1. All DOC is not the same:
DOC classified by functional properties
and their environmental significance
Andy Baker
University of
Birmingham
a.baker.2@bham.ac.uk

2. Battin et al. doi:10.1038/ngeo618
The microbial loop. Fenchel,
doi:10.1016/j.jembe.2008.07.013

3. (In predominantly natural systems)
Evidence of DOC processing within rivers. DOC becomes increasingly ‘young’ in 14C age
and hydrophilic with distance from source. Rivers evade CO2. Photodegradation
and biodegradation occurs, arguably of all DOM fractions.
Seasonal variations in riverine DOM character, typically a hydrophobic / aromatic
‘flush’. Differences in DOM character between catchments, depending on soil
type, land cover and human impact.
Evidence of greater variability in DOC characteristics in headwaters and low order
streams with ‘fresh’ DOM. Downstream DOC might be 14C ‘young’, but it is more
homogenous and biogeochemically ‘aged’.
Anthropogenic inputs typically introduce hydrophilic, relatively colourless, DOC.
Clear links between DOC character and function. Aromatic DOC has greater chemical
and ecological function (metal binding, contaminant binding, UV screening), and is
easy to treat. Hydrophilic DOC difficult to remove during drinking water treatment.

4. Peak C fluorescence
Time /
Processing
Variable and high fluorescence / g C in
bog waters
Less variable and less fluorescent / g C
river waters
IHSS standards have atypically low
fluorescence

5. Mean and standard deviation colour/DOC
CBweir 10.7 (1.4)
Pweir 10.0 (1.2)
PGweir 8.4 (2.5)
ME 10.8 (3.7)
MC 9.5 (0.8) Different DOC character
FE 12.4 (3.7)
between sub-catchments
FC 11.5 (2.0)
‘fresh’ DOC is
more coloured
CB we ir P we ir PG we ir ME MC FE FC
1500
Peak Cint/a340
1250
1000
750 ‘fresh’ DOC is more fluorescent
500
per unit absorbance
250

6. Photodegradation of
lignin over two months
Lignin phenol
concentration and
relationship with
optical
characteristics
through the ‘wet’

9. Summary
River microbial ecosystem processes DOC. Aromatic bonds in DOC relatively
easier to break. DOC therefore less aromatic with residence /travel time.
Easily measured ‘in-situ’ using UV absorbance or fluorescence.
River experience seasonal variations in riverine DOC character. Typically with
‘flush’ of relatively fresh (therefore aromatic) DOC. Groundwater rivers
will have a groundwater hydrophilic DOC source.
Catchment mean DOC character depending on soil type, land cover and
human impact.
Evidence of greater variability in DOC characteristics in headwaters and low
order streams with ‘fresh’ DOM; variability decreases downstream as this
is processed.
Anthropogenic inputs typically introduce relatively hydrophilic, colourless,
DOC.
Aromatic DOC has greater chemical and ecological function (metal binding,
contaminant binding, UV screening), and is easy to treat. Hydrophilic DOC
difficult to remove during drinking water treatment.

10. 2
13 13
7 14 14
1713
17
27 32 14
8 33
17
4723
851821
3315
60
2611
18
661 61
30
32
11 21
30
6213 12
12
611 23
11
12 1626 16
15
29
28 25 21
18
11
18
10
12
2310
2130
26
9 32
19 6 2312
33
38 1 46 46 60 417
24 14 25
864
10 46 463831 7
16 63
59
25 62 31
36 15 13 50
33 3
37 20 38 10 52
1 19 26
32 55
7 18 49
34 41 64 8 34
9 48
6
1560
2
22 44 48 16 2335 54
50 21 30 58
DOC (mg/l)
1 242 46 63
36 43 56
40 5 28 36 43 927 20 14 44
17
48 20 48
2740
48 61
4 363349 41
3 37 29 43 43 3847 51 57
44
19 3628 37
24 2 6330
3710
35 29
39 27 20 4444 32 28 64
38 47 55 4 26
25
1 27 50 585616950 43 62
47
49 5 34 42 8
6 22
39 49 45
3937 7 52 22
45 3440 54 41 15 61
4251 28
35
40 60
51 47
45
63
51 3
29
3 49 22 50
34
57 25 53 41 62 55
20
2 41 54
3 10
22 56
40 31
1 45
35
42 5539
0.01 0.1
UV Absorbance (410 nm) /cm