Harry M. Edenborn

Geochemical and Strontium Isotope Characterization of Produced Waters from Marcellus Shale Natural Gas Extraction

Extraction of natural gas by hydraulic fracturing of the Middle Devonian Marcellus Shale, a major gas-bearing unit in the Appalachian Basin, results in significant quantities of produced water containing high total dissolved solids (TDS). We carried out a strontium (Sr) isotope investigation to determine the utility of Sr isotopes in identifying and quantifying the interaction of Marcellus Formation produced waters with other waters in the Appalachian Basin in the event of an accidental release, and to provide information about the source of the dissolved solids. Strontium isotopic ratios of Marcellus produced waters collected over a geographic range of ~375 km from southwestern to northeastern Pennsylvania define a relatively narrow set of values (ε(Sr)(SW) = +13.8 to +41.6, where ε(Sr) (SW) is the deviation of the (87)Sr/(86)Sr ratio from that of seawater in parts per 10(4)); this isotopic range falls above that of Middle Devonian seawater, and is distinct from most western Pennsylvania acid mine drainage and Upper Devonian Venango Group oil and gas brines. The uniformity of the isotope ratios suggests a basin-wide source of dissolved solids with a component that is more radiogenic than seawater. Mixing models indicate that Sr isotope ratios can be used to sensitively differentiate between Marcellus Formation produced water and other potential sources of TDS into ground or surface waters.

Plant-soil feedback: testing the generality with the same grasses in serpentine and prairie soils

Plants can alter soil properties in ways that feed back to affect plant performance. The extent that plant-soil feedback affects co-occurring plant species differentially will determine its impact on plant community structure. Whether feedback operates consistently across similar plant communities is little studied. Here, the same grasses from two eastern U.S. serpentine grasslands and two midwestern tallgrass prairie remnants were examined for plant-soil feedback in parallel greenhouse experiments. Native soils were homogenized and cultured (trained) for a year with each of the four grasses. Feedback was evaluated by examining biomass variation in a second generation of (tester) plants grown in the trained soils. Biomass was lower in soils trained by conspecifics compared to soils trained by heterospecifics in seven of 15 possible cases; biomass was greater in conspecific soils in one other. Sorghastrum nutans exhibited lower biomass in conspecific soils for all four grasslands, so feedback may be characteristic of this species. Three cases from the Hayden prairie site were explained by trainer species having similar effects across all tester species so the relative performance of the different species was little affected; plants were generally larger in soils trained by Andropogon gerardii and smaller in soils trained by S. nutans. Differences among sites in the incidence of feedback were independent of serpentine or prairie soils. To explore the causes of the feedback, several soil factors were measured as a function of trainer species: nutrients and pH, arbuscular mycorrhizal (AM) spore communities, root colonization by AM fungi and putative pathogens, and functional diversity in bacterial communities as indicated by carbon substrate utilization. Only variation in nutrients was consistent with any patterns of feedback, and this could explain the greater biomass in soils trained by A. gerardii at Hayden. Feedback at Nottingham (one of the serpentine sites) differed, most notably for A. gerardii, from that of similar past studies that used different experimental protocols. To understand the consequences of feedback for plant community structure, it is important to consider how multiple species respond to the same plant-induced soil variation as well as differences in the feedback detected between greenhouse and field settings.

Bacteria in gel probes: comparison of the activity of immobilized sulfate-reducing bacteria with in situ sulfate reduction in a wetland sediment.

A novel method was used to examine the microbial ecology of iron-rich wetland sediments receiving neutral-pH coal mine drainage. Gel probes inserted into the sediments allowed analysis of the distribution and activity of bacterial sulfate reduction (BSR). A mixed population of sulfate-reducing bacteria enriched from anoxic wetland sediments was immobilized in low temperature-gelling agarose held in grooved rods or probes. The probes were inserted vertically into sediments and were allowed to incubate in situ for 48 h. After their retrieval, the gels were sectioned and analyzed for residual BSR activity and were compared to in situ BSR rates and chemical porewater profiles. The depth distribution of residual BSR activity in the immobilized cell gel probes differed significantly from the BSR measured in situ. Approximately 51% of the total integrated residual sulfate reduction activity measured in the gel probes occurred between 0 and 7 cm of the upper 20 cm of sediment. In contrast, ca. 99% of the integrated in situ BSR occurred between 7- and 20-cm depth, and only 1% of the total integrated rate occurred between 0- and 7-cm depth. Lactate-enriched bacteria immobilized in the gel may have been atypical of the majority of sulfate-reducing bacteria in the sediment. Agarose-immobilized sulfate-reducing bacteria might also be able to proliferate in the otherwise inhospitable zone of iron reduction, where sulfate and labile carbon compounds for which they are usually outcompeted can diffuse freely into the gel matrix. Gel probes containing particulate iron monosulfide (FeS) indicated that FeS remained stable in sediments at depths greater than 2 to 3 cm below the sediment-water interface, consistent with the shallow penetration of oxygen into surface sediments.

Influence of biochar application methods on the phytostabilization of a hydrophobic soil contaminated with lead and acid tar.

A hardwood biochar was examined for its potential use as an amendment to aid in the phytostabilization of a severely-contaminated soil at a former sulfuric acid recycling factory site. The soil, which has remained unvegetated for nearly a century, contained high pseudo-total concentrations of lead, arsenic and antimony and was both highly acidic and hydrophobic due to the presence of petroleum-based acid tar. Three application approaches were tested with 10 and 20% (vol/vol) biochar: Incorporation into soil, top-dressing on the surface, and layering within the soil. The results suggest that the homogeneous mixing of the hardwood biochar into soil would not promote the long-term restoration at this site due to its inherently low alkalinity relative to the very high net acidity of the existing soil. In contrast, surface application of biochar resulted in the most successful growth of Canada wild-rye grass by exploiting the properties inherent to biochar alone.

Amendment of a hardwood biochar with compost tea: effects on plant growth, insect damage and the functional diversity of soil microbial communities

Abstract Biochar is an organic soil amendment that has been shown to improve plant growth and increase resistance to plant diseases and insect damage in certain soils. Organic growers have been known to use compost teas to amend biochar, claiming that this practice adds nutrients and beneficial microorganisms that can improve plant growth and resistance to pathogens and insect pests. However, few data exist to support this hypothesis. This study investigated the effects of a hardwood biochar amended with different types of compost teas and microbial enrichments (prepared from vermicompost) on eggplant (Solanum melongena var. Rosa Bianca) growth, flea beetle (Epitrix fuscula) damage, and soil microbial activity and functional diversity in two temperate soils. No positive short-term effects were observed on eggplant growth or flea beetle damage when biochar amended with compost teas prepared from horse manure, mushroom compost or vermicompost were added to a temperate agricultural soil. However, a second experiment suggested that biochar amended with microbial enrichments from vermicompost tea may improve eggplant growth if matched with the physical and chemical properties of a given soils. Results from Community Level Physiological Profiling (CLPP) revealed that biochar amended with compost teas altered soil microbial activity and functional diversity differently to that of biochar alone, and that these changes corresponded with plant growth and insect damage.

In situ measurements of calcium carbonate dissolution under rising CO2 pressure using underwater laser-induced breakdown spectroscopy

In the present study, we applied underwater laser-induced breakdown spectroscopy (underwater LIBS) for rapid in situ measurements of calcium carbonate (CaCO3) dissolution as a function of CO2 pressure (pCO2). A pulsed Nd:YAG laser at 1064 nm was used to produce gaseous plasma in the fluid surrounding a pressed pellet of CaCO3 powder. The ensuing plasma emission was spectrally analyzed, and the intensity of the calcium emission line at 422.67 nm was used to monitor Ca2+ cation released to the water. Barium emission line at 455.40 nm was simultaneously recorded as an internal standard to calibrate calcium signal intensity. The study shows that relatively strong and well-resolved spectral lines of both Ca2+ and Ba2+ cations can be obtained in CO2-saturated water. More importantly, the results show that underwater LIBS is capable of performing quantitative analysis at elevated pCO2, with an estimated Ca2+ detection limit of about 9 ppm over 50–350 bar. In the solution with the initially added CaCO3 pellet, the concentration of Ca2+ increases by a factor of 2 as pCO2 increases from 50 to 150 bar and remains nearly constant when pCO2 is further increased up to 350 bar. Finally, our study provides evidence that underwater LIBS could be a useful tool to investigate/monitor carbonate dissolution (at low ppm levels) in various geochemical applications.

Development and Testing of Hydrogel Beads as Potential Floating Tracers of Contaminant Movement in Karst Aquifers

The transport of light non-aqueous phase liquids (LNAPLs) is not well understood in karst settings. Traditional tracers do not predict the movement of free product; therefore, this study was undertaken to develop a better tracer proxy for LNAPL. The floating hydrogel tracer beads were created using alginate polymers and adding fluorescent pigments and density-modifying additives to alter their physical characteristics. Two sets of multi-tracer field tests (beads plus a conservative solute tracer) were completed in a 60-m section of cave stream. The beads were quantified via counting for the first set of tests and using particle image velocimetry (PIV) for the second. During the 2012 tests (170 L/s discharge), the beads travelled faster than the solute tracer; however, in the 2014 tests (9.1 L/s) the results were less conclusive (the beads arrived before the solute but had a later peak time and a lower mean velocity). Most of the particle studies have reported that particles travel faster than solutes, in accordance with our 2012 studies. Although the beads are particles and thus not an ideal proxy for LNAPL contaminants, they hold promise for future experimental studies and highlight the complexity of LNAPL transport in cave systems.

Passive detection of Pb in water using rock phosphate agarose beads

In this study, passive detectors for Pb were prepared by immobilizing powdered rock phosphate in agarose beads. Rock phosphate has been used to treat Pb-contaminated waters and soil by fixing the metal as an insoluble pyromorphite mineral. Under lab conditions, Pb was rapidly adsorbed from aqueous solution by the beads over time, consistent with the acidic dissolution of rock phosphate, the precipitation of pyromorphite within the pore space of the agarose gel matrix, and surface exchange reactions. Net accumulation of Pb occurred when beads were exposed to simulated periodic releases of Pb over time. Under field conditions, beads in mesh bags were effective at detecting dissolved Pb being transported as surface runoff from a site highly contaminated with Pb. Rates of Pb accumulation in beads under field conditions appeared to be correlated with the frequency of storm events and total rainfall. The rock phosphate agarose bead approach could be an inexpensive way to carry out source-tracking of Pb pollution, to verify the successful remediation of sites with Pb-contaminated soil, and to routinely monitor public water systems for potential Pb contamination.