Water quality monitoring and assessment of the Northern Baltic Sea using Earth Observation

Jenni Attila

Water quality monitoring and assessment of the Northern Baltic Sea using Earth Observation

Julkaisun otsikon käännös: Suomen rannikkovesien vedenlaadun seuranta ja tila-arvio kaukokartoitusmenetelmin

Jenni Attila

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Väitöskirjassa selvitettiin kaukokartoitusmenetelmien käyttökelpoisuutta Suomen rannikon vedenlaadun määrityksessä. Vedenlaadulla tarkoitetaan veden kemiallisia, fysikaalisia tai biologisia ominaisuuksia, joiden perusteella arvioidaan vesialueiden tilaa. Tilan arvioimiseen käytetään vedenlaatumuuttujia, jotka kuvaavat muun muassa sitä, miten paljon vedessä on levää tai miten sameaa vesi on. Väitöskirjassa keskityttiin erityisesti levän määrää kuvaavan a-klorofyllin määritysmenetelmien valintaan sekä siihen, mikä menetelmien tarkkuus on Suomen rannikkovesissä. Lisäksi tarkasteltiin veden sameuden, humuksen ja näkösyvyyden määrittämiseen soveltuvia kaukokartoitusmenetelmiä. Työssä tarkasteltiin satelliittihavaintojen käyttökelpoisuutta rannikolla Euroopan Unionin (EU) vesipuitedirektiivin (VPD) ja lisäksi Suomenlahden avomerialueen tila-arvion tarpeisiin. Satelliittihavainnoista voidaan määrittää vedenlaatumuuttujia hyvällä alueellisella ja ajallisella kattavuudella sekä tarkkuudella vertailuaineistoihin nähden. Tarkkuusarviot tehtiin vertaamalla kaukokartoitusmenetelmiä ympäristöhallinnon seuranta-asemilta kerättyihin ja laboratoriossa analysoituihin näytteisiin. Lisäksi menetelmiä verrattiin läpivirtamittaus-aineistoihin, joita on havainnoitu sekä rannikolla järjestetyissä optisissa maastokampanjoissa, että automaattimittauksin kauppalaivoille asennetun Alg@line-järjestelmän mittalaitteilla. Työssä käytettiin pääasiassa ENVISAT-satelliitin MERIS (MEdium Resolution Imaging Spectrometer) instrumentin havaintoja, jotka soveltuvat hyvin vedenlaadun määritykseen. Lisäksi hyödynnettiin lentokäyttöisen AISA-instrumentin havaintoja. Tulosten perusteella erityisesti bio-optiset mallit, joita on kehitetty MERIS-instrumentille useita, soveltuvat hyvin vedenlaadun määrittämiseen Suomen rannikkovesillä. Veden a-klorofyllipitoisuus voidaan määrittää satelliittihavaintoihin perustuen luotettavasti, arvio poikkeaa asemahavainnoista keskimäärin 0.6 μg l-1, mikä on lähellä vesinäytteiden laboratorioanalyysien määritystarkkuutta. Tarkkuusarvioiden alueellista tarkastelua varten kehitettiin satelliittimenetelmien laadunmääritysjärjestelmä, jonka mukaan satelliittihavaintojen luotettavuus on asemahavaintoja vastaava 62%:lla analysoiduista 129:stä rannikon vesimuodostumasta. Dynaamisissa jokisuistoissa, joissa valuma-alueelta tulevan kiinteän aineksen ja humukseen määrä on ajoittain suuri, a-klorofyllipitoisuuden määritystarkkuutta voidaan vielä parantaa. Laadunmääritysjärjestelmän mukaan tällaisia vesimuodostumia on vain seitsemän analysoiduista alueista (2,8 % pinta-alasta). Satelliittiaineistojen suuri määrä sekä ajallinen kattavuus levän vuosittaisen kasvukauden aikana lisäävät jatkossa tila-arvioiden luotettavuutta. MERIS-tulokset antoivat vahvan pohjan nykyisen EU:n Copernicus-ohjelman Sentinel-3 ja Sentinel-2 satelliittisarjojen havaintojen hyödyntämiselle. Satelliittisarjoille on taattu jatko vuoteen 2030 asti, joten niiden peräkkäisten instrumenttien ja jo edesmenneen MERIS-instrumentin elinkaaren ajalta satelliittiaineistoja voidaan hyödyntää Suomen rannikkovesien ja ympäröivien avomerialueiden tila-arvioissa.

Julkaisun otsikon käännös	Suomen rannikkovesien vedenlaadun seuranta ja tila-arvio kaukokartoitusmenetelmin
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Rautiainen, Miina, Vastuuprofessori Pulliainen, Jouni, Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-8866-2
Sähköinen ISBN	978-952-60-8867-9
Tila	Julkaistu - 2019
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

kaukokartoitus
satelliitti-instrumentti
a-klorofylli
sameus
vedenlaatu

YK:n kestävän kehityksen tavoitteet

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http://urn.fi/URN:ISBN:978-952-60-8867-9

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@phdthesis{b4aee836e44b4814b1d088fa95c75ab3,

title = "Water quality monitoring and assessment of the Northern Baltic Sea using Earth Observation",

abstract = "This thesis concentrates on determining how accurate Earth Observation (EO), i.e. satellite instrument observation methods are for water quality estimation in the coastal waters of Finland, in the Northern Baltic Sea. Water quality refers to the characteristics of water that define its chemical, physical or biological properties. These are used to assess the ecological and chemical status of the waters based on various environmental regulations, such as the European Union (EU) Water Framework Directive (WFD). In water areas, where the quality is not good, such as in eutrophicated sea areas, the water quality parameters have high spatial and temporal variability. EO observations capability to cover this variability is beyond the possibilities of conventional station-wise water sampling. This is valuable in Finland with numerous coastal and lake water bodies. In this thesis, phytoplankton chlorophyll-a (chl-a) – as a direct indicator of eutrophication and one of the WFD's biological quality elements – is the key water quality parameter. Water quality parameters derived from one airborne and two satellite instruments algorithms are analysed against two types of field measurements: automated flow-through measurement systems and monitoring station water samples. The flow-through systems, either installed on smaller coastal boats or on board merchant ships (ferrybox), provide an efficient way for collecting a wide range of ground truth samples for EO algorithm development and validation. The routine water samples are collected at the station sites throughout the coastal waters of Finland and are used as the basis for the status assessment of water bodies. Finnish coastal waters represent an optically extreme and complex water type: absorption dominated humic waters, where EO algorithms often produce incorrect results. A Quality Grade (QG) method confirmed that the analysed EO model to determine chl-a concentrations is reliable for 62% (80 of the examined 129) coastal water bodies. Summarising results over the coastal monitoring sites confirm that the accuracy of the EO method is close to the determination accuracy of station sampling (0.6 μg l-1) near the chl-a target for WFD. The difference in statistical metrics calculated by EO and station sampling is 23% – well within the uncertainty limits of chl-a laboratory analyses. The statistical measures (mode and the geometric mean) are optimal for non-normally distributed EO observations for utilising them in the water bodies for assessment. Only in the optically specific estuaries (2.8 % of the examined area 7 out of 129 water bodies), the optical properties of the water can reach the extremes of their ranges and the chl-a estimation fails. This occurs particularly when the loading from the drainage basin is intensive (such as in the melting season in spring and after heavy rains). Moreover, EO algorithms for determining turbidity, absorption of coloured dissolved organic matter and Secchi disk depth were analysed and found to perform well. The work done with past EO instruments – medium resolution satellite and high resolution airborne - anticipated the efficient use of the EU Copernicus programme Sentinel-series instruments for the monitoring of the water areas of Finland.",

keywords = "Earth Observation, EO, remote sensing, chlorophyll-a, turbidity, water quality, kaukokartoitus, satelliitti-instrumentti, a-klorofylli, sameus, vedenlaatu, Earth Observation, EO, remote sensing, chlorophyll-a, turbidity, water quality",

author = "Jenni Attila",

year = "2019",

language = "English",

isbn = "978-952-60-8866-2",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "229",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Water quality monitoring and assessment of the Northern Baltic Sea using Earth Observation

AU - Attila, Jenni

PY - 2019

Y1 - 2019

N2 - This thesis concentrates on determining how accurate Earth Observation (EO), i.e. satellite instrument observation methods are for water quality estimation in the coastal waters of Finland, in the Northern Baltic Sea. Water quality refers to the characteristics of water that define its chemical, physical or biological properties. These are used to assess the ecological and chemical status of the waters based on various environmental regulations, such as the European Union (EU) Water Framework Directive (WFD). In water areas, where the quality is not good, such as in eutrophicated sea areas, the water quality parameters have high spatial and temporal variability. EO observations capability to cover this variability is beyond the possibilities of conventional station-wise water sampling. This is valuable in Finland with numerous coastal and lake water bodies. In this thesis, phytoplankton chlorophyll-a (chl-a) – as a direct indicator of eutrophication and one of the WFD's biological quality elements – is the key water quality parameter. Water quality parameters derived from one airborne and two satellite instruments algorithms are analysed against two types of field measurements: automated flow-through measurement systems and monitoring station water samples. The flow-through systems, either installed on smaller coastal boats or on board merchant ships (ferrybox), provide an efficient way for collecting a wide range of ground truth samples for EO algorithm development and validation. The routine water samples are collected at the station sites throughout the coastal waters of Finland and are used as the basis for the status assessment of water bodies. Finnish coastal waters represent an optically extreme and complex water type: absorption dominated humic waters, where EO algorithms often produce incorrect results. A Quality Grade (QG) method confirmed that the analysed EO model to determine chl-a concentrations is reliable for 62% (80 of the examined 129) coastal water bodies. Summarising results over the coastal monitoring sites confirm that the accuracy of the EO method is close to the determination accuracy of station sampling (0.6 μg l-1) near the chl-a target for WFD. The difference in statistical metrics calculated by EO and station sampling is 23% – well within the uncertainty limits of chl-a laboratory analyses. The statistical measures (mode and the geometric mean) are optimal for non-normally distributed EO observations for utilising them in the water bodies for assessment. Only in the optically specific estuaries (2.8 % of the examined area 7 out of 129 water bodies), the optical properties of the water can reach the extremes of their ranges and the chl-a estimation fails. This occurs particularly when the loading from the drainage basin is intensive (such as in the melting season in spring and after heavy rains). Moreover, EO algorithms for determining turbidity, absorption of coloured dissolved organic matter and Secchi disk depth were analysed and found to perform well. The work done with past EO instruments – medium resolution satellite and high resolution airborne - anticipated the efficient use of the EU Copernicus programme Sentinel-series instruments for the monitoring of the water areas of Finland.

AB - This thesis concentrates on determining how accurate Earth Observation (EO), i.e. satellite instrument observation methods are for water quality estimation in the coastal waters of Finland, in the Northern Baltic Sea. Water quality refers to the characteristics of water that define its chemical, physical or biological properties. These are used to assess the ecological and chemical status of the waters based on various environmental regulations, such as the European Union (EU) Water Framework Directive (WFD). In water areas, where the quality is not good, such as in eutrophicated sea areas, the water quality parameters have high spatial and temporal variability. EO observations capability to cover this variability is beyond the possibilities of conventional station-wise water sampling. This is valuable in Finland with numerous coastal and lake water bodies. In this thesis, phytoplankton chlorophyll-a (chl-a) – as a direct indicator of eutrophication and one of the WFD's biological quality elements – is the key water quality parameter. Water quality parameters derived from one airborne and two satellite instruments algorithms are analysed against two types of field measurements: automated flow-through measurement systems and monitoring station water samples. The flow-through systems, either installed on smaller coastal boats or on board merchant ships (ferrybox), provide an efficient way for collecting a wide range of ground truth samples for EO algorithm development and validation. The routine water samples are collected at the station sites throughout the coastal waters of Finland and are used as the basis for the status assessment of water bodies. Finnish coastal waters represent an optically extreme and complex water type: absorption dominated humic waters, where EO algorithms often produce incorrect results. A Quality Grade (QG) method confirmed that the analysed EO model to determine chl-a concentrations is reliable for 62% (80 of the examined 129) coastal water bodies. Summarising results over the coastal monitoring sites confirm that the accuracy of the EO method is close to the determination accuracy of station sampling (0.6 μg l-1) near the chl-a target for WFD. The difference in statistical metrics calculated by EO and station sampling is 23% – well within the uncertainty limits of chl-a laboratory analyses. The statistical measures (mode and the geometric mean) are optimal for non-normally distributed EO observations for utilising them in the water bodies for assessment. Only in the optically specific estuaries (2.8 % of the examined area 7 out of 129 water bodies), the optical properties of the water can reach the extremes of their ranges and the chl-a estimation fails. This occurs particularly when the loading from the drainage basin is intensive (such as in the melting season in spring and after heavy rains). Moreover, EO algorithms for determining turbidity, absorption of coloured dissolved organic matter and Secchi disk depth were analysed and found to perform well. The work done with past EO instruments – medium resolution satellite and high resolution airborne - anticipated the efficient use of the EU Copernicus programme Sentinel-series instruments for the monitoring of the water areas of Finland.

KW - Earth Observation

KW - EO

KW - remote sensing

KW - chlorophyll-a

KW - turbidity

KW - water quality

KW - kaukokartoitus

KW - satelliitti-instrumentti

KW - a-klorofylli

KW - sameus

KW - vedenlaatu

KW - Earth Observation

KW - EO

KW - remote sensing

KW - chlorophyll-a

KW - turbidity

KW - water quality

M3 - Doctoral Thesis

SN - 978-952-60-8866-2

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Water quality monitoring and assessment of the Northern Baltic Sea using Earth Observation

Abstrakti

Tutkimusalat

YK:n kestävän kehityksen tavoitteet

Pääsy asiakirjaan

Sormenjälki

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