0

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1.12 1.17 1.22 1.27 1.32

206Pb/207 Pb

Peat

Local brown coal

Russian gasoline 1995 г (Mukai et al, 2001)

Preanthopogenic deposition

0

50

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550

0.01 0.1 1 10 100 1000

Pb ppm

Pb/Ti*1000

Pb/Sc

Pb/Ash

Pb/Li

154

1592

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550

0.001 0.1 10 1000 100000

Ti ppm

Li ppm

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K ppm

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0 1 10 100

Ash, %

Core SM

Monolith

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0.0 0.1 0.2 0.3 0.4 0.5

Bulk density, g cm-3

Core SM1

Core SM1а

Core SM

Monolith

5500 YEARS OF LEAD DEPOSITION RECORDED IN STAROSELSKII MOCH, AN OMBROTROPHIC

PEAT BOG IN NW RUSSIA Tatiana Pampura1, E. Novenko2, S. Dril3, O. Zarubina3, T. Vladimirova3, M. Meili4

1Institute of Physicochemical and Biological Problems in Soil Science RAS, Pushchino, Russia

2M.V. Lomonosov Moscow State University, Geographical department, Moscow, Russia

3A.P. Vinogradov Institute of Geochemistry RAS, Irkutsk, Russia

4Stockholm University, Department of Environmental Science and Analytical Chemistry (ACES), Stockholm, Sweden

pampura@mail.ru

INTRODUCTION Ombrotrophic peat is widely used as an archive for reconstructing atmospheric deposition of Pb and other elements. Profiles dated

with 210Pb and 137Cs and covering the past 100-150 years allow tracing of changes in Pb sources and deposition fluxes, reflecting industrial activity and

also consequences of the introduction and ban of leaded gasoline over the past decades. Recent changes can be related to pre-industrial changes

recorded in deep peat layers dated with 14C. Application of Pb isotope geochemistry facilitates the identification of Pb sources and their changes over

time. However, no such documentation is available for the vast territory of Russia. The aim of this study was the reconstruction of the natural and

anthropogenic Pb deposition history over several millennia, based on a combination of elemental concentrations and isotopic ratios in dated

ombrotrophic peat.

STUDY AREA Peat cores were collected in the ombrotrophic peat bog Staroselskii Moch located in the Central Forest State Natural Biosphere Reserve,

Tver region, NW Russia (56.47588°N, 33.04627°E) in August 2013: three 5.5 m cores covering almost 9000 years and a 64 cm surface monolith were taken

using a Russian and a Wardenaar corer, respectively. The lower margin of ombrotrophic peat was determined at 4.0 m (5500 years).

METHODS Peat cores and monolith were sliced into 2-cm sections, and bulk density and loss on ignition (550, 900°C) were determined. The upper part

of the peat was dated from profile of unsupported 210Pb (t 1/2 22.3 yr) determined by alpha spectrometry (Flett Research Ltd., Canada). Two dating models

(linear regression model LRM and constant rate of supply model CRS, Appleby, 2001) provided very similar results, and also showed good agreement

with 137Cs profiles determined by gamma spectrometry (Stockholm University) revealing a distinct peak from the Chernobyl fallout in 1986. The lower

part of the core was dated using 14C (Institute of Geography RAS, Moscow). After ashing (550 °C), samples were totally digested in concentrated HF,

HNO3 and HCl at 120 °C, dried, and diluted in 3% HNO3 for determination of element concentrations and Pb isotopes by ICP-MS (NexION 300D, Institute of

Geochemistry RAS, Irkutsk).

Supported by a grant of the Russian Foundation for Basic Research № 13-05-00958а

Results Deep layers in the ombrotrophic (atmospherically fed) peat represent background conditions 2700-5700 yr ago with respect to ash, Pb atmospheric

deposition flux and isotopic composition: 1.47 ± 0.51 Ash %, 0.013 ± 0.011 Pb mg m-2 yr-1, 206Pb/207Pb background = 1.197 ± 0.006, 208Pb/206Pb =

2.080 ± 0.006.

Already about 2000 years ago, Pb concentrations started to grow and isotopic composition started to shift towards less radiogenic ore-Pb (Fig 1).

Deposition of Pb reached a maximum of about 17 mg m-2 yr-1 in the 1930s, exceeding the background level about 1200 times. Despite a pronounced

decrease in Pb deposition since the 1970s, the modern deposition (0.7 mg m-2 yr-1) still exceeds the background value about 50 times (Fig 2a).

Shift of isotopic ratios with time towards the less radiogenic values confirms the dominating role of ore-derived Pb in anthropogenic deposition.

Fractions of natural (background) and anthropogenic (ore/gasoline) Pb in deposition were calculated using a mixing model based on 206Pb/207Pb

ratios. Results show that the fraction of ore/gasoline-Pb reached a maximum of 80% in the last decade of the XX century, while in the modern

deposition the fraction is about 70%. However, the uncertainty of such calculations is considerable (standard error about 20%) (Fig. 2b).

8th International Conference on Heavy Metals in the Environment 12 to 15 September 2016 Ghent, Belgium

SOURCES OF Pb in ombrotrophic peat

Anthropogenic

1. Brown coal excavated from local mines in 1948-1996 yr, the

slagheaps still remain at a distance of about 40 km. Мaximum coal

production was >1 000 000 t in 1975, totally > 30 000 000 t

206Pb/207Pb coal = 1.285 ± 0.063, 208Pb/206Pb = 1.954 ± 0.095

2. Leaded gasoline used in Russia from the 1930s until 2003. The

isotopic composition of gasoline Pb agrees well with the average

isotopic composition of the main Pb-ore deposits in Russia and

the former USSR (Mukai et al., 2001, Haak et al., 2000) and

average Russian aerosols in 1990-1999 (Mukai et al. 2001):

206Pb/207Pb gasoline = 1.151 ± 0.009 (used for mixing model), 208Pb/206Pb gasoline = 2.115 ± 0.007 (Mukai et al., 2001).

206Pb/207Pb ore = 1.161 ± 0.060, 208Pb/206Pb ore = 2.103 ± 0.069 (based on Mukai et al., 2001,

Haak et al., 2003). 206Pb/207Pb aerosols = 1.140 ± 0.020, 208Pb/206Pb aerosols= 2.122 ± 0.019 (based on Mukai et al., 2001).

Natural

Geogenic Pb in dry and wet deposition. Isotopic composition of

pre-anthropogenic Pb deposition determined as an average for

deep layers of ombrotrophic peat (207-365 cm, 2700-5700 yr BP)

206Pb/207Pb background = 1.197 ± 0.006 (used for mixing

model) 208Pb/206Pb background = 2.080 ± 0.006

Fig. 2. History of Pb deposition (a) and fraction of anthropogenic ore(gasoline)-derived Pb in atmospheric deposition (b). Dates are

calculated using CRS model (Pb-210) above the depth of 64 cm, and linear regression model based on C-14 dates (calibrated yr BP)

below 64 cm.

Fig. 1. Characteristics of peat profile

Nelidovo, Tver region, Russia, mine №3

56.24788°N, 32.78986°E

Slagheaps

Pre-anthropogenic atmospheric deposition

56.47588°N, 33.04627°E

1979

1936

1953

1820 AD

1949 BC

2311 BC

3822 BC

6098 BC

7779 BC

-100

-80

-60

-40

-20

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-6500-6000-5500-5000-4500-4000-3500-3000-2500-2000-1500-1000 -500 0 500 1000 1500 2000 2500

Year BC(-) /AD

b

Fraction of Pb-ore (=Pb-gasoline), %

Our data on Pb deposition agree well with Pb deposition, modeled for our sampling site by MSC EAST EMEP

http://www.msceast.org/index.php/reports (1990-2012), and with Pb deposition data for southern Sweden, based on herbaria mosses (1870-1960)

and on forest moss biomonitoring program (data from IVL.se,1975-2005) (cited from Hansson et al., 2015) (Fig. 2a).

Conclusion

Our study demonstrated a predominance of anthropogenic Pb

in modern deposits of lead in NW Russia, even after the

significant reduction of Pb (deposition) emissions during the

past decades.

MINEROTROPHIC PEAT

OMBROTROPHIC PEAT

501

0

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1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020

Year

Fraction of Pb-ore (=Pb-gasoline), %

Period of coal mining

Period of leaded gasoline

The Second World War

1990

0.100

1.000

10.000

100.000

1000.000

1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020

Peat, Pb mg/m2/yr

Model deposition, Pb mg/m2/yr, EMEP

Anthropogenic emission of Pb, Former USSR, 1000 t/yr (Pacyna and Pacyna, 2000)Pb mg/m2/yr, Sweden, biomonitiring (from Hansson et al., 2015)

1975

1936

0.00

0.01

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1.00

10.00

100.00

-6500-6000-5500-5000-4500-4000-3500-3000-2500-2000-1500-1000 -500 0 500 1000 1500 2000 2500

a

Pb мг/м2/г

183 AD

1416 AD

445 AD

1820 AD 602 AD

0

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1 10 100 1000 10000

Dep

th, c

m

Age, yr BP

Pb-210 (CRS)

Cs-137, Chernobyl 1986

C-14, Cal yr BP

PB-210 (LRM)

445 AD

183 AD

1415 AD

1949 BC

2311 BC

3822 BC

6098 BC

7779 BC

602 AD

OMBROTROPHIC PEAT

TRANSITIONAL PEAT

MINEROTROPHIC PEAT

GYTTJA