Environmental Chemistry

Spectral data was collected in the Spring 2003, Fall 2004, and Fall 2006 with permission from Cal-Trans.

The soil lead sample were collected adjacent to the heavily used urban highway.  In 2004 and 2006, in situ XRF measurements were recorded and each individual spectral measurement was a 60 second exposure and four spectra were averaged at each selected location on the field site.

The field portable XRF was calibrated each day using NIST Standard Reference Materials (SRM) 2710 and 2711.  The XRF typically yielded values within 10 % of the NIST SRMs, which matches the instrument specifications.

The triangular highway median appeared undisturbed in Spring 2003, however a car fire incident occurred in Summer 2003. ( Photo of site below) Since this time, Cal-Trans has placed mulch on the site, so students must determine the soil horizon to make surface measurements.  Since the 2006 sampling, the far western portion of the median was cemented so that portion is now inaccessible. 

Highway 24 Field Site:  The triangular highway median on the northern side of Highway 24 was sampled.  The traffic closest to the parcel is going West on the highway.















Average Soil Lead Values Determined by XRF for Highway Site

Numerical values, standard deviations and number or sample locations are reported for each parallel line.

Sampling Period


Spring 2003

Soil Lead (mg/kg)

Fall 2004

Soil Lead (mg/kg)

Fall 2006

Soil Lead (mg/kg)

15 ft. parallel to highway
4940 +/- 2399 (5)
2361 +/- 1418 (7)
3122 +/- 2586 (6)
30 ft. parallel to highway
809 +/- 188 (4)
615 +/- 185 (7)
637 +/- 158 (3)
Notes Site was not previously sampled.  A reference point was selected on the Eastern end of the 15 foot line. Site was disturbed. A burning auto wreck was positioned approx. 100 feet from the reference point. Sampling at the far Western end of median was the focus for this year and the eastern location was again used as a reference.