Arsenic dynamics in soils placed near old mining sites in SE Spain

Carmen Pérez-Sirvent,Maria Jose Martínez Sánchez,Carmen Hernández Pérez,Jaume Bech,Carmen Gomez Martinez,Manuel Hernández-Córdoba,Salvadora Martínez López,Lucia Belén Martínez Martínez

doi:10.5194/egusphere-egu22-10446

Abstract

&lt;p&gt;Arsenic is a Potentially Toxic Element (PTE), which is present in the soils/sediments of abandoned mining areas, such as the Sierra Minera de Cartagena La-Uni&amp;#243;n and the mining site of Mazarron (SE Spain) and its areas of influence. In order to assess the risk to human health and the ecosystem, it is necessary to know the nature of the materials that contain this PTE, their alterability and their speciation.&lt;/p&gt;&lt;p&gt;On the one hand, there is a geogenic relationship between this element and materials rich in phyllosilicates and Fe minerals. These minerals can constitute primary mineralisation such as sulphide veins (pyrite, arsenopyrite, etc.) or secondary mineralisation such as haematite, goethite, siderite, jarosite, etc., and can even be found as a mineral phase forming various arsenates. Another very important aspect is the climatology of the area, which coincides with a semi-arid Mediterranean climate with infrequent but very heavy rainfall.&lt;/p&gt;&lt;p&gt;The As concentration range in the studied areas is very wide (5000 -70 mg.Kg-&lt;sup&gt;1&lt;/sup&gt;), with an average value of 150 mg.Kg&lt;sup&gt;-1&lt;/sup&gt;, being As (V) the predominant species. Only soils located in wetland areas with permanent waterlogging can show significant concentrations of As(III).&amp;#160;&lt;/p&gt;&lt;p&gt;The As content in surface waters, such as runoff water, is low, only reaching significant values (&gt;2 mg.L&lt;sup&gt;-1&lt;/sup&gt;) when these waters are acid mine drainage and have pH values &lt;2, coinciding in these cases with the presence of reduced As forms.&lt;/p&gt;&lt;p&gt;Particulate As is associated both with Fe oxides and hydroxides, through surface adsorption processes on Fe(OH)&lt;sub&gt;3&lt;/sub&gt; particles, and with carbonates, through precipitation reactions as calcium arsenate. These reactions are evident in some places such as wadis that transport particulate and dissolved materials from areas affected by mining, and mainly take place both in the riverbed and in flooding areas when rainfall events occur.&lt;/p&gt;&lt;p&gt;For an appropriate understanding of the main processes involved, a detailed scheme is given. It should be noted that the dynamics of this PTE is of a particular interest in the zones studied due to the proximity of urban sites.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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