Open-File Report 2006-1374
U.S. GEOLOGICAL SURVEY
Open-File Report 2006-1374
Water-level measurements, sample collection and processing, and field analyses were in accordance with applicable USGS procedures (U.S. Geological Survey, 1997–2005), except that samples were collected using a peristaltic pump. Geochemical measurements and concentrations determined for samples from 13 wells and 9 piezometers included dissolved hydrogen (H2), dissolved oxygen (DO), filtered organic carbon, filtered nitrate plus nitrite, filtered manganese, filtered iron (II), filtered sulfate, unfiltered sulfide, dissolved methane, dissolved carbon dioxide, pH, specific conductance, oxidation-reduction potential (ORP), and filtered chloride. Concentrations of 64 volatile organic compounds (VOCs) were determined for samples from 3 of the 13 wells, from all 9 piezometers, and from all of the passive-diffusion samplers that were deployed. The concentrations of the dissolved gasses ethane, ethene, and methane were also determined for samples from three wells, from all piezometers, and from all of the diffusion samplers.
After measuring depth to water, all well and piezometer samples were collected with a peristaltic pump and single-use polyurethane tubing. A stainless-steel weight was attached to the bottom of the tubing to accurately collect the sample from the mid-screen elevation in each well. Samples were collected after approximately three casing-volumes of water were purged from the wells and after allowing pH, specific conductance, and DO to stabilize within 0.1 units, 5 percent, and 0.3 mg/L, respectively. Those three analytes and ORP were measured in a flow-through chamber using temperature compensated probes from a YSITM data sonde. The specific conductance probe was checked daily with standard reference solutions; the pH probe was calibrated daily with two pH standards; and the dissolved-oxygen probe was calibrated daily using the water-saturated air method and occasionally verified with zero dissolved-oxygen solution. Dissolved-oxygen analyses were confirmed for most samples using 0 to 1 mg/L CHEMets Rhodazine-DTM colorimetric ampoules (manufactured by CHEMetrics, Inc., Calverton, Virginia). These ampoules were filled directly from the sampling tube after well purging was complete.
Concentrations of iron (II) were measured in the field in a sample filtered through a 0.45-µm membrane filter using a colorimetric 1,10 phenanthroline indicator method and a Hach Model 2010 spectrophotometer following Hach Method 8146 [Hach Company, 1998; adapted from America Public Health Association (1980)]. Sulfide concentrations were measured in the field using a colorimetric methylene-blue indicator method immediately using the same spectrophotometer according to Hach Method 81360 [Hach Company, 1998; procedure is equivalent to U.S. Environmental Protection Agency (USEPA) method 376.2 U.S. Environmental Protection Agency (1983)]. Information about the methodologies used to determine iron and sulfide concentrations is described at http://www.hach.com, accessed on June 1, 2005. Dissolved carbon dioxide (CO2) concentrations were measured in the field with Titret®-Sodium hydroxide titrant with a pH indicator (manufactured by CHEMetrics, Inc., Calverton, Virginia).
Dissolved H2 in ground water was sampled using the bubble-strip method of Chapelle and others (1997) and concentrations were measured in the field using a gas chromatograph equipped with a reduction gas detector. Initial gas samples from each well were collected and analyzed after at least 20 minutes of stripping; subsequent samples were collected and analyzed at about 5-minute intervals until consecutive H2 concentrations stabilized to within 10 percent, a process that often required an hour or more.
Samples for determination of nitrate plus nitrite, manganese, sulfate, and chloride concentrations were filtered through a 0.45-µm membrane filter into polyethylene bottles, chilled, and sent to the USGS National Water Quality Laboratory (NWQL) in Lakewood, Colorado. Manganese samples were acidified in the field with nitric acid to a pH of less than 2, and then analyzed at NWQL by inductively coupled plasma as described by Fishman (1993). Chloride and sulfate were analyzed using ion chromatography as described by Fishman and Friedman (1989). Nitrate plus nitrite were analyzed colorimetrically by cadmium reduction and diazotization as described by Fishman (1993). The results for the nitrate plus nitrite analyses are referred to simply as nitrate in this report because nitrite was not detected at the site (Dinicola and others, 2002).
Samples for dissolved organic carbon analysis were filtered through a 0.45-µm filter, collected in amber glass bottles, acidified in the field with sulfuric acid to a pH of less than 2, chilled to less than 4°C, and shipped to the NWQL. Organic carbon concentrations were determined using persulfate oxidation as described by Brenton and Arnett (1993).
Samples for VOC analysis were collected in pre-acidified 40-mL glass vials, placed on ice, and shipped to the NWQL for subsequent analysis at Severn Trent Laboratories (STL) in Denver, Colorado, using purge and trap capillary-column gas chromatography/mass spectrometry (USEPA Method SW846 8260B; accessed November 2005 at http://www.epa.gov/epaoswer/hazwaste/test/pdfs/8260b.pdf). Samples for analysis of ethane, ethene, and methane were collected in pre-acidified 40-mL glass vials, placed on ice, and shipped to the NWQL for subsequent analysis at Severn Trent Laboratories (STL) in Denver, Colorado, using gas chromatography with a flame-ionization detector (U.S. Environmental Protection Agency Method RSK SOP-175; Kampbell and Vandegrift, 1998).
VOCs in shallow ground-water directly beneath the marsh stream were determined at 10 locations using passive-diffusion samplers, and VOCs in surface water in the marsh stream were determined from grab samples from 2 locations (fig. 2). Ground-water samples were collected using passive-diffusion samplers deployed along an approximate 320-ft reach of the marsh stream adjacent to the southern phytoremediation plantation, and surface-water grab samples were collected from the marsh stream at the upstream and the downstream ends of the reach. The most downstream passive-diffusion sampler site (S-1) was located at the pre-existing MA-12 surface-water sampling site. The most upstream passive-diffusion sampler site (S-6) was located at the newly established SW-S6 surface-water sampling site. The eight additional passive-diffusion samplers were distributed about evenly along the length of the stream reach. Six sites (S-1, S-2, S-3, S-4, S-5, and S-6) were sampled in previous years, and four sites (S-2B, S-3B, S-4B, and S-5B) were newly established. The diffusion samplers were constructed by the USGS in Tacoma, Washington, and consisted of 8-in.-long by 2-in.-diameter polyethylene lay-flat tubing that was filled with deionized water and heat sealed at both ends. The filled bags were inserted into plastic mesh sleeves to protect them from damage, and were buried by hand in about 12 in. of mud beneath the marsh creek. The holes were backfilled with native materials and tamped down and left to equilibrate with pore water for more than 2 weeks. The locations of the samplers were marked with wooden stakes and approximately located on a site map. Samplers were retrieved by hand and immediately processed. A corner of each bag was cut and three pre-acidified 40-mL glass VOC vials were filled, sealed, and kept on ice for shipment to NWQL for VOC analysis at STL using purge and trap capillary-column gas chromatography/mass spectrometry (USEPA Method SW846 8260B), and for ethane, ethene, and methane analysis using gas chromatography with a flame-ionization detector (USEPA Method RSK SOP-175). Surface water was sampled at sites MA-12 and SW-S6 by filling a polyethylene bottle from mid depth in the center of the marsh stream. The sample was immediately poured into three pre-acidified 40-mL glass VOC vials, sealed, and kept on ice for shipment to NWQL for VOC analysis at STL using the same methods.
Quality assurance and control of geochemical and contaminant sampling included collecting two duplicate samples for selected redox-sensitive analytes and VOCs and analyzing one field blank sample for VOCs. No substantial quality issues were identified in those samples (appendix A).
U.S.
Department of the Interior | U.S. Geological
Survey
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