EutrophicationEutrophication 2 2Causes of EutrophicationCauses of Eutrophication

Alice NewtonAlice NewtonUniversity of AlgarveUniversity of Algarve

Causes of EutrophicationCauses of EutrophicationBiogeochemical Cycles and Biogeochemical Cycles and NutrientsNutrientsNitrogen cycleNitrogen cycleAtmospheric deposition Atmospheric deposition Loss of Wetlands Loss of Wetlands Animal wastesAnimal wastesFertilizer use and surplusFertilizer use and surplus

Causes of EutrophicationCauses of EutrophicationPerturbation of N & P Perturbation of N & P biogeochemical biogeochemical

cyclescyclesSynthetic Synthetic FertilizersFertilizersBurning of Burning of Fossil FuelsFossil FuelsMonoculture of Monoculture of LegumesLegumesAnimal Wastes and Animal Wastes and ManureManureSewageSewage: Sewage treatment reduces BOD and : Sewage treatment reduces BOD and

some P inputs but no significant reduction of some P inputs but no significant reduction of NN

Loss of wetlandLoss of wetlandLoss of riperian vegetationLoss of riperian vegetation

1996 Total annual 1996 Total annual anthropogenic N inputsanthropogenic N inputs ~140Tg ~140Tg (Teragrams = 1 million metric tonnes)(Teragrams = 1 million metric tonnes)

Important nutrients N:P:SiImportant nutrients N:P:Si esa.sdsc.edu/issues.htmesa.sdsc.edu/issues.htm RatiosRatios N:P and N: Si are especially N:P and N: Si are especially

importantimportantPP most important in most important in freshwaterfreshwater lakes lakesNN is usually limiting nutrient in is usually limiting nutrient in coastal coastal

waters and estuaries.waters and estuaries.P limitation has been documented in P limitation has been documented in

coastal waters and estuaries:coastal waters and estuaries:Apalachicola (Gulf of Florida)Apalachicola (Gulf of Florida)some Dutch estuariessome Dutch estuariesTropical systems with carbonate sandsTropical systems with carbonate sands

Redfield ratio N:P 16:1Redfield ratio N:P 16:1N limited when <16:1 N limited when <16:1 P limited when >16:1 P limited when >16:1 Range of 10 to 25 is “normal”Range of 10 to 25 is “normal”N:P in sewage, manure and fertilizers is N:P in sewage, manure and fertilizers is

different from Refield ratio different from Refield ratio N:Si 1:1N:Si 1:1Upstream eutrophication in rivers traps Si Upstream eutrophication in rivers traps Si

in sediments before it reaches estuariesin sediments before it reaches estuariesDams: trap SiDams: trap SiSi availability controls diatom growth Si availability controls diatom growth Decrease in Si relative to N & P linked to Decrease in Si relative to N & P linked to

HABHAB

Nitrogen cycleNitrogen cycle

Simplified N CycleSimplified N Cyclehttp://www.geog.ouc.bc.ca/physgeog/contents/9s.htmlhttp://www.geog.ouc.bc.ca/physgeog/contents/9s.html

Biology of NBiology of N

Gaseous NGaseous N22 not useful to most not useful to most photosynthesizersphotosynthesizers

N fixationN fixation eg eg TrichodesmiumTrichodesmium can produce NH can produce NH44 from N from N22 Microbes and BG algae may form NOMicrobes and BG algae may form NO22 and NO and NO33

NHNH44, NO, NO22 and NO and NO33 can be used as can be used as nutrients by nutrients by photosynthesizersphotosynthesizers

Proteins in Organic matter are excreted or Proteins in Organic matter are excreted or decompose as NHdecompose as NH44

Quantifying the N cycleQuantifying the N cycleN cycle:N cycle:

Natural Sources of NNatural Sources of NAnthropogenic sourcesAnthropogenic sources

Natural SourcesNatural SourcesLighteningLightening fixation fixation 5-10Tg pa 5-10Tg paNatural N fixationNatural N fixation (non crop) (non crop)

90-140 Tg p.a.90-140 Tg p.a.MarineMarine fixation fixation 30-300 Tg pa??? 30-300 Tg pa???

Anthropogenic sources of NAnthropogenic sources of NIndustrial fixationIndustrial fixation inc Fertilizer 80Tg of N pa inc Fertilizer 80Tg of N pa

(NH(NH33 & N & N22O) O) 2020 projection 134 Tg pa 2020 projection 134 Tg pa

Agricultural LegumeAgricultural Legume Fixation Fixation32-53 Tg pa32-53 Tg pa

Fossil fuelsFossil fuels 20 Tg pa (NO & NH 20 Tg pa (NO & NH33) ) 2020 projection 46Tg pa2020 projection 46Tg pa

Forests BurningForests Burning 40 Tg pa 40 Tg pa (NO, N(NO, N22O & NHO & NH3 3 ))

Loss of wetlandsLoss of wetlands (denitrifying) (denitrifying) 10 Tg pa10 Tg pa

Land clearingLand clearing for crops 20 Tg pa for crops 20 Tg paDomestic Domestic Animal WasteAnimal Waste

32 Tg pa (NH32 Tg pa (NH33))

Atmospheric deposition Atmospheric deposition

NOx and NHxNOx and NHx in the in the AtmosphereAtmosphere

OriginsOriginsDomesticDomestic combustioncombustion IIndustrial processesndustrial processesTrafficTrafficAAgricultural sourcesgricultural sources

AAnimal housingnimal housing SSpreading of manurepreading of manure

AAtmospherictmospheric D Deposition ofeposition of N N in thein the N Northorth A Atlantictlantic OOceancean

AD-NAD-N to the NAOto the NAO basin arises from basin arises from pollution sources in North America and pollution sources in North America and Western EuropeWestern Europe

SSources have increased drastically (5-ources have increased drastically (5-10-fold) since the Industrial Revolution 10-fold) since the Industrial Revolution and continue to increase in both and continue to increase in both geographic and depositional magnitude. geographic and depositional magnitude.

AD-N flux (11.2 Tg N yrAD-N flux (11.2 Tg N yr-1-1 ) accounts for ) accounts for 46-57% of the total "new" or 46-57% of the total "new" or anthropogenic nitrogen flux to the NAO. anthropogenic nitrogen flux to the NAO.

Human-Caused Global Human-Caused Global Nitrogen EmissionsNitrogen Emissions

Ammonia data are fromSchlesinger and Hartley (1992) Nitric oxide from Delmas et

al. ,Nitrous oxide from Prather et al. (1995).

Human activities are responsible for a large proportion of the global emissions of nitrogen-containing trace gases, including 40% of the nitrous oxide, 80% or more of nitric oxide, and 70% of ammonia releases.

Increasing atmospheric concentrations of the greenhouse gas nitrous oxide, of the nitrogen precursors of smog, and of biologically available nitrogen that falls from the atmosphere to fertilize ecosystems.

Loss of Wetlands Loss of Wetlands

Loss of WetlandsLoss of WetlandsImportant Important denitrifying denitrifying zoneszonesUSAUSA

Midwest 16 million hectares have Midwest 16 million hectares have been drainedbeen drained

egeg Iowa had 1 million hectares, Iowa had 1 million hectares, now has 16 000 hectaresnow has 16 000 hectares

Netherlands Netherlands most altered landscapemost altered landscape wetlands drained, network of canals wetlands drained, network of canals

pipe nutrients into coastal waterspipe nutrients into coastal waters

Changes in N cycleChanges in N cycleRevised Kates et al. (1990).

The chart shows the year when changes in human population growth, carbon dioxide release, deforestation, and fertilizer production had reached 25%, 50%, and 75% of the extent seen in the late 1980s.

Human alteration to N cycleHuman alteration to N cycleN has doubled in 50 years N has doubled in 50 years

(C has only increased 10%)(C has only increased 10%)80 Tg of N pa applied as fertilizer 80 Tg of N pa applied as fertilizer 174 kg/ha/pa Xs 174 kg/ha/pa Xs Impacts include:Impacts include:

Increase NIncrease N22O, (nitrous oxide, a greenhouse O, (nitrous oxide, a greenhouse gas), due to burning of fossil fuelsgas), due to burning of fossil fuels

Increased NO (nitric oxide, photochemical Increased NO (nitric oxide, photochemical smog formation)smog formation)

Acidification of soils and freshwaterAcidification of soils and freshwaterErosion & leaching of N to estuaries and coastErosion & leaching of N to estuaries and coast

Transfers of nutrientsTransfers of nutrientsN fixed in industrial areasN fixed in industrial areasN transported to agricultural areasN transported to agricultural areas

N applied to fields, some retained in cropsN applied to fields, some retained in cropsN loss to atmosphere and waterN loss to atmosphere and waterCrops transported to livestock producing Crops transported to livestock producing

areas and citiesareas and citiesCrops consumed in cities and N enters Crops consumed in cities and N enters

sewagesewageAnimal feed crops consumed in livestock Animal feed crops consumed in livestock

farms farms Livestock transported to citiesLivestock transported to citiesManure spread on fields, enters atmosphere Manure spread on fields, enters atmosphere

and waterand water

Natural transfersNatural transfers

Sea Birds and guanoSea Birds and guanoSalmon migration and deathSalmon migration and death

N input into Aquatic N input into Aquatic SystemsSystems

Modified from Howarth et al.

(1996)

Movements of N into most of the temperate-zone rivers that empty into the North Atlantic Ocean have increased by 2 to 20-fold since pre-industrial times.

N increases in these rivers are highly correlated with increasing human-generated nitrogen inputs into the watersheds, particularly fertilizer use and rising atmospheric deposition of nitrogen.

Point SourcesPoint Sources

Point SourcesPoint SourcesPoint Point sources:sources:

Wastewater drainsWastewater drainsDomestic SewageDomestic SewageSewage treatment plantsSewage treatment plantsLivestock productionLivestock productionStorm sewersStorm sewersCan monitor & regulate or treatCan monitor & regulate or treat

Non-Point SourcesNon-Point SourcesNonpoint Nonpoint sourcessources

Agricultural runoffAgricultural runoffManure spreadingManure spreadingAtmospheric Deposition over water Atmospheric Deposition over water Urban runoff & septic leachateUrban runoff & septic leachateSeasonal effects eg rainfall, Seasonal effects eg rainfall,

meltwatermeltwaterMajor source (~ 90 %) of N & P to Major source (~ 90 %) of N & P to

surface waterssurface watersDiffuse, difficult to monitor or manageDiffuse, difficult to monitor or manage

Animal wastesAnimal wastes

Intensive Animal FarmingIntensive Animal Farming

Animal wasteAnimal wasteUSA 5 tonnes animal wastes per resident p.a.USA 5 tonnes animal wastes per resident p.a.Netherlands: (2000)Netherlands: (2000)

Human pop.= Human pop.= 15 700 000 15 700 000 Cattle = Cattle = 4 200 000 4 200 000 Pigs = Pigs = 14 000 000 14 000 000 ChickensChickens 108 000 000108 000 000 6 tonnes animal wastes per resident pa6 tonnes animal wastes per resident pa Government Levy Bureau monitorGovernment Levy Bureau monitor

Farm inputs (feeds,etc)Farm inputs (feeds,etc)Output (meat & dairy)Output (meat & dairy)Manure and what happens to itManure and what happens to it

Denmark (2004)Denmark (2004) Human pop.Human pop. 5 300 000 5 300 000 PigsPigs 25 000 00025 000 000

Fertilizer use and surplusFertilizer use and surplus

Fertilizer use Fertilizer use http://www.efma.orghttp://www.efma.org

Industrial N fertilizer process Industrial N fertilizer process invented during WW1invented during WW1

Not widely used ‘til 1950’sNot widely used ‘til 1950’sSteady increase ‘til late 1980sSteady increase ‘til late 1980sSlight decline to 1994 (collapse of Slight decline to 1994 (collapse of

Soviet collective farms)Soviet collective farms)Rapid increase since 1995 (China Rapid increase since 1995 (China

& India)& India)1996: annual fertilizer use 1996: annual fertilizer use

~83 Tg~83 Tg

Fertiliser applicationFertiliser application

19901990 19931993 19951995

AustriaAustria    1616

BelgiumBelgium 106106 109109 103103

DenmarkDenmark 9393 9292 7272

FinlandFinland       5151

FranceFrance 4747 5454 5757

GermanyGermany 105105 101101 102102

GreeceGreece 8484 6161 5858

IrelandIreland 4747 6060 6262

ItalyItaly 6262 8383 7676

LuxembourgLuxembourg 124124 124124 121121

NetherlandsNetherlands 229229 212212 213213

PortugalPortugal 2727 2323 2222

SpainSpain 4040 3737 3737

SwedenSweden       3838

UKUK 4040 3939 4040

N use in EU 1990-95 Unit: kg nitrogen/ha utilised agricultural area (UAA)

Nitrogen balance in EU Nitrogen balance in EU agricultural soil 1990-95agricultural soil 1990-95

About a third of nitrogen applied to agricultural land is not removed with the harvest (EEA)

Nitrogen run-off Nitrogen run-off EUEU 1988 and 1996 1988 and 1996

Agriculture is the main source of nitrate pollution. Nitrogen run-off in areas with intensive agricultureis over 5, and often more than 10 times higher, than that from forested areas. EEA.

NONO33 in major EU rivers 1980- in major EU rivers 1980-9595

Nitrate concentrations have been largely unchanged since 1980

EEA

NONO33 in in EU EU coastal waters coastal waters 1985-91985-988

Nitrate concentrations in coastal waters fell in nearly half OSPAR and HELCOM coastal waters within the EU and Norway between 1985 and 1998. However, there were also some increases. EEA

Human alteration to P cycleHuman alteration to P cycle600 Tg applied as fertilizer from 1950 to 600 Tg applied as fertilizer from 1950 to

19951995

~250 Tg of P harvested as crops~250 Tg of P harvested as crops

~50 Tg used as feed crops returned to ~50 Tg used as feed crops returned to soil as manuresoil as manure

Net XS addition 400 Tg in 45 years, ~10 Net XS addition 400 Tg in 45 years, ~10 Tg p.a.Tg p.a.

Sources of Sources of PP in in EUEU19881988--9696Households and industry are the biggest contributors of phosphorus to the environment. However, in those parts of Europe with intensive agriculture, the contribution from agriculture approaches 50 % of the total. EEA.

P sources in the UKP sources in the UKEA UKEA UK

P in major EU rivers 1980-P in major EU rivers 1980-9595

Phosphorus concentrations in some EU rivers have fallen since the mid-1980s, particularly in the largest and most polluted rivers. EEA.

P P in coastal watersin coastal waters 1985-91985-98. 8. EEAEEA

NO3 &PO4 in EU coastal waters, NO3 &PO4 in EU coastal waters, 1985-19961985-1996

Most coastal waters show little or no change in phosphate concentrations. However, there is a substantial decrease in 35 % of OSPAR and HELCOM coastal waters within the EU and Norway

Nutrient concentrations in coastal waters show little overall improvement