Do water sampling techniques affect aluminum speciation?

PI: Ken Johnson

Project Summary
Certain species of aluminum (Al) are toxic to Atlantic salmon. This project will analyze the effects of different water sampling techniques on Al speciation in the Dennys River in downeast Maine.

Objectives
The Dennys River in Edmunds Township, Washington County, Maine is a potential site for a calcium enhancement experiment (CEDAR), funded and directed by the National Oceanic and Atmospheric Administration (NOAA). The objective of the CEDAR project is to characterize water chemistry of the Dennys River prior to any chemical additions and then to monitor those conditions after the addition. One expected outcome of the CEDAR project is the reduction of the magnitude of pH depressions during rain events. This change in pH will change Al speciation, very important to Atlantic salmon because of the toxic nature of some species of Al. This project will assess the validity of the water sampling and processing techniques currently in place for accurate Al speciation analysis.

Standard methods prescribe that samples taken at the river, the samples are sealed and stored on ice until analysis. During this time carbon dioxide (CO2) may off-gas and change the pH of the sample, thus changing the speciation of Al and resulting in a non-representative sample of the river water. During processing the samples are filtered before total Al analysis, neglecting the particulate fraction of Al. In order to adequately assess the success of the CEDAR project, we must be sure that the techniques used to sample, store, process, and analyze water are robust enough to detect any changes in Al speciation that may occur in order to assess the effects on Atlantic salmon.

The calcium addition is tentatively scheduled for spring, 2006, so it is important to validate all sampling strategies prior to the proposed addition. A better understanding of methods needed to sample and analyze Al in surface waters will benefit all fisheries scientists by providing consistent, reproducible results that are representative of the conditions in Atlantic salmon rivers. Standardized sampling and analysis methods allow scientists and resource managers to share data, compare research, and work together to address common challenges.

The objectives of this project are to process water samples at different time intervals to determine when Al begins to re-speciate due to CO2 off-gassing and to determine the difference between particulate Al and dissolved Al. This experiment will assess sampling and processing techniques currently in place to ensure they are adequate for the project needs.