Alison R. Keimowitz

In Situ Oxalic Acid Injection to Accelerate Arsenic Remediation at a Superfund Site in New Jersey

Arsenic is a prevalent contaminant at a large number of US Superfund sites; establishing techniques that accelerate As remediation could benefit many sites. Hundreds of tons of As were released into the environment by the Vineland Chemical Co. in southern New Jersey during its manufacturing lifetime (1949-1994), resulting in extensive contamination of surface and subsurface soils and sediments, groundwater, and the downstream watershed. Despite substantial intervention at this Superfund site, sufficient aquifer cleanup could require many decades if based on traditional pump and treat technologies only. Laboratory column experiments have suggested that oxalic acid addition to contaminated aquifer solids could promote significant As release from the solid phase. To evaluate the potential of chemical additions to increase As release in situ and boost treatment efficiency, a forced gradient pilot scale study was conducted on the Vineland site. During spring/summer 2009, oxalic acid and bromide tracer were injected into a small portion (~50 m2) of the site for 3 months. Groundwater samples indicate that introduction of oxalic acid led to increased As release. Between 2.9 and 3.6 kg of As were removed from the sampled wells as a result of the oxalic acid treatment during the 3-month injection. A comparison of As concentrations on sediment cores collected before and after treatment and analyzed using X-ray fluorescence spectroscopy suggested reduction in As concentrations of ~36% (median difference) to 48% (mean difference). While further study is necessary, the addition of oxalic acid shows potential for accelerating treatment of a highly contaminated site and decreasing the As remediation time-scale.

Identification of Ombrotrophic Bogs in the Catskill Mountains, NY by Geochemical and Isotopic Methods

Ombrotrophic peatlands are those that are purely fed by precipitation and are unconnected to groundwaters. Identification of ombrotophic peatlands is of interest because of their utility as a depositional archive, their unique botanical characteristics, and their sensitivity to climate change. Seven high elevation peatlands in the Catskill Mountains of New York state are investigated in this paper; six of these are identified as ombrotrophic bogs and one is determined to be a minerotrophic (groundwater-fed) poor fen. In order to identify these peatlands as ombrotrophic, concentrations of major ions in surface pools are examined; the proportion of calcium and magnesium in surface pools is particularly indicative of ombrotrophy. Average Ca/Mg (mg L−1) ratios in bogs, precipitation, and springs are 4.3, 5.0, and 6.7, respectively. Stable isotopes of water (deuterium and 18O) are examined as well and may provide a novel method of determining the water source to peatlands; peatland isotopic data plot along what appears to be a local evaporation line.

Calibration and Evaluation of an X-Ray Fluorescence Method for the Determination of Lead and Arsenic in Soils

A portable X-ray fluorescence method is described for the measurement of lead and arsenic in soils based on calibration with standard reference materials. Both elements exhibited good linear calibration curves. The method was used to analyze dried and ground soil samples obtained from the metropolitan New York City area. Results were compared to measurements obtained by graphite furnace atomic absorption spectrometry with microwave assisted acid leaching. No significant difference was found for lead measurements between the two methods however, arsenic values were significantly different with XRF exhibiting higher values. It is hypothesized that incomplete leaching and spectral interference are the predominant causes of this discrepancy. The XRF method provides a simple, quick, and nondestructive method for the determination of total lead and arsenic content in soils.

Manganese redox buffering limits arsenic release from contaminated sediments, Union Lake, New Jersey

The sediments of Union Lake in Southern New Jersey are contaminated with arsenic released from the Vineland Chemical Company Superfund site 11 km upstream. Seasonal anoxia has been shown to release arsenic from sediments to similar lakes; this process was hypothesized as a major arsenic source to Union Lake. Data indicate, however, that releases of arsenic to bottom waters from the sediments or from pore waters within the sediments are relatively minor: bottom water arsenic concentrations reached ~30 ppb (~12 μM) at most, representing <13% of the dissolved arsenic content of the lake. Manganese concentrations increase more quickly and to higher levels than arsenic and iron concentrations; maximum [Mn]= ~13 ppm (~250 μM), maximum [Fe] = ~6 ppm (~120 μM). Incubation experiments support the hypothesis that manganese acts as a redox buffer and prevents large arsenic releases. Under the observed conditions, little of the arsenic in the water column is from contaminated sediment. This study also suggests that arsenic release from sediment to lake water may be more important in lakes that remain anoxic more continuously.

Hydrogeochemistry of the Catskill Mountains of New York

Major ion chemistry of Catskill region groundwater is characterized on the basis of 207 analyses compiled from three sources, including a web‐based U.S. Geological Survey database, state agency regulatory compliance data, and sampling of trailside springs performed by the authors. All samples were analyzed for the complete set of major ions, including calcium, magnesium, sodium, potassium, bicarbonate, chloride, sulfate, and nitrate. Groundwater in pristine, high‐elevation areas of the Catskill Peaks was found to be predominantly of calcium bicarbonate, calcium sulfate, or calcium bicarbonate–sulfate types, with relatively low ionic strength. Groundwater at lower elevations along the margins of the region or in valley bottoms was predominantly of sodium–chloride or sodium–bicarbonate types, showing the effects of road salt and other local pollution sources. Nitrate and sulfate enrichment attributable to regional air pollution sources were most evident in the high‐elevation spring samples, owing to the generally low concentrations of other major ions. Trailside springs appear to be viable low‐cost sources for obtaining samples representative of groundwater, especially in remote and inaccessible areas of the Catskill forest preserve.