The circumvention of the natural biopurification of calcium along nutrient pathways by atmospheric inputs of industrial lead

Biopurification factors for Ca with respect to Sr, Ba, and natural, uncontaminated Pb were measured for different nutrient-consumer pairs in a remote subalpine ecosystem. The factor for Sr is expressed as: (nutrient Sr Ca ) ÷ (consumer Sr Ca ). Similar expressions were used for Ba Ca and Pb Ca . It was found that Ca was biopurified of Sr 3-fold, of Ba 16-fold, and of Pb 100-fold in going from rock to sedge leaves. In going from sedge leaf to vole, Ca was biopurified of Sr 4-fold, of Ba 8-fold, and of Pb 16-fold. In going from meadow vole to pine marten, Ca was biopurified of Sr 6-fold, of Ba 7-fold, and of Pb 1.1-fold. Similar ranges of values for these factors were obtained for detrital and amphibian food chains. Fluxes of industrial lead entering the ecosystem as precipitation and dry deposition were measured and it was found that 40% of the lead in soil humus and soil moisture, 82% of the lead in sedge leaves, 92% of the lead in vole, and 97% of the lead in marten was industrial. The natural skeletal Pb Ca ratio in carnivores (4 × 10 −8) was determined by means of corrections for inputs of industrial lead, food chain relationships, and measured biopurification factors for the ecosystem studied. This represents a 1700-fold reduction of the average Pb Ca ratio in igneous rocks at the earth's surface (6.4 × 10 −5) by the compounding of successive Pb biopurification factors in transferring Ca from rock to carnivore. The natural ratio is similar to the value of 6 × 10 −8 observed for Pb Ca in the bones of Peruvians who lived 2000 years ago but is 1/900th of the value of about 3.5 × 10 −5 for the skeletal Pb Ca ratio found in present day Americans. This study shows experimentally how the Ba Ca ratio in average surface igneous rock (3 × 10 −3) has been reduced 800-fold through compounding of successive biopurification steps to provide the skeletal Ba Ca ratio of about 4 × 10 −6 observed in humans. It also provides biopurification factors for Sr and Ba among a number of nutrient-consumer pairs which anthropologists can use to delineate degrees of herbivory in diets of hominids within the last 10,000 years.