Distribution of As and Zn in Soils Affected by the Spill of a Pyrite Mine and Effectiveness of the Remediation Measures

Abstract

The concentrations of As and Zn in 100 georeferenced soils uniformly distributed throughout the area affected by the spill from the Aznalcóllar mine (April 1998) were analysed at three depths (0-10, 10-30, and 30-50 cm) and on four dates (autumn-winter 1998, 1999, 2001, and 2004). For an estimate of the geochemical background, 30 unaffected soils near the edge of the spill were also analysed at the same depths. The soils were contaminated before the spill and, the accident seriously increased the concentration of As and Zn in the first 10 cm of almost all the affected soils. After the enormous efforts of cleaning up the tailings, around 45% of the soils had a concentration higher than 100 mg As kg −1 dry soil, and some 35% had a concentration higher than 1,000 mg Zn kg −1 dry soil. Both As and Zn penetrated between 10 and 30 cm in 25% and 45% of the soils, respectively, but reached 30 cm in only 12% of the soils. The remediation actions, especially the tilling and homogenisation of the uppermost 25 cm of the all soils, caused the As and Zn concentrations to decline in the soils, but this change was not very effective from the standpoint of pollution. Thus, 6 years after the spill, the uppermost 10 cm of 30% of the soils continued to have an As concentration higher than 100 mg As kg −1 , while the Zn concentration diminished considerably on the surface due to its greater mobility, accumulating between 10 and 30 cm in depth, where 20% of the soils continued to register more than 1,000 mg Zn kg −1 dry soil.

Groundwater contamination evolution in the Guadiamar and Agrio aquifers after the Aznalcóllar spill: assessment and environmental implications

“…Also, the existence of wells flooded by the spill where after repeated pumping and addition of neutralizing materials remain acidic indicates that an important volume of aquifer surrounding the wells was Although there are no data on the groundwater quality before 1998, the high levels of toxic elements found in the waters of the Agrio and Guadiamar rivers prior to the failure of the dam (Cabrera et al 1984;Cabrera et al 1987;Arambarri et al 1996), even higher than those found after the spill (Olías et al 2006), clearly show the existence of this previous contamination. This is also noted in other studies conducted on the soils (Kraus and Wiegand 2006;Simón et al 2009) and the river sediments (Martin et al 2000;Hudson-Edwards et al 2003;Turner et al 2008). …”

“…Iron-rich clayey materials were also added in some areas (Aguilar et al 2007), and the surface was plowed to mix more contaminated surface horizons with deeper layers and so to thin down toxic element levels (Galán et al 2002;Simón et al 2009). Toxic element levels in soils are still high in many areas (Kraus and Wiegand 2006;Alvarez-Ayuso et al 2008;Simón et al 2009).…”

“…Many of them have evidenced a rapid initial recovery along with the existence of important residual contamination levels (Alvarez-Ayuso et al 2008), especially in the area closest to the mine, both in soils (Galán et al 2002;Kraus and Wiegand 2006;Simón et al 2009), river sediments (e.g., Hudson-Edwards et al 2003;Turner et al 2008), and vegetation or fauna (e.g., Sánchez López et al 2004;Madejón et al 2006;Márquez-Ferrando et al 2009). In general, for all groups of living beings, the degree of damage has been parallel to that of contaminant levels, with still higher concentrations than in noncontaminated areas (Garrido 2008).…”

Monitoring of Pb Exposure in Waterfowl Ten Years after a Mine Spill through the Use of Noninvasive Sampling

“…Hence, immediately after the spill the Andalusian and Spanish authorities began to clean and restore the affected areas, undertaking preventive and mitigating measures [3], [4]. Nevertheless, low-level residual heavy metal contamination remained [9]–[13].…”

Arsenic Behaviour in Polluted Soils After Remediation Activities

“…The final measurement was the stabilization of the soils by revegetation with native plants. A monitoring of the area in 2004 (6 years after the accident) revealed that although the remediation measurements lowered the As concentrations, the percentage of soils exceeding the maximum permitted level for agricultural soils was around 65% of the total affected soils, while around 30% of the soils had even doubled the maximum permitted of As (100 mg kg −1 ; Simón et al, 2009). In this chapter, we present a general overview of the time course of As content in soils during the remediation actions undertaken in the affected area.…”