Phytoextraction of heavy metals after application of bottom ash and municipal sewage sludge considering the risk of environmental pollution - Jacek Antonkiewicz; Maja Bryk; Agnieszka Kowalewska; Sylwia Mikołajczak; Beata Kołodziej; Ewa Spychaj-Fabisiak; Koliopoulos Tilemachos; Jacek Babuła (2022)
Waste management to reduce the loss of natural resources has become a basis of sustainable21 development and a circular economy. When using waste, the heavy metal (HM) concentration22 must be taken into account since HMs can be potentially released to the environment, posing23 a toxicity threat. The aim of the study was thus to estimate the availability for plants of Cr, Ni,24 Cu, Zn, Cd, and Pb introduced into the soil with waste. We hypothesized that the prepared25 waste mixtures containing coal or biomass ash and municipal sewage sludge would reduce the26 environmental risk compared to the studied waste used separately. The research was conducted during a 6-year field experiment with grasses 1 and legumes. HM concentration in2 soil, waste, and plant biomass; tolerance index; and uptake of HMs by plants were measured.3 The ash–sludge mixtures had a more favourable effect on the soil in terms of pHKCl, TOC,4 total nitrogen, and total exchangeable bases than the waste used separately. This provided5 beneficial conditions for plant growth and development. Consequently, the ash–sludge6 mixtures increased the plant yield as compared to ash alone, while the mixture containing the7 biomass ash also enhanced the yield in relation to the sewage sludge. The study showed that8 the mixtures allowed for a reduction of environmental risk arising from the HM input with9 waste to the soil. It was proven that HM availability for plants could be beneficially modified10 by mixing waste. Combining the coal ash with the sewage sludge is particularly11 recommended, owing to the unfavourable properties of coal ash for plants. The application of12 the higher dose of the coal ash–sludge mixture showed a better effect than the lower dose,13 while the influence of both doses of the biomass ash–sludge mixture was similar. Under the14 ash–sludge treatment, plants took up more HM than under the ash used separately, and the15 HM concentration in the obtained biomass did not generally exceed that observed under16 single wastes. This should reduce the accumulation of HMs in the soil during a long-term use17 of the waste and facilitates the utilisation of the produced biomass.
Keywords: coal ash; biomass ash; municipal sewage sludge; plants; uptake of heavy metals; 20 concentration of heavy metals