S1

Supporting information for “Comparison of analytical techniques for

dynamic trace metal speciation in natural freshwaters” ES051245k

Laura Sigg, Frank Black, Jacques Buffle, Jun Cao, Rob Cleven, William Davison,

Josep Galceran, Peggy Gunkel, Erwin Kalis, David Kistler, Michel Martin, Stéphane

Noël, Yusuf Nur, Niksa Odzak, Jaume Puy, Willem van Riemsdijk, Erwin

Temminghoff, Mary-Lou Tercier-Waeber, Stefanie Toepperwien, Raewyn M. Town,

Emily Unsworth, Kent W. Warnken, Liping Weng, Hanbin Xue, Hao Zhang

Contents pp.

Experimental part 2 -12

Table S1. Parameters for calculation of permeability criterion for HFPLM and

FTPLM 9

Table S2: Blank values of the methods 13

Table S3: Total dissolved concentrations measured in samples of Lake Greifen and of

Furtbach by four laboratories using ICP-MS 14

Fig. S1. Total dissolved concentrations of Cu, Zn, Cd and Pb as measured by four laboratories 15

Table S4: Total unfiltered and dissolved concentrations measured in samples of River

Wyre by four laboratories using ICP-MS. 16-19

Table S5: Concentrations measured by DGT on three successive days in River Wyre

20

Table S6: Single measurements obtained by GIME-VIA-Field over two days in River

Wyre 21-22

References 23-24

S2

Experimental part

Major ion and DOC measurements

Major cation concentrations in Lake Greifen and Furtbach were measured by ICP-

OES (Spectro Ciros). Major cation concentrations in River Wyre were measured by

flame photometry (Model 410 flame photometer, Corning, Essex, UK) for Na and K

and flame atomic absorption (AAnalyst atomic absorption spectrometer, Perkin

Elmer, Buckinghamshire, UK) for Ca and Mg. Major anions were measured by ion

chromatography in Lake Greifen and Furtbach (Metrohm IC 761) and in River Wyre

(Dionex 4000I ion chromatography system with a AS14 4x250 mm column, Dionex

corporation). Dissolved organic carbon was measured by oxidative combustion in

River Wyre (Shimadzu TOC-VCPH analyser) and in Lake Greifen and in Furtbach

(High TOCII, Gerber Instruments). Alkalinity was determined by titration with

hydrochloric acid.

DGT sampling and handling

DGT Lancaster. An acrylamide diffusive gel was prepared as using 40% w/v

acrylamide solution (Electran, BDH) 3.75 cm3, 2% gel cross-linker (DGT Research

Ltd, Lancaster, UK.) 1.5 cm3, purified water (18 MΩ, Milli-Q, Millipore SA,

Molshelm, France) 4.75cm3, a 10% solution of ammonium persulphate (Electran,

BDH) 0.070 cm3 and N,N,N’N’-tetramethylethylenediamine (TEMED, Electran,

BDH) 0.025 cm3, to give a final composition of 15% monomer and 0.3% cross-linker.

After the gel had been set in the oven (45°C for 1 hour) it was soaked in purified

water, to both hydrate the gel and to allow unreacted reagents to diffuse out of the gel

(1). One litre of water was used per sheet of gel and was changed three times, with a

two to three hour soaking period between each change. The pH of the water decreased

S3

between successive washes from pH 10 to 6. The gel was transferred into a 10 mM

NaNO3 solution for overnight conditioning prior to use. The various components of

the DGT plastic units were assembled in a laminar flow hood within a clean room. A

0.14 mm thick filter membrane (Supor-450, PALL Life Sciences, USA) overlay a

layer of diffusive gel (1.2mm thick) and then a layer of Chelex-100 resin (Bio-Rad,

Hercules, CA, USA) embedded in gel. For in-situ deployment, DGT units were held

in a Perspex cube shaped holder with two open sides, which was attached to the

underside of a plastic foam float. After deployment the whole cube was taken out of

the water, rinsed with MQ water, and taken back to the laboratory before the DGT

units were disassembled under clean room conditions. The gel layers were separated

and the resin-gel layer was placed in a 1.5 cm3 plastic tube. 1 cm3 of 1 M nitric acid

(prepared from Suprapure nitric acid) was added, the tube shaken and left overnight to

extract the metal from the Chelex-100. Samples were analysed by ICP-MS (Thermo

X-7, Thermo Elemental, Cheshire, UK) using indium 115 (SpectrosoL standard

solution, BDH) as an internal standard. The metal concentration measured in the

eluent from the resin gel was converted in to a ‘mass of metal bound by the resin-gel’

and then into the concentration of ‘labile metal species’ using established procedures

(2) and were corrected for the blanks (Table S2). The blank value for Mn was 0.002

nmol/gel unit.

DGT Duebendorf. Gels were prepared according to the same procedures as described

above in a clean bench. Diffusive gel (0.8 mm thickness) and resin gel (0.4 mm

thickness) were prepared according to the procedure recommended by (3). After

hydration, the gel sheets were cut into discs (d = 25 mm) and assembled into the

plastic gel holders (made by EAWAG Workshop) according to the procedure

recommended by (4). In Lake Greifen, DGT units were deployed for three days at of

S4

2.5, 5 and 28 m depth. At each depth, 4 DGT units were attached to the rope

(connected to a buoy and a 10-kg weight) using acid-washed reusable plastic strip

(PE) made at EAWAG Workshop. On recovery, DGT holders were rinsed thoroughly

with deionized water and immediately stored in clean zip-lock plastic bags. In stream

Furtbach, DGT units were deployed for three days at a depth of about 20 cm. In River

Wyre, DGT units were deployed on one hand over 75 hours, and on the other hand

over 3 1-day periods.

At each deployment the background concentrations of trace metals were checked by

analysing the resin gel layers from 4 DGT units which were prepared the same way

but not deployed in the water column (blank samples). These concentrations were

used to correct those of the units deployed.

Upon return to the laboratory, the resin gel layers were carefully removed from the

DGT holders and transferred to the 15-ml pre-cleaned PP-Test tubes (Greiner

labortechnik, Cellstar), each containing 2 ml of 2 M HNO3 (Merck, Suprapur). This

procedure was performed under a clean bench, using plastic tools. To elute metals, the

resin gel was kept in the acid for 48 h. The trace metal concentrations were analysed

by inductively coupled plasma – mass spectrometry (ICP-MS, Perkin-Elmer ELAN

5000). The diffusion coefficients used for calculation of the DGT-labile

concentrations are those for free aquo ions, as measured by Hao Zhang, DGT

Research Ltd., Lancaster, UK (personal communication). The calculated DGT-labile

concentrations are corrected for the blanks.

DGT Bilthoven. DGT units were assembled in the lab according to the manufacturers

instructions, subsequently sealed in clean plastic bags impregnated with a few drops

of 0.01 M NaNO3 and transported to the sampling sites. In the field, the DGT units

were attached in a deployment device and immersed in the river water, and time and

S5

tempearture were measured. After one or two days, DGT units were retrieved from

device, washed with Milli-Q water, and kept with a minimum air space in clean

plastic bags. They were then transported in a cool box. Upon retrieval of the DGT

units from the field sites, the river water temperature and pH were again measured

and a water sample was taken for additional analyses. After retrieval of the DGT units

to the laboratory, the Chelex resin layer was placed in 2- cm3 vials and 1.0 cm3 of 1.0

M HNO3 solution was added. The Chelex resin was kept in this solution at least one

night to elute the metal ions from the resin. The solution was then analyzed by

inductively coupled plasma mass spectrometry (ICP-MS - HP4500plus for Cd, Pb and

Zn, and ELEMENT2 for Cu).

In situ / on-site GIME measurements

In situ GIME measurements in lake Greifen were performed using the VIP system.

The system consists on: i) a submersible unit which comprises a voltammetric probe,

an on-line oxygen removal system and a multiparameter probe integrated in a

protective titanium cage, and ii) a telemetry deck unit and an IBM compatible PC

(5,6). The VIA-Field, used for measurements in Furtbach and Wyre is a compact

version of the VIP developed for on site measurements. A detailed description of this

system is given in (www.idronaut.it/research_project/VAMP/pdf/vip.pdf).

The heart of both systems is a gel integrated microelectrode (GIME) which consists of

an 100 interconnected Hg-plated Ir-based microelectrode array covered by a 300 µm

thin layer of agarose gel (7).

Hg deposition on the 5x20 interconnected Ir microdisk arrays was performed

at a constant E of –400 mV in a N2 degassed 5 mM Hg(CH3COO)2, 10-2 M HClO4,

S6

using a deposition time of 7 min (8). The same Hg layers were used over the complete

field work period. An average Hg radius of 5.41 µm was obtained from the Hg

deposition charge Qred (8). In-field trace metal measurements on GIME sensors were

performed using square wave anodic stripping voltammetry (SW-SV). Conditions

used were as follows: pumping time of the sample before each measurement = 8 min

using a flow-rate of 4 ml min-1 which allows 3 times complete renewal of the sample

in the fluidic system (i.e. sampling tube + GOD-module + voltammetric flow-through

cell); equilibration of the agarose gel with the sample = 6 min; SWASV: pre-cleaning

E = final E, pre-cleaning t = 60 sec, equilibrium E = Edep, equilibrium t = 30 s, Ed = -

1200 to -1050 mV; td = 8 to 40 min; final E = +70 to +110 mV, pulse amplitude = 25

mV, step amplitude = 8 mV; frequency = 200 Hz. Deposition times at the electrode

were 25 to 40 min in Lake Greifen, 8 to 10 min in Furtbach and 20 to 30 min in River

Wyre.

Laboratory calibration of the VIP and VIA-Field were performed in N2

degassed 0.1 M NaNO3 suprapure solutions spiked with various concentrations of Cu,

Pb, Cd and Zn the day before the start of the field work. Influence of the deposition

time, in a range of 5 to 30 min, on the peak current intensities of the three metals, as

well as the possible formation of Cu-Zn intermetallic compounds during the pre-

concentration step (9) was also checked.

PLM sampling and handling

Hollow Fiber PLM (HFPLM). An Accurel® ppq3/2 (Akzo) hydrophobic

polypropylene hollow fiber membrane (inner diameter = 600 µm; outer diameter =

800 µm; pore size = 0.2 µm; porosity = 75%; length between 15-25 cm) was used. It

was impregnated with the carrier solution, by slowly running a solution of 0.1 M

S7

1,10-didecyl-1,10-diaza-18-crown-6 and 0.1 M lauric acid in a 1/1 (v/v) mixture of

toluene/phenyl hexane, outside the fiber. The strip solution, in the lumen of the

hollow fiber, was 5.10-4 mol/L CDTA (cyclohexane diamine tetraacetic acid) at pH =

6.. After filling the lumen, the two ends of the fibre were connected together to form

a loop which was attached to a plexiglass frame hung inside the test water body and

largely open to the natural water flow. After deployment the strip solution in the

lumen was collected and analysed by ICPMS. Pre-concentration factors for a

deployment time ≥ 2 hours are typically 1200, 5000 and 100 for Cu2+, Pb2+, and Cd2+

respectively.

Flow-through PLM (FTPLM). A Celgard 2500 (Celanese Plastic, Charlotte, NC)

membrane (membrane thickness 25 µm, active surface area 1.98 cm2 , pore diameter

0.04 µm) was impregnated with the same carrier solution as the HFPLM and was

rinsed with water before being mounted. A new membrane was used for the

successive replicates measurements. The strip solution was a 10-2 M pyrophosphate

solution adjusted to pH 6.0 with HNO3.

Filtered samples from Lake Greifen , Furtbach and River Wyre were pumped at a

constant flow rate of of 0.087 ml/s through the FTPLM system during a

preconcentration time of 30 minutes (River Wyre), or 90 minutes (Lake Greifen and

Furtbach). Under the conditions used, the pre-concentration factors for Cu were

typically 2300 for measurements of lake Greifen and Furtbach stream samples and

350 for measurements of the river Wyre samples. The strip solution was then

collected and the metal concentration in the strip solution was analysed by ICP-MS.

S8

Calculation of permeability criterion for HFPLM and FTPLM

The measured PLM flux is controlled by i) the free metal ion concentration or

ii) the sum of the dynamic complexes, depending on the nature of the rate limiting

step, namely diffusion through the PLM (for (i)) or diffusion through the aqueous

source diffusion layer at the PLM surface (case (ii)). Which situation applies depends

on the permeability criterion (Π) (10, 11) .

Π = (KD.DMC.δso) / (Dso.l.αso) (1)

Where KD =distribution coefficient of the metal between the aqueous and organic

phase, DMC= diffusion coefficient of the metal-complex in the membrane, δso = mean

source diffusion layer thickness, Dso = diffusion coefficient of the free metal ion in

solution, l = membrane thickness, αso = degree of complexation (= ratio of total to free

M ion) in the source solution. These parameters are given in Table S1. αso is not

known in a test medium, but a minimum (αsomin) and a maximum value (αso

max) can

be computed from the experimentally measured preconcentration factor, F (= ratio of

total metal concentrations in the strip and the source solution) and the theoretical

value of F (10, 11) assuming either fully inert complexes or fully labile complexes

respectively. αsomin can also be obtained by computing the maximum free metal ion

concentration in the source solution using a value of F determined experimentally

with standard solutions of fully inert complexes.

For Π<<1, the diffusion through PLM is rate-limiting and free metal ion is measured,

in absence of lipophilic complexes, whereas for Π>>1, diffusion through the source

diffusion layer is rate limiting and the dynamic complexes contribute to the metal

concentration measured in the strip solution.

The values of αsomin were used to compute the upper limit of Π (eq. 1) for both

HFPLM and FTPLM. The value of δso around the HFPLM deployed in situ, could not

S9

be measured, but it was assumed to be in between 20 µm (well-stirred medium) and

100 µm (poor-stirred medium). The upper limits of Π for HFPLM were obtained with

δso = 100 µm and were in the ranges 0.005 – 0.02 for Cu, 0.01 – 0.2 for Pb, and

0.0003 to 0.04 for Cd in all natural waters. Thus the condition Π << 1 was always

fulfilled with HFPLM.

For FTPLM measurements in the river Wyre, the Π values were 0.4 - 0.8 for

Cu. Since Π is close to 1, it can be expected that a fraction of the dynamic complexes

may contribute to the measured flux. On the other hand, for both the lake Greifen and

the Furtbach stream, values of Π for Cu were in the range 0.04 and 0.1, i.e. Π << 1.

Table S1. Parameters for calculation of permeability criterion for HFPLM and

FTPLM

a) Diffusion coefficients and distribution coefficient of metals

Parameter Cu Pb Cd

KD 1200 832 13

DMC cm2 s-1 5.2x10-8 5.2x10-8 5.2x10-8

Dso cm2 s-1 7.8x10-6 9.5x10-6 7.2x10-6

KD = distribution coefficient of the metal between the aqueous and organic phase.

DMC = diffusion coefficient of the metal-complex in the membrane

Dso = diffusion coefficient of the free metal ion in solution

b) Diffusion layer and membrane thickness

HFPLM FTPLM

δso µm 20 – 100 90

l µm 100 25

δso = mean source diffusion layer thickness

S10

l = membrane thickness

DMT : in-situ measurement of free metal ion concentrations

The in-situ measurements with DMT were carried out using cells designed for field

application (field DMT cells). Whereas the lab DMT cell consisted of two chambers

(12), a donor and an acceptor side, the field DMT cell has only one chamber

(acceptor), on two sides separated from the donor (the lake, river, etc.) by a negatively

charged cation exchange membrane (BDH Laboratory Supplies, Poole, UK) (13,14).

The membrane has a matrix of polystyrene and divinylbenzene with sulphonic acid

groups, which are fully deprotonated at pH > 2. The negative potential in the

membrane allows cations to pass through the membrane with a much higher flux than

uncharged complexes and anions. Before being applied, the membranes were washed

successively with 0.1 M HNO3, 1 M Ca(NO3)2 and the background solution of the

acceptor side. Because the free metal ion concentrations in surface waters are usually

below the detection limit of the ICP-MS, 30 mg dm-3 purified humic acid (15) was

added to the acceptor side of the DMT to accumulate metal ions.

After hanging the DMT cells in-situ into the surface water for two to four days,

samples were taken from both the surface water and the acceptor solution of the

DMT. Besides measuring the pH, macro-elements (Ca, Mg, Na, K) were measured

with ICP-OES and micro-elements (Cu, Pb, Cd, Zn, Ni) with ICP-MS. The free metal

ion concentrations were then derived based on either the Donnan membrane

equilibrium or ion transport kinetics.

1). Equilibrium approach. Using the total metal concentrations in the acceptor

solution measured after the deployment, the free metal ion concentrations in the

acceptor were calculated by taking into account ion complexation with inorganic ions

S11

(hydrolysis, carbonate) and with the purified humic acid added. The calculation was

done using the computer program ECOSAT, in which ion binding to the humic acid is

described using the NICA-Donnan model (16). The free ion concentrations in the

sample waters are then derived from the calculated free ion concentrations in the

acceptor solution using the Donnan membrane equilibrium principle (12):

zj

j

jzi

ri

i

a

a

a

a1

acceptor,

donor,

1

accepto,

donor,

=

(1)

where ai and aj are the activity of ion i and j respectively, and z represents the charge

of the ion. Ionic strength of the donor and acceptor solution was calculated from the

concentration of the major ions measured and the activity coefficients of the ions is

calculated using the adjusted Davies equation.

2). Kinetic approach. The free metal ion concentration in the samples can be derived

from the total ion concentration in the acceptor measured at the end of the deployment

time using the kinetic approach when ion diffusion in the membrane is limiting ion

transport (17). The free metal ion concentrations can be calculated according to the

following formula (17):

t

CC

BDA

VC t

z

0Tacceptor,tot,Tacceptor,tot,

m

m

e

acceptordonorfree,

== −=

δ (2)

in which Cfree,donor is the free metal ion concentration in the surface water (mol/m3),

Vacceptor is the acceptor solution volume (m3), Ae is the effective surface area of the

membrane (m2), Dm is the diffusion coefficient of the free metal ion in the membrane

(m2/s), B is the Boltzmann factor for a monovalent cation in the Donnan phase of the

membrane, δm is the membrane thickness (m), Ctot,acceptor,T=t is the total metal

S12

concentration (mol/m3) in the acceptor side at time t (S) after the deployment, and

Ctot,acceptor,T=0 is the total metal concentration in the acceptor side before the cells are

deployed into the samples. Details of the used parameters are available in (12, 17).

CLE-SV measurements of cadmium speciation

Differential pulse stripping voltammetry (DP-SV) measurements were performed with

a hanging mercury drop electrode, an Ag/AgNO3 reference and a graphite counter

electrode held in a Metrohm 746 VA analyzer combined with 694 VA processor or

757 VA computrace. The working parameters are the following: stirring speed 1200

rpm, purging time 5 min, and accumulation at potential -1.1 V for 240s on the 757

VA and for 260s on the 694 VA, rest time 15s, scanning pulse height 50 mV, and

scanning rate 15 mV s-1. The detection limit for labile Cd was checked in a UV-

oxidized lake Greifen sample as 0.090 nM.

S13

Table S2: Blank values of the methods

Method Laboratory Field

campaign1 Cu /nM Zn/ nM Cd /nM Pb/ nM

ICP-MS Lancaster D 0.40 0.80 0.002 0.003 L 0.40 0.80 0.002 0.003

ICP-MS Duebendorf D 0.2 1 <0.04 0.05 L 0.2 1 <0.04 0.05

ICP-MS Geneva D < 0.4 0.3 1.2 < 0.03 L < 0.4 1.8 <0.05 0.1

ICP-MS Wageningen D 0.15 23 0.01 0.06 L 0.15 23 0.01 0.06

DGT 2 Lancaster D 0.015 0.21 0.000307 0.00046 L 0.0065 0.068 0.000026 0.00013

DGT 2 Duebendorf D 0.036 0.08 0.00018 0.00071 L 0.037 0.12 0.00016 0.0012

DGT 2 Bilthoven D 0.09 2 0.01 0.002 L

GIME Geneva D VIP <0.15 <0.013 <0.010 D VIA <0.15 <0.013 <0.010 L 20 0.20±0.02 <0.2 <0.013 <0.010 L 21 <0.15 <0.2 0.028±0.005 <0.010

SCP Belfast D 0.02 0.2 0.02 0.02 L 0.02 0.2 0.02 0.02

HFPLM Geneva D 0.005 0.0005 0.0003 L 0.0047 0.0005 0.0003

FTPLM3 Geneva D 0.001 L 0.006

DMT 4 Wageningen D 0.0048 0.026 0.00081 L 0.002 < 5E-04 < 5E-04

CLE-ASV 5 Duebendorf D <0.07 L <0.07

1 field campaign: D = Duebendorf, Switzerland; L = Lancaster, England,

L20: Lancaster, 20 April 2004, L21: Lancaster, 21 April 2004

2 Blanks for DGT measurements in nmol/gel unit

3 Strip solution

4 Free metal concentrations in the humic acids in acceptor solution

5 Labile Cd concentration

< indicates blank measurements below the detection limit of the method.

S14

Table S3: Total dissolved concentrations measured in samples (0.45 µm filtered)

of Lake Greifen and of Furtbach by four laboratories using ICP-MS

Lake Greifen, 2.5 m Cu/ nM Zn/ nM * Cd/ nM Pb/ nM

Date Lab 02.09.2003 Duebendorf 17 8 0.04 0.24

Geneva 22 15 0.10 Wageningen 17 <dl 0.19 0.22

04.09.2003 Duebendorf 17 5 0.04 0.19 Geneva 23 11 0.10 average 19 ± 3 10 ± 4 0.09 ± 0.06 0.22 ± 0.03

Lake Greifen, 5.0 m 02.09.2003 Duebendorf 17 12 0.05 0.19

Geneva 21 21 0.09 < dl Wageningen 18 0.06 0.17

04.09.2003 Duebendorf 14 6 < 0.04 0.10 Geneva 23 14 <dl <dl average 19 ± 3 13 ± 6 0.07 ± 0.02 0.15 ± 0.05

Furtbach 03.09.2003 Duebendorf am 25 60 0.11 0.58

Duebendorf pm 24 44 0.08 0.34 Geneva am 38 116 <dl Geneva pm 35 74 Wageningen 32 0.10 0.65 Lancaster 40 76 0.11 0.62 average 32 ± 7 74 ± 27 0.10 ± 0.01 0.55 ± 0.14

05.09.2003 Duebendorf am 20 40 0.06 0.34 Duebendorf pm 22 29 0.06 0.29 Geneva am 38 90 average 27 ± 10 53 ± 33 0.06 0.32 ± 0.04

3 - 5.9.03, 24 samples Duebendorf 27 ± 2 39 ± 16 0.08 ± 0.01 0.19 ± 0.03

* Large standard deviations between results for Zn from the different laboratories indicate difficulties in reliably measuring Zn.

S15

Fig. S1. Total concentrations of Cu, Zn, Cd and Pb as measured by four laboratories in Lake Greifen and Furtbach

0

5

10

15

20

25

30

35

40

45

Lake Greifen 2.5 lake Greifen 5 Furtbach

Cu

nM

D

G

W

D

G

D

G

L

0

20

40

60

80

100

120

140

Lake Greifen 2.5 lake Greifen 5 Furtbach

Zn

nM

D

G

D

G

L

D

G

0.00

0.10

0.20

0.30

0.40

Lake Greifen 2.5 lake Greifen 5 Furtbach

Cd

nM

D

G

W

L

D

G

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Lake Greifen 2.5 lake Greifen 5 Furtbach

Pb

nM

D

W

L

D

D

D

S1

6

Tab

le S

4: T

otal

unf

ilter

ed a

nd d

isso

lved

con

cent

rati

ons

mea

sure

d in

sam

ples

of

Riv

er W

yre

by f

our

labo

rato

ries

usi

ng I

CP

-

MS.

Fou

r ty

pes

of s

ampl

es w

ere

obta

ined

: unf

ilter

ed o

n-si

te (

fille

d in

to b

ottle

s on

-sit

e); u

nfilt

ered

bul

k la

b (f

illed

into

bot

tles

from

the

bulk

sam

ples

take

n to

the

labo

rato

ry);

filt

ered

on-

site

: (fi

ltere

d on

-sit

e us

ing

syri

nges

and

in-l

ine

filte

r ho

lder

s); f

ilter

ed la

bora

tory

(bul

k sa

mpl

e fi

ltere

d in

the

labo

rato

ry).

a)

Cu

and

Zn;

b)

Cd

and

Pb; c

) di

ssol

ved

conc

entr

atio

ns in

fie

ld f

ilter

ed s

ampl

es b

y L

anca

ster

labo

rato

ry.

Tw

o se

para

te m

easu

rem

ents

on

diff

eren

t sam

ples

wer

e ob

tain

ed in

Gen

eva.

*: c

onta

min

atio

n su

spec

ted.

The

re w

as in

par

ticu

lar

a pr

oble

m w

ith

Cd

in th

e la

bora

tory

filt

ered

sam

ples

.

S1

7

Tab

le S

4 a)

C

u / n

M

Zn/

nM

Dat

e

Lab

un

f. o

n-si

te

unf.

bul

k la

b fi

lt. o

n-si

te

filt.

lab

un

f. O

n-si

te

unf.

bul

k la

b fi

lt. o

n-si

te

filt.

lab

19

.04.

2004

L

anca

ster

21

19

36

45

Due

bend

orf

24

± 2

31

± 2

26

± 2

22

55

± 5

*

48 ±

5

35

G

enev

a

24

38

± 4

W

agen

inge

n

22

<

dl

av

erag

e

23

± 1

37 ±

2

20.0

4.20

04

Lan

cast

er

21

22

36

39

D

uebe

ndor

f

29 ±

2

26 ±

2

24

77

± 5

57

± 5

48

G

enev

a

27±

5 28

± 0.

7

24±

0.7

54±

1.3

62±

3

40±

2

Gen

eva

2

26

± 0.

5

25±

0.7

88

± 5

60

± 4

W

agen

inge

n

22

<

dl

av

erag

e

2

3 ±

1

47 ±

10

21.0

4.20

04

Lan

cast

er

20

20

18

31

D

uebe

ndor

f

28 ±

2

26 ±

2

21

56

87

38

G

enev

a

22±

0.7

24±

0.4

21

± 0.

3 37

± 1

39±

1

31±

1

Gen

eva

2

30

± 2.

8

27±

1.6

70

± 4.

7

68±

7.7

W

agen

inge

n

20

<

dl

av

erag

e

22

± 3

42 ±

18

22.0

4.20

04

Lan

cast

er a

m

17

19

18

36

L

anca

ster

pm

20

29

Due

bend

orf

18

20

21

22

26

38

39

*

G

enev

a

21±

0.4

20±

0.6

18±

0.3

21±

0.4

50±

1.4

29±

0.6

22±

0.5

32±

3

Gen

eva

2

20±

0.5

19±

0.4

45±

1 35

± 2.

8

Wag

enin

gen

19

<dl

aver

age

1

9 ±

2 20

± 2

34 ±

2

S1

8

Tab

le S

4 b)

Cd/

nM

P

b /n

M

Dat

e

Lab

un

f. o

n-si

te

unf.

bul

k la

b fi

lt. o

n-si

te

filt.

lab*

un

f. o

n-si

te

unf.

bul

k la

b fi

lt. o

n-si

te

filt.

lab

19

.04.

2004

L

anca

ster

0.

22

2.

2

D

uebe

ndor

f

0.35

±

0.05

0.

43 ±

0.0

5 *

* 2.

7 ±

0.1

2.8

± 0.

1 1.

8 ±

0.1

1.5

G

enev

a

*

1.4±

0.03

Wag

enin

gen

*

1.

4

aver

age

*

1.4

± 0.

1 20

.04.

2004

L

anca

ster

0.

28

*

2.

5 1.

5

Due

bend

orf

0.

41

0.33

* 3.

1 2.

1

1.5

G

enev

a

0.18

± 0.

03

0.34

± 0.

1

* 1.

0±0.

01

3.1±

0.0

4

1.1±

0.03

Gen

eva

2

0.

49±

0.03

*

2.8±

0.1

1.7±

0.06

Wag

enin

gen

*

0.

9

aver

age

*

1.3

± 0.

3 21

.04.

2004

L

anca

ster

0.

2 *

1.6

1.1

D

uebe

ndor

f

0.36

0.

29

*

2.6

1.9

1.

1

Gen

eva

0.

15±

0.1

0.26

±0.0

6

* 0.

9±0.

03

1.9±

0.4

1.

1±0.

03

G

enev

a 2

0.16

± 0.

05

*

2.

7± 0

.7

1.

3±0.

03

W

agen

inge

n

*

0.9

av

erag

e

*

1.

1 ±

0.1

22.0

4.20

04

Lan

cast

er a

m

0.12

*

1.0

1.7

L

anca

ster

pm

0.

22

2.

0

D

uebe

ndor

f

0.19

0.

22

0.25

*

1.0

1.2

1.8

1.6

G

enev

a

0.13

± 0.

06

0.16

± 0.

05

0.11

± 0.

08

* 0.

7± 0

.02

1.4±

0.03

0.

5±0.

02

1.3±

0.02

Gen

eva

2

0.16

± 0.

05

0.18

± 0.

04

0.8±

0.0

2 1.

4± 0

.02

W

agen

inge

n

*

1.2

av

erag

e

0.18

±

0.07

*

1.3

± 0.

7 1.

5 ±

0.2

S1

9

Tab

le S

4 c)

Dis

solv

ed c

once

ntra

tion

s m

easu

red

in f

ield

filt

ered

sam

ples

of

Riv

er W

yre

by IC

P-M

S (L

anca

ster

labo

rato

ry);

rep

licat

es

are

show

n fo

r ea

ch s

ampl

ing

tim

e.

T

ime

h

Clo

ck

tim

e

Cu

nM

Stde

v Z

n nM

St

dev

Cd

nM

Stde

v Pb

nM

St

dev

Fe

µM

St

de

v A

l µ

M

St

dev

Mn

nM

St

dev

0.00

3:

00 P

M

22.0

0.

55

36.9

1.

02

0.24

9 0.

027

2.37

0.

005

6.34

0.

15

4.40

0.

03

266

5

22

.0

0.66

35

.4

0.29

0.

196

0.00

9 2.

31

0.01

0 5.

37

0.03

3.

38

0.00

19

8 1

20.0

0 11

:00

AM

23

.4

0.38

43

.0

0.35

0.

222

0.02

7 2.

33

0.02

4 5.

85

0.06

4.

80

0.25

27

4 4

22.6

0.

58

44.3

0.

66

0.24

9 0.

027

2.18

0.

029

5.43

0.

14

4.23

0.

06

289

6 26

.00

5:00

PM

23

.2

0.13

36

.9

0.70

0.

249

0.01

8 2.

34

0.03

9 5.

19

0.02

5.

13

0.26

27

6 3

23.1

0.

19

36.3

0.

66

0.24

9 0.

018

2.52

0.

039

5.91

0.

07

5.32

0.

11

285

1 43

.00

11:1

5 A

M

20.1

0.

54

27.8

0.

18

0.19

6 0.

018

1.44

0.

019

5.36

0.

03

2.39

0.

03

276

4

20

.6

0.52

30

.7

0.84

0.

178

0.00

9 1.

59

0.02

9 5.

23

0.06

2.

64

0.03

26

9 5

49.7

5 4:

45 P

M

18.4

0.

54

20.6

0.

57

0.14

2 0.

018

1.15

0.

005

4.65

0.

09

2.24

0.

01

221

4

17

.3

0.35

15

.5

0.21

0.

160

0.02

7 1.

16

0.01

9 4.

70

0.05

2.

31

0.04

22

4 2

68.5

0 11

:30

AM

16

.9

0.42

18

.3

0.63

0.

133

0.01

8 1.

04

0.01

9 4.

44

0.10

1.

78

0.07

17

8 3

16.8

0.

33

17.6

0.

17

0.15

1 0.

000

1.05

0.

029

4.35

0.

04

1.84

0.

01

177

1 71

.75

2:45

PM

20

.0

0.60

29

.1

0.37

0.

187

0.01

8 2.

17

0.05

8 4.

80

0.09

4.

65

0.08

24

1 3

19.6

0.

22

24.9

0.

40

0.19

6 0.

027

1.99

0.

029

5.33

0.

11

4.27

0.

08

214

3

S2

0

Tab

le S

5: C

once

ntra

tion

s m

easu

red

by D

GT

on

thre

e su

cces

sive

day

s in

Riv

er W

yre

(all

data

in n

M).

Dep

loym

ent t

imes

wer

e 22

– 2

7 ho

urs.

Dat

e C

u

Zn

C

d Pb

19-2

0/04

/04

2.5

± 0.

4 8.

2 ±

1.6

0.08

± 0

.01

0.07

± 0

.01

20-2

1/04

/04

2.2

± 0.

4 9.

3 ±

1.2

0.09

± 0

.02

0.06

± 0

.02

21-2

2/04

/04

3.4

± 0.

2 10

.4 ±

0.8

0.

12 ±

0.0

2 0.

09 ±

0.0

1

S2

1

Tab

le S

6: S

ingl

e m

easu

rem

ents

obt

aine

d by

GIM

E-V

IA-F

ield

ove

r tw

o da

ys in

Riv

er W

yre.

The

se r

esul

ts m

ay in

clud

e in

addi

tion

to a

naly

tica

l unc

erta

inti

es te

mpo

ral v

aria

tion

s in

the

rive

r.

a) 2

0/04

/200

4: M

easu

rem

ents

per

form

ed a

t an

aver

age

T o

f 10.

1°C

; rep

orte

d co

nc. a

t T =

22°

C

Tim

e E

d1 /mV

t d

1 /min

Z

n /n

M

Cd

/nM

P

b /n

M

Cu

/nM

12:1

0 -1

050

20

0.

24

0.07

1.

18

13

:10

-120

0 20

11

.4

0.23

0.

04

1.11

13:4

5 "

20

13.9

0.

19

0.04

0.

92

14

:20

" 20

13

.2

0.21

0.

03

1.15

14:5

5 -1

100

20

0.

21

0.04

1.

50

15

:35

" 20

0.19

0.

03

1.42

16:1

0 -1

050

20

0.

19

0.04

1.

38

17

:00

-110

0 20

0.18

0.

04

1.24

A

vera

ge

12

.9±1

.3

0.20

±0.0

2 0.

04±0

.01

1.24

±0.1

9

1 E

d: d

epos

itio

n po

tent

ial,

t d :

depo

siti

on ti

me

S2

2

b) 2

1.04

.200

4: M

easu

rem

ents

per

form

ed a

t an

aver

age

T o

f 10.

3°C

; rep

orte

d co

nc. a

t T =

22°

C

Tim

e E

d 1 /m

V

t d1 / m

in

Zn

/nM

C

d /n

M

Pb

/nM

C

u /n

M

11

:05

-110

0 20

0.23

0.

04

1.06

11:3

5 "

20

0.

28

0.04

1.

12

12

:15

" 25

0.20

0.

05

1.18

12:5

5 "

30

0.

22

0.05

1.

13

13

:50

-115

0 20

0.15

0.

05

1.25

14:2

5 "

20

0.

18

0.05

1.

36

15

:00

-120

0 20

8.

3 0.

14

0.05

1.

21

15

:35

" 20

5.

2 0.

13

0.05

1.

31

16

:15

" 20

4.

7 0.

14

0.04

1.

33

Ave

rage

6.1

± 2.

0 0.

19 ±

0.0

5 0.

04±

0.01

1.

22 ±

0.1

0

1 E

d: d

epos

itio

n po

tent

ial,

t d :

depo

siti

on ti

me

S23

References

(1) Warnken, K. W.; Zhang, H.; Davison, W. Trace metal measurements in low ionic strength synthetic solutions by diffusive gradients in thin films. Anal. Chem. 2005, 77, 5440-5446. (2) Zhang, H.; Davison, W. Performance characteristics of diffusion gradients in thin films for the in situ measurements of trace metals in aqueous solution. Anal. Chem. 1995, 67, 3391-3400. (3) Zhang, H. "Practical guide for making gels for DGT and DET," DGT Research Ltd., 1997. (4) Zhang, H. "Practical guide to using DGT and DET," DGT Research Ltd., 1997. (5) Tercier-Waeber, M.-L.; Buffle, J.; Koudelka-Hep, M.; Graziottin, F. Submersible voltammetric probes for real-time continuous monitoring of trace elements in natural aquatic systems. In Environmental Electrochemistry. analyses of trace element biogeochemistry; Taillefert, M., Rozan, T. F., Eds.; American Chemical Society: Washington DC, 2002; Vol. 811, pp 16-39. (6) Tercier-Waeber, M.-L.; Buffle, J. Submersible online oxygen removal system coupled to an in situ voltammetric probe for trace element monitoring in freshwater. Environ. Sci. Technol. 2000, 34, 4018-4024. (7) Tercier, M.-L.; Parthasarathy, N.; Buffle, J. Reproducible, reliable and rugged Hg-plated Ir-based microelectrode for in situ measurements in natural waters. Electroanalysis 1995, 7, 55-63. (8) Belmont-Hébert, C.; Tercier, M.-L.; Buffle, J.; Fiaccabrino, G. C.; Koudelka-Hep, M. Gel-integrated microelectrode arrays for direct voltammetric measurements of heavy metals in natural waters an other complex media. Anal. Chem. 1998, 70, 2949-2956. (9) Pei, J.; Tercier-Waeber, M.-L.; Buffle, J. Simultaneous determination and specation of zinc, cadmium, lead and copper in natural water with minimum handling and artifacts, by voltammetry on a gel-integrated microelectrode array. Anal. Chem. 2000, 72, 161-171. (10) Buffle, J.; Parthasarathy, N.; Djane, N. K.; Matthiasson, L. Permeation Liquid Membrane for Field Analysis and Speciation of Trace Compounds in Waters. In In Situ Monitoring of Aquatic Systems; Chemical Analysis and Speciation; Buffle, J., Horvai, G., Eds.; Wiley, 2000. (11) Salaun, P.; Buffle, J. Integrated microalanytical system coupling permeable liquid membrane and voltammetric detection for trace metal speciation. Theory and applications. Anal. Chem. 2004, 76, 31-39. (12) Temminghoff, E. J. M.; Plette, A. C. C.; Van Eck, R.; Van Riemsdijk, W. H. Determination of the chemical speciation of trace metals in aqueous systems by the Wageningen Donnan membrane technique. Anal. Chim. Acta 2000, 417, 149-157. (13) Stelt, B. v. d.; Temminghoff, E. J. M.; van Riemsdijk, W. H. Measurement of ion speciation in slurry manures using Donnan Membrane Technique. Anal. Chim. Acta 2005, 552, 135-140. (14) Kalis, E. J. J.; Weng, L. P.; Dousma, F.; Temminghoff, E. J. M.; van Riemsdijk, W. H. Measuring free metal ion concentrations in-situ in natural waters using Donnan Membrane Technique. Environ. Sci. Technol. 2006, 40, in press .

S24

(15) Temminghoff, E. J. M.; Van der Zee, S. E. A. T. M.; De Haan, F. A. M. Copper mobility in a copper-contaminated sandy soil as affected by pH and solid and dissolved organic matter. Environ. Sci. Technol. 1997, 31, 1109-1115. (16) Kinniburgh, D. G.; van Riemsdijk, W. H.; Koopal, L. K.; Borkovec, M.; Benedetti, M. F.; Avena, M. J. Ion binding to natural organic matter: competition, heterogeneity, stoichiometry and thermodynamic consistency. Colloid Surf. A 1999, 151, 147-166. (17) Weng, L. P.; Van Riemsdijk, W. H.; Temminghoff, E. J. M. Kinetic aspects of DMT for measuring free metal ion concentrations. Anal. Chem. 2005, 77, 2852-2861.