Award Date

1-1-2003

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Committee Member

Vernon F. Hodge

Number of Pages

108

Abstract

Two analytical methods employing an ion chromatograph-inductively coupled plasma mass spectrometer were used to separate inorganic arsenite from arsenate and trivalent from hexavalent chromium in southern Nevada groundwater. Method detection limits were found to be 0.011 ppb and 0.005 ppb for arsenite and arsenate respectively, and 0.015 ppb and 0.02 ppb for trivalent and hexavalent chromium respectively. Following an investigation of the stability of the oxidation states of arsenic and chromium in aqueous solution with time, the following procedures were adopted. Samples collected in the field for arsenic were filtered, stored at 4°C, and analyzed within 7 days; and those collected for chromium analysis were filtered, stored at 4°C, and analyzed within 24 hours of collection. Groundwater samples analyzed were from wells of the Nye County Early Warning Drilling Program (NCEWDP) in Nye County, Nevada in fall 2002 and 2003, from wells in the Nevada Test Site (NTS) and Nellis Testing and Training Range (NTTR) in 2003, and from wells and springs in Inyo County in 2003. It was found that the concentrations in these waters consisted of total arsenic concentrations were between 1--45 ppb, with the majority of the groundwater wells containing more arsenate than arsenite. The total concentration of chromium in these wells was found to range between 0.25--4 ppb, with the majority of the groundwater wells containing more hexavalent chromium than trivalent chromium; A comparison of the calculated Eh values from As(III) and As(V) concentrations with the calculated Eh from the measured concentrations of Cr(III) and Cr(VI) was examined. It was found that the Eh calculated from arsenic redox couples and the Eh calculated from the chromium redox couples positively correlated with an R2 of 0.89.

Keywords

Arsenic; Chromatography; Chromium; Coupled; Groundwater; Inductively; Inorganic; Ion; Mass; Measurements; Nevada; Plasma; Southern; Species; Spectrometry

Controlled Subject

Chemistry, Analytic; Environmental sciences

File Format

pdf

File Size

2611.2 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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