Masters Theses

Date of Award

8-1977

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Joseph H. Rule

Committee Members

Don W. Byerly, Roger Minear

Abstract

Large volume (80 liter) water samples were collected from five sites on four streams in the New River Basin of Tennessee for study of the suspended sediment. Parameters selected for investigation were:

(1) Sediment size distribution

(2) Mineral composition of the sediment

(3) Metal content of the sediment

(4) Extractable Fe-Mn Oxide content of the sediment

(5) Association of heavy metals with Fe-Mn oxides

Sediment was separated by gravity settling and continuous flow centrifugation. Size separations showed that most of the sediment was in the 2-5μm size range and 0.2-2μm particles were second most abundant in most samples regardless of the degree of surface disturbance in the watershed. Streams in extensively mined watersheds carried heavier loads of suspended sediment than a stream in an unmined watershed.

The most abundant minerals in the suspended sediment in this region wee quartz, kaolinite, and illite. Chlorite, vermiculite, lepidocrocite, and mixed layer clays were identified as minor components of the sediment. Fe and Mn oxides were found to be important as a cementing agent of flocculated particles and tended to obscure sized distinction of the clay minerals. Chlorite content of argillaceous bedrock was higher than that of the sediment indicating that weathering processes allowed vermiculite to form in soils.

Sediment was analyzed for Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn by atomic absorption following total acid digestion using hydrofluoric and perchloric acids. Analysis of size separated samples showed that levels of most metals increased with decreasing particle size. Mn tended to accumulate in the coarser size fractions of the sediment. Fe, Mn, and Zn levels were higher in mined watersheds than in unmined watersheds. Other metals were present in about the same levels in suspended sediment from all streams sampled. Assessment of the total suspended load in each stream would indicate that a higher total volume of metals is carried in the sediment in mined watersheds than in unmined watersheds.

High levels (>50 weight percent) of dithionite extractable Fe and Mn oxides were found in sediment from an extensively mined watershed and lower levels were found in streams less affected by mining. Levels of extractable oxides corresponded with total Fe content of size separated samples and increased with decreasing particle size.

Acid extraction of Fe and Mn oxides and analysis of the extract solutions showed that the Zn content of the sediment was strongly associated with Fe content and Co and Cu were associated with Fe but to a lesser extent. Analysis of residues remaining after this extraction showed that Cr, Ni, and Pb were nearly evenly distributed between acid and extractable forms and residue materials.

This study showed that coal mining affects the suspended sediment by increasing levels of Fe, Mn, and Zn; which are present in oxide precipitates. Suspended sediment load is increased by mining activities with a resulting increase in the total metal volume transported in suspended particulates. Vermiculite content of suspended sediment in mined watersheds was lower than in unmined watersheds. Bulk mineralogy was little affected by mining but formation of oxide coating on sediment particles was heavier in mined watersheds than in unmined areas.

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