Biomedical subjects

W B Gillespie

Publications and source records attributed to W B Gillespie.

8 recordsLinked to original sources

PubMed2001

Arsenic and mercury concentrations in major landscape components of an intensively cultivated watershed.

To provide an understanding of arsenic (As) and mercury (Hg) concentrations in soil, sediment, water, and fish tissues, samples were collected from a Mississippi River alluvial floodplain located in northwest Mississippi. As concentrations increased approximately an order of magnitude from water (5.12 micrograms/l) to fish tissues (36.99 micrograms/kg) and an additional two orders of magnitude in soils, lake sediments, and wetland sediments (5728, 5614, and 6746 micrograms/kg), respectively. Average Hg concentrations in water, soils, lake sediments, and fish were 2.16 micrograms/l, 55.1, 14.5 and 125 micrograms/kg, respectively. As and Hg concentrations were within published ranges for uncontaminated soil, water, and sediments. As concentrations represented a low risk. Hg concentrations were also low but showed a greater tendency to concentrate in fish tissue. The dominant mode of entry of these materials into aquatic systems is through storm-generated runoff. Since both metals accompany sediments, agricultural conservation practices such as reduced tillage, buffer riparian strips, and bordering sediment ponds or drainage wetlands will minimize watershed input to aquatic systems.

Animals↗

PubMed2000

Using constructed wetlands to treat biochemical oxygen demand and ammonia associated with a refinery effluent.

This study evaluated the effectiveness of constructed wetlands for tertiary treatment of a petroleum refinery effluent. Specific performance objectives were to decrease 5-day biochemical oxygen demand (BOD(5)) and ammonia by at least 50% and to reduce toxicity associated with this effluent. Two bench-scale wetlands (replicates) were constructed in a greenhouse to provide tertiary treatment of effluent samples shipped from the refinery to the study site. Integrated wetland features included Typha latifolia Linnaeus planted in low organic (0.2%), sandy sediment, 48-h nominal hydraulic retention time, and 15-cm overlying water depth. Targeted constituents and aqueous toxicity were monitored in wetland inflows and outflows for 3 months. Following a 2 to 3-week stabilization period, effective and consistent removal of BOD(5) and ammonia (as NH(3)-N) from the effluent was observed. Average BOD(5) removal was 80%, while NH(3)-N decreased by an average of 95%. Survival of Pimephales promelas Rafinesque and Ceriodaphnia dubia Richard (7-day, static, renewal exposures) increased by more than 50% and 20%, respectively. Reproduction of C. dubia increased from zero in undiluted wetland inflow to 50% of controls in undiluted wetland outflow. This study demonstrated the potential for constructed wetlands to decrease BOD(5), ammonia, and toxicity in this refinery effluent.

Ammonia↗

PubMed1999

Transfers and transformations of zinc in flow-through wetland microcosms.

Two microcosm-scale wetlands (570-liter containers) were integratively designed and constructed to investigate transfers and transformations of zinc associated with an aqueous matrix, and to provide future design parameters for pilot-scale constructed wetlands. The fundamental design of these wetland microcosms was based on biogeochemical principles regulating fate and transformations of zinc (pH, redox, etc.). Each wetland consisted of a 45-cm hydrosoil depth inundated with 25 cm of water, and planted with Scirpus californicus. Zinc ( approximately 2 mg/liter) as ZnCl2 was amended to each wetland for 62 days. Individual wetland hydraulic retention times (HRT) were approximately 24 h. Total recoverable zinc was measured daily in microcosm inflow and outflows, and zinc concentrations in hydrosoil and S. californicus tissue were measured pre- and post-treatment. Ceriodaphnia dubia and Pimephales promelas7-day aqueous toxicity tests were performed on wetland inflows and outflows, and Hyalella azteca whole sediment toxicity tests (10-day) were performed pre- and post-treatment. Approximately 75% of total recoverable zinc was transferred from the water column. Toxicity decreased from inflow to outflow based on 7-day C. dubia tests, and survival of H. azteca in hydrosoil was >80%. Data illustrate the ability of integratively designed wetlands to transfer and sequester zinc from the water column while concomitantly decreasing associated toxicity.

Animals↗

PubMed1999

Copper bioavailability in Steilacoom Lake sediments.

Sediments were collected from Steilacoom Lake, Pierce County, in Washington State, and amended with copper sulfate (nominal concentrations of 800, 1,000, 1,500, and 2,000 mg Cu/kg dry weight) to assess copper bioavailability to Hyalella azteca, Chironomus tentans, or Ceriodaphnia dubia. H. azteca survival and C. tentans survival and growth were not significantly affected, with 10-day no observed effects concentrations (NOEC) and lowest observed effects concentrations (LOEC) of 2,010 and >2,010 mg Cu/kg, respectively. C. dubia was the most sensitive organism tested with 10-day NOEC and LOECs for survival and reproduction of 906 and 1,469 mg Cu/kg, respectively. Sediment AVS concentrations were <0.15 micromol/g, while simultaneously extracted metal (SEM) concentrations were >/=5. 71 micromol Cu/g. Dissolved interstitial water concentrations ranged from below detection (0.010 mg/L) to 0.24 mg Cu/L, with interstitial water toxicity units as high as 3.4. Based on this study, effects to C. dubia may occur at bulk sediment concentrations >906 mg Cu/kg. Further, AVS and interstitial water concentrations are not accurate predictors of copper bioavailability in Steilacoom Lake.

Animals↗

PubMed1998

Responses of aquatic invertebrates to a linear alcohol ethoxylate surfactant in stream mesocosms.

Responses of aquatic invertebrates to 30-day exposures to a nonionic linear alcohol ethoxylate (LAE) surfactant (C12-13AE-6.5) were evaluated in 10 outdoor stream mesocosms. Responses were measured as changes in invertebrate densities and invertebrate drift densities during a 14-day pretreatment period, a 30-day treatment period, and a 14-day posttreatment period relative to untreated control stream densities. Mean measured surfactant concentrations in duplicate streams were 0.32, 0.88, 1.99, and 5.15 mg LAE/liter, with two streams serving as untreated controls. Statistically significant effects were observed on simulid, copepod, and cladoceran population densities during the treatment period. Based on these effects, the no-observed-effect concentration (NOEC) for invertebrate densities was <0.32 mg LAE/liter and the lowest-observed-effect concentration (LOEC) was 0.32 mg LAE/liter. No statistically significant differences due to treatment were detected in drifting invertebrates; however, a trend was observed with increased numbers of invertebrates drifting in the streams treated with 5.15 mg LAE/liter as compared with controls.

Alcohols↗

PubMed1997

Design and construction of wetlands for aqueous transfers and transformations of selected metals.

Two pilot-scale wetland cells (6.1 x 30.5 m) were integratively designed and constructed to emphasize and enhance transfers and transformations of selected metals (Cu, Pb, and Zn) in an aqueous matrix. A series of preliminary experiments and analyses were conducted to select macrofeatures (hydroperiod, hydrosoil, and vegetation) of the constructed wetland system. These wetland cells were designed to operate in series or parallel with nominal hydraulic retention times of 24-48 hr, respectively. With water at a depth of 30 cm, both wetland cells had hydrosoil (45 cm) planted with Scirpus californicus. After 250 days of wetland operation, average hydrosoil redox potentials in each wetland cell decreased from +90 mV to -165 mV, and average plant height increased from 0.3 to 2.7 m. Aqueous samples were collected over a 4.5-month period at the inflow and outflow sites of the wetland cells. Average inflow concentrations of total recoverable Cu, Pb, and Zn were 22.4, 10.5, and 565.9 micrograms/L, respectively. After a 46-hr HRT, average outflow concentrations of total recoverable Cu, Pb, and Zn were 15, 2.2, and 85.9 micrograms/L, resulting in removals of 33, 79, and 85%, respectively. Initial results suggest that these constructed wetlands can be designed to remove targeted metals in wastewater.

Industrial Waste↗

PubMed1996

Design and construction of model stream ecosystems.

A series of 12 outdoor model stream mesocosms was designed to evaluate the effects of chemicals and mixtures on the biota in stream ecosystems. An integrated design plan incorporated physical, chemical, and biological factors as well as the specific experimental objectives and effects parameters to be evaluated. Analysis of biological assemblages such as macroinvertebrates and periphyton in the model stream mesocosms demonstrated the presence of diverse and sensitive taxa. These model stream mesocosms also included the ability to evaluate responses of sentinel fish species such as Pimephales promelas and Lepomis macrochirus as well as macrophytes. The design and construction of the stream are discussed in detail and a brief description of a typical experimental protocol is provided. Experiments, to date, have spanned 14-30 days pretreatment "colonization" with 30 days of treatment and 15 days of posttreatment observation. Precision and accuracy of test chemical delivery to the stream have been excellent and the overall experimental design has been useful for delivering threshold toxicity concentrations and evaluating ecosystem potency for the chemicals tested.

Analysis of Variance↗

PubMed1996

Assessing the effects of a C14-15 linear alcohol ethoxylate surfactant in stream mesocosms.

Fish, benthic macroinvertebrate, and plant responses to 30-day exposures of C14-15 linear alcohol ethoxylate surfactant with an average of 7 mol of ethylene oxide (LAE) were measured in flowthrough stream mesocosms. Replicate stream mesocosms were treated in two experiments with concentrations of LAE ranging from 80 to 550 microg/liter. Macroinvertebrates were relatively insensitive with the exception of Simuliidae density which was significantly affected at 160 microg/liter. Fathead minnow (Pimephales promelas R.) reproduction was significantly reduced at >280 microg/liter and larval survival decreased significantly at 330 microg/liter. Growth and mortality of bluegill sunfish (Lepomis macrochirus L.) were not affected at the highest exposure concentration of 330 microg/liter in the first experiment. No ecologically significant effects were observed for vascular aquatic plants or periphyton. The laboratory and stream mesocosm results were similar with NOECs ranging between 80 and 550 microg/liter surfactant. The study provided data for an improved risk assessment of this nonionic surfactant, by reducing the uncertainty associated with extrapolation from laboratory data.

Animals↗