Effects of long-term radionuclide and heavy metal contamination on the activity of microbial communities, inhabiting uranium mining impacted soils

Abstract

Ore mining and processing have greatly altered ecosystems, often limiting their capacity to provide ecosystem services critical to our survival. The soil environments of two abandoned uranium mines were chosen to analyze the effects of long-term uranium and heavy metal contamination on soil microbial communities using dehydrogenase and phosphatase activities as indicators of metal stress. The levels of soil contamination were low, ranging from 'precaution' to 'moderate', calculated as Nemerow index. Multivariate analyses of enzyme activities revealed the following: (i) spatial pattern of microbial endpoints where the more contaminated soils had higher dehydrogenase and phosphatase activities, (ii) biological grouping of soils depended on both the level of soil contamination and management practice, (iii) significant correlations between both dehydrogenase and alkaline phosphatase activities and soil organic matter and metals (Cd, Co, Cr, and Zn, but not U), and (iv) multiple relationships between the alkaline than the acid phosphatase and the environmental factors. The results showed an evidence of microbial tolerance and adaptation to the soil contamination established during the long-term metal exposure and the key role of soil organic matter in maintaining high microbial enzyme activities and mitigating the metal toxicity. Additionally, the results suggested that the soil microbial communities are able to reduce the metal stress by intensive phosphatase synthesis, benefiting a passive environmental remediation and provision of vital ecosystem services.

Microorganisms in soils with elevated heavy metal concentrations in southern Serbia

“…It is noted that long-term exposure of microbial communities to heavy metals can influence their tolerance and adaptation to soil contamination. Soil organic matter is considered the main factor for high microbial enzyme activities in such soils and mitigation of heavy metal toxicity [42].…”

Microorganisms in Soils with High Nickel and Chromium Concentrations in Western Serbia

“…Additionally, the microbial community may adapt to the heavy metal concentrations overcoming the negative effects of contamination [52][53][54]. None of the microbial parameters (biomass, respiration or respiratory quotient, or diversity) were correlated to the gradient in heavy metals of ultramafic soils, suggesting adaptation by the microbial community to the stress imposed by edaphic conditions [12].…”

“…None of the microbial parameters (biomass, respiration or respiratory quotient, or diversity) were correlated to the gradient in heavy metals of ultramafic soils, suggesting adaptation by the microbial community to the stress imposed by edaphic conditions [12]. Some studies showed microbial tolerance and adaptation to soil contamination due to the long-term metal exposure and indicated that soil organic matter is a key factor in maintaining high microbial enzyme activities and mitigating metal toxicity [53]. In general, microorganisms from serpentine soils showed a high level of tolerance to trace metals, such as Ni, Co, and Cr.…”

Single and joint effects of Zn and Cu to ATP pool and microbial recovery in continuous growth systems

“…Most studies on microbial resistance to toxic metals do not specify whether the tolerance of microorganisms is due to physiological acclimation (during exposure to the metals), or due to adaptation involving a genetically‐based resistance . Adaptation and acclimation of microorganisms to heavy metals have recently been investigated by various researchers indicating the important focus of this research.…”