Evaluation of the effects of coal fly ash amendments on the toxicity of a contaminated marine sediment.

Approaches for cleaning up contaminated sediments range from dredging to in situ treatment. In this study, we discuss the effects of amending reference and contaminated sediments with coal fly ash to reduce the bioavailability and toxicity of a field sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). Six fly ashes and a coconut charcoal were evaluated in 7-d whole sediment toxicity tests with a marine amphipod (Ampelisca abdita) and mysid (Americamysis bahia). Fly ashes with high carbon content and the coconut charcoal showed proficiency at reducing toxicity. Some of the fly ashes demonstrated toxicity in the reference treatments. It is suspected that some of this toxicity is related to the presence of ammonia associated with fly ashes as a result of postoxidation treatment to reduce nitrous oxide emissions. Relatively simple methods exist to remove ammonia from fly ash before use, and fly ashes with low ammonia content are available. Fly ashes were also shown to effectively reduce overlying water concentrations of several PAHs. No evidence was seen of the release of the metals cadmium, copper, nickel, or lead from the fly ashes. A preliminary 28-d polychaete bioaccumulation study with one of the high-carbon fly ashes and a reference sediment was also performed. Although preliminary, no evidence was seen of adverse effects to worm growth or lipid content or of accumulation of PAHs or mercury from exposure to the fly ash. These data show fly ashes with high carbon content could represent viable remedial materials for reducing the bioavailability of organic contaminants in sediments.

Mercury and stable isotopes of carbon and nitrogen in mink.

Total Hg concentrations and values of stable isotopes (delta(15)N, delta(13)C) in tissues of mink (Mustela vison) captured in Rhode Island (USA) during winters of 1999 to 2004 were statistically distinct based on location. Mink captured in salt marsh environments (salt marsh group mink [SMGM]) had significantly lower mean Hg concentrations in liver and muscle tissue, and significantly higher delta(15)N and delta(13)C values in muscle, than those in corresponding samples of mink from upland freshwater locations (upland group mink [UPGM]). Stomach content samples obtained from the mink carcasses showed that fish, frogs, and crayfish were the dominant food items in UPGM, but in SMGM, fish predominated. Significant correlations were found for total Hg concentrations and stable isotope values between stomach contents and tissues. Comparisons of increases in Hg concentrations and delta(15)N values from stomach contents to muscle tissue showed nonsignificant differences between UPGM and SMGM for Hg concentrations (SMGM, factor of 4.2; UPGM, factor of 3.9) and delta(15)N values (SMGM, difference of 3.9 per thousand; UPGM, difference of 3.1 per thousand). These results suggest that the length of the trophic step and the extent of accumulation of Hg were approximately equal in both mink groups despite the differences in dietary composition and possible differences in accumulation of organic and inorganic Hg. The correspondence of stable isotope values and Hg concentrations between mink tissues and their stomach contents indicates that use of stomach content analysis to identify major prey items, followed by collection and analysis of appropriate field prey, may represent an approach for estimating Hg exposure to mink.

Marine sediment toxicity identification evaluation methods for the anionic metals arsenic and chromium.

Marine sediments accumulate a variety of contaminants and, in some cases, demonstrate toxicity because of this contamination. Toxicity identification evaluation (TIE) methods provide tools for identifying the toxic chemicals causing sediment toxicity. Currently, whole-sediment TIE methods are not available for anionic metals like arsenic and chromium. In the present paper, we describe two new anion-exchange resins used in the development of whole-sediment TIE methods for arsenic and chromium. Resins were shown to reduce whole-sediment toxicity and overlying water concentrations of the anionic metals. Sediment toxicity, expressed as the median lethal concentration, was reduced by a factor of two to a factor of nearly six between amended sediment treatments containing resin and those without resin. Aqueous concentrations of arsenic and chromium in the toxicity exposures decreased to less than the detection limits or to concentrations much lower than those measured in treatments without resin. Interference studies indicated that the anion-exchange resins had no significant effect on concentrations of the representative pesticide endosulfan and minimal effects on concentrations of ammonia. However, the anion-exchange resins did significantly reduce the concentrations of a selection of cationic metals (Cd, Cu, Ni, Pb, and Zn). These data demonstrate the utility of anion-exchange resins for determining the contribution of arsenic and chromium to whole-sediment toxicity. The present results also indicate the importance of using TIE methods in a formal TIE structure to ensure that results are not misinterpreted. These methods should be useful in the performance of marine whole-sediment TIEs.

Interaction of planar and nonplanar organic contaminants with coal fly ash: effects of polar and nonpolar solvent solutions.

Coal fly ash has a very high sorption capacity for a variety of anthropogenic contaminants and has been used to cleanse wastewater of pollutants for approximately 40 years. Like other black carbons, the planar structure of the residual carbon in fly ash results in elevated affinities for planar organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs) and some polychlorinated biphenyls (PCBs). The present study was performed to understand better the mechanisms affecting the strong interaction between planar contaminants and coal fly ash. The removal of 10 PCBs and 10 PAHs by several fly ashes and other sorbents was evaluated under different experimental conditions to highlight the intermolecular forces influencing adsorption. Varying fly ash concentration and solvent system composition indicated that dispersive interactions were most prevalent. For the PCBs, empirical results also were compared to molecular modeling estimates of the energy necessary for the PCB molecule to assume a planar conformation (PCe). The PCe levels ranged from 8 to 25 kcal/mol, depending on the degree of ortho-substituted chlorination of the PCB. A significant correlation between PCe and PCB removal from solution was observed for the fly ashes and activated carbon, whereas the nonplanar sorbent octadecyl (C18) indicated no relationship. These findings demonstrate the strong interaction between black carbon fly ash and planar organic contaminants. Furthermore, as exemplified by the PCBs, these results show how this interaction is a function of a contaminant's ability to assume a planar conformation.

Effects of different forms of organic carbon on the partitioning and bioavailability of nonylphenol.

Oxygenated nonpolar organic contaminants (NOCs) are underrepresented in studies of the partitioning and bioavailability of NOCs, including nonylphenol. In this investigation, we evaluated the toxicity, partitioning, and bioavailability of nonylphenol as affected by different forms of organic carbon. Along with organic carbon content, the role of organic carbon polarity was assessed. Toxicity of nonylphenol to a mysid and amphipod was comparable to results reported in the literature for marine organisms with median lethal concentrations (LC50s) of 82.3 and 236 microg/L, respectively. The presence of the different forms of organic carbon in every instance altered, often statistically significantly, the toxicity and bioavailability of the nonylphenol and increased the LC50 by approximately a factor of two. Partition coefficients (KPs) for nonylphenol ranged from 21.3 for cellulose to 9,770 for humic acid; log organic carbon-normalized partition coefficients (KOCs) ranged from 1.71 for cellulose to 4.71 for sediment. An exercise to predict nonylphenol effects using our toxicity data and normalized partition coefficients indicated organic carbon content was most protective and also highlighted the need for further research to better understand nonylphenol bioavailability. These data suggested that with regard to partitioning and bioavailability, the oxygenated NOC nonylphenol behaves like conventional NOCs. The data also suggest that, with refinements, polarity may have some advantages in predicting nonylphenol bioavailability.

Effects of sample preparation on the measurement of organic carbon, hydrogen, nitrogen, sulfur, and oxygen concentrations in marine sediments.

The elemental composition of marine sediment provides useful information for the study of environmental processes including biogeochemical cycling and contaminant partitioning. It is common practice to acidify marine sediment samples to remove carbonate before measuring the concentrations of organic carbon (C). To date, however the effects of acidification on the concentrations of hydrogen (H), nitrogen (N), sulfur (S) and oxygen (O) in marine sediments have not been explicitly addressed. Acidification may contaminate or alter the sediment samples and create experimental artifacts affecting the validity of resulting H/C, C/N and O/C ratios. The objective of this study was to quantify how various preparation techniques affect the measured concentrations of C, H, N, S and O in marine sediments. Effects of four different pretreatments: unacidified (whole), acidification by HCl vapor, acidification by direct addition of HCl, and combustion were evaluated using five marine sediments and a standard reference material. The magnitude of carbonate loss between the vapor and direct acidification treatments was evaluated using stable C isotope analysis. Carbonates were most effectively removed by direct addition of HCl; and our results agree with findings of other studies which found direct addition of HCl to be the most accurate method for measuring organic C. However, the acid treatments elevated the apparent concentration of H and O; and in a few cases concentrations of N and S were significantly affected by acidification. In general, combustion significantly reduced all elemental concentrations compared to the whole sample. Based on these results, we recommend analysis of the untreated whole sediment for determining N, H, O, and S.

Sorption of 2,4'-dichlorobiphenyl and fluoranthene to a marine sediment amended with different types of black carbon.

Recent studies demonstrate that sedimentary black carbon (BC) affects the sorption of some hydrophobic organic contaminants (HOCs) to a greater extent than sedimentary organic carbon (OC). Among HOC, polycyclic aromatic hydrocarbons (PAHs) are known to interact extensively with BC. Currently, data on the sorption of various kinds of HOCs to different types of BC are limited. In this study, we amended a marine sediment with BC from several different sources, humic acid, and inert sand. Equilibration studies with 14C fluoranthene and the polychlorinated biphenyl (PCB) 3H 2,4'-dichlorinated biphenyl were performed to determine the magnitude of sorption as a function of contaminant and BC type. The magnitude of sorption to the BC-amended sediments was greater for the PAH than the PCB as compared to the sediment alone, humic acid, and sand. For example, differences between the log partition coefficient (K(P)) for the PAH and PCB ranged from 0.41 to 0.69 log units for humic acid and sand treatments, while differences ranged from 0.88 to 1.57 log units for the BC-amended sediments. As a result, BC-normalized partition coefficients (log K(BC)) for the PAH averaged 6.41, whereas the PCB log K(BC) values averaged 5.33. These results demonstrate that PAH sorption and most likely bioavailability are influenced strongly by the presence of BC of different types, while sorption of a nonplanar PCB was affected to a lesser degree.