Clair C. Patterson

Greenland Ice Evidence of Hemispheric Lead Pollution Two Millennia Ago by Greek and Roman Civilizations

Analysis of the Greenland ice core covering the period from 3000 to 500 years ago—the Greek, Roman, Medieval and Renaissance times—shows that lead is present at concentrations four times as great as natural values from about 2500 to 1700 years ago (500 B.C. to 300 A.D.). These results show that Greek and Roman lead and silver mining and smelting activities polluted the middle troposphere of the Northern Hemisphere on a hemispheric scale two millennia ago, long before the Industrial Revolution. Cumulative lead fallout to the Greenland Ice Sheet during these eight centuries was as high as 15 percent of that caused by the massive use of lead alkyl additives in gasoline since the 1930s. Pronounced lead pollution is also observed during Medieval and Renaissance times.

Lead concentrations in the northeast Pacific: evidence for global anthropogenic perturbations

Lead concentrations were determined by isotope dilution mass spectrometry in 34 surface- and deep-water samples collected in the northeast Pacific between Hawaii and California and off the California coast using a deep-water sampler protected against fouling by contamination from the ship and hydrowire. Measured concentrations lie more than one order of magnitude below previously published open ocean values and they show that in most cases 90% or more of the total lead is in a dissolved form. Lead concentrations are about 10-fold higher in surface and thermocline waters than in deep waters; values drop as low as 1 ng/kg (5 pmol/kg) below 3500 m depth. Lead profiles thus appear different compared to those of most trace metals, which show enrichment in deep waters compared to surface concentrations. Lead concentrations in surface waters increase from 5 to 15 ng/kg (25 to 75 pmol/kg) along a transect starting from a location 200 km off the California coast and continuing towards the center of the North Pacific Gyre. This increase is congruent with that observed for ^(210)Pb concentrations in the same waters sampled at the same time. Lead is supplied to the open North Pacific largely from the atmosphere, at a rate of about 60 ng/cm^2 yr, which exceeds the prehistoric oceanic output flux of authigenic lead recorded in pelagic sediments about tenfold. This excess originates from emissions from smelters and combustion of leaded gasoline, overwhelming natural lead inputs that entered the ocean during prehistoric time probably largely through rivers. Vertical lead concentration profiles below the surface mixed layer are probably not in steady state. There, concentrations must be increasing in response to the increase of anthropogenic inputs because the estimated lead residence times are more than 20 years in the thermocline and about 80 years in deep waters. Based on an estimated 10-fold input and concentration increase since the mid-eighteenth century in the surface mixed layer in the central northeast Pacific, it is calculated that the 10 ng/kg average concentration between 100 and 900 m is 2 to 5 times larger, and the 1.8 ng/kg average concentration between 900 and 5000 m depth is about 2 times larger than it was in the mid-eighteenth century. Profiles of lead concentrations in the North Atlantic are expected to be shifted generally to larger values by a factor of 2 to 3 compared to those in the North Pacific because of the effects of greater industrial lead contamination, while lead concentration profiles in the South Pacific are expected to be shifted generally to lower values compared to the North Pacific by about this same factor because of the effects of lesser industrial lead contamination.

Contaminated and Natural Lead Environments of Man

(1965). Contaminated and Natural Lead Environments of Man. Archives of Environmental Health: An International Journal: Vol. 11, No. 3, pp. 344-360.

The occurrence and significance of lead isotopes in pelagic sediments

Leads representing a major portion of the continental surface of the earth have been sampled in pelagic sediments and isotopically analysed. About two-thirds of the lead in all Pleistocene pelagic sediments have been chemically precipitated from lead dissolved in sea water. The remaining one-third has been transported as a constituent of solid particles. The rate of chemical deposition of lead tends to be uniform everywhere, while the rate of mechanical deposition of lead varies considerably so that the .abundance ratio of these two types of occurrences is different in various pelagic deposits. Dissolved lead in the oceans originates from the chemical denudation of continents, and different drainage regions contribute leads of different isotopic composition to the oceans. The travel time of the dissolved lead which is chemically precipitated is short compared to the mixing time of different large water masses so that lead of a uniform isotopic composition is not simultaneously deposited everywhere on the ocean floors. This phenomenon prevents the use of lead as a chronometrie index in lead-rich, uranium-poor marine sediments for intervals shorter than 100 million years. The present rate of soluble lead denudation, free of industrial contamination, is seven times greater than the average rate of chemical precipitation for the Pleistocene. Lead is transported from the continents to pelagic regions in dispro-portionately greater amounts than uranium and thorium, so that the isotopic evolution of lead in surface materials of the continents is measurably affected, and the lead denuded from some regions of extensively reworked sediments contains abnormally large proportions of Pb206. The gross features of the isotopic variations of leads denuded from continental surfaces can be accounted for by postulating: 1. (1) that these leads have evolved within the continental crust above the Mohorovicic discontinuity; 2. (2) that the crust consists of two phases, an exterior phase of high U/Pb and an interior phase of low U/Pb; 3. (3) that the exterior phase contains lead isotopically homogeneous with the rest of the crust at the time the exterior phase was formed; and 4. (4) that isotopic variations arise from different periods of aging within the exterior phase., The mean isotopic composition of lead to-day within the continental crust is obtained from the intersection of the marine lead isotopic regression line and the primary isochron of zero age for the earth. The values arer Pb206Pb204 = 18.58, Pb207/P.b204 = 15.77, Pb208/Pb204 = 38.87.

History of Ancient Copper Smelting Pollution During Roman and Medieval Times Recorded in Greenland Ice

Determination of copper concentrations in Greenland ice dated from seven millennia ago to the present showed values exceeding natural levels, beginning about 2500 years ago. This early large-scale pollution of the atmosphere of the Northern Hemisphere is attributed to emissions from the crude, highly polluting smelting technologies used for copper production during Roman and medieval times, especially in Europe and China. This study opens the way to a quantitative assessment of the history of early metal production, which was instrumental in the development of human cultures during ancient eras.

Natural concentrations of lead in ancient Arctic and Antarctic ice

Concentrations of Pb and K were determined in a series of veneer layers chiseled in sequence from the outside toward the center of each of the five 1500–5500yr old ice core sections that had been drilled in Greenland and Antarctic ice. They were analogs of very old ice samples analyzed earlier by Herronet al. (1977) and Craginet al. (1975), who reported high concentrations of Pb in them. Lead contamination, existing at exterior concentrations of about 10^6 ng/kg ice, had intruded to the centers of the cores, establishing interior values of at least 1.4 ng/kg ice in three electromechanically drilled Camp Century core sections taken from fluid filled drill holes. Corresponding Pb concentration changes were 3 × 10^4 ng/kg ice to 1.2 ng/kg ice in two thermally drilled New Byrd Station core sections taken from non-fluid filled drill holes. Contamination made the lowest center concentrations serve only as upper limits to the original concentrations of Pb in the ice. Potassium concentrations decreased from exterior values of about 5 × 10^5 ng/kg ice to an interior value of 2 × 10^3 ng/kg ice in the Camp Century core sections and from 8 × 10^4 ng/kg ice to 9 × 10^2 ng/kg ice in New Byrd Station core sections. Potassium contamination effects were not large within the central portions of the cores. These data verify earlier findings by Murozumiet al. (1969) and extend to a broader geographical significance the general validity of their observation of a ~ 300-fold increase of Pb concentrations in the Greenland ice sheet during the past 3000 yr. Our findings refute claims by Herronet al. (1977) and Craguinet al. (1975) that 100-fold excesses of natural Pb exist in 800 yr old Greenland ice above levels contributed by silicate dusts. Our new data also show that average Pb concentrations of 26 ng Pb/kg ice, claimed by Boutron and Lorius (1979) to be natural and present for 60 yr in snow strata in Antarctica, did not exist in old Antarctic ice, and that Pb concentrations have increased at least 10-fold in that ice during the past century. Virtually all of the present day ~300-fold excess of Pb above natural levels in Greenland ice can be shown to be caused by industrial Pb emissions to the atmosphere on the basis of the following factors: (1) the historic increase of Pb in snow strata coincides with the historic increase of industrial Pb production and atmospheric emissions (2) mass inventories of industrial emissions can account for the excess Pb in polar snow (3) new quantitative measurements of Pb emissions from volcanic plumes by Buat-Menard and Arnold (1978), Pattersonet al. (1981), and Buat-Menardet al. (1981), and from sea spray by Ng and Patterson (1981) and Settle and Patterson (1981). show that these natural sources cannot account for 99% of the excess Pb above contributions by silicate dusts observed today in the atmosphere; and (4) the historic increase of Pb in snow strata is paralleled by analogous increases of excess Pb shown by isotopic tracers to be industrial in water-laid sediments in a remote continental region (Shirahataet al., 1980). It is now known, however, that snows display about a 10-fold greater excess of industrial Pb above crustal silicate concentrations than exists in the air above the snows.

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 St/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 earths 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.

Skeletal concentrations of lead in ancient Peruvians.

The level of biologic lead (expressed as the ratio of atomic lead to atomic calcium) in bones of Peruvians buried 1600 years ago was found to be 3 x 10(-8), as compared to 2100 to 3500 x 10(-8) in the bones of present-day residents of England and the United States. The ratio of barium to calcium was 2 to 3 x 10(-6) in bones of ancient Peruvians and present-day Americans. Barium and lead have similar morphologic distributions in organisms, so this discrepancy for lead must result from overexposure of present-day people to industrial lead and not from natural variations. The magnitude of this discrepancy has been confirmed by two different lines of investigation not reported in this article. This new evidence suggests that natural interactions of lead in human cells have not yet been determined because reagents, nutrients and controls used in laboratory and field studies have been contaminated with lead far in excess of naturally occurring levels.

Perturbations of the Natural Lead Depth Profile in the Sargasso Sea by Industrial Lead

Concentrations of dissolved lead were determined by isotope dilution mass spectrometry in 17 seawater samples of a depth profile collected under strict contamination control at a station in the northern Sargasso Sea, 250 km northwest of Bermuda. Dissolved lead concentrations were about 170 pmol•kg −1 from the surface down to 400 m, then declined sharply to relatively constant values of 25 pmol•kg−1 below 2000 m depth. This large concentration enrichment in the upper part of the water column is concordant with the distribution observed earlier in the central northeast Pacific, and it confirms the unique character of the occurrence of lead in open ocean water columns: the depth profile for lead differs markedly from those for most other trace metals, which show concentration depletions in surface waters instead.

The occurrence of lead in Antarctic recent snow, firn deposited over the last two centuries and prehistoric ice

Concentrations of lead have been measured by ultraclean Isotope Dilution Mass Spectrometry in snow cores covering the last two centuries collected at an inland site in East Antarctica using an ultra clean all plastic hand operated auger and in a prehistoric blue ice block collected at an Antarctic coastal site. Lead contamination of 16 to 200 pg Pb/g existed on the outside of the snow cores, but the measured concentrations decreased more or less abruptly along a radius from the outside to the centers of the snow cores, establishing interior values in the 1 to 5 pg Pb/g range. Some of these interior values are however possibly still slightly affected by lead contamination which could have intruded to the center of the cores because of slight melting of some of the snow cores before laboratory analysis. The interior of the blue ice block appears not to have been significantly contaminated, and contains about 1.7 pg Pb/g. These new data show that most previously published data on lead in Antarctic snow and ice were in high positive error because of contamination during field sampling, laboratory analysis or both. They show that lead concentrations could not have increased in Antarctic snows or ice from prehistoric times to present more than 2 to 3 fold, confirming that the remote polar areas of the Southern Hemisphere are still little affected by industrial lead pollution. Prehistoric Antarctic ice is shown to contain about 1 pg Pb/g natural excess lead above silicate dust lead; this excess cannot be entirely accounted for by volcanoes or sea spray, which suggests the possible existence of some other unknown natural source of prehistoric excess lead. Present day mean eolian fallout flux of lead in Antarctica is estimated to be about 0.07 ng Pb cm^(−2) yr^(−1), which stands in about the same proportion to that in the South Pacific Westerlies (about 1:30) as the flux in Greenland is observed to stand to those in the North Pacific and North Atlantic Westerlies.