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c Thiabendazole (TBZ), imazalil (IMZ), ortho-phenylphenol (OPP), diphenylamine (DPA), and ethoxyquin (EQ) are used in fruitpackaging plants (FPP) with the stipulation that wastewaters produced by their application would be depurated on site. However, no such treatment systems are currently in place, leading FPP to dispose of their effluents in agricultural land. We investigated the dissipation of those pesticides and their impact on soil microbes known to have a key role on ecosystem functioning. OPP and DPA showed limited persistence (50% dissipation time [DT 50 ], 0.6 and 1.3 days) compared to TBZ and IMZ (DT 50 , 47.0 and 150.8 days). EQ was rapidly transformed to the short-lived quinone imine (QI) (major metabolite) and the more persistent 2,4-dimethyl-6-ethoxyquinoline (EQNL) (minor metabolite). EQ and OPP exerted significant inhibition of potential nitrification, with the effect of the former being more persistent. This was not reflected in the abundance (determined by quantitative PCR [qPCR]) of the amoA gene of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Considering the above discrepancy and the metabolic pattern of EQ, we further investigated the hypothesis that its metabolites and not only EQ were toxic to ammonia oxidizers. Potential nitrification, amoA gene abundance, and amoA gene transcripts of AOB and AOA showed that QI was probably responsible for the inhibition of nitrification. Our findings have serious ecological and practical implications for soil productivity and N conservation in agriculturally impacted ecosystems and stress the need to include metabolites and RNAbased methods when the soil microbial toxicity of pesticides is assessed. During postharvest handling, fruits are subjected to treatments with fungicides like thiabendazole (TBZ), imazalil (IMZ), and ortho-phenyl phenol (OPP) (1, 2) and antioxidants like diphenylamine (DPA) and ethoxyquin (EQ) (3), resulting in the production of large volumes of pesticide-contaminated wastewaters. The direct environmental discharge of those effluents without prior depuration entails a serious risk for the integrity of receiving ecosystems, considering the high aquatic toxicity of the pesticides (4, 5). This concern has been addressed by the European Commission (EC), and authorization for those pesticides was given with the stipulation "that an efficient treatment of the produced wastewaters should be operative at a local scale" (6, 7).Various processes and systems have been tested for the treatment of wastewaters produced by fruit-packaging plants (FPP) including adsorption onto activated carbon (8), photocatalytic degradation (9, 10), and biological degradation (11, 12). However, their high cost, their elevated technological requirements, and the frequent production of oxidized metabolites which are of unknown toxicity compared to the parent compound have hampered their full-scale implementation. Thus, to date effluents from FPP are either discharged in municipal wastewater treatment systems or they are disposed via land-spreading on the s...

To provide sufficient quantities of food and feed, farming systems have to overcome limiting factors such as the nutrient depletion of arable soils. Nitrogen being the main mineral element required for plant growth, has led to the extensive use of chemical fertilizers causing nitrogen pollution of the ecosystems. This field study investigates the use of biogas residues (BRs) as biofertilizers and their contribution to the mitigation of nitrate leaching in agricultural soils, while also demonstrating the polluting nature of chemical fertilizers. Nine different fertilization treatments classified in three schemes and two nitrogen doses were tested for three consecutive years on a grassland in the Walloon Region of Belgium. Residual soil mineral nitrogen, percentage contribution of treatments in residual nitrate and agronomic performance were assessed for each fertilization treatment. The results obtained showed significant differences on treatment and scheme level regarding nitrate accumulation in the soil, with chemical fertilizers posing the highest nitrate leaching risk. BRs did not cause nitrate accumulation in the soil, and were N rate and rainfall independent, while the chemical treatments indicated a cumulative tendency under high N rate and low precipitation. Forage yield did not demonstrate statistical differences on treatment and scheme level but varied with changing precipitation, while the maximum application rate suggested a

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