No abstract

Although mercury (Hg) mining in the Almadén district ceased in May 2002, the consequences of 2000 years of mining in the district has resulted in the dissemination of Hg into the surrounding environment where it poses an evident risk to biota and human health. This risk needs to be properly evaluated. The uptake of Hg has been found to be plant-specific. To establish the different manners in which plants absorb Hg, we carried out a survey of Hg levels in the soils and plants in the most representative habitats of this Mediterranean area and found that the Hg concentrations varied greatly and were dependent on the sample being tested (0.13-2,695 microg g(-1) Hg). For example, the root samples had concentrations ranging from 0.06 (Oenanthe crocata, Rumex induratus) to 1095 (Polypogon monspeliensis) microg g(-1) Hg, while in the leaf samples, the range was from 0.16 (Cyperus longus) to 1278 (Polypogon monspeliensis) microg g(-1) Hg. There are four well-differentiated patterns of Hg uptake: (1) the rate of uptake is constant, independent of Hg concentration in the soil (e.g., Pistacia lentiscus, Quercus rotundifolia); (2) after an initial linear relationship between uptake and soil concentration, no further increase in Hg(plant) is observed (e.g., Asparagus acutifolius, Cistus ladanifer); (3) no increase in uptake is recorded until a threshold is surpassed, and thereafter a linear relationship between Hg(plant) and Hg(soil) is established (e.g., Rumex bucephalophorus, Cistus crispus); (4) there is no relationship between Hg(plant) and Hg(soil )(e.g., Oenanthe crocata and Cistus monspeliensis). Overall, the Hg concentrations found in plants from the Almadén district clearly reflect the importance of contamination processes throughout the study region.

The Mt. Amiata volcano is the youngest and largest volcanic edifice in Tuscany (central-northern Italy) and is characterized by a geothermal field, exploited for the production of electrical energy. In the past Mt. Amiata was also known as a world-class Hg district whose mining activity was mainly distributed in the central-eastern part of this silicic volcanic complex, and particularly in the municipality of Abbadia San Salvatore. In the present work we report a geochemical survey on Hg(0) measurements related to the former mercury mine facilities prior the reclamation project. The Hg(0) measurements were carried out by car for long distance regional surveys, and on foot for local scale surveys by using two LUMEX (915+ and M) devices. This study presents the very first Hg(0) data obtained with this analytical technique in the Mt. Amiata area. The facilities related to the mining areas and structures where cinnabar was converted to metallic Hg are characterized by high Hg values (>50,000ngm(-3)), although the urban center of Abbadia San Salvatore, few hundred meters away, does not appear to be receiving significant pollution from the calcine area and former industrial edifices, all the recorded values being below the values recommended by the issuing Tuscany Region authorities (300ngm(-3)) and in some cases approaching the Hg background levels (3-5ngm(-3)) for the Mt. Amiata area.

Metallurgic calcines with very high mercury and methylmercury content from the Almadén mining district were analyzed by synchrotron-based microprobe techniques. Information about mercury speciation was obtained by micro-EXAFS (microscopic extended X-ray absorption fine structure) spectroscopy, whereas elemental associations were evaluated by micro-XRF (microscopic X-ray fluorescence analysis) mapping. Complementary characterization methodologies, including X-ray diffraction (XRD), inductively coupled plasma-optical spectroscopy (ICP-OES), as well as a sequential extraction scheme (SES), were used to predict the potential availability of mercury. Analysis of total metal content revealed extremely high concentrations of mercury and iron (between 7 and 35 and 65-70 g kg(-1), respectively) and high zinc concentrations (2.2-2.5 g kg(-1)), whereas other metals such as copper, nickel, and lead were found at low concentration levels (30-300 mg kg(-1)). Micro-EXAFS results indicate that cinnabar (HgS(red)) is one of the main species within the studied mercury-rich particles (5-89% of total mercury content), together with more soluble mercury compounds such as Hg3(SO4)02 (schuetteite) and HgO (5-55% of total mercury content). Additionally, element-specific micro-XRF maps of selected mercury-rich particles in the studied samples revealed an evident correlation among Hg-Pb-Ni (and S), indicating a possible geochemical linkage of these elements. Correlations were also found among Fe-Mn and Hg, which have been attributed to sorption of mercury onto oxyhydroxides of Fe and Mn. This finding was supported by results from a sequential extraction scheme, where a significant