Historical records of trace organic contamination in continental shelf, estuarine and lucustrine sediment cores /
The historical records of trace organics can be determined in sediment cores from different aquatic environments. Vertical distributions of trace organic contaminants were determined in sediment cores collected from three different aquatic environments from five locations. Sampling sites were loca...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739668951&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The historical records of trace organics can be determined in sediment cores from different aquatic environments. Vertical distributions of trace organic contaminants were determined in sediment cores collected from three different aquatic environments from five locations. Sampling sites were located off the coast of Louisiana in the Mississippi River Delta, the Saint Johns River estuary, Florida, and the Lakes Texcoco, Xochimilco and Huapango located near Mexico City. The ages of the sediment core sections from Mississippi River Delta, Saint Johns River estuary and Lake Texcoco were assigned using sedimentation rates of 0.81, 1.0 cm yr- I and 0.95 g cm-2 yr-1, respectively. These sedimentation rates were obtained from 210Pb measurements and verified using 137Cs vertical profiles. The sediment cores were fairly undisturbed by bioturbation. The Mississippi River Delta total concentrations of PAHs, hexachlorocyclohexanes (HCHs), chlordane related compounds, DDTs and PCBs ranged from 200- 795 ppb, non-detected (ND)-O.33 ppb, ND-0.28 ppb, ND-1.64 ppb and 0.25-20.9 ppb, respectively. Concentrations of these contaminants increased rapidly during the 1940's. The Saint Johns River estuary total concentrations of aliphatics, PAHs, HCHs, chlordane related compounds, DDTs and PCBs ranged from 7,830-26,900 ppb, 1,540-6,090 ppb, ND-1.28 ppb, ND-5.08 ppb, 0.09-14.36 ppb and 4.52-330 ppb, respectively. The Lake Texcoco total concentrations of aliphatics, PAHS, HCHS, chlordane related compounds, DDTs and PCBs ranged from 4,600- 22,000 ppb, 67.0-440 ppb, ND-6.24 ppb, ND-1.33 ppb, ND-13.69 ppb and 0.88-22.1 ppb, respectively. Contaminants were compared in families (i.e., naphthalenes, DDTs) and individually. In most instances, lower contaminant concentrations occurred in bottom core sections. Contaminant concentrations in surface core sections indicate their continued presence in the aquatic environments after their control and bans. The complexity of the processes involved in transport and deposition of contaminants is reflected in the vertical profiles obtained. Historical records in a sediment core indicate only variations in time of contaminants for one specific location. Direct comparison of historical records of different aquatic environments should be done cautiously. The historical record indicates that the concentrations of some contaminants decreased after restrictions in their use were implemented. |
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| Item Description: | Vita. "Major Subject: Oceanography". |
| Physical Description: | xiv, 240 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 216-237. |