Michael H. Paller

Sequestering Agents for Active Caps—Remediation of Metals and Organics

This research evaluated organoclays, zeolites, phosphates, and a biopolymer as sequestering agents for inorganic and organic contaminants. Batch experiments were conducted to identify amendments and mixtures of amendments for metal and organic contaminant removal and retention. Contaminant removal was evaluated by calculating partitioning coefficients. Metal retention was evaluated by desorption studies in which residue from the removal studies was extracted with 1 M MgCl2 solution. The results indicated that phosphate amendments, some organoclays, and the biopolymer, chitosan, were very effective sequestering agents for metals in fresh and salt water. Organoclays were very effective sorbents for phenanthrene, pyrene, and benzo(a)pyrene. Partitioning coefficients for the organoclays were 3000–3500 L g−1 for benzo(a)pyrene, 400–450 L g−1 for pyrene, and 50–70 L g−1 for phenanthrene. Remediation of sites with a mixture of contaminants is more difficult than sites with a single contaminant because metals and organic contaminants have different fate and transport mechanisms in sediment and water. Mixtures of amendments (e.g., organoclay and rock phosphate) have high potential for remediating both organic and inorganic contaminants under a broad range of environmental conditions, and have promise as components in active caps for sediment remediation.

Amendments for the in situ remediation of contaminated sediments: evaluation of potential environmental impacts.

Active sediment caps represent a comparatively new technology for remediating contaminated sediments. They are made by applying chemically active amendments that reduce contaminant mobility and bioavailability to the sediment surface. The objective of this study was to determine if active cap amendments including organoclay, apatite, and biopolymers have the potential to harm benthic organisms. Methods included laboratory bioassays of amendment toxicity and field evaluations of amendment impacts on organisms held in cages placed within pilot-scale active caps located in Steel Creek, a South Carolina (USA) stream. Test organisms included Hyalella azteca, Leptocheirus plumulosus, Lumbriculus variegatus, and Corbicula fluminea to represent a range of feeding modes, burrowing behaviors, and both fresh and saltwater organisms. In addition to the laboratory and field assays, chemical extractions were performed to determine if the amendments contained harmful impurities that could leach into the ambient environment. Laboratory bioassays indicated that 100% apatite had minimal effects on Hyalella in freshwater and up to 25% organoclay was nontoxic to Leptocheirus in brackish water. Field evaluations indicated that pilot-scale caps composed of up to 50% apatite and 25% organoclay did not harm Hyalella, Lumbriculus, or Corbicula. In contrast, organisms in caps containing biopolymers died because of physical entrapment and/or suffocation by the viscous biopolymers. The extractions showed that the amendments did not release harmful concentrations of metals. These studies indicated that apatite and organoclay are nontoxic at concentrations (up to 50% and 25% by weight, respectively) needed for the construction of active caps that are useful for the remediation of metals and organic contaminants in sediments.

Distribution of Larval Fish between Macrophyte Beds and Open Channels in a Southeastern Floodplain Swamp

ABSTRACT Larval fish assemblages drifting in the open channels and those in adjacent macrophyte beds differed in standing stock and species composition. Standing stocks were approximately 160 times higher in the macrophyte beds than in the open channels during the day but, due to an increase in the number of drifting larvae, only 13 times higher in the macrophyte beds than in the open channels at night. Larvae concentrated in the interior of the macrophyte beds rather than at the ecotone between the macrophyte beds and the open channels. Notropis spp. and Lepomis spp. predominated in the drift while Notropis spp., Elassoma zonatum, Erimyzon succetta, and Lepomis spp. predominated in the macrophyte beds. Drift among all taxa involved only small postlarvae. The drift of Lepomis spp. larvae appeared to be associated with dispersal from the nest at the time of yolk sac depletion.

Interactions among phosphate amendments, microbes and uranium mobility in contaminated sediments

The use of sequestering agents for the transformation of radionuclides in low concentrations in contaminated soils/sediments offers considerable potential for environmental cleanup. This study evaluated the influence of three types of phosphate (rock phosphate, biological phosphate, and calcium phytate) and two microbial amendments (Alcaligenes piechaudii and Pseudomonas putida) on U mobility. All tested phosphate amendments reduced aqueous U concentrations more than 90%, likely due to formation of insoluble phosphate precipitates. The addition of A. piechaudii and P. putida alone were found to reduce U concentrations 63% and 31%, respectively. Uranium removal in phosphate treatments was significantly reduced in the presence of the two microbes. Two sediments were evaluated in experiments on the effects of phosphate amendments on U mobility, one from a stream on the Department of Energys Savannah River Site near Aiken, SC and the other from the Hanford Site, a Department of Energy facility in Washington state. Increased microbial activity in the treated sediment led to a reduction in phosphate effectiveness. The average U concentration in 1 M MgCl(2) extract from U contaminated sediment was 437 microg/kg, but in the same sediment without microbes (autoclaved), the extractable U concentration was only 103 microg/kg. The U concentration in the 1 M MgCl(2) extract was approximately 0 microg/kg in autoclaved amended sediment treated with autoclaved biological apatite. These results suggest that microbes may reduce phosphate amendment remedial effectiveness.

Effects of stream size on taxa richness and other commonly used benthic bioassessment metrics

Benthic macroinvertebrate samples were collected from natural substrates in disturbed and undisturbed South Carolina upper coastal plain streams to determine if taxa richness and other bioassessment metrics were significantly related to stream size as predicted by the River Continuum Concept (RCC). Linear, quadratic, and lognormal regression models indicated that stream width was positively related to total number of taxa; number of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa; and total number of organisms. Linear regression showed that the expected number of taxa at undisturbed sites ranged from 35 in 2.0xa0m wide streams to 64 in 16.0xa0m streams. Comparable values were 8–20 for EPT and 109–261 for number of organisms. Stream width was inversely related to biotic index values indicating a decrease in average organism tolerance with increasing stream size. ANCOVA showed that the effects of stream size were similar for disturbed and undisturbed sites. Rank correlations and multidimensional scaling (MDS) showed that Lepidoptera and Trichoptera were more abundant in larger streams and Annelida in smaller streams. Stream size related changes in benthic macroinvertebrate community composition are often ignored in bioassessment protocols; however, failure to adjust metrics for stream size can lead to erroneous conclusions. Adjustments are possible by analyzing regression residuals stripped of stream size related variance, dividing the area beneath the maximum taxa richness line into equal size units for metric scoring, or scaling metrics based on predicted reference values.

Impact of Forest Seral Stage on use of Ant Communities for Rapid Assessment of Terrestrial Ecosystem Health

Abstract Bioassessment evaluates ecosystem health by using the responses of a community of organisms that integrate all aspects of the ecosystem. A variety of bioassessment methods have been applied to aquatic ecosystems; however, terrestrial methods are less advanced. The objective of this study was to examine baseline differences in ant communities at different seral stages from clear cut to mature pine plantation as a precursor to developing a broader terrestrial bioassessment protocol. Comparative sampling was conducted at nine sites having four seral stages: clearcut, 5 year recovery, 15 year recovery, and mature stands. Soil and vegetation data were also collected at each site. Ants were identified to genus. Analysis of the ant data indicated that ants respond strongly to habitat changes that accompany ecological succession in managed pine forests, and both individual genera and ant community structure can be used as indicators of successional change. Ants exhibited relatively high diversity in both early and mature seral stages. High ant diversity in mature seral stages was likely related to conditions on the forest floor favoring litter dwelling and cold climate specialists. While ants may be very useful in identifying environmental stress in managed pine forests, adjustments must be made for seral stage when comparing impacted and unimpacted forests.

Ichthyoplankton transport in relation to floodplain width and inundation and tributary creek discharge in the lower Savannah River of Georgia and South Carolina

We report the results of a 3-year study of ichthyoplankton in the lower Savannah River and its coastal plain tributaries. Sampling was weekly from February through July in 1983, 1984 and 1985. Ichthyoplankton transport was used as an estimate of ichthyoplankton production. Ichthyoplankton transport in the river, for both total and most common taxa, was highest in 1983 and lowest in 1985. Ichthyoplankton transport into the river from tributary streams was also highest in 1983 and lowest in 1985. Ichthyoplankton transported from these tributaries sometimes comprised a significant percent of the larval transport at the next river station downstream from the tributary mouth. The highest larval transport occurred when the spring flood pulse was most elevated for the longest time, and larval transport at particular river stations or creeks was correlated with floodplain width in 1983 and 1984, years when flood pulses were high enough so that the adjacent floodplain was inundated during or following spawning. In 1985 the flood pulse was brief, inundation levels were low, and inundation occurred in February before most fish had spawned. Except for American shad and sunfishes, larval transport for all common taxa was greatly reduced in 1985 compared to 1983.

Ecological half-lives of 137Cs in fishes from the Savannah River Site.

Ecological half-lives (Tes) were estimated for 137Cs in largemouth bass, sunfishes, and bullheads from two reservoirs and three streams on the Savannah River Site, a nuclear weapons material production facility in South Carolina. Ecological half-life is the time required for a given contaminant concentration to decrease by 50% as a result of physical, chemical, and/or biological processes that remove it from an ecosystem or render it biologically unavailable. Tes were estimated from whole-fish 137Cs concentrations in samples collected during 1972-1996, following radionuclide releases that occurred primarily during the 1960s and early 1970s. Tes ranged from 3.2 to 16.7 y, and all were shorter than expected from the half-life for radioactive decay (Tp = 30.2 y) alone. Fish taxa from the same locations differed in mean 137Cs concentrations (highest in largemouth bass and lowest in sunfishes) but, in most cases, exhibited similar 137Cs Tes. Rates of 137Cs removal in fishes were strongly correlated with rates of 137Cs removal in water. The shortest Tes occurred in the upper portions of the streams. Tes in lower portions of the streams were longer, as were Tes in one of the reservoirs. Tes in the second reservoir, which had a much shorter water residence time, were nearly comparable to those in the upper portions of the streams until 1991. At that time, 137Cs concentrations in fishes began to increase following drainage and refilling of the reservoir, which apparently resuspended 137Cs buried in the sediments.

Effective half-life of caesium-137 in various environmental media at the Savannah river site.

During the operational history of the Savannah River Site (SRS), many different radionuclides have been released from site facilities into the SRS environment. However, only a relatively small number of pathways, most importantly (137)Cs in fish and deer, have contributed significantly to doses and risks to the public. The effective half-lives (Te) of (137)Cs (which include both physical decay and environmental dispersion) in Savannah River floodplain soil and vegetation and in fish and white-tailed deer from the SRS were estimated using long-term monitoring data. For 1974-2011, the Tes of (137)Cs in Savannah River floodplain soil and vegetation were 17.0 years (95% CIxa0=xa014.2-19.9) and 13.4 years (95% CIxa0=xa010.8-16.0), respectively. These Tes were greater than in a previous study that used data collected only through 2005 as a likely result of changes in the flood regime of the Savannah River. Field analyses of (137)Cs concentrations in deer collected during yearly controlled hunts at the SRS indicated an overall Te of 15.9 years (95% CIxa0=xa012.3-19.6) for 1965-2011; however, the Te for 1990-2011 was significantly shorter (11.8 years, 95% CIxa0=xa04.8-18.8) due to an increase in the rate of (137)Cs removal. The shortest Tes were for fish in SRS streams and the Savannah River (3.5-9.0 years), where dilution and dispersal resulted in rapid (137)Cs removal. Long-term data show that Tes are significantly shorter than the physical half-life of (137)Cs in the SRS environment but that they can change over time. Therefore, it is desirable have a long period of record for calculating Tes and risky to extrapolate Tes beyond this period unless the processes governing (137)Cs removal are clearly understood.

Effects of disturbance at two spatial scales on macroinvertebrate and fish metrics of stream health

We analyzed macroinvertebrate and fish assemblage data collected from the upper southeastern coastal plain of the USA to (1) assess the relative sensitivities of bioassessment metrics to in-stream habitat quality, catchment scale land disturbance, and the presence of a reservoir in the catchment and (2) determine whether fish differ from macroinvertebrates in their responses to these variables. Fish and macroinvertebrates responded differently to anthropogenic disturbance: macroinvertebrates were affected most strongly by in-stream habitat quality and fish by the presence of a reservoir in the catchment. Neither taxonomic group were significantly affected by the catchment scale disturbance, probably because the proportions of disturbed land in the study areas were low. Fish may be particularly sensitive to the presence of reservoirs because of their need to cover relatively large distances to complete life cycles and maintain viable populations and because of their sensitivity to the effects of invasive reservoir species, particularly predator fishes. Although not an important predictor in itself, disturbance at the watershed scale was significantly and positively related to in-stream habitat quality, indicating that watershed disturbance had an important indirect effect on aquatic organisms. Direct and indirect ordination showed that the metric data were more strongly related to the disturbance variables than the taxonomic data from which the metrics were derived, possibly because the metrics were less sensitive than the taxon-specific abundances to nondisturbance-related factors. Other factors that may have contributed to this result include greater statistical tractability of the metric data and the relatively high sensitivity of the collective properties represented by the metrics to disturbance-related environmental changes.