Distribution of 210Po and export of organic carbon from the euphotic zone in the southwestern East Sea (Sea of Japan)     

Gi-Hoon Hong  Young-Ill Kim  Mark Baskaran  Suk-Hyun Kim  Chang-Soo Chung 《Journal of Oceanography》2008,64(2):277-292

The distribution of the natural radionuclide ²¹⁰Po in the water column along a horizontal transect of the continental shelf, slope and deep basin regions of the East Sea (Sea of Japan), a marginal sea of the Northwest Pacific Ocean, was investigated, and its behavior is described here. The settling fluxes of particulate ²¹⁰Po in the deep basin along with ²¹⁰Pb, ²³⁴Th and biogenic matter were also determined. ²¹⁰Po inventories in the water column were observed to decrease from winter to summer in all stations, probably due to increased influx of ²¹⁰Po-poor Kuroshio Water of the Northwest Pacific Ocean during summer. Vertical profiles of dissolved and particulate ²¹⁰Po along with the settling fluxes of particulate ²¹⁰Po in the deep basin station have enabled us to evaluate temporal variations and residence times of ²¹⁰Po. In the slope and basin, activities of dissolved ²¹⁰Po generally decreased from the surface to the bottom water, with maximum activity just below the subsurface chlorophyll a maximum at 50–75 m depth in spring and summer. These subsurface peaks of dissolved ²¹⁰Po activity were attributed to the release of ²¹⁰Po from the decomposition of ²¹⁰Po-laden biogenic particulate organic matter. In the deep basin, despite the decrease in total mass flux, the sinking flux of particulate ²¹⁰Po was higher in the deeper trap (2000 m) than in the shallower one (1000 m), probably due to scavenging of dissolved ²¹⁰Po from the water column during particle descent and/or break-down of ²¹⁰Po-depleted particulate matter between 1,000 m and 2,000 m depths. In general, the ratios of the particulate phase to the dissolved phase of ²¹⁰Po (K_d) increased with depth in the slope and basin stations. ²¹⁰Po removal from the water column appears to depend on the primary productivity in the upper waters. There is an inverse relationship between K_d and suspended particulate matter (SPM) concentration in the water column. From the ²¹⁰Po activity/chlorophyll a concentration ratios, it appears that sinking particles arriving at 1000 m depth were similar to those in the surface waters.  相似文献   

Particulate organic carbon export fluxes on Chukchi Shelf,western Arctic Ocean,derived from 210Po/210Pb disequilibrium     

HE Jianhua  YU Wen  LIN Wuhui  MEN Wu  CHEN Liqi 《中国海洋湖沼学报》2015,33(3)

Fluxes of particulate organic carbon(POC) were derived from 2 10 Po/ 210 Pb disequilibrium during the 4th Chinese National Arctic Research Expedition(CHINARE-4) from July 1 to September 28,2010. Average residence times of particulate 2 10 P o in the euphotic zone were-16.00 a to 1.54 a,which are higher than those of dissolved 2 10 Po(-6.89 a to-0.70 a). Great excesses of dissolved 210 Po were observed at all stations,with an average 2 10 Po/ 210 Pb ratio of 1.91±0.20,resulting from 2 10 Pb atmospheric deposition after sea ice melt. POC fluxes from the euphotic zone were estimated by two methods(E and B) in the irreversible scavenging model. Estimated POC fluxes were 945–126 mmol C/(m2·a) and 1 848–109 mmol C/(m2·a) by methods E and B,respectively,both decreasing from low to high latitude. The results are comparable to previous works for the same region,indicating efficient biological pumping in the Chukchi Sea. The results can improve understanding of the carbon cycle in the western Arctic Ocean.  相似文献   

Levels of Po and Pb in mussel and sediments in Candarlı Gulf and the related dose assessment to the coastal population     

S. Aközcan 《Marine pollution bulletin》2013

²¹⁰Po and ²¹⁰Pb in mussel (Mytilus galloprovincialis) and sediment samples collected at Candarl? Gulf during the period of 2010–2012 are presented and discussed. The activity concentrations of ²¹⁰Po and ²¹⁰Pb were measured by means of alpha spectrometry. Activity concentrations of ²¹⁰Po and ²¹⁰Pb in mussels are in the ranged of 332 ± 17–776 ± 23 Bq kg⁻¹ dw and 14 ± 1–40 ± 5 Bq kg⁻¹ dw, for sediments the ranges for 52 ± 5–109 ± 8 Bq kg⁻¹ dw and 38 ± 5–92 ± 9 Bq kg⁻¹ dw, respectively. The estimated consequent annual effective ingestion dose due to ²¹⁰Po and ²¹⁰Pb from mussel consumption in Candarl? Gulf coastal region were calculated. The highest dose due to ²¹⁰Po and ²¹⁰Po were calculated to be 4232 ± 126 μSv and 126 ± 16 μSv, respectively.  相似文献   

镍箔恒温自沉积总α、总β计数法同时或连续测定样品中²¹⁰Pb、²¹⁰Bi、²¹⁰Po   总被引：1，自引：0，他引：1  

王玉学  郭冬发  黄秋红 《铀矿地质》2012,28(3):165-172,180

研究了210Bi、210Po同时恒温自沉积于镍箔的最佳制源环境,建立了岩石、土壤以及水体样品中210 Pb、210 Bi、210 Po同时或连续测定的方法——镍箔恒温自沉积总α、总β计数法。试验发现,当镍镀片面积为3.14cm2,盐酸浓度为1.0mol/L,溶液体积为25mL,恒温90℃,振荡频率180次/min,振幅20mm,制源60min,210Bi和210Po可同步定量自沉积。210 Po加入量与总α净计数率相关系数为0.9998,210Bi加入量与总β净计数率相关系数为0.9997。放置衰变法可以消除Bi和Po其它短寿命放射性同位素对测量产生的影响,盐酸肼及酒石酸存在时大量共存离子不干扰测定。方法的精密度优于5%,全程加标回收率在99.5%～100.5%。  相似文献   

钻孔岩心剖面210Po测定及其找矿意义     

巢小林 《铀矿地质》2007,23(5):305-309,315

在苗儿山地区已知花岗岩型铀矿床上的试验结果显示,在矿化规模较大、品位较高的钻孔岩心剖面上观察到了分布范围大大超过矿体,且强度较高的210Po异常。据此认为,在勘探最后阶段通过测定钻孔岩心的210Po可以判断钻孔深部以及周围是否还存在隐伏矿体,以指导进一步钻探。本技术有望用于花岗岩型铀矿床的勘查工作。  相似文献   

A century of land subsidence in Ravenna, Italy   总被引：4，自引：2，他引：4  

P. Teatini  M. Ferronato  G. Gambolati  W. Bertoni  M. Gonella 《Environmental Geology》2005,47(6):831-846

Over the last century the Ravenna area has been affected by a widespread land subsidence process of both natural and anthropogenic origin which has become a matter of increasingly great concern. Land settlement, initially of the order of a few mm/year, dramatically increased up to 110 mm/year after World War II primarily due to groundwater pumping and, subordinately, gas production from a number of deep on-shore and off-shore reservoirs. Spirit leveling was carried out in the area of the Ravenna Municipality by various authorities and agencies ever since the end of the nineteenth century using an increasingly refined network of benchmarks. The available information, spanning the time interval from 1897 to 2002, has been implemented and homogenized into a Geographic Information System (GIS). Measurements processed by kriging provide the pattern of the subsidence rates over the municipal territory during eight sub-periods. The reliability of data processing is discussed for both magnitude and areal distribution of the occurrence, showing a pronounced nonlinear behavior in time, as related to the major responsible factors. Cumulative land subsidence approaches almost 1 m over more than one third of the municipality area including the city and a significant fraction of the coastland, with peaks larger than 1.5 m over a 10 km² zone located between the historical center and the coastline. Most recent records show that at present the mainland appears to be substantially stable, whereas some coastal areas are still subsiding at a rate of about 10 mm/year with a significant threat to the environment and the infrastructures as well, although to a lesser extent than in the past decades.  相似文献   

Behaviors of ²¹⁰Pb and ²¹⁰Po around hydrothermal vents in the Okinawa Trough     

Yang Yongliang  Masashi Kusakabe  Yoshiyuki Yamamoto 《海洋学报(英文版)》2002,21(1):95-114

Vertical profiles for the uranium-series radioisotopes 210Pb and 210Po were obtained at thetwo hydrothermal vent sites, the Iheya Ridge and the Minami-Ensei Knoll, in the Mid-Okinawa Trough in 1993 and 1994, respectively. In 1995, both radioisotopes were measured at the Minami-Ensei Knoll a-gain. At the Iheya Ridge, where the hydrothermal activity is not active as reflected by the CH_4, and 222Rn data, both the total 210Pb and 210Po activities show deficiency relative to their parents, and the mean residence time of 210Pb and 210Po is approximately equal to 20 and 2-5 a, respectively. At the Minami-Ensei Knoll, which is characterized by black smokers, the total 210Pb(0.167 × 10~(-3)-2.5 × 10~(-3)_ Bq/kg) around the plumes is deficient relative to 226Ra but the total 210Po activities (1.83 × 10 ~(-3) - 2.83 × 10~(-3) Bq/kg) are in excess relative to 210Pb. The 210Po activities are higher than those in the East China Sea and the Okinawa Trough and excess 210Po has been found. The 210Pb/226Ra and 210Po/  相似文献   

3-D Structure of the Marine Coastal Front and Quantitative Estimate of Nutrient Budgets in a Seawater Volume of the NW Adriatic Sea     

Stefano Cozzi  Giovanni Bortoluzzi  Antonia Di Maio  Marco Marcelli 《Marine Ecology》2002,23(S1):111-121

  相似文献   

Geoeconom ic Processesin the Northwestern Adriatic CoastalPlain     

Bruno Menegatti 《地理学报》1999,54(6):550-558

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Three‐fold nature of coastal progradation during the Holocene eustatic highstand,Po Plain,Italy – close correspondence of stratal character with distribution patterns     

Alessandro Amorosi  Giulia Barbieri  Luigi Bruno  Bruno Campo  Tina M. Drexler  Wan Hong  Veronica Rossi  Irene Sammartino  Daniele Scarponi  Stefano Claudio Vaiani  Kevin M. Bohacs 《Sedimentology》2019,66(7):3029-3052

Although general trends in transgressive to highstand sedimentary evolution of river‐mouth coastlines are well‐known, the details of the turnaround from retrogradational (typically estuarine) to aggradational–progradational (typically coastal/deltaic) stacking patterns are not fully resolved. This paper examines the middle to late Holocene eustatic highstand succession of the Po Delta: its stratigraphic architecture records a complex pattern of delta outbuilding and coastal progradation that followed eustatic stabilization, since around 7·7 cal kyr bp . Sedimentological, palaeoecological (benthic foraminifera, ostracods and molluscs) and compositional criteria were used to characterize depositional conditions and sediment‐dispersal pathways within a radiocarbon‐dated chronological framework. A three‐stage progradation history was reconstructed. First, as soon as eustasy stabilized (7·7 to 7·0 cal kyr bp ), rapid bay‐head delta progradation (ca 5 m year^?1), fed mostly by the Po River, took place in a mixed, freshwater and brackish estuarine environment. Second, a dominantly aggradational parasequence set of beach‐barrier deposits in the lower highstand systems tract (7·0 to 2·0 cal kyr bp ) records the development of a shallow, wave‐dominated coastal system fed alongshore, with elongated, modestly crescent beaches (ca 2·5 m year^?1). Third, in the last 2000 years, the development of faster accreting and more rapidly prograding (up to ca 15 m year^?1) Po delta lobes occurred into 30 m deep waters (upper highstand systems tract). This study documents the close correspondence of sediment character with stratal distribution patterns within the highstand systems tract. Remarkable changes in sediment characteristics, palaeoenvironments and direction of sediment transport occur across a surface named the ‘A–P surface’. This surface demarcates a major shift from dominantly aggradational (lower highstand systems tract) to fully progradational (upper highstand systems tract) parasequence stacking. In the Po system, this surface also reflects evolution from a wave‐dominated to river‐dominated deltaic system. Identifying the A–P surface through detailed palaeoecological and compositional data can help guide interpretation of highstand systems tracts in the rock record, especially where facies assemblages and their characteristic geometries are difficult to discern from physical sedimentary structures alone.  相似文献