Abstract Introduction Study Area Coring & Pore Water Extraction Analytical Methods Results & Discussion Summary Acknowledgments References PDF Version

Filtered pore water samples collected from the squeezer were distributed into various containers for analysis. Titration alkalinity, pH, and H₂S were determined immediately after collection. Pore water for pH and H₂S was collected in disposable plastic syringes to minimize degassing and oxidation by contact with the atmosphere. Pore water for titration alkalinity was transferred to clean polyethylene bottles, titrated with 0.1 M HCl to a fixed pH between 3.5 and 2.8, and finally acidified with 0.1 ml of concentrated Ultrex HNO₃. This same sample was then stored for later analysis of major cations (Na, K, Ca, Mg, Sr). Pore water for reactive phosphate and ammonium was stored frozen on dry ice in clean plastic bottles for 1 to 5 days before analysis in the field. Pore water samples for analysis of anions by ion chromatography (F, Cl, Br, SO₄2-) were transferred to clean plastic bottles, and 0.1 M zinc zcetate (0.1 ml per 1.0 ml sample) was added to precipitate sulfide and avoid artifacts from oxidation to sulfate during storage. Pore water for DOC analysis was transferred to clean plastic bottles or glass tubes, and the samples for DOC and anions analysis were stored frozen on dry ice until return to laboratory facilities.

Surface waters were first subsampled with a disposable plastic syringe for analysis of pH and H₂S, then filtered (0.4 µm Nuclepore filters) using a plastic Millipore filtering apparatus and a hand pump. Distribution, storage and analysis of surface water samples was otherwise the same as for pore waters.

Polyethylene bottles for titration alkalinity and storage of water samples for metals analysis were cleaned by soaking overnight in 10% ultrex HNO₃ followed by thorough washing with deionized/distilled water. Glass tubes for storage of water samples for DOC analysis were washed with 10% HCl, rinsed with deionized/distilled water, and baked overnight at 450° C. Plasticware used in the collection and filtration of surface water samples, and plastic bottles for storage of nutrient, anion, and DOC water samples were soaked overnight in 10% HCl followed by thorough rinsing in deionized/distilled water. Deionized/distilled water blanks were run through the entire filtration, handling, and storage scheme used for the samples. No significant contamination was observed for any of the analyses reported here, indicating that the cleaning and handling approach used for the surface and pore water samples was adequate.

The analytical procedures used and their precision (reported as % relative standard deviation except for pH and titration alkalinity) are shown in Table 2. In the field we used a Brinkman fiber optic probe spectrophotometer for the phosphate and ammonium analyses, and an Orion portable pH/mv meter and Orion electrodes for the pH, titration alkalinity, and H₂S analyses. The DOC analyses were performed at USGS laboratories in Reston, VA using an O.I. Corporation model 700 TOC analyzer. Ion Chromatography analyses for anions and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses for metals were conducted at USGS laboratories in Denver, CO. Trade names used are for descriptive purposes only and do not constitute endorsement of products by the U.S. Geological Survey.