Tsaihwa J. Chow

Chemical concentrations of pollutant lead aerosols, terrestrial dusts and sea salts in Greenland and Antarctic snow strata☆

Abstract In this study we report analyses of lead in annual ice layers from the interior of northern Greenland and in annual layers of ice from the interior of the Antarctic continent. We show that lead concentrations increase from 0.200 γPb/kg ice today in north pole ice sheets, the sharpest rise occurring after 1940, and that the levels of lead in south polar ice sheets are generally below our detection limits before 1940 and rise only to about 0.020 γPb/kg ice after 1940 (in this paper the symbol gamma, γ, means microgram, 10 −6 g). The increase of lead with time in north polar snows is ascribed mainly to lead smelteries before 1940 and to burned lead alkyls after 1940. The difference between the concentrations of lead in northern and southern polar snows is ascribed to barriers to north-south tropospheric mixing which originate from meridional circulating cells and which hinder the migration of aerosol pollutants from the northern hemisphere to the Antarctic. Our observations of the chemical concentrations of the common elements in ice from the interior of Greenland and Antarctica can be explained in terms of simple relations among sea salts and terrestrial dusts. We found about ten times more dust in Greenland interior ice (35 γ/kg) than in Antarctic interior ice (~2 γ/kg), but found twice as much sea salt in Antarctic interior ice (110 γ/kg) than in Greenland interior ice (67 γ/kg). We found that the proportions of sodium, chlorine, magnesium, calcium, and potassium adhered closely to sea salt ratios in ices that were relatively free of silicate dusts, even when the concentrations of sea salts decreased from 1100 γ/kg in NW coastal Greenland ice to 110 γ/kg in Rockefeller Plateau ice in the Antarctic interior. We also found that the amounts and chemical composition of silicate dusts in Greenland were no different in coastal and interior ices, averaging 3 γ Mg, 5.6 γCa, 2.0 γK, 0.1 γTi and 6.8 γSi per kg ice respectively in the interior. We found that there are seasonal variations in the amounts of pollutant lead, sea salts and silicate dusts in the snows, pollutant lead and sea salts being two or three times more concentrated in winter than in summer snows, while silicate dusts were three times more concentrated in spring than in winter snows. The above interpretation, which unifies all the data, is consistent with most related chemical and meteorological observations at temperate latitudes.

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: n1. n(1) that these leads have evolved within the continental crust above the Mohorovicic discontinuity; n n2. n(2) that the crust consists of two phases, an exterior phase of high U/Pb and an interior phase of low U/Pb; n n3. n(3) that the exterior phase contains lead isotopically homogeneous with the rest of the crust at the time the exterior phase was formed; and n n4. n(4) that isotopic variations arise from different periods of aging within the exterior phase., n n nThe 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.

Lead Isotopes in Gasoline and Aerosols of Los Angeles Basin, California

The isotopic composition of lead isolated from antiknock gasolines and the aerosols of the Los Angeles basin was determined. The lead isotopic composition of the aerosols was similar to that of rural snow. The high concentration of lead in water of precipitation and that of the surface of the sea can be attributed to automobile exhausts.

Lead Aerosols in the Atmosphere: Increasing Concentrations

The concentrations of atmospheric lead around San Diego, California, have been determined and their geographic and seasonal variations are explained. The lead aerosol concentration at San Diego is increasing at a rate of 5 percent per year. The isotopic composition of lead aerosols is similar to that of the lead additives isolated from gasoline, which are the largest contributors to atmospheric lead pollution.

Lead Isotopes in North American Coals

Lead isotopes in North American coals are equally or much more radiogenic than those in the present continental crust (a mean composition for the continental crust is used). It is practicable to distinguish coal and gasoline lead pollutants by examining their isotopic compositions.

The240Pu239Pu ratio, a potential geochronometer

Abstract The Arctic and Antarctic ice sheets maintain records of the atmospheric fallout in their datable strata. The 240Pu239Pu ratios in these polar reservoirs uniquely distinguish particulate fallout from the pre-moratorium nuclear atmospheric weapons tests, dominated by the U.S., and the post-moratorium atmospheric weapons tests, dominated by the U.S.S.R. Thus, they offer the possibility of use as a geochronological tool for some marine, glacial, lacustrine and soil systems.

Determination of nitrate in sea water

Abstract Nitrate in sea water is determined by reduction to nitrite with zinc metal in ammoniacal solution in the presence of manganese (IV) as catalyst. The effects of hydrogen ion concentration, reduction temperature, reaction time and the order of reagent addition are discussed. The nascent nitrite diazotizes with sulfanilamide and is then coupled by N-1-naphthylethylenediamine in acid medium forming a diazo-dye which is measured spectrophotometrically.

LEAD ISOTOPES IN MANGANESE NODULES

Abstract The isotopic compositions of leads which were isolated from manganese nodules of the Atlantic and the Pacific Oceans were determined. The Atlantic leads were more radiogenic than those of the Pacific. The Pacific samples showed a trend of increasing radiogenic leads from the north-west toward the south-east Pacific. The relationship between the collecting sites and the isotopic compositions of leads can be used to trace the circulation patterns of deep-water masses. The oceanic leads originated from rock systems whose uranium and lead contents have differentiated at various times appreciably later than 4·5 × 109 years.

Lead accumulation rates in tissues of the estuarine teleost fish, Gillichthys mirabilis: salinity and temperature effects.

Tissue-specific lead accumulation rates were determined in the estuarine teleost fish,Gillichthys mirabilis, as a function of four variables; sea water lead concentration, duration of exposure to lead, salinity, and temperature. Distinct tissue-specific accumulation rates were found. Spleen, gills, fins, and intestine accumulated the greatest amounts of lead; liver and muscle accumulated the least lead.Decay of lead from tissues of lead-exposed fish was observed only for gills, fins, and intestine, tissues which all possess an outer or inner covering of mucus. Our data suggest that the rapid turnover of lead in these mucus-covered tissues is a result of lead complexing with mucus and subsequent loss of lead when the mucus layer is sloughed off. In spleen and vertebrae, lead levels continued to rise in fish returned to natural (unspiked) sea water from lead-spiked sea water.The rate of lead accumulation was dependent on both the holding salinity and the temperature. Fish held at high temperature accumulated lead more rapidly than fish held at low temperature. The rate of lead accumulation was inversely proportional to the salinity of the medium. Both of these environmental effects on lead accumulation rates could be significant in estuarine habitats where lead concentrations, salinity, and temperature are all apt to vary seasonally.

Mussels (Mytilus sp.) as an indicator of lead pollution

The lead contents of two species of mussels (Mytilus californianus and M. edulis) collected along the Pacific coast from Piedras Blancas, California to Punta Banda, Baja California were determined by isotope dilution method. The whole soft parts of the mussels, on a dry weight basis, contained from 0.27 to 42 ppm of lead, which can be related to their local habitats. The gill tissues of the mussels showed the highest lead concentration.