Fluoroquinolones in agricultural soils: Multi-temporal variation and risks in Rio de Janeiro upland region

Tetracycline and fluoroquinolone antibiotics contamination in agricultural soils fertilized long-term with chicken litter: Trends and ravages

We investigated the potential accumulation of tetracyclines (TCs) such as chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DC), and fluoroquinolones (FQs) like enrofloxacin (ENR) and ciprofloxacin (CIP) in chicken litter and agricultural soils fertilized over short-term to long-term (<1-30 yrs) with chicken litter in a poultry hub for the first time from Tamil Nadu, India. CTC, OTC, DC, CIP, and ENR were detected in 46-92 % of the selected chicken litter samples, with mean levels ranging from 2.90 to 23.30 μg kg-1. Higher concentrations of TCs and FQs were observed in freshly collected chicken litter from poultry sheds than in those stockpiled in cultivated lands. CTC was the prevalent antibiotic in chicken litter. The overall occurrence, as well as the ecological risks of TCs and FQs, changed over a 30-yr period. The accumulation of veterinary antibiotics (VAs) (in μg kg-1) in short-term (>1 yr) to medium-term (1-3 yrs) chicken litter-fertilized soils reached a maximum of 11.60 for CTC, 6.50 for OTC, 0.80 for DC, 3.70 for CIP, and 3.60 for ENR, but decreased in long-term (10-30 yrs) fertilized soils. Ecological risk assessment revealed a Risk Quotient (RQ) of ≤0.10 for CTC, OTC, and DC in all soils, while an average risk (RQ >0.10-<1.0) was evident with CIP and ENR in short-term and medium-term fertilized soils. Antibiotic resistance genes (ARGs), including tetA, tetB, qnrA, qnrB and qnrS were detected in most of the chicken litter samples and litter-fertilized soils. Thus, it is critical to develop and adopt effective mitigation strategies before applying chicken litter in farmlands to decrease VAs and ARGs, reducing their associated risks to public health and ecosystems in India considering 'One Health' approach. Future investigations on the occurrence of other VAs and ARGs in soils fertilized with poultry litter at regional scale are required for effective risk mitigation of the widely used VAs.

Poultry slaughterhouse wastewater as a source of bacterial antimicrobial resistance

Slaughterhouses produce huge volumes of effluents throughout the production chain that, when discharged untreated into bodies of water, can become a source of environmental contamination. This is particularly worrisome if these effluents are used for irrigation since they increase contamination levels and spread pathogens and resistance determinants to humans and animals. Therefore, in this study, we assessed antimicrobial resistance in bacteria isolated from inlet water, equalization wastewater tanks, treatment plant wastewater, and treated wastewater in slaughterhouse facilities in Rio de Janeiro, Brazil. Four samples were collected at each of the collection points, between June 2021 and July 2022. Following bacterial isolation and identification, the samples were analyzed for antimicrobial resistance using the disk diffusion method to test aminoglycoside, beta-lactam, and fluoroquinolone antimicrobials. A total of 229 bacteria were isolated, with 74 isolates selected from the genera Citrobacter (12), Enterobacter (14), Klebsiella (35), Serratia (5), and Pseudomonas (8). Inlet water had the lowest number of isolates and was the only point with gentamicin-resistant isolates. Raw effluent from the equalization tank showed the highest number of isolated bacteria and resistance levels, followed by treated wastewater and the treatment plant. Across all samples, a high rate of cefoxitin-resistance was observed among the isolated bacteria. Klebsiella pneumoniae stood out as the species that demonstrated the greatest resistance to a variety of antimicrobials. These results highlight the importance of water quality monitoring in mitigating public health and environmental risks and high antimicrobial resistance levels.

A Review on Fluoroquinolones' Toxicity to Freshwater Organisms and a Risk Assessment

Fluoroquinolones (FQs) have achieved significant success in both human and veterinary medicine. However, regulatory authorities have recommended limiting their use, firstly because they can have disabling side effects; secondly, because of the need to limit the spread of antibiotic resistance. This review addresses another concerning consequence of the excessive use of FQs: the freshwater environments contamination and the impact on non-target organisms. Here, an overview of the highest concentrations found in Europe, Asia, and the USA is provided, the sensitivity of various taxa is presented through a comparison of the lowest EC50s from about a hundred acute toxicity tests, and primary mechanisms of FQ toxicity are described. A risk assessment is conducted based on the estimation of the Predicted No Effect Concentration (PNEC). This is calculated traditionally and, in a more contemporary manner, by constructing a normalized Species Sensitivity Distribution curve. The lowest individual HC5 (6.52 µg L-1) was obtained for levofloxacin, followed by ciprofloxacin (7.51 µg L-1), sarafloxacin and clinafloxacin (12.23 µg L-1), and ofloxacin (17.12 µg L-1). By comparing the calculated PNEC with detected concentrations, it is evident that the risk cannot be denied: the potential impact of FQs on freshwater ecosystems is a further reason to minimize their use.

A landscape source-sink model to understanding the seasonal dynamics of antibiotics in soils at watershed scale

Human and veterinary antibiotics occur widely in soil ecosystems and pose a serious threat to soil health. Landscape structure can be linked to Earth surface processes and anthropogenic footprints and may influence the variability of antibiotics in soil. In this study, an improved landscape source-sink model was used to characterize source-sink structures using the location-weighted landscape index (LWLI), which can be linked to antibiotic seasonality. The topographic wetness index was employed to identify source and sink landscapes, which represent antibiotic transport pathways via topography-driven hydrological processes. The results indicate that LWLI values and antibiotic seasonality are typically higher in farmland soils than in forest and orchard soils. LWLI values exhibit significant positive correlations with antibiotic seasonality in soils (R2: 0.33-0.58). Furthermore, landscape source-sink structures have a significant influence on antibiotic seasonality between winter and other seasons in farmland soils; however, these structures affect antibiotic seasonality between summer and other seasons in forest and orchard soils. The results of this study indicate that water movement regulated by landscape structure may play a crucial role in influencing antibiotic seasonality in soils at the watershed scale, and the landscape source-sink model can be used to quantitatively evaluate antibiotic seasonality in soil environment.

Fate of fluoroquinolones in field soil environment after incorporation of poultry litter from a farm with enrofloxacin administration via drinking water

The practice of incorporating animal manure into soil is supported within the European Circular economy as a possible substitute for mineral fertilizers and will become crucial for the sustainability of agriculture. However, this practice may indirectly contribute to the dissemination of antibiotics, resistance bacteria, and resistance genes. In this study, medicated drinking water and poultry litter samples were obtained from a broiler-chick farm. The obtained poultry litter was incorporated into the soil at the experimental field site. The objectives of this research project were first to develop analytical methods able to quantify fluoroquinolones (FQs) in medicated drinking water, poultry litter, and soil samples by LC-MS; second to study the fate of these FQs in the soil environment after incorporation of poultry litter from flock medicated by enrofloxacin (ENR); and third to screen the occurrence of selected fluoroquinolone resistance encoding genes in poultry litter and soil samples (PCR analysis). FQs were quantified in the broiler farm's medicated drinking water (41.0 ± 0.3 mg∙L-1 of ENR) and poultry litter (up to 70 mg∙kg-1 of FQs). The persistence of FQs in the soil environment over 112 days was monitored and evaluated (ENR concentrations ranged from 36 μg∙kg-1 to 9 μg∙kg-1 after 100 days). The presence of resistance genes was confirmed in both poultry litter and soil samples, in agreement with the risk assessment for the selection of AMR in soil based on ENR concentrations. This work provides a new, comprehensive perspective on the entry and long-term fate of antimicrobials in the terrestrial environment and their consequences after the incorporation of poultry litter into agricultural fields.

Organic diffusive gradients in thin films (o-DGT) for determining environmental behaviors of antibiotics: A review

Antibiotics are recognized as effective medicine that has been extensively used in human and veterinary. Since the rate of releasing into the environment is stronger than the rate of elimination, antibiotics are regarded as persistent or "pseudo-persistent" organic compounds that result in the development of microbial antibiotic resistance. Therefore, assessment for their ecological risks to the environment are essential. Diffusive gradients in thin films for organic compounds (o-DGT) have been adapted to investigate the environmental behaviors of antibiotics. Currently, more than 20 compounds have been tested by o-DGT in waters and soil environments. In this review, we explained the theoretical reason that o-DGT is feasible to determine the labile fraction of antibiotics in different environmental media. The most used agarose diffusive gel, and various binding agents such as resin, porous carbon and nano-scale materials have been compared to optimize the sampling of antibiotics by o-DGT. Results of deploying o-DGT devices in waters and soils from previous studies were discussed to understand the bioavailability and dynamic transport of antibiotics. Also, we provided the feasibility analysis of using o-DGT in sediments for antibiotics measurements, which is required to be carried out in future studies. To have a deep view on the development of o-DGT, its technical limitations and viable improvements were summarized in this study for further applications on antibiotics research.

Insights into the driving factors of vertical distribution of antibiotic resistance genes in long-term fertilized soils

The prevalence of antibiotic resistance genes (ARGs) in soils has aroused wide attention. However, the influence of long-term fertilization on the distribution of ARGs in different soil layers and its dominant drivers remain largely unknown. In this study, a total of 203 ARGs were analyzed in greenhouse vegetable soils (0-100 cm from a 13-year field experiment applied with different fertilizers (control, chemical fertilizer, organic manure, and mixed fertilizer). Compared with unfertilized and chemically fertilized soils, manure application significantly increased the abundance and alpha diversity of soil ARGs, where the assembly of ARG communities was strongly driven by stochastic processes. The distribution of ARGs was significantly driven by manure application within 60 cm, while it was insignificantly changed in soil below 60 cm under different fertilization regimes. The inter-correlations of ARGs with mobile genetic elements (MGEs) and microbiota were strengthened in manured soil, indicating manure application posed a higher risk for ARGs diffusion in subsurface soil. Bacteria abundance and MGEs directly influenced ARG abundance and composition, whereas soil depth and manure application indirectly influenced ARG abundance and composition by affecting antibiotics. These results strengthen our understanding of the long-term anthropogenic influence on the vertical distribution of soil ARGs and highlight the ecological risk of ARGs in subsurface soil induced by long-term manure application.

Urbanization-land-use interactions predict antibiotic contamination in soil across urban-rural gradients

Antibiotics ubiquitously occur in soils and pose a potential threat to ecosystem health. Concurrently, urbanization and land-use intensification have transformed soil ecosystems, but how they affect antibiotic contamination remain largely unknown. Therefore, we profiled a broad-scale pattern of antibiotics in soil from agricultural lands and green spaces across urbanization gradients, and explored the hypothetical models to verify the effects of urbanization and land-use intensity on antibiotic contamination. The results showed that antibiotic concentrations and seasonality were higher in agricultural soil than in green spaces, which respectively showed linear or hump-shaped declines along with the increasing distance to urban centers. However, the response of antibiotic pollution to land-use intensity depended strongly on the urbanization level. More importantly, interactions between urbanization and land-use explained, on average, 59.6 % of the variation in antibiotic concentrations in soil across urbanization gradients. The proposed interactions can predict the non-linear changes in soil vulnerability to antibiotic contamination. Our study revealed that the urbanization can modulate the effects of land-use intensity on antibiotic concentration and seasonality in the soil environment, and that there is high stress on peri-urban soil ecosystems due to ongoing land-use changes arising from rapid urbanization processes.

Poultry manure gleaned antibiotic residues in soil environment: A perspective of spatial variability and influencing factors

The antibiotics released by human and animals end up in the environmental sinks like soil and water to cause contamination and induce resistance in the microflora. The knowledge of fate and behavior of antibiotics in diverse geographical, climatological, and physicochemical is limited. Therefore, present study investigated the spatial distribution of antibiotics and their relationship with various factors and the source-sink relationship between soil and poultry manure. This was achieved by employing spatially constrained hierarchical clustering, global and local spatial autocorrelation, and spatial regression techniques. Most of the antibiotics co-occurred in both soil and poultry manure matrices, however antibiotic concentration in soil (1.20 μg kg^-1 < antibiotics ≤21.38 μg kg^-1) was lower than that in the poultry manure (7.05 μg kg^-1< antibiotics ≤60.2 μg kg^-1). Majority of the antibiotics showed spatial independence in both poultry manure and soil, except for sulfadiazine, sulfanilamide and sulfapyridine with Moran's I > - 0.111. Local indicator of spatial association indicated localized spatial clustering and outlier behavior of antibiotics. The underlying reasons for spatial heterogeneity of antibiotics resolved by spatial regression models indicated elevation, S%, C%, pH and mean annual temperature as the major factors. The influence of antibiotic concentration in poultry manure as a source was significant but marginal compared to the other predictors of spatial heterogeneity.

Intensive poultry farming: A review of the impact on the environment and human health

Poultry farming is one of the most efficient animal husbandry methods and it provides nutritional security to a significant number of the world population. Using modern intensive farming techniques, global production has reached 133.4 mil. t in 2020, with a steady growth each year. Such intensive growth methods however lead to a significant environmental footprint. Waste materials such as poultry litter and manure can pose a serious threat to environmental and human health, and need to be managed properly. Poultry production and waste by-products are linked to NH₃, N₂O and CH₄ emissions, and have an impact on global greenhouse gas emissions, as well as animal and human health. Litter and manure can contain pesticide residues, microorganisms, pathogens, pharmaceuticals (antibiotics), hormones, metals, macronutrients (at improper ratios) and other pollutants which can lead to air, soil and water contamination as well as formation of antimicrobial/multidrug resistant strains of pathogens. Dust emitted from intensive poultry production operations contains feather and skin fragments, faeces, feed particles, microorganisms and other pollutants, which can adversely impact poultry health as well as the health of farm workers and nearby inhabitants. Fastidious odours are another problem that can have an adverse impact on health and quality of life of workers and surrounding population. This study discusses the current knowledge on the impact of intensive poultry farming on environmental and human health, as well as taking a look at solutions for a sustainable future.

Irrigation Ponds as Sources of Antimicrobial-Resistant Bacteria in Agricultural Areas with Intensive Use of Poultry Litter

Poultry litter is widely used worldwide as an organic fertilizer in agriculture. However, poultry litter may contain high concentrations of antibiotics and/or antimicrobial-resistant bacteria (ARB), which can be mobilized through soil erosion to water bodies, contributing to the spread of antimicrobial resistance genes (ARGs) in the environment. To better comprehend this kind of mobilization, the bacterial communities of four ponds used for irrigation in agricultural and poultry production areas were determined in two periods of the year: at the beginning (low volume of rainfall) and at the end of the rainy season (high volume of rainfall). 16S rRNA gene sequencing revealed not only significantly different bacterial community structures and compositions among the four ponds but also between the samplings. When the DNA obtained from the water samples was PCR amplified using primers for ARGs, those encoding integrases (intI1) and resistance to sulfonamides (sul1 and sul2) and β-lactams (blaGES, blaTEM and blaSHV) were detected in three ponds. Moreover, bacterial strains were isolated from CHROMagar plates supplemented with sulfamethoxazole, ceftriaxone or ciprofloxacin and identified as belonging to clinically important Enterobacteriaceae. The results presented here indicate a potential risk of spreading ARB through water resources in agricultural areas with extensive fertilization with poultry litter.

Plants Mitigate Nitrous Oxide Emissions from Antibiotic-Contaminated Agricultural Soils

Vegetable production systems are hotspots of nitrous oxide (N₂O) emissions and antibiotic pollution. However, little is known about the interconnections among N₂O emissions, vegetable growth, and antibiotic contamination. To understand how plants regulate N₂O emissions from enrofloxacin (ENR)-contaminated soils, in situ N₂O emissions were measured in pot experiments with cherry radish and pakchoi. Gross N₂O production and consumption processes were discriminated based on an acetylene inhibition experiment. Results indicated that vegetable growth decreased the cumulative N₂O flux from 0.71 to -0.29 kg ha^-1 and mitigated the ENR-induced increase in N₂O emissions. Radish displayed better mitigation of N₂O emissions than pakchoi. By combining the analysis of N₂O flux with soil physicochemical and microbiological properties, we demonstrated that growing vegetables could either promote gross N₂O consumption or decrease gross N₂O production, primarily by interacting with soil nitrate, clade II nosZ (nosZII)-carrying bacteria, and Deinococcus-Thermus. ENR inhibited N₂O consumption more than N₂O production, with the nosZII-carrying bacteria, represented by Gemmatimonadetes, as the main inhibition target. However, increasing nosZII-carrying bacteria by growing radish offsets the inhibitory effect of ENR. These findings provide new insights into N₂O emissions and antibiotic pollution in vegetable-soil ecosystems and broaden the options for mitigating N₂O emissions.

Antioxidant system alterations and biological health status of earthworms following long-term exposure to antibiotic-contaminated poultry litter

Poultry litter is widely applied as a fertilizer even though it is one of the main antibiotic sources to agricultural soils. Long-term sublethal effects (56 days) on the antioxidant system of Eisenia andrei earthworms following exposure to fluoroquinolone-contaminated poultry litter (enrofloxacin + ciprofloxacin) at 5.0, 10, and 20 g kg^-1 were evaluated. The following biomarkers were assessed: superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), reduced glutathione (GSH), and a lipid peroxidation (LPO) proxy. Significant CAT and SOD increases, and a moderate positive correlation (ρ = 0.67, p < 0.05) between these enzymes was observed. Glutathione-S-transferase levels increased significantly at 10 g kg^-1, while GSH exhibited a dose-dependent response at 5.0 mg kg^-1 (4-106%), 10 mg kg^-1 (28-330 %), and 20 mg kg^-1 (45-472%). LPO levels exhibited a decreasing trend with increasing poultry litter concentrations of 8-170% (5.0 g kg^-1), 7-104% (10 mg kg^-1), and 3-6% (20 mg kg^-1). A principal component analysis (PCA) highlighted increased SOD and CAT activities, possibly due to increased reactive oxygen species (ROS) concentrations. Biological health status assessments based on the biomarker response index indicate major alterations in the first month of exposure and becoming moderate in the second month. These findings indicate an antioxidant system attenuation trend. It is possible, however, that successive poultry litter applications may reduce the long-term recovery capacity of the evaluated biomarkers.

Occurrence and removal of 25 antibiotics during sewage treatment processes and potential risk analysis

The occurrence and removal of 25 antibiotics, including ten quinolones (QNs), four macrolides (MLs), four tetracyclines (TCs) and seven sulfonamides (SNs), were analysed at two sewage treatment plants (STPs) with different treatment units in Guangxi Province, China. The results showed that 14 and 16 antibiotics were detected in the influent of the two STPs, with concentrations ranging from 13.7-4265.2 ng/L and 14.5-10761.7 ng/L, respectively. Among the antibiotics, TCs were the main type in the study area, accounting for more than 79% of the total concentration of all antibiotics. The antibiotic removal efficiencies of the different process units ranged from -56.73% to 100.0%. It was found that the SN removal efficiency of the multistage composite mobile bed membrane bioreactor (MBBR) process was better than that of the continuous-flow Intermission biological reactor (IBR) process, while the IBR process was better than the MBBR process in terms of removing TCs and MLs; however, there was no obvious difference in the QN removal efficiencies of these two processes. Redundancy analysis (RDA) showed a strong correlation between antibiotic concentration and chemical oxygen demand (COD). Risk assessments indicated that algae, followed by invertebrates and fish, were the most sensitive aquatic organisms to the detected antibiotics.

Soil type shapes the antibiotic resistome profiles of long-term manured soil

Animal manure fertilization facilitates the proliferation and dissemination of antibiotic resistance genes (ARGs) in soil, posing high risks to humans and ecosystem health. Although studies suggest that soil types could shape the ARG profiles in greenhouse soil, there is still a lack of comparative studies on the fate of ARGs in different types of manured soils under field trials. Thus, a metagenomic approach was used to decipher the fate of ARGs in 12-year long-term fertilized (inorganic fertilizer, compost manure and a mix of them) acidic, near-neutral and alkaline soils. A total of 408 unique ARG subtypes with multidrug, glycopeptide, beta-lactam and aminoglycoside resistance genes were identified as the most universal ARG types in all soil samples. Genes conferred to beta-lactam was the predominant ARG type in all the manure-amended soils. Genomic and statistical analyses showed that manure application caused the enrichment of 98 and 91 ARG subtypes in acidic and near-neutral soils, respectively, and 8 ARG subtypes in alkaline soil. The abundances of Proteobacteria (acidic and near-neutral soils) and Actinobacteria (alkaline soil), which are the potential hosts of ARGs, were clearly increased in manured soils. Random forest modelling and Pearson correlation analysis revealed that the soil properties (pH and bio-available Zn) and mobile genetic elements had considerable impacts on the transmission of ARGs. A structural equation model further indicated that soil types shaped the ARG profiles by significantly (P < 0.01) influencing the soil properties, bacterial abundance and bacterial diversity, where bacterial abundance was the major factor influencing the ARG profiles. This study systematically explored the mechanisms shaping the ARG profiles of long-term manured soils, and this information could support strategies to manage the dissemination of ARGs in different soil types.

Crop irrigation (soybean, bean, and corn) with enrofloxacin-contaminated water leads to yield reductions and antibiotic accumulation

The increasing use of antibiotics in animal production has become an emergent environmental problem. The large percentages of applied antibiotic doses eliminated in animal excrement often end up contaminating water resources, which are then used for irrigation - compromising agricultural production and/or food security. Here, we evaluated the effects of crop irrigation with water artificially contaminated by enrofloxacin (10 μg l-1) and its accumulation in soybean, bean, and corn tissues. Grain production was evaluated on the basis of grain dry weight plant-1, while enrofloxacin and ciprofloxacin (its breakdown metabolite) concentrations in plant tissues were evaluated by HPLC after harvesting. Diminished production was observed only in soybean plants irrigated with antibiotic-contaminated water. Enrofloxacin [1.68 ng g fresh weight (FW)-1 to 26.17 µg g FW-1] and ciprofloxacin (8.23 ng g FW-1 to 51.05 ng g FW-1), were found in all of the plant tissues (roots, leaves, and seeds) of the three species. Regardless of the species, the highest enrofloxacin concentrations were observed in their roots, followed by the leaves and seeds, while ciprofloxacin concentrations varied among the different plant tissues of the different species. The presence of enrofloxacin in the water used for irrigating soybeans can result in productivity losses and, as that antibiotic was encountered in plant tissues (leaves and seeds) of all of the three species analyzed that are consumed in the diets of both humans and animals, it can interfere with food security.

Bacterial diversity changes in agricultural soils influenced by poultry litter fertilization

Poultry litter is widely applied as agricultural fertilizer and can affect the soil microbiome through nutrient overload and antibiotic contamination. In this study, we assessed changes in soil bacterial diversity using high-throughput sequencing approaches. Four samples in triplicate were studied: soils with short- and long-term fertilization by poultry litter (S1 = 10 months and S2 = 30 years, respectively), a soil inside a poultry shed (S3), and a forest soil used as control (S0). Samples S0, S1, and S2 revealed a relatively high richness, with confirmed operational taxonomic units (OTUs) in the three replicates of each sample ranging from 1243 to 1279, while richness in S3 was about three times lower (466). The most abundant phyla were Proteobacteria, Bacteroidetes, and Actinobacteria. Acidobacteria, Planctomycetes, and Verrucomicrobia were also abundant but highly diminished in S3, while Firmicutes was less abundant in S0. Changes in bacterial communities were very evident at the genera level. The genera Gaiella, Rhodoplanes, Solirubacter, and Sphingomonas were predominant in S0 but strongly decreased in the other soils. Pedobacter and Devosia were the most abundant in S1 and were diminished in S2, while Herbiconiux, Brevundimonas, Proteiniphilum, and Petrimonas were abundant in S2. The most abundant genera in S3 were Deinococcus, Truepera, Rhodanobacter, and Castellaniella. A predictive analysis of the metabolic functions with Tax4Fun2 software suggested the potential presence of enzymes associated with antibiotic resistance as well as with denitrification pathways, indicating that the S3 soil is a potential source of nitrous oxide, a powerful greenhouse gas.

Fluoroquinolone-contaminated poultry litter strongly affects earthworms as verified through lethal and sub-lethal evaluations

Poultry litter is one of the main sources of fluoroquinolones (FQs) in agricultural soils. In this study, our main goal was to investigate FQ-contaminated poultry litter effects on Eisenia andrei earthworms. To achieve this, acute and chronic tests covered several endpoints, such as avoidance, biomass, lethality, reproduction and changes to immune cells. FQs (enrofloxacin and ciprofloxacin) were determined in a poultry litter sample through high performance liquid chromatography with a fluorescence detector. The avoidance test indicates that poultry litter strongly repels earthworms, even at the lowest concentration (50 g kg^-1). In the acute test, the lethal concentration of poultry litter to 50% of the earthworms (LC₅₀), was estimated at 28.5 g kg^-1 and a significant biomass loss (p < 0.05) occurred at 40 g kg^-1. In the chronic test, a significant reproduction effect was observed at 20 g kg^-1. Cell typing, density and feasibility indicated significant effects ranging from 5 to 20 g kg^-1. A high risk quotient was estimated based on recommended poultry litter applications in field studies. Although FQ contamination in poultry litter and soils has been widely reported in previous studies, this is, to the best of our knowledge, the first toxicological assessment concerning earthworms exposed to FQ-contaminated poultry litter.

Fluoroquinolones and trace elements in poultry litter: estimation of environmental load based on nitrogen requirement for crops

Poultry litter soil application contributes to sustainability of agricultural systems and is in accordance with the United Nations Sustainable Development Goals (UN-SDG). Poultry litter recommended rates are based on crop nitrogen (N) needs, however, their application can be a potential source of antibiotics and trace elements overload. The aim of the study was to estimate the role of poultry litter application on soil contamination by fluoroquinolones [enrofloxacin (ENR) and ciprofloxacin (CIP)] and trace elements, based on N requirements for crops. Analytical and sampling techniques were used to estimate the loads from poultry litter application. Only CIP was found in poultry litter samples (283 ± 124 µg kg^-1) and its load was estimated to be of 9.89 ± 4.33 g ha^-1, for the poultry litter application (35 t ha^-1). The estimated loads (g ha^-1) of trace elements were: Cr 9.19 ± 3.26, Ni 12.3 ± 4.93, Pb 22.0 ± 8.26, Cu 229 ± 85.6, Mn 691 ± 259 and Zn 1,011 ± 378. These estimates were 900% higher than those recommended by the technical guidance, while N exceeded 600% the recommended application. In order to achieve UN-SDGs, local policies to disseminate knowledge and technologies are required for consolidating sustainable agricultural practices.

Multimedia mass balance approach to characterizing the transport potential of antibiotics in soil-plant systems following manure application

Antibiotics are ubiquitous in agro-ecosystems worldwide, which can pose remarkable risks to ecological security and human health. However, comprehensive evaluation on the multimedia fate and transport potential of antibiotics in soil-plant systems is still lacking. A mass balance approach was performed to gain insights into the transport and fate of antibiotics in soil-plant systems following manure application. Our results showed that more than 99 % of antibiotics were released from applied manure fertilizer into the soil-plant system. Antibiotic concentrations in soil and plant compartments increased over 120 days. Most of the antibiotics persisted in soil (about 65 %), while less than 0.1 % accumulated in the plants. Rainfall-induced runoff, subsurface interflow and soil water infiltration were alternative transport pathways for antibiotics in soil-plant systems although their contributions were limited. Dissipation was the main removal pathway for antibiotics accounting for about 33 % of total input mass. Tetracyclines had higher mass proportion in soil following by quinolones, whereas most of sulfonamides and macrolides were dissipated. Mass balance approach based on tracking environmental fates of antibiotics can facilitate the understandings in the source comparisons and mitigation strategies, and therefore provide insights to inform modeling and limiting the transport of manure-borne antibiotics to neighboring environmental compartments.

Effects of land use and rainfall on sequestration of veterinary antibiotics in soils at the hillslope scale

Veterinary antibiotics have been detected as contaminants of emerging concern in soil environment worldwide. Animal manure is frequently applied to agricultural fields to improve soil fertility, which can result in introducing large amount of antibiotics into soil environment. However, few attempts have been made to identify the spatial and temporal dynamics of veterinary antibiotics in soil at the hillslope scale with different land uses. This study was performed to explore the pattern and variability of veterinary antibiotics in the soil in response to rainfall events. Results showed that higher concentrations of veterinary antibiotics were generally found in cropland (292.6 ± 280.1 ng/g) and orchard (228.1 ± 230.5 ng/g) than in forestland (13.5 ± 9.9 ng/g). After rainfall events, antibiotics accumulated in the soil at the positions where manure was applied, especially under high-intensity rainfall conditions. However, the antibiotic concentration in soil slightly increased from the top to the bottom of hills, thus indicating the restricted contribution of runoff to antibiotic transport, especially under low-intensity rainfall conditions. In addition, most antibiotics were sequestered in the surface soil (0-10 cm), and higher antibiotic concentrations were observed in deep soil (20-40 cm) in cropland than orchard. The soil aggregate, organic matter, and clay content played important roles in antibiotic sequestration along the hillslope subject to low-, medium-, and large-amount rainfall events, respectively. This study identified that land use, rainfall conditions, and soil structures jointly affect the spatial and temporal variability of antibiotics in soils on hillslopes.

An innovative modeling approach of linking land use patterns with soil antibiotic contamination in peri-urban areas

Due to the intensive use and continuous release, high and persistent concentrations of antibiotics are found in soils worldwide. This severe contamination elevates the risks associated with antibiotic exposure and resistance for soil ecosystems and human health. Estimating antibiotic concentrations in soils is a complex and important challenge because the limited information is available on antibiotic use and emission and the high exposure risk to human health occurred in peri-urban areas. In this study, soil antibiotic contamination was linked with land use patterns in a data-scarce peri-urban area in four different seasons, and we established a modeling framework based on land use to estimate spatially explicit distribution of antibiotics in soils. The soil antibiotic concentration was found to be substantially affected by surrounding land use patterns in buffer zones with a radius of 350 m. Agricultural land was the main source of antibiotics entering the soil. Notably, road networks also had considerable impacts on antibiotic residues in soils. Then, a statistical model was developed in describing the linkage between land use patterns and soil antibiotic concentration. Model evaluation suggested that the proposed model successfully simulated the variation of antibiotics in soil with good statistical performance (R² > 0.7). Finally, the model was extrapolated to investigate detailed distribution of antibiotics in soils. Clear spatial and seasonal dynamics can be found in soil antibiotic concentration. To our knowledge, this was the first attempt to adopt a model focusing on land use pattern to estimate the spatially explicit distribution of antibiotics in soils. Despite of some uncertainties, the research provides a land-use-based modeling approach as a reference for preventing and controlling soil antibiotic contamination in the future.

Current progress in the adsorption, transport and biodegradation of antibiotics in soil

Antibiotic residues in soil may cause potential risks to human health and soil ecosystems. To avoid these potential risks, comprehensive study of the adsorption, transport and biodegradation of antibiotics in soil is very imperative. This review provided current views about the most recent studies, which have been conducted toward the adsorption, transport and biodegradation of antibiotics in soil. The influencing factors affecting the adsorption behaviors of antibiotics in soil, including the antibiotics properties (e.g., molecular structure, hydrophobicity, polarity, polarizability, and spatial configuration) and the soil characteristics (e.g., soil type, soil pH, coexisting ions, and soil organic matter), were discussed. The effects of fertilizer colloids, porous media, and pH of soil on the transport behaviors of antibiotics were analyzed. The biodegradation of antibiotics in soil were also highlighted by investigating the effects of soil microbiome, soil pH, soil temperature, and interactions between antibiotics. Prospects of antibiotics adsorption, transport and biodegradation were also proposed.