Effect of quantity and fractionation of loaded humic acid (HA) on biochar sorption for sulfonamides was investigated. The HA was applied in two different modes, i.e. pre-coating and co-introduction with sorbate. In pre-coating mode, the polar fractions of HA tended to interact with low-temperature biochars via H-bonding, while the hydrophobic fractions were likely to be adsorbed by high-temperature biochars through hydrophobic and π-π interactions, leading to different composition and structure of the HA adlayers. The influences of HA fractionation on biochar sorption for sulfonamides varied significantly, depending on the nature of interaction between HA fraction and sorbate. Meanwhile, co-introduction of HA with sulfonamides revealed that the effect of HA on sulfonamide sorption was also dependent on HA concentration. These findings suggest that the amount and fractionation of adsorbed HA are tailored by the surface properties of underlying biochars, which differently affect the sorption for organic contaminants.

Bacterial antibiotic resistance has long been a public health concern worldwide. Although antibiotic abuse highly correlates with occurrence of resistant pathogens in hot spots like animal feedlots, it remains obscure how frequently these resistance genotypes would emerge and/or retain in natural circumstances. In this study, we monitored seven antibiotic resistance genes in various surface waters. All seven resistance genes were detectable in Puzih River samples, including strA (40.6 %), cmlA (29.7 %), blaTEM (9.1 %), tet(B) (8.5 %), sul1 (7.9 %), mecA (3.6 %), and tet(A) (2.4 %). Among these genes, strA was observed in four out of five sampling occasions during the 1.5-year monitoring period and most of the genes were detected at least two times over five samplings. These results imply that surface waters in Taiwan act as potential reservoirs for several resistance genotypes. Moreover, high prevalence of tet(A) (92.0 %) and sul1 (96.0 %) in swine farm wastewater samples suggests routine antibiotic usage and particularly, the fodder supplements could indeed be a risk factor to antibiotic resistance in environments. sul1, tet(A), blaTEM, and strA were detectable in domestic water treatment plants and reservoirs, suggesting that several resistance genotypes against antibiotics as streptomycin, ampicillin, tetracycline, and sulfonamides are likely to persist in natural circumstance and may consequently contaminate the drinking water systems.

The recycling of reclaimed wastewater for irrigation and road cleaning is an important strategy to minimize water scarcity in megacities. However, little is known regarding the potential accumulation of antibiotics contained in reclaimed wastewater in urban soil. We investigated the occurrence and distribution of eight quinolones (QNs), nine sulfonamides (SAs), and five macrolides (MLs) antibiotics in urban surface soil in Beijing and Shanghai, China. QNs, especially norfloxacin (NOR), ofloxacin (OFL), and ciprofloxacin (CIP) were the predominant antibiotics in urban surface soil, and NOR revealed the highest average concentration of 94.6 μg kg⁻¹. The antibiotic concentrations in urban soil in our study were higher than those detected in agricultural soils after long-term wastewater irrigation and manure fertilization. The concentrations of antibiotics in Shanghai urban soil showed a significant negative correlation with soil pH and a positive correlation with total organic carbon (TOC), reflecting the effect of speciation and soil organic matter content on sorption and retention. In addition, antibiotic concentrations in the urban soil were positively correlated with heavy metal contents, likely due to their coexistence in reclaimed wastewater and the promoting effect of metals on the sorption of antibiotics. In several soil samples, NOR, OFL, CIP, enrofloxacin (ENR), and fleroxacin (FLE) showed higher concentrations than the trigger value of 100 μg kg⁻¹ in soil, indicating a potential risk for the environment.

A feasible and rapid analysis for the simultaneous determination of sulfonamides (SAs), tetracyclines (TCs), fluoroquinolones (FQs), macrolides (MACs) and nitrofurans (NFs) in livestock manure and soils was established by solid-phase extraction (SPE)-ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS). A total of 32 manure and 17 amended soil samples from the Liaoning and Tianjin areas in Northern China were collected for analysis. The largest detected frequencies and concentrations in manure samples were those of TCs (3326.6 ± 12,302.6 μg/kg), followed by FQs (411.3 ± 1453.4 μg/kg), SAs (170.6 ± 1060.2 μg/kg), NFs (85.1 ± 158.1 μg/kg), and MACs (1.4 ± 4.8 μg/kg). In general, veterinary antibiotics (VAs) were detected with higher concentrations in swine and chicken manure than in cattle manure, reflecting the heavy usage of VAs in swine and chicken husbandry in the studied area. Furthermore, higher residues of antibiotics were found in piglet and fattening swine manure than in sow manure. In addition, TCs were the most frequently (100 %) detected antibiotics in amended soil with higher concentrations (up to 10,967.1 μg/kg) than any other VAs. The attenuation of SAs was more obvious than TCs in amended soil after fertilization, which can most likely be attributed to the stronger sorption of TCs than SAs to soil organic matter through cation exchange. This study illustrated the prevalence of TCs detected in both animal manure and fertilized agricultural soils in Northern China, which may increase the risk to human health through the food chain. Thus, TCs should be given more attention in the management of veterinary usage in livestock husbandry.

An optimized solid-phase extraction (SPE) and ultra-high performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS) method was developed for the effective analysis of 35 antibiotics including sulfonamides (SAs), quinolones (QLs), tetracyclines (TCs), macrolides (MALs), lincomycin (LIN), and chloramphenicol (CAP). The addition of 0.1 % formic acid to the mobile phase was favorable for the formation of [M + H]⁺ and the enhancement in the detection signals, but using ammonium formate decreased [M + H]⁺ with a corresponding reduction in the response of CAP. The optimal pH range for the SPE was 4.5 ∼ 5.0 with 6 mL aqueous ammonia/methanol (5/95, v/v) as the optimized eluent. An internal standard (IS) was selected for each type of analytes based on similarities in classification and retention time. The detection was completed in less than 10 min and was excellent with method detection limits (MDL) of 0.29 ∼ 4.03 ng/L. The recoveries of the antibiotics in samples from ultrapure water and groundwater were 67.13 ∼ 93.00 % and 68.91 ∼ 92.67 %, respectively. The antibiotics in samples collected from wastewater, surface water, and groundwater were also effectively detected. This newly developed method has the advantages of short detection times, small sample consumption, excellent reproducibility, and high sensitivity. This provides a reliable and promising technique for the simultaneous detection and monitoring of various residual antibiotics in aqueous environmental samples.

This study investigated the residues of four sulfonamides, four quinolones, and four tetracyclines in surface water as well as surficial sediment samples, of Bosten Lake, in Xinjiang, China. The results showed the presence of 10 out of the 12 selected antibiotics in both water and sediment. Lomefloxacin was not detected in any of the samples. Among the 12 antibiotics considered, ciprofloxacin, with median concentrations of 39.22 ng L⁻¹ in surface water and 76.51 μg kg⁻¹ in surficial sediment, was the dominant antibiotic in all samples. The sorption coefficient values presented higher sorption capacities of tetracycline and chlortetracycline than the other antibiotics. The cluster analysis revealed elevated levels of pollution in sampling sites 1, 2, and 3, which were situated in a nearby urban area and in the estuary of Kaidu River. This study demonstrates the necessity of regulating the use of antibiotics and improving the management and treatment of their release.

Veterinary antibiotics (VAs) are emerging contaminants and enter into soil principally by agricultural application of organic fertilizer. A total of 33 solid animal manures and 17 compost samples from protected vegetable farms in nine areas of China were analyzed for the antibiotic classes of tetracyclines, fluoroquinolones, sulfonamides, and macrolides (17 substances in total). Oxytetracycline was found as a dominant compound in the samples, and its highest concentration reached 416.8 mg kg⁻¹in a chicken manure sample from Shouguang, Shandong Province. Among the samples, animal manures (especially pig manure) contained higher VA residues than composts. However, fluoroquinolones exhibited higher persistence in the compost samples than other antibiotic classes. This is particularly the case in the rice husk compost, which contained the highest level of ofloxacin and ciprofloxacin (1334.5 and 1717.4 μg kg⁻¹on average, respectively). The veterinary antibiotic profile in the risk husk compost had a good relationship with that in the corresponding manures. The refined commercial compost had the lowest VA residues among the compost samples in general. This implied that composting process might be important to reduce the antibiotic residue. High residue of antibiotics in soil was assumed to be a hazard to ecosystem. This is especially noticeable under current application rates (150 t ha⁻¹ a⁻¹) in protected vegetable farming because over half of the samples exhibited a risk quotient (RQ) >1 for one or more antibiotics.

Although sulfonamides (SAs) are among the most commonly used veterinary drugs and their presence in the environment is well documented, knowledge of their fate and behavior in the soil environment is still limited, especially for sulfisoxazole (SSX) which is characterized by the lowest (among other SAs) pK ₐ value associated with acid-base equilibrium of sulfonamide group. Thus, this work was focused on determining the sorption potential of SSX onto natural soils differing in physicochemical properties. All the results were modeled using linear, Freundlich, Langmuir, Dubinin–Radushkevich, and Temkin sorption isotherms. The established sorption coefficients (K d) for SSX were quite low (from 0.27 to 0.95 L kg⁻¹), which indicated that this substance is highly mobile and has the potential to run off into surface waters and/or infiltrate ground water. The sorption data of SSX is well fitted to the Freundlich isotherm model (R ² > 0.968). Moreover, we assessed the sorption mechanism of these compounds in the edaphic environment with respect to organic matter (OM) content, pH, and ionic strength. To clarify the current state of knowledge, these factors were examined much more thoroughly than in previous investigations concerning other SAs. The wide range of ionic strength examined showed positive correlation of this factor and sorption of SAs. The results also yielded new insight into dependency of sorption of SAs on organic matter content in soil.

The overuse of antibiotics in livestock farms is general, leading to a wide distribution of antibiotic resistance genes (ARGs) in aquatic environment adjacent to livestock farms. However, researches of the distribution and types of ARGs in aquatic environment of China are still in the initial stage. In this study, wastewater and surface water samples were collected from 12 livestock farms (four pig farms, four cattle farms, and four chicken farms) in Jiangsu Province of China. The prevalence, abundance, and distribution of 22 ARGs were investigated, which were categorized into six groups, including nine tetracyclin resistance genes, three sulfonamides resistance genes, three quinolone resistance genes, two macrolide resistance genes, three aminoglycoside resistance genes, and two multidrug resistance genes, employing quantitative real-time PCR (qPCR). The results suggested that all of the 22 ARGs were detected in samples. Sul1, sul2, and tetM were the most abundant with the average concentration of 3.84 × 10¹ copies/16S recombinant RNA (rRNA) gene copies, 1.62 × 10¹ copies/16S rRNA gene copies, 2.33 × 10¹ copies/16S rRNA gene copies, respectively. Principle component analysis revealed that the comprehensive pollution of ARGs in northern Jiangsu was more serious. ARGs in wastewater were more abundant when compared to that in surface water. A preliminary study regarding the fate of ARGs after an aerobiotic process showed that tetA, tetC, sul1, sul2, oqxB, and qnrS were significantly increased. And, among the tetracycline resistance genes, the efflux pump genes were enriched while the ribosomal protection protein encoding genes were decreased in the aerobiotic process. The prevalance of ARGs in water environment is of concern; more surveillance is required to determine the pollution level and pattern of antibiotic resistance genes.