Sediment salt-load in the St Lucia Estuary during the severe drought of 2002–2006

The purpose of this study was to determine whether there was a sufficiently high residual salt load in the dry sediments of the St Lucia Estuary to cause salinity problems should it later fill up with either freshwater or seawater. The estuary lakes have suffered the effects of a severe drought since 2002 with the result that many areas were dry, and the salinity of the residual water varied between 4 psu and up to five times that of seawater. Measurements of the salts content in the sediments to a depth of 20 cm showed that more than 2 million tonnes of salt was held in this layer of the sediment in 2006. Recent management of the estuary (since 1970) has ensured that the mouth was not artificially opened. This was to prevent the inflow of seawater, with its salts, that would otherwise enter while the drought was in place. The results of the sediment salinity data showed that if the drought had been broken and the lake area filled with rain and river water, the resulting salinity would be about 6 psu. In March 2007, Cyclone Gamede in the Indian Ocean off the east coast of South Africa produced a wave climate at sea that resulted in the mouth breaching; thus introducing an estimated 12 million tonnes of salts. The high salinity in the system resulting from this breach is expected to have an adverse effect on the ecology of the system, whereas the residual salinity in the sediments would not have caused an environmental problem. If the estuary and lake system were to fill completely with seawater, the residual salts together with seawater will raise the salinity to an initial value higher than 40 psu, which will have the effect of suppressing much of the important submerged vegetation that is vital for sustaining juvenile fish in the system. Many of the large fauna will also suffer from a shortage of freshwater.     

Environmental contamination of Zn,Cd, Ni,Cu, and Pb from industrial areas in Hamadan Province,western Iran

Eleven surface soil samples from calcareous soils of industrial areas in Hamadan Province, western Iran were analyzed for total concentrations of Zn, Cd, Ni, Cu and Pb and were sequentially extracted into six fractions to determine the bioavailability of various heavy metal forms. Total Zn, Cd, Ni, Cu and Pb concentrations of the contaminated soils were 658 (57–5,803), 125.8 (1.18–1,361), 45.6 (30.7–64.4), 29.7 (11.7–83.5) and 2,419 (66–24,850) mg kg⁻¹, respectively. The soils were polluted with Zn, Pb, and Cu to some extent and heavily polluted with Cd. Nickel values were not above regulatory limits. Copper existed in soil mainly in residual (RES) and organic (OM) fractions (about 42 and 33%, respectively), whereas Zn occurred essentially as RES fraction (about 69%). The considerable presence of Cd (30.8%) and Pb (39%) in the CARB fraction suggests these elements have high potential biavailability and leachability in soils from contaminated soils. The mobile and bioavailable (EXCH and CARB) fractions of Zn, Cd, Ni, Cu, and Pb in contaminated soils averaged (7.3, 40.4, 16, 12.9 and 40.8%), respectively, which suggests that the mobility and bioavailability of the five metals probably decline in the following order: Cd = Pb > Ni > Cu > Zn.     

Deciphering potential groundwater zone in hard rock through the application of GIS

Remote Sensing and Geographic Information System has become one of the leading tools in the field of hydrogeological science, which helps in assessing, monitoring and conserving groundwater resources. It allows manipulation and analysis of individual layer of spatial data. It is used for analysing and modelling the interrelationship between the layers. This paper mainly deals with the integrated approach of Remote Sensing and geographical information system (GIS) to delineate groundwater potential zones in hard rock terrain. The remotely sensed data at the scale of 1:50,000 and topographical information from available maps, have been used for the preparation of ground water prospective map by integrating geology, geomorphology, slope, drainage-density and lineaments map of the study area. Further, the data on yield of aquifer, as observed from existing bore wells in the area, has been used to validate the groundwater potential map. The final result depicts the favourable prospective zones in the study area and can be helpful in better planning and management of groundwater resources especially in hard rock terrains.     

Bedrock, soils, and hillslope hydrology in the Central Texas Hill Country, USA: implications on environmental management in a carbonate-rock terrain

The Hill Country of Central Texas, USA, is undergoing rapid socioeconomic development, but environmental management of this region is hampered by misconceptions about local bedrock, soils, terrain, and hydrologic processes. The Hill Country is underlain mostly by Glen Rose Limestone (Lower Cretaceous) and exhibits a stepped terrain, which has been incorrectly attributed to alternating hard and soft bedrock strata. Other characteristics mistakenly attributed to this landscape include thin soils with scant water-retention capabilities, and rapid runoff as the dominant hydrologic process. This report presents new findings: unweathered bedrock is well indurated, but interbeds exhibit variable weathering rates. Recessive slopes (“risers”) on this stepped terrain result from rapid deterioration of strata having generally heterogeneous depositional fabrics (bioturbation and irregular clay partings) in contrast to ledge-forming strata having homogeneous fabrics. A stony regolith is thus formed beneath risers, providing porous and permeable ground that retards runoff and promotes the formation of moderately deep to deep (two-tiered) regolith/soil zones. These surficial materials on local steep slopes compose important natural environmental buffers; they support diverse biota and enhanced geochemical cycling of nutrients; they also exhibit significant water retention and enhanced erosion abatement. Proper land management demands recognition of these attributes in the siting, design, and construction of facilities.     

Anthropogenic influence on trace element geochemistry of healing mud (peloid) from Makirina Cove (Croatia)

Due to their balneotherapeutic features, the organic-rich sediments in Makirina Cove are an important source of healing mud. An environmental geochemistry approach using normalization techniques was applied to evaluate the anthropogenic contribution of trace metals to sediments used as healing mud. Sediment geochemistry was found to be associated with land-use change and storm events, as well as with proximity of a road with heavy traffic in the summer months. Local valley topography preferentially channels lithogenic and pollutant transport to the cove. Concentrations and distribution of trace metals indicate lithogenic (Ni, Cr, Co) and anthropogenic (Pb, Cu, Zn and Se) contributions to the sediments. The calculation of enrichment factors indicates a moderate (EFs between 2–3.5) input of anthropogenic Cu and Pb in surficial sediments to a depth of 10 cm. Patients using the Makirina Cove sediments as healing mud could be to some extent exposed to enhanced uptake of metals from anthropogenic sources via dermal contact.     

The relationship between hydrodynamic properties and weathering of soils derived from volcanic rocks,Galapagos Islands (Ecuador)

The aim of this interdisciplinary study is to examine a component of the hydrological cycle in Galapagos by characterizing soil properties. Nine soil profiles were sampled on two islands. Their physical and hydrodynamic properties were analyzed, along with their mineralogical composition. Two groups of soils were identified, with major differences between them. The first group consists of soils located in the highlands (>350 m a.s.l.), characterized by low hydraulic conductivity (<10⁻⁵ m s⁻¹) and low porosity (<25%). These soils are thick (several meters) and homogeneous without coarse components. Their clay fraction is considerable and dominated by gibbsite. The second group includes soils located in the low parts of the islands (<300 m a.s.l.). These soils are characterized by high hydraulic conductivity (>10⁻³ m s⁻¹) and high porosity (>35%). The structure of these soils is heterogeneous and includes coarse materials. The physical properties of the soils are in good agreement with the variations of the rainfall according to the elevation, which appears as the main factor controlling the soil development. The clayey alteration products constrain soils physical and hydrodynamic properties by reducing the porosity and consequently the permeability and also by increasing water retention.     

Neural network prediction of nitrate in groundwater of Harran Plain, Turkey

Monitoring groundwater quality by cost-effective techniques is important as the aquifers are vulnerable to contamination from the uncontrolled discharge of sewage, agricultural and industrial activities. Faulty planning and mismanagement of irrigation schemes are the principle reasons of groundwater quality deterioration. This study presents an artificial neural network (ANN) model predicting concentration of nitrate, the most common pollutant in shallow aquifers, in groundwater of Harran Plain. The samples from 24 observation wells were monthly analysed for 1 year. Nitrate was found in almost all groundwater samples to be significantly above the maximum allowable concentration of 50 mg/L, probably due to the excessive use of artificial fertilizers in intensive agricultural activities. Easily measurable parameters such as temperature, electrical conductivity, groundwater level and pH were used as input parameters in the ANN-based nitrate prediction. The best back-propagation (BP) algorithm and neuron numbers were determined for optimization of the model architecture. The Levenberg–Marquardt algorithm was selected as the best of 12 BP algorithms and optimal neuron number was determined as 25. The model tracked the experimental data very closely (R = 0.93). Hence, it is possible to manage groundwater resources in a more cost-effective and easier way with the proposed model application.     

Environmental risk evaluation of the use of mine spoils and treated sewage sludge in the ecological restoration of limestone quarries

The ecologic restoration criteria in areas degraded from extraction activities require making use of their mine spoils. These materials do not meet fertility conditions to guarantee restoration success and therefore, need the incorporation of organic amendments to obtain efficient substratum. Reducing the deficiencies in the organic material and restoration material nutrients with the contribution of treated sewage sludge is proposed in this work. This experiment was based on a controlled study using columns. The work was conducted with two mine spoils, both very rich in calcium carbonate. The first mineral, of poor quality, came from the formation of aggregates of crushed limestone (Z). The other residual material examined originated in limestone extraction, formed by the levels of interspersed non-limestone materials and the remains of stripped soils (D). Two treatments were undertaken (30,000 and 90,000 kg/ha of sewage sludge), in addition to a control treatment. The water contribution was carried out with a device that simulated either short-duration rain or a flooding irrigation system in order to cover the surface and then percolate through the soil. The collection of leached water took place 24 h after the applications. Different parameters of the leached water were determined, including pH, electrical conductivity, nitrate anions, ammonium, phosphates, sulphates and chlorides. The values obtained for each irrigation application are discussed, and the nitrate values obtained were very elevated.     

Landslide susceptibility and hazard mapping in Australia for land-use planning — with reference to challenges in metropolitan suburbia

This paper provides an overview of the history and current status of landslide susceptibility and hazard mapping for land-use zoning in Australia. It also describes a case study of landslide hazard mapping in a medium density, coastal, suburban residential area of metropolitan Sydney, New South Wales, Australia, with relatively steep terrain. Issues covered include identification and mapping of existing and potential landslides, and susceptibility and hazard zoning for regulatory management and land-use planning. The method involves application of the principles contained within the AGS (2000) guideline, and as updated by the AGS (2007 a,b,c,d,e) suite of guidelines.     

Design of shallow foundations under tensile loading for transmission line towers: An overview

Tensioned foundations are common in civil engineering applications such as transmission towers, harbors, offshore structures, basement slabs under pressure, industrial equipment, etc. Procedures for the design of tensioned foundations are discussed in this paper, including specific recommendations for more common transmission tower foundations. Starting from a distinction between shallow and deep modes of failure, the paper presents the most common failure mechanisms for shallow failure in tension, including procedures for calculation of foundation tensile capacity under vertical and inclined loading. Emphasis is given to the influence of the strength of the compacted backfill compared to the strength of the natural soil, including presentation of results of full-scale loading tests.