Estimation of Sediment Properties during Benthic Impact Experiments

Sediment properties, such as water content and density, have been used to estimate the dry and wet weights, as well as the volume of sediment recovered and discharged, during benthic impact experiments conducted in the Pacific and Indian Oceans. The estimates show that the weights of dry (355-1332 t) and wet sediment (1651-4888 t) recovered during the experiments, are not only a function of the total duration and distance covered during the experiment, but also depend on water content and density of the sediment. Estimation of dry sediment and its volumetric ratio in the discharge, are key parameters for calculating the discharged volume. The estimated volume of wet sediment recovered (1427-4049 m 3 ) as well as discharged (2693-6951 m 3 ) during the experiments, provide important inputs to evaluate the sediment resettlement and migration. Using these estimates, the average depth of excavation on the seafloor, can also been calculated. However, the stages of sediment recovery and discharge are expressed differently in some of the experiments. In order to standardize these, different stages have been identified, and definitions of certain terms have been suggested, for use in the future. The methods of calculating different properties, as well as weight and volume of discharged sediment are described in the paper for use in other applications concerning deep-sea discharges.     

Chemical and isotopic methods for management of artificial recharge in Mazraha Station (Damascus Basin,Syria)

Artificially enhancing recharge rate into groundwater aquifer at specially designed facilities is an attractive option for increasing the storage capacity of potable water in arid and semi‐arid region such as Damascus basin (Syria). Two dug wells (I and II) for water injection and 24 wells for water extraction are available in Mazraha station for artificial recharge experiment. Chemical and stable isotopes (δ²H and δ¹⁸O) were used to evaluate artificial recharge efficiency. 400 to 500*10³ m³ of spring water were injected annually into the ambient shallow groundwater in Mazraha station, which is used later for drinking purpose. Ambient groundwater and injected spring water are calcium bicarbonate type with EC about 880 ± 60 μS/cm and 300 ± 50 μS/cm, respectively. The injected water is under saturated versus calcite and the ambient groundwater is over saturated, while the recovered water is near equilibrium. It was observed that the injection process formed a chemical dilution plume that improves the groundwater quality. Results demonstrate that the hydraulic conductivity of the aquifer is estimated around 6.8*10^?4 m/s. The effective diameter of artificial recharge is limited to about 250 m from the injection wells. Mixing rate of 30% is required in order to reduce nitrate concentration below 50 mg/l which is considered the maximum concentration limit for potable water. Deuterium and oxygen‐18 relationship demonstrates that mixing line between injected water and ambient groundwater has a slope of 6.1. Oxygen‐18 and Cl^? plot indicates that groundwater salinity origin is from mixing process, and no dissolution and evaporation were observed. These results demonstrate the efficiency of the artificial recharge experiments to restore groundwater storage capacity and to improve the water quality. Copyright © 2011 John Wiley & Sons, Ltd.     

露天煤矿生态重建技术研究——以黔北某露天煤矿为例

土地资源是国家重要的自然资源,土地资源的合理开发利用有力地支持了国民经济的发展。但在闭坑的露天煤矿中,对矿山地形地貌、土地资源、生态植被等影响较大,为促进生态可持续发展,应积极采取自然恢复、辅助再生、生态重建等措施,及时对损毁区域进行生态修复,改善生态环境。实现煤炭开采扰动区域的地质环境达到稳定、损毁土地得到治理利用、生态系统功能得到恢复和提升、废弃资源得到综合利用等目标。本文以黔北某露天煤矿为例,通过采取生态重建技术该露天煤矿进行修复,恢复耕地33682 4 hm2,林地14262 6 hm2,农村道路1389 7 hm2,公路用地0271 8 hm2。通过地貌重塑、土壤重构、植被重建等生态重建技术对矿山损毁区进行修复,以期为同类型矿山生态修复提供借鉴。     

Factors influencing seed germination of Cyperus capitatus, inhabiting the moving sand dunes in southern Europe

Cyperus capitatus Vandelli (Cyperaceae) is distributed in coastal sandy habitats and mobile dunes of south Europe. Its seed germination ecology is not known, despite its potential to be used in re-vegetation projects. Laboratory experiments were conduced to assess the effects of salinity, light regime, cold stratification and burial on seed germination of this species. Overall, increasing salinity delayed germination, increased seed dormancy and mean time to germination (MTG), and reduced final germination percentage, inhibiting it completely above 1% of salinity; although it did not affect seed viability. C. capitatus seeds exhibited their greatest germination at levels between 0 and 1% in non-stratified seeds, and between 0 and 0.5% for stratified seeds. Thus, the effect of salt was greater for stratified seeds at 5 °C. Germination in light/darkness conditions was similar to that in full darkness. Finally, burial in sand of C. capitatus seeds appeared to have a significant effect on cumulative percentage of germination. Seeds buried at depths greater than 2 and 3 cm showed a lower germination success than those on sand surface or buried at shallower depths. Burial also affected the beginning and speed of seed germination.     

Impact and recovery associated with the deposition of capital dredgings at UK disposal sites: Lessons for future licensing and monitoring

The majority of studies relating to impacts and recovery at dredgings disposal sites have concentrated on areas subject to regular and frequent disposals of maintenance dredgings over relatively long time periods. In comparison less is known regarding the significance of impacts and the recovery processes associated with the disposal of capital dredgings that commonly involves the infrequent deposition of heterogenous material over relatively restricted time periods. Impacts and recovery processes are likely to be different to those associated with the disposal of maintenance dredgings. For example, findings suggest that capital dredgings deposited at both the Roughs Tower and Barrow-in-Furness result in the occurrence of persistent changes to seafloor substrata within the license area and this subsequently effects the composition of associated faunal communities present. Moreover, whilst the two disposal sites are geographically distinct similar species are identified as being particularly sensitive to capital disposal activities in both areas.     

Long-term divergent tidal flat benthic community recovery following hypoxia-induced mortality

Macrobenthos recovery after hypoxia-induced mass mortality was assessed in an estuarine tidal mudflat during 3 years. During the first 2 years, a Pearson-Rosenberg type of community recovery took place along with the improving bottom water oxygen conditions. After 3 months, spionid polychaetes became superabundant (i.e. opportunistic peak), followed rapidly by a steep decline (i.e. ecotone point). Subsequently, a moderate increase in species richness and a steep increase in biomass, related to the growth of long-lived species occurred (i.e. transition region). Afterwards, however, the recovering community diverged again from the ambient, undisturbed, sediments due to enhanced recruitment success of long-lived species presumably resulting from the lowered interference from bioturbation during early recovery stages in the disturbed plots. Hence, despite early community recovery may be more or less deterministic, lagged divergent community reassembling may occur at the longer-term, thereby contributing to benthos patchiness in areas which are frequently subjected to disturbances.     

Different levels of macroalgal sampling resolution for pollution assessment

The effects of using reduced sampling resolutions to study macroalgal vegetation patterns have not been studied sufficiently. Here, we test the influence of taxonomic resolution level, removal of occasional species, aggregation of species abundances into functional groups and data transformation in the detection of a long-term recovery process by phytobenthic intertidal assemblages. Results indicate that the aggregation of species data into the genus level has very little influence. Likewise, almost any significant information is lost when occasional algae are removed. Analyses at the level of families and orders still clearly detect differences between highly degraded and reference vegetation. By contrast, analyses based on class and functional group abundances capture quite different information. The effect of transformation is similar at the different taxonomic levels. Most surrogate measures properly reflect changes in diversity. It is concluded that genus level is the most appropriate surrogate approach for detecting the recovery process.     

Regeneration and Reuse of a Seaweed‐Based Biosorbent in Single and Multi‐Metal Systems

A seaweed‐waste material resulting from the processing of Ascophyllum nodosum was previously shown to be very efficient at removing Zn(II), Ni(II) and Al(III) both in single and multi‐metal waste streams. In this study, the regeneration of the biosorbent using an acid wash resulted in the release of high metal concentrations during multiple desorption cycles. Maximum desorption efficiencies (DE) of 183, 122 and 91% were achieved for Zn(II), Ni(II) and Al(III), respectively, for subsequent metal loading cycles, significantly exceeding the desorption rates observed for conventional sorbents. The regeneration of the sorbent was accomplished with very little loss in metal removal efficiency (RE) for both single and multi‐metal systems. Values of 92, 96 and 94% RE were achieved for Zn(II), Ni(II) and Al(III), respectively, for the 5^th sorption cycle in single metal aqueous solutions. A slight decrease was observed for the same metals in multi‐metal systems with maximum REs of 85, 82 and 82% for Zn(II), Ni(II) and Al(III), respectively. This study showed that the novel sorbent derived from a seaweed industrial waste would be suitable for multiple metal sorption cycles without any significant loss in RE.     

暴时内辐射带高能质子的损失和恢复机制探究

我们利用NOAA17卫星对内辐射带高能质子的观测结果研究了大磁暴期间内辐射带质子通量的变化过程.我们发现内辐射带质子出现两种不同的暴时损失事件.在大磁暴发生时,内辐射带外边界质子通量会迅速减小,然后缓慢恢复;而在内辐射带中心区的质子通量(即南大西洋异常区(SAA)质子通量最大值)的暴时变化表现为质子通量的一个迅速的减小和迅速恢复.内辐射带外边界的损失事件主要发生在较低能量质子能档,而内辐射带中心处的损失事件发生在所有质子能档.两种损失事件中质子通量的不同变化意味着内辐射带质子可能有不同的损失和产生机制.通过分析,我们认为内辐射带外边界处质子通量损失事件主要由磁场曲率散射机制造成,而其恢复机制主要是宇宙线反照中子衰变(CRAND).内辐射带中心区(即南大西洋异常区质子通量最大处)质子通量损失事件可能与Dst效应有关.     

Recovery rates of microbiotic crusts within a dune ecosystem in the Negev Desert

Despite the important role played by microbiotic crusts in desert ecosystems, data concerning their recovery rates are scarce and are mainly based on estimates that fluctuate between several years to a few hundred years. In order to study the recovery rates of microbiotic crusts inhabiting sand dunes in the western Negev Desert, Israel, annual measurements of chlorophyll, protein, carbohydrates and moss counts were carried out during 1990–1995. Measurements were taken in two pairs of plots (1.5–6.3 m²) established in each north- and south-facing aspect from which the upper 10 cm surface from one plot of each pair was removed. Recovery of the crusts was fast with surface-removed plots showing a complete recovery of chlorophyll a within 6–7 years, of protein within 6–8 years and of carbohydrates within 8–9 years. Recovery of the mosses was slightly longer at 17–22 years. The data are higher than the lower estimates of recovery but much lower than the higher estimates proposed in the literature. The data also suggest that upon prohibition of goat and sheep grazing (and consequently trampling) a relatively rapid stabilization process may take place in the north-eastern Sinai dune field.