RELATING DISSOLVED ORGANIC MATTER FLUORESCENCE TO ...
Transcript of RELATING DISSOLVED ORGANIC MATTER FLUORESCENCE TO ...
RELATING DISSOLVED ORGANIC MATTER FLUORESCENCE TO
FUNCTIONAL PROPERTIES
Andy Baker
Connected Waters Initiative,
University of New South Wales,
Australia,
� 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
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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
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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?