1. Honors Env Sci 19 Oct 2009 This week: Water pollution labs – I’m setting up three different labs for this week. We need water samples to work with. Today, you have time to work on assignments while I get the labs set up. Please stay on track to complete 10 assignments by the end of the quarter!

2. Honors Env Sci 20 Oct 2009 Today: Developing bioassays – We are generally looking to find out if adding pollutants will affect the biological activity in the water – Nitrogen and phosphorous are usually the “limiting nutrients” in aquatic systems – they control growth – Each group should be 2-3 people, each should use different waters or dilutions thereof

3. Honors Env Sci 23 Oct 2009 Today: Using the spectrophotometer – We want to be able to measure nutrients (nitrate and phosphate) in water samples – The easiest way to do this is using a color test and a spectrophotometer to detect the light absorbance in a sample – We will learn today how use the spectrophotometers, and next week we can use them to analyze the nutrient levels in water samples

4. Using the “spec” Use the blue dye to create a gradient of color intensity (how is your choice) Find the absorbance of the sample along the visible light spectrum (I’ll explain) Measure absorbance vs. concentration at the most sensitive wavelength – Set the spec to the desired wavelength, and test all samples from lowest to highest concentration