RELATING DISSOLVED ORGANIC MATTER FLUORESCENCE TO

FUNCTIONAL PROPERTIES

Andy Baker

Connected Waters Initiative,

University of New South Wales,

Australia,

a.baker@unsw.edu.au

� Overview

� Linking organic matter fluorescence to environmental

function (Thacker et al 2005; Baker et al 2008)

� Applications: predicting organic matter removal at WTW

� Conclusions

Outline

Historical Overview

Some published pre-EEM evidence of relationship between NOM

fluorescence and physio-chemical properties

Stewart and Wetzel, 1980

Limnol. Oceanogr.

Historical Overview

McKnight et al 2001

Limnol. Oceanogr.

+ +

• Research question – can we use dissolved NOM fluorescence

EEM data to infer environmental function?

• Wide range of environmental functions

• Wider range of fluorescence wavelengths

• Process based link between function and NOM fluorescence

• Revisit fluorescence indices - are there ratios that could be

used for in-situ monitoring of environmental function?

Linking natural DOM fluorescence to function

“FunVar” – NERC

funded, 2004-2007

Aim – to develop a set of functional assays for DOM

Simple, reproducible measurements that provide information

about the environmental roles of DOM, rather than its more basic

physico-chemical properties

• Water samples were collected from UK freshwater sites and

fluorescence measured (‘peak picking’) on 0.7 µm filter fraction.

• 20-50 L water, filtered at 0.7 µm, rotary evaporated at 45 °C to

500 ml, then passed through ion exchange resin and 0.7 and 0.22

µm filters. Resultant solutions were ~150-600 mg/l and stored

cool and in the dark.

• These stock solutions used at 10 mg/l concentration in 0.05M

NaCl and 0.075M phosphate buffer at pH 7 when tested for

environmental function.

• SRHA was used as a QC/QA standard

Environmental assays used – for full details see Thacker et al (2005).

Eleven assays in total on ~30 lake and river samples plus associated QA/QC

samples. Three years of post-doc effort to collect samples and perform

assays.

0 200 400 600 800 1000

0

200

400

600

800

1000

400 410 420 430 440 450 460 470 480 490

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

410

415

420

425

430

435

440

445

450

455

460

465

470

475

EHB1

EHB2

EW1EW2

EW3EW4AEW4B

EW5EW6EW7EW8EW9EW10AEW10B

GG1

GG2

RS1RS2RS3

RS4RS5RS6

EHB1

EHB2

EW1

EW2

EW3EW4A

EW4B

EW5EW6

EW7

EW8EW9

EW10AEW10B

GG1GG2

RS1

RS2RS3RS4

RS5RS6

EHB1

EHB2

EW1EW2

EW3

EW4A

EW4BEW5

EW6

EW7

EW8

EW9EW10AEW10B

GG1

GG2

RS1

RS2

RS3RS4

RS5

RS6

Pe

ak T

Inte

nsity (

un

its)

Peak C Intensity (units)

Pe

ak T

/ P

ea

k C

in

ten

sity r

atio

Peak C emission wavelength (nm)

c

ba

Pe

ak C

em

issio

n w

ave

len

gth

(nm

)

Peak C intensity / a340

‘FunVar’ sample DOM fluorescence

(red) compared to River Tyne dataset

(green), Baker and Inverarity, 2004)

collected under same laboratory

protocols (raman standardised, no

other corrections)

Baker, A. and Inverarity, R., 2004. Protein-like fluorescence intensity as a possible tool for determining river water quality. Hydrol. Proc., 18: 2927-2945

Consistent and logical correlations between fluorescence and UV absorbance

and buffering capacity, hydrophilicity and benzopyrene and Al binding.

A340, Peak Cem and peak Aem all co-relate, and inversely co-relate with peak Tint

and Peak Cint/a340 ratio.

Remember, all data is normalised to 10 mg/l DOC samples

No consistent relationship with photodegradation and copper binding.

Recently, two PhD researchers (Magda Bieroza and Jessie Roe) have been

funded by SevernTrent Water to characterise DOM to improve drinking water

treatment processes.

Magda Bieroza considered fluorescence analyses.

Roe et al considered hydrophobicity, HP-SEC, THM-FP, etc.

Monthly fluorescence samples (DOM) from 16 sites. XAD-8 resin extraction every three

months to determine %hydrophobic and %hydrophilic. Functional assay protocols not

identical to Thacker et al (2005) and Baker et al (2008).

Same relationship observed between peak Cem and hydrophobicity.

Prediction of percentage TOC removal from raw water organic matter

fluorescence (Bieroza et al 2009):TOC removal (%) = 65.96 – 0.77* Tint (r = 0.64)

TOC removal (%)=-244.09 - 0.50* Tint + 0.70* Cem (r=0.73)

Conclusions

For our small sample set of DOM:

A340 per g C, Peak Cem and peak Aem all co-relate, and inversely co-relate with

peak Tint per g C and Peak Cint/a340 ratio.

These co relate with hydrophobicity, Al and benzopyrene binding and buffering

capacity, but not Cu binding or photodegradation.

Some optical measurements are independent of concentration – ideal for in-situ

applications.

Do these relationships still apply:

• …when the fluorescent DOM fraction is smaller?

• …to a wider range of environments (e.g. groundwaters)?

• …when anthropogenic OM is present?

• …to different size fractions (e.g. colloidal OM)?

• …what about ecological function?