ABSTRACT
Open-field small plot long-term experiment was set up during April 2011 with willow (Salix triandra x S. viminalis ‘Inger’), grown as a short rotation coppice energy crop in Nyíregyháza, Hungary. The sandy loam Cambisol with neutral pH was treated three times (during June 2011, May 2013, and May 2016) with 15 t ha-1 municipal sewage sludge compost (MSSC) and with 600 kg ha-1 (June 2011, May 2013) or 300 kg ha-1 (May 2016) willow ash (WA). In June 2018, the MSSC treated plots were amended with 7.5 t ha-1 municipal sewage sediment (MSS), and 300 kg ha-1 WA. MSSC and WA or MSS and WA were also applied to the soil in combinations during all treatments. Control plots remained untreated since 2011. Repeated application of wastewater solids (MSSC, MSS) and wood ash (WA) significantly enhanced the amounts of As, Ba, Cd, Cu, Mn, Pb, and Zn in topsoil or subsoil of willows, as compared to control. Besides “pseudo-total”, also the “plant available” potentially toxic elements (PTE) concentrations were changed in treated soils. MSSC+MSS application in combination with WA resulted in significantly higher Mn and Zn, and lower As, Ba, Cd, Cr, and Pb concentrations in topsoil or subsoil than MSSC+MSS treatment of soil without WA. All soil treatments enhanced the uptake or accumulation of PTEs in leaves or harvested twigs of willows significantly during yr 2018-2020. Significantly higher Mn or Zn concentrations were measured in MSSC+MSS+WA than in MSSC+MSS treatments. Based on bioconcentration factors, it was confirmed that willows are effective phytoextractors of Cd and Zn. It can be concluded that with regular harvesting of willow shoots, significant amounts of Cd and Zn, and moderate or low amounts of Cu, Ba, As, Cr, Mn, Pb, and Ni can be phytoextracted from a soil, which is mildly contaminated with PTEs through regular application of wastewater solids or wood ash.
