6. Ellen Swallow Richards, Part 2

TL;DR

Dissolved oxygen plays a crucial role in the health of rivers, with levels below 5 PPM causing stress to aquatic life and levels below 2 PPM leading to fish kills. The solubility of dissolved gases in water is determined by Henry's Law, and factors such as atmospheric pressure, water vapor pressure, and temperature affect the concentration of dissolved oxygen. pH also influences river health, with values ranging from 6.5 to 8.5 considered normal.

Transcript

[SQUEAKING] [RUSTLING] [CLICKING] JOHN DOLHUN: Good afternoon, everyone. Welcome to The Ellen Swallow Richards lab part two. There is-- the room will be a little bit more sparsely populated today. I wonder why. Lab reports are due, right? So we're going to get started. And I'm going to start off by talking about probably the most important paramete... Read More

Key Insights

• 🥺 Concentrations of dissolved oxygen below 5 PPM cause stress to aquatic life, and levels below 2 PPM lead to fish kills.
• 🫢 The solubility of dissolved gases in water is determined by Henry's Law, which takes into account factors such as atmospheric pressure and temperature.
• 😥 pH ranging from 6.5 to 8.5 is considered normal in rivers and affects factors such as metal solubility and forms of phosphorous. Acidic conditions can be detrimental to aquatic life.
• 🥹 Henry's Law constant provides a way to calculate the potential of a body of water to hold oxygen based on temperature and pressure.
• 💦 The Winkler method, developed in 1888, is a reliable method to measure dissolved oxygen concentration in water.
• 🍵 Sodium azide is a dangerous chemical used in the Winkler method and should be handled with caution.

Questions & Answers

Q: How does the concentration of dissolved oxygen affect aquatic life?

Concentrations of dissolved oxygen below 5 PPM cause stress to aquatic life, while levels below 2 PPM lead to fish kills. Fish will move erratically in search of oxygen when concentrations are low.

Q: How is the solubility of dissolved gases in water determined?

The solubility of dissolved gases in water is determined by Henry's Law, which states that the solubility is proportional to the partial pressure of the gas over the water.

Q: What factors affect the concentration of dissolved oxygen in rivers?

Factors such as atmospheric pressure, water vapor pressure, and temperature affect the concentration of dissolved oxygen in rivers. Higher atmospheric pressure and lower water vapor pressure increase the concentration of dissolved oxygen, while higher temperatures decrease it.

Q: How does pH affect river health?

pH ranging from 6.5 to 8.5 is considered normal in rivers. pH influences the solubility of metals, with more acidic conditions leading to increased metal solubility and potentially harmful effects on aquatic life. It also affects the forms of phosphorous present in the water.

Summary & Key Takeaways

• Dissolved oxygen concentrations below 5 PPM cause stress to aquatic life, while concentrations below 2 PPM lead to fish kills.

• The solubility of dissolved gases in water is determined by Henry's Law, which states that the solubility is proportional to the partial pressure of the gas over the water.

• pH ranges from 6.5 to 8.5 in rivers, and it affects factors such as the solubility of metals and the forms of phosphorous.