INFLUENCE OF METHOD FOR REMOVAL OF SESTON ON THE DISSOLVED ORGANIC MATTER(1)

Area of Science:

• Environmental Science
• Analytical Chemistry
• Water Quality Analysis

Background:

• Accurate analysis of dissolved organic matter (DOM) in water samples is crucial for understanding aquatic ecosystems.
• Pre-treatment methods to remove seston can introduce errors affecting DOM measurements.
• Various filtration and centrifugation techniques are employed, each with potential limitations.

Purpose of the Study:

• To compare different methods for removing seston from water samples before DOM analysis.
• To identify and evaluate sources of error associated with these pre-treatment methods.
• To assess the effectiveness and limitations of novel techniques like biodialysis.

Main Methods:

• Comparison of cellulose ester filters (0.45 μm vs. 0.22 μm) and pre-washing protocols.
• Evaluation of filtration to dryness, wet filtration, continuous-flow centrifugation (10,000 x g, 100 cc/min), and regular centrifugation.
• Assessment of a newly developed biodialysis technique for DOM collection.

Main Results:

• Cellulose ester filters require washing to remove elutable carbon.
• Filtration to dryness can cause artifacts due to cell injury.
• A significant difference in retention exists between 0.45 μm and 0.22 μm membranes.
• Wet filtration and continuous-flow centrifugation are satisfactory but have limitations.
• Biodialysis yielded lower DOM values than centrifugation but varied compared to filtration methods.

Conclusions:

• Proper washing of filters and avoiding filtration to dryness are essential for accurate DOM analysis.
• Wet filtration and continuous-flow centrifugation are effective but not without drawbacks.
• Biodialysis shows potential as a supplementary and potentially more accurate method for DOM studies, particularly in specific water types.