sediment sedimentation rate values in the manila bay and thailand gulf using 210pb method l.
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Sediment Sedimentation rate values in the Manila Bay and Thailand Gulf using 210Pb method. Che Abd Rahim Mohamed Marine Ecosystem Research Centre (EKOMAR) Faculty of Science & Technology Universiti Kebangsaan Malaysia 43600 Bangi, Selangor Malaysia E-mail: carmohd@ukm.my. Topics. Introduction

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sediment sedimentation rate values in the manila bay and thailand gulf using 210pb method

Sediment Sedimentation rate values in the Manila Bay and Thailand Gulf using 210Pb method

Che Abd Rahim MohamedMarine Ecosystem Research Centre (EKOMAR)Faculty of Science & TechnologyUniversiti Kebangsaan Malaysia43600 Bangi, SelangorMalaysia

E-mail: carmohd@ukm.my

topics
Topics
  • Introduction
  • Chronology
  • Sampling & Analytical procedure
  • Results & Discussion
  • Major Past, Current & Future Research Plans
introduction
Introduction
  • Why Date Marine Sediments?Usually dated with two goals in mind:
      • (1) to establish the timing of past environmental change, and
      • (2) to determine the accumulation of materials (e.g. sediment, pollutants, micro-fossils) in the reservoirs.
slide4
Radioactive classified into two group as;

1. Natural – cosmogenic and primodial

  • cosmogenic – 26Al, 10Be, 7Be, etc
  • primodial – 238U series, 232Th series

2. Artificial or man-made – 137Cs, 241Am

slide5

The natural Uranium-Thoriumdecayseries

© AWI

geochemistry  

Responsible: Michiel Rutgers v. d. Loeff

Webmaster

Last modified: 20.2.2001

slide6

Dating method

Half-life

Dating range

Application

230Thexcess

75,200 yr

< 300,000 yr

Deep sea sedimentation rates, Mn nodule formation rate

231Paexcess

34,300 yr

< 150,000 yr

Deep sea sedimentation rates, Mn nodule formation rate

226Ra

1,602 yr

10,000 yr

Marine and terrestrial

210Pbexcess

22.3 yr

100 yr

Sedimentation rate in lakes, estuaries and coastal marine environment

228Thexcess

1.913 yr

10 yr

Rapid sedimentation rates in shallow waters

234Thexcess

24.1 days

100 days

Rapid sedimentation rates in shallow waters

Summary of U-Th decay series dating methods

why using short half life radionuclide
Why using short half-life radionuclide?

Deposition of sediment at the coastal water, lake and estuary areas was controlled by;

a. bioturbation

b. tidal cycles

c. bottom currents

d. human activity

e. suspended solid input

why using 210 pb methods
Why using 210Pb methods?

Lead-210 Chronology

- Studies for human impacts (e.g. pollution, eutrophication, erosion), which typically focus on the last 100-200 years, the dating method of choice is 210Pb.

  • Lead-210 is a naturally occurring radioisotope in the 238U-decay series formed by decay of 226Ra, and the subsequent evasion of the intermediary 222Rn (an inert gas) from the earth's surface.
  • Radon-222 decays through a series of short-lived daughters to 210Pb which is stripped from the atmosphere in precipitation and accumulates in lake sediments and wetlands where it decays away with a half-life of 22 years.
  • Cores are typically dated by analyzing a series of stratigraphic levels from the core surface to a depth where unsupported 210Pb is no longer measurable (roughly 5-8 half-lives).
  • From the resulting 210Pb profile, dates are calculated according one of several mathematical models that make assumptions regarding the accumulation of 210Pb and sediment at the core site.
slide9

The model assumed that;

a. the flux of excess nuclides to the sediment-water interface is constant

b. the sedimentation rate is constant at all times.

c. there is no post-depositional migration of the radionuclide within the sediments.

d. the activity of daughter supported by parents in the sediments is independent with depth.

calculation
Calculation

Sedimentation rate from vertical profile of excess nuclide in core can be calculated from the relation;

Az = Aoe(-t) ------- 1

where,

Az is the activity of excess study nuclide (dpm/g) in the sediment at any depth Z (cm) from the sediment-water interface

Ao is the activity of excess study nuclide (dpm/g) in the freshly deposited at depth Z = 0 (sediment-water interface)

t is time (year) or t = Z/S

S is the sedimentation rate (cm/yr)

210Pb is decay constant/half-life or 0.0318/yr

Az = Aoe(-)(Z/S) --------- 2

analytical procedure
Analytical procedure
  • Generally, analytical procedure for uranium-thorium nuclides in sediments, suspended solid (TSS), seawater, freshwater and organisms are combination with acidification, precipitation, purification and electrodeposition.
  • The analytical methods using anion or cation are well established [i.e, Koide & Bruland, 1975; McCabe et al., 1979; Harada & Tsunogai, 1985; Mohamed et al., 1996 & etc.,].
slide14

Sediment Sample Analysis

1~2 g dried sediment samples (< 125 um)

Digestion with HNO3 + HCLO4 + H2O2

Spike with Pb and Ba carrier solution

Digest 2 hours

Filter with 0.45 um

Sample solution

Heating on the hotplate

Dryness

Dissolved with 50 ml of 1% HCLO4

+

CATION COLUMN

slide21

10.00

1.00

210Pbexcess (dpm/g)

0.10

0.01

0

10

20

30

40

50

60

Depth (cm)

RESULTS

Thailand Gulf at GT 15

manila bay
Manila Bay

S =0.721+0.002 cm/yr

major past current future research plans
Major Past, Current & Future Research Plans
  • Past
    • Setup Marine Ecosystem Research Centre for conducting research in various field such science & non-science.
  • Current
    • Transboundary research in various elements
  • Future
    • South China Sea cruise on July 2008
    • National & International research on marine radiochemistry
slide27

thanks

POME Family at Jakarta 2007