Preparation and characterization of nickel-spiked freshwater sediments for toxicity tests: toward more environmentally realistic nickel partitioning.

Two spiking methods were compared and nickel (Ni) partitioning was evaluated during a series of toxicity tests with 8 different freshwater sediments having a range of physicochemical characteristics. A 2-step spiking approach with immediate pH adjustment by addition of NaOH at a 2:1 molar ratio to the spiked Ni was effective in producing consistent pH and other chemical characteristics across a range of Ni spiking levels. When Ni was spiked into sediment having a high acid-volatile sulfide and organic matter content, a total equilibration period of at least 10 wk was needed to stabilize Ni partitioning. However, highest spiking levels evidently exceeded sediment binding capacities; therefore, a 7-d equilibration in toxicity test chambers and 8 volume-additions/d of aerobic overlying water were used to avoid unrealistic Ni partitioning during toxicity testing. The 7-d pretest equilibration allowed excess spiked Ni and other ions from pH adjustment to diffuse from sediment porewater and promoted development of an environmentally relevant, 0.5- to 1-cm oxic/suboxic sediment layer in the test chambers. Among the 8 different spiked sediments, the logarithm of sediment/porewater distribution coefficient values (log Kd ) for Ni during the toxicity tests ranged from 3.5 to 4.5. These Kd values closely match the range of values reported for various field Ni-contaminated sediments, indicating that testing conditions with our spiked sediments were environmentally realistic.

Sensitivity of early life stages of freshwater mussels (Unionidae) to acute and chronic toxicity of lead, cadmium, and zinc in water.

Toxicity of lead, cadmium, or zinc to early life stages of freshwater mussels (fatmucket, Lampsilis siliquoidea; Neosho mucket, L. rafinesqueana) was evaluated in 48-h exposures with mussel larvae (glochidia), in 96-h exposures with newly transformed (5-d-old) and two- or six-month-old juvenile mussels, or in 28-d exposures with two- or four-month-old mussels in reconstituted soft water. The 24-h median effect concentrations (EC50s) for fatmucket glochidia (>299 microg Pb/L, >227 microg Cd/L, 2,685 microg Zn/L) and 96-h EC50s for two- or six-month-old fatmucket (>426 microg Pb/L, 199 microg Cd/L, 1,700 microg Zn/L) were much higher than 96-h EC50s for newly transformed fatmucket (142 and 298 microg Pb/L, 16 microg Cd/L, 151 and 175 microg Zn/L) and Neosho mucket (188 microg Pb/L, 20 microg Cd/L, 145 microg Zn/L). Chronic values for fatmucket were 10 microg Pb/L, 6.0 microg Cd/L, and 63 and 68 microg Zn/L. When mussel data from the present study and the literature were included in updated databases for deriving U.S. Environmental Protection Agency water quality criteria, mussel genus mean acute values were in the lower percentiles of the sensitivity distribution of all freshwater species for Pb (the 26th percentile), Cd (the 15th to 29th percentile), or Zn (the 12th to 21st percentile). The mussel (Lampsilis) genus mean chronic value was the lowest value ever reported for Pb (the 9th percentile) but was near the middle of the sensitivity distribution for Cd (the 61st percentile) or Zn (the 44th percentile). These results indicate that mussels were relatively sensitive to the acute toxicity of these three metals and to the chronic toxicity of Pb, but were moderately sensitive to the chronic toxicity of Cd or Zn compared to other freshwater species.

Metal exposure and effects in voles and small birds near a mining haul road in Cape Krusenstern National Monument, Alaska.

Voles and small passerine birds were live-captured near the Delong Mountain Regional Transportation System (DMTS) haul road in Cape Krusenstern National Monument in northwest Alaska to assess metals exposure and sub-lethal biological effects. Similar numbers of animals were captured from a reference site in southern Cape Krusenstern National Monument for comparison. Histopathological examination of selected organs, and analysis of cadmium, lead, and zinc concentrations in liver and blood samples were performed. Voles and small birds captured from near the haul road had about 20 times greater blood and liver lead concentrations and about three times greater cadmium concentrations when compared to those from the reference site, but there were no differences in zinc tissue concentrations. One vole had moderate metastatic mineralization of kidney tissue, otherwise we observed no abnormalities in internal organs or DNA damage in the blood of any of the animals. The affected vole also had the greatest liver and blood Cd concentration, indicating that the lesion might have been caused by Cd exposure. Blood and liver lead concentrations in animals captured near the haul road were below concentrations that have been associated with adverse biological effects in other studies; however, subtle effects resulting from lead exposure, such as the suppression of the activity of certain enzymes, cannot be ruled out for some individual animals. Results from our 2006 reconnaissance-level study indicate that overall, voles and small birds obtained from near the DMTS road in Cape Krusenstern National Monument were not adversely affected by metals exposure; however, because of the small sample size and other uncertainties, continued monitoring of lead and cadmium in terrestrial habitats near the DMTS road is advised.

Distribution of pesticides, PAHs, PCBs, and bioavailable metals in depositional sediments of the lower Missouri River, USA.

The lower Missouri River was studied to determine the distribution of selected persistent organic pollutants and bioavailable metals in depositional sediments. Nineteen sites between Omaha, Nebraska and Jefferson City, Missouri were sampled. This stretch of the river receives point-source and non-point-source inputs from industrial, urban, and agricultural activities. As part of an ecological assessment of the river, concentrations of 29 legacy organochlorine pesticides (OC pesticides), including chlordanes, DDTs, and hexachlorocyclohexanes; a select list of current-use pesticides, including trifluralin, diazinon, chlorpyrifos, and permethrin, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), divalent metals (copper, nickel, zinc, cadmium, and lead), and polybrominated diphenyl ethers (PBDEs) were determined. Concentrations (dry weight basis) of OC pesticides in the sediments were less than 1 ng/g, with the exception of the backwater sediment collected from the mouth of the Blue River in the Kansas City metropolitan area, which contained up to 20 ng/g total chlordane, 8.1 ng/g p,p'-DDE, 1.5 ng/g lindane, 4.8 ng/g dieldrin, and 3 ng/g endrin. Concentrations of chlorpyrifos and permethrin ranged from less than 1 ng/g to 5.5 ng/g and 44 ng/g, respectively. Concentrations of PCBs ranged from less than 11 ng/g to 250 ng/g, with the Blue River and Sibley sediments containing 100 and 250 ng/g total PCBs, respectively. Concentrations of total PAHs at 17 of the 19 sites ranged from 250 to 700 ng/g, whereas the Riverfront and Blue River sites in Kansas City contained 1100 ng/g and nearly 4000 ng/g, respectively. Concentrations of the metals did not vary significantly among most sites; however, the Blue River site contained elevated concentrations of zinc (104 microg/g), cadmium (0.7 microg/g), and lead (34 microg/g) compared to the other sites. The moderately high concentrations of acid-volatile sulfide in the sediments suggest a low potential for metal toxicity to benthic organisms along this reach of the Missouri River. The depositional area sediments contained concentrations of the targeted persistent organic chemicals and metals that were below published probable effect level concentrations.

Sensitivity of mottled sculpins (Cottus bairdi) and rainbow trout (Onchorhynchus mykiss) to acute and chronic toxicity of cadmium, copper, and zinc.

Studies of fish communities of streams draining mining areas suggest that sculpins (Cottus spp.) may be more sensitive than salmonids to adverse effects of metals. We compared the toxicity of zinc, copper, and cadmium to mottled sculpin (C. bairdi) and rainbow trout (Onchorhynchus mykiss) in laboratory toxicity tests. Acute (96-h) and early life-stage chronic (21- or 28-d) toxicity tests were conducted with rainbow trout and with mottled sculpins from populations in Minnesota and Missouri, USA, in diluted well water (hardness = 100 mg/L as CaCO3). Acute and chronic toxicity of metals to newly hatched and swim-up stages of mottled sculpins differed between the two source populations. Differences between populations were greatest for copper, with chronic toxicity values (ChV = geometric mean of lowest-observed-effect concentration and no-observed-effect concentration) of 4.4 microg/L for Missouri sculpins and 37 microg/L for Minnesota sculpins. Cadmium toxicity followed a similar trend, but differences between sculpin populations were less marked, with ChVs of 1.1 microg/L (Missouri) and 1.9 microg/L (Minnesota). Conversely, zinc was more toxic to Minnesota sculpins (ChV = 75 microg/L) than Missouri sculpins (chronic ChV = 219 microg/L). Species-average acute and chronic toxicity values for mottled sculpins were similar to or lower than those for rainbow trout and indicated that mottled sculpins were among the most sensitive aquatic species to toxicity of all three metals. Our results indicate that current acute and chronic water quality criteria for cadmium, copper, and zinc adequately protect rainbow trout but may not adequately protect some populations of mottled sculpins. Proposed water quality criteria for copper based on the biotic ligand model would be protective of both sculpin populations tested.

Biomonitoring of lead, zinc, and cadmium in streams draining lead-mining and non-mining areas, southeast Missouri, USA.

We evaluated exposure of aquatic biota to lead (Pb), zinc (Zn), and cadmium (Cd) in streams draining a Pb-mining district in southeast Missouri. Samples of plant biomass (detritus, periphyton, and filamentous algae), invertebrates (snails, crayfish, and riffle benthos), and two taxa of fish were collected from seven sites closest to mining areas (mining sites), four sites further downstream from mining (downstream sites), and eight reference sites in fall 2001. Samples of plant biomass from mining sites had highest metal concentrations, with means 10- to 60-times greater than those for reference sites. Mean metal concentrations in over 90% of samples of plant biomass from mining sites were significantly greater than those from reference sites. Mean concentrations of Pb, Zn, and Cd in most invertebrate samples from mining sites, and mean Pb concentrations in most fish samples from mining sites, were also significantly greater than those from reference sites. Concentrations of all three metals were lower in samples from downstream sites, but several samples of plant biomass from downstream sites had metal concentrations significantly greater than those from reference sites. Analysis of supplemental samples collected in the fall of 2002, a year of above-average stream discharge, had lower Pb concentrations and higher Cd concentrations than samples collected in 2001, near the end of a multi-year drought. Concentrations of Pb measured in fish and invertebrates collected from mining sites during 2001 and 2002 were similar to those measured at nearby sites in the 1970s, during the early years of mining in the Viburnum Trend. Results of this study demonstrate that long-term Pb mining activity in southeast Missouri has resulted in significantly elevated concentrations of Pb, Cd, and Zn in biota of receiving streams, compared to biota of similar streams without direct influence of mining. Our results also demonstrate that metal exposure in the study area differed significantly among sample types, habitats, and years, and that these factors should be carefully considered in the design of biomonitoring studies.

Concentrations of cadmium, lead, and zinc in fish from mining-influenced waters of northeastern Oklahoma: sampling of blood, carcass, and liver for aquatic biomonitoring.

The Tri-States Mining District (TSMD) of Missouri (MO), Kansas (KS), and Oklahoma (OK), USA, was mined for lead (Pb) and zinc (Zn) for more than a century. Mining ceased more than 30 years ago, but wastes remain widely distributed in the region, and there is evidence of surface- and groundwater contamination in the Spring River-Neosho River (SR-NR) system of northeastern OK. In October 2001, we collected a total of 74 fish from six locations in the SR-NR system that included common carp (Cyprinus carpio), channel- and flathead catfish (Ictalurus punctatus and Pylodictis olivaris), largemouth- and spotted bass (Micropterus salmoides and Micropterus punctulatus), and white crappie (Pomoxis annularis). We obtained additional fish from locations in MO that included three reference sites and one site that served as a "positive control" (heavily contaminated by Pb). Blood, carcass (headed, eviscerated, and scaled) and liver (carp only) samples were analyzed for cadmium (Cd), Pb, and Zn. Our objectives were to assess the degree to which fish from the OK portion of the SR-NR system are contaminated by these elements and to evaluate fish blood sampling for biomonitoring. Concentrations of Cd and Pb in carp and catfish from OK sites were elevated and Pb concentrations of some approached those of the highly contaminated site in MO, but concentrations in bass and crappie were relatively low. For Zn, correlations were weak among concentrations in the three tissues and none of the samples appeared to reflect site contamination. Variability was high for Cd in all three tissues of carp; differences between sites were statistically significant (p < 0.05) only for blood even though mean liver concentrations were at least 100-fold greater than those in blood. Blood concentrations of Cd and Pb were positively correlated (r2 = 0.49 to 0.84) with the concentration of the same element in carp and catfish carcasses or in carp livers, and the corresponding multiple regression models were highly significant (p < or = 0.001). Our data indicate that potentially nonlethal blood sampling can be useful for monitoring of selected metals in carp, catfish, and perhaps other fishes.

Effects of organic amendments on the toxicity and bioavailability of cadmium and copper in spiked formulated sediments.

We evaluated the partitioning and toxicity of cadmium (Cd) and copper (Cu) spiked into formulated sediments containing two types of organic matter (OM), i.e., cellulose and humus. Amendments of cellulose up to 12.5% total organic carbon (TOC) did not affect partitioning of Cd or Cu between sediment and pore water and did not significantly affect the toxicity of spiked sediments in acute toxicity tests with the amphipod Hyalella azteca. In contrast, amendments of natural humus shifted the partitioning of hoth Cd and Cu toward greater concentrations in sediment and lesser concentrations in pore water and significantly reduced toxic effects of both metals. Thresholds for toxicity, based on measured metal concentrations in whole sediment, were greater for both Cd and Cu in sediments amended with a low level of humus (2.9% TOC) than in sediments without added OM. Amendments with a high level of humus (8.9% TOC) eliminated toxicity at the highest spike concentrations of both metals (sediment concentrations of 12.4 microg Cd/g and 493 microg Cu/g). Concentrations of Cd in pore water associated with acute toxicity were similar between sediments with and without humus amendments, suggesting that toxicity of Cd was reduced primarily by sorption to sediment OM. However, toxic effects of Cu in humus treatments were associated with greater pore-water concentrations than in controls, suggesting that toxicity of Cu was reduced both by sorption and by complexation with soluble ligands. Both sorption and complexation by OM tend to make proposed sediment quality guidelines (SQGs) based on total metal concentrations more protective for high-OM sediments. Our results suggest that the predictive ability of SQGs could be improved by models of metal interactions with natural OM in sediment and pore water.