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Abstract  

A total of eight sediment cores with 50 cm length were taken in the Sabah and Sarawak coastal waters using a gravity corer in 2004 to estimate sedimentation rates using four mathematical models of CIC, Shukla-CIC, CRS and ADE. The average of sedimentation rate ranged from 0.24 to 0.48 cm year−1, which is calculated based on the vertical profile of 210Pbex in sediment core. The finding also showed that the sedimentation rates derived from four models were generally shown in good agreement with similar or comparable value at some stations. However, based on statistical analysis of paired sample t-test indicated that CIC model was the most accurate, reliable and suitable technique to determine the sedimentation rate in the coastal area.

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Abstract  

Sedimentation rates in Guanabara Bay were determined by applying the210Pb CRS method to sediment cores collected at five different stations. The results showed a pronounced increase from 0.1–0.2 cm·year−1 to 1–2 cm·year−1, in sedimentation rate, over the last 40–50 years. Observed heavy metal profiles in sediment could also be explained on the basis210Pb dating and local industrial history.

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Sediment core samples were collected in the largest urban Lake Donghu (Stations I and II) in China, and the activities of 210Pb, 226Ra and 137Cs were measured by gamma-ray spectrometry. The sedimentation rates, calculated by 210Pb constant rate of supply (CRS) model, ranged from 0.11 to 0.65 (average 0.39) cm. y-1at Station I, and from 0.21 to 0.78 (average 0.46) cm. y-1at Station II. Sedimentation rate calculated by 137Cs as a time marker was 0.55 cm. y-1at Station II. Based on the average sedimentation rate, we obtained 769 and 147 t. y-1for nitrogen and phosphorus retentions in Lake Donghu sediments, respectively.

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In order to clarify the sedimentation rate of 210Pbexcess and 137Cs in brackish Lake Obuchi, bordered by nuclear fuel facilities in Rokkasho Village, Aomori, Japan, sediment core samples were collected at three points in the lake, and the rates were calculated by the chronological measurement method using 210Pb and 137Cs. The sedimentation rates were 0.29±0.04 g . cm-2 . y-1 in the estuary of the Futamata River (water depth of 1.2 m), 0.13±0.02 g . cm-2 . y-1 in the 3 m water depth area, and 0.11±0.02 g . cm-2 . y-1 at the center point (water depth of 4.5 m), respectively. The Futamata River estuary was found to be greatly affected by land erosion.

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Abstract  

The Rio Grande reservoir lies southeast of the Metropolitan Area of São Paulo. In order to evaluate if the sediments contain a historical registration of anthropogenic activity, four sediment cores were sampled from the reservoir. In these cores the Hg concentration was determined by the CV AAS technique, major and trace elements by instrumental neutron activation analysis and the sedimentation rates by the 210Pb method. The results obtained for Hg are much higher than expected, showing an anthropogenic contribution. As a general trend, the elemental concentration decreases with depth, indicating recent contamination.

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Abstract  

Sediment cores were obtained from Teluk Brunei, Sipitang, Teluk Kimanis, Kota Kinabalu and Kuala Penyu at the coastal water of Sabah and analyzed for 210Pb and 210Po to estimate the sedimentation rates. The calculated sedimentation rates of 210Pb and 210Po varied from 0.003 to 0.049 cm/y and 0.74 to 8.77 cm/y, respectively. The highest sedimentation rates were determined for 210Pb and 210Po at stations located at Sipitang (mean: 0.027 cm/y) and Teluk Kimanis (mean: 5.53 cm/y), respectively. The sedimentation rate estimated for 210Pb is not fully reliable because the activity of 226Ra was higher than that of 210Pb and bioturbation was active at the sampling stations.

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Abstract  

Laguna del Plata (Cordoba, Argentina) is a small saline lake connectedto Laguna Mar Chiquita. Its level fluctuations have changed notably throughthe centuries with both high level (HLP) and low level (LLP) periods. Theradionuclides 226 Ra and 210 Pb were analyzed in a core to determine datesand sedimentation rates. The elements As, Ba, Br, Co, Cr, Cs, Fe, Hf, Na,Rb, Sb, Sc, Se, Ta, Th, U, Zn, Zr and rare earth Ce, Eu, La, Lu, Nd, Sm, Tband Yb were determined by instrumental neutron activation analysis. Statisticalanalysis of elemental concentrations (cluster analysis) reflects the associationof the samples along the core according to the provenance of the sedimentsand if they had been deposited during HLP or LLP.

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Abstract  

It has been generally accepted when estimating sedimentation rates using the 137Cs dating method that the position of the 137Cs maximum in a sediment profile represents the year 1963. In this paper we validated this approach by developing a model in which the annual 137Cs global fallout flux for the Yangtze River estuary was established on the basis of the Tokyo flux corrected for precipitation rates observed in Shanghai. As the 137Cs maxima in the sediment deposition profiles depend on the sedimentation rates, the sub-sampling intervals were calculated accordingly. Higher measured than the calculated values were found in some cores, what may be due to fluctuating sedimentation rates and an additional deposition of 137Cs from land-based sources. The study provides useful information on the reliability of the measured 137Cs maxima in sediment profiles frequently used for dating of sediments in marine (coastal regions, open seas) as well as in terrestrial (lakes) environments.

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Downcore variation of trace metals in sediment cores along the coastal line is one of the markers to assess the intrusion of industrial pollutants into the aquatic environment. Fifty sediment core samples from the Mumbai Harbour Bay (MHB), were studied for the trace element content. MHB is a recipient of effluents from different industries situated all along its coast around Thane–Belapur region. The average concentrations of Titanium (Ti), Manganese (Mn), Iron (Fe), Nickel (Ni), Copper (Cu), Zinc (Zn) were determined by inductively coupled plasma-optical emission spectroscopy and complemented by analysing with energy dispersive X-ray fluorescence spectrometry. In addition to this, depth profiles of K and Ca were also studied to assess the homogeneity of the geological strata of the region. Trace metals such as Cu, Ni and Zn show enrichment between 16 to 28 cm, whereas, uniform distribution through out the core was observed for K, Ca, Ti, Mn and Fe. Chronology of the heavy metal deposition was predicated based on the average sedimentation rate (0.92 ± 0.08 cm year−1) derived using depth-wise 137Cs concentration profile in core of bottom sediment. The results of the analysis showed that MHB had received excess inputs of Cu, Ni and Zn in the year 1981, 1988 and 1982, respectively. Surface concentration of Cu, Ni, Zn and Fe compared to the reference site indicates moderate pollution in the recent years whereas for elements K, Ca, Ti and Mn, the values are normal indicating MHB unpolluted for the latter elements.

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Abstract  

The isotopes 137Cs and 210Pb were determined in sediment cores originating from the floodplain of the river Yamuna (the largest tributary in the Ganges river system, India). Sampling was done at five locations: Sharanpur (next to the Himalayan foothills), Delhi, Jagmanpur, Hamirpur and Allahabad, where Yamuna meets the Ganges. The rate of sedimentation derived from both techniques, 137Cs and 210Pb, appears to be quite similar. At the station Sharanpur the highest rate of sedimentation (5.99 cm/y) was noticed, most probably due to deforestation and other human influences in the Himalayan regions, while the lowest rate was observed in Hamirpur (2.48 cm/y). All the five cores studied showed a 137Cs peak of 1963, due to radioactive fallout, caused by weapon tests. The three upstream stations (Sharanpur, Delhi and Jagmanpur) showed a 137Cs peak due to the Chernobyl event. These measurements reflect that Chernobyl debris have been transferred to the low latitude river system across the Himalayas.

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