Approximately 300 kg/day of food-grade CO 2 was injected through a perforated pipe placed horizontally 2-2.3 m deep during July 9-August 7, 2008 at the MSU-ZERT field test to evaluate atmospheric and near-surface monitoring and detection techniques applicable to the subsurface storage and potential leakage of CO 2 . As part of this multidisciplinary research project, 80 samples of water were collected from 10 shallow monitoring wells (1.5 or 3.0 m deep) installed 1-6 m from the injection pipe, at the southwestern end of the slotted section (zone VI), and from two distant monitoring wells. The samples were collected before, during, and following CO 2 injection. The main objective of study was to investigate changes in the concentrations of major, minor, and trace inorganic and organic compounds during and following CO 2 injection. The ultimate goals were (1) to better understand the potential of groundwater quality impacts related to CO 2 leakage from deep storage operations, (2) to develop geochemical tools that could provide early detection of CO 2 intrusion into underground sources of drinking water (USDW), and (3) to test the predictive capabilities of geochemical codes against field data. Field determinations showed rapid and systematic changes in pH (7.0-5.6), alkalinity (400-1,330 mg/l as HCO 3 ), and electrical conductance (600-1,800 lS/cm) following CO 2 injection in samples collected from the 1.5 m-deep wells. Laboratory results show major increases in the concentrations of Ca (90-240 mg/l), Mg (25-70 mg/l), Fe (5-1,200 ppb), and Mn (5-1,400 ppb) following CO 2 injection. These chemical changes could provide early detection of CO 2 leakage into shallow groundwater from deep storage operations. Dissolution of observed carbonate minerals and desorptionion exchange resulting from lowered pH values following CO 2 injection are the likely geochemical processes responsible for the observed increases in the concentrations of solutes; concentrations generally decreased temporarily following four significant precipitation events. The DOC values obtained are 5 ± 2 mg/l, and the variations do not correlate with CO 2 injection. CO 2 injection, however, is responsible for detection of BTEX (e.g. benzene, 0-0.8 ppb), mobilization of metals, the lowered pH values, and increases in the concentrations of other solutes in groundwater. The trace metal and BTEX concentrations are all significantly below the maximum contaminant levels (MCLs). Sequential leaching of core samples is being carried out to investigate the source of metals and other solutes.

A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO 2 transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO 2 release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO 2 transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO 2 from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO 2 through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented.

Five, second-order, acidic streams in West Virginia were treated with instream applications of fine-grained limestone. Three variations in treatment were tested to optimize limestone dissolution: the particle size of the limestone, the amount used, and the number of application points. The goal of the study was to develop a cost-effective method to restore water quality that would sustain fisheries for native brook trout Salvelinus fontinalis. In all of the treatments, water quality improved and the fish communities were either restored or enhanced. Before limestone treatment, only one of the study streams contained a reproducing brook trout population. Following treatment, the fish communities expanded rapidly from 0.01 kg/ha to a high of 38 kg/ha, and the number of species increased to a high of eight. The untreated control stream remained unchanged. Due to a lack of duplicate streams, a statistical comparison could not be made between the different sizes of limestone tested or the amounts added. However, sand and crusher-run-sized limestone appeared to be more effective than coarse gravel in improving water quality. An initial treatment equivalent to two times the stream's estimated annual acid load was as effective in neutralizing acid flow as a treatment of four times the estimated annual acid load. Treatment at one stream point was as effective as treatment at three stream points. The instream addition of fine-grained limestone can restore fish communities to streams acidified by acid deposition at a substantially lower cost than most other treatment methods.

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Laboratory dissolution of Middle Ordovician rock samples from central Pennsylvania was studied at 23°C and 1 atm carbon dioxide pressure. Carbonate dissolution rates were compared at 22% bicarbonate saturation with respect to both calcite and dolomite. The results show that carbonate lithology exerts a strong influence on the dissolution rate and hence on the degree of cavity development in karst aquifers. The dissolution rate is most significantly affected by dolomite and impurity content. The rate decreases as percentages of dolomite and disseminated insolubles increase. Maximum dissolution rates occur for carbonate rocks with 1.0–2.5% MgO content and having abundant silty streaks. The sparite content is inversely related to cave development but is independent of dissolution rates measured under the laboratory conditions adopted in this study.