Biomonitoring of urban industrial pollution using total reflection X‐ray fluorescence

Environmental pollution as a result of industrial activity is widespread in many urban areas including Chicago. In an effort to evaluate the heavy metal fraction originating from industrial activities, plant samples of Daucus Carota or wild carrot were collected at or adjacent to six sites located in two of Chicago's designated industrial corridors. Plants, especially herbaceous species, have been deemed suitable as environmental pollution monitors as they are able to provide information about the heavy metal fraction accessible to biota. The leaves of Daucus Carota were acid digested and analyzed with total reflection X‐ray fluorescence spectrometry TXRF. The results showed elevated heavy metal mass fractions for at least one collection site which is close to an operational railyard. Other studies investigating heavy metals in proximity to railroad operations found elevated mass fractions for several elements, but specifically manganese as well. This suggests that abrasion from shunting and breaking releases certain pollutants into the local environment. The data were compared with studies executed in Rome, Italy, and Pakistan, which used Daucus Carota to evaluate heavy metal pollution. It was found that the heavy metal mass fractions obtained for Chicago were higher for some elements indicating an increased pollutant burden for these elements. The same samples were also analyzed by graphite furnace atomic absorption spectrometry GFAAS for the elements copper and lead and the data compared. Those two elements were chosen as they were present at each location and GFAAS has proven to be highly sensitive for them. It was found that the two methods provided comparable results for copper, whereas for lead, TXRF overestimated the mass fractions most likely due to limitations of the spectra evaluation software. The analysis of a certified reference material ‘BCR 679 white cabbage’ showed that most data obtained by TXRF were in good agreement with the certified values, with the exception of lead, which was not certified. However, since GFAAS has high sensitivity toward lead and is considered reference method for that element by regulatory agencies, a comparison between GFAAS and TXRF data for lead in the same sample can serve as good indicator for TXRF performance.