Alternative method of groundwater sparging for petroleum hydrocarbon remediation

An alternative method of in-situ groundwater sparging, termed density-driven convection (patent pending), is presented. This method has been successfully used to remediate eight underground storage tank releases involving a wide distillation range of petroleum hydrocarbons (gasoline to waste oil) and in a variety of site soils (clay to sandy gravel). Application of the density-driven convection method is detailed in a case study. The system, installed to remediate a gasoline and diesel release from an underground storage tank, was operated and monitored for a period of one year. Monitoring data indicate reductions in total petroleum hydrocarbon concentrations in groundwater and in soil. Concentrations of aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylenes, and naphthalene) also decreased in both media. Stimulation of natural biodegradation, the primary mechanism of removal, occurred rapidly. Natural biological activity gradually declined over the subsequent 150 days. After one year of operation, the sparging system has achieved or is rapidly approaching the regulatory cleanup goals for both soil and groundwater, including reduction of dissolved concentrations below maximum contaminant levels established under the Safe Drinking Water Act.     

Airborne emissions of mercury from municipal solid waste. I: new measurements from six operating landfills in Florida

Mercury-bearing material enters municipal landfills from a wide array of sources, including fluorescent lights, batteries, electrical switches, thermometers, and general waste; however, the fate of mercury (Hg) in landfills has not been widely studied. Using automated flux chambers and downwind atmospheric sampling, we quantified the primary pathways of Hg vapor releases to the atmosphere at six municipal landfill operations in Florida. These pathways included landfill gas (LFG) releases from active vent systems, passive emissions from landfill surface covers, and emissions from daily activities at each working face (WF). We spiked the WF at two sites with known Hg sources; these were readily detected downwind, and were used to test our emission modeling approaches. Gaseous elemental mercury (Hg(O)) was released to the atmosphere at readily detectable rates from all sources measured; rates ranged from approximately 1-10 ng m(-2) hr(-1) over aged landfill cover, from approximately 8-20 mg/hr from LFG flares (LFG included Hg(O) at microg/m3 concentrations), and from approximately 200-400 mg/hr at the WF. These fluxes exceed our earlier published estimates. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(O), the entire waste mass acts as a source. We estimate that atmospheric Hg releases from municipal landfill operations in the state of Florida are on the order of 10-50 kg/yr, substantially larger than our original estimates, but still a small fraction of current overall anthropogenic losses.     

Airborne emissions of mercury from municipal solid waste. II: potential losses of airborne mercury before landfill

Waste distribution and compaction at the working face of municipal waste landfills releases mercury vapor (Hg(o)) to the atmosphere, as does the flaring of landfill gas. Waste storage and processing before its addition to the landfill also has the potential to release Hg(o) to the air if it is initially present or formed by chemical reduction of Hg(II) to Hg(o) within collected waste. We measured the release of Hg vapor to the atmosphere during dumpster and transfer station activities and waste storage before landfilling at a municipal landfill operation in central Florida. We also quantified the potential contribution of specific Hg-bearing wastes, including mercury (Hg) thermometers and fluorescent bulbs, and searched for primary Hg sources in sorted wastes at three different landfills. Surprisingly large fluxes were estimated for Hg losses at transfer facilities (approximately 100 mg/hr) and from dumpsters in the field (approximately 30 mg/hr for 1000 dumpsters), suggesting that Hg emissions occurring before landfilling may constitute a significant fraction of the total emission from the disposal/landfill cycle and a need for more measurements on these sources. Reducing conditions of landfill burial were obviously not needed to generate strong Hg(o) signals, indicating that much of the Hg was already present in a metallic (Hg(o)) form. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(o), the entire waste mass acts as a source. Broken fluorescent bulbs and thermometers in dumpsters emitted Hg(o) at 10 to >100 microg/hr and continued to act as near constant sources for several days.     

Phenotype-environment matching in the shore crab (Carcinus maenas)

The shore crab (Carcinus maenas) exhibits a range of carapace pattern polymorphisms, but little is known regarding their function or maintenance. If patterns represent some form of crypsis, then associations between carapace colouration and substrate are expected; to determine whether such relationships exist, frequency of crab morphs and quantity of substrate type were measured from fifteen 10×40 m² quadrats at each of three sites along the southern shore of the Firth of Forth, Scotland. Five thousand one hundred and thirty-seven crabs and 3.6 km of line intercept transect data were collected during a 9-week period. Crab abundance, relative frequency of morphs and substrate type varied significantly among the three sites. Plain crabs were strongly associated with macro-algal substrates whereas patterned crabs were associated with mussel beds. This pronounced phenotype-environment matching, as well as various characteristics of the carapace patterns themselves, suggests that patterned crabs are cryptic on polychromatic backgrounds. The frequency of patterned crabs and the percentage of white pigment on the carapace both declined significantly with carapace width. The loss of pattern coincides with an ontogenetic shift in habitat use and we present evidence to suggest that individual crabs lose their pigment, rather than larger patterned crabs being preferentially removed from the population by predators. Throughout their life history, shore crabs encounter high variation in predation, food supply, and physical habitat; to survive they have evolved a strategy that includes elements of pattern polymorphism, crypsis, ontogenetic shifts, and plastic responses.     

Factors affecting food chain transfer of mercury in the vicinity of the Nyanza Site,Sudbury River,Massachusetts

The influence of the Nyanza Chemical Waste Dump Superfund Site on the Sudbury River, Massachusetts, was assessed by analysis of sediment, fish prey organisms, and predator fish from four locations in the river system. Whitehall Reservoir is an impoundment upstream of the site, and Reservoir #2 is an impoundment downstream of the site. Cedar Street is a flowing reach upstream of the site, and Sherman Bridge is a flowing reach downstream of the site. Collections of material for analysis were made three times, in May, July, and October. Sediment was analyzed for acid-volatile sulfide (AVS), simultaneously-extracted (SEM) metals (As, Cd, Cr, Hg, Pb, Sb, Zn), and total recoverable Hg. The dominant predatory fish species collected at all sites, largemouth bass (Micropterussalmoides), was analyzed for the same suite of metals as sediment. Analysis of stomach contents of bass identified smallfish (yellow perch Perca flavescens, bluegill Lepomismacrochirus, and pumpkinseed Lepomis gibbosus), crayfish,and dragonfly larvae as the dominant prey organisms. Samples of the prey were collected from the same locations and at the sametimes as predator fish, and were analyzed for total and methyl mercury. Results of AVS and SEM analyses indicated that sediments were not toxic to aquatic invertebrates at any site. The SEM concentrations of As, Cd, and Cr were significantly higher at Reservoir #2 than at the reference sites, and SEM As and Cdwere significantly higher at Sherman Bridge than at Cedar St. Sediment total Hg was elevated only at Reservoir #2. Hg washigher at site-influenced locations in all fish speciesexcept brown bullhead (Ameiurus nebulosus). Cd washigher in bluegill, black crappie (Pomoxis nigromaculatus),and brown bullhead, and Cr was higher in largemouth bass filletsamples but not in whole-body samples. There were no seasonal differences in sediment or prey organism metals, but some metalsin some fish species did vary over time in an inconsistent manner. Predator fish Hg concentration was significantly linearlyrelated to weighted prey organism methyl Hg concentration. Largemouth bass Hg was significantly lower at Reservoir #2 in our study than in previous investigations in 1989 and 1990. High concentrations of inorganic Hg remain in river sediment asa result of operation of the Nyanza site, and fish Hg concentrations in river reaches downstream of the site areelevated compared to upstream reference sites. However, thedifferences are relatively small and Hg concentrations inlargemouth bass from the site-influenced locations are nohigher than those from some other, nearby uncontaminatedsites. We hypothesize that this results from burial ofcontaminated sediment with cleaner material, which reducesbioavailability of contaminants and possibly reducesmethylation of mercury.     

Solubilities of hydrophobic compounds in aqueous-organic solvent mixtures

Solubilities of several hydrophobic organic substances (paradichlorobenzene, endrin, naphthalene, and dibutyl phthalate) in aqueous solutions containing up to 0.10 mole fraction of common alcohols and ketones, were measured by gas chromatography. The solubilities are significantly increased by the alcohols and ketones. The results are interpreted in terms of the association of n molecules of alcohol or ketone with each hydrophobic organic molecule. Values of n and the equilibrium constant for this association are reported for each hydrophobic organic-alcohol and organic-ketone combination. The implications of these results for the disposal of toxic wastes by landfilling is discussed.     

Improving arsenopyrite oxidation rate laws: implications for arsenic mobilization during aquifer storage and recovery (ASR)

Aquifer storage and recovery (ASR) and aquifer recharge (AR) provide technical solutions to address water supply deficits and growing future water demands. Unfortunately, the mobilization of naturally present arsenic due to ASR/AR operations has undermined its application on a larger scale. Predicting arsenic mobility in the subsurface during ASR/AR is further complicated by site-specific factors, including the arsenic mobilization mechanisms, groundwater flow conditions, and multi-phase geochemical interactions. In order to ensure safe and sustainable ASR/AR operation, a better understanding of these factors is needed. The current study thus aims to better characterize and model arsenic remobilization at ASR/AR sites by compiling and analyzing available kinetic data on arsenic mobilization from arsenopyrite under different aqueous conditions. More robust and widely applicable rate laws are developed for geochemical conditions relevant to ASR/AR. Sensitivity analysis of these new rate laws gives further insight into the controlling geochemical factors for arsenic mobilization. When improved rate laws are incorporated as the inputs for reactive transport modeling, arsenic mobilization in ASR/AR operations can be predicted with an improved accuracy. The outcomes will be used to guide groundwater monitoring and specify ASR/AR operational parameters, including water pretreatment requirements prior to injection.     

Symbiont specificity and bleaching susceptibility among soft corals in the 1998 Great Barrier Reef mass coral bleaching event

Considerable variability in bleaching was observed within and among soft coral taxa in the order Alcyonacea (Octocorallia: Cnidaria) on the central Great Barrier Reef (GBR, latitude 18.2°–19.0°S, longitude 146.4°–147.3°E) during the 1998 mass coral bleaching event. In April 1998, during a period of high sea surface temperatures, tissue samples were taken from bleached and unbleached colonies representative of 17 soft coral genera. The genetic identities of intracellular dinoflagellates (Symbiodinium spp.) in these samples were analyzed using PCR-denaturing gradient gel electrophoresis fingerprinting analysis of the internal transcribed spacer regions 1 and 2. Alcyonaceans from the GBR exhibited a high level of symbiont specificity for Symbiodinium types mostly in clade C. A rare clade D type (D3) was associated only with Clavularia koellikeri, while Nephthea sp. hosted symbionts in clade B (B1n and B36). Homogenous Symbiodinium clade populations were detected in all but one colony. Colonies that appeared bleached possessed symbiont types that were genetically indistinguishable from those in nonbleached conspecifics. These data suggest that parameters other than the resident endosymbionts such as host identity and colony acclimatization are important in determining bleaching susceptibility among soft corals. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Functional response of sport divers to lobsters with application to fisheries management.

Fishery managers must understand the dynamics of fishers and their prey to successfully predict the outcome of management actions. We measured the impact of a two-day exclusively recreational fishery on Caribbean spiny lobster in the Florida Keys, USA, over large spatial scales (>100 km) and multiple years and used a theoretical, predator-prey functional response approach to identify whether or not sport diver catch rates were density-independent (type I) or density-dependent (type II or III functional response), and if catch rates were saturated (i.e., reached an asymptote) at relatively high lobster densities. We then describe how this predator-prey framework can be applied to fisheries management for spiny lobster and other species. In the lower Keys, divers exhibited a type-I functional response, whereby they removed a constant and relatively high proportion of lobsters (0.74-0.84) across all pre-fishing-season lobster densities. Diver fishing effort increased in a linear manner with lobster prey densities, as would be expected with a type-I functional response, and was an order of magnitude lower in the upper Keys than lower Keys. There were numerous instances in the upper Keys where the density of lobsters actually increased from before to after the fishing season, suggesting some type of "spill-in effect" from surrounding diver-disturbed areas. With the exception of isolated reefs in the upper Keys, the proportion of lobsters removed by divers was density independent (type-I functional response) and never reached saturation at natural lobster densities. Thus, recreational divers have a relatively simple predatory response to spiny lobster, whereby catch rates increase linearly with lobster density such that catch is a reliable indicator of abundance. Although diver predation is extremely high (approximately 80%), diver predation pressure is not expected to increase proportionally with a decline in lobster density (i.e., a depensatory response), which could exacerbate local extinction. Furthermore, management actions that reduce diver effort should have a concomitant and desired reduction in catch. The recreational diver-lobster predator-prey construct in this study provides a useful predictive framework to apply to both recreational and commercial fisheries, and on which to build as management actions are implemented.     

The spatial pattern of nitrogen cycling in the Adirondack Park, New York

Maps of canopy nitrogen obtained through analysis of high-resolution, hyperspectral, remotely sensed images now offer a powerful means to make landscape-scale to regional-scale estimates of forest N cycling and net primary production (NPP). Moreover, recent research has suggested that the spatial variability within maps of canopy N may be driven by environmental gradients in such features as historic forest disturbance, temperature, species composition, moisture, geology, and atmospheric N deposition. Using the wide variation in these six features found within the diverse forest ecosystems of the 2.5 million ha Adirondack Park, New York, USA, we examined linkages among environmental gradients and three measures of N cycling collected during the 2003 growing season: (1) field survey of canopy N, (2) field survey of soil C:N, and (3) canopy N measured through analysis of two 185 x 7.5 km Hyperion hyperspectral images. These three measures of N cycling strongly related to forest type but related poorly to all other environmental gradients. Further analysis revealed that the spatial pattern in N cycling appears to have distinct inter- and intraspecific components of variability. The interspecific component, or the proportional contribution of species functional traits to canopy biomass, explained 93% of spatial variability within the field canopy N survey and 37% of variability within the soil C:N survey. Residual analysis revealed that N deposition accounted for an additional 2% of variability in soil C:N, and N deposition and historical forest disturbance accounted for an additional 2.8% of variability in canopy N. Given our finding that 95.8% of the variability in the field canopy N survey could be attributed to variation in the physical environment, our research suggests that remotely sensed maps of canopy N may be useful not only to assess the spatial variability in N cycling and NPP, but also to unravel the relative importance of their multiple controlling factors.