Science Buddies: "Ask an Expert"

I am doing a science project using your vh1 sun photometer. I have made
the instrument and taken the measurements. My project is about different pollution
levels across Cape Town .

I am unable to find on any other sites a comparison for the figures i get after applying AOT
formula. I need to give a comparison of sorts as to what would be a acceptable number according to
world standards, otherwise the figures don't have any impact, they just show varying levels and not if they
are bad or good. How do I know which AOT figures show little and which show lots of pollution.

Many thanks

Hi Aaron,

I would be happy to try and help you but i need a bit more information. Can you please supply the link to the description of this project? I did a search on Scibuddies for 'sun photometer' and found some posts but no usable information.

I learned that 'AOT' stands for 'aerosol optical thickness' . Is that the value you are trying to calculate using light measurements from your photometer? What is the formula you are using to calculate AOT?

Did you calibrate the photometer? It has to be calibrated properly in order for you to compare your readings with those in other parts of the world. I found a site that has instructions for doing this using a TERC-VHS-1 photometer: http://haze.concord.org/calibrate.html
Is this the same device as you are using?

Please send more complete details of your procedure and the links you are using and we will try to troubleshoot for you.

Sybee

Thanks. I have successfully built the sun photometer on Haze span that you saw and have already calculated the AOT. I am testing different areas
and can see the difference in AOT but what I am unsure of is what is considered to be good and Bad AOT readings (in terms of pollution) and
how I could convert this data into what percentage of light is being blocked (For figures that are simpler to understand by others for my project). If you could help
me with that, that would be great. Thank you so much for your kind assistance.

Did you go to the link i sent you about calibration? I think that is the only way you can compare your AOTs to others around the world. Search for AOT readings from Shanghai, Beijing or Mexico City--these have to be some of the worst air pollution and smog areas on the planet. Then you can find AOTs from places that have clean air and use those as your normal readings.