Miriam Glendell
Richard Brazier
Aller: 17 km2 lower lying catchment
dominated by mineral soils intensive
arable
/ short-term
farming and
index
(PSI)
as a toolleyfor
livestock rearing
• Poster #21 – Testing the pressure-specific
determining ecologically relevant water quality sedimentation targets
Fluvial export of total organic carbon (DOC & POC) from the two
contrasting study catchments and the implications for WQ
Horner: 22km2 upland catchment
with extensive semi-natural
habitats on organo-mineral soils
Fluvial export of TOC
 TOC (incl. DOC and POC) is an important intermediary stage




in the global carbon cycle - each year rivers transform or store
app. 2 Gt of terrestrial organic carbon – a large fraction of the
global terrestrial NEP
DOC - “chemical backbone” of aquatic ecosystems influences light regime, energy, nutrient supply, pH, metal
toxicity
Increasing DOC concentrations in rivers across Western
Europe and North America over the past decades (Evans
2006), however the ecological consequences are not yet clear
Research on export of fluvial TOC to date focussed on forested
and peatland ecosystems with limited studies in agricultural
systems
How does agricultural land use impact on the fluvial
export of total organic carbon?
Methods
 Soil characterisation - 205
soil samples taken across
3 soil types and 4
landuses, analysed for
bulk density, total C, N , P,
C:N and δ15N
 Storm-integrated
sampling at two
catchment outlets
January 2011-January
2012 (35 events)
 Monthly base flow
sampling Feb 2010- Nov
2012
δ
Research hypothesis
Agricultural catchment will
support increased
concentrations, fluxes and
yields of SS due to more
intensive land use and higher
soil bulk density
Semi-natural catchment will
support higher concentrations,
fluxes and yields of TPC and
DOC due to carbon rich soils
and greater carbon pool
Hydrological differences
P < 0.032
P < 0.001
N=35, Mann-Whitney U test
P < 0.001
P < 0.045
Differences in water quality
P < 0.029
P < 0.01
Mann-Whitney U test
P < 0.001
P < 0.03
Hydrological drivers - SS concentration
2000
1200
Peak SS conc mg/L
Peak SS conc mg/L
Peak Q vs peak SS conc without extreme
1400
events
Aller SS max
conc. mg/l
Horner SS max
conc. mg/l
1000
800
600
400
Peak Q vs peak SS conc with extreme
events
1500
1000
500
200
0
0,00
1,00
2,00
3,00
3
Peak discharge m /s
Water quality Catchment
parameter
Log peak SS
Horner
concentration
mg/l without
extreme events Aller
0
0,00
4,00
Hydrological control
5,00
R2
Constant
Standardised
coefficients
0.001
0.938
1.568
0.686
-
Log peak Q m3/s
0.418
Log peak Q m3/s
Log lag peak rainfall
intensity to peak Q (min)
0.001
0.736
2.942
0.653
-0.373
Event duration (min)
0.001
0.840
1.724
0.572
Log peak Q m3/s
15,00
P<
Event duration (min)
Log peak SS
Horner
concentration
mg/l with
extreme events Aller
10,00
Peak discharge m3/s
0.593
20,00
25,00
200
Peak Q vs peak TPC conc without
extreme events
Peak Q vs TPC conc with extreme
events
250
150
Aller
100
Horner
50
0
0,00
1,00
2,00
3,00
TPC conc. mg/L
Peak TPC conc mg/L
TPC concentration
200
150
100
50
0
0,00
4,00
Peak discharge m3/s
5,00
10,00
15,00
Peak discharge
Water quality
parameter
Catchment
Hydrological
control
P<
Log TPC
maximum
concentration mg/l
without extreme
events
Horner
Aller
Event duration (min) 0.001
Log TPC
maximum
concentration mg/l
with extreme
events
Horner
Log peak Q m3/s
Aller
Log peak rainfall
intensity to peak Q
(min)
Event duration (min) 0.001
R2
Constant
Standardised
coefficients
0.865
0.674
0.550
Log peak Q m3/s
Log peak Q m3/s
0.521
0.001
20,00
m3/s
0.644
2.544
0.508
-0.470
0.875
0.829
0.685
0.407
25,00
DOC concentration
Peak Q vs DOC conc with extreme
events
12
12
10
10
Peak DOC conc mg/L
Peak DOC conc mg/L
Peak Q vs peak DOC concentration
without extreme events
8
6
Aller
4
Horner
2
0
0,00
8
6
4
2
0
1,00
2,00
Peak discharge
3,00
4,00
0
5
m3/s
Water quality
parameter
Catchment
Hydrological
control
Log DOC
maximum
concentration
mg/l without
extreme events
Log DOC
maximum
concentration
mg/l with
extreme events
Horner
Aller
-
Horner
Aller
Log peak Q m3/s
10
15
Peak discharge
m3/s
P<
R2
Constant
Standardised
coefficients
0.038
0.435
0.661
0.660
20
25
25
Yields
Yield kg ML-1 km-2
20
15
10
5
0
SS estimated from
turbidity record
SS estimated using TPC estimated from TPC estimated from DOC estimated from DOC estimated
conc. / Q rating turbidity derived SS SS conc. / Q rating inst. load / Q rating Walling formula 5
equation
load and average %
equation and
equation
TPC content
average % TPC
content
Horner Water
SS
TPC
DOC
DOC:TPC ratio
Total discharge (ML)
Aller
Discharge weighted yield (kg ML-1 km-2)
Horner Water
Aller
3 – 4.4
7.80 – 15.45
0.51 – 0.75
0.77 – 1.70
0.26 – 0.32
0.48 – 0.52
0.25 – 10.02
0.15 – 1.01
10,140
4,941
DOC quality
9
8
7
6
5
4
3
2
1
0
5
4
3
2
1
UV absorbance ratio
6
22:48
21:36
20:24
19:12
16:48
18:00
0
15:36
Discharge m3 s-1
4
3,5
3
2,5
2
1,5
1
0,5
0
Discharge
E2:E3
E4:E6
SUVA254
7:12
4:48
2:24
0:00
21:36
19:12
10
9
8
7
6
5
4
3
2
1
0
UV absorvance ratio
Horner Water 22-23/11/2012
16:48
of more aromatic,
higher molecular
weight humic
compounds in
agricultural
catchment
 Less aromatic, lower
molecular weight
fulvic compounds in
the semi-natural
catchment
Discharge m3 s-1
 Higher proportion
Aller 22/11/ 2012
Conclusions
 Hydrology exerts a greater control over fluvial organic
carbon dynamics in the agricultural catchment with
pollutant concentrations showing a lower response
threshold to increasing discharge
What are the consequences of the ehanced organic
 Agriculture alters both the quantity and quality of
carbon fluxes in agricultural landscapes for the
fluvial TOC export
ecological status of waterbodies and the global
 Cumulatively,
carbon cycle? agricultural catchments may be more
important in terms of fluvial organic carbon losses
than previously thought
Acknowledgements
 Nigel Hester, Project Manager, The National Trust
 Dr Rachael Dils, Dr Neasa McDonnel, Lynn Jenkins -
Environment Agency, UK
 Nev England, Jim Grapes, Angela Elliott, Sue Franklin, Anita
Cottrell, Nick Yeo, Maria Penas, Pia Benaud, Amanda Awbi,
Michael Gardner, University of Exeter
 Jonathan Fohrer, Florence Ferretti, Barbora Tomisova – Ecole
Nationale du Génie de l’Eau et de l’Environnement de
Strasbourg, France