Trace elements in groundwater as indicators of anthropogenic impact

The distribution of several minor and trace elements mainly in fresh (dominating TDS 160–400 mg/l) groundwater of Latvia have been investigated by the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) technique. An evaluation of results of about 700 analyses leads to the conclusion that concentrations of these elements is influenced by: pH–Eh conditions, groundwater residence time and diffuse contamination, whereas the role of water-bearing sediments is of secondary importance. Most trace elements are characterised by low mobility under alkaline and reducing conditions; concentrations in confined aquifers are much smaller than the Maximum Permissible Values for drinking water. The strongest anomalies of REE, Al and P were found in shallow groundwater around the former agrochemical storehouses.     

Mineralogy and geochemistry of the Texeo Cu–Co mine site (NW Spain): screening tools for environmental assessment

The Cu–Co–Ni Texeo mine has been the most important source of Cu in NW Spain since Roman times and now, approximately 40,000 m³ of wastes from mine and metallurgical operations, containing average concentrations of 9,263 mg kg⁻¹ Cu, 1,100 mg kg⁻¹ As, 549 mg kg⁻¹ Co, and 840 mg kg⁻¹ Ni, remain on-site. Since the cessation of the activity, the abandoned works, facilities and waste piles have been posing a threat to the environment, derived from the release of toxic elements. In order to assess the potential environmental pollution caused by the mining operations, a sequential sampling strategy was undertaken in wastes, soil, surface and groundwater, and sediments. First, screening field tools were used to identify hotspots, before defining formal sampling strategies; so, in the areas where anomalies were detected in a first sampling stage, a second detailed sampling campaign was undertaken. Metal concentrations in the soils are highly above the local background, reaching up to 9,921 mg kg⁻¹ Cu, 1,373 mg kg⁻¹ As, 685 mg kg⁻¹ Co, and 1,040 mg kg⁻¹ Ni, among others. Copper concentrations downstream of the mine works reach values up to 1,869 μg l⁻¹ and 240 mg kg⁻¹ in surface water and stream sediments, respectively. Computer-based risk assessment for the site gives a carcinogenic risk associated with the presence of As in surface waters and soils, and a health risk for long exposures; so, trigger levels of these elements are high enough to warrant further investigation.     

Numerical modeling assessment of three-gate structures for capturing contaminated groundwater

This modeling study evaluated the capability of alternative funnel-and-gate structures with three gates for capturing contaminated groundwater in a hypothetical unconfined aquifer. Simulated interceptor structures were linear and 45 m wide, consisting of three gates and two funnels (walls). One gate occupied the center and two gates occupied the ends of the interceptor structures. The structures, positioned perpendicular to regional groundwater flow, traversed the entire thickness of the aquifer. A total of four structures were evaluated (numbers designate widths of end, center, and end gates, respectively, in meters): 3-3-3, 2-5-2, 1-7-1, and 4-1-4. Particle tracking and zonal water budgets identified shapes of capture zones and discharge patterns for each interceptor structure. A mass transport model, accounting for advection and hydrodynamic dispersion, tested the capability of each structure for capturing a contaminant plume. Results suggest that: time-dependent capture zones underestimate the amount of time to capture a contaminant plume, wide center gates facilitate plume capture, and wide end gates facilitate lateral containment of contaminants. Of the structures simulated, the 2-5-2 configuration was relatively efficient at processing and containing the simulated contaminant plume.     

Regional distribution pattern of groundwater heavy metals resulting from agricultural activities

Contaminations of groundwater by heavy metals due to agricultural activities are growing recently. The objective of this study was to evaluate and map regional patterns of heavy metals (Cd, Zn and Cu) in groundwater on a plain with high agricultural activities. The study was conducted to investigate the concentration of heavy metals and distribution in groundwater in regions of Shush Danial and Andimeshk aquifers in the southern part of Iran. Presently, groundwater is the only appropriate and widely used source of drinking water for rural and urban communities in this region. The region covers an area of 1,100 km² between the Dez and Karkhe rivers, which lead to the Persian Gulf. For this study, the region was divided into four sub-regions A, B, C and D. Additionally, 168 groundwater samples were collected from 42 water wells during the earlier months of 2004. The flame atomic absorption spectrometry (AAS-Flame) was used to measure the concentration of heavy metals in water samples and the Surfer software was used for determination of the contour map of metal distribution. The results demonstrated that in all of the samples, Cd and Zn concentrations were below the EPA MCLG and EPA secondary standard, respectively. However, the Cu contents of 4.8 % of all samples were higher than EPA MCL. It is also indicated that the concentrations of metals were more pronounced at the southern part of the studied region than at the others. The analysis of fertilizers applied for agricultural activities at this region also indicated that a great majority of the above-mentioned heavy metals were discharged into the environment. Absence of confining layers, proximity to land surface, excess agricultural activities in the southern part and groundwater flow direction that is generally from the north to the southern parts in this area make the southern region of the Shush plain especially vulnerable to pollution by heavy metals than by other contaminants.     

Groundwater recharge of carbonate aquifers of the Silesian-Cracow Triassic (southern Poland) under human impact

A Triassic carbonate unit has been intensively drained by zinc and lead ore mines and numerous borehole fields since the nineteenth century. Its groundwater recharge has increased due to: pumping of water from boreholes, mining activity, and urbanization. An approach to determine the amounts of the recharge at a variety of spatial scales is presented in the paper. Different methods were used to identify and quantify recharge components on a regional and local scale: mathematical modelling was performed for four aquifers included in an aquifer system, an analytical estimation based on the assumption that an average recharge is equal to the average discharge of the hydrogeological system—for six man-made drainage centres, and the method of water level fluctuation (WLF) was applied in one observation borehole. Results of modelling have been supplemented by observation of environmental tracers (δ¹⁸O, δ²H, ³H), noble gases temperatures, and ⁴He_exc in groundwater. The regional aquifer’s current recharge according to estimations performed by means of modelling varies from 39 to 101 mm/year on average. Depending on the aquifer site the average precipitation ranges from 779 to 864 mm/year. In the confined part of the aquifer average recharge ranges from 26 to 61 mm/year. Within outcrops average recharge varies from 96 to 370 mm/year. Current recharge estimated by the analytical method for man-made drainage centres varies from 158 up to 440 mm/year. High values are caused by different recharge sources like precipitation, induced leakage from shallow aquifers, and water losses from streams, water mains and sewer systems. Pumping of water, mining and municipal activities constitute additional factors accounting for the intensified recharge.     

Mapping susceptibility of rainfall-triggered shallow landslides using a probabilistic approach

To prepare a landslide susceptibility map is essential to identify hazardous regions, construct appropriate mitigation facilities, and plan emergency measures for a region prone to landslides triggered by rainfall. The conventional mapping methods require much information about past landslides records and contributing terrace and rainfall. They also rely heavily on the quantity and quality of accessible information and subjectively of the map builder. This paper contributes to a systematic and quantitative assessment of mapping landslide hazards over a region. Geographical Information System is implemented to retrieve relevant parameters from data layers, including the spatial distribution of transient fluid pressures, which is estimated using the TRIGRS program. The factor of safety of each pixel in the study region is calculated analytically. Monte Carlo simulation of random variables is conducted to process the estimation of fluid pressure and factor of safety for multiple times. The failure probability of each pixel is thus estimated. These procedures of mapping landslide potential are demonstrated in a case history. The analysis results reveal a positive correlation between landslide probability and accumulated rainfall. This approach gives simulation results compared to field records. The location and size of actual landslide are well predicted. An explanation for some of the inconsistencies is also provided to emphasize the importance of site information on the accuracy of mapping results.     

Experimental study on the deterioration and natural remediation of the Ariake Sea tidal mud caused by the sea laver treatment acid practice and the upward seepage of pore water liquid

This study presents a laboratory study of the following two aspects: (1) the influence of sea laver treatment acid on the geoenvironmental properties of Ariake Sea tidal mud, and (2) the natural remediation effect on the sea laver treatment acid contaminated Ariake Sea tidal mud caused by the upward seepage of pore water liquid in the mud. Firstly, the mechanisms of the transport of sea laver treatment acid in the Ariake Sea tidal mud and the generation mechanisms of the upward seepage flow in the Ariake Sea tidal mud are discussed. Secondly, a series of one-dimensional laboratory infiltration tests were carried out to investigate the deterioration of the Ariake Sea tidal mud caused by the sea laver acid treatment practice. Test results reveal that the acid treatment practice caused considerable change in the geochemical properties of the mud in terms of increase in sulfide content and decrease in pH value. After the treatment by the sea laver treatment acid, the sulfide content of the mud even exceeded the safe limit value for the benthos, which represents undesirable living condition for benthos. Thirdly, series of laboratory fresh seawater infiltration tests for the deteriorated Iida site mud were conducted to illustrate this natural remediation efficiency. It is found that with the infiltration of the fresh seawater, the sulfide content of the Iida site mud was considerably reduced and pH value increased to an acceptable range for benthos living in the tidal flat mud. With the increase in the infiltration time and the hydraulic gradient, the remediation efficiency could be increased.     

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.     

Mobilization analysis of the dolmen of Dombate (Northwest Spain)

This paper presents an analysis of the mobilization of the dolmen of Dombate, a megalithic monument situated in the Northwest of Spain. The study is founded on simple static principles, with the application of basic concepts of soil mechanics (soil reactions were computed by the reaction modulus method) and rock mechanics (a simple secant approach was adopted to model the contact between orthostats). In addition, a simplified geometric model for dolmens was adopted. On the basis of these concepts, a numerical solver able to provide quick estimations of the system's mobilization was developed. Using this tool, a number of sensitivity analyses were conducted to estimate the mobilization that could be caused by a conservation project currently under consideration. It was found that mobilization might be excessive, and therefore, a safer procedure is proposed. In short, this paper puts forth a new rational approach for archaeological practices which may help to estimate the possible consequences of excavations and rehabilitations on megalithic structures.