quantifying access and mobility of toxic elements in nlm ... · quantifying access and mobility of...
TRANSCRIPT
Quantifying access and mobility of
toxic elements in NLM smelter slags
A.L. Morrison
July 2015
Scale of the slag issue
• Approximately 2.1 M tonnes (~650,000 m3) of
slag exported to the community;
• Pb in exported slag (~1-2%) represents >1000
years of declared* smelter stack emissions;
• A covering of the residential area of Boolaroo to a
depth of 300mm;
• Waste costs externalised around $400M in todays
$’s (@$200/tonne).
*National Pollution Inventory (NPI) 1999-2003 maximum 20 tonnes/yr (2001)
1 Km
Creek Reserve Road
Tredennick Oval
Eleebana
North Lake Macquarie, NSW
50m
Creek Reserve Road, Boolaroo (CR)Slag infill during creek bank restoration
50m
Tredennick Oval, Boolaroo (TN)Slag layer over old landfill
50m
Lion’s Park, Eleebana (ELB)Slag used in stabilisation berm during landslip remediation
“Slag produced by Pasminco Metals-Sulphide has a
lead content of about 0.7%. The lead is bound up in
a glass like structure and does not readily leach
out. Lead in crystal drinking glass for example is
about 22% and is chemically bound up in the glass in a
similar way.”
Pasminco Community Newsletter cited in LMCC
Planning and Environment Minutes, July 1992.
The Myth
“most of the heavy metals present in the slag are in
readily bioavailable forms. It is likely that ingested
slag, reaching the gut would readily release lead,
zinc, cadmium and copper, and this could have
toxic consequences”
G.E Batley, CSIRO Investigation Report CET/LHIR077,
June 1992.
The Withheld Truth
These earlier results were confirmed in the study of bioaccessibility
(Morrison and Gulson) published in 2007 and subsequently by
others (Kim et al., 2009).
Hypothesis
• Slag is benign in the environment
• Metals contained in the slag remain insitu
when exposed to infiltrating fluids e.g.
rainwater, seawater, acidic leachates
Toxic metal inclusions are all
surrounded by an impervious
silicate slag matrix
Toxic metals form part of the
structure of the impervious
silicate slag matrix
and/or
Morphology needed for hypothesis
to be correct
SEM QEMSCAN
Allows detailed examination of
individual particles and the
attached EDS system can
determine semi-quantitative
chemistry over a wide range of
elements.
Automated analyses using EDS of
~1-2µm “spots”, software then
maps individual particles over a
sample. Automation allows large
numbers of particles to be
chemically mapped but at a lower
degree of precision.
SEM Analyses
Sample sized -250+180 µm
SEM Analyses Sample sized -250+180 µm
SEM Analyses Sample sized -250+180 µm
SEM Analyses Sample sized -20 µm
0.00 0.40 0.80 1.20 1.60 2.00 2.40 2.80 3.20 3.60
keV
001
0
800
1600
2400
3200
4000
4800
5600
6400C
oun
ts
OK
a
SK
a
SK
b
PbM
z
Pb
Ma
Pb
Mb
Pb
Mr
ZAF Method Quantitative Analysis
Element (keV) mass% At% O K 0.525 11.3 52.2S K 2.307 8.2 19.0
Pb M 2.342 80.5 28.8Total 100.0 100.0
0.00 0.40 0.80 1.20 1.60 2.00 2.40 2.80 3.20 3.60
keV
001
0
800
1600
2400
3200
4000
4800
5600
6400C
oun
ts
OK
a
SK
a
SK
b
PbM
z
Pb
Ma
Pb
Mb
Pb
Mr
ZAF Method Quantitative Analysis
Element (keV) mass% At% O K 0.525 11.3 52.2S K 2.307 8.2 19.0
Pb M 2.342 80.5 28.8Total 100.0 100.0
Spectral analysis of nodules
These results suggest that the compound formed is likely to be metallic lead and its
oxidation products possibly PbO.PbSO4 (monobasic lead sulfate, larnachite) which
would have elemental ratios of 2:1:5 (Pb:S:O). Larnachite had been previously also
identified as a component of the slag by XRD
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
002
0
400
800
1200
1600
2000
2400
2800
3200
3600
4000
Co
un
ts
OK
a
NaK
a
AlK
aS
iKa
SK
aS
Kb
CaK
a
CaK
b
Mn
Ll
Mn
La
Mn
Ka
Mn
Kb
FeL
lF
eL
a
FeK
esc
FeK
a
FeK
b
Zn
Ll
Zn
La
Zn
Ka
Zn
Kb
ZAF Method Standardless Quantitative AnalysisFitting Coefficient : 0.1504Element (keV) mass% At% Element (keV) mass% At%O K 0.525 32.7 57.0 Ca K 3.960 11.3 7.9
Na K 1.041 1.9 2.4 Mn K 5.894 2.3 1.4Al K 1.486 3.4 3.5 Fe K 6.398 24.6 12.3Si K 1.739 8.3 8.3 Zn K 8.630 13.5 5.8 S K 2.307 2.0 1.8
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
keV
002
0
400
800
1200
1600
2000
2400
2800
3200
3600
4000
Co
un
ts
OK
a
NaK
a
AlK
aS
iKa
SK
aS
Kb
CaK
a
CaK
b
Mn
Ll
Mn
La
Mn
Ka
Mn
Kb
FeL
lF
eL
a
FeK
esc
FeK
a
FeK
b
Zn
Ll
Zn
La
Zn
Ka
Zn
Kb
ZAF Method Standardless Quantitative AnalysisFitting Coefficient : 0.1504Element (keV) mass% At% Element (keV) mass% At%O K 0.525 32.7 57.0 Ca K 3.960 11.3 7.9
Na K 1.041 1.9 2.4 Mn K 5.894 2.3 1.4Al K 1.486 3.4 3.5 Fe K 6.398 24.6 12.3Si K 1.739 8.3 8.3 Zn K 8.630 13.5 5.8 S K 2.307 2.0 1.8
Spectral analysis of glassy phase
Pb, Sb, As,
Cd, AgZn
Location for significant trace elements
Availability of toxic species to
infiltrating fluids
QEMSCAN particle
mapping
Background
Pb.S
Pb.S.Sb
Pb.Fe.S
Pb.Cu.S
Pb.S.SnL
Silicates
Sulphides
Sulphates
Carbonates
Phosphates
Others
QEMSCAN particle
mapping
Background
Pb Met (Low Ox)
Pb Met (High Ox)
Fe Ox (Low Pb)
Cu Met (Low Pb)
Fe.As (Low Cu)
As Oxides
Silicates
Sulphides
Sulphates
Carbonates
Phosphates
Oxides
Others250 µm
Modal Mineralogy
Outcomes: Mineral Mapping
• Slag contain ~1% Pb phases and 97% vitreous
silicate glass
Creek Reserve (CR1) Tredennick Oval (TN2)
Pb Met (Low Ox)
Pb Met (High Ox)
Fe Ox (Low Pb)
Cu Met (Low Pb)
Fe.As (Low Cu)
As Oxides
Silicates (glassy matrix)
Sulphides
Sulphates
Carbonates
Phosphates
Oxides
Others
Pb Met (Low Ox)
Pb Met (High Ox)
Fe Ox (Low Pb)
Cu Met (Low Pb)
Fe.As (Low Cu)
As Oxides
Silicates (glassy matrix)
Sulphides
Sulphates
Carbonates
Phosphates
Oxides
Others
Pb in contact with Si
(or anything else other
than Pb) but not epoxy
Si (or anything other
than Pb) boundary
with epoxy/background
Pb in contact with Pb
only
Pb in contact with
epoxy/background
Si in contact with Si (or
anything else other
than Pb)
Phase Association Schematic
ACCESSIBILITY MODEL
>90% reaction
surface exposed
>9% reaction surface
exposed
Reaction surface
exposed limited to
<9%
LIBERATED ACCESSIBLE LOCKED
Background
Pb Met (Low Ox)
Pb Met (High Ox)
Fe Ox (Low Pb)
Cu Met (Low Pb)
Fe.As (Low Cu)
As Oxides
Silicates
Sulphides
Sulphates
Carbonates
Phosphates
Oxides
Others
SIZE (µm) LIBERATED ACCESSIBLE LOCKED TOTAL
-3350/2000 6.83 72.39 20.77 100-2000/1000 0.52 85.27 14.21 100-1000/500 0.56 58.79 40.65 100-500/250 86.04 11.50 2.47 100-250/150 87.92 11.16 0.92 100-150/90 78.72 20.25 1.03 100-90/53 73.37 24.36 2.27 100
-53 37.66 59.02 3.32 100
Size dependence of accessibility of Pb
species in sample TN1 (%)
SAMPLE LIBERATED ACCESSIBLE LOCKED TOTAL
CR1-2 76.7 21.8 1.5 100CR1-3 56.4 41.0 2.6 100CR2-2 69.6 25.6 4.8 100CR2 (comb) 42.3 51.2 6.5 100TN1-2 59.1 39.8 1.2 100TN1 (comb) 65.3 30.7 4.1 100TN2-2 79.7 19.0 1.4 100TN2-3 56.0 43.0 1.1 100
Overall accessibility of Pb species in samples
(-250 µm) (%)
0
20
40
60
80
100
120
0 50 100 150 200 250
Average particle screen size (µm)
Le
ad
bio
ac
ce
ss
ibil
ity
(%
)S1
S2
S4
Bioaccessibility of Pb species in slag
samples (-250 µm) (%)
Screen
Size
(µm)
Pb LOW
OX
av.dia
(µm)
Pb HIGH
OX
av.dia
(µm)
Bio-
accessibility
%
LIBERATED
(%)ACCESSIBLE
(%)
LOCKED
(%)
-250+180 12 9 23.2 35.6 50.3 14.1
-180+150 16 12 51.8 40.4 42.2 17.4
-150+125 22 10 55.6 34.3 51.7 14.0
-125+90 17 12 58.7 39.7 50.0 10.4
-90+75 10 7 75.4 61.3 31.4 7.4
-75+53 11 8 76.8 55.9 38.5 5.6
-53+32 9 9 77.4 51.0 44.1 4.9
-32+20 5 7 83.1 62.3 34.9 2.9
-20 6 6 100.0 56.4 41.4 2.2
Overall accessibility of Pb species in samples
(S1) (-250 µm) (%)
•Pb phases in the slags are mostly separate
from the glassy slag matrix
•The Pb phases are generally unprotected
from infiltrating fluids
• A consequence is that the Pb contained in
the slags will be vulnerable to leaching over
time
Conclusions on Accessibility
Sampling Program Extension
• Develop chemical soil profiles at three
locations
• Sample at known slag emplacements
• Incrementally sample to subsoil below slag
layer
• Chemically and morphologically analyse
sample increments
Sampling and Analysis Methods
• Auger Sampling (100 mm Φ /100mm increments)
• Duplicate holes for each site approximately 1m apart
• Subsampling and sizing of increments
• Comprises 35 replicated samples
• Chemistry using X-Ray Fluorescence (XRF)
• Chemistry using ICP-AES (for Pb, Zn, Cu) and ICP-MS (for Ag, As, Cd, Sb,Se)
• Elemental mapping using electron dispersive spectrometry (EDS)
Generic soil/slag infill profileGrass (sometimes)
and topsoil
(sometimes) of
varying thicknessMixed soil/slag
at interface
Slag only layer of
varying thickness
(400 – 600mm)
Underlying
subsoil or fill
Mixed soil/slag
at interface
Range of Pb and Zn values
measured
• Pb
1785 – 17,100 ppm
• Zn
10,700 – 80,850 ppm
Slag/soil lead (Pb) profiles
0
100
200
300
400
500
600
700
0 10000 20000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
CR1 CR2 CR (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 10000 20000 30000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
TN1 TN2 TN (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 5000 10000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB1 ELB2 ELB (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
throughout
0
100
200
300
400
500
600
700
0 10000 20000
Soil Pb (mg/kg)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 10000 20000 30000
Soil Pb (mg/kg)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 5000 10000
Soil Pb (mg/kg)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
throughout
Slag/soil zinc (Zn) profiles
0
100
200
300
400
500
600
700
0 10000 20000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
CR1 CR2 CR (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 10000 20000 30000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
TN1 TN2 TN (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 5000 10000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB1 ELB2 ELB (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
throughout
0
100
200
300
400
500
600
700
0 30000 60000 90000
Soil Zn (mg/kg)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 30000 60000 90000
Soil Zn (mg/kg)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 20000 40000 60000
Soil Zn (mg/kg)A
ve
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
throughout
0
100
200
300
400
500
600
700
0 10000 20000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
CR1 CR2 CR (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 10000 20000 30000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
TN1 TN2 TN (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 5000 10000
Soil Pb (ppm)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB1 ELB2 ELB (AVERAGE)
Soil/Clay
Mixed
Slag/Soil
throughout
0
100
200
300
400
500
600
700
0 30000 60000 90000
Soil Zn (mg/kg)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 30000 60000 90000
Soil Zn (mg/kg)
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
Mostly
Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 20000 40000 60000
Soil Zn (mg/kg)A
ve
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
Soil/Clay
Mixed
Slag/Soil
throughout
Slag/soil elemental ratio profiles
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.0001 0.0002 0.0003 0.0004
Ag/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
0
100
200
300
400
500
600
700
0 0.1 0.2
Cu/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
(a) Cu/Zn (b) Pb/Zn (c) Ag/Zn
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.0001 0.0002 0.0003 0.0004
Ag/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
0
100
200
300
400
500
600
700
0 0.1 0.2
Cu/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.2 0.4
Pb/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
ELB CR TN
0
100
200
300
400
500
600
700
0 0.0001 0.0002 0.0003 0.0004
Ag/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
0
100
200
300
400
500
600
700
0 0.1 0.2
Cu/Zn ratio
Ave
rag
e d
ista
nce
fro
m s
urf
ace
(m
m)
(a) Cu/Zn (b) Pb/Zn (c) Ag/Zn
Significance of the soil/slag profile
• Contaminant values are very high when compared to
ANZECC soil health investigation levels (HILs)
– Pb 300 ppm (homes) ; 600 ppm (parks)
– Zn 7000 ppm (homes) ; 14000 ppm (parks)
• Pb is ~1% of the total material
• Pb (and associated elements) appear to be leaching
out of the slag
• Zn (and likely other elements in the glass) appear to
be relatively conserved
Where to from here?• Leach analysis of these stratigraphically
collected slag samples from three selected
locations
Sequential Leach Extraction for
heavy metals :
*includes exchangeable fraction and occluded carbonates
Fraction Leaching Agent pH
Mobile 1M NH4NO3 ~6-7
Easily dissolved* 1M NH4OAC 6.0
Bound to Mn oxides 0.1M HNO3-HCl + 1M NH4OAC 6.0
Bound to organic matter 0.025M NH4-EDTA 4.6
Bound to poorly crystalline Fe oxides 0.2M NH4-Oxalate 3.25
Bound to crystalline Fe oxides 0.1M ascorbic acid+0.2M NH4-Oxalate 3.25
Residual heavy metals “near” total digestion conc HCl/HNO3
Pb
0
20
40
60
80
100
10100100010000
Log Particle Size (µm)
Cu
mu
lati
ve E
xtra
ctio
n (
%)
Leach #1
Leach #2
Leach #3
Leach #4
Leach #5
Leach #6
Total available Pb
Sample TN1
Sequential leach outcomesPb
0
20
40
60
80
100
10100100010000
Log Particle Size (µm)
Cu
mu
lati
ve E
xtra
ctio
n (
%)
Leach #1
Leach #2
Leach #3
Leach #4
Leach #5
Leach #6
Total available Pb
Sample CR2
1. Mobile heavy metals
2. Easily dissolved heavy metals
3. Heavy metals bound to Mn oxide
4. Heavy metals bound to organic compounds
5. Heavy metals bound to poorly crystalline Fe oxides
6. Heavy metals bound to crystalline Fe oxides
7. Residual heavy metals
Sequential leach outcomes
1. Mobile heavy metals
2. Easily dissolved heavy metals
3. Heavy metals bound to Mn oxide
4. Heavy metals bound to organic compounds
5. Heavy metals bound to poorly crystalline Fe oxides
6. Heavy metals bound to crystalline Fe oxides
7. Residual heavy metals
Zn
0
20
40
60
80
100
10100100010000
Log Particle Size (µm)
Cu
mu
lati
ve E
xtra
ctio
n (
%)
Leach #1
Leach #2
Leach #3
Leach #4
Leach #5
Leach #6
Total available Zn
Sample TN1 Zn
0
20
40
60
80
100
10100100010000
Log Particle Size (µm)
Cu
mu
lati
ve E
xtra
ctio
n (
%)
Leach #1
Leach #2
Leach #3
Leach #4
Leach #5
Leach #6
Total available Zn
Sample CR2
Leach outcomes for the composite
sample (-3.35mm)(cumulative extraction %)
Composite
sample
Leach
#1
Leach
#2
Leach
#3
Leach
#4
Leach
#5
Leach
#6
Leach
#7
CR1 (Pb) 11.8 29.3 32.0 36.2 36.7 37.2 100.0
TN1 (Pb) 15.2 31.5 33.2 36.4 36.7 37.8 100.0
CR1 (Zn) 0.3 0.8 1.0 4.4 11.0 15.0 100.0
TN1 (Zn) 0.2 0.6 0.8 6.0 10.9 13.4 100.0
• ~30% of the Pb in the composite samples was mobile or
easily dissolved, this is compared to only ~0.7% of the
Zn.
Leach outcomes for the composite
sample(cumulative extraction %)
Composite
sample
Leach
#1
Leach
#2
Leach
#3
Leach
#4
Leach
#5
Leach
#6
Leach
#7
CR1 (Pb) 11.8 29.3 32.0 36.2 36.7 37.2 100.0
TN1 (Pb) 15.2 31.5 33.2 36.4 36.7 37.8 100.0
CR1 (Zn) 0.3 0.8 1.0 4.4 11.0 15.0 100.0
TN1 (Zn) 0.2 0.6 0.8 6.0 10.9 13.4 100.0
• ~30% of the Pb in the composite samples was mobile or
easily dissolved, this is compared to only ~0.7% of the
Zn.
Pb at sample site TN
0
100
200
300
400
500
600
700
0 20 40 60 80 100
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Average cumulative extracted Pb (%)
Mobile
Easily dissolved
Bound to Mn oxides
Bound to organics
Bound to poorlycrystalline Fe oxides
Bound to crystallineFe oxides
Residual heavymetals
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Soil Pb (mg/kg)
TN1 Octile sample
TN2 Octile sample
TN (AVERAGE)
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Average cumulative extracted Pb (mg/kg)
TN1 ∑Leach (1-7)
TN2 ∑Leach (1-7)
Some soil near surface
Mostly slag
Mixed slag/soil
Soil/clay
Pb at sample site TN
0
100
200
300
400
500
600
700
0 20 40 60 80 100
Avera
ge d
ista
nce
fro
m s
urf
ace
(m
m)
Average cumulative extracted Pb (%)
Mobile
Easily dissolved
Bound to Mn oxides
Bound to organics
Bound to poorlycrystalline Fe oxides
Bound to crystallineFe oxides
Residual heavymetals
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Soil Pb (mg/kg)
TN1 Octile sample
TN2 Octile sample
TN (AVERAGE)
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Average cumulative extracted Pb (mg/kg)
TN1 ∑Leach (1-7)
TN2 ∑Leach (1-7)
Some soil near surface
Mostly slag
Mixed slag/soil
Soil/clay
0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Average extracted Pb (mg/kg)
CR1 ∑Leach (1-7)
CR2 ∑Leach (1-7)
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface
Pb at sample site CR0
100
200
300
400
500
600
700
0 10000 20000
Avera
ge d
ista
nce
fro
m s
urf
ace
(m
m)
Soil Pb (mg/kg)
CR1 Octile sample
CR2 Octile sample
CR (AVERAGE)
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 20 40 60 80 100
Avera
ge d
ista
nce
fro
m s
urf
ace
(m
m)
Average extracted Pb (%)
Mobile
Easily dissolved
Bound to Mn oxides
Bound to organics
Bound to poorlycrystalline Fe oxides
Bound to crystalline Feoxides
Residual heavy metals
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Average extracted Pb (mg/kg)
CR1 ∑Leach (1-7)
CR2 ∑Leach (1-7)
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface
Pb at sample site CR0
100
200
300
400
500
600
700
0 10000 20000
Avera
ge d
ista
nce
fro
m s
urf
ace
(m
m)
Soil Pb (mg/kg)
CR1 Octile sample
CR2 Octile sample
CR (AVERAGE)
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 20 40 60 80 100
Avera
ge d
ista
nce
fro
m s
urf
ace
(m
m)
Average extracted Pb (%)
Mobile
Easily dissolved
Bound to Mn oxides
Bound to organics
Bound to poorlycrystalline Fe oxides
Bound to crystalline Feoxides
Residual heavy metals
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface
0
100
200
300
400
500
600
700
0 20 40 60 80 100
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Average extracted Pb (%)
Mobile
Easily dissolved
Bound to Mn oxides
Bound to organics
Bound to poorlycrystalline Fe oxides
Bound to crystalline Feoxides
Residual heavy metals
Soil/Clay
0
100
200
300
400
500
600
700
0 10000 20000
Avera
ge d
ista
nce
fro
m s
urf
ace
(m
m)
Average extracted Pb (mg/kg)
ELB1 ∑Leach (1-7)
ELB2 ∑Leach (1-7)
Soil/Clay
Mixed slag and soil
throughout
0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Soil Pb (mg/kg)
ELB1 Octile sample
ELB2 Octile sample
ELB (AVERAGE)
Soil/Clay
Mixed Slag/Soil
throughout
Pb at sample site ELB
0
100
200
300
400
500
600
700
0 20 40 60 80 100
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Average extracted Pb (%)
Mobile
Easily dissolved
Bound to Mn oxides
Bound to organics
Bound to poorlycrystalline Fe oxides
Bound to crystalline Feoxides
Residual heavy metals
Soil/Clay
0
100
200
300
400
500
600
700
0 10000 20000
Avera
ge d
ista
nce
fro
m s
urf
ace
(m
m)
Average extracted Pb (mg/kg)
ELB1 ∑Leach (1-7)
ELB2 ∑Leach (1-7)
Soil/Clay
Mixed slag and soil
throughout
0
100
200
300
400
500
600
700
0 10000 20000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Soil Pb (mg/kg)
ELB1 Octile sample
ELB2 Octile sample
ELB (AVERAGE)
Soil/Clay
Mixed Slag/Soil
throughout
Pb at sample site ELB
Sampling
Locality
Mobile
(%)
Mobile + Easily
Dissolved (%)
TN 16.1 36.1
CR 7.8 27.0
ELB 0.1 8.4
Percentage of total Pb remaining in the soil column
available to be easily transported into the
environment
0
100
200
300
400
500
600
700
0 30000 60000 90000
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Soil Zn (mg/kg)
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface 0
100
200
300
400
500
600
700
0 20 40 60 80 100
Ave
rage
dis
tan
ce
fro
m s
urf
ace
(m
m)
Extracted Zn (%)
Mobile
Easily dissolved
Bound to Mn oxides
Bound to organics
Bound to poorlycrystalline Fe oxides
Bound to crystallineFe oxides
Residual heavymetals
Soil/Clay
Mixed Slag/Soil
Mostly Slag
Some soil near surface
Zn at sample site TN
Outcomes from leach testing
The level of mobile and easily extractable Pb (and associated elements) in the smallest size fractions is high;
• Provides a partial explanation (along with surface area) for the high levels of bioaccessibility in the smallest slag fractions;
• Evidence of redistribution and attachment of Pb to other phases as an indicator of metal migration which has already occurred;
• Saline environment seems to have ensured high levels of Pb mobilisation;
• Overall results suggest that around 30% of the available Pb in the slags may migrate over time;
• Elements like Zn held as part of glassy slag are likely to continue to remain relatively immobile.
Conclusions
• Given the work to date the hypothesis that the smelter slag is benign appears to be incorrect
• Mineralogical mapping of the slag materials shows clear evidence that most of the Pb in the slag is not contained within the siliceous glassy matrix but is liberated or accessible
• Liberation allows oxidation and leaching to more easily occur
• Evidence is present that migration of some of the Pb has already occurred and contaminants seem to be leaching from the slag into the underlying stratum
Possible Future Work
• Examine potential leaching rate from existing slag
deposits with different infiltrating fluids
• Look at potential for insitu stabilisation of heavy
metals using phosphate solutions.
• Determine penetration of Pb (and other
contaminants) deep into the subsurface below
existing slag layers
• Look at mobility of lead (and other contaminants )
in sub-surface layers
Policy Implications
• Slag contaminants are likely to continue leaching into the surrounding environment
• In-situ maintenance will be complex and ongoing
• Slag deposits occur on private as well as public property
• Determination of who is responsible for clean-up and rehabilitation is likely to be contentious.
Leach Total = 1.02±0.03[ICP(2012)]R² = 0.97
∑Leach(1-7) = 1.00±0.02[ICP(2012)]R² = 0.99
0
5000
10000
15000
20000
0 5000 10000 15000 20000
ICP
-AE
S (
2014/1
5)
(Pb
) (
pp
m)
ICP-AES-2012 (Pb)(ppm)
Leach Total
∑Leach(1-7)
Pb
Leach Total = 0.97±0.02[ICP(2012)]R² = 0.98
∑Leach(1-7) = 0.97±0.02[ICP(2012)]R² = 0.99
0
30000
60000
90000
0 30000 60000 90000
ICP
-AE
S (
20
14
/15)
(Zn
) (p
pm
)
ICP-AES-2012 (Zn)ppm
Leach Total
∑Leach(1-7)
Zn
Leach Total = 0.94±0.04[ICP(2012)]R² = 0.91
∑Leach(1-7) = 0.97±0.03[ICP(2012)]R² = 0.97
0
2000
4000
6000
0 2000 4000 6000
ICP
-AE
S (
20
14
/15)
(Cu
) (p
pm
)
ICP-AES-2012 (Cu)(ppm)
Leach Total
∑Leach(1-7)
Cu