Determination of Bioavailable Aluminum in Natural Waters in the Presence of Suspended Solids

Crafting Consensus Methods for Environmental Sampling and Measurement
Oral Presentation

Prepared by W. Adams1, A. Cardwell2, W. Stubblefield2, E. Nordheim3
1 - Red Cap Consulting, 7760 North Boulder Drive, TOOELE, UT, 84074, United States
2 - Oregon State University, , Corvallis, Oregon, United States
3 - European Aluminum Association, , Brussels, , Belgium

Contact Information: [email protected]; 801-558-0222


Analyses of natural waters frequently show elevated levels of total aluminum (Al) attributable to acid extraction of
Al from the total suspended solids (TSS) minerals. Hence, there is a need for an analytical method that measures only
bioavailable Al. Natural waters high in TSS were collected to study the chronic effects of Al on Ceriodaphnia dubia. In the
collected waters TSS ranged from 30 to 411 mg/L; total Al concentrations ranged from 2.0 to 44.8 mg/L. To demonstrate that toxicity can be measured in natural waters, samples with elevated TSS were spiked with soluble Al, and survival and reproduction were measured in chronic studies performed at pH 6.3 and 8.0. To properly characterize the Al concentrations in the toxicity studies, a method was needed that could discriminate bioavailable Al from mineral forms of Al. An extraction method at pH 4 for bioavailable Al was developed and evaluated using C. dubia chronic toxicity studies in the presence of TSS. It is concluded that the proposed method is better able to discriminate chronic toxicity effects attributable to bioavailable Al from mineralized nontoxic forms of Al compared with existing methods using total or total recoverable Al (i.e., extraction at pH ≤ 1.5). We propose that this new method be used when assessing the potential for Al in natural surface waters to cause toxicity.