Roles of photochemical consumption of VOCs on regional background O3 concentration and atmospheric reactivity over the pearl river estuary, Southern China.

Understanding of the photochemical ozone (O3) pollution over the Pearl River Estuary (PRE) of southern China remains limited. We performed an in-depth analysis of volatile organic compounds (VOCs) data collected on an island (i.e., the Da Wan Shan Island, DWS) located at the downwind of Pearl River Delta (PRD) from 26 November to 15 December 2021. Abundances of O3 and its precursors were measured when the air masses originated from the inland PRD. We observed that the VOCs levels at the DWS site were lower, while the mixing ratio of O3 was higher, compared to those reported at inland PRD, indicating the occurrence of photochemical consumption of VOCs during the air masses transport, which was further confirmed by the composition and diurnal variations of VOCs, as well as ratios of specific VOCs. The simulation results from a photochemical box model showed that the O3 level in the outflow air masses of inland PRD (O3(out-flow)) was the dominant factor leading to the intensification of O3 pollution and the enhancement of atmospheric radical concentrations (ARC) over PRE, which was mainly contributed by the O3 production via photochemical consumption of VOCs during air masses transport. Overall, our findings provided direct quantitative evidence for the roles of outflow O3 and its precursors from inland PRD on O3 abundance and ARC over the PRE area, highlighting that alleviation of O3 pollution over PRE should focus on the impact of photochemical loss of VOCs in the outflow air masses from inland PRD.

Performance evaluation for the inactivation of multidrug-resistant bacteria in wastewater effluent by different disinfection technologies.

The escalating presence of antibiotic-resistant bacteria (ARB) in aquatic ecosystems underscores the critical role of wastewater treatment plants (WWTPs) in mitigating antibiotic resistance. Disinfection is the final, pivotal step in WWTPs, and it is essential to control the dissemination of ARB before water discharge. This study utilized both phenotypic analysis and transcriptome (RNA-seq) approach to investigate the efficiency and mechanisms of disinfection using chlorination, ultraviolet (UV), and peracetic acid (PAA) on multidrug-resistant bacteria (MRB). Our results demonstrated that the use of 100 mg min L-1 of chlorine, 8.19 mJ cm-2 of UV irradiation or 50 min mg L-1 of PAA significantly reduced the abundance of MRB. Intriguingly, RNA-seq clarified distinct mechanisms of chlorination and UV disinfection. UV radiation triggered the SOS response to cope with DNA damage, induced the expression of multi-drug resistance genes by increasing the expression of efflux pump transporters. UV radiation also promoted the absorption of iron through chelation and transportation to participate in various cell life processes. Chlorination, on the other hand, significantly up-regulated osmotic response elements, including the synthesis of glycine betaine, iron-sulfur clusters, and related transporters. Both chlorination and UV significantly down-regulated key metabolic pathways (P < 0.05), inhibiting the process of amino acid synthesis and energy metabolism. Imbalance in energy homeostasis was the most important factor leading to cytotoxicity. These results provide useful insights into optimizing the wastewater disinfection process in order to prevent the dissemination of ARB in aquatic environment.

Aging of plastics in aquatic environments: Pathways, environmental behavior, ecological impacts, analyses and quantifications.

The ubiquity of plastics in our environment has brought about pressing concerns, with their aging processes, photo-oxidation, mechanical abrasion, and biodegradation, being at the forefront. Microplastics (MPs), whether originating from plastic degradation or direct anthropogenic sources, further complicate this landscape. This review delves into the intricate aging dynamics of plastics in aquatic environments under various influential factors. We discuss the physicochemical changes that occur in aged plastics and the release of oxidation products during their degradation. Particular attention is given to their evolving environmental interactions and the resulting ecotoxicological implications. A rigorous evaluation is also conducted for methodologies in the analysis and quantification of plastics aging, identifying their merits and limitations and suggesting potential avenues for future research. This comprehensive review is able to illuminate the complexities of plastics aging, charting a path for future research and aiding in the formulation of informed policy decisions.

Marine oil spill photodegradation: Laboratory simulation, affecting factors analysis and kinetic model development.

Photodegradation significantly influences marine oil spill behavior, yet its role remains underrepresented in current models, impairing predictive accuracy. Addressing this, our study rigorously examined oil properties and environmental determinants affecting marine oil spill photodegradation through laboratory simulations. We identified and quantified key factors and their interactions, noting particularly the positive influence of asphaltene and negative implications of oil density. We also discerned a negative correlation between n-alkane degradation and carbon numbers. Our findings underscored the pivotal roles of temperature and irradiance in photodegradation. All tested oils adhered to first-order kinetics, with rate constants ranging from 0.0348 to 0.0645 day-1. Finally, we introduced a novel model incorporating temperature, irradiance and their interactions, ensuring reasonable simulations for marine oil spill photodegradation, fortifying marine oil spill management strategies.

Emission of marine volatile organic compounds (VOCs) by phytoplankton- a review.

Oceans cover over 71% of the Earth's surface and play crucial roles in regulating the global climate. In the marine boundary layer, the levels of volatile organic compounds (VOCs) have been shown to have positive relations with the marine algal biomass, indicating that the marine biological activities can be an important biogenic VOCs (BVOCs) source. The emitted BVOCs will enhance the formation of secondary organic aerosols, and perturb the radiative forcing, which ultimately affects the climate. To date, knowledge on the emission processes (i.e., synthesis processes and emission rates) of BVOCs from marine phytoplankton is still lacking compared to the more well-known BVOCs released from terrestrial plants. In this review, we focus on the BVOCs emissions from the marine phytoplankton. Based on the available literature from field and laboratory studies, we listed the types of BVOCs being emitted by different marine phytoplankton species, summarized the diversity of BVOCs related to phytoplankton taxonomy and physiology and abiotic factors affecting their emissions in various marine environments, and discussed the biosynthesis and ecological function of important marine VOCs such as DMS, terpenoids and VHCs from phytoplankton. Finally, we highlighted the existing gaps in the current knowledge and the needs of future study for better understanding the physiological and ecological roles of BVOCs emission from marine phytoplankton.

Variations in the concentration, source and flux of polycyclic aromatic hydrocarbons in sediments of the Pearl River Estuary: Implications for anthropogenic impacts.

Variations in the distribution, source composition, mass inventory and burial flux of polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Pearl River Estuary (PRE) collected in 2011 and 2019 were analyzed to investigate the influence of the anthropogenic activities. Total concentrations of 16 priority PAHs in 2019 (200.40 ± 188.86 ng g-1 dry weight on average) were at the medium level among global bays/estuaries/coastal areas. In 2019, PAH concentrations have decreased by about 50% compared to 2011 and the dominant composition has changed from low- to high-molecular-weight PAHs. The qualitative and quantitative source apportionment analysis indicates that the dominant source of PAHs has shifted from petroleum (40.33%) in 2011 to traffic emission (44.17%) in 2019. The source variation in the PRE can be attributed to the transformation of the energy source structure from petrogenic to pyrogenic in the Pearl River Delta. The estimated PAH mass inventory of the top 5-cm sediment was 38.70 metric tons in 2019, which was about 41 metric tons lower than that in 2011. The average deposition fluxes have dropped from 418.91 ± 261.02 ng cm-2 yr-1 in 2011 to 215.52 ± 246.63 ng cm-2 yr-1 in 2019. The decreasing PAH concentration is related to the sediment coarsening and decline of total organic carbon. These findings in the PRE can be applied to other estuarine environments influenced by anthropogenic activities.

Characterization of airborne bacteria and fungi at a land-sea transition site in Southern China.

Airborne microbe can have impact on regional to global climate as ice nuclei and cloud condensation nuclei. In coastal region, microbial aerosols are simultaneously contributed by terrestrial and marine sources under the influence of land-sea air exchange. We present a study on the characteristics of airborne bacteria and fungi, including their concentrations and communities, at a land-sea transition site in Southern China from December 2019 to December 2020. Seasonal variations of microbial communities were observed with evident profiles in summer, especially for fungal aerosols. The significant enhancement of Basidiomycota abundance in summer was contributed by local biogenic release under the influence of meteorological factors. Terrestrial sources are suggested as the dominant contributors to both bacterial and fungal aerosols rather than marine sources during the whole year period. Source-tracking analysis identified that marine contributions to airborne bacteria and fungi were 3.1-14.2 % and 4-24 %, respectively. It suggests that airborne fungi should be more suitable for long-range transport than airborne bacteria. This study improves the understanding of the conversional contribution of marine and terrestrial sources to airborne microbes in coastal region and the influencing environmental factors under land-sea exchange.

DBWM: A diluted bitumen weathering model.

To help better assist the management of Diluted bitumen (DilBit) spills in marine environment, a model named as DilBit Weathering Model (DBWM) was developed in this study to simulate DilBits weathering in marine environment. The DBWM was developed based on specific algorithms for evaporation, dispersion, biodegradation, as well as density and viscosity changes for DilBit weathering and other widely used algorithms for conventional oil weathering in marine environment. To validate the model, a series of DilBit weathering simulation were conducted and compared with the experimental data. Furthermore, the performance of DBWM was compared with a widely used oil weathering model (Automated Data Inquiry for Oil Spills, ADIOS2). The results demonstrated the feasibility and advantages of the developed DBWM in simulating the weathering of marine DilBit spills. Thus, the proposed DBWM can provide effective decision support to marine DilBit spill management.

Pollution level and health risk assessment of polycyclic aromatic hydrocarbons in marine fish from two coastal regions, the South China Sea.

Marine fishes are consumed in large quantities by humans as nutritious food. However, the intake of fish polluted by chemicals may pose a severe threat to human health. This study measured the concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) in the muscles of 22 species of marine fish from two coastal regions, i.e., Tanmen and Zhuhai, identified the source of PAHs, and assessed the human health risk by dietary exposure. Total PAH (Σ16PAHs) levels in Tanmen and Zhuhai fish were in the range of 24.29-684.83 ng g-1 dry weight (dw) and 13.74-42.59 ng g-1 dw, averaging 161.46 ng g-1 dw and 31.21 ng g-1 dw, respectively. Compared with other regions in the world, PAH concentrations in Tanmen fish were at median levels, and Zhuhai fish were at low levels. Low molecular weight PAHs (with 2- and 3-rings) were the predominant compounds detected. Molecular diagnostic ratios suggested that PAHs in Tanmen mainly originated from petrogenic sources such as vessel operations or tanker accidents, while Zhuhai fish were mainly polluted by pyrolytic sources such as combustion of coal and wood. The human health risk assessment results indicated that the risk of PAH intake via fish consumption from Zhuhai was negligible, while five species from Tanmen may pose potential health risks to local residents.

Photochemistry of ozone pollution in autumn in Pearl River Estuary, South China.

To explore the photochemical O3 pollution over the Pearl River Estuary (PRE), intensive measurements of O3 and its precursors, including trace gases and volatile organic compounds (VOCs), were simultaneously conducted at a suburban site on the east bank of PRE (Tung Chung, TC) in Hong Kong and a rural site on the west bank (Qi'ao, QA) in Zhuhai, Guangdong in autumn 2016. Throughout the sampling period, 3 days with high O3 levels (maximum hourly O3 > 100 ppbv) were captured at both sites (pattern 1) and 13 days with O3 episodes occurred only at QA (pattern 2). It was found that O3 formation at TC was VOC-limited in both patterns because of the large local NOx emissions. However, the O3 formation at QA was co-limited by VOCs and NOx in pattern 1, but VOC-limited in pattern 2. In both patterns, isoprene, formaldehyde, xylenes and trimethylbenzenes were the top 4 VOCs that modulated local O3 formation at QA, while they were isoprene, formaldehyde, xylenes and toluene at TC. In pattern 1, the net O3 production rate at QA (13.1 ± 1.6 ppbv h-1) was high, and comparable (p = 0.40) to that at TC (12.1 ± 1.5 ppbv h-1), so was the hydroxyl radical (i.e., OH), implying high atmospheric oxidative capacity over PRE. In contrast, the net O3 production rate was significantly higher (p < 0.05) at QA (16.3 ± 0.4 ppbv h-1) than that at TC (4.7 ± 0.2 ppbv h-1) in pattern 2, and the OH concentration and cycling rate were also higher, indicating much stronger photochemical reactions at QA. These findings enhanced our understanding of O3 photochemistry in the Pearl River estuary, which could be extended to other estuaries.

A polymeric solid-phase microextraction fiber for the detection of pharmaceuticals in water samples.

A novel disposable styrene based solid-phase microextraction (SPME) fiber was synthesized for the detection of lipid-lowering and antihypertensive drugs in real aquatic environment. Styrene and poly(ethylene glycol) diacrylate were co-polymerized on quartz fibers by thermal polymerization in capillary molds. The polymeric fiber possessed a homogeneous, dense as well as porous surface, showing excellent chemical and mechanical stability. The performance of the fiber was evaluated through the extraction of seven pharmaceuticals by coupling SPME with high performance liquid chromatography-tandem mass spectrometry under the optimized extraction conditions. The extraction efficiency of the fiber was up to 278 times of PDMS fiber and the enrichment factors ranged from 55 to 1183. The limits of detection were in the range from 1.7 ng L-1 to 11.7 ng L-1, with good reproducibility. Moreover, the fiber was used in the real water samples of the Pearl River Delta. The recoveries of the target analytes from river water and sea water samples at different spiked concentrations were in the range from 84.1% to 133.4% and from 81.5% to 105.5%, respectively.

Evaluating the effectiveness of multiple emission control measures on reducing volatile organic compounds in ambient air based on observational data: A case study during the 2010 Guangzhou Asian Games.

Volatile organic compounds (VOCs) play a crucial role in modulating air pollution by ozone and fine particles, particularly in urban areas. While in recent years short-term intervention actions for better air quality during big events in China did present good opportunities to examine the effectiveness of control measures in reducing anthropogenic VOCs emission, it is highly challenging to interpret the real effect of a specific control measure based on field monitoring data when a cocktail of control measures were adopted. Here we took the air quality intervention actions during the 16th Asian Games (AG) in Guangzhou as a case study to explore the impact of short-term multiple measures on VOCs reduction. The average mass concentrations of VOCs decreased by 52-68% during the AG. These percentages could not reflect emission reduction rates as the concentration might be also heavily impacted by dispersion conditions. Diagnostic ratios, such as methyl tert-butyl ether to carbon monoxide (MTBE/CO) and i-pentane/CO, decreased by over 60% during the AG, suggesting a substantial reduction in gasoline related emissions. A method linking emission reduction rates of two sources with their contribution percentages before and during the AG by using a receptor model was further formulated. With the available reduction rate of 34% for vehicular exhaust obtained during the traffic restriction drill in our previous study, VOCs emissions from gasoline evaporation and solvent use reduced by 45.7% and 13.6% during the AG, respectively. Total VOCs emissions decreased by 25.3% on average during the AG, and the emission control of vehicular exhaust, oil evaporation, and solvent use accounted for 17.0%, 6.3% and 2.0% of total VOCs emission reduction, respectively. This study presented an observed-based method with diagnostic/quantitative approaches to single out the effectiveness of each control measures in reducing VOCs emissions.

A case study on the characterization of non-methane hydrocarbons over the South China Sea: Implication of land-sea air exchange.

We present the characteristics of non-methane hydrocarbons (NMHCs) over the northern South China Sea (SCS) during a cruise campaign from September to October 2013. The mixing ratios of the total NMHCs ranged from 1.45 to 7.13 ppbv with an average of 3.54 ±â€¯1.81 ppbv. Among the measured NMHCs, alkanes and aromatics were the major groups, accounting for 45.8 ±â€¯8.7% and 28.7 ±â€¯12.3% of the total NMHCs, respectively. Correlations of NMHCs with typical source tracers suggest that light alkanes and benzene were largely contributed by vehicular exhaust via long-range transport, while the other aromatics might be related to industrial sources and marine ship emissions. The spatial variations of NMHCs were observed with higher mixing ratios of NMHCs in the samples collected in the offshore areas than those in the coastal areas. Air mass back-trajectory analysis and diagnostic ratios of NMHCs show that the elevations of the total NMHCs were caused by the regional pollution transport from the southeast coast of China and/or southern China. The ozone formation potentials (OFPs) of NMHCs were calculated and the results show that the aromatics associated with marine ship emissions were the important contributors to the total OFP. This study provides useful information on the interaction between continental outflow and marine atmosphere.

Photochemical evolution of continental air masses and their influence on ozone formation over the South China Sea.

To investigate photochemical ozone (O3) pollution over the South China Sea (SCS), an intensive sampling campaign was conducted from August to November simultaneously at a continental site (Tung Chung, TC) and a marine site (Wan Shan Island, WSI). It was found that when continental air masses intruded the SCS, O3 episodes often occurred subsequently. To discover the causes, a photochemical trajectory model (PTM) coupled with the near-explicit Master Chemical Mechanism (MCM) was adopted, and the photochemical processes of air masses during the transport from TC to WSI were investigated. The simulated O3 and its precursors (i.e. NOx and VOCs) showed a reasonably good agreement with the observations at both TC and WSI, indicating that the PTM was capable of simulating O3 formation for air masses traveling from TC to WSI. The modeling results revealed that during the transport of air masses from TC to WSI, both VOC and NOx decreased in the morning while O3 increased significantly, mainly due to rapid chemical reactions with elevated radicals over the SCS. The elevated radicals over the SCS were attributable to the fact that higher NOx at TC consumed more radicals, whereas the concentration of radicals increased from TC to WSI because of NOx dilution and destruction. Subsequently, the photochemical cycling of radicals accelerated, leading to high O3 mixing ratios over the SCS. Furthermore, based on the source profiles of the emission inventory used, the contributions of six sources, i.e. gasoline vehicle exhaust, diesel vehicle exhaust, gasoline evaporation and LPG usage, solvent usage, biomass and coal burning, and biogenic emissions, to maritime O3 formation were evaluated. The results suggested that gasoline vehicles exhaust and solvent usage largely contributed the O3 formation over the SCS (about 5.2 and 3.8 ppbv, respectively). This is the first time that the contribution of continental VOC sources to the maritime O3 formation was quantified.

An in-needle solid-phase microextraction device packed with etched steel wires for polycyclic aromatic hydrocarbons enrichment in water samples.

A novel, low-cost and effective in-needle solid-phase microextraction device was developed for the enrichment of trace polycyclic aromatic hydrocarbons in water samples. The in-needle solid-phase microextraction device could be easily assembled by inserting hydrofluoric acid-etched wires, which were used as adsorbent, into a 22-gauge needle tube within spring supporters. Compared with the commercial solid-phase microextraction fiber, the developed device has higher efficiency for the extraction of polycyclic aromatic hydrocarbons with four to six rings from water samples using the optimized extraction conditions. With gas chromatography equipped with a flame ionization detector, the limits of detection for the polycyclic aromatic hydrocarbons with four to six rings ranged from 0.0020 to 0.0067 ng/mL. The relative standard deviations for one needle and needle-to-needle extractions were in the range of 5.2-9.9% (n = 5) and 3.4-12.3% (n = 5), respectively. The spiked recoveries of the polycyclic aromatic hydrocarbons in tap water samples ranged from 73.2 to 95.4%. This in-needle solid-phase microextraction device could be a good field sampler because of the low sample loss over a long storage time.

Characterization of airborne antibiotic resistance genes from typical bioaerosol emission sources in the urban environment using metagenomic approach.

The wide spread of antibiotic resistance genes (ARGs) has attracted increasing concern. However, the occurrence and diversity of ARGs in airborne particles remains to be understood. In this study, total suspended particles (TSP) in the atmosphere were collected from typical sources of ARG pollution, including animal farms and wastewater treatment plant (WWTP), as well as the downtown area in Zhuhai, China. Metagenomic profiling demonstrated that ARGs were abundant and diverse in the TSP from animal farms and WWTP, but significant differences in ARG composition pattern between these samples were observed. ARGs associated with the resistance to aminoglycoside, macrolide-lincosamide-streptogramin (MLS) and tetracycline were dominant over other ARGs in the TSP of the animal farms, whereas multidrug and bacitracin resistance genes were more abundant than other ARGs in the TSP of the WWTP. In the animal farms, ARG profiles of the TSP were consistent with those of animal feces, indicating that animal feces could be one of the most contributing sources of airborne ARGs in animal farms. In contrast to representative sources of ARG pollution, ARG abundance and diversity in the TSP collected from the downtown area was relatively low, with multidrug resistance genes being predominant. This study suggests that metagenomic profiling of the ARGs in airborne TSP could enhance our comprehensive understanding of ARGs dissemination in the environment and their potential health threats.

Characterizing the antibiotic resistance genes in a river catchment: Influence of anthropogenic activities.

Previous studies on environmental antibiotics resistance genes (ARGs) have focused on the pollution sources such as wastewater treatment plants, aquaculture and livestock farms, etc. Few of them had addressed this issue in a regional scale such as river catchment. Hence, the occurrence and abundances of 23 ARGs were investigated in surface water samples collected from 38 sites which located from the river source to estuary of the Beijiang River. Among them, 11 ARGs were frequently detected in this region and 5 ARGs (sulI, sulII, tetB, tetC, and tetW) were selected for their distribution pattern analysis. The abundances of the selected ARGs were higher in the upstream (8.70×106copies/ng DNA) and downstream areas (3.17×106copies/ng DNA) than those in the midstream areas (1.23×106copies/ng DNA), which was positively correlated to the population density and number of pollution sources. Pollution sources of ARGs along the Beijiang River not only had a great impact on the abundances and diversity, but also on the distribution of specific ARGs in the water samples. Both sulI and sulII were likely originated from aquaculture farms and animal farms, tetW gene was possibly associated with the mining/metal melting industry and the electric waste disposal and tetC gene was commonly found in the area with multiple pollution sources. However, the abundance of tetB was not particularly related to anthropogenic impacts. These findings highlight the influence of pollution sources and density of population on the distribution and dissemination of ARGs at a regional scale.

Exploring the differences of antibiotic resistance genes profiles between river surface water and sediments using metagenomic approach.

To better understand the potential genic communication and dissemination of antibiotic resistance genes (ARGs) in different environmental matrices, the differences of ARG profiles between river surface water and sediments were explored. Metagenomic analysis was applied to investigate the comprehensive ARG profiles in water and sediment samples collected from the highly human-impacted catchment of the Beijiang River and its river source. A total of 135 ARG subtypes belonging to 18 ARG types were identified. Generally, ARGs in surface water were more diverse and abundant than those in sediments. ARG profiles in the surface water and sediment samples were distinct from each other, but some ARGs were shared by the surface water and sediments. Results revealed that multidrug and bacitracin resistance genes were the predominant ARGs types in both surface water (0.30, 0.17 copies/cell) and sediments (0.19, 0.15 copies/cell). 73 ARG subtypes were shared by the water and sediment samples and had taken over 90% of the total detected ARG abundance. Most of the shared ARGs are resistant to the clinically relevant antibiotics. Furthermore, significant correlations between the ARGs and 21 shared genera or mobile genetic elements (MGEs) (plasmids and integrons) were found in surface water and sediments, suggesting the important role of genera or MGEs in shaping ARGs profiles, propagation and distribution. These findings provide deeper insight into mitigating the propagation of ARGs and the associated risks to public health.

Photochemical Formation of C1-C5 Alkyl Nitrates in Suburban Hong Kong and over the South China Sea.

Alkyl nitrates (RONO2) are important reservoirs of atmospheric nitrogen, regulating nitrogen cycling and ozone (O3) formation. In this study, we found that propane and n-butane were significantly lower at the offshore site (WSI) in Hong Kong ( p < 0.05), whereas C3-C4 RONO2 were comparable to the suburban site (TC) ( p > 0.05). Stronger oxidative capacity at WSI led to more efficient RONO2 formation. Relative incremental reactivity (RIR) was for the first time used to evaluate RONO2-precursor relationships. In contrast to a consistently volatile organic compounds (VOC)-limited regime at TC, RONO2 formation at WSI switched from VOC-limited regime during O3 episodes to VOC and nitrogen oxides (NO x) colimited regime during nonepisodes. Furthermore, unlike the predominant contributions of parent hydrocarbons to C4-C5 RONO2, the production of C1-C3 RONO2 was more sensitive to other VOCs like aromatics and carbonyls, which accounted for ∼40-90% of the productions of C1-C3 alkylperoxy (RO2) and alkoxy radicals (RO) at both sites. This resulted from the decomposition of larger RO2/RO and the change of OH abundance under the photochemistry of other VOCs. This study advanced our understanding of the photochemical formation of RONO2, particularly the relationships between RONO2 and their precursors, which were not confined to the parent hydrocarbons.

Complex pollution of antibiotic resistance genes due to beta-lactam and aminoglycoside use in aquaculture farming.

The prevalence of antibiotic resistance in the modern world has raised global concerns for public health. Establishing relationships between antibiotic use and antibiotic resistance genes (ARGs) is essential to understanding the dissemination and accumulation of ARGs in a human-impacted environment. In this study, ARG profiles in the sediments from a bullfrog farm, where penicillin and amoxicillin (beta-lactams) and gentamicin (aminoglycoside) were used for prophylactic purposes, were analyzed using metagenomic approaches. Analysis of both extracellular and intracellular DNA (eDNA and iDNA) demonstrated that use of the above-mentioned antibiotics led to complex pollution of ARGs not only related to beta-lactams and aminoglycoside but also to sulfonamides, tetracyclines, and macrolides. Most of the ARGs in the sediments from the bullfrog farm were likely carried by plasmids. A significant correlation was observed between the total abundance of ARG-related plasmids and that of plasmid-carrying ARGs. Approximately 85% of the plasmids likely present in the sediment from the bullfrog farm possessed at least 3 ARG subtypes, which conferred the resistance of bacterial hosts to different antibiotic categories. Our results suggest that antibiotics could lead to complex pollution of ARGs unrelated to those administered due to the concurrence of ARGs in the plasmids.