Water Resources Professional Project Reports

Document Type

Report

Publication Date

Winter 2019

Abstract

Water quality has become an increasing concern in recent years. The environmental challenges surrounding water quality include the presence of dissolved metals and their potential impact on human health and the environment. The challenge is exacerbated because many important metals have multiple oxidation states, which affect the health and environmental behavior of the metal. Many metals are known carcinogens and increased anthropogenic effects have inexorably made metals’ accumulation an imposing threat. Analytical instrumentation has advanced in many areas, making it now possible to measure very low concentrations of multiple elements in water. Current interest is determining the chemical speciation of metals such as arsenic (As), chromium (Cr) and selenium (Se) which have multiple oxidation states in environmental systems. Conventional protocols involve analysis of filtered and acid-preserved samples which measures the total soluble concentration. However acid preservation can affect metal speciation. The primary objective of this research was to investigate non-acid preservatives. In this research, experiments were conducted on water samples subjected to different sample preservation methods and no preservation as a control. Metals studied were arsenic (III), arsenic (V), chromium (VI), chromium (III), selenium (IV), and selenium (VI). It was hypothesized that a non-acid preservation would limit redox reactions that would affect the speciation of these metals. Water samples were collected representing a range of different aqueous conditions and subjected to two alternate preservatives: EDTA+TBAOH and HEPES. Samples were then analyzed by a High-Pressure Liquid Chromatography (HPLC) instrument coupled to an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) to determine the concentration of species for each element. Data analysis followed appropriate data quality standards to validate the accuracy and precision of all results and analyzed data was evaluated to draw conclusions on the preservation techniques used. Data revealed that the HEPES and EDTA+TBAOH preservative were able to preserve most species for at least seven days.

Keywords

water, metals, oxidation, arsenic, chromium, selenium

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