SUPPLEMENTAL DATA
The Gellyfish: An In-Situ Equilibrium-Based Sampler for Determining
Multiple Free Metal Ion Concentrations in Marine Ecosystems
Zhao Dong, Christopher G. Lewis, Robert M. Burgess, James P. Shine
Table of Contents
Page
Table S1. Quality assurance information for lab and field metal analysis
2
Figure S1. Gellyfish extraction time experiment with Ni
3
Figure S2. Picture of a Gellyfish sampler, with and without membrane filters
4
Figure S3. Multi-metal Gellyfish equilibration time experiment
5
Figure S4. Single-metal Gellyfish calibration experiments
6
Figure S5. Modeled total metal concentrations from blank Gellyfish versus spiked
total metals in single-metal calibration experiments
7
Figure S6. Equilibration of new versus once-used Gellyfish samplers
8
Figure S7. Temporal profiles of total dissolved Cu, Zn, Pb, Ni and Cd
concentrations at the five sampling locations in Boston Harbor
9
Figure S8. Temporal profiles of pH, salinity and DOC and the fiving field sampling
locations
10
Appendix I. Multi-metal Gellyfish speciation and equations in GELLYMOD
11
Appendix II. Ionic strength correction
16
1
Table S1. Quality assurance (QA) information for metal analysis of both the lab and field samples.
Type
QA
Cu
Zn
Pb
NIST recovery (%)
101.4 ± 14.3 107.3 ± 13.6
96.9 ± 8.6
Lab
Detection limit (μg/L)
0.13
0.58
0.014
Field
Ni
106.7 ± 8.8
0.35
Cd
104.0 ± 1.4
0.0013
NIST recovery (%)
104.3 ± 9.0
108.1 ± 7.8
95.5 ± 7.3
97.3 ± 5.1
101.9 ± 7.0
SLEW-3 recovery (%)
88.8
142.2
126.5
80.2
76.9
Extraction detection limit (μg/L)
0.044
0.061
0.012
0.26
0.003
Extraction blanks (μg/L)
Overall blank (filtration+extraction) (μg/L)
0.08 ± 0.01
0.14 ± 0.07
0.12 ± 0.02
0.12 ± 0.02
0.01 ± 0.004
0.04 ± 0.01
0.64 ± 0.08
0.67 ± 0.01
0.006 ± 0.001
0.01 ± 0.002
2
Ni2+ = 3.47E-7 M
Ni2+ = 1.71E-10 M
% Recovery
120
100
80
60
40
20
0
24
48
Time (h)
74
Figure S1. Extraction time experiment with Ni. Triplicates of Gellyfish samplers were
extracted in 5% ultrapure HNO3 for 24, 48, and 74 hours, respectively, at two different
Ni2+ concentrations; 1.71E-10 M and 3.47E-7 M. Differences in percent recoveries
among the three extraction times were statistically insignificant, and no significant
difference was found between percent recoveries and 100 percent.
3
Figure S2. Appearance and dimensions of a Gellyfish sampler, with (right) or without
(left) membrane filters and filter holder.
4
(B) Zn
(C) Pb
30
Pb-Gf (ppb)
Zn-Gf (ppb)
35
30
25
20
15
10
5
0
25
20
15
10
Ct =
23.6×(1-e-0.11*t),
t90 = 20.9 h
Ct = 17.0×(1-e-0.67*t), t90 = 3.4 h
5
0
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
20
40
60
Time (hour)
80
100
0
20
40
60
80
Time (hour)
100
(D) Ni
8
7
6
5
4
3
2
1
0
1
2
Ct = 4.7×(1-e-0.94*t), t90 = 2.4 h
3
0
20
40
60
Time (hour)
80
(E) Cd
10
Cd-Gf (ppb)
0
Ni-Gf (ppb)
Cu-Gf (ppb)
(A) Cu
8
6
4
60
50
40
30
20
2
Ct = 9.1×(1-e-0.04*t), t90 = 57.6 h
Ct = 50.0×(1-e-0.13*t), t90 = 17.7 h
10
0
0
0
20
40
60
Time (hour)
80
100
0
20
40
60
Time (hour)
80
100
Figure S3. Multi-metal equilibration time experiment at (A) Cu2+ = 1.02E-10 M; (B) Zn2+ = 1.39E-8 M; (C) Pb2+ = 8.48E-9 M; (D) Ni2+ =
4.63E-10 M; and (E) Cd2+ = 1.51E-8 M. Triplicates of Gellyfish were retrieved at 0, 1, 3, 7, 12, 18, 25, 32, 40, 52, 64, and 88 hours after
deployment. Error bars represent one standard deviation from the mean of triplicate measurements.
5
100
(A) Cu
200
150
logKCuOH-Id = 10.98
95% CI = (10.76, 11.13)
50
0
10
20
30
2+
Cu (nM)
40
2.5
200
150
100
logKZnCl-Id = 9.13
95% CI = (8.96, 9.25)
50
0
50
0
200
400
600
Zn2+ (nM)
12
300
10
Cd-Gf (μM)
250
200
150
logKNiCl-Id = 9.94
95% CI = (9.90, 9.98)
25
26
800
200
Ni2+ (nM)
logKPbCl-Id = 6.70
95% CI = (6.60, 6.78)
300
5
Pb2+ (nM)
10
8
6
4
logKCdCl-Id = 7.24
95% CI = (7.22, 7.25)
0
400
0
(E) Cd
0
100
1.0
1000
2
0
0
1.5
0.0
350
50
2.0
0.5
0
(D) Ni
100
(C) Pb
3.0
Pb-Gf (μM)
250
Zn-Gf (μM)
300
300
250
100
(B) Zn
350
350
Ni-Gf (μM)
Cu-Gf (μM)
400
5
10
15
Cd2+ (nM)
20
25
Figure S4. Gellyfish calibration experiment: measured (dots) versus modeled (lines) Gellyfish uptake of (A) Cu, (B) Zn, (C) Pb, (D) Ni and (E)
Cd. Error bars represent standard deviations of duplicate samples.
6
15
(A) Cu
(C) Pb
(B) Zn
4.0
Modeled
Total Cu
from 3.0
Blanks
(×10-4 M) 2.0
15.0
Modeled
Total Zn 12.0
from
Blanks
9.0
(×10-5 M)
6.0
1.0
y = 1.02x + 0.03
R² = 0.96
1.0
2.0
3.0
Spiked Total Cu
y = 1.14x - 0.10
R² = 0.97
3.0
0.0
4.0
(×10-4
y = 1.16x + 0.31
R² = 0.98
3.0
0.0
0.0
15.0
Modeled
Total Pb 12.0
from
Blanks 9.0
(×10-6 M)
6.0
0.0
0.0
3.0
6.0
M)
9.0
12.0 15.0
0.0
3.0
Spiked Total Zn (×10-5 M)
6.0
9.0
12.0 15.0
Spiked Total Pb (×10-6 M)
(E) Cd
(D) Ni
4.0
Modeled
Total Ni
3.0
from
Blanks
(×10-4 M) 2.0
4.0
Modeled
Total Cd
3.0
from
Blanks
(×10-6 M) 2.0
1.0
1.0
y = 0.70x + 0.12
R² = 0.95
0.0
0.0
1.0
2.0
3.0
y = 1.02x + 0.05
R² = 0.92
0.0
4.0
0.0
Spiked Total Ni (×10-4 M)
1.0
2.0
3.0
4.0
Spiked Total Cd (×10-6 M)
Figure S5. Modeled total metals from blank Gellyfish versus spiked total metals for (A) Cu, (B) Zn, (C) Pb, (D) Ni and (E) Cd. Data were
obtained from single-metal calibration experiments.
7
120
Cu-Id (µM)
100
80
60
40
New: Ct=86.2*(1-e-0.083t), t90= 27.7h
Reused: Ct=86.5*(1-e-0.11t), t90=20.9
20
0
0
10
20
30
Time (h)
40
50
60
Figure S6. Equilibration of new and once-used Gellyfish with Cu. Solid circles and
line represent actual measured data and empirically fit curve for the new Gellyfish,
open circles and dashed line represent Gellyfish that were used once before. Equations
and calculated equilibration time are shown under the curves. Paired t-test suggested
no significant difference between Cu-Id within the new and used samplers (p=0.42).
8
Figure S7. Temporal profiles of total dissolved metal concentrations (in nM) at the five sampling locations in Boston Harbor for Cu, Zn, Pb, Ni
and Cd. Each data point represents single or average of duplicate measurements.
9
Figure S8. Temporal profiles of (A) pH, (B) salinity and (C) dissolved organic carbon
(DOC) during field deployment at the five sampling locations in Boston Harbor.
10
Appendix I. Multi-metal Gellyfish Equilibrium: Equations and Speciation in
GELLYMOD
Among all the trace metals that might be present in marine aquatic systems, we
assume that complexation by IDA only occurs significantly for Cu, Zn, Pb, Ni and Cd,
due to their higher abundances than other trace metals. We also assume that the major
cationic complex for Cu, Zn, Pb, Ni and Cd are CuOH+, ZnCl+, PbCl+, NiCl+ and
CdCl+, respectively.
At equilibrium:
[Id]𝑡𝑜𝑡𝑎𝑙 = [Id]𝑓𝑟𝑒𝑒 + [Cu − Id] + 2[Cu − Id2 ] + [CuOH − Id] + [Zn − Id]
+ 2[Zn − Id2 ] + [ZnCl − Id] + [Pb − Id] + [PbCl − Id] + [Ni − Id]
+ 2[Ni − Id2 ] + [NiCl − Id] + [Cd − Id] + 2[Cd − Id2 ] + [CdCl − Id]
+ [H − Id] + [H2 − Id] + [Na − Id] + [Ca − Id] + [K − Id]
+ [Mg − Id]
(1)
where [Id]total is the total IDA concentration in solution; [Id]free is the free IDA
concentration; [Cu-Id], [Cu-Id2], [Zn-Id], [Zn-Id2], [Pb-Id], [Ni-Id], [Ni-Id2], [Cd-Id]
and [Cd-Id2] are the concentrations of metal-IDA species (note that no data was
available for the formation of Pb-Id2 species); [CuOH-Id], [ZnCl-Id], [PbCl-Id],
[NiCl-Id], [CdCl-Id] are the concentrations of the binding products for cationic metal
complexes and IDA; [H-Id] and [H2-Id] are hydrogen complexes with IDA; [Na-Id],
[Ca-Id], [K-Id] and [Mg-Id] are the concentrations of other major cations bound to
IDA.
According to equilibrium thermodynamics, for the complexation of Cu with IDA,
there is:
Cu2+ + Id → Cu − Id; K 𝐶𝑢−𝐼𝑑
(2)
where KCu-Id is the equilibrium constant, or stability constant for complex Cu-Id, and
is defined as:
11
K 𝐶𝑢−𝐼𝑑 =
[Cu − Id]
[Cu2+ ][Id]𝑓𝑟𝑒𝑒
(3)
By rearranging (3), we get:
[Cu − Id]
K 𝐶𝑢−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒
(4)
[Zn2+ ] =
[Zn − Id]
K 𝑍𝑛−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒
(5)
[Pb2+ ] =
[Pb − Id]
K 𝑃𝑏−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒
(6)
[Ni2+ ] =
[Ni − Id]
K 𝑁𝑖−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒
(7)
[Cd2+ ] =
[Cd − Id]
K 𝐶𝑑−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒
(8)
[Cu − Id2 ]
K 𝐶𝑢−𝐼𝑑2 [Id]2𝑓𝑟𝑒𝑒
(9)
[Zn2+ ] =
[Zn − Id2 ]
K 𝑍𝑛−𝐼𝑑2 [Id]2𝑓𝑟𝑒𝑒
(10)
[Ni2+ ] =
[Ni − Id2 ]
K 𝑁𝑖−𝐼𝑑2 [Id]2𝑓𝑟𝑒𝑒
(11)
[Cd2+ ] =
[Cd − Id2 ]
K 𝐶𝑑−𝐼𝑑2 [Id]2𝑓𝑟𝑒𝑒
(12)
[Cu2+ ] =
Similarly, we can get:
and
[Cu2+ ] =
For the major caions:
[H − Id] = K 𝐻−𝐼𝑑 [H + ][Id]𝑓𝑟𝑒𝑒
(13)
[H2 − Id] = K 𝐻2 −𝐼𝑑 [H 2+ ]2 [Id]𝑓𝑟𝑒𝑒
(14)
[Na − Id] = K 𝑁𝑎−𝐼𝑑 [Na+ ][Id]𝑓𝑟𝑒𝑒
(15)
[Ca − Id] = K 𝐶𝑎−𝐼𝑑 [Ca2+ ][Id]𝑓𝑟𝑒𝑒
(16)
12
[K − Id] = K 𝐾−𝐼𝑑 [K + ][Id]𝑓𝑟𝑒𝑒
(17)
[Mg − Id] = K 𝑀𝑔−𝐼𝑑 [Mg 2+ ][Id]𝑓𝑟𝑒𝑒
(18)
We assume [OH-]total ≈ [OH-]free and [Cl-]total ≈ [Cl-]free, and for the cationic
metal complexes, there are:
[Cu2+ ] =
[CuOH + ]
K 𝐶𝑢𝑂𝐻 [OH − ]𝑡𝑜𝑡𝑎𝑙
[CuOH + ] =
(19)
[CuOH − Id]
K 𝐶𝑢𝑂𝐻−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒
(20)
in which KCuOH is the stability constant of CuOH+. Combining (19) and (20), we get:
[Cu2+ ] =
[CuOH − Id]
K 𝐶𝑢𝑂𝐻 ∙ 𝐾𝐶𝑢𝑂𝐻−𝐼𝑑 [OH − ]𝑡𝑜𝑡𝑎𝑙 [Id]𝑓𝑟𝑒𝑒
(21)
Similarly, for Zn, Pb, Ni, and Cd:
[Zn2+ ] =
[ZnCl − Id]
K 𝑍𝑛𝐶𝑙 ∙ 𝐾𝑍𝑛𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id]𝑓𝑟𝑒𝑒
(22)
[Pb2+ ] =
[PbCl − Id]
K 𝑃𝑏𝐶𝑙 ∙ 𝐾𝑃𝑏𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id]𝑓𝑟𝑒𝑒
(23)
[Ni2+ ] =
[NiCl − Id]
K 𝑁𝑖𝐶𝑙 ∙ 𝐾𝑁𝑖𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id]𝑓𝑟𝑒𝑒
(24)
[Cd2+ ] =
[CdCl − Id]
K 𝐶𝑑𝐶𝑙 ∙ 𝐾𝐶𝑑𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id]𝑓𝑟𝑒𝑒
(25)
Considering what we measured in Gellyfish for each metal M ([M-Gf]) is a sum
of [M-Id], [M-Id2] and [ML-Id] (L is OH- or Cl-), we have:
[Cu − Gf] = [Cu − Id] + [Cu − Id2 ] + [CuOH − Id]
(26)
Rearranging (4), (9), (21) and combining them with (26), we get:
[Cu − Gf] = K 𝐶𝑢−𝐼𝑑 [Cu2+ ][Id]𝑓𝑟𝑒𝑒 + K 𝐶𝑢−𝐼𝑑2 [Cu2+ ][Id] 2𝑓𝑟𝑒𝑒 + K 𝐶𝑢𝑂𝐻
∙ K 𝐶𝑢𝑂𝐻−𝐼𝑑 [Cu2+ ][OH − ]𝑡𝑜𝑡𝑎𝑙 [Id] 𝑓𝑟𝑒𝑒
(27)
Rearranging (27) reveals the relationship between [Cu2+] and [Cu-Gf]:
13
[Cu2+ ]
=
K 𝐶𝑢−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒 + K 𝐶𝑢−𝐼𝑑2 [Id]
[Cu − Gf]
+ K 𝐶𝑢𝑂𝐻 ∙ K 𝐶𝑢𝑂𝐻−𝐼𝑑 [OH − ]𝑡𝑜𝑡𝑎𝑙 [Id] 𝑓𝑟𝑒𝑒
2
𝑓𝑟𝑒𝑒
(28)
Similarly, from (5), (10) and (22) we can derive:
[Zn2+ ]
=
[Zn − Gf]
K 𝑍𝑛−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒 + K 𝑍𝑛−𝐼𝑑2 [Id]
+ K 𝑍𝑛𝐶𝑙 ∙ K 𝑍𝑛𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id] 𝑓𝑟𝑒𝑒
2
𝑓𝑟𝑒𝑒
(29)
From (6) and (23):
[Pb2+ ] =
[Pb − Gf]
K 𝑃𝑏−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒 + K 𝑃𝑏𝐶𝑙 ∙ K 𝑃𝑏𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id] 𝑓𝑟𝑒𝑒
(30)
From (7), (11) and (24):
[Ni2+ ]
=
[Ni − Gf]
K 𝑁𝑖−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒 + K 𝑁𝑖−𝐼𝑑2 [Id]
+ K 𝑁𝑖𝐶𝑙 ∙ K 𝑁𝑖𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id] 𝑓𝑟𝑒𝑒
2
𝑓𝑟𝑒𝑒
(31)
From (8), (12) and (25):
[Cd2+ ]
=
[Cd − Gf]
K 𝐶𝑑−𝐼𝑑 [Id]𝑓𝑟𝑒𝑒 + K 𝐶𝑑−𝐼𝑑2 [Id] 2𝑓𝑟𝑒𝑒 + K 𝐶𝑑𝐶𝑙 ∙ K 𝐶𝑑𝐶𝑙−𝐼𝑑 [Cl− ]𝑡𝑜𝑡𝑎𝑙 [Id] 𝑓𝑟𝑒𝑒
(32)
When [Id]free is small, equation (1) can be approximately written as:
[Id]𝑡𝑜𝑡𝑎𝑙 = [Id]𝑓𝑟𝑒𝑒 + [Cu − Gf] + [Zn − Gf] + [Pb − Gf] + [Ni − Gf] + [Cd − Gf]
+ [H − Id] + [H2 − Id] + [Na − Id] + [Ca − Id] + [K − Id]
+ [Mg − Id]
(33)
Plugging (13)-(18) into (33), we can solve for [Id]free as follows:
14
[Id]𝑓𝑟𝑒𝑒 = ([Id]𝑡𝑜𝑡𝑎𝑙 − [Cu − Gf] − [Zn − Gf] − [Pb − Gf] − [Ni − Gf] − [Cd − Gf])
/ (1 + K 𝐻−𝐼𝑑 [H + ] + K 𝐻2 −𝐼𝑑 [H + ]2 + K 𝑁𝑎−𝐼𝑑 [Na+ ] + K 𝐶𝑎−𝐼𝑑 [Ca2+ ]
+ K 𝐾−𝐼𝑑 [K + ] + K 𝑀𝑔−𝐼𝑑 [Mg 2+ ])
(34)
in which [Id]total is at a fixed concentration of 280 μM; [Cu-Gf], [Zn-Gf], [Pb-Gf],
[Ni-Gf] and [Cd-Gf] are measured total metal concentrations in the Gellyfish, after
accounting for dilution and extraction; [H+] is calculated from measured pH; [Na+],
[Ca2+], [K+], and [Mg2+] are estimated from salinity based on the ionic composition of
Aquil; KH-Id, K 𝐻2 −𝐼𝑑 , KNa-Id, KCa-Id, KK-Id, and KMg-Id are apparent stability constants,
ionic strength-corrected from literature reported conditional stability constants at I = 0
[1] based on salinity. The details of ionic strength corrections are described in
Appendix II.
We can now calculate the free metal ion concentrations of Cu, Zn, Pb, Ni and Cd
by knowing [Id]free and all the K values in equation (28) through (32). Specifically,
KM-Id, K 𝑀−𝐼𝑑2 , and KML are also corrected from literature reported values [1] based on
ionic strength, and KML-Id is the apparent stability constant for the binding of major
cationic metal complexes to IDA estimated in our study, which is reported in Table 1
as conditional stability constants at I = 0.1 M, and corrected for ionic strength when
used in the calculations.
An important assumption for this method is that the free ion concentrations at
equilibrium (i.e. [Cu2+], [Zn2+], [Pb2+], [Ni2+] and [Cd2+]) are not changed by the
deployment of the Gellyfish samplers. In other words, we assume that the free ion
concentrations calculated here, which are the equilibrium concentrations after the
deployment of the Gellyfish, are the same as the free ion concentrations before the
deployment. Compared to the amount of IDA in each Gellyfish (1.05 × 10-7 mol), the
amount of total metals in a typical field deployment can be considered as infinite,
15
therefore this should be a valid assumption.
Appendix II. Ionic Strength Correction
An ionic strength (I) of the solution was calculated from salinity, based on the
ionic composition of Aquil:
n
1
I = ∑ zi2 c𝑖
2
(35)
i
in which ci is the concentration of major ion i (i includes H+, OH-, Na+, K+, Ca2+,
2−
2−
Mg2+, Cl-, Br-, BO3−
and HCO−
3 SO4 , CO3
3 ); zi is the valency of ion i.
Since I is usually above 0.1 M in seawater, we use the Davies equation here to
calculate the activity coefficients (γ). All neutral complexes were assumed to have γ0
= 1.13, while for monovalent and bivalent ions, the activity coefficient γmono and γbi,
respectively, are calculated as [1]:
γmono = e
γbi = e
−1.17∗12 ∗[
−1.17∗22 ∗[
√I
−0.3∗I]
1+√I
√I
−0.3∗I]
1+√I
(36)
(37)
Therefore, for the formation of Mg-Id, Ca-Id, Cu-Id, Zn-Id, Pb-Id, Ni-Id and
Cd-Id, the apparent stability constant Kapp can be calculated from the literature
reported stability constant (K) at I = 0:
K 𝑎𝑝𝑝 = 𝐾 ∗
𝛾𝑏𝑖 ∗ 𝛾𝑏𝑖
𝛾0
(38)
For H-Id, Na-Id, CuOH+, ZnCl-, PbCl-, NiCl-, CdCl-, CuOH-Id, ZnCl-Id, PbCl-Id,
NiCl-Id and CdCl-Id:
K 𝑎𝑝𝑝 = 𝐾 ∗
𝛾𝑚𝑜𝑛𝑜 ∗ 𝛾𝑏𝑖
𝛾𝑚𝑜𝑛𝑜
For Cu-Id2, Zn-Id2, Ni-Id2, and Cd-Id2 species:
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(39)
K 𝑎𝑝𝑝 = 𝐾 ∗
𝛾𝑏𝑖 ∗ 𝛾𝑏𝑖
𝛾𝑏𝑖
(40)
For H2-Id:
K 𝑎𝑝𝑝
2
𝛾𝑚𝑜𝑛𝑜
∗ 𝛾𝑏𝑖
=𝐾∗
𝛾0
(41)
3
𝛾𝑚𝑜𝑛𝑜
∗ 𝛾𝑏𝑖
𝛾𝑚𝑜𝑛𝑜
(42)
For H3-Id:
K 𝑎𝑝𝑝 = 𝐾 ∗
All equations in Appendix I used the Kapp values calculated above.
Reference
1.
Morel FMM, Hering JG. 1993. Principles and Applications of Aquatic
Chemistry. Wiley-Interscience, New York.
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