Magnitudes and sources of precipitation and dry deposition fluxes of indestrial and natural leads to the North Pacific at Enewetak

A total atmospheric Pb input flux of 7 ng Pb cm^−2 yr^−1 was measured in the North Pacific Easterlies at Enewetak. Parameters used to measure this flux were ratio of dry deposition flux to precipitation flux; Pb/^(210)Pb in precipitation and seawater; ^(210)Pb flux; washout factor; and Pb concentrations in air, rain, and dry deposition deposits. Relations among these parameters established at Enewetak were used to recompute and confirm previous estimates of lead fluxes to the oceans (ng Pb cm^−2 yr^−1) at the following locations: North Atlantic Westerlies, 170; North Pacific Westerlies, 50; and South Pacific Easterlies, 3. Prehistoric lead output fluxes to sediments (ng Pb cm^−2 yr^−1) at these locations have been previously measured and were 4 (Enewetak); 30 North Atlantic Westerlies; 3 North Pacific Westerlies; 4 South Pacific Easterlies. These data show that the rates of atmospheric inputs of lead to the oceans vary directly with variations in rates of upwind emissions of industrial lead from urban complexes on land. In the North Pacific and North Atlantic, present rates of atmospheric lead inputs are 10-fold greater than prehistoric outputs. In equatorial regions, present inputs and past outputs are more nearly equal. These observations disclose the effects of intense industrial atmospheric emissions of lead in the northern hemisphere westerlies which have overwhelmed prehistoric natural fluxes of lead to the oceans. The average concentration of lead in marine air at Enewetak is 170 pg m−3 and varies less than a factor of 2 from that mean. One to 15% of this lead comes from seaspray, while the remainder comes from sources on land. About 90% of the seaspray lead is industrial, while 80 to 99% of that originating from land sources is industrial. Concentrations of lead in rain at Enewetak range from 6 to 63 pg/g with a mean value of 28. The mean precipitation flux, corrected for recycled lead in sea salts, measured by four different methods, was 6 ng Pb cm^−2 yr^−1, while the net dry deposition flux measured on horizontal plastic plates was 0.6 ng Pb cm^−2 yr^−1. The total dry deposition flux measured was 6 ng cm^−2 yr^−1, but 90% of this lead came from recycled seaspray. Lead isotope tracers show that Japan is the major source of industrial lead at Enewetak during the dry season, while the United States is the major source during the wet season

The distribution of lead between sea salt dust, and lead-rich aerosols in the mid South Pacific easterlies at American Samoa

Aerosols in the South Pacific Easterlies have been sampled at American Samoa with a cascade impactor and analysed for Pb, Ba, K, Ca, Sr, and Rb by isotope dilution mass spectrometry using ultraclean procedures. Some 84% of the Pb was found in fine (≤ 0.5 μm) aerosols which were collected on the backup filter with an efficiency of only 33%. Sea salt and eroded terrestrial material (dust) containing 6% and <1% respectively, of the Pb (sea salt indexed by the metals K, Ca, Sr, and Rb and dust indexed by Ba) were collected on early stages of the impactor, although 65% of the dust, because of its larger size, was lost to surfaces of the rain shelter before reaching the impactor. The remaining 10% of the Pb was associated with plant leaf waxes of continental origin which produced Pb and Ba peaks on stage 4 (0.5 μ) of the impactor

Magnitude of lead flux to the atmosphere from volcanoes

Pb/S, Tl/S and Bi/S ratios were measured in eruptive and fumarolic volcanic gases and indexed to the global flux of volcanic S to characterize approximate global volcanic emissions of these three metals to the atmosphere, which are about 1200 tons Pb/yr, 600 tons Tl/yr, and 4000 tons Bi/yr. This volcanic Pb input is similar to the magnitude of natural soil dust Pb input, which is about 1400 tons Pb/yr during the Holocene Interglacial. Both are negligible compared to annual industrial inputs of ~ 300,000 tons Pb/yr which maintain the present tropospheric reservoir of Pb. However, polar ice records indicate that thousands of years ago the atmospheric Pb reservoir was only ~ 1% of its present size, which means that volcanic Pb was the source of about half the Pb in the atmosphere during preindustrial Holocene times

Lead in Albacore: Guide to Lead Pollution in Americans

Lead contamination in canned tuna, exceeding natural concentrations 10,000-fold, went undiscovered for decades because of analytical error. The magnitude of this pollution effects helps explain the difference between the lead concentration in the diets of present-day. Americans (0.2 part per million) and in the diets of prehistoric peoples (estimated to be less than 0.002 part per million). It also explain how skeletal concentrations of lead in typical Americans became elevated 500-fold above the natural concentrations measured in bones of Peruvian's who lived in a unpolluted environment 1800 years ago. It has been tacitly assumed that natural biochemical effects of lead in human cells have been studied, but this is not so because reagents, nutrients, and controls used in laboratory and field studies have been unknowingly contaminated with lead far in excess of naturally occurring levels. An unrecognized form of poisoning caused by this excessive exposure to lead may affect most Americans because magnitudes of biochemical dysfunctions are proportional to degrees of exposure

Comparative increases of lead and barium with age in human tooth enamel, rib and ulna

Lead and Ba in postmortem tooth enamel, rib and ulna of six contemporary people (67–96 years; ave. 80) were shown to exhibit similar accumulations with age in the three different types of osseous tissue: Pb/Ca (wt) = 3.0, 5.2, and 3.9 × 10^(−5) in rib, ulna, and tooth enamel; and Ba/Ca (wt) = 2.4, 2.4, and 1.8 × 10^(−5) in rib, ulna, and tooth enamel, respectively. Mean concentrations of Pb were 11, 19, and 14 μg g^(−1) in rib (ash), ulna (ash), and enamel (dry), respectively. Means for Ba were 8.7, 8.9, and 6.4 μg g^(−1) in rib (ash), ulna (ash), and enamel (dry), respectively. Comparison of Ba in ulna of our 80-year-old subjects with Ba determined by other investigators in bones of younger contemporary populations indicated that Ba accumulates with age at about half the rate of Pb accumulation in bone. Concentrations of Ba in rib, ulna and enamel were positively correlated and similar within an individual, but varied among subjects in proportion to variations in absorptive uptake in portal blood. Barium may diffuse from a blood-dentine source into enamel, where it replaces Ca and accumulates with age. Because of extreme Pb pollution of our 80-year-old subjects and its variation of intake with age, the correlation of Pb in tooth enamel with Pb in bone was more scattered than for Ba. It is shown by means of stable Pb isotopic tracers that: (i) among the three types of osseous tissue, the residence time of Pb is longest in enamel, where it apparently accumulates with age by diffusion with little loss through exchange; and (ii) the residence time of Pb is longer in compact ulna than in trabecular rib, as it accompanies Ca in its osteoblastic transfer from blood to bone and then in its osteoclastic transfer back to blood from bone