Heavy Metal Concentration Survey in Soils and Plants of the Les Malines Mining District (Southern France): Implications for Soil Restoration

Abstract

Mining activities generate spoils and effluents with extremely high metal concentrations of heavy metals that might have adverse effects on ecosystems and human health. Therefore, information on soil and plant metal concentrations is needed to assess the severity of the pollution and develop a strategy for soil reclamation such as phytoremediation. Here, we studied soils and vegetation in three heavily contaminated sites with potential toxic metals and metalloids (Zn, Pb, Cd, As, TI) in the mining district of Les Malines in the Languedoc region (southern France). Extremely high concentrations were found at different places such as the Les Aviniéres tailing basins (up to 160,000 mg kg -1 Zn, 90,000 mg kg -1 Pb, 9,700 mg kg -1 of As and 245 mg kg -1 of Tl) near a former furnace. Metal contamination extended several kilometres away from the mine sites probably because of the transport of toxic mining residues by wind and water. Spontaneous vegetation growing on the three mine sites was highly diversified and included 116 plant species. The vegetation cover consisted of species also found in non-contaminated soils, some of which have been shown to be metaltolerant ecotypes (Festuca arvernensis, Koeleria vallesiana and Armeria arenaria) and several Zn, Cd and Tl hyperaccumulators such as Anthyllis vulneraria, Thlaspi caerulescens, Iberis intermedia and Silene latifolia. This latter species was highlighted as a new thallium hyperaccumulator, accumulating nearly 1,500 mg kg -1. These species represent a patrimonial interest for their potential use for the phytoremediation of toxic metal-polluted areas.

Release Law of Sb, As, and Hg in Antimony Smelting Slag Under Simulated Acid Rain

“…The smelting slag yard covers an area of 22,000 m 2 , with a stockpiling of about 30,000 tons of smelting slag. 20 sampling sites were selected around the slag yard with each sampling site being a square (1×1m).…”

“…This may be because after the first three days of leaching, the enamel surface structure of smelting slag was destroyed and stibnite (Sb 2 S 3 ) was oxidized to SbO 3 -1 in the oxygen-enriched environment to the leachate [39]. The specific reaction is as follows: (2) During the period from days 4 to 12, because of the neutralizing reaction of the carbonate minerals the leachate was weakly alkaline, and there was a certain amount of OH -in the solution, which may react with Al 3+ and Fe 3+ in the leachate, generating gels like Al(OH) 3 and Fe(OH) 3 , which formed a thin film covering the smelting slag surface to prevent further oxidation of stibnite. Moreover, as can be seen from Fig.…”

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The exploitation and smelting of heavy metals causes serious environmental pollution, which has received extensive attention from researchers all over the world [1][2][3]. The smelting slag produced by the smelting mines is not only land-occupying, but also causes lasting environmental pollution, for large amounts of harmful elements in the smelting slag are released after rain [4][5][6][7].

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Metal concentration and metal mass of metallicolous, non metallicolous and serpentine Noccaea caerulescens populations, cultivated in different growth media

“…In each population, seeds from 20-30 flowering plants were collected. To analyse the extractable Zn, Cd, Pb and Ni concentrations of soil, bulk samples were air-dried, ground and the <2 mm fractions were separated from coarse rock (Frérot et al 2006) Total Zn 126126±17620 mg/kg; total Cd 899±200 n=3 (Escarré et al 2011) b (Dechamps et al 2008a,b;Molitor et al 2005) c Total Zn concentration (Reeves et al 2001) d Total Ni concentration: 146 to 2500 mg/kg (Chardot et al 2007) e Total Ni concentration:784-1984 mg/kg (Reeves et al 2001) fragments by sieving. All chemical analyses were performed on the <2 mm soil fractions.…”

“…According to these results, MET populations from southern France are not zinc hyperaccumulators on average according to the "classic" concentration treshold (Baker and Brooks 1989). AV individuals harvested in situ had Zn mean values of 7310 mg/kg (±646) (Escarré et al 2011). However, Noccaea caerulescens from PR (MET) (Zn in soil 18360 mg/kg) had mean leaf Zn concentrations up to 13400 mg/kg (Faucon 2004).…”