Total Recoverable Aluminum: Not Totally Relevant for Water Quality Standards. (2nd September 2019)

• Record Type: Journal Article
• Authors: Ryan, Adam C; Santore, Robert C; Tobiason, Scott; WoldeGabriel, Giday; Groffman, Armand R
• Is Part Of: Integrated environmental assessment and management. Volume 15:Number 6(2019)
• Page Start: 974
• Page End: 987
• Publication Date: 2019-09-02
• Subjects: Aluminum -- Water quality criteria -- Pajarito Plateau -- Suspended sediment -- New Mexico; Environmental management -- Periodicals; Pollution -- Periodicals; Environmental toxicology -- Periodicals; Environmental risk assessment -- Periodicals; Environmental impact analysis -- Periodicals; 628
• DOI: 10.1002/ieam.4177
• Languages: English
• ISSNs: 1551-3777

Abstract

ABSTRACT: A large water quality data set, representing more than 100 surface‐water locations sampled from 2007 to 2017 in the Los Alamos area of New Mexico, USA's Pajarito Plateau, was assembled to evaluate Al concentrations in unfiltered and filtered samples. Aluminum concentrations often exceeded United States Environmental Protection Agency (USEPA) and New Mexico ambient water quality criteria (AWQC), regardless of filter size and sample location. However, AWQC are based on laboratory toxicity studies using soluble Al salts and do not reflect natural conditions in Pajarito Plateau surface waters. The plateau is predominately covered by glassy and recrystallized volcanic ashes (e.g., Bandelier Tuff) containing colloidal to sand‐sized aluminosilicates. Samples from natural background drainages and areas downstream of developed regions exhibited similar Al concentrations, suggesting that AWQC exceedances are caused by naturally elevated Al concentrations. Solubility calculations indicated that most samples were oversaturated with respect to amorphous Al(OH)3 (s). Therefore, AWQC exceedances are likely artifacts of the "total recoverable" sample preparation, which includes acidification and partial digestion, thereby liberating nonbioavailable Al from aluminosilicates. Accordingly, Al concentrations were strongly associated with suspended sediment concentrations (SSCs), implying that aluminosilicates in suspended sediment contributed to AWQC exceedances and Al oversaturation. Solid‐phase particle characterization, using X‐ray diffraction (XRD) and scanning electron microscopy with electron dispersive spectroscopy (SEM/EDS) did not identify potentially bioavailable amorphous Al(OH)3 (s) in any sample tested. Thus, current sample collection and analysis protocols should not be used to evaluate attainment of Al AWQC on the Pajarito Plateau or locations where aluminosilicates are substantial contributors to total recoverable Al. A sample preparation method (e.g., pH 4 extraction) capable of differentiating nonbioavailable and bioavailable forms of Al is recommended. Otherwise, current New Mexico and USEPA sample preparation approaches will continue to generate artifactual AWQC exceedances in surface waters that contain aluminosilicates. Integr Environ Assess Manag 2019;00:1–14. © 2019 SETAC Key Points: Current methods associated with sample preparation and analysis of surface‐water samples for Al include contributions from aluminosilicates in suspended sediment. Because total recoverable Al measurements in surface‐water samples include contributions from aluminosilicates, total recoverable Al concentrations should not be used to evaluate attainment of ambient water quality criteria. The problem with using total recoverable Al to evaluate attainment of water quality criteria is demonstrated with a large data set for New Mexico, but this issue is relevant for other waters of the United States.