Case Study in Environmental Chemistry....

Author: Sarunya Hengpraprom and Cindy M.Lee, Environmental Engineering and Science, Clemson University.

Introduction

During 2000, 293 billion pounds of about 8000 different organic compounds were manufactured in the United States (1). Many millions of pounds of synthetic organic compounds are deliberately introduced into the environment for weed and pest control, and many millions of pounds of other chemicals are introduced into the environment through their proper uses. However, an increase in production and dispersion of synthetic organic chemicals is reported to be responsible for species extinction and several hundred thousand of human cancers per year (2). Several years ago, the government began to regulate the manufacture and use of selected chemicals, such as DDT, which had been shown to be exceptionally hazardous to the biological environment (3). In addition, federal registrations such as the Toxic Substance Control Act regulate the introduction of hazardous chemicals into the environment (3).

Fortunately, the environment has the capacity to transform many kinds of chemicals through a variety of chemical and biological degradative processes (4). In aquatic systems, reaction of a compound with water ("hydrolysis") is perhaps the most important and significant chemical degradative process since many hydrolysable chemicals, including pesticides and plasticizers, eventually find their way into groundwater, streams, and rivers through leaching and runoff (4). In addition, hydrolysis by-products are normally less toxic to organisms than parent compounds. The rates of hydrolysis in aquatic systems are greatly dependent on environmental factors such as sunlight, microbial populations, and oxygen supply (5). Researchers in environmental chemistry investigate the effects of some of the key environmental factors such as pH, temperature, solvent composition, metal ion catalysis (mineral components), ionic strength and buffer effects (5). In this case study, one such experiment explores the effect of pH on the hydrolysis reaction of a commonly used insecticide.