Abstract:
More than 65,000 organic chemicals are currently in commercial production with
approximately 1000 added each year. Many chemicals are released into the environment as organic mixtures derived from complex hazardous or solid wastes. Of these, more than 1000 chemicals are of environmental concern because of their production quantities, toxicity, persistence, and tendency to bioaccumulate. To manage the impacts of these chemicals to the environment, the environmental chemodynamics of such Complex Organic Mixtures (COMs) or Solid Waste Materials (SWMs) must be predicted accurately. Required information includes the molecular organic composition of SWMs/COMs and/or their leachates, the transport processes and migration in and between the various multimedia environments, chemical and biochemical transformation processes, and effects on the interacting organisms. A technique is developed to predict the potential impact of SWMs/COMs based on the organic chemical composition of the extracts from such complex materials and/or their leachates. In addition, the methodology can be used to estimate the potential hazards of organic pollutants in such complex mixture, ultimate fate and environmental toxicity. This technique consists of three fundamental approaches: characterization and source partitioning, chemodynamics and Environmental Impact Assessment (EIA) models. The characterization and source partitioning model of SWMs/COMs and their leachates are based on their lipid molecular marker (MM) signatures. Chemodynamics (i.e., Fate-Transport) model is based on experiments such as leaching, sorption, volatilization, photolysis, and biodegradation. These experiments are carried out for different SWM leachates and a group of polycyclic aromatic hydrocarbons (PAHs) that are characteristic to the studied leachates. The Environmental Impact Assessment (EIA) model estimates the probability of 96-hr fresh water alga Selenastrum capricornutum chronic toxicity of EPAH-containing SWMs/COMs using a combination of leaching kinetics, equilibrium partitioning, QSPR-QSAR, toxic unit, multicomponent joint toxic effect of mixtures (i.e., additivity, synergism, or antagonism) and dose-response models. The EPAH model is verified by comparing both predicted and observed toxicity in different waste materials. Molecular Connectivity-Quantitative Structure Activity
Relationship (MC-QSAR) techniques then are used to develop a predictive model to
estimate the concentrations of PAH components in mixtures derived from SWMs/COMs leachates that would jointly cause 50% inhibition of alga Selenastrum capricornutum toxicity.
