Uncertainty-based concentration estimation of chlortetracycline antibiotics in swine farms and risk probability assessment for agricultural application of manure

Construction of nitrogen-doped carbon dots-based fluorescence probe for rapid, efficient and sensitive detection of chlortetracycline

Antibiotics are widely used in clinical medicine due to their excellent antibacterial abilities. As typical emerging pollutants, their misuse can lead to excess antibiotics entering the environment, causing antimicrobial resistance and leading to serious health problems via food chain. Herein, a nano-fluorescent probe based on nitrogen-doped carbon dots (N-CDs) was constructed for the sensitive detection of chlortetracycline (CTC). N-CDs with stable fluorescence were synthesized by hydrothermal method using alizarin red and melamine as raw materials. The N-CDs exhibited significant independence to excitation wavelength. The fluorescence of N-CDs was significantly quenched by CTC ascribing to the fluorescence resonance energy transfer mechanism. The concentration of N-CDs, solution pH and incubation time were optimized to obtain the optimal detection parameters. Under optimal conditions, CTC exhibited excellent linearity over the range of 20-1200 μg/L, and the detection limit was 8.74 μg/L. The method was validated with actual water samples and achieved satisfied spiked recoveries of 97.6-102.6%. Therefore, the proposed method has significant application value in the detection of CTC in waters.

Evaluating antibiotic occurrence, degradation, and environmental risks in poultry litter within Argentina's agricultural hub

This study explores the relationship between poultry farming's antibiotic administration practices and residual antibiotic levels in the litter before its application onto agricultural soils. Twenty-three antibiotics were performed across 19 Argentinean farms representing diverse antibiotic management practices. Analysis revealed up to 20 antibiotics from eight chemical classes in poultry litter samples, with tylosin, enrofloxacin, and salinomycin being the most relevant drugs. Farms with restricted antibiotic use in feed exhibited lower residual concentrations. A self-heating treatment was tested to reduce litter antibiotic levels. Although a 60 % reduction of antibiotics was found after treatment, prevalent compounds persisted at residual levels. Regulatory measures and comprehensive litter treatments pre-application are crucial to mitigate environmental risks. This is the first study that provides insight on the occurrence of >20 drugs in real poultry production scenarios from Latin America and demonstrates how relatively simple treatments can be readily applied to decrease the associated environmental risks.

Reducing risks of antibiotics to crop production requires land system intensification within thresholds

Land system intensification has substantially enhanced crop production; however, it has also created soil antibiotic pollution, undermining crop production. Here, we projected soil antibiotic pollution risks to crop production at multiple geographical scales in China and linked them to land system intensification (including arable land expansion and input increase). Our projections suggest that crop production will substantially decrease when the soil antibiotic pollution risk quotient exceeds 8.30-9.98. Land systems explain most of the variability in antibiotic pollution risks (21-66%) across spatial scales. The convex nonlinearities in tradeoffs between antibiotic pollution risk and crop production indicate that vegetable and wheat production have higher thresholds of land system intensification at which the risk-yield tradeoffs will peak than do maize and rice production. Our study suggests that land system intensification below the minimum thresholds at multiple scales is required for acceptable antibiotic pollution risks related to crop yield reduction.

Comparison of bacterial and fungal communities structure and dynamics during chicken manure and pig manure composting

Composting is a sustainable and eco-friendly technology that turns animal waste into organic fertilizers. It remains unclear whether differences exist in the structure of microbial communities during different livestock manure composting. This study analyzed the dynamic change of bacterial and fungal communities, metabolic function, and trophic mode during chicken manure (CM) and pig manure (PM) composting based on 16S rRNA and ITS sequencing. Environmental factors were investigated for their impact on microbial communities. During composting, bacterial diversity decreased and then increased, while fungal diversity slightly increased and then decreased. Saccharomonospora and Aspergillus were the dominant genera and key microorganisms in CM and PM, respectively, which played crucial roles in sustaining the stability of the ecological network structure in the microbial ecology and participating in metabolism. Saccharomonospora gradually increased, while Aspergillus increased at first and then decreased. PM had better microbial community stability and more keystone taxa than CM. In CM and PM, the primary function of bacterial communities was metabolism, while saprotroph was the primary trophic mode of fungal communities. Dissolved organic carbon (DOC) was the primary factor influencing the structure and function of microbial communities in CM and PM. In addition to DOC, pH and moisture were important factors affecting the fungal communities in CM and PM, respectively. These results show that the succession of bacteria and fungi in CM and PM proceeded in a similar pattern, but there are still some differences in the dominant genus and their responses to environmental factors.

Potential output and risk of commonly administered veterinary antibiotics from small-scale livestock farms to surrounding areas in Northwest China

The concern over antibiotic pollution from animal husbandry has significantly increased over recent years. However, few studies on output and environmental risk of veterinary antibiotics (VAs) throughout different exposure matrices from small-scale livestock farms (SSLFs) have been explored. This study explored the output and environmental risk of three classes of VAs (sulfonamides (SAs), tetracyclines (TCs), fluoroquinolones (FQs)) in three different types of environmental media (manure, soil, and plants/vegetables) derived from four livestock feedlots in the Hexi Corridor of Northwest China. Following, a risk assessment was conducted to identify the hazardous potential of these VAs on the ecological health of the surrounding environment. A total of 108 soil, 36 manure, 12 plants/vegetables, and 15 animal product samples were collected from the animal feedlots for analysis. The results showed that each of the three groups of VAs were detected in the soil, manure and plant samples derived from all four feedlots in varying levels. In the soil samples, the detection rate of SAs (68%) was higher than the TCs (57%) and the FQs (27%). The total concentration of VAs ranged from not detected (n.d.) to 275 ng/g, while chlortetracycline (CTC) was the most abundant (275 ng/g) of the VAs in soil samples. The SAs had the highest detection rate (100%), followed by TCs (89%), and FQs (78%) in manure samples. The total concentration of VAs residues ranged from n. d. to 105 ng/g, of which CTC was as high as 91 ng/g in manures. In the plant/vegetable samples, the TCs had the highest detection rate (58%), while sulfamethazine (SDM) was the most abundant (32 ng/g). The total concentration of the VAs ranged from n. d. to 65 ng/g in the plant/vegetable samples. The target VAs were not detected in animal products. Measurements of the composition of VAs in soil samples at different vertical depths as well as horizontal distances from the manure accumulation sites showed that VAs were partially retained in the soil of the feedlots and were distributed into the surrounding environment both horizontally and vertically. It is suspected that the detected VAs could be accumulated in agricultural soils since they could be found in most of the sampled manures and soils in SSLFs. These results highlighted the necessity of considering SSLF practices to mange the accumulation and disposal of manure mitigating and controlling VA pollution.

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.

Long-term inhibition of chlortetracycline antibiotics on anaerobic digestion of swine manure

This study aimed to identify whether chronic effects are present in the anaerobic digestion (AD) of swine manure (SM) containing chlortetracycline (CTC), which is one of the major broad-spectrum veterinary antibiotics, and to elucidate the long-term inhibitory effects and recovery from the inhibition based on AD performance and microbial community. Two continuous-stirred tank reactors treating SM with and without CTC spiking (3 mg/L) were operated for 900 days. Due to the degradation and transformation, the total concentration including CTC's epimer and isomer in the test reactor was 1.5 mg/L. The exposure level was determined according to probabilistically estimated concentrations with uncertainties in field conditions. Until the cessation of CTC exposure on day 585, the methane generation of test reactor continuously decreased to 55 ± 17 mL/g-VS/day, 53% that of control. The methane generation and organic removal were not recovered within 300 days after the CTC exposure was stopped. During the experiment, stability parameters such as pH, total ammonium nitrogen, the composition of methane and alkalinity were the same for both reactors. The concentration and composition of VFAs in the test reactor were different with those of control but not in inhibition level. Microbial profiles revealed that reduction in bacterial diversity and changed balance in microbial species resulted in the performance downgrade under the long-term antibiotic pressure. Since it is hard to recover from the inhibition and difficult to predict the inhibition using physicochemical indicators, continuous exposure to CTC needs to be avoided for the sustainable management of AD plants treating SM.

Can agricultural land use alter the responses of soil biota to antibiotic contamination?

Antibiotics accumulate in soils via various agricultural activities, endangering soil biota that play fundamental roles in maintaining agroecosystem function. However, the effects of land-use heterogeneity on soil biota tolerance to antibiotic stresses are not well understood. In this study, we explored the relationships between antibiotic residues, bacterial communities, and earthworm populations in areas with different land-use types (forest, maize, and peanut fields). The results showed that antibiotic levels were generally higher in maize and peanut fields than in forests. Furthermore, land use modulated the effects of antibiotics on soil bacterial communities and earthworm populations. Cumulative antibiotic concentrations in peanut fields were negatively correlated with bacterial diversity and earthworm abundance, whereas no significant correlations were detected in maize fields. In contrast, antibiotics improved bacterial diversity and richness in forest soils. Generally, earthworm populations showed stronger tolerance to antibiotics than did soil bacterial communities. Agricultural land use differentially modified the responses of the soil bacterial community and earthworm population to antibiotic contamination, and earthworms might provide an alternative for controlling antibiotic contamination.

Source-specific risk apportionment and critical risk source identification of antibiotic resistance in Fenhe River basin, China

A comprehensive understanding of the sources and distribution of antibiotic resistance risk is essential for controlling antibiotic pollution and resistance. Based on surface water samples collected from the Fenhe River basin in the flood season, using the positive matrix factorization (PMF) model, the risk quotient (RQ) method and the multiple attribute decision making (MADM) method, the resistance risk and source-specific resistance risk of antibiotics were analyzed in this study. The results showed that sulfonamides (SAs) were the dominant antibiotics with a mean concentration of 118.30 ng/L, whereas tetracyclines (TCs) and macrolides (MLs) had the highest detection frequencies (100%). The significant resistance risk rate of antibiotics in the entire river basin was 48%, but no high risk occurred. The significant resistance risk rate of quinolones (QNs) was the highest (100%), followed by that of MLs and TCs. Owing to human activities, the most serious resistance risk occurred in the midstream of the river basin. The resistance risk was the lowest upstream. The antibiotics were mainly contributed by six sources. Pharmaceutical wastewater was the main source, accounting for 30%, followed by livestock discharge (22%). The resistance risk from the six sources showed clear differences, but none of the sources caused a high risk of antibiotic resistance. Pharmaceutical wastewater poses the greatest risk of antibiotic resistance in the Fenhe River basin and is widely distributed. The second greatest source was livestock discharge, which was mainly concentrated in the upstream and midstream areas. The critical sources upstream, midstream, and downstream were all pharmaceutical wastewater, whereas the sequences of other sources were different because different areas were affected by different human activities. The proposed method might provide an important reference for the identification the key source of antibiotics and management of antibiotic pollution, as well as help for the management of antibiotics in Fenhe and Shanxi Province.

Ammonium Utilization in Microalgae: A Sustainable Method for Wastewater Treatment

In plant cells, ammonium is considered the most convenient nitrogen source for cell metabolism. However, despite ammonium being the preferred N form for microalgae, at higher concentrations, it can be toxic, and can cause growth inhibition. Microalgae’s tolerance to ammonium depends on the species, with various taxa showing different thresholds of tolerability and symptoms of toxicity. In the environment, ammonium at high concentrations represents a dangerous pollutant. It can affect water quality, causing numerous environmental problems, including eutrophication of downstream waters. For this reason, it is important to treat wastewater and remove nutrients before discharging it into rivers, lakes, or seas. A valid and sustainable alternative to conventional treatments could be provided by microalgae, coupling the nutrient removal from wastewater with the production of valuable biomass. This review is focused on ammonium and its importance in algal nutrition, but also on its problematic presence in aquatic systems such as wastewaters. The aim of this work is to provide recent information on the exploitation of microalgae in ammonium removal and the role of ammonium in microalgae metabolism.