Author: Austin Charles DossPublisher:
ISBN:
Category :
Languages : en
Pages : 155
Book Description
"Phosphate treatments are used to immobilize lead in soil by forming pyromorphite. Soil from Bonne Terre, Mo was collected to study whether such treatment decreases the bioaccessibility of lead. The soil was treated using 0.5 soil wt% of phosphate. Treatments were: none, phosphoric acid, triple super phosphate, and organic bone meal. Each sample was studied after one, four, sixteen, and twenty weeks; during this time span, water was added approximating the average rainfall rate. Percolated water was collected to test the leached phosphate concentrations. Phosphate was below the detection limit in that leachate. Remediated soil samples were used in Physiologically Based Extraction Tests (PBET) and In Vitro Gastrointestinal Method Tests (IVG). Lead concentrations were determined using Flame Atomic Adsorption (FAA) and Graphite Furnace Atomic Adsorption (GFAA). Titrations of synthetically formed chloropyromorphite were conducted to determine the effect of pH on the dissolution of chloropyromorphite. Results showed that as pH decreased, dissolution between lead and phosphate increased. Ksp's of chloropyromorphite ranged from 10[sup -33.3] to 10[sup -84.4] depending on the varying pH and phosphate source. Remediated soil samples were used in a density separation analysis to determine heavy metal composition. Lead compounds such as lead sulfide, lead oxide and lead dioxide were found in trace amounts. The adsorption rate of lead through the stomach lining has been considered but not analyzed throughout this research. A decrease in lead bioaccessibility was observed after a remediation period of 20 weeks"--Abstract, page iii.