DDT in Great Lakes Air:
Long-Range Transport or Home-Grown?
Terry Bidleman1, Fiona Wong1, Henry Alegria2, Perihan Kurt-Karakus3,
Kevin Jones3, Ralf Staebler1, Céline Audette1, Pierrette Blanchard1
1. Science & Technology Branch, Environment Canada.
2. California Lutheran University, U.S.A.
3. Lancaster University, U.K.
Thanks to: U.S. EPA Gt. Lakes National Program Office, North American
Commission for Environmental Cooperation, Mexican collaborators Miguel
Salvador, Gerardo Gold-Bouchot, Stefan Waliszewski, Raul Infanzon.
New sources, old sources …
Legacy pesticides are still found in air and precipitation
Potential Sources:
¾ Recent use in Mexico – Central America
¾ Emissions of “legacy” residues from soil and water
¾ Trans-oceanic
Technical DDT
H
C
CCl3
Cl
p,p’-DDT ~77%
Cl
Cl
H
C
CCl3
o,p’-DDT ~15-20%
ƒ
Used worldwide for disease vector control and
agriculture since 1945.
ƒ
ƒ
Total estimated global usage 2.4 megatonnes1.
Global elimination under Stockholm Convention,
except for vector control.
1. Li et al., Sci. Total Environ., 2005
Cl
Use of DDT in North America1
ƒ
United States used 590 kt for agriculture and 55 kt
for public health between 1947-72. Deregistered in 1972.
ƒ
Phased out in Canada during mid-1970s and all remaining
uses cancelled by 1985.
ƒ
Mexico used 180 kt for agriculture and 71 kt for malaria
control between 1953-00. “Official” used stopped in 2000.
1. Li et al., Sci. Total Environ., 2005; N. Amer. Comm. Environ. Cooperation
http://www.cec.org/files/PDF/POLLUTANTS/HistoryDDTe_EN.PDF
Geopolitics of DDT
ƒ
Stockholm Convention permits production and use of
DDT for disease vector control under World Health
Organisation guidelines.
ƒ
Requires that DDT be used only when locally safe,
effective and affordable alternatives are not available.
ƒ
WHO states1: “It is anticipated that, for some time to
come, there will continue to be a role for DDT in combating
malaria, particularly in the poorest endemic countries.”
1. World Health Organisation, 2005. WHO position on DDT use in disease
vector control under the Stockholm Convention on POPs. WHO Roll Back
Malaria Department, Geneva, Switzerland, WHO/HTM/RMB/2004.53.
Integrated Atmospheric Deposition Program (IADN)
early-mid 1990s to present
Eagle
Harbor
Brule
River
L. Superior
L. Michigan
Sleeping
Bear Dunes
Burnt
Island
Egbert
Pt.
Petre
L. Huron
Toronto
L. Ontario
Chicago
Illinois
Inst. Tech.
Sturgeon
Pt.
L. Erie
ΣDDTs in air
IADN stations & others
120
5
4
L. Superior
16
13
5 L. Huron
40
12
20
72
42
L. Michigan
Toronto
80
32
60
L. Ontario
30
Chicago
L. Erie
IADN data base, Motelay-Massei et al., ES&T 2005; Shen et al., ES&T 2005
40
20
0
(pg/m3)
Air sampling in Mexico & Belize, 1995-2004
Veracruz.
City, 03-04
Tabasco
03-04
Chetumal,
00-01
Chiapas
00-03
Alegria et al., ES&T 2000; Environ. Pollut., 2006,
Shen et al., ES&T 2005; Wong, Alegria, et al,, DIOXIN-05
Belize
95-96,
00-01
Total DDTs in air are higher
in southern Mexico- Belize
1000
1000
Range and mean
of site averages
6
pg/m3
100
100
7
13
10
10
9
1
1
tic
c
Ar
st
e
w N
id CA
M SU
th
u
So
A
S
U
o
c
i
e
ex eliz
M B
&
DDTs (pg m-3) in Mexican air, 2002-04
10%
ΣDDT
2300 ± 780
2%
15%
1%
37%
2%
4%
11%
73%
46%
Chiapas
Mountain
Chiapas
Tapachula
7% 5%
ΣDDT
240 ± 245
ΣDDT
520 ± 190
45%
19%
1%
3%
2%
11%
68%
Tabasco
o,p'-DDE
p,p'-DDE
ΣDDT
1200 ± 490
38%
Veracruz
City
p,p'-DDD
o,p'-DDT
p,p'-DDT
DDTs are metabolised to DDEs and DDDs
p,p’-DDT
H
C
CCl3
Cl
Cl
C
CCl2
p,p’-DDE
Cl
Cl
H
C
Cl
CH Cl2
p,p’-DDD
Similarly for o,p’-DDT
Cl
Ratio of DDT/DDE roughly indicates age of residues
High DDT/DDE
Newer
Low DDT/DDE
Older
Problems:
ƒ Metabolism rates in soils differ greatly.
Ratio of DDT/DDE roughly indicates age of residues
High DDT/DDE
Newer
Low DDT/DDE
Older
Problems:
ƒ Metabolism rates in soils differ greatly.
ƒ Limits on ratios:
>1 = “new” and <1 = “old”?
Ratio of DDT/DDE roughly indicates age of residues
High DDT/DDE
Low DDT/DDE
Newer
Older
Problems:
ƒ Metabolism rates in soils differ greatly.
ƒ Limits on ratios: >1 = “old” and < 1 = “new”?
ƒ DDT and DDE have different volatilities;
fractionation from soil to air.
Expressing proportions of DDT and DDE
ƒ
Ratios easy to understand, difficult to average.
RDDTE = p,p’-DDT/p,p’-DDE
ƒ
Fractions preferred to ratios for statistics1.
ƒ
Results expressed as FDDTE:
FDDTE = p,p’-DDT/(p,p’-DDT + p,p’-DDE)
FDDTE = RDDTE/(RDDTE + 1)
1. Harner et al., ES&T
2000; Ulrich et al.,
Chemosphere 2003
RDDTE
0.25
1.00
4.00
FDDTE
0.20
0.50
0.80
Are old residues emitted from soils?
p,p’-DDE in air sampled 40 cm above farm soils in the southern U.S.A.
Ratio of Cair over soil to background air, Cair,back = 28 pg/m3
10000
Points = measurements
Cair/Cair,back
1000
Lines = modelled
(till and no-till)
100
10
1.0
0.1
0.01
0.1
1.0
10
100
1000
Csoil, ng/g dry wt.
Bidleman & Leone, Environ. Pollut., 2004; Scholtz & Bidleman, Sci. Total Environ., in press
A
p,p'-DDE
2
o,p'-DDT
(Kurt-Karakus et al., submitted)
p,p'-DDT
1.5
z (m)
Soil-air fluxes of DDTs
in southern Ontario
14 / 05 / 2005
1
0.5
0
0.0
1.0
2.0
3.0
3
C (ng/m )
sonic anemometer
& temperature probes
4.0
filter-PUF
samplers
ΣDDTs in agricultural soils, ng/g dry weight
50
50
Aigner et al., ES&T 1998; Bidleman & Leone, Environ. Pollut., 2004;
Kannan et al., Arch. Env. Contam. Tox., 2003
0
00
> 10
>1
-1
0
>1
010
>1
0
00
-1
00
0
>1
00
0
-10
0
0
0
>10
0
10
-10
0
10
> 10
20
0
20
>11
30
> 0.
1- 1
40
30
<1
% of soils
40
southern U.S.
n = 100
<0.
1
midwest U.S.
n = 40
FDDTE in North American soils, 1985 - 2005
FDDTE = 0.5, RDDTE = 1
1.0
7
FDDTE
0.8
8
13
0.6
17
21
9
95
84
0.4
0.2
0.0
ON
r
g
a
r
t
r
r
h
h
r
r
g
s
c
g
g
c
g
g
a
r
r
e
a
a
a
a
r
o
o
A
o
A
C
f
A
K
S
N
S
B
S
C
BC ME
O
U
.U
.
W
S
M
DDTs in soil emissions
Assume volatilisation from soil is related to
liquid-phase vapour pressure (VP)
VP1 at 20oC:
p,p’-DDT:
0.00026 Pa,
p,p’-DDE:
0.0018 Pa
VPDDT/VPDDE = 0.14
(RDDTE )air = (RDDTE )soil x VPDDT/VPDDE
Does this work?
1. VPs from Hinckley et al., J. Chem. Eng. Data, 1990
Soil-Air Exchange Experiments, 2000-05
ƒ Soil samples collected from farm fields.
ƒ RDDTE in air predicted from soil residues
using VP ratios.
ƒ Converted to FDDTE.
ƒ Air samples collected over the soil (5-40
cm) and FDDTE compared to predictions.
Bidleman & Leone, Environ. Pollut., 2004;
Bidleman et al., ET&C, in press; Kurt-Karakus et al., submitted
FDDTE in air measured over soil
and predicted from soil residues
soil
air predicted
air measured
1.0
7
1
FDDTE
0.8
0.6
14
4
19
0.4
0.2
0.0
14
26
8
BC farm
BC orchard
ON farm
S. USA
FDDTE in ambient air
IADN stations & others
0.48
0.47
0.32
L. Superior
0.10
0.23
0.39
L. Huron
0.22
0.31 0.18
0.33
0.38
L. Michigan
0.11 0.42
L. Ontario
Chicago
L. Erie
IADN data base, Motelay-Massei et al., ES&T 2005; Shen et al., ES&T 2005
0.5
0.4
0.3
0.2
0.1
0.0
FDDTE in ambient air and predicted from soil emissions
soil
air predicted
ambient air
0.8
FDDTE
0.6
31
13
midwest
sites
0.4
7
sites
0.8
0.6
84
4
sites
0.4
0.2
0.2
0.0
0.0
MW US-CAN
S. USA
Mexico
& Belize
FDDTE in ambient air and predicted from soil emissions
soil
air predicted
ambient air
0.8
FDDTE
0.6
31
13
midwest
sites
0.4
7
sites
60
sites
0.6
84
4
sites
0.4
0.2
0.0
0.8
0.2
MW US-CAN
S. USA
Mexico
& Belize
1. China, Japan, Korea, Singapore: Jaward et al., ES&T 2005
Asia1
0.0
Enantiomer fractions (EFs) of o,p’-DDT in southern U.S.
agricultural soil and overlying air at 40 cm
(Bidleman & Leone, Environ. Pollut., 2004)
0.54
EF air
0.52
0.50
0.48
0.46
0.44
0.42
0.44
0.46
0.48
EF soil
0.50
0.52
0.54
Ambient air shows (+) degradation (EF ~0.47) in Canada & U.S.,
racemic (EF = 0.50) in Mexico – C.A. (Shen et al., ES&T 2005)
Summary
ƒ
Fractionation of p,p’-DDT and p,p’-DDE between
soil and air is well predicted from relative VP.
ƒ
FDDTE in ambient air of Great Lakes - midwest is
similar, but slightly greater, than predicted from
soil emissions.
ƒ
Discrepancy is greater in southern U.S., although
small air data set.
ƒ
LRT from Mexico-Central America?
Final Words
ƒ Soil emissions place limits on “old” FDDTE in air.
ƒ Compare with ambient air signals to judge
possible “new” DDT input.
ƒ Useful in N. America, and also countries which
have recently stopped, or are still using, DDT.
Continuing passive campaign, 2003-present