TEMPORAL AND SPATIAL VARIATIONS OF HEAVY METAL CONCENTRATIONS IN MODERATELY DEVELOPED MARSH SEDIMENTS ON SKIDAWAY ISLAND, GEORGIA

This work is part of a three year NSF funded Research Experience for Undergraduates (ACRES) part of which aims to study the temporal and spatial distribution of heavy metals in salt marsh sediments of Georgia.  Previous regional studies have shown that anthropogenically derived heavy metals can be sequestered in fine-grained estuarine sediments (Alexander et al., 1997).  Summer 2003 data focus on long cores recovered from Skidaway Island.  Skidaway Island is located in the Ogeechee River drainage basin. Sediments originating from the Southern Piedmont are transported into the salt marsh via the Ogeechee River.  Skidaway Island is moderately developed.

A 3.77m vibracore was retrieved from the low marsh area at Skidaway Island, Georgia.  The core was split in half, described and sub-sampled for geochemistry, radiochemistry, clay analysis, sedimentology, and micropaleontology.  Samples for geochemical analysis were frozen immediately (-4°C) and subsequently split.  One portion of the sediment (procedure I) was washed, dried (80 °C), and crushed whole in a stainless steel micro-mill.  The other split (procedure II) was wet sieved through a 63mm sieve, dried (80°C), and the <63mm fraction ground.  A comparison between partial sediment digestion (Loring and Rantala, 1992) normalized to aluminum of the SKIO marsh (Dechant et al., 2003) and total digestion normalized to lithium (Loring, 1991) will serve to illustrate the efficacy of the partial digestion and quantitatively compare the two normalization methods.  Furthermore, a comparison between whole sample digestion and <63mm fraction digestion will provide insight as to the most efficient sample preparation methodology.  Both procedure I and II splits (0.25g) were digested using a 2:1:1:1 ratio of HF, HNO₃, HClO₄, and HCl.The digestate was resuspended in 1% trace metal grade HNO₃ and brought to volume (50mL).  Diluted 10mL aliquots were prepared from the stock solutions and heavy metal (Al, Fe, Mn, Zn, Co, Cr, Cu, Pb, Ni, Cd, Mo, U, V) analysis conducted on a Finnegan Element 2 ICP-MS.