Lateral transport of sediment particles in the Okinawa Trough determined by natural radionuclides.

Narita, Hisashi; Harada, Koh; Tsunogai, Shizuo

doi:10.2343/geochemj.24.207

Cited by 50 publications

(23 citation statements)

References 41 publications

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“…As major mechanisms (1) horizontal transport by the surface current (i.e., Oyashio) from high-latitude regions (Griffin et al, 1968), (2) glacial transport of volcanic materials (Bailey, 1993), (3) atmospheric input from the Asian continent (Iwasaka et al, 1983;Tsunogai et al, 1985), (4) transport from the East China Sea (Narita et al, 1990;Yamada and Aono, 2003), (5) suspended load from rivers to estuaries (Milliman and Meade, 1983) and (6) re-suspension of sediments on the continental slope (Nakatsuka et al, 1997;Itou et al, 2000;Otosaka and Noriki, 2000) have been pointed out. Terrigenous materials have been concluded to have mainly originated from island arcs such as the Kurile Islands for (1) and (2), from arid areas of central Asia for (3) and (4), and coastal areas of the Japan Islands and the Kurile Islands for (5) and (6).…”

Section: Temporal and Vertical Change Of Elemental Composition In Setmentioning

confidence: 99%

“…Because analysis of 231 Pa xs in settling particles was not carried out, we used R V from a sediment trap experiment at Stn. KNOT during 1989-1990(6.5: Narita et al, 2003. Recent studies have suggested that the 230 Th xs / 231 Pa xs ratio in settling particles varies depending on the shape of sampling collector on the sediment trap (e.g., Baker et al, 1988;Gardner et al, 1997).…”

Section: Transport Processes Of Aluminosilicates In the Western Northmentioning

confidence: 99%

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La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

2004

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In order to understand the origins and transport processes of lithogenic aluminosilicate in the western North Pacific, time-series sediment traps were deployed at Stn. KNOT at 44∞N 155∞E (water depth: 5320 m). Annual mean content of aluminum (Al) which is a proxy of lithogenic material in settling particles was 0.38% at 1 km depth, 0.78% at 3 km depth and 1.14% at 5 km depth, respectively. Mass fluxes were corrected by 230 Th and 231 Pa activities in particles and seawater. Annual mean corrected Al fluxes at 1, 3 and 5 km depths were calculated to 0.45, 0.46 and 0.33 g/m 2 /year, respectively. Lanthanum/ytterbium (La/Yb) and thorium/scandium (Th/Sc) ratios were used as proxies for estimating the origin of lithogenic aluminosilicate in settling particles. Both La/Yb and Th/Sc ratios in settling particles increased with depth, and the seasonal variation was the smallest at 5 km depth. It was considered that variations of La/Yb and Th/Sc ratios in settling particles reflected the change of source material of lithogenic aluminosilicates. Origins of lithogenic materials in the settling particles were summarized using two end-members, loess from central Asian continent (AL) and basalts from the Kurile-Kamchatka Islands (KK). Contributions of end-members in settling particles were estimated from the La/Yb and Th/Sc ratios. The contribution of KK particles in lithogenic materials was calculated to be 84% at 1 km depth, and 61% at 3 and 5 km depths, respectively. Although the KK material was the dominant constituent of the terrigenous component in settling particles at Stn. KNOT, the KK flux decreased with depth. On the other hand, the AL flux increased with depth and the significant increase of the AL flux was presumably due to the lateral import of AL particles to the deep layer at Stn. KNOT. From these results we conclude that the distribution of lithogenic materials recorded in sediments in the western North Pacific are influenced by the northward transport of AL within the deep layer.

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Section: Temporal and Vertical Change Of Elemental Composition In Setmentioning

confidence: 99%

Section: Transport Processes Of Aluminosilicates In the Western Northmentioning

confidence: 99%

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

2004

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“…Some of the manganese in the shelf zone must be trapped in the Okinawa Trough. Narita et al (1991) collected settling particles at 1390 m depth in the Okinawa Trough using sediment traps , which were composed almost exclusively of the shelf derived particles transported laterally along the near-bottom layer of the shelf zone. Saito (1991) reported that the (Mn/Al) ratio of these particles was 6.79 x 10-2 at 1390 m depth.…”

Section: Lateral Transport Of Mnmentioning

confidence: 99%

Manganese in the East China Sea and the Yellow Sea.

1996

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Total dissolvable manganese (TDMn) was measured at 13 stations in the East China Sea and the Yellow Sea. High manganese concentrations of more than 100 nmol/1 were observed at stations near the Yangtze River estuary and in the bottom water of the central Yellow Sea, while the manganese concentration dramatically decreased toward the shelf break and reached a constant value less than 5 nmol/l in the Kuroshio water. The manganese concentration increased toward the bottom at almost stations. These data confirm that manganese is released from the seafloor of the continental shelf. Applying a box model to the continental shelf water shallower than 150 m deep, the residence time and the benthic flux of manganese have been calculated to be (140 ± 62) days, (I 1 ± 4) x 103 nmol/m2/day from the whole bottom area of 0.9 x 1012 m2, respectively. The fraction of manganese transported into the East China Sea across the 700 km-long border from outside the sea via the near bottom layer is estimated at 55% of total input to the region. The flux of terrigenous particles exported to the pelagic ocean amounts to 8% of the total suspended load discharged from the Yangtze and Yellow rivers.

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“…Narita et al (1990) posed by Tsunogai (1987). These results are: the fairly large vertical change index (IM) of Al which is a representative of clay particles lateral ly transported; the larger IM value of Mn regenerated from the anoxic shallow sea sediments; the largest IM value of a long-lived ra dionuclide 230Th or "'Pa which is produced from a parent nuclide dissolved uniformly in seawater; the large negative IM value of 228Th hav ing a small source function in the pelagic deep water; nearly the same small negative IM value of a short-lived nuclide 234Th as that of total par ticulate flux; the IM value of 210Pb smaller than that of 230Th corresponding to 13 years of age for transporting vertically and laterally in the deep ocean; the apparent settling velocity of 228Th of 1.0 km / yr and the similar bulk settling velocities of 234Th, 230Th, and 231Pa of 40-50 m/yr for the median fluxes.…”

Section: 'Opb and 210pomentioning

confidence: 99%

Vertical-change index for the particulate transport of chemical and isotopic components in the ocean.

et al. 1990

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Data obtained by recent sediment-trap experiments were compiled to discuss the mechanism for the removal of trace metals from the ocean. The vertical-change index (IM), or the rate constants of first order change with depth, were estimated. The results and the IM values in km-' shown in parentheses are as follows. The total particulate matter flux(-0.05) is nearly constant with depth due to rapid sinking of its major components of tests of biogenic silica(-0.03) and calcium carbonate( 0.05) to the bottom. The organic fraction(-0.27) of settling particles reduces with depth together with components contain ed in soft tissue of organisms such as Cd(-0.23). The fluxes of the lithophile components of Al(+ 0 .22), Fe(+0.17), and 232Th(+0.19) largely increase with depth due to the lateral transport of particles from the continental margin. The large index of Mn(+0.47) is due to the early diagenetic process in the sur face sediment in addition to the simple resuspension. The flux of short-lived 234Th(-0 .01) is saturated, but that of 228Th(-0.14) having no substantial source in the pelagic ocean is the smallest among radiogenic nuclides in seawater. The largest index is found for the long-lived radionuclides such as 230Th(+0 .50) and 231Pa(+0.56). The effect of radioactive decay is somewhat reflected in the indices of 210Pb(+0 .41) and 210Po(+0.43). These results support the train-passengers model proposed by Tsunogai (1987) for the behavior of chemical elements in the ocean.

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Lateral transport of sediment particles in the Okinawa Trough determined by natural radionuclides.

Cited by 50 publications

References 41 publications

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

La/Yb and Th/Sc in settling particles: Vertical and horizontal transport of lithogenic material in the western North Pacific

Manganese in the East China Sea and the Yellow Sea.

Vertical-change index for the particulate transport of chemical and isotopic components in the ocean.

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