Relative Levels of Natural and Anthropogenic Lead

Concentrations of lead have been Patterson, 1986]. Soil dusts were shown to be the measured by ultraclean isotope dilution mass major source of natural lead. The volcanic spectrometry in large blocks of surface snow contribution was found to be significant during collected along a 433-km coast-interior axis in low-lead time periods only and the contribution East Antarctica and near the geographic south from sea salts always insignificant. pole. Slight contamination existed on the outside On the other hand, there are almost no reliable of the blocks, but concentration profiles from data on present-day tropospheric concentrations of their exteriors to their interiors indicate that lead in the Antarctic tropospheric cell. •his cell lead concentrations in the innermost parts of the is today the least-contaminated portion of the blocks do represent the original concentrations in earth's troposphere with respect to industrial present-day Antarctic snow. Geographical lead, which makes it of great interest for variations of lead concentrations appear to be investigators studying relative emissions of mainly due to local emissions from Dumont industrial and natural lead to the troposphere. d'Urville and Amundsen Scott stations. The These present-day Antarctic tropospheric globally significant lead concentration in concentrations can be either measured directly on present-day Antarctic snow is found to be about 2 air filters or retrieved from concentrations pg Pb/g. The corresponding value in_Antarctic air recorded in surface snows combined with is estimated to be about 7pg Pb/m • STP, which is atmospheric scavenging ratios. Most corresponding approximately fivefo d larger than total natural data (see for instance Duce et al. •1975•, lead contributed by soil dusts, volcanoes and sea Maenhaut et al. •1979], Peel andWolff 1982 , salts. A tentative temporal curve of globally Boutron [1978, 1980,1981, 1982], Boutron and and significant lead concentrations in Antarctic ice Lorius [1979], Jaworowski et al. [1981]) have and snow for the last 13,O00 years is given. It indeed been shown to be erroneous by up to several shows concentrations of about 0.4 pg Pb/g orders of magnitude because of improper control of throughout most of the Holocene, with recent lead contamination during field sampling and fivefold increases to about 2 pg Pb/g today. The laboratory analysis [Patterson et al., 1985 general picture is then that four-fifths of total Wolff and Peel, 1985b ; Dick and Peel, 1985 lead in the Antarctic troposphere today is Boutron, 1986]. The only reliable data for anthro•pogenic. Antarctic present-day air are now thought to be the few ones recently published by Dick and Peel