Madrepora oculata and Lophelia pertusa mass and 210Pb-226Ra chronology, Røst Reef, Norway, 2011

Here we show the use of the 210Pb-226Ra excess method to determine the growth rate of corals from one of the world's largest known cold-water coral reef, the Røst Reef off Norway. Two large branching framework-forming cold-water coral specimens, one Lophelia pertusa and one Madrepora oculata were collected alive at 350 m water depth from the Røst Reef at ~67° N and ~9° E. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and the corals trace element compositions were studied using ICP-QMS. Due to the different chemical behaviors of Pb and Ra in the marine environment, 210Pb and 226Ra were not incorporated the same way into the aragonite skeleton of those two cold-water corals. Thus to assess of the growth rates of both specimens we have here taken in consideration the exponential decrease of initially incorporated 210Pb as well as the ingrowth of 210Pb from the decay of 226Ra. Moreover a~post-depositional 210Pb incorporation is found in relation to the Mn-Fe coatings that could not be entirely removed from the oldest parts of the skeletons. The 226Ra activities in both corals were fairly constant, then assuming constant uptake of 210Pb through time the 210Pb-226Ra chronology can be applied to calculate linear growth rate. The 45.5 cm long branch of M. oculata reveals an age of 31 yr and a~linear growth rate of 14.4 ± 1.1 mm yr-1, i.e. 2.6 polyps per year. However, a correction regarding a remaining post-depositional Mn-Fe oxide coating is needed for the base of the specimen. The corrected age tend to confirm the radiocarbon derived basal age of 40 yr (using 14C bomb peak) with a mean growth rate of 2 polyps yr-1. This rate is similar to the one obtained in Aquaria experiments under optimal growth conditions. For the 80 cm-long specimen of L. pertusa a remaining contamination of metal-oxides is observed for the middle and basal part of the coral skeleton, inhibiting similar accurate age and growth rate estimates. However, the youngest branch was free of Mn enrichment and this 15 cm section reveals a growth rate of 8 mm yr-1 (~1 polyp every two to three years). However, the 210Pb growth rate estimate is within the lowermost ranges of previous growth rate estimates and may thus reflect that the coral was not developing at optimal growth conditions. Overall, 210Pb-226Ra dating can be successfully applied to determine the age and growth rate of framework-forming cold-water corals, however, removal of post-depositional Mn-Fe oxide deposits is a prerequisite. If successful, large branching M. oculata and L. pertusa coral skeletons provide unique oceanographic archive for studies of intermediate water environmentals with an up to annual time resolution and spanning over many decades.

Radiological aspects of petroleum exploration and production in the sultanate of Oman

This thesis is a study of naturally occurring radioactive materials (NORM) activity concentration, gamma dose rate and radon (222Rn) exhalation from the waste streams of large-scale onshore petroleum operations. Types of activities covered included; sludge recovery from separation tanks, sludge farming, NORM storage, scaling in oil tubulars, scaling in gas production and sedimentation in produced water evaporation ponds. Field work was conducted in the arid desert terrain of an operational oil exploration and production region in the Sultanate of Oman. The main radionuclides found were 226Ra and 210Pb (238U - series), 228Ra and 228Th (232Th - series), and 227Ac (235U - series), along with 40K. All activity concentrations were higher than the ambient soil level and varied over several orders of magnitude. The range of gamma dose rates at a 1 m height above ground for the farm treated sludge had a range of 0.06 0.43 µSv h 1, and an average close to the ambient soil mean of 0.086 ± 0.014 µSv h 1, whereas the untreated sludge gamma dose rates had a range of 0.07 1.78 µSv h 1, and a mean of 0.456 ± 0.303 µSv h 1. The geometric mean of ambient soil 222Rn exhalation rate for area surrounding the sludge was mBq m 2 s 1. Radon exhalation rates reported in oil waste products were all higher than the ambient soil value and varied over three orders of magnitude. This study resulted in some unique findings including: (i) detection of radiotoxic 227Ac in the oil scales and sludge, (ii) need of a new empirical relation between petroleum sludge activity concentrations and gamma dose rates, and (iii) assessment of exhalation of 222Rn from oil sludge. Additionally the study investigated a method to determine oil scale and sludge age by the use of inherent behaviour of radionuclides as 228Ra:226Ra and 228Th:228Ra activity ratios.

The effects of human induced disturbances on the sediment geochemistry of Baltic Sea embayments with a focus on eutrophication history

Historical sediment nutrient concentrations and heavy-metal distributions were studied in five embayments in the Gulf of Finland and an adjacent lake. The main objective of the study was to examine the response of these water bodies to temporal changes in human activities. Sediment cores were collected from the sites and dated using 210Pb and 137Cs. The cores were analyzed for total carbon (TC), total nitrogen (TN), total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (IP), biogenic silica (BSi), loss on ignition (LOI), grain size, Cu, Zn, Al, Fe, Mn, K, Ca, Mg and Na. Principal component analysis (PCA) was used to summarize the trends in the geochemical variables and to compare trends between the different sites. The links between the catchment land use and sediment geochemical data were studied using a multivariate technique of redundancy analysis (RDA). Human activities produce marked geochemical variations in coastal sediments. These variations and signals are often challenging to interpret due to various sedimentological and post-depositional factors affecting the sediment profiles. In general, the sites studied here show significant upcore increases in sedimentation rates, TP and TN concentrations. Also Cu, which is considered to be a good indicator of anthropogenic influence, showed clear increases from 1850 towards the top part of the cores. Based on the RDA-analysis, in the least disturbed embayments with high forest cover, the sediments are dominated by lithogenic indicators Fe, K, Al and Mg. In embayments close to urban settlement, the sediments have high Cu concentrations and a high sediment Fe/Mn ratio. This study suggests that sediment accumulation rates vary significantly from site to site and that the overall sedimentation can be linked to the geomorphology and basin bathymetry, which appear to be the major factors governing sedimentation rates; i.e. a high sediment accumulation rate is not characteristic either to urban or to rural sites. The geochemical trends are strongly site specific and depend on the local geochemical background, basin characteristics and anthropogenic metal and nutrient loading. Of the studied geochemical indicators, OP shows the least monotonic trends in all studied sites. When compared to other available data, OP seems to be the most reliable geochemical indicator describing the trophic development of the study sites, whereas Cu and Zn appear to be good indicators for anthropogenic influence. As sedimentation environments, estuarine and marine sites are more complex than lacustrine basins with multiple sources of sediment input and more energetic conditions in the former. The crucial differences between lacustrine and estuarine/coastal sedimentation environments are mostly related to Fe. P sedimentation is largely governed by Fe redox-reactions in estuarine environments. In freshwaters, presence of Fe is clearly linked to the sedimentation of other lithogenic metals, and therefore P sedimentation and preservation has a more direct linkage to organic matter sedimentation.

Radiometric validation of age, growth, and longevity for the blackgill rockfish (Sebastes melanostomus)

As nearshore fish populations decline, many commercial fishermen have shifted fishing effort to deeper continental slope habitats to target fishes for which biological information is limited. One such fishery that developed in the northeastern Pacific Ocean in the early 1980s was for the blackgill rockfish (Sebastes melanostomus), a deep-dwelling (300−800 m) species that congregates over rocky pinnacles, mainly from southern California to southern Oregon. Growth zone-derived age estimates from otolith thin sections were compared to ages obtained from the radioactive disequilibria of 210Pb, in relation to its parent, 226Ra, in otolith cores of blackgill rockfish. Age estimates were validated up to 41 years, and a strong pattern of agreement supported a longevity exceeding 90 years. Age and length data fitted to the von Bertalanffy growth function indicated that blackgill rockfish are slow-growing (k= 0.040 females, 0.068 males) and that females grow slower than males, but reach a greater length. Age at 50% maturity, derived from previously published length-at-maturity estimates, was 17 years for males and 21 years for females. The results of this study agree with general life history traits already recognized for many Sebastes species, such as long life, slow growth, and late age at maturation. These traits may undermine the sustainability of blackgill rockfish populations when heavy fishing pressure, such as that which occurred in the 1980s, is applied.

Tracing sediment transport and bed regime in Nha Trang Bay

Three spatial structure groups of radionuclides in U and Th series, 210Pb-excess and 137Cs, and 40K were found based on analyzing temporal and spatial datum of their content by factor analysis with oblique rotation in Nhatrang bay. U and Th spatial structure with their contours decreased toward the offshore, ran longshore and divided seawater of bay into two parts with strong gradient on both sides. Inside part located from center of Nhatrang bay toward the seashore with three main deposit centers of their contents higher than 23 Bq/kg.dry for 238U and 40 Bq/kg.dry for 232Th, indicated unstability of shoreline. Almost sediments coming from river extended toward the offshore, were stopped and transported toward southeastern. The outside part was less than above mentioned content. The boundary line between two parts superposed with the constantly limit line of turbid plume in the rainy season. Direct influence of the continental runoff was limited by the 9 Bq/kg.dry contour of 238U, 19 Bq/kg.dry contour of 232Th. Longshore current was a predominant process whereas lateral transport as sifting and winnowing process of finer grains in sediments of Nhatrang bay. Areas that had very low content of 137Cs and 210 Pb-excess adjoining shoreline showed areas being eroded. Accumulation of 137Cs and 210 Pbexcess nearby river mouth characterized for fine compositions of sediments controlled by seasonal plumes and sites further toward the south indicated finer materials transported from river and accumulated in lack of hydrodynamic process. Near shore accumulation of 40K revealed the sediments there originated from bed erosion.

武汉月湖沉积物中硅藻的垂直分布与水质变化

采用活塞取样器采集了月湖湖中央2处钻孔沉积物,分析了其中硅藻种类与密度的垂直变化,同时采用210Pb/137Cs推测沉积物的沉积速率,并进行了总有机质、生物硅含量分析,以了解月湖各个不同年代的水质变化。结果表明,2个柱状沉积物中硅藻的优势属为:小环藻属、直链藻属、舟形藻属、Cyclostephanos属。Z-1钻孔优势种为:梅尼小环藻、颗粒直链藻、Navicula porifera、Cyclostephanos tholifomis。Z-2钻孔中优势种为:梅尼小环藻、颗粒直链藻、舟形藻、Cyclostep

~(210)Pb和~(137)Cs法对比研究武汉东湖现代沉积速率

对采自东湖 站和 站的沉积物采用210Pb和137Cs相结合的方法测定沉积速率,210Pb法测出东湖 站和 站的沉积速率为8.73mm/a和6.90mm/a,137Cs测出东湖 站和 站的沉积速率为7.4mm/a和5.8mm/a.分析了两种方法测定结果差异产生的原因,并与以往的研究相对比,探讨东湖沉积速率空间分布的规律性,沉积速率变化与人类活动的关系、沉积速率与扰动的关系.

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.

Eutrophication process recorded in dinoflagellate cyst assemblages — a case of Yokohama Port, Tokyo Bay, Japan

To investigate temporal changes of water quality, a role of dinoflagellate cysts preserved in surface sediments was examined in Yokohama Port in Tokyo Bay, Japan. Two cores were collected, and sedimentation rates and ages of both were dated as approximately 1900 years or slightly older on the basis of 210Pb and 137Cs concentrations. The temporal change in dinoflagellate cyst assemblages in the two cores reflects eutrophication in Yokohama Port in the 1960s. Abrupt increases in the cysts of Gyrodinium instriatum cysts strongly suggests that a red tide was caused by this species around 1985. Dinoflagellate cyst assemblages in surface sediments appear to be good biomarkers of changes in the water quality of enclosed seas.

210Pbex沉积通量突发增大对湖泊生产力的指示

210Pb沉积计年的基本假设是大气沉降并经由湖水转入沉积物的210Pbex 通量稳定. 当沉积速率相对稳定时, 沉积物中210Pbex 的比活度将随沉积年代呈指数衰减. 湖泊水体中的210Pbex 主要随有机微粒的沉降而进入沉积物. 如果湖泊水体中有机质沉积通量出现突发增大时, 则可能显著地增大210Pbex 被清洗而转入沉积物的通量. 这种突发性清洗效应, 一方面显然不符合210Pb沉积计年的基本前提; 另一方面可能指示湖泊水体初级生产力的明显变化. 根据云南程海近代沉积物210Pbex 垂直剖面的特殊变化, 对这一问题进行讨论. 沉积物柱芯于1997年6月采自程海深水湖区. 137Cs比活度垂直剖面呈现出3峰特征, 给出了可靠的计年结果并显示出近几十年间沉积物堆积的稳定性. 而210Pbex 比活度垂直剖面呈现出特异的峰值分布, 并与Corg垂直剖面相似. 这一现象可能与制约210Pbex 转入沉积物的机制有关. 程海沉积物中Horg/Corg和Corg/Norg原子比平均值分别为5.51和7.04, 表明其有机质主要源于内生藻类残骸. 根据沉积物有机质“沉降-降解-堆积”的3阶段特征, 模拟计算出1970年以来有机碳Corg的沉积通量(F(Corg)). 不同年代210Pbex 的沉积通量(F(210Pbex ))与F(Corg)显示出很好的同步关系. 特别是1972～1974年和1986～1989年的两个时段, 二者同步增大. F(Corg)的变化导致F(210Pbex )的变化; F (210Pbex)的变化在一定程度上反映出湖泊生产力的历史变化

地球化学示踪在现代土壤侵蚀研究中的应用

土壤侵蚀导致土地退化，农产品产量和品质下降，水环境污染等诸多问题，引起各方面的广泛关注，而且这个问题随着持续增长的人口压力和农业生产方式深刻变革的影响而日益严重，由于目前广泛使用的高差法，遥感研究法，RUSLE，野外调查法，水土流失监测点法等土壤侵蚀研究方法存在着一些不足，因此，核素地球化学示踪法，稀土元素示踪法，土壤地球化学指标法等地球化学示踪方法应运而生，在土壤侵蚀研究中发挥其独特作用，在比较了各种传统的土壤侵蚀研究方法的优势和不足的基础上，作者认为：（1）^137Cs,^210Pb可用于研究30、40年左右平均土壤侵蚀速率，^7Be可用于示踪季节性土壤侵蚀和一次降雨事件的土粒运移，并说明这些核素的示踪原理和侵蚀速率的定量依据；（2）人为施放稀土元素（REE）示踪法适合定量一次或多次降雨事件的侵蚀速率，可用于土壤侵蚀理论的研究，尤其适合于室内模拟实验的研究；（3）土壤磁化率法和土壤理化性质指标法研究土壤侵蚀是一种处于起步阶段的侵蚀研究方法，适用于土壤质量退化研究，但要用于土壤侵蚀研究特别是侵蚀速率的定量研究还很不成熟。

长江中下游湖泊的环境演化：沉积物的碳、氮同位素记录研究

本项研究以长江中下游地区的浅水湖泊（太湖、巢湖、龙感湖）为研究对象，碳、氮同位素为研究手段，结合210Pb和14C年代学，以及沉积物中TOC、TN、C/N比值、TP等多种地球化学参数，对近代沉积环境演化过程，沉积物有机质来源以及西太湖形成演化的古环境进行分析研究。通过研究，得到以下主要认识： 1. 太湖沉积物剖面上δ13Corg和C/N比值分布范围指示太湖沉积物的有机物质来源主要是水生藻类。竺山湾T3点基本没有陆源物质输入；梅梁湾T2点有部分陆源物质输入；湖心T4点沉积物有机质来源还可能是不同于梅梁湾和竺山湾的水生植物。沉积物的地球化学参数剖面指示太湖从1920s始，沉积环境受人为因素的影响而逐渐营养化。 2. 巢湖沉积物δ13Corg和δ15N的研究结果，不仅指示沉积物有机质来源主要是水生藻类，受城市污染和农业面源污染输入的一定影响，而且指示了在沉积历史上因为巢湖闸的建成，湖泊生产力和浮游植物物种也发生了改变，湖泊富营养化。 3. 龙感湖沉积物δ13Corg和δ15N的研究分析，表明湖泊有机沉积以自身有机物源为主，受陆源输入影响小。1960s围垦造成营养盐输入量的增加，因为草型湖泊这一特征有利于营养盐的积累，缓解水体的富营养化程度，龙感湖始终处于中营养程度。 4. 太湖、巢湖和龙感湖表层沉积物孔隙水中NO3－和SO42-含量的差异，主要受水域污染状况、底泥有机质的丰富情况、环境水动力条件的变化、泥沙沉积和再悬浮过程引起的元素累积和释放影响，也是藻型湖泊与草型湖泊生产力大小、有机质沉积通量以及微生物丰度和活性等差异的表征。 5. 沉积物表层吸附态NH4+-N含量，体现了水域环境受污染的严重程度是：龙感湖<巢湖<太湖梅梁湾。三个湖泊中底泥有机质丰度差异和生物参与的氨化作用差别都非常显著。三个湖泊的沉积物表层铵态氮的含量，均表明了沉积物表层向上覆水体可能具有潜在的铵态氮迁移趋势。 6. 太湖古环境分析研究中，竺山湾和梅梁湾沉积物剖面的粒度分析、δ13Corg、δ15N、TOC、TN、C/N比值和TP都随沉积深度，对应14C定年结果，指示了西太湖沉积演化历程的三个阶段及其有机质来源。6870~6670 a B.P.，研究区被咸水覆盖，有机质来源是典型的水体自生来源，在竺山湾有逐渐增加的C4植物的输入。6670~5140 a B.P.，可能形成瀉湖并出现沉积间断。5140 a B.P.至今，形成淡水湖泊，沉积有机质主要来自湖泊自生物源，存在沉积间断。 7. 长江中下游的浅水湖泊沉积物中的有机质来源主要以湖泊自生来源为主，因为水体初级生产力的升高受陆源物质输入增加的影响，流域内人类活动引起的陆源物质输入不容忽视。长江中下游湖泊的近代沉积环境演化过程因为近岸距离、水动力强度和发育不同的水生植物等因素存在区域性差异，导致湖泊富营养化的最大根源是人为因素的影响发生的环境演变。