A concise scientific look at contaminants in Big Bend National Park, focused on the Rio Grande ecosystem and its wildlife. This edition presents an initial survey of chemicals in fish, sediments, and birds, with practical context for conservation and park management. The study explains how samples were collected at Castolon and Solis along the Rio Grande in 1986, and how laboratory analyses were performed for a broad set of chemicals. It is clearly described as exploratory, not a comprehensive follow-up, and it outlines the criteria used to choose the contaminants included. - What you’ll learn about: the scope of chemicals tested, including organochlorines, metals, and polycyclic aromatic hydrocarbons. - The sampling approach: how sediments, aquatic life, and birds were gathered at two park sites. - The methods: how tissues and sediments were prepared and measured, and how results were checked for accuracy. - The context: why this work matters for peregrine falcons, other wildlife, and park health. Ideal for readers of environmental science, wildlife management, and park-focused research who want a concrete, initial look at contaminant levels in this region.