####3. Use of spectrometers in environmental science

**3.1 Background reading** (45 minutes)

Read these short synopses about how spectrometry has been used in environmental science, and what types of data and advocacy can result from the use of a spectrometer. 

	One sentence overview: Fluorescence spectroscopy is a widely useful technique. Similarly to how blood or bodily fluids at a crime scene are revealed by shining a UV light, oil also fluoresces. 


_from https://publiclab.org/notes/eustatic/4-20-2012/370nm-uv-detection-corexit-dispersed-oil-gulf-coast-beaches_


From the texbook, Oil Spill Science and Technology chapters 4, 5, 7, we learn about more about this method to identify oil in the environment:


	The combination of spectroscopy and UV lasers is used to identify oil in the environment. Oil has a “unique oil fluorescence spectral signature” (p 171); when ultraviolet light (300 to 355 nm) is shined on petrochemicals, they fluoresce (release) light in visible wavelengths that are specific to the kind of oil it is. Chlorophyll and other biological materials also fluoresce, but (fortunately) at significantly different wavelengths to avoid confusion. 

From the abstract of the 2012 article, “Findings of Persistency of Polycyclic Aromatic Hydrocarbons in Residual Tar Product Sourced from Crude Oil Released during the Deepwater Horizon MC252 Spill of National Significance” produced by James H “Rip” Kirby III, of the University of South Florida Dept of Geology, and also of The Emerald Coast Chapter of Surfrider:

	The use of ultraviolet light equipment in the field showed distinct fluorescent responses to illumination by a 370nm UV light source. UV light equipment was found to be very efficient in identifying tar product on the beach for evaluating the visual level of contamination on the beach. Fluorescent responses from tar product found in the field and laboratory created tar product were measured by fluorometry equipment. [link](http://surfrider.org/images/uploads/publications/Corexit_Connections.pdf)

From the 2012 article, “State of the art satellite and airborne marine oil spill remote sensing: Application to the BP Deepwater Horizon oil spill”, we learn how different methods are used in times of a spill: 


	This technical article begins by stating how valuable people are in times of disaster: “experienced observers are a spill response’s mainstay.” Since there are few experienced observers available, and the weather and environmental conditions present access challenges to getting a holistic view of the situation, responding to the Deepwater Horizon oil disaster also involved extensive airborne and spaceborne passive and active remote sensing. An airplane carried a Visible/Infrared Spectrometer over the spill to derive oil slick thickness and oil-to-water emulsion ratios. Other equipment on planes and satellites helped extrapolate this understanding to the geographic extent of the entire spill, find the extent of burned oil carried into the air as smoke, and track oil as it sunk to the seafloor. http://www.sciencedirect.com/science/article/pii/S0034425712001563 

There was a January 2016 discussion on the plots-spectrometry mailing list that referenced the 2011 article "Prediction of crude oil properties and chemical composition by means of steady-state and time-resolved fluorescence." by p.3600 of Pantoja, Patricia A., et al. Energy & Fuels 25.8 (2011): 3598-3604:
	
	This graph from the article shows peak shift due to dilution of crude oil:
 

	Public Lab Oil Testing Fellow Ethan has been working on a dilution test to see if diluting oil samples with mineral oil changes their spectrum, and if there's a way to adjust for that. The main gist of this article is about exactly the kind of fluorescence based oil differentiation we're attempting with the Oil Testing Kit. They use a 337nm excitation light source, not the 405nm that Public Lab has been working with, but the peaks in the graph occur at wavelengths longer than 405nm, so some active developers of the spectrometer feel this is not improbably related to the blue=>red shift we're looking for in lighter=>heavier oils:



As a group, discuss these brief summaries and your ideas.