Frédéric Feder

Fate and impacts of pharmaceuticals and personal care products after repeated applications of organic waste products in long-term field experiments

Recycling organic waste products in agriculture is a potential route for the dispersion of pharmaceutical residues in the environment. In this study, the concentrations of thirteen pharmaceuticals and the personal care product triclosan (PPCPs) were determined in different environmental matrices from long-term experimental fields amended with different organic waste products (OWPs), including sludge, composted sludge with green wastes, livestock effluents and composted urban wastes applied at usual agricultural rates. PPCP concentrations were different in OWPs, varying from a few micrograms to milligrams per kilogram dry matter or per litre for slurry. OWPs from sludge or livestock effluents primarily contained antibiotics, whereas composted urban wastes primarily contained anti-inflammatory compounds. PPCP contents in soils amended for several years were less than a few micrograms per kilogram. The most persistent compounds (fluoroquinolones, carbamazepine) were quantified or detected in soils amended with sludge or composted sludge. In soils amended with composted municipal solid waste, carbamazepine was quantified, and fluoroquinolones, ibuprofen and diclofenac were sometimes detected. The small increases in fluoroquinolones and carbamazepine in soils after individual OWP applications were consistent with the fluxes from the applied OWP. The measured concentrations of pharmaceuticals in soil after several successive OWP applications were lower than the predicted concentrations because of degradation, strong sorption to soil constituents and/or leaching. Dissipation half-lives (DT50) were approximately 750-2500, 900 and <300days for fluoroquinolones, carbamazepine and ibuprofen, respectively, in temperate soils and <350 and <80days for fluoroquinolones and doxycycline, respectively, in tropical soils. Detection frequencies in soil leachates were very low (below 7%), and concentrations ranged from the limits of detection (0.002-0.03μg/L) and exceptionally to 0.27μg/L. The most frequently detected pharmaceuticals were carbamazepine and ibuprofen. Based on the risk quotient, the estimated ecotoxicological risks for different soil organisms were low.

Repeated pig manure applications modify nitrate and chloride competition and fluxes in a Nitisol.

Solute transport was studied in a variable-charge soil (Nitisol) with two following pig manure applications. There were three identical soil columns (diameter=37.5 cm; soil depth=85 cm) equipped with TDR probes and tensiometers, one of which served as an untreated control. Dispersivities inferred using the CXTFIT 2.1 code presented inverse patterns with depth for nitrate and chloride breakthrough curves, while the normalized intensities had the same patterns with depth for both applications. For nitrates, the retardation factors steadily decreased with depth from 4.85 and 3.57 at 17 cm depth to 2.1 and 1.86 PV (pore volume) at 85 cm depth for each column, respectively. For chlorides, the retardation factor increased lineary with depth, from 1.05 at 17 cm depth to 1.76 and 1.86 PV at 85 cm depth. After the first application, the mean difference between nitrate and chloride retardation factors was 3.8 PV at 17 cm depth and it regularly decreased to 0.34 PV at 85 cm depth. For the second application, the mean difference was 2.52 PV at 17 cm depth and it regularly decreased to 0 PV at 85 cm depth. The kinetics of nitrate production by the pig manure nitrification process modified the pH, the ionic strength of the soil solution and then the anionic exchange capacity. This could explain the high nitrate retardation factors until 55 cm depth and the difference between nitrate and chloride retardation factors. The earlier chloride adsorption at anionic exchange sites, combined with a selectivity coefficient to the detriment of nitrates, counterbalanced the delay in nitrate production due to the kinetic mineralisation of pig manure. Nitrate fluxes then caught up with the chloride fluxes at the outlet.