Mercury Speciation in Contaminated Soils from Old Mining Activities in Mexico Using a Chemical Selective Extraction

Abstract

Amalgamation was heavily used in mining since 1557 in Spanish Colonies. In Mexico and other parts of Latin-America,this process generated tailings which were left aside in the mine backyards. In the valley of Zacatecas, tailings were carried out of the mines due to the run-off from the mountains and contaminated most of the Zacatecan Valley which most important economic activity is agricultural (crop and livestock raising). The main concern in this area is the high level of total mercury found in previous studies. So far, various research studies have been conducted in Mexico toidentify the contamination by total mercury in contaminated soils. However, research has not been developed to determine the available fraction by an analysis of the chemical species present in contaminated sites, which represent a risk to human health and the environment. The aim of this study is to develop a mercury sequential chemical extraction methodology with appropriate conditions for identifying: 1) water-soluble fraction, 2) elemental fraction, 3) interchangeable fraction, 4) strongly bound fraction, 5) organic fraction, 6) fraction as sulphides and 7) residual fraction. With this, it might be determined if the mercury species present in mining soils in the state of Zacatecas, Mexico represent a potential risk because of its mobility in the different environmental compartments. Results show that chemical species in the towns of Osiris and La Zacatecana (HgS and amalgamated mercury) have high stability and low mobility.
 
 , Soil contamination, Mining wastes,Chemical selective extraction

Solid-phase partitioning of mercury in artisanal gold mine tailings from selected key areas in Mindanao, Philippines, and its implications for mercury detoxification

“…Route 2) was conducted. Strongly bound (F3) and sulphide (F5) fractions were also found in Li-BM and P-CIP samples in relatively significant amounts, but these fractions are not a problem because of their high stability, low solubility and limited bio-availability (Gavilán-García et al, 2008; Wang et al, 2012). Mercury in the sulphide fraction was observed only in Li-BM and P-CIP samples, while residual mercury was only detected in P-CIP samples.…”

“…Water soluble (F1), exchangeable species (F2) and organic forms (F3) of mercury were also detected in Li-BM and W-BM samples. The presence of mercury in water soluble, organic and exchangeable forms presents a potential health and environmental risk since these forms of mercury are easily transformed and redistributed in the environment (Gavilán-García et al, 2008).…”

“…The solid-phase partitioning of mercury was determined by the sequential extraction procedure employed by Gavilán-García et al (2008) (Table 2), which was based on the techniques developed and/or used by five research groups: Tessier et al (1979), Di Giulio and Ryan (1987), Wallschläger et al (1998), Ebinghaus et al (1999) and Bloom et al (2003). This sequential extraction procedure is divided into two routes (Figure 2).…”

“…In comparison, Route 2 divided mercury into six fractions: water soluble species (F1), exchangeable species (F2), strongly bound species (F3), organic species (F4), sulphide fraction (F5) and residual (F6). For mercury in the sulphide fraction (F5), this was obtained by subtracting F1, F2, F3, F4 and F6 from the total mercury concentration since excess sulphide from F5 could generate interference during CVAAS analysis (Gavilán-García et al, 2008). All experiments were done in triplicates to ascertain that differences and trends observed were statistically significant.…”

“…One of the most commonly used methods to determine the solid-phase partitioning of mercury is sequential extraction, a technique that involves treatment of the sample with a series of solvents that specifically attack certain minerals in the sample matrix (e.g. carbonates, sulphides and oxides) (Gavilán-García et al, 2008; Tabelin and Igarashi, 2009; Tabelin et al, 2014; Tessier et al, 1979). This technique has been successfully employed to estimate the mobility and potential bioavailability of mercury in contaminated soils of the Idrija mercury mine region (Kocman et al, 2004) and in some gold mining areas in Mexico (Gavilán-García et al, 2008).…”