New isotopic evidence for chronic lead contamination in the San Francisco Bay estuary system: Implications for the persistence of past industrial lead emissions in the biosphere

Abstract

Measurements of lead isotope compositions in unfiltered San

A Review of Factors Influencing Measurements of Decadal Variations in Metal Contamination in San Francisco Bay, California

“…Industrial lead fluxes were then compounded with inputs from the Selby lead smelter, which went into operation in the later half of the 19th century. The smelter operations continued until 1970, thereby altering lead isotopic compositions and markedly elevating lead concentrations in the Bay and its watershed (Rabinowitz and Wetherill, 1972;Ritson et al, 1999;Steding et al, 2000). Other inputs of industrial lead, notably leaded gasoline, further altered lead isotopic compositions, and contaminant lead concentrations steadily increased until the 1980s, when controls were placed on those emissions and the phase-out of leaded gasoline was being completed (Steding et al, 2000).…”

“…The smelter operations continued until 1970, thereby altering lead isotopic compositions and markedly elevating lead concentrations in the Bay and its watershed (Rabinowitz and Wetherill, 1972;Ritson et al, 1999;Steding et al, 2000). Other inputs of industrial lead, notably leaded gasoline, further altered lead isotopic compositions, and contaminant lead concentrations steadily increased until the 1980s, when controls were placed on those emissions and the phase-out of leaded gasoline was being completed (Steding et al, 2000). Despite these controls and the passing of time, isotopic compositions of those diverse lead inputs are still evident in both Bay sediments and surface waters (Ritson et al, 1999;Dunlap et al, 2000;Steding et al, 2000) because of the recycling of contaminant lead between those phases within the Bay (Rivera-Duarte and Ritson et al, 1999;Dunlap et al, 2000;Steding et al, 2000).…”

“…Because different sources of lead inputs to the Bay can be characterized by their isotopic composition ratios, those ratios have been used in mixing models to calculate decadal changes in industrial lead fluxes to San Francisco Bay waters (Steding et al, 2000). The models were used to resolve the apparent absence of decline in lead concentrations in Bay waters, even after (1) atmospheric emissions of industrial lead declined by two orders of magnitude with the elimination of leaded gasoline and (2) lead loadings to the estuary from POTW effluents were reduced 20-fold, to 46 t year )1 over the past three decades (Squire San Francisco Airport Primary POTW sites Industrial Discharge Sites Figure 3.…”

“…This plot of isotopic compositions shows that historic industrial inputs still dominate lead concentrations in the Bay. The isotopic composition data are synthesized from reports by Ritson et al (1999), Dunlap et al (2000), and Steding et al (2000).…”

Pyrogenic Remobilization of Historic Industrial Lead Depositions

“…2,3 Moreover, much of those historic depositions have been retained in terrestrial sediments, soils and vegetation in forests throughout the state where they may be remobilized by anthropogenic and natural processes-including forest fires.…”