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conveyed into the river through direct city runoff. However, due to strong hydraulic currents existing at this reach, the contaminated flow ofthe Buffalo Rive r is entirely diverted into the Niagara River and out ofthe lake. Therefore, no significant sediment contamination is caused by this flow in other portions ofthe Eastern Basin. The above described pattern leaves the northern pan ofthe Central and. Eastern Basins relatively unpolluted (Fig. 5.3.1). The background levels ofcontamination found here can possibly be attributed to seepage ofhydrocarbons from the underlying reservoirs and/or spills and leaks ofpetrolewn products during production operations. The processes ofatmospheric deposition do not seem very important in the fonnation ofPAH assemblage in sediments. However, traces ofcity-derived airborne pollutants can be found in remote regions of lhe Central and Eastern Basins. Finally. processes of natural weathering altering the PAH assemblage have been found important. These processes seem especially active in the northern areas, where hydrocarbons might be present in sediments. Hence, deferential degradation ofthe assemblage fonned by the above mechanisms accounts for the observed molecular and isotopic compositions of PAH in sediments. 230
6. CONCLUSIONS The major conclusions that emerge from the study described above can be summ arized as follows: Three prominent zonescharacterized by similar molecularandisotopiccomposition of compounds can be identified in the lake. The PAH fluvially introduced at major cities. are further transported and redistributed by surface andbottom circulation. The latter creates a specific pattern ofdistribution ofdifferentially contaminated sediments. This pattern. superimposed on some background level ofcontamination. seems to be responsible for the three-cluster structure observed in the lake. A subtle interplay between different combustion and petroleum sources and ongoing processes ofnatural degradation seems to be responsiblefor the observed wilhin-zone variability in molecular and isotopic composition. Produced mostly from urban centers, combustion-derived PAH appear to dominate in the contaminated zones while the background zone shows high contribution ofpetroleum-type sources to the formation of PAHassemblage. The lattermight result from seepageofhydrocarbonsknownto underlie this area and/or leaksand seeps from productionoperations. This zone is aJso marked by intensivedegradation of less stable compounds. Finally, identification of the isotopiccompositionofPAH in sediment sampleswas again shown a techniquehighly supplementaryto the mote conventionalstudies of their 231
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POLYCYCLIC AROMATIC HYDROCARBONS IN
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composition. Portions ofthe lake th
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TABLE OF CONTENTS . ABSTRAcr._._ _
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6. CONCLUSIONS_._ _....._._._ _ ._
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FIGURE 3.104 CONfIGURATION OF ISOCH
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FIGURE 4 .2.12 SAMPLES AND PROMINEN
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fIGURE 5.3.1 DESCR1Pl1VE MODEL OF S
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APPENDIX B 3 _ T HEoerwt Of A PtUNC
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Ip » Ideno(l,2.3 cd)pyrene NIST =
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Figure L 1.1 The 16 parental polycy
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After release by the primary source
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decomposition processes (O'Malley e
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Figure 2.1.1 The Great Lakes draina
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;: Duluth Chicago 1 J Lake Superior
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are the Black River, the Cuyaho ga
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Figure 1.1.5 The pattern of permane
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sedimentary basins, Western. Centra
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Figure 2. 1.8 Summer (July) air and
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Natural Resources: The lower Great
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American waters under the current U
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continuously overflowed com bined s
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3.1 EXPERIMENTAL 3. METHODS 3.1.1 S
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Table 3,1.1 Locations and types ofs
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Figure 3.12 Extraction and purifica
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hexane. 2) the unsaturated aliphati
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this problem. Ratios ofthe two stab
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Figure 3. 1.4 Configuration ofIsoch
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3.2.1 UNl- AND BIVAJUATE METHODS Th
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f igure 3.2. 1 Mean and range (± s
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utilized the same instrument (Isoch
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Selecting lIt1J'iahlu: It was demon
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w- _ 71
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seven variables with fewer missing
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analysis also employed a greate r n
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description. The second cluster ana
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elationships between different site
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Figure 4.1.3 Regression ofthree fir
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Figure 4.[.5 Isotopic composition (
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Figure 4.1.6 Weights ofvariables (c
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Figure 4.1.8 Distri bution ofsample
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those at the majority ofstations. S
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Ion, 969, 971, 357, 358). In additi
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Figure 4.2.3 Samples and prominent
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analysis supported some ofthc previ
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, ", Is , , >\ ryr " II ,- - , I ,
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11'
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sources (Fi g. 4.2 .5c). This compo
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Figure 4.2.7 The relative contribut
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".1.1.2 Miring CllrIIU (isotopic co
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Figure 42.9 Samples and promin ent
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Figure 4.2. 13 Samples and prominen
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It is difficult to differentiate be
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Figure 4.2.18 Weights ofvariables (
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Figure 42.19 Distribution ofsamples
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5.1 SPATIAL DI STRIBUTION s. DISCUS
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f igure 5.1.1 Zones coinciding with
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f igure 5. 1.2 Average and range (
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Figure 5.1.4 Zones (clusters) in th
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Figure 5.1.5 Direction ofthe mean s
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The location ofthe third station at
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Figure 5.1.7 Station locations and
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Figure 5.1.8 Station locations and
Page 201 and 202: 5.1.4 and Section 4.1.2). This clus
Page 204: Figure 5.1.1 1 Statioo locations an
Page 208 and 209: unaffected by the contaminated flow
Page 211 and 212: this station is die clo$esf to the
Page 213 and 214: samples and sources (Fig. 52.1 and
Page 216 and 217: There is yet another observation po
Page 218 and 219: with the relative contribution ofdi
Page 221 and 222: Table S.l.1 Six dusters identified
Page 224 and 225: the three previous ly identified zo
Page 226: Figure 5.2.4 Station locations and
Page 229 and 230: contribution from petroleum related
Page 231 and 232: (Fig. 4.2.7). Finally. this site co
Page 233 and 234: Snow melt and sewer releases seem t
Page 235 and 236: importance ofcombustion-derived PAR
Page 237 and 238: Intens ity o(degradation (the South
Page 239 and 240: where this importance is somewhat r
Page 241: Figure 5.2.5 Station tocatices andz
Page 244 and 245: :2 for molecular composition assume
Page 247 and 248: ange of Slatistica1 variat ion of t
Page 249: Figure 5.].1 Descriptive model ofso
Page 254 and 255: molecular composition. Its applicat
Page 256 and 257: Canton L. and Grimal t 1. O. (1992)
Page 258 and 259: Howell E. T., Marvin C. H., Bilyea
Page 260 and 261: Olson F. C. W. (l950) The currents
Page 263 and 264: Willett P. (1981) Similarity and cl
Page 266: t Apprndb AI. [cout.) bl S,.lioD A<
Page 271 and 272: Appendill A6. The two-component mas
Page 273: Appendix A7. (cont.) Xl. = X llVt r
Page 277: • ass
Page 281: Appendix 82. (cont.)
Page 285: Appendix IU. (cant.) oj Tue Dec 24
Page 290: AppendiI C3. (cont.) Coo c.eo lrati
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