Catastrophic Decline in Mollusc Diversity in Eastern Tasmania and Its Concurrence with Shellfish Fisheries

Abstract:  We used historical patterns of deposition of mollusc shells to infer changes to inshore benthic assemblages in the southeastern Tasmanian region over the past 120 years. We identified and counted shells in slices embedded within 1m long ²¹⁰Pb-dated sediment cores were collected at 13 sites in water depths of 8–16 m. Declines in mollusc species richness and shell production occurred during the past century at all sites studied, with a mean decline per 5-cm sediment slice from 21 species in 1890 to 7 species in 1990 and in shell abundance from 150 to 30 individuals over the same period. The time course of decline notably corresponded with the history of the scallop dredge fishery, presumably either because scallop dredging caused general declines in populations of mollusc species or because other factors caused a catastrophic regional decline in molluscs that included scallops. As a consequence, the fishery was forced to close. Of major concern is that losses had not previously been recognized but extended throughout the 100-km coastal span of the study. Given that fishing and other anthropogenic impacts, as well as a lack of observational data, are virtually ubiquitous for the coastal zone, major recent losses in mollusc biodiversity may be globally widespread but have gone unnoticed.     

云南省程海现代沉积物中137Cs、210Pb的分布及计年研究

程海沉积物柱芯中存在三个峰形完好的137Cs蓄积峰。 94%的137Cs累计值分配于 1985年以前 ,表明程海沉积物中的13 7Cs能较好地保存在沉积年代的相应层节中。该沉积物柱芯中2 10 Pbex的分布特殊 ,据此将近五十年来程海的沉积过程分为三个稳定沉积阶段和两个快速沉积阶段。两种计年方法的结合有助于认识沉积速率变化较大情况下湖泊的沉积状况 ,也有助于加深对核素计年方法的理解     

大亚湾沉积物中137Cs纵向迁移研究

鉴于海洋沉积物是^137Cs在海域内迁移的最终归宿．建立了沉积物中污染物纵向迁移分布的定量模型，在机理分析中充分考虑了海水-表层沉积物界面上通过沉降、扩散、吸附-解吸等作用完成的物质传输，并对大亚湾内4个监测点底质芯样中^137Cs活度进行了模拟分析，对未来底质中^137Cs的富集趋势进行了预测。     

中国边缘海柱样沉积物中239+240Pu的分布与时标价值

根据中国边缘海已研究的77根^239+240Pu柱样沉积物,分析了柱样沉积物中^239+240Pu的来源、分布和时标特征.结果表明理论上给出的利用²¹⁰Pb、¹³⁷Cs和^239+240Pu 3种核素进行定年可能出现的26种情况,与实际情况完全吻合.中国边缘海海陆交汇,柱样沉积物中不同来源的^239+240Pu沉积叠加使得近岸海域（尤其是河口区）柱样沉积物中^239+240Pu的峰型轮廓明显.从近岸到远海,受到沉积物来源方式、海水深度、黑潮混合、扩散效应和边界清除效应等综合因素的影响,柱样沉积物中^239+240Pu的分布可能出现双峰（多峰）、单峰和无峰的情况.其中,柱样中^239+240Pu呈现单峰分布时,与全球大气沉降的高峰年1963年相对应,时标价值可靠.不同海洋环境条件下²¹⁰Pb、¹³⁷Cs和^239+240Pu定年的可靠性,应根据具体海洋沉积环境进行分析;海水中¹³⁷Cs和^239+240Pu核素沉积性质的差异,可能导致沉积峰不一致而影响定年的判断.     

Modelling the reworking effects of bioturbation on the incorporation of radionuclides into the sediment column: implications for the fate of particle-reactive radionuclides in Irish Sea sediments

A microcosm laboratory experiment was conducted to determine the impact of biological reworking by the ragworm Nereis diversicolor on the redistribution of particle-bound radionuclides deposited at the sediment-water interface. Over the course of the 40-day experiment, as much as 35% of a ¹³⁷Cs-labelled particulate tracer deposited on the sediment surface was redistributed to depths of up to 11 cm by the polychaete. Three different reworking models were employed to model the profiles and quantify the biodiffusion and biotransport coefficients: a gallery-diffuser model, a continuous sub-surface egestion model and a biodiffusion model. Although the biodiffusion coefficients obtained for each model were quite similar, the continuous sub-surface egestion model provided the best fit to the data. The average biodiffusion coefficient, at 1.8 ± 0.9 cm² y⁻¹, is in good agreement with the values quoted by other workers on the bioturbation effects of this polychaete species. The corresponding value for the biotransport coefficient was found to be 0.9 ± 0.4 cm y⁻¹. The effects of non-local mixing were incorporated in a model to describe the temporal evolution of measured ⁹⁹Tc and ⁶⁰Co radionuclide sediment profiles in the eastern Irish Sea, influenced by radioactive waste discharged from the Sellafield reprocessing plant. Reworking conditions in the sediment column were simulated by considering an upper mixed layer, an exponentially decreasing diffusion coefficient, and appropriate biotransport coefficients to account for non-local mixing. The diffusion coefficients calculated from the ⁹⁹Tc and ⁶⁰Co cores were in the range 2-14 cm² y⁻¹, which are consistent with the values found by other workers in the same marine area, while the biotransport coefficients were similar to those obtained for a variety of macrobenthic organisms in controlled laboratories and field studies.     

Phytoremediation of radiostrontium ((90)Sr) and radiocesium ((137)Cs) using giant milky weed (Calotropis gigantea R.Br.) plants

Potential of plants to remove radionuclides/toxic elements from soils and solutions can be successfully applied for removal of important radionuclides such as strontium-90 (⁹⁰Sr) and cesium-137 (¹³⁷Cs). When uptake of ¹³⁷Cs and ⁹⁰Sr by Calotropis gigantea plants incubated in distilled water spiked with the radionuclides either alone or in combination was studied, it was found to have a high efficiency for the removal of ⁹⁰Sr, with 90% being removed from solutions (5 × 10³ kBq l⁻¹) within 24 h of incubation. However, in case of ¹³⁷Cs, about 44% could be removed from solutions (5 × 10³ kBq l⁻¹) at the end of 168 h of incubation. Accumulation of ⁹⁰Sr and ¹³⁷Cs was higher in roots compared to shoots. The plants could remediate both ⁹⁰Sr and ¹³⁷Cs when they were added together to the solution. When two months old plants were incubated in low level nuclear waste, 99% of activity disappeared at the end of 15 days. The present study suggests that C. gigantea could be used as a potential candidate plant for phytoremediation of ⁹⁰Sr and ¹³⁷Cs.     

江南造山带东段鄣源枕状玄武岩的年代学与构造属性研究

江南造山带东段鄣源地区广泛发育呈构造岩块产出的镁铁质岩浆岩,包括空间上密切共生的蚀变枕状-块状玄武岩、辉长岩、辉绿岩等。玄武岩地球化学特征上总体富集轻稀土,亏损重稀土和高场强元素(Nb,P,Ti),类似于岛弧环境下岩浆活动的产物。SHRIMP锆石U-Pb测年结果显示,枕状玄武岩形成于(832±19)Ma,与伏川蛇绿岩和庐山地区枕状玄武岩形成时代一致。结合区域资料,认为鄣源枕状玄武岩形成于弧后小洋盆环境,与其东侧的伏川蛇绿岩和西侧的庐山地区枕状熔岩同属新元古代中期弧后洋盆的产物。     

赤水河流域不同土地利用类型土壤侵蚀的137Cs法研究

本研究采用137Cs法对赤水河流域不同土地利用类型土壤侵蚀强度展开调查研究,以期为赤水河流域生态环境保护和实现流域的可持续发展提供基础数据。通过对赤水河中上游地区4种土地利用类型土壤剖面中137Cs含量的测定和分析,结果表明:坡耕地以侵蚀为主,平均坡度在11°~19°之间时,侵蚀模数介于3630~6776 t/(km2·a),其中,习水和叙永研究区坡耕地平均坡度均大于15°,土壤侵蚀强烈,侵蚀模数在6050~6776 t/(km2·a)之间;草地平均侵蚀模数为4235 t/(km2·a);(2)林地有微弱堆积,堆积模数为1331 t/(km2·a);水稻田堆积模数为3872 t/(km2·a)。可见,当平均坡度大于15°时,坡耕地土侵蚀强度较大,因地制宜的采取相应的水保措施是有效遏制水土流失的关键。     

水文模型与生态环境发展纵览

水文模型是水文科学研究的重要方法.文章详细梳理了自1851年Mulvancy推理公式以来水文模型的发展历史,为原始萌芽时期、近代发展时期、现代变革时期三个发展时期,总结了21世纪以来水文模型研究的最新动态,绘制了水文模型发展的时间轴,对生态环境与水文模型的耦合进行了探讨,包括生态环境对人类的影响和水文模型对生态环境的影响,最后给出了未来水文模型发展趋势的展望及所要面对的主要难题;以期推动水文模型研究工作的进一步发展.     

RESIDENCE TIME OF WATER DISCHARGING FROM THE HANGING GARDENS OF ZION PARK1

ABSTRACT: The Hanging Gardens are a unique feature of Zion National Park. Knowledge of the source and residence time of water discharging from the Hanging Gardens is necessary to help preserve these features. Ground-water chemical and isotopic data distinguish the discharge from seeps and springs into two groups, one of low and one of high conductivity. Water with low conductivity likely originates as recharge near the seeps and springs, and it only interacts with the Navajo Sandstone. High conductivity water, on the other hand, originates as recharge on the tops of plateaus to the east, where it interacts with marine rocks of the Carmel Formation. Carbon dating of these ground waters indicates that the low conductivity water is essentially modern recharge, while the high conductivity water was recharged 1,000 to 4,000 years ago.