Spectrum of pharmaceutical residues in commercial manure-based organic fertilizers from multi-provinces of China mainland in relation to animal farming and possible environmental risks of fertilization

Abstract

With a long-term amendment of manure-based organic fertilizers (MOFs), significant elevations of antibiotics and their resistance genes in agricultural soil have aroused great concerns worldwide, but their relationships to animal farming and possible environmental risks of fertilization lack systematic studies. This study collected 41 commercial MOFs made from manures of chicken, swine, sheep/goat, and cattle, respectively, in 10 provinces (including autonomous regions) of China mainland with large animal farming industries. Twenty-nine compounds, consisting of 20 antibiotic compounds, sulfonamides' synergist (trimethoprim) and 8 non-antibiotic pharmaceuticals, were quantified in the collected MOF samples, ranging from below the quantification limits (<0.02 μg kg^-1 dry mass) up to 110 mg kg^-1 dry mass (oxytetracycline), using a high throughput protocol with 83 target compounds (37 antibiotic ones) of 6 pharmaceutical categories. Antibiotic compounds of tetracyclines and fluoroquinolones collectively dominated pharmaceutical residues in the MOF samples, accounting for 71.9-99.9 % of total loads, except 6 samples. Pharmaceuticals for human use only (4 antibiotic and 4 non-antibiotic compounds) and for both human and veterinary uses (5 antibiotic and 1 non-antibiotic compounds) were quantified in the MOF samples according to the Chinese pharmacopeia. The MOF samples made from chicken and swine manures (mainly captivity) had greater number, frequency, and level of the quantified pharmaceutical compounds than the ones made from sheep/goat and cattle manures (mainly grazing). Antibiotics, particularly enrofloxacin and oxytetracycline, in the MOF samples would lead to medium risks to microorganisms and invertebrates in soil and high risk to plants, and considerable risk to antibiotic resistance selection if applied in agricultural soils. Findings of this study suggest that pharmaceutical contaminations should be taken into account for the quality guidelines of the commercial MOFs as well as other pollutants (such as heavy metals), especially the MOFs made from manures of the captive chicken and swine.

Keywords: Antibiotic resistance selection; Farming animals; Manure-based organic fertilizer (MOF); Pharmaceutical residues; Risk assessment.