Comparison of groundwater colloids in adjoining soils of Florida flatwoods

Colloids in soil water are a constituent of natural geochemical fluxes and have the potential to facilitate contaminant transport, but few data are av ailable on their composition and concentration. This study addresses how th e composition and concentration of groundwater solids relate to hydrologica l and soil morphological variables of the Florida flatwoods landscape. Grou ndwater from saturated soil horizons was sampled biweekly for 1 year along an Aquod/Udult boundary using piezometers designed specifically to minimize disturbance and to permit the valid assessment of suspended solids. Readil y dispersible clay from core samples of soil horizons was collected and qua ntified. Groundwater and soil colloids were analyzed physically, chemically , and mineralogically. Aquod groundwater had consistently lower pH, higher electrical conductivity, and more total solids (TS) and organic carbon (OC) than did Udult groundwater. Significant decreases in both TS and OC concen trations in groundwater occurred with depth for both soils. In contrast, th e mineralogy of groundwater colloids was insensitive to soil and horizon di fferences. Quartz dominated inorganic colloid fractions in groundwater samp les from all horizons, even in argillic horizons where clay fractions conta ined little or no quartz. No statistical correlations were found between ma sses of groundwater colloids and soil water-dispersible clay. However, the proportion of organic carbon was higher in groundwater than in soil matrice s. Results are consistent with carbon and colloidal quartz movement in shal low groundwater of the soils studied and document that natural colloid and solute fluxes can be highly soil specific.