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Spatial distribution and temporal evolution of polycyclic aromatic hydrocarbons in sediment and water in the northern part of Taihu Lake, China

Li, Aili (2019)
Spatial distribution and temporal evolution of polycyclic aromatic hydrocarbons in sediment and water in the northern part of Taihu Lake, China.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

Taihu Lake is the third largest freshwater lake in China, playing an important role for flood control, tourism, shipping and especially as a drinking water source for its neighboring cities, but the lake has been seriously polluted and drinking water supply has been threatened. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously distributed in the environment with petrogenic and pyrogenic sources, and they are carcinogenic and mutagenic to humans and other organisms. With the development of economy and industries, the rapid increase of fuel and biomass consumption results in significant PAH emission to the environment. In this study, we focus on PAHs in the sediments and water body in the northern part of Taihu Lake where is more polluted than the other part of the lake. We analyzed the concentration patterns of 20 PAHs in 25 surface sediments, 11 sediment cores and 41 water samples which were collected from the northern part of Taihu Lake during 4 times of field campaign (2015-11, 2016-06, 2017-02 and 2017-09). Three of the cores were dated based on 137Cs activity for the deposition age of the sediment. The data on energy consumption and type of vehicles in the lake catchment in the last two decades were collected from regional official websites to explain potential PAH emission histories in the area. The literature data on PAH emissions from their potential sources and on PAH distributions in particle sizes were collected to generalize PAH emission and distribution features. PAH patterns from different emission sources and also from the sediment results of this study were combined to verify the two assumptions for the methods of PAH source track in the environment. The spatial distributions of the PAH concentrations (perylene excluded) show that the inflow rivers into Zhushan bay and Meiliang bay were the main pathways for PAHs and sediments input into the northern part of the lake. This results in substantially higher PAH concentrations (up to 5000 ng/g) and sedimentation rates (higher than the average of 3 – 4 mm/a) in the area close to the river outlets. In addition, the results also show that PAH concentrations in the sediments considerably increased from the late 1950s due to the development of economy and industries, but the relatively decreased or stable concentrations in the upper layers of the sediments could be attributed to the gradual changes in energy structures, emission control in coal combustions since the 1990s and emission control in vehicle exhaust since ca. 2000 in this area. PAHs determined in the sediment cores (perylene excluded) are dominated by 4 light ones (phenanthrene (phen), anthracene (anthra), fluoranthene (fluor), pyrene) and 6 heavy ones (benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), benzo[e]pyrene (BeP), indeno[1,2,3-c,d]pyrene (INcdP), benzo[g,h,i]perylene (BghiP)) whose concentrations typically reach up to 70% – 80% of that of the 19 PAHs. The concentration fractions of the 6 heavy PAHs are almost double of the fractions of the 4 light ones, and the fractions of the heavy PAHs increase with decreasing depth in the cores, but the fractions of the light PAHs show the opposite trends (except cores GH38 and ZS23 with special features). PAH emission patterns from wood combustion, coal combustion and vehicle exhausts together can, to a great extent, illustrate the distribution patterns of the concentration fractions between the light and the heavy PAHs in the cores. Wood combustion has evidently higher emission fractions of the 4 light PAHs than the fractions of the 6 heavy PAHs compared to the emission patterns from coal and oil combustions, but wood has been gradually phased out as an important energy source since the beginning of industrialization in the 1950s. PAH patterns from coal combustions can somewhat explain the concentration fraction distributions of the two groups of PAHs in the cores through four points: the continuous decrease of residential coal consumption and the significantly increased consumption of emission-controlled coal combustion in this area during the last decades, relatively more ultrafine particles emitted from emission-controlled coal combustion, heavy PAHs bond more in ultrafine particles. Meanwhile, PAH patterns from vehicle exhausts contribute to the distributions of the concentration fractions in the cores through three points: the linear increase of oil consumption in transport, around 24-time increase in the number of light-duty vehicles but only 2-time increase in the number of heavy-duty vehicles in this area during the last two decades, and noticeably higher emission fraction of the heavy PAHs from light-duty vehicle exhausts than that from heavy-duty vehicle exhausts. Several methods are frequently used to interpret PAH source track in the environment, and these methods are based on two assumptions: PAH patterns from different sources are specific and distinguishable from each other; the patterns maintain stable after emission to the environment. The first assumption was mainly verified by the PAH patterns from different emission sources, which shows that PAH patterns from different sources indistinguishably overlap from each other. The second assumption was verified by the spatial and temporal distributions of PAH patterns in the sediment of this study, which shows that PAH patterns in the sediment are ambiguous and variable. Therefore, both of the two assumptions are not valid for PAH source track in the sediment. There were both anthropogenic and biogenic origins of perylene in the lake sediments, which were distinguished based on its spatial distribution patterns and also the concentration proportions of perylene to the sum of the 20 PAHs. In the cores collected close to the river outlets, the concentration proportions of perylene typically range from 0.02 to 0.18 and there are significant positive linear correlations between the concentration of perylene and three anthropogenic PAHs (BaP, BeP, Pyrene), suggesting that perylene was dominated by anthropogenic input. However, the cores collected further away from the river outlets show the concentration proportions between 0.13 and 0.96, and present significant negative correlations or no correlations between perylene and the three PAHs, suggesting that perylene was mainly formed by biogenic activities. Furthermore, the different perylene sources accompanied with the core location distributions imply that anthropogenic activities could inhibit its biogenic formation. In the water samples, naphthalene (naph), 1-methylnaphthalene (1methylnaph) and 2-methylnaphthalene (2methylnaph) have considerably higher concentrations in the samples (2016-06 and 2017-09) taken in warm seasons than the concentrations in the samples (2015-11 and 2017-02) taken in cold seasons, but the concentrations of the other PAHs do not vary with seasonal variations. The distribution patterns of these PAHs might be mainly attributed to ambient temperature effects on the PAH solubility in the water body. It is noteworthy that in the campaign 2017-09, the concentrations of 2methylnaph are particularly around twice as high as the concentrations of naph and reach up to 1350 ng/L. As the emission rates of naph are generally higher than methylnaph from anthropogenic activities, so it is suspected that the relatively higher concentrations of 2methylnaph should be attributed to additional biogenic input in the lake water. Furthermore, the samples collected in cold seasons show that high concentrations are mostly located in the northwestern part of the lake and relatively low concentrations are in the northeastern part of lake, but the concentrations from the warm season samples are homogeneous in the whole sampling area. The reason for the different spatial distributions between the cold and warm seasons is that during the sampling campaigns in cold seasons, there was water recharge from the Yangtze River through the Wangyu River connecting the northeastern part of Taihu Lake, which diluted PAH concentrations in the northeastern part of the lake.

Typ des Eintrags: Dissertation
Erschienen: 2019
Autor(en): Li, Aili
Art des Eintrags: Erstveröffentlichung
Titel: Spatial distribution and temporal evolution of polycyclic aromatic hydrocarbons in sediment and water in the northern part of Taihu Lake, China
Sprache: Englisch
Referenten: Schueth, Prof. Dr. Christoph ; Urban, Prof. Dr. Wilhelm
Publikationsjahr: 13 August 2019
Ort: Darmstadt
Datum der mündlichen Prüfung: 5 August 2019
URL / URN: https://tuprints.ulb.tu-darmstadt.de/8990
Kurzbeschreibung (Abstract):

Taihu Lake is the third largest freshwater lake in China, playing an important role for flood control, tourism, shipping and especially as a drinking water source for its neighboring cities, but the lake has been seriously polluted and drinking water supply has been threatened. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously distributed in the environment with petrogenic and pyrogenic sources, and they are carcinogenic and mutagenic to humans and other organisms. With the development of economy and industries, the rapid increase of fuel and biomass consumption results in significant PAH emission to the environment. In this study, we focus on PAHs in the sediments and water body in the northern part of Taihu Lake where is more polluted than the other part of the lake. We analyzed the concentration patterns of 20 PAHs in 25 surface sediments, 11 sediment cores and 41 water samples which were collected from the northern part of Taihu Lake during 4 times of field campaign (2015-11, 2016-06, 2017-02 and 2017-09). Three of the cores were dated based on 137Cs activity for the deposition age of the sediment. The data on energy consumption and type of vehicles in the lake catchment in the last two decades were collected from regional official websites to explain potential PAH emission histories in the area. The literature data on PAH emissions from their potential sources and on PAH distributions in particle sizes were collected to generalize PAH emission and distribution features. PAH patterns from different emission sources and also from the sediment results of this study were combined to verify the two assumptions for the methods of PAH source track in the environment. The spatial distributions of the PAH concentrations (perylene excluded) show that the inflow rivers into Zhushan bay and Meiliang bay were the main pathways for PAHs and sediments input into the northern part of the lake. This results in substantially higher PAH concentrations (up to 5000 ng/g) and sedimentation rates (higher than the average of 3 – 4 mm/a) in the area close to the river outlets. In addition, the results also show that PAH concentrations in the sediments considerably increased from the late 1950s due to the development of economy and industries, but the relatively decreased or stable concentrations in the upper layers of the sediments could be attributed to the gradual changes in energy structures, emission control in coal combustions since the 1990s and emission control in vehicle exhaust since ca. 2000 in this area. PAHs determined in the sediment cores (perylene excluded) are dominated by 4 light ones (phenanthrene (phen), anthracene (anthra), fluoranthene (fluor), pyrene) and 6 heavy ones (benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), benzo[e]pyrene (BeP), indeno[1,2,3-c,d]pyrene (INcdP), benzo[g,h,i]perylene (BghiP)) whose concentrations typically reach up to 70% – 80% of that of the 19 PAHs. The concentration fractions of the 6 heavy PAHs are almost double of the fractions of the 4 light ones, and the fractions of the heavy PAHs increase with decreasing depth in the cores, but the fractions of the light PAHs show the opposite trends (except cores GH38 and ZS23 with special features). PAH emission patterns from wood combustion, coal combustion and vehicle exhausts together can, to a great extent, illustrate the distribution patterns of the concentration fractions between the light and the heavy PAHs in the cores. Wood combustion has evidently higher emission fractions of the 4 light PAHs than the fractions of the 6 heavy PAHs compared to the emission patterns from coal and oil combustions, but wood has been gradually phased out as an important energy source since the beginning of industrialization in the 1950s. PAH patterns from coal combustions can somewhat explain the concentration fraction distributions of the two groups of PAHs in the cores through four points: the continuous decrease of residential coal consumption and the significantly increased consumption of emission-controlled coal combustion in this area during the last decades, relatively more ultrafine particles emitted from emission-controlled coal combustion, heavy PAHs bond more in ultrafine particles. Meanwhile, PAH patterns from vehicle exhausts contribute to the distributions of the concentration fractions in the cores through three points: the linear increase of oil consumption in transport, around 24-time increase in the number of light-duty vehicles but only 2-time increase in the number of heavy-duty vehicles in this area during the last two decades, and noticeably higher emission fraction of the heavy PAHs from light-duty vehicle exhausts than that from heavy-duty vehicle exhausts. Several methods are frequently used to interpret PAH source track in the environment, and these methods are based on two assumptions: PAH patterns from different sources are specific and distinguishable from each other; the patterns maintain stable after emission to the environment. The first assumption was mainly verified by the PAH patterns from different emission sources, which shows that PAH patterns from different sources indistinguishably overlap from each other. The second assumption was verified by the spatial and temporal distributions of PAH patterns in the sediment of this study, which shows that PAH patterns in the sediment are ambiguous and variable. Therefore, both of the two assumptions are not valid for PAH source track in the sediment. There were both anthropogenic and biogenic origins of perylene in the lake sediments, which were distinguished based on its spatial distribution patterns and also the concentration proportions of perylene to the sum of the 20 PAHs. In the cores collected close to the river outlets, the concentration proportions of perylene typically range from 0.02 to 0.18 and there are significant positive linear correlations between the concentration of perylene and three anthropogenic PAHs (BaP, BeP, Pyrene), suggesting that perylene was dominated by anthropogenic input. However, the cores collected further away from the river outlets show the concentration proportions between 0.13 and 0.96, and present significant negative correlations or no correlations between perylene and the three PAHs, suggesting that perylene was mainly formed by biogenic activities. Furthermore, the different perylene sources accompanied with the core location distributions imply that anthropogenic activities could inhibit its biogenic formation. In the water samples, naphthalene (naph), 1-methylnaphthalene (1methylnaph) and 2-methylnaphthalene (2methylnaph) have considerably higher concentrations in the samples (2016-06 and 2017-09) taken in warm seasons than the concentrations in the samples (2015-11 and 2017-02) taken in cold seasons, but the concentrations of the other PAHs do not vary with seasonal variations. The distribution patterns of these PAHs might be mainly attributed to ambient temperature effects on the PAH solubility in the water body. It is noteworthy that in the campaign 2017-09, the concentrations of 2methylnaph are particularly around twice as high as the concentrations of naph and reach up to 1350 ng/L. As the emission rates of naph are generally higher than methylnaph from anthropogenic activities, so it is suspected that the relatively higher concentrations of 2methylnaph should be attributed to additional biogenic input in the lake water. Furthermore, the samples collected in cold seasons show that high concentrations are mostly located in the northwestern part of the lake and relatively low concentrations are in the northeastern part of lake, but the concentrations from the warm season samples are homogeneous in the whole sampling area. The reason for the different spatial distributions between the cold and warm seasons is that during the sampling campaigns in cold seasons, there was water recharge from the Yangtze River through the Wangyu River connecting the northeastern part of Taihu Lake, which diluted PAH concentrations in the northeastern part of the lake.

Alternatives oder übersetztes Abstract:
Alternatives AbstractSprache

Taihu Lake ist der drittgrößte Süßwassersee in China, spielt eine wichtige Rolle für Denflut, Tourismus, Schifffahrt und vor allem als Trinkwasserquelle für seine nachbarstädte, aber der See wurde stark verschmutzt und die Trinkwasserversorgung wurde gefährdet. Polyzyklische aromatische Kohlenwasserstoffe (PAK) sind in der Umwelt mit petrogenen und pyrogenen Quellen allgegenwärtig und krebserregend und für Menschen und andere Organismen erbgutverändernd. Mit der Entwicklung von Wirtschaft und Industrie führt der rasche Anstieg des Kraftstoff- und Biomasseverbrauchs zu erheblichen PAK-Emissionen in die Umwelt. In dieser Studie konzentrieren wir uns auf PAK in den Sedimenten und Gewässern im nördlichen Teil des Taihu-Sees, wo sie stärker verschmutzt sind als der andere Teil des Sees. Wir analysierten die Konzentrationsmuster von 20 PAK in 25 Oberflächensedimenten, 11 Sedimentkernen und 41 Wasserproben, die während der 4-fachen Feldkampagne aus dem nördlichen Teil des Taihu-Sees gesammelt wurden (2015-11, 2016-06, 2017-02 und 2017-09). Drei der Kerne wurden auf der Grundlage von 137Cs Aktivität für das Abscheidungsalter des Sediments datiert. Die Daten über den Energieverbrauch und die Art der Fahrzeuge im Seeeinzugsgebiet in den letzten zwei Jahrzehnten wurden auf regionalen offiziellen Websites gesammelt, um mögliche PAK-Emissionshistorien in der Region zu erklären. Die Literaturdaten über PAK-Emissionen aus ihren potenziellen Quellen und über PAK-Verteilungen in Partikelgrößen wurden gesammelt, um PAK-Emissions- und Verteilungsmerkmale zu verallgemeinern. PAH-Muster aus verschiedenen Emissionsquellen und auch aus den Sedimentergebnissen dieser Studie wurden kombiniert, um die beiden Annahmen für die Methoden der PAK-Quellenspur in der Umwelt zu überprüfen. Die räumlichen Verteilungen der PAK-Konzentrationen (ausgenommen Perylen) zeigen, dass die Zuflüsse in die Zhushan-Bucht und die Meiliang-Bucht die Hauptwege für PAK und Sedimente waren, die in den nördlichen Teil des Sees eindrangen. Dies führt zu wesentlich höheren PAK-Konzentrationen (bis zu 5000 ng/g) und Sedimentationsraten (höher als der Durchschnitt von 3 – 4 mm/a) im Bereich in der Nähe der Flussaustritte. Darüber hinaus zeigen die Ergebnisse auch, dass die PAK-Konzentrationen in den Sedimenten seit den späten 1950er Jahren aufgrund der Entwicklung von Wirtschaft und Industrie erheblich angestiegen sind, aber die relativ verringerten oder stabilen Konzentrationen in den oberen Schichten der Sedimente die sukzessive Veränderung der Energiestrukturen, die Emissionskontrolle bei Kohleverbrennungen seit den 1990er Jahren und die Emissionskontrolle in Fahrzeugabgasen seit ca. 2000 in diesem Bereich.

Die in den Sedimentkernen (ausgenommen Perylen) ermittelten PAK werden von 4 leichten (Phen), Anthracen (Anthra), Fluoranthen (Fluor), Pyrenus) und 6 schweren (Benzo[k]fluoranthene (BkF), Benzo[a]pyren (BaP), Benzo[b]fluoranthen (BbF) dominiert. , Benzo[e]pyren (BeP), indeno[1,2,3-c,d]pyren (INcdP), benzo[g,h,i]perylen (BghiP)), dessen Konzentrationen in der Regel bis zu 70% – 80% der Konzentrationen der 19 PAK erreichen. Die Konzentrationsfraktionen der 6 schweren PAK sind fast doppelt so hoch wie die Der 4 leichten, und die Fraktionen der schweren PAK nehmen mit abnehmender Tiefe in den Kernen zu, aber die Fraktionen der leichten PAK zeigen die entgegengesetzten Trends (außer den Kernen GH38 und ZS23). mit Besonderheiten). PAK-Emissionsmuster aus Holzverbrennung, Kohleverbrennung und Fahrzeugabgasen können in hohem Maße die Verteilungsmuster der Konzentrationsfraktionen zwischen den leichten und den schweren PAK in den Kernen veranschaulichen. Die Holzverbrennung hat offensichtlich höhere Emissionsfraktionen der 4 leichten PAK als die Fraktionen der 6 schweren PAK im Vergleich zu den Emissionsmustern aus Kohle- und Ölverbrennungen, aber Holz wurde von Anfang an schrittweise als wichtige Energiequelle ausgelagert. Industrialisierung in den 1950er Jahren. PAK-Muster aus Kohleverbrennungen können die Konzentrationsfraktionsverteilungen der beiden POB-Gruppen in den Kernen durch vier Punkte erklären: den kontinuierlichen Rückgang des Wohnkohleverbrauchs und den deutlich erhöhten Verbrauch von Emissionsgesteuerte Kohleverbrennung in diesem Bereich in den letzten Jahrzehnten, relativ mehr ultrafeine Partikel aus der emissionsgesteuerten Kohleverbrennung emittiert, schwere PAK binden mehr in ultrafeine Partikel. In der Zwischenzeit tragen PAK-Muster aus Fahrzeugabgasen zu der Verteilung der Konzentrationsfraktionen in den Kernen durch drei Punkte bei: der lineare Anstieg des Ölverbrauchs im Verkehr, eine rund 24-fache Erhöhung der Zahl der leichten Nutzfahrzeuge, in den letzten zwei Jahrzehnten nur um das Zweifache und in den letzten zwei Jahrzehnten deutlich mehr Ausstoß von schweren PAK aus leichten Fahrzeugabgasen als die von schweren Fahrzeugabgasen. Mehrere Methoden werden häufig verwendet, um PAH-Quellspuren in der Umgebung zu interpretieren, und diese Methoden basieren auf zwei Annahmen: PAH-Muster aus verschiedenen Quellen sind spezifisch und voneinander zu unterscheiden; die Muster bleiben nach der Emission an die Umwelt stabil. Die erste Annahme wurde hauptsächlich durch die PAK-Muster aus verschiedenen Emissionsquellen bestätigt, was zeigt, dass sich PAK-Muster aus verschiedenen Quellen nicht ununterscheidbar überschneiden. Die zweite Annahme wurde durch die räumlichen und zeitlichen Verteilungen von PAH-Mustern im Sediment dieser Studie bestätigt, was zeigt, dass PAH-Muster im Sediment mehrdeutig und variabel sind. Daher sind beide Annahmen für die PAH-Quellenspur im Sediment nicht gültig. Es gab sowohl anthropogene als auch biogene Ursprünge von Perylen in den Seesedimenten, die anhand ihrer räumlichen Verteilungsmuster und auch der Konzentrationsanteile von Perylen zur Summe der 20 PAKs unterschieden wurden. In den in der Nähe der Flussauslässen gesammelten Kerne liegen die Konzentrationsanteile von Perylen typischerweise zwischen 0,02 und 0,18, und es bestehen signifikante positive lineare Korrelationen zwischen der Konzentration von Perylen und drei anthropogenen PAK (BaP, BeP, Pyrenäen), was darauf hindeutet, dass Perylen von anthropogenen Inputs dominiert wurde. Die weiter von den Flussauslässen gesammelten Kerne zeigen jedoch die Konzentrationsanteile zwischen 0,13 und 0,96 und weisen signifikante negative Korrelationen oder keine Korrelationen zwischen Perylen und den drei PAK auf, was darauf hindeutet, dass Perylen hauptsächlich durch biogene Aktivitäten gebildet werden. Darüber hinaus implizieren die verschiedenen Perylenquellen, die mit den Kernstandortverteilungen einhergehen, dass anthropogene Aktivitäten ihre biogene Bildung hemmen könnten. In den Wasserproben weisen Naphthalin (Naph), 1-Methylnaphthalin (1methylnaph) und 2-Methylnaphthalin (2methylnaph) in den Proben (2016-06 und 2017-09) in warmen Jahreszeiten deutlich höhere Konzentrationen auf als die Insamples ( 2015-11 und 2017-02) in kalten Jahreszeiten genommen, aber die Konzentrationen der anderen PAK variieren nicht mit saisonalen Schwankungen. Die Verteilungsmuster dieser PAK können hauptsächlich auf die Auswirkungen der Umgebungstemperatur auf die PAK-Löslichkeit im Wasserkörper zurückgeführt werden. Bemerkenswert ist, dass in der Kampagne 2017-09 die Konzentrationen von 2Methylnaph besonders etwa doppelt so hoch sind wie die Naph-Konzentrationen und bis zu 1350 ng/L erreichen. Da die Ausleinenemissionen von Naph im Allgemeinen höher sind als Methylnaph aus anthropogenen Aktivitäten, wird vermutet, dass die relativ höheren Konzentrationen von 2Methylnaph auf zusätzliche biogene Inputs im Seewasser zurückgeführt werden sollten. Darüber hinaus zeigen die in der kalten Jahreszeit gesammelten Proben, dass sich die hohen Konzentrationen meist im nordwestlichen Teil des Sees und die relativ niedrigen Konzentrationen im nordöstlichen Teil des Sees befinden, aber die Konzentrationen aus den Proben der warmen Jahreszeit homogen im gesamten Probenahmegebiet. Der Grund für die unterschiedlichen räumlichen Verteilungen zwischen der kalten und warmen Jahreszeit ist, dass während der Probenahmekampagnen in kalten Jahreszeiten Wasser aus dem Jangtse-Fluss durch den Wangyu-Fluss aufgetürmt wurde, der den nordöstlichen Teil des Taihu-Sees verbindet, der den nordöstlichen Teil des Taihu-Sees verbindet, der den verdünnte PAK-Konzentrationen im nordöstlichen Teil des Sees.

Deutsch
URN: urn:nbn:de:tuda-tuprints-89906
Sachgruppe der Dewey Dezimalklassifikatin (DDC): 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften
Fachbereich(e)/-gebiet(e): 11 Fachbereich Material- und Geowissenschaften
11 Fachbereich Material- und Geowissenschaften > Geowissenschaften
11 Fachbereich Material- und Geowissenschaften > Geowissenschaften > Fachgebiet Hydrogeologie
Hinterlegungsdatum: 25 Aug 2019 19:55
Letzte Änderung: 25 Aug 2019 19:55
PPN:
Referenten: Schueth, Prof. Dr. Christoph ; Urban, Prof. Dr. Wilhelm
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: 5 August 2019
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