Environmental Impact of Abandoned Mine Waste: a review

1.1. Resource

Mineral exploitation, smelting and recovery of useful and/or precious metals in several countries of Europe dates back to VII century B.C. (Etruscan times) or even before (Thornton, 1996). After a large diffusion of Fe, Cu, Au, Ag, Sn, Pb mining during the Roman expansion in Europe and Britain, ore exploitation virtually ceased during the Middle Age (5^th to 11^th centuries), and became economically important again after the 15^th century, when there was an increasing demand for silver for coinage, and lead for armaments. (Davies, 1987). Afterwards, alternate fortunes accompanied mine works, particularly during the Industrial Revolution and until the first decades of 20^th century, when mining activity in the Old Continent ceased and most mines were abandoned, for both exhaustion of metal veins, price drop and major sensitivity of people to human and environmental health. Silver and mercury, for instance, have been used since early historic times, as reported by Bargagli (1995) and Forel et al. (2010). Silver exploitation in the Vosges Mountains is attested since the 10^th century in the Val d’Argent (NE France), where up to 600 mines have been accounted for at least 3000 miners (Forel et al., 2010). Cinnabar exploitation in the Mediterranean basin (Spain, Italy, Croatia, Turkey, Tunisia) began in Etruscan times, was expanded by Romans and dominated the world mercury production for long time (Bargagli, 1995). Mercury production, as well as that of other metals such as copper, lead, silver, zinc, etc. depended on the market price, which reached 700US dollars/kg during early ‘70s (Gemici et al., 2009). The gradual decline in the demand, caused by the increasing environmental concerns of Hg, resulted in lowered price, drastic reduction in mining, and the final closing of many Hg mines until the early ‘80s.

Metals are indissolubly linked to the progress of mankind, having greatly contributed to the evolution of civilization, from the stone age (Neolithic period, 6.000 BC), through copper, bronze, iron and “gold age” (the California gold rush), to present time. Exploitation of metals such as Cu, Au and Ag, for example, is among the most long lasting mining operations, since their recovery started with the chalcolithic age (copper-bronze age), between 5500 and 3000 BC (Dill, 2009).

Combining archaeological and geological investigations, numerous studies have focused on ancient settlements, artifacts and archaeometallurgical slags found at different sites, shading some light on the techniques applied for the recovery of pure metals (Cu, Au, Ag, Pb, Sb, Sn and Fe) from the various raw materials (Francovich, 1985; Stiles et al., 1995; Mascaro et al., 1995; Heimann et al., 1998; Manasse et al., 2001; Manasse and Mellini, 2002; Costagliola et al., 2008; Dill, 2009).

Table 1. Mine production of heavy metals

Element	Mine production 1990
antimony	55
arsenic	45
cadmium	19
chromium	6800
copper	8110
lead	3100
mercury	6.8
nickel	778
zinc	6040

Data is in metric tonnes x10³ / year.

Modified after McGrath, 1995.

Metals have been, and are still, mined in the majority of the countries of the world, and primary production of many metals continues to rise (Thornton, 1996). In 1950, the production of Pb was 1.7 million tonnes (Table 1), and that of Cu 2.8Mt, Cr 2.2Mt, Zn 1.9Mt, Ni 0.14Mt; in 1995, Pb production was up to 3.3 million tonnes; Cu 9.4Mt; Cr 12.8Mt; Zn 7.1Mt; Ni 0.9Mt (Thornton, 1996). The main reason for this interest towards metals is, obviously, related to their large utilization at worldwide level.

Nowadays, heavy metals are vital components of modern technology, being utilized in many industrial and agricultural activities (electronic, galvanic, metallurgy, varnish, tannery, wood preservation, fertilizers, pesticides, etc.) (Davies, 1987; Adriano, 2001). The metal over-utilization at worldwide level is responsible for serious threats to the environment, with potential risk for human health. Besides the occasional lead poisoning recorded during Roman domination ( Nriagu, 1983; Stiles et al., 1995), the first signals of threats appeared on agricultural land contaminated with heavy metals. In the middle of the 19^th century, farmers living close to lead-silver mine areas in England complained that mine waste was deposited on fields by river floods, contaminating their land (Davies, 1980). It has been calculated that approximately 35% of the mineral waste discharged on the land was released to the environment. Overall, it can be estimated that for every ton of silver-free lead which was produced, as much as 2tons may have been lost to the environment (Davies, 1987). Similarly, Helios-Rybicka (1996) reported that approximately 700M tonnes for year of mineral commodities have been exploited in Poland, strongly influencing the hydrological system. Geomechanical processes (subsidence, slumps, landslides, erosion) led to the complete destruction of soils and irreversible changes of the landscape.

From that time, repeated threats to the environment have been recorded in current literature, (see f.i. Cappuyns et al., 2006; Palumbo-Roe et al., 2009), suggesting heavy metals to represent a concrete environmental concern.