Prairie View A&M UniversityPrairie View A&M UniversityHBCU/MIHBCU/MI

Environmental Technology ConsortiumEnvironmental Technology Consortium

Hylton G. McWhinney, Ph.D.Principal Investigator

John R. Williams, Ph.D.Steering Committee Member

March 10, 2003

A Study of Sediment A Study of Sediment Composition and its Effects on Composition and its Effects on Hazardous Metal Ion SorptionHazardous Metal Ion Sorption

Brief project backgroundResearch Goals and ObjectivesSpecific Studies of InterestProject Deliverables

Project BackgroundProject Background

Knowledge of sorption and partitioning of heavy metal ions on particles is fundamental to the understanding of transport mechanisms and the fate of these contaminants in the environment.

X-ray photoelectron spectroscopy (XPS) studies are useful in delineating the effects of solution chemistry (concentration, competing ions, and pH) on selected highly toxic metal ions.

Project BackgroundProject Background

The adsorption in soils of toxic metal ions such as Cr, Zn, Cu, Pb, and Cd, as well as radioactive ions and their analogs, is of tremendous importance.

Although, these ions may adsorb at low concentrations, colloid aggregation and sedimentation may result in concentrating these materials in sediments.

Pesticides, metals, chlorinated hydrocarbons and other contaminants absorbed to particles carried by rivers may be transported to the sediments of lakes and estuaries.

Project BackgroundProject Background

Previous work has relied upon “bulk” characterization of metals.

Detailed surface and interfacial analysis and the processes controlling metal adsorption and transport have not been thoroughly addressed so far.

In natural systems, mixtures of inorganic solutes compete for adsorption sites on particles. The nature of this competition determines the ultimate distribution of metals between dissolved and colloidal phases.

Project BackgroundProject Background

Process is more complex in systems such as the Houston watershed, where particles and contaminants undergo a drastic change in solution chemistry as they are transported to the more saline estuarine environment. Adsorptive equilibria and colloidal stability may change.

The relationship between adsorption of inorganic species and colloids stability is of particular interest since aggregation may enhance the transport of adsorbed species in sediments.

Research Goals and ObjectivesResearch Goals and Objectives

Project is designed to Increase understanding of the role of sedimentation in the transport and build up of toxic metals in lakes, harbors, and estuaries.

Primary Objective is to study the surface compositions of natural particles and to investigate their effects on competitive adsorption of hazardous metal ions (Zn, Pb, Cu, Cr) on colloids and sediments.

Proposed StudiesProposed Studies

It is proposed to carry out surface and bulk studies on:– Competitive adsorption and desorption of selected metal

ions on sediments of 1µ - 250µ size distributions. Particular interest will be placed on the behavior of particle sizes less that 5µ because these represent particles of great interest.

– Sorption on particles in the presence of simulated waste runoff.

– Sorption on sediments in estuarine conditions (Various degrees of salinity and ionic strength media).

– The use of X-ray Photoelectron Spectroscopy to establish the elemental composition (semi-quantitative) of sediments on a routine basis.

X-Ray Photoelectron SpectrometerX-Ray Photoelectron Spectrometer

PHI 5600ci

XPS/ISS

Instrument located in the

Surface Science

Facility of the Department of Chemistry at

PVAMU

Expected Project DeliverablesExpected Project Deliverables

Required Quarterly and Annual Reports, Manuscripts for publication and presentations at regional and national professional meetings.

Undergraduate and Graduate Student, Staff, and Faculty development.