The relationship between antimicrobial residues, antibiotic resistance prevalence and bacterial community composition in hospital effluent and in the receiving wastewater treatment plant was studied. Samples from hospital effluent, raw inflow and final effluent of the receiving wastewater treatment plant were characterized for amoxicillin and ciprofloxacin resistance prevalence, content of heavy metals and antimicrobial residues and bacterial community
A previously developed potential cleanup tool for atrazine contaminated soils was evaluated in larger open soil microcosms for optimization under more realistic conditions, using a natural crop soil spiked with an atrazine commercial formulation (Atrazerba FL). The doses used were 20x or 200x higher than the recommended dose (RD) for an agricultural application, mimicking over-use or spill situations. Pseudomonas sp. strain ADP was used for bioaugmentation (around 10(7) or 10(8) viable cells g(-1) of soil) and citrate for biostimulation (up to 4.8 mg g(-1) of soil). Bioremediation treatments providing fastest and higher atrazine biodegradation proved to differ according to the initial level of soil contamination. For 20x RD of Atrazerba FL, a unique inoculation with Pseudomonas sp. ADP (9 +/- 1 x 10(7) CFU g(-1)) resulted in rapid atrazine removal (99% of the initial 7.2 +/- 1.6 microg g(-1) after 8d), independent of citrate. For 200x RD, an inoculation with the atrazine-degrading bacteria (8.5 +/- 0.5 x 10(7) CFU g(-1)) supplemented with citrate amendment (2.4 mg g(-1)) resulted in improved biodegradation (87%) compared with bioaugmentation alone (79%), even though 7.8 +/- 2.1 microg of atrazine g(-1) still remained in the soil after 1 wk. However, the same amount of inoculum, distributed over three successive inoculations and combined with citrate, increased Pseudomonas sp. ADP survival and atrazine biodegradation (to 98%, in 1 wk). We suggest that this bioremediation tool may be valuable for efficient removal of atrazine from contaminated field soils thus minimizing atrazine and its chlorinated derivatives from reaching water compartments.
Purpose To mitigate the environmental effects of atrazine, one of the cleanup strategies available is based on the use of atrazine-degrading bacteria. This work aimed to evaluate the efficacy of a previously developed bioremediation tool for atrazine-contaminated soils (combining bioaugmentation with Pseudomonas sp. ADP, hereafter designated as P. ADP, and biostimulation with citrate) on both soil habitat and retention functions, by performing ecotoxicological tests with standard soil and aquatic species. Materials and methods Soil microcosms (incorporating earthworms, collembolans, and plants) were spiked with three doses of Atrazerba FL, an atrazine commercial formulation: the recommended dose (RD; 2 L/ha), 10×RD and 20×RD to simulate overuse/accidental spills scenarios. The experiment included two main groups of treatments:(1) microcosms sprayed solely with Atrazerba, i.e., nonbioremediated soils (NB) and (2) microcosms sprayed with both Atrazerba and the bioremediation tool (addition of P. ADP plus citrate), i.e., bioremediated soils (B). Control microcosms with no herbicide or P. ADP plus citrate addition were also set up. Besides soil chemical analysis, the following ecotoxicological endpoints were assessed to monitor bioremediation: plant biomass production, earthworm reproduction, microalgae growth (in eluatescollected 5 and 10 days after the bioremediation treatmentand leachates-collected on day seven), and cladoceran reproduction (in soil eluates). Results In NB soils, all Atrazerba doses induced a severe reduction in plant biomass production, and no effects were found for earthworm's reproduction. Eluates and leachates obtained from the NB soils caused deleterious effects on both microalgae growth and cladoceran reproduction. Chemical analysis showed that atrazine degradation was faster in B soils than in the correspondent NB soils. Data from toxicity tests indicated that test organism performance was enhanced in B soils and respective eluates and leachates, compared to the NB samples. In fact, for soils contaminated with 10 and 20×RD Atrazerba doses, plant biomass production was significantly higher in the B soils than in the correspondent NB soils. Regarding the effects of soil bioremediation on the toxicity of soil eluates and leachates, for the soil contaminated with 10 ×RD of Atrazerba, over a 5-day treatment period, both microalgae growth and cladoceran reproduction were significantly higher in water extracts obtained from the B soils when compared with the NB extracts and also similar to the control. By the contrary, for the highest Atrazerba dose tested (20×RD), no significant differences were found on the toxicity of B and NB eluates toward both aquatic test organisms. However, for this same dose, after 7 days, microalgae growth was higher in B than in the NB leachates and similar to the control. Yet, after a longer bioremediation period of 10 days, eluates were also no longer toxic to both aquatic organisms. Discussion Based on atrazine soil chemical analysis, one can state that the addition ...
Atrazine (ATZ) and S-metolachlor (S-MET) are two herbicides widely used, often as mixtures. The present work examined whether the presence of S-MET affects the ATZ-biodegradation activity of the bioaugmentation bacterium Pseudomonas sp. strain ADP in a crop soil. S-MET concentrations were selected for their relevance in worst-case scenarios of soil contamination by a commercial formulation containing both herbicides. At concentrations representative of application of high doses of the formulation (up to 50 µg g−1 of soil, corresponding to a dose approximately 50× higher than the recommended field dose (RD)), the presence of pure S-MET significantly affected neither bacteria survival (∼107 initial viable cells g−1 of soil) nor its ATZ-mineralization activity. Consistently, biodegradation experiments, in larger soil microcosms spiked with 20× or 50×RD of the double formulation and inoculated with the bacterium, revealed ATZ to be rapidly (in up to 5 days) and extensively (>96%) removed from the soil. During the 5 days, concentration of S-MET decreased moderately to about 60% of the initial, both in inoculated and non-inoculated microcosms. Concomitantly, an accumulation of the two metabolites S-MET ethanesulfonic acid and S-MET oxanilic acid was found. Despite the dissipation of almost all the ATZ from the treated soils, the respective eluates were still highly toxic to an aquatic microalgae species, being as toxic as those from the untreated soil. We suggest that this high toxicity may be due to the S-MET and/or its metabolites remaining in the soil.
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