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A new environmental‐tracking, sun‐lit controlled‐environment facility (terracosm) that can control and manipulate climatic and edaphic factors while maintaining natural environmental variability was developed to study the effects of environmental stresses on a model ecosystem (i.e., plant and soil processes). An analysis of terracosm performance data indicates that the terracosms simulated natural seasonal and diurnal changes in atmospheric CO2, air and soil temperatures, vapor pressure deficit (VPD), and soil moisture. The terracosm performance data indicate that between 92 and 100% of the hourly CO2 concentrations are within ±50 µmol mol−1 of the target concentrations for both ambient and elevated treatments (1 Nov. 1993 through 30 Nov. 1994). Air temperatures are within 2°C of the target temperature between 85 and 100% of the hours for both ambient and elevated temperature treatments. The VPD was approximately the same (0.09 kPa difference between treatments) in the ambient and elevated temperature treatments. Distributed process control was implemented to minimize downtime. Terracosm downtime, periods when terracosm environmental conditions could not be reliably controlled, varied between 2.4 and 2.8% of all hours, and was equally distributed between biological sampling and equipment problems.

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This report was .prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibiiity for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

The findings of this report are not to be construed as official Department of the Army positions unless so designated by other authorized documents DISClAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes .tny wMr.Jnty, expressed or implied, or assumes .tny legal liability or responsibility for the accur.tcy, completeness, or usefulness of .1ny information, apparatus, product, or process disclosed, or represents th.tt its use would not infringe printely owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government of any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Polychlorinated dibenzo-p-dioxins and dibenzofurans were found in sediment from Siskiwit Lake on Isle Royale, Lake Superior, a location which can receive only atmospheric inputs. The source of these compounds is the atmospheric transport of dioxins and furans formed by combustion of domestic and chemical waste.

Ingestion of contaminated food is considered the primary route of exposure in birds to agricultural chemicals. Routes of exposure other than ingestion are not often considered in risk assessments of agricultural chemicals to avian wildlife. However, recent studies demonstrated anorexic or avoidance behaviors in birds exposed to organophosphate (OP) insecticides. These behaviors would tend to limit exposure if ingestion alone were considered. The contribution, if any, of dermal, preening, and respiratory pathways to the exposure of birds to pesticides under field conditions is unknown. In addition, oral exposures are currently assessed in artificial environments that do not reflect real‐life exposure scenarios. To determine the relative contribution of these pathways and to assess exposures under ecological conditions, 270 northern bobwhite (Colinus virginianus) were exposed to simulated aerial crop applications of methyl parathion in an environmentally controlled wind tunnel. The wind tunnel environment consisted of a 25‐cm cotton plant canopy, a 5‐cm‐thick floor of silt‐loam, a temperature of 25°C, 50% RH, UV intensity similar to summer sunlight, and a wind speed of 3.2 km/h. Inhalation, preening, and dermal routes were isolated in groups of birds exposed to each application. Five birds from each group were collected at 1, 4, 8, 24, and 48 h post‐spray to determine cholinesterase (ChE) response to the exposures. Contaminated and uncontaminated darkling beetle (Tenebrio molitar) larvae were presented to free‐ranging sprayed birds in the wind tunnel to assess oral uptake. ChE response was determined at 4, 8, 24, and 48 h postspray. All exposures were replicated. All four routes contributed to the inhibition of brain ChE at different post‐spray periods. Dermal uptake and preening were major contributors to the overall dose and toxic response of birds to methyl parathion. Inhalation was the major route of exposure at 1 h post‐spray. At 4 h post‐spray, uptake through preening caused the greatest inhibition of brain ChE activity. Oral ingestion resulted in less than 20% inhibition of brain ChE during the test. Routes of uptake in order of contribution to toxicologic response from 8 to 48 h post‐spray were dermal > preening ≥ oral > inhalation.

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