Nitrous Oxide Focus Group Nitrous Oxide Focus Group launch event Friday February 22 nd, 2008 Dr Kevin Hiscock and Professor Julian Andrews School of Environmental Sciences University of East Anglia N 2 O production in different environments – the consequences for environmental management

Content of presentation: N 2 O and ….. … links between land use and surface and ground waters … links between coastal defence and biogeochemical cycling

N2ON2O N2ON2O The soil nitrogen cycle

Linking land use and N 2 O loss Denitrification N2ON2O Nitrification N2ON2O N2ON2O N2ON2O Nitrogen sources Riparian buffer zone

Direct soil emissions * Animal production * Indirect emissions (including nitrogen leaching and runoff) * Emission rate of 2.1 Tg N a -1 Atmospheric N 2 O increase = 3.9 Tg N a -1 Indirect emission account for 2/3 of the uncertainty in the total global N 2 O emissions due to uncertainty in the estimated emission factors, especially EF5-g (= 0.015) Total emissions of N 2 O associated with agriculture (IPCC methodology):

Groundwater N 2 O concentration data for British limestone aquifers

Effect of land use on surface water and groundwater N 2 O concentrations

Groundwater environmentLand use N 2 O (nM) Mass ratio N 2 O-N/NO 3 -N Chalk, Cambs. & NorfolkArable Weathered bedrock, England & Scotland Uncultivated upland Poorly consolidated clay, silt, sand and gravel Rangeland, arable and cattle< Alluvium, sands and gravelsForest and cropped field soils ~0.003 SandWoodland with manure disposal Karstic limestoneSewage effluent disposal SandSewage effluent disposal Clay soils, agricultural drainsArable11-356,571~0.001-~0.01 Alluvial riparian zone underlain by clay aquiclude Maize, riparian forestMean = 17, Clay and loess soils, agricultural drains Grassland Mixed arable and grass <143 < Hydromorphic silty clay loam soils, shallow water table Arable and pasture214-21,

Calculation of indirect N 2 O emissions from groundwater and agricultural drainage (revised IPCC methodology): N 2 O(L) = NLEACH x EF5-g NLEACH = 0.3 x 130 kg N 2 O-N/ha/a EF5-g = N 2 O(L) = 0.07 kg N 2 O-N/ha/a

Calculation of indirect N 2 O emissions from groundwater and agricultural drainage (using hydrogeological data): N 2 O(L) = mean N 2 O concentration x groundwater flux Cambridgeshire groundwater data (area = 130 km 2 ): = 0.04 kg N 2 O-N/ha/a N 2 O emissions from UK soils = kg N 2 O-N/ha/a

Total N 2 O emissions from major UK aquifers: (assuming emission rate equal to the Cambridgeshire Chalk): 3.45 x 105 kg N 2 O/a Modelled fertiliser-induced N 2 O emissions from arable and grassland soils (Sozanska et al. 2002): 56 x 106 kg N 2 O-N/a i.e. groundwater emissions are ~0.6% of soil emissions

Summary so far... Large range of N 2 O concentrations in surface and ground waters Nitrification and denitrification dependent on hydrological conditions (soil moisture content; water table depth; residence time) Significance of indirect N 2 O emissions from agriculture as a source of to the global N 2 O budget dependent on land use – potential for “pollution swapping” Groundwater emissions represent only a small fraction (<1%) of the modelled fertiliser-induced N 2 O emissions from arable and grassland soils in the UK

Links between coastal defence and biogeochemical cycling Julian Andrews, Tim Jickells & Kerry Turner

Managing sea-level rise?

Thames Fenland Humber Broadland North Sea

Context for coastal managers? Biogeochemical value of sediments

Realignment and Nutrient Transport (Context) Nutrient concentrations are high in NW European rivers posing a threat to water quality in the North Sea There are ministerial commitments to reduce these inputs but there has been limited success particularly for nitrate The Humber is the largest source of riverine nitrate to the North Sea from the UK

Flood Defences (source: EA 2000)

Managed Realignment

Biogeochemical store and ‘reactor’ Added Value?

Burial of organic matter CO 2

‘Extended deep green’ realignment

Biogeochemical Storage Approximate area = 75 km2 120,000 tonnes of sediment per year 3500 tonnes Corg per year 180 tonnes Norg per year 72 tonnes P, 21 tonnes Zn, 10 tonnes Pb and 10 tonnes Cu (all net values per year)

Burial of organic matter + denitrification CO 2 N2ON2O

Realignment and Nutrient Transport Restoring intertidal areas allows more effective nutrient retention in estuaries via burial and denitrification In our EDG realignment scenario nutrient retention would increase by 83%(N) and 50%(P)

Location of realignment Strong Denitrification Weaker Denitrification

Measuring gas fluxes

Example fluxes courtesy of Chris Adams (Essex marshes) (g m -2 yr -1 ) High marsh Pioneer marsh (eroding creek) Creek base CH N2ON2O Applying GWP gives max (rounded) rates of: CH X 21 = 120 g CO 2 m -2 yr -1 N 2 O 1.8 X 310 = 550 g CO 2 m -2 yr -1

Burial of organic matter + microbial sulphate reduction CO 2 Seaward End of Estuary (2CH 2 O + SO 4 2- H 2 S + 2HCO 3 - )

CO 2 + CH 4 Riverine End of Estuary (2CH 2 O CO 2 + CH 4 ) CO 2

Nitrogen Budgets Present Day Humber (10 3 tonnes yr -1 ) Input 57 Denitrification 1 Burial 0.2 Output 55 Humber 3000 years ago (10 3 tonnes yr -1 ) Input 1- 2 Denitrification 2 Burial 19 Input 19

Nitrous Oxide Focus Group Nitrous Oxide Focus Group launch event Friday February 22 nd,