Acid-generating salts and their relationship to the chemistry of groundwater and storm runoff at an abandoned mine site in southwestern Indiana, U.S.A.

Cation distributions in twenty samples of acid-generating salts were compared to those in groundwater and storm runoff from a coal-refuse deposit in an effort to identify source-product relationships. Two mineral suites, one primarily composed of melanterite, rozenite and szomolnokite, and the other composed almost entirely of copiapite, were found to be most abundant at the study site. Comparisons of cation distributions in salts with those in water samples lead to an hypothesis that a copiapite-rich suite precipitated from vadose-zone ground-water that was brought to the surface by evaporative forcing. The copiapite-rich suite, which contained larger concentrations of aluminum, calcium and zinc that the melanterite-rozenite-szomolnokite mineral suite, was the primary source of solutes in captured storm runoff. An analysis of samples collected during a summer thunderstorm indicated that the chemistry of surface runoff varied little with time or with distance downstream. The cation distributions in samples of groundwater indicated that iron-rich pore waters observed near the surface in late autumn may have influenced water chemistry in the deeper portions of the unsaturated zone during the 1989 recharge season. The results of this study show that the solutes produced by the two observed salt suites can be distinguished by their mole percent iron and that the source-product relationships can explain observed variability in mine drainage chemistry at the study site.     

Elements of a Predictive Model for Determining Beach Closures on a Real Time Basis: The Case of 63rd Street Beach Chicago

Data on hydrometeorological conditions and E. coli concentration were simultaneously collected on 57 occasions during the summer of 2000 at 63rd Street Beach, Chicago, Illinois. The data were used to identify and calibrate a statistical regression model aimed at predicting when the bacterial concentration of the beach water was above or below the level considered safe for full body contact. A wide range of hydrological, meteorological, and water quality variables were evaluated as possible predictive variables. These included wind speed and direction, incoming solar radiation (insolation), various time frames of rainfall, air temperature, lake stage and wave height, and water temperature, specific conductance, dissolved oxygen, pH, and turbidity. The best-fit model combined real-time measurements of wind direction and speed (onshore component of resultant wind vector), rainfall, insolation, lake stage, water temperature and turbidity to predict the geometric mean E. coli concentration in the swimming zone of the beach. The model, which contained both additive and multiplicative (interaction) terms, accounted for 71% of the observed variability in the log E. coli concentrations. A comparison between model predictions of when the beach should be closed and when the actual bacterial concentrations were above or below the 235 cfu 100 ml(-1) threshold value, indicated that the model accurately predicted openings versus closures 88% of the time.     

Effect of pore-water velocity on chemical nonequilibrium transport of Cd,Zn, and Pb in alluvial gravel columns

This paper investigates the effects of pore-water velocity on chemical nonequilibrium during transport of Cd, Zn, and Pb through alluvial gravel columns. Three pore-water velocities ranging from 3 to 60 m/day were applied to triplicate columns for each metal. Model results for the symmetric breakthrough curves (BTCs) of tritium (3H2O) data suggest that physical nonequilibrium components were absent in the uniformly packed columns used in these studies. As a result, values of pore-water velocity and dispersion coefficient were estimated from fitting 3H2O BTCs to an equilibrium model. The BTCs of metals display long tailing, indicating presence of chemical nonequilibrium in the system, which was further supported by the decreased metal concentrations during flow interruption. The BTCs of the metals were analysed using a two-site model, and transport parameters were derived using the CXTFIT curve-fitting program. The model results indicate that the partitioning coefficient (beta), forward rate (k1), and backward rate (k2) are positively correlated with pore-water velocity (V); while the retardation factor (R), mass transfer coefficient ((omega), and ratio of k1/k2 are inversely correlated with V. There is no apparent relationship between the fraction of exchange sites at equilibrium (f) and V. The influence of Von k2 is much greater than on R, beta, omega, and k1. A one-order-of-magnitude change in V would cause a two-order-of-magnitude change in k2 while resulting in only a one order-of-magnitude change in R, beta, omega, and k1. The forward rates for the metals are found to be two to three orders-of-magnitude greater than the corresponding backward rate. However, the difference between the two rates reduces with increasing pore-water velocity. Model results also suggest that Cd and Zn behave similarly, while Pb is much more strongly sorbed. At input concentrations of about 4 mg/l and pore-water velocities of 3-60 m/day in the groundwater within alluvial gravel, this study suggests retardation factors of 26-289 for Cd, 24-255 for Zn, and 322-6377 for Pb.     

Characterization and phosphate stabilization of dusts from the vitrification of MSW combustion residues

The use of soluble PO₄³⁻ as a heavy metal chemical stabilization agent was evaluated for a dust generated from melting or vitrification of municipal solid waste combustion residues. Vitrification dusts contain high concentrations of volatile elements such as Cl, Na, K, S, Pb, and Zn. These elements are present in the dusts largely as simple salts (e.g. PbCl₂, ZnSO₄) which are highly leachable. At an experimental dose of 0.4 moles of soluble PO₄³⁻ per kg of residue, the pH-dependent leaching (pH 5,7,9) showed that the treatment was able to reduce equilibrium concentrations by factors of 3 to 100 for many metals; particularly Cd, Cu, Pb and Zn. Bulk and surface spectroscopies showed that the insoluble reaction products are tertiary metal phosphate [e.g. Zn₃(PO₄)₂] and apatite [e.g. Pb₅(PO₄)₃Cl] family minerals. Geochemical thermodynamic equilibrium modeling showed that apatite family and tertiary metal phosphate phases act as controlling solids for the equilibrium concentrations of Ca²⁺, Zn²⁺, Pb²⁺, Cu²⁺, and Cd²⁺ in the leachates during pH-dependent leaching. Both end members and ideal solid solutions were seen to be controlling solids. Soluble phosphate effectively converted soluble metal salts into insoluble metal phosphate phases despite the relatively low doses and dry mixing conditions that were used. Soluble phosphate is an effective stabilization agent for divalent heavy metals in melting dusts where leachable metals are present in high concentrations.     

Performance of conventional remedial technology for treatment of MTBE and benzene at UST sites in Kansas

Groundwater at most underground storage tank (UST) spills sites in Kansas contains both methyl tertiary butyl ethylene (MTBE) and benzene, and both contaminants must be effectively treated to close the sites. Soil vacuum extraction, air sparging, and excavation are the most common treatment technologies in Kansas. To compare the relative performance of these conventional remedial technologies for treating MTBE as compared to benzene, 66 sites in the Kansas UST Trust Fund were identified that had initial concentrations of both MTBE and benzene above the reporting limit of 1 μg/L, and that had at least two rounds of analytical data. Sites were excluded from the comparison if the monitoring wells had free product. Of the 66 sites, 15 had met the clean‐up goal for benzene, and 50 had met the goal for MTBE. The extent of treatment for MTBE and benzene was calculated as the ratio of the highest concentration in any well at the site in the most recent round of sampling to the maximum concentration in any well at the site in the previous rounds of sampling. The extent of treatment was greater for MTBE (statistically significant at p = 0.032). The geometric mean of the extent of treatment in the 66 sites was 0.057 for MTBE, compared to 0.14 for benzene. In Kansas, conventional technologies removed MTBE from the source areas of groundwater plumes at least as effectively as they removed benzene. © 2003 Wiley Periodicals, Inc.     

Monitoring global change: Comparison of forest cover estimates using remote sensing and inventory approaches

Satellite-based remote sensing offers great potential for frequent assessment of forest cover over broad spatial scales, however, calibration and validation using ground-based surveys are needed. In this study, forest cover estimates for the United States from a recently developed land surface cover map generated from satellite remote sensing data were compared to state-level inventory data from the U.S. National Resources Planning Act Timber Database. The land cover map was produced at the U.S. Geological Survey EROS Data Center and is based on imagery from the AVHRR sensor (spatial resolution 1.1 km). Vegetation type was classified using the temporal signal in the Normalized Difference Vegetation Index derived from AVHRR data. Comparisons revealed close agreement in the estimate of forest cover for extensively forested states with large polygons of relatively similar vegetation such as Oregon. Larger forest cover differences were observed in other states with some regional patterns in the level of agreement apparent.Comparisons in inventory- and remote sensing-based estimates of current forested area with potential vegetation maps indicated the magnitude of past land use change and the potential for future changes. The remote sensing approach appears to hold promise for conducting surveys of forest cover where inventory data are limited or where rates of vegetation change, due to human or climatic factors, are rapid.     

Method for rapid on-site identification of VOCs

Rapid on-site identification of volatile organic compounds (VOCs) in ambient air is an important first step in remediation efforts. This study describes modification of a commercially available, portable GC/MS system and development of an analysis protocol for rapid (<3 min) sampling and identification of VOCs typically found at contaminated sites at the low ppbv level.     

Remaking the world in our own image: vulnerability,resilience and adaptation as historical discourses

A warming climate and less predictable weather patterns, as well as an expanding urban infrastructure susceptible to geophysical hazards, make the world an increasingly dangerous place, even for those living in high‐income countries. It is an opportune moment, therefore, from the vantage point of the second decade of the twenty‐first century, to review the terms and concepts that have been employed regularly over the past 50 years to assess risk and to measure people's exposure to such events in the light of the wider geopolitical context. In particular, it is useful to examine ‘vulnerability’, ‘resilience’, and ‘adaptation’, the principal theoretical concepts that, from an historical perspective, have dominated disaster studies since the end of the Second World War. In addition, it is valuable to enquire as to the extent to which such discourses were ideological products of their time, which sought to explain societies and their environments from the stance of competing conceptual frameworks.     

Near-boundary velocity and turbulence in depth-varying stream flows

This research examined the temporal distribution of turbulent structure near a streambank toe through the progression of a flood wave in West Run (Morgantown, WV, USA). Three-dimensional velocities and water depths were measured through a 17-h flood event. Turbulence characteristics were examined: Reynolds stresses, turbulent kinetic energy, and turbulence intensities. On average, near-boundary velocity during the rising stage was less than the falling stage, likely due to the measurement location and local roughness. The velocity vectors shifted from towards bed before the flood wave to toward the streambank during progression of the flood wave. Turbulent kinetic energy increased with increasing water depth during the rising stage. Reynolds stress, τ_xz, increased with increasing water depth during the rising stage, but the majority of the stresses were negative through the storm event. Reynolds stress, τ_xy, was positive throughout the event and did not vary with depth. This work is among the first to evaluate turbulence during depth-varying flows in the field.     

Behavioral consequences of exotic host plant adoption and the differing roles of male harassment on female movement in two checkerspot butterflies

Herbivorous insects may evolve convergent behaviors when independent adoption of a shared novel host plant places populations in environmental conditions that diverge from the ancestral state. We investigated the behavioral consequences of adopting Plantago lanceolata, an exotic species to North America, in populations of Euphydryas p. phaeton and Euphydryas editha taylori, on the east and west coasts of North America. Activity budgets and short-term movements suggested that innate species tendencies exert a greater impact on behavior than adoption of the same exotic host plant. However, female E. phaeton from a Plantago-dependent population spent more time inspecting host plants than females from a population dependent on the native host plant, Chelone glabra. Both checkerspot species had similar diffusion coefficients (D) regardless of host plant association. But, E. e. taylori step-lengths appeared bimodal and power law distributed while E. phaeton step-lengths were unimodal and best fit by an exponential distribution. We attribute this bimodal step-length distribution to the persistent harassment of courting males which induces a “long-distance” evasive flight in otherwise sedentary E. e. taylori females. In contrast, the longer distance step-lengths of E. phaeton were associated with the inspection of oviposition plants. These two checkerspot species appear to move greater distances across the reproductive landscape with contrasting motivational states that could lead to either intimate mapping (E. phaeton) or coarse mapping (E. e. taylori) of host resources.