were analyzed for heavy metals (Cd, Cu, Ni, Pb, Zn) using aqua regia digestion and inductively coupled plasma—atomic emission spectroscopy. Sand content varies from over 90% at the base of the core in apparent channel deposits to 25% higher in the core. Clay content varies from less than 10% near the base to a maximum of near 30%. The range (and average) heavy metal values in μg/g are Cd: bdl – 11.7 (3.9), Cu: 2.5 – 52.8 (15.5), Ni: 2.1 – 12.9 (5.2), Pb: 0.9 – 33.4 (10.2), Zn: 9.4 – 95.5 (36.6). Heavy metal concentrations are approximately three times higher in the upper 1.5 m of core relative to the lower 1.5 m. Peak heavy metals concentrations occur between depths of 0.5 and 1.2 m. There is some correlation between sediment clay content and heavy metals concentrations but for all analyzed metals except Cd, variation in metal concentration is significantly greater than clay content variations.