ACS 4 March 2012 Azra

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ASL Conference 2011

Azra Daud

Winthrop Prof. Carolyn Oldham

Dr Suzanne McDonald

³Inside Informal, Outside Stormy´



Sunday, March 04, 2012 2

Motivation

Aims

Introduction

Approach

Methodology

Challenges

Outcomes

Take home message

OUTLINES




DOC controls geochemical andecological processes in aquatic

ecosystems.

Quantifying and characterising DOC,

including its spatial and temporal

variability, is critical to understand itsrole in these processes.

Metal-humic issue can be acute in

wetland affected by acid sulfate soils

or acid mine drainage, whichfrequently contain high DOC and

metal concentrations under low pH

conditions.

MOTIVATION



5.8 x 106 ha

in Australia 0.76%

Potential ASS

Actual ASS

INTRODUCTION




ASS are of major environmental concern for many wetlands

and is made up of oxidisable sulfidic material, usually pyrite,FeS2 (Green et al ., 2006)

INTRODUCTION

Iron is one of the main

weathering products of pyrite, Fe2SO4 (Peiffer et

al ., 1999)





INTRODUCTION

Swan Coastal Plain, 180 km south of

Perth, Western Australia ~30 ha

Hot dry summers (16 ± 30¶C) and

Cool wet winter (7 ± 17¶C)

Rainfall: ~700 mm

Evaporation: ~1500 mm A

A¶




Field measurement : pH, EC, ORP, Temp, depth

Laboratory analysis : HPSEC, UV-vis, TOC, cation

exchange, fractionation, phenanthroline, ICP-AES

Survey work ± site elevation

Collecting meteorological data from BOM, WA

Damkohler number Water and chemical mass balance

Reaction rate

APPROACH

Inside:

Outside:

Model:




METHODOLOGY

DOM

Natural Organic Matter

Humus Undecomposed Matter

Humin Humic Substances

Humic Acid Fulvic Acid

0.45 µm membrane

syringe filter

DOC




METHODOLOGY

Pure

Sample

DOC

Characterization

Laboratory

Analysis

0.45 µm filter

SRFAFe Total TOC

APHA

Method5310A

5 310C

SECSUVA

Phenanthroline

pH adjustment

LOI

254 nm

Optimum

510 nm

Without Fe

With

known Fe(20 ± 1000

mg/L)

Mw

Mn

3 years sampling

August 09 ± July 11

Seasonal

High water table

Low water table

CE RF




CHALLENGES & SOLUTIONS

1. Loss on ignition method was not applicable for [C] measurement

(negative reading of [C] ± TOC analysis).

2. TOC Standard Method 5310A was not consistent, and no similarity

as compared to Method 5310C. Optimisation was performed and

results were validated (5 months).

3. Results by phenanthroline method were not in the range.

Modification was undertaken. Reduce sample volume, 1:10 ratio to

standard).

4. Purification of carbon by reverse osmosis did not succeed.

Aggregation problem occur, less [C] were measured. (CationExchange and Rapid Fractionation).




TAKE HOME MESSAGES

1. Multiple tools analysis provides different view of characterisingDOC and provides improved understanding in the variability of

DOC characteristics and reactivity.

2. When dealing with waters and organic matter under variable pHs,

method validation is very CRUCIAL !

3. Surface and ground water in an aquatic system do not always

exhibit similar behavior spatially and temporally, especially under

high variability of DOC, heavy metals and pHs.

4. Results have flagged significant remarks on handling naturalwaters affected by ASS.




ACKNOWLEDGEMENT

Funding Malaysian Ministry of Higher Education (Tuition)

Universiti Tun Hussein Onn Malaysia (Stipend)

Australian Government (Natural Heritage Trust Regional (project 53454)

Curtin Water Quality Research Centre (Laboratories)

People Adam Lilicrap

Bibhash Nath

Daniel Boland

Laura Ellis

SESE postgrads

Family




THANK YOU«




CHALLENGES : [DOC] and [FET]

0

2

4

6

810

12

14

16

18

2 4 4.5 6 8

D O C ( m g / L

)

pH

1.5 mL

3.0 mL

5.0 mL

HTC

0

5

10

15

20

25

30

35

40

1 3 5 7

D O C ( m g / L )

Bores

1.5 mL, 3%

3.0 mL, 4%

HTC

0

10

20

30

40

50

60

70

80

2 4 4.5 6 8

D O C ( m g / L )

pH

1.5 mL

3.0 mL

5.0 mL

HTC




RESULTS AND DISCUSSION : PAPER 1 & 2

50 mg/L C from International Humic Substances Society Suwannee

River Fulvic Acid with different known concentrations of Fe

0

20

40

60

80

100

120

100010000100000

A b s 2

5 4 nm

Mw

1000mg/L Fe

200mg/L Fe

100mg/L Fe

80mg/L Fe

60mg/L Fe

40mg/L Fe

20mg/L Fe

Without Fe




RESULTS AND DISCUSSION : PAPER 1

Trends of pH, Fe and DOC across

wetland in wet season (2009)

0

10

20

30

40

50

60

70

0

1

2

3

4

5

6

7

8

9

Bore1

Bore2

Bore3

Bore4

Bore5

Bore6

Bore7

Bore8

SWN SWS

pH Fe DOC

p H

Sample

F e ,D O C ( m g

/ L )

Sample DOC Fe pH Mw SUVA

Name Wet Oxidation

High Temp

Catalytic (mg/L) at pH 7

Bore 1 8.0 - 19.8 8.0 4.92 8.1 2492 1.26 0.22

Bore 3 36.5 - 37.2 31.0 0.19 7.9 3074 1.13 1.44

Bore 5 2.6 - 4.3 3.4 62.14 3.2 1379 3.46 0.77

Bore 7 18.0 - 20.1 16.0 19.92 2.9 1670 3.06 3.04

SUVA

values for

waters in

Bore 1, 3,

5 and 7




RESULTS AND DISCUSSION : PAPER 1

0

20

40

60

80

100

120

100010000

A b s 2 5 4 nm

MwBore1 pH7 Bore2 pH7 Bore3 pH7 Bore4 pH7 Bore5 pH7Bore6 pH7 Bore7 pH7 Bore8 pH7 N pH7 S pH7

i ii

0

20

40

60

80

100

120

100010000

A b s 2 5 4 nm

Mw

Bore1 pH8.09 Bore2 pH8.43 Bore3 pH7.90 Bore4 pH8.25 Bore5 pH3.17

Bore6 pH8.48 Bore7 pH2.93 Bore8 pH8.22 N pH2.69 S pH2.76

i ii




METHOD:BACKGROUND

Physicochemical parameters:

pH

Loss on ignition

Electrical conductivity

Temperature

Oxidation reduction (redox) potential

Chemical analysis: Fe

DOC

Al

QA/QC:

Sample collected Samples were stored on ice, transferred to

the laboratory and then stored in the darkat 4oC until analysis.

Depth to groundwater (relative to LocalDatum) was measured prior to samplecollection.




BACKGROUND




RESULTS AND DISCUSSION

Trends of pH, Fe andDOC across wetland in

wet season (2009)

Trends of pH, Fe andDOC across wetland in

wet season (2010)

0

10

20

30

40

50

60

70

0

1

2

3

4

5

6

7

8

9

Bore1

Bore2

Bore3

Bore4

Bore5

Bore6

Bore7

Bore8

SWNSWS

pH Fe DOC

p H

Sample

F e ,D O C ( m g / L )

0

10

20

30

40

50

60

70

0

1

2

3

4

5

6

7

8

9

Bore1

Bore2

Bore3

Bore4

Bore5

Bore6

Bore7

Bore8

SWN SWS

pH Fe DOC

Sampl

F e ,D O C ( m g / L )

p H




ASS are of major environmental concern for many wetlands

and is made up of oxidisable sulfidic material, usually pyrite,

FeS2 (Green et al ., 2006)

INTRODUCTION

Iron is one of the main

weathering products of pyrite (Peiffer et al ., 1999)




METHODOLOGY

Size Exclusion Chromatography (SEC)

Chromatographic method (molecules in

solution are separated by size)

Also known as permeation gel method

Use organic solvent as a mobile phase

Provide good molar mass distribution for

polymers

Principles:

A very large molecule will elute earlier when

mobile phase passed through the column.

A small molecule will elute late when the

pore- and interparticle volume passed throughthe column.




BACKGROUND

FeS2(s) + O2 SO42- + Fe(II)

Fe(II) + S22-

(dissolved)

(slow)

+ O2

(a)

(a¶)

(b)

+ O2

(c)

(oxidized)

(fast)

+F

eS2(s)

Fe(III) Fe(OH)3 (s)

(soluble)

Releasing

additional acidity

and new Fe(II)




BACKGROUND

DOM

Natural Organic Matter

Humus Undecomposed Matter

Humin Humic Substances

Humic Acid Fulvic Acid

0.45 micron filter DOC




RESULTS AND DISCUSSION

SampleDOC

Fe pH Mw SUVA

Name Wet Oxidation High Temp Catalytic (mg/L) at pH 7

Bore 1 8.0 - 19.8 8.0 8.1 2492 1.26 0.22

Bore 3 36.5 - 37.2 31.0 7.9 3074 1.13 1.44

Bore 5 2.6 - 4.3 3.4 3.2 1379 3.46 0.77

Bore 7 18.0 - 20.1 16.0 2.9 1670 3.06 3.04




Site Description

Small seasonally inundated wetland in the MinningupWetland Chain

10 km south of Bunbury

Mediterranean type climate (wet and dry)

Average annual rainfall : 850 mm (May-Oct) and 130 mm

(Nov-Apr)

Air temperature : 8.2o

C (July) - 27.6o

C (Feb) Annual potential evaporation : 1400 -1600 mm

BACKGROUND

ACS 4 March 2012 Azra

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