The ability of contaminated farmland soils reclaimed by remediation to dissipate pesticides and thus to mitigate their unwanted environmental effects, i.e., leaching and run-off, was studied. Novel EDTA-based soil washing technology was applied. The dissipation from remediated soils was faster than the average DT50 of tested herbicides published in the Pesticides Properties DataBase. Results demonstrate that EDTA-based remediation of the studied soils does not pose any threat of extended herbicide persistence.
COBISS.SI-ID: 9268857
Efficiency and the preservation of soil functions are key requirements for sustainable remediation of contaminated soil. Microbial decomposition and conversion of substrates is a fundamental soil function. Pilot-scale EDTA-based soil washing had an insignificant effect on microbial respiration in acidic soil. In contrast, remediation of calcareous soil reduced cumulative CO2 production after glucose (simple) and alfalfa (complex substrate) addition, by up to 40%. Remediation reduced the nitrification rate (denoting the N-cycle) in acidic soil by 30% and halved nitrification in calcareous soil. Remediation in both soils slightly or positively affected dehydrogenase and ß-glucosidase activity (associated with C-cycle), and decreased urease activity (N-cycle).
COBISS.SI-ID: 9026937
The use of EDTA-based soil washing is prevented by chelant environmental persistence and the hazard of toxic post-remedial emissions. Emissions of residual EDTA and chelated metals from remediated soils were mitigated by adsorption on zero-valent Fe (ZVI), which was added to the slurry of washed soil immediately before rinsing. ZVI addition prevented the initial post-remedial surge of toxic metals leachability and minimised toxic emissions from calcareous and acidic soil as soon as 6 and 7 days after remediation, respectively. Efficient curbing of toxic post-remediation emissions as demonstrated herein is of paramount importance for recognition of EDTA-based remediation as environmentally safe.
COBISS.SI-ID: 9077369
We investigated the feasibility of using EDTA and biodegradable GLDA, EDDS and IDS under conditions pertinent to operational remediation technology, in a pilot-scale experiment. In process parameters, chelator supplement, Na-saturation of process solutions and processing time, EDTA outperformed biodegradable chelators. Treatment with EDTA was also the most effective in total Pb and Zn removal and least impacted soil properties. GLDA was slightly better in Cd removal. EDDS and IDS were inefficient. All chelators effectively removed easily-available Pb, Zn and Cd from the exchangeable soil fraction. EDTA was the most efficient chelator in reducing the bioaccessibility of Pb and GLDA in reducing the bioaccessibility of Cd from simulated human gastrointestinal tract. Treatment with GLDA had an edge in reducing plant bioaccessibility of toxic metals, but induced worrying leachability of Pb. This was 8.3-times higher than with the process with EDTA and 3.4-times higher than in original soil. In general, our results demonstrate the advantage of EDTA over tested biodegradable chelators.
COBISS.SI-ID: 29308419
Persistent EDTA and biodegradable GLDA, EDDS and IDS have been used as chelators in the ReSoil soil washing technology, which recycles chelator and curbs toxic emissions. The washed soils supported similar growth of buckwheat (F. esculentum) and better growth of Chinese cabbage (B. rapa) compared with the original soil. The growth of buckwheat on EDDS-washed soil was an exception and was 67% suppressed. The activities of enzymes of the plant antioxidant preventive system were assessed in roots and leaves of Chinese cabbage. Similar activities were measured, confirming that washed soils were not harmful to the plants. Plant uptake of potentially toxic elements was reduced from all washed soils. The initial Pb emissions in leachate from GLDA and IDS washed soils were up to 89 and 92% higher than those of the original soil, respectively. Soil physical properties (water holding capacity, aggregate stability) and soil functionality, assessed as soil respiration and activity of enzymes indicative for soil C, N and P cycle, were similar in all soils after 10 weeks of plant growth experiment. The overall results indicate a low impact of the remediation on soil quality. EDTA performed slightly better compared to GLDA-, EDDS- and IDS.
COBISS.SI-ID: 29306627