Phytoremediation of an arsenic-contaminated site using Pteris vittata L. and Pityrogramma calomelanos var. austroamericana: a long-term study

This field study investigated the phytoremediation potential of two arsenic (As) hyperaccumulating fern species, Pityrogramma calomelanos var. austroamericana and Pteris vittata over 27-month duration at a disused As-contaminated cattle-dip site located at Wollongbar, NSW, Australia. Ferns planted in January 2009 were harvested following 10, 22 and 27 months of growth. A detailed soil sampling was undertaken in June 2009 (initial, n?=?42 per plot) and limited sampling in April 2011 (after 27 months, n?=?15 per plot) to measure total and phosphate-extractable As concentrations in soil at 0?-?20-, 20?-?40- and 40?-?60-cm depths. The choice of the limited number of samples was considered sufficient to estimate the changes in soil As concentration following phytoremediation based on a geostatistical model. The average frond dry biomass, As concentration and As uptake were significantly (P??0.05), respectively, by P. vittata. Our results show that phytoremediation time based on observed changes in soil As based on limited sampling is not reliable; hence, it is recommended that the frond As uptake should be considered in order to evaluate the phytoremediation efficiency of the two fern species at the experimental site. Using As uptake of the two fern species, we estimate that with P. calomelanos var. austroamericana it would take 55?-?125 years to decrease mean total As content below the ecological investigation level (20 mg kg(-1)) in the surface and subsurface soils, whereas with P. vittata 143?-?412 years would be required to achieve this target.     

Factors diminishing the effectiveness of phosphorus loading from municipal effluent: critical information for TMDL analyses

Factors that diminish the effectiveness of phosphorus inputs from a municipal wastewater treatment facility (Metro) in contributing to phosphorus levels and its availability to support algae growth in a culturally eutrophic urban lake (Onondaga Lake, NY) were characterized and quantified. These factors included the bioavailability and settling characteristics of particulate phosphorus from this effluent, the dominant form (70%) of phosphorus in this input, and the plunging of the discharge to stratified layers in the lake. Supporting studies included: (1) chemical and morphometric characterization of the phosphorus-enriched particles of this effluent, compared to particle populations of the tributaries and lake, with an individual particle analysis technique; (2) conduct of algal bioavailability assays of the particulate phosphorus of the effluent; (3) conduct of multiple size class settling velocity measurements on effluent particles; and (4) determinations of the propensity of the discharge to plunge, and documentation of plunging through three-dimensional monitoring of a tracer adjoining the outfall. All of these diminishing effects were found to be operative for the Metro effluent in Onondaga Lake and will be integrated into a forthcoming phosphorus "total maximum daily load" analysis for the lake, through appropriate representation in a supporting mechanistic water quality model. The particulate phosphorus in the effluent was associated entirely with Fe-rich particles formed in the phosphorus treatment process. These particles did not contribute to concentrations in pelagic portions of the lake, due to local deposition associated with their large size. Moreover, this particulate phosphorus was found to be nearly entirely unavailable to support algae growth. While substantial differences are to be expected for various inputs, the effective loading concept and the approaches adopted here to assess the diminishing factors are broadly applicable.     

Energy supplies and future engines for land, sea, and air

The years 2012 and beyond seem likely to record major changes in energy use and power generation. The Japanese tsunami has resulted in large countries either scaling back or abolishing the future use of nuclear energy. The discovery of what seems like vast amounts of economically deliverable natural gas has many forecasting a rapid switch from coal- to gas-fired generating plants. On the other hand, environmentalists have strong objections to the production of natural gas and of petroleum by hydraulic fracturing from shale, or by extraction of heavy oil. They believe that global warming from the use of fossil fuels is now established beyond question. There has been rapid progress in the development of alternative energy supplies, particularly from on-shore and off-shore wind. Progress toward a viable future energy mix has been slowed by a U.S. energy policy that seems to many to be driven by politics. The author will review the history of power and energy to put all of the above in context and will look at possible future developments. He will propose what he believes to be an idealized energy policy that could result in an optimum system that would be arrived at democratically.     

Emerging technologies for removing nonpoint phosphorus from surface water and groundwater: introduction

Coastal and freshwater eutrophication continues to accelerate at sites around the world despite intense efforts to control agricultural P loss using traditional conservation and nutrient management strategies. To achieve required reductions in nonpoint P over the next decade, new tools will be needed to address P transfers from soils and applied P sources. Innovative remediation practices are being developed to remove nonpoint P sources from surface water and groundwater using P sorbing materials (PSMs) derived from natural, synthetic, and industrial sources. A wide array of technologies has been conceived, ranging from amendments that immobilize P in soils and manures to filters that remove P from agricultural drainage waters. This collection of papers summarizes theoretical modeling, laboratory, field, and economic assessments of P removal technologies. Modeling and laboratory studies demonstrate the importance of evaluating P removal technologies under controlled conditions before field deployment, and field studies highlight several challenges to P removal that may be unanticipated in the laboratory, including limited P retention by filters during storms, as well as clogging of filters due to sedimentation. Despite the potential of P removal technologies to improve water quality, gaps in our knowledge remain, and additional studies are needed to characterize the long-term performance of these technologies, as well as to more fully understand their costs and benefits in the context of whole-farm- and watershed-scale P management.     

Using flue gas desulfurization gypsum to remove dissolved phosphorus from agricultural drainage waters

High levels of accumulated phosphorus (P) in soils of the Delmarva Peninsula are a major source of dissolved P entering drainage ditches that empty into the Chesapeake Bay. The objective of this study was to design, construct, and monitor a within-ditch filter to remove dissolved P, thereby protecting receiving waters against P losses from upstream areas. In April 2007, 110 Mg of flue gas desulfurization (FGD) gypsum, a low-cost coal combustion product, was used as the reactive ingredient in a ditch filter. The ditch filter was monitored from 2007 to 2010, during which time 29 storm-induced flow events were characterized. For storm-induced flow, the event mean concentration efficiency for total dissolved P (TDP) removal for water passing through the gypsum bed was 73 ± 27% confidence interval (α = 0.05). The removal efficiency for storm-induced flow by the summation of load method was 65 ± 27% confidence interval (α = 0.05). Although chemically effective, the maximum observed hydraulic conductivity of FGD gypsum was 4 L s(-1), but it decreased over time to <1 L s(-1). When bypass flow and base flow were taken into consideration, the ditch filter removed approximately 22% of the TDP load over the 3.6-yr monitoring period. Due to maintenance and clean-out requirements, we conclude that ditch filtration using FGD gypsum is not practical at a farm scale. However, we propose an alternate design consisting of FGD gypsum-filled trenches parallel to the ditch to intercept and treat groundwater before it enters the ditch.     

Whole-stream response to nitrate loading in three streams draining agricultural landscapes

Physical, chemical, hydrologic, and biologic factors affecting nitrate (NO3(-)) removal were evaluated in three agricultural streams draining orchard/dairy and row crop settings. Using 3-d "snapshots" during biotically active periods, we estimated reach-level NO3(-) sources, NO3(-) mass balance, in-stream processing (nitrification, denitrification, and NO3(-) uptake), and NO3(-) retention potential associated with surface water transport and ground water discharge. Ground water contributed 5 to 11% to stream discharge along the study reaches and 8 to 42% of gross NO3(-) input. Streambed processes potentially reduced 45 to 75% of ground water NO3(-) before discharge to surface water. In all streams, transient storage was of little importance for surface water NO3(-) retention. Estimated nitrification (1.6-4.4 mg N m(-2) h(-1)) and unamended denitrification rates (2.0-16.3 mg N m(-2) h(-1)) in sediment slurries were high relative to pristine streams. Denitrification of NO3(-) was largely independent of nitrification because both stream and ground water were sources of NO3(-). Unamended denitrification rates extrapolated to the reach-scale accounted for <5% of NO3(-) exported from the reaches minimally reducing downstream loads. Nitrate retention as a percentage of gross NO3(-) inputs was >30% in an organic-poor, autotrophic stream with the lowest denitrification potentials and highest benthic chlorophyll a, photosynthesis/respiration ratio, pH, dissolved oxygen, and diurnal NO3(-) variation. Biotic processing potentially removed 75% of ground water NO3(-) at this site, suggesting an important role for photosynthetic assimilation of ground water NO3(-) relative to subsurface denitrification as water passed directly through benthic diatom beds.     

The Predatory Bird Monitoring Scheme: identifying chemical risks to top predators in Britain

The Predatory Bird Monitoring Scheme (PBMS) is a long term (>40 y), UK-wide, exposure monitoring scheme that determines the concentration of selected pesticides and pollutants in the livers and eggs of predatory birds. This paper describes how the PBMS works, and in particular highlights some of the key scientific and policy drivers for monitoring contaminants in predatory birds and describes the specific aims, scope, and methods of the PBMS. We also present previously unpublished data that illustrates how the PBMS has been used to demonstrate the success of mitigation measures in reversing chemical-mediated impacts; identify and evaluate chemical threats to species of high conservation value; and finally to inform and refine monitoring methodologies. In addition, we discuss how such schemes can also address wider conservation needs.     

Estimating waste transfer station delays using GPS

This paper examines the use of on-board global positioning system (GPS) data recorders as a method to collect field data on the movements of solid waste collection vehicles at transfer stations. The movements of five waste collection vehicles using four different transfer facilities were compared over a period of 1 year. The spatial data were analyzed using geofences to determine the amount of time each truck spent on each of four activities: queuing for access to the weigh scale, sitting on the weigh scale, queuing for access to the tipping floor, and unloading waste. The study found that queuing delays can be identified and measured using GPS data. The average time at a facility for all trucks was 16.4min per visit, with a standard deviation of 14.3min. Time at the facility ranged between 2 and 111min per visit and the distribution of time at the facility was positively skewed. Multi-compartment vehicles (co-collection and recycling trucks) spent significantly more time at unloading facilities. There were also significant differences in the length and the location of the queues at different facilities. At one facility, the longest delays were encountered while waiting for the weigh scale, at two facilities trucks experienced delays in obtaining access to the tipping floor, while at the fourth facility no significant delays developed.     

Feeding, growth and reproduction of sea urchins (Strongylocentrotus droebachiensis) on single and mixed diets of kelp (Laminaria spp.) and the invasive alga Codium fragile ssp. tomentosoides

Since its introduction to Nova Scotia in the early 1990s, the invasive green alga Codium fragile ssp. tomentosoides has spread rapidly to become a dominant and persistent component of seaweed assemblages in the rocky subtidal zone. To examine the potential of sea urchins (Strongylocentrotus droebachiensis) to regulate Codium, and the potential of the alga to support urchin growth and reproduction, we fed urchins Codium and/or kelp (Laminaria spp., a high quality and preferred native food) in the laboratory for 11 months. Urchins showed a strong and active preference for kelp: they consumed more Laminaria than Codium (as dry weight) in single and mixed diet treatments. Urchins fed only Codium consumed 3.5 times more of the alga than those on a mixed diet, but did not increase their feeding rate in winter when kelp consumption was greatest. Laminaria was consumed at the same rate in single and mixed diets, indicating that the presence of an alternative food had no effect on kelp consumption. Survival and growth (change in test diameter) were lowest on the Codium diet, although the differences among diets were not statistically significant. Urchins on the Codium diet showed no gonadal production over the annual reproductive cycle, compared to a marked rise in gonad index on the Laminaria and mixed diets. Our results indicate that Codium is an unattractive, unpalatable and poor quality food, which is not readily consumed by urchins. Thus we predict that urchins at moderate densities will be much more likely to graze kelp than Codium in mixed stands, creating a mosaic of Codium patches and barren areas. At high densities, however, urchins are likely to destructively graze all seaweeds, although dense stands of the invasive alga may prolong the widespread formation of barrens.     

Characterization of organic chemical contaminants in sediments from Jobos Bay, Puerto Rico

Jobos Bay, located on the southeastern coast of Puerto Rico, contains a variety of habitats including mangroves, seagrass meadows, and coral reefs. The watershed surrounding the bay includes a number of towns, agricultural areas, and the Jobos Bay National Estuarine Research Reserve (NERR). Jobos Bay and the surrounding watershed are part of a Conservation Effects Assessment Project (CEAP), involving the Jobos Bay NERR, the US Department of Agriculture, and the National Oceanic and Atmospheric Administration (NOAA) to assess the benefits of agricultural best management practices (BMPs) on the terrestrial and marine environments. As part of the Jobos Bay CEAP, NOAA collected sediment samples in May 2008 to characterize over 130 organic chemical contaminants. This paper presents the results of the organic contaminant analysis. The organic contaminants detected in the sediments included polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and the pesticide DDT. PAHs at one site in the inner bay near a boat yard were significantly elevated; however, all organic contaminant classes measured were below NOAA sediment quality guidelines that would have indicated that impacts were likely. The results of this work provide an important baseline assessment of the marine environment that will assist in understanding the benefits of implementing BMPs on water quality in Jobos Bay.