Chemical and ecotoxicological effects of the use of drinking-water treatment residuals for the remediation of soils degraded by mining activities

Abstract

The aim of this study was to evaluate the use of drinking-water treatment residuals (DWTR) in the amendment of a soil affected by mining activities (Aljustrel mine, Portuguese sector of the Iberian Pyrite Belt), considering the effects on its chemical, biochemical and ecotoxicological characteristics. The DWTR had neutral characteristics (pH 6.7) and an organic matter (OM) content of 575 g kg dry matter (DM), which makes them a potential amendment for the remediation of mine degraded soils, as they may correct soil acidity and reduce the extractable metal fraction. An incubation assay, with soil and DWTR, with or without lime, was carried out to test the doses to be used in the assisted-phytostabilization experiment. Based on the results obtained, the doses of DWTR used were the equivalent to 48, 96, and 144 t DM ha, with and without lime application (CaCO 11 t DM ha). Agrostis tenuis Sibth was used as the test plant. Some amendments doses were able to improve soil characteristics (pH and OM content), to decrease metal extractability by 0.01 M CaCl (especially for Cu and Zn), and to allow plant growth, that did not occur in the non-amended soil. Copper, Pb and Zn concentrations in the plant material were lower than the maximum tolerable level for cattle feed, used as an indicator of risk of entry of those metals into the human food chain. The simultaneous application of DWTR (96 and 144 t ha), with lime, allowed a reduction in the mine soil ecotoxicity, as evaluated by some lethal and sub-lethal bioassays, including luminescence inhibition of Vibrio fischeri, Daphnia magna acute immobilization test, mortality of Thamnocephalus platyurus, and 72-h growth inhibition of the green microalgae Pseudokirchneriella subcapitata. However, DWTR were unable to increase soil microbial activity, evaluated by dehydrogenase activity, an important soil-health indicator. Also, OM content and N, concentrations increased slightly but remained low or very low (P and K extractable concentrations were not affected). In general, the bioassays highlighted a decrease in soil ecotoxicity with the presence of lime and DWTR (144 t DM ha). In conclusion, DWTR are recommended to amend acidic soils, with high concentrations of trace elements, but an additional application of organic or mineral fertilizers should be considered.

Evaluation of bioremediation strategies for treating recalcitrant halo-organic pollutants in soil environments

“…DHA is considered as a biomarker of microbial oxidative activity and soil detoxification (Dawson et al, 2007;Alvarenga et al, 2018). In all bioremediation treatments, DHA increased at 90 d. The higher values of DHA activity in soil mycoaugmented with P. sajor-caju LBM 105 compared to controls may be explained by enhanced PCBs removal, contributing in decreasing the prejudicial pollutant effects on soil microbiota, with a consequent improvement in soil biochemical parameters (Ba� cmaga et al, 2017).…”

Potentially Toxic Elements’ Contamination of Soils Affected by Mining Activities in the Portuguese Sector of the Iberian Pyrite Belt and Optional Remediation Actions: A Review

“…However, the physical and chemical properties of these soils (low nutrient and organic matter content and extreme pH), associated with high concentrations of PTEs, sometimes hinder the vegetation establishment in contaminated sites [196], and, to be successful in a phytostabilization strategy, it is very important to improve the soil's capacity to sustain vegetation cover [161], which can be achieved by adequately amending the soil, for example with organic and inorganic additives [43,57,58,81,127,197,198].…”

“…(iii) Ash-based materials, which are very alkaline (i.e., pH ranging from 9 to 13), used mainly as liming agents, increasing the pH and buffering capacity of acid soils, but that can also provide nutrients, such biomass-ash or biomass-ash-based material (e.g., granules) from the pulp and paper industry) [81,[229][230][231][232][233], or coal combustion fly ash [36]. (iv) More uncommon wastes (organic or inorganic) which are not so usually used as agricultural soil amendments, but could be used in the rehabilitation of mine soils, avoiding their landfilling, and allowing their valorization, such as drinking water treatment residuals [198], polyacrylate polymers [234], or hydroxyapatite, chegemite, and calthemite [29]. (v) Biochar, a material which results from the pyrolysis of different organic materials under limiting oxygen conditions [235], has been proposed successfully to remediate soils affected by high concentrations of PTEs [196,[236][237][238].…”

Use of wastes from the pulp and paper industry for the remediation of soils degraded by mining activities: Chemical, biochemical and ecotoxicological effects

“…The soil retention function, i.e., the capacity to immobilize pollutants and reduce the eluate/leachate toxicity, was evaluated using a soil-water extract, solid-to-liquid ratio of 1:10 (Persoone, 1999), and (iv) 72 hours population growth of the green microalgae Pseudokirchneriella subcapitata (OECD 201, 2006). A thorough description of the methodology used is described in Alvarenga et al (2018). Whenever possible, the EC 50 values (soil-water extract concentration, % v/v, at which a toxic effect on 50% of the exposed organisms can be observed) were calculated.…”