Estimation method for contribution of emission to trace metal concentrations in urban atmosphere based o

Principal Research Results
Background
Clarification of the contribution of emission sources to trace metal concentrations in the atmosphere is useful for an accurate
evaluation of the environmental impacts of trace metals to efficiently proceed with emission control measures. However, the emission
sources of trace metals are often unknown. Even if they are known, the substantial fluctuation of the concentrations in exhaust gas
make it generally difficult to accurately measure such concentrations. Consequently, the conventional chemical element balance
method which relies on the mass balance of marker elements to estimate the contribution of emission sources has failed to produce
reliable data except for some elements. Meanwhile, an estimation method for lead has been studied based on the lead isotope ratios
＊1
which
characterizes each specific emission source and which can be measured with high accuracy.
Objectives
To propose an estimation method which is applicable to the urban atmosphere in Japan for the contribution of emission
sources to trace metal concentrations in the atmosphere based on the lead isotope ratios.
Principal Results
1. Emission Sources of Lead in Urban Areas
The lead isotope ratios in the atmosphere in A City, selected as the urban atmosphere study site, were almost constant
regardless of fluctuations of the lead concentration (Fig. 1). The established values were identical to those measured in seven cities in
Japan as well as those of fly ash produced by refuse incineration (Fig. 1). These results suggest that lead in the urban atmosphere in
Japan is mainly discharged by refuse incineration with the isotope ratios being fairly constant except in certain areas which are
affected by specific local emission sources.
2. Correlation Between Lead Concentration and Other Trade Metal Concentrations (Cd, Cr, Cu, Mn, Ni
and Zn) in Urban Atmosphere
The study on the relationship between the lead concentration and other trace metal concentrations in the atmosphere in A
City and at 16 stations of the National Air Surveillance Network (Environment Agency, Japan) found that the emission ratios of lead
and other trace metals from refuse incineration plants are roughly identical nationwide (Fig. 2). Accordingly, the contribution of refuse
incineration to trace metal concentrations can be estimated by comparing the trace metal/lead ratios (concentration ratios) in dust from
refuse incineration plants and the atmosphere.
3. Proposal of Estimation Method for Contribution of Emission Sources to Trace Metal Concentrations
Based on Lead Isotope Ratios
Based on the consideration that lead in the atmosphere originates from refuse incineration and other sources, a new

estimation method for the contribution of emission sources to trace metal concentrations using the contribution of lead from such
sources, determined by the lead isotope ratios, is proposed (Fig. 3). This method can be used to evaluate the environmental impacts of
trace metals in (1) areas surrounding specific emission sources of lead (coal-combustion and lead smelting, etc.) and (2) areas affected
by lead transported for a long distance from the Chinese continent (emission of lead through the use of leaded gasoline and the
combustion of coal, etc.)
Future Developments
To investigate the applicability of the new estimation method in areas along the Sea of Japan and also in large cities.
Main Researcher: Masahiro Sakata
Research Fellow, Atmospheric Science Department, Komae Research Laboratory
Reference
“Estimation Method for Contributions from Emission Sources to Trace Metal Concentrations in Urban Atmosphere Based on Lead
Isotope Ratios,” CRIEPI Report No. T97050, May, 1998 (Japanese only)
＊1：The lead isotope ratios (
206
Pb/
207
Pb and
206
Pb/
208
Pb, etc.) of lead ores vary depending on the time of ore formation as well as the
geological conditions. Lead released into the atmosphere has a characteristic value reflecting the isotope ratios of the original
lead ores. It is, therefore, possible to estimate the contribution of a specific source to lead concentration by accurate measuring.
30
Estimation Method for Contribution of Emission Sources to Trace
Metal Concentrations in Urban Atmosphere Based on Lead Isotope
3. Environment - Local Environment
31
2.5
2

1.5
1
0.5
0
0.5
0.48
0.46
0.44
0.42
0.4
020406080100
1.2
1.18
1.16
1.14
1.12
1.1
0 40 80 120 160 200 240
206
Pb／
208
Pb=

0.47478
＋
−
0.00064
206
Pb／
207

Pb=

1.1570
＋
−
0.0017
206
pb／
207
pb
206
pb／
208
pb
F1 F2
f1 f2
Lead Concentration (ng/m
3
)
206
Pb/
207
Pb
Cadmium Concentration (ng/m
3
)
206
Pb/
207
Pb

Fig. 1 Relationship between Lead Concentration
and Lead Isotope Ratios in Atmosphere
● ○ Lead Isotope Ratios (measured)
■ □ Mean Ratios in Atmosphere in 7 Cities (n = 18, from
literature)
▲ △ Mean Ratios of Fly Ashes from Refuse Incineration (n
= 7, measured)
While the lead concentration in the atmosphere substantially
fluctuates due to different meteorological conditions, the lead
isotope ratios in the atmosphere remain almost constant,
presumably because of the mixing and uniformatization of a large
amount of waste containing lead in refuse incineration plants.
Fig. 2 Correlation between Lead and Cadmium
Concentrations
● Annual Mean Values at 16 Stations of the National Air
Surveillance Network (from literature)
＊ Mean Value at 7 Refuse Incineration Plants (from
literature)
The ratios of the Pb and Cd concentrations in the atmosphere
obtained by the National Air Surveillance Network are almost
identical to those of the study site in A City and dust from
refuse incineration, implying that almost of the total amount
of Cd in the atmosphere originates from refuse incineration as
in the case of Pb.
Fig. 3 Schematic Drawing of Estimation Method for Contribution of Emission Sources
to Trace Metal Concentrations
Atmosphere in
7 Cities
Fly Ashes from
Refuse

Incineration
Lead Concentration (ng/m
3
)
Dust from Refuse
Incineration
(Cd/Pb = 0.029)
Atmosphere in A
City
(Cd/Pb = 0.025)
Dust from Refuse
Incineration
Dust from Other Sources
Lead Concentration
Trace Metal Concentrations
Lead Concentration
Trace Metal Concentrations
Emission
Sources
Mixing
Airborne Dust
Contribution
Estimation Process
Atmosphere
Lead Concentration
Trace Metal Concentrations
Contribution of Trace
Metals f1 f2
Contribution
of Lead

F1 F2
Lead Isotope
Ratio
Trace
Metal/Lead
Concentration
Ratio