The effect of sediment mixing on Pb-210 accumulation rates for the Washington continental shelf

Nittrouer, Charles A.; DeMaster, David J.; McKee, Brent A.; Cutshall, N.H.; Larsen, I.L.

doi:10.1016/0025-3227(84)90038-0

Cited by 209 publications

(80 citation statements)

References 26 publications

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“…However, it should be noted, that x calculated from profiles of 210 Pb xs often overestimate the actual accumulation rates, as gradually decreasing mixing efficiency with sediment depth might result in a depth profile indicating exponential decay, which is falsely interpreted as undisturbed sediment accumulation (e.g. Nittrouer et al 1984). In all, six multicores have been dated and Fig.…”

Section: Estimates Of Mass Accumulation Using 210 Pbmentioning

confidence: 98%

Variability in upwelling intensity and nutrient regime in the coastal upwelling system offshore Namibia: results from sediment archives

Emeis

Struck

Leipe

et al. 2007

Int J Earth Sci (Geol Rundsch)

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The coastal upwelling system offshore Namibia is ideally suited to address a focal question of the Integrated Marine Biogeochemistry and Ecosystem Research Programme: what are the mechanisms that drive long-term changes in ecosystems? Considerable interannual variability in climatic forcing is indicated by long time series of meteorological and remote sensing observation; these accompany considerable interannual to interdecadal changes in the upwelling intensity over the last 100 years, as well as a centennial trend. On longer time scales, the only archives available are sediment records spanning the late Holocene. To decipher the sediment record, we mapped surface-sediment patterns of proxies for physical (sea surface temperature/SST from alkenone unsaturation indexes) and nutrient (d 15 N on bulk sedimentary N) variables. Their present-day surface-sediment patterns outline the coastal upwelling cells and filaments and associated high productivity area. Analysed in an array of dated sediment cores, the spatial patterns of SST suggest long-term ([100 years) variability in the location and intensity of individual upwelling cells. The patterns of d 15 N outline an area of intense denitrification near the coast, and advection of water with low-oxygen concentrations in the undercurrent from the North. d 15 N exhibits considerable downcore variability, in particular over the last 50 years. The variability appears to be governed by differences in extent of denitrification and thus of the shelf oxygen balance, which appears to have deteriorated in the last 50 years. Together, the data suggest that SST and denitrification conditions have remained in the narrow bounds outlined by today's patterns in surface sediments, but that spatially small variability in upwelling intensity and make-up of upwelling feed waters induced considerable changes in the lower trophic levels of the coastal upwelling ecosystem over the last 6,000 years. Attempts to correlate proxy records from sediments with observational time series and regional climate reconstructions were not successful, possibly because annual to interannual environmental signals are erased in the process of sediment formation.

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Section: Estimates Of Mass Accumulation Using 210 Pbmentioning

confidence: 98%

Variability in upwelling intensity and nutrient regime in the coastal upwelling system offshore Namibia: results from sediment archives

Emeis

Struck

Leipe

et al. 2007

Int J Earth Sci (Geol Rundsch)

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“…Where mixing occurs at the surface, as for the present cores, the predicted depth of penetration is equal to St + L [12]. The predicted penetration depth of 137 Cs was calculated considering that the first input into these sediments began in 1950.…”

Section: Cs Test Of Sedimentation Ratesmentioning

confidence: 99%

Dating of sediments in the Biscay bay: Implication for pollution chronology

et al. 2005

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Abstract. Important historical informations on the temporal changes of anthropogenic pollution in marine environment can be assessed using sediment analysis. Dating is a crucial prerequisite to reconstruct pollution events, to calculate fluxes, and thus to allow comparison between different sites. This work presents estimates of accumulation rates of sediments in the Bay of Biscay. Fives cores were collected during RIKEAU 2002 cruise on board o/v Thalia in order to study temporal changes in PAH and organohalogens compounds content of sediment. We compare chronostratigraphic estimates on cores derived from the natural radionuclide 210 Pb in excess with estimates from the known times of introduction of the artificial radionuclide 137 Cs to the environment. 210 Pb, 226 Ra and 137 Cs were measured directly by non-destructive gamma spectrometry using a well type γ-detector. Total 210 Pb and 226 Ra activities vary from 30 to 150 mBq g -1 , and 20 to 36 mBq g -1 respectively; 137 Cs presents lower levels (< 5 mBq g -1 ). Profiles of 210 Pb xs in three cores present a well mixed layer, from 2-3 to 10 cm, in the uppermost sediments, followed by an exponential decrease of activities, suitable for the determination of sedimentation rates. Under constant flux and sedimentation rate assumptions, vertical accretion rates derived from 210 Pb xs present a large range from nearly 0.1 cm yr -1 up to almost 0.3 cm yr -1 . Differences are mainly due to relative position of studied cores regarding the muddy patch. Although the moderate level of 137 Cs limits the accuracy of this dating method, profiles of 137 Cs with depth strengthen mean rates derived from 210 Pb xs data. The implication of this dating on pollutant inputs in sediments of the Bay of Biscay is briefly discussed.

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“…Sedimentation rates (r) were derived from the slope (S) of linear regression in those parts of the sediments that appeared to be unaffected by mixing (Carpenter et al, 1982) indicating exponential decay which is falsely interpreted as undisturbed sediment accumulation (e.g. Nittrouer et al, 1984).…”

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confidence: 99%

How depositional conditions control input, composition, and degradation of organic matter in sediments from the Chilean coastal upwelling region

Niggemann

Ferdelman

Lomstein

et al. 2007

Geochimica et Cosmochimica Acta

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. (2007) of autochthonous TOC and TIC, were higher at 36°S than at 23°S. We propose that sampling of isolated deposition centers, that collect particles originally distributed over a much wider 15 area led to unexpectedly high sediment accumulation rates in the northern area. Bioturbation was intense at 36°S even in sediments within the oxygen minimum zone, whereas there were no indications for sediment mixing at 23°S.

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The effect of sediment mixing on Pb-210 accumulation rates for the Washington continental shelf

Cited by 209 publications

References 26 publications

Variability in upwelling intensity and nutrient regime in the coastal upwelling system offshore Namibia: results from sediment archives

Variability in upwelling intensity and nutrient regime in the coastal upwelling system offshore Namibia: results from sediment archives

Dating of sediments in the Biscay bay: Implication for pollution chronology

How depositional conditions control input, composition, and degradation of organic matter in sediments from the Chilean coastal upwelling region

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