Abstract:           

Data collected about gasses present in Watsonville air has shown that, while overall concentrations are relatively small, there are outlying areas with unusually high levels of pollutants that eventually affect the entire city.  The wind and change in traffic during the day in various parts of the city has been concluded to be the cause of this spread. 

Methodology:

Air content was determined by measurements taken twice a day, two days a week with a Science Scope Logbook to detect gasses present and a Garmin GPS to place these measurements geographically, with the aid of JData3D software.  Each set of measurements was taken at eight points on three concentric circles around Watsonville High School and Moreland Notre Dame Charter School.  These circles had radii of 1500, 1000 and 500 feet.  The collection of data was then uploaded to the HEAN Action website.  Here the data were presented graphically with colored points on a map, redder points indicating higher concentrations of CO, NO­2, and SO­2, and greener points indicating lower concentrations.  The data was then analyzed. 

Findings:

It appears that in the morning, carbon monoxide (CO) emissions are more concentrated in certain high-traffic locations.  In the afternoon these have diffused, increasing gas concentration throughout the city.  The specific points of particularly high gas-concentration in the morning, however, have a lower concentration in the afternoon. 
Measurements taken around Moreland Notre Dame School on May 26th are a particularly good example of this.  It is apparent with just a quick glance at the Logbook data that CO­ concentrations are higher in the afternoon due to the redder points scattered throughout the city of the map.  Interestingly, however, the measurement taken near the intersection of Brennan Street and Palm Avenue shows a distinctively higher concentration reading in the morning- 4 ppm as compared to just 1.  It is almost as if most of the gasses were given off near that point in the morning and spread throughout the city during the course of the day.            

The measurements around Watsonville High School on June 5th indicate a similar pattern.  The afternoon gas concentrations are clearly much higher than the morning ones, but the two points on Brennan Street, once again, clear up later in the day, going from 2.1 ppm to approximately 0.8 ppm. 

The other gasses, such as NO­2 and SO­2 were also present in various points, but it was much harder to make a generalization about these.  The presence of these gasses was generally much lower than that of CO and the changes did not seem to correlate with the time of day.  NO­2 in particular was nearly absent, rarely showing up on the Logbook at all.  Whether this was because of its actual absence or because of a problem with the Logbook itself is not certain. 

Conclusion:

The low concentrations of NO­2 and SO­2 is actually somewhat surprising, given that Watsonville is primarily a fruit/vegetable-growing city with many farm fields, packing warehouses and large freight trucks.1  SO­2 in particular is used as a preservative in many fruits2 while NO­2 is an expected product of internal combustion engines.3  The equalizing spread of CO throughout the day can be explained by the change of traffic types throughout the day as well as the wind.  While morning traffic is dominated by commuters, traffic later in the day consists mostly of trucks carrying their cargo and other kinds of worker transport. 

Recommendations:
There are large concentrations of the measured gasses on certain high traffic areas.  To reduce the potential harmful side effects of this to human health, it would probably be ideal to find a way to spread traffic more widely around the road networks of the city or reduce traffic in the first place by promoting car pooling and cleaner industrial operations. 

Endnotes:

1 Watsonville, California. (2009, June 16). In Wikipedia, The Free Encyclopedia. Retrieved 15:00, June 16, 2009, from http://en.wikipedia.org/w/index.php?title=Watsonville,_California&oldid=296767242

2 Sulfur dioxide. (2009, June 21). In Wikipedia, The Free Encyclopedia. Retrieved 21:13, June 21, 2009, from http://en.wikipedia.org/w/index.php?title=Sulfur_dioxide&oldid=297793406

3 Nitrogen dioxide. (2009, June 23). In Wikipedia, The Free Encyclopedia. Retrieved 17:14, June 23, 2009, from http://en.wikipedia.org/w/index.php?title=Nitrogen_dioxide&oldid=298159777