The ocean is an important sink of land-based pollutants. Previous studies showed that serious antibiotic pollution occurred in the coastal waters, but limited studies focused on their presence in offshore waters. In this study, eleven antibiotics in three different categories were investigated in offshore waters of the Bohai Sea and the Yellow Sea in China. The results indicated that three antibiotics dehydration erythromycin, sulfamethoxazole and trimethoprim occurred throughout the offshore waters at concentrations of 0.10–16.6 ng L−1 and they decreased exponentially from the rivers to the coastal and offshore waters. The other antibiotics all presented very low detection rates (<10%) and concentrations (<0.51 ng L−1). Although the concentrations were very low, risk assessment based on the calculated risk quotients (RQs) showed that sulfamethoxazole, dehydration erythromycin and clarithromycin at most of sampling sites posed medium or low ecological risks (0.01 < RQ < 1) to some sensitive aquatic organisms, including Synechococcus leopoliensis and Pseudokirchneriella subcapitata.

We tested antioxidant responses of the green microalga Pseudokirchneriella subcapitata exposed to different concentrations of the three antibiotics erythromycin (ETM), ciprofloxacin (CPF) and sulfamethoxazole (SMZ). Measurements included the level of lipid peroxidation, the total antioxidative capacity and three major antioxidant mechanisms: the ascorbate–glutathione cycle, the xanthophyll cycle and the enzyme activities of catalase (CAT), superoxide dismutase (SOD), guaiacol glutathione peroxidase (GPX) and glutathione-S-transferase (GST). Three antibiotics significantly affect the antioxidant system of P. subcapitata, but in different ways the alga was more tolerant to CPF and SMZ exposures than to ETM exposure. ETM caused reductions in AsA and GSH biosynthesis, ascorbate–glutathione cycle, xanthophylls cycle and antioxidant enzyme activities. The toxicity of CPF seems to be mainly overcome via induction of the ascorbate–glutathione cycle and CAT, SOD and GPX activities, while the toxicity of SMZ on the photosynthetic apparatus is predominantly reduced by the xanthophyll cycle and GST activity.

The occurrence and distribution of five groups of antibiotics were investigated in the surface water of Yangtze Estuary over four seasons. Of the 20 antibiotics, only sulfamerazine was not detected at all sampling sites, indicating widespread occurrence of antibiotic residues in the study area. Detection frequencies and concentrations of antibiotics were generally higher in January, indicating that low flow conditions and low temperature might enhance the persistence of antibiotics in water. Antibiotic levels varied with location, with the highest concentrations being observed around river discharge and sewage outfall. Furthermore, a positive correlation between total antibiotic and DOC concentrations revealed the significant role played by DOC. Risk assessment based on single compound exposure showed that sulfapyridine and sulfamethoxazole could cause medium risk to daphnid in the Yangtze Estuary.

The Polar Organic Chemical Integrative Sampler (POCIS) is a new tool for the sampling of organic pollutants in water. We tested this device for the monitoring of pharmaceuticals in hospital wastewater. After calibration, a field application was carried out in a French hospital for six pharmaceutical compounds (Atenolol, Prednisolone, Methylprednisolone, Sulfamethoxazole, Ofloxacin, Ketoprofen).POCIS were calibrated in tap water and wastewater in laboratory conditions close to relevant environmental conditions (temperature, flow velocity). Sampling rates (Rs) were determined and we observed a significant increase with flow velocity and temperature. Whatever the compound, the Rs value was lower in wastewater and the linear phase of uptake was shorter.POCIS were deployed in a hospital sewage pipe during four days and the estimated water concentrations were close to those obtained with twenty-four hour composite samples.

We investigated the effect of soil pH, organic carbon, ionic strength and steroid hormones on the sorption of sulfamethoxazole (SMO) and sulfachloropyridazine (SCP) in three pastoral soils of New Zealand. A model linking sorbate speciation with species-specific sorption coefficients describing the pH dependence of the apparent sorption coefficients was used to derive the fraction of each species of SMO. All soils displayed a decrease in sorption when pH was increased, with SMO exhibiting the highest sorption at pH 2. The cationic form of SMO appeared to sorb more close to pH ≥ pKa1 and, when pH ≥ pKa2 (6.5, 7.5 and 8.5) the anionic species seems to dominate, however, its sorption affinity to all soils was low. SMO sorption was affected by ionic strengths and organic carbon content, while the presence of hormones showed only a subtle decrease in SCP sorption in a selected model pasture soil.

Degradation of three sulfonamides (SAs), namely sulfamethoxazole (SMX), sulfamethazine (SMZ), and sulfadimethoxine (SDM) in surface water and sediments collected from Taihu Lake and Dianchi Lake, China was investigated in this study. The surface water (5–10 cm) was collected from the east region of Taihu Lake, China. Two sets of degradation experiments were conducted in 3-L glass bottles containing 2 L of fresh lake water and 100 μg/L of individual SAs aerated by bubbling air at a rate of approximately 1.2 L/min, one of which was sterilized by the addition of NaN₃ (0.1 %). Sediment samples were taken from Taihu Lake and Dianchi Lake, China. For the sediment experiment, 5 g of sediment were weighed into a 50-mL glass tube, with 10 mg/kg of individual SAs. Different experimental conditions including the sediment types, sterilization, light exposure, and redox condition were also considered in the experiments. The three SAs degraded in lake water with half-lives (t ₁/₂) of 10.5–12.9 days, and the half-lives increased significantly to 31.9–49.8 days in the sterilized water. SMZ and SDM were degraded by abiotic processes in Taihu and Dianchi sediments, and the different experimental conditions and sediments characteristics had no significant effect on their declines. SMX, however, was mainly transformed by facultative anaerobes in Taihu and Dianchi sediments under anaerobic conditions, and the degradation rate of SMX in non-sterile sediment (t ₁/₂ of 9.6–16.7 days) were higher than in sterilized sediment (t ₁/₂ of 18.7–135.9 days). Under abiotic conditions, degradation of SMX in Dianchi sediment was faster than in Taihu sediment, probably due to the higher organic matter content and inorganic photosensitizers concentrations in Dianchi sediment. High initial SAs concentration inhibited the SAs degradation, which was likely related to the inhibition of microorganism activities by high SAs levels in sediments. Results from this study could provide information on the persistence of commonly used sulfanomides antibiotics in lake environment.

The occurrence and fate of eight PPCPs was studied in river waters from upstream to downstream of the three rivers in the Pearl River Delta, China. The correlations of PPCP levels and water quality parameters were also investigated. The analytes of the highest concentrations were caffeine, acetaminophen, and ciprofloxacin. Carbamazepine and erythromycin-H2O were detected at the lowest concentrations. The highest concentrations of PPCPs were found in the Shijing River, with 865 ng/L caffeine, 339 ng/L acetaminophen, and 304 ng/L ciprofloxacin. In general, the levels of PPCPs in the Zhujiang River were higher at sites where the metropolitan city Guangzhou is located and decreased from the epicenter along the river. Low levels of PPCPs were generally found in the Beijiang River. Positive correlations were found between PPCP levels, total nitrogen, ammonium nitrogen, and cumulative fluorescence excitation-emission matrix (EEM) volume. Among the four PPCPs evaluated (caffeine, acetaminophen, ciprofloxacin, and sulfamethoxazole), caffeine had the best correlations with the correlation coefficients ranging from 0.62 to 0.98. The prediction of PPCP concentrations at specified locations can be substantially simplified.

Sub-inhibitory concentrations of antibiotics, which are found in environmental water systems and sewage plants due to an increased use in therapeutical and preventive fields, influence bacterial behavior in biofilms. The application of sulfamethoxazole, erythromycin, and roxithromycin induced changes in biofilm dynamics regarding biomass formation, spatial structure and specific gene expression in different Pseudomonas aeruginosa isolates. Exposing multi-resistant environmental isolated strains for 17 h to environmental concentrations of antibiotics or wastewater, directly, an increase in biofilm biomass and thickness could be observed for each strain. Additionally, multi-resistant strains responded to the applied growth conditions with changes in transcriptional activity. Here, sub-inhibitory concentrations of macrolides specifically upregulated expression of quorum sensing genes (rhlR, lasI), whereas sulfonamides and municipal wastewater, instead upregulated expression of specific resistant genes (sul1) and efflux pumps (mexD). Antibiotic sensitive isolates demonstrated an overall higher transcriptionally activity, but did not show a specific gene response to the applied exogenous stimuli. Furthermore, the presence of low concentrated antibiotics induced also phenotypical change in the biofilm architecture observed by 3D-imaging.