The paradigm of Circular Mining in the world: the Iberian Pyrite Belt as a potential scenario of interaction

Water is one of the receptors most affected by the impacts caused, especially in the case of mining sulphides and, to a lesser extent, of coal. Acid Mine Drainage (AMD) is the main problem associated with these mining operations, producing extremely high impacts, and in many cases irreversible impacts, until now. A new concept of mining can make this activity compatible with the environmental preservation and also to the recovery of the environment affected by the old mining operations that today are in the process of reopening. This new concept implicates the paradigm of Circular Mining as a derivative of the concept of Circular Economy, considered as a strategy that aims to reduce both the entry of materials and the production of virgin waste, closing the “loops” or economic and ecological flows of resources. The present work discusses the paradigm of Circular Mining, focused on the Iberian Pyrite Belt, one of the most paradigmatic metallogenetic regions in the world. Based on some examples, expeditious calculations show the possibility of recovering base metals as well as strategic elements from acid mine drainage, thus obtaining important economic assets.     

A study of heavy metal pollution in the Tinto-Odiel estuary in southwestern Spain using factor analysis

The estuary of Odiel and Tinto rivers, located on the southwestern coast of the Iberian Peninsula, receives acidic fluvial water discharges with high concentrations of sulphates and heavy metals from these rivers. In addition, a big industrial complex which efflues directly on the system is located in the same estuary. The effluents induce the presence in the estuary of high concentrations of heavy metals and phospates (nutrients). The application of factorial analysis techniques on the nutrients and heavy metal concentrations in 46 water samples taken from 32 different sampling stations located along the estuary, allows three groups of elements and compounds with a distinct origin to be determinated. So, Cu and Zn have a clear fluvial provenance, whereas PO₄ and As are clearly industrial wastes and Cl, K, Ca, Li, Rb and Sr come from the sea. From the factorial analyses we can deduce the existence of two agents controlling the behavior of the analyzed elements, which are: the tidal exchange with the open sea and the fluvial supply. Received: 20 November 1998 · Accepted: 11 August 1999     

Transient Structures and Stream Interaction Regions in the Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO HI and Venus Express ASPERA-4 Measurements

We discuss the detection and evolution of a complex series of transient and quasi-static solar-wind structures in the days following the well-known comet 2P/Encke tail disconnection event in April 2007. The evolution of transient solar-wind structures ranging in size from <10⁵ km to >10⁶ km was characterised using one-minute time resolution observation of Interplanetary Scintillation (IPS) made using the European Incoherent SCATter (EISCAT) radar system. Simultaneously, the global structure and evolution of these features was characterised by the Heliospheric Imagers (HI) on the Solar TERrestrial RElations Observatory (STEREO) spacecraft, placing the IPS observations in context. Of particular interest was the observation of one transient in the slow wind, apparently being swept up and entrained by a Stream Interaction Region (SIR). The SIR itself was later detected in-situ at Venus by the Analyser of Space Plasma and Energetic Atoms (ASPERA-4) instrument on the Venus Express (VEX) spacecraft. The availability of such diverse data sources over a range of different time resolutions enables us to develop a global picture of these complex events that would not have been possible if these instruments were used in isolation. We suggest that the range of solar-wind transients discussed here may be the interplanetary counterparts of transient structures previously reported from coronagraph observations and are likely to correspond to transient magnetic structures reported in in-situ measurements in interplanetary space. The results reported here also provide the first indication of heliocentric distances at which transients become entrained.     

Undrained behaviour of silt under static and cyclic loading

In this study, the undrained behaviour of silt under low stress level is studied. An effective preparation method for built—in silt samples in the triaxial test was firstly developed. By triaxial testing of samples at low confining pressures it was found that silt easily loses stability and liquefies. Loose silt may show temporary liquefaction under static loading, and develop full liquefaction under cyclic loading. The most important factors influencing the silt behaviour are porosity, confining pressure, consolidation state, cyclic loading level and number of cycles. The maximum obtainable shear stress is primarily a function of the confining pressure and the internal frictional angle. The actual structure of the silt material is the key factor in controlling its behaviour.     

Spatial evolution of an AMD stream in the Iberian Pyrite Belt: process characterization and control factors on the hydrochemistry

ABSTRACT

This paper presents hydrochemical data of an AMD stream, Poderosa Creek, in the Iberian Pyrite Belt, obtained between its source, in the Poderosa Mine portal, and its confluence with the Odiel River. The main objective is to establish potential interdependent relationships between sulphate and metal loads and the following physico-chemical variables: pH, electrical conductivity (EC), redox potential (EH) and dissolved oxygen (DO). All the parameters show an overall increasing tendency from the tunnel exit to the confluence at the Odiel River. The TDS and EC are two relevant exceptions. They behave similarly, showing a decreasing trend and a strong inflection that describes a minimum immediately after the discharging point. Spatial analysis combined with statistical tools reveal typical AMD processes and the respective physico-chemical implications. Inputs with distinctive hydrochemical signatures impose relevant modifications in the Poderosa Creek waters. This indicates low hydrochemical inertia and high vulnerability to external stimuli.

Editor D. Koutsoyiannis; Associate editor not assigned     

Liquefaction of sand under low confining pressure

Undrained behaviour of sand under low cell pressure was studied in static and cyclic triaxial tests. It was found that very loose sand liquefies under static loading with the relative density being a key parameter for the undrained behaviour of sand. In cyclic triaxial tests, pore water pressures built up during the cyclic loading and exceeded the confining cell pressure. This process was accompanied by a large sudden increase in axial deformation. The necessary number of cycles to obtain liquefaction was related to the confining cell pressure, the amplitude of cyclic loading and the relative density of sand. In addition, the patterns of pore water pressure response are different from those of sand samples with different relative densities. The test results are very useful for expounding scour mechanism around coastal structures since they relate to the low stress behaviour of the sand.     

Catchment storage and residence time in a periodically irrigated watershed

Understanding anthropogenic impacts on water storage and water flow pathways in catchments is an ongoing challenge in hydrology. Here, we study the dynamics of subsurface storage and residence time of water in a catchment in Berkeley, California, that is within a regional park but contains diverse land use within its perimeter, including a periodically irrigated golf course. Our study combines several isotopic tracers with water budget data to examine sources of water in a stream draining the site. Irrigation water, applied to a small area of the watershed, is a minor component of the water budget. However, geochemical tracers reveal that irrigation water is a significant fraction of stream flow downstream of the golf course during baseflow and during precipitation events. Isotopic tracers indicate that the watershed has a preference to release young water for stream flow generation, resulting in contrasting tritium ages for stream water and groundwater of 1.3 ± 0.5 year and 8.2 ± 1.7 year, respectively. We determined that the older water is a very small component (0.7%) of the stream water in the tail of an assumed exponential distribution. We used the seasonal variation of stable water isotopes in precipitation and stream water over two water years to explain the damping of the isotopic signature of stream water, which yields information about the catchment's response to the input signal. The methods described here may be applicable to other urban or suburban headwater catchments in areas with a component of non-natural recharge from, for example, leaky infrastructure, storm water routing or dry season irrigation.