江苏省地下水水位红线控制水平评估方法探讨

江苏省人民政府于2013年划定了地下水水位控制红线,是我国率先实施地下水水位红线控制的省份之一。从江苏水文地质条件和地下水开发利用实际出发,提出了地下水水位红线控制水平评估的体系、标准及方法,适用于对省、市、县及乡镇的地下水水位红线控制管理工作评估,为掌握地下水资源管理成效、客观反映地下水水位红线控制水平提供了一套管理辅助评估方法体系。     

The influence of seasonal precipitation and temperature regimes on lake levels in the northeastern United States during the Holocene

AMS-dated sediment cores combined with ground-penetrating radar profiles from two lakes in southeastern Massachusetts demonstrate that regional water levels rose and fell multiple times during the Holocene when the known climatic controls (i.e., ice extent and insolation) underwent unidirectional changes. The lakes were lowest between 10,000 and 9000 and between 5500 and 3000 cal yr B.P. Using a heuristic moisture-budget model, we explore the hypothesis that changes in seasonal precipitation regimes, driven by monotonic trends in ice extent and insolation, plausibly explain the multiple lake-level changes. Simulated lake levels resulting from low summer precipitation rates match observed low lake levels of 10,000-9000 cal yr B.P., whereas a model experiment that simply shifts the seasonality of the modern Massachusetts precipitation regime (i.e., moving the peak monthly precipitation from winter to summer) produces levels that are ∼2 m lower than today as observed for 5500-3000 cal yr B.P. The influence of the Laurentide ice sheet could explain dry summers before ca. 8000 cal yr B.P. A later shift from a summer-wet to a winter-wet moisture-balance regime could have resulted from insolation-driven changes in the influence of the Bermuda subtropical high. Temperature changes probably further modified lake levels by affecting snowmelt and transpiration.     

Radiological risk assessment of naturally occurring radioactive materials in marine sediments and its application in industrialized coastal areas: Bay of Algeciras,Spain

Radioactivity levels in aquatic environments can be assessed through the study of superficial sediments. Anthropogenic activities may alter radioactivity levels leading to the anomalous accumulation of natural radionuclides in coastal areas. In this work, marine sediments from a significant area subjected to severe industrial development were collected in order to measure activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K by gamma spectrometry. Radium equivalent index (Ra_eq), absorbed gamma dose rate in air (D) and annual effective dose equivalent (H) were also calculated and used as risk assessment tools. Results showed low levels of radioactivity in marine sediments from the Bay of Algeciras, discarding any significant radiological risks. Furthermore, the obtained data set could be used as background levels for future research applications and development of environmental regulatory frameworks.     

Thermo-mechanical Stability Analysis for a Multi-level Radioactive Waste Disposal Concept

To dispose of the spent fuels generated from the Korean nuclear power plants in an underground repository, a large area of about 4 km² is required. This could be a constraint for selecting an adequate repository site and it is required to investigate the possibility of a multi-level repository design. In this study different parameters related to the multi-level repository design such as the level distance, waste type disposed of at each level, and the time interval between the operations at the levels, were investigated using the three-dimensional code, FLAC3D. For obtaining more reliable results, rock properties measured from deep boreholes were used. From the analysis, it was possible to conclude that a multi-level repository concept could be an attractive alternative to reduce the underground area as well as to dispose of the spent fuels from Pressurized Water Reactors (PWR) and Canadian Deuterium Uranium (CANDU) reactors at different levels with different time schedules.     

Biogeochemical anomalies in fennoscandia: A study of copper, lead and nickel levels in Melandrium dioicum and Viscaria alpina

Herbarium specimens (over 700) of Melandrium dioicum and Viscaria alpina from throughout Fennoscandia were analysed for their Cu, Pb and Ni content. About 80 specimens had anomalous levels of one or more of these elements as determined by cumulative frequency plots. Inspection of collection localities of plants with anomalous heavy metal levels showed that some of the main copper mining districts of Norway and Sweden had been identified as well as several major ultrabasic regions of Fennoscandia. Although over half of the observed anomalies could be explained from previous knowledge of nearby sulphide mineralization, it is suggested that the more promising of the remainder are worthy of follow-up investigations.     

Gold and other metals in big sagebrush (Artemisia tridentata Nutt.) as an exploration tool, Gold Run District, Humboldt County, Nevada

Big sagebrush — a cold-desert species that dominates the terrain over large parts of western United States — was sampled along several traverses that crossed thermally metamorphosed limestone, phyllitic shale, and schist of the Middle and Upper Cambrian Preble Formation that host skarn-, disseminated gold and silver-, and hot springs gold-type mineral occurrences. Patterns of detectable levels of gold (8 to 28 ppb or ng g⁻¹) in ash of new growth were consistent with areas affected by known or suspected gold mineralization. Soils collected along one of the traverses where a selenium-indicator plant was common contained no gold above background levels of 2ppb, but were consistently high in As, Sb, and Zn, and several samples were unusually high in Se (maximum 11 ppm or μg g⁻¹). Sagebrush along this traverse contained Li at levels above norms for this species. We also found a puzzling geochemical anomaly at a site basinward from active hot springs along a range-front fault scarp. Sagebrush at this site contained a trace of gold and an unusually high concentration of Cd (13 ppm) and the soil had anomalous concentrations of Cd and Bi (3.2 and 6 ppm, respectively). The source of this anomaly could be either metal-rich waters from an irrigation ditch or leakage along a buried fault. Despite the limited nature of the study, we conclude that gold in sagebrush could be a cost-effective guide to drilling locations in areas where the geology seems favorable for disseminated and vein precious metals.     

Mapping radon-prone areas - a geophysical approach

 Radon-prone areas in Israel were mapped on the basis of direct measurements of radon (²²²Rn) in the soil/rock gas of all exposed geological units, supported by the accumulated knowledge of local stratigraphy and sub-surface geology. Measurements were carried out by a modified alpha-track detection system, resulting in high radon levels mainly in rocks of the Senonian-Paleocene-aged Mount Scopus Group, comprised of chert-bearing marly chalks, rich in phosphorite which acts as the major uranium source. Issues of source depth, seasonal variations and comparison with indoor radon levels are addressed as well. This approach could be applied to other similar terrains, especially the Mediterranean Phosphate Belt.     

Effects of climate change on the groundwater system in the Grote-Nete catchment,Belgium

The effects of climate change on the groundwater systems in the Grote-Nete catchment, Belgium, covering an area of 525 km², is modeled using wet (greenhouse), cold or NATCC (North Atlantic Thermohaline Circulation Change) and dry climate scenarios. Low, central and high estimates of temperature changes are adopted for wet scenarios. Seasonal and annual water balance components including groundwater recharge are simulated using the WetSpass model, while mean annual groundwater elevations and discharge are simulated with a steady-state MODFLOW groundwater model. WetSpass results for the wet scenarios show that wet winters and drier summers are expected relative to the present situation. MODFLOW results for wet high scenario show groundwater levels increase by as much as 79 cm, which could affect the distribution and species richness of meadows. Results obtained for cold scenarios depict drier winters and wetter summers relative to the present. The dry scenarios predict dry conditions for the whole year. There is no recharge during the summer, which is mainly attributed to high evapotranspiration rates by forests and low precipitation. Average annual groundwater levels drop by 0.5 m, with maximum of 3.1 m on the eastern part of the Campine Plateau. This could endanger aquatic ecosystem, shrubs, and crop production.     

Levels and sources of polycyclic aromatic hydrocarbons (PAHs) in selected irrigated urban agricultural soils in Accra, Ghana

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants in urban environments including urban soils. Elevated concentrations of PAHs in urban soils are caused by incomplete combustion of petroleum and coal. This study assesses 16 individual PAH compounds in a total of 112 surficial soil samples. The objective was to assess and compare the levels of contamination as well as examine the main sources of PAHs in four urban agricultural soils using molecular ratios of some specific hydrocarbons. The study showed that PAH levels in soil ranged from 1.23 ng/kg in soil collected from Dzorwulu to 2.95 ng/kg in soil collected from Ghana Broadcasting Cooperation (GBC) vegetable irrigation site. Of the total PAHs, the more water soluble PAHs (2–4 rings), which tend to be concentrated in the vapour phase were found to dominate the soils. The percentage dominance were Dzorwulu (52.8 %), Marine Drive (62.5 %), CSIR (53.2 %) and GBC (49.2 %). However, there were significant levels of the more carcinogenic PAHs (5–6 rings) present with percentages as 47.1, 37.5 46.8 and 50.8 % for Dzorwulu, Marine Drive, CSIR and GBC vegetable irrigation sites, respectively, and therefore, may impact negatively on public health. Based on the classification by the Institute of Soil Science and Plant Cultivation in Pulawy, Poland, urban soils in Accra could be classified as contaminated to different levels. Molecular ratios of Flu/pyr and PA/Ant were calculated to determine the main sources of PAHs. Results showed that PAHs could originate mainly from incomplete combustion of petroleum products, especially from atmospheric fallout from automobile exhausts. The study further showed that B(a)P concentration of 0.05 ng/kg in soil from GBC urban vegetable irrigation site requires immediate clean-up exercise and monitoring to mitigate human health impact.     

Some conceptual models for geochemistry in areas of preglacial deep weathering

In some glaciated regions, weathered mantles, formed under previous climatic regimes, were not always eroded bare by glacial activity, but instead lie buried beneath the glacial overburden. It is obviously important that geochemical exploration programs in such terrain should take into account some of the known regolith features seen in deeply weathered regions. The effects of glacial action upon deeply weathered terrain are considered in three conceptual models. The critical factor in each is the depth of truncation of the preglacial weathering profile. All three proposed models are dynamic systems and a wide range of intermediate situations must be expected.In Model 1 a complete, largely undisturbed, weathering profile is preserved beneath till. The key characteristic is preservation of a lateritic duricrust which may contain areally large (up to 200 km²) geochemical anomalies. It would be critical, firstly, that the duricrust be sufficiently continuous to allow a reasonable success rate in its being sampled, and secondly that the duricrust be recognizable in drill spoil. The most efficient geochemical exploration could be based upon wide-spaced overburden drilling directed at sampling the duricrust. For reconnaissance, holes could be based upon a 1-km grid where stratabound massive polymetallic sulphide or stratabound gold deposits are sought. Even wider spacing could be tried where larger-sized ore deposits are expected.Model 2 is characterized by a weathered profile that was partly stripped prior to glaciation. The essential feature is a vertically zoned weathering profile in the basement rock in which the upper levels of the weathering profile have undergone leaching of certain elements and lower levels contain enrichments of these elements. Any gossans present would show strong vertical zonation. Relatively strong sources for dispersion in till are likely to be enriched gossans where erosion has cut deep into the profile, zones of supergene enrichment of ore deposits, and supergene ore deposits themselves. In many situations, saprolite under glacial drift would be too soft to provide boulders so important in conventional till prospecting.The essential ingredient in hypothetical Model 3 involves progressive planing away of the weathering profile by glacial action. Thus any halo in duricrust is initially dispersed, followed by dispersion of progressively deeper levels of saprolite. If taken deep enough the supergene enriched zone of a mineral deposit could add to the glacial dispersion. A broadly zoned anomaly would be expected; a till anomaly would be characterized distally by elements from the former duricrust anomaly, with elements more characteristic of supergene zones closer to the source.     

Risk prediction of rural public security environmental carrying capacity based on the risk entropy

In order to achieve effective early warning and prediction for the risk of ecological environmental carrying capacity of rural public security, this paper put forward risk assessment indicators from the perspective of rural ecological, infrastructure, social, and population carrying capacity. And then, this paper constructs risk assessment model of rural ecological environment carrying capacity on the base of genetic projection pursuit model, information diffusion theory, and risk entropy method. First of all, the genetic projection pursuit model is introduced to perform one-dimensional projection for high-dimensional data according to optimal projection direction, and the projection value is fitted with time series together, thus, the risk of rural ecological environment carrying capacity could be divided into four risk levels according to established standard; secondly, we spread the one-dimensional projection value of each sample into four risk levels by information diffusion theory, and calculate the risk entropy of rural environmental carrying capacity by risk entropy method; at last, the empirical analysis shows that the model constructed in this paper is simple and effective, which could provide effective reference and suggestion for environmental protection and public safety department.     

Nourishment of perched sand dunes and the issue of erosion control in the Great Lakes

Although limited in coverage, perched sand dunes situated on high coastal bluffs are considered the most prized of Great Lakes dunes. Grand Sable Dunes on Lake Superior and Sleeping Bear Dunes on Lake Michigan are featured attractions of national lakeshores under National Park Service management. The source of sand for perched dunes is the high bluff along their lakeward edge. As onshore wind crosses the bluff, flow is accelerated upslope, resulting in greatly elevated levels of wind stress over the slope brow. On barren, sandy bluffs, wind erosion is concentrated in the brow zone, and for the Grand Sable Bluff, it averaged 1 m³/yr per linear meter along the highest sections for the period 1973–1983. This mechanism accounts for about 6,500 m³ of sand nourishment to the dunefield annually and clearly has been the predominant mechanism for the long-term development of the dunefield. However, wind erosion and dune nourishment are possible only where the bluff is denuded of plant cover by mass movements and related processes induced by wave erosion. In the Great Lakes, wave erosion and bluff retreat vary with lake levels; the nourishment of perched dunes is favored by high levels. Lake levels have been relatively high for the past 50 years, and shore erosion has become a major environmental issue leading property owners and politicians to support lake-level regulation. Trimming high water levels could reduce geomorphic activity on high bluffs and affect dune nourishment rates. Locally, nourishment also may be influenced by sediment accumulation associated with harbor protection facilities and by planting programs aimed at stabilizing dunes.     

Heavy metal contamination of cultivated wetland soils along a typical plateau lake from southwest China

Topsoil (0–20 cm) samples were collected from four cultivated wetlands including Northern and Western Fields (about 30-year tillage), and Southern and Western Fields (about 20-year tillage) along the Yilong Lake of China in October, 2005. Total concentrations of As, Cr, Cu, Pb, and Zn were determined using the inductively coupled plasma atomic absorption spectrometry in order to assess contamination status in four sampling plots. Results showed that the average concentrations of these heavy metals in Northern and Western Fields were significantly (P < 0.01) higher than those in reference soils, while they were generally lower in Southern and Eastern Fields. All the mean concentrations of heavy metals were lower, except that the average concentrations of As and Cr in Northern Field slightly exceeded the soil quality guidelines. The contamination indices showed low-contamination levels for As, Cu, Pb, and Zn in Northern and Western Fields, while no contamination levels could be observed in Southern and Eastern Fields. As for Cr, they showed moderate-contamination levels in Northern Field, but low or no contamination levels in other three Fields. The integrated contamination index values indicated Northern and Western Fields were moderately contaminated, while Southern and Eastern Fields were less contaminated. The same contamination sources of these heavy metals were identified in these fields using factor- and cluster analysis.     

Holocene sea-level fluctuation in the southern hemisphere

If rising sea levels dominate in the northern hemisphere (NH), falling or fluctuating sea levels predominate in the southern hemisphere (SH). Endogenic processes (tectonics, isostasy or geoidal changes) could explain local or regional mean sea level (MSL) fluctuations but not an hemispherical one.Evidence from South America, Africa, Antarctica, Australia and the Pacific and Indian Oceans suggest that the Holocene transgression rose above the present MSL, in higher latitudes before the tropics. By plotting latitude against the age of MSL arrival at present coasts, good correlation is observed.Oceanic salinity mixing has been already proposed to explain this mid-Holocene sea-level fluctuation. Climate could be the only factor responsible for this hemisphere-wide behavior of MSL. It has been suggested previously that the climate of the SH precedes that of the NH by 3000 years. The climatic optimum, or maximum warmth, occurred predominantly about 6000 BP in the NH, but about 10–9000 BP in the SH.Short-term climatic effects on the sea level (monsoons, southern oscillation/El Niño phenomena) should have significant occurrences during the past in the windiest oceanic hemisphere.This latitudinal trend in former MSL should be considered when using shorelines as reference points for measuring vertical crustal movements.     

Buffering from secondary minerals as a migration limiting factor in lead polluted soils at historical smelting sites

Examination of calcareous slags from several historical smelting sites has indicated that the specific soil environment, in particular the soil pH, may have a very significant effect on the rate of weathering and metal release. A series of acid titration experiments were used to investigate whether the weathering of the calcareous slags could be increasing the buffering effect of the soils through accumulating CaCO₃ in the slag-rich horizons. Such a buffering mechanism would maintain high pH levels and so limit the migration of Pb through the soil profile. Three sites were chosen; one with high levels of Ca in the soil, one with relatively low Ca levels and one with intermediate Ca levels. Analysis of metal concentrations was determined using ICP-AES. The results support the hypothesis that, while the soil pH remains between 8 and 5, the CaCO₃ provides an effective buffer against the mobilisation of Pb. Between soil pH 5 and 4 it is suggested that both CaCO₃ and PbCO₃ participate in the buffering reaction, which slows down with a further drop in pH. However, this reaction ultimately releases Pb into the soil solution, although at a much slower rate than would be the case in an unbuffered soil. An important implication of these findings is that migration rates of metals in soils cannot be assumed to be constant over time, if such buffering mechanisms are operational.     

Fragility of a dark gray shale in northeastern Jamaica: effects and implications of landslip exposure

Rapid weathering of strong, hitherto un-weathered shale rocks was fast enough to have been measurable weekly (>4 mm depth per week). Regular early morning rain showers followed by hot, dry afternoons caused frequent wet/dry cycles which facilitated rapid slaking of the shale. Other landslips occurred concurrently on the south bank of the Wild Cane River, where the rock beds dip towards lower ground. Resistance to impacts in the rock fabric was equally low after decades, or weeks of exposure. It was concluded that the combination of high frequency wet/dry cycles on steeply dipping shale beds, and rock attitude caused very rapid weathering. Rapid slaking of the illitic shales could cause high turbidity levels in contiguous aquatic environments. Building foundations and roads could be rapidly de-stabilized even on such freshly exposed, apparently consolidated sites.     

木质素纤维红黏土强度及变形特性试验研究

利用工业废料改良土体性能不仅具有实用价值而且能够保护环境。采用室内土工试验及SEM试验,针对木质素纤维加筋红黏土的效果,以及木质素纤维掺量对红黏土强度及变形特性的影响规律和作用机理进行研究。试验结果表明:木质素红粘土压缩模量随着纤维掺量的增加先增加后减小,2%纤维掺量时,模量最高;不同木质素掺量红粘土的内摩擦角基本保持不变;红黏土黏聚力随木质素掺量的增加先减小后增大再减小。2%是纤维最优掺量,土体黏聚力出现最大值;在三轴实验中,加筋红黏土试样均发生鼓胀变形,没有明显的破裂面,具有典型的应变硬化特征。研究结果表明木质素纤维能一定程度提高红粘土的强度,提升红粘土的工程应用价值。      

Glacial rebound and relative sea levels in Europe from tide-gauge records

Relative sea levels recorded by tide gauges during the past century in northern Europe are dominated by isostatic readjustment of the land following the latest deglaciation of Scandinavia and Scotland. Maximum relative uplift of the land is centered near the northern Gulf of Bothnia (at a rate of 6–7 mm/yr), with a smaller secondary maximum over Scotland (also at a rate of 6–7 mm/yr). Although there probably is a relaxing peripheral bulge surrounding the regions of maximum uplift, such a former bulge is poorly defined by coastal tide gauges; in the North Sea evidence for sinking of a former peripheral bulge of glacial origin is complicated by post-Carboniferous basin deepening with sediment loading and possible rejuvenation associated with glaciation. Other data (gravity, radiocarbon, geomorphology) support the interpretation that glacial isostasy controls the structure of relative sea-level change. Included in this pattern of relative rise of land is a eustatic signal that biases the estimates of glacial rebound. Such a eustatic signal could not be isolated from the isostatic signal using the present data, but glacial isostasy clearly is a major control for relative sea levels of the region.

Absence of significant higher frequency (2–50 yr) cycles in mean annual sea levels of northern Europe reflects the complex hydrologic/oceanographic forces to which sea levels must respond. Whereas other coastal regions show significant higher frequency peaks in the energy spectra of relative sea levels, the many marginal seas in northern Europe preclude a clear relation between hydrologic/oceanographic forcing and relative sea levels, although this relation must exist on a more local scale.     

Water level variations in fractured,semi-confined aquifers of Anantapur district,Southern India

The study on water level conditions of fractured aquifer system in northeastern part of Anantapur district is of immense importance as the area is covered by varied geological formations and has different irrigation patterns. The monthly groundwater level data of 154 observation wells for five year period (2001–06) is analyzed to decipher the behavior of water levels in different seasons and geo-environments. The hydrographs of the average water level data of each Mandal (group of villages) indicate steady declining trend ranging from 0.50 to 2.91m/yr. Yellanuru Mandal has both the shallowest and the deepest water levels among eight Mandals, highly undulating terrain could be one of the reasons for this contrasting condition. The pre-monsoon water levels show decline of 8.22 m in one year from May 2002 to 2003. A negative seasonal fluctuation of ?1.49m has occurred in the year 2002 during which the area received 32% less than normal rainfall. The mean water levels are deeper by 42% in areas covered by sedimentary formations than those of granite terrain. Raise in water levels is significant where monthly rainfall is more than 200 mm. Due to erratic rainfall in space and time, deeper water levels are noticed even in post-monsoon period and shallow in February month at some locations. The water levels in command areas are deep and exhibit falling trend as the area forms the tail end part of the Tunga Bhadra High Level Canal. The deeper water level conditions and its declining feature is directly related to groundwater development in the form of increased agriculture activity, reduced area under rain-fed crops, high horticulture development. Arid climatic conditions, low precipitation and continuous exploitation of groundwater resources could be other factors contributing for steady decline in water levels in the area. The wide variations in groundwater levels could be due to uneven topography, heterogeneous and anisotropic conditions of granites and poor porosity — permeability of shales, lack of vegetation, and increased groundwater extraction.     

Particle breakage and deformation of carbonate sands with wide range of densities during compression loading process

In this technical note, evolutions of the particle size distribution, particle breakage, volume deformation and input work of carbonate sands with varying relative densities were investigated through performing a series of one-dimensional compression tests. Loading stress levels ranged from 0.1 to 3.2 MPa. It was found that the initial relative density could greatly affect the magnitude of particle size distribution, particle breakage, volume deformation and input work. Particularly, it was observed that the specimen at a lower relative density underwent much more particle breakage than that at a higher relative density. This could be attributed to the change of the coordination number with the initial density. However, a unique linear relationship between the particle breakage and input work per volume could be obtained, which is independent of the initial relative density.