EOM4SOIL WP 5.1: Synthesis report of current limitations of contaminants in external organic matter (EOM) regulated by law and of different monitoring studies of member countries

The project EOM4SOIL aims, amongst others, at proposing best management practices of organic matter (OM) for soil amendment and improving soil health. Therefore,  data of contaminants such as metals, organic compounds, impurities and pathogens in OM such as compost, digestate, (sewage) sludge, etc. were gathered from ten different countries (Austria, Belgium, Italy, Finland, France, Lithuania, Spain, Sweden, Switzerland, and Turkey). The “e” of EOM defines “external” and is OM added to soil as fertilizer that did not origin from the same field as applied and/or has undergone
transformations. 

Authors from the different countries compiled datasets of contaminants in EOM regulated by law and monitored in their countries. All data were joint in a database distinguishing between regulated and monitored contaminants in the countries and various OM. Mean values of contaminant concentrations
of monitoring studies and reports were copied into the database and transformed, where possible (for instance all concentrations needed to be mg/kgdry matter (dm)), so that they could be analyzed and compared with regulated limit values. From all contaminants regulated, inorganic contaminants made
three fourths, whereas from all monitored contaminants metals were half of all entries. In contrast, far more organic contaminants were monitored (46%) than regulated (4%). Additionally, regulated organic contaminants contained rather legacy compounds such as PAHs, PCBs or OCP whereas
monitoring studies investigated PFOS, sulfonamides, parabens, phthalates, and flame retardants (for abbreviations see Table A 2). Obviously, regulation in most countries is “behind” environmental science investigating emerging contaminants.

Organic matter covered by laws and in monitoring studies were compost, digestate, (sewage) sludge, manure, biochar, and various other organic matrices not belonging in one of the aforementioned categories. Animal by-products and nitrogen (N), phosphorous (P), and potassium (K) NPK
combinations in unspecific OM were only reported in regulations but not in any monitoring study or report.

Regulated and monitored means of cadmium (Cd), the sum (Σ) of the 16 polycyclic aromatic hydrocarbons (ΣPAH16) assigned priority compounds by the US environmental protection agency, and the Σ of the polychlorinated biphenyls (ΣPCB6, 7, 8) of six, seven or eight PCB congeners were compared. These contaminants monitored were, on the basis of the present data, all well below most regulated limits except for Cd in miscellaneous OM, which was only below regulated limits. This was an overall positive result. However, due to the mean (but not the extreme or single) value(s) of individual studies considered for this overall data evaluation the concentrations could well spread over a wider range than reported here. Also, monitored concentrations reported by the different authors below the limit of quantification (LoQ) could not be considered as a value because <10 mg/kgdm is not a number. Therefore, distributions of monitored concentrations could also well be lower than the
reported ones here.

Overall, from the available data, chemical contamination of EOM was mainly below corresponding regulated concentration values and its application in the respective context therefore not limited. However, the current data proofed to be limited (e.g. in terms of countries), hard to retrieve (e.g. often only published in grey literature not reporting for instance on LoQ, number of replicates, etc.), heterogeneous (e.g. in terms of congeners/representative compounds assessed, analytical methodologies), partly inappropriate (reported concentrations other than mg/kgdm such as g/ha, g/ha in 1, 2 or 10 years, mg/kgP2O5, %fresh weight, ng TE/kgdm, etc., could not be included here,) and scattered (e.g. in terms of EOM categories, analytes covered).