Pyrogenic Remobilization of Historic Industrial Lead Depositions

Abstract

Relatively high levels (4.3 to 51 μg/g) of labile lead (Pb) in ash from the 2009 Jesusita Fire in Santa Barbara County, California attest to the pyrogenic remobilization of historic industrial lead depositions in this relatively pristine area in Southern California, USA. The primarily industrial origin of that lead was evidenced by its poor correlations (simple linear regressions) with lithogenic aluminum (r = 0.18, p = 0.354, n = 30) and iron (r = 0.21, p = 0.270, n = 30) concentrations and by its associated enrichment factors (EFs): EF using aluminum as conservative element (f-Al) vs lead concentration [Pb] (r = 0.79, p < 0.001, n = 30), and EF using iron as conservative element (f-Fe) vs [Pb] (r = 0.83, p < 0.001, n = 30). The industrial origins of much of that lead were corroborated by its isotopic compositions ((206)Pb/(207)Pb and (208)Pb/(207)Pb), which fell between those of natural lead in the Santa Barbara Basin and previous leaded gasoline emissions in Southern California. This apparent pyrogenic remobilization of legacy lead pollution indicates that it-and other persistent pollutants-will increase with the projected increase in the frequency and intensity of forest fires in the Southwest U.S. and elsewhere as a consequence of climate change.