ARSENIC SPECIATION, 18O AND 2H ISOTOPIC COMPOSITION OF GROUND WATER AT A LANDFILL SITE IN CENTRAL MASSACHUSETTS
Each of the above listed sources of As can be by itself observed as the principal source of arsenic for groundwater contamination at different locations in the vicinity of the studied landfill site. Geochemical indicators at these locations include correlations with other trace metals (Ni, Co, Cu, and others), spatial distribution, concentration levels, redox potential, pH, presence of sulphates, and alkalinity.
Arsenic speciation and variations of stable isotope compositions of groundwater samples (D & 18O) from different sampling points at and near the landfill are addtional geochemical parameters we hope to use to gain a better understanding of arsenic mobilization and arsenic sources. Arsenic species, including inorganic As(III), As(V), plus organic monomethyl arsenic acid (MMA) and dimethyl arsenic acid (DMA) are separated on a HPLC column and analyzed by HG/AFS system. Field samples were collected into 125 mL amber bottles each containing 1.7 mL of 0.1 M EDTA (Samanta and Clifford, 2006) to preserve As speciation from ferrihydroxide precipitation. Preserved and unpreserved samples yielded nearly identical values when analyzed within a few hours after field sampling. After 24 hours the EDTA samples remained unchanged while unpreserved samples lost significant total As as well as As(III). Samples for isotope analysis were collected into separate standard bottles and sent for analysis by a CRDS methodology. Results from both sets of analyses, once completed, will be compared with the existing geochemical parameters.