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

Lina Weissengruber,Jürgen K Friedel,Kurt Möller,Markus Puschenreiter

doi:10.1007/s10705-018-9907-9

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.

Highlights

Phosphorus (P) is an essential element for all living organisms and food production, but it is not treated sustainably in Europe
The assessment of the 200-years potentially toxic elements (PTEs) inputs by fertilizers, liming and atmospheric deposition indicated that these inputs are expected to be small compared to the already existing PTE background concentrations in soil (Table 5)
The results indicate that recycled P fertilizers (RPFs) like sewage sludge and products obtained from sewage like struvite or from thermal approaches like the production of calcined phosphates via AshDecÒ, Mephrec converter slags or LeachphosÒ can reduce the PTE accumulation risk

Summary

Introduction

Phosphorus (P) is an essential element for all living organisms and food production, but it is not treated sustainably in Europe Through fertilization it ends up in surface water bodies or it is irretrievably lost by coincineration in municipal solid waste incinerators, power plants or cement kilns (Egle et al 2015, 2016). At the current rate of extraction, phosphate rock reserves could peak in 2033 (Cordell and White 2011) and will be exhausted in the few centuries (Elser 2012; Desmidt et al 2014) This demonstrates that the reliance on non-renewable P sources for production of P fertilizers directly contradicts both the principles of sustainable development and the principle of care in organic farming (IFOAM 2017). We need a more efficient and sustainable P recycling within our societies

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