Evaluation of Sampling and Field-Filtration Methods for the Analysis of Trace Metals in Ground Water
Selected ground water sampling and field-filtration methods were evaluated to determine their effects on field parameters and trace metal concentrations in samples collected under several types of field conditions. The study focused on conditions where traditional approaches may produce turbid samples, which often leads to filtration of suspended particles from the sample before laboratory chemical analysis. However, filtration may also remove colloidal particles that may be important to the transport of hydrophobic organic contaminants and trace metals. The specific sampling and filtration variables investigated in this study were (1) filtration with 0.45-mm or 5.0- mm pore size filters versus no filtration, (2) sampling device, specifically, bladder pump, submersible-centrifugal pump, and bailer, and (3) sampling pump discharge rate during purging and sample collection using a “low” rate of 300 mL/min and a “moderate” rate of 1000 mL/min. Three field sites were visited: an active municipal solid waste landfill in Wisconsin, a closed solid waste landfill in Washington, and a site contaminated by industrial waste in Nevada. The evaluation included three wells each at the Wisconsin and Washington sites and two wells at the Nevada site. Filtration with 5.0-mm filters was conducted only at one well at each site.