|Fluorescent Whitening Agents as Facile Pollution Markers in Shellfishing Waters
|Eugene A. Cioffi
Department of Chemistry, University of South Alabama, Mobile AL 36688-0002
|Within the past several
years, the Alabama Department of Public Health (ADPH) has closed
numerous shellfish resources to the taking of shellfish due to elevated
bacteriological levels coliform bacteria. Often, closure is a result of
either overloaded point sources (sewage treatment plant) during a storm
event, or non-point source pollution due to septic failure, illicit
storm drain connections, etc. Besides the obvious health-related impact
due to potential disease vectors, concomitant increased nutrient loading
promotes eutrophication and diminished water quality.
One of the main problems associated in determining the cause (human/nonhuman) and prevention of fecal coliform bacteria contamination is the inability to precisely determine the source of contamination. Fecal coliform may incubate and multiply in stream waters, and in sandy outwash areas, bacterial transport may be attenuated after only 1-2 meters of subsurface transport, while resilient bacteria and viruses may transport unimpeded. In order to successfully determine the origin (human/nonhuman) of nonpoint source pollution, a study will have to demonstrate a correlation with bacteriological indicators and other water quality indices.
A newer technique utilized to help identify the source of pollution attributed to human activity is fluorometry. Detergents are used in very large quantities, and contribute a significant portion of the load of anthropogenic chemicals to the aquatic environment. Fluorescent whitening agents (FWAs) contribute only 0.15% of the total mass of most laundry detergents, and may be discharged to a septic system (Individual Sewage Disposal System or ISDS) or to a stormwater drainage system (through an illegal connection). The moderately water soluble, fluorescent organic compounds have a high affinity for cellulosic material. Since all FWAs absorb UV light at approximately 350nm and emit visible blue light at a maximum of 430nm, they may readily be detected with a high-resolution spectrofluorometer at a high sensitivity (<10 parts per trillion).
The recovery of FWAs in nearby waters (surface, ground, or estuarine waters), in conjunction with elevated bacteriological results, is indicative of ineffective natural cleansing of wastewaters.
The recovery of FWAs in stormdrain systems in conjunction with elevated bacteriological (and/or nutrient) results indicates human-related contamination such as an illegal wastewater discharge to the storm drain system. A recent preliminary study, which utilized a combination of solid-phase extraction, ion-pairing chromatography, and field fluorometry, demonstrated for the first time, the direct applicability of utilizing FWAs as facile anthropogenic pollution tracers in freshwater, marine and estuarine samples. Although the combination of selective extraction and chromatography afforded a reasonably low limit of detection (<6ppb) with a high reproducibility (0.4 to 5.5% RSD), the classes of FWAs (and E-, Z-isomers therein) were not separated. If the origin and behavior of FWAs in the environment are to be investigated, quantification of individual classes (and E-, A- isomers) is important, because isomers of the same FWA show different sorption behavior, and the E-:Z-isomeric ratio plays an important role in ultimate degradation.
This study will: (1) investigate the use of fluorescent whitening agents (FWAs) as anthropogenic markers of ISDS pollution and human-associated storm-drain contamination in the Mobile Bay estuarine system; (b) evaluate newer solid-phase supports (ex. Carbongraph«) in the laboratory for the selective preconcentration of individual FWA classes; (c) investigate new selective field sampling techniques; (d) identify the specific class of FWAs (and E-,Z- isomers) directly using 1H and 13C nuclear magnetic resonance spectroscopy (NMR) coupled with computer assisted pattern-recognition techniques; (3) investigate polymer-fiber Solid-Phase Microextraction (SPME) technology as inexpensive in situ sampling technique, which could optimally afford the unattended sampling of an entire watershed.