Metal Sorption Properties
1
Metal Sorption Properties The binding behavior of Zn, Cu, and Pb relates to the surface complexation constant, K int . Dzombak and Morel, 1990 Assessment of Zinc, Copper, and Lead in the Streams and Streambed Sediments of the Lefthand Creek Watershed, Northwestern Boulder County, Colorado A.R. Wood, J.N. Ryan, R. Cholas, L. Harrington, L. Isenhart, and N. Turner Department of Civil, Environmental, and Architectural Engineering University of Colorado at Boulder Many thanks to all of the individuals who assisted with this research, and to the organizations who provided resources and funding: – Colorado Department of Public Health and Environment – Environmental Protection Agency – Honeywell, International – University of Colorado Laboratory for Environmental and Geological Sciences – Ohana Scholarship Fund – Research Experience for Undergraduates – Undergraduate Research Opportunity Program – University of Colorado Outreach Program – University Government of Graduate Students Conclusions This study shows that tracer tests and synoptic sampling are effective methods for the identification of metal sources and the quantification of metal loads in streams impacted by acid mine drainage. The zinc, copper, and lead data presented here reflected the known solubility properties of these metals, indicating that metal speciation in the Lefthand Creek watershed relates to instream pH. Stream bed sediment metal concentrations exhibited a spatial lag downstream of instream metal spikes. This suggests that bed sediment metal concentration increases are the result of metal sorption onto sediment particles and/or the settling of colloidal metal species onto the bed. Zn Cu Pb Log K int 0.99 2.89 4.65 Research Goal and Hypothesis Goal: Identify and quantify sources of metal loading to Lefthand, James, and Little James Creeks. Hypothesis: Metal inputs from both surface and subsurface flows can be identified and quantified with metal loading tracer tests and synoptic sampling. Analysis of stream bed sediment metal concentrations further defines metal sources. Study Area An active mining past left a legacy of hundreds of abandoned or inactive hardrock mining and milling sites in the Lefthand Creek watershed. Some of these sites leach acidity and toxic metals to surrounding streams, threatening aquatic life and downstream water consumers. Local stakeholders and state and federal agencies desired an understanding of toxic metal sources, transport, and fate to better prioritize contaminated sites and develop efficient reclamation strategies. Methods Sampling was conducted on approximately 300 sites along the three major streams in the watershed, using a conservative LiCl tracer to determine stream flow and synoptic sampling to collect stream water metal concentrations (Kimball, 1997). Metal loads were calculated as the products of stream flows and metal concentrations. An HCl-H 2 O 2 partial digestion of the sub-62 μm size fraction of stream bed sediments was analyzed at 55 sites following the methods of Church (1993). 0.0 0.5 1.0 1.5 2.0 2.5 3.0 stream flow (L s -1 ) 0 100 200 300 400 500 Little Jam es C reek tributaries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Zn concentration ( g L -1 ) 0 200 400 600 16800 16900 total Zn,Little Jam es C reek dissolved Zn,Little Jam es C reek total Zn,tributaries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 C u concentration ( g L -1 ) 0 25 50 75 100 250 300 total C u,Little Jam es C reek dissolved C u,Little Jam es C reek total C u,tributaries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Pb concentration ( g L -1 ) 0 10 20 30 40 50 60 70 total Pb,Little Jam es C reek dissovled Pb,Little Jam es C reek total Pb,tributaries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 pH 3 4 5 6 7 8 Lefthand C reek tributaries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 C u load (kg day -1 ) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 total C u,Little Jam es C reek dissolved C u,Little Jam es C reek total C u,tributaries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Pb load (kg day -1 ) 0.0 0.2 0.4 0.6 0.8 1.0 total Pb,Little Jam es C reek dissolved Pb,Little Jam es C reek total Pb,tributaries Little Jam es C reek distance (km ) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 sedim entPb (m ol/kg) 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 Little Jam es C reek tributaries Liittle Jam es C reek distance (km ) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 sedim entZn (m ol/kg) 0.000 0.005 0.010 0.015 0.020 0.025 LIttle Jam es C reek tributaries Liittle Jam es C reek distance (km ) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 sedim entC u (m ol/kg) 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 Little Jam es C reek tributaries 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Zn load (kg day -1 ) 0 2 4 6 8 10 12 14 total Zn,Little Jam es C reek dissolved Zn,Little Jam es C reek total Zn,tributaries Balarat Road unnamed gully, south waste rock pile, north Balarat Creek mine waste pile, north unnamed tributary, south “streamside tailings” “Bueno Mtn Gully” waterfal l County Road 102J Argo mine Burlington mine Emmett adit “Argo mine gully” Balarat Road unnamed gully, south waste rock pile, north Balarat Creek mine waste pile, north unnamed tributary, south “streamside tailings” “Bueno Mtn Gully” waterfal l County Road 102J Argo mine Burlington mine Emmett adit “Argo mine gully” Balarat Road unnamed gully, south waste rock pile, north Balarat Creek mine waste pile, north unnamed tributary, south “streamside tailings” “Bueno Mtn Gully” waterfal l County Road 102J Argo mine Burlington mine Emmett adit “Argo mine gully” 0 5 10 15 20 25 30 35 40 0 10 20 30 colloidal m etal concentration (ppb) dissolved m etal concentration (ppb) zinc copper lead
description
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Transcript of Metal Sorption Properties
Metal Sorption PropertiesThe binding behavior of Zn, Cu, and Pb relates
to the surface complexation constant, Kint.
Dzombak and Morel, 1990
Assessment of Zinc, Copper, and Lead in the Streams and Streambed Sediments of the Lefthand Creek Watershed, Northwestern Boulder County, Colorado
A.R. Wood, J.N. Ryan, R. Cholas, L. Harrington, L. Isenhart, and N. TurnerDepartment of Civil, Environmental, and Architectural Engineering
University of Colorado at Boulder
Many thanks to all of the individuals who assisted with this research, and to the organizations who provided resources and funding:
– Colorado Department of Public Health and Environment– Environmental Protection Agency– Honeywell, International– University of Colorado Laboratory for Environmental and Geological Sciences– Ohana Scholarship Fund– Research Experience for Undergraduates – Undergraduate Research Opportunity Program – University of Colorado Outreach Program– University Government of Graduate Students
ConclusionsThis study shows that tracer tests and synoptic sampling are effective methods for the identification of metal
sources and the quantification of metal loads in streams impacted by acid mine drainage. The zinc, copper, and lead data presented here reflected the known solubility properties of these metals, indicating
that metal speciation in the Lefthand Creek watershed relates to instream pH.Stream bed sediment metal concentrations exhibited a spatial lag downstream of instream metal spikes.
This suggests that bed sediment metal concentration increases are the result of metal sorption onto sediment particles and/or the settling of colloidal metal species onto the bed.
Zn Cu PbLog Kint 0.99 2.89 4.65
Research Goal and Hypothesis
Goal: Identify and quantify sources of metal loading to Lefthand, James, and Little James Creeks.
Hypothesis: Metal inputs from both surface and subsurface flows can be identified and quantified with metal loading
tracer tests and synoptic sampling. Analysis of stream bed sediment metal concentrations further defines metal
sources.
Study AreaAn active mining past left a legacy of hundreds of
abandoned or inactive hardrock mining and milling sites in the Lefthand Creek watershed. Some of these sites leach acidity and toxic metals to surrounding streams,
threatening aquatic life and downstream water consumers. Local stakeholders and state and federal
agencies desired an understanding of toxic metal sources, transport, and fate to better prioritize
contaminated sites and develop efficient reclamation strategies.
MethodsSampling was conducted on approximately 300 sites along
the three major streams in the watershed, using a conservative LiCl tracer to determine stream flow and
synoptic sampling to collect stream water metal concentrations (Kimball, 1997). Metal loads were
calculated as the products of stream flows and metal concentrations. An HCl-H2O2 partial digestion of the sub-
62 μm size fraction of stream bed sediments was analyzed at 55 sites following the methods of Church
(1993).
0.0 0.5 1.0 1.5 2.0 2.5 3.0
stre
am
flo
w (
L s
-1)
0
100
200
300
400
500
Little James Creektributaries
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Zn
co
nce
ntr
atio
n ( g
L-1
)
0
200
400
600
16800
16900
total Zn, Little James Creekdissolved Zn, Little James Creektotal Zn, tributaries
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Cu
conc
entr
atio
n (
g L
-1)
0
25
50
75
100
250
300
total Cu, Little James Creekdissolved Cu, Little James Creektotal Cu, tributaries
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Pb
con
cent
ratio
n ( g
L-1
)
0
10
20
30
40
50
60
70
total Pb, Little James Creekdissovled Pb, Little James Creektotal Pb, tributaries
0.0 0.5 1.0 1.5 2.0 2.5 3.0
pH
3
4
5
6
7
8
Lefthand Creektributaries
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Cu
loa
d (
kg d
ay-1
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
total Cu, Little James Creekdissolved Cu, Little James Creektotal Cu, tributaries
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Pb
load
(kg
day
-1)
0.0
0.2
0.4
0.6
0.8
1.0
total Pb, Little James Creekdissolved Pb, Little James Creektotal Pb, tributaries
Little James Creek distance (km)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
sedi
me
nt P
b (m
ol/k
g)
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035 Little James Creektributaries
Liittle James Creek distance (km)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
sedim
en
t Zn
(m
ol/k
g)
0.000
0.005
0.010
0.015
0.020
0.025 LIttle James Creektributaries
Liittle James Creek distance (km)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
sedi
men
t Cu
(mol
/kg)
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07 Little James Creektributaries
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Zn
load
(kg
day
-1)
0
2
4
6
8
10
12
14
total Zn, Little James Creekdissolved Zn, Little James Creektotal Zn, tributaries
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0
5
10
15
20
25
30
35
40
0 10 20 30
colloidal metal concentration (ppb)
dis
solv
ed
me
tal c
on
cen
tra
tion
(p
pb
)
zinc
copper
lead
