Abstract of the Thesis

Organic Sorption and Cation Exchange Capacity of Glacial Sand, Long Island

by

Sonya Boguslavsky

Master of Science

in

Geosciences

State University of New York at Stony Brook

2000

Cation exchange capacity (CEC) of glacial sand from different locations on Long Island was analyzed, using 0.1 M BaCl2 extraction. The glacial sand consists of primarily quartz. Most quartz grains contain coatings on the surface. The CEC of sand analyzed in this study varies from 0.85 meq/100g for coarse sand-gravel to 21.3 meq/100g for fine sand. The CEC of sediments is function of grain size, mineralogy, amount of organic matter and amount of coatings on the grains. In this study grain size seems to be the most important factor in determining CEC. The distribution of exchangeable cations with depth was observed in the core 0-480 cm below the surface. The main exchangeable cation in 0-120 cm below the surface is Al (75-82% of the total CEC), at the depth 150 cm exchangeable Al contains < 2% of the total CEC. The fraction of exchangeable Na generally increases with depth from 10% of total CEC at 0-60 cm to 78% of total CEC at 420-440 cm. In the upper part of the sequence exchangeable Ca occupied 8% of the total CEC and below 90 its fraction is negligible. The distilled water and BaCl2 pH was measured in the core. At 90-120 cm below the surface the BaCl2 pH is lower than water pH, but below 120 cm water pH is lower than BaCl2 pH. The CEC of untreated sand, naked sand and coatings was measured. In this sample coatings contribute 87% of the CEC. The fraction of the coatings in these samples varies from 0.8% to 13%.

Composition of these coatings were analyzed by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Total organic carbon (TOC) was measured on the sand and coatings. Results suggest that coatings composed of clay minerals (illite, kaolinite and chlorite) with minor amount of organic matter and iron compounds. Fraction of organic (foc) carbon on sand varies from 0.0002 to 0.00027. The foc on the coatings varies in the range from 0.0021 to 0.0076.

Results of short term hydrophobic organic compound sorption experiment suggest that the Kd (hexachlorobenzene) (HCB) for glacial sand varies from 2.5 ml/g to 10.7 ml/g. The Kd for coatings lies between 396 ml/g and 1480 ml/g. The Kd for naked sand is always lower than that observed for untreated sand and coatings varies between 1.55 ml/g and 9.02 ml/g. The coatings appear to be the main sorbent for HCB, 72.8 - 85 % of HCB sorbed on the coatings. Sonication of the sand increases Kd by 20.1-73.1 %. Sorption of HCB by the coatings is consistent with the amount of organic matter onto the coatings. The partitioning of HCB into coatings organic matter is likely control sorption. Some amount of organic matter remains unavailable for sorption of HOC. The results of this study suggest that in cation exchange and hydrophobic organic compound sorption the coatings play the major role.

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