INNOVATIVE IN-SITU REMEDIATION OF CONTAMINATED SEDIMENTS FOR SIMULTANEOUS CONTROL OF CONTAMINATION AND EROSION

New technologies are needed that neutralize contaminant toxicity and control physical transport mechanisms that mobilize sediment contaminants. The last 12 months of this comprehensive project investigated the use of combinations of sequestering agents to develop in situ active sediment caps that stabilize mixtures of contaminants and act as a barrier to mechanical disturbance under a broad range of environmental conditions. Efforts focused on the selection of effective sequestering agents for use in active caps, the composition of active caps, and the effects of active cap components on contaminant bioavailability and retention. Results from this project showed that phosphate amendments, some organoclays, and the biopolymer, chitosan, were very effective at removing metals from both fresh and salt water. These amendments also exhibited high retention (80% or more) of most metals indicating reduced potential for remobilization to the water column. Experiments on metal speciation and retention in contaminated sediment showed that apatite and organoclay can immobilize a broad range of metals under both reduced and oxidized conditions. These studies were followed by sequential extractions to evaluate the bioavailability and retention of metals in treated sediments. Metal fractions recovered in early extraction steps are more likely to be bioavailable and were termed the Potentially Mobile Fraction (PMF). Less bioavailable fractions collected in later extraction steps were termed the Recalcitrant Factor (RF). Apatite and organoclay reduced the PMF and increased the RF for several elements, especially Pb, Zn, Ni, Cr, and Cd. Empirically determined partitioning coefficients and modeling studies were used to assess the retention of organic contaminants on selected sequestering agents. Organoclays exhibited exceptionally high sorption of polycyclic aromatic hydrocarbons as indicated by a comparison of K{sub d} values among 12 amendments. These results suggested that organoclays have high potential for controlling organic contaminants. Measured partitioning coefficients were used to model the time required for a contaminant to penetrate sediment caps composed of organoclay. The results showed that a thin layer of highly sorptive organoclay can lead to very long migration times, perhaps longer than the expected lifetime of the contaminant in the sediment environment. A one-dimensional numerical model was used to examine the diffusion of metals through several cap material based on measured and assumed material and transport properties. These studies showed that active caps composed of apatite or organoclay have the potential to delay contaminant breakthrough due to diffusion by hundreds of years or more compared with passive caps composed of sand. Advectively dominated column experiments are currently underway to define effective sorption related retardation factors in promising amendments for various hydrophobic organic compounds. Upon completion of these experiments, advection transient models will be used to estimate the time required for the breakthrough of various contaminants in caps composed of different experimental materials. Biopolymer products for inclusion in active caps were evaluated on the basis of resistance to biodegradation, sorption capacity for organic and inorganic contaminants, and potential for erosion control. More than 20 biopolymer products were evaluated resulting in the selection of chitosan/guar gum cross-linked with borax and xanthan/chitosan cross-linked with calcium chloride for inclusion in active caps to produce a barrier that resists mechanical disturbance. A process was developed for coating sand with cross-linked biopolymers to provide a means for delivery to the sediment surface. Properties of biopolymer coated sand such as carbon fraction (indicating biopolymer coverage), porosity, bulk density, and biodegradability have been evaluated, and experiments are currently underway to assess the resistance of biopolymer coated sand to erosion. Although the ability of active cap materials to remediate contaminants has been emphasized in this study, it is also important to ensure that these materials do not have deleterious effects on the environment. Therefore, promising amendments were evaluated for toxicity using 10 day sediment toxicity tests, the standardized Toxicity Characteristic Leaching Procedure (TCLP), and measurement of metal concentrations in aqueous extracts from the amendments. Metal concentrations were below TCLP limits, EPA ambient water quality criteria, and other ecological screening values These results showed that apatite, organoclay, and biopolymer coated sand do not release metals. The sediment toxicity tests indicated that apatite and biopolymer coated sand are unlikely to adversely affect benthic organisms, even when used in high concentrations

Toxic and contaminant concerns generated by Hurricane Katrina

Journal of Environmental Engineering-Asce, 132(6): pp. 565-566

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 contaminants 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 MgCl{sub 2} 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 ml g{sup -1} for benzo(a)pyrene, 400-450 ml g{sup -1} for pyrene, and 50-70 ml g{sup -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

Seasonal Toxicity Observed with Amphipods (Eohaustorius estuarius) at Paleta Creek, San Diego Bay, USA

To assess potential impacts on receiving systems, associated with storm water contaminants, laboratory 10‐d amphipod (Eohaustorius estuarius) survival toxicity tests were performed using intact sediment cores collected from Paleta Creek (San Diego Bay, CA, USA) on 5 occasions between 2015 and 2017. The approach included deposition‐associated sediment particles collected from sediment traps placed at each of 4 locations during the 2015 to 2016 wet seasons. The bioassays demonstrated wet season toxicity, especially closest to the creek mouth, and greater mortality associated with particles deposited in the wet season compared with dry season samples. Grain size analysis of sediment trap material indicated coarser sediment at the mouth of the creek and finer sediment in the outer depositional areas. Contaminant concentrations of metals (Cd, Cu, Hg, Ni, Pb, and Zn) and organic compounds (polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], and pesticides) were quantified to assess possible causes of toxicity. Contaminant concentrations were determined in the top 5 cm of sediment and porewater (using passive samplers). Whereas metals, PAHs, and PCBs were rarely detected at sufficient concentrations to elicit a response, pyrethroid pesticides were highly correlated with amphipod toxicity. Summing individual pyrethroid constituents using a toxic unit approach suggested that toxicity to E. estuarius could be associated with pyrethroids. This unique test design allowed delineation of spatial and temporal differences in toxicity, suggesting that storm water discharge from Paleta Creek may be the source of seasonal toxicity. Environ Toxicol Chem 2019;39:229–239. © 2019 SETACPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152638/1/etc4619_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152638/2/etc4619.pd

Low-level amplification of oncogenes correlates inversely with age for patients with nontypical meningiomas

BACKGROUND: This study sought to identify genes in nontypical meningiomas with gains in copy number (CN) that correlate with earlier age of onset, an indicator of aggressiveness. METHODS: Among 94 adult patients, 91 had 105 meningiomas that were histologically confirmed. World Health Organization grades I (typical), II (atypical), and III (anaplastic) were assigned to tumors in 76, 14, and 1 patient, respectively. Brain invasion indicated that two World Health Organization grade I meningiomas were biologically atypical. DNA from 15 invasive/atypical/anaplastic meningiomas and commercial normal DNA were analyzed with multiplex ligation dependent probe amplification. The CN ratios (fold differences from normal) for 78 genes were determined. The CN ratio was defined as [tumor CN]/[normal CN] for each gene to normalize results. RESULTS: Characteristic gene losses (CN ratio \u3c 0.75) occurred in \u3e50% of the invasive/atypical/anaplastic meningiomas at 22q11, 1p34.2, and 1p22.1 loci. Gains (CN ratio ≥ 2.0) occurred in each tumor for 2 or more of 19 genes. Each of the 19 genes\u27 CN ratio was ≥ 2.0 in multiple tumors, and their collective sums (up to 49.1) correlated inversely with age (r = -0.72), minus an outlier. In patients ≤ 55 versus \u3e55 years, 5 genes (BIRC2, BRAF, MET, NRAS, and PIK3CA) individually exhibited significantly higher CN ratios (P \u3c 0.05) or a trend for them (P \u3c 0.09), with corrections for multiple comparisons, and their sums correlated inversely with age (r = -0.74). CONCLUSIONS: Low levels of amplification for selected oncogenes in invasive/atypical/anaplastic meningiomas were higher in younger adults, with the CN gains potentially underlying biological aggressiveness associated with early tumor development

Bioavailability and assimilation of sediment-associated benzo[a]pyrene by Ilyodrilus templetoni (Oligochaeta)

Benzo[a]pyrene (BaP)-amended sediment was desorbed by a sequential batch method using an isopropanol solution wash. The observed isotherm showed no evidence of desorption resistance, as indicated by increased partitioning to the solid phase at low concentrations. This was consistent with the prediction of minimal desorption resistance for highly hydrophobic compounds using a biphasic model. Bioavailability of BaP in desorbed sediments was assessed by toxicokinetic measures of uptake, bioaccumulation, and elimination in the deposit-feeding, freshwater tubificid oligochaete Ilyodrilus templetoni. Worms were exposed to sediments with BaP concentrations of approximately 26 and 11 microg/g dry weight sediment after desorption for one and three batches, respectively. The I. templetoni tissue concentration attained an apparent steady state after approximately one month and resulted in a biota-sediment accumulation factor of approximately 1.3 for both sediments. This is consistent with the paradigm that pore-water concentration predicts the uptake of organic contaminants into lipids despite the literature data showing that the major uptake route for BaP is likely from the ingestion of sediment particles. Ilyodrilus templetoni exhibited a high assimilation efficiency (80%) during a single-gut passage, a low elimination rate (k(c) = 0.0032 h(-1)), and negligible biotransformation of sediment-associated BaP

Relative importance of ingested sediment versus pore water as uptake routes for PAHs to the deposit-feeding oligochaete Ilyodrilus templetoni

The relative role of sediment pore water and ingested sediment particles to the total uptake of sediment-associated hydrophobic organic contaminants was examined by estimation from a water-only exposure experiment and from a bioenergetic-based toxicokinetic model utilizing experimentally measured sediment ingestion rates, assimilation efficiencies, and elimination rates. Phenanthrene (PHE) and benzo[a]pyrene (BaP) uptake in the bulk deposit-feeding oligochaete, Ilyodrilus templetoni, was measured. Assimilation efficiencies (ASE) were measured using a pulse-chase technique, based on a single-gut-passage time. Sediment-associated phenanthrene exhibited a lower ASE (50%) compared to B aP (80%), possibly due to a general relationship between assimilation and compound log K(ow). Estimated uptake of phenanthrene from pore water alone was essentially equal to the observed total uptake from both ingested sediment and sediment pore water. Estimated contribution of sediment-bound phenanthrene accounted for less than 20% of the total uptake. For benzo[a]pyrene, estimated uptake from sediment ingestion accounted for essentially all of the total uptake and estimated absorption from pore water accounted for \u3c5% of the total uptake. This research provides direct experimental evidence for a predicted increase in the importance of sediment ingestion relative to the pore water route of exposure as the hydrophobicity of organic contaminants increases