Use of heavy liquid density separation to remove pyrite from sediment samples for radiocarbon dating     

《Quaternary Geochronology》2015

Sample preparation protocols for concentrating organic material from sediments for radiocarbon dating often include a large number of steps and the use of hazardous chemicals. Thus, these protocols are often problematic for pollen-poor sediments as material can get lost or may become degraded. Pyrite in samples for radiocarbon dating hinders an effective graphitisation process and thus needs to be removed during sample preparation. Standard protocols require the use of nitric acid, a strong oxidant that corrodes organic material. Therefore, the use of nitric acid needs to be avoided when preparing pollen-poor but pyrite-rich sediments.We present a method that minimises the sample preparation steps by replacing acid treatment with heavy liquid separation. Using non-toxic LST at a density of 2.0 g cm⁻³ is shown to be effective for separating the organic fraction from sulphides, silicates and carbonates. We applied this method to pyrite-rich and pollen-poor sediments from Western Australia that had previously been problematic to date. The successful AMS radiocarbon dating of all samples pre-treated with LST demonstrates the effectiveness of this method.  相似文献   

Toward a luminescence chronology for coastal dune and beach deposits on Calvert Island,British Columbia central coast,Canada     

《Quaternary Geochronology》2015

The Quaternary geology of the central coast of British Columbia contains a rich and complex record of glacial activity, post-glacial sea level and landscape change, and early human occupation spanning the last ∼10,000 years. At present, however, this region remains a largely understudied portion of coastal North America. This study describes the luminescence characteristics of quartz and K-feldspar from coastal dune and beach sands on Calvert Island and develops a suitable optical dating protocol that will allow for a more rigorous chronology for post-glacial landscape evolution and human occupation on British Columbia's central coast. Luminescence signals from Calvert Island quartz are dim, and appear to lack the so-called “fast” component that is most desirable for optical dating. K-feldspar signals are sufficiently bright for optical dating. We test and refine a single-aliquot regenerative-dose (SAR) protocol for K-feldspar specific to Calvert Island samples through a series of dose recovery and preheat plateau tests. Two approaches for correcting a sample age for anomalous fading are compared and a correction for phototransfer is introduced and applied. Measured fading rates vary from sample to sample implying that, in this region, it is not sufficient to rely on two or three representative fading rates as has sometimes been done elsewhere. Refined age estimates show consistency with independent radiocarbon dating control and help identify radiocarbon-dated organic-rich sediments that have been reworked.  相似文献   

游客生态旅游认知及其对环境管理措施的态度——以井冈山风景区为例   总被引：3，自引：1，他引：2  

钟林生  宋增文 《地理研究》2010,29(10):1814-1821

以井冈山风景区为例,采用问卷调查和统计分析方法,研究了游客的生态旅游认知及其对环境管理措施的态度,并分析两者之间的相关性。结果表明:游客对生态旅游"基于自然"、"旅游对象受到保护"、"环境教育"认知率较高,对"社区利益"的认知率尚低,且不同类型游客对生态旅游认知不同。游客对"对环境负责任"、"保护环境资源"、"注意环境影响"、"重视环境教育"、"尊重地方文化"五类旅游环境管理措施持积极态度,但对"加强游客管理"的措施持消极态度。而且生态旅游的认知与某些生态旅游环境管理态度也直接相关,认识到生态旅游"基于自然"、"旅游对象受到保护"以及"社区利益"的游客更认同"重视环境教育"的环境管理措施。最后,还就提高生态旅游认知和加强生态旅游区环境管理提出了具体建议。  相似文献   

Geo-hazards with characteristics and prevention measures along the coastal regions of China   总被引：1，自引：0，他引：1  

Ye-Shuang Xu  De-Xuan Zhang  Shui-Long Shen  Long-Zhu Chen 《Natural Hazards》2009,49(3):479-500

China has more than 18,000 km long coastline. Along the coastline, there are various configurations of topography, geomorphology, and geology condition. In the coastal regions, geological disasters, including seawater intrusion, coast scouring, land subsidence, karst collapse, soil erosion, collapse-landslide-debris flow (CLDF), and human activity-induced disasters, occur frequently. All of these disasters have their own forming causes, characteristics, and distribution regions. Seawater intrusion and coast scouring only occur in the coastal regions while the others occur in both coastal regions and in-land regions. Land subsidence occurring in the coastal region is of larger scale and entails greater economic loss than that occurring in the in-land region. For the other disasters, although the scale of disaster in the coastal regions is smaller than that happened in the in-land regions, the economic loss in the former case is greater than that in the latter. This is because populations are dense and economy is developed along the coastal regions of China. To mitigate the disasters and reduce the economic loss, countermeasures are discussed.  相似文献   

Natural and anthropogenic influences in the northeastern coast of the Nile delta,Egypt   总被引：4，自引：0，他引：4  

Mahmoud M. El Banna  Omran E. Frihy 《Environmental Geology》2009,57(7):1593-1602

Landsat enhanced thematic mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret coastal changes in the zone between Kitchener drain and Damietta spit in the northeastern Nile delta, previously recognized as a vulnerable zone to the effects of any sea level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km2 to the agricultural deltaic land. About 48 km2 of backshore flats, marshes, salt pans and Manzala lagoon have been converted to productive fish farms. The main urban centers have expanded; nearly 12.1 km² have been added to their areas, and new urban centers (Damietta harbor and the New Damietta city) with total area reach of ~35.3 km² have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As a consequence of human activities, the size of Manzala lagoon has been reduced to more than 65%. Shoreline changes have been determined from beach profile survey (1990–2000), and comparison of 1955 aerial photographs and ETM satellite image of 2002 reveal alongshore patterns of erosion versus accretion. The short-term rate of shoreline retreat (1990–2000) has increased in the downdrift side of Damietta harbor (≃14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwaters system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures.  相似文献   

Spatial and seasonal variation of salt ions under the influence of halophytes,in a coastal flat in eastern China   总被引：1，自引：0，他引：1  

Yanyou Wu  Rongcheng Liu  Yuguo Zhao  Pingping Li  Congqiang Liu 《Environmental Geology》2009,57(7):1501-1508

The high salinity of coastal saline field is a key factor limiting the reclamation. Halophytes have been utilized in the reclamation of saline land. The study area is in Yancheng, China. An analysis of the concentrations of Rb, Cs, Sr, and Ba, the ratio of Rb/Cs, and Sr/Ba in soils in autumn shows that the soil of this study area has great homogeneity. Artemisia halodendron, Gossypium hirsutum, and Sesbania cannabina were selected as the reclamation plants in the present study. In order to know the spatial-temporal distribution of soil salinity, the influence of plant-specific vegetation, and the difference of desalination among these halophytes in coastal flat, the authors analyze the soil-layers and seasonal variation in salt ions. Sodium chloride was accumulated in 0–5 cm topsoil with no vegetation during the winter and spring. The effect of desalinization of halophytes is significant. Of the three plant species, Sesbania cannabina has the greatest desalinization. The difference of ions composition of soils covered with various plant species is significant. It can be concluded that halophytes have better amelioration of coastal soil salinity. Special attention should be paid to the selection of plant species and measures to plant and cultivate crops in the reclamation of saline land.  相似文献   

The shape parameter and its modification for defining coastal profiles     

Umut Türker  M. Sedat Kabdaşli 《Environmental Geology》2009,57(2):259-266

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Sustainable groundwater extraction in coastal areas: a Belgian example   总被引：1，自引：0，他引：1  

Alexander Vandenbohede  Emmanuel Van Houtte  Luc Lebbe 《Environmental Geology》2009,57(4):735-747

Water extractions in coastal areas have to deal with salt water intrusion and lowering of hydraulic heads in valuable ecosystems. Therefore, sustainable management of fresh water resources in these areas is crucial. This is illustrated here with two water extractions in the western Belgian coastal plain which extract groundwater from a phreatic dune aquifer. One water extraction faced problems with salt water intrusion, while lowering of hydraulic heads was an issue for both. To remedy the salt water intrusion, it was found that decreasing the extraction rate was the only solution. To offset this and to increase hydraulic heads around both extractions, it was decided to artificially recharge the aquifer of the second extraction with tertiary treated wastewater. By taking these interventions, the combined production capacity of the water extractions was increased with 56% whereas 27% less water was extracted from the dune aquifer itself. Extraction history and the effects of interventions are illustrated for both water extractions with water quality data and fresh water head observations. A more detailed insight in groundwater flow and fresh–salt water distribution in the aquifer is provided by simulating the evolution of the water extractions with a 3D density dependent groundwater flow model.  相似文献   

Heavy metals in the benthic foraminifera from the coastal lagoons,Red Sea,Egypt: indicators of anthropogenic impact on environment (case study)     

Hashem Abbas Madkour  Mohamed Youssef Ali 《Environmental Geology》2009,58(3):543-553

Concentrations of Fe, Mn, Zn, Cu, Pb, Ni, and Cd were measured in several species and genera of Recent benthic foraminifera from three coastal lagoons, namely Abu-Shaar, Umm al-Huwaytat, and Marsa Shuni lagoons located along the Egyptian Red Sea coast. Spatially significant differences in the metal concentrations of benthic foraminifera were recorded among different sites. However, some foraminiferal species display deformation in their coiling, general shape of chambers and the apertures. Abu-Shaar and Umm al-Huwaytat lagoons are virtually influenced by anthropogenic activities while Marsa Shuni lagoon is affected by natural inputs. Benthic foraminifer shows high concentrations of Fe and Mn, especially in Umm al-Huwaytat lagoon. Foraminiferal black tests support this result and reflect selectivity for iron absorption. Among the metals analyzed, Cd, Pb, and Cu showed significant high concentrations in benthic foraminifera at the study areas. The anthropogenic activities and natural inputs are responsible for the abnormalities in benthic foraminifera. Therefore, benthic foraminifera can be used as a good indicator of the environmental changes.  相似文献   

Establishing a monitoring network for an impoundment-induced landslide in Three Gorges Reservoir Area, China   总被引：2，自引：1，他引：1  

Xianqi Luo  Fawu Wang  Zhenhua Zhang  Ailan Che 《Landslides》2009,6(1):27-37

A methodology for monitoring system of an impoundment-induced landslide in Three Gorges Reservoir Area, China is introduced. Currently, based on landslide geological classification, the monitoring regions and methods which include types of monitoring instruments, placement and calibration precision of instruments, and appropriate periods for instrumental placement is confirmed. To optimize the monitoring system, sensitivity analysis of displacements and the water table in landslides affected by reservoir surface fluctuation is completed to determine the layout of the monitoring cross sections and the monitoring points. As a case study, the behavior of displacements and the potential fluctuation of the water table in the Shiliushubao landslide, produced by the gradual water impoundment at Three Gorges Reservoir, has been simulated using 3D finite element method analysis. The sensitivity analysis of Shiliushubao landslide is investigated by the fuzzy set evaluation method. As a result, the monitoring network of Shiliushubao landslide is established.  相似文献