Dissolved organic carbon: sources, sinks and future trends

Transcription

1 Dissolved organic carbon: sources, sinks and future trends Eleanor Jennings 1, Elizabeth Ryder 1, Elvira de Eyto 2, Mary Dillane 2, Russell Poole 2, Rowan Fealy 3. 1 Centre for Freshwater and Environmental Studies, Dundalk institute of Technology. 2 Marine Institute, Burrishoole, Newport, Mayo. 3 Department of Geography, National University of Ireland Maynooth

2 Percentage peat cover in Europe Mayo, Ireland Peat cover in Europe: Monterella et al. 2006

3 Dissolved Organic Carbon High DOC concentrations in streams draining peat soils Major carbon source in downstream systems Issues for water treatment DOC + chlorination = THMs e.g. CHCl 3 e.g. CHBr 2 Cl major health implications

4 Poulaphuca: colour 1980 to 2002 Data: Dublin City Council

5 Long-term increases in have been reported from many sites in Europe and N America Forsberg and Petersen, 1990 S Sweden Hongve et al SE Norway Worrel et al % of 198 catchments Andersen et al. (1991) Sweden Skjelkvåle et al. (2001) Norway, Sweden and Finland

6 is largely driven by climate Temperature Soil moisture deficit Rainfall Discharge Production of DOC In soil Transport

7 water colour (Hazen) Effect of drought on water colour/doc droughts time (years) Water colour observed at Ewden treatment works, UK: a response to recent droughts (after Watts et al., 2001).

8 Effect of drought on water colour/doc Enzymic latch mechanism Freeman et al Activity of hydrolase enzymes restricted by phenolic compounds Water table drawn down phenol oxidase activity increases phenols decrease Hydrolase enzymes switched on by water table drawdown but not switched off on rewetting Switched on for 3-5 years

9 Showed changes in DOC are related in part to long-term decreases in acidification Monteith et al Nature 450,

10 Burrishoole catchment rain gauge GG1 rain gauge GG2 Glenamong sub-catchment area 1821 ha Forested area 408 ha = 22% Annual rainfall = 2000mm Lough Feeagh 392 ha, oligotrophic humic lake Maximum depth 45m

11 Burrishoole catchment Glenamong River Lough Feeagh

12 Burrishoole catchment Important site for salmon, trout and eel research (Marine Institute)

13 Historical trends Burrishoole catchment Cattle Sheep People Forestry 1900 to 2006 Dalton et al. 2010

14 Catchment instrumentation Glenamong River Automatic River Monitor (ARMS) ph, conductivity, temperature, dissolved oxygen, CDOM fluorometer and nephelometer Lough Feeagh Automatic Water Quality Monitoring Station (AWQMS) ph, conductivity, temperature, dissolved oxygen, CDOM fluorometer, Chl fluorometer, nephelometer, thermistor chain and weather station

15 In-situ C instrumentation CDOM fluorometer: Chromophoric dissolved organic matter is used as a proxy for dissolved organic carbon (DOC)

16 issues November 2010 December 2010 January 2011 December 2010 November 2010 Glenamong January 2011 Lough Feeagh The degree of temperature quenching is not constant Suggests that composition fluorescing substances changes Temperature correction ranges from 1% to 3% per degree Ryder et al L&O: methods

17 Corrected and uncorrected CDOM data Glenamong River Raw fluorescence data were corrected using stream temperature data Ryder et al L&O: methods

18 DOC (mg L -1 ) DOC (mgl -1 ) DOC (mg L -1 ) Turbidity and CDOM fluorescence DOC mg L y = 0.14x y = 0.09x y = 0.098x r 2 = 0.43 r 2 = 0.58 r 2 = 0.76 r² 0.43 Aug 2010 r² = 0.53 r² Sept A All data B FTU < C FTU < QSU QSU RFU RFU QSU RFU Results indicate that concentrations of suspended sediments greater than 10 mg L -1 interfere with CDOM fluorescence signal

19 Rainfall and flow Rainfall Flow

20 Mean daily DOC concentration the Glenamong River 9.75t C km -2 yr t C km -2 yr Ryder et al. (submitted)

21 Mean daily DOC concentration the Glenamong River 9.75t C km -2 yr t C km -2 yr Ryder et al. (submitted)

22 Standardised Precipitation Index 2002 to 2011

23 Mean daily DOC concentration the Glenamong River No step change response to forestry clearfelling Clearfelling 9.75t C km -2 yr t C km -2 yr Ryder et al. (submitted)

24 Drivers of in the Burrishoole catchment General additive model: Significant factor: drought Drought, soil temperature, and streamflow explain 60% of variance in DOC

25 Model of used in RESCALE Soil temperature Peat decomposition Soil moisture level Available DOC in soil Washout via hydrological pathways DOC in streamwater Naden et al. 2010

26 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04 Aug-04 Oct-04 Dec-04 Feb-05 Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00 Model of used in RESCALE Hydrological parameters m 3 s Modelled Measured 3 DOC production: rate of decomposition temperature dependence soil moisture dependence 2 DOC transport: rate of washout partitioning between surface and subsurface pathways Naden et al DOC mg L Measured Modelled

27 Climate change projections Climate change scenarios Selected GCMS (SRES A2 and B2): Control period ( ) Statistical downscaling DOC-GWLF model Climate impact on DOC Model parameters Calibrated using measured data 100 realisations 3 GCMs 2 SRES

28 Projected change in maximum air temperature Burrishoole catchment Fealy et al. 2010

29 Projected change in precipitation Burrishoole catchment Fealy et al. 2010

30 Projected increase in DOC concentrations A A A2 DOC mg L DOC mg L DOC mg L DOC mg L J F M A M J J A S O N D B2 DOC mg L J F M A M J J A S O N D B2 DOC mg L J F M A M J J A S O N D B J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D Fealy et al mg DOC L -1 A2 scenario B2 scenario

31 Air temp o C Drivers of increase in DOC concentrations A2 scenario Unsat zone cm A Flow m 3 s -1 J F M A M J J A S O N D Soil temperature A J F M A M J J A S O N D Streamflow DOC mg L Peat decomposition Available DOC in soil A2 J F M A M J J A S O N D A2 J F M A M J J A S O N D Soil moisture DOC Fealy et al. 2010

32 Conclusions Summary is highly sensitive to climatic factors. In-situ instrumentation can be used to give more accurate estimates of. Temperature quenching of CDOM fluorescence is variable and a correction should be applied. The inhibitory effect of turbidity should also be taken into account. projections: increase of 15% to 36% in DOC concentrations exported from peat catchments. Implications for ecology, drinking water, and long-term carbon storage.

33 Thank You

34 References: Ryder E, Jennings E, de Eyto E, Dillane M, Nic Aongusa C, Pierson DC, Moore K, Rouen M, Poole R Temperature quenching of CDOM fluorescence sensors: temporal and spatial variability in the temperature response and a recommended temperature correction equation. Limnology & Oceanography: Methods. 10 Fealy, R., Allott, N., Broderick, C., de Eyto, E., Dillane, M., Erdil, R.M., Jennings, E., McCrann, K., Murphy, C., O'Toole, C., Poole, R., Rogan, G., Ryder, L., Taylor, D., Whelan K. and White, J. (2010) RESCALE: Review and Simulate Climate and Catchment Responses at Burrishoole Project-Based Award, Final Summary Report. Marine Research Sub-Programme (NDP ) Series Dalton, C., Jennings, E., Taylor, D., O Dwyer, B., Murnaghan, S., Bosch, K., de Eyto, E. & Sparber, K. (2010). Past, current and future Interactions between pressures, chemical status and biological quality elements for lakes IN contrasting catchments in IrEland (ILLUMINATE). EPA/ERTDI Project # 2005-W-MS-40 Final Report 290 pp Naden, P., Allott, N., Arvola, L., Jarvinen, M., Jennings, E., Moore, K., Nic Aongusa, C., Pierson, D. and Schneidermen, E. (2010) Modelling the effects of climate change on dissolved organic carbon. In D.G. George (ed.) The Impact of Climate Change on European Lakes. Springer.