Geology topics

G.J. Atchison

Publications and source records attributed to G.J. Atchison.

6 recordsLinked to original sources

USGS2000

Whole-lake burdens and spatial distribution of cadmium in sediments of Wisconsin seepage lakes, USA

Cadmium was quantified in the surface sediments of six seepage lakes ranging from 8 to 70 ha in surface area, 6 to 20 m in maximum depth, 5.2 to 7.0 in mean epilimnetic pH, and 1.7 to 6.8 mg·L −1 in dissolved organic carbon. Within each lake, dry-weight concentrations of cadmium (range, 0.02–7.17 μg·g −1 ) were positively correlated with volatile matter content of the sediments, which increased with water depth. Volumetric concentrations (i.e., mass per volume of wet sediment) were correlated with water depth in only one lake, and they more accurately represented the spatial distribution of sedimentary cadmium within the lakes. Analysis of sediment cores from two of the lakes indicated that surface sediments were enriched with cadmium. The source of cadmium and the within-lake processes controlling deposition to the sediments were presumably similar among the lakes, as demonstrated by the strong correlation between lake area and whole-lake burdens of cadmium in the surface sediments (range, 625–5785 g/lake). Hence, cadmium in these lakes appears to be derived largely from atmospheric deposition. When normalized for lake area, cadmium burdens in the surface sediments ranged from 62 to 92 g·ha −1 and were strongly correlated with dissolved organic carbon, but not with lake pH, which suggests a link between the transport of cadmium and organic matter to the sediments.

Wisconsin↗

USGS1999

The effects of chlorpyrifos on cholinesterase activity and foraging behavior in the dragonfly, Anax junius (Odonata)

We examined head capsule cholinesterase (ChE) and foraging behavior in nymphs of the dragonfly, Anax junius, exposed for 24 h to 0.2, 0.6 and 1.0 ??g l-1 of the organophosphorus (OP) insecticide, chlorpyrifos [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate]. The invertebrate community is an important component of the structure and function of wetland ecosystems, yet the potential effects of insecticides on wetland ecosystems are largely unknown. Our objectives were to determine if exposure to environmentally realistic concentrations of chlorpyrifos affected foraging behavior and ChE activity in head capsules of dragonfly nymphs. Nymphs were exposed to different concentrations of chlorpyrifos and different prey densities in a factorial design. ChE activities and foraging behaviors of treated nymphs were not statistically different (p ??? 0.05) from control groups. Prey density effects exerted a greater effect on dragonfly foraging than toxicant exposures. Nymphs offered higher prey densities exhibited more foraging behaviors but also missed their prey more often. High variability in ChE activities within the control group and across treated groups precluded determination of relationships between ChE and foraging behaviors. It appears that A. junius is relatively tolerant of chlorpyrifos, although the concentrations we tested have been shown in other work to adversely affect the prey base; therefore the introduction of this insecticide may have indirect adverse affects on top invertebrate predators such as Odonata.

Hydrobiologia↗

USGS1995

Cadmium and mercury in sediment and burrowing mayfly nymphs (Hexagenia) in the upper Mississippi River, USA

Longitudinal patterns in the cadmium and mercury content of burrowing mayflies ( Hexagenia ) and surrounding sediments were examined along a 572-km reach of the upper Mississippi River. Surficial sediments and Hexagenia nymphs were sampled in 1989 at 12 sites extending from Pool 2 through Pool 16 and analyzed for total recoverable cadmium and total mercury. In sediment and nymphs, concentrations of both metals were highest in Pools 2, 3, and 4, which are just downstream from the Twin Cities (Minneapolis-St. Paul, Minnesota) metropolitan area, the primary anthropogenic source of metals to the studied reach of river. Concentrations of the two metals in sediments indicated a significant anthropogenic contribution, which was most pronounced for cadmium. The cadmium concentrations in surficial sediment varied less than 3-fold (range, 1.19–3.23 μg/g dry weight) among the 12 sites, whereas concentrations in Hexagenia varied almost 20-fold (range, 0.13–2.35 μg/g dry weight). Nymphs from Pools 2–4 had much greater concentrations of cadmium than nymphs from sites further downstream, even though the mean concentration of cadmium in sediment from Pools 2–4 (3.0 μg/g) was just twice that (1.6 μg/g) for the nine sites downstream. Mercury in sediments from the 12 sites ranged from 0.038 to 0.165 μg/g dry weight, averaging 0.14 μg/g in Pools 2–4 and 0.056 μg/g in the nine sites downstream. In nymphs, mercury concentrations ranged from 0.041 to 0.134 μg/g dry weight. The bioavailability of sediment-associated cadmium seemed greater in Pools 2, 3, and 4 than in the sites further downstream, based on the relative cadmium concentrations in Hexagenia nymphs and sediment. Moreover, it is concluded that the trapping of sediment and associated metals in Lake Pepin (a natural riverine lake in Pool 4) significantly reduces the exposure of the ecosystem further downstream to metals from the Twin Cities and other upstream anthropogenic sources.

Illinois, Iowa, Minnesota, Wisconsin↗

USGS1994

Hepatic cadmium, metal-binding proteins and bioaccumulation in bluegills exposed to aqueous cadmium

We examined sublethal responses of juvenile bluegills Lepomis macrochirus to aqueous cadmium in two 28-d tests (test I, 0.0-8.4 μg Cd per liter; test II, 0.0-32.3 μg Cd per liter) in an intermittent-flow diluter. The experimental design was completely randomized, with two replicates in each of eight treatments (seven Cd exposures and one water control with 25 fish per replicate). Cadmium did not affect the growth of test fish. The mean whole-body concentrations of Cd in exposed fish were 1.8- to 44-fold those in controls in the two tests. Mean concentrations of hepatic nonthionein cytosolic Cd (not bound by metal-binding proteins, MBP) in all Cd treatments greatly exceeded those in controls, and mean concentrations of hepatic MBP in all treatments except one (0.8 μg Cd per liter in test I) exceeded those in controls. Nonthionein cytosolic Cd, hepatic MBP, and whole-body Cd in bluegills were linearly related to exposure concentrations within the range 0 to 20 μg Cd per liter. Much of the total Cd-binding capacity of hepatic MBP per fish was occupied by Cd after the 28-d exposures, although additional Cd-binding capacity remained unoccupied by Cd in fish in all treatments. The mean total Cd-binding capacity of hepatic MBP per fish, which ranged from 1.7 to 14 nmol Cd in test I and from 0.8 to 24 nmol Cd in test II, increased in a concentration-response manner at exposure concentrations below 13 μg/L. Nonthionein cytosolic Cd was the most sensitive indicator of Cd exposure, based on an LOEC of 0.8 μg Cd per liter.

Environmental Toxicology and Chemistry↗

USGS1992

Sublethal effects of cadmium on physiological responses in the pocketbook mussel, Lampsilis ventricosa

Recent studies indicate that the density and diversity of freshwater mussels are declining in many large river systems, possibly from low-level chemical contamination. Exposure of Lam-psilis ventricosa (Barnes, 1823) to 0, 22, 111, and 305 μg/L of cadmium for 28 d in a proportional diluter resulted in a significant decrease ( p ≤ 0.05) in respiration rate as cadmium concentration increased. Although variations in cadmium concentrations did not significantly affect food clearance rates or ammonia excretion rates, mussels exposed to 305 μg cadmium per liter showed a decrease in ammonia excretion rates and a decrease in food clearance rates over the 28-d study. Assimilation efficiencies increased during the test in all treatments. Oxygen-to-nitrogen ratios were significantly increased in mussels exposed to either 111 or 305 μg cadmium per liter by day 28. Tissue condition index (TCI) values were significantly lower in mussels in the toxicity test than those in a field sample. The significant change in respiration rate after only a 28-d exposure to cadmium suggests that freshwater mussels may be sensitive indicators of sublethal contaminant exposure. However, the large variability in other physiological responses indicates that the study of contaminant effects requires careful selection of appropriate physiological indicators.

Environmental Toxicology and Chemistry↗

USGS1992

A sediment suspension system for bioassays with small aquatic organisms

Exposure of aquatic organisms to suspended sediments can impair growth and survival and increase bioaccumulation of sediment-associated contaminants. However, evaluation of the effects of suspended sediments and their associated contaminants on aquatic organisms has been hampered by the lack of a practical and inexpensive exposure system for conducting bioassays. We present a cost-effective system for assessing the effects of suspended sediments and associated contaminants on small aquatic organisms. A 7-day suspension test was conducted with nominal sediment concentrations ranging from 0.0 to 5.0 g 1 −1 . The system maintained relatively constant suspended sediment concentrations, as measured by turbidity, and caused minimal mortality to test organisms.

Hydrobiologia↗