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[{"key": "dc.contributor.author", "value": "Koikkalainen, Mikko", "language": null, "element": "contributor", "qualifier": "author", "schema": "dc"}, {"key": "dc.date.accessioned", "value": "2013-12-12T12:14:25Z", "language": null, "element": "date", "qualifier": "accessioned", "schema": "dc"}, {"key": "dc.date.available", "value": "2013-12-12T12:14:25Z", "language": null, "element": "date", "qualifier": "available", "schema": "dc"}, {"key": "dc.date.issued", "value": "2013", "language": null, "element": "date", "qualifier": "issued", "schema": "dc"}, {"key": "dc.identifier.other", "value": "oai:jykdok.linneanet.fi:1290166", "language": null, "element": "identifier", "qualifier": "other", "schema": "dc"}, {"key": "dc.identifier.uri", "value": "https://jyx.jyu.fi/handle/123456789/42650", "language": null, "element": "identifier", "qualifier": "uri", "schema": "dc"}, {"key": "dc.description.abstract", "value": "Radioaktiivisuudella tarkoitetaan ep\u00e4stabiilin ytimen hajoamista toiseksi ytimeksi. K\u00e4yt\u00e4nn\u00f6ss\u00e4 ydin voi hajota kolmella perusprosessilla; alfa-, beeta tai gammahajoamisella, joista gammahajoamisessa virittyneen ytimen viritystila purkautuu emittoimalla gammahiukkasen, fotonin, jonka energia vastaa viritystilan tai viritystilojen v\u00e4list\u00e4 energiaa.\n\nLyijyn isotoopin 210Pb (puoliintumisaika noin 22 vuotta) gammahajoamiseen perustuvalla lyijyajoituksella voidaan m\u00e4\u00e4ritt\u00e4\u00e4 j\u00e4rvenpohjien sedimenttikerrosten ik\u00e4 syvyyden funktiona. Sedimentteihin 210Pb kertyy kahdella tavalla: hajoamalla radioaktiivisesti maaper\u00e4ss\u00e4 olevasta radiumista sek\u00e4 ilmakeh\u00e4st\u00e4 suoraan esimerkiksi sateiden v\u00e4lityksell\u00e4 tai ep\u00e4suoraan vesist\u00f6jen rannoilta eroosion vaikutuksella. Radiumista hajoavaa 210Pb-pitoisuutta kutsutaan kantavaksi pitoisuudeksi ja ilmakeh\u00e4st\u00e4 l\u00e4ht\u00f6isin olevaa kantamattomaksi pitoisuudeksi. Kantamaton pitoisuus noudattaa radioaktiivisuuden hajoamislakia, joten mittaamalla sedimenttin\u00e4ytteist\u00e4 lyijyn kokonaispitoisuuden ja erottamalla siit\u00e4 kantamattoman pitoisuuden, voidaan sopivilla matemaattisilla ajoitusmalleilla m\u00e4\u00e4ritt\u00e4\u00e4 kerrosten i\u00e4t.\n\nSedimenttin\u00e4ytteiden lyijypitoisuuksia mitataan gammaspektroskopialla, joka on k\u00e4yt\u00e4nn\u00f6ss\u00e4 ydinten viritystilojen purkautumisessa emittoituvan gammas\u00e4teilyn havaitsemista ja analysointia. Sopivalla mittauslaitteistolla voidaan mitata eri l\u00e4hteiden tuottamaa gammas\u00e4teily\u00e4 ja edelleen muodostaa gammaspektri, joka on tapana esitt\u00e4\u00e4 s\u00e4teilyn intensiteettin\u00e4 energian funktiona. Spektrin yksityiskohtainen analysointi mahdollistaa tutkitussa n\u00e4ytteess\u00e4 olevien aktiivisuuksien m\u00e4\u00e4ritt\u00e4misen.\n\nTutkielmassa k\u00e4ytetyt sedimenttin\u00e4ytteet on kaikki kairattu 20 cm syvyyteen asti ja per\u00e4isin kahden erilaisen profiilin omaavista j\u00e4rvist\u00e4. Vatiaj\u00e4rvi ja Lepp\u00e4vesi ovat muiden l\u00e4hteiden mukaan vesist\u00f6j\u00e4, joissa koko kairaussyvyydell\u00e4 p\u00e4\u00e4st\u00e4\u00e4n maksimissaan vain 25 vuoden ik\u00e4\u00e4n, joten osoittautui, ett\u00e4 p\u00e4\u00e4asiassa isotoopin 210Pb lyhyest\u00e4 puoliintumisajasta johtuen kyseisten vesist\u00f6jen tarkka i\u00e4nm\u00e4\u00e4ritys ei onnistu lyijyajoituksella. Sen sijaan Keiteleen sedimentoitumisnopeus on ollut huomattavasti hitaampaa ja lyijyajoituksella onnistuttiin saamaan suuntaa antava arvio kerrosten ik\u00e4jakaumasta. Tosin kovin tarkkoja tuloksia ei Keiteleest\u00e4k\u00e4\u00e4n saatu, joten k\u00e4yt\u00f6ss\u00e4ni olevalla mittauslaitteistolla ei luotettavaan lyijyajoitukseen p\u00e4\u00e4sty, vaan lis\u00e4ksi tarvittaisiin my\u00f6s muita tukevia ajoitusmenetelmi\u00e4.", "language": "fi", "element": "description", "qualifier": "abstract", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted using Plone Publishing form by Mikko Koikkalainen (miunsako) on 2013-12-12 12:14:25.194119. Form: Pro gradu -lomake (1 tekij\u00e4) (https://kirjasto.jyu.fi/julkaisut/julkaisulomakkeet/pro-gradu-lomake-1-tekijae). JyX data:", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Submitted by jyx lomake-julkaisija (jyx-julkaisija@noreply.fi) on 2013-12-12T12:14:25Z\nNo. of bitstreams: 2\nURN:NBN:fi:jyu-201312122791.pdf: 760864 bytes, checksum: 1c4391ed7a416daf4496db9d88aabc74 (MD5)\nlicense.html: 4898 bytes, checksum: 555c63dac77f41ec041277ff5ad501f0 (MD5)", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.description.provenance", "value": "Made available in DSpace on 2013-12-12T12:14:25Z (GMT). No. of bitstreams: 2\nURN:NBN:fi:jyu-201312122791.pdf: 760864 bytes, checksum: 1c4391ed7a416daf4496db9d88aabc74 (MD5)\nlicense.html: 4898 bytes, checksum: 555c63dac77f41ec041277ff5ad501f0 (MD5)\n Previous issue date: 2013", "language": "en", "element": "description", "qualifier": "provenance", "schema": "dc"}, {"key": "dc.format.extent", "value": "1 verkkoaineisto.", "language": null, "element": "format", "qualifier": "extent", "schema": "dc"}, {"key": "dc.format.mimetype", "value": "application/pdf", "language": null, "element": "format", "qualifier": "mimetype", "schema": "dc"}, {"key": "dc.language.iso", "value": "fin", "language": null, "element": "language", "qualifier": "iso", "schema": "dc"}, {"key": "dc.rights", "value": "In Copyright", "language": "en", "element": "rights", "qualifier": null, "schema": "dc"}, {"key": "dc.subject.other", "value": "lyijyajoitus", "language": null, "element": "subject", "qualifier": "other", "schema": "dc"}, {"key": "dc.title", "value": "J\u00e4rvisedimenttien i\u00e4nm\u00e4\u00e4ritys lyijyajoituksella", "language": null, "element": "title", "qualifier": null, "schema": "dc"}, {"key": "dc.type", "value": "master thesis", "language": null, "element": "type", "qualifier": null, "schema": "dc"}, {"key": "dc.identifier.urn", "value": "URN:NBN:fi:jyu-201312122791", "language": null, "element": "identifier", "qualifier": "urn", "schema": "dc"}, {"key": "dc.type.dcmitype", "value": "Text", "language": "en", "element": "type", "qualifier": "dcmitype", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Pro gradu -tutkielma", "language": "fi", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.type.ontasot", "value": "Master\u2019s thesis", "language": "en", "element": "type", "qualifier": "ontasot", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Matemaattis-luonnontieteellinen tiedekunta", "language": "fi", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.faculty", "value": "Faculty of Sciences", "language": "en", "element": "contributor", "qualifier": "faculty", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Fysiikan laitos", "language": "fi", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.department", "value": "Department of Physics", "language": "en", "element": "contributor", "qualifier": "department", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "University of Jyv\u00e4skyl\u00e4", "language": "en", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.contributor.organization", "value": "Jyv\u00e4skyl\u00e4n yliopisto", "language": "fi", "element": "contributor", "qualifier": "organization", "schema": "dc"}, {"key": "dc.subject.discipline", "value": "Fysiikka", "language": "fi", "element": "subject", "qualifier": "discipline", "schema": "dc"}, {"key": "dc.subject.discipline", "value": "Physics", "language": "en", "element": "subject", "qualifier": "discipline", "schema": "dc"}, {"key": "dc.date.updated", "value": "2013-12-12T12:14:26Z", "language": null, "element": "date", "qualifier": "updated", "schema": "dc"}, {"key": "dc.type.coar", "value": "http://purl.org/coar/resource_type/c_bdcc", "language": null, "element": "type", "qualifier": "coar", "schema": "dc"}, {"key": "dc.rights.accesslevel", "value": "openAccess", "language": "fi", "element": "rights", "qualifier": "accesslevel", "schema": "dc"}, {"key": "dc.type.publication", "value": "masterThesis", "language": null, "element": "type", "qualifier": "publication", "schema": "dc"}, {"key": "dc.subject.oppiainekoodi", "value": "4021", "language": null, "element": "subject", "qualifier": "oppiainekoodi", "schema": "dc"}, {"key": "dc.subject.yso", "value": "radioaktiivisuus", "language": null, "element": "subject", "qualifier": "yso", "schema": "dc"}, {"key": "dc.subject.yso", "value": "hajoaminen", "language": null, 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