quantifying organic carbon fluxes from upland peat

28 Figure 2.4 Location of sampling points at eroded and vegetated uneroded sub-catchments in the Crowden Great Brook catchment.. a Chambered-type auger and incubation bottlewith an airti

Quantifying organic carbon fluxes from

upland peat

A thesis submitted to the University of Manchester for the degree of PhD in the Faculty

of Engineering and Physical Sciences

2012

Do Duy Phai

List of contents

Page

1 General introduction……… 18

1.1 Introduction and justification for research……… 18

2 Characteristics of research sites and general methods………. 27

2.1 Research sites………. 27

2.2 General methods……… 32

2.2.1 Peat sampling……… 32

2.2.2 Water sampling……… 33

2.2.3 Sediment sampling……… 34

2.2.4 In-situ monitoring………. 35

2.2.4.1 Determination of discharge……… 35

2.2.4.2 Continuous gas measurement……… 36

2.2.5 Ex-situ monitoring……… 37

2.2.5.1 Anaerobic incubation……… 37

2.2.5.2 Aerobic incubation……… 38

2.2.5.3 Measurement of concentration and calculation of gas production… 38 2.2.5.4 Aerobic incubation of peat slurry and calculation of gas production 40 2.2.6 Separation of particle size distribution (PSD)……… 42

2.2.6.1 Choosing technique……… 42

2.2.6.2 Procedure of cleaning TFU……… 44

2.2.6.3 Preparing TFU standard solution……… 44

2.2.6.4 Testing separation ratio of TFU……… 45

2.2.7 Sample analysis……… 45

2.2.8 Total organic carbon……… 46

2.2.8.1 Prepared total carbon and inorganic carbon standards……… 47

2.2.8.2 Drift correction……… 48

2.2.9 Freeze-dried sample……… 50

2.2.10 Characterization of organic matter composition - methodology development for molecular analyses……… 51

2.2.10.1 Extraction and fractionation of the sediment samples……… 51

2.2.10.2 Gas chromatography–Mass spectrometry (GC-MS)……… 53

2.2.10.3 Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS)

procedure adopted……… 55

2.2.10.4 Tetramethylammonium hydroxide (TMAH)-enhanced thermochemolysis Pyrolysis-Gas chromatography-Mass spectrometry (TMAH + Py-GC-MS)……… 56

3 Characterization of peat……… 59

3.1 Introduction……… 59

3.2 Aims and objectives……… 62

3.3 Methods……… 63

3.3.1 Peat sampling……… 63

3.3.2 Sample preparation and Py-GC-MS analyses……… 63

3.3.3 Determination of water content……… 64

3.4 Results……… 65

3.4.1 Water content of the peat……… 65

3.4.2 Optimising pyrolysis (Py) temperature……… 66

3.4.3 Determining optimum mass of peat for Py-GC-MS……… 67

3.4.4 Classification using the scheme of Vancampenhout et al (2009)…… 68

3.4.5 Classification into pedogenic (Pd) and aquagenic (Aq)……… 75

3.5 Discussion……… 78

3.5.1 Optimum methods for organic analysis of peat……… 78

3.5.2 Environmentally relevant classification of peat composition……… 78

3.6 Conclusions……… 82

4 Direct greenhouse gas fluxes from upland peat……… 83

4.1 Introduction……… 83

4.2 Aims and objectives……… 91

4.3 Methods……… 93

4.3.1 Ex-situ gas production………… ……… 93

4.3.1.1 Peat sampling to quantify ex-situ gas production……… 93

4.3.1.2 Aerobic incubation……… 94

4.3.1.3 Aerobic incubation of peat slurry……… 95

4.3.2 Gas production in-situ……… 97

4.4 Results……… 99

4.4.1 Ex-situ gas production……… 99

4.4.2 In-situ gas production……… 105

4.4.3 Ratios of gas production……… 114

4.4.4 Changes in peat composition after 309 incubated days……… 115

4.5 Discussion……… 118

4.5.1 Rates of present day GHG production……… 118

4.5.2 Rates of future GHG production……… 119

4.5.3 Validation of ex-situ gas production rates……… 121

4.5.4 Controls on in-situ gas production……… 121

4.5.5 Changes in peat composition associated with GHG emissions……… 122

4.6 Conclusions……… 123

5 Indirect greenhouse gas fluxes……… 125

5.1 Introduction……… 125

5.2 Aims and objectives……… 130

5.3 Methods……… 131

5.3.1 Sampling……… 131

5.3.2 Analysis……… 133

5.3.3 Calculation……… 134

5.4 Results……… 136

5.4.1 Mass flux of SsOC……… 136

5.4.2 Mass flux of components of SsOC……… 139

5.4.3 Variability in composition of SsOC – PSD……… 143

5.4.4 Variability in composition of SsOC – Compound classes……… 147

5.4.5 SsOC composition related to processes within the catchment……… 152

5.5 Discussion……… 157

5.5.1 Mass flux of SsOC……… 157

5.5.2 Mass flux of components of SsOC……… 159

5.5.3 Variability in composition of SsOC – PSD……… 160

5.5.4 Variability in composition of SsOC – Compound classes……… 161

5.5.5 SsOC composition related to processes within the catchment……… 162

5.6 Conclusions……… 165

6 General conclusions………. 167

References……… 172

Final word count 34,788

List of Figures

Page

Figure 1.1 Natural carbon cycle C reservoir masses are in gigatonnes (Gt) =

109tonnes of carbon Figures beside arrow denote flux rates in Gt C

yr-1from Moore et al (1996)……… 19

Figure 1.2 Diagram of direct and indirect greenhouse gas fluxes from an

upland peat catchment……… 21

Figure 1.3 Scenarios of potential future release GHGs from two types of

upland peat: Vegetated (uneroded) and eroded peat……… 23

Figure 1.4 Illustrative diagram of experimental design for present and future

(climate change) scenarios of two peats……… 24

Figure 1.5 Illustrative diagram of the thesis………. 26

Figure 2.1 Location of Crowden Great Brook near Manchester, UK for (a)

figure reproduced from ©2009 Google - Map data ©2011 Tele

Atlas and (b) figure reproduced from Ordnance Survey map data by

permission of Ordnance Survey, © Crown copyright……… 27

Figure 2.2 The vegetated (uneroded) peat sub-catchment A photo viewed to

the west of the monitoring equipment, labeled 30 in Figure 2.4 B.

Schematic representation of key vegetated peat with gaseous,

fluvial fluxes and high water table……… 28

Figure 2.3 The unvegetated (eroded) peat sub-catchment A photo viewed to

the north of the monitoring equipment, labeled 50 in Figure 2.4 B.

Schematic representation of key eroded peat with gaseous, fluvial

fluxes and low water table……… 28

Figure 2.4 Location of sampling points at eroded and vegetated (uneroded)

sub-catchments in the Crowden Great Brook catchment Figure

adapted from Todman (2005) and reproduced from Ordnance

Survey map data by permission of Ordnance Survey, © Crown

copyright Sub-catchments: the eroded peat site has a greater

surface area of bare peat than the sub- catchment at the uneroded

peat site which is covered by vegetation Photos were taken in

Figure 2.5 The geology of the study catchment (a) map and (b) cross section

with red line representing the position of cross section Figure

reproduced from Ordnance Survey map data by permission of

Ordnance Survey, © Crown copyright Figure adapted from

Figure 2.6 Peat sampling (a) Chambered-type auger and incubation bottle

with an airtight lid and two valves and (b) order of peat core

samples were taken on 14 and 15 December 2009 from eroded and

uneroded sites at the Crowden catchment Numbers beside on the

right of bottles are different depths of peat Numbers on the bottles

are order of samples……… 33

Figure 2.7 Diagrammatic collecting water column and sediment samples in

river water of upland peat catchment for (a) bottle with a volume of

5 L was used to take water column sample and (b) glass plates were

setup to collect sediment……… 34

Figure 2.8 Illustration of a dilution gauging curve……… 35

Figure 2.9 Peat borehole Each peat borehole has a plastic pipe, an airtight lid,

switches and drill holes and a GasClam to measure CO2, CH4, O2

concentrations, temperature and atmospheric pressure every hour… 37

Figure 2.10 Measuring gas production system: (a) the GasClam (Salamander

Ltd, UK), (b) operation diagram of the GasClam, (c) the GasClam

was linked with a computer by a cable and controlled by a GasClam

software version 2.5.6 and (d) two lines of plastic tubing were

connected between the GasClam, the valves of the bottle and the

hose from the nitrogen gas station……… 40

Figure 2.11 Aerobic slurry peat in OxiTop®-C bottles at 15oC……… 42

Figure 2.12 Diagram separation process of particle size distribution in stream

water using filter glass membrane (1.6 µm) and Tangential flow

ultrafiltration (TFU) membrane plates (0.2 µm, 50 kDa and 10

Figure 2.13 Sample analysis process for (a) peat, (b) water and (c) sediment

samples of Crowden Great Brook catchment……… 46

Figure 2.14 Shimadzu 5050A TOC analyzer for (a) TOC analyzer and (b)

automatic sampler……… 47

Figure 2.15 Edwards freeze-dryer.

51

Figure 2.16 Flow chart analysis of glass plate sample; TLE: total lipid

extraction; Py: pyrolysis; PLFA: phospho lipid fatty acid; BSTFA:

bis(-trimethylsilyl)trifluroacetamide……… 53

Figure 2.17 Partial chromatogram of the total ion current of Gas

chromatography–Mass spectrometry (GC-MS) chromatograms of a

sediment sample: acid fraction; neutral polar fraction and neutral

apolar fraction downstream of an eroded sub-catchment, the sample

was taken in November 2008; ?: unknown compound……… 54

Figure 2.18 Pyrolysis-Gas Chromatography-Mass Spectrometry analysis

system (Py-GC-MS): (a) Pyrolyzer, (b) Gas chromatography and

(c) Mass spectrometry……… 56

Figure 2.19 Partial total ion current chromatograms of pyrolysis (700oC): (a)

normal and (b) TMAH pyrolysis of the sediment sample

downstream of an eroded sub-catchment The sample was taken in

Figure 3.1 Py-GC-MS products at different temperatures (300oC, 500oC and

700oC) of a peat core sample in depth 0-50 cm at the eroded site… 66

Figure 3.2 Pyrolysis - Gas chromatography - Mass spectrometry products at

700oC of a peat sample in depth 0-50cm at the eroded site, using

different amount of the samples such as 0.1 mg, 0.5 mg, 1 mg and

Figure 3.3 Partial chromatogram of the total ion current of the peat core

samples at 0-50 cm in depth at the (a) eroded and (b) uneroded

sites Peak symbols correspond to compounds listed in Table 3.2.

68

Figure 3.4 Percentages of six organic compound groups as defined by

Vancampenhout et al (2009) in peat at the eroded and uneroded

sites Data presented as mean of percentage of total compounds (%)

and standard error (SE), n=3……… 74

Figure 3.5 Chromatograms of the total ion current of the Pd and Aq materials.

Peaks correspond to compounds listed in Table 3.2……… 75

Figure 3.6 Percentages of six organic compound groups as defined by

Vancampenhout et al (2009) in Humic acid (Pd standard material),

and dextran and alginic acid (Aq standard materials), (mean (%) ±

standard error (SE) of replication analyses (n=3))……… 76

Figure 3.7 Classification of organic compounds in the peat into Pd and Aq… 76

Figure 3.8 Ratio of Sphagnum contribution to the peat I% = [I] / [I+G+S]

I: 4-Isopropenylphenol); G: Guaiacol (2-Methoxy phenol); S:

Syringol (2,6-dimethoxyphenol)……… 77

Figure 4.1 Problems of in-situ and ex-situ GHG measurement A.

Environmental variable affecting subsurface GHG concentration

and therefore GHG fluxes B Environmental variables controlled

in ex-situ monitoring……… 87

Figure 4.2 Equilibration of CH4and CO2gas concentrations A Chamber

equilibrates with subsurface B Borehole equilibrates with the

section of subsurface to which it is open……… 90

Figure 4.3 Fresh peat core samples inside the glass bottles, taken on 14 and 15

December 2009 at the eroded and uneroded sites, kept on a shelf

and incubated in a cold room at 10oC……… 94

Figure 4.4 Separation of incubation bottles after 309 days……… 95

Figure 4.5 Optimal amount of fresh peat for peat slurry experiment………… 96

Figure 4.6 Peat boreholes with different depths Each peat borehole has a

plastic pipe, an airtight lid, switches and scratches and a GasClam 98

Figure 4.7 Cumulative CH4and CO2production of peat soil in anaerobic

incubation at 10oC Data presented as mean of amount (mole

tonne-1) and standard errors (SE), n=3……… 99

Figure 4.8 Cumulative CH4and CO2production of solid peat and slurry peat

in aerobic and anaerobic conditions at 15oC Incubated time of

solid aerobic and anaerobic was 333 days Incubated time of slurry

aerobic was 142 days Data presented amount (mole tonne-1)…… 101

Figure 4.9 Eroded site in-situ continuous measurement CH4, CO2and O2

concentrations, atmospheric pressure and soil temperature within

three boreholes in the three depths in the year 2009 at the Crowden

Great Brook catchment……… 106

Figure 4.10 Uneroded site in-situ continuous measurement CH4, CO2and O2

concentrations, atmospheric pressure and soil temperature within

two boreholes in the two depths in the year 2011 at the Crowden

Great Brook catchment R2is the coefficient of determination to

show the degree of variability of CH4and CO2concentrations (%)

due to impact of the atmosphere (mBar) on 25thJanuary and 14th

March 2011 107

Figure 4.11 Relationship between gas production and environmental factors… 112

Figure 4.12 Relationship between gas production and water table Data points

were recorded every hour of continuous measurement from 05th

-13thOctober 2009 at the eroded site……… 113

Figure 4.13 Changes in peat composition in in-situ and ex-situ conditions.

Fresh peat samples (t0) and incubated peat samples t309and t142

(after 309 and 142 incubated days)……… 115

Figure 4.14 Py-GC-MS total ion current chromatogram of the peat core

samples at 0-50 cm in depth at the (a) eroded and (b) uneroded

sites Red colour refers to fresh peat samples (t0) and blue colour is

incubated peat core samples (t1) after 309 incubated days in

anaerobic 10oC Peak symbols correspond to compounds listed in

Figure 4.15 Percentages of six organic compound classes as defined by

Vancampenhout et al (2009) in fresh peat (t0) and incubated peat

(t1) after 309 incubated days in anaerobic 10oC at the eroded and

Figure 4.16 Comparison of classification of organic compounds in the fresh

peat (t0) and incubated peat (t1) after 309 incubated days in

anaerobic 10oC at the eroded and uneroded sites into Pd and Aq… 117

Figure 5.2 Typical examples of glass plates with and without material

collected for (a) blank glass plate, (b) glass plates in eroded site and

(c) glass plates in uneroded site These plates had been in the stream

for (b) and (c) 110 days They were collected on 14 December

Figure 5.3 Separation of sediment material on glass plate for (a) scraping off

sediment on the top and bottom faces, (b) removing sediment from

all faces ultrasonically……… 133

Figure 5.4 (a) Diagram separation process of particle size distribution in

stream water using filter glass membrane (1.6 µm) and tangential

flow ultrafiltration (TFU) membrane plates (0.2 µm, 50 kDa and 10

kDa) and (b) Vivaflow 50 system (Viva Science, UK), master-flex

pump-head (Sartorius, Germany) and TFU membrane plates……… 135

Figure 5.5 Discharge-Q (l/s) and OC UF (mg/l) concentration at the outlet of

eroded and uneroded subcatchments in 2010……… 138

Figure 5.6 Relationship between organic carbon unfiltered (OC UF), organic

carbon <0.2 µm (OC<0.2 µm) and discharge at the outlet of eroded

and uneroded sub-catchments……… 139

Figure 5.7 Mass flux of SsOC, total and partitioned by PSD and compound

class (Interpolation of total OC from daily samples + partitioning

by average composition)……… 142

Figure 5.8 PSD of OC under different discharges (Q) at the eroded site The

discharge (l/s) and the organic carbon (OC) concentration (mg/l)

appear beneath each column Discharge increases approximately

linearly along the x-axis The thumbnail graphs show relative Q

five days prior to sampling, also OC (mg/l)……… 144

Figure 5.9 PSD of OC under different discharges (Q) at the uneroded site.

The discharge (l/s) and the organic carbon concentration (mg/l)

appear beneath each column Discharge increases approximately

linearly along the x-axis The thumbnail graphs show relative Q

five days prior to sampling, also OC (mg/l)……… 145

Figure 5.10 PSD of OC under different seasons at the eroded and uneroded

site The discharge (l/s) and the total carbon concentration (mg/l)

appear beneath each column……… 146

Figure 5.11 Relative composition of SsOC to in-situ peat at the eroded site… 148

Figure 5.12 Relative composition of SsOC to in-situ peat at the uneroded site 149

Figure 5.13 Relative Pd and Aq compositions of SsOC to in-situ peat at the

Figure 5.14 Relative Pd and Aq compositions of SsOC to in-situ peat at the

Figure 5.15 Mass of OC in different days in-situ on top and bottom faces of

glass plates at the (E) eroded and (U) uneroded sites……… 154

Figure 5.16 Composition of OC in sediment on (T) top and (B) bottom faces

of glass plates at the (E) eroded and (U) uneroded sites The T and

B faces and days in-situ appear beneath each column……… 154

Figure 5.17 Average percentage of total organic compounds in peat,

suspended and deposited sediment Ar-aromatics and

polyaromatics, Ph-phenols, Lg-lignin compounds, Lp-soil lipids,

Ps-polysaccharide compounds and N-compounds……… 155

Figure 5.18 Average percentage of total Pd and Aq compositions in peat,

suspended and deposited sediment……… 156

Figure 5.19 Illustrative diagram of hysteresis A clockwise hysteresis and B.

anti-clockwise hysteresis……… 162

List of Tables

Page

Table 2.1 Sub-catchments, area and elevation for each sampling point

containing continuous monitoring equipment Average data of

water table height were measured at the eroded site from 29

September to 13 October 2009……… 28

Table 2.2 Typical TOC sample sequence for automatic sampling ASI 5000A 49

Table 3.1 Water content (% weight of dry peat) of the peat core layers, data

present the mean ± standard error (SE) of three replication samples 65

Table 3.2 List of Py-GC-MS compounds found in the fresh and incubated peat

core samples, containing average retention time (RT), molecular

weight (MW), major ion and molecular formula (MF) Peak signs

correspond to those of Figure 3.3……… 69

Table 4.1 Effects of depth and site (eroded and uneroded) on rates of CH4and

CO2at 100C using analysis of variance (ANOVA): Two-Factor

with replication (P<0.05)……… 100

Table 4.2 Gas production rates (mMol t-1d-1) from peat incubated for 309 days

(A) and subsequent to changed conditions 333 days (B); 60 days

and 142 days (C) Data presented as mean of rates of triplicate

samples ± SE (standard errors), n=3……… 103

Table 4.3 Average concentration of gas (% v/v) of in-situ continuous

measurement at the eroded and uneroded sites at Crowden Great

Table 4.4 Effects of seasons on in-situ concentration (% v/v) of CH4and CO2

using analysis of variance (ANOVA): Single factor (P<0.05)…… 111

Table 4.5 Ratios of in-situ and ex-situ gas production from eroded and

uneroded peat at the Crowden Great Brook catchment……… 114

Table 4.6 Gas production rates of CH4and CO2of peat in anaerobic condition 118

Table 5.1 OC UF and OC <0.2 µm fluxes in different periods at the outlet of

eroded and uneroded sub-catchments in Crowden Great Brook

Table 5.2 Mass fluxes of SsOC of different size fractions and compound

classes in 2010 at the outlet of eroded and uneroded

sub-catchments Ar-aromatics and polyaromatics, Ph-phenols,

Lg-lignin, Lp-lipid, Ps-polysaccharide compounds and N-compounds

Table 5.3 Average PSD (% SsOC) The data presented as mean of percentage

and relative standard deviation (RSD), n=9……… 143

Table 5.4 Average compound class composition (% SsOC) The data

presented as mean of percentage and relative standard deviation

Table 5.5 Ranges of OC fluxes in the literature, along with notes on the

catchments studied and the source of data……… 158

The University of Manchester

Do Duy PhaiPhDQuantifying organic carbon fluxes from upland peat

21stMarch 2012Present organic carbon fluxes from an upland peat catchment were quantified through

measurement of in-situ direct and indirect greenhouse gas fluxes To predict future

greenhouse gas (GHG) fluxes, peat from eroded (E) and uneroded (U) site of an uplandpeat catchment was characterized

Composition of peat from E and U sites at the Crowden Great Brook catchment, PeakDistrict Nation Park, UK that was characterized by Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS) at 700oC Pyrolysis products of the peat were thenclassified using the Vancampenhout classification into 6 compound classes - viz

aromatic and polyaromatic (Ar), phenols (Ph), lignin compounds (Lg), soil lipids (Lp),polysaccharide compounds (Ps) and N-compounds (N) There was no significant

difference in the composition between the eroded and uneroded sites within the studyarea or between peats from different depths within each site Nevertheless, there was a

significant difference between sites in the proportions of Sphagnum that had contributed

to the peat Pyrolysis products of the peat were also classified into pedogenic (Pd) andaquagenic (Aq) OC – the mean percentage of Pd in both eroded and uneroded peats was43.93 ± 4.30 % with the balance of the OC classified as Aq

Greenhouse gas (GHG) fluxes were quantified directly by in-situ continuous

measurement of GHG was carried out at the E and U sites of the catchment using a

GasClam: mean in-situ gas concentrations of CH4(1.30 ± 0.04 % v/v (E), 0.59 ± 0.05 %v/v (U) and CO2(8.83 ± 0.22 % v/v (E), 1.77 ± 0.03 % v/v (U)) were observed, withboth the CH4and CO2concentrations apparently unrelated to atmospheric pressure and

temperature changes Laboratory measurements of ex-situ gas production - for both

CH4and CO2this was higher for U site soils than for E site soils At the U site,

maximum production rates of both CH4(46.11±1.47 mMol t-1day-1) and CO2(45.56 ±10.19 mMol t-1day-1) were observed for 0-50 cm depth in soils Increased temperaturedid not affect gas production, whilst increased oxygen increased gas production The

CH4/CO2ratios observed in-situ are not similar to those observed in the ex-situ

laboratory experiments; suggest that some caution is advised in interpreting the latter

However, the maximum OC loss of 2.3 wt % observed after 20 weeks of ex-situ

incubation is nevertheless consistent with the long-term degradation noted by Bellamy

et al (1985) from organic-rich UK soils.

Indirect greenhouse gas (GHG) fluxes were quantified through the mass flux of

suspended organic carbon (SsOC) drained from studied catchments The SsOC wasquantified by interpolating and rating methods Unfiltered (UF) organic carbon (OC)fluxes in 2010 were calculated to be 8.86 t/km2/yr for the eroded sub-catchment and6.74 t/km2/yr for the uneroded sub-catchment All the rating relationships have a largeamount of scatter Both UF OC and <0.2 µm fraction OC are positively correlated withdischarge at the eroded site, whilst there is no discernable relationship with discharge atthe uneroded site SsOC is dominated by Pd type OC (95.23 ± 10.20 % from E; 92.84 ±

ii Copies of this thesis, either in full or in extracts and whether in hard or electroniccopy, may be made only in accordance with the Copyright, Designs and PatentsAct 1988 (as amended) and regulations issued under it or, where appropriate, inaccordance with licensing agreements which the University has from time to time.This page must form part of any such copies made.

iii The ownership of certain Copyright, patents, designs, trade marks and otherintellectual property (the “Intellectual Property”) and any reproductions ofcopyright works in the thesis, for example graphs and tables (“Reproductions”),which may be described in this thesis, may not be owned by the author and may

be owned by third parties Such Intellectual Property and Reproductions cannotand must not be made available for use without the prior written permission ofthe owner(s) of the relevant Intellectual Property and/or Reproductions

iv Further information on the conditions under which disclosure, publication andcommercialisation of this thesis, the Copyright and any Intellectual Propertyand/or Reproductions described in it may take place is available in the University

IP Policy (see http://documents.manchester.ac.uk/DocuInfo.aspx?DocID=487), inany relevant Thesis restriction declarations deposited in the University Library,The University, Library’s regulations (see

http://www.manchester.ac.uk/library/aboutus/regulations) and in The

University’s policy on Presentation of Theses

The author would like to thank very deeply all supervisors Drs Clare H Robinson,Bart E van Dongen, Stephen Boult and Prof Dave Polya for their kind and helpfuladvice throughout the study period and during preparation of this thesis

Thanks also go to Drs Peter Morris, John Gaffney and Alison Jackson for their helpwith field and laboratory work Thanks are also due to Paul Lythgoe, Alastair Bewsherand Cath Davies, in the Manchester Analytical Geochemistry Unit of the School ofEarth, Atmospheric and Environmental Sciences for their practical help and advice inthe laboratory My thanks also to the staff of the John Rylands library for their kindhelp

I thank my parents, brothers, sister, my wife and kids for their morale support andencouragement in my study

I thank as well my colleagues and official staff of the Soils and Fertilizers ResearchInstitute (SFRI) - Vietnam Academy of Agricultural Sciences (VAAS) and VietnamInternational Education Development (VIED) - Ministry of Education and Training(MOET) who regularly kept in touch with me during this PhD programme

Finally my thanks to the Vietnamese government - “Key programme of developmentand application of biotechnology to agricultural field and rural development up to2020” of the Ministry of Agriculture and Rural Development (MARD) through thecoordinator organization Vietnam International Education Development (VIED) -Ministry of Education and Training (MOET) and The University of Manchester

Overseas Research Scholarship (ORS) for their financial support for this PhD

programme and during writing the thesis Thank you

Ar Aromatics and polyaromatics

CSD Chemical Data Systems

DIW Deionised water

DOC Dissolved organic carbon

DO Dissolved oxygen

EC Electrical conductivity

EPS Extracellular polymeric substances

GC-MS Gas Chromatography-Mass Spectrometry

PSD Particle Size Distribution

Py-GC-MS Pyrolysis-Gas Chromatography-Mass Spectrometry

RSE Relative standard error

SsOC Suspended organic carbon

SE Standard error

TFU Tangential flow ultrafiltration

TOC Total organic carbon

v/v Volume per volume

Chapter 1

General introduction

1.1 Introduction and justification for research

The greenhouse effect is the process by which the presence of certain gases in theatmosphere traps long-wave radiation emitted from the Earth’s surface thereby makingthe Earth warm enough to support life The gases responsible are known as greenhousegases (GHGs): they include carbon dioxide (CO2) and methane (CH4) Along with otherGHGs, they cause global mean temperature to be 15oC rather than a modelled -18oCthat it would be in the absence of an atmosphere (Mitchell, 1989) In recent decades,the concentration of greenhouse gases in the atmosphere has rapidly increased (IPCC,2007), thereby trapping increased amounts of radiation and probably causing changes inglobal climate (Schneider, 1989)

The major GHGs contain carbon (C), CO2is the most important because it has a

relatively high concentration of 388 ppm (Nolta, 2011) However, although at muchlower concentration, CH4has a GHG potential 22 times that of CO2, and is therefore asignificant contributor to greenhouse warming Concentrations of both CO2and CH4are increasing yearly at approx 1.5 ppm yr-1and 7.0 ppb yr-1respectively (IPCC, 2001).The concentrations of both these gases are controlled by the global carbon (C) cycle

Atmospheric concentrations (e.g of CO2) are controlled by cycling between

atmosphere, ocean and earth materials; both the solid geology and its uppermost

covering, the soil (Figure 1.1) Soils contain carbon, and are by far the largest

terrestrial carbon reservoir (Gorham, 1991) and therefore an important component of the

to 1991 were 4550 million tonnes of C (Wigley & Schimel, 2000) However, changes

in soil because of changes in land management may be equally or more important.During the period from 1850 to 2000, globally, carbon flux from changes in land useand management released an estimated 156 Pg of C into the atmosphere (Houghton,2003) Changes in rice paddies from drying to flooding in the process of cultivationleads to anaerobic soils and the release of CH4(Neue et al., 1996) In addition, there are

changes in drainage of soils which lower the water table extending aerobic conditionsdownward and increasing oxidation of C releasing CO2(Evans et al., 1999).

Such changes in soil will have most impact when soils with high carbon content areaffected Soils with very high C content are known as histosols and, of these, peatshave the highest C content (>50%) (Baldock & Nelson, 1999; Brady, 1990) Peatscover 4 x 106km2of the global ice-free land area (Gorham, 1991; Wilding, 1999), andthey cover 3.46 x 106km2in the arctic/tundra (Vitt, 2006) and 0.36 x 106km2in tropics(Andriesse, 1988) Many of these peats are fairly inaccessible, which has limited

confidence in estimating their GHG emissions Besides the inaccessibility, peats inupland areas are also subject to hydrometeorology characterised by low frequency, highintensity events, such as storms, which are likely to make representative measurement

of GHG emissions even more difficult, because of lacking equipment GHG fluxesfrom peat are likely to be a significant contributor to atmospheric concentrations, andthese fluxes are not well quantified in upland environments The aim of this research is

to quantify present and to attempt to predict under a possible climate change scenario,using an increase of 5oC in temperature and a fall in water table, GHG fluxes fromupland peat in the United Kingdom Quantification of present GHG fluxes being both

an important aim in itself but also necessary in order to predict future changes

associated with land management changes

Present and future GHG fluxes from upland peat are both direct; those to atmosphere

from in-situ intact primary peat, and indirect; those from transported and dispersed peat

(Figure 1.2) The present direct flux of GHG can be quantified by making

measurements in in-situ peat, while prediction of GHG fluxes requires ex-situ peat to be

manipulated experimentally to model changing environmental factors However,

prediction of future fluxes is also possible from in-situ peat because spatial variability in

natural peat allows field-scale experiments; eroded peat is a field-scale model of thefuture as climatic warming is expected to dry peat and make it more liable to erosion

(Nearing et al., 2004) Chapter 2 describes such a field site in which uneroded and

eroded peat are adjacent and therefore subject to otherwise identical hydrometeorology

Chapter 4 explains the methods and errors in making such measurements of direct

GHG fluxes

Indirect GHG fluxes from peat are those spatially or temporally dislocated from the peatdeposits In temperate zones, this dislocation is primarily caused by fluvial transportand there is a requirement to quantify GHG emission from this transported peat Directmeasurement is not possible because of the extent of the area across which the peatbecomes dispersed and the requirement to separate the GHG signal of the peat from that

of the background material into which it has been dispersed However, it is possible to

quantify how much peat is transported from a catchment (Figure 1.2) prior to its further

dispersion and the GHG flux from this mass of peat can be inferred from the

measurements of in-situ peat This inference may need some modification because

transportation may not only alter the location of the peat but may also alter its

composition and thereby its GHG generating potential Quantification of fluvial fluxes

of organic carbon (OC) and alterations in composition through transportation, with

respect to GHG generating potential, are the aims of Chapter 5.

Figure 1.2 Diagram of direct and indirect greenhouse gas fluxes from an upland peat

catchment.

Climate change will be manifested in various ways and each of these can have differentinteractions with peat deposits Dependent on location general global warming (Moore

et al., 1996) may result in local cooling (Folland et al., 1990) Furthermore such

warming is likely to result in generally drier conditions but in some places higher

intensity rainfall (Mansell, 1997; Yu & Neil, 1991) Peat is by definition

water-saturated and throughout its profile largely anoxic for most of the year Therefore thesetypes of climatic changes will have direct impacts on the integrity of the deposit andthereby the absolute and relative amounts of CO2and CH4produced within it Giventhe variety of climatic change and interaction with peat there are a wide range of

scenarios that could arise The latest climatic change scenarios indicate that most ofEurope will be warmer in all seasons, drier in Summers and wetter in Winter (Ekström

et al., 2007) In terms of the UK climate change in the future, the most recent climate

change scenarios were published by the UK climate impacts programme (UKCIP)produced by the Meteorological Office’s Hadley Centre regional model (HadRM3) Inthe UKCIP02 report, the temperature of the UK will increase 3.5oC by 2080 and all

seasons will be warmer (Hulme et al., 2002) Some detailed examples for the UK are

given in Figure 1.3 Present conditions are representative of rainfall and temperature to

give the present impact on vegetated and eroded peats Future scenarios are

representative of climate change [low rainfall (lowered water table) and temperatureincrease] to give impact on the peat types, then ratios of CH4, CO2and total amount ofGHG will be changed Understanding of the net GHG potential (CO2+ (CH4*22)) ofeach of these scenarios will be a requirement for those charged with the management of

upland peats now and as any climatic change proceeds The findings of Chapters 3-5 are relevant to this understanding and Chapter 6 synthesises their findings to this end.

Present conditions

Future scenarios

Figure 1.3 Scenarios of potential future release GHGs from two types of upland peat:

Vegetated (uneroded) and eroded peat.

In order to test these scenarios, an experimental design is presented in Figure 1.4.

Uneroded and eroded peats are two research materials that will quantify in-situ GHG

and fluvial OC fluxes (present scenarios), whilst future scenarios (climate change) will

quantify GHG fluxes in ex-situ conditions by temperature increase simulation.

Figure 1.4 Illustrative diagram of experimental design for present and future (climate change)

scenarios of two peats.

A study of upland peat requires knowledge of its composition: In order to set a specific

investigation into a global context and because composition of the in-situ material is a

prerequisite of investigating its transformation, whether directly (Chapter 4) or

indirectly (Chapter 5) to GHG Therefore, a necessary preliminary to the work

described in the preceding paragraphs is to determine the best way to analyse and toclassify a heterogeneous material An appropriate classification is one that relates toeither or both processes of peat formation and the processes of its transformation to

GHG The aim of Chapter 3 is to characterise the peat and develop or verify such a

Temperature simulation to quantify rates of CH4 and CO2

Quantifying CH4, CO2 concentration

Quantifying

CH 4 , CO 2

concentration

Temperature simulation to quantify rates of

Eroded peat

classification, whilst Chapter 2 describes in detail the methods by which analyses and

data collection was carried out for all chapters

Quantifying OC fluxes from upland peat had previously been studied (Hope et al., 1997; Pawson et al., 2008; Worrall & Burt, 2005) However, these OC fluxes were

only quantified in fluvial transport on general catchments and composition of peat wasnot characterized In this study, the OC fluxes were quantified in a synchronised waythrough the direct and indirect GHG fluxes on specific sub-catchments The direct

GHG fluxes were quantified in both ex-situ and in-situ conditions (Chapter 4) that

quantified ex-situ rates of GHG production (mMol/t/d) and in-situ GHG concentration (% v/v) In-situ ratios of CH4:CO2 will be conducted to validate ex-situ ratios of

CH4:CO2, because they considers the environmental factor variables such as emperature

and pressure Furthermore, ex-situ rates of GHG production, simulated increase

temperature, present future GHG fluxes under impact of climate change Indirect GHGfluxes were quantified through fluvial OC fluxes to determine amount of OC fluxes(t/km2/yr) (Chapter 5) Total direct and indirect GHG fluxes from each sub-catchemt

indicate OC flux is lost from the catchment Composition of peat in two catchments was classified into 6 compound classes and further classify into Pd and Aq

sub-(Chapter 3) Particle size distribution (PSD) of suspended OC (SsOC) and deposited sediment (Chapter 5) were also characterized to compare with composition of the peat.

These results will indicate oxidation possibility of OC particles in transport processfrom upland peat to aquatic ecosystem within each sub-catchment This overall

structure of the thesis described in the preceding paragraphs is summarised in Figure

1.5.

Figure 1.5 Illustrative diagram of the thesis.

Characterization

of peat

(Chapter 3)

Direct GHG fluxes

(Chapter 4)

Indirect GHG fluxes

(Chapter 5)

the Crowden Great Brook catchment, near Manchester, UK (Figure 2.1) All waters of

the catchment are collected by stream systems which originate from Black Hill (530 ma.m.s.l) and then drain into the Torside Reservoir, which supplies drinking water toGreater Manchester Peat sample locations were selected to obtain a set of sampleswhich had been impacted by erosion to different degrees: specific locations were based

on a previous survey by Dr Boult’s research team (Gaffney, 2008; Todman, 2005)

(Figure 2.2).

Figure 2.1 Location of Crowden Great Brook near Manchester, UK for (a) figure reproduced

from ©2009 Google - Map data ©2011 Tele Atlas and (b) figure reproduced from Ordnance

Crowden Great Brook

Table 2.1 Sub-catchments, area and elevation for each sampling point containing continuous

monitoring equipment Average data of water table height were measured at the eroded site from 29 September to 13 October 2009.

Sub-catchment Sampling site Area (km2) Elevation

(m a.s.l)

Water table(m)Vegetated

Figure 2.2 The vegetated (uneroded) peat sub-catchment A photo viewed to the west of the

monitoring equipment, labeled 30 in Figure 2.4 B Schematic representation of key vegetated

peat with gaseous, fluvial fluxes and high water table.

Figure 2.3 The unvegetated (eroded) peat sub-catchment A photo viewed to the north of the

monitoring equipment, labeled 50 in Figure 2.4 B Schematic representation of key eroded

peat with gaseous, fluvial fluxes and low water table.

Border of Crowden Great Brook catchment

Border of sub-catchments

O Outlet of sub-catchments

Peat cores were taken and in-situ gas measurements were performed at the

eroded and vegetated (uneroded) sub-catchments

Water and deposited sediment samples were taken, and discharge was measured

at the eroded and vegetated (uneroded) sub-catchments

Figure 2.4 Location of sampling points at eroded and vegetated (uneroded) sub-catchments in

the Crowden Great Brook catchment Figure adapted from Todman (2005) and reproduced from Ordnance Survey map data by permission of Ordnance Survey, © Crown copyright Sub- catchments: the eroded peat site has a greater surface area of bare peat than the sub-

catchment at the uneroded peat site which is covered by vegetation Photos were taken in

Black Hill

Torside Reservoir

Located near Manchester, UK, in the Peak District National Park, Crowden Great Brookcatchment has a total area of 7 km2, of which the eroded (E) sub-catchment has an area

of 0.5 km2and the uneroded (U) sub-catchment has an area of 3 km2 Elevation of thecatchment ranges from 220 m to 550 m a.s.l (Todman, 2005) There are two mainsampling locations that are shown: site 30 uneroded (vegetated) sub-catchment and site

50 eroded sub-catchment (Figure 2.4).

Geological maps (Figure 2.5) show that bed rocks at the Crowden Great Brook

catchment consist of four kinds: Kinder Grit, Shale Grit, Heydon Rock and

Huddersfield White Rock Drift Geology includes Boulder Clay, Gravel, Alluvium,Sand and Gravel These evidences indicate the catchment is underlain by Millstone gritand shales (Jackson, 2010) Peat covers approximately 70 % surface area of the

Crowden Great Brook catchment t (Todman, 2005)

Peat cores were taken and in-situ gas measurements were performed at the

eroded and uneroded sub-catchments

Water and deposited sediment samples were taken, and discharge was measured

at the eroded and uneroded sub-catchments

Figure 2.5 The geology of the study catchment (a) map and (b) cross section with red line

representing the position of cross section Figure reproduced from Ordnance Survey map data

by permission of Ordnance Survey, © Crown copyright Figure adapted from Todman (2005).

Drift Geology

Orange Gravel

Horizontal scale: 1 km

Vegetated

Eroded

2.2 General methods

2.2.1 Peat sampling

Peat samples were taken at the E and U sites using a peat auger (Eijkelkamp Ltd, the

Netherlands) at the Crowden Great Brook catchment near Manchester, UK (Figure 2.6

a) The peat auger, used for taking peat samples, was a chambered-type auger with

handle-bars and many connectors Thus, the peat auger allowed us to take peat samples

at different depths The peat auger measured 10 cm in diameter and 50 cm in length,when it was rotated clockwise 180o, the sharpened edge of the chamber cut a peat

core/borehole that contained a peat volume sample by the cover plate (Figure 2.6 a).

Six fresh peat samples, three samples from the E site (53o30’ 35’’ N, 1o55’ 36’’ W) andthree other samples from the U site (53o31’ 33’’ N, 1o54’ 40’’ W) were taken at thecatchment on 14 and 15 December 2009 Three peat samples that were representative

of three replications were taken in a 1 m2area at the each site (Figure 2.4) Depth of

peat at the E site was 200 cm Depth of peat at the U was 160 cm, because the augercould not penetrate the peat beyond this depth The peat samples were divided intothree different depths At the eroded site, the peat core samples were divided into threedifferent depths: 0-50 cm; 50-100 cm and 150-200 cm, whereas at the U site, the peatcore samples were separated into three different depths: 0-50 cm; 50-100 cm and 110-

160 cm, for a total of 18 samples (Figure 2.6 b) The fresh peat core samples were then

separated into two sub-samples along the length of each sample A sub-sample (about

700 g) of each peat core sample was immediately placed into a 1000 ml glass bottle

(incubation bottle) for ex-situ gas production experiments (Chapter 4) and another was

collected in an envelope made of pre-combusted aluminum foil for further analyses:

composition of peat (Chapter 3), peat slurry (Chapter 4), and determining water

content and density of peat These sub-samples were stored at -20oC until analysis Anincubated bottle has an airtight lid and attached two valves that can be opened and

closed to measure gas fluxes (Figure 2.6 a).

Figure 2.6 Peat sampling (a) Chambered-typeaugerand incubation bottle with an airtight lid and two valves and (b) order of peat core samples were taken on 14 and 15 December 2009 from eroded and uneroded sites at the Crowden catchment Numbers beside on the right of bottles are different depths of peat Numbers on the bottles are order of samples.

2.2.2 Water sampling

Natural stream water samples were collected at the stream outlets of E and U catchments where were the same locations collecting sediment samples from the erodedsite (53o30’ 17’’ N, 1o54’ 53’’ W) and from the uneroded site (53o31’ 27’’ N, 1o54’28’’ W) The samples were taken from February 2010 to May 2011 There were twokinds of water samples: Daily and monthly water samples Daily 500 ml water sampleswere collected at 1 am by auto sampler and monthly 5000 ml water samples were takenmanual Polypropylene 500 ml and 5000 ml bottles pre-washed with HNO3(10%,Analytical grade, Fisher chemicals, UK) were used to take samples

sub-2.2.3 Sediment sampling

This section relates to the utility of sediment collection plates as integrators of the

inherently variable amounts of suspended OC (Chapter 5) Plates of frosted glass were

used to take sediment samples Each plate has length, width and thickness 8 x 4.5 x 0.4

cm, and was numbered on each face and pre-weighed Then, the glass plates were

fastened on to the metal racks (Figure 2.7) that were fit on bed rocks and sunk in water

of the stream at the outlet streams of each sub-catchment (E and U) at the CrowdenGreat Brook catchment The flat rocks used to avoid the bottom of the glass platescoming into contact with mud of the stream bed Generally, three glass plates weresunk in water at the outlet streams at the same time and were also taken out at the sametime in order to calculate standard error of sediment samples

Figure 2.7 Diagrammatic collecting water column and sediment samples in river water of upland

peat catchment for (a) bottle with a volume of 5 L was used to take water column sample and (b) glass plates were setup to collect sediment.

2.2.4 In-situ monitoring

2.2.4.1 Determination of discharge

Dilution gauging technique was used to determine discharge (Wood and Dykes, 2002).The technique used NaCl as a conservative tracer and determination of its electricalconductivity (EC) to establish its dilution The value of discharge is calculated based on

a combination of measurement results between EC, mass of tracer and time In order todetermine the parameters, a four pole EC probe, with a measuring range of 0-2500µS/cm and pre-calibrated with a known NaCl standard was connected to a Sentry II datalogger (Intelisys, UK) The data logger was programmed to log at 3 second intervals

and was placed into the stream at the outlet of each sub-catchment (Figure 2.4) A

pre-weighed amount of NaCl was dissolved in a 0.5 L plastic bottle and released into thestream water a distance above 10 m upstream from the position of the probe A hand-held probe was also used to measure EC upstream and down stream from where the

NaCl was added until the readings were consistent (Figure 2.8) This work was

repeated every time when suspended samples were taken at the outlet of each catchment

sub-Figure 2.8 Illustration of a dilution gauging curve.

Finally, discharge was calculated based on the parameters such as the EC value, mass of

NaCl and time that were downloaded from the logger by using Equation 2.1 as follows.



 A A

m

Q ; (t * m) – (t * b) * n

Equation 2.1 Calculation of discharge by dilution gauging Where Q= discharge (l/s);

m = mass of NaCl (g); A = area under curve (g l/s) (Fig 2.8); t = time interval (s); b = baseline

value (g/l); n = number of data points.

2.2.4.2 Continuous gas measurement

In order to setup in-situ continuous gas measurement, a chambered-type auger (Figure

2.6 a) was used to make boreholes at different depths Next, pieces of plastic pipe were

placed in the boreholes Each piece had an airtight lid and two switches to close andopen borehole On the length of the pipe, holes were scratched that allowed gas topermeate through Then, the boreholes were flushed by pure compressed nitrogen gas(CalGaz Ltd, USA) and checked oxygen concentration in the boreholes This workmaintained an anaerobic atmosphere in the boreholes Finally, two outlets of a

GasClam (Salamander Ltd, UK) were then connected with two switches on the airtight

lid of pipe to record all the continuous monitoring and put on the top of the pipe (Figure

2.9).

Figure 2.9 Peat borehole Each peat borehole has a plastic pipe, an airtight lid, switches and

drill holes and a GasClam to measureCO2, CH4, O2concentrations, temperature andatmospheric pressure every hour.

2.2.5 Ex-situ monitoring

2.2.5.1 Anaerobic incubation

At the field-sites, peat samples were immediately placed into incubation bottles andwere flushed with pure compressed nitrogen gas (CalGaz Ltd, USA) Subsequently, thebottles were transported to the laboratory and were purged again with pure compressednitrogen gas (BOC Ltd, UK) and checked for any oxygen gas concentration in thebottles by using the GasClam (Salamander Ltd, UK) to ensure that the environmentinside the bottles was completely anaerobic

2.2.5.2 Aerobic incubation

Oxygen concentration in the incubation bottles was checked using the GasClam

Generally, when oxygen concentration decreased from 21.0 % to 17.0 % then the

airtight lids of the bottles were opened to allow oxygen gas to come in Time durationfor opening the lids was about 10 minutes After that, the airtight lids were closed Gas

productions were released in the incubation bottles through Equation 2.2 as follows

Equation 2.2 Respiration of organic materials in incubation bottles (a) and (b) in

anaerobic and (c) in aerobic conditions (from Brady, 1990; Moore et al., 1996).

2.2.5.3 Measurement of concentration and calculation of gas production

To avoid errors from the measurement, the GasClam serial number 00018 (SalamanderLtd, UK) has been used to measure gas production in the incubated bottles since 14

December 2009 (Figure 2.10) The GasClam used two alkaline batteries size D to

operate In order to measure concentrations of CH4, CO2and O2, gas fluxes were

sampled during a minute through valve 1 and a filter by a pump and pushed through thesensor system to quantify concentrations of CH4, CO2and O2and then the gas fluxes go

out through valve 2 Atmospheric pressure was measured through valve 3 (Figure 2.10

b) Concentrations of CH4, CO2and O2were measured by infra-red sensors with the

resolution at 0.01 % The GasClam is the first product of in-situ borehole gas monitor

in the world that is suitable for detection of GHG fluxes in borehole monitoring such as

CO2, CH4, O2and other parameters such as temperature, barometric pressure and

borehole pressure (Ion Science Ltd, 2008) The GasClam was used which linked with acomputer by a cable and was controlled by GasClam software version 2.5.6 Two lines

of plastic tubing were used to connect between the GasClam, the valves of the bottle

and the hose from the nitrogen gas station (Figure 2.10) Before opening the valves to

measure gas production, the incubation bottle was repeatedly shaken a few minutesprior to each measurement in order to homologize gas concentration in the bottle andthe headspace of two lines of plastic tubing was flushed with pure nitrogen until therewas no oxygen gas inside the system First, the valve one (V1) was opened in order toallow nitrogen gas to push oxygen to the pump of the GasClam Then, the pump tookair samples and transported to the sensor system for checking oxygen concentration Atthe same time, the valve two (V2) was opened to push waste air samples out of thetubing system, whereas the valves three and four (V3) and (V4) were still closed Next,when the pump was stopped, the V1 and V2 were closed This step avoided oxygen gas

to come in from the atmosphere and created a closed tubing system After that, checking

if the closed tubing system was not oxygen, then V3 and V4 were opened for GHGfluxes from the incubated bottles took up the closed tubing system The GHG fluxesfrom the incubated bottles were sampled during a minute by the pump and pushedthrough the sensor system to quantify concentration of CH4, CO2and O2and then theGHG fluxes were pushed back the incubated bottles At that time, when the pumpstopped then the V3 and V4 were closed Finally, using the GasClam, we measuredCH4, CO2, O2(in volts and percentages), barometric pressure, and borehole pressure by

infrared and electrical sensor systems, were measured (Figure 2.10).

Figure 2.10 Measuring gas production system: (a) the GasClam (Salamander Ltd, UK), (b)

operation diagram of the GasClam, (c) the GasClam was linked with a computer by a cable and controlled by a GasClam software version 2.5.6 and (d) two lines of plastic tubing were

connected between the GasClam, the valves of the bottle and the hose from the nitrogen gas station.

Concentration of gas production in the incubation bottles were calculated by equation asbelow

Equation 2.3 Amount of gas produced inside bottle Where gas concentration is mole/tonne

(mol t-1), headspace is gap volume of the incubated bottle (L), concentration (%) is

concentration (%) of gas productions in the incubation bottle, 100 is percentage of gas

production in 100 L, 22.4 is standard transfer coefficient to mole, mass of dry peat is tonne.

2.2.5.4 Aerobic incubation of peat slurry and calculation of gas production

OxiTop®-C bottles (WTW Ltd, Germany) were used to measure respiration of peatslurry samples in the aerobic condition The OxiTop®-C bottle consisted of three parts: