The characterization and chlorination of an isolated aquatic humic substance

Naturally occurring humic substances are a combination of decayed plant and soil materials that have been incorporated into a complex matrix with other organic substrates. These acidic humic substances account for a portion of the organic matter found in soil and in the soluble organic portion of fresh water. These humic acids, which are polar and straw-colored, are derived from soil humus and terrestrial and aquatic plants. Considerable attention has been given to these naturally occurring humic materials since the chlorination of these acids in our drinking water results in the formation of trihalomethanes and other chloro-organic compounds. Many of these chlorinated compounds have been determined by the standard Ames Salmonela test to be mutagenic. Despite extensive research concerning humic materials, their structure, and the environmental impact of the derived chlorinated organics are still not fully understood. This research involved an extensive analytical study on a local water source, Forge Pond, which is located in Granby, Massachusetts. The pond water was collected, chlorinated, and analyzed by gas chromatography with electron capture detection to determine the levels of chloro-organics formed when the pH, chlorine dose, and reaction time were varied. It was determined that these variables are critical in the formation of chlorinated organic products. Water was also collected from this pond and the humic material extracted by adsorption and concentration on XAD-8 resin. The thermal properties of the humic materials was studied by Thermal Gravimetric Analysis, and Pyrolysis/Gas Chromatography-Mass Spectrometry was used for chemical characterization. In general, humic acid showed prominent signals related to polysaccharides and phenolic derivatives whereas fulvic acid showed more polysaccharides, and less phenolic signals. A commercial humic acid showed analytical composition mainly related to benzene derivatives