Relationship between sediment clay minerals and total mercury

Abstract

A group of 262 sediment samples were collected from various lakes, rivers, reservoirs, and bayous of Louisiana. All samples were analyzed for total mercury. Twenty nine of the samples with total mercury content ranging from 11 to 401 ppb (μg/kg) were analyzed for clay minerals and other sediment physical and chemical properties. Clay content in sediments varied from 3 to 72%. Clay minerals were determined by X-ray diffraction (XRD) technique. Identification of clay minerals was determined by MacDiff software and quantification of clay minerals was obtained by Peak Height Percentage (PHP) calculation. The dominant clay mineral was Hydrated Interlayer Vermiculite (HIV), which represented 51–83% of the total clay mineral. Significant linear correlations were observed between Hg and total clay content (r= 0.538**). However Smectite was the only individual clay type correlated (r= 0.465**) with mercury in sediment. Cation exchange capacity (r= 0.404*), organic matter (r= 0.577**), and sulfur (r= 0.676**) were also correlated significantly with mercury level in sediment.

Keywords:

• Sediment
• clay mineral
• organic matter
• total mercury
• lake
• Louisiana

Acknowledgments

Funding was provided in part by Louisiana Department of Environmental Quality.