~(137)Cs示踪研究小流域土壤侵蚀与沉积空间分布特征

通过在0.17 km~2面积的小流域198个点、525个样品表层土壤中~(137)Cs含量的分析、研究,结果表明:不同地貌部位~(137)Cs含量有明显分异,为~(137)Cs法定量研究土壤侵蚀与沉积提供了科学依据;~(137)Cs含量升高的部位多出现在沟缘线附近和沟口附近;小流域土壤侵蚀强度从梁峁顶向沟坡逐渐增大,这是黄土高原广大水土流失区自然状态的或初步治理的小流域侵蚀强度空间变化的基本特征.

Distribution characteristics of (CS)-C-137 in wind-eroded soil profile and its use in estimating wind erosion modulus

Due to its inert reaction in soil system and distinctive vertical distribution in soil profile, caesium-137 (Cs-137) has been used as a tracer to assess wind erosion. In this study, 62 soil samples were collected from 4 sampling sites in Taipusi County, Inner Mongolia; Caesium-137 activities for those soil samples were measured using a gamma-ray spectrometry in Sichuan University, Chengdu. Distribution pattern of Cs-137 in vertical soil profile was different for different land use and land cover types. Caesium-137 was distributed homogeneously in plow layer of cropland, and negatively exponential in low to medium cover grassland. Distribution pattern in high covered grassland was represented by a peak at 2-4 cm soil depth followed by a negative exponential curve. Based on those findings, simplified mass balance model was chosen to estimate the rate of wind erosion for cropland, while profile distribution model was used for grassland. Estimated wind erosion rates were 7990, 4270 and 1808 Mg(.)km(-2.)a(-1) for cropland, low cover grassland and medium cover grassland, respectively. Wind erosion intensity correlated negatively with plant cover.

红枫湖沉积物~(137)Cs扩散迁移性研究员

保存在湖泊沉积物~(137)Cs剖面中的环境信息记录，可能因~(137)Cs沉积后的再迁移作用而失真。~(137)Cs吸附动力学及离子交换实验表明红枫湖沉积物中的~(137)Cs绝大部分处于固定态，少量处于交换态和造反性吸附态。同时Cs~（+）浓度很低时，高Cs~(+)浓度下在各吸附态与粘土矿物表面的特定吸附部位之间，通常比较明确的对应关系变得有些模糊。本文以界面过程的数学模型为核心，通过模式分析，重建了红枫湖地区历年的~(137)Cs大气沉降通量值，获得了红枫湖集水区 ~(137)Cs流域侵蚀寄宿时间，约为550年。 ~(137)Cs的扩散和其它沉积后再迁移作用。虽然导致~(137)Cs剖面发生了一些变化，但通过适当的数据处理，仍可从中提取出有价值环境信息。

Artificial and natural radioactivity in edible mushrooms from Sao Paulo, Brazil

Environmental biomonitoring has demonstrated that organisms such as crustaceans, fish and mushrooms are useful to evaluate and monitor both ecosystem contamination and quality. Particularly, some mushroom species have a high capacity to retain radionuclides and some toxic elements from the soil and the air. The potential of mushrooms to accumulate radionuclides in their fruit-bodies has been well documented. However, there are no studies that determine natural and artificial radionuclide composition in edible mushrooms, in Brazil. Artificial (Cs-137) and natural radioactivity (K-40. Ra-226. Ra-228) were determined in 17 mushroom samples from 3 commercialized edible mushroom species. The edible mushrooms collected were Agaricus sp., Pleurotus sp. and Lentinula sp. species. The activity measurements were carried out by gamma spectrometry. The levels of Cs-137 varied from 1.45 +/- 0.04 to 10.6 +/- 0.3 Bq kg(-1), K-40 levels varied from 461 +/- 2 to 1535 +/- 10 Bq kg(-1), Ra-226 levels varied from 14 +/- 3 to 66 +/- 12 Bq kg(-1) and Ra-228 levels varied from 6.2 +/- 0.2 to 54.2 +/- 1.7 Bq kg(-1). Cs-137 levels in Brazilian mushrooms are in accordance with the radioactive fallout in the Southern Hemisphere. The artificial and natural activities determined in this study were found to be below the maximum permissible levels as established by national legislation. Thus, these mushroom species can be normally consumed by the population without any apparent risks to human health.

(Table 1) Cesium-137 concentrations and salinity in surface waters from the Atlantic and Pacific Oceans in January-May 1978

Cesium-137 concentrations of surface waters were measured during Cruise 20 of R/V Dmitry Mendeleev across the Atlantic and Pacific Oceans. The measurements were combined with simultaneous salinity measurements. The radioactivity field of surface waters is governed by presence of closed circulation systems and their component currents. Crossing the oceans from west to east decrease in cesium-137 concentrations was noted. In surface waters in the northeastern periphery of the southern anticyclonic gyre in the Pacific Ocean Cs-137 concentrations increased (up to 21.5 Bq/m**3) due to a series of nuclear tests on the Muroroa Atoll.

Hammasröntgentutkimusten termoluminesenssidosimetria

Tavanomaisten hammasröntgenlaitteiden säteilyannoksia valvotaan postitettavien testipakettien ja paikan päällä tehtävien tarkastusten avulla. Säteilyannoksen valvontaan käytetään termoluminesenssidosimetrejä (Thermoluminescence Dosimetry, TLD). Dosimetreissä on TL-materiaalista valmistettuja loistekiteitä, joihin absorboitunut säteilyenergia vapautuu valona materiaalia lämmitettäessä. Prosessissa vapautuvan valon intensiteetti on suoraan verrannollinen absorboituneeseen säteilyannokseen. TLD:llä mitataan rekisteröityjen intraoraalilaitteiden tuottamaa säteilyannosta potilaan posken kohdalla. Säteilyturvakeskus (STUK) ylläpitää rekisteriä ilmoitusvelvollisuuden alaisista hammasröntgenlaitteista. Nyt hammaslaiterekisteriä ollaan uudistamassa siten, että TLD-mittaustulosten käsittely ja annoslaskenta siirtyvät rekisteristä WinTLD-laskentaohjelmaan, jossa on kaikki tarvittavat parametrit annoksen laskemiseksi. Tässä työssä TLD-mittausjärjestelmän kalibrointituloksia analysoitiin vuosilta 1996-2011 ja määritettiin uudelleen laskennassa käytetty energiakorjauskerroin, joka on osa tulevaa WinTLD-konfigurointia. Mittauksissa tarvittavat standardisäteilylaadut (ISO H-laadut) pystytettiin osana työtä. Henkilödosimetrien suorituskykytestauksessa käytetään ISO N-säteilylaatuja. Mirion Technologies (RADOS) käyttää TLD-systeemiä henkilödosimetriassa, ja hammas-TLD on tämän järjestelmän sovellus potilasdosimetriaan. ISO H-laadut otettiin käyttöön, jotta dosimetrien vastetta voitiin ISO N-laatujen tapaan tutkia jatkuvana fotonienergian funktiona Cs-137 ja Co-60 gammasäteilylaatuihin asti ja koska niillä voitiin jäljitellä todellista kliinistä suodatusta. Energiakorjauskerroin kalibroinnissa käytettävän Co-gammasäteilyn ja intraoraalikuvauksissa käytettävän röntgensäteilyn välillä määritettiin uudelleen. Sen arvoksi (yksikkö mGy/mGy) saatiin ISO N-60-laadulla 0,671 ja ISO H-60-laadulla 0,677, jotka ovat numeerisesti hyvin lähellä aikaisemmin määritettyä kerrointa 0,679. Energiakorjauskertoimen epävarmuudeksi saatiin 3,5 % (2std) ja annosmittauksen epävarmuudeksi 7,8 %. Energiavasteiden perusteella dosimetreissä käytetty materiaali on kahdesta vaihtoehdosta MTS-N (LiF:Mg,Ti) eikä MCP-N (LiF:Mg,Cu,P). TLD-järjestelmää voidaan kehittää ja konfiguroida uusien tulosten perusteella, jolloin otetaan käyttöön muun muassa uudelleenmääritetty energiakorjauskerroin. ISO H-säteilylaadut otettiin 22.3.2011 virallisesti käyttöön STUKissa ja niitä käytetään dosimetritestauksessa tarvittaessa suuria annosnopeuksia ja annoksia.

Sedimentary records of water environment in lake Chaohu in the Yangtze delta region, China

Three lacustrine core samples were collected from Chaohu lake in December 2002 in the Yangtze delta region. The grain sizes were analyzed using a Laser Analyzer to obtain grain-size parameters. Sediment geochronology was determined in radioisotopes Cs-137 and the average sedimentary rates are 0.29cm.a(-1), 0.35 cm.a(-1) and 0.24cm-a(-1) in Cores C 1, C2 and C3, respectively. The grain-size parameters of the deposits vary regularly with the fluctuation of hydrodynamics. From 1950s to the beginning of 20th century, coarse-grained sediment was deposited, suggesting strong hydraulic conditions and high water-level periods with much precipitation; from the start of 20(th) century to latter half of 18(th) century, fine-grained sediment was deposited, indicating that weak hydraulic conditions and low water-level periods with less precipitation; before the first half of 18(th) century, coarse-grained sediment was deposited, suggesting great velocity of flow and high water-level periods of more precipitation.

Sedimentation rates, nitrogen and phosphorus retentions in the largest urban Lake Donghu, China

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

Temperature effects of CsI(Tl) crystal detector with APD readout

The temperature dependences of the light output of CsI(Tl) crystal grown at IMP and of the gain of the Hamamatsu S8664-1010 avalanche photodiode (APD) have been investigated systematically. The light output of the CsI(Tl) crystal increases with temperature by 0.67%/degrees C in the region from -2 degrees C to 8 degrees C, and by 0.33%/degrees C in the region from 8 degrees C to 25 degrees C, while the gain of the tested APD decreases by -3.68%/degrees C (working voltage 400V) on average in the room temperature range. The best energy resolution 5.1% of the CsI(Tl) with APD was obtained for the 662keV gamma ray from Cs-137 radiation source.

Response of the diatom flora in Jiaozhou Bay, China to environmental changes during the last century

The diatom flora in a 164 cm long sediment core obtained from Jiaozhou Bay (Yellow Sea, China) was analyzed in order to trace the response of diatoms to environmental changes over the past 100 years. The sediment core was dated by Pb-210 and Cs-137 and represented approximately 100 years (1899-2001 A.D.). The flora was mainly composed of centric diatoms (59-96%). The concentration of diatoms declined sharply above 30 cm (after similar to 1981 A.D.), while the dominant species changed from Thalassiosira anguste-lineatus, Thalassiosira eccentria, Coscinodiscus excentricus, Coscinodiscus concinnus and Diploneis gorjanovici to Cyclotella stylorum and Paralia sulcata. Species richness decreased slightly, and the cell abundance of warm-water species increased. We argue that these floral changes were probably caused by climate change in combination with eutrophication resulting from aquaculture and sewage discharge. (c) 2007 Elsevier B.V. All rights reserved.

湖光岩玛珥湖沉积物硅藻硅同位素研究

本论文选取我国的典型玛珥湖－湖光岩玛珥湖为研究对象，在国内外率先系统开展湖泊沉积物硅藻硅同位素研究。为获取过去2000a来的气候环境记录，对原有沉积物-水界面采样装置进行了改进，将沉积物柱芯无扰动采集深度从60cm提高到150cm。建立了一套有效的五阶段硅藻提纯方法，成功从初始硅藻含量大于7%的沉积物中提取出纯度达90％以上的硅藻样品，为广泛开展沉积物硅藻硅氧同位素研究奠定了基础。放射性核素Pb-210、Cs-137、C-14计年结果表明，该湖沉积物堆积速率稳定，具连续、稳定的堆积特点，是气候和环境变化的良好记录体。湖光岩玛珥湖沉积物硅藻硅同位素记录了硅藻利用水体溶解硅的比例变化。沉积物硅藻硅同位素与生物硅含量的变化关系为揭示湖泊古环境提供了重要线索。当硅藻硅同位素组成与生物硅含量呈正相关变化时，湖水溶解硅利用比例主要受温度控制，硅藻硅同位素可反映古温度变化。当硅藻硅同位素组成与生物硅含量不呈相似变化时，湖水溶解硅利用比例主要受有效养分控制，沉积物硅藻硅同位素仅仅反映硅藻利用水体溶解硅的比例，不反映古温度变化。湖光岩玛珥湖沉积物柱芯硅藻硅同位素组成的变化范围为 -0.6‰～1.1‰，其最小值出现于1580～1920年间，指示了1580～1920年为湖光岩地区过去2000年来最冷的时期，为中国南方热带地区现代小冰期的存在提供了新的证据。

Nineteenth and twentieth century sea-level changes in Tasmania and New Zealand

Positive deviations from linear sea-level trends represent important climate signals if they are persistent and geographically widespread. This paper documents rapid sea-level rise reconstructed from sedimentary records obtained from salt marshes in the Southwest Pacific region (Tasmania and New Zealand). A new late Holocene relative sea-level record from eastern Tasmania was dated by AMS(14)C (conventional, high precision and bomb-spike), Cs-137, Pb-210, stable Pb isotopic ratios, trace metals, pollen and charcoal analyses. Palaeosea-level positions were determined by foraminiferal analyses. Relative sea level in Tasmania was within half a metre of present sea level for much of the last 6000 yr. Between 1900 and 1950 relative sea level rose at an average rate of 4.2 +/- 0.1 mm/yr. During the latter half of the 20th century the reconstructed rate of relative sea-level rise was 0.7 +/- 0.6 mm/yr. Our study is consistent with a similar pattern of relative sea-level change recently reconstructed for southern New Zealand. The change in the rate of sea-level rise in the SW Pacific during the early 20th century was larger than in the North Atlantic and could suggest that northern hemisphere land-based ice was the most significant melt source for global sea-level rise. (C) 2011 Elsevier B.V. All rights reserved.

Onset of recent rapid sea-level rise in the western Atlantic Ocean

A high-resolution record of sea-level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2m thick salt-marsh peat sequence at Chezzetcook, Nova Scotia, Canada. Former mean tide level positions are reconstructed with a precision of +/- 0.055 in using a transfer function derived from distributions of modern salt-marsh foraminifera. Our age model for the core section older than 300 years is based on 19 AMS C-14 ages and takes into account the individual probability distributions of calibrated radiocarbon ages. The past 300 years is dated by pollen and the isotopes Pb-206, Pb-207, Pb-210, Cs-137 and Am-241. Between AD 1000 and AD 1800, relative sea level rose at a mean rate of 17cm per century. Apparent pre-industrial rises of sea level dated at AD 1500-1550 and AD 1700-1800 cannot be clearly distinguished when radiocarbon age errors are taken into account. Furthermore, they may be an artefact of fluctuations in atmospheric C-14 production. In the 19th century sea level rose at a mean rate of 1.6mm/yr. Between AD 1900 and AD 1920, sea-level rise accelerated to the modern mean rate of 3.2mm/yr. This acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming. (c) 2005 Elsevier Ltd. All rights reserved.

Radiocronologia dos sedimentos do Lago de Constança

The dating of sediments in lakes, estuaries and rivers through radionuclides, when applied in association with other analitic methods (heavy metals, organic contaminants, etc.) allows analyses of the anthropogenic interference in the environment along the years. A geochronology of a sediment core from Untersee in Lake Constance, one of the most important hydric resources of Europe, was established through the Pb-210 method and adopting the CRS parameter (Constant Rate of Supply). The Cs-137 was successfully used to give basis to the results, as its additional input occurred in Chernobyl’s accident can be used as a marker to the year 1986. Associating the dating with the cores depth, the average mass accumulation rate and the sedimentation rate for the site were assessed (0,14 g/cm²/year and 4 mm/year respectively).

Historical record of polycyclic aromatic hydrocarbons (PAHs) and spheroidal carbonaceous particles (SCPs) in marine sediment cores from Admiralty Bay, King George Island, Antarctica

This paper describes the first results of polycyclic aromatic hydrocarbons (PAHs) and spheroidal carbonaceous particles (SCPs) in sediment cores of Admiralty Bay, Antarctica. These markers were used to assess the local input of anthropogenic materials (particulate and organic compounds) as a result of the influence of human occupation in a sub-Antarctic region and a possible long-range atmospheric transport of combustion products from sources in South America. The highest SCPs and PAHs concentrations were observed during the last 30 years, when three research stations were built in the area and industrial activities in South America increased. The concentrations of SCPs and PAHs were much lower than those of other regions in the northern hemisphere and other reported data for the southern hemisphere. The PAH isomer ratios showed that the major sources of PAHs are fossil fuels/petroleum, biomass combustion and sewage contribution generally close to the Brazilian scientific station. (C) 2009 Elsevier Ltd. All rights reserved.