Long-term soil accumulation of potentially toxic elements and selected organic pollutants through application of recycled phosphorus fertilizers for organic farming conditions

Abstract

The pollutant input and the risk of contamination by long-term application of recycled P fertilizers (RPFs) in European agricultural soils were estimated by a mass balance approach. Calculations based on literature data were carried out for the potentially toxic elements (PTEs) Cd, Cr, Cu, Ni, Pb, Zn and for the persistent organic pollutants (POPs) PCBs, PAHs and polychlorinated dibenzo-dioxins and -furans. The PTE accumulation estimation during 200 years of fertilizer application, equivalent to 11 kg P ha -1 year -1 , the mean P export via harvested products on European stockless organic farms, regarded soil background concentrations and proposed threshold concentrations. For PTEs, inputs were fertilizer application, atmospheric deposition and liming, output processes were leaching and crop harvest. The effect of varying site conditions was assessed by considering two precipitation excess (F) values and two soil pH values. For POPs, fertilizer application and the half-life time were considered. The PTE accumulation risk was low for most RPFs. For the analysed POPs no accumulation was found. The highest accumulation was found for all PTEs at pH 7 and F = 0.1 m year -1 , the lowest at pH 5 and F = 0.3 m year -1 . A high P concentration in fertilizers resulted in a low PTE flow per unit of P. Composts had the highest PTE accumulation risk due to lowest P contents. Struvite, meat and bone meal, digestate of catering waste, ash and biosolids would be better suited as P fertilizers. The use of fertilizers should be regulated based on their pollutant-to-nutrient ratio.

Options for Improved Phosphorus Cycling and Use in Agriculture at the Field and Regional Scales

“…The recycling and recovery of P from waste streams is widely regarded as essential to the sustainability of global P management (Chen and Graedel, 2016; Cordell et al, 2011; Withers et al, 2015; Powers et al, 2019). Waste streams with high potential for P recycling and recovery include livestock manures, wastes from food processing industries such as slaughterhouses and dairies, domestic wastewater (i.e., human waste), and urban organic wastes (Hargreaves et al, 2008; Yuan et al, 2012; Weissengruber et al, 2018; Muhmood et al, 2019). Chen and Graedel (2016) estimated global organic P wastes (human and animal sources) in 2013 (>30 Tg) to be similar in magnitude to the total crop P demand (17–35 Tg).…”

“…Efforts to close regional and global P cycles through P recovery and reuse face a number of obstacles. Contamination of waste streams with pathogens, pharmaceuticals, and potentially toxic elements can make wastes unfit for use as agricultural fertilizers due to adverse effects on crop quality, soil quality, and/or human and environmental health (Hargreaves et al, 2008; Lu et al, 2012; Weissengruber et al, 2018). In many jurisdictions, use of domestic wastewater and sewage sludge as soil amendments is restricted (Egle et al, 2016; Løes et al, 2017).…”

“…These obstacles may be addressed by subjecting wastes to biological, chemical, thermal, or physical processes that isolate relatively pure P‐rich compounds, destroy pathogens, and/or reduce bulk. A number of P recovery techniques have been described and evaluated in the literature (Yuan et al, 2012; Schoumans et al, 2015; Egle et al, 2016; Cieślik and Konieczka, 2017; Melia et al, 2017; Roy, 2017; Amann et al, 2018; Peng et al, 2018; Weissengruber et al, 2018; Muhmood et al, 2019; Walling et al, 2019). In assessing the relative value of various approaches to P recovery, factors deserving consideration include the proportion of P that is recoverable, the presence of contaminants in recovered products, energy requirements, environmental impact of the process, value of the recovered products as fertilizer, and cost—recognizing that trade‐offs between desirable characteristics may be necessary (Egle et al, 2016; Cieślik and Konieczka, 2017; Roy, 2017; Amann et al, 2018;).…”

“…Certain recovered P products, such as biosolids, composts, and dehydrated pelletized manures, may face similar obstacles as their raw source materials, such as low P concentrations or presence of contaminants (Lu et al, 2012; Yuan et al, 2012; Schoumans et al, 2015; Weissengruber et al, 2018). Recovered products may also be economically and/or energetically expensive to produce or have low bioavailability to crops, making their use undesirable compared with soluble fertilizers made from mined phosphate rock (Egle et al, 2016; Mayer et al, 2016; Roy, 2017).…”

“…Among recovered P products, struvite recovery through precipitation and crystallization from wastewater and sewage sludge shows promise as a cost-effective technique yielding a relatively pure product (Ronteltap et al, 2007;Schürmann et al, 2012;Lou et al, 2018) with greater value as a fertilizer than many other recovered P products (Cabeza et al, 2011;Vogel et al, 2017b;Huygens and Saveyn, 2018;Wollmann et al, 2018). Further, Weissengruber et al (2018) concluded that potentially toxic element and persistent organic pollutant accumulations would be low to negligible even after 200 yr of struvite application (at 11 kg P ha -1 yr -1 ). In addition to recovery from municipal wastewater, recovery and use (as a fertilizer) of struvite from human urine, livestock urine and manure, and food processing wastes have received considerable attention (Antonini et al, 2012;Achat et al, 2014;Uysal et al, 2014;Katanda et al, 2016;Brown et al, 2018;Katanda et al, 2019;Muhmood et al, 2019).…”