Long-term application of lead arsenate in orchards has led to a significant accumulation of Pb and As in the topsoil. Reclamation of old orchards for agricultural purposes entails the exposure of humans to Pb and As, which can be reduced by adequate remediation actions. In this study, we assessed the remediation efficiency of compost addition, commonly used as a sustainable agricultural practice. The remediation was evaluated based on Pb and As bioavailability, assessed by means of two selective non-exhaustive chemical extractions and with a novel in vivo bioaccumulation test with isopods (Porcellio scaber). All the tests showed that compost addition consistently reduced Pb bioavailability but increased As bioavailability. However, the As bioavailable share assessed with the widely used modified Morgan extraction test was lower by factors up to 2.5 than when assessed with bioaccumulation. Conversely, it was higher by factors up to 7.2 when assessed with the physiologically based extraction test, indicating that the bioavailability of As could be under- or overestimated using solely chemical extraction tests. This is the first report on the use of As accumulation in P. scaber as a tool for the assessment of As bioavailability in contaminated orchard soil.
COBISS.SI-ID: 6954873
Remediation techniques for soils polluted with toxic metals can be divided into two main groups. Immobilization technologies leave metals in the soil, but minimize their availability, while technologies such as soil washing with chelating agents remove metals from the soil. Metals in soil are not entirely accessible to chelating agents and they are consequently not entirely removed. Residual metals left in the soil after remediation remain present in chemically stable species bound to non-labile soil fractions and are considered non-mobile and non-bioavailable and thus not-toxic (bioavailability stripping remediation concept). However, with the re-introduction of remediated soil into the environment, we expose the soil to various environmental factors. They could eventually promote or initiate the transition of the residual metals back to more labile forms to re-establish the disturbed equilibrium. Such a shift would increase the toxicity of the residual metals and, consequently, decrease the final efficiency of soil remediation. Different extraction techniques are used to assess metals bioavailability and the efficiency of soil remediation. Reduced bioavailability of contaminants for organisms is most often assessed by established chemical extraction tests. However, do the chemical extraction tests really provide (include) reliable information on availability of metals for soil fauna?
COBISS.SI-ID: 6841465
The in situ stabilization of potentially toxic metals (PTMs), using various easily available amendments, is a cost-effective remediation method for contaminated soils. In the present study, we investigated the effectiveness of apatite and a commercial mixture of dolomite, diatomite, smectite basaltic tuff, bentonite, alginite and zeolite (Slovakite) on Pb, Zn, Cu and Cd stabilization by means of decreasing their bioavailability in contaminated soil from an old lead and zinc smelter site in Arnoldstein, Austria. We also investigated the impact of 5% (w/w) apatite and Slovakite applications on soil functionality and quality, as assessed by glucose-induced soil respiration, dehydrogenase, acid and alkaline phosphatase and b-glucosidase activity. Both amendments resulted in increased soil pH and decreased PTM potential bioavailability assessed by diethylenetriamine pentaacetic acid extraction and by sequential extractions in the water-soluble and exchangeable fractions. The efficiency of stabilization was reflected in the soil respiration rate and in enzymatic activity. The b-glucosidase activity assay was the most responsive of them.
COBISS.SI-ID: 6755449
The terrestrial isopod (Porcellio scaber) was used to assess the remediation efficiency of limestone and a mixture of gravel sludge and red mud as stabilizing agents of Pb, Zn and Cd in industrially polluted soil, which contains 800, 540 and 7 mg kg-1 of Pb, Zn and Cd, respectively. The aim of our study was to compare and evaluate the results of the biological and non-biological assessment of metal bioavailability after soil remediation. Results of a 14 d bioaccumulation test with P. scaber showed that that Pb and Zn stabilization were more successful with gravel sludge and red mud, while Cd was better stabilized and thus less bioavailable following limestone treatment. In vivo bioaccumulation tests confirmed the results of chemical bioaccessibility, however it was more sensitive. Biotesting with isopods is a relevant approach for fast screening of bioavailability of metals in soils which includes temporal and spatial components.
COBISS.SI-ID: 7458425
Remediation soil is exposed to various environmental factors over time that can affect the final success of the operation. In the present study, we assessed Pb bioaccessibility and microbial activity in industrially polluted soil (Arnoldstein, Austria) stabilized with 5% (w/w) of Slovakite and 5% (w/w) of apatite soil after exposure to two earthworm species, Lumbricus terrestris and Dendrobaena veneta, used as model environmental biotic soil factors. Stabilization resulted in reduced Pb bioaccessibility, as assessed with one-step extraction tests and six-step sequential extraction, and improved soil functioning, mirrored in reduced b-glucosidase activity in soil. Both earthworm species increased Pb bioaccessibility, thus decreasing the initial stabilization efficacy and indicating the importance of considering the long-term fate of remediated soil. The earthworm species had different effects on soil enzyme activity, which can be attributed to species-specific microbial populations in earthworm gut acting on the ingested soil.
COBISS.SI-ID: 7368057