Soil biological attributes in arsenic-contaminated gold mining sites after revegetation

Abstract

Recovery of arsenic contaminated areas is a challenge society faces throughout the world. Revegetation associated with microbial activity can play an essential role in this process. This work investigated biological attributes in a gold mining area with different arsenic contents at different sites under two types of extant revegetation associated with cover layers of the soil: BS, Brachiaria sp. and Stizolobium sp., and LEGS, Acacia crassicarpa, A. holosericea, A. mangium, Sesbania virgata, Albizia lebbeck and Pseudosamanea guachapele. References were also evaluated, comprising the following three sites: B1, weathered sulfide substrate without revegetation; BM, barren material after gold extraction and PRNH (private reserve of natural heritage), an uncontaminated forest site near the mining area. The organic and microbial biomass carbon contents and substrate-induced respiration rates for these sites from highest to lowest were: PRNH > LEGS > BS > B1 and BM. These attributes were negatively correlated with soluble and total arsenic concentration in the soil. The sites that have undergone revegetation (LEGS and BS) had higher densities of bacteria, fungi, phosphate solubilizers and ammonium oxidizers than the sites without vegetation. Principal component analysis showed that the LEGS site grouped with PRNH, indicating that the use of leguminous species associated with an uncontaminated soil cover layer contributed to the improvement of the biological attributes. With the exception of acid phosphatase, all the biological attributes were indicators of soil recovery, particularly the following: microbial carbon, substrate-induced respiration, density of culturable bacteria, fungi and actinobacteria, phosphate solubilizers and metabolic quotient.

Contamination and Soil Biological Properties in the Serra Pelada Mine - Amazonia, Brazil

“…Significant negative correlations were observed between the qMic and available As contents (Table 8). The microbial quotient usually varies from 1 to 4 % of the soil organic carbon (Jakelaitis et al, 2008;Santos et al, 2013); ratios lower than 1 % indicate some limiting factor, in this study, the limiting factor is the high available As contents.…”

Heavy Metal Contamination of Soils

“…Arsenic is toxic to almost all bacteria by inhibiting basic cellular functions, which are linked with energy metabolism. Most enzymes exhibit significant decrease under As pollution; however, several authors report a specific behavior of acid phosphatase showing no significant effect due to As presence in soil (dos Santos et al 2013;Lyubun et al 2013;Stazi personal communication), preventing this hydrolase from being a good indicators of soil quality under As pollution. Table 6.2 reports a synthesis of the effects of diverse As concentrations in soil on several microbial parameters contaminated by natural and anthropic sources.…”

“…Many areas were simply abandoned, which caused several problems, such as acid mine drainage, visual impact and the erosion and release of gases into the atmosphere, which compromised the quality of the air, water and soil; the resulting impacts still persist in the coal mining region. The substrate of mined areas is characterised by a high degree of disintegration, acidic pH, HM toxicity (such as that of Cd, Al, Mn, Zn, Cu, Pb and Fe) and a very crumbly texture, which makes it very susceptible to erosion (Silva et al 2013). Its physical properties and low reserves of essential nutrients for plant growth impose severe restrictions on its use for agriculture and forestry.…”

“…Although there is still microbial activity in the soil, various biological processes essential to its functionality are compromised because of the excessive metal content (Dias-Junior et al 1998;Santos et al 2013), which prevents spontaneous revegetation in most locations. Therefore, there is a strong need for human intervention through the use of appropriate techniques to stop the advance of degradation and to reverse the environmental hazard threat.…”

Soil attributes in coal mining areas under recovery with bracatinga ( Mimosa scabrella )

“…; Santos et al . ). In this way, this work aims to characterize the chemical attributes and to evaluate the microbiological attributes of the soil in areas degraded by coal mining under recovery with the species bracatinga.…”